A review of available sources identified a LOC and several acute toxicity data (LC50, LD50) for various species (rat, dog, rabbit, guinea pig) and routes (dermal, 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 was scaled to 60-minute equivalent using the ten Berge equation (Section 3.3.4). The LOC was considered as the TEEL-2; however, available acute toxicity data generated TEEL-3 values (1.4 to 6.8 mg/m3) that indicate the LOC is not sufficiently conservative. 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 (88 mg/m3/4H)
This review generated PAC values inconsistent with Rev. 29A. The Rev. 29A review selected the LOC as the TEEL-2, from which TEEL-1 and TEEL-3 values were derived. Instead, the current TEEL-3 basis is acute toxicity data, from which TEEL-2 and TEEL-1 values were derived. Additional available toxicity data (dog, rat) supports this more conservative approach.