[Problems associated with setting maximum allowable concentrations (MAC) of harmful substances present in the work environment]

The major aim of setting MAC values is to reduce the risk of occupational exposure to harmful substances to the acceptable level. In the process of setting MAC values, a critical analysis of the toxicological and medical literature, used by teams of experts who try to estimate the probability of health effects with different concentrations and different duration of exposures, is most essential. This process is usually very difficult since the epidemiological data and the results of animal experiments are often incomplete, and extrapolation of experimental results from animals to humans entails a lot of doubts. Moreover, one never knows which level of the risk can be considered as acceptable. That is why MAC values set by groups of experts cannot be treated as absolutely safe to the human health. They should be verified if new data on biological effect of substances harmful to health and new criteria for occupational risk assessment become available.