PFAS-Contaminated Pesticides Applied near Public Supply Wells Disproportionately Impact Communities of Color in California

Contaminated drinking water from widespread environmental pollutants such as perfluoroalkyl and polyfluoroalkyl substances (PFAS) poses a rising threat to public health. PFAS monitoring in groundwater is limited and fails to consider pesticides found to contain PFAS as a potential contamination source. Given previous findings on the disproportionate exposure of communities of Color to both pesticides and PFAS, we investigated disparities in PFAS-contaminated pesticide applications in California based on community-level sociodemographic characteristics. We utilized statewide pesticide application data from the California Department of Pesticide Regulation and recently reported concentrations of PFAS chemicals detected in eight pesticide products to calculate the areal density of PFAS applied within 1 km of individual community water systems’ (CWSs) supply wells. Spatial regression analyses suggest that statewide, CWSs that serve a greater proportion of Latinx and non-Latinx People of Color residents experience a greater areal density of PFAS applied and greater likelihood of PFAS application near their public supply wells. These results highlight agroecosystems as potentially important sources of PFAS in drinking water and identify areas that may be at risk of PFAS contamination and warrant additional PFAS monitoring and remediation.


Note:
a PFAS application from 2019-2021 is reported in milligrams (mg).
b Although perfluorooctanoic acid (PFOA) and perfluoroheptanesulfonic acid (PFHpS) were detected in Malathion 5EC, this product was not found to have been applied within the public supply well buffer areas likely due to its presence on the DPR's Groundwater Protection List which restricts the use of specific pesticides near drinking water wells.Note.Socioeconomic variables were accessed from the U.S. Census Bureau's American Community Survey (ACS) 2016-2020 5-year estimates and assigned to water system service boundaries using areal apportionment.Models included fitted splines for population density (people/100 square meters) and for latitude and longitude (decimal degrees).
a Geometric mean ratio assessing PFBA+PFBS application with respect to sociodemographic characteristics.
b Odds ratio assessing likelihood of PFBA+PFBS application with respect to sociodemographic characteristics.
c The sum of milligrams of PFBA and PFBS applied per km2 within public supply well buffer areas via pesticide application.
d n refers to the number of Community water systems included in each model.
e Number of supply wells excluded because outcome already adjusted for buffer area, a variable related to the number of supply wells.Note.Socioeconomic variables were accessed from the U.S. Census Bureau's American Community Survey (ACS) 2016-2020 5-year estimates and assigned to water system service boundaries using areal apportionment.
a Geometric mean ratio assessing PFAS application with respect to sociodemographic characteristics.
b PFAS refers to the sum of milligrams of PFBS, PFBA, and PFOS applied per km 2 within public supply well buffer areas via PFAS-pesticide application.
c n refers to the number of community water systems included in each model.
d %Latinx and %non-Latinx People of Color [Reference Group: % non-Latinx White] were included as racial/ethnic categories in the same unadjusted bivariate model.Note.Socioeconomic variables were accessed from the U.S. Census Bureau's American Community Survey (ACS) 2016-2020 5-year estimates and assigned to water system service boundaries using areal apportionment.Each column indicates the subsequent addition of an adjustment variable to the model (in addition to the others already adjusted for in the columns to the right).
a Geometric mean ratio assessing PFAS application with respect to sociodemographic characteristics.
b PFAS refers to the sum of milligrams of PFBS, PFBA, and PFOS applied per km 2 within public supply well buffer areas via PFAS-pesticide application.
c n refers to the number of community water systems included in each model.
d Addition of coordinates (centroid of water system service area boundaries in decimal degrees) as adjustment variable in the model.
e Addition of population density (people/100 square meters) as adjustment variable in the model.
f Addition of modifier (% rented households) as adjustment variable in the model.
g Models do not yet adjust for % rented households as a modifier.Note.Socioeconomic variables were accessed from the U.S. Census Bureau's American Community Survey (ACS) 2016-2020 5-year estimates and assigned to water system service boundaries using areal apportionment.Each column indicates the subsequent addition of an adjustment variable to the model (in addition to the others already adjusted for in the columns to the right).
a Odds ratio assessing likelihood of PFAS application with respect to sociodemographic characteristics.
b PFAS refers to any amount (or none) of PFBS, PFBA, and PFOS applied within public supply well buffer areas via PFAS-pesticide application.
c n refers to the number of community water systems included in each model.
d Addition of coordinates (centroid of water system service area boundaries in decimal degrees) as adjustment variable in the model.
e Addition of population density (people/100 square meters) as adjustment variable in the model.
f Addition of the number of public supply wells as adjustment variable in the model.
g Addition of modifier (% rented households) as adjustment variable in the model.

Table S3 . Two-Part Generalized Additive Model Results: Sensitivity Analysis Estimating the Association Between Sociodemographic Variables and PFBA+PFBS Application Among Community Water Systems, California, 2019-2021 Independent Variables Geometric Mean Ratios a Milligrams of PFBA+PFBS c per km 2 (n d =639) Odds Ratios b PFBA+PFBS c applied (Yes/No) (n d =2,444)
4  cPercentages were calculated by dividing the total PFAS applied in buffer areas by statewide total.

Table S5 . Odds Ratios for Unadjusted Bivariate Logistic Models Estimating the Association Between Sociodemographic Variables and PFAS Application Among Community Water Systems, California, 2019-2021
a Odds ratio assessing likelihood of PFAS application with respect to sociodemographic characteristics.bPFASrefers to any amount (or none) of PFBS, PFBA, and PFOS applied within public supply well buffer areas via PFAS-pesticide application.cn refers to the number of community water systems included in each model.d %Latinx and %non-Latinx People of Color [Reference Group: % non-Latinx White] were included as racial/ethnic categories in the same unadjusted bivariate model.

Table S6 . Geometric Mean Ratios for Progressively Adjusted Log-Linear Models Estimating the Association Between Sociodemographic Variables and PFAS Application Among Community Water Systems, California, 2019-2021 Geometric
Mean Ratios a Milligrams of PFAS b per km 2 (n c =732)