Exposure assessment for occupational epidemiology.

Exposure evaluation for epidemiology has special requirements, which can be derived from the pharmacological processes that determine the exposure-effect relationship. Since environmental concentrations of toxic agents typically are highly variable over time, the tissue concentrations they produce will vary over time, and consequently the level of effects will also vary over time. A general, six-step approach is proposed for developing an exposure assessment for an epidemiologic study. This approach uses pharmacologic models to guide the choice of exposure measurement parameters and to guide the epidemiologic data analysis. The approach is illustrated for evaluations of reversible airway effects of ozone and irreversible pulmonary effects of a mixed silica dust. Effect indices are introduced as a means of quantifying the temporal interrelationships of the exposure profiles and the pharmacologic models. These indices have advantages over both dose indices and simple dose-outcome models.