Lead Analyses of Hair as an Indication of Exposure to Lead

Abstract

Meillère 1 believed that the hair acts as a channel of lead excretion from the body. The implications of this finding, if correct, in relation to medical and industrial problems involving serious exposure to lead are obvious. Inasmuch as Meillère made no attempt to determine the extent of contamination of his material, his thesis requires further support before it can be accepted. Previous work in this laboratory 2 has confirmed that of numerous investigators indicating that lead is extremely widespread. It is obvious, therefore, that before this question of true lead content of hair can be studied properly, it is necessary first of all to obtain a complete removal of that which is present as an external contaminant. Experiments were performed for the purpose of revealing how such contaminating lead may be removed. For example, after treatment with ether to remove lipoidal material, hair was washed in soap solution, and then in acetic and nitric acids with the idea that the lead could be removed as the soluble salts, but this technic gave unsatisfactory results. Finally, trials were made of the efficacy of treatment with diphenylthiocarbarzone in chloroform, the reagent found so useful in analysis for lead. When lead in known amounts was added to hair to simulate natural conditions of contamination, it was not possible by any of the above methods used to bring the concentration down to what might be regarded as normal levels, such as those characteristic of Group IA in Table II.

The problem of metabolic loss of lead through the hair was then approached by means of experiments on rats. The animals, the hair of which had been clipped, subsisted on a low-lead diet for a period of about 3 weeks, during which an amount of hair sufficient for analysis had grown back; at this time the animals were clipped again, and the hair examined for lead. The rats then received lead, in the form of the acetate, both by mouth and by subcutaneous injection, until a new crop of hair appeared, a period again of approximately 3 weeks. In taking hair for the second analyses, care was exercised to avoid the region where the injections were made. The data obtained are presented in Table I. All analyses were made by the Horwitt-Cowgill method. 3