A review of available sources identified exposure limits (OEL-TWAs) and acute toxicity data (LD50) for several species and routes. 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. The TEEL-2 value was derived according to Table 3.5. The OEL-TWA was selected as the TEEL-1.
• TEEL-1 = OEL-TWA (Finland, Spain, Sweden, 0.02 mg/m3) x 3
• TEEL-2 = TEEL-3/6
• TEEL-3 = Rat oral LD50 (80 mg/kg)
This review generated TEEL values that are inconsistent with Rev. 29A. The Rev. 29A and current TEEL-3 bases are the same, a rat oral LD50; however, the dose use in Rev. 29A was not found in the review. Analysts instead used the available, lower dose LD50. The Rev. 29 was a TDLo not found during the current review; instead, analysts derived the TEEL-2 from the TEEL-3 (Table 3.5). The Rev. 29A TEEL-1 was a MW-adjusted TLV-TWA for cobalt compounds, while the current TEEL-3 basis is an OEL-TWA for cobalt chloride.