PEMBROOKE, N.H. — PFAS contamination of drinking water supplies may be more widespread than previously thought.

Last month scientists with the U.S. Geological Survey published a study that estimated around 20% of untreated groundwater supplies in the country may contain “detectable amounts” of the per- and polyfluoroalkyl substances more commonly known as PFAS, or forever chemicals. The first-of-its-kind estimate analyzed 1,238 samples of groundwater nationwide at varying depths to build a predictive model for public and private drinking water supplies, such as wells.

PFAS contamination levels are linked to the amount of human development, a factor which, unsurprisingly, means smaller southern New England states like Rhode Island are more likely to have contamination in their groundwater supplies.

Data from the model’s analysis suggests that for 76% to 92% of people in Rhode Island who rely on public groundwater supplies for drinking water, those supplies could be contaminated with forever chemicals. In Massachusetts, the range is higher, between 86% to 98%. In Connecticut, source water for around 67% to 87% of people who rely on groundwater from private wells could be contaminated with PFAS.

The USGS estimates nationwide between 70 million and 90 million people in the continental United States could be relying on groundwater that contains detectable concentrations of PFAS for drinking water.

“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 the study. “This new predictive model can help prioritize areas for future sampling to help ensure people aren’t unknowingly drinking contaminated water.”

The USGS has also released an interactive map, detailing which areas of the country have groundwater likely to be contaminated with PFAS.

The thousands of different chemicals classified as PFAS or PFOA substances have come under greater scrutiny in recent years. Sustained exposure to PFAS can reduce the ability of the immune system to fight infections, decrease fertility, increase risk of delayed development in children, and increase the risk of several cancers.

Scientists working for DuPont synthesized the first forever chemical in the late 1930s, and their historical use has been the ability to create products that are resistant to water, grease, and stains. Thanks to these properties, they are commonly found in a wide array of products, from cookware, to firefighting foam, to fast-food containers.

In Rhode Island, the town of Burrillville has made repeated PFAS-related headlines, first when a drinking water well in the village of Oakland tested high for the chemicals in 2017, leading to a no drinking water order to be issued by the Rhode Island Department of Health. The town has made headlines again this year as town officials moved to install an artificial turf field at the high school, when the material used in the turf is known to leach chemicals into the groundwater.

The contamination in Burrillville in 2017 propelled policymakers to regulate the chemicals. In 2022 the General Assembly passed legislation (and amended it the following year) to limit the acceptable amount of PFAs chemicals in drinking water, groundwater and surface waters in Rhode Island, charging the DOH and the Rhode Island Department of Environmental Management with implementing the limits. The law sets an interim drinking water state standard at 20 parts per trillion for six types of PFAS, and public water systems are required to test regularly for PFAS.

In April, the Environmental Protection Agency set its own standards for six PFAS compounds at between 4 and 10 parts per trillion, depending on the specific chemical.

As part of executing the new state law, DEM also issued a draft report late last year detailing known sources of PFAS contamination in groundwater. The sites included current and former landfills, gravel pits, Department of Defense sites, airports, fire stations, and textile mills and other known industrial sites.

As of March of this year, only 11 public water systems tested for PFAS levels greater than 20 parts per trillion. Three additional sites, two in Exeter and another in Burrillville, had PFAS exceed 70 parts per trillion.

The odds of PFAS contamination are not in the state’s favor as time goes on, according to the USGS study.

“The footprint of PFAS occurrence at the depth of public and domestic water supply may continue to expand as groundwater is recharged to aquifers and migrates downward over time,” reads the study, “given the extensive PFAS contamination reported in air, rain, and soil, among many other sources.”