[Experimental studies of acute and chronic toxic effects of vinyl acetate]

In view of divergent opinions concerning MAC value for vinyl acetate, a study on acute and chronic inhalatory toxic effect of this compound on animals was carried out. The scope of the study included determination of CL50 value after Litchfield and Wilcoxon and 10-month exposure of animals to vinyl acetate at concentrations 10, 100 and 500 mg/m3, 5 days weekly, 5 hours daily. During 10-month experiment the animals were observed and body weight controlled. In addition, periodically some hematological examinations and biochemical of blood serum as well as histopathological examinations of inner organs were carried on. Post-mortally the weight of inner organs was determined. CL50 value determined on rats has amounted to 4100 ppm. In the study on chronic effect, the prevalence and the degree of intensity of the changes of the used by us indicators was the least in the group of animals exposed to vinyl acetate at concentration of 10 mg/m3. These changes were transient not involved reticulopenia and animals' body weight decrease. Histopathological examinations revealed some inflammatory changes in respiratory system both in control and exposed animals. Only planoepithelial metaplasia of bronchi was found exclusively in animals exposed to vinyl acetate at all concentrations used. The changes within liver were found only in animals exposed to vinyl acetate at concentration of 100 and 500 mg/m3. These changes involved fatty degeneration of hepatic parenchyma, proliferation and extension of smooth endoplasmatic reticulum and the changes within the biliary canaliculi. Taking the above results into account it seems that the lowest of the recommended in the world MAC value--10 mg/m3 may be accepted as the upper limit of the maximum admissible concentration for vinyl acetate.