Classification of carcinogenic chemicals in the work area by the German MAK Commission: current examples for the new categories

The German Commission for the Investigation of Health Hazards of Chemical C ompounds in the Work Area (MAK Commission) introduced an extended classific ation scheme in 1998. In addition to the traditional three categories still used to date, now called Category 1 (human carcinogen), Category 2 (animal carcinogen), and Category 3 (suspected carcinogen), two new Categories (4 and 5) were added. Classification of substances into the new Categories 4 a nd 5 is based on the knowledge of mode of action and the potency of carcino gens. The essential feature Of Substances classified in the new Categories 4 and 5 is that exposure to these chemicals does not contribute significant ly to the risk of cancer to man, provided that an appropriate exposure limi t (MAK value) is observed. Chemicals known to act typically by non-genotoxi c mechanisms are classified in Category 4. Genotoxic chemicals for which lo w carcinogenic potency can be assessed on the basis of dose-response relati onships and toxicokinetics are classified in Category 5. Since the use of t his scheme for 3 years, various chemicals have been classified in one of th e new categories. However, in several cases data to sufficiently substantia te a MAK value are missing, Such substances are now classified in a Subcate gory of Category 3, called Category 3 A, which indicates that further data are required for final classification. Examples are given for classificatio n of dichloromethane into Category 3 A, chloroform and sulfuric acid into C ategory 4 and ethanol into Category 5. (C) 2001 Published by Elsevier Scien ce Ireland Ltd.