Rapidly rising cases of uterine cancer among American women in recent years might be linked to the chemical products they are using to straighten their hair, a new government study suggests.
In the study published on Oct. 17, researchers at the U.S. National Institute of Environmental Health Sciences (NIEHS) examined data from 33,947 adult women participating in another government-sponsored study. The women, ages 35 to 74, were tracked for almost 11 years and 378 cases of uterine cancer were identified during that time.
The researchers found that women who identified as “frequent users” of chemical hair straighteners, or those who straightened their hair chemically more than four times in the year prior to being surveyed, were more than twice as likely to later be diagnosed with uterine cancer, compared with women who had never used those products.
Specifically, according to the findings, women who never used chemical hair straightening products would have a 1.64 percent chance of developing uterine cancer before they turned 70. For women who frequently used the products, that number jumps to 4.05 percent, which is much higher, though still small.
“This doubling rate is concerning,” said Dr. Alexandra White, head of the NIEHS Environment and Cancer Epidemiology group and the study’s leading author. “However, it is important to put this information into context—uterine cancer is a relatively rare type of cancer.”
Uterine cancer accounts for a little more than 3 percent of new cancer cases, with an estimated 65,950 new cases recorded in 2022, according to the National Cancer Institute, although it remains one of the most common types of cancer among American women. Most uterine cancers are found in women who are going through or have gone through menopause—the time of life when they stop menstruating.
Researchers also said the findings may be more relevant to black women, considering that some 60 percent of the participants who reported using straighteners in the previous year were black. A 2019 study shows that incidence rates of uterine cancer have been rising in the United States, particularly among black women, who use chemical hair straighteners more frequently and are more likely to start using them at younger ages than women of other races or ethnicities.
The researchers did not identify particular brands or ingredients in the hair products the women used. However, they did list several suspects, including parabens, bisphenol A, metals, and formaldehyde. Chemicals like parabens are able to disrupt the normal function of the endocrine system, which regulates hormones that control metabolism, growth, and reproduction.
Meanwhile, the researchers didn’t find any link between hair dyes and uterine cancer.