So, hair isn’t an important route of mercury “excretion” – isn’t it a marker for poor excretion in the rest of the body?
A. As mentioned above, mercury gets into hair by diffusing out of the blood and into the hair. Since the hair grows fairly slowly (about a centimeter a month), and because of the cysteine in hair, the concentration of mercury in the hair is much higher than in the blood – even with steady mercury intake. However, this process is completely passive. It requires nothing more than the physical property of diffusion and the chemical affinity of mercury for sulfur, none of which is determined by the physiology of the hair grower. The two determining factors seem to be blood flow to the hair follicle and the amount of mercury in the blood [ e.g. Mottet, Body, Wilkins and Burbacher (1987) ]. Even transplanting human hair follicles into a different species (nude mice) didn’t change the hair:blood ratio significantly, so this seems to be something intrinsic to the hair and not dependent on the rest of the body. A number of studies have shown that there are individual differences in the ratio of
