In the first study of its kind, researchers from the Keck School of Medicine of USC found an association between levels of manmade “forever chemicals” in drinking water and the incidence of certain digestive, endocrine, respiratory, and mouth and throat cancers.
Communities exposed to drinking water contaminated with manufactured chemicals known as per- and polyfluoroalkyl substances (PFAS) experience up to a 33% higher incidence of certain cancers, according to new research from the Keck School of Medicine of USC.
The study, funded by the National Institutes of Health and just published in the Journal of Exposure Science and Environmental Epidemiology, is the first to examine cancer and PFAS contamination of drinking water in the U.S.
PFAS, which are used in consumer products such as furniture and food packaging, have been found in about 45% of drinking water supplies across the United States. Past research has linked the chemicals, which are slow to break down and accumulate in the body over time, to a range of health problems, including kidney, breast and testicular cancers.
To paint a more comprehensive picture of PFAS and cancer risk, Keck School of Medicine researchers conducted an ecological study, which uses large population-level datasets to identify patterns of exposure and associated risk. They 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. 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).
“These findings allow us to draw an initial conclusion about the link between certain rare cancers and PFAS,” said Shiwen (Sherlock) Li, PhD, a postdoctoral researcher in the Department of Population and Public Health Sciences at the Keck School of Medicine and first author of the study. “This suggests that it’s worth researching each of these links in a more individualized and precise way.”
In addition to providing a roadmap for researchers, the findings underscore the importance of regulating PFAS. Starting in 2029, the EPA will police levels of six types of PFAS in drinking water, but stricter limits may ultimately be needed to protect public health, Li said.
The toll of PFAS
To understand how PFAS contamination relates to cancer incidence, the researchers compared two exhaustive datasets—one covering all reported cancer cases and the other including all data on PFAS in drinking water data across the country. 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.
Li and his colleagues controlled for a number of factors that could influence cancer risk. At the individual level, these included age and sex; at the county level, they ruled out changes in cancer incidence due to socioeconomic status, smoking rates, obesity prevalence, urbanicity (how urban or rural an area is) and the presence of other pollutants.