67 Criteria for the assessment of the percutaneous absorption of hazardous substances at the workplace – The German MAK Commission approach

Abstract The uptake of hazardous substances at the workplace through the skin can be one major route of exposure and therefore add to the occupational health risk for employees. More than one third of all substances with a limit value in workplace air in Germany have been designated with ‘H’ by the MAK Commission of the Deutsche Forschungsgemeinschaft (DFG), indicating that the percutaneous absorption under workplace conditions can make a significant contribution to the systemic exposure of an employee. The recommendations of the MAK Commission are one major source for regulatory decisions taken by the German Ministry of Labor and Social Affairs for sustaining health and safety in the work area. This presentation summarizes the general approach of the MAK Commission’s working group on percutaneous absorption, the selection and ranking of data (workplace studies, animal studies, in vitro studies, mathematical models or algorithms) as well as the quantitative criteria for an assignment with ‘H’. For the final assessment, the estimated absorbed amount of a substance is compared with the systemically tolerable amount extrapolated from the no observed adverse effect level (NOAEL). A designation with ‘H’ is recommended if the percutaneous uptake accounts for approximately 25 % or more of the tolerable quantity. Only in the case of genotoxic substances without limit values is the ability of a substance to cross the skin barrier sufficient in itself to recommend designation with an ‘H’. The assessment process as well as its merits and challenges are illustrated by some examples.