Studying the determinants of exposure: A review of methods

To better understand where, when, and how to control occupational exposures , it is vital that hygienists understand the factors that contribute to ele vated or reduced exposure levels, Over the last two decades a burgeoning li terature examining the determinants of exposure has developed, yet to date the methods used in this regard have rarely been summarized in texts or els ewhere. The purpose of this article is to provide an overview of the techni ques used to study the predictors of workplace exposures. Both Experimental and observational studies are examined, and the advantages and limitations of each are discussed. Fundamental study design features are reviewed. The se include the selection and measurement of factors potentially related to exposure, as well as the measurement of exposure itself. Decisions reached by investigators in selecting the number of sites and workers, the number o f repeated observations per worker, and the duration of sampling are discus sed. Also examined are issues that commonly arise in the course of data ana lysis of exposure determinants. These include transformation of exposure va riables, correlation of predictor variables, empirical model building, and interpretation of results. Finally, methods employed to evaluate the validi ty of findings are summarized.