Health Assessment Document for Vinylidene Chloride. Final Report
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Vinylidene chloride is a highly reactive, flammable, clear colorless liquid. In the absence of chemical inhibitors, it can produce violently explosive, complex peroxides. The estimated, ambient air level of vinylidene chloride in urban-suburban areas of the United States is 20 micrograms/cu m. The median concentration (14 micrograms/cu m) for ambient air at point sources of emission is substantially higher. Following oral or inhalation exposure, mammals readily absorb vinylidene chloride. Metabolites of vinylidene chloride, formed in the liver, produce toxic lesions in the liver and kidneys (the target organs), with inhibitors of metabolism providing protection from vinylidene chloride toxicity. The acute hepatotoxicity of vinylidene chloride is greater than that of any other chloroethylene. Based on the overall evidence, VDC would be a Group 3 chemical according to the IARC (International Agency for Research in Cancer's) approach, and by definition, a Group 3 chemical cannot be classified according to its carcinogenicity to humans. However, the mutagenic activity of VDC, its chemical structure, its activity as a tumor initiator in mouse skin, and the ability of its metabolites to react with DNA raise concern that the total body of evidence should not be lightly dismissed.