Toxic effects of metals from the environment on hair growth and structure.

Diffuse alopecia related to ingestion of toxic metals from the environment has been observed in 36 patients. Copper, arsenic, mercury and cadmium were involved and the intensity of disturbance of the hair cycle, heralded by presence of dystrophic hairs, was proportional to the amount of toxic material detected in blood and urine. Toxicity can be observed in vitro by measuring labeled cells on squash preparations after incorporation of tritiated uridine and thymidine in plucked hairs. The labeling indexes, as well as the ratio between cells entering the S phase and the viable cells were always lower in toxic alopecia than in normal hair. Toxic metals do not seem to affect the morphology of the hair shaft.