USGS study estimates 45% of U.S. tap water contains PFAS

According to a new study by the U.S. Geological Survey (USGS), at least 45 percent of the nation’s tap water is estimated to have one or more types of PFAS “present” in its system.

Not all PFAS (there are reportedly more 12,000 different types) can be detected through current testing. The USGS study tested for the presence of 32 types.

According to the USGS, this research marks the first time a study was conducted that tested for and compared PFAS in tap water from both private and government-regulated public water supplies on a broad scale throughout the country. The data was used to model and estimate PFAS contamination nationwide. The USGS says 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.

“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 United States Furthermore, PFAS concentrations were similar between public supplies and private wells.”

PFAS has dominated conversations in the water sector recently. Because they break down very slowly, PFAS are commonly called “forever chemicals.” Their persistence in the environment and prevalence across the country make them a unique water quality concern. 

In March, the U.S. Environmental Protection Agency (EPA) announced its proposal for the first-ever national drinking water standard for six PFAS. If finalized, the standard would regulate PFOA and PFOS in drinking water as individual contaminants to 4 parts per trillion (ppt), and will regulate four other PFAS – PFNA, PFHxS, PFBS and HFPO-DA (also known as GenX chemicals) – as a mixture. All six of these PFAS were included in the USGS analysis.

But industry associations representing drinking water systems have suggested EPA may have gone too far in the rulemaking, citing the proposed maximum contaminant levels being too low, as well the high cost of remediation and compliance challenges.

The USGS study tested for 32 individual PFAS compounds using a method developed by its 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. 

A USGS map of the U.S. with dots representing tap water sample sites across the nation, varying in size and shade of blue to represent the number of PFAS detections from 0 to 9. The map does not represent the only locations in the U.S. with PFAS.  

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.  

According to USGS, 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 percent in rural areas and around 25 percent in urban areas.

Learn more about USGS research on PFAS by reading the USGS strategy for the study of PFAS and visiting the PFAS Integrated Science Team’s website. The new study builds upon previous research by the USGS and partners regarding human-derived contaminants, including PFAS, in drinking water and PFAS in groundwater

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