A review of available sources identified rat toxicity data (LD50, LC50) for various routes (oral, inhalation). 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 exposure data, a 4-hour rat LC50, was selected as the TEEL-3 basis and scaled to a 60-minute equivalent using the ten Berge equation (Section 3.3.4). TEEL-1 and TEEL-2 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 LC50 (2.63 mg/L/4H => 2630 mg/m3/4H)
This review generated PAC values inconsistent with Rev. 29A. The Rev. 29A and current source and methodology are consistent (rat LC50); however, Rev. 29 incorrectly reports the TEELs values in units of ppm, instead of mg/m3.