RATIONAL AND IRRATIONAL ASPECTS OF TOXICO LOGICAL RISK ASSESSMENT ANDRISK MANAGEMENT

Worldwide, the management and evaluation of risks caused by chemical c ompounds are handled by the aid of threshold concentrations below of w hich one can be sure that no biological effect whatsoever can be obser ved. At the working place, we use the maximally tolerated concentratio n of the chemicals (MAK) and, in addition, the biologically tolerated concentrations (ETC) of the compounds either in blood or in other body fluids to which a male and/or female worker is exposed. These thresho ld concentrations should cover any toxic effect including on the one h and mere deviations of clinical chemical values without a disturbed fu nction, i.e. symptoms of a disease as well as, on the other hand, carc inogenic, mutagenic and even allergic effects. Threshold concentration s, however, exist only for acute and chronic toxic effects and not for carcinogenic and/or mutagenic effects. In these cases, again, worldwi de, the concept of minimizing the risks by the exposure is preferred s ince no toxicologist can be found to assure a ''safe'' concentration o f 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 t he basis of animal experiments or in vitro models. However, there exis t also paradigms of a clearcut connection between a chemical substance or its metabolites causing carcinogenic and/or mutagenic effects in m odel experiments from which a clearcut suspect of similar reactions af ter the exposure of human beings can be drawn. In general, carcinogeni c risks are overestimated in our societies. Following the data of expe rienced British epidemiologist most tumor diseases can be traced back to food consumption, bewerages and tobacco and even sexual behavior mu st be ranked as cause for tumors before the rare exposure to dangerous chemicals at the working place. It is worthwhile to mention that natu ral toxins produced by bacteria and even infectious diseases or diseas es caused by parasites are far more serious than the exposure to any m an made chemical product including the Seveso poison, i.e. 2,3,7,8-TCD D, and related compounds. Vice-versa, the assumption that naturally oc curing 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 pur purea poisoned ''Musli'' produced by rye collected in the fields and g round in a hand mill. In Middle-Europe, since 1880, when the threshold of 0,1% claviceps pupurea in rye was established, no poisonous epidem ia of St. Anton's fire was observed.