A review of available sources identified mouse and rat acute toxicity data (LD50) for several routes. In addition, exposure limits for selenium (TLV-TWA, CASRN: 7782-49-2) were also explored for TEEL development. 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 toxicity data, a rat oral LD50, was selected as the TEEL-3 basis. TEEL-2 values were derived according to Table 3.5. The TLV-TWA was selected as the TEEL-1 basis and a compound adjustment factor was applied (Section 3.2.2).
• TEEL-1 = MW-adjusted TLV-TWA (selenium, CASRN: 7782-49-2, 0.2 mg/m3) x 3
• TEEL-2 = TEEL-3/6
• TEEL-3 = Rat oral LD50 (68,100 µg/kg)
This review generated TEEL-3 and TEEL-2 values inconsistent with Rev. 29A. The Rev. 29A and current TEEL-1 values and source are consistent. The Rev. 29A TEEL-3 was based also a rat oral LD50 (48 mg/kg), however that data was for selenium, not selenium oxide. The current TEEL-3 basis is comparable in magnitude but is acute toxicity data for selenium oxide. The Rev.29A and current TEEL-2 values were derived using the same methodology (Table 3.5), with differences due to the change in TEEL-3.