Experimental Evaluation of Air Pollutants in Humans as a Basis for Estimating Risk

Abstract

The purpose of this paper is to provide a brief “guided tour” of human experimental studies of air pollution exposure. This field of investigation is rather new and small compared to the related fields of animal toxicology and epidemiology, which are discussed in some of the accompanying papers. In human studies—sometimes called “human toxicology” or “clinical toxicology” or “clinical environmental stress testing”—the investigator creates or finds a polluted air environment of interest, recruits volunteer subjects, exposes them to the pollution under well-controlled conditions, and looks for responses which could in any sense be considered adverse effects on health. Controlled human exposure studies play an important part in environmental risk assessment as it relates to air pollution, because they can often provide firm, credible scientific information not available otherwise. Needless to say, human experimentation has strict ethical and practical limitations. Nevertheless, a broad range of environmental problems can be investigated, given proper concern for the health and welfare of the subjects. Investigation of any real risks—those to which the subject is, or could reasonably be, exposed in the course of his normal activities— presents few ethical problems. Investigation of potential risks— those which the subject has not previously experienced, but could reasonably encounter in the future—likewise can be justified. Such activities provide benefits to the individual subjects, since they obtain potentially valuable information on their responses to certain environmental stressors.