Risks posed by various components of hair dyes.

In this study, I calculated the risks presented by the use of several chemicals that are or were used in hair dyes and for which a good animal bioassay is available. The risks were calculated using the carcinogenic potency measure used in the National Cancer Institute bioassays concerning the exposure of rats and mice to these chemicals. The procedure used was that previously discussed by Zeise et al.; it is similar to, but logically more complete, than those normally used by Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA). The expected value of the risk for the worst dye that has now been discontinued is as high as that of smoking 6 cigarettes in a lifetime; the 95th percentile gives a risk equivalent to that of smoking 120 cigarettes in a lifetime or 2 per year. Even when the upper limits of carcinogenic potency of the untested chemicals are employed using correlations with toxicity, the estimated risk remains small.