PFAS Contaminate Nearly Half of US Tap Water, Agency Finds

PFAS can be found in about 45% of US drinking water sources, including public water systems and private water wells, US Geological Survey scientists estimate in research published Wednesday.

Urban areas are most at risk of PFAS contamination in tap water, and their most likely to be found in taps in the Great Plains and Great Lakes regions, the East Coast, and central and southern California.

The findings show how widespread PFAS contamination is in tap water, especially in the water that comes from unregulated private water wells for which there is very little data, according to the study published in the August edition of the journal Environment International.

“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,” USGS research hydrologist Kelly Smalling, the study’s lead author, said in a statement.

PFAS, used in thousands of industrial and consumer products for decades, have been linked to cancer and other public health problems.

Scientists and regulators know very little about PFAS contamination in private water wells. USGS researchers hoping to fill in the data gap tested tap water samples from 269 private water wells and 447 public water systems nationwide between 2016 and 2021.

They found that at least one of thousands of possible per- and polyfluoroalkyl substances (PFAS) could be found in about 45% of the drinking water samples. Similar concentrations of the substances were found in samples taken from private water wells and public drinking water systems.

The most common substances they found were perfluorooctanoic acid (PFOA), perfluorobutanesulfonic acid (PFBS), and perfluorohexanoic acid (PFHxA).

‘Conservative Estimate’

The Environmental Protection Agency in March proposed limits for PFAS in drinking water, including a standard of no more than 4 parts per trillion of either PFOA or perfluorooctanesulfonic acid (PFOS). It also proposed to limit four other PFAS, including PFBS. The EPA expects to finalize the regulations in late 2024.

The USGS study shows that PFOS and PFOA pose the highest human exposure risk in drinking water.

The EPA’s proposed limits for PFOS were below the detection abilities of two of the three laboratories the USGS scientists used to detect the substances in the drinking water samples included in the study.

The study authors said that their estimates of samples exceeding the proposed maximum contaminant limit “should be considered conservative.”

The proposed limits for PFOA were exceeded in 6.7% of the tap water samples in the study, and the limits for PFOS were exceeded in 4.2%.