A review of available sources identified the following: LOC, OEL-STEL, TWAs (OEL, PEL, REL, TLV), and several acute toxicity data (LC50, LD50) from various species (dog, mouse, rat, cat, rabbit), and routes (inhalation, oral). 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, the 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 OEL-STEL (Austria & Denmark) was selected as the TEEL-1.
• TEEL-1 = OEL-STEL (Austria and Denmark, 0.2 mg/m3)
• TEEL-2 = LOC (0.0009 g/m3)
• TEEL-3 = Rat LC50 (74 mg/m3/4H)
This review generated TEEL-1 and TEEL-3 values inconsistent with Rev. 29A. The Rev. 29A TEEL-3 basis was a 1-hour rat LC50 that could not be found during this review, and the analysts therefore used a 4-hour rat LC50, which resulted in a slightly less conservative value. For TEEL-1, the Rev. 29A value was based on the TLV-TWA, however, the recommended value is based on a higher priority OEL-STEL. The TEEL-2 methodology and value remains consistent.