Multiple exposure to chemicals.

In order to evaluate the possible interactive effects of simultaneous exposure to more than one chemical, leading toxicological journals over the period 1981-1987 were reviewed for articles on combined exposure. Additive effects or less or no interaction were reported in most cases. More than additive effects were reported in 20 out of 104 studies (excluding alcohol), but this conclusion was sometimes not supported by the data. Examples of studies on changes in metabolisms caused by multiple exposure to solvents are given. Metabolic interaction may take place if the chemicals share a common step in their metabolism. Assumption of additive effects in the case of chemicals that share similar action in toxicity can be considered safe enough.