RESUMO
The numbers of sister chromatid exchanges (SCE) were determined in the lymphocytes of ten volunteers (males and females) whose hair was dyed 13 times at intervals of 3-5 wk. Each volunteer used throughout the study a single commercial preparation containing a mixture of aminotoluenes, aminophenols and hydroxybenzenes, and in some cases naphthol, as the active ingredients. The findings were compared with those in a control group matched for age and sex. SCE were determined in blood samples taken before the first exposure, after a sham dyeing and after the first three and the last three actual dyeing procedures. Volunteers were carefully screened for disease, for use of medicines and for radiation exposure. Consumption of alcohol was the same in both groups, but there were more smokers in the treated group. No evidence was found of any effect of repeated hair dyeing on the frequency of SCE. In both the controls and in the hair-dyed subjects a slight decrease in SCE was detected during the course of the experiment; this was independent of sex as well as of the dyeing procedure.