Investigators may have uncovered an association between manufactured per- and polyfluoroalkyl substances (PFAS) levels in drinking water and the incidence of certain digestive, endocrine, lung, oral, and pharyngeal cancers, according to a novel study published by Li et al in the Journal of Exposure Science & Environmental Epidemiology.
Background
PFAS—also known as forever chemicals because they’re slow to break down and accumulate in the body over time—are used in consumer products such as furniture and food packaging. They have been found in about 45% of drinking water supplies across the United States.
Previous research has linked the chemicals to a range of health problems, including renal cell carcinoma, breast cancer, and testicular cancer. Overall, PFAS in drinking water is 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).
Study Methods and Results
In the ecological study, the investigators examined the relationship between cancer and exposure to PFAS through drinking water in the United States. To better understand how PFAS contamination relates to cancer incidence, the investigators compared two large population-level data sets: one from the National Cancer Institute’s Surveillance, Epidemiology, and End Results Program, covering all reported cancer cases between 2016 and 2021, and a second from the EPA’s Unregulated Contaminant Monitoring Rule programs, supplying information on PFAS levels in U.S. public drinking water between 2013 and 2024.
The investigators controlled for a number of factors that could influence cancer risk. At the individual level, they included age and sex, whereas at the county level, they ruled out changes in cancer incidence as a result of socioeconomic status, smoking rates, obesity prevalence, urbanicity, and the presence of other pollutants.
The investigators then compared cancer incidence in each county with PFAS contamination in the drinking water, using the EPA’s recommended cutoffs for each type of PFAS. Counties in which drinking water surpassed recommended maximum levels of PFAS had a higher incidence of digestive, endocrine, lung, oral, and pharyngeal cancers.
The investigators found that between 2016 and 2021, U.S. counties exposed to drinking water contaminated with PFAS experienced up to a 33% higher incidence of certain cancer types. Increases in incidence ranged from slightly elevated at 2% to substantially elevated at 33% (the increased incidence of oral and pharyngeal cancers linked to perfluorobutanesulfonic acid).
Further, the rate of cancer incidence differed by sex. For instance, male residents 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 with male residents in areas with uncontaminated water. Female residents had a higher incidence of thyroid, oral, pharyngeal, and soft-tissue cancers. Based on the latest available EPA data, the investigators estimated that PFAS contamination of drinking water may contribute to 6,864 cancer cases per year.
“When [individuals] hear that PFAS is associated with cancer, it’s hard to know how it’s relevant. By calculating the number of attributable cancer cases, we’re able to estimate how many [patients] may be affected,” detailed lead study author Shiwen (Sherlock) Li, PhD, a postdoctoral researcher in the Department of Population and Public Health Sciences at the Keck School of Medicine at the University of Southern California. This impact included the personal and financial toll of these cases year after year.
Conclusions
“These findings allow us to draw an initial conclusion about the link between certain rare cancers and PFAS,” emphasized Dr. Li. “This suggests that it’s worth researching each of these links in a more individualized and precise way,” he continued.
In addition to providing a roadmap for researchers, the findings highlighted the importance of regulating PFAS. Starting in 2029, the EPA will police levels of six types of PFAS in drinking water; however, the investigators underscored that stricter limits may ultimately be needed to protect public health.
The research revealed links between PFAS and rare cancer types that might otherwise go unnoticed. The investigators stressed that individual-level studies are needed to determine whether the connections are causal and to explore what biological mechanisms may be involved.
On the regulation side, the results add to the mounting evidence that PFAS levels should be limited, indicating that current proposed changes may not provide enough protection for the public. “Certain PFAS that were less studied need to be monitored more, and regulators need to think about other PFAS that may not be strictly regulated yet,” Dr. Li concluded.
Disclosure: The research in this study was supported by a pilot grant from the Southern California Environmental Health Sciences Center and the National Cancer Institute. For full disclosures of the study authors, visit nature.com.
