A review of available sources identified exposure limits (LOC) and acute toxicity data (LCLo, LC50) for several species and routes. 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. Inhalation exposures were scaled to 60-minute equivalents using the ten Berge equation (Section 3.3.4). Although the mouse LC50 was the highest priority source and was listed on the PubChem and Haz-Map websites, it was not selected for TEEL development because the source was not listed. Instead, a 10-minute mouse LCLo that was the same dose as the LC50 and that had a source listed, was selected as the TEEL-3 basis. The LOC was evaluated but not selected because it resulted in TEEL-2 > TEEL-3 when considering the available toxicity data for the TEEL-3. TEEL-1 and TEEL-2 values was derived according to Table 3.5.
• PAC-1 = TEEL-1 = TEEL-2/11
• PAC-2 = TEEL-2 = TEEL-3/6
• PAC-3 = TEEL-3 = Mouse LCLo (200 mg/m3/10 min)
This review generated PAC values inconsistent with Rev. 29A. In Rev. 29A, TEEL-3 was derived according to Table 3.5; however, the recommended TEEL-3 is based on mouse LCLo toxicity data. The Rev. 29A TEEL-2 basis was the LOC, whereas the current recommendation derived the value according to Table 3.5. The Rev. 29A and current TEEL-1 methodology are consistent, with the difference values due to the change of the TEEL-2 basis.