Metabolic studies and the evaluation of genetic risk from the viewpoint of industrial toxicology.

In recent years some important industrial chemicals, e.g. solvents, and monomers used in the production of plastics, have been found to be more dangerous than had been suspected. Some of them are mutagens and carcinogens. The active substance may be the compound itself, but more frequently it is a reactive intermediate, an alkylating agent, formed from the parent compound by oxidation under the influence of liver-microsome mixed-function oxidases. Trichloroethylene, vinyl chloride, 1,1-dichloroethylene and 2-chloro-1,3-butadiene can be mentioned as examples, where mutagenic or carcinogenic activity has been demonstrated; similar activity of some others is to be suspected. Metabolic studies may explain unexpected effects or they may allow one to predict such effects. Tests on microorganisms with a metabolic activation in vitro seem to be extremely valuable for fast and efficient screening of man-made chemicals to be introduced into the environment, because such tests combine the use of liver microsomes and bacteria for detection and classification of the effect. Mutagenicity tests in mammals do not lose their usefulness, since thay take into account the distribution of the compound in the body, its transport to the target organ, species-specific differences etc. As exposures of workers to chemicals mentioned above have been quantitatively measured regularly, epidemiological studies should be performed with regard to mutagenic and carcinogenic effects in relation to the degree of exposure. Here is a chance for better understanding of how to extrapolate experimental results to human populations and how to establish safe levels of chemicals in the environment if at all possible and acceptable.