Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:5:p5
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 5 (pt 5/7)
Character Range: 2828003–2831305

older than that considered by WHO and US EPA and does not include any consideration of early life sensitivity.

RIVM (2001)           SF = 0.17 (mg/kg/day)-1                               Slope factor derived on the basis of hepatocellular carcinomas, angiosarcomas and neoplastic nodules in female rats as markers for carcinogenic response, and a linear extrapolation model.
                      UR = 2.8x10-5 (g/m3)-1                               Inhalation unit risk derived on the basis liver effects in an inhalation study on female rats and mice and an extrapolation model.
                                                                            No consideration of early-life sensitivity was considered by RIVM.
                                                                            Threshold values were also derived for non-carcinogenic effects with a TDI = 0.0013 mg/kg/day which is based on the same study as considered in the ADWG, but with a less conservative uncertainty factor of 100. An inhalation TC = 0.056 mg/m3 was derived based on an inhalation study. RIVM notes that the carcinogenic end points are most sensitive.
ATSDR (2006)          No quantitative assessment of carcinogenic effects    ATSDR does not provide quantitative estimates of carcinogenic effects. However for non-carcinogenic effects a chronic oral MRL = 0.003 associated with non-neoplastic effects in livers from a chronic oral rat study was derived.
US EPA (IRIS 2012)    SF = 1.5 (mg/kg/day)-1 (for exposures over lifetime)  Slope factor (last reviewed in 2000) derived on the basis of hepatocellular carcinomas, angiosarcomas and neoplastic nodules in female rats as markers for carcinogenic response, a PBPK model to estimate human equivalent dose and linearised multistage model. Based on animal evidence of age-dependent sensitivity an additional 2-fold uncertainty has been included to address early-life sensitivity in exposures from birth.
                      SF = 0.75 (mg/kg/day)-1 (for exposures as adult)      Inhalation unit risk derived on the basis liver angiosarcomas, angiomas, hepatomas and neoplastic nodules in an inhalation study on female rats and mice and an extrapolation model. Based on animal evidence of age-dependent sensitivity an additional 2-fold uncertainty has been included to address early-life sensitivity in exposures from birth.
                      UR = 8.8x10-6 (g/m3)-1 for exposures over lifetime)  The US EPA review also identified threshold values for the assessment of non-carcinogenic effects with an oral RfD = 0.003 mg/kg/day (same as derived by ATSDR) and an RfC = 0.1 mg/m3 based on route-extrapolation from the oral value.
                      UR = 4.4x10-6 (g/m3)-1 for exposures as adult)

Both WHO and US EPA recognise age-sensitivity is important with respect to the assessment of exposure to vinyl chloride and hence it is appropriate to adopt toxicity values that take these issues into consideration. On this basis, of the non-threshold reference values available, the inhalation values presented by US EPA are the most relevant and current (and adequately address early lifetime exposures) and suitable for the derivation of soil vapour Interim HILs.

    5.5.3         Recommendation
In relation to vinyl chloride, only soil vapour