A review of available sources identified the following: acute toxicity data (LC50, LD50). Additionally, there are exposure limits for cobalt metal (Co, 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. The most preferred route toxicity data, a rat LC50, was selected as the TEEL-3 basis. The TEEL-2 value was derived according to Table 3.5. A 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 LC50 (0.05 mg/L/4H)
This review generated TEEL-3 and TEEL-2 values that are inconsistent with Rev. 29A. The Rev. 29A TEEL-3 basis was a weight adjusted IDLH (1990); while an IDLH is a preferred source, there was available acute toxicity data for cobalt hydroxide that 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