Incidence of per- and polyfluoroalkyl substances (PFAS) in private drinking water supplies in Southwest Virginia, USA.

Per- and polyfluoroalkyl substances (PFAS) are a class of man-made contaminants of human health concern due to their resistance to degradation, widespread environmental occurrence, bioaccumulation in living organisms, and potential negative health impacts. Private drinking water supplies may be uniquely vulnerable to PFAS contamination in impacted areas, as these systems are not protected under federal regulations and often include limited treatment or remediation, if contaminated, prior to use. The goal of this study was to determine the incidence of PFAS contamination in private drinking water supplies in two counties in Southwest Virginia, USA (Floyd and Roanoke) that share similar bedrock geologies, are representative of different state Department of Health risk categories, and to examine the potential for reliance on citizen-science based strategies for sample collection in subsequent efforts. Samples for inorganic ions, bacteria, and PFAS analysis were collected on separate occasions by participants and experts at the home drinking water point of use (POU) for comparison. Experts also collected outside tap samples for analysis of 30 PFAS compounds. At least one PFAS was detectable in 95 % of POU samples collected (n = 60), with a mean total PFAS concentration of 23.5 ± 30.8 ppt. PFOA and PFOS, two PFAS compounds which presently have EPA health advisories, were detectable in 13 % and 22 % of POU samples, respectively. On average, each POU sample contained >3 PFAS compounds, and one sample contained as many as 8 compounds, indicating that exposure to a mixture of PFAS in drinking water may be occurring. Although there were significant differences in total PFAS concentrations between expert and participant collected samples (Wilcoxon, alpha = 0.05), collector bias was inconsistent, and may be due to the time of day of sampling (i.e. morning, afternoon) or specific attributes of a given home. Further research is required to resolve sources of intra-sample variability.

Quantitative analysis of microbial contamination in private drinking water supply systems.

Over one million households rely on private water supplies (e.g. well, spring, cistern) in the Commonwealth of Virginia, USA. The present study tested 538 private wells and springs in 20 Virginia counties for total coliforms (TCs) and Escherichia coli along with a suite of chemical contaminants. A logistic regression analysis was used to investigate potential correlations between TC contamination and chemical parameters (e.g. NO3(-), turbidity), as well as homeowner-provided survey data describing system characteristics and perceived water quality. Of the 538 samples collected, 41% (n = 221) were positive for TCs and 10% (n = 53) for E. coli. Chemical parameters were not statistically predictive of microbial contamination. Well depth, water treatment, and farm location proximate to the water supply were factors in a regression model that predicted presence/absence of TCs with 74% accuracy. Microbial and chemical source tracking techniques (Bacteroides gene Bac32F and HF183 detection via polymerase chain reaction and optical brightener detection via fluorometry) identified four samples as likely contaminated with human wastewater.