RESUMEN
The combined action of substances having a munidirectional toxic effect on the organism was studied for several typical chlorine derivatives of hydrocarbons (1,2-dichloropropane, 1,2,3,-trichloropropane, and perchloroethylene). Since a correct assessment of the combined action of substances is based on the comparison of the effect of mixed compounds and the effects observed for each component alone, research was conducted on each individual substances on the basis of the "concentration--time" relationship. The reaction of several mixtures of substances was also studied at various concentration levels, from high to low concentration levels of substances which are actually present in the atmosphere. Research result showed that the character of the mixture at both high and low levels of concentration was identical and approximate to the overall effects.