A review of available sources identified acute toxicity data (LC50, LCLo, LD50) for several 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. The most preferred species and route toxicity data, a 4-hour rat LCLo, was selected as the TEEL-3 basis and it was scaled to (a) 60-minute equivalent using the ten Berge equation (Section 3.3.4). The TEEL-2 and TEEL-1 values were derived according to Table 3.5.
• PAC-1 = TEEL-1 = TEEL-2/11
• PAC-2 = TEEL-2 = TEEL-3/6
• PAC-3 = TEEL-3 = Rat LCLo (5300 mg/m3/4H)
This review generated a PAC-3 value consistent with Rev. 29A and inconsistent PAC-2 and PAC-1 values. The Rev. 29A and current TEEL-3 source, and methodology are consistent. The Rev. 29A TEEL-2 basis was a rat TCLo not identified during this review; instead, the TEEL-2 was derived from the TEEL-3 (Table 3.5). The Rev. 29A and current TEEL-1 use the same methodology, with differences due to the change of TEEL-2.