Study links PFAS contamination of drinking water to series of rare 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 from USC.

The study, published in the Journal of Exposure Science and Environmental Epidemiologyis the first to examine cancer and PFAS contamination of drinking water in the United States.

PFAS, which are used in consumer products such as furniture and food packaging, have been found in about 45% of U.S. drinking water supplies. Previous research has linked these chemicals, which are slow to break down and build up in the body over time, to a range of health problems, including kidney, breast and testicular cancers. .

To paint a more complete picture of PFAS and cancer risk, Keck School of Medicine researchers conducted an ecological study, which used large population-level data sets to identify exposure patterns and associated risks.

They found that between 2016 and 2021, U.S. counties where drinking water was contaminated with PFAS had higher incidences of certain types of cancer, which differed by gender. Overall, PFAS in drinking water is estimated to contribute to more than 6,800 cases of cancer each year, based on the most recent data from the U.S. Environmental Protection Agency (EPA) .

“These results allow us to draw a first conclusion about the link between certain rare cancers and PFAS,” said Shiwen (Sherlock) Li, Ph.D., 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 is worth studying each of these links in a more individualized and precise way.”

In addition to providing a roadmap for researchers, the findings highlight the importance of regulating PFAS. Starting in 2029, the EPA will monitor levels of six types of PFAS in drinking water, but stricter limits may ultimately be needed to protect public health, Li said.

The assessment of PFAS

To understand the link between PFAS contamination and cancer incidence, researchers compared two comprehensive datasets: one covering all reported cancer cases and the other including all PFAS data in the world. drinking water 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 EPA’s unregulated contaminant monitoring rule programs.

Li and colleagues controlled for a number of factors that might influence cancer risk. At the individual level, these criteria included age and gender; at the county level, they excluded 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.

The researchers then compared cancer incidence in each county to PFAS contamination in drinking water, using EPA-recommended thresholds for each type of PFAS.

Counties where drinking water exceeded maximum recommended levels of PFAS had higher incidences of digestive, endocrine, respiratory, and mouth and throat cancers. Incidence increases ranged from slightly elevated at 2% to significantly elevated at 33% (the increased incidence of mouth and throat cancers linked to perfluorobutanesulfonic acid, or PFBS).

Men living in counties where drinking water was contaminated had a higher incidence of leukemia, as well as cancers of the urinary system, brain, and soft tissues, compared to men living in areas where drinking water was unsafe. contaminated.

Women had a higher incidence of thyroid, mouth, throat and soft tissue cancers. Based on the latest available data from the EPA, researchers estimate that PFAS contamination of drinking water contributes to 6,864 cases of cancer per year.

“When people hear that PFAS are associated with cancer, it’s difficult to know why this is relevant. By calculating the number of attributable cancer cases, we are able to estimate how many people may be affected,” he said. declared Li, in particular by deducting the personal consequences and the financial toll of these affairs, year after year.

Protect public health

These population-level findings reveal associations between PFAS and rare cancers that might otherwise go unnoticed. Next, studies at the individual level are needed to determine whether the link is causal and explore the biological mechanisms involved.

On the regulatory side, the findings add to growing evidence that PFAS levels should be limited and suggest the proposed changes may not go far enough.

“Some PFAS that have been less studied need to be monitored more, and regulators need to think about other PFAS that may not yet be strictly regulated,” Li said.

The work is part of a collaboration between the Environmental Health Sciences Center of Southern California and the USC Norris Comprehensive Cancer Center at the Keck School of Medicine.