For decades, scientists have debated whether hair dyes frequently used by women might contribute to cancer. The research has been mixed and inconclusive, but now government investigators have turned up a disturbing new possibility.
Black women who regularly used permanent dyes to color their hair were 60 percent more likely to develop breast cancer, compared to black women who did not report using dye, according to an analysis published this week in The International Journal of Cancer, The New York Times reports.
White women using hair dye did not see a significantly increased risk. The reasons are unclear: It may be because different products are designed for women of different ethnic and racial backgrounds, or that variations in hair texture alter the amounts of dye that are applied or absorbed through the skin.
The study also implicated hair straighteners, finding a 30 percent increase in the risk of breast cancer among women of all races who reported regular use of the products. African-American women were much more likely than white women to use hair straighteners, the researchers noted.
The analysis does not prove hair treatments cause breast cancer, several experts said, and the overall risk for African-American women is difficult to know. Fewer than 10 percent of the study’s participants were black women, their use of hair products was assessed only once, and they were tracked for just eight years on average.
Generally, scientists become concerned when an environmental exposure doubles or triples cancer risk, meaning the relative risk rises by 100 percent or more. The figures reported in the new study fall short of that threshold.
“You cannot, based on these data, make the statement that hair dyes and straighteners cause breast cancer,” said Dr. Larry Norton, medical director of the Evelyn H. Lauder Breast Center at Memorial Sloan Kettering Cancer Center in New York. “These effects were small.”
Still, some scientists said the findings were concerning because of how popular hair products are. In the study, more than half said they had used hair dye, and nearly three-quarters of black women reported using hair straighteners.
“Our advice is that if you want to take a cautionary approach, limiting the use of these types of products is warranted,” said Robin Dodson, a research scientist at the Silent Spring Institute in Newton, Mass., who studies environmental risks to women’s health.