To arrive at that estimate, epidemiologist Shelia Zahm and her colleagues questioned several hundred Nebraska cancer sufferers, along with 1,400 cancer-free residents. Women with non-Hodgkin’s lymphoma were 1.5 times as likely as women in the control group to recall using hair-coloring products. Those with the longest histories of hair dyeing had the highest disease rates, and lymphoma was more common in women using permanent dyes than in those using washable ones. As in some previous studies, dark dyes appeared more hazardous than light ones; the researchers didn’t investigate the effects of dye-free lighteners.
The new study isn’t definitive. Zahm readily concedes that the statistical links may not reflect a cause-and-effect relationship. And some epidemiologists, including Dr. Alvan Feinstein of Yale and Dr. Charles Hennekens of Harvard, voice strong doubts, saying chance alone could explain her findings. The Cosmetic, Toiletry and Fragrance Association is urging consumers not to worry. In a statement issued last week, the trade association maintained that hair dyes “have a strong safety record supported by… extensive … research.” But given that 20 to 40 percent of American women use hair-coloring products-and that non-Hodgkin’s lymphoma is among the nation’s most rapidly increasing malignancies-the association Zahm detected surely warrants a closer look.
