A review of available sources identified acute toxicity data (LD50, LDLo) for several species and routes. In addition, analysts identified a TLV-TWA for soluble molybdenum compounds (as molybdenum, CASRN: 7439-98-7). 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, a rat oral LD50, was selected as the TEEL-3 basis. The TEEL-2 was 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 molybdenum x 3 (molybdenum and compounds, soluble; CASRN: 7439-98-7, 0.5 mg/m3)
• TEEL-2 = TEEL-3/6
• TEEL-3 = Rat LD50 oral 333 mg/kg
This review generated TEEL-2 and TEEL-3 values that are inconsistent with Rev. 29A. The recommended TEEL-3 is based on a more conservative rat oral LD50 dose than used in Rev. 29A. The Rev. 29A and current TEEL-2 use the same methodology, with differences due to the change in TEEL-3. The Rev. 29A and current TEEL-1 values, source, and methodology are consistent.