A review of available sources identified acute toxicity data (LD50) for several species and routes and an exposure limit (OEL-TWA). 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, a rat oral LD50, was selected as the TEEL-3 basis. The TEEL-2 value was derived according to Table 3.5. The OEL-STEL (Denmark) was considered as a TEEL-1 basis, but not selected because the duration of this short-term limit was not reported. Instead, the OEL-TWA (Denmark) was selected as the TEEL-1 basis.
• PAC-1 = TEEL-1 = OEL-TWA (0.5 mg/m3) x 3
• PAC-2 = TEEL-2 = TEEL-3/6
• PAC-3 = TEEL-3 = Rat oral LD50 (570 mg/kg)
This review generated PAC values inconsistent with Rev 29A. The Rev. 29A and current TEEL-3 basis are both a rat oral LD50¬; however, analysts did not identify the source used in Rev. 29A, instead they used the available, lower dose. The Rev. 29A and current TEEL-2 use the same methodology¬, with differences due to the change in TEEL-3. The Rev. 29A TEEL-1 was derived from the TEEL-2, while the current TEEL-1 basis is an exposure limit (Section 3.4.2).