Women with higher blood levels of two widely used per- and polyfluoroalkyl substances (PFAS), commonly known as “forever chemicals,” may face a higher risk of developing an aggressive form of breast cancer, according to a new study by the US National Institutes of Health (NIH).
The study found an association between two PFAS compounds, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), and an increased incidence of estrogen receptor-negative (ER-negative) breast cancer. However, researchers did not find a clear association between these chemicals and breast cancer risk overall.
PFAS are a large group of chemicals used in various consumer products. They are known as forever chemicals because they do not break down easily in the environment and can remain in the human body for years.
PFAS Exposure Linked to Higher Risk of Aggressive Breast Cancer
Researchers found that women with the highest blood levels of PFOA had a 67% higher rate of ER-negative breast cancer than those with the lowest levels. Similarly, women with higher PFOS levels had a 93% higher rate of this cancer type.
These figures represent relative differences in cancer rates between the study groups and do not indicate an individual’s absolute risk of developing breast cancer.
ER-negative breast tumours lack estrogen receptors, which means estrogen cannot directly stimulate their growth through these receptors. Compared with hormone receptor-positive breast cancers, ER-negative tumours tend to be more aggressive and are often associated with poorer outcomes. Researchers also have limited knowledge of the factors that contribute to this cancer subtype.
NIH Study Examines Blood Samples and Breast Cancer Risk
The research team measured 17 different PFAS compounds in blood samples collected years before participants received a breast cancer diagnosis.
The study used data from the Sister Study, conducted by the NIH’s National Institute of Environmental Health Sciences (NIEHS). The larger study enrolled 50,884 women aged 35–74 years across the United States and Puerto Rico between 2003 and 2009. None had breast cancer at enrolment, although all had a full or half-sister previously diagnosed with the disease.
For the PFAS analysis, researchers included 1,609 women who subsequently developed breast cancer and a comparison group of 2,269 women.
The researchers also confirmed their findings through a meta-analysis of previous studies, strengthening the evidence linking certain legacy PFAS compounds with ER-negative breast cancer.
Researchers Call for Further Investigation
According to the study’s lead investigator, Alexandra White, PhD, the findings highlight a possible link between certain long-lasting environmental chemicals and a more aggressive breast cancer subtype with relatively few established risk factors.
Researchers suggested that PFAS may influence breast cancer development through biological pathways other than hormonal activity. These could include changes in gene expression or immune system function. However, the study did not directly investigate these mechanisms.
The research team has called for further studies involving populations with higher PFAS exposure, particularly groups that experience a greater burden of ER-negative breast cancer.
Reducing PFAS Exposure Could Support Prevention Efforts
Although PFOA and PFOS have been largely phased out and replaced by newer PFAS compounds, many people still have measurable levels of these chemicals in their bodies.
Researchers emphasised that PFAS exposure remains a potentially modifiable environmental risk factor. Therefore, understanding exposure sources and identifying ways to reduce contact with these chemicals could help inform future prevention strategies. The findings were published in the Journal of Clinical Oncology. The researchers also highlighted the need to investigate whether newer PFAS replacement compounds may influence breast cancer risk.
As reported by pharmabiz.com, NIH findings highlight a potential association between exposure to PFOA and PFOS and an increased risk of aggressive ER-negative breast cancer, underscoring the need for further research into the long-term health effects of PFAS exposure.