A review of available sources identified acute toxicity data (LCLo, LD50, LDLo) for various species and routes, and exposure limits (MAK-STEL, multiple TWAs). 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. Multiple LD50 and LCLo toxicity data were evaluated for the TEEL-3 basis and resulted in TEEL-3 values ranging from 3.7 to 25 mg/m3. The most preferred species and exposure data, a 4-hour rat LCLo, was selected as the TEEL-3 basis and was scaled to 60-minute equivalent using the ten Berge equation (Section 3.3.4). The TEEL-2 value was derived according to Table 3.5. The MAK-STEL (Germany, DFG) was selected as the TEEL-1.
• PAC-1 = TEEL-1 = MAK-STEL
• PAC-2 = TEEL-2 = TEEL-3/6
• PAC-3 = TEEL-3 = Rat LCLo (86 mg/m3/4H)
This review generated PAC values inconsistent with Rev. 29A. The Rev. 29A TEEL-1 basis was the TLV-TWA from which the TEEL-2 and TEEL-3 were derived (Table 3.5). Instead, the current review selected a 4-hour a rat LCLo as the TEEL-3 basis, derived TEEL-2 from the TEEL-3 (Table 3.5), and selected the MAK-STEL as the TEEL-1.