all women and appears to be increasing for non-Hispanic black women, who also are more likely to be diagnosed with more aggressive forms of the disease and more likely to die from it.
Hair products contain more than 5,000 chemicals, according to researchers, including those with mutagenic and endocrine-disrupting properties such as aromatic amines, which can raise cancer risk, according to White.
When it came to chemical straighteners, the risk didn’t vary by race. Both black and white women who used hair straighteners were about 30% more likely to develop breast cancer than those who didn’t use the products.
However, black women are more likely to use them, with about 75% of black women in the study reporting they straighten their hair.
“For the chemical straighteners one of the big concerns there is formaldehyde, which is a known carcinogen,” says White. She notes that in the early 2000s just before the study began, Brazilian keratin treatments came on the market.
This new treatment, commonly called a Brazilian blowout, contains formaldehyde, while earlier hair straightening treatments did not.
The study findings should be understood in context, says Dr. Otis Brawley, a medical oncologist with Johns Hopkins University. The actual risk found for use of these hair treatments is quite low, he adds, especially compared with other known carcinogens like tobacco or radiation.
“This is a very weak signal that these things might be causing cancer in the population,” he says.
“Much more research is needed,” he says, “to know for sure how risky these products are. For example, long-term clinical trials with a control group and placebo would be more definitive.”