PFAS in Wells

 Andrea K. Tokranov et al, Prediction of Groundwater PFAS Occurrence at Drinking Water Supply Depths in the United States. Science 386, 748-755 (2024). DOI:10.1126/science.ado6638

In the research study cited above published at the end of October 2024, the U.S Geological Survey estimated that approximately 71 to95 million people in the Lower 48 states – more than 20% of the country’s population – may obtain their drinking water from groundwater that contains detectable concentrations of per- and polyfluoroalkyl substances, also known as PFAS, for their drinking water supplies. 

PFAS are a group of synthetic chemicals used in a wide variety of common applications, from the linings of fast-food boxes and non-stick cookware to fire-fighting foams and other purposes. This category of chemical has been widely used for over 80 years mainly for their ability to repel oil, grease, water, and heat. PFOS and PFOA found in Scotch Guard and an ingredient in Teflon and traditional Aqueous Film-Forming Foam (AFFF) - the Class B firefighting foam used to fight aviation and other chemical fires -were the first to become widely commercially successful.

PFAS are commonly called “forever chemicals” because many of them do not easily break down and can build up over time, making them a concern for drinking water quality. Exposure to certain PFAS may lead to adverse health risks in people, according to the U.S. Environmental Protection Agency.

Per- and Polyfluoroalkyl Substances (PFAS) do not occur in nature, they are an entirely synthetic substance. Yet, most people in the United States have been exposed to PFAS and have PFAS in their blood, especially perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA).  Last year EPA release the final drinking water regulation for six PFAS including perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorononanoic acid (PFNA), hexafluoropropylene oxide dimer acid (HFPO-DA, commonly known as GenX Chemicals), perfluorohexane sulfonic acid (PFHxS), and perfluorobutane sulfonic acid (PFBS).

For this study, the USGS scientists built a predictive model of PFAS occurrence in groundwater at the depths of drinking water supplies across the continental United States, before any treatment. They trained the model on groundwater samples collected by the US Geological Survey (USGS) from 2019-2022 from three types of well networks: (i) public supply networks spanning principal aquifers,  (ii) observation networks targeting urban and agricultural land uses, and (iii) domestic supply well networks in principal aquifers. 

The team then conducted extensive PFAS source mapping, and the final model included 25 potential PFAS sources such as airports, metal coating facilities, plastics and resins facilities, printing facilities, fire training areas, chemical manufacturing facilities, and national defense sites, among many others. At least one PFAS out of the 24 individual PFAS analyzed was detected in 37% (n = 1238) of the groundwater samples analyzed for the model training dataset.  Observation wells had the highest detection frequency of any PFAS at 60% (n = 257), followed by production (public supply) wells (42%, n = 539); miscellaneous, other, and irrigation wells (29%, n = 59); and domestic wells (17%, n = 383). By individual compound, the highest detection frequencies were observed for perfluorobutane sulfonate (PFBS; 24.6%), PFOS (24.3%), PFOA (24.1%), and perfluorohexane sulfonate (PFHxS; 23.7%). All four compounds are included in the EPA’s PFAS National Primary Drinking Water Regulation rulemaking (6).  

“This study’s findings indicate widespread PFAS contamination in groundwater that is used for public and private drinking water supplies in the U.S.,” said Andrea Tokranov, USGS research hydrologist and lead author of this study. “This new predictive model can help prioritize areas for future sampling to help ensure people aren’t unknowingly drinking contaminated water. This is especially important for private well users, who may not have information on water quality in their region and may not have the same access to testing and treatment that public water suppliers do.”

My corner of Prince William County