(NBC News) — Women using chemical hair-straightening products are at a higher risk of uterine cancer than women who reported not using them, a new study by the National Institutes of Health found. Researchers noted that Black women may have a higher risk because they are more likely to use such products more frequently. 

A group of researchers with the NIH’s National Institute of Environmental Health Sciences looked at the hair care habits of more than 33,000 women and found that those who used chemical hair straightening products at least four times a year were more than twice as likely to develop uterine cancer. 

Researchers said chemicals like parabens, phthalates and fragrances in hair care products disrupt the endocrine system, which helps regulate hormones. That could, in turn, raise the risk of uterine cancer, the most common cancer of the female reproductive system.

“Sixty percent of the participants who reported using straighteners were Black women. The bottom line is that the exposure burden appears to be higher among Black women,” said Chandra Jackson, a participant in the National Institute of Environmental Health Sciences Earl Stadtman Investigators program, who co-authored the study. 

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