Intuitive toxicology: expert and lay judgments of chemical risks

Human beings have always been intuitive toxicologists, relying on their senses of sight, taste, and smell to detect harmful or unsafe food, water, and air. As we have come to recognize that our senses are not adequate to assess the dangers inherent in exposure to a chemical substance, we have created the sciences of toxicology and risk assessment to perform this function. Yet despite this great effort to overcome the limitations of intuitive toxicology, it has become evident that even our best scientific methods still depend heavily on extrapolations and judgments in order to infer human health risks from animal data. Many observers have acknowledged the inherent subjectivity in the assessment of chemical risks and have indicated a need to examine the subjective or intuitive elements of expert and lay risk judgments. Such an examination was begun by surveying members of the Society of Toxicology and the lay public about basic toxicological concepts, assumptions, and interpretations. The results demonstrated large differences between toxicologists and laypeople, as well as differences among toxicologists working in industry, academia, and government. In addition, toxicologists were found to be sharply divided in their opinions about the ability to predict a chemical's effect on human health on the basis of animal studies. These results place the problems of risk communication in a new light. Although the survey identifies misconceptions that experts should clarify for the public, it also suggests that controversies over chemical risks may be fueled as much by limitations of the science of risk assessment and disagreements among experts as by public misconceptions.