A review of available sources identified exposure limits (IDLH, TWAs) and acute toxicity data (LD50, LDLo) for numerous species and routes. 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. Analysts determined not to use the IDLH because it reports a combined value for polychlorinated biphenyls (PCBs) with 42% and 54% chlorine, PCBs that have dissimilar reported toxicities, Instead, analysts selected the lowest rat oral LD50 as the TEEL-3 basis. The TEEL-2 was derived according to Table 3.5. The PEL-TWA was selected as the TEEL-1 basis.
• PAC-1 = TEEL-1 = PEL-TWA (0.5 mg/mg3) x3
• PAC-2 = TEEL-2 = TEEL-3/6
• PAC-3 = TEEL-3 = Rat oral LD50 (1010 mg/kg)
This review generated PAC-3 and PAC-1 values consistent with Rev. 29A, and an inconsistent PAC-2 value. The Rev. 29A and current TEEL-3 and TEEL-1 sources and methodologies are consistent. The Rev. 29A TEEL-2 basis was a rat oral TDLo not identified during this review; instead, the TEEL-2 was derived from the TEEL-3 (Table 3.5).