A review of available sources identified exposure limits (OEL-TWA, OEL-STEL) and acute toxicity data (LC50, LD50) for various 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. The most preferred species and route data, a 4-hour rat LC50, 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 OEL-STEL (Romania, 15-min average) was selected as the TEEL-1.
• PAC-1 = TEEL-1 = OEL-STEL (4 mg/m3, Romania)
• PAC-2 = TEEL-2 = TEEL-3/6
• PAC-3 = TEEL-3 = Rat LC50 (5100 mg/m3/4H)
This review generated PAC-3 and PAC-2 values consistent with Rev. 29A, and an inconsistent PAC-1 value. The Rev. 29A and current TEEL-3 and TEEL-2 values, sources, and methodology remain consistent. The Rev. 29A TEEL-1 value was derived from the TEEL-2 (Table 3.5), while the current value is an exposure limit (OEL-STEL).