Classification Principles of the European Union

Compounds classified as carcinogens, mutagens, and substances toxic to reproduction are grouped by the European Union in categories one, two, and three. In the literature, the abbreviation cmr is used to express these properties  

Category 1 Compounds which have already shown the mentioned property in humans. 

This information is based mainly on epidemiological investigations and experience at the workplace. As a consequence of the occupational hygiene situation today, epidemiological experience has disappeared over the years. Additionally, it is difficult to prove a clear effect on humans in a small exposure group at the workplace. Consequently, the results from animal studies become of increased importance. 

Category 2 Compounds which, in adequate animal studies, have shown clear effects which seem to be applicable to humans. 

In adequate animal studies, these effects should be relevant to humans. The exposure situations should be similar and transferable to the situations at the workplace. Nevertheless, animal studies have clear limitations, which have to be considered. Usually, the concentrations used in the animal studies are higher than the concentrations at the workplace, usually by a factor of 10 up to over 1000. On the other hand, it has to be borne in mind, especially in the interpretation of aerosol results, that the upper respiratory tract of rodents is different from that of humans. As obligatory nose breathers their nasal filtration systems are considerably better. For example, the fibers from asbestos did not reach the alveolar region in inhalation studies. Similar findings were seen in the case of wood particles. 

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