PFAS Health Effects

What Forever
Chemicals Do to
the Human Body

PFAS accumulate in the body over a lifetime and do not break down. They build up in blood, liver, and kidney tissue and stay there for years. Exposure begins before birth. The evidence linking PFAS to cancer, immune dysfunction, thyroid disease, and developmental harm has grown substantially since the mid-2000s. What was once a collection of early associations has become a body of consistent findings across multiple study populations worldwide.

The Scale

97%

Americans with Detectable PFAS in Blood (CDC NHANES)

2023

IARC Upgraded PFOA to Group 1 Confirmed Human Carcinogen

3–8 yrs

Estimated Half-Life of PFOA and PFOS in the Human Body

12,000+

PFAS Compounds Exist. Health Data Available on Only a Handful.

How to Read the Evidence

Evidence Labels Used on This Page

Each condition below carries an evidence label reflecting the current scientific consensus as of early 2026.

Strong evidence Probable link Emerging evidence Contested / Evolving

Science changes. Labels here reflect the weight of published peer-reviewed research, not the position of any single study or litigation panel.

Cancer

Cancer

Strong evidence

Kidney Cancer

PFOA was classified as a Group 1 confirmed human carcinogen by IARC in 2023, with kidney cancer identified as the primary cancer site. The classification is based on studies of workers at PFOA manufacturing plants, community studies near contaminated sites including the C8 cohort in West Virginia, and supporting animal data. PFOS was classified as a Group 2B possible human carcinogen in the same review.

Probable link

Testicular Cancer

The C8 Science Panel established a probable link between PFOA exposure and testicular cancer in 2012. Subsequent research has generally supported the association. The biological mechanism is plausible: PFAS disrupt androgen signaling and the hormonal environment of testicular development and function.

Contested / Evolving

Thyroid Cancer

The relationship between PFAS and thyroid cancer is one of the most actively debated areas in PFAS research. A 2023 study from the Icahn School of Medicine at Mount Sinai found a 56% increased rate of papillary thyroid cancer per doubling of PFOS concentration in blood. At the same time, a 2025 systematic review concluded that more recent epidemiological studies do not support a clear causal relationship. The science here is genuinely unsettled.

Emerging evidence

Other Cancers

Research is active on associations between PFAS and bladder cancer, prostate cancer, breast cancer, non-Hodgkin lymphoma, and liver cancer. For most of these cancer types, the evidence is suggestive but not sufficient to establish causation as of early 2026.

Thyroid and Hormones

Thyroid Function and Hormone Disruption

Strong evidence

Thyroid Hormone Disruption

Multiple large studies including NHANES data from the U.S. general population show that PFAS exposure is associated with alterations in thyroid-stimulating hormone, free T4, and total T3. PFAS structurally resemble thyroid hormones and compete for binding sites on thyroid hormone transport proteins. Effects appear most significant during pregnancy. A 2024 review confirmed that PFAS definitively alter human thyroid hormones.

Probable link

Liver Disease

The liver is the primary storage organ for long-chain PFAS. Animal studies consistently show PFAS cause liver cell damage, fat infiltration, and disrupted fatty acid metabolism. Human studies link PFAS exposure to elevated liver enzymes and non-alcoholic fatty liver disease. Liver function is a standard endpoint in PFAS health surveillance studies.

Immune System

Immune System and Vaccine Response

Strong evidence

Reduced Vaccine Effectiveness

The most well-documented immune effect of PFAS is suppression of antibody response to vaccines. Multiple studies of children in the Faroe Islands found that children with higher PFAS blood levels had substantially lower antibody titers after standard childhood vaccinations including tetanus and diphtheria. A doubling of PFAS concentration was associated with up to a 50% reduction in vaccine-induced antibody levels in some studies. The EPA cited immune suppression as a key health endpoint in setting the 2024 drinking water MCLs.

Probable link

General Immune Suppression

Beyond vaccine response, PFAS appear to broadly suppress immune function. Studies have found associations between PFAS exposure and reduced counts of natural killer cells and other immune cells involved in fighting infection and cancer.

Reproductive Health

Reproductive and Developmental Outcomes

Outcome

Evidence Level

Summary

Reduced Birth Weight

Strong Evidence

One of the most consistently replicated PFAS findings. Higher prenatal PFAS exposure is associated with lower birth weight across multiple large cohort studies.

Reduced
Fertility (women)

Probable Link

Multiple studies associate higher PFAS blood levels with longer time to pregnancy and reduced fecundability. PFAS disrupt estrogen and progesterone signaling.

Preeclam
-psia

Probable Link

The C8 Science Panel established a probable link between PFOA and pregnancy-induced hypertension. Multiple subsequent studies have supported this association.

Altered Puberty Timing

Emerging Evidence

NIEHS-funded research found PFAS exposure is associated with delayed onset of puberty in girls, consistent with PFAS acting as endocrine disruptors.

Reduced
Fertility (men)

Emerging Evidence

Occupational studies of men with high PFOA exposure found altered reproductive hormone levels. Population studies on sperm quality are ongoing.

Type 2 Diabetes

Emerging Evidence

A long-term NIEHS-funded study found a link between PFAS exposure and increased risk of Type 2 diabetes in women. Research ongoing.

High Choles
-terol

Strong Evidence

One of the most consistent findings across studies. PFAS exposure correlates with elevated total cholesterol and LDL cholesterol levels.

Ulcerative
Colitis

Probable Link

Established as a probable link by the C8 Science Panel. An active area of AFFF MDL litigation.

The Mixture Problem

Most people are exposed to dozens of PFAS simultaneously, not just PFOA or PFOS in isolation. A December 2024 study found that PFAS mixtures are more harmful to health than exposure to a single compound at the same total concentration. Nearly all human health research to date has studied individual PFAS, meaning current risk estimates may understate real-world harm from combined exposure.

What You Can Do

Reducing Ongoing Exposure

You cannot eliminate PFAS from your body, but you can reduce ongoing exposure, which allows your body burden to decline over time as existing PFAS are slowly cleared.

  • Test your drinking water. PFAS in drinking water is the most significant controllable exposure for most people. Find a certified lab through the EPA’s laboratory accreditation program.
  • Filter your water. A reverse osmosis system certified under NSF/ANSI Standard 58 removes 90 to 99 percent of most PFAS. Install one at the kitchen tap used for drinking and cooking.
  • Reduce product exposure. Avoid non-stick cookware with worn coatings, stain-treated upholstery and carpets, and PFAS-containing food packaging where alternatives exist.
  • Talk to your doctor. If you live near a known PFAS contamination site or have had significant occupational exposure, discuss PFAS-related health monitoring with your physician.
  • Pregnant women and young children. Reducing exposure is most urgent during pregnancy and early childhood. Prioritize filtered water and avoid PFAS-containing products in the home during these periods.
Key Sources

Primary Research Sources


IARC Monographs on PFOA and PFOS (2023)

Official cancer classification authority. Upgraded PFOA to Group 1 confirmed human carcinogen in 2023.


ATSDR PFAS Toxicological Profile

Comprehensive federal review of PFAS health effects evidence, updated regularly.


NIEHS PFAS Research

National Institute of Environmental Health Sciences research summaries and ongoing study updates.


NCI PFAS and Cancer Research

National Cancer Institute research portfolio on PFAS and cancer risk.


EPA PFAS Human Health Effects

EPA summary of human health effects used in setting the April 2024 drinking water MCLs.