Between 71 and 95 million individuals in the contiguous United States—over 20% of the nation’s population—might be depending on groundwater that has measurable levels of per- and polyfluoroalkyl substances, commonly referred to as PFAS, in their drinking water. These insights come from a study conducted by the U.S. Geological Survey and published on October 24.
The results from the predictive model can assist the public, water providers, and regulatory bodies in grasping the risk of PFAS contamination, guiding future research, and aiding strategic planning for water resources.
This is the first time USGS scientists have provided national estimates about PFAS presence in untreated groundwater that feeds public and private wells. This study also sheds light on how many people nationally might be at risk due to PFAS in their drinking water sources.
Along with their research paper, the USGS has created an interactive online map that allows users to view the likelihood of PFAS occurrences. It is essential to recognize that these predictive results should be assessed at broader state, regional, or national levels—not at the level of individual households. The estimates reflect the chance of PFAS existing in groundwater but do not take into consideration any measures that states, localities, or individuals might have taken to treat their drinking water. The model does not estimate PFAS concentrations; actual testing is required to confirm the presence of these contaminants.
The U.S. Environmental Protection Agency indicates that exposure to certain PFAS compounds may pose significant health risks. These substances are synthetic chemicals found in a range of everyday products, from fast-food box linings and non-stick cookware to fire-fighting foams. Often referred to as “forever chemicals,” many PFAS compounds do not readily decompose and can accumulate over time, raising concerns regarding the quality of drinking water.
“The results of this study highlight a substantial issue of PFAS contamination in groundwater utilized for public and private drinking supplies across the U.S.,” stated Andrea Tokranov, a USGS research hydrologist and the lead author of the study. “This new predictive model can assist in prioritizing areas for future sampling, ensuring that people don’t unintentionally consume contaminated water, which is crucial for private well users who may lack accessibility and information concerning water quality and testing compared to public water systems.”
The EPA has set legally enforceable limits, known as maximum contaminant levels, for six specific PFAS types in drinking water. While the EPA oversees public water supplies, many states implement additional regulations regarding drinking water. In cases where private water supplies are used, residents must manage the upkeep, testing, and treatment of their own water. Those seeking information about treatment methods and testing options can consult the EPA’s guidelines or reach out to their state authorities or water suppliers.
States with the highest numbers of people depending on public water systems with potentially contaminated groundwater include Florida and California. In terms of private wells, Michigan, Florida, North Carolina, Pennsylvania, New York, and Ohio have the largest populations potentially affected by contaminated groundwater.
The study also includes data sorted by population percentage. For instance, in Massachusetts, the water source for 86 to 98% of individuals relying on groundwater from public supplies could be tainted with PFAS. In Connecticut, this could affect 67 to 87% of those using groundwater from private wells. More detailed state-level information is available in the report’s tables S6 through S8.
“To arrive at these estimates, our team analyzed 1,238 groundwater samples gathered by USGS scientists, examining how variables like urban development and well depth can influence PFAS presence,” Tokranov continued. “This information was then utilized to create an advanced machine learning model, identifying geographic areas with a higher probability of contamination. This data was combined with existing USGS research to determine how many people in an area utilize groundwater for drinking.”
Differentiating between public and private wells is crucial since they frequently draw from different groundwater depths, with public wells typically being deeper.
There are over 12,000 types of PFAS, but current testing methods can only identify certain variants; the USGS study checked for 24 common PFAS types. The estimates reflect the presence of at least one among these 24 detection types. The compounds most frequently found were perfluorobutane sulfonate (PFBS), perfluorooctane sulfonate (PFOS), and perfluorooctanoate (PFOA).
This research gives a comprehensive overview for the 48 contiguous states while offering state-specific estimates. However, the scientists did not conduct detailed assessments of cities or provide specific estimates about the types or concentrations of PFAS found.
