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Effect of Ozone, Clothing, Temperature, and Humidity on the Total OH Reactivity Emitted from Humans

  • Nora Zannoni*
    Nora Zannoni
    Atmospheric Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany
    *Email: [email protected]
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    Orcidhttps://orcid.org/0000-0003-2721-5362
  • , 
  • Mengze Li
    Mengze Li
    Atmospheric Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany
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    Orcidhttps://orcid.org/0000-0003-0620-6301
  • , 
  • Nijing Wang
    Nijing Wang
    Atmospheric Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany
    More by Nijing Wang
    Orcidhttps://orcid.org/0000-0003-3197-8151
  • , 
  • Lisa Ernle
    Lisa Ernle
    Atmospheric Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany
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  • , 
  • Gabriel Bekö
    Gabriel Bekö
    International Centre for Indoor Environment and Energy, Department of Civil Engineering, Technical University of Denmark, 2800 Lyngby, Denmark
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    Orcidhttps://orcid.org/0000-0001-6107-8336
  • , 
  • Pawel Wargocki
    Pawel Wargocki
    International Centre for Indoor Environment and Energy, Department of Civil Engineering, Technical University of Denmark, 2800 Lyngby, Denmark
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  • , 
  • Sarka Langer
    Sarka Langer
    IVL Swedish Environmental Research Institute, 41133 Göteborg, Sweden
    Division of Building Services Engineering, Department of Architecture and Civil Engineering, Chalmers University of Technology, 41296 Göteborg, Sweden
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    Orcidhttps://orcid.org/0000-0002-6580-8911
  • , 
  • Charles J. Weschler
    Charles J. Weschler
    International Centre for Indoor Environment and Energy, Department of Civil Engineering, Technical University of Denmark, 2800 Lyngby, Denmark
    Environmental and Occupational Health Sciences Institute, Rutgers University, Piscataway, New Jersey 08854, United States
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    Orcidhttps://orcid.org/0000-0002-9097-5850
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  • Glenn Morrison
    Glenn Morrison
    Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7431, United States
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    Orcidhttps://orcid.org/0000-0001-6876-7185
  • , and 
  • Jonathan Williams
    Jonathan Williams
    Atmospheric Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany
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    Orcidhttps://orcid.org/0000-0001-9421-1703
Cite this: Environ. Sci. Technol. 2021, 55, 20, 13614–13624
Publication Date (Web):September 30, 2021
https://doi.org/10.1021/acs.est.1c01831
Copyright © 2021 The Authors. Published by American Chemical Society
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Abstract

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People influence indoor air chemistry through their chemical emissions via breath and skin. Previous studies showed that direct measurement of total OH reactivity of human emissions matched that calculated from parallel measurements of volatile organic compounds (VOCs) from breath, skin, and the whole body. In this study, we determined, with direct measurements from two independent groups of four adult volunteers, the effect of indoor temperature and humidity, clothing coverage (amount of exposed skin), and indoor ozone concentration on the total OH reactivity of gaseous human emissions. The results show that the measured concentrations of VOCs and ammonia adequately account for the measured total OH reactivity. The total OH reactivity of human emissions was primarily affected by ozone reactions with organic skin-oil constituents and increased with exposed skin surface, higher temperature, and higher humidity. Humans emitted a comparable total mixing ratio of VOCs and ammonia at elevated temperature-low humidity and elevated temperature-high humidity, with relatively low diversity in chemical classes. In contrast, the total OH reactivity increased with higher temperature and higher humidity, with a larger diversity in chemical classes compared to the total mixing ratio. Ozone present, carbonyl compounds were the dominant reactive compounds in all of the reported conditions.

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Synopsis

In the presence of ozone, humans emit more OH-reactive compounds at higher indoor temperatures and humidity, and with less clothing coverage.

Introduction

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On average, we spend 85–90% of our time indoors, (1,2) that is, at home, in offices, and schools. While indoor environments afford some protection against outdoor ozone and fine particles, confined volume and limited ventilation can increase exposure to multiple volatile organic and inorganic compounds from indoor sources. (3) Indoor air chemistry is influenced by the strength and nature of the indoor sources, the ventilation rate and quality of outdoor air, the ratio of exposed surfaces to volume of the space, and occurrence of natural light sources that drive photochemistry outdoors. (4) In occupied environments, human beings and their associated activities such as cooking and cleaning represent the dominant source of gaseous and particulate emissions. (5,6) Human beings emit numerous reactive volatile organic compounds (VOCs) through their breath and skin. (7−10) The main VOCs reported from breath emissions of healthy individuals include hydrocarbons such as isoprene, alcohols, ketones, and compounds containing nitrogen and sulfur. (11) Common skin VOCs include compounds directly emitted by the body as well as those resulting from oxidation of such compounds (e.g., 6-methyl-5-hepten-2-one and geranyl acetone). In total, approximately 500 compounds have been identified as emissions from skin, compared to almost 900 identified in breath. (7,12) Ozone (O3), the main indoor oxidant, is also the main chemical sink of human emissions, although present at only 10–70% of the outdoor levels due to losses (reaction) during the building envelope penetration and on indoor surfaces. (13) Ozone deposition velocities have been calculated for materials used in building furnishings, (14−16) occupied environments, (8,17) aircrafts interiors, (18) skin, (19) hair, (20) and clothing. (18,19,21) Values can range from <1 to >20 m/h, (22) but the central tendency for area-averaged surfaces indoors is about 1.4 m/h. The largest reported deposition velocities were associated with human skin, soiled hair, and clothing. Adult human skin has a large surface area (1.5–2.0 m2) and, due to secretions from glands across the body, it is covered with proteins and lipids such as fatty acids, triglycerides, cholesterol, and squalene (C30H50). (23) The latter contributes roughly to 50% of the C═C bonds available for O3 reactions. (20) Squalene reacts rapidly with O3 generating first-generation products including ketones such as acetone (C3H6O), 6-methyl-5-hepten-2-one (6-MHO, C8H14O), and geranyl acetone (C13H22O). Further O3 reactions with the primary products lead to secondary products such as additional acetone, 4-oxopentanal (4-OPA, C5H8O2), 1,4-butanedial (C4H6O2), and levulinic acid (C5H8O3). The generation of gas-phase products is dependent on environmental factors such as O3 concentration and relative humidity. (24)
One of the most critical aspects for understanding indoor air chemistry and quality is a comprehensive knowledge of the VOCs present indoors and emitted by humans, (25) as well as their reactivity and lifetime. A relatively new measurement, namely, the total hydroxyl radical (OH) reactivity, (26) allows direct assessment of the entire chemical budget of compounds that react with the OH radical. Coupled with measurements of individual VOCs, it can be used to determine how complete is the chemical characterization of reactive organic compounds in air. The total OH reactivity is defined as the total loss frequency of OH, the inverse being the OH lifetime. Since the development of the concept of total OH reactivity as a “top-down” parameter, (26) a number of instruments measuring OH reactivity have been deployed in a diverse set of outdoor environments, (27−30) with the goal of investigating budgets of reactive VOCs as well as OH (31) and O3. (32)
The Indoor Chemical Human Emissions and Reactivity (ICHEAR) project aimed at quantifying VOC emissions and OH reactivity from adult volunteers exposed in groups of four in a controlled climate chamber. (33) In Wang et al., (34) we analyzed the OH reactivity of isolated breath and dermal emissions as well as whole-body emissions from volunteers of different age groups in the presence and absence of O3. We showed that the reactive VOCs budget was closed, that when O3 was present, “OH reactivity approximately doubled” with the increase due chiefly to unsaturated secondary products of O3-skin-oil chemistry (57%), and that no significant difference was observed among different age groups. (34) In this study, using results from a different set of experiments, we examine the effects of indoor O3 concentration, clothing, temperature, and relative humidity on the total OH reactivity of whole body emissions from experiments involving two different groups of adult volunteers.

Methods

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Experimental Design and Methods

The experiments were conducted in a 22.5 m3 stainless steel climate chambers at the Technical University of Denmark (DTU) as part of the ICHEAR project (Table S1). The focus of this research was on human bioeffluents, so other emission sources were minimized. The chamber was furnished with a table and four wire-meshed chairs, and measurements of the empty chambers were taken before volunteers entered to characterize background conditions. Prefiltered outdoor O3-free air was used to ventilate the chamber with an average air change rate (ACR) of 3.2 h–1. Mixing was ensured with two fans in the chamber, directed to the walls. The environmental conditions were either moderate temperature and low humidity (set points 25 °C and 25%, respectively), or high temperature and high humidity (set points 31 °C and 65%, respectively). Ozone was added into the supply air either before the start of the experiment, so that its concentration had reached steady state (SS) before the volunteers entered (short experimental days—morning only), or it was introduced into the chamber air after the human emitted volatile organic compounds reached steady state (long experimental days—morning and afternoon). Although the two scenarios result in identical steady-state ozone concentration with occupancy (around 35 ppb), they have different dynamics; when steady state is approached from an ozone-rich state more ozone-initiated chemistry occurs than when steady state is approached from an ozone-poor state. (35) In the latter case, the volunteers left the chamber for a 10 min lunch break after 3 h of O3-free condition. Ozone generation commenced 10 min after they returned to the chamber for another 2.5 h exposure. The target O3 mixing ratio in the unoccupied chamber was ∼100 ppb, which resulted in a chamber level of ∼35 ppb when four volunteers were present.
Two groups with young adult volunteers participated in the present experiments, originally termed as groups A1 and A2. (31) Each group was composed of two females and two males being ∼25 years old. They were asked to refrain from drinking alcohol and eating spicy food one day prior to and during the days of the experiments. The night before each experimental day they were washed with provided fragrance-free soap and shampoo; no shower was taken in the morning. During the experiments, they wore a provided set of new prewashed (fragrance-free detergent) and tumble-dried “long” or “short” clothing. “Long clothing” consisted of sweatpants, long-sleeve shirts, and calf socks, while “short clothing” consisted of shorts, t-shirts, and ankle socks.
Separate experiments on O3 exposure (concentration at the inlet ∼100 ppb, ACR ∼3.2 h–1) of clothing only were conducted with four clean t-shirts and four soiled (worn) t-shirts, of the same type given to the volunteers. Soiled t-shirts were worn overnight and hung inside-out in the chamber. Detailed information on the experimental design is provided in Bekö et al. (33)
Total OH reactivity was measured using a custom-built comparative reactivity method (CRM) instrument previously deployed in multiple outdoor atmosphere measurement campaigns (32) and validated in a large inter-comparison exercise. (36) The CRM (37) combines a glass flow reactor with a proton transfer reaction-quadrupole mass spectrometer (PTR-QMS, Ionicon Analytik GmbH, Austria (38)) to measure the concentration of a reference compound normally not found in ambient or indoor air (here pyrrole, C4H5N), whose reaction rate with OH is known, and whose concentration can be unambiguously detected by PTR-MS (C4H5NH+, m/z 68). The PTR-MS was operated at standard conditions (Pdrift = 2.2 mbar, E/N = 130Td, Tinlet = 60 °C) to monitor m/z 68 with a dwell time of 20 s. A pressurized gas standard of pyrrole (Westfalen AG, Germany) was diluted in the flow reactor and the concentration, C, was measured under three sequential conditions: with clean air and dry N2 after photolysis (C1), after OH is generated (C2), with chamber air replacing clean air (C3). Hydroxyl radicals were generated in the glass flow reactor through photolysis of water vapor (Hg UV lamp emitting at 184.9 nm). Assuming a pseudo-first-order kinetics regime inside the reactor ([pyrrole] ≫ [OH]), the OH reactivity Rair was determined from pyrrole concentrations C1, C2, and C3 with eq 1
(1)
where kpyrrole+OH is the rate constant of the reaction between pyrrole and OH and equals (1.20 ± 0.16) × 10–10 cm3 molecule–1 s–1. (39,40) The concentration C1 was quantified after each experiment using an OH scavenger. (41) The OH scavenger used during the campaign was propane at a concentration ∼3.6 × 103 ppm inside the reactor. The pyrrole mixing ratio C1 measured when the reactor was wet with the OH scavenger was 59 ± 15 ppb (mean campaign value ±1σ), and the pyrrole mixing ratio C1 measured when the reactor was dry without any OH scavenger was 55 ppb. An automated system switched between clean air (to determine C2) and chamber air (to determine C3) every 5 min. The data processing consists of a PTR-MS calibration with pyrrole at different levels of humidity, humidity correction on C2 to correct for OH recycling when humidity changed, NOx and O3 corrections on C3 for OH recycling, reactivity calibration for deviation from pseudo-first-order kinetics with test gas having different OH rate coefficients, and dilution of the sampling flow into the flow reactor. All correction factors were determined experimentally. (34,42) Correction for NOx and O3 interference for recycling OH were not necessary as the NO concentration measured inside the chamber was ∼1 ppb (corresponding to a change in reactivity <3%), and increasing concentrations of O3 (0–110 ppb) were tested and found not to interfere with the chamber CRM set-up. The resolution of the OH reactivity measurements was 1–10 min, the limit of detection (1σ) was ∼5 s–1 and the quantified total uncertainty was ∼48%. The total uncertainty was calculated as the propagated uncertainty on the pyrrole standard (10%), on the rate constant of the reaction between pyrrole and OH (14%), on the dilution of the sampled flow (0.16%), on the corrections used (31% for kinetics conditions, 29% for humidity), and on signal precision (∼15%).
Ancillary measurements performed during the ICHEAR campaign and used in this study included: volatile organic compounds (VOCs) detected with a PTR-MS equipped with a time of flight detector (ToF), and with a fast gas chromatograph–mass spectrometer (fast GC-MS); carbon dioxide (CO2) and ammonia (NH3) detected with cavity ring-down spectroscopy (Picarro, G2401 and G2103, respectively), ozone (O3), temperature and relative humidity (RH). (33,34,43)
A common fluorinated ethylene propylene (FEP) inlet (OD 1/2 in., length 5 m) was installed in the chamber’s air exhaust outlet and air was drawn (sampling flow ∼7 L min–1) to the sampling devices to measure VOCs, OH reactivity, and CO2 concentration. Background measurements of the supply air just before it entered the chamber were taken periodically before, during, and after each experiment. Ozone was measured from a separate inlet in the middle of the chamber, and the air temperature and humidity sensors were placed in the chamber.
PTR-ToF-MS (PTR-ToF-MS 8000, Ionicon Analytik GmbH, Austria (38)) was operated under standard conditions (Pdrift = 2.2 mbar, Tinlet = 60 °C and E/N = 137Td) with m/z up to 450 (mass resolution 4000 at 96 amu). A certified gas standard mixture (Apel-Riemer Environmental Inc.) containing 14 compounds was used to calibrate the instrument during the campaign. Calibrations were performed at stepwise increasing concentrations at different humidity levels (10–80%). The sensitivity was generally not affected by humidity (below 10% for most compounds, except for benzene and toluene, where sensitivity varied within 20%). A humidity-dependent sensitivity curve was derived and used to determine the concentrations of the species included in the calibration gas. A theoretical method was applied to determine the mixing ratios of the masses of the compounds not included in the gas standard. (44) The time resolution of the measurements was 20 s, the uncertainty was up to 11% for the compounds in the calibration mixture (including uncertainty derived from the humidity dependency), and ∼50% for those compounds not included in the calibration mixture.
The fast GC-MS instrument (SOFIA—System for Organic Fast Identification Analysis (45)) was equipped with a cryogenic pre-concentrator. A sampling volume of 20–40 mL was collected. A quartz particle filter impregnated with a 10% w/w solution of sodium thiosulfate was installed at the inlet to scrub O3. Calibrations were performed using a certified gas standard mixture (Apel-Riemer Environmental Inc.) containing 79 compounds. The time resolution of the measurements was 3 min, the limit of detection was <25 ppt, and the uncertainty was <10%.
The time resolution of CO2 and NH3 was 2 s. Ozone was monitored with a 2B Technologies model 205 ozone monitor (2B Technologies, Boulder, CO) with a time resolution of 10 s (accuracy: 1.0 ppb or 2% of reading). Air temperature and RH were monitored with Vaisala GMW90 (accuracy: temperature ±0.5 °C, RH ±2.5% below 60%; Vaisala Corporation, Helsinki, Finland) connected to a HOBO UX120-006M 4-channel analog data logger (Onset Computer Corporation, Bourne, MA) with a time resolution of 1 min. (33)

Skin Wipes Samples

Skin wipes were collected from the volunteers’ right forearm before and from the left forearm after each experiment. Pre-cleaned sterilized cotton pads wetted with 2-propanol were used to thoroughly wipe (7 strokes) a skin area of 100 cm2. Squalene (C30H50) and pyroglutamic acid (C5H7NO3) concentrations were determined in the collected samples through extraction with an organic solvent and analyzed by gas and liquid chromatography coupled with mass spectrometry GC/MS and LC/MS/MS.

OH Reactivity Budget

Volatile organic compounds and ammonia concentrations (Xi) and their rate coefficients of reaction with OH (ki+OH) were used to determine the species-specific OH reactivity. The sum of species-specific OH reactivities for all measured compounds yields the summed calculated OH reactivity (eq 2)
(2)
Table S2 lists the compounds used to calculate the reactivity. From the measured PTR-ToF-MS masses (21–450 m/z), only masses above the instrumental limit of detection and known to be related to human emissions (higher mixing ratios detected from the occupied chamber in comparison with the unoccupied chamber) were selected to calculate their OH reactivity. The uncertainty of the calculated OH reactivity (∼30%) was determined from the propagation of the uncertainty of the measured concentration Xi (10–50%) and the error in the rate coefficient of the reaction between i and OH (ki+OH, 10–100%). The comparison between the total measured OH reactivity and the calculated OH reactivity allows verification of whether all of the OH-reactive VOCs were identified and quantified. As discussed in Wang et al., (34) the length and material of the sampling system used during the ICHEAR campaign differed from those used in previous experiments, (8,35) and this may have led to sampling artifacts. Specifically, in the presence of ozone, adsorption of geranyl acetone on the main inlet FEP surface may have led to consequent reactions with ozone, decreasing the measured steady-state concentration of geranyl acetone and increasing that of 6-MHO. This artifact would not affect the VOC budget analysis reported in this work as the OH reactivity and VOCs were measured with the same sampling system.

Ozone Deposition Velocities on Occupant Surfaces

The first-order rate constant for O3 loss by all mechanisms, kd, was calculated based on eq 3 (6)
(3)
where CO3,inlet is the chamber inlet O3 mixing ratio, CO3,outlet is the chamber outlet O3 mixing ratio, and λ is the air change rate. For an occupied chamber, O3 loss is dominated by deposition to the occupants; in this case, the loss rate constant in eq 3 is equal to that associated with the occupant, kocc. For experiments in which only clean or soiled t-shirts are present in the chamber, O3 loss is dominated by deposition to clothing and the removal rate constant is kcloth,only. Ozone removal associated with chamber surfaces was negligible compared to that on occupants or clothing surfaces (kchamber = 0.15–0.17 h–1  (33,35)). For surface removal, each rate constant can be expressed as the product of a mass transfer coefficient (deposition velocity, v) and the area of the reactive surface, A, divided by the chamber volume, V. Therefore
(4)
where the subscripts refer to occupants (occ). The deposition velocity to the four occupants, νocc, can be solved directly from eq 4 using the total body surface area (BSA) of the participants calculated according to Du Bois and Du Bois (46) (7.3 m2 in agreement with the average BSA 1.9 m2 of a healthy adult (47)). For an experiment with clothing only (no occupants) in the chamber, vcloth,only can be solved directly from eq 5, where Acloth,only is 0.7 m2 per medium-sized shirt times the number of shirts deployed in the chamber.
(5)

Reactivity-Influencing Factors

Dominance analysis is designed to determine the relative importance of one variable over another in a given data set. (48,49) It measures the relative importance in all possible subset models in a pairwise manner (in total 2n – 1 models, n: number of variables), i.e., all pairs of variables are compared. (50) The dominance of one variable over another is calculated by comparing their incremental R2 contributions over the complete data set. (48,49) In this study, dominance analysis (in Python) was applied to determine the relative importance of a set of target variables discussed in the manuscript for the total OH reactivity and the OH reactivity of some important reactive VOCs associated with dermal emissions. Specifically, the following target variables were tested: indoor O3 concentration, indoor air temperature and relative humidity, clothing, age, and volunteer group (six variables). Ozone, temperature, RH, and clothing factors are discussed in this manuscript, while age and volunteer groups were discussed in Wang et al. (34) The clothing factor was used to distinguish between volunteers wearing long clothing or short clothing. As the age factor, the average age of the volunteers occupying the chamber was used. The volunteer group factor was used to distinguish between the five different groups of subjects occupying the chamber during the ICHEAR experiments. Steady-state values of OH reactivity, O3, temperature, and RH data were used in these analyses. The data set comprised all experiments performed during the ICHEAR campaign on whole body emissions. For long experimental days, both morning and afternoon steady-state values were used separately in the analyses (n = 33). (33)

Results and Discussion

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Ozone and Clothing Effect

Experiments (6), (7), (8), (9) and their respective replicates (21), (22), (23), (24) (Table S1), all conducted with volunteer group A2, probed differences in OH reactivity from occupant emissions under different clothing conditions. During these experiments, the chamber air temperature was moderate (set point 25 °C) and its relative humidity low (set point 25%). Figure 1 shows the measured total OH reactivity (filled bars) and the summed calculated OH reactivity (empty bars) averaged over the final 15 min of each experiment (emissions at steady state (33)) for each condition: long clothing before O3 addition (6 and 21 morning); long clothing with O3 added after emissions reached SS (6 and 21 afternoon); long clothing with O3 present from the start of the experiment (7 and 22); short clothing before O3 addition (8 and 23 morning); short clothing with O3 added after emissions reached SS (8 and 23 afternoon); and short clothing with O3 present from the start of the experiment (9 and 24).

Figure 1

Figure 1. (a) Measured OH reactivity from occupant emissions at steady state. Experiments involved the same four adult volunteers occupying a chamber wearing long clothing or short clothing, under the same conditions on different days. Two replicates were done for the same condition with the same volunteers on different days (n = 2). Ozone was absent (red), introduced to the chamber when VOC reached SS (blue), or introduced to the chamber from the start of the experiment (black). (b) Measured (filled bars) and calculated (empty bars) OH reactivity from occupant emissions at steady state. Each bar corresponds to the mean among SS values between the two replicates conducted for each condition. Error bars indicate the method uncertainties (∼48% for measured reactivity, ∼30% for calculated reactivity). Steady-state values were determined during the last 15 min before occupants left the chamber.

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With O3 present, the measured total OH reactivity for the same group of volunteers ranged between 25 ± 2 and 35 ± 0.2 s–1 (mean value across replicates ± 1 standard deviation). In the absence of O3, the OH reactivity was smaller (8 ± 3 to 11 ± 7 s–1 for short and long clothing) consistent with the experiments examined in Wang et al. (34) Differences in OH reactivity for O3-free conditions are attributed primarily to variability in isoprene (C5H8) emission rates (33) (differences in measured OH reactivity up to 24% and in calculated OH reactivity up to 22%). In the presence of O3, the measured OH reactivity between replicates agree within 1–18%. A similar agreement was observed for the respective calculated values (agreement within 1–18%, uncertainty on measurements ∼48%, uncertainty of calculations ∼30%). The replicates suggest that small differences in VOC emissions were present within the same group of volunteers on different experimental days.
For both clothing conditions, an increasing trend of OH reactivity was observed when O3 was introduced after steady-state conditions had been reached (29 ± 5 and 35 ± 0.2 s–1, mean measured OH reactivity for long and short clothing and standard deviation among replicates, respectively), compared to when O3 was introduced from the start of the experiment (25 ± 1.5 and 31 ± 2.4 s–1, mean measured OH reactivity for long and short clothing, respectively); see Figure 1. Differences were statistically significant (p < 0.05, paired sample t-test) when occupants wore short clothing. With O3 present, the OH reactivity was significantly larger with short clothing compared to the condition when long clothing was worn (p < 0.05, paired sample t-test).
As shown in Figure 1, differences between the measured total OH reactivity and the summed OH reactivity from the individually measured compounds are not significant, meaning that for the investigated conditions the reactive VOC budget, within the margin of uncertainty, is closed. Figure S1 examines the OH reactivity per chemical compound class, divided into hydrocarbons, alcohols, carboxylic acids, aromatic oxygenated compounds, carbonyl compounds, other oxygenated compounds, nitrogen-containing compounds, and sulfur-containing compounds (Table S2). In the absence of O3, when occupants wore long clothing, hydrocarbons (mainly represented by isoprene) explained 79% of the total OH reactivity, followed by carbonyls (15.7%, mainly formaldehyde, acetaldehyde, 1,4-butanedial, 6-MHO, 4-OPA, and geranyl acetone), other oxygenated compounds (1.45%), aromatics (1%), alcohols (1%), sulfur-containing compounds (0.8%), carboxylic acids (0.7%), and nitrogen-containing compounds (0.4%). Small differences were reported in the absence of O3, when occupants wore short clothing (hydrocarbons, carbonyls, and nitrogen-containing compounds explained 76%, 17%, and 1.2% of the OH reactivity, respectively). In the presence of O3, and with occupants wearing long clothing, their OH reactivity was explained by carbonyls (59%), hydrocarbons (34%), others (2.8%), aromatics (1.7%), carboxylic acids (1%), sulfur-containing compounds (0.5%), alcohols (0.4%), and nitrogen-containing compounds (0.3%). When occupants were wearing short clothing, carbonyls explained 65% of the total OH reactivity, followed by hydrocarbons (27.4%), others (2.9%), aromatics (2%), carboxylic acids (1.2%), sulfur-containing compounds (0.8%), nitrogen-containing compounds (0.3%), and alcohols (0.3%).
In terms of specific species, when long clothing was worn and O3 was present from the start of experiments, the compounds most influencing the reactivity were 6-MHO (C8H14O, 9.4 ± 2.2 s–1) and isoprene (C5H8, 9.3 ± 1.3 s–1), followed by 4-OPA (C5H8O2, 1.8 ± 0.4 s–1), 1,4-butanedial (C4H6O2, 1.4 ± 0.3 s–1), and acetaldehyde (C2H4O, 1.4 ± 0.2 s–1); values in parentheses correspond to the OH reactivity ± 1 standard deviation reported for the experimental replicates of the same condition (Table S3). In comparison, when O3 was added after the gas-phase concentration of occupant emitted compounds reached steady state (afternoon), compounds related to dermal emissions such as geranyl acetone (0.50 ± 0.06 s–1) and 6-MHO (9.91 ± 0.02 s–1) had a larger OH reactivity. Carbonyls had an even larger influence on the OH reactivity for occupants wearing short clothing: 6-MHO (14 ± 0.6 s–1) and isoprene (10.2 ± 0.8 s–1), followed by 4-OPA (3.2 ± 0.1 s–1), 1,4-butanedial (2 ± 0.03 s–1), and acetaldehyde (1.6 ± 0.03 s–1). In the case of occupants wearing short clothing when O3 was added in the afternoon, the OH reactivity of some carbonyl compounds, including 6-MHO (15.3 ± 0.4 s–1) and geranyl acetone (1 ± 0.1 s–1) further increased. Figure 2 shows the time series of 6-MHO, 4-OPA, and geranyl acetone concentrations. A 35–51% increase in the concentrations of those three compounds is associated with occupants wearing short rather than long clothing. In the presence of O3, clothing coverage of bare skin significantly influences the OH reactivity.

Figure 2

Figure 2. Concentrations of 6-MHO, 4-OPA, and geranyl acetone measured in the chamber occupied from 9:30 by four adults wearing long/short clothing. For each condition, two replicate experiments (N = 2) were conducted (long clothing conditions (6), (21), short clothing conditions (8), (23); see Table S1). The dashed line indicates when ozone was mixed into the chamber air. The dips correspond to measurements of the chamber supply air.

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Depending on the clothing worn and the timing of the O3 introduction to the chamber, four cases can be distinguished: (i) clean long clothing worn just prior to O3 exposure (O3 from start), (ii) long clothing worn for ∼3 h prior to O3 exposure (O3 from SS), (iii) clean short clothing worn just prior to O3 exposure (O3 from start), and (iv) short clothing worn for ∼3 h prior to O3 exposure (O3 from SS). The O3 deposition velocity on the occupants (νocc) was calculated for each of these cases to investigate whether the observed OH reactivity and VOC mixing ratios are compatible with bare skin-surface-to-clothed-surface area, and how clothing cleanliness influences emission (Table S4). Ozone deposition velocities calculated in our experiments are close to the upper limits of values previously reported in the literature (8,20) for similar conditions. This is due to possibly higher air mixing achieved by the fans in the chamber. When O3 was added in the chamber from steady state in the afternoon (and occupants had been wearing the clothes for a longer time), O3 deposition velocity showed a small increase, while a larger increase and consistent trend was reported for kocc, VOC concentrations, and OH reactivity (Table S4). The yield was presumably enhanced by the presence of skin flakes or skin oil deposited on the clean clothing during the day, in agreement with the results reported by Lakey et al. (51)
In comparison, the O3 deposition velocity of four clean t-shirts (6.9 m/h) and four soiled t-shirts (9.4 m/h), exposed to O3 in the chamber are reported in Table S5. Results are in agreement with values reported in the literature (18,19,52) but are substantially lower than those measured for the clothed occupants in this study. We observed very little difference in O3 removal for occupants wearing long or short clothing; therefore, the deposition velocity of clothing that is being worn is nearly the same as that of skin but higher than that of the clothing that was tested on its own. It is possible that the deposition velocity for clothing worn by people is higher because of enhanced convection around a body. The measured total OH reactivity of clean clothing was below the limit of detection (5 s–1) and of soiled clothing was 7 ± 3 s–1. The total OH reactivity of clothing and occupants depends on concentrations of the most reactive compounds generated from O3-initiated chemistry with skin oil. This chemistry depends on the O3 concentration inside the chamber and the mass-transport limited O3 flux to surfaces. Taking this into account, the OH reactivity is expected to scale with O3 concentration in an occupied, or recently occupied indoor environment.

Effect of Temperature and Humidity

To assess the effect of temperature and humidity, conditions (1), (4), and (2) (33) (Table S1) are examined in Figure 3, for the measured total OH reactivity, summed calculated OH reactivity, 6-MHO, 4-OPA, and geranyl acetone OH reactivities. Specifically, four adult volunteers (group A1) occupied the chamber, wearing long clothing, at moderate air temperature (set point 25 °C) and low RH (set point 25%), at high temperature (set point 31 °C) and low RH, and at high temperature and RH (set point 65%); the actual temperatures were higher than the set points (see Table S1). In all cases, O3 was added to the chamber air after the occupant VOC emissions reached steady-state condition. Similar to the case of clothing, OH reactivity increased when O3 was present due to the presence of reactive carbonyls generated from skin ozonolysis reactions. With O3 present, the total OH reactivity measured at steady state (15 min before end of the exposure) varied between 41 s–1 (moderate temperature, low RH) and 63 s–1 (high temperature, high RH). For each positive change in condition (increased air temperature, increased relative humidity), higher concentrations of reactive compounds were present. In all three cases, the reactive VOC budget was closed within the margin of uncertainty (Figure 3).

Figure 3

Figure 3. Measured and calculated OH reactivity from four adults occupying the chamber from 9:30, wearing long clothing, exposed to moderate or high temperature (T), and low or high humidity (RH). Ozone was added to the chamber air when occupant emissions reached steady state (dashed vertical line). Total measured and calculated OH reactivities are reported with their associated method uncertainties, 48 and 30%, respectively. 6-MHO, 4-OPA, and geranyl acetone (GA) OH reactivities are reported with the gray area and colored lines, respectively. Missing data points for the first 1.5 h in the bottom panel are due to instrument failure. The dip in the experiment at a high T and a low RH corresponds to the measurement of the chamber supply air.

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The classes of chemical compounds contributing to the total OH reactivity and their mixing ratios are shown in Figure 4. At a moderate temperature and a low RH, the dominant reactive compounds were carbonyls (51%), followed by hydrocarbons (41%), others (2.3%), aromatics (1.5%), nitrogen-containing compounds (1.4%, 96% of this fraction is represented by NH3), carboxylic acids (1%), sulfur compounds (0.6%), and alcohols (0.5%). In contrast to the OH reactivity, the total mixing ratio of the chemical compounds, which depends only on the abundance of the measured chemicals, is dominated by nitrogen-containing compounds, specifically by ammonia (NH3, 58%), carbonyl compounds (30%), alcohols (3.8%), carboxylic acids (3.4%), hydrocarbons (3.2%), others (0.5%), aromatics (0.3%), and sulfur compounds (0.2%). The reader should note that NH3 measurements were not available during the experiments involving group A2 (O3 and clothing effect). Results reported in Figure S1 (group A1) and Figure 4 (group A2) are in agreement, within the variability between groups observed in Wang et al. (34)

Figure 4

Figure 4. Speciated total OH reactivity (top row) and speciated total mixing ratios (bottom row) measured at the steady state with O3 present; four adults wearing long clothing occupied the climate chamber at various temperatures (T) and relative humidities (RH). Total OH reactivities represented in the pie charts in the top row are 32 ± 10, 41 ± 12, and 40 ± 12 s–1, for the three cases, moderate T and low RH, high T and low RH, and high T and high RH, respectively. Total mixing ratios represented in the pie charts in the bottom row are 190 ± 13, 405 ± 33, and 393 ± 32 ppb, for the three cases, moderate T and low RH, high T and low RH, and high T and high RH, respectively. The size of the pie charts is scaled to the total values, different scales are used between pies representing OH reactivity and pies representing the mixing ratios. Steady-state values were determined during the last 15 min before occupants left the chamber.

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A small increase in temperature (at low RH), leaves the speciation of OH reactivity almost unchanged relative to the base case (the total hydrocarbon and carbonyl fractions OH reactivities increase, respectively, by 5.5 and 3 s–1). In contrast, the fractional mixing ratio is remarkably different, with the fraction of nitrogen-containing compounds (primarily NH3) increasing to 78%. The temperature-dependent emissions of ammonia were reported by Li et al. (43) for the same experiments. The fractional contribution of other groups of compounds to the total mixing ratio decreased with increasing temperature (Figure 4). However, an increase in concentration was seen for geranyl acetone, a primary product of squalene ozonolysis, and 6-MHO, which is both a primary and secondary product of the reaction between squalene and O3 (Figure S2). Given the relatively small changes in absolute temperature in the chamber, changes in the gas-phase rate coefficients are anticipated to be small. Higher temperatures will increase the volatility of compounds from all surfaces in the chamber. However, human skin surface temperature changes are modulated metabolically. Increased sweat production will increase water vapor at the skin surface, favoring production of carbonyls over less volatile secondary ozonides. (24) Further, sweat may alter the metabolic activity of the skin microbiome, resulting in a different suite of microbial emissions. At a high temperature and a high RH, carbonyl compounds dominated the total OH reactivity (58%), followed by hydrocarbons (35%), nitrogen-containing compounds (3%, of which 98% is NH3), others (1.3%), carboxylic acids (1.2%), S-compounds (1%), alcohols (0.4%), and aromatics (0.3%). The total concentration instead, was dominated by NH3 (75%, 99.5% of the total concentration of nitrogen-containing compounds), carbonyls (+3% compared to low RH), and carboxylic acids (+0.6%). With respect to the base case (moderate temperature, low RH), the steady-state 6-MHO concentration increased by 9% with the increase in temperature and by 27% with the increase in temperature and RH. Geranyl acetone concentration increased by 27% with the increase in temperature and 54% with the increase in temperature and RH. The 4-OPA concentration did not increase significantly (<1%) when temperature increased, while it increased by 34% when temperature and RH increased (Figure S2). The results from this study are in agreement with the study from Arata et al. (24) for heterogeneous ozonolysis of squalene in a flow tube and skin oils on soiled t-shirts in the same climate chamber, where higher RH caused a greater yield of carbonyls from the Criegee intermediates of the squalene-O3 reaction.

OH Reactivity-Influencing Factors

A dominance analysis was conducted to investigate the relative importance of the factors discussed in this study (indoor O3 concentration, clothing, temperature, and humidity) and in Wang et al. (age and group variability), (34) for the total OH reactivity and individual OH reactivities of geranyl acetone, 6-MHO, and 4-OPA. The analysis aims at identifying the main drivers of human OH reactivity indoors through the relative importance of the target variables (see the Methods section). The OH reactivity data set comprises experiments conducted on whole body emissions of four volunteers occupying the chamber. (33) The target factors varied in the following experimental ranges: indoor O3 concentration: 0–44.2 ppb; air temperature: 26–32.8 °C, air humidity: 18–63%, clothing coverage: short/long; age group: teenager/adult/senior; and five different groups of volunteers: A1, A2, A3, T4, S5. (33)
The dominance analysis of total OH reactivity (Figure S3) shows that O3 has the largest impact on the total OH reactivity (85%), followed by clothing (6%), variability between the groups of subjects occupying the chamber (group factor), temperature and humidity having comparable impact (2.5–3%), while the age of volunteers has a negligible impact in comparison. Ozone initiates surface reactions with skin lipids generating reactive VOCs whose OH reactivity is represented under the total OH reactivity term. When the same analysis is conducted without O3 as a target variable, the ranking of the other factors is preserved. The skin-related compounds, namely, geranyl acetone, 6-MHO, and 4-OPA, have OH reactivities influenced mostly by the factors O3 and clothing. 6-MHO, which is both a primary and secondary product of squalene ozonolysis, and 4-OPA, a secondary product only, are considerably more influenced by O3 than geranyl acetone, a primary product of squalene ozonolysis. Among clothing, temperature, and humidity, the analysis finds that clothing is the most important factor. In our experiments, the clothing effect was examined with group A2, while temperature and humidity were examined with group A1. Total OH reactivity of group A1 emissions was higher than the total OH reactivity of group A2 emissions, masking the relative importance of the clothing factor compared to humidity and temperature. The squalene reduction observed from the skin wipes sampled before and after each experiment from the individuals in groups A1 and A2 is in general agreement with the total OH reactivity. That is, a larger reduction in squalene is observed for the higher reactivity (up to 77% reduction of squalene for up to 63 s–1 OH reactivity), and a larger reduction is observed in A1 (68% on average) than A2 (20% on average).
These results highlight the importance of skin emissions and their ozonolysis products for the OH reactivity of human occupants indoors, their variability with temperature, relative humidity, and clothing, and ultimately their importance for indoor air quality.
Outdoor to indoor transport of O3 and exposed skin surface area are especially important factors. On a hot summer day spent indoors in a city with high concentrations of ground-level O3, more ventilation (increasing indoor O3), or less clothing (increasing O3 flux to bare skin) may be necessary to improve comfort. If more people occupy the same indoor environment, the effect on indoor air chemistry will be further amplified. 4-OPA and 6-MHO are known respiratory irritants, (53,54) while the concomitant effect of exposure to multiple chemicals and the risk to certain population sectors is yet unknown. (55) Remarkably, the indoor OH reactivity measured here for the first time was comparable to the OH reactivity measured in a variety of outdoor environments, including cities (56−58) and forests. (58,59)

Current Results in Relation to the Findings from Wang et al. and Previous Studies

Results reported in Wang et al. (34) comprised experiments (1), (6), (21), (10), (18), (26), (16), (25), (12), and (13); results from the current study comprise experiments (1), (2), (4), (6), (7), (8), (9), (21), (22), (23), and (24). (33) Recall that Wang et al. (34) analyzed the OH reactivity of isolated breath and dermal emissions as well as whole-body emissions from volunteers of different age groups in the presence and absence of ozone and found that the OH reactivity could be accounted for by the trace gases measured and that it was sensitive to ozone but not to age. The current study focuses on the impact of varied environmental factors on two groups of adult volunteers, as well as reproducibility for sets of duplicated experiments. Results from these experiments have not been previously reported and are particularly relevant to the dependency of human OH reactivity on the absence or presence of O3, and the change in the OH reactivity of human emissions with changes in skin coverage by clothing, air temperature, and relative humidity. Skin coverage by clothing and worn/soiled clothing play an important role in the ozonolysis of skin-oil constituents. The role of clothing has been previously investigated in a number of O3 and VOCs experiments, (18,21,52,60) modeling studies (19,51) and now through measurements of occupant OH reactivity (this work). Additionally, to our knowledge, this is the first study reporting the effect of temperature on occupant VOC emissions and their OH reactivity. The experimental reproducibility of OH reactivity measurements across replicated experiments (6–21, 7–22, 8–23, and 9–24) reported in this work demonstrates that this technique can be used with confidence in indoor air studies. With O3 present, the standard deviation among steady-state values was <18%, and the method uncertainty was ∼48%. With O3 absent, the mean measured OH reactivity was 10 ± 2 s–1 and the standard deviation among the steady-state reactivity values was 24%, which is mainly explained by the increased uncertainty of the method for measuring OH reactivity when values are close to the instrumental limit of detection. (42)

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.est.1c01831.

  • Experimental conditions included in this study (Table S1); volatile organic compounds and their classification in compounds classes used to determine the summed calculated OH reactivity (Table S2); speciated OH reactivity from occupants wearing long clothing and short clothing, before ozone exposure, with ozone added at the steady state of emissions (afternoon), and with ozone added from the beginning of the experiment (Figure S1); 10 most reactive volatile organic compounds emitted by four adult volunteers wearing long clothing and short clothing exposed to ozone from start of the experiment and in the afternoon, from SS of the emissions (Table S3); calculated O3 deposition velocity on four occupants (vocc), first-order rate constant for O3 loss (kd), measured 6-MHO, 4-OPA, geranyl acetone concentrations, and measured total OH reactivity at SS for each experimental condition (Table S4); ozone deposition velocity and OH reactivity of four clean and soiled (worn overnight ∼8 h) t-shirts, and corresponding parameters used (Table S5); 10 most reactive volatile organic compounds emitted by four adult volunteers wearing long clothing exposed to ozone, at moderate temperature and low RH, high temperature and low RH, and high temperature and high RH (Table S6); concentrations of 6-MHO, 4-OPA, and geranyl acetone measured in the chamber occupied by four adults from 9:30, wearing long clothing, and exposed to low/high temperature and low/high relative humidity (Figure S2); dominance analysis for the total OH reactivity of human beings, with varying conditions of ozone exposure, short/long clothing, volunteers groups, relative humidity, temperature, and age of volunteers (teens/adults/seniors) (Figure S3) (PDF)

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  • Corresponding Author
  • Authors
    • Mengze Li - Atmospheric Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany;  Orcidhttps://orcid.org/0000-0003-0620-6301
    • Nijing Wang - Atmospheric Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany;  Orcidhttps://orcid.org/0000-0003-3197-8151
    • Lisa Ernle - Atmospheric Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany
    • Gabriel Bekö - International Centre for Indoor Environment and Energy, Department of Civil Engineering, Technical University of Denmark, 2800 Lyngby, Denmark;  Orcidhttps://orcid.org/0000-0001-6107-8336
    • Pawel Wargocki - International Centre for Indoor Environment and Energy, Department of Civil Engineering, Technical University of Denmark, 2800 Lyngby, Denmark
    • Sarka Langer - IVL Swedish Environmental Research Institute, 41133 Göteborg, Sweden;  Division of Building Services Engineering, Department of Architecture and Civil Engineering, Chalmers University of Technology, 41296 Göteborg, Sweden;  Orcidhttps://orcid.org/0000-0002-6580-8911
    • Charles J. Weschler - International Centre for Indoor Environment and Energy, Department of Civil Engineering, Technical University of Denmark, 2800 Lyngby, Denmark;  Environmental and Occupational Health Sciences Institute, Rutgers University, Piscataway, New Jersey 08854, United States;  Orcidhttps://orcid.org/0000-0002-9097-5850
    • Glenn Morrison - Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7431, United States;  Orcidhttps://orcid.org/0000-0001-6876-7185
    • Jonathan Williams - Atmospheric Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany;  Orcidhttps://orcid.org/0000-0001-9421-1703
  • Funding

    Open access funded by Max Planck Society.

  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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This study was funded by the Alfred P. Sloan Foundation (Grant no. G-2018-11233). Nico Ziersen, Thomas Klüpfel, and Rolf Hofmann are acknowledged for their support. The authors are thankful to the volunteers for participating in the study.

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    Wisthaler, Armin; Weschler, Charles J.
    Proceedings of the National Academy of Sciences of the United States of America (2010), 107 (15), 6568-6575, S6568/1-S6568/4CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
    This study has used proton transfer reaction-mass spectrometry (PTR-MS) for direct air analyses of volatile products resulting from the reactions of O3 with human skin lipids. An initial series of small-scale in vitro and in vivo expts. were followed by expts. conducted with human subjects in a simulated office. The latter were conducted using realistic O3 mixing ratios (≈15 ppb with occupants present). Detected products included mono- and bifunctional compds. that contain carbonyl, carboxyl, or α-hydroxy ketone groups. Among these, 3 previously unreported dicarbonyls were identified, and 2 previously unreported α-hydroxy ketones were tentatively identified. The compds. detected in this study (excepting acetone) have been overlooked in surveys of indoor pollutants, reflecting the limitations of the anal. methods routinely used to monitor indoor air. The results are fully consistent with the Criegee mechanism for O3 reacting with squalene, the single most abundant unsatd. constituent of skin lipids, and several unsatd. fatty acid moieties in their free or esterified forms. Quant. product anal. confirms that squalene is the major scavenger of O3 at the interface between room air and the human envelope. Reactions between O3 and human skin lipids reduce the mixing ratio of O3 in indoor air, but concomitantly increase the mixing ratios of volatile products and, presumably, skin surface concns. of less volatile products. Some of the volatile products, esp. the dicarbonyls, may be respiratory irritants. Some of the less volatile products may be skin irritants.
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  9. 9
    Lakey, P. S. J.; Wisthaler, A.; Berkemeier, T.; Mikoviny, T.; Pöschl, U.; Shiraiwa, M. Chemical Kinetics of Multiphase Reactions between Ozone and Human Skin Lipids: Implications for Indoor Air Quality and Health Effects. Indoor Air 2017, 27, 816– 828,  DOI: 10.1111/ina.12360
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    9
    Chemical kinetics of multiphase reactions between ozone and human skin lipids: Implications for indoor air quality and health effects
    Lakey, P. S. J.; Wisthaler, A.; Berkemeier, T.; Mikoviny, T.; Poeschl, U.; Shiraiwa, M.
    Indoor Air (2017), 27 (4), 816-828CODEN: INAIE5; ISSN:1600-0668. (Wiley-Blackwell)
    Ozone reacts with skin lipids such as squalene, generating an array of org. compds., some of which can act as respiratory or skin irritants. Thus, it is important to quantify and predict the formation of these products under different conditions in indoor environments. We developed the kinetic multilayer model that explicitly resolves mass transport and chem. reactions at the skin and in the gas phase (KM-SUB-Skin). It can reproduce the concns. of ozone and org. compds. in previous measurements and new expts. This enabled the spatial and temporal concn. profiles in the skin oil and underlying skin layers to be resolved. Upon exposure to ∼30 ppb ozone, the concns. of squalene ozonolysis products in the gas phase and in the skin reach up to several ppb and on the order of ∼10 mmol m-3. Depending on various factors including the no. of people, room size, and air exchange rates, concns. of ozone can decrease substantially due to reactions with skin lipids. Ozone and dicarbonyls quickly react away in the upper layers of the skin, preventing them from penetrating deeply into the skin and hence reaching the blood.
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  10. 10
    Kruza, M.; Carslaw, N. How Do Breath and Skin Emissions Impact Indoor Air Chemistry?. Indoor Air 2019, 29, 369– 379,  DOI: 10.1111/ina.12539
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    10
    How do breath and skin emissions impact indoor air chemistry?
    Kruza, Magdalena; Carslaw, Nicola
    Indoor Air (2019), 29 (3), 369-379CODEN: INAIE5; ISSN:1600-0668. (Wiley-Blackwell)
    People are an important source of pollution indoors, through activities such as cleaning, and also from "natural" emissions from breath and skin. This paper investigates natural emissions in high-occupancy environments. Model simulations are performed for a school classroom during a typical summer in a polluted urban area. The results show that classroom occupants have a significant impact on indoor ozone, which increases from ~ 9 to ~ 20 ppb when the pupils leave for lunch and decreases to ~ 14 ppb when they return. The concns. of 4-OPA, formic acid, and acetic acid formed as oxidn. products following skin emissions attained max. concns. of 0.8, 0.5, and 0.1 ppb, resp., when pupils were present, increasing from near-zero concns. in their absence. For acetone, methanol, and ethanol from breath emissions, max. concns. were ~ 22.3, 6.6, and 21.5 ppb, resp., compared to 7.4, 2.1, and 16.9 ppb in their absence. A rate of prodn. anal. showed that occupancy reduced oxidant concns., while enhancing formation of nitrated org. compds., owing to the chem. that follows from increased aldehyde prodn. Occupancy also changes the peroxy radical compn., with those formed through isoprene oxidn. becoming relatively more important, which also has consequences for subsequent oxidant concns.
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  11. 11
    Amann, A.; Costello, B.; Miekisch, W.; Schubert, J.; Buszewski, B.; Pleil, J.; Ratcliffe, N.; Risby, T. The Human Volatilome: Volatile Organic Compounds (VOCs) in Exhaled Breath, Skin Emanations, Urine, Feces and Saliva. J. Breath Res. 2014, 8, 034001  DOI: 10.1088/1752-7155/8/3/034001
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    11
    The human volatilome: volatile organic compounds (VOCs) in exhaled breath, skin emanations, urine, feces and saliva
    Amann, Anton; de Lacy Costello, Ben; Miekisch, Wolfram; Schubert, Jochen; Buszewski, Boguslaw; Pleil, Joachim; Ratcliffe, Norman; Risby, Terence
    Journal of Breath Research (2014), 8 (3), 034001CODEN: JBROBW; ISSN:1752-7155. (IOP Publishing Ltd.)
    A review. Breath anal. is a young field of research with its roots in antiquity. Antoine Lavoisier discovered carbon dioxide in exhaled breath during the period 1777-1783, Wilhelm (Vilem) Petters discovered acetone in breath in 1857 and Johannes Muller reported the first quant. measurements of acetone in 1898. A recent review reported 1765 volatile compds. appearing in exhaled breath, skin emanations, urine, saliva, human breast milk, blood and feces. For a large no. of compds., real-time anal. of exhaled breath or skin emanations has been performed, e.g., during exertion of effort on a stationary bicycle or during sleep. Volatile compds. in exhaled breath, which record historical exposure, are called the exposome. Changes in biogenic volatile org. compd. concns. can be used to mirror metabolic or (patho)physiol. processes in the whole body or blood concns. of drugs (e.g. propofol) in clin. settings, even during artificial ventilation or during surgery. Also compds. released by bacterial strains like Pseudomonas aeruginosa or Streptococcus pneumonia could be very interesting. Me methacrylate (CAS 80-62-6), for example, was obsd. in the headspace of Streptococcus pneumonia in concns. up to 1420 ppb. Fecal volatiles have been implicated in differentiating certain infectious bowel diseases such as Clostridium difficile, Campylobacter, Salmonella and Cholera. They have also been used to differentiate other non-infectious conditions such as irritable bowel syndrome and inflammatory bowel disease. In addn., alterations in urine volatiles have been used to detect urinary tract infections, bladder, prostate and other cancers. Peroxidn. of lipids and other biomols. by reactive oxygen species produce volatile compds. like ethane and 1-pentane. Noninvasive detection and therapeutic monitoring of oxidative stress would be highly desirable in autoimmunol., neurol., inflammatory diseases and cancer, but also during surgery and in intensive care units. The study of cell cultures opens up new possibilities for elucidation of the biochem. background of volatile compds. In future studies, combined studies of a particular compd. with regard to human matrixes such as breath, urine, saliva and cell culture studies will lead to novel scientific progress in the field.
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  12. 12
    Furukawa, S.; Sekine, Y.; Kimura, K.; Umezawa, K.; Asai, S.; Miyachi, H. Simultaneous and Multi-Point Measurement of Ammonia Emanating from Human Skin Surface for the Estimation of Whole Body Dermal Emission Rate. J. Chromatogr. B 2017, 1053, 60– 64,  DOI: 10.1016/j.jchromb.2017.03.034
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    12
    Simultaneous and multi-point measurement of ammonia emanating from human skin surface for the estimation of whole body dermal emission rate
    Furukawa, Shota; Sekine, Yoshika; Kimura, Keita; Umezawa, Kazuo; Asai, Satomi; Miyachi, Hayato
    Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences (2017), 1053 (), 60-64CODEN: JCBAAI; ISSN:1570-0232. (Elsevier B.V.)
    Ammonia is one of the members of odor gases and a possible source of odor in indoor environment. However, little has been known on the actual emission rate of ammonia from the human skin surface. Then, this study aimed to est. the whole-body dermal emission rate of ammonia by simultaneous and multi-point measurement of emission fluxes of ammonia employing a passive flux sampler - ion chromatog. system. Firstly, the emission fluxes of ammonia were non-invasively measured for ten volunteers at 13 sampling positions set in 13 anatomical regions classified by Kurazumi et al. The measured emission fluxes were then converted to partial emission rates using the surface body areas estd. by wts. and heights of volunteers and partial rates of 13 body regions. Subsequent summation of the partial emission rates provided the whole body dermal emission rate of ammonia. The results ranged from 2.9 to 12 mg h-1 with an av. of 5.9 ± 3.2 mg h-1 per person for the ten healthy young volunteers. The values were much greater than those from human breath, and thus the dermal emission of ammonia was found more significant odor source than the breath exhalation in indoor environment.
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  13. 13
    Weschler, C. J.; Carslaw, N. Indoor Chemistry. Environ. Sci. Technol. 2018, 52, 2419– 2428,  DOI: 10.1021/acs.est.7b06387
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    13
    Indoor Chemistry
    Weschler, Charles J.; Carslaw, Nicola
    Environmental Science & Technology (2018), 52 (5), 2419-2428CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    A review. This review aims to encapsulate the importance, ubiquity, and complexity of indoor chem. We discuss the many sources of indoor air pollutants and summarize their chem. reactions in the air and on surfaces. We also summarize some of the known impacts of human occupants, who act as sources and sinks of indoor chems., and whose activities (e.g., cooking, cleaning, smoking) can lead to extremely high pollutant concns. As we begin to use increasingly sensitive and selective instrumentation indoors, we are learning more about chem. in this relatively understudied environment.
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  14. 14
    Grøntoft, T.; Raychaudhuri, M. R. Compilation of Tables of Surface Deposition Velocities for O3, NO2 and SO2 to a Range of Indoor Surfaces. Atmos. Environ. 2004, 38, 533– 544,  DOI: 10.1016/j.atmosenv.2003.10.010
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    14
    Compilation of tables of surface deposition velocities for O3, NO2 and SO2 to a range of indoor surfaces
    Grontoft, Terje; Raychaudhuri, Michele R.
    Atmospheric Environment (2004), 38 (4), 533-544CODEN: AENVEQ; ISSN:1352-2310. (Elsevier Science B.V.)
    Surface deposition velocities of O3, NO2, and SO2 were measured in chamber expts. at relative air humidity from 0 to 90%, and obtained from literature screening, for a range of material surfaces typically found indoors. Data were compiled in tables comprising 24 material classes and 5 relative humidity values for each gas. Interpolation among data points and extrapolation based on measurements on similar materials were used to fill in the tables where measurement values were lacking. Tabulated values should be useful in estg. indoor concns. of these gases when outdoor concns. are known and there are no indoor sources.
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  15. 15
    Morrison, G. C.; Nazaroff, W. W. The Rate of Ozone Uptake on Carpets: Experimental Studies. Environ. Sci. Technol. 2000, 34, 4963– 4968,  DOI: 10.1021/es001361h
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    15
    The Rate of Ozone Uptake on Carpets: Experimental Studies
    Morrison, Glenn C.; Nazaroff, William W.
    Environmental Science and Technology (2000), 34 (23), 4963-4968CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Ozone can react with surfaces, reducing indoor concns. Carpets may be important ozone sinks because of their high surface area. We conducted lab. expts. to measure ozone uptake on four samples of whole carpet and on the corresponding carpet fibers and carpet backing. Results were parametrized in terms of reaction probability, defined as the rate of ozone loss on a surface normalized by the rate of ozone-surface collisions. For whole carpet and carpet-backing samples, we found the apparent reaction probability to be of magnitude 10-5 to 10-4. These results are referenced to the floor area that would be covered by the carpet, rather than to the total surface area of the carpet and its fibers. Reaction probabilities of the order of 10-7 to 10-6 were measured on carpet fibers, referenced to total estd. fiber area. The results indicate that carpet is of comparable significance to painted walls in scavenging ozone from indoor air. All samples tested exhibited aging, such that the rate of ozone uptake diminished with increasing cumulative exposure. Although reactions on carpeting can reduce human exposure to ozone, we caution that the reaction products may include volatile carbonyls that have low odor or irritation thresholds.
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  16. 16
    Gall, E.; Darling, E.; Siegel, J. A.; Morrison, G. C.; Corsi, R. L. Evaluation of Three Common Green Building Materials for Ozone Removal, and Primary and Secondary Emissions of Aldehydes. Atmos. Environ. 2013, 77, 910– 918,  DOI: 10.1016/j.atmosenv.2013.06.014
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    16
    Evaluation of three common green building materials for ozone removal, and primary and secondary emissions of aldehydes
    Gall, Elliott; Darling, Erin; Siegel, Jeffrey A.; Morrison, Glenn C.; Corsi, Richard L.
    Atmospheric Environment (2013), 77 (), 910-918CODEN: AENVEQ; ISSN:1352-2310. (Elsevier Ltd.)
    Ozone reactions that occur on material surfaces can lead to elevated concns. of oxidized products in the occupied space of buildings. However, there is little information on the impact of materials at full scale, esp. for green building materials. Expts. were completed in a 68 m3 climate-controlled test chamber with three certified green building materials that can cover large areas in buildings: (1) recycled carpet, (2) perlite-based ceiling tile and (3) low-VOC paint and primer on recycled drywall. Ozone deposition velocity and primary and secondary emission rates of C1 to C10 satd. carbonyls were detd. for two chamber mixing conditions and three values of relative humidity. A direct comparison was made between ozone deposition velocities and carbonyl yields obsd. for the same materials analyzed in small (10 L) chambers. Total primary carbonyl emission rates from carpet, ceiling tile and painted drywall ranged from 27 to 120 μg m-2 h-1, 13 to 40 μg m-2 h-1, 3.9 to 42 μg m-2 h-1, resp. Ozone deposition velocity to these three materials averaged 6.1 m h-1, 2.3 m h-1 and 0.32 m h-1, resp. Total secondary carbonyl emissions from these materials ranged from 70 to 276 μg m-2 h-1, 0 to 12 μg m-2 h-1, and 0 to 30 μg m-2 h-1, resp. Carbonyl emissions were detd. with a transient approxn., and were found to be in general agreement with those found in the literature. These results suggest that care should be taken when selecting green building materials due to potentially large differences in primary and secondary emissions.
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  17. 17
    Bako-Biro, Z.; Weschler, C. J.; Wargocki, P.; Fanger, P. O. Effects of Indoor Pollution Sources and Ventilation Rate on Ozone Surface Removal Rate and the Occurrence of Oxygenated VOCs in an Office Space. In 10th International Conference on Indoor Air Quality and Climate , 2005; pp 2320– 2324.
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  18. 18
    Tamás, G.; Weschler, C. J.; Bakó-Biró, Z.; Wyon, D. P.; Strøm-Tejsen, P. Factors Affecting Ozone Removal Rates in a Simulated Aircraft Cabin Environment. Atmos. Environ. 2006, 40, 6122– 6133,  DOI: 10.1016/j.atmosenv.2006.05.034
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    18
    Factors affecting ozone removal rates in a simulated aircraft cabin environment
    Tamas, Gyoengyi; Weschler, Charles J.; Bako-Biro, Zsolt; Wyon, David P.; Strom-Tejsen, Peter
    Atmospheric Environment (2006), 40 (32), 6122-6133CODEN: AENVEQ; ISSN:1352-2310. (Elsevier Ltd.)
    O3 concns. were measured concurrently inside a simulated aircraft cabin and in the airstream providing ventilation air to the cabin. O3 decay rates were also measured after cessation of O3 injection into the supply airstream. By systematically varying the presence or absence of people, soiled T-shirts, aircraft seats, and a used HEPA (high efficiency particulate air) filter, in the course of 24 expts., the authors isolated the contributions of these and other factors to O3 removal from cabin air. For this simulated aircraft, people were responsible for ∼60% of O3 removal occurring in the cabin and recirculation system; respiration was only responsible for ∼4% of this removal. Aircraft seats removed ∼25% of O3; the loaded HEPA filter, 7%; and other surfaces, 10%. A T-shirt which had been slept in overnight removed ∼70% as much O3 as a person, indicating the importance of skin oils in O3 removal. The presence of the used HEPA filter in the recirculated airstream reduced perceived air quality. Over a 5-h period, the overall O3 removal rate by cabin surfaces decreased at ∼3%/h. With people present, the measured ratio of O3 concn. in the cabin vs. that outside the cabin was 0.15-0.21, smaller than that reported in the literature. Results reinforced the conclusion that the optimal way to reduce human exposure to O3 and O3 oxidn. products is to efficiently remove O3 from the air supply system of an aircraft.
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    Rim, D.; Gall, E. T.; Ananth, S.; Won, Y. Ozone Reaction with Human Surfaces: Influences of Surface Reaction Probability and Indoor Air Flow Condition. Build. Environ. 2018, 130, 40– 48,  DOI: 10.1016/j.buildenv.2017.12.012
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  20. 20
    Pandrangi, L. S.; Morrison, G. C. Ozone Interactions with Human Hair: Ozone Uptake Rates and Product Formation. Atmos. Environ. 2008, 42, 5079– 5089,  DOI: 10.1016/j.atmosenv.2008.02.009
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    20
    Ozone interactions with human hair: Ozone uptake rates and product formation
    Pandrangi, Lakshmi S.; Morrison, Glenn C.
    Atmospheric Environment (2008), 42 (20), 5079-5089CODEN: AENVEQ; ISSN:1352-2310. (Elsevier Ltd.)
    The cumulative ozone uptake, the ozone reaction probability, and product yields of volatile aldehydes and ketones were quantified for human scalp hair. Hair was chosen because ozone reacts readily with skin oils and the personal care products that coat hair. Due to their proximity to the breathing zone, these reactions can influence personal exposure to ozone and its volatile reaction products. Hair samples were collected before and after washing and/or application of personal hair care products. Samples were exposed to ozone for 24 h in a tubular Teflon reactor; ozone consumption rates and product emission rates were quantified. The mean values of integrated ozone uptake, initial and final follicle reaction probability values for 8 washed and unwashed samples were, resp., 5.1±4.4 μmol O3 g-1, (13±8) × 10-5, and (1.0±1.3) × 10-5. Unwashed hair taken close to the scalp exhibited the highest integrated ozone uptake and reaction probability, indicating that scalp oils are responsible for much of the ozone reactivity. Otherwise there was no significant difference between washed and unwashed hair. Compds. (geranyl acetone, 6-methyl-5-hepten-2-one, and decanal) assocd. with ozone reacting with sebum were obsd. as secondary products more frequently from unwashed hair than for washed hair and the summed yield of aldehydes ranged 0.00-0.86. Based on reaction probabilities, cumulative ozone uptake, and typical sebum generation rates, ozone flux to skin and hair is anticipated to be nearly transport limited, reducing personal exposure to ozone and increasing exposure to reaction products.
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  21. 21
    Coleman, B. K.; Destaillats, H.; Hodgson, A. T.; Nazaroff, W. W. Ozone Consumption and Volatile Byproduct Formation from Surface Reactions with Aircraft Cabin Materials and Clothing Fabrics. Atmos. Environ. 2008, 42, 642– 654,  DOI: 10.1016/j.atmosenv.2007.10.001
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    21
    Ozone consumption and volatile byproduct formation from surface reactions with aircraft cabin materials and clothing fabrics
    Coleman, Beverly K.; Destaillats, Hugo; Hodgson, Alfred T.; Nazaroff, William W.
    Atmospheric Environment (2008), 42 (4), 642-654CODEN: AENVEQ; ISSN:1352-2310. (Elsevier Ltd.)
    We measured ozone consumption and byproduct formation on materials commonly found in aircraft cabins at flight-relevant conditions. Two series of small-chamber expts. were conducted, with most runs at low relative humidity (10%) and high air-exchange rate (∼20 h-1). New and used cabin materials (seat fabric, carpet, and plastic) and laundered and worn clothing fabrics (cotton, polyester, and wool) were studied. We measured ozone deposition to many material samples, and we measured ozone uptake and primary and secondary emissions of volatile org. compds. (VOCs) from a subset of samples. Deposition velocities ranged from 0.06 to 0.54 cm s-1. Emissions of VOCs were higher with ozone than without ozone in every case. The most commonly detected secondary emissions were C1 through C10 satd. aldehydes and the squalene oxidn. products 6-methyl-5-hepten-2-one and acetone. For the compds. measured, summed VOC emission rates in the presence of 55-128 ppb (residual level) ozone ranged from 1.0 to 8.9 μmol h-1 m-2. Total byproduct yield ranged from 0.07 to 0.24 mol of product volatilized per mol of ozone consumed. Results were used to est. the relative contribution of different materials to ozone deposition and byproduct emissions in a typical aircraft cabin. The dominant contributor to both was clothing fabrics, followed by seat fabric. Results indicate that ozone reactions with surfaces substantially reduce the ozone concn. in the cabin but also generate volatile byproducts of potential concern for the health and comfort of passengers and crew.
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    Nagda, N.; Nazaroff, W.; Gadgil, A.; Weschler, C. STP13101S Modeling of Indoor Air Quality and Exposure; ASTM International: West Conshohocken, PA, 1993.
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    Yang, S.; Gao, K.; Yang, X. Volatile Organic Compounds (VOCs) Formation Due to Interactions between Ozone and Skin-Oiled Clothing: Measurements by Extraction-Analysis-Reaction Method. Build. Environ. 2016, 103, 146– 154,  DOI: 10.1016/j.buildenv.2016.04.012
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    Arata, C.; Heine, N.; Wang, N.; Misztal, P. K.; Wargocki, P.; Bekö, G.; Williams, J.; Nazaroff, W. W.; Wilson, K. R.; Goldstein, A. H. Heterogeneous Ozonolysis of Squalene: Gas-Phase Products Depend on Water Vapor Concentration. Environ. Sci. Technol. 2019, 53, 14441– 14448,  DOI: 10.1021/acs.est.9b05957
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    24
    Heterogeneous Ozonolysis of Squalene: Gas-Phase Products Depend on Water Vapor Concentration
    Arata, Caleb; Heine, Nadja; Wang, Nijing; Misztal, Pawel K.; Wargocki, Pawel; Beko, Gabriel; Williams, Jonathan; Nazaroff, William W.; Wilson, Kevin R.; Goldstein, Allen H.
    Environmental Science & Technology (2019), 53 (24), 14441-14448CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Previous work examg. the condensed-phase products of squalene particle ozonolysis detd. an increased water vapor concn. led to lower secondary ozonide concns., increased carbonyl concns., and smaller particle diam., suggesting water changed the fate of Criegee intermediates. To det. if this vol. loss corresponded to an increase in gas-phase products, gas-phase volatile org. compd. (VOC) concns. were measured by proton-transfer-reaction, time-of-flight mass spectrometry. Work was performed in a flow tube reactor at atmospherically relevant O3 exposure levels (5-30 ppb/h) with pure squalene particles. Increased water vapor concns. led to strongly enhanced gas-phase oxidn. products at all tested O3 exposures. Increased water vapor from near 0 to 70% relative humidity (RH) at high O3 exposure increased the gas-phase VOC total mass concn. by a factor of three. The obsd. fraction of C in the gas-phase correlated with the fraction of particle vol. lost. Expts. involving O3 oxidn. of shirts soiled with skin oil confirmed the RH dependence of gas-phase reaction product generation occurred similarly on surfaces contg. skin oil under realistic conditions. Similar behavior was expected for O3 reactions with other surface-bound orgs. contg. unsatd. C bonds.
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    Abbatt, J. P. D.; Wang, C. The Atmospheric Chemistry of Indoor Environments. Environ. Sci.: Processes Impacts 2020, 22, 25– 48,  DOI: 10.1039/C9EM00386J
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    25
    The atmospheric chemistry of indoor environments
    Abbatt, Jonathan P. D.; Wang, Chen
    Environmental Science: Processes & Impacts (2020), 22 (1), 25-48CODEN: ESPICZ; ISSN:2050-7895. (Royal Society of Chemistry)
    Through air inhalation, dust ingestion and dermal exposure, the indoor environment plays an important role in controlling human chem. exposure. Indoor emissions and chem. can also have direct impacts on the quality of outdoor air. And so, it is important to have a strong fundamental knowledge of the chem. processes that occur in indoor environments. This review article summarizes our understanding of the indoor chem. field. Using a mol. perspective, it addresses primarily the new advances that have occurred in the past decade or so and upon developments in our understanding of multiphase partitioning and reactions. A primary goal of the article is to contrast indoor chem. to that which occurs outdoors, which we know to be a strongly gas-phase, oxidant-driven system in which substantial oxidative aging of gases and aerosol particles occurs. By contrast, indoor environments are dark, gas-phase oxidant concns. are relatively low, and due to air exchange, only short times are available for reactive processing of gaseous and particle constituents. However, important gas-surface partitioning and reactive multiphase chem. occur in the large surface reservoirs that prevail in all indoor environments. These interactions not only play a crucial role in controlling the compn. of indoor surfaces but also the surrounding gases and aerosol particles, thus affecting human chem. exposure. There are rich research opportunities available if the advanced measurement and modeling tools of the outdoor atm. chem. community continue to be brought indoors.
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  26. 26
    Williams, J.; Brune, W. A Roadmap for OH Reactivity Research. Atmos. Environ. 2015, 106, 371– 372,  DOI: 10.1016/j.atmosenv.2015.02.017
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    26
    A roadmap for OH reactivity research
    Williams, Jonathan; Brune, William
    Atmospheric Environment (2015), 106 (), 371-372CODEN: AENVEQ; ISSN:1352-2310. (Elsevier Ltd.)
    A review describing the roadmap for OH reactivity research. Ever since the discovery of the OH radical's importance to tropospheric chem., the characterization of its overall loss rate (OH reactivity) has remained a key question. Direct OH reactivity measurements in the lab. based on LIDAR and in the ambient air based on in situ laser induced fluorescence detection of OH was demonstrated. Detn. of OH reactivity is bound to deliver new challenges and yield insights on questions such as the oxidizing capacity and the tropospheric ozone budget.
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  27. 27
    Nölscher, A. C.; Yañez-Serrano, A. M.; Wolff, S.; de Araujo, A. C.; Lavrič, J. V.; Kesselmeier, J.; Williams, J. Unexpected Seasonality in Quantity and Composition of Amazon Rainforest Air Reactivity. Nat. Commun. 2016, 7, 10383  DOI: 10.1038/ncomms10383
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    Unexpected seasonality in quantity and composition of Amazon rainforest air reactivity
    Nolscher A C; Yanez-Serrano A M; Wolff S; Kesselmeier J; Williams J; Yanez-Serrano A M; Wolff S; de Araujo A Carioca; Lavric J V
    Nature communications (2016), 7 (), 10383 ISSN:.
    The hydroxyl radical (OH) removes most atmospheric pollutants from air. The loss frequency of OH radicals due to the combined effect of all gas-phase OH reactive species is a measureable quantity termed total OH reactivity. Here we present total OH reactivity observations in pristine Amazon rainforest air, as a function of season, time-of-day and height (0-80 m). Total OH reactivity is low during wet (10 s(-1)) and high during dry season (62 s(-1)). Comparison to individually measured trace gases reveals strong variation in unaccounted for OH reactivity, from 5 to 15% missing in wet-season afternoons to mostly unknown (average 79%) during dry season. During dry-season afternoons isoprene, considered the dominant reagent with OH in rainforests, only accounts for ∼20% of the total OH reactivity. Vertical profiles of OH reactivity are shaped by biogenic emissions, photochemistry and turbulent mixing. The rainforest floor was identified as a significant but poorly characterized source of OH reactivity.
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  28. 28
    Fuchs, H.; Tan, Z.; Lu, K.; Bohn, B.; Broch, S.; Brown, S. S.; Dong, H.; Gomm, S.; Häseler, R.; He, L.; Hofzumahaus, A.; Holland, F.; Li, X.; Liu, Y.; Lu, S.; Min, K.-E.; Rohrer, F.; Shao, M.; Wang, B.; Wang, M.; Wu, Y.; Zeng, L.; Zhang, Y.; Wahner, A.; Zhang, Y. OH Reactivity at a Rural Site (Wangdu) in the North China Plain: Contributions from OH Reactants and Experimental OH Budget. Atmos. Chem. Phys. 2017, 17, 645– 661,  DOI: 10.5194/acp-17-645-2017
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    OH reactivity at a rural site (Wangdu) in the North China Plain: contributions from OH reactants and experimental OH budget
    Fuchs, Hendrik; Tan, Zhaofeng; Lu, Keding; Bohn, Birger; Broch, Sebastian; Brown, Steven S.; Dong, Huabin; Gomm, Sebastian; Haeseler, Rolf; He, Lingyan; Hofzumahaus, Andreas; Holland, Frank; Li, Xin; Liu, Ying; Lu, Sihua; Min, Kyung-Eun; Rohrer, Franz; Shao, Min; Wang, Baolin; Wang, Ming; Wu, Yusheng; Zeng, Limin; Zhang, Yinson; Wahner, Andreas; Zhang, Yuanhang
    Atmospheric Chemistry and Physics (2017), 17 (1), 645-661CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    In 2014, a large, comprehensive field campaign was conducted in the densely populated North China Plain. The measurement site was located in a botanic garden close to the small town Wangdu, without major industry but influenced by regional transportation of air pollution. The loss rate coeff. of atm. hydroxyl radicals (OH) was quantified by direct measurements of the OH reactivity. Values ranged between 10 and 20 s-1 for most of the daytime. Highest values were reached in the late night with max. values of around 40 s-1. OH reactants mainly originated from anthropogenic activities as indicated (1) by a good correlation between measured OH reactivity and carbon monoxide (linear correlation coeff. R2 = 0.33) and (2) by a high contribution of nitrogen oxide species to the OH reactivity (up to 30% in the morning). Total OH reactivity was measured by a laser flash photolysis-laser-induced fluorescence instrument (LP-LIF). Measured values can be explained well by measured trace gas concns. including org. compds., oxygenated org. compds., CO and nitrogen oxides. Significant, unexplained OH reactivity was only obsd. during nights, when biomass burning of agricultural waste occurred on surrounding fields. OH reactivity measurements also allow investigating the chem. OH budget. During this campaign, the OH destruction rate calcd. from measured OH reactivity and measured OH concn. was balanced by the sum of OH prodn. from ozone and nitrous acid photolysis and OH regeneration from hydroperoxy radicals within the uncertainty of measurements. However, a tendency for higher OH destruction compared to OH prodn. at lower concns. of nitric oxide is also obsd., consistent with previous findings in field campaigns in China.
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  29. 29
    Zannoni, N.; Gros, V.; Sarda Esteve, R.; Kalogridis, C.; Michoud, V.; Dusanter, S.; Sauvage, S.; Locoge, N.; Colomb, A.; Bonsang, B. Summertime OH Reactivity from a Receptor Coastal Site in the Mediterranean Basin. Atmos. Chem. Phys. 2017, 17, 12645– 12658,  DOI: 10.5194/acp-17-12645-2017
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    29
    Summertime OH reactivity from a receptor coastal site in the Mediterranean Basin
    Zannoni, Nora; Gros, Valerie; Esteve, Roland Sarda; Kalogridis, Cerise; Michoud, Vincent; Dusanter, Sebastien; Sauvage, Stephane; Locoge, Nadine; Colomb, Aurelie; Bonsang, Bernard
    Atmospheric Chemistry and Physics (2017), 17 (20), 12645-12658CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    Total hydroxyl radical (OH) reactivity, the total loss frequency of the hydroxyl radical in ambient air, provides the total loading of OH reactants in air. We measured the total OH reactivity for the first time during summertime at a coastal receptor site located in the western Mediterranean Basin. Measurements were performed at a temporary field site located in the northern cape of Corsica (France), during summer 2013 for the project CARBOSOR (CARBOn within continental pollution plumes: SOurces and Reactivity)-ChArMEx (Chem. and Aerosols Mediterranean Expt.). Here, we compare the measured total OH reactivity with the OH reactivity calcd. from the measured reactive gases. The difference between these two parameters is termed missing OH reactivity, i.e., the fraction of OH reactivity not explained by the measured compds. The total OH reactivity at the site varied between the instrumental LoD (limit of detection = 3 s-1) to a max. of 17 ± 6 s-1 (35 % uncertainty) and was 5 ± 4 s-1 (1σ SD - std. deviation) on av. It varied with air temp. exhibiting a diurnal profile comparable to the reactivity calcd. from the concn. of the biogenic volatile org. compds. measured at the site. For part of the campaign, 56 % of OH reactivity was unexplained by the measured OH reactants (missing reactivity). We suggest that oxidn. products of biogenic gas precursors were among the contributors to missing OH reactivity.
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    Kumar, V.; Chandra, B. P.; Sinha, V. Large Unexplained Suite of Chemically Reactive Compounds Present in Ambient Air Due to Biomass Fires. Sci. Rep. 2018, 8, 626  DOI: 10.1038/s41598-017-19139-3
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    30
    Large unexplained suite of chemically reactive compounds present in ambient air due to biomass fires
    Kumar V; Chandra B P; Sinha V
    Scientific reports (2018), 8 (1), 626 ISSN:.
    Biomass fires impact global atmospheric chemistry. The reactive compounds emitted and formed due to biomass fires drive ozone and organic aerosol formation, affecting both air quality and climate. Direct hydroxyl (OH) Reactivity measurements quantify total gaseous reactive pollutant loadings and comparison with measured compounds yields the fraction of unmeasured compounds. Here, we quantified the magnitude and composition of total OH reactivity in the north-west Indo-Gangetic Plain. More than 120% increase occurred in total OH reactivity (28 s(-1) to 64 s(-1)) and from no missing OH reactivity in the normal summertime air, the missing OH reactivity fraction increased to ~40 % in the post-harvest summertime period influenced by large scale biomass fires highlighting presence of unmeasured compounds. Increased missing OH reactivity between the two summertime periods was associated with increased concentrations of compounds with strong photochemical source such as acetaldehyde, acetone, hydroxyacetone, nitromethane, amides, isocyanic acid and primary emissions of acetonitrile and aromatic compounds. Currently even the most detailed state-of-the art atmospheric chemistry models exclude formamide, acetamide, nitromethane and isocyanic acid and their highly reactive precursor alkylamines (e.g. methylamine, ethylamine, dimethylamine, trimethylamine). For improved understanding of atmospheric chemistry-air quality-climate feedbacks in biomass-fire impacted atmospheric environments, future studies should include these compounds.
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    Whalley, L.; Stone, D.; Heard, D. New Insights into the Tropospheric Oxidation of Isoprene: Combining Field Measurements, Laboratory Studies, Chemical Modelling and Quantum Theory. Top. Curr. Chem. 2014, 339, 55– 95,  DOI: 10.1007/128_2012_359
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    31
    New Insights into the Tropospheric Oxidation of Isoprene: Combining Field Measurements, Laboratory Studies, Chemical Modelling and Quantum Theory
    Whalley, Lisa; Stone, Daniel; Heard, Dwayne
    Topics in Current Chemistry (2014), 339 (Atmospheric and Aerosol Chemistry), 55-95CODEN: TPCCAQ; ISSN:1436-5049. (Springer GmbH)
    In this chapter we discuss some of the recent work directed at further understanding the chem. of our atm. in regions of low NO x , such as forests, where there are considerable emissions of biogenic volatile org. compds., for example reactive hydrocarbons such as isoprene. Recent field measurements have revealed some surprising results, for example that OH concns. are measured to be considerably higher than can be understood using current chem. mechanisms. It has also not proven possible to reconcile field measurements of other species, such as oxygenated VOCs, or emission fluxes of isoprene, using current mechanisms. Several complementary approaches have been brought to bear on formulating a soln. to this problem, namely field studies using state-of-the-art instrumentation, chamber studies to isolate sub-sections of the chem., lab. studies to measure rate coeffs., product branching ratios and photochem. yields, the development of ever more detailed chem. mechanisms, and high quality ab initio quantum theory to calc. the energy landscape for relevant reactions and to enable the rates of formation of products and intermediates for previously unknown and unstudied reactions to be predicted. The last few years have seen significant activity in this area, with several contrasting postulates put forward to explain the exptl. findings, and here we attempt to synthesize the evidence and ideas.
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  32. 32
    Pfannerstill, E. Y.; Wang, N.; Edtbauer, A.; Bourtsoukidis, E.; Crowley, J. N.; Dienhart, D.; Eger, P. G.; Ernle, L.; Fischer, H.; Hottmann, B.; Paris, J.-D.; Stönner, C.; Tadic, I.; Walter, D.; Lelieveld, J.; Williams, J. Shipborne Measurements of Total OH Reactivity around the Arabian Peninsula and Its Role in Ozone Chemistry. Atmos. Chem. Phys. 2019, 19, 11501– 11523,  DOI: 10.5194/acp-19-11501-2019
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    Shipborne measurements of total OH reactivity around the Arabian Peninsula and its role in ozone chemistry
    Pfannerstill, Eva Y.; Wang, Nijing; Edtbauer, Achim; Bourtsoukidis, Efstratios; Crowley, John N.; Dienhart, Dirk; Eger, Philipp G.; Ernle, Lisa; Fischer, Horst; Hottmann, Bettina; Paris, Jean-Daniel; Stoenner, Christof; Tadic, Ivan; Walter, David; Lelieveld, Jos; Williams, Jonathan
    Atmospheric Chemistry and Physics (2019), 19 (17), 11501-11523CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    The Arabian Peninsula is characterized by high and increasing levels of photochem. air pollution. Strong solar irradn., high temps. and large anthropogenic emissions of reactive trace gases result in intense photochem. activity, esp. during the summer months. However, air chem. measurements in the region are scarce. In order to assess regional pollution sources and oxidn. rates, the first ship-based direct measurements of total OH reactivity were performed in summer 2017 from a vessel traveling around the peninsula during the AQABA (Air Quality and Climate Change in the Arabian Basin) campaign. Total OH reactivity is the total loss frequency of OH radicals due to all reactive compds. present in air and defines the local lifetime of OH, the most important oxidant in the troposphere. During the AQABA campaign, the total OH reactivity ranged from below the detection limit (5.4 s-1) over the northwestern Indian Ocean (Arabian Sea) to a max. of 32.8 ± 9.6 s-1 over the Arabian Gulf (also known as Persian Gulf) when air originated from large petroleum extn./processing facilities in Iraq and Kuwait. In the polluted marine regions, OH reactivity was broadly comparable to highly populated urban centers in intensity and compn. The permanent influence of heavy maritime traffic over the seaways of the Red Sea, Gulf of Aden and Gulf of Oman resulted in median OH sinks of 7.9-8.5 s-1.
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  33. 33
    Bekö, G.; Wargocki, P.; Wang, N.; Li, M.; Weschler, C. J.; Morrison, G.; Langer, S.; Ernle, L.; Licina, D.; Yang, S.; Zannoni, N.; Williams, J. The Indoor Chemical Human Emissions and Reactivity (ICHEAR) Project: Overview of Experimental Methodology and Preliminary Results. Indoor Air 2020, 30, 1213– 1228,  DOI: 10.1111/ina.12687
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    33
    The Indoor Chemical Human Emissions and Reactivity (ICHEAR) project: Overview of experimental methodology and preliminary results
    Beko Gabriel; Wargocki Pawel; Weschler Charles J; Wang Nijing; Li Mengze; Ernle Lisa; Zannoni Nora; Williams Jonathan; Weschler Charles J; Morrison Glenn; Langer Sarka; Langer Sarka; Licina Dusan; Yang Shen
    Indoor air (2020), 30 (6), 1213-1228 ISSN:.
    With the gradual reduction of emissions from building products, emissions from human occupants become more dominant indoors. The impact of human emissions on indoor air quality is inadequately understood. The aim of the Indoor Chemical Human Emissions and Reactivity (ICHEAR) project was to examine the impact on indoor air chemistry of whole-body, exhaled, and dermally emitted human bioeffluents under different conditions comprising human factors (t-shirts/shorts vs long-sleeve shirts/pants; age: teenagers, young adults, and seniors) and a variety of environmental factors (moderate vs high air temperature; low vs high relative humidity; presence vs absence of ozone). A series of human subject experiments were performed in a well-controlled stainless steel climate chamber. State-of-the-art measurement technologies were used to quantify the volatile organic compounds emitted by humans and their total OH reactivity; ammonia, nanoparticle, fluorescent biological aerosol particle (FBAP), and microbial emissions; and skin surface chemistry. This paper presents the design of the project, its methodologies, and preliminary results, comparing identical measurements performed with five groups, each composed of 4 volunteers (2 males and 2 females). The volunteers wore identical laundered new clothes and were asked to use the same set of fragrance-free personal care products. They occupied the ozone-free (<2 ppb) chamber for 3 hours (morning) and then left for a 10-min lunch break. Ozone (target concentration in occupied chamber ~35 ppb) was introduced 10 minutes after the volunteers returned to the chamber, and the measurements continued for another 2.5 hours. Under a given ozone condition, relatively small differences were observed in the steady-state concentrations of geranyl acetone, 6MHO, and 4OPA between the five groups. Larger variability was observed for acetone and isoprene. The absence or presence of ozone significantly influenced the steady-state concentrations of acetone, geranyl acetone, 6MHO, and 4OPA. Results of replicate experiments demonstrate the robustness of the experiments. Higher repeatability was achieved for dermally emitted compounds and their reaction products than for constituents of exhaled breath.
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  34. 34
    Wang, N.; Zannoni, N.; Ernle, L.; Bekö, G.; Wargocki, P.; Li, M.; Weschler, C. J.; Williams, J. Total OH Reactivity of Emissions from Humans: In Situ Measurement and Budget Analysis. Environ. Sci. Technol. 2021, 55, 149– 159,  DOI: 10.1021/acs.est.0c04206
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    34
    Total OH Reactivity of Emissions from Humans: In Situ Measurement and Budget Analysis
    Wang, Nijing; Zannoni, Nora; Ernle, Lisa; Bekoe, Gabriel; Wargocki, Pawel; Li, Mengze; Weschler, Charles J.; Williams, Jonathan
    Environmental Science & Technology (2021), 55 (1), 149-159CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Humans are a potent, mobile source of various volatile org. compds. (VOCs) in indoor environments. Such direct anthropogenic emissions are gaining importance, as those from furnishings and building materials have become better regulated and energy efficient homes may reduce ventilation. While previous studies have characterized human emissions in indoor environments, the question remains whether VOCs remain unidentified by current measuring techniques. In this study conducted in a climate chamber occupied by four people, the total OH reactivity of air was quantified, together with multiple VOCs measured by proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) and fast gas chromatog.-mass spectrometry (fast-GC-MS). Whole-body, breath, and dermal emissions were assessed. The comparison of directly measured OH reactivity and that of the summed reactivity of individually measured species revealed no significant shortfall. Ozone exposure (37 ppb) was found to have little influence on breath OH reactivity but enhanced dermal OH reactivity significantly. Without ozone, the whole-body OH reactivity was dominated by breath emissions, mostly isoprene (76%). With ozone present, OH reactivity nearly doubled, with the increase being mainly caused by dermal emissions of mostly carbonyl compds. (57%). No significant difference in total OH reactivity was obsd. for different age groups (teenagers/young adults/seniors) without ozone. With ozone present, the total OH reactivity decreased slightly with increasing age.
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    Salvador, C. M.; Bekö, G.; Weschler, C. J.; Morrison, G.; Le Breton, M.; Hallquist, M.; Ekberg, L.; Langer, S. Indoor Ozone/Human Chemistry and Ventilation Strategies. Indoor Air 2019, 29, 913– 925,  DOI: 10.1111/ina.12594
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    35
    Indoor ozone/human chemistry and ventilation strategies
    Salvador, Christian Mark; Bekoe, Gabriel; Weschler, Charles J.; Morrison, Glenn; Le Breton, Michael; Hallquist, Mattias; Ekberg, Lars; Langer, Sarka
    Indoor Air (2019), 29 (6), 913-925CODEN: INAIE5; ISSN:1600-0668. (Wiley-Blackwell)
    This study aimed to better understand and quantify the influence of ventilation strategies on occupant-related indoor air chem. The oxidn. of human skin oil constituents was studied in a continuously ventilated climate chamber at two air exchange rates (1 h-1 and 3 h-1) and two initial ozone mixing ratios (30 and 60 ppb). Addnl. measurements were performed to investigate the effect of intermittent ventilation ("off" followed by "on"). Soiled t-shirts were used to simulate the presence of occupants. A time-of-flight-chem. ionization mass spectrometer (ToF-CIMS) in pos. mode using protonated water clusters was used to measure the oxygenated reaction products geranyl acetone, 6-methyl-5-hepten-2-one (6-MHO) and 4-oxopentanal (4-OPA). The measurement data were used in a series of mass balance models accounting for formation and removal processes. Reactions of ozone with squalene occurring on the surface of the t-shirts are mass transport limited; ventilation rate has only a small effect on this surface chem. Ozone-squalene reactions on the t-shirts produced gas-phase geranyl acetone, which was subsequently removed almost equally by ventilation and further reaction with ozone. About 70% of gas-phase 6-MHO was produced in surface reactions on the t-shirts, the remainder in secondary gas-phase reactions of ozone with geranyl acetone. 6-MHO was primarily removed by ventilation, while further reaction with ozone was responsible for about a third of its removal. 4-OPA was formed primarily on the surfaces of the shirts (∼60%); gas-phase reactions of ozone with geranyl acetone and 6-MHO accounted for ∼30% and ∼10%, resp. 4-OPA was removed entirely by ventilation. The results from the intermittent ventilation scenarios showed delayed formation of the reaction products and lower product concns. compared to continuous ventilation.
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  36. 36
    Fuchs, H.; Novelli, A.; Rolletter, M.; Hofzumahaus, A.; Pfannerstill, E. Y.; Kessel, S.; Edtbauer, A.; Williams, J.; Michoud, V.; Dusanter, S.; Locoge, N.; Zannoni, N.; Gros, V.; Truong, F.; Sarda-Esteve, R.; Cryer, D. R.; Brumby, C. A.; Whalley, L. K.; Stone, D.; Seakins, P. W.; Heard, D. E.; Schoemaecker, C.; Blocquet, M.; Coudert, S.; Batut, S.; Fittschen, C.; Thames, A. B.; Brune, W. H.; Ernest, C.; Harder, H.; Muller, J. B. A.; Elste, T.; Kubistin, D.; Andres, S.; Bohn, B.; Hohaus, T.; Holland, F.; Li, X.; Rohrer, F.; Kiendler-Scharr, A.; Tillmann, R.; Wegener, R.; Yu, Z.; Zou, Q.; Wahner, A. Comparison of OH Reactivity Measurements in the Atmospheric Simulation Chamber SAPHIR. Atmos. Meas. Tech. 2017, 10, 4023– 4053,  DOI: 10.5194/amt-10-4023-2017
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    Comparison of OH reactivity measurements in the atmospheric simulation chamber SAPHIR
    Fuchs, Hendrik; Novelli, Anna; Rolletter, Michael; Hofzumahaus, Andreas; Pfannerstill, Eva Y.; Kessel, Stephan; Edtbauer, Achim; William, Jonathan; Michoud, Vincent; Dusanter, Sebastien; Locoge, Nadine; Zannoni, Nora; Gros, Valerie; Truong, Francois; Sarda-Esteve, Roland; Cryer, Danny R.; Brumby, Charlotte A.; Whalley, Lisa K.; Stone, Daniel; Seakins, Paul W.; Heard, Dwayne E.; Schoemaecker, Coralie; Blocquet, Marion; Coudert, Sebastien; Batut, Sebastien; Fittschen, Christa; Thames, Alexander B.; Brune, William H.; Ernest, Cheryl; Harder, Hartwig; Muller, Jennifer B. A.; Elste, Thomas; Kubistin, Dagmar; Andres, Stefanie; Bohn, Birger; Hohaus, Thorsten; Holland, Frank; Li, Xin; Rohrer, Franz; Kiendler-Scharr, Astrid; Tillmann, Ralf; Wegener, Robert; Yu, Zhujun; Zou, Qi; Wahner, Andreas
    Atmospheric Measurement Techniques (2017), 10 (10), 4023-4053CODEN: AMTTC2; ISSN:1867-8548. (Copernicus Publications)
    Hydroxyl (OH) radical reactivity (kOH) has been measured for 18 years with different measurement techniques. In order to compare the performances of instruments deployed in the field, two campaigns were conducted performing expts. in the atm. simulation chamber SAPHIR at Forschungszentrum Juelich in Oct. 2015 and Apr. 2016. Chem. conditions were chosen either to be representative of the atm. or to test potential limitations of instruments. All types of instruments that are currently used for atm. measurements were used in one of the two campaigns. The results of these campaigns demonstrate that OH reactivity can be accurately measured for a wide range of atmospherically relevant chem. conditions (e.g. water vapor, nitrogen oxides, various org. compds.) by all instruments. The precision of the measurements (limit of detection<1 s-1 at a time resoln. of 30 s to a few minutes) is higher for instruments directly detecting hydroxyl radicals, whereas the indirect comparative reactivity method (CRM) has a higher limit of detection of 2 s-1 at a time resoln. of 10 to 15 min. The performances of the instruments were systematically tested by stepwise increasing, for example, the concns. of carbon monoxide (CO), water vapor or nitric oxide (NO). In further expts., mixts. of org. reactants were injected into the chamber to simulate urban and forested environments. Overall, the results show that the instruments are capable of measuring OH reactivity in the presence of CO, alkanes, alkenes and arom. compds. The transmission efficiency in Teflon inlet lines could have introduced systematic errors in measurements for low-volatile org. compds. in some instruments. CRM instruments exhibited a larger scatter in the data compared to the other instruments. The largest differences to ref. measurements or to calcd. reactivity were obsd. by CRM instruments in the presence of terpenes and oxygenated org. compds. (mixing ratio of OH reactants were up to 10 ppbv). In some of these expts., only a small fraction of the reactivity is detected. The accuracy of CRM measurements is most likely limited by the corrections that need to be applied to account for known effects of, for example, deviations from pseudo first-order conditions, nitrogen oxides or water vapor on the measurement. Methods used to derive these corrections vary among the different CRM instruments. Measurements taken with a flowtube instrument combined with the direct detection of OH by chem. ionisation mass spectrometry (CIMS) show limitations in cases of high reactivity and high NO concns. but were accurate for low reactivity (<15 s-1) and low NO (<5 ppbv) conditions.
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  37. 37
    Sinha, V.; Williams, J.; Crowley, J. N.; Lelieveld, J. The Comparative Reactivity Method – a New Tool to Measure Total OH Reactivity in Ambient Air. Atmos. Chem. Phys. 2008, 8, 2213– 2227,  DOI: 10.5194/acp-8-2213-2008
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    The comparative reactivity method - a new tool to measure total OH reactivity in ambient air
    Sinha, V.; Williams, J.; Crowley, J. N.; Lelieveld, J.
    Atmospheric Chemistry and Physics (2008), 8 (8), 2213-2227CODEN: ACPTCE; ISSN:1680-7316. (Copernicus Publications)
    Hydroxyl (OH) radicals play a vital role in maintaining the oxidizing capacity of the atm. To understand variations in OH radicals both source and sink terms must be understood. Currently the overall sink term, or the total atm. reactivity to OH, is poorly constrained. Here, we present a new online method to directly measure the total OH reactivity (i.e. total loss rate of OH radicals) in a sampled air mass. In this method, a reactive mol. (X), not normally present in air, is passed through a glass reactor and its concn. is monitored with a suitable detector. OH radicals are then introduced in the glass reactor at a const. rate to react with X, first in the presence of zero air and then in the presence of ambient air contg. VOCs and other OH reactive species. Comparing the amt. of X exiting the reactor with and without the ambient air allows the air reactivity to be detd. In our existing set up, X is pyrrole and the detector used is a proton transfer reaction mass spectrometer. The present dynamic range for ambient air reactivity is about 6 to 300 s-1, with an overall max. uncertainty of 25% above 8 s-1 and up to 50% between 6-8 s-1. The system has been tested and calibrated with different single and mixed hydrocarbon stds. showing excellent linearity and accountability with the reactivity of the stds. Potential interferences such as high NO in ambient air, varying relative humidity and photolysis of pyrrole within the setup have also been investigated. While interferences due changing humidity and photolysis of pyrrole are easily overcome by ensuring that humidity in the set up does not change drastically and the photolytic loss of pyrrole is measured and taken into account, resp., NO> 10 ppb in ambient air remains a significant interference for the current configuration of the instrument. Field tests in the tropical rainforest of Suriname (∼53 s-1) and the urban atm. of Mainz (∼10 s-1) Germany, show the promise of the new method and indicate that a significant fraction of OH reactive species in the tropical forests is likely missed by current measurements. Suggestions for improvements to the technique and future applications are discussed.
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    Lindinger, W.; Jordan, A. Proton-Transfer-Reaction Mass Spectrometry (PTR–MS): On-Line Monitoring of Volatile Organic Compounds at Pptv Levels. Chem. Soc. Rev. 1998, 27, 347– 375,  DOI: 10.1039/a827347z
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    Proton-transfer-reaction mass spectrometry (PTR-MS): online monitoring of volatile organic compounds at pptv levels
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    Chemical Society Reviews (1998), 27 (5), 347-354CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
    A review with 32 refs. A system for online measurements of trace components with concns. as low as a few pptv was developed from proton transfer reactions. Medical applications by breath anal. allow the monitoring of metabolic processes in the human body, examples of food research include studies of volatile org. compd. (VOC) emissions from fruit, coffee and meat. Studies of VOC emissions from decaying biomatter and online monitoring of the diurnal variations of VOCs in ambient air are typical examples of environmental applications.
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    Atkinson, R.; Aschmann, S. M.; Winer, A. M.; Carter, W. P. L. Rate Constants for the Gas Phase Reactions of OH Radicals and O3 with Pyrrole at 295 ± 1 K and Atmospheric Pressure. Atmos. Environ. (1967) 1984, 18, 2105– 2107,  DOI: 10.1016/0004-6981(84)90196-3
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    Rate constants for the gas phase reactions of hydroxyl radicals and ozone with pyrrole at 295 ± 1 K and atmospheric pressure
    Atkinson, Roger; Aschmann, Sara M.; Winer, Arthur M.; Carter, William P. L.
    Atmospheric Environment (1967-1989) (1984), 18 (10), 2105-7CODEN: ATENBP; ISSN:0004-6981.
    As part of a program to investigate the atm. chem. and lifetimes of heteroatom-contg. orgs., rate consts. were detd. for the reaction of OH radicals and O3 with pyrrole [109-97-7] in 1 atm. of air at 295 ± 1 K. The rate consts. obtained were 1.20 × 10-10 and 1.57 × 10-17 cm3/mol-s for reaction with OH radicals and O3, resp. With these rate consts., it can be calcd. that under atm. conditions, the major loss process of pyrrole will be via reaction with the OH radical, with a lifetime due to reaction with OH radicals of ∼2 h at a OH radical concn. of 1 × 106 mol./cm3.
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    Dillon, T. J.; Tucceri, M. E.; Dulitz, K.; Horowitz, A.; Vereecken, L.; Crowley, J. N. Reaction of Hydroxyl Radicals with C4H5N (Pyrrole): Temperature and Pressure Dependent Rate Coefficients. J. Phys. Chem. A 2012, 116, 6051– 6058,  DOI: 10.1021/jp211241x
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    Reaction of Hydroxyl Radicals with C4H5N (Pyrrole): Temperature and Pressure Dependent Rate Coefficients
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    Journal of Physical Chemistry A (2012), 116 (24), 6051-6058CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
    Abs. (pulsed laser photolysis, 4-639 torr N2 or air, 240-357 K) and relative rate methods (50 and 760 torr air, 296 K) were used to measure rate coeffs. k1 for the title reaction, OH + C4H5N → products (R1). Although the pressure and temp. dependent rate coeff. is adequately represented by a falloff parametrization, calcns. of the potential energy surface indicate a complex reaction system with multiple reaction paths (addn. only) in the falloff regime. At 298 K and 760 torr (1 torr = 1.33 mbar) the rate coeff. obtained from the parametrization is k1 = (1.28 ± 0.1) × 10-10 cm3 mol.-1 s-1, in good agreement with the value of (1.10 ± 0.27) × 10-10 cm3 mol.-1 s-1 obtained in the relative rate study (relative to C5H8, isoprene) at this temp. and pressure. The accuracy of the abs. rate coeff. detn. was enhanced by online optical absorption measurements of the C4H5N concn. at 184.95 nm using a value σ184.95nm = (1.26 ± 0.02) × 10-17 cm2 mol.-1, which was detd.
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    Zannoni, N.; Dusanter, S.; Gros, V.; Sarda Esteve, R.; Michoud, V.; Sinha, V.; Locoge, N.; Bonsang, B. Intercomparison of Two Comparative Reactivity Method Instruments Inf the Mediterranean Basin during Summer 2013. Atmos. Meas. Tech. 2015, 8, 3851– 3865,  DOI: 10.5194/amt-8-3851-2015
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    Michoud, V.; Hansen, R. F.; Locoge, N.; Stevens, P. S.; Dusanter, S. Detailed Characterizations of the New Mines Douai Comparative Reactivity Method Instrument via Laboratory Experiments and Modeling. Atmos. Meas. Tech. 2015, 8, 3537– 3553,  DOI: 10.5194/amt-8-3537-2015
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    Li, M.; Weschler, C. J.; Bekö, G.; Wargocki, P.; Lucic, G.; Williams, J. Human Ammonia Emission Rates under Various Indoor Environmental Conditions. Environ. Sci. Technol. 2020, 54, 5419– 5428,  DOI: 10.1021/acs.est.0c00094
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    Human Ammonia Emission Rates under Various Indoor Environmental Conditions
    Li, Mengze; Weschler, Charles J.; Bekoe, Gabriel; Wargocki, Pawel; Lucic, Gregor; Williams, Jonathan
    Environmental Science & Technology (2020), 54 (9), 5419-5428CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    NH3 is typically present at higher concns. in indoor air(∼10-70 ppb) vs. outdoor air (∼50 ppt to 5 ppb). It is the dominant neutralizer of acidic species in indoor environments, strongly affecting partitioning of gaseous acidic and basic species to aerosols, surface films, and bulk water. The authors measured NH3 emissions from humans in an environmentally-controlled chamber. Expts., each with four volunteers, quantified NH3 emissions as a function of temp. (25.1-32.6°), clothing (long-sleeved shirts/pants or T-shirts/shorts), age (teenagers, adults, seniors), relative humidity (low or high), and O3 (<2 to ∼35 ppb). Higher temp. and more skin exposure (T-shirts/shorts) significantly increased emission rates. For adults and seniors (long clothing), NH3 emissions were estd. to be 0.4 mg/h-person at 25°, 0.8 mg/h-person at 27°, and 1.4 mg/h-person at 29°, based on the temp. relationship obsd. in this work. Human NH3 emissions are sufficient to neutralize the acidifying impacts of human CO2 emissions. Results can be used to more accurately model indoor and inner-city outdoor NH3 concns. and assocd. chem.
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    Zhao, J.; Zhang, R. Proton Transfer Reaction Rate Constants between Hydronium Ion (H3O+) and Volatile Organic Compounds. Atmos. Environ. 2004, 38, 2177– 2185,  DOI: 10.1016/j.atmosenv.2004.01.019
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    Zhao, Jun; Zhang, Renyi
    Atmospheric Environment (2004), 38 (14), 2177-2185CODEN: AENVEQ; ISSN:1352-2310. (Elsevier Science B.V.)
    We report proton transfer reaction rate consts. between the hydronium ion (H3O+) and selected atmospherically important volatile org. compds. (VOCs). The quantum chem. method was used to det. the structures of the org. species employing the d. function theory-B3LYP. The ion-mol. reaction rates were detd. using the av.-dipole-orientation theory, along with the permanent dipole moment and polarizability of the org. species predicted from the quantum chem. calcns. The theor. results are compared to available literature data of the permanent dipole moment, polarizability, and ion-mol. reaction rate. The newly calcd. proton transfer rate consts. facilitate the use of the proton transfer reaction mass spectrometry (PTR-MS) technique in applications of lab. investigation of photochem. hydrocarbon oxidn. reactions and field measurements of the abundance of VOCs.
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    Bourtsoukidis, E.; Helleis, F.; Tomsche, L.; Fischer, H.; Hofmann, R.; Lelieveld, J.; Williams, J. An Aircraft Gas Chromatograph–Mass Spectrometer System for Organic Fast Identification Analysis (SOFIA): Design, Performance and a Case Study of Asian Monsoon Pollution Outflow. Atmos. Meas. Tech. 2017, 10, 5089– 5105,  DOI: 10.5194/amt-10-5089-2017
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    An aircraft gas chromatograph-mass spectrometer System for Organic Fast Identification Analysis (SOFIA): design, performance and a case study of Asian monsoon pollution outflow
    Bourtsoukidis, Efstratios; Helleis, Frank; Tomsche, Laura; Fischer, Horst; Hofmann, Rolf; Lelieveld, Jos; Williams, Jonathan
    Atmospheric Measurement Techniques (2017), 10 (12), 5089-5105CODEN: AMTTC2; ISSN:1867-8548. (Copernicus Publications)
    Here, we present a new System for Org. Fast Identification Anal. (SOFIA), which is a custom-built fast gas chromatog.-mass spectrometry (GC-MS) system with a time resoln. of 2-3 min and the ability to quantify atm. mixing ratios of halocarbons (e.g. chloromethanes), hydrocarbons (e.g isoprene), oxygenated VOCs (acetone, propanal, butanone) and aroms. (e.g. benzene, toluene) from sub-ppt to ppb levels. The relatively high time resoln. is the result of a novel cryogenic pre-concn. unit which rapidly cools ( ∼6°C s-1) the sample enrichment traps to -140°C, and a new chromatog. oven designed for rapid cooling rates (∼30°C s-1) and subsequent thermal stabilization. SOFIA was installed in the High Altitude and Long Range Research Aircraft (HALO) for the Oxidn. Mechanism Observations (OMO) campaign in August 2015, aimed at investigating the Asian monsoon pollution outflow in the tropical upper troposphere. In addn. to a comprehensive instrument characterization we present an example monsoon plume crossing flight as a case study to demonstrate the instrument capability. Hydrocarbon, halocarbon and oxygenated VOC data from SOFIA are compared with mixing ratios of carbon monoxide (CO) and methane (CH4), used to define the pollution plume. By using excess (ExMR) and normalized excess mixing ratios (NEMRs) the pollution could be attributed to two air masses of distinctly different origin, identified by back-trajectory anal.
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    US EPA. National Center for Environmental Assessment, W. D. Exposure Factors Handbook 2011th ed. (Final Report). https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=236252 (accessed March 12, 2021).
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    Azen, R.; Budescu, D. V. The Dominance Analysis Approach for Comparing Predictors in Multiple Regression. Psychol. Methods 2003, 8, 129– 148,  DOI: 10.1037/1082-989X.8.2.129
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    Azen Razia; Budescu David V
    Psychological methods (2003), 8 (2), 129-48 ISSN:1082-989X.
    A general method is presented for comparing the relative importance of predictors in multiple regression. Dominance analysis (D. V. Budescu, 1993), a procedure that is based on an examination of the R2 values for all possible subset models, is refined and extended by introducing several quantitative measures of dominance that differ in the strictness of the dominance definition. These are shown to be intuitive, meaningful, and informative measures that can address a variety of research questions pertaining to predictor importance. The bootstrap is used to assess the stability of dominance results across repeated sampling, and it is shown that these methods provide the researcher with more insights into the pattern of importance in a set of predictors than were previously available.
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    Azen, R.; Budescu, D. V. Comparing Predictors in Multivariate Regression Models: An Extension of Dominance Analysis. J. Educ. Behav. Stat. 2006, 31, 157– 180,  DOI: 10.3102/10769986031002157
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    Azen, R.; Budescu, D. V.; Reiser, B. Criticality of Predictors in Multiple Regression. Br. J. Math. Stat. Psychol. 2001, 54, 201– 225,  DOI: 10.1348/000711001159483
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    Azen R; Budescu D V; Reiser B
    The British journal of mathematical and statistical psychology (2001), 54 (Pt 2), 201-25 ISSN:0007-1102.
    A new method is proposed for comparing all predictors in a multiple regression model. This method generates a measure of predictor criticality, which is distinct from and has several advantages over traditional indices of predictor importance. Using the bootstrapping (resampling with replacement) procedure, a large number of samples are obtained from a given data set which contains one response variable and p predictors. For each sample, all 2p-1 subset regression models are fitted and the best subset model is selected. Thus, the (multinomial) distribution of the probability that each of the 2p-1 subsets is 'the best' model for the data set is obtained. A predictor's criticality is defined as a function of the probabilities associated with the models that include the predictor. That is, a predictor which is included in a large number of probable models is critical to the identification of the best-fitting regression model and, therefore, to the prediction of the response variable. The procedure can be applied to fixed and random regression models and can use any measure of goodness of fit (e.g., adjusted R2, Cp, AIC) for identifying the best model. Several criticality measures can be defined by using different combinations of the probabilities of the best-fitting models, and asymptotic confidence intervals for each variable's criticality can be derived. The procedure is illustrated with several examples.
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    Lakey, P. S. J.; Morrison, G. C.; Won, Y.; Parry, K. M.; von Domaros, M.; Tobias, D. J.; Rim, D.; Shiraiwa, M. The Impact of Clothing on Ozone and Squalene Ozonolysis Products in Indoor Environments. Commun. Chem. 2019, 2, 56  DOI: 10.1038/s42004-019-0159-7
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    Rai, A. C.; Guo, B.; Lin, C.-H.; Zhang, J.; Pei, J.; Chen, Q. Ozone Reaction with Clothing and Its Initiated VOC Emissions in an Environmental Chamber. Indoor Air 2014, 24, 49– 58,  DOI: 10.1111/ina.12058
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    Rai, A. C.; Guo, B.; Lin, C.-H.; Zhang, J.; Pei, J.; Chen, Q.
    Indoor Air (2014), 24 (1), 49-58CODEN: INAIE5; ISSN:0905-6947. (Wiley-Blackwell)
    Human health is adversely affected by ozone and the volatile org. compds. (VOCs) produced from its reactions in the indoor environment. Hence, it is important to characterize the ozone-initiated reactive chem. under indoor conditions and study the influence of different factors on these reactions. This investigation studied the ozone reactions with clothing through a series of expts. conducted in an environmental chamber under various conditions. The study found that the ozone reactions with a soiled (human-worn) T-shirt consumed ozone and generated VOCs. The ozone removal rate and deposition velocity for the T-shirt increased with the increasing soiling level and air change rate, decreased at high ozone concns., and were relatively unaffected by the humidity. The deposition velocity for the soiled T-shirt ranged from 0.15 to 0.29 cm/s. The ozone-initiated VOC emissions included C6-C10 straight-chain satd. aldehydes, acetone, and 4-OPA (4-oxopentanal). The VOC emissions were generally higher at higher ozone, humidity, soiling of T-shirt, and air change rate. The total molar yield was approx. 0.5 in most cases, which means that for every two moles of ozone removed by the T-shirt surface, one mole of VOCs was produced.
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    Anderson, S. E.; Franko, J.; Jackson, L. G.; Wells, J. R.; Ham, J. E.; Meade, B. J. Irritancy and Allergic Responses Induced by Exposure to the Indoor Air Chemical 4-Oxopentanal. Toxicol. Sci. 2012, 127, 371– 381,  DOI: 10.1093/toxsci/kfs102
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    Irritancy and Allergic Responses Induced by Exposure to the Indoor Air Chemical 4-Oxopentanal
    Anderson, Stacey E.; Franko, Jennifer; Jackson, Laurel G.; Wells, J. R.; Ham, Jason E.; Meade, B. J.
    Toxicological Sciences (2012), 127 (2), 371-381CODEN: TOSCF2; ISSN:1096-0929. (Oxford University Press)
    Over the last 2 decades, there was an increasing awareness regarding the potential impact of indoor air pollution on human health. People working in an indoor environment often experience symptoms such as eye, nose, and throat irritation. Investigations into these complaints have ascribed the effects, in part, to compds. emitted from building materials, cleaning/consumer products, and indoor chem. One suspect indoor air contaminant that was identified is the dicarbonyl 4-oxopentanal (4-OPA). The 4-OPA is generated through the ozonolysis of squalene and several high-vol. prodn. compds. that are commonly found indoors. Following preliminary workplace sampling that identified the presence of 4-OPA, these studies examd. the inflammatory and allergic responses to 4-OPA following both dermal and pulmonary exposure using a murine model. The 4-OPA was tested in a combined local lymph node assay and identified to be an irritant and sensitizer. A Th1-mediated hypersensitivity response was supported by a pos. response in the mouse ear swelling test. Pulmonary exposure to 4-OPA caused a significant elevation in nonspecific airway hyperreactivity, increased nos. of lung-assocd. lymphocytes and neutrophils, and increased interferon-γ prodn. by lung-assocd. lymph nodes. These results suggest that both dermal and pulmonary exposure to 4-OPA may elicit irritant and allergic responses and may help to explain some of the adverse health effects assocd. with poor indoor air quality.
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    Wolkoff, P. Indoor Air Pollutants in Office Environments: Assessment of Comfort, Health, and Performance. Int. J. Hyg. Environ. Health 2013, 216, 371– 394,  DOI: 10.1016/j.ijheh.2012.08.001
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    Indoor air pollutants in office environments: Assessment of comfort, health, and performance
    Wolkoff, Peder
    International Journal of Hygiene and Environmental Health (2013), 216 (4), 371-394CODEN: IJEHFT; ISSN:1438-4639. (Elsevier GmbH)
    A review. Concns. of volatile org. compds. (VOCs) in office environments are generally too low to cause sensory irritation in the eyes and airways on the basis of estd. thresholds for sensory irritation. Furthermore, effects in the lungs, e.g. inflammatory effects, have not been substantiated at indoor relevant concns. Some VOCs, including formaldehyde, in combination may under certain environmental and occupational conditions result in reported sensory irritation. The odor thresholds of several VOCs are low enough to influence the perceived air quality that result in a no. of acute effects from reported sensory irritation in eyes and airways and deterioration of performance. The odor perception (air quality) depends on a no. of factors that may influence the odor impact. There is neither clear indication that office dust particles may cause sensory effects, even not particles spiked with glucans, aldehydes or phthalates, nor lung effects; some inflammatory effects may be obsd. among asthmatics. Ozone-initiated terpene reaction products may be of concern in ozone-enriched environments (≥0.1 mg/m3) and elevated limonene concns., partly due to the prodn. of formaldehyde. Ambient particles may cause cardio-pulmonary effects, esp. in susceptible people (e.g. elderly and sick people); even, short-term effects, e.g. from traffic emission and candle smoke may possibly have modulating and delayed effects on the heart, but otherwise adverse effects in the airways and lung functions have not been obsd. Secondary org. aerosols generated in indoor ozone-initiated terpene reactions appear not to cause adverse effects in the airways; rather the gaseous products are relevant. Combined exposure to particles and ozone may evoke effects in subgroups of asthmatics.Based on an anal. of thresholds for odor and sensory irritation selected compds. are recommended for measurements to assess the indoor air quality and to minimize reports of irritation symptoms, deteriorated performance, and cardiovascular and pulmonary effects.
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    Mitchell, C. S.; Zhang, J. J.; Sigsgaard, T.; Jantunen, M.; Lioy, P. J.; Samson, R.; Karol, M. H. Current State of the Science: Health Effects and Indoor Environmental Quality. Environ. Health Perspect. 2007, 115, 958– 964,  DOI: 10.1289/ehp.8987
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    Mitchell Clifford S; Zhang Junfeng Jim; Sigsgaard Torben; Jantunen Matti; Lioy Paul J; Samson Robert; Karol Meryl H
    Environmental health perspectives (2007), 115 (6), 958-64 ISSN:0091-6765.
    Our understanding of the relationship between human health and the indoor environment continues to evolve. Previous research on health and indoor environments has tended to concentrate on discrete pollutant sources and exposures and on specific disease processes. Recently, efforts have been made to characterize more fully the complex interactions between the health of occupants and the interior spaces they inhabit. In this article we review recent advances in source characterization, exposure assessment, health effects associated with indoor exposures, and intervention research related to indoor environments. Advances in source characterization include a better understanding of how chemicals are transported and processed within spaces and the role that other factors such as lighting and building design may play in determining health. Efforts are under way to improve our ability to measure exposures, but this remains a challenge, particularly for biological agents. Researchers are also examining the effects of multiple exposures as well as the effects of exposures on vulnerable populations such as children and the elderly. In addition, a number of investigators are also studying the effects of modifying building design, materials, and operations on occupant health. Identification of research priorities should include input from building designers, operators, and the public health community.
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    Hydroxyl radicals play a central role in the troposphere as they control the lifetime of many trace gases. Measurement of OH reactivity (OH loss rate) is important to better constrain the OH budget and also to evaluate the completeness of measured VOC budget. Total atm. OH reactivity was measured for the first time in an European Megacity: Paris and its surrounding areas with 12 million inhabitants, during the MEGAPOLI winter campaign 2010. The method deployed was the Comparative Reactivity Method (CRM). The measured dataset contains both measured and calcd. OH reactivity from CO, NOx and VOCs measured via PTR-MS, GC-FID and GC-MS instruments. The reactivities obsd. in Paris covered a range from 10 s-1 to 130 s-1, indicating a large loading of chem. reactants. The present study showed that, when clean marine air masses influenced Paris, the purely local OH reactivity (20 s-1) is well explained by the measured species. Nevertheless, when there is a continental import of air masses, high levels of OH reactivity were obtained (120-130 s-1) and the missing OH reactivity measured in this case jumped to 75%. Using covariations of the missing OH reactivity to secondary inorg. species in fine aerosols, we suggest that the missing OH reactants were most likely highly oxidized compds. issued from photochem. processed air masses of anthropogenic origin.
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    Hydroxyl (OH) and hydroperoxy (HO2) radicals (collectively called HOx) were measured by a laser-induced fluorescence instrument during the PMTACS-NY (PM2.5 Technol. Assessment and Characterization Study-New York) intensive campaign in New York City in summer 2001. Measurement results for OH and HO2 are presented for the month-long study. The detection limits were about 3.0×105 cm-3 for OH and 2.5×106 cm-3 (∼0.1 ppt) for HO2 with a 1-min integration time and a 2σ confidence level. The daytime max. concns. were 5-20×106 cm-3 for OH and 0.4-6×108 cm-3 (2-24 pptv) for HO2, usually appearing later than the peak of ozone photolysis frequency, J(O1D). Relative high OH and HO2 persisted into early evening and were frequently obsd. during nighttime. The ratios of HO2 to OH were typically between 5 and 40, which are smaller than those obtained in relatively clean environments. The OH reactivity, measured by an instrument named total OH loss rate measurement was on av. 19±3 s-1 in this urban environment. It was the highest in the morning and the lowest in the afternoon. The comparison of measured OH and HO2 with model calcns. is given in a companion paper (OH and HO2 chem. in the urban atm. of New York City, Atm. Environment (2003a) this issue).
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    Environmental Science and Technology (2005), 39 (13), 4823-4832CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
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This article is cited by 6 publications.

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  4. Glenn Morrison, Azin Eftekhari, Aixing Fan, Francesca Majluf, Jordan E. Krechmer, . The influence of personal care products on ozone-skin surface chemistry. PLOS ONE 2022, 17 (9) , e0268263. https://doi.org/10.1371/journal.pone.0268263
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  • Abstract

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    Figure 1

    Figure 1. (a) Measured OH reactivity from occupant emissions at steady state. Experiments involved the same four adult volunteers occupying a chamber wearing long clothing or short clothing, under the same conditions on different days. Two replicates were done for the same condition with the same volunteers on different days (n = 2). Ozone was absent (red), introduced to the chamber when VOC reached SS (blue), or introduced to the chamber from the start of the experiment (black). (b) Measured (filled bars) and calculated (empty bars) OH reactivity from occupant emissions at steady state. Each bar corresponds to the mean among SS values between the two replicates conducted for each condition. Error bars indicate the method uncertainties (∼48% for measured reactivity, ∼30% for calculated reactivity). Steady-state values were determined during the last 15 min before occupants left the chamber.

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    Figure 2

    Figure 2. Concentrations of 6-MHO, 4-OPA, and geranyl acetone measured in the chamber occupied from 9:30 by four adults wearing long/short clothing. For each condition, two replicate experiments (N = 2) were conducted (long clothing conditions (6), (21), short clothing conditions (8), (23); see Table S1). The dashed line indicates when ozone was mixed into the chamber air. The dips correspond to measurements of the chamber supply air.

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    Figure 3

    Figure 3. Measured and calculated OH reactivity from four adults occupying the chamber from 9:30, wearing long clothing, exposed to moderate or high temperature (T), and low or high humidity (RH). Ozone was added to the chamber air when occupant emissions reached steady state (dashed vertical line). Total measured and calculated OH reactivities are reported with their associated method uncertainties, 48 and 30%, respectively. 6-MHO, 4-OPA, and geranyl acetone (GA) OH reactivities are reported with the gray area and colored lines, respectively. Missing data points for the first 1.5 h in the bottom panel are due to instrument failure. The dip in the experiment at a high T and a low RH corresponds to the measurement of the chamber supply air.

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    Figure 4

    Figure 4. Speciated total OH reactivity (top row) and speciated total mixing ratios (bottom row) measured at the steady state with O3 present; four adults wearing long clothing occupied the climate chamber at various temperatures (T) and relative humidities (RH). Total OH reactivities represented in the pie charts in the top row are 32 ± 10, 41 ± 12, and 40 ± 12 s–1, for the three cases, moderate T and low RH, high T and low RH, and high T and high RH, respectively. Total mixing ratios represented in the pie charts in the bottom row are 190 ± 13, 405 ± 33, and 393 ± 32 ppb, for the three cases, moderate T and low RH, high T and low RH, and high T and high RH, respectively. The size of the pie charts is scaled to the total values, different scales are used between pies representing OH reactivity and pies representing the mixing ratios. Steady-state values were determined during the last 15 min before occupants left the chamber.

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  • References

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      A compendium of all the volatile organic compounds (VOCs) emanating from the human body (the volatolome) is for the first time reported. 1840 VOCs have been assigned from breath (872), saliva (359), blood (154), milk (256), skin secretions (532) urine (279), and faeces (381) in apparently healthy individuals. Compounds were assigned CAS registry numbers and named according to a common convention where possible. The compounds have been grouped into tables according to their chemical class or functionality to permit easy comparison. Some clear differences are observed, for instance, a lack of esters in urine with a high number in faeces. Careful use of the database is needed. The numbers may not be a true reflection of the actual VOCs present from each bodily excretion. The lack of a compound could be due to the techniques used or reflect the intensity of effort e.g. there are few publications on VOCs from blood compared to a large number on VOCs in breath. The large number of volatiles reported from skin is partly due to the methodologies used, e.g. collecting excretions on glass beads and then heating to desorb VOCs. All compounds have been included as reported (unless there was a clear discrepancy between name and chemical structure), but there may be some mistaken assignations arising from the original publications, particularly for isomers. It is the authors' intention that this database will not only be a useful database of VOCs listed in the literature, but will stimulate further study of VOCs from healthy individuals. Establishing a list of volatiles emanating from healthy individuals and increased understanding of VOC metabolic pathways is an important step for differentiating between diseases using VOCs.
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    8. 8
      Wisthaler, A.; Weschler, C. J. Reactions of Ozone with Human Skin Lipids: Sources of Carbonyls, Dicarbonyls, and Hydroxycarbonyls in Indoor Air. Proc. Natl. Acad. Sci. USA 2010, 107, 6568– 6575,  DOI: 10.1073/pnas.0904498106
      [Crossref], [PubMed], [CAS], Google Scholar
      8
      Reactions of ozone with human skin lipids: Sources of carbonyls, dicarbonyls, and hydroxycarbonyls in indoor air
      Wisthaler, Armin; Weschler, Charles J.
      Proceedings of the National Academy of Sciences of the United States of America (2010), 107 (15), 6568-6575, S6568/1-S6568/4CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
      This study has used proton transfer reaction-mass spectrometry (PTR-MS) for direct air analyses of volatile products resulting from the reactions of O3 with human skin lipids. An initial series of small-scale in vitro and in vivo expts. were followed by expts. conducted with human subjects in a simulated office. The latter were conducted using realistic O3 mixing ratios (≈15 ppb with occupants present). Detected products included mono- and bifunctional compds. that contain carbonyl, carboxyl, or α-hydroxy ketone groups. Among these, 3 previously unreported dicarbonyls were identified, and 2 previously unreported α-hydroxy ketones were tentatively identified. The compds. detected in this study (excepting acetone) have been overlooked in surveys of indoor pollutants, reflecting the limitations of the anal. methods routinely used to monitor indoor air. The results are fully consistent with the Criegee mechanism for O3 reacting with squalene, the single most abundant unsatd. constituent of skin lipids, and several unsatd. fatty acid moieties in their free or esterified forms. Quant. product anal. confirms that squalene is the major scavenger of O3 at the interface between room air and the human envelope. Reactions between O3 and human skin lipids reduce the mixing ratio of O3 in indoor air, but concomitantly increase the mixing ratios of volatile products and, presumably, skin surface concns. of less volatile products. Some of the volatile products, esp. the dicarbonyls, may be respiratory irritants. Some of the less volatile products may be skin irritants.
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    9. 9
      Lakey, P. S. J.; Wisthaler, A.; Berkemeier, T.; Mikoviny, T.; Pöschl, U.; Shiraiwa, M. Chemical Kinetics of Multiphase Reactions between Ozone and Human Skin Lipids: Implications for Indoor Air Quality and Health Effects. Indoor Air 2017, 27, 816– 828,  DOI: 10.1111/ina.12360
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      9
      Chemical kinetics of multiphase reactions between ozone and human skin lipids: Implications for indoor air quality and health effects
      Lakey, P. S. J.; Wisthaler, A.; Berkemeier, T.; Mikoviny, T.; Poeschl, U.; Shiraiwa, M.
      Indoor Air (2017), 27 (4), 816-828CODEN: INAIE5; ISSN:1600-0668. (Wiley-Blackwell)
      Ozone reacts with skin lipids such as squalene, generating an array of org. compds., some of which can act as respiratory or skin irritants. Thus, it is important to quantify and predict the formation of these products under different conditions in indoor environments. We developed the kinetic multilayer model that explicitly resolves mass transport and chem. reactions at the skin and in the gas phase (KM-SUB-Skin). It can reproduce the concns. of ozone and org. compds. in previous measurements and new expts. This enabled the spatial and temporal concn. profiles in the skin oil and underlying skin layers to be resolved. Upon exposure to ∼30 ppb ozone, the concns. of squalene ozonolysis products in the gas phase and in the skin reach up to several ppb and on the order of ∼10 mmol m-3. Depending on various factors including the no. of people, room size, and air exchange rates, concns. of ozone can decrease substantially due to reactions with skin lipids. Ozone and dicarbonyls quickly react away in the upper layers of the skin, preventing them from penetrating deeply into the skin and hence reaching the blood.
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    10. 10
      Kruza, M.; Carslaw, N. How Do Breath and Skin Emissions Impact Indoor Air Chemistry?. Indoor Air 2019, 29, 369– 379,  DOI: 10.1111/ina.12539
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      10
      How do breath and skin emissions impact indoor air chemistry?
      Kruza, Magdalena; Carslaw, Nicola
      Indoor Air (2019), 29 (3), 369-379CODEN: INAIE5; ISSN:1600-0668. (Wiley-Blackwell)
      People are an important source of pollution indoors, through activities such as cleaning, and also from "natural" emissions from breath and skin. This paper investigates natural emissions in high-occupancy environments. Model simulations are performed for a school classroom during a typical summer in a polluted urban area. The results show that classroom occupants have a significant impact on indoor ozone, which increases from ~ 9 to ~ 20 ppb when the pupils leave for lunch and decreases to ~ 14 ppb when they return. The concns. of 4-OPA, formic acid, and acetic acid formed as oxidn. products following skin emissions attained max. concns. of 0.8, 0.5, and 0.1 ppb, resp., when pupils were present, increasing from near-zero concns. in their absence. For acetone, methanol, and ethanol from breath emissions, max. concns. were ~ 22.3, 6.6, and 21.5 ppb, resp., compared to 7.4, 2.1, and 16.9 ppb in their absence. A rate of prodn. anal. showed that occupancy reduced oxidant concns., while enhancing formation of nitrated org. compds., owing to the chem. that follows from increased aldehyde prodn. Occupancy also changes the peroxy radical compn., with those formed through isoprene oxidn. becoming relatively more important, which also has consequences for subsequent oxidant concns.
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    11. 11
      Amann, A.; Costello, B.; Miekisch, W.; Schubert, J.; Buszewski, B.; Pleil, J.; Ratcliffe, N.; Risby, T. The Human Volatilome: Volatile Organic Compounds (VOCs) in Exhaled Breath, Skin Emanations, Urine, Feces and Saliva. J. Breath Res. 2014, 8, 034001  DOI: 10.1088/1752-7155/8/3/034001
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      11
      The human volatilome: volatile organic compounds (VOCs) in exhaled breath, skin emanations, urine, feces and saliva
      Amann, Anton; de Lacy Costello, Ben; Miekisch, Wolfram; Schubert, Jochen; Buszewski, Boguslaw; Pleil, Joachim; Ratcliffe, Norman; Risby, Terence
      Journal of Breath Research (2014), 8 (3), 034001CODEN: JBROBW; ISSN:1752-7155. (IOP Publishing Ltd.)
      A review. Breath anal. is a young field of research with its roots in antiquity. Antoine Lavoisier discovered carbon dioxide in exhaled breath during the period 1777-1783, Wilhelm (Vilem) Petters discovered acetone in breath in 1857 and Johannes Muller reported the first quant. measurements of acetone in 1898. A recent review reported 1765 volatile compds. appearing in exhaled breath, skin emanations, urine, saliva, human breast milk, blood and feces. For a large no. of compds., real-time anal. of exhaled breath or skin emanations has been performed, e.g., during exertion of effort on a stationary bicycle or during sleep. Volatile compds. in exhaled breath, which record historical exposure, are called the exposome. Changes in biogenic volatile org. compd. concns. can be used to mirror metabolic or (patho)physiol. processes in the whole body or blood concns. of drugs (e.g. propofol) in clin. settings, even during artificial ventilation or during surgery. Also compds. released by bacterial strains like Pseudomonas aeruginosa or Streptococcus pneumonia could be very interesting. Me methacrylate (CAS 80-62-6), for example, was obsd. in the headspace of Streptococcus pneumonia in concns. up to 1420 ppb. Fecal volatiles have been implicated in differentiating certain infectious bowel diseases such as Clostridium difficile, Campylobacter, Salmonella and Cholera. They have also been used to differentiate other non-infectious conditions such as irritable bowel syndrome and inflammatory bowel disease. In addn., alterations in urine volatiles have been used to detect urinary tract infections, bladder, prostate and other cancers. Peroxidn. of lipids and other biomols. by reactive oxygen species produce volatile compds. like ethane and 1-pentane. Noninvasive detection and therapeutic monitoring of oxidative stress would be highly desirable in autoimmunol., neurol., inflammatory diseases and cancer, but also during surgery and in intensive care units. The study of cell cultures opens up new possibilities for elucidation of the biochem. background of volatile compds. In future studies, combined studies of a particular compd. with regard to human matrixes such as breath, urine, saliva and cell culture studies will lead to novel scientific progress in the field.
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    12. 12
      Furukawa, S.; Sekine, Y.; Kimura, K.; Umezawa, K.; Asai, S.; Miyachi, H. Simultaneous and Multi-Point Measurement of Ammonia Emanating from Human Skin Surface for the Estimation of Whole Body Dermal Emission Rate. J. Chromatogr. B 2017, 1053, 60– 64,  DOI: 10.1016/j.jchromb.2017.03.034
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      12
      Simultaneous and multi-point measurement of ammonia emanating from human skin surface for the estimation of whole body dermal emission rate
      Furukawa, Shota; Sekine, Yoshika; Kimura, Keita; Umezawa, Kazuo; Asai, Satomi; Miyachi, Hayato
      Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences (2017), 1053 (), 60-64CODEN: JCBAAI; ISSN:1570-0232. (Elsevier B.V.)
      Ammonia is one of the members of odor gases and a possible source of odor in indoor environment. However, little has been known on the actual emission rate of ammonia from the human skin surface. Then, this study aimed to est. the whole-body dermal emission rate of ammonia by simultaneous and multi-point measurement of emission fluxes of ammonia employing a passive flux sampler - ion chromatog. system. Firstly, the emission fluxes of ammonia were non-invasively measured for ten volunteers at 13 sampling positions set in 13 anatomical regions classified by Kurazumi et al. The measured emission fluxes were then converted to partial emission rates using the surface body areas estd. by wts. and heights of volunteers and partial rates of 13 body regions. Subsequent summation of the partial emission rates provided the whole body dermal emission rate of ammonia. The results ranged from 2.9 to 12 mg h-1 with an av. of 5.9 ± 3.2 mg h-1 per person for the ten healthy young volunteers. The values were much greater than those from human breath, and thus the dermal emission of ammonia was found more significant odor source than the breath exhalation in indoor environment.
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    13. 13
      Weschler, C. J.; Carslaw, N. Indoor Chemistry. Environ. Sci. Technol. 2018, 52, 2419– 2428,  DOI: 10.1021/acs.est.7b06387
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      13
      Indoor Chemistry
      Weschler, Charles J.; Carslaw, Nicola
      Environmental Science & Technology (2018), 52 (5), 2419-2428CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      A review. This review aims to encapsulate the importance, ubiquity, and complexity of indoor chem. We discuss the many sources of indoor air pollutants and summarize their chem. reactions in the air and on surfaces. We also summarize some of the known impacts of human occupants, who act as sources and sinks of indoor chems., and whose activities (e.g., cooking, cleaning, smoking) can lead to extremely high pollutant concns. As we begin to use increasingly sensitive and selective instrumentation indoors, we are learning more about chem. in this relatively understudied environment.
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    14. 14
      Grøntoft, T.; Raychaudhuri, M. R. Compilation of Tables of Surface Deposition Velocities for O3, NO2 and SO2 to a Range of Indoor Surfaces. Atmos. Environ. 2004, 38, 533– 544,  DOI: 10.1016/j.atmosenv.2003.10.010
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      14
      Compilation of tables of surface deposition velocities for O3, NO2 and SO2 to a range of indoor surfaces
      Grontoft, Terje; Raychaudhuri, Michele R.
      Atmospheric Environment (2004), 38 (4), 533-544CODEN: AENVEQ; ISSN:1352-2310. (Elsevier Science B.V.)
      Surface deposition velocities of O3, NO2, and SO2 were measured in chamber expts. at relative air humidity from 0 to 90%, and obtained from literature screening, for a range of material surfaces typically found indoors. Data were compiled in tables comprising 24 material classes and 5 relative humidity values for each gas. Interpolation among data points and extrapolation based on measurements on similar materials were used to fill in the tables where measurement values were lacking. Tabulated values should be useful in estg. indoor concns. of these gases when outdoor concns. are known and there are no indoor sources.
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    15. 15
      Morrison, G. C.; Nazaroff, W. W. The Rate of Ozone Uptake on Carpets: Experimental Studies. Environ. Sci. Technol. 2000, 34, 4963– 4968,  DOI: 10.1021/es001361h
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      15
      The Rate of Ozone Uptake on Carpets: Experimental Studies
      Morrison, Glenn C.; Nazaroff, William W.
      Environmental Science and Technology (2000), 34 (23), 4963-4968CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Ozone can react with surfaces, reducing indoor concns. Carpets may be important ozone sinks because of their high surface area. We conducted lab. expts. to measure ozone uptake on four samples of whole carpet and on the corresponding carpet fibers and carpet backing. Results were parametrized in terms of reaction probability, defined as the rate of ozone loss on a surface normalized by the rate of ozone-surface collisions. For whole carpet and carpet-backing samples, we found the apparent reaction probability to be of magnitude 10-5 to 10-4. These results are referenced to the floor area that would be covered by the carpet, rather than to the total surface area of the carpet and its fibers. Reaction probabilities of the order of 10-7 to 10-6 were measured on carpet fibers, referenced to total estd. fiber area. The results indicate that carpet is of comparable significance to painted walls in scavenging ozone from indoor air. All samples tested exhibited aging, such that the rate of ozone uptake diminished with increasing cumulative exposure. Although reactions on carpeting can reduce human exposure to ozone, we caution that the reaction products may include volatile carbonyls that have low odor or irritation thresholds.
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    16. 16
      Gall, E.; Darling, E.; Siegel, J. A.; Morrison, G. C.; Corsi, R. L. Evaluation of Three Common Green Building Materials for Ozone Removal, and Primary and Secondary Emissions of Aldehydes. Atmos. Environ. 2013, 77, 910– 918,  DOI: 10.1016/j.atmosenv.2013.06.014
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      16
      Evaluation of three common green building materials for ozone removal, and primary and secondary emissions of aldehydes
      Gall, Elliott; Darling, Erin; Siegel, Jeffrey A.; Morrison, Glenn C.; Corsi, Richard L.
      Atmospheric Environment (2013), 77 (), 910-918CODEN: AENVEQ; ISSN:1352-2310. (Elsevier Ltd.)
      Ozone reactions that occur on material surfaces can lead to elevated concns. of oxidized products in the occupied space of buildings. However, there is little information on the impact of materials at full scale, esp. for green building materials. Expts. were completed in a 68 m3 climate-controlled test chamber with three certified green building materials that can cover large areas in buildings: (1) recycled carpet, (2) perlite-based ceiling tile and (3) low-VOC paint and primer on recycled drywall. Ozone deposition velocity and primary and secondary emission rates of C1 to C10 satd. carbonyls were detd. for two chamber mixing conditions and three values of relative humidity. A direct comparison was made between ozone deposition velocities and carbonyl yields obsd. for the same materials analyzed in small (10 L) chambers. Total primary carbonyl emission rates from carpet, ceiling tile and painted drywall ranged from 27 to 120 μg m-2 h-1, 13 to 40 μg m-2 h-1, 3.9 to 42 μg m-2 h-1, resp. Ozone deposition velocity to these three materials averaged 6.1 m h-1, 2.3 m h-1 and 0.32 m h-1, resp. Total secondary carbonyl emissions from these materials ranged from 70 to 276 μg m-2 h-1, 0 to 12 μg m-2 h-1, and 0 to 30 μg m-2 h-1, resp. Carbonyl emissions were detd. with a transient approxn., and were found to be in general agreement with those found in the literature. These results suggest that care should be taken when selecting green building materials due to potentially large differences in primary and secondary emissions.
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    17. 17
      Bako-Biro, Z.; Weschler, C. J.; Wargocki, P.; Fanger, P. O. Effects of Indoor Pollution Sources and Ventilation Rate on Ozone Surface Removal Rate and the Occurrence of Oxygenated VOCs in an Office Space. In 10th International Conference on Indoor Air Quality and Climate , 2005; pp 2320– 2324.
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    18. 18
      Tamás, G.; Weschler, C. J.; Bakó-Biró, Z.; Wyon, D. P.; Strøm-Tejsen, P. Factors Affecting Ozone Removal Rates in a Simulated Aircraft Cabin Environment. Atmos. Environ. 2006, 40, 6122– 6133,  DOI: 10.1016/j.atmosenv.2006.05.034
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      18
      Factors affecting ozone removal rates in a simulated aircraft cabin environment
      Tamas, Gyoengyi; Weschler, Charles J.; Bako-Biro, Zsolt; Wyon, David P.; Strom-Tejsen, Peter
      Atmospheric Environment (2006), 40 (32), 6122-6133CODEN: AENVEQ; ISSN:1352-2310. (Elsevier Ltd.)
      O3 concns. were measured concurrently inside a simulated aircraft cabin and in the airstream providing ventilation air to the cabin. O3 decay rates were also measured after cessation of O3 injection into the supply airstream. By systematically varying the presence or absence of people, soiled T-shirts, aircraft seats, and a used HEPA (high efficiency particulate air) filter, in the course of 24 expts., the authors isolated the contributions of these and other factors to O3 removal from cabin air. For this simulated aircraft, people were responsible for ∼60% of O3 removal occurring in the cabin and recirculation system; respiration was only responsible for ∼4% of this removal. Aircraft seats removed ∼25% of O3; the loaded HEPA filter, 7%; and other surfaces, 10%. A T-shirt which had been slept in overnight removed ∼70% as much O3 as a person, indicating the importance of skin oils in O3 removal. The presence of the used HEPA filter in the recirculated airstream reduced perceived air quality. Over a 5-h period, the overall O3 removal rate by cabin surfaces decreased at ∼3%/h. With people present, the measured ratio of O3 concn. in the cabin vs. that outside the cabin was 0.15-0.21, smaller than that reported in the literature. Results reinforced the conclusion that the optimal way to reduce human exposure to O3 and O3 oxidn. products is to efficiently remove O3 from the air supply system of an aircraft.
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    19. 19
      Rim, D.; Gall, E. T.; Ananth, S.; Won, Y. Ozone Reaction with Human Surfaces: Influences of Surface Reaction Probability and Indoor Air Flow Condition. Build. Environ. 2018, 130, 40– 48,  DOI: 10.1016/j.buildenv.2017.12.012
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    20. 20
      Pandrangi, L. S.; Morrison, G. C. Ozone Interactions with Human Hair: Ozone Uptake Rates and Product Formation. Atmos. Environ. 2008, 42, 5079– 5089,  DOI: 10.1016/j.atmosenv.2008.02.009
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      20
      Ozone interactions with human hair: Ozone uptake rates and product formation
      Pandrangi, Lakshmi S.; Morrison, Glenn C.
      Atmospheric Environment (2008), 42 (20), 5079-5089CODEN: AENVEQ; ISSN:1352-2310. (Elsevier Ltd.)
      The cumulative ozone uptake, the ozone reaction probability, and product yields of volatile aldehydes and ketones were quantified for human scalp hair. Hair was chosen because ozone reacts readily with skin oils and the personal care products that coat hair. Due to their proximity to the breathing zone, these reactions can influence personal exposure to ozone and its volatile reaction products. Hair samples were collected before and after washing and/or application of personal hair care products. Samples were exposed to ozone for 24 h in a tubular Teflon reactor; ozone consumption rates and product emission rates were quantified. The mean values of integrated ozone uptake, initial and final follicle reaction probability values for 8 washed and unwashed samples were, resp., 5.1±4.4 μmol O3 g-1, (13±8) × 10-5, and (1.0±1.3) × 10-5. Unwashed hair taken close to the scalp exhibited the highest integrated ozone uptake and reaction probability, indicating that scalp oils are responsible for much of the ozone reactivity. Otherwise there was no significant difference between washed and unwashed hair. Compds. (geranyl acetone, 6-methyl-5-hepten-2-one, and decanal) assocd. with ozone reacting with sebum were obsd. as secondary products more frequently from unwashed hair than for washed hair and the summed yield of aldehydes ranged 0.00-0.86. Based on reaction probabilities, cumulative ozone uptake, and typical sebum generation rates, ozone flux to skin and hair is anticipated to be nearly transport limited, reducing personal exposure to ozone and increasing exposure to reaction products.
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    21. 21
      Coleman, B. K.; Destaillats, H.; Hodgson, A. T.; Nazaroff, W. W. Ozone Consumption and Volatile Byproduct Formation from Surface Reactions with Aircraft Cabin Materials and Clothing Fabrics. Atmos. Environ. 2008, 42, 642– 654,  DOI: 10.1016/j.atmosenv.2007.10.001
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      21
      Ozone consumption and volatile byproduct formation from surface reactions with aircraft cabin materials and clothing fabrics
      Coleman, Beverly K.; Destaillats, Hugo; Hodgson, Alfred T.; Nazaroff, William W.
      Atmospheric Environment (2008), 42 (4), 642-654CODEN: AENVEQ; ISSN:1352-2310. (Elsevier Ltd.)
      We measured ozone consumption and byproduct formation on materials commonly found in aircraft cabins at flight-relevant conditions. Two series of small-chamber expts. were conducted, with most runs at low relative humidity (10%) and high air-exchange rate (∼20 h-1). New and used cabin materials (seat fabric, carpet, and plastic) and laundered and worn clothing fabrics (cotton, polyester, and wool) were studied. We measured ozone deposition to many material samples, and we measured ozone uptake and primary and secondary emissions of volatile org. compds. (VOCs) from a subset of samples. Deposition velocities ranged from 0.06 to 0.54 cm s-1. Emissions of VOCs were higher with ozone than without ozone in every case. The most commonly detected secondary emissions were C1 through C10 satd. aldehydes and the squalene oxidn. products 6-methyl-5-hepten-2-one and acetone. For the compds. measured, summed VOC emission rates in the presence of 55-128 ppb (residual level) ozone ranged from 1.0 to 8.9 μmol h-1 m-2. Total byproduct yield ranged from 0.07 to 0.24 mol of product volatilized per mol of ozone consumed. Results were used to est. the relative contribution of different materials to ozone deposition and byproduct emissions in a typical aircraft cabin. The dominant contributor to both was clothing fabrics, followed by seat fabric. Results indicate that ozone reactions with surfaces substantially reduce the ozone concn. in the cabin but also generate volatile byproducts of potential concern for the health and comfort of passengers and crew.
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    22. 22
      Nagda, N.; Nazaroff, W.; Gadgil, A.; Weschler, C. STP13101S Modeling of Indoor Air Quality and Exposure; ASTM International: West Conshohocken, PA, 1993.
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      Yang, S.; Gao, K.; Yang, X. Volatile Organic Compounds (VOCs) Formation Due to Interactions between Ozone and Skin-Oiled Clothing: Measurements by Extraction-Analysis-Reaction Method. Build. Environ. 2016, 103, 146– 154,  DOI: 10.1016/j.buildenv.2016.04.012
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      There is no corresponding record for this reference.
    24. 24
      Arata, C.; Heine, N.; Wang, N.; Misztal, P. K.; Wargocki, P.; Bekö, G.; Williams, J.; Nazaroff, W. W.; Wilson, K. R.; Goldstein, A. H. Heterogeneous Ozonolysis of Squalene: Gas-Phase Products Depend on Water Vapor Concentration. Environ. Sci. Technol. 2019, 53, 14441– 14448,  DOI: 10.1021/acs.est.9b05957
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      24
      Heterogeneous Ozonolysis of Squalene: Gas-Phase Products Depend on Water Vapor Concentration
      Arata, Caleb; Heine, Nadja; Wang, Nijing; Misztal, Pawel K.; Wargocki, Pawel; Beko, Gabriel; Williams, Jonathan; Nazaroff, William W.; Wilson, Kevin R.; Goldstein, Allen H.
      Environmental Science & Technology (2019), 53 (24), 14441-14448CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Previous work examg. the condensed-phase products of squalene particle ozonolysis detd. an increased water vapor concn. led to lower secondary ozonide concns., increased carbonyl concns., and smaller particle diam., suggesting water changed the fate of Criegee intermediates. To det. if this vol. loss corresponded to an increase in gas-phase products, gas-phase volatile org. compd. (VOC) concns. were measured by proton-transfer-reaction, time-of-flight mass spectrometry. Work was performed in a flow tube reactor at atmospherically relevant O3 exposure levels (5-30 ppb/h) with pure squalene particles. Increased water vapor concns. led to strongly enhanced gas-phase oxidn. products at all tested O3 exposures. Increased water vapor from near 0 to 70% relative humidity (RH) at high O3 exposure increased the gas-phase VOC total mass concn. by a factor of three. The obsd. fraction of C in the gas-phase correlated with the fraction of particle vol. lost. Expts. involving O3 oxidn. of shirts soiled with skin oil confirmed the RH dependence of gas-phase reaction product generation occurred similarly on surfaces contg. skin oil under realistic conditions. Similar behavior was expected for O3 reactions with other surface-bound orgs. contg. unsatd. C bonds.
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    25. 25
      Abbatt, J. P. D.; Wang, C. The Atmospheric Chemistry of Indoor Environments. Environ. Sci.: Processes Impacts 2020, 22, 25– 48,  DOI: 10.1039/C9EM00386J
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      25
      The atmospheric chemistry of indoor environments
      Abbatt, Jonathan P. D.; Wang, Chen
      Environmental Science: Processes & Impacts (2020), 22 (1), 25-48CODEN: ESPICZ; ISSN:2050-7895. (Royal Society of Chemistry)
      Through air inhalation, dust ingestion and dermal exposure, the indoor environment plays an important role in controlling human chem. exposure. Indoor emissions and chem. can also have direct impacts on the quality of outdoor air. And so, it is important to have a strong fundamental knowledge of the chem. processes that occur in indoor environments. This review article summarizes our understanding of the indoor chem. field. Using a mol. perspective, it addresses primarily the new advances that have occurred in the past decade or so and upon developments in our understanding of multiphase partitioning and reactions. A primary goal of the article is to contrast indoor chem. to that which occurs outdoors, which we know to be a strongly gas-phase, oxidant-driven system in which substantial oxidative aging of gases and aerosol particles occurs. By contrast, indoor environments are dark, gas-phase oxidant concns. are relatively low, and due to air exchange, only short times are available for reactive processing of gaseous and particle constituents. However, important gas-surface partitioning and reactive multiphase chem. occur in the large surface reservoirs that prevail in all indoor environments. These interactions not only play a crucial role in controlling the compn. of indoor surfaces but also the surrounding gases and aerosol particles, thus affecting human chem. exposure. There are rich research opportunities available if the advanced measurement and modeling tools of the outdoor atm. chem. community continue to be brought indoors.
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    26. 26
      Williams, J.; Brune, W. A Roadmap for OH Reactivity Research. Atmos. Environ. 2015, 106, 371– 372,  DOI: 10.1016/j.atmosenv.2015.02.017
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      26
      A roadmap for OH reactivity research
      Williams, Jonathan; Brune, William
      Atmospheric Environment (2015), 106 (), 371-372CODEN: AENVEQ; ISSN:1352-2310. (Elsevier Ltd.)
      A review describing the roadmap for OH reactivity research. Ever since the discovery of the OH radical's importance to tropospheric chem., the characterization of its overall loss rate (OH reactivity) has remained a key question. Direct OH reactivity measurements in the lab. based on LIDAR and in the ambient air based on in situ laser induced fluorescence detection of OH was demonstrated. Detn. of OH reactivity is bound to deliver new challenges and yield insights on questions such as the oxidizing capacity and the tropospheric ozone budget.
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    27. 27
      Nölscher, A. C.; Yañez-Serrano, A. M.; Wolff, S.; de Araujo, A. C.; Lavrič, J. V.; Kesselmeier, J.; Williams, J. Unexpected Seasonality in Quantity and Composition of Amazon Rainforest Air Reactivity. Nat. Commun. 2016, 7, 10383  DOI: 10.1038/ncomms10383
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      27
      Unexpected seasonality in quantity and composition of Amazon rainforest air reactivity
      Nolscher A C; Yanez-Serrano A M; Wolff S; Kesselmeier J; Williams J; Yanez-Serrano A M; Wolff S; de Araujo A Carioca; Lavric J V
      Nature communications (2016), 7 (), 10383 ISSN:.
      The hydroxyl radical (OH) removes most atmospheric pollutants from air. The loss frequency of OH radicals due to the combined effect of all gas-phase OH reactive species is a measureable quantity termed total OH reactivity. Here we present total OH reactivity observations in pristine Amazon rainforest air, as a function of season, time-of-day and height (0-80 m). Total OH reactivity is low during wet (10 s(-1)) and high during dry season (62 s(-1)). Comparison to individually measured trace gases reveals strong variation in unaccounted for OH reactivity, from 5 to 15% missing in wet-season afternoons to mostly unknown (average 79%) during dry season. During dry-season afternoons isoprene, considered the dominant reagent with OH in rainforests, only accounts for ∼20% of the total OH reactivity. Vertical profiles of OH reactivity are shaped by biogenic emissions, photochemistry and turbulent mixing. The rainforest floor was identified as a significant but poorly characterized source of OH reactivity.
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    28. 28
      Fuchs, H.; Tan, Z.; Lu, K.; Bohn, B.; Broch, S.; Brown, S. S.; Dong, H.; Gomm, S.; Häseler, R.; He, L.; Hofzumahaus, A.; Holland, F.; Li, X.; Liu, Y.; Lu, S.; Min, K.-E.; Rohrer, F.; Shao, M.; Wang, B.; Wang, M.; Wu, Y.; Zeng, L.; Zhang, Y.; Wahner, A.; Zhang, Y. OH Reactivity at a Rural Site (Wangdu) in the North China Plain: Contributions from OH Reactants and Experimental OH Budget. Atmos. Chem. Phys. 2017, 17, 645– 661,  DOI: 10.5194/acp-17-645-2017
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      28
      OH reactivity at a rural site (Wangdu) in the North China Plain: contributions from OH reactants and experimental OH budget
      Fuchs, Hendrik; Tan, Zhaofeng; Lu, Keding; Bohn, Birger; Broch, Sebastian; Brown, Steven S.; Dong, Huabin; Gomm, Sebastian; Haeseler, Rolf; He, Lingyan; Hofzumahaus, Andreas; Holland, Frank; Li, Xin; Liu, Ying; Lu, Sihua; Min, Kyung-Eun; Rohrer, Franz; Shao, Min; Wang, Baolin; Wang, Ming; Wu, Yusheng; Zeng, Limin; Zhang, Yinson; Wahner, Andreas; Zhang, Yuanhang
      Atmospheric Chemistry and Physics (2017), 17 (1), 645-661CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      In 2014, a large, comprehensive field campaign was conducted in the densely populated North China Plain. The measurement site was located in a botanic garden close to the small town Wangdu, without major industry but influenced by regional transportation of air pollution. The loss rate coeff. of atm. hydroxyl radicals (OH) was quantified by direct measurements of the OH reactivity. Values ranged between 10 and 20 s-1 for most of the daytime. Highest values were reached in the late night with max. values of around 40 s-1. OH reactants mainly originated from anthropogenic activities as indicated (1) by a good correlation between measured OH reactivity and carbon monoxide (linear correlation coeff. R2 = 0.33) and (2) by a high contribution of nitrogen oxide species to the OH reactivity (up to 30% in the morning). Total OH reactivity was measured by a laser flash photolysis-laser-induced fluorescence instrument (LP-LIF). Measured values can be explained well by measured trace gas concns. including org. compds., oxygenated org. compds., CO and nitrogen oxides. Significant, unexplained OH reactivity was only obsd. during nights, when biomass burning of agricultural waste occurred on surrounding fields. OH reactivity measurements also allow investigating the chem. OH budget. During this campaign, the OH destruction rate calcd. from measured OH reactivity and measured OH concn. was balanced by the sum of OH prodn. from ozone and nitrous acid photolysis and OH regeneration from hydroperoxy radicals within the uncertainty of measurements. However, a tendency for higher OH destruction compared to OH prodn. at lower concns. of nitric oxide is also obsd., consistent with previous findings in field campaigns in China.
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    29. 29
      Zannoni, N.; Gros, V.; Sarda Esteve, R.; Kalogridis, C.; Michoud, V.; Dusanter, S.; Sauvage, S.; Locoge, N.; Colomb, A.; Bonsang, B. Summertime OH Reactivity from a Receptor Coastal Site in the Mediterranean Basin. Atmos. Chem. Phys. 2017, 17, 12645– 12658,  DOI: 10.5194/acp-17-12645-2017
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      29
      Summertime OH reactivity from a receptor coastal site in the Mediterranean Basin
      Zannoni, Nora; Gros, Valerie; Esteve, Roland Sarda; Kalogridis, Cerise; Michoud, Vincent; Dusanter, Sebastien; Sauvage, Stephane; Locoge, Nadine; Colomb, Aurelie; Bonsang, Bernard
      Atmospheric Chemistry and Physics (2017), 17 (20), 12645-12658CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      Total hydroxyl radical (OH) reactivity, the total loss frequency of the hydroxyl radical in ambient air, provides the total loading of OH reactants in air. We measured the total OH reactivity for the first time during summertime at a coastal receptor site located in the western Mediterranean Basin. Measurements were performed at a temporary field site located in the northern cape of Corsica (France), during summer 2013 for the project CARBOSOR (CARBOn within continental pollution plumes: SOurces and Reactivity)-ChArMEx (Chem. and Aerosols Mediterranean Expt.). Here, we compare the measured total OH reactivity with the OH reactivity calcd. from the measured reactive gases. The difference between these two parameters is termed missing OH reactivity, i.e., the fraction of OH reactivity not explained by the measured compds. The total OH reactivity at the site varied between the instrumental LoD (limit of detection = 3 s-1) to a max. of 17 ± 6 s-1 (35 % uncertainty) and was 5 ± 4 s-1 (1σ SD - std. deviation) on av. It varied with air temp. exhibiting a diurnal profile comparable to the reactivity calcd. from the concn. of the biogenic volatile org. compds. measured at the site. For part of the campaign, 56 % of OH reactivity was unexplained by the measured OH reactants (missing reactivity). We suggest that oxidn. products of biogenic gas precursors were among the contributors to missing OH reactivity.
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    30. 30
      Kumar, V.; Chandra, B. P.; Sinha, V. Large Unexplained Suite of Chemically Reactive Compounds Present in Ambient Air Due to Biomass Fires. Sci. Rep. 2018, 8, 626  DOI: 10.1038/s41598-017-19139-3
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      30
      Large unexplained suite of chemically reactive compounds present in ambient air due to biomass fires
      Kumar V; Chandra B P; Sinha V
      Scientific reports (2018), 8 (1), 626 ISSN:.
      Biomass fires impact global atmospheric chemistry. The reactive compounds emitted and formed due to biomass fires drive ozone and organic aerosol formation, affecting both air quality and climate. Direct hydroxyl (OH) Reactivity measurements quantify total gaseous reactive pollutant loadings and comparison with measured compounds yields the fraction of unmeasured compounds. Here, we quantified the magnitude and composition of total OH reactivity in the north-west Indo-Gangetic Plain. More than 120% increase occurred in total OH reactivity (28 s(-1) to 64 s(-1)) and from no missing OH reactivity in the normal summertime air, the missing OH reactivity fraction increased to ~40 % in the post-harvest summertime period influenced by large scale biomass fires highlighting presence of unmeasured compounds. Increased missing OH reactivity between the two summertime periods was associated with increased concentrations of compounds with strong photochemical source such as acetaldehyde, acetone, hydroxyacetone, nitromethane, amides, isocyanic acid and primary emissions of acetonitrile and aromatic compounds. Currently even the most detailed state-of-the art atmospheric chemistry models exclude formamide, acetamide, nitromethane and isocyanic acid and their highly reactive precursor alkylamines (e.g. methylamine, ethylamine, dimethylamine, trimethylamine). For improved understanding of atmospheric chemistry-air quality-climate feedbacks in biomass-fire impacted atmospheric environments, future studies should include these compounds.
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    31. 31
      Whalley, L.; Stone, D.; Heard, D. New Insights into the Tropospheric Oxidation of Isoprene: Combining Field Measurements, Laboratory Studies, Chemical Modelling and Quantum Theory. Top. Curr. Chem. 2014, 339, 55– 95,  DOI: 10.1007/128_2012_359
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      31
      New Insights into the Tropospheric Oxidation of Isoprene: Combining Field Measurements, Laboratory Studies, Chemical Modelling and Quantum Theory
      Whalley, Lisa; Stone, Daniel; Heard, Dwayne
      Topics in Current Chemistry (2014), 339 (Atmospheric and Aerosol Chemistry), 55-95CODEN: TPCCAQ; ISSN:1436-5049. (Springer GmbH)
      In this chapter we discuss some of the recent work directed at further understanding the chem. of our atm. in regions of low NO x , such as forests, where there are considerable emissions of biogenic volatile org. compds., for example reactive hydrocarbons such as isoprene. Recent field measurements have revealed some surprising results, for example that OH concns. are measured to be considerably higher than can be understood using current chem. mechanisms. It has also not proven possible to reconcile field measurements of other species, such as oxygenated VOCs, or emission fluxes of isoprene, using current mechanisms. Several complementary approaches have been brought to bear on formulating a soln. to this problem, namely field studies using state-of-the-art instrumentation, chamber studies to isolate sub-sections of the chem., lab. studies to measure rate coeffs., product branching ratios and photochem. yields, the development of ever more detailed chem. mechanisms, and high quality ab initio quantum theory to calc. the energy landscape for relevant reactions and to enable the rates of formation of products and intermediates for previously unknown and unstudied reactions to be predicted. The last few years have seen significant activity in this area, with several contrasting postulates put forward to explain the exptl. findings, and here we attempt to synthesize the evidence and ideas.
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    32. 32
      Pfannerstill, E. Y.; Wang, N.; Edtbauer, A.; Bourtsoukidis, E.; Crowley, J. N.; Dienhart, D.; Eger, P. G.; Ernle, L.; Fischer, H.; Hottmann, B.; Paris, J.-D.; Stönner, C.; Tadic, I.; Walter, D.; Lelieveld, J.; Williams, J. Shipborne Measurements of Total OH Reactivity around the Arabian Peninsula and Its Role in Ozone Chemistry. Atmos. Chem. Phys. 2019, 19, 11501– 11523,  DOI: 10.5194/acp-19-11501-2019
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      32
      Shipborne measurements of total OH reactivity around the Arabian Peninsula and its role in ozone chemistry
      Pfannerstill, Eva Y.; Wang, Nijing; Edtbauer, Achim; Bourtsoukidis, Efstratios; Crowley, John N.; Dienhart, Dirk; Eger, Philipp G.; Ernle, Lisa; Fischer, Horst; Hottmann, Bettina; Paris, Jean-Daniel; Stoenner, Christof; Tadic, Ivan; Walter, David; Lelieveld, Jos; Williams, Jonathan
      Atmospheric Chemistry and Physics (2019), 19 (17), 11501-11523CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      The Arabian Peninsula is characterized by high and increasing levels of photochem. air pollution. Strong solar irradn., high temps. and large anthropogenic emissions of reactive trace gases result in intense photochem. activity, esp. during the summer months. However, air chem. measurements in the region are scarce. In order to assess regional pollution sources and oxidn. rates, the first ship-based direct measurements of total OH reactivity were performed in summer 2017 from a vessel traveling around the peninsula during the AQABA (Air Quality and Climate Change in the Arabian Basin) campaign. Total OH reactivity is the total loss frequency of OH radicals due to all reactive compds. present in air and defines the local lifetime of OH, the most important oxidant in the troposphere. During the AQABA campaign, the total OH reactivity ranged from below the detection limit (5.4 s-1) over the northwestern Indian Ocean (Arabian Sea) to a max. of 32.8 ± 9.6 s-1 over the Arabian Gulf (also known as Persian Gulf) when air originated from large petroleum extn./processing facilities in Iraq and Kuwait. In the polluted marine regions, OH reactivity was broadly comparable to highly populated urban centers in intensity and compn. The permanent influence of heavy maritime traffic over the seaways of the Red Sea, Gulf of Aden and Gulf of Oman resulted in median OH sinks of 7.9-8.5 s-1.
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    33. 33
      Bekö, G.; Wargocki, P.; Wang, N.; Li, M.; Weschler, C. J.; Morrison, G.; Langer, S.; Ernle, L.; Licina, D.; Yang, S.; Zannoni, N.; Williams, J. The Indoor Chemical Human Emissions and Reactivity (ICHEAR) Project: Overview of Experimental Methodology and Preliminary Results. Indoor Air 2020, 30, 1213– 1228,  DOI: 10.1111/ina.12687
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      33
      The Indoor Chemical Human Emissions and Reactivity (ICHEAR) project: Overview of experimental methodology and preliminary results
      Beko Gabriel; Wargocki Pawel; Weschler Charles J; Wang Nijing; Li Mengze; Ernle Lisa; Zannoni Nora; Williams Jonathan; Weschler Charles J; Morrison Glenn; Langer Sarka; Langer Sarka; Licina Dusan; Yang Shen
      Indoor air (2020), 30 (6), 1213-1228 ISSN:.
      With the gradual reduction of emissions from building products, emissions from human occupants become more dominant indoors. The impact of human emissions on indoor air quality is inadequately understood. The aim of the Indoor Chemical Human Emissions and Reactivity (ICHEAR) project was to examine the impact on indoor air chemistry of whole-body, exhaled, and dermally emitted human bioeffluents under different conditions comprising human factors (t-shirts/shorts vs long-sleeve shirts/pants; age: teenagers, young adults, and seniors) and a variety of environmental factors (moderate vs high air temperature; low vs high relative humidity; presence vs absence of ozone). A series of human subject experiments were performed in a well-controlled stainless steel climate chamber. State-of-the-art measurement technologies were used to quantify the volatile organic compounds emitted by humans and their total OH reactivity; ammonia, nanoparticle, fluorescent biological aerosol particle (FBAP), and microbial emissions; and skin surface chemistry. This paper presents the design of the project, its methodologies, and preliminary results, comparing identical measurements performed with five groups, each composed of 4 volunteers (2 males and 2 females). The volunteers wore identical laundered new clothes and were asked to use the same set of fragrance-free personal care products. They occupied the ozone-free (<2 ppb) chamber for 3 hours (morning) and then left for a 10-min lunch break. Ozone (target concentration in occupied chamber ~35 ppb) was introduced 10 minutes after the volunteers returned to the chamber, and the measurements continued for another 2.5 hours. Under a given ozone condition, relatively small differences were observed in the steady-state concentrations of geranyl acetone, 6MHO, and 4OPA between the five groups. Larger variability was observed for acetone and isoprene. The absence or presence of ozone significantly influenced the steady-state concentrations of acetone, geranyl acetone, 6MHO, and 4OPA. Results of replicate experiments demonstrate the robustness of the experiments. Higher repeatability was achieved for dermally emitted compounds and their reaction products than for constituents of exhaled breath.
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    34. 34
      Wang, N.; Zannoni, N.; Ernle, L.; Bekö, G.; Wargocki, P.; Li, M.; Weschler, C. J.; Williams, J. Total OH Reactivity of Emissions from Humans: In Situ Measurement and Budget Analysis. Environ. Sci. Technol. 2021, 55, 149– 159,  DOI: 10.1021/acs.est.0c04206
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      34
      Total OH Reactivity of Emissions from Humans: In Situ Measurement and Budget Analysis
      Wang, Nijing; Zannoni, Nora; Ernle, Lisa; Bekoe, Gabriel; Wargocki, Pawel; Li, Mengze; Weschler, Charles J.; Williams, Jonathan
      Environmental Science & Technology (2021), 55 (1), 149-159CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Humans are a potent, mobile source of various volatile org. compds. (VOCs) in indoor environments. Such direct anthropogenic emissions are gaining importance, as those from furnishings and building materials have become better regulated and energy efficient homes may reduce ventilation. While previous studies have characterized human emissions in indoor environments, the question remains whether VOCs remain unidentified by current measuring techniques. In this study conducted in a climate chamber occupied by four people, the total OH reactivity of air was quantified, together with multiple VOCs measured by proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) and fast gas chromatog.-mass spectrometry (fast-GC-MS). Whole-body, breath, and dermal emissions were assessed. The comparison of directly measured OH reactivity and that of the summed reactivity of individually measured species revealed no significant shortfall. Ozone exposure (37 ppb) was found to have little influence on breath OH reactivity but enhanced dermal OH reactivity significantly. Without ozone, the whole-body OH reactivity was dominated by breath emissions, mostly isoprene (76%). With ozone present, OH reactivity nearly doubled, with the increase being mainly caused by dermal emissions of mostly carbonyl compds. (57%). No significant difference in total OH reactivity was obsd. for different age groups (teenagers/young adults/seniors) without ozone. With ozone present, the total OH reactivity decreased slightly with increasing age.
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    35. 35
      Salvador, C. M.; Bekö, G.; Weschler, C. J.; Morrison, G.; Le Breton, M.; Hallquist, M.; Ekberg, L.; Langer, S. Indoor Ozone/Human Chemistry and Ventilation Strategies. Indoor Air 2019, 29, 913– 925,  DOI: 10.1111/ina.12594
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      35
      Indoor ozone/human chemistry and ventilation strategies
      Salvador, Christian Mark; Bekoe, Gabriel; Weschler, Charles J.; Morrison, Glenn; Le Breton, Michael; Hallquist, Mattias; Ekberg, Lars; Langer, Sarka
      Indoor Air (2019), 29 (6), 913-925CODEN: INAIE5; ISSN:1600-0668. (Wiley-Blackwell)
      This study aimed to better understand and quantify the influence of ventilation strategies on occupant-related indoor air chem. The oxidn. of human skin oil constituents was studied in a continuously ventilated climate chamber at two air exchange rates (1 h-1 and 3 h-1) and two initial ozone mixing ratios (30 and 60 ppb). Addnl. measurements were performed to investigate the effect of intermittent ventilation ("off" followed by "on"). Soiled t-shirts were used to simulate the presence of occupants. A time-of-flight-chem. ionization mass spectrometer (ToF-CIMS) in pos. mode using protonated water clusters was used to measure the oxygenated reaction products geranyl acetone, 6-methyl-5-hepten-2-one (6-MHO) and 4-oxopentanal (4-OPA). The measurement data were used in a series of mass balance models accounting for formation and removal processes. Reactions of ozone with squalene occurring on the surface of the t-shirts are mass transport limited; ventilation rate has only a small effect on this surface chem. Ozone-squalene reactions on the t-shirts produced gas-phase geranyl acetone, which was subsequently removed almost equally by ventilation and further reaction with ozone. About 70% of gas-phase 6-MHO was produced in surface reactions on the t-shirts, the remainder in secondary gas-phase reactions of ozone with geranyl acetone. 6-MHO was primarily removed by ventilation, while further reaction with ozone was responsible for about a third of its removal. 4-OPA was formed primarily on the surfaces of the shirts (∼60%); gas-phase reactions of ozone with geranyl acetone and 6-MHO accounted for ∼30% and ∼10%, resp. 4-OPA was removed entirely by ventilation. The results from the intermittent ventilation scenarios showed delayed formation of the reaction products and lower product concns. compared to continuous ventilation.
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    36. 36
      Fuchs, H.; Novelli, A.; Rolletter, M.; Hofzumahaus, A.; Pfannerstill, E. Y.; Kessel, S.; Edtbauer, A.; Williams, J.; Michoud, V.; Dusanter, S.; Locoge, N.; Zannoni, N.; Gros, V.; Truong, F.; Sarda-Esteve, R.; Cryer, D. R.; Brumby, C. A.; Whalley, L. K.; Stone, D.; Seakins, P. W.; Heard, D. E.; Schoemaecker, C.; Blocquet, M.; Coudert, S.; Batut, S.; Fittschen, C.; Thames, A. B.; Brune, W. H.; Ernest, C.; Harder, H.; Muller, J. B. A.; Elste, T.; Kubistin, D.; Andres, S.; Bohn, B.; Hohaus, T.; Holland, F.; Li, X.; Rohrer, F.; Kiendler-Scharr, A.; Tillmann, R.; Wegener, R.; Yu, Z.; Zou, Q.; Wahner, A. Comparison of OH Reactivity Measurements in the Atmospheric Simulation Chamber SAPHIR. Atmos. Meas. Tech. 2017, 10, 4023– 4053,  DOI: 10.5194/amt-10-4023-2017
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      36
      Comparison of OH reactivity measurements in the atmospheric simulation chamber SAPHIR
      Fuchs, Hendrik; Novelli, Anna; Rolletter, Michael; Hofzumahaus, Andreas; Pfannerstill, Eva Y.; Kessel, Stephan; Edtbauer, Achim; William, Jonathan; Michoud, Vincent; Dusanter, Sebastien; Locoge, Nadine; Zannoni, Nora; Gros, Valerie; Truong, Francois; Sarda-Esteve, Roland; Cryer, Danny R.; Brumby, Charlotte A.; Whalley, Lisa K.; Stone, Daniel; Seakins, Paul W.; Heard, Dwayne E.; Schoemaecker, Coralie; Blocquet, Marion; Coudert, Sebastien; Batut, Sebastien; Fittschen, Christa; Thames, Alexander B.; Brune, William H.; Ernest, Cheryl; Harder, Hartwig; Muller, Jennifer B. A.; Elste, Thomas; Kubistin, Dagmar; Andres, Stefanie; Bohn, Birger; Hohaus, Thorsten; Holland, Frank; Li, Xin; Rohrer, Franz; Kiendler-Scharr, Astrid; Tillmann, Ralf; Wegener, Robert; Yu, Zhujun; Zou, Qi; Wahner, Andreas
      Atmospheric Measurement Techniques (2017), 10 (10), 4023-4053CODEN: AMTTC2; ISSN:1867-8548. (Copernicus Publications)
      Hydroxyl (OH) radical reactivity (kOH) has been measured for 18 years with different measurement techniques. In order to compare the performances of instruments deployed in the field, two campaigns were conducted performing expts. in the atm. simulation chamber SAPHIR at Forschungszentrum Juelich in Oct. 2015 and Apr. 2016. Chem. conditions were chosen either to be representative of the atm. or to test potential limitations of instruments. All types of instruments that are currently used for atm. measurements were used in one of the two campaigns. The results of these campaigns demonstrate that OH reactivity can be accurately measured for a wide range of atmospherically relevant chem. conditions (e.g. water vapor, nitrogen oxides, various org. compds.) by all instruments. The precision of the measurements (limit of detection<1 s-1 at a time resoln. of 30 s to a few minutes) is higher for instruments directly detecting hydroxyl radicals, whereas the indirect comparative reactivity method (CRM) has a higher limit of detection of 2 s-1 at a time resoln. of 10 to 15 min. The performances of the instruments were systematically tested by stepwise increasing, for example, the concns. of carbon monoxide (CO), water vapor or nitric oxide (NO). In further expts., mixts. of org. reactants were injected into the chamber to simulate urban and forested environments. Overall, the results show that the instruments are capable of measuring OH reactivity in the presence of CO, alkanes, alkenes and arom. compds. The transmission efficiency in Teflon inlet lines could have introduced systematic errors in measurements for low-volatile org. compds. in some instruments. CRM instruments exhibited a larger scatter in the data compared to the other instruments. The largest differences to ref. measurements or to calcd. reactivity were obsd. by CRM instruments in the presence of terpenes and oxygenated org. compds. (mixing ratio of OH reactants were up to 10 ppbv). In some of these expts., only a small fraction of the reactivity is detected. The accuracy of CRM measurements is most likely limited by the corrections that need to be applied to account for known effects of, for example, deviations from pseudo first-order conditions, nitrogen oxides or water vapor on the measurement. Methods used to derive these corrections vary among the different CRM instruments. Measurements taken with a flowtube instrument combined with the direct detection of OH by chem. ionisation mass spectrometry (CIMS) show limitations in cases of high reactivity and high NO concns. but were accurate for low reactivity (<15 s-1) and low NO (<5 ppbv) conditions.
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    37. 37
      Sinha, V.; Williams, J.; Crowley, J. N.; Lelieveld, J. The Comparative Reactivity Method – a New Tool to Measure Total OH Reactivity in Ambient Air. Atmos. Chem. Phys. 2008, 8, 2213– 2227,  DOI: 10.5194/acp-8-2213-2008
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      The comparative reactivity method - a new tool to measure total OH reactivity in ambient air
      Sinha, V.; Williams, J.; Crowley, J. N.; Lelieveld, J.
      Atmospheric Chemistry and Physics (2008), 8 (8), 2213-2227CODEN: ACPTCE; ISSN:1680-7316. (Copernicus Publications)
      Hydroxyl (OH) radicals play a vital role in maintaining the oxidizing capacity of the atm. To understand variations in OH radicals both source and sink terms must be understood. Currently the overall sink term, or the total atm. reactivity to OH, is poorly constrained. Here, we present a new online method to directly measure the total OH reactivity (i.e. total loss rate of OH radicals) in a sampled air mass. In this method, a reactive mol. (X), not normally present in air, is passed through a glass reactor and its concn. is monitored with a suitable detector. OH radicals are then introduced in the glass reactor at a const. rate to react with X, first in the presence of zero air and then in the presence of ambient air contg. VOCs and other OH reactive species. Comparing the amt. of X exiting the reactor with and without the ambient air allows the air reactivity to be detd. In our existing set up, X is pyrrole and the detector used is a proton transfer reaction mass spectrometer. The present dynamic range for ambient air reactivity is about 6 to 300 s-1, with an overall max. uncertainty of 25% above 8 s-1 and up to 50% between 6-8 s-1. The system has been tested and calibrated with different single and mixed hydrocarbon stds. showing excellent linearity and accountability with the reactivity of the stds. Potential interferences such as high NO in ambient air, varying relative humidity and photolysis of pyrrole within the setup have also been investigated. While interferences due changing humidity and photolysis of pyrrole are easily overcome by ensuring that humidity in the set up does not change drastically and the photolytic loss of pyrrole is measured and taken into account, resp., NO> 10 ppb in ambient air remains a significant interference for the current configuration of the instrument. Field tests in the tropical rainforest of Suriname (∼53 s-1) and the urban atm. of Mainz (∼10 s-1) Germany, show the promise of the new method and indicate that a significant fraction of OH reactive species in the tropical forests is likely missed by current measurements. Suggestions for improvements to the technique and future applications are discussed.
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      Lindinger, W.; Jordan, A. Proton-Transfer-Reaction Mass Spectrometry (PTR–MS): On-Line Monitoring of Volatile Organic Compounds at Pptv Levels. Chem. Soc. Rev. 1998, 27, 347– 375,  DOI: 10.1039/a827347z
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      Proton-transfer-reaction mass spectrometry (PTR-MS): online monitoring of volatile organic compounds at pptv levels
      Lindinger, W.; Jordan, A.
      Chemical Society Reviews (1998), 27 (5), 347-354CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      A review with 32 refs. A system for online measurements of trace components with concns. as low as a few pptv was developed from proton transfer reactions. Medical applications by breath anal. allow the monitoring of metabolic processes in the human body, examples of food research include studies of volatile org. compd. (VOC) emissions from fruit, coffee and meat. Studies of VOC emissions from decaying biomatter and online monitoring of the diurnal variations of VOCs in ambient air are typical examples of environmental applications.
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      Atkinson, R.; Aschmann, S. M.; Winer, A. M.; Carter, W. P. L. Rate Constants for the Gas Phase Reactions of OH Radicals and O3 with Pyrrole at 295 ± 1 K and Atmospheric Pressure. Atmos. Environ. (1967) 1984, 18, 2105– 2107,  DOI: 10.1016/0004-6981(84)90196-3
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      Rate constants for the gas phase reactions of hydroxyl radicals and ozone with pyrrole at 295 ± 1 K and atmospheric pressure
      Atkinson, Roger; Aschmann, Sara M.; Winer, Arthur M.; Carter, William P. L.
      Atmospheric Environment (1967-1989) (1984), 18 (10), 2105-7CODEN: ATENBP; ISSN:0004-6981.
      As part of a program to investigate the atm. chem. and lifetimes of heteroatom-contg. orgs., rate consts. were detd. for the reaction of OH radicals and O3 with pyrrole [109-97-7] in 1 atm. of air at 295 ± 1 K. The rate consts. obtained were 1.20 × 10-10 and 1.57 × 10-17 cm3/mol-s for reaction with OH radicals and O3, resp. With these rate consts., it can be calcd. that under atm. conditions, the major loss process of pyrrole will be via reaction with the OH radical, with a lifetime due to reaction with OH radicals of ∼2 h at a OH radical concn. of 1 × 106 mol./cm3.
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      Dillon, T. J.; Tucceri, M. E.; Dulitz, K.; Horowitz, A.; Vereecken, L.; Crowley, J. N. Reaction of Hydroxyl Radicals with C4H5N (Pyrrole): Temperature and Pressure Dependent Rate Coefficients. J. Phys. Chem. A 2012, 116, 6051– 6058,  DOI: 10.1021/jp211241x
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      Reaction of Hydroxyl Radicals with C4H5N (Pyrrole): Temperature and Pressure Dependent Rate Coefficients
      Dillon, Terry J.; Tucceri, Maria E.; Dulitz, Katrin; Horowitz, Abraham; Vereecken, Luc; Crowley, John N.
      Journal of Physical Chemistry A (2012), 116 (24), 6051-6058CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
      Abs. (pulsed laser photolysis, 4-639 torr N2 or air, 240-357 K) and relative rate methods (50 and 760 torr air, 296 K) were used to measure rate coeffs. k1 for the title reaction, OH + C4H5N → products (R1). Although the pressure and temp. dependent rate coeff. is adequately represented by a falloff parametrization, calcns. of the potential energy surface indicate a complex reaction system with multiple reaction paths (addn. only) in the falloff regime. At 298 K and 760 torr (1 torr = 1.33 mbar) the rate coeff. obtained from the parametrization is k1 = (1.28 ± 0.1) × 10-10 cm3 mol.-1 s-1, in good agreement with the value of (1.10 ± 0.27) × 10-10 cm3 mol.-1 s-1 obtained in the relative rate study (relative to C5H8, isoprene) at this temp. and pressure. The accuracy of the abs. rate coeff. detn. was enhanced by online optical absorption measurements of the C4H5N concn. at 184.95 nm using a value σ184.95nm = (1.26 ± 0.02) × 10-17 cm2 mol.-1, which was detd.
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      Zannoni, N.; Dusanter, S.; Gros, V.; Sarda Esteve, R.; Michoud, V.; Sinha, V.; Locoge, N.; Bonsang, B. Intercomparison of Two Comparative Reactivity Method Instruments Inf the Mediterranean Basin during Summer 2013. Atmos. Meas. Tech. 2015, 8, 3851– 3865,  DOI: 10.5194/amt-8-3851-2015
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      Michoud, V.; Hansen, R. F.; Locoge, N.; Stevens, P. S.; Dusanter, S. Detailed Characterizations of the New Mines Douai Comparative Reactivity Method Instrument via Laboratory Experiments and Modeling. Atmos. Meas. Tech. 2015, 8, 3537– 3553,  DOI: 10.5194/amt-8-3537-2015
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      Li, M.; Weschler, C. J.; Bekö, G.; Wargocki, P.; Lucic, G.; Williams, J. Human Ammonia Emission Rates under Various Indoor Environmental Conditions. Environ. Sci. Technol. 2020, 54, 5419– 5428,  DOI: 10.1021/acs.est.0c00094
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      Human Ammonia Emission Rates under Various Indoor Environmental Conditions
      Li, Mengze; Weschler, Charles J.; Bekoe, Gabriel; Wargocki, Pawel; Lucic, Gregor; Williams, Jonathan
      Environmental Science & Technology (2020), 54 (9), 5419-5428CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      NH3 is typically present at higher concns. in indoor air(∼10-70 ppb) vs. outdoor air (∼50 ppt to 5 ppb). It is the dominant neutralizer of acidic species in indoor environments, strongly affecting partitioning of gaseous acidic and basic species to aerosols, surface films, and bulk water. The authors measured NH3 emissions from humans in an environmentally-controlled chamber. Expts., each with four volunteers, quantified NH3 emissions as a function of temp. (25.1-32.6°), clothing (long-sleeved shirts/pants or T-shirts/shorts), age (teenagers, adults, seniors), relative humidity (low or high), and O3 (<2 to ∼35 ppb). Higher temp. and more skin exposure (T-shirts/shorts) significantly increased emission rates. For adults and seniors (long clothing), NH3 emissions were estd. to be 0.4 mg/h-person at 25°, 0.8 mg/h-person at 27°, and 1.4 mg/h-person at 29°, based on the temp. relationship obsd. in this work. Human NH3 emissions are sufficient to neutralize the acidifying impacts of human CO2 emissions. Results can be used to more accurately model indoor and inner-city outdoor NH3 concns. and assocd. chem.
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      Zhao, J.; Zhang, R. Proton Transfer Reaction Rate Constants between Hydronium Ion (H3O+) and Volatile Organic Compounds. Atmos. Environ. 2004, 38, 2177– 2185,  DOI: 10.1016/j.atmosenv.2004.01.019
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      Proton transfer reaction rate constants between hydronium ion (H3O+) and volatile organic compounds
      Zhao, Jun; Zhang, Renyi
      Atmospheric Environment (2004), 38 (14), 2177-2185CODEN: AENVEQ; ISSN:1352-2310. (Elsevier Science B.V.)
      We report proton transfer reaction rate consts. between the hydronium ion (H3O+) and selected atmospherically important volatile org. compds. (VOCs). The quantum chem. method was used to det. the structures of the org. species employing the d. function theory-B3LYP. The ion-mol. reaction rates were detd. using the av.-dipole-orientation theory, along with the permanent dipole moment and polarizability of the org. species predicted from the quantum chem. calcns. The theor. results are compared to available literature data of the permanent dipole moment, polarizability, and ion-mol. reaction rate. The newly calcd. proton transfer rate consts. facilitate the use of the proton transfer reaction mass spectrometry (PTR-MS) technique in applications of lab. investigation of photochem. hydrocarbon oxidn. reactions and field measurements of the abundance of VOCs.
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      Bourtsoukidis, E.; Helleis, F.; Tomsche, L.; Fischer, H.; Hofmann, R.; Lelieveld, J.; Williams, J. An Aircraft Gas Chromatograph–Mass Spectrometer System for Organic Fast Identification Analysis (SOFIA): Design, Performance and a Case Study of Asian Monsoon Pollution Outflow. Atmos. Meas. Tech. 2017, 10, 5089– 5105,  DOI: 10.5194/amt-10-5089-2017
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      An aircraft gas chromatograph-mass spectrometer System for Organic Fast Identification Analysis (SOFIA): design, performance and a case study of Asian monsoon pollution outflow
      Bourtsoukidis, Efstratios; Helleis, Frank; Tomsche, Laura; Fischer, Horst; Hofmann, Rolf; Lelieveld, Jos; Williams, Jonathan
      Atmospheric Measurement Techniques (2017), 10 (12), 5089-5105CODEN: AMTTC2; ISSN:1867-8548. (Copernicus Publications)
      Here, we present a new System for Org. Fast Identification Anal. (SOFIA), which is a custom-built fast gas chromatog.-mass spectrometry (GC-MS) system with a time resoln. of 2-3 min and the ability to quantify atm. mixing ratios of halocarbons (e.g. chloromethanes), hydrocarbons (e.g isoprene), oxygenated VOCs (acetone, propanal, butanone) and aroms. (e.g. benzene, toluene) from sub-ppt to ppb levels. The relatively high time resoln. is the result of a novel cryogenic pre-concn. unit which rapidly cools ( ∼6°C s-1) the sample enrichment traps to -140°C, and a new chromatog. oven designed for rapid cooling rates (∼30°C s-1) and subsequent thermal stabilization. SOFIA was installed in the High Altitude and Long Range Research Aircraft (HALO) for the Oxidn. Mechanism Observations (OMO) campaign in August 2015, aimed at investigating the Asian monsoon pollution outflow in the tropical upper troposphere. In addn. to a comprehensive instrument characterization we present an example monsoon plume crossing flight as a case study to demonstrate the instrument capability. Hydrocarbon, halocarbon and oxygenated VOC data from SOFIA are compared with mixing ratios of carbon monoxide (CO) and methane (CH4), used to define the pollution plume. By using excess (ExMR) and normalized excess mixing ratios (NEMRs) the pollution could be attributed to two air masses of distinctly different origin, identified by back-trajectory anal.
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      A formula to estimate the approximate surface area if height and weight be known. 1916
      Du Bois D; Du Bois E F
      Nutrition (Burbank, Los Angeles County, Calif.) (1989), 5 (5), 303-11; discussion 312-3 ISSN:0899-9007.
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      US EPA. National Center for Environmental Assessment, W. D. Exposure Factors Handbook 2011th ed. (Final Report). https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=236252 (accessed March 12, 2021).
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      Azen, R.; Budescu, D. V. The Dominance Analysis Approach for Comparing Predictors in Multiple Regression. Psychol. Methods 2003, 8, 129– 148,  DOI: 10.1037/1082-989X.8.2.129
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      The dominance analysis approach for comparing predictors in multiple regression
      Azen Razia; Budescu David V
      Psychological methods (2003), 8 (2), 129-48 ISSN:1082-989X.
      A general method is presented for comparing the relative importance of predictors in multiple regression. Dominance analysis (D. V. Budescu, 1993), a procedure that is based on an examination of the R2 values for all possible subset models, is refined and extended by introducing several quantitative measures of dominance that differ in the strictness of the dominance definition. These are shown to be intuitive, meaningful, and informative measures that can address a variety of research questions pertaining to predictor importance. The bootstrap is used to assess the stability of dominance results across repeated sampling, and it is shown that these methods provide the researcher with more insights into the pattern of importance in a set of predictors than were previously available.
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      Azen, R.; Budescu, D. V. Comparing Predictors in Multivariate Regression Models: An Extension of Dominance Analysis. J. Educ. Behav. Stat. 2006, 31, 157– 180,  DOI: 10.3102/10769986031002157
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      Azen, R.; Budescu, D. V.; Reiser, B. Criticality of Predictors in Multiple Regression. Br. J. Math. Stat. Psychol. 2001, 54, 201– 225,  DOI: 10.1348/000711001159483
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      Criticality of predictors in multiple regression
      Azen R; Budescu D V; Reiser B
      The British journal of mathematical and statistical psychology (2001), 54 (Pt 2), 201-25 ISSN:0007-1102.
      A new method is proposed for comparing all predictors in a multiple regression model. This method generates a measure of predictor criticality, which is distinct from and has several advantages over traditional indices of predictor importance. Using the bootstrapping (resampling with replacement) procedure, a large number of samples are obtained from a given data set which contains one response variable and p predictors. For each sample, all 2p-1 subset regression models are fitted and the best subset model is selected. Thus, the (multinomial) distribution of the probability that each of the 2p-1 subsets is 'the best' model for the data set is obtained. A predictor's criticality is defined as a function of the probabilities associated with the models that include the predictor. That is, a predictor which is included in a large number of probable models is critical to the identification of the best-fitting regression model and, therefore, to the prediction of the response variable. The procedure can be applied to fixed and random regression models and can use any measure of goodness of fit (e.g., adjusted R2, Cp, AIC) for identifying the best model. Several criticality measures can be defined by using different combinations of the probabilities of the best-fitting models, and asymptotic confidence intervals for each variable's criticality can be derived. The procedure is illustrated with several examples.
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      Lakey, P. S. J.; Morrison, G. C.; Won, Y.; Parry, K. M.; von Domaros, M.; Tobias, D. J.; Rim, D.; Shiraiwa, M. The Impact of Clothing on Ozone and Squalene Ozonolysis Products in Indoor Environments. Commun. Chem. 2019, 2, 56  DOI: 10.1038/s42004-019-0159-7
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      Rai, A. C.; Guo, B.; Lin, C.-H.; Zhang, J.; Pei, J.; Chen, Q. Ozone Reaction with Clothing and Its Initiated VOC Emissions in an Environmental Chamber. Indoor Air 2014, 24, 49– 58,  DOI: 10.1111/ina.12058
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      Ozone reaction with clothing and its initiated VOC emissions in an environmental chamber
      Rai, A. C.; Guo, B.; Lin, C.-H.; Zhang, J.; Pei, J.; Chen, Q.
      Indoor Air (2014), 24 (1), 49-58CODEN: INAIE5; ISSN:0905-6947. (Wiley-Blackwell)
      Human health is adversely affected by ozone and the volatile org. compds. (VOCs) produced from its reactions in the indoor environment. Hence, it is important to characterize the ozone-initiated reactive chem. under indoor conditions and study the influence of different factors on these reactions. This investigation studied the ozone reactions with clothing through a series of expts. conducted in an environmental chamber under various conditions. The study found that the ozone reactions with a soiled (human-worn) T-shirt consumed ozone and generated VOCs. The ozone removal rate and deposition velocity for the T-shirt increased with the increasing soiling level and air change rate, decreased at high ozone concns., and were relatively unaffected by the humidity. The deposition velocity for the soiled T-shirt ranged from 0.15 to 0.29 cm/s. The ozone-initiated VOC emissions included C6-C10 straight-chain satd. aldehydes, acetone, and 4-OPA (4-oxopentanal). The VOC emissions were generally higher at higher ozone, humidity, soiling of T-shirt, and air change rate. The total molar yield was approx. 0.5 in most cases, which means that for every two moles of ozone removed by the T-shirt surface, one mole of VOCs was produced.
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      Anderson, S. E.; Franko, J.; Jackson, L. G.; Wells, J. R.; Ham, J. E.; Meade, B. J. Irritancy and Allergic Responses Induced by Exposure to the Indoor Air Chemical 4-Oxopentanal. Toxicol. Sci. 2012, 127, 371– 381,  DOI: 10.1093/toxsci/kfs102
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      Irritancy and Allergic Responses Induced by Exposure to the Indoor Air Chemical 4-Oxopentanal
      Anderson, Stacey E.; Franko, Jennifer; Jackson, Laurel G.; Wells, J. R.; Ham, Jason E.; Meade, B. J.
      Toxicological Sciences (2012), 127 (2), 371-381CODEN: TOSCF2; ISSN:1096-0929. (Oxford University Press)
      Over the last 2 decades, there was an increasing awareness regarding the potential impact of indoor air pollution on human health. People working in an indoor environment often experience symptoms such as eye, nose, and throat irritation. Investigations into these complaints have ascribed the effects, in part, to compds. emitted from building materials, cleaning/consumer products, and indoor chem. One suspect indoor air contaminant that was identified is the dicarbonyl 4-oxopentanal (4-OPA). The 4-OPA is generated through the ozonolysis of squalene and several high-vol. prodn. compds. that are commonly found indoors. Following preliminary workplace sampling that identified the presence of 4-OPA, these studies examd. the inflammatory and allergic responses to 4-OPA following both dermal and pulmonary exposure using a murine model. The 4-OPA was tested in a combined local lymph node assay and identified to be an irritant and sensitizer. A Th1-mediated hypersensitivity response was supported by a pos. response in the mouse ear swelling test. Pulmonary exposure to 4-OPA caused a significant elevation in nonspecific airway hyperreactivity, increased nos. of lung-assocd. lymphocytes and neutrophils, and increased interferon-γ prodn. by lung-assocd. lymph nodes. These results suggest that both dermal and pulmonary exposure to 4-OPA may elicit irritant and allergic responses and may help to explain some of the adverse health effects assocd. with poor indoor air quality.
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      Wolkoff, P. Indoor Air Pollutants in Office Environments: Assessment of Comfort, Health, and Performance. Int. J. Hyg. Environ. Health 2013, 216, 371– 394,  DOI: 10.1016/j.ijheh.2012.08.001
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      Indoor air pollutants in office environments: Assessment of comfort, health, and performance
      Wolkoff, Peder
      International Journal of Hygiene and Environmental Health (2013), 216 (4), 371-394CODEN: IJEHFT; ISSN:1438-4639. (Elsevier GmbH)
      A review. Concns. of volatile org. compds. (VOCs) in office environments are generally too low to cause sensory irritation in the eyes and airways on the basis of estd. thresholds for sensory irritation. Furthermore, effects in the lungs, e.g. inflammatory effects, have not been substantiated at indoor relevant concns. Some VOCs, including formaldehyde, in combination may under certain environmental and occupational conditions result in reported sensory irritation. The odor thresholds of several VOCs are low enough to influence the perceived air quality that result in a no. of acute effects from reported sensory irritation in eyes and airways and deterioration of performance. The odor perception (air quality) depends on a no. of factors that may influence the odor impact. There is neither clear indication that office dust particles may cause sensory effects, even not particles spiked with glucans, aldehydes or phthalates, nor lung effects; some inflammatory effects may be obsd. among asthmatics. Ozone-initiated terpene reaction products may be of concern in ozone-enriched environments (≥0.1 mg/m3) and elevated limonene concns., partly due to the prodn. of formaldehyde. Ambient particles may cause cardio-pulmonary effects, esp. in susceptible people (e.g. elderly and sick people); even, short-term effects, e.g. from traffic emission and candle smoke may possibly have modulating and delayed effects on the heart, but otherwise adverse effects in the airways and lung functions have not been obsd. Secondary org. aerosols generated in indoor ozone-initiated terpene reactions appear not to cause adverse effects in the airways; rather the gaseous products are relevant. Combined exposure to particles and ozone may evoke effects in subgroups of asthmatics.Based on an anal. of thresholds for odor and sensory irritation selected compds. are recommended for measurements to assess the indoor air quality and to minimize reports of irritation symptoms, deteriorated performance, and cardiovascular and pulmonary effects.
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      Mitchell, C. S.; Zhang, J. J.; Sigsgaard, T.; Jantunen, M.; Lioy, P. J.; Samson, R.; Karol, M. H. Current State of the Science: Health Effects and Indoor Environmental Quality. Environ. Health Perspect. 2007, 115, 958– 964,  DOI: 10.1289/ehp.8987
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      Current state of the science: health effects and indoor environmental quality
      Mitchell Clifford S; Zhang Junfeng Jim; Sigsgaard Torben; Jantunen Matti; Lioy Paul J; Samson Robert; Karol Meryl H
      Environmental health perspectives (2007), 115 (6), 958-64 ISSN:0091-6765.
      Our understanding of the relationship between human health and the indoor environment continues to evolve. Previous research on health and indoor environments has tended to concentrate on discrete pollutant sources and exposures and on specific disease processes. Recently, efforts have been made to characterize more fully the complex interactions between the health of occupants and the interior spaces they inhabit. In this article we review recent advances in source characterization, exposure assessment, health effects associated with indoor exposures, and intervention research related to indoor environments. Advances in source characterization include a better understanding of how chemicals are transported and processed within spaces and the role that other factors such as lighting and building design may play in determining health. Efforts are under way to improve our ability to measure exposures, but this remains a challenge, particularly for biological agents. Researchers are also examining the effects of multiple exposures as well as the effects of exposures on vulnerable populations such as children and the elderly. In addition, a number of investigators are also studying the effects of modifying building design, materials, and operations on occupant health. Identification of research priorities should include input from building designers, operators, and the public health community.
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      Dolgorouky, C.; Gros, V.; Sarda-Esteve, R.; Sinha, V.; Williams, J.; Marchand, N.; Sauvage, S.; Poulain, L.; Sciare, J.; Bonsang, B. Total OH Reactivity Measurements in Paris during the 2010 MEGAPOLI Winter Campaign. Atmos. Chem. Phys. 2012, 12, 9593– 9612,  DOI: 10.5194/acp-12-9593-2012
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      Total OH reactivity measurements in Paris during the 2010 MEGAPOLI winter campaign
      Dolgorouky, C.; Gros, V.; Sarda-Esteve, R.; Sinha, V.; Williams, J.; Marchand, N.; Sauvage, S.; Poulain, L.; Sciare, J.; Bonsang, B.
      Atmospheric Chemistry and Physics (2012), 12 (20), 9593-9612CODEN: ACPTCE; ISSN:1680-7316. (Copernicus Publications)
      Hydroxyl radicals play a central role in the troposphere as they control the lifetime of many trace gases. Measurement of OH reactivity (OH loss rate) is important to better constrain the OH budget and also to evaluate the completeness of measured VOC budget. Total atm. OH reactivity was measured for the first time in an European Megacity: Paris and its surrounding areas with 12 million inhabitants, during the MEGAPOLI winter campaign 2010. The method deployed was the Comparative Reactivity Method (CRM). The measured dataset contains both measured and calcd. OH reactivity from CO, NOx and VOCs measured via PTR-MS, GC-FID and GC-MS instruments. The reactivities obsd. in Paris covered a range from 10 s-1 to 130 s-1, indicating a large loading of chem. reactants. The present study showed that, when clean marine air masses influenced Paris, the purely local OH reactivity (20 s-1) is well explained by the measured species. Nevertheless, when there is a continental import of air masses, high levels of OH reactivity were obtained (120-130 s-1) and the missing OH reactivity measured in this case jumped to 75%. Using covariations of the missing OH reactivity to secondary inorg. species in fine aerosols, we suggest that the missing OH reactants were most likely highly oxidized compds. issued from photochem. processed air masses of anthropogenic origin.
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      Ren, X. HOx Concentrations and OH Reactivity Observations in New York City during PMTACS-NY2001. Atmos. Environ. 2003, 37, 3627– 3637,  DOI: 10.1016/S1352-2310(03)00460-6
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      HOx concentrations and OH reactivity observations in New York City during PMTACS-NY2001
      Ren, Xinrong; Harder, Hartwig; Martinez, Monica; Lesher, Robert L.; Oliger, Angelique; Shirley, Terry; Adams, Jennifer; Simpas, James B.; Brune, William H.
      Atmospheric Environment (2003), 37 (26), 3627-3637CODEN: AENVEQ; ISSN:1352-2310. (Elsevier Science B.V.)
      Hydroxyl (OH) and hydroperoxy (HO2) radicals (collectively called HOx) were measured by a laser-induced fluorescence instrument during the PMTACS-NY (PM2.5 Technol. Assessment and Characterization Study-New York) intensive campaign in New York City in summer 2001. Measurement results for OH and HO2 are presented for the month-long study. The detection limits were about 3.0×105 cm-3 for OH and 2.5×106 cm-3 (∼0.1 ppt) for HO2 with a 1-min integration time and a 2σ confidence level. The daytime max. concns. were 5-20×106 cm-3 for OH and 0.4-6×108 cm-3 (2-24 pptv) for HO2, usually appearing later than the peak of ozone photolysis frequency, J(O1D). Relative high OH and HO2 persisted into early evening and were frequently obsd. during nighttime. The ratios of HO2 to OH were typically between 5 and 40, which are smaller than those obtained in relatively clean environments. The OH reactivity, measured by an instrument named total OH loss rate measurement was on av. 19±3 s-1 in this urban environment. It was the highest in the morning and the lowest in the afternoon. The comparison of measured OH and HO2 with model calcns. is given in a companion paper (OH and HO2 chem. in the urban atm. of New York City, Atm. Environment (2003a) this issue).
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    58. 58
      Williams, J.; Keßel, S. U.; Nölscher, A. C.; Yang, Y.; Lee, Y.; Yáñez-Serrano, A. M.; Wolff, S.; Kesselmeier, J.; Klüpfel, T.; Lelieveld, J.; Shao, M. Opposite OH Reactivity and Ozone Cycles in the Amazon Rainforest and Megacity Beijing: Subversion of Biospheric Oxidant Control by Anthropogenic Emissions. Atmos. Environ. 2016, 125, 112– 118,  DOI: 10.1016/j.atmosenv.2015.11.007
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      Opposite OH reactivity and ozone cycles in the Amazon rainforest and megacity Beijing: Subversion of biospheric oxidant control by anthropogenic emissions
      Williams, Jonathan; Kessel, Stephan U.; Noelscher, Anke C.; Yang, Yudong; Lee, Yue; Yanez-Serrano, Ana Maria; Wolff, Stefan; Kesselmeier, Juergen; Kluepfel, Thomas; Lelieveld, Jos; Shao, Min
      Atmospheric Environment (2016), 125 (Part_A), 112-118CODEN: AENVEQ; ISSN:1352-2310. (Elsevier Ltd.)
      The Amazon rainforest in Brazil and the megacity of Beijing in China are two of the most strongly contrasting habitats on Earth. In both locations, volatile chems. are emitted into the atm. affecting the local atm. chem., air quality and ecosystem health. In this study, the total reactivity in air available for reaction with the atm.'s primary oxidant the OH radical, has been measured directly in both locations along with individual volatile org. compds.(VOC), nitrogen oxides(NOx), ozone(O3) and carbon dioxide(CO2). Peak daily OH-reactivity in the Amazon 72 s-1, (min. 27 s-1) was approx. three times higher than Beijing 26 s-1 (min. 15 s-1). However, diel ozone variation in Amazonia was small (∼5 ppb) whereas in Beijing ∼70 ppb harmful photochem. ozone was produced by early afternoon. Amazon OH-reactivity peaked by day, was strongly impacted by isoprene, and anticorrelated to CO2, whereas in Beijing OH-reactivity was higher at night rising to a rush hour peak, was dominated by NO2 and correlated with CO2. These converse diel cycles between urban and natural ecosystems demonstrate how biosphere control of the atm. environment is subverted by anthropogenic emissions.
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      Zannoni, N.; Gros, V.; Lanza, M.; Sarda, R.; Bonsang, B.; Kalogridis, C.; Preunkert, S.; Legrand, M.; Jambert, C.; Boissard, C.; Lathiere, J. OH Reactivity and Concentrations of Biogenic Volatile Organic Compounds in a Mediterranean Forest of Downy Oak Trees. Atmos. Chem. Phys. 2016, 16, 1619– 1636,  DOI: 10.5194/acp-16-1619-2016
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      OH reactivity and concentrations of biogenic volatile organic compounds in a Mediterranean forest of downy oak trees
      Zannoni, N.; Gros, V.; Lanza, M.; Sarda, R.; Bonsang, B.; Kalogridis, C.; Preunkert, S.; Legrand, M.; Jambert, C.; Boissard, C.; Lathiere, J.
      Atmospheric Chemistry and Physics (2016), 16 (3), 1619-1636CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      Total OH reactivity, defined as the total loss frequency of the hydroxyl radical in the atm., has proved to be an excellent tool to identify the total loading of reactive species in ambient air. High levels of unknown reactivity were found in several forests worldwide and were often higher than at urban sites. Our study presents atm. mixing ratios of biogenic compds. and total OH reactivity measured during late spring 2014 at the forest of downy oak trees of the Observatoire de Haute Provence (OHP), France. Air masses were sampled at two heights: 2 m, i.e., inside the canopy, and 10 m, i.e., above the canopy, where the mean canopy height is 5 m. We found that the OH reactivity at the site mainly depended on the main primary biogenic species emitted by the forest, which was isoprene and to a lesser extent by its degrdn. products and long-lived atm. compds. (up to 26% during daytime). During daytime, no significant missing OH reactivity was reported at the site, either inside or above the canopy. However, during two nights we detd. a missing fraction of OH reactivity up to 50 %, possibly due to unmeasured oxidn. products. We confirmed that no significant oxidn. of the primary species occurred within the canopy; primary compds. emitted by the forest were fast transported to the atm. Finally, the OH reactivity at this site was max. 69 s-1, which is a high value for a forest characterized by a temperate climate. Observations in various and diverse forests in the Mediterranean region are therefore needed to better constrain the impact of reactive gases over this area.
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      Wisthaler, A.; Tamás, G.; Wyon, D. P.; Strøm-Tejsen, P.; Space, D.; Beauchamp, J.; Hansel, A.; Märk, T. D.; Weschler, C. J. Products of Ozone-Initiated Chemistry in a Simulated Aircraft Environment. Environ. Sci. Technol. 2005, 39, 4823– 4832,  DOI: 10.1021/es047992j
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      Products of Ozone-Initiated Chemistry in a Simulated Aircraft Environment
      Wisthaler, Armin; Tamas, Gyoengyi; Wyon, David P.; Strom-Tejsen, Peter; Space, David; Beauchamp, Jonathan; Hansel, Armin; Maerk, Tilmann D.; Weschler, Charles J.
      Environmental Science and Technology (2005), 39 (13), 4823-4832CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      We used proton-transfer-reaction mass spectrometry (PTR-MS) to examine the products formed when ozone reacted with the materials in a simulated aircraft cabin, including a loaded high-efficiency particulate air (HEPA) filter in the return air system. Four conditions were examd.: cabin (baseline), cabin plus ozone, cabin plus soiled T-shirts (surrogates for human occupants), and cabin plus soiled T-shirts plus ozone. The addn. of ozone to the cabin without T-shirts, at concns. typically encountered during com. air travel, increased the mixing ratio (vol.:vol. concn.) of detected pollutants from 35 to 80 ppb. Most of this increase was due to the prodn. of satd. and unsatd. aldehydes and tentatively identified low-mol.-wt. carboxylic acids. The addn. of soiled T-shirts, with no ozone present, increased the mixing ratio of pollutants in the cabin air only slightly, whereas the combination of soiled T-shirts and ozone increased the mixing ratio of detected pollutants to 110 ppb, with >20 ppb originating from squalene oxidn. products (acetone, 4-oxopentanal, and 6-methyl-5-hepten-2-one). For the 2 conditions with ozone present, the more-abundant oxidn. products included acetone/propanal (8-20 ppb), formaldehyde (8-10 ppb), nonanal (∼6 ppb), 4-oxopentanal (3-7 ppb), acetic acid (∼7 ppb), formic acid (∼3 ppb), and 6-methyl-5-hepten-2-one (0.5-2.5 ppb), as well as compds. tentatively identified as acrolein (0.6-1 ppb) and crotonaldehyde (0.6-0.8 ppb). The odor thresholds of certain products were exceeded. With an outdoor air exchange of 3/h and a recirculation rate of 20/h, the measured ozone surface removal rate const. was 6.3/h when T-shirts were not present, compared to 11.4/h when T-shirts were present.
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    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.est.1c01831.

    • Experimental conditions included in this study (Table S1); volatile organic compounds and their classification in compounds classes used to determine the summed calculated OH reactivity (Table S2); speciated OH reactivity from occupants wearing long clothing and short clothing, before ozone exposure, with ozone added at the steady state of emissions (afternoon), and with ozone added from the beginning of the experiment (Figure S1); 10 most reactive volatile organic compounds emitted by four adult volunteers wearing long clothing and short clothing exposed to ozone from start of the experiment and in the afternoon, from SS of the emissions (Table S3); calculated O3 deposition velocity on four occupants (vocc), first-order rate constant for O3 loss (kd), measured 6-MHO, 4-OPA, geranyl acetone concentrations, and measured total OH reactivity at SS for each experimental condition (Table S4); ozone deposition velocity and OH reactivity of four clean and soiled (worn overnight ∼8 h) t-shirts, and corresponding parameters used (Table S5); 10 most reactive volatile organic compounds emitted by four adult volunteers wearing long clothing exposed to ozone, at moderate temperature and low RH, high temperature and low RH, and high temperature and high RH (Table S6); concentrations of 6-MHO, 4-OPA, and geranyl acetone measured in the chamber occupied by four adults from 9:30, wearing long clothing, and exposed to low/high temperature and low/high relative humidity (Figure S2); dominance analysis for the total OH reactivity of human beings, with varying conditions of ozone exposure, short/long clothing, volunteers groups, relative humidity, temperature, and age of volunteers (teens/adults/seniors) (Figure S3) (PDF)


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