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New research is raising concerns about the safety of permanent hair dye and chemical hair straighteners, especially among African American women. NPR's Patti Neighmond reports on the study published online in the International Journal of Cancer.
PATTI NEIGHMOND, BYLINE: Previous research with animals has found links between chemicals in hair dye and straighteners and cancer. Researchers wanted to know whether women who regularly dyed or straightened their hair were also at greater cancer risk. They analyzed data from a large ongoing study of more than 46,000 women between the ages of 35 and 74.
ALEXANDRA WHITE: Fifty-five percent of women in our study reported using permanent hair dye in the last year.
NEIGHMOND: Researcher Alexandra White, with the National Institute of Environmental Health Sciences, studies environmental risk factors for breast cancer. After eight years, she found a much stronger increase in breast cancer risk among black women compared to white women.
WHITE: In white women, we saw that permanent hair dye use was associated with about a 9% higher risk, whereas in black women, that risk was about 45%.
NEIGHMOND: The risk increased even more among black women who dyed their hair frequently, every one or two months. Researchers don't know what exactly might be the cause. The study did not look at the ingredients in the products women were using, only whether they had used the product and whether they developed breast cancer. As for chemical straighteners, 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.
WHITE: For the chemical straighteners, one of the big concerns there is formaldehyde, which is a known carcinogen.
NEIGHMOND: Dr. Otis Brawley is a medical oncologist with Johns Hopkins University.
OTIS BRAWLEY: We've got numerous studies to show us in the laboratory that these hair dyes, and especially hair straighteners, cause cancer in laboratory animals. And this study is one of several, now, that suggests that they also cause cancer in human beings.
NEIGHMOND: The elevations in breast cancer risk may sound high, but Brawley says they don't compare to known risk factors like obesity and lack of exercise. To know for sure what risk hair dyes and straighteners pose, Brawley says long-term clinical trials with a control group and placebo are needed, which would be difficult, if not impossible, to do.
BRAWLEY: Sometimes science just cannot give us the answers that we want it to give us.
NEIGHMOND: For both races, there was no increased risk for women who used semi-permanent or temporary dyes, the kind that eventually wash out with shampooing. To reduce risk, researcher White says women might want to choose these products instead. Patti Neighmond, NPR News.
[POST-BROADCAST CORRECTION: Alexandra White misspoke when she said that permanent hair dye use was associated with a 9% higher breast cancer risk in white women in her study. It is associated with a 7% higher risk.]
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