Almost half of the United States’ tap water is estimated to have one or more “forever chemicals,” known as PFAS, according to a new study.

The U.S. Geological Survey tested tap water from 716 locations, including 269 private wells and 447 public supply sites, in all 50 states, Puerto Rico, the U.S. Virgin Islands and the District of Columbia. Data, which was collected from 2016 to 2021, found PFAS in at least 45% of the faucets, the study said.

The tests searched for the presence of 32 different per- and polyfluorinated alkyl substances. More than 12,000 types of PFAS exist, and these “forever chemicals” have been linked to a range of health problems, including certain forms of cancer. They persist in an environment for extended periods, hence their nickname, and have been widely used for decades. CBS News previously reported that research shows that more than 95% of Americans have “detectable levels” of PFAS in their blood. 

“USGS scientists tested water collected directly from people’s kitchen sinks across the nation, providing the most comprehensive study to date on PFAS in tap water from both private wells and public supplies,” said USGS research hydrologist Kelly Smalling, the study’s lead author, in a news release. “The study estimates that at least one type of PFAS – of those that were monitored – could be present in nearly half of the tap water in the U.S. Furthermore, PFAS concentrations were similar between public supplies and private wells.”  

This study was the first time researchers had tested for and compared PFAS levels in tap water from both private and government-regulated water supplies. The data collected was used to model and estimate contamination nationwide. The study found that two types of PFAS found exceeded the health advisory range recommended by the Environmental Protection Agency, which only began tracking PFAS information in 2016. 

Urban areas and areas near potential PFAS sources, like industry or waste sites, are more likely to have higher levels of PFAS, the study found. Drinking water exposures may be more common in the Great Plains, Great Lakes, Eastern Seaboard and Central and Southern California, according to the study. 

The EPA has taken some steps to warn consumers about the risk of PFAS chemicals in products. The agency has proposed a federal rule that would order companies to report whether their products contain the chemicals. The EPA estimates that complying with this rule will cost the chemical and semiconductor industries about $1 billion annually, though the sectors generate about $500 billion per year.

Kerry Breen

Kerry Breen is a news editor and reporter for CBS News. Her reporting focuses on current events, breaking news and substance use.