America’s drinking water may be far more polluted than previously thought.
A new study from the U.S. Geological Survey (USGS) estimates that between 71 and 95 million Americans are relying on groundwater contaminated with “forever chemicals”—synthetic compounds linked to cancer, fertility issues, and other health problems. These chemicals, known as PFAS, have been widely used and remain in the environment for decades.
The study, published in Science, is the first of its kind to map the extent of PFAS contamination in the country’s groundwater. Researchers collected water samples from wells between 2019 and 2022, testing for 24 different PFAS compounds. The results showed that at least one type of PFAS was present in 37% of the samples.
Scientists used this data to model the estimated extent of nationwide contamination. According to the findings, about half to two-thirds of Americans who rely on groundwater—whether from public utilities or private wells—may be drinking water containing PFAS before any treatment.
Florida and California had the highest number of residents using public water systems with PFAS contamination, with between 9.5 and 13 million people potentially exposed.
Massachusetts had the highest percentage of affected residents, with estimates suggesting as much as 98% of its population relying on contaminated groundwater. Those with private wells in Michigan, Florida, North Carolina, Pennsylvania, New York, and Ohio are also among the most at risk.
PFAS contamination comes from a variety of sources. These chemicals are commonly found in non-stick cookware, waterproof clothing, food packaging, firefighting foam, and industrial waste. They contaminate groundwater through wastewater discharge, landfill runoff, and other sources. Because PFAS move easily in water, contamination extends beyond industrial areas.
The study also found that certain environmental factors influence how PFAS spread. Groundwater in urban areas and regions with shallow wells was more likely to be contaminated.
Soil type played a role as well, with sandy soils allowing PFAS to move more freely, while medium-clay soils appeared to act as a barrier. However, researchers were surprised to find that heavily clay-based soils, which were once thought to be protective, showed increased contamination levels. One possible explanation is that clay-rich soil tends to crack, creating pathways for chemicals to reach groundwater.
Some of the most frequently detected PFAS compounds in the study included PFBS, PFOS, and PFOA, which have already been the focus of regulatory action. The Environmental Protection Agency (EPA) has recently set legal limits for six types of PFAS in drinking water, and many public water suppliers have started monitoring and treating for these chemicals.
However, treatment is costly and difficult for smaller communities, particularly those that rely on private wells. In states like Connecticut, an estimated 67 to 87 percent of private well users may be drinking water with detectable PFAS, yet most have no access to regular testing or filtration.
Health risks associated with PFAS exposure include an increased likelihood of cancer, liver damage, immune system suppression, thyroid disorders, and reproductive issues. Because PFAS accumulate in the body over time, even low levels of exposure can have long-term consequences.
Public water systems that detect these chemicals can take steps to remove them, but many private well users are left to deal with the problem on their own. Effective filtration systems, such as activated carbon and reverse osmosis, can reduce PFAS levels, but they can be expensive, and not everyone has the means to install them.
The USGS has made its research available through an interactive online map, allowing people to check estimated PFAS contamination levels in their area. However, the study only accounted for 24 PFAS compounds, while over 12,000 variations exist. This means that the true scale of contamination may be even larger than what has been measured.
State and federal officials are increasing efforts to regulate and remove PFAS from drinking water, but the challenge is immense. The EPA’s new drinking water standards represent progress, but enforcing them nationwide will take time.
As research on these chemicals advances, more questions are being raised about the long-term risks they pose and whether enough is being done to address the problem before it worsens.