PFAS May Cause Nearly 7000 Cancer Cases Each Year
PFAS in US drinking water contributes to 6,800 cancer cases yearly, urging stronger regulation and broader monitoring.

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While many Americans rely on tap water without a second thought, new research highlights a hidden concern: per- and polyfluoroalkyl substances (PFAS), chemicals found in nearly half of US drinking water supplies.
Conducted at the Keck School of Medicine of the University of Southern California (USC) and published in the Journal of Exposure Science & Environmental Epidemiology, the study estimates that PFAS contamination contributes to over 6,800 cancer cases annually, highlighting the urgent need for stronger regulatory measures.
The invisible threat in drinking water
The water we drink can harbor invisible dangers. Among these are PFAS, a group of synthetic chemicals that have infiltrated the environment and can persist for decades. Known as "forever chemicals," PFAS are used in countless consumer products, including non-stick cookware, stain-resistant fabrics and food packaging. Their resilience to degradation ensures their ubiquitous presence in air, soil and water, with drinking water being one of the most common routes of human exposure.
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Subscribe for FREEWhile PFAS have long been suspected of posing health risks, research connecting them to cancer has been limited. Previous studies have primarily linked PFAS to kidney and testicular cancers, as well as to hormonal disruptions and metabolic changes. However, these findings were often based on specific regions, such as the well-documented cases of contamination in the Mid-Ohio River Valley, and focused predominantly on a few compounds like perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). Consequently, there has been a lack of comprehensive, nationwide assessments of how PFAS in drinking water may influence cancer incidence across the US.
PFAS increased the incidence of certain cancers by 33%
The recent study incorporates data on over six PFAS compounds, accounting for various confounding factors such as socioeconomic status, urbanization and other pollutants. Researchers used extensive datasets, including the Environmental Protection Agency’s (EPA) monitoring data on PFAS levels in drinking water and cancer statistics from the National Cancer Institute’s Surveillance, Epidemiology and End Results (SEER) program, spanning from 2016 to 2021. The study examined cancer trends in counties across the US, comparing areas with high PFAS contamination to those with lower levels.
“When people 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 people may be affected,” said lead author Dr. Shiwen (Sherlock) Li, a postdoctoral researcher in the department of population and public health sciences at the Keck School of Medicine.
Counties with PFAS-contaminated drinking water showed up to a 33% higher incidence of certain cancers, such as mouth, throat and endocrine system cancers. Gender-specific patterns also emerged: females in these counties faced elevated risks of thyroid and oral cancers, while males experienced higher rates of urinary and brain cancers. Based on the latest available data, the study estimates that PFAS exposure contributes to 6,864 cancer cases annually in the US.
Broader implications: Health, policy and action
These results align with earlier research linking PFAS to kidney and testicular cancers, but they also expand the scope to include less-studied cancer types. By highlighting these associations, the study emphasizes the pressing need for regulatory measures and more granular research into PFAS’s effects on human health.
Starting in 2029, the EPA will enforce new regulations on six types of PFAS in drinking water. However, the study’s authors argue that these measures may not go far enough. Stricter standards and broader monitoring of additional PFAS compounds are critical to fully safeguarding public health.
“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,” said Li.
In addition to regulatory action, understanding the biological mechanisms of PFAS is essential. As endocrine disruptors, PFAS can interfere with hormonal pathways, exacerbating cancer risks. This highlights the importance of investigating how PFAS interact with the body at a molecular level, providing insights that could inform both prevention and treatment strategies.
“These findings allow us to draw an initial conclusion about the link between certain rare cancers and PFAS. This suggests that it’s worth researching each of these links in a more individualized and precise way,” Li added.
Reference: Li S, Oliva P, Zhang L, et al. 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. J Expo Sci Environ Epidemiol. 2025. doi: 10.1038/s41370-024-00742-2
This article is a rework of a press release issued by the Keck School of Medicine of USC. Material has been edited for length and content.