The significance of Cd in hair. Influence of the level of intake and the external contamination in the rat.

A standardized procedure in the rat was used to study the deposition of Cd in newly grown hair and its relation to ingested Cd. The internal deposition and the absorption in the intestine were evaluated using 109Cd and 115m Cd as radiotracers. Stable Cd was supplied at different levels with the drinking water and analysed in hair, and in some cases also in the liver and the kidneys, by flameless atomic absorption spectrometry. It was demonstrated by the tracer that the internal deposition is proportional to the amount ingested. The time of exposure and the body burden had no influence. The external contamination with stable Cd was very high in animals kept conventionally, but can be reduced by using metabolic cages. It was, however, not possible to appreciably isolate the "background level", i.e. Cd was also found in hair of "unexposed" animals kept in metabolic cages. A significant increase above "background" could only be achieved at a Cd intake of greater than 1 mg/d. Following a prolonged period of exposure, levels of Cd newly deposited in hair were reduced to background levels, within a few days, in spite of very high Cd concentrations in the liver and kidneys of these animals. It is concluded that the internal deposition of Cd in hair is proportional to the amount absorbed, and that it is largely masked by the external contamination and the relatively high "background" level; the internal deposition only reflects intake. The body burden or the Cd accumulated in specific organs has no influence on the deposition of Cd in hair.