Millions of people in the U.S. rely on contaminated groundwater 

A recent study by the U.S. Geological Survey (USGS) reveals that between 71 and 95 million people in the United States – more than 20% of the country’s population – may be relying on groundwater containing detectable levels of per- and polyfluoroalkyl substances (PFAS) for their drinking water. 

PFAS are synthetic chemicals commonly used in various products, including non-stick cookware, fast-food packaging, and firefighting foams. 

Often referred to as “forever chemicals,” PFAS are resistant to breaking down in the environment and can accumulate over time, raising concerns about drinking water quality.

Estimates of contaminated groundwater

This research provides the first national estimates of PFAS occurrence in untreated groundwater that supplies both public and private wells.

The USGS scientists analyzed 1,238 groundwater samples collected nationwide to determine how factors like urban development and well depth impact PFAS presence. 

The study also offers an interactive online map, allowing users to view probability estimates of PFAS contamination across different regions. These predictive results are intended for evaluation at state, regional, and national levels rather than individual households.

Health risks and regulatory standards

Exposure to certain PFAS compounds has been linked to adverse health effects in humans, according to the U.S. Environmental Protection Agency (EPA). 

Recognizing the potential risks, the EPA has established legally enforceable maximum contaminant levels for six types of PFAS in drinking water supplied by public systems. 

However, private well owners are responsible for the maintenance, testing, and treatment of their water, and may not have the same access to resources as public water suppliers. 

Those concerned about PFAS levels in their drinking water are advised to consult EPA guidelines or contact local officials and water suppliers for testing and treatment options.

Distribution of contaminated groundwater

The study identifies states with the largest populations relying on potentially contaminated groundwater. 

For public water supplies, Florida and California top the list. Regarding private wells, Michigan, Florida, North Carolina, Pennsylvania, New York, and Ohio have the highest numbers of people potentially affected. 

In Massachusetts, for instance, the source water for 86% to 98% of people relying on groundwater from public supplies could be contaminated with PFAS. 

Similarly, in Connecticut, 67% to 87% of private well users may be exposed to contaminated groundwater.

Methodology and key findings

USGS researchers utilized machine learning models to predict areas with a higher likelihood of PFAS contamination. They combined this information with data on population reliance on groundwater for drinking purposes. 

The researchers found that both public and private wells are at risk, though they typically draw water from different depths – public wells are usually deeper than private ones.

The analysis tested for 24 common types of PFAS out of more than 12,000 known varieties. The most frequently detected compounds were perfluorobutane sulfonate (PFBS), perfluorooctane sulfonate (PFOS), and perfluorooctanoate (PFOA).

Widespread groundwater contamination

“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. 

Tokranov noted that the new predictive model can help prioritize areas for future sampling to help ensure people aren’t unknowingly drinking contaminated water.

“This is especially important for private well users, who may not have information on water quality in their region and may not have the same access to testing and treatment that public water suppliers do,” said Tokranov.

The study underscores the need for increased testing and monitoring of groundwater sources, particularly in areas identified as high-risk. 

While the predictive model does not provide PFAS concentration levels or account for any remediation efforts, it serves as a valuable tool for guiding future research and informing public health strategies.

Understanding the scope of the issue

The USGS emphasizes that testing is the only definitive way to confirm the presence of PFAS contaminants in drinking water. 

The predictive model is a starting point for understanding the scope of the issue at larger scales. 

Communities, policymakers, and individuals are encouraged to utilize these findings to address potential risks associated with PFAS in groundwater and to take appropriate measures to ensure safe drinking water for all.

The study is published in the journal Science.

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