PROPOSED CHANGES IN THE CLASSIFICATION OF CARCINOGENIC CHEMICALS IN THE WORK AREA

Carcinogenic chemicals in the work area are currently classified into three categories in Section III of the German List of MAK and BAT Valu es. This classification is based on qualitative criteria and reflects essentially the weight of evidence available for judging the carcinoge nic potential of the chemicals, It is proposed that these Categories-I IIA1, IIIA2, and IIIB-be retained as Categories 1, 2, and 3, to confor m with EU regulations. On the basis of our advancing knowledge of reac tion mechanisms and the potency of carcinogens, it is now proposed tha t these three categories be supplemented with two additional categorie s. The essential feature of substances classified in the new categorie s is that exposure to these chemicals does not convey a significant ri sk of cancer to man, provided that an appropriate exposure limit (MAK value) is observed, It is proposed that chemicals known to act typical ly by nongenotoxic mechanisms and for which information is available t hat allows evaluation of the effects of low-dose exposures be classifi ed in Category 4. Genotoxic chemicals for which low carcinogenic poten cy can be expected on the basis of dose-response relationships and tox icokinetics and for which risk at low doses can be assessed will be cl assified in Category 5. The basis for a better differentiation of carc inogens is discussed, the new categories are defined, and possible cri teria for classification are described, Examples for Category 4 (1,4-d ioxane) and Category 5 (styrene) are presented. The proposed changes i n classifying carcinogenic chemicals in the work area are presented fo r further discussion, (C) 1997 Academic Press.