EXPOSURE ASSESSMENT IN OCCUPATIONAL EPIDEMIOLOGY - MEASURING PRESENT EXPOSURES WITH AN EXAMPLE OF A STUDY OF OCCUPATIONAL ASTHMA

The aim of the present paper is to present a comprehensive review of t he issues involved in exposure assessment for occupational epidemiolog y studies and to provide an example. Exposure assessment for occupatio nal epidemiology studies is becoming more quantitatively refined. This paper discusses important issues that need to be taken into account f or exposure assessment, with particular reference to occupational asth ma. It discusses issues such as survey design, data collection, the ef fect of measurement error and data interpretation. It presents recentl y developed methodology to evaluate exposure variability and its effec t on the attenuation of risk estimates. It also presents methodology t o control for such variability. It uses examples from a recent cohort study of flour millers and bakers. This example shows various characte ristics of exposure and demonstrates that various measures of exposure , such as peak and full-shift exposure measurements, are regularly cor related, which has consequences for the analyses of exposure-response relationships. This paper stresses the importance of the recognition a nd evaluation of exposure variability and its effect on risk estimates and shows that with different exposure grouping schemes, different he alth risk estimates can be obtained. Quantitative exposure assessment is generally difficult, time-consuming and expensive and many issues n eed to be taken into account, but it can be rewarding and has become a n absolute necessity for many occupational epidemiology studies. Evalu ation of components of exposure variance is absolutely necessary. Expo sure variability could lead to serious attenuation of risk estimates.