Intentional exposure studies of environmental agents on human subjects: assessing benefits and risks.

In this article, I assess the benefits and risks of studies that intentionally expose research subjects to environmental agents. I describe these types of studies, identify their benefits and risks, compare them to other research methods that can be used to investigate the relationship between environmental exposures and disease, and discuss some issues related to research design and risk minimization. I argue that the benefits of intentional environmental exposure studies outweigh the risks when 1) the knowledge gained is likely to improve our understanding of the relationship between environmental exposure and disease, 2) this knowledge cannot be obtained by other methods, 3) the experiments are well designed, 4) the subjects will receive some benefits, such as medical evaluations, 5) risks are minimized, and 6) the risks to human subjects are less than those encountered in a typical Phase I drug study. Only in rare circumstances (i.e., when an intentional environmental exposure study is needed to implement an important environmental or public health intervention or regulation) may such studies expose research subjects to risks as high as those encountered in a typical Phase I drug trail.