VARIABILITY IN TARGET ORGAN DEPOSITION AMONG INDIVIDUALS EXPOSED TO TOXIC SUBSTANCES

Substantial variability occurs in the doses received by individuals within a group of humans or laboratory animals exposed to a toxic substance through inhalation or ingestion. This is due to individual differences in anatomical and physiological factors controlling deposition, absorption and subsequent internal organ redistribution. Analysis of well-controlled inhalation studies with laboratory animals reveals that about 2% of the animals in an exposure level group may receive more than three times the average organ doses of the total group. In laboratory studies where animals ingested substances, 2% received more than two times the average doses. For exposures of humans to substances distributed uniformly in the environment, experience has shown that a few percentage of the individuals in an exposed population may receive more than five times the average doses. As in studies with animals, the internal organ doses" from ingested substances in humans were somewhat less variable than those seen after inhalation. © 1979."