To identify the potential hazards associated with human exposure to chemicals in general at the work place, through the environment or during the use of a chemical-based product, chemical classification and labelling schemes have been formulated to help reduce potential risks. The objectives of such systems are to identify in a systematic way the hazards of chemicals (‘classification'), to draw attention of the workers or users to those hazards (‘labelling') and to enable them to take action to protect themselves as appropriate or use the chemicals safely (Pratt, 2002). Hazard classifications are entirely based on the inherent properties of the chemical in question. They do not provide information on the level of human risk, e.g., cancer risk that will be associated with a given chemical exposure.
Various chemical hazard classification systems exist. Although closely correlated from a scientific point of view, one has to distinguish between risk management systems such as the United Nations globally harmonised system of classification and labelling of chemicals (UN GHS) which are legally required to be followed by chemical manufacturers according to the respective national implementation laws of the responsible jurisdiction and, hazard classification schemes, such as those developed by the International Agency for Research on Cancer (IARC) or the German MAK-Commission for the setting of exposure limits (‘MAK'). The latter two schemes are advisory and do not have direct regulatory consequences, but informs the regulator making classification and labelling decisions or the setting of occupational exposure limits.
The following chapter provides an overview of key chemical classification schemes focusing on those classifications that may be triggered by the tumorigenic or non- tumorigenic effects seen in long(er) term rodent inhalation studies with PSPs. It also highlights issues associated with the application of existing classification criteria and guideline values and identifies where further clarifications are deemed necessary.