A review of available sources identified acute toxicity data (LD50) for various species and routes, and exposure limits (WEEL-TWA, OEL-STEL, 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 data, 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 and OEL-TWA were evaluated as the TEEL-1 basis but resulted in TEEL-1 > TEEL-2; therefore, they were not selected for TEEL development. Instead, the WEEL-TWA was selected as the TEEL-1 basis.
• PAC-1 = TEEL-1 = WEEL-TWA (1 mg/m3) x 3
• PAC-2 = TEEL-2 = TEEL-3/6
• PAC-3 = TEEL-3 = Rat oral LD50 (5 g/kg)
This review generated PAC-1 and PAC-3 values consistent with Rev. 29A, and an inconsistent PAC-2 value. The Rev. 29A and current TEEL-1 and TEEL-3 values, sources, and methodology remain consistent. The Rev. 29A TEEL-2 was based on a rat oral TDLo that was not found in the current review; instead, it was derived from the TEEL-3 (Table 3.5).