Risk comparison in toxicology

Abstract

Statisticians have calculated probabilities for most of the circumstances of everyday life, including the chances that an individual will become ill, have an accident, or die. The danger profile for a single individual is divided into a multitude of individual risks, which are unequally distributed, sometimes starting from birth. For example, 2 % of all diseases are genetically determined. Even people who arrive in the world healthy, however, have disadvantages, but factors such as success in an occupation and high income are protective against early death. Statistically high risks are associated with smoking and poor nutrition, whereas the risk of death from viruses, radiation, or chemicals is low. The calculation of risks is difficult and dangers often arise. Experts as well as laypeople may fall victim to “cognitive dissonance,” where knowledge that disturbs established beliefs and habits is not perceived. Risk assessment thus becomes difficult, as seen by the following phenomena: The occurrence of rare hazards (e.g., snake bite) is overestimated, whereas that of frequent hazards (e.g., death caused by cardiac infarct resulting from obesity) is underestimated. People are subject to an imperfect assessment of probabilities; for example, driving in a car is more dangerous than flying in a plane, but the fear of flying is common compared with the fear of driving. People tend to overestimate their own abilities (e.g., they believe they are immune from disease). Fears are minimized for things people believe they can control (e.g., smoking). Fears are maximized for things people believe they cannot control (e.g., a toxic waste repository). Psychological studies show that events with a high “horror factor” (e.g., being eaten by a shark) are particularly feared, even if they occur extremely rarely. Human behavior is less determined by numbers and facts than by faith, desires, and fears.