NIH Study Links PFAS Chemicals to Breast Cancer Risk

Higher blood levels of two PFAS compounds were associated with more estrogen-receptor-negative breast cancer in a large U.S. cohort study.

Updated on Nov. 5, 2026 in Cancer

Isometric editorial illustration of a row of unlabeled glass sample vials on a plain bench in muted slate and cream tones. — A National Institutes of Health study found higher blood levels of PFOA and PFOS linked to more estrogen-receptor-negative breast cancer among U.S. women. AI Illustration. Upload story photo >

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A National Institutes of Health study found that women with higher blood levels of PFOA and PFOS had higher rates of ER-negative breast cancer, based on blood samples collected years before diagnosis. The findings were published in the Journal of Clinical Oncology.

Why it matters

The results add to concerns about long-lived PFAS chemicals and cancer risk, particularly for the ER-negative subtype, which is harder to treat with hormone-targeted therapies. The authors suggest PFAS may affect cancer risk through non-hormonal biologic pathways.

The analysis compared 1,609 women who developed breast cancer with 2,269 women in a comparison sample, drawn from 50,884 Sister Study enrollees aged 35-74. Whether the association holds across more heavily exposed populations remains unresolved.

The players

National Institutes of Health

The NIH is the primary federal agency for biomedical and health research in the United States, conducting and funding studies on diseases including cancer.

Journal of Clinical Oncology

A peer-reviewed medical journal published by the American Society of Clinical Oncology that reports research on cancer diagnosis and treatment.

The details

Researchers measured 17 PFAS compounds in blood plasma collected years before diagnosis and compared breast cancer incidence across blood-level groups in the Sister Study cohort. PFOA and PFOS have been largely phased out and replaced with newer PFAS compounds, so current exposure patterns may differ.

Sister Study enrolled women between 2003 and 2009.
NIH published the study findings on November 5, 2026.

Research Context

The findings build on the Sister Study, a long-running NIH cohort that has tracked environmental exposures and breast cancer outcomes among women in the United States and Puerto Rico. They extend that work by focusing on ER-negative subtypes and on PFAS chemicals measured before diagnosis.

For women concerned about environmental chemical exposure, the study does not yet establish changes to screening or treatment recommendations. Its findings may inform future research on exposure reduction and breast cancer prevention.

The takeaway

Blood levels of certain PFAS chemicals were associated with a higher rate of ER-negative breast cancer in a large U.S. cohort, though the study does not prove cause and effect. Readers concerned about chemical exposure can follow updates from the NIH as follow-up research is published.