New study reveals associations between PFAS contamination and cancers, highlighting significant risks to digestive, endocrine, respiratory, and other systems, with sex-specific differences in cancer incidence.
Study: Associations between per-and polyfluoroalkyl substances (PFAS) and county-level cancer incidence between 2016 and 2021 and incident cancer burden attributable to PFAS in drinking water in the United States. Image Credit: zimmytws/Shutterstock.com
In a recent study published in the Journal of Exposure Science & Environmental Epidemiology, a group of researchers evaluated the relationship between per- and polyfluoroalkyl substances (PFAS) contamination in drinking water and county-level cancer incidence in the United States (US) from 2016 to 2021, estimating the cancer burden attributable to PFAS exposure.
Background
PFAS are synthetic chemicals widely used since the 1940s, accumulating in the environment due to their resistance to degradation. Drinking water is a significant source of PFAS exposure, with recent studies detecting PFAS in nearly half of U.S. water systems, particularly in urban areas and near potential sources.
PFAS exposure has been linked to cancer through mechanisms like endocrine disruption, epigenetic changes, and oxidative stress. Despite emerging evidence, current research is limited in scope, particularly regarding source-specific effects and U.S.-based data. Further research is essential to quantify cancer risks and inform targeted public health interventions.
About the study
Cancer incidence data were obtained from the U.S. National Cancer Institute’s (NCI) Surveillance, Epidemiology, and End Results (SEER) program, covering 22 registries and approximately half of the U.S. population. Geographic coverage included various states and regions such as Connecticut, Iowa, California, and Texas.
Age-adjusted cancer incidence rates per 100,000 were calculated for each county and cancer site for 2016-2021 using the SEER*Stat program. Cancer sites were classified by the International Classification of Diseases for Oncology, 3rd Edition/World Health Organization (ICD-O-3/WHO) categories, excluding rare cases like mesothelioma and Kaposi sarcoma. Stratified analyses assessed sex-specific cancer incidence rates.
PFAS data were sourced from the U.S. Environmental Protection Agency's (EPA’s) Unregulated Contaminant Monitoring Rules ((UCMR)3, 2013-2015, and UCMR5, 2023-2024). UCMR3 monitored six PFAS in public water systems (PWS) across the U.S., serving populations of varying sizes, with minimum reporting levels ranging from 0.01 to 0.09 µg/L.
UCMR5 expanded the scope to 29 PFAS with lower detection limits, potentially addressing exposure misclassification. Geographic boundaries of PWSs were linked to PFAS data using a combination of state-provided boundaries, town matching, and statistical modeling.
Associations between PFAS and county-level cancer incidence were analyzed using negative binomial regression, adjusting for socioeconomic and environmental confounders.
Cancer cases attributable to PFAS exposure were calculated using population-attributable fractions and incidence rate ratios. Sensitivity analyses further examined exposure misclassification and model robustness.
Study results
Data covered 1,080 counties, representing approximately half of the U.S. population, with PFAS data available for 686 counties in UCMR3 and 663-665 counties in UCMR5. At the water system level, PFAS were mostly undetected in both monitoring periods, though UCMR5 detected more PFAS, likely due to improved detection sensitivity.
The analysis identified four cancer types- digestive, endocrine, oral cavity/pharynx, and respiratory- associated with PFAS in drinking water, with incidence rate ratios (IRR) ranging from 1.02 to 1.33.
Key findings included significant associations between perfluorobutanesulfonic acid (PFBS) and increased risk of the oral cavity and pharynx cancers, and perfluorononanoic acid (PFNA) and perfluoroheptanoic acid (PFHpA) with thyroid cancers. PFBA and perfluorohexanesulfonic acid (PFHxS) were linked to digestive system cancers, including colorectal and liver cancers.
PFBA and perfluorooctanoic acid (PFOA) were also associated with respiratory cancers, notably lung cancer. Interestingly, PFBA detection correlated with reduced risks of skin cancer and leukemia, although the biological basis for these inverse associations remains unclear.
Sex-specific analyses revealed that males had higher risks of urinary system cancers, brain cancers, leukemia, and soft tissue cancers linked to PFAS exposure.
In females, thyroid, oral cavity/pharynx, and soft tissue cancers were more strongly associated with PFAS. These differences suggest possible interactions between PFAS exposure and sex-specific factors such as hormonal or metabolic variations.
The study estimated 4,626 cancer cases annually attributable to PFAS based on UCMR3 data and 6,864 cases annually based on UCMR5 data, emphasizing the significant public health burden.
Sensitivity analyses confirmed consistent results, though some associations varied between UCMR3 and UCMR5 due to differences in detection thresholds and classification of exposure.
Conclusions
To summarize, this ecological study links exposure to PFAS in drinking water with increased cancer risks, including endocrine, digestive, oral cavity, pharynx, skin, and respiratory cancers. These associations emphasize the pressing need for further research to understand PFAS-related health impacts better.
With recent U.S. EPA regulations targeting PFAS in drinking water, these findings highlight the importance of implementing effective strategies to reduce cancer risks associated with PFAS exposure, prioritizing both public health interventions and policy-driven mitigation efforts.
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