Relation of surrogate measures to actual measures of exposure.
NIOSH 1985 May; :1-20
Using surrogate measures of exposure in epidemiological studies was discussed. The author states that when a chemical agent is absorbed, the biologically active dose can differ from the administered dose as a result of absorption, metabolism, excretion, or other processes. Any exposure data other than the biologically active dose represents a surrogate dose. When the effects of a toxic agent are investigated, the experimentally measured quantity is usually the surrogate dose which is assumed to bear some relationship to the biologically active dose. The closer the surrogate is to the true dose, the less the bias that is introduced into the analysis. Examples of uses of surrogate dose in epidemiological studies of the effects of chemical exposure were given. In a study of a population exposed to polybrominated- biphenyl (36355018) (PBB) in Michigan after a commercial PBB mixture was inadvertently mixed with cattle feed, blood PBB concentrations were measured to assess exposure. Blood PBB concentration is considered to be a surrogate for fat PBB concentration. In studies of the effects of lead (7439921) on intelligence in children, high lead concentrations in teeth dentine were correlated with low performance on intelligence tests. Although the dentine lead content is regarded as the best index of long term exposure, it is not the best screening method for identifying children at high risk of lead poisoning. It is noted that most screening programs do not use blood lead concentrations but instead screen with erythrocyte protoporphyrin, which can be regarded as a surrogate for lead. Using the mutagenic activity of urine as an index of exposure to chemical exposures was discussed. It is noted that the presence of mutagens in urine is not really an index of exposure, as mutagens may reflect the outcome of an exposure.
Biochemical-indicators; Occupational-exposure; Epidemiology; Environmental-exposure; Lead-absorption; Halogenated-hydrocarbons; Mycotoxins; Biological-monitoring
Proceedings of a Symposium on Epidemiology and Health Risk Assessment, Columbia, Maryland, May 14-16, 1985, Centers for Disease Control/NIOSH, 20 pages, 16 references