FRIDAY, Nov. 6, 2026 (HealthDay News) — Two “forever chemicals” have been linked to a more deadly form of breast cancer, a new study says.
Women with higher blood levels of the two common per- and polyfluoroalkyl substances (PFAS) are more likely to develop a tougher-to-treat type of breast cancer, researchers reported Thursday in the Journal of Clinical Oncology.
Specifically, they had a 67% to 93% increased risk of ER-negative breast cancers, which are not fueled by the female hormone estrogen, researchers found. These cancers tend to be more aggressive and have worse outcomes.
“These findings matter for women’s health broadly,” said lead investigator Che-Jung Chang, a senior epidemiologist at the healthcare and security think-tank DLH Corporation in Atlanta.
“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,” she said in a news release.
PFAS are called “forever chemicals” because they combine carbon and fluorine molecules, one of the strongest chemical bonds possible. This makes PFAS removal and breakdown very difficult.
PFAS compounds have been used in consumer products since the 1940s, including fire extinguishing foam, nonstick cookware, food wrappers, stain-resistant furniture and waterproof clothing.
For the new review, researchers analyzed data from a long-term study that recruited nearly 51,000 U.S. women ages 35 to 74 between 2003 and 2009.
None of the women had breast cancer when they joined the study, but each had a full or half-sister who had been previously diagnosed with breast cancer, researchers said.
Researchers compared about 1,600 women who went on to develop breast cancer against nearly 2,300 women who remained cancer-free, examining their blood for levels of 17 different PFAS chemicals.
Results showed that women with the highest levels of perfluorooctanoic acid (PFOA) in their blood were 67% more likely to develop ER-negative breast cancer.
Likewise, women with the heaviest blood levels of perfluorooctanesulfonic acid (PFOS) had a 93% higher risk of ER-negative breast cancer.
Because these cancers are not driven by hormones, researchers speculated that PFAS might increase women’s risk by affecting gene activity or altering the immune response to cancer.
Future studies will be needed to see if these potential explanations are accurate, and to assess whether more modern types of PFAS pose a similar health hazard, researchers said.
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, researchers noted.
“More research is needed, particularly evaluating the risk of breast cancer associated with newer replacement PFAS chemicals,” senior researcher Alexandra White, an investigator in environment and cancer epidemiology at the National Institutes of Health, said in a news release.
The Environmental Working Group says women can protect themselves from PFAS exposure by:
Filtering their drinking water
Using online resources to check PFAS levels in cosmetics, personal care products and household cleaners
Avoiding the use of nonstick cookware and utensils
Making sure that fabrics labeled stain- and water-repellent haven’t been treated with PFAS
Cutting back on fast food, which is often sold in containers and wrappers treated with PFAS
More information
The Environmental Working Group has more on avoiding PFAS “forever chemicals.”
SOURCE: National Institutes of Health, news release, Nov. 5, 2026
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