IRIS Toxicological Review of Benzene (Noncancer Effects) (1998 External Review Draft)
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A LOAEL (HEC) was adjusted to 8.6 mg/m3 for the occupational ventilation rate and for an intermittent work week schedule of 24 hr exposure, 7 days/week. The adjusted LOAEL (HEC) and 1000-fold uncertainty factors (for lack of NOAEL, subchronic to chronic extrapolation and data deficiencies) were used to derive an RfC of 9 E-3 mg/m3. The human chronic dose of ingested benzene considered to be without any appreciable risk (RfD) is 1 E-3 mg/kg-day, and it is supported by an RfD value of 8 E-4 mg/kg-day, which is 1/10,000 of the LOAEL identified for hematological effects in subchronic drinking water study of Hseih et al. (1988). The overall confidence in the RfC/RfD is medium because there are few human studies with reliable estimates of exposure to benzene and few long-term low-dose studies in test animals to establish reliable NOAELs.
U.S. EPA. IRIS Toxicological Review of Benzene (Noncancer Effects) (1998 External Review Draft). U.S. Environmental Protection Agency, Washington, DC, NCEA-S-0455, 1998.
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