A review of available sources identified the following: several human (LDLo), and numerous animal toxicity sources, in addition to a TLV-TWA. 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. Of the available human sources, the lowest reported dose was selected, a female LDLo, 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.
• TEEL-1 = 2 mg/m3 TLV-TWA x 3
• TEEL-2 = TEEL-3/6
• TEEL-3 = woman LDLo oral (200 mg/kg)
This review generated TEEL-3 and TEEL-2 values that are inconsistent with those in Rev. 29A. The Rev. 29A TEEL-3 basis was a dog oral LD50 toxicity dose (2,000 mg/kg), while the current TEEL-3 is based on higher priority species (human > dog). The Rev. 29A TEEL-2 basis was a rat oral TDLo, which was not found during current research. The current and Rev. 29A TEEL-1 method and values are consistent.