Two chemicals that can remain in the human body for years have been linked to a higher incidence of an aggressive form of breast cancer, according to new research from the National Institutes of Health (NIH). The findings, announced November 5, add to growing scientific concerns about the potential health effects of substances commonly known as “forever chemicals.”
Researchers examined blood samples collected years before participants developed cancer and found that women with higher concentrations of two chemicals, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), were more likely to develop estrogen receptor-negative (ER-negative) breast cancer. These tumors lack receptors for the hormone estrogen and tend to be more difficult to treat than cancers that respond to hormone-based therapies. Importantly, the study did not identify a clear association between these chemicals and breast cancer overall.
The analysis included 1,609 women who developed breast cancer and a comparison group of 2,269 women from the NIH’s Sister Study, a long-running research project involving women whose sisters had previously been diagnosed with breast cancer. Women with the highest PFOA levels had a 67% higher rate of ER-negative breast cancer than those with the lowest levels. For PFOS, the rate was 93% higher. Those figures represent differences between study groups, not an individual woman’s probability of developing the disease.
PFOA and PFOS belong to a larger family of chemicals called per- and polyfluoroalkyl substances (PFAS), which have been used in consumer and industrial products because of their resistance to heat, water and grease. PFOA was historically used in the manufacture of some nonstick cookware coatings, while PFOS was used in stain-resistant treatments for carpets, upholstery and other fabrics. The chemicals were also used in certain firefighting foams, and the broader PFAS family has been used in water-resistant clothing and grease-resistant food packaging.
Although PFOA and PFOS have largely been phased out in the United States, they can persist in the environment, including drinking water, for years. Not all products in these categories contain the two chemicals studied, and researchers emphasized that the findings establish an association rather than proving that exposure directly causes breast cancer.
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One of the study’s most significant findings is the distinction between breast cancer overall and a specific, more aggressive form of the disease. That suggests environmental exposures may affect different forms of the disease in different ways, potentially revealing risk factors that broader cancer studies have overlooked. It also underscores the importance of studying chemicals that remain in the environment long after their widespread use has declined.
The researchers say further investigation is needed to understand the biological mechanisms involved and determine whether newer PFAS replacements carry similar risks. For consumers, the findings reinforce the value of reliable information about environmental exposure without suggesting that any single product or chemical exposure determines whether someone will develop cancer. The research offers an important new direction for prevention studies, but not yet a definitive explanation of the disease.
