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Triumph and Misery of Measurement ScienceClick to copy article linkArticle link copied!
- Eric Bakker
This publication is licensed for personal use by The American Chemical Society.
Living near Geneva, close to the shores of beautiful Lac Léman, the largest lake of the Alps, I tend to admire the view of the magnificent mountains on the French side. Those mountains act as natural filters for the rain and molten snow to emerge at a spring called Cachat near Évian-les-Bains. As you might know, this water is bottled without any additives as Evian, and distributed all over the world as premium spring water.
Just recently, in mid-July, I was surprised to see a headline in the news stating “Evian drinking water tainted with pesticides, Swiss researchers find”. (1) The story was shared by most local news outlets, and came at a volatile political time in Switzerland. Two popular initiatives, that aim to ban federal subsidies for farmers that use pesticides and herbicides, are currently being discussed in parliament, and will soon be voted on by the electorate.
So, what is going on? The research story showcases the power of modern analytical sciences to identify and track transformation products of synthetic substances—in this case, the fungicide chlorothalonil. It had been used for half a century until it was recently banned in the EU and Switzerland because of its suspected carcinogenic properties. The authors of the study, (2) Juliane Hollender and co-workers from the Swiss Federal Institute of Aquatic Science and Technology (Eawag), developed and applied analytical approaches to assess the fate of such molecules. Just last year, this group reported on transformation products of chlorothalonil in the environment, of which one key candidate, a polar, sulfonic acid derivative called R471811, was found for the very first time along with 11 other transformation products never reported before. (3) For this, the authors performed a targeted screening of all pesticides used in Switzerland in the past few years, a total of 396 organic molecules. Added to this list were 1120 possible transformation products they looked for. High resolution mass spectrometry, together with prioritization and identification routines, allowed the researchers to arrive at 187 detected suspect structures that were then further narrowed down and identified. The limit of quantitation for the technique, stated as about 0.5 ng L–1 (about 1 pM), was achieved by vacuum-assisted evaporative concentration of the samples followed by HPLC-MS/MS.
It turns out that the transformation product R471811, the toxicity of which is unclear, is detectable in all tested water sources, even where anthropogenic influences are known to be extremely low. This points to a high stability and environmental persistence of the compound. The average concentration in groundwater samples influenced by agriculture was 515 ng L–1. In contrast, the compound was found at 5 ng L–1 in Lake Zurich, and at 6 ng L–1 in Evian water (used as a gold standard for uncontaminated water). (2) If one would manually introduce R471811 into an untainted Lake Zurich (3.9 km3 water volume), how much would be needed to reach this concentration? Twenty kilograms. To compare, the FDA estimates an annual use of 6.8 million kg of chlorothalonil per year in the U.S. alone. (4)
For the measurement sciences, such studies are a triumph because they showcase the power of modern analytical techniques that can identify and quantify the fate of micropollutants in complex aquatic systems. For the chemical sensing community, on the other hand, this should serve to guide us where expectations lie. Think of the difficulty and complexity of this challenge the next time you are describing the detection of a pesticide with a sensor. Environmental systems are dynamic and complex, and pollutants will form transformation products that are chemically distinct from the parent molecule. And this will all happen in a complicated matrix at impossibly low concentrations.
For the general public, reading about pollutants found everywhere is certainly very distressing. But a challenging study such as this should be celebrated for what it is, and not reduced to a catchy but misleading headline. Concentrations do matter, as the Swiss alchemist Paracelsus already knew in the early 1500’s. We do not yet understand the toxicity of this transformation product, and of course such studies strongly suggest that we need to learn more. If we can detect something now that we could not before, one more piece of the puzzle of our interwoven and complicated world is being revealed. It allows us to make better decisions cautiously and accompanied by good science. To better grasp such complex systems, good data originating from the measurement sciences and a wider appreciation for complex problems, not only in the scientific community, but also in the wider public, is needed.
Author Information
- Eric Bakker, Executive Editor, The University of Geneva, Geneva, Switzerland,
http://orcid.org/0000-0001-8970-4343
References
This article references 4 other publications.
- 1Evian drinking water tainted with pesticides, Swiss researchers find; https://www.swissinfo.ch/eng/even-evian-drinking-water-tainted-wtih-pesticides--swiss-researchers-find/45898078 (Accessed on July 23, 2020).Google ScholarThere is no corresponding record for this reference.
- 2Kiefer, K.; Bader, T.; Minas, N.; Salhi, E.; Janssen, E. M.-L.; von Gunten, U.; Hollender, J. Chlorothalonil transformation products in drinking water resources: Widespread and challenging to abate. Water Res. 2020, 183, 116066, DOI: 10.1016/j.watres.2020.116066Google Scholar2https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhtlCkt7jE&md5=c8a906f0ad1914fd914e53d78566f8edChlorothalonil transformation products in drinking water resources: Widespread and challenging to abateKiefer, Karin; Bader, Tobias; Minas, Nora; Salhi, Elisabeth; Janssen, Elisabeth M.-L.; von Gunten, Urs; Hollender, JulianeWater Research (2020), 183 (), 116066CODEN: WATRAG; ISSN:0043-1354. (Elsevier Ltd.)Chlorothalonil, a fungicide applied for decades worldwide, has recently been banned in the European Union (EU) and Switzerland due to its carcinogenicity and the presence of potentially toxic transformation products (TPs) in groundwater. The chlorothalonil sulfonic acid TPs (R471811, R419492, R417888) occurred more frequently and at higher concns. (detected in 65-100% of the samples, ≤2200 ngL-1) than the phenolic TPs (SYN507900, SYN548580, R611968; detected in 10-30% of the samples, ≤130 ngL-1). The abatement of chlorothalonil TPs was investigated in lab. and pilot-scale expts. and along the treatment train of various water works, comprising aquifer recharge, UV disinfection, ozonation, advanced oxidn. processes (AOPs), activated carbon treatment, and reverse osmosis. In contrast, the sulfonic acid TPs, which occurred in higher concns. in drinking water resources, react only very slowly with ozone (kO3 <0.04 M-1s-1) and ·OH (kOH <5.0 x 107 M-1s-1) and therefore persist in ozonation and ·OH-based AOPs. Activated carbon retained the very polar TP R471811 only up to a specific throughput of 25 m3kg-1 (20% breakthrough), similarly to the X-ray contrast agent diatrizoic acid.
- 3Kiefer, K.; Müller, A.; Singer, H.; Hollender, J. New relevant pesticide transformation products in groundwater detected using target and suspect screening for agricultural and urban micropollutants with LC-HRMS. Water Res. 2019, 165, 114972, DOI: 10.1016/j.watres.2019.114972Google Scholar3https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhs1emsLnN&md5=9bb29e6932b0cf9b8337199a3649db48New relevant pesticide transformation products in groundwater detected using target and suspect screening for agricultural and urban micropollutants with LC-HRMSKiefer, Karin; Muller, Adrian; Singer, Heinz; Hollender, JulianeWater Research (2019), 165 (), 114972CODEN: WATRAG; ISSN:0043-1354. (Elsevier Ltd.)Groundwater is a major drinking water resource, but its quality is threatened by a broad variety of anthropogenic micropollutants (MPs), originating from agriculture, industry, or households, and undergoing various transformation processes during subsurface passage. To det. a worst-case impact of pesticide application in agriculture on groundwater quality, a target and suspect screening for more than 300 pesticides and more than 1100 pesticide transformation products (TPs) was performed in 31 Swiss groundwater samples which predominantly originated from areas with intensive agriculture. To assess addnl. urban contamination sources, more than 250 common urban MPs were quantified. Most of the screened pesticide TPs were exptl. obsd. by the pesticide producers within the European pesticide registration. To cover very polar pesticide TPs, vacuum-assisted evaporative concn. was used for enrichment, followed by liq. chromatog. high-resoln. tandem mass spectrometry (LC-HRMS/MS). Based on intensity, isotope pattern, retention time, and in silico fragmentation, the suspect hits were prioritised and verified. We identified 22 suspects unequivocally and five tentatively; 13 TPs are reported here for the first time to be detected in groundwater. In 13 out of 31 groundwater samples, the total concn. of the 20 identified and quantified suspects (1 pesticide and 19 pesticide TPs) exceeded the total concn. of the 519 targets (236 pesticides and TPs; 283 urban MPs) for which we screened. Pesticide TPs had higher concns. than the parent pesticides, illustrating their importance for groundwater quality. The newly identified very polar chlorothalonil TP R471811 was the only compd. detected in all samples with concns. ranging from 3 to 2700 ng/L. Agricultural MP concn. and detection frequency correlated with agricultural land use in the catchment, except for aquifers, where protective top layers reduced MP transport from the surface. In contrast to agricultural MPs, urban MPs displayed almost no correlation with land use. The dominating entry pathway of urban MPs was river bank filtration.
- 4Reregistration Eligibility Decision (RED): Chlorothalonil; US Environmental Protection Agency; https://archive.epa.gov/pesticides/reregistration/web/pdf/0097red.pdf (Accessed on July 23, 2020).Google ScholarThere is no corresponding record for this reference.
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References
This article references 4 other publications.
- 1Evian drinking water tainted with pesticides, Swiss researchers find; https://www.swissinfo.ch/eng/even-evian-drinking-water-tainted-wtih-pesticides--swiss-researchers-find/45898078 (Accessed on July 23, 2020).There is no corresponding record for this reference.
- 2Kiefer, K.; Bader, T.; Minas, N.; Salhi, E.; Janssen, E. M.-L.; von Gunten, U.; Hollender, J. Chlorothalonil transformation products in drinking water resources: Widespread and challenging to abate. Water Res. 2020, 183, 116066, DOI: 10.1016/j.watres.2020.1160662https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhtlCkt7jE&md5=c8a906f0ad1914fd914e53d78566f8edChlorothalonil transformation products in drinking water resources: Widespread and challenging to abateKiefer, Karin; Bader, Tobias; Minas, Nora; Salhi, Elisabeth; Janssen, Elisabeth M.-L.; von Gunten, Urs; Hollender, JulianeWater Research (2020), 183 (), 116066CODEN: WATRAG; ISSN:0043-1354. (Elsevier Ltd.)Chlorothalonil, a fungicide applied for decades worldwide, has recently been banned in the European Union (EU) and Switzerland due to its carcinogenicity and the presence of potentially toxic transformation products (TPs) in groundwater. The chlorothalonil sulfonic acid TPs (R471811, R419492, R417888) occurred more frequently and at higher concns. (detected in 65-100% of the samples, ≤2200 ngL-1) than the phenolic TPs (SYN507900, SYN548580, R611968; detected in 10-30% of the samples, ≤130 ngL-1). The abatement of chlorothalonil TPs was investigated in lab. and pilot-scale expts. and along the treatment train of various water works, comprising aquifer recharge, UV disinfection, ozonation, advanced oxidn. processes (AOPs), activated carbon treatment, and reverse osmosis. In contrast, the sulfonic acid TPs, which occurred in higher concns. in drinking water resources, react only very slowly with ozone (kO3 <0.04 M-1s-1) and ·OH (kOH <5.0 x 107 M-1s-1) and therefore persist in ozonation and ·OH-based AOPs. Activated carbon retained the very polar TP R471811 only up to a specific throughput of 25 m3kg-1 (20% breakthrough), similarly to the X-ray contrast agent diatrizoic acid.
- 3Kiefer, K.; Müller, A.; Singer, H.; Hollender, J. New relevant pesticide transformation products in groundwater detected using target and suspect screening for agricultural and urban micropollutants with LC-HRMS. Water Res. 2019, 165, 114972, DOI: 10.1016/j.watres.2019.1149723https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhs1emsLnN&md5=9bb29e6932b0cf9b8337199a3649db48New relevant pesticide transformation products in groundwater detected using target and suspect screening for agricultural and urban micropollutants with LC-HRMSKiefer, Karin; Muller, Adrian; Singer, Heinz; Hollender, JulianeWater Research (2019), 165 (), 114972CODEN: WATRAG; ISSN:0043-1354. (Elsevier Ltd.)Groundwater is a major drinking water resource, but its quality is threatened by a broad variety of anthropogenic micropollutants (MPs), originating from agriculture, industry, or households, and undergoing various transformation processes during subsurface passage. To det. a worst-case impact of pesticide application in agriculture on groundwater quality, a target and suspect screening for more than 300 pesticides and more than 1100 pesticide transformation products (TPs) was performed in 31 Swiss groundwater samples which predominantly originated from areas with intensive agriculture. To assess addnl. urban contamination sources, more than 250 common urban MPs were quantified. Most of the screened pesticide TPs were exptl. obsd. by the pesticide producers within the European pesticide registration. To cover very polar pesticide TPs, vacuum-assisted evaporative concn. was used for enrichment, followed by liq. chromatog. high-resoln. tandem mass spectrometry (LC-HRMS/MS). Based on intensity, isotope pattern, retention time, and in silico fragmentation, the suspect hits were prioritised and verified. We identified 22 suspects unequivocally and five tentatively; 13 TPs are reported here for the first time to be detected in groundwater. In 13 out of 31 groundwater samples, the total concn. of the 20 identified and quantified suspects (1 pesticide and 19 pesticide TPs) exceeded the total concn. of the 519 targets (236 pesticides and TPs; 283 urban MPs) for which we screened. Pesticide TPs had higher concns. than the parent pesticides, illustrating their importance for groundwater quality. The newly identified very polar chlorothalonil TP R471811 was the only compd. detected in all samples with concns. ranging from 3 to 2700 ng/L. Agricultural MP concn. and detection frequency correlated with agricultural land use in the catchment, except for aquifers, where protective top layers reduced MP transport from the surface. In contrast to agricultural MPs, urban MPs displayed almost no correlation with land use. The dominating entry pathway of urban MPs was river bank filtration.
- 4Reregistration Eligibility Decision (RED): Chlorothalonil; US Environmental Protection Agency; https://archive.epa.gov/pesticides/reregistration/web/pdf/0097red.pdf (Accessed on July 23, 2020).There is no corresponding record for this reference.