Hair Dyes Get The `All Clear' Signal...For Now

When Jacqueline Kennedy Onassis died of non-Hodgkins lymphoma five years ago, her picture showed up in several health-related sites on the Internet. At the time, questions were raised about whether the cancer had been caused by her obvious use of hair dye. The suggestion had some validity for preliminary studies have shown a slightly increased rate of non-Hodgkins lymphoma among people who used permanent hair dye, especially the dark colors--black, brown, and red. The latest study, however, found little convincing evidence linking non-Hodgkins lymphoma with normal use of hair-color products in humans.

Non-Hodgkins lymphoma, which is a cancer of the immune system, has increased in incidence over the last 20 years: 4% per year in men and 3% per year in women. There are few clues as to why. Fifteen years ago researchers found a link between this form of cancer and exposure to the herbicide 2,4-D (dichlorophenoxyacetic acid). In time, the link was confirmed by several other studies. But the studies linking non-Hodgkins lymphoma to hair dye have not produced consistent results; some found no relationship. Initial suspicions about the safety of hair dye came from animal studies showing that certain chemicals in hair dyes can cause cancer and mutations in the DNA.

San Francisco was the site chosen for the latest hair-dye study, which was conducted by Elizabeth A. Holly, Ph.D., M.P.H., University of California School of Medicine, and colleagues (American Journal of Public Health, December 1998). This city has a hair-dye usage rate that is much higher than the normal range of 20-40%. Through a system operated by the Northern California Cancer Center, the investigators found 1,593 men and women who had recently been diagnosed with non-Hodgkins lymphoma. Over 2,500 men and women selected randomly by telephone served as the control group. All were interviewed extensively about use of hair-dye products.

Dr. Holly and colleagues found that the people with non-Hodgkins lymphoma had the same rate of usage as the people who did not. They wrote, Our results in conjunction with others are reassuring for the many women and men who use hair-color products in the United States. The study was funded by the National Cancer Institute. These results are strengthened by those of two earlier studies. The Nurses Health Study, for example, which has collected extensive data on thousands of women since 1976, found no increased risk of cancer among hair-dye users. Nor did a 1994 study sponsored by the American Cancer Society which followed over half a million women after they completed an extensive questionnaire about hair-dye use. After seven years of follow-up, no increased rate of cancer was found among the hair-dye users. There was one exception, however; the women who used very dark, permanent dyes for over 20 years had a higher rate of non-Hodgkins lymphoma and of bone cancer.

Sheila Hoar Zahm, Sc.D., who co-authored the first major study (1992) to find a link between hair dye and cancer, was asked to comment on the San Francisco study. Its well done, a good design, and it adds to the body of knowledge that sways in the direction indicating that maybe this isnt a very big problem, said Dr. Zahm, in a telephone interview. On the other hand, the Nurses Health Study and the American Cancer Society studies were of a less-trustworthy design, according to Dr. Zahm, who is the deputy director of the National Cancer Institutes division of epidemiology and genetics. Both were cohort studies, a type of study that gives more emphasis to questions asked early in the phase of the project, she explained, And, of course, hair dyes tend to be used by more people later in life.

Will the new San Francisco study end all speculation about the risks of hair dyes? No, she answered with a laugh, One study is not the final word.

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