USGS study estimates 45% of tap water has PFAS present

A new study by the U.S. Geological Survey (USGS) estimates that at least 45% could have one or more types of the chemicals known as per- and polyfluoroalkyl substances (PFAS).

"USGS scientists tested water collected directly from people’s kitchen sinks across the nation, providing the most comprehensive study to date on PFAS in tap water from both private wells and public supplies,” said USGS research hydrologist Kelly Smalling, the study’s lead author. “The study estimates that at least one type of PFAS — of those that were monitored — could be present in nearly half of the tap water in the U.S. Furthermore, PFAS concentrations were similar between public supplies and private wells.”

The study tested for 32 individual PFAS compounds using a method developed by the USGS National Water Quality Laboratory. The most frequently-detected compounds in this study were PFBS, PFHxS and PFOA. The interim health advisories released by the EPA in 2022 for PFOS and PFOA were exceeded in every sample in which they were detected in this study.

Of all the PFAS observed, concentrations ranged from 0.348 ng/L to 346 ng/L.

Scientists collected tap water samples from 716 locations representing a range of low, medium and high human-impacted areas. The low category includes protected lands; medium includes residential and rural areas with no known PFAS sources; and high includes urban areas and locations with reported PFAS sources such as industry or waste sites.

Most of the exposure was observed near urban areas and potential PFAS sources. This included the Great Plains, Great Lakes, Eastern Seaboard, and Central/Southern California regions. The study’s results are in line with previous research concluding that people in urban areas have a higher likelihood of PFAS exposure. USGS scientists estimate that the probability of PFAS not being observed in tap water is about 75% in rural areas and around 25% in urban areas.

This USGS research marks the first time anyone has tested for and compared PFAS in tap water from both private and government-regulated public water supplies on a broad scale throughout the country. There are more than 12,000 types of PFAS, not all of which can be detected with current tests; the USGS study tested for the presence of 32 types.

The data was used to model and estimate PFAS contamination nationwide. The study can help members of the public to understand their risk of exposure and inform policy and management decisions regarding testing and treatment options for drinking water.

The EPA regulates public water supplies, and homeowners are responsible for the maintenance, testing and treatment of private water supplies. Those interested in testing and treating private wells should contact their local and state officials for guidance. Testing is the only way to confirm the presence of these contaminants in wells.