Forever Chemicals PFOS and PFOA Tied to Aggressive Breast Cancer
A National Institutes of Health study found women with the highest blood levels of PFOA and PFOS had 67% and 93% higher rates of ER-negative breast cancer. Researchers found no clear link to breast cancer overall, and outside experts say causation is unproven.
Women with high blood levels of two common "forever chemicals" may face a higher risk of an aggressive form of breast cancer, according to a study by the National Institutes of Health (NIH) published in the Journal of Clinical Oncology. The research links exposure to certain forever chemicals, PFOA and PFOS, to estrogen receptor-negative (ER-negative) breast cancer.
Women in the highest PFOA group had a 67% higher rate of this cancer than women in the lowest group. For PFOS, the rate was 93% higher, NIH said.
Researchers found "no clear association" between either chemical and breast cancer overall, according to NIH.
The percentages are relative differences between groups. They do not give the chance that an individual woman will develop the disease, and the study shows an association, not proof of cause.
What the study found
ER-negative tumors lack the receptors that let estrogen help cancer cells grow. They tend to be more aggressive and have worse outcomes, and scientists know less about what raises the risk.
"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 Dr. Alexandra White, the NIH investigator who led the study.
The team used data from the Sister Study, a long-term NIH project that enrolled 50,884 women ages 35 to 74 in the United States and Puerto Rico between 2003 and 2009. Every participant had a sister who had been diagnosed with breast cancer, but none had the disease at enrollment.
Researchers compared blood samples from 1,609 women who later developed breast cancer with samples from 2,269 other women. The samples were collected years before diagnosis. NIH scientists measured concentrations of 17 different PFAS chemicals.
The study did not determine how the chemicals might contribute to breast cancer.
Caution from outside experts
Dr. Timothy Rebbeck, a professor of cancer prevention at Dana-Farber Cancer Institute and Harvard, said the work adds to research linking forever chemicals to certain cancers. He cautioned against reading too much into it.
"The data so far have really been correlation, not causation, in humans," Rebbeck said in an interview Wednesday. He added that few risk factors are known for ER-negative breast cancer, so "if forever chemicals play some role in that, that's important knowledge."
HHS Secretary Robert F. Kennedy, Jr. said the study "demands further investigation."
Where the chemicals are found
PFOA and PFOS belong to a large family called per- and polyfluoroalkyl substances, or PFAS. They are called forever chemicals because they break down slowly and can stay in the human body for years.
Both were used for decades in products such as non-stick cookware, food packaging and stain-resistant clothes. They have mostly been phased out in the US since the early 2000s but remain widespread.
Nearly all people in the US have PFAS in their blood, according to the Centers for Disease Control and Prevention (CDC). Between 1999 and 2019, blood PFOS levels fell by more than 85%, and PFOA levels fell by more than 70%, the CDC reported.
