A review of available sources identified a LOC and acute toxicity data (several LC50). In addition, analysts identified proposed AEGLs. 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 AEGLs are high priority (Section 1), they were not selected for further evaluation since they were proposed values, or values are still under review by the public and committee; however, upon completion of review TEEL values may need to be re-evaluated. Instead, the lowest reported rat LC50 was selected as the TEEL-3 basis. The LOC was selected as the TEEL-2. The TEEL-1 was derived according to Table 3.5.
• TEEL-1 = TEEL-2/11
• TEEL-2 = LOC (0.0017 g/m3)
• TEEL-3 = Rat inhalation LC50 (56 mg/m3/4H)
This review generated TEEL-2 and TEEL-1 values consistent with Rev 29A, and an inconsistent TEEL-3 value. The Rev. 29A and current TEEL-3 sources are both rat LC50; however, the current dose is more conservative. Note that the TEEL-3 is between the 1-hour and 4-hour proposed AEGL-3 (5.3 mg/m3 and 2.2 mg/m3, respectively) and the TEEL-2 is comparable to the proposed AEGL-2 (1.8 mg/m3).