A review of available sources identified acute toxicity data (LDLo, TDLo) for animals and human oral routes. In addition, analysts evaluated exposure limits for lead (CASRN: 7439-92-1; IDLH, TWAs), the most toxic component of this compound. Data sources were selected according to the hierarchy listed in Table 3.1. Toxicity data were selected according to type of exposure, species, and route according to the hierarchies stated in Sections 3.3.1, 3.3.2, and evaluated using factors in Tables 3.2, 3.3, and 3.4. The 1990 IDLH was considered but not selected because it was not based on acute toxicity data. Instead, analysts selected a human oral LDLo as the TEEL-3 basis. For this LDLo, the sex of the human subject was not reported; therefore, analysts assumed male. The lowest duration TDLo¸ a dog oral TDLo, was selected as the TEEL-2 basis. The PEL-TWA was selected as the TEEL-1 basis and a compound adjustment factor was applied (Section 3.2.2).
• PAC-1 = TEEL-1 = MW-adjusted PEL-TWA (lead, CASRN: 7439-92-1; 0.050 mg/m3) x 3
• PAC-2 = TEEL-2 = Dog oral TDLo (4500 mg/kg/90D; toxicity endpoints: ataxia)
• PAC-3 = TEEL-3 = Human oral LDLo (571 mg/kg; male, assumed)
This review generated PAC-2 and PAC-1 values consistent with Rev. 29A, and an inconsistent PAC-3 value. The Rev. 29A TEEL-3 basis was weight adjusted 1990 IDLH, while the current TEEL-3 basis is a human LDLo. The Rev. 29A and current TEEL-2 and TEEL-1 values, sources, and methodologies are consistent.