Biopersistence of respirable synthetic fibers and minerals: the point of view of the epidemiologist.

Biopersistence of fibers and minerals in human respiratory tissues is an important aspect of the toxicity of these agents. However, few data are available from human studies. Although a number of studies have measured the lung burden of asbestos and other minerals in exposed humans, few presented information relevant to biopersistence of these agents. The studies analyzing asbestos lung burden in workers at different intervals following cessation of exposure suggest a linear decrease in concentration over time, that is independent of duration of exposure. However, the available evidence on asbestos is too sparse to allow a firm conclusion; almost no data are available on other minerals.