African-American women are at greater risk of dying from breast cancer than white women. Researchers in Boston, Massachusetts, hope to learn why through the Black Women's Health Study. The study -- underway for more than a decade -- looks at exposures unique to African-American women to see what factors may contribute to increased risk.

One of those unique exposures is hair relaxer. Many African-American woman and, in fact women of African descent around the world, use chemical relaxers to straighten their hair.

Professor Lynn Rosenberg says there are some potent chemicals in these products. "The main ingredients in hair relaxers are substances like lye or calcium hydroxide. These are substances that are not carcinogens. But the thing about hair relaxers is that they can contain other substances, and they are not monitored by the Food and Drug Administration. These other substances, they can be fragrances or they can be trade secrets."

The study followed 59,000 African-American women. In 1997, researchers asked the women about their use of hair relaxers. Close to 95 percent of the women reported having used hair relaxers at one time or another. Years later, Rosenberg looked at which women got breast cancer, and reports, "The good news is that we found no relationship at all between hair relaxer use and incidence of breast cancer. So whether women have used these products for many years or whether they had begun use at an early age, there was no increased risk of breast cancer."

Rosenberg says more results from the on-going Black Women's Health Study will be published in upcoming years. Researchers are gathering data on issues such as physical activity, obesity, diabetes and diet, and how they affect the health of black women. Rosenberg's latest research is published in the journal Cancer Epidemiology Biomarkers and Prevention.