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IRIS Toxicological Review and Summary Documents for Vinyl Chloride (External Review Draft)
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The Draft Toxicological Review was developed to evaluate both the cancer and non cancer human health risks from environmental exposure to vinyl chloride. A reference concentration (RfC), and a reference dose (RfD) were developed based upon induction of liver cell polymorphism in a chronic dietary study utilizing Wistar rats. An RfC of 1E-1 mg/m3 and an RfD of 5E-3 mg/kg-d are recommended. On the basis of sufficient evidence for carcinogenicity in human epidemiology studies vinyl chloride is reaffirmed to be a known human carcinogen. Cancer potencies were derived for oral and inhalation exposure. An oral slope factor of 1.3 per (mg/kg-day) for continuous exposure during adulthood and 2.5 per (mg/kg-day) for continuous lifetime exposure from birth, based upon a chronic dietary study in female Wistar rats is recommended; an inhalation unit risk of 4.3 E-6 per (55g/m3) for continuous exposure during adulthood and 8.7 E-6 per (55g/m3) for continuous lifetime exposure from birth is also recommended, based upon exposure of male and female Sprague Dawley rats and Swiss mice, via inhalation, for a lifetime. A PBPK model was used in the derivation of the RfC, RfD, and cancer potency estimates. Its use is based on the assumption that equal tissue concentrations of reactive metabolite, chlorethylene oxide or chloracetaldehyde, at the critical target site will result in equivalent toxicity between species.
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