PFAS, the "forever chemicals" found in nonstick pans, food packaging and stain-resistant fabrics, are in the blood of nearly every American. On November 5, 2026, the Journal of Clinical Oncology published a large National Institutes of Health (NIH) analysis of almost 3,900 women: those with the highest blood levels of two older PFAS, PFOA and PFOS, had a higher rate of estrogen receptor-negative breast cancer, a more aggressive form of the disease. Overall breast cancer risk did not change. Here is what the study found, what it does not prove, and whether a PFAS blood test is worth asking your doctor about.
What are PFAS, and why are they in our blood?
PFAS (per- and polyfluoroalkyl substances) are a family of thousands of man-made chemicals used since the 1950s because they repel water, grease and stains and resist heat. They break down extremely slowly, build up in the body and can stay there for years. People are exposed mainly through drinking water, food and food packaging, household dust and some consumer products.
In 2023, the International Agency for Research on Cancer (IARC) classified PFOA as carcinogenic to humans (Group 1) and PFOS as possibly carcinogenic (Group 2B). Until now, studies on PFAS and breast cancer had produced mixed results, partly because few of them looked at breast cancer subtypes separately.
What the NIH study measured
Researchers at the National Institute of Environmental Health Sciences (NIEHS) used the Sister Study, which enrolled 50,884 women aged 35 to 74 in the United States and Puerto Rico between 2003 and 2009. None had breast cancer at enrollment, but each had a sister who had been diagnosed with it, and each gave a blood sample at the start.
- 1,609 women who later developed breast cancer were compared with 2,269 women randomly selected from the cohort.
- Seventeen PFAS were measured in plasma collected years before any diagnosis, using high-resolution mass spectrometry.
- Results were analyzed by tumor type and adjusted for other risk factors and other chemical exposures.
- The team also pooled seven earlier studies that had measured PFAS in blood before diagnosis (a meta-analysis).
What the results show
There was no clear link between these chemicals and breast cancer overall. The signal was limited to estrogen receptor-negative (ER-negative) tumors, which do not rely on estrogen to grow, tend to be more aggressive and cannot be treated with hormone therapy.
| Chemical | Comparison | ER-negative breast cancer |
|---|---|---|
| PFOA | Highest vs lowest blood levels | 67% higher rate |
| PFOS | Highest vs lowest blood levels | 93% higher rate (nearly double) |
| Both | All breast cancers combined | No clear association |
The pooled analysis of earlier studies pointed in the same direction, especially for PFOA. These percentages compare groups of women; they do not describe any one woman's chance of getting breast cancer. The authors suggest PFAS may act through non-hormonal pathways, such as changes in gene activity or the immune system, but the study did not test this.
What the study does not tell us
- It is an observational study: it shows an association, not proof that PFAS cause breast cancer.
- All participants had a sister with breast cancer, so the findings need to be confirmed in other groups, including women more often affected by ER-negative disease.
- Only older "legacy" PFAS were assessed; newer replacement chemicals were not.
- A single blood measurement reflects past exposure and may not match exposure today.
Which tests can monitor or screen for this?
The most useful step is still regular breast cancer screening. The U.S. Preventive Services Task Force recommends a mammogram every 2 years for women aged 40 to 74. Women with a strong family history may be offered earlier or additional imaging.
A PFAS blood test is available through some commercial labs with a doctor's order. In 2022, the National Academies of Sciences, Engineering, and Medicine (NASEM) advised clinicians to offer it to people likely to have had high exposure: certain jobs, communities with documented water contamination, or homes near fluorochemical plants or military bases. Results are reported as the sum of seven PFAS in serum or plasma:
| Sum of 7 PFAS | What NASEM says | Suggested follow-up |
|---|---|---|
| Below 2 ng/mL | Adverse health effects not expected | Usual care |
| 2 to 20 ng/mL | Potential for adverse effects, especially in sensitive groups | Reduce exposure; prioritize screening for high cholesterol, high blood pressure in pregnancy and breast cancer, based on age and risk factors |
| Above 20 ng/mL | Higher risk of adverse effects | All of the above, plus thyroid function testing and checks for signs of kidney and testicular cancer and ulcerative colitis |
A PFAS level tells you about past exposure, not whether you will develop cancer, and there is no approved treatment to remove PFAS from the body. That is why the routine blood tests in the follow-up column matter:
- Lipid panel: several PFAS are linked to higher cholesterol.
- TSH: a first check of thyroid function.
- Liver function tests and kidney function panel: the liver and kidneys are among the organs monitored after heavy exposure.
- CA 15-3: a tumor marker used to follow breast cancer that has already been treated, never to screen for it.
Recent research advances
Two meta-analyses published in 2026, each pooling dozens of earlier studies, found at most a weak, borderline link between PFAS and breast cancer as a whole. In plain terms, PFAS do not appear to raise overall breast cancer risk by much. The NIH study fits that picture and adds something new: by separating tumor types, it suggests the risk may be concentrated in ER-negative cancers, a form with few known preventable risk factors. For you, this means lowering PFAS exposure is a reasonable prevention step, not a reason to panic.
Practical steps include checking your local water quality report, using a certified home water filter if your water is affected, replacing worn nonstick cookware, avoiding heating food in plastic or grease-resistant packaging, and keeping household dust down with a damp cloth and a HEPA vacuum.
When to see a doctor
- A new lump in the breast or armpit, skin dimpling, nipple changes or discharge: book a visit right away rather than waiting for your next mammogram.
- Several relatives with breast or ovarian cancer: ask whether genetic counseling or earlier screening makes sense for you.
- Known high PFAS exposure at work or from contaminated water: tell your primary care clinician, who can decide whether a PFAS blood test and follow-up tests are useful.
- For a medical emergency, call 911.
Glossary
- PFAS: per- and polyfluoroalkyl substances, a large family of very persistent man-made chemicals nicknamed "forever chemicals."
- PFOA: perfluorooctanoic acid, a legacy PFAS classified by IARC as carcinogenic to humans.
- PFOS: perfluorooctanesulfonic acid, a legacy PFAS classified by IARC as possibly carcinogenic.
- ER-negative breast cancer: a tumor whose cells lack estrogen receptors, so it does not respond to hormone therapy.
- ng/mL: nanograms per milliliter, the unit used to report PFAS levels in blood.
- Observational study: research that follows people without intervening; it can show links but not prove cause and effect.
- Meta-analysis: a statistical method that combines results from several studies on the same question.
Frequently asked questions
Do forever chemicals cause breast cancer?
The NIH study found no link with breast cancer overall. It linked high PFOA and PFOS levels to a higher rate of one subtype, ER-negative breast cancer. That is an association that still needs confirmation, not proof of cause.
Can I get a PFAS blood test?
Yes. Some commercial labs offer PFAS testing with a clinician's order. National Academies guidance recommends offering it mainly to people with a history of high exposure; for most people, the result does not change medical care.
What is a normal PFAS level in blood?
There is no "normal" level, since almost everyone has some PFAS. NASEM uses the sum of seven PFAS: below 2 ng/mL, no adverse effects are expected; above 20 ng/mL, closer follow-up is advised.
How do you get PFAS out of your body?
There is no proven treatment. Levels fall slowly over several years once exposure goes down. Detox products sold online have not been shown to work.
Should I start mammograms earlier because of PFAS?
Screening age depends on your age and family history, not on PFAS exposure. If you have a strong family history, talk with your doctor about a personalized screening plan.
Sources
- Chang CJ, Pullella K, Keil AP, et al. Per- and Polyfluoroalkyl Substance Exposure and Breast Cancer Incidence in the Sister Study. J Clin Oncol. 2026. DOI: 10.1200/JCO-26-00318
- National Institutes of Health. Two "forever chemicals" associated with higher risk of aggressive breast cancer in NIH analysis. November 5, 2026
- The ASCO Post. Two forever chemicals associated with higher risk of ER-negative breast cancer. November 2026
- National Academies of Sciences, Engineering, and Medicine. New report calls for expanded PFAS testing for people with history of elevated exposure. July 2022
- National Academies of Sciences, Engineering, and Medicine. Guidance on PFAS Exposure, Testing, and Clinical Follow-Up. 2022. DOI: 10.17226/26156
- Zahm S, Bonde JP, Chiu WA, et al. Carcinogenicity of perfluorooctanoic acid and perfluorooctanesulfonic acid. Lancet Oncol. 2024;25:16-17. DOI: 10.1016/S1470-2045(23)00622-8
- Shen HY, Jin MH, Wu ZC, et al. Per- and polyfluoroalkyl substances and the risk of thyroid and breast cancer: evidence from a meta-analysis and computational toxicology. Toxicol Appl Pharmacol. 2026;514:117933. DOI: 10.1016/j.taap.2026.117933
- Li S, Rene ER, Lu P, Ma W. Organ-specific carcinogenic risk heterogeneity of perfluorooctanoic acid exposure. J Hazard Mater. 2026;514:142831. DOI: 10.1016/j.jhazmat.2026.142831
- U.S. Preventive Services Task Force. Breast Cancer: Screening. April 2024
- U.S. Environmental Protection Agency. Per- and Polyfluoroalkyl Substances (PFAS) in drinking water
Further reading
- Breast cancer: symptoms, diagnosis and treatment
- Breast cancer screening guidelines in 2026
- Tumor antigen CA 15-3 explained
- Lipid panel: what your results mean
- TSH thyroid hormone analysis
- Cadmium exposure: urine vs blood test
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