Statistical issues in assessing human population exposures

Relating an exposure level to a particular outcome in occupational and environmental epidemiology studies may be challenging. In these studies, researchers are interested in the health effects from exposure. Two factors that complicate this process are the measurement error that is usually present in exposure assessment and the complex nature of the exposure–dose relationship. Statistical aspects of the measurement error problem has been the focus of many researchers in the past few years. However, less attention has been given to the second issue of incorporating the relationship between exposure and dose and directly modeling the dose–response relationship, when this is of primary scientific interest. For complex exposure–dose relationships, a direct application of statistical methods to relate exposure to the health outcome may lead to bias and loss of efficiency in estimates of the dose–response relationship. In this paper, we present some of the statistical issues that arise using a study of the health effects of arc welding fumes as an illustration.