Extended work shifts and MAK values
MAK Value Documentation – Translation of the German version from 2022
Andrea Hartwig1 (Chair of the Permanent Senate Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area, Deutsche Forschungsgemeinschaft)MAK Commission2
1 Institute of Applied Biosciences, Department of Food Chemistry and Toxicology, Karlsruhe Institute of Technology (KIT), Adenauerring 20a, Building 50.41, 76131 Karlsruhe, Germany
2 Permanent Senate Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area, Deutsche Forschungsgemeinschaft, Kennedyallee 40, 53175 Bonn, Germany
Abstract
MAK values (maximum concentrations at the workplace) are valid for exposure periods of 8 hours per day and 40 hours per week. In case of extended work shifts, it may be necessary to reduce the exposure concentration below the MAK value. This depends on the mechanism of action (either controlled by the concentration or by the concentration-time-product, C × T) and the half-life of the substance or its active metabolite. Publications addressing this issue were reviewed. In general, exposure levels do not need to be reduced for irritant substances that act primarily by a concentration-based mechanism. The use of linear C × T extrapolation is proposed for systemically acting substances with an unknown mechanism of action and half-life. The reduction of exposure levels based on worst-case considerations is recommended for systemically acting substances with a known mechanism of action and/or half-life. For practical reasons, linear C × T extrapolation as prescribed by DIN EN 689 is sufficient to prevent toxicity after extended work shifts irrespective of the mechanism of action of the substance. In any case, the BAT value (biological tolerance value) of the substance has to be observed.
