[Toxicologic risk assessment and prevention: rational and irrational approaches].

Worldwide, the management and evaluation of risks caused by chemical compounds are handled by the aid of threshold concentrations below of which one can be sure that no biological effect whatsoever can be observed. At the working place, we use the maximally tolerated concentration of the chemicals (MAK) and, in addition, the biologically tolerated concentrations (BTC) of the compounds either in blood or in other body fluids to which a male and/or female worker is exposed. These threshold concentrations should cover any toxic effect including on the one hand mere deviations of clinical chemical values without a disturbed function, i.e. symptoms of a disease as well as, on the other hand, carcinogenic, mutagenic and even allergic effects. Threshold concentrations, however, exist only for acute and chronic toxic effects and not for carcinogenic and/or mutagenic effects. In these cases, again, worldwide, the concept of minimizing the risks by the exposure is preferred since no toxicologist can be found to assure a "safe" concentration of a chemical compound that exert carcinogenic and/or mutagenic effects. With respect to these effects a proven carcinogenic and/or mutagenic effect in human beings must be discerned from a suspected effect on the basis of animal experiments or in vitro models. However, there exist also paradigms of a clearcut connection between a chemical substance or its metabolites causing carcinogenic and/or mutagenic effects in model experiments from which a clearcut suspect of similar reactions after the exposure of human beings can be drawn. In general, carcinogenic risks are overestimated in our societies. Following the data of experienced British epidemiologist most tumor diseases can be traced back to food consumption, beverages and tobacco and even sexual behavior must be ranked as cause for tumors before the rare exposure to dangerous chemicals at the working place. It is worthwhile to mention that natural toxins produced by bacteria and even infectious diseases or diseases caused by parasites are far more serious than the exposure to any man made chemical product including the Seveso poison, i.e. 2,3,7,8-TCDD, and related compounds. Vice-versa, the assumption that naturally occurring poisons could be neglected may lead to fatal experiences as for instances the outbreak of St-Anton's fire, i.e. the gangraeneous type of ergot alacaloide intoxication after having swallowed claviceps purpurea poisoned "Müsli" produced by rye collected in the fields and ground in a hand mill. In Middle-Europe, since 1880, when the threshold of 0.1% claviceps purpurea in rye was established, no poisonous epidemia of St. Anton's fire was observed.