PFAS Health Effects
What Forever Chemicals Do to the Human Body
PFAS health effects are a growing public health concern. These chemicals accumulate in the body over a lifetime and do not break down. Scientists call them “forever chemicals” for a reason. They build up in blood, liver, and kidney tissue, and they stay there for years.
Exposure begins before birth. PFAS cross the placenta and appear in breast milk. From that point, exposure continues through drinking water, food packaging, cookware, and dozens of consumer products most people use daily.
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.
This page explains what the research shows, where the science is settled, and where it is still developing.
What the Research Shows
PFAS enter the body through contaminated drinking water, food, dust, and direct contact with PFAS-containing products. Once absorbed, most PFAS bind to proteins in blood, liver, and kidney tissue. They do not break down. Exposure accumulates over a lifetime from multiple sources simultaneously.
The strongest health evidence exists for the legacy long-chain compounds PFOA and PFOS, which were produced at high volume for decades and are now the most studied. Evidence for newer short-chain replacements like GenX and PFBS is less complete.
How to Read the Evidence Labels
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. Where findings are debated, that is noted directly.
Cancer
Kidney Cancer
Strong evidence
PFOA was classified as a Group 1 confirmed human carcinogen by IARC in 2023, with kidney cancer identified as the primary cancer site. This upgraded its earlier classification as a “possible” carcinogen. 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.
A 2025 review in Frontiers in Public Health noted that more recent epidemiological studies have produced mixed results on the kidney cancer link, and that improved methodology in newer studies has raised questions about the strength of the original C8 Science Panel conclusions. The weight of evidence still supports a real association, but the magnitude of risk is debated.
PFOS was classified as a Group 2B possible human carcinogen by IARC in 2023, a lower confidence level than PFOA.
Testicular Cancer
Probable link
The C8 Science Panel established a probable link between PFOA exposure and testicular cancer in 2012, based on studies of the Parkersburg, West Virginia community. Subsequent research has generally supported the association. Testicular cancer is one of the most commonly alleged injuries in the AFFF MDL litigation, where military personnel and airport workers claim PFAS exposure through firefighting foam.
The biological mechanism is plausible: PFAS disrupt androgen signaling and the hormonal environment of testicular development and function.
Thyroid Cancer
Contested / Evolving
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, which was statistically significant. Residents of Merrimack, New Hampshire, a community with known PFAS water contamination, have had higher rates of thyroid cancer than the national average.
At the same time, a 2025 systematic review concluded that more recent epidemiological studies do not support a clear causal relationship between PFOA exposure and thyroid cancer. Study results vary, with some finding significant positive associations and others finding no association. The NCI’s Finnish Maternity Cohort study found no clear overall association between PFAS and papillary thyroid cancer, with only suggestive results in women diagnosed before age 40.
The science here is genuinely unsettled. PFAS are plausible thyroid cancer risk factors based on biological mechanisms, but population-level proof of causation is not yet established.
Other Cancers
Emerging evidence
Research is active on associations between PFAS and bladder cancer, prostate cancer, breast cancer, non-Hodgkin lymphoma, and liver cancer. A 2025 study published in Nature estimated the cancer burden attributable to PFAS in drinking water across U.S. counties. PFOA carries evidence for multiple cancer sites in occupational studies. Non-Hodgkin lymphoma is under active study by the NCI using banked serum specimens from the PLCO cohort. For most of these cancer types, the evidence is suggestive but not sufficient to establish causation as of early 2026.
Thyroid Function and Hormone Disruption
Thyroid Hormone Disruption
Strong evidence
Separate from thyroid cancer, PFAS have well-documented effects on thyroid hormone levels. Multiple large studies including NHANES data from the U.S. general population show that PFAS exposure is associated with alterations in thyroid-stimulating hormone (TSH), 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. Higher TSH in the second trimester of pregnancy has been reported in multiple studies of PFAS-exposed women. Elevated TSH in early pregnancy is associated with adverse fetal outcomes. Research also suggests PFAS may contribute to thyroid autoimmunity, though this link is less well established.
A 2024 review confirmed that PFAS definitively alter human thyroid hormones. The clinical significance of these changes at the lower exposure levels typical of the general population is still being quantified.
Testicular Cancer
Strong evidence
The C8 Science Panel established a probable link between PFOA exposure and testicular cancer in 2012, based on studies of the Parkersburg, West Virginia community. Subsequent research has generally supported the association. Testicular cancer is one of the most commonly alleged injuries in the AFFF MDL litigation, where military personnel and airport workers claim PFAS exposure through firefighting foam.
The biological mechanism is plausible: PFAS disrupt androgen signaling and the hormonal environment of testicular development and function.
Liver Disease
Probable link
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 (NAFLD). A 2024 NIEHS-funded study evaluated the effect of PFAS on liver cells, finding dose-dependent cellular effects. The human evidence is strong enough that liver function is a standard endpoint in PFAS health surveillance studies.
Immune System and Vaccine Response
Reduced Vaccine Effectiveness
Strong evidence
The most well-documented immune effect of PFAS is suppression of antibody response to vaccines. Multiple studies of children in the Faroe Islands, where PFAS exposure occurs through seafood, 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.
This finding has been replicated in other populations and has direct public health implications. A child with reduced vaccine response may not be adequately protected after routine immunization. The EPA cited immune suppression as a key health endpoint in setting the 2024 drinking water MCLs, which were driven in part by the immune effects data.
General Immune Suppression
Probable link
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. PFAS exposure has also been linked to increased susceptibility to infection in some populations. Research on PFAS and autoimmune conditions including inflammatory bowel disease is ongoing, with mixed findings.
Children and Prenatal Exposure
Why Children Face Greater Risk
Children are not simply small adults when it comes to PFAS exposure. Several factors make them more vulnerable than adults at equivalent exposure levels.
- Developmental periods in the womb, infancy, and puberty involve rapid hormonal signaling and organ formation. Even small disruptions to thyroid or sex hormone levels during these windows produce effects that persist for life.
- Children drink more water relative to body weight than adults, increasing their dose from contaminated drinking water.
- PFAS pass through the placenta during pregnancy and are present in breast milk, meaning exposure begins before birth.
- The immune system is still developing in early childhood, when the vaccine suppression effects are most consequential.
Prenatal and infant exposure
PFAS cross the placenta and accumulate in fetal blood. Studies consistently find PFAS in umbilical cord blood. Prenatal PFAS exposure has been linked to lower birth weight, reduced gestational age, and altered fetal growth. Maternal PFAS exposure affects fetal thyroid hormone levels through disruption of maternal TSH during pregnancy.
PFAS are present in breast milk, though concentrations vary by maternal exposure history. The benefits of breastfeeding are generally considered to outweigh the risks from PFAS at typical exposure levels, but reducing maternal PFAS exposure before and during pregnancy lowers infant exposure through this pathway.
Puberty and adolescent development
NIEHS-funded research found that PFAS exposure is associated with delayed onset of puberty in girls. This delay has downstream effects on breast cancer risk, kidney disease risk, and thyroid disease risk later in life. A separate study found that PFAS exposure in adolescents is linked to reduced bone mineral density over time, a risk factor for osteoporosis in adulthood.
Immune development
The vaccine suppression effects described above are most pronounced in children. The Faroe Islands studies that formed part of the basis for the EPA’s 2024 MCL decisions were conducted in children. Studies in Taiwanese children also found associations between PFAS and immune markers, though findings on childhood allergy and asthma are mixed.
Neurodevelopment
Research on PFAS and children’s neurodevelopment is emerging. Some studies report associations between prenatal PFAS exposure and lower scores on cognitive and behavioral assessments, attention issues, and altered neurological development. This area of research is earlier stage than the cancer and immune evidence, and findings are not yet consistent across studies.
Health Effect of PFAS on Reproductive Health
Outcome
Evidence Level
Summary
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 involved in ovulation and implantation.
Reduced fertility (men)
Emerging evidence
Occupational studies of men with high PFOA exposure found altered reproductive hormone levels. Population studies on sperm quality and PFAS are ongoing.
Pregnancy-induced hypertension / preeclampsia
Probable link
The C8 Science Panel established a probable link between PFOA and pregnancy-induced hypertension. Multiple subsequent studies have supported this association.
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 in different countries.
Ulcerative colitis
Probable link
Established as a probable link by the C8 Science Panel. An active area of AFFF MDL litigation with bellwether trials being selected as of late 2025.
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.
Additional Conditions Under Study
The following conditions have at least some research suggesting a connection to PFAS exposure. The evidence is not yet strong enough to establish probable links, but research is active.
- Kidney disease (non-cancer): PFAS accumulate in kidney tissue. Studies have found associations between PFAS levels and reduced kidney function in adults and children.
- Asthma and allergies: Findings are mixed. Some studies of children find associations with specific PFAS and allergy markers; others do not. Age, sex, and which PFAS are measured affect results.
- Obesity and metabolic syndrome: PFAS disrupt lipid metabolism through PPAR pathways. Research on PFAS and weight gain, insulin resistance, and metabolic syndrome is ongoing.
- Bone density: Adolescent PFAS exposure has been linked to lower bone mineral density. Potential long-term implications for fracture risk and osteoporosis.
- Autoimmune conditions: Some evidence connects PFAS to altered autoimmune markers. Research on specific conditions including lupus and rheumatoid arthritis is early stage.
What You Can Do
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 are available.
- Talk to your doctor. If you live near a known PFAS contamination site or have had significant exposure through military service or occupational contact with AFFF, 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
- IARC Monographs on PFOA and PFOS (2023): iarc.who.int — Official cancer classification authority. Upgraded PFOA to Group 1 confirmed human carcinogen in 2023.
- ATSDR PFAS Toxicological Profile (2021): atsdr.cdc.gov — Comprehensive federal review of PFAS health effects evidence, updated regularly.
- NIEHS PFAS Research: niehs.nih.gov — National Institute of Environmental Health Sciences research summaries and ongoing study updates.
- NCI PFAS and Cancer Research: dceg.cancer.gov — National Cancer Institute research portfolio on PFAS and cancer risk.
- EPA PFAS Human Health Effects: epa.gov/pfas — EPA summary of human health effects used in setting the April 2024 drinking water MCLs.
Medical Disclaimer
ForeverChemicals.info provides educational information for general consumers. Product recommendations reflect publicly available certification and regulatory data as of February 2026. Brand and certification status changes frequently. Verify current product status directly with manufacturers. Last updated February 2026.