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 Toxciology and the lay public about basic toxicological concepts, assumptions, and interpretations. The results demonstrated large differences between toxicologists and laypeople, as well as differences between 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. Neil et al. »• 5 Intuitive Toxicology

This study is a replication and extension in Canada of a previous study in the United States in which toxicologists and members of the public were surveyed to determine their attitudes, beliefs, and perceptions regarding risks from chemicals. This study of "intuitive vs. scientific showed that Canadian toxicologists had far lower perceptions of risk and more favorable attitudes toward chemicals than did the Canadian public. The public's attitudes were quite negative and showed the same lack of dose-response sensitivity found in the earlier U.S. study. Both the public and the toxicologists lacked confidence in the value of animal studies for predicting human health risks. However, the public had great confidence in the validity of animal studies that found evidence of carcinogenicity, whereas such evidence was not considered highly predictive of human health risk by many toxicologists. Technical judgments of toxicologists were found to be associated with factors such as affiliation, gender, and worldviews. Implications of these data for risk communication are briefly discussed.

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The early development of the peripheral adrenergic neurons of the rat was followed with the Falck‐Hillarp fluorescence technique. In the 13 day embryo small fluorescent sympathicoblasts with short processes were found in segmentally arranged groups along the dorsal aspect of the embryo. The larger sympathetic ganglia and the strongly fluorescent adrenal medullary cells were easily identifiable at this stage. In the 18 day embryo, fluorescent axon bundles were found in most larger nerve trunks. The outgrowing fluorescent axons had a stronger fluorescence intensity than non‐terminal axons of adult animals until at least 2 weeks after birth. The postnatal development of the plexuse of adrenergic nerves was followed in the iris, auricles of the heart, salivary glands, vas deferens and small intestine. The adrenergic innervation of the gut seemed to develop earlier than that of the other organs. Thus, the duodenal muscle layer had a well developed adrenergic innervation of the plexus of Auerbach at birth while the other organs investigated demonstrated well developed networks of adrenergic nerves from about the fourth day on. It was concluded from some pharmacological experiments that, under optimal conditions, the fluorescence technique can reveal all or almost all adrenergic nerves also during early development.

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The concept of exposure is central to chemical risk assessment and plays an important role in communicating to the public about the potential health risks of chemicals. Research on chemical risk perception has found some indication that the model lay people use to judge chemical exposure differs from that of toxicologists, thereby leading to different conclusions about chemical safety. This paper presents the results of a series of studies directed toward developing a model for understanding how lay people interpret the concept of chemical exposure. The results indicate that people's beliefs about chemical exposure (and its risks) are based on two broad categories of inferences. One category of inferences relates to the nature in which contact with a chemical has taken place, including the amount of a chemical involved and its potential health consequences. A second category of inferences about chemical exposure relates to the pragmatics of language interpretation, leading to beliefs about the motives and purposes behind chemical risk communication. Risk communicators are encouraged to consider how alternative models of exposure and language interpretation can lead to conflicting conclusions on the part of the public about chemical safety.