Communities exposed to drinking water contaminated by PFAS experience up to a 33% higher incidence of certain cancers, according to new research from the Keck School of Medicine of USC. Data on cancer cases between 2016 and 2021 were obtained from the National Cancer Institute’s Surveillance, Epidemiology, and End Results Program, while data on PFAS levels in public drinking water (2013-2024) came from the EPA’s Unregulated Contaminant Monitoring Rule programs. Researchers found that between 2016 and 2021, counties across the U.S. with PFAS-contaminated drinking water had higher incidence of certain types of cancer, which differed by sex. Increases in incidence ranged from slightly elevated at 2% to substantially elevated at 33% (the increased incidence of mouth and throat cancers linked to perfluorobutanesulfonic acid, or PFBS). Males in counties with contaminated drinking water had a higher incidence of leukemia, as well as cancers of the urinary system, brain and soft tissues, compared to males living in areas with uncontaminated water. Females had a higher incidence of cancers in the thyroid, mouth and throat, and soft tissues. Overall, PFAS in drinking water are estimated to contribute to more than 6,800 cancer cases each year, based on the most recent data from the U.S. Environmental Protection Agency (EPA). The results add to the mounting evidence that PFAS levels should be limited, and suggest that proposed changes may not go far enough.