A review of available sources identified a LOC and acute toxicity data (LD50, LDLo) for various routes and species. 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. For the TEEL-3, multiple toxicity data were evaluated and resulted in a range of values (3.9 - 12 mg/m3), which demonstrated that extra conservatism is needed. The data of the highest priority route and species, a rat oral LD50, was selected as the TEEL-3 basis. The LOC was evaluated as the TEEL-2 but resulted in a TEEL-2 > TEEL-3; therefore, it was not selected for TEEL development. 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 oral LD50 (60 mg/kg)
This review generated PAC values that are inconsistent with Rev. 29A. The Rev. 29A TEEL-3 basis was a weight adjusted 1990 IDLH for cyanides (CASRN: 57-12-5), while the current TEEL-3 is based on oral acute toxicity data for methyl thiocyanate. The LOC was used as the Rev. 29A TEEL-2 basis, however, this review calculated TEEL-2 according to Table 3.5. The Rev. 29A TEEL-1 basis was a weight adjusted MAK-TWA for cyanides (CASRN: 57-12-5), while the current TEEL-1 was derived from the TEEL-2 (Table 3.5).