Experimental studies on the chronic toxic effects of vinyl chloride in rats.

Male rats were exposed to vinyl chloride at the concentrations of 50, 500, and 20 000 ppm, 5 hours daily, 5 days a week for 10 months. Morphological lesions in the liver and the testes detected by light and electron microscope and depression in body weight increase intensified with the duration of exposure. Increased relative weights of some organs and slight hematological and biochemical changes in blood during the course of the experiment were also observed. Some toxic effects including morphological liver injuries arose at the smallest exposure level, i. e., 50 ppm. Assuming 50 ppm as the threshold concentration for rats, the 5 ppm level has been estimated as the safe exposure limit in industry in relation to systemic effects of vinyl chloride.