About 18% of private wells in Pennsylvania are contaminated with toxic PFAS chemicals, according to a new Pennsylvania State University study.

State and federal regulations restrict the so-called “forever chemicals” in public drinking water. However, private wells are not state or federally regulated, meaning homeowners are responsible for testing and treating their own water.

More than 1 million households in Pennsylvania rely on private wells.

“PFAS is something that’s prevalent. It’s not something that is unique to private wells. It’s not unique to public water systems,” said Faith Kibuye, a water resources extension specialist at Penn State. “It’s a global problem that I think researchers as a whole should come together to figure out how to support communities who may be impacted vastly.”

PFAS, widely used in consumer products such as nonstick cookware and waterproof clothing, as well as in firefighting foam, have been linked to serious health problems, including some cancers, thyroid disease, developmental delays in children and other health conditions.

The health risks associated with PFAS, which can stay in the human bloodstream for years, have sparked numerous lawsuits against chemical manufacturers, such as DuPont and 3M.

PFAS, which can stay in the environment for decades, have tainted water supplies across the U.S., including in private wells in Horsham, Warminster and Warrington — because of past uses of firefighting foam.

In an effort to improve health outcomes, the U.S. Environmental Protection Agency implemented regulations last year requiring water providers to test and treat “forever chemicals” to reduce their presence to almost zero by 2029.

Penn State researchers say 18% of the 167 private wells tested across Pennsylvania over three years contained “forever chemicals” above the new federal limits. The findings are similar to the percentage of public drinking water supplies that contain PFAS in Pennsylvania, according to a 2024 WHYY News investigation.

“If we compare some of the concentrations we are seeing in groundwater, they are within the same ranges that have been reported in surface water sources at the state level, and also at a national level in drinking water sources,” Kibuye said.

The concentrations ranged from nondetectable levels to around 125 parts per trillion. The study only evaluated raw water from the well, and did not evaluate whether the water was being treated at the tap.

The highest concentrations of PFAS were detected in the most developed parts of the state, particularly in Montgomery County and other parts of Southeastern Pennsylvania. The researchers did not find any correlation between PFAS contamination and the proximity of wells to rural areas impacted by sewage sludge or biosolids.

Though the contamination was widespread, the total concentrations were not exceedingly high, said researcher Heather Preisendanz, a professor of agricultural and biological engineering at Penn State.

“I was concerned that we might see numbers hundreds or thousands of times higher than the drinking water standards,” she said.

Preisendanz warns the results may not be representative of all private wells, and said there could be hot spots elsewhere in the state.

“It also made me wonder who we missed in the sampling because we’re bound to have people in the state that do have higher concentrations,” she said.

The researchers hope the study will help inform homeowners of their risk based on where they live.

“It’s also a good thing that we’re getting a lot of awareness out there about PFAS in general and what people can do, because it’s a global problem, it seems like as the research is developing we are learning more about what people can do at a personal level within the home to manage their exposure through drinking water,” Kibuye said.

Residents with private wells in Pennsylvania can hire certified laboratories to test their drinking water for PFAS. If the water is contaminated, there are a number of ways to treat it.

Read more from our partners, WHYY.