Millions of People in Lower 48 States May Be Relying on PFAS-Contaminated Groundwater for Drinking

Roughly 71 to 95 million people living in the contiguous United States — more than one-fifth of the population — may be reliant on groundwater with detectable concentrations of per- and polyfluoroalkyl substances (PFAS) for their drinking water, according to a new study by the U.S Geological Survey (USGS).

The research provides the first national estimates of PFAS in untreated groundwater that serves as a water supply for public and private wells, a press release from USGS said. The study also gives the first estimate of how many people in the U.S. are potentially affected by groundwater contaminated with PFAS.

“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 lead author of the study Andrea Tokranov, a USGS research hydrologist, in the press release.

The results can help consumers, regulators and water suppliers understand the potential for contamination from PFAS, inform strategic water resources planning and guide future studies.

In addition to the report, USGS has published an online, interactive map for users to be able to view estimates of the probability of the presence of PFAS.

The study’s findings are intended for use at national, regional and state scales rather than individual households.

“Probability estimates are for the presence of PFAS in groundwater and do not account for any subsequent actions taken by states, municipalities or individuals to treat drinking water. The model does not include estimates of PFAS concentrations; testing is the only way to confirm the presence of contaminants,” the press release said.

PFAS are a class of more than 12,000 synthetic chemical compounds used in many common applications, such as nonstick cookware, firefighting foam, food packaging and many other purposes. They are referred to as “forever chemicals” because of their inability to easily break down in the environment, where they can accumulate over time. Exposure of people to certain PFAS can cause adverse health risks, the U.S. Environmental Protection Agency (EPA) has said.

Legally enforceable maximum contaminant levels have been established by the EPA for six kinds of PFAS found in drinking water. Public water supplies are regulated by the EPA, as well as by some states, which have additional drinking water regulations.

People who use private water supplies and are interested in testing and treatment can contact their state officials, water suppliers or consult EPA’s guidance.

The most heavily populated states that rely on potentially contaminated public water supplies that come from groundwater are California and Florida. Michigan, New York, Ohio, Pennsylvania, North Carolina and Florida have the largest populations that currently rely on private wells supplied by potentially contaminated groundwater.

In Massachusetts, 86 to 98 percent of those whose public water comes from groundwater could be impacted by PFAS contamination. Meanwhile, in Connecticut, 67 to 87 percent of people reliant on private wells that source groundwater could be affected.

“To derive these estimates, the team analyzed 1,238 groundwater samples collected by USGS scientists and determined how factors such as urban development and well depth can impact PFAS occurrence,” Tokranov said in the press release. “With that information, a detailed machine learning model was developed and used to identify which geographic areas have a higher likelihood for contamination. That information was combined with existing USGS research on the number of people in a given area who rely on groundwater for drinking water to establish population estimates.”

Separate estimates were given for private and public wells since they usually get groundwater from different depths. Public wells that use groundwater as their primary source are typically deeper than private wells.

Not all PFAS can currently be detected, but the study tested for 24 common types. The most commonly detected compounds were perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA) and perfluorobutane sulfonate (PFBS).

“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,” Tokranov said.