How PFAS Affects Your Health: What the Science Says

The Growing Body of Evidence

Decades of epidemiological studies, laboratory research, and community health investigations have built a substantial case linking PFAS exposure to serious health outcomes. The science is not speculative — much of it comes from large-scale studies of communities with contaminated drinking water, including the landmark C8 Health Project that followed nearly 70,000 people exposed to PFOA near a DuPont manufacturing plant in West Virginia.

Here is what the research shows across the most studied health endpoints.

Cancer

PFAS exposure has been most strongly linked to kidney cancer and testicular cancer. The International Agency for Research on Cancer (IARC) classified PFOA as a Group 1 carcinogen (carcinogenic to humans) in 2023, and PFOS as a Group 2B possible carcinogen.

The C8 study found a statistically significant increase in kidney and testicular cancer among people with higher PFOA blood levels. More recent research has also identified potential associations with bladder cancer, breast cancer, and prostate cancer, though these links are still being studied.

The mechanism appears to involve oxidative stress and interference with cellular signaling pathways that regulate cell growth.

Thyroid Disruption

PFAS compounds interfere with thyroid hormone production and transport. Multiple studies have found that people with higher PFAS blood levels are more likely to have hypothyroidism (underactive thyroid) and abnormal levels of T3 and T4 hormones.

This is particularly concerning because thyroid hormones regulate metabolism, energy, and — critically in children — brain development. Even modest thyroid disruption during pregnancy or early childhood can have lasting developmental consequences.

Immune System Suppression

One of the most well-established effects of PFAS exposure is reduced immune function. Research has consistently shown:

• Lower vaccine antibody responses — Children with higher PFAS blood levels produce fewer antibodies after routine vaccinations, including diphtheria and tetanus. This was one of the key findings that led the National Academies of Sciences to conclude that PFAS impairs immune function.
• Increased infection susceptibility — Epidemiological studies have found higher rates of infectious illness in PFAS-exposed populations.
• Potential autoimmune effects — Emerging research suggests PFAS may contribute to autoimmune conditions such as ulcerative colitis, though the evidence here is still developing.

The immune effects are observed at blood PFAS levels common in the general U.S. population, not just in highly exposed communities.

Cholesterol and Cardiovascular Effects

Even at relatively low exposure levels, PFAS has been consistently associated with elevated total cholesterol and LDL cholesterol. The C8 study, NHANES data analyses, and multiple independent studies all converge on this finding.

Higher cholesterol is a well-established risk factor for cardiovascular disease. Researchers estimate that PFAS-related cholesterol increases could contribute to thousands of additional cardiovascular events annually across the U.S. population.

Reproductive and Developmental Effects

PFAS exposure has been linked to a range of reproductive and developmental problems:

• Reduced fertility — Both PFOA and PFOS have been associated with longer time-to-pregnancy and decreased fecundability in women.
• Pregnancy complications — Higher PFAS levels have been linked to preeclampsia (pregnancy-induced hypertension), gestational diabetes, and preterm birth.
• Lower birth weight — Multiple studies have found that maternal PFAS exposure correlates with reduced infant birth weight, a risk factor for long-term health problems.
• Endocrine disruption — PFAS can interfere with estrogen and testosterone signaling, potentially affecting sexual development and reproductive function.

For a detailed look at the pregnancy-specific risks — including preeclampsia, gestational diabetes, birth weight, and thyroid disruption during the first trimester — see our dedicated article on PFAS exposure during pregnancy.

Children’s Vulnerability

Children face disproportionate risk from PFAS for several reasons:

• They drink more water per pound of body weight than adults
• Their organs and immune systems are still developing
• Early-life exposure can set the stage for chronic health problems decades later
• PFAS crosses the placental barrier, meaning exposure begins before birth

Studies have found associations between childhood PFAS exposure and delayed puberty, lower vaccine effectiveness, and potential impacts on bone density and metabolic function.

What Level of PFAS Is Dangerous?

There is no established “safe” level of PFAS exposure. The EPA’s Maximum Contaminant Levels of 4 ppt for PFOA and PFOS reflect the lowest concentrations at which health effects have been observed in epidemiological studies, with safety margins applied.

In 2022, the National Academies of Sciences, Engineering, and Medicine (NASEM) published a landmark report on PFAS exposure and health effects. The report established clinical guidance based on blood PFAS levels:

• Below 2 ng/mL total PFAS: Continue healthy behaviors; no specific clinical action required beyond standard care.
• 2–7 ng/mL total PFAS: Discuss exposure history with a physician; consider increasing healthy behaviors such as breastfeeding, diet adjustments, and monitoring of cholesterol and thyroid function.
• Above 7 ng/mL total PFAS: Discuss risk reduction and screening with a clinician; consider testing for thyroid abnormalities, lipid panels, blood pressure monitoring, and kidney function checks.

You can request a PFAS blood test through a physician or send a sample to certified labs such as those listed by the National PFAS Testing Project. This is especially recommended for people with known high PFAS water exposure or who live near industrial or military PFAS sources.

The NASEM report also concluded that some of the EPA’s limits — including the 4 ppt MCL — may not fully protect the most vulnerable populations, particularly infants, pregnant women, and people with pre-existing immune conditions.

Protecting Yourself

If your water contains PFAS — or if you are unsure — these steps can reduce your exposure:

1. Check your water: Our free lookup uses EPA UCMR 5 data to show PFAS detections by ZIP code.
2. Install an effective filter: Reverse osmosis removes over 99% of PFAS. Activated carbon filters certified to NSF 53 or P473 are also effective.
3. Learn about what PFAS are and where they come from to reduce exposure from non-water sources as well.
4. Browse our filter reviews for tested, certified options at every price point.

The health science on PFAS is serious, but it is also actionable. Knowing your exposure level is the first step. Look up your ZIP code now to see what EPA testing found in your area.