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PFAS and Cancer: Kidney, Testicular, and What the Evidence Shows

By Alexander W. · Editorial Lead

The connection in brief

The cancers most strongly linked to PFAS are kidney cancer and testicular cancer. In 2023, the International Agency for Research on Cancer (IARC) classified PFOA as a Group 1 carcinogen — “carcinogenic to humans” — the highest certainty category. PFOS was classified as Group 2B, “possibly carcinogenic.” This was a significant shift, reflecting decades of accumulated evidence.

This article focuses on cancer. For the full range of health effects, see how PFAS affects your health.

What IARC’s 2023 classification means

IARC, part of the World Health Organization, reviews the global evidence and places substances into categories based on the strength of evidence that they can cause cancer — not how potent they are. Group 1 (“carcinogenic to humans”) is the same category as tobacco smoke and asbestos. That does not mean PFOA is as potent as those substances; it means the evidence that it can cause cancer in humans is now considered sufficient.

The reclassification of PFOA to Group 1 was driven heavily by evidence for kidney cancer, supported by mechanistic data on how PFOA affects human cells.

Kidney and testicular cancer

The strongest human evidence comes from the C8 Health Project, which studied nearly 70,000 people exposed to PFOA-contaminated drinking water near a manufacturing plant in West Virginia. Its independent science panel concluded there was a “probable link” between PFOA exposure and both kidney cancer and testicular cancer — meaning the evidence supported a connection more likely than not.

The kidneys are particularly relevant because they filter the blood and concentrate many substances, and PFAS are known to accumulate there.

Other cancers under investigation

Researchers continue to examine possible associations with other cancers, including breast, prostate, ovarian, and liver cancers. The evidence for these is less settled — some studies find associations and others don’t — so they remain areas of active research rather than established links. We report them as “under investigation,” not as confirmed.

Putting risk in perspective

A carcinogen classification describes a hazard (the potential to cause cancer), not the size of the risk for any individual. Your personal risk depends on how much PFAS you’ve been exposed to, for how long, alongside genetics and other factors. For most people, drinking-water PFAS represents a modest incremental risk — but it’s an avoidable one, which is exactly why the EPA set enforceable limits and why reducing exposure is worthwhile.

What you can do

  1. Know your exposure. Check your ZIP code against EPA UCMR 5 data to see whether PFAS are in your water and at what level. Our contamination rankings show the most affected systems nationally.
  2. Reduce it at the tap. A reverse osmosis or NSF/ANSI 53-certified filter removes most PFAS — see how to remove PFAS and our filter reviews.
  3. Reduce other sources. Learn where else PFAS come from in what are PFAS.
  4. Discuss high exposure with your doctor, especially if you’ve lived near a known industrial or military PFAS source.

The science here is serious but actionable. Knowing your exposure is the first step — look up your ZIP code to see what EPA testing found in your area.

This article is part of our PFAS and your health guide, which covers each major health effect with primary sources.

References

Editorial standards: primary sources only for health-effect claims. See our editorial standards page for the sourcing rubric.

  1. IARC Monographs, Volume 135 (2023). International Agency for Research on Cancer — Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). PFOA classified Group 1 (carcinogenic to humans); PFOS Group 2B. iarc.who.int
  2. C8 Science Panel Probable Link Reports (2011–2013). Findings of probable links between PFOA exposure and kidney and testicular cancer. c8sciencepanel.org
  3. ATSDR Toxicological Profile for Perfluoroalkyls (2021, updated 2023). Agency for Toxic Substances and Disease Registry — federal toxicological reference. atsdr.cdc.gov/toxprofiles
  4. NIH National Toxicology Program. Carcinogenicity and toxicology research on PFOA and PFOS.
  5. EPA Drinking Water Final Rule (April 2024). PFAS National Primary Drinking Water Regulation — source for federal MCL values. epa.gov/sdwa/and-polyfluoroalkyl-substances-pfas
  6. EPA UCMR 5 Occurrence Data (released January 2026). Source of U.S. drinking-water PFAS occurrence data. epa.gov/dwucmr

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