Trends and Disparities in Contamination by Per- and Polyfluoroalkyl Substances in United States Community Water Systems

Abstract

Per- and polyfluoroalkyl substances (PFAS) are a large class of anthropogenic compounds that have been widely used in consumer products and industrial processes for decades. Exposures to PFAS are ubiquitous and can occur through many routes. Hundreds of millions of United States (US) residents are estimated to be exposed to PFAS in drinking water and PFAS are detectable in the blood of nearly all US residents. Associations between PFAS exposures and several adverse health outcomes—including measures related to hepatotoxicity, immunotoxicity, and metabolic disruption—are well established. Despite the ubiquity of PFAS drinking water contamination and human exposure, past assessments have been limited by a lack of comprehensive PFAS drinking water monitoring and high reporting limits in drinking water datasets. Recently available statewide drinking water monitoring datasets provide an opportunity not only to re-examine the relationships between PFAS contaminated sites and drinking water concentrations in public water systems, but also to pursue environmental justice issues posed by PFAS contamination, which have been generally underexamined within the context of PFAS exposure routes and health risks. This dissertation first compiles a statewide monitoring dataset to examine sociodemographic disparities in PFAS contamination, further uses this dataset to investigate associations between PFAS-contaminated drinking water and COVID-19 mortality, and examines disparities in infrastructure to remedy PFAS contamination among water systems affected by PFAS contamination and at the national level. In Chapter 1, I use monitoring data from 7,873 US community water systems (CWS) in 18 states and find that PFAS detections were positively associated with the number of PFAS sources and proportions of people of color served by these water systems. Numerous contamination sources, including industrial facilities, military fire training areas, airports, municipal solid waste landfills, and wastewater treatment plants, were associated with increases in drinking water concentrations of multiple PFAS (including perfluorooctanoic acid [PFOA], perfluorooctanesulfonic acid [PFOS], perfluorohexanesulfonic acid [PFHxS], and perfluorobutanesulfonic acid [PFBS]). These associations were similar in directionality to prior work, despite differences in geographies, inclusion of a greater proportion of CWS serving smaller populations, and lower uniform detection limits. CWS sharing watersheds with PFAS sources served higher proportions of Hispanic/Latino and non-Hispanic Black residents compared to those without PFAS sources. CWS serving higher proportions of Hispanic/Latino and non-Hispanic Black residents had significantly increased odds of detecting several PFAS, which is likely a reflection of disparities in the siting of PFAS contamination sources. Results of this work suggest addressing environmental justice concerns should be a component of risk mitigation planning for areas affected by drinking water PFAS contamination. In Chapter 2, I examine associations between PFAS contamination of US CWS and county-level COVID-19 mortality records prior to widespread availability of the COVID-19 vaccines. These analyses leverage two datasets: one at the subnational scale (5,371 CWS serving 621 counties; derived from the dataset compiled in Chapter 1) and one at the national scale (4,798 CWS serving 1,677 counties; derived from the US Environmental Protection Agency's (EPA) Third Unregulated Contaminant Monitoring Rule). These datasets are analyzed in parallel using multilevel quasi-Poisson regressions. In the subnational analysis, detection of at least one PFAS over 5 ng/L was associated with 12% higher [95% CI: 4%, 19%] COVID-19 mortality. In the national analysis, detection of at least one PFAS above the reporting limits (20-90 ng/L) was associated with 13% higher [95% CI: 8%, 19%] COVID-19 mortality. These findings support a positive association between county-level drinking water PFAS contamination and COVID-19 mortality. They also bolster the importance of systematic federal drinking water monitoring efforts for PFAS and remediation of contaminated areas for public health protection, potentially including infectious disease epidemics. In Chapter 3, I evaluate whether water system characteristics and sociodemographic composition are associated with early adoption of advanced water treatment processes effective for PFAS removal (reverse osmosis, ion exchange, and activated carbon) among US CWS. I use time-to-event statistical methods to analyze US EPA treatment records available over the 2004-2022 period for 2,697 CWS with known PFAS detections and 36,611 CWS nationally. I find that, among systems not reporting use of the target treatment processes at baseline, 5.1% of systems (serving an estimated 20% of the population) reported adoption by the end of the follow-up period. Among systems with known PFAS detections and systems nationally, large and very large systems (serving larger populations) were significantly more likely to report adoption of the treatment processes. Racial/ethnic disparities were observed and were consistent across system sizes, particularly for the proportion of non-Hispanic Black residents. In contrast, disparities related to area-level socioeconomic status measures varied significantly by system size and I observed evidence of non-linear relationships for these measures. This study can inform ongoing national efforts to treat drinking water contamination by PFAS and its study design can be adopted to analyze the progress of drinking water regulations. My dissertation presents evidence of sociodemographic disparities in PFAS contamination, the siting of PFAS-contaminated sites, and access to the treatment processes that can be used to remedy contamination. It also presents new evidence on the population health impacts of widespread PFAS drinking water contamination. Conclusions from this thesis further highlight not only the problem of PFAS contamination, but also the necessity of drinking water monitoring and national efforts to remediate contamination while ensuring environmental justice.