PFAS and Cancer: What the Scientific Evidence Actually Shows

Last updated: May 2026

By PFAS Exposure Claims Resource Center Published: April 2026 9 min read

The chemical industry spent decades insisting that PFAS were safe. The scientific record tells a different story. Epidemiological studies spanning more than 30 years have linked PFAS exposure to kidney cancer, testicular cancer, thyroid disease, and other serious health conditions. This article reviews that evidence and explains how it forms the foundation of PFAS personal injury litigation.

The C8 Science Panel: The Foundation of the Evidence

The most important early evidence came from the communities near DuPont's Washington Works plant in Parkersburg, West Virginia, which discharged PFOA (C8) into the Ohio River for decades. After a class action lawsuit, DuPont agreed to fund an independent scientific review called the C8 Science Panel — a team of epidemiologists who studied health outcomes in the 70,000+ people with PFOA-contaminated drinking water.

After years of research, the C8 Science Panel found "probable links" — a defined legal and scientific standard — between PFOA exposure and six health conditions:

• Kidney cancer
• Testicular cancer
• Thyroid disease
• Ulcerative colitis
• Diagnosed high cholesterol (hypercholesterolemia)
• Pregnancy-induced hypertension (preeclampsia)

These findings became foundational to PFAS litigation nationwide. They represented the first large-scale, rigorous epidemiological study specifically designed to assess whether PFAS causes human disease — and the answer, for these six conditions, was yes.

Kidney Cancer: The Strongest Association

Of all PFAS-linked cancers, the association with kidney cancer (renal cell carcinoma) is among the most consistently documented. Multiple independent epidemiological studies have found elevated kidney cancer rates in populations with high PFAS exposure:

• The C8 Science Panel found a statistically significant association between PFOA exposure and kidney cancer in the West Virginia cohort.
• Studies of occupationally exposed workers at 3M facilities in Minnesota found elevated kidney cancer rates relative to the general population.
• A 2020 analysis published in Environmental Health Perspectives examining data from multiple high-exposure cohorts confirmed the kidney cancer association across different exposure sources and geographic settings.
• Studies of military firefighters and other AFFF-exposed populations have found consistent kidney cancer signals.

The International Agency for Research on Cancer (IARC) classified PFOA as a Group 1 carcinogen (definitively carcinogenic to humans) and PFOS as a Group 2A carcinogen (probably carcinogenic to humans) in its 2023 monograph review. The kidney cancer evidence was central to the PFOA classification.

Testicular Cancer: A Younger Population at Risk

Testicular cancer is relatively rare overall, but it disproportionately affects young men. The C8 Science Panel found a probable link between PFOA exposure and testicular cancer in the West Virginia cohort. Subsequent studies have reinforced this finding:

• A study of military personnel at AFFF-contaminated bases found elevated testicular cancer rates compared to military personnel at non-contaminated bases.
• The National Cancer Institute has investigated PFAS and testicular cancer in occupational cohort studies, finding consistent associations with PFAS serum levels.
• Young men who lived near PFAS-contaminated water sources during childhood or adolescence and later developed testicular cancer represent a significant portion of PFAS personal injury plaintiffs.

Thyroid Cancer and Thyroid Disease

PFAS compounds are known to interfere with thyroid hormone metabolism. The evidence links PFAS to both thyroid cancer and non-malignant thyroid conditions (hypothyroidism, hyperthyroidism):

• Multiple population studies have found associations between elevated PFAS serum levels and altered thyroid hormone levels.
• A 2020 study in Thyroid found elevated thyroid cancer risk in populations with high PFAS exposure.
• The thyroid disruption mechanism is biologically plausible: PFAS compounds bind to thyroid hormone transport proteins and may compete with thyroid hormones at receptor sites.

Bladder Cancer and Liver Disease: Emerging Evidence

Beyond the original C8-identified conditions, more recent research has examined additional health endpoints:

Bladder cancer: Several occupational cohort studies have found elevated bladder cancer rates in workers with high PFAS exposure. The evidence is not as consistently replicated as the kidney cancer data but is considered sufficient to warrant inclusion in many litigation programs.

Non-alcoholic fatty liver disease: PFAS compounds accumulate in liver tissue and interfere with lipid metabolism. Epidemiological studies have found associations between PFAS exposure and liver enzyme abnormalities and non-alcoholic fatty liver disease (NAFLD).

Breast cancer: The evidence for a PFAS-breast cancer link is more mixed. Some studies find elevated risk; others do not. As of 2026, breast cancer is not a primary condition in most PFAS litigation programs, though research continues.

How the Science Translates to Legal Claims

For a personal injury lawsuit, plaintiffs must establish general causation (PFAS can cause this type of cancer in humans as a matter of science) and specific causation (PFAS caused this particular plaintiff's cancer). The scientific evidence described above supports general causation for the primary PFAS-linked conditions.

The defense will argue alternative causation — that your cancer was caused by other factors (obesity, smoking, family history, age). Plaintiffs' expert witnesses use epidemiological and toxicological methodologies to assess the relative contribution of PFAS exposure versus other risk factors in each individual case.

Having a documented exposure history (blood serum results, contaminated water system data), a clear diagnosis, and a timeline that is consistent with PFAS-induced cancer (exposure precedes diagnosis, typically by years) all strengthen the specific causation argument.

What 3M and DuPont Knew — and When

One of the most damaging aspects of PFAS litigation for the defendants is the internal documents showing that 3M and DuPont were aware of PFAS toxicity concerns decades before the public was informed. Internal 3M studies from the 1970s and 1980s showed that PFOS and PFOA were accumulating in human blood. DuPont's own internal health studies showed kidney tumors in animal studies. These documents — obtained through litigation discovery — support punitive damage claims by showing conscious disregard for known risks.