Individual Versus Group Differences in Exposure and Risk

The part of the assignment of particular interest was investigating intrapersonal variation as a proportion of total variation in exposure levels within job categories. This clearly required that there be multiple measurements on a number of individuals in specific job categories associated with a particular company, location, and unit. This chapter discusses the model used in the analysis of the individual versus job category aspects of the benzene study. In the case of chronic exposures, there is the implicit assumption in the standard setting process in the US, and in much of the risk assessment literature, that health risk is a function of the cumulative dose of the toxic agent. The general attraction of the model in this context arises from the fact that WPF data are traditionally assumed to be lognormally distributed and one is interested in the variability in protection experienced by a particular individual from wearing to wearing as well as the variability between different individuals.