Abstract

Risk assessment/limit value setting for metals at the workplace is often based primarily on animal data. Epidemiological data providing information on quantitative exposure-response relationships is rarely available, but should be used preferentially if of sufficient quality, as in the case of chromium(VI). In Germany, the Committee of Hazardous Substances has derived an assessment criterion for chromium(VI) of 1 µg/m³ reflecting a tolerable risk of 4 additional cancer cases in 1000 workers exposed over their whole working life. For various metals human data is less informative. Thus, for cobalt, a tolerable concentration of 5 µg/m³ (respirable fraction) as been calculated based on inhalation studies in rats and mice which developed lung tumors after exposure to more than 1 mg/m³. However, recently published epidemiological studies among more than 30 000 hardmetal and cobalt production workers do not provide any evidence for carcinogenicity in humans at exposures in the range from 10–100 µg/m³ - between the tolerable concentration based on animal data and the concentration used in the animal experiments. The implications for risk assessment will be discussed also taking into account additional epidemiological data addressing potential inflammatory or fibrogenic effects with impairment of lung function at higher workplace exposures. Copper is another compound for which in Germany a limit value has been proposed by the MAK (maximal workplace concentration) commission based on animal data. Based on a 28 day rat inhalation study with copper(I) oxide which demonstrated inflammatory effects at concentrations starting around 200 µg/m³ a MAK value of 10 µg/m³ (respirable fraction) has been derived. However, copper has been used at workplaces for centuries at concentrations even in the mg range without observation of clear health effects. Potential explanations for these discrepancies as well as requirements of additional health data will be presented.