You’ll often hear that those so-called “forever chemicals” (PFAS) stay in the environment (and in your body) indefinitely and are implicated in a number of health conditions.
Now you can add certain types of breast cancer to the list, according to a study by the National Institutes of Health (NIH).
The study found that women with higher blood plasma levels of two PFAS substances, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), were associated with a higher incidence of ER-negative breast cancer. No clear association was observed between the two chemicals and breast cancer risk overall.
“Women deserve clear answers about how chemicals in their environment may affect their health,” said HHS Secretary Robert F. Kennedy, Jr. “This NIH study links two forever chemicals to a higher risk of ER-negative breast cancer and demands further investigation.”
About the study
NIH researchers and their collaborators measured 17 PFAS in blood, collected years before women were diagnosed with cancer. Women in the group with the highest PFOA levels had a 67% higher rate of ER-negative breast cancer than those in the lowest group. For PFOS, the rate was 93% higher, or nearly twice as high. These numbers describe relative differences between groups, not an individual woman’s chance of getting breast cancer.
The research drew on the Sister Study, led by NIH’s National Institute of Environmental Health Sciences (NIEHS). The larger study enrolled 50,884 women ages 35–74 in the United States and Puerto Rico from 2003 to 2009. None had breast cancer when they joined the Sister Study, but each had a full or half-sister who had been previously diagnosed with breast cancer. For the PFAS study, researchers included 1,609 women who developed breast cancer and a comparison sample of 2,269 women.
ER-negative tumors lack receptors that allow hormone estrogen to help cancer cells grow. Compared with breast cancers that respond to hormone estrogen, ER-negative breast cancers tend to be more aggressive and have worse outcomes. Scientists know less about what raises the risk of this type of breast cancer.
“Our findings, which we confirmed using a meta-analysis of prior research, indicate that certain legacy PFAS, including PFOA and PFOS, are associated with a higher risk of ER-negative breast cancer, a more aggressive tumor type with few known risk factors,” explained NIH Stadtman Investigator Alexandra White, Ph.D., who led the study. The findings are reported in the Journal of Clinical Oncology.
New avenues for prevention
“These findings matter for women’s health broadly,” said first author, Che-Jung Chang, Ph.D., a former research fellow at NIH and a current researcher at DLH, a scientific research organization. “Although PFAS are persistent in the environment and in our bodies, exposure to them is still potentially modifiable, meaning people can take steps to reduce their exposure, and these findings could open new avenues for prevention.”
Although most individuals have measurable levels of PFOA and PFOS in their bodies, these compounds have been largely phased out and replaced with new PFAS compounds. “More research is needed, particularly evaluating the risk of breast cancer associated with newer replacement PFAS chemicals,” White said.
NewsTracker: PFAS and forever chemicals
Recent PFAS stories of interest:
- October 23, 2026 — PFAS levels in drinking water may be higher than official estimates. New research suggests conventional reporting may substantially underestimate PFAS concentrations in American drinking water.
- October 18, 2026 — Oral-B Glide, competitors removing PFAS from their super slippery dental floss. Dental floss manufacturers are reformulating popular products to eliminate PFAS-based materials as health concerns grow.
- May 6, 2026 — Simple kitchen tricks may cut pesticide residues on produce, study finds. Research on reducing pesticide contamination includes discussion of PFAS-based pesticides.
- April 13, 2026 — PFAS research roundup: What studies say about health risks, exposure, and uncertainty. A review of scientific evidence linking PFAS exposure to immune, metabolic, developmental and other health effects.
- April 13, 2026 — PFAS chemicals in Lululemon? Texas opens an investigation. Texas authorities investigate potential PFAS contamination in athletic apparel.
- March 12, 2026 — PFAS forever chemicals found on majority of California stone fruits, new analysis shows. Testing raises questions about persistent chemical residues on peaches, plums and other produce.
- September 4, 2025 — Advanced PFAS water filters deliver unexpected health benefits by removing multiple toxic chemicals. Research finds that some PFAS filtration technologies also remove other potentially harmful water contaminants.
- June 9, 2025 — Is that frying pan really non-toxic ceramic? A look at alternative nonstick cookware, including performance claims and the trade-offs involved in avoiding PFAS coatings.
- Feb. 2025 — Trump trashes environmental rules, claiming it will boost affordability of cars. Broader environmental deregulation coverage includes discussion of PFAS chemical regulation.