Vinyl Chloride - Texas Commission on Environmental Quality

<strong>Vinyl</strong> chloride
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Wisniewska-Knypl et al. (1980) evaluated the toxicity of VC in male Wistar rats. Rats (7-10 per group)
were exposed via inhalation to 0, 50, 500, and 20,000 ppm VC for 5 h/day, 5 days/week for up to 10
months. Sacrifices were performed at 1, 3, 6, and 10 months. This experiment was designed to examine
the effects of VC on the activity of cytochrome P-450 monooxygenase and the ultrastructure of the liver.
A statistically significant decrease in body weight was reported at 20,000 ppm after 10 months. Relative
liver weight was significantly increased at 500 and 20,000 ppm after all sacrifices. Electron microscopic
examination of the liver tissue from rats exposed to 50 ppm showed hepatocellular changes characterized
by proliferation of the smooth endoplasmic reticulum at 3 months (although this effect subsided by 6
months) and accumulation of lipid droplets in the cytoplasm after 10 months. Rats exposed to 500 and
20,000 ppm for 3 months exhibited hypertrophy of the smooth endoplasmic reticulum, distension of
canals of rough-surfaced membranes, swelling of mitochondria, and an increased number of lipid droplets
in cytoplasm. These changes persisted through the 10 months of the study and were more intensive at
20,000 ppm. A LOAEL of 50 ppm was identified in this study for the 10 month exposure period based on
minor liver effects (accumulation of lipid droplets).
Torkelson et al. (1961) evaluated the toxicity of VC in rats, guinea pigs, rabbits, and dogs. Animals were
exposed by inhalation to 0, 50, 100, 200, or 500 ppm VC for 1.5 to 7 h/day for 4.5 to 6 months. Growth,
mortality, organ weight, and body weight were recorded for all animals. Hematology, histopathology, and
urinalysis were also performed. Histopathological changes and increased liver weights were observed
after repeated exposure to 500 ppm in rats. Repeated exposure to 200 ppm for 6 months resulted in
increased average liver weights of rats and micropathological changes in livers of rabbits. Repeated
exposure to 100 ppm 7 h/day for 6 months resulted in increased liver weight in rats. The NOAEL reported
for this study is 50 ppm and the LOAEL is 100 ppm for increased relative liver weight in rats.