A group of chemicals known as PFAS is linked to a wide range of cancers affecting the digestive, respiratory, and endocrine systems in humans, according to NIEHS-funded research. The study is the first to comprehensively assess the association between PFAS in drinking water and cancer incidence across multiple organ systems using large-scale, county-level data in the U.S.

“The key takeaway is that PFAS contamination in everyday water sources is a risk factor for long-term health consequences, including cancers,” said Shiwen (Sherlock) Li, Ph.D., who is the first author of the study published Jan. 9 in the Journal of Exposure Science & Environmental Epidemiology. Li is a postdoctoral scholar at the Keck School of Medicine of the University of Southern California, Los Angeles.

“The significant associations identified between PFAS in drinking water and various cancers underscore the urgent need for more comprehensive research,” said Claudia Thompson, Ph.D., chief of the Population Health Branch at NIEHS. “Given the recent regulation of PFAS in drinking water by the U.S. Environmental Protection Agency, the findings highlight the critical importance of developing effective strategies to mitigate cancer risks from exposure to PFAS through drinking water.”

Cancers affect various tissues

In the new study, Li and collaborators aimed to screen for associations between PFAS in drinking water and county-level cancer incidence, with the goal of guiding future epidemiological and experimental research on PFAS and cancer. The researchers hypothesized that there are cancers caused by PFAS in drinking water that have not been identified previously because of the limited sample size of cancer cases and the lack of PFAS quality data.

To better understand the cancer burden due to PFAS, the researchers analyzed data from public drinking water systems and cancer incidence data between 2016 and 2021. The 22 cancer registries analyzed cover approximately one-half of the U.S. population. The results revealed associations between PFAS — including PFOS, PFBS, PFHxS, PFOA, PFNA, PFBA, and PFHpA — and increased incidence rates of cancers in the oral and pharynx, digestive, respiratory, and endocrine systems.

The findings showed that in males, PFAS exposure was associated with cancers in the urinary system, brain and other nervous system, leukemia, and soft tissues. In females, PFAS exposure was associated with cancers in the endocrine system, oral cavity and pharynx, and soft tissue. Some of the cancers identified had not previously been studied for their associations with PFAS. The researchers estimated that 4,626-6,864 cases of cancer were attributed to PFAS in drinking water.

Implications for public health

According to Li, the next steps are to conduct more targeted epidemiological studies with individual-level data to confirm these associations and explore biological mechanisms using toxicological and molecular research. Currently, the researchers are assessing the level of PFAS contamination in drinking water in Los Angeles and working with community leaders to design tailored interventions to meet community needs.

“These findings can be used to inform regulations on PFAS in drinking water, guide public health interventions such as PFAS exposure screening and cancer prevention strategies, and encourage further biomonitoring of PFAS exposure,” Li said.