A review of available sources identified the following: oral acute toxicity data (LD50¬) for cobalt(II) oxide, in addition to exposure limits for cobalt metal (TLV-TWA, IDLH, CASRN: 7440-48-4). 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. Although the cobalt IDLH was evaluated as a TEEL-3 basis, there was available acute toxicity data for cobalt oxide that was selected instead. The most preferred route, a rat oral LD¬¬50, was selected as the TEEL-3 basis. The TEEL-2 value was derived according to Table 3.5. The cobalt TLV-TWA was selected as the TEEL-1 basis and adjusted using a compound adjustment factor (Section 3.2.2).
• TEEL-1 = MW-adjusted TLV-TWA (cobalt, CASRN: 7440-48-4, 0.02 mg/m3) x 3
• TEEL-2 = TEEL-3/6
• TEEL-3 = Rat oral LD50 (202 mg/kg)
This review generated TEEL-3 and TEEL-2 values that are inconsistent with those found in Rev 29A. The Rev.29A and current TEEL-1 values, source, and methodology are consistent. The Rev. 29A TEEL-3 basis was the cobalt IDLH; while this was considered, there was available toxicity data for cobalt(II) oxide which was selected instead. Differences in TEEL-2 values are due to the change in TEEL-3. The Rev. 29A and current TEEL-1 values, source, and methodology are consistent.