A review of available sources identified acute intravenous toxicity data (LD50) for several species. Reported GHS health hazards (H319, Category 2) indicate a mid-to-high level hazard level. 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 toxicity data, a rat intravenous LD50, was selected as the TEEL-3 basis. 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 intravenous LD50 (37720 µg/kg)
This review generated PAC values that are inconsistent with Rev. 29A. The Rev. 29A TEEL-1 basis was a TLV-TWA for particles not otherwise specified (Section 3.5.2), from which the TEEL-2 and TEEL-3 were derived (Table 3.5). The current TEEL-3 basis is a rat LD50 for the chemical of interest, from which TEEL-2 and TEEL-1 were derived (Table 3.5).