PFOS levels track 93% higher aggressive breast cancer rate

NIH researchers linked high PFOS blood levels to a 93% higher rate of ER-negative breast cancer in a Journal of Clinical Oncology study published Nov. 12.

The NIH study matters because it used blood collected before diagnosis from 1,609 breast-cancer cases and 2,269 comparison participants in the Sister Study, a U.S. and Puerto Rico cohort enrolled between 2003 and 2009.

The research examined 17 per- and polyfluoroalkyl substances, or PFAS, a family of chemicals that persist in the environment and can remain in the body for years. Two older PFAS stood out: perfluorooctanoic acid, or PFOA, and perfluorooctanesulfonic acid, or PFOS.

Women in the highest PFOA group had a 67% higher rate of ER-negative breast cancer than women in the lowest group, according to the study. For PFOS, the highest group had a 93% higher rate. The figures describe relative differences between exposure groups, not an individual woman’s absolute chance of cancer.

ER-negative breast cancer means tumor cells do not have estrogen receptors that help drive some breast cancers. These cancers are generally more aggressive and have fewer established risk factors than estrogen receptor-positive tumors.

“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,” said Alexandra White, an NIH Stadtman Investigator who led the study.

The study did not find a clear link between either chemical and breast cancer risk overall. That distinction is central: the signal appeared for one tumor subtype, not for all breast cancers combined.

The study cannot show that PFOA or PFOS directly produced ER-negative breast cancer. It was observational, and the reported mechanism remains uncertain. The NIH release said possible pathways include changes in gene activity or immune-system alterations, but the study did not test those mechanisms directly.

The findings apply most directly to women ages 35 to 74 who were enrolled in the Sister Study and had a full or half-sister with breast cancer. They may not represent women without that family history or populations outside the United States and Puerto Rico.

PFOA and PFOS have largely been phased out, according to the NIH release, but measurable amounts remain in most people’s bodies. First author Che-Jung Chang said the findings could support prevention research because “exposure to them is still potentially modifiable.”

White said more work is needed on newer replacement PFAS chemicals and on groups with higher PFAS exposure or higher rates of ER-negative breast cancer. The research received support from National Institute of Environmental Health Sciences grants Z01ES044005, Z1AES103332 and R01ES032831.

Source: NIH/Office of the Director press release via ScienceDaily, Nov. 12; Journal of Clinical Oncology study, 2026.

Atlas360 reports health research and does not provide medical advice.