A review of available sources identified the following: European occupational exposure limits (OELs) and acute oral toxicity data (LD50) for several species. 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 toxicity data, a rat oral LD50, was selected as the TEEL-3 basis. The TEEL-2 value was derived according to Table 3.5. A 15-minute OEL-STEL (Romania) was selected as the TEEL-1.
• TEEL-1 = OEL-STEL (Romania, 15-min, 6 mg/m3)
• TEEL-2 = TEEL-2/6
• TEEL-3 = Rat oral LD50 (1120 mg/kg)
This review generated a TEEL-3 source and value that is consistent with Rev. 29A. The TEEL-2 for Rev. 29A was based on rat oral TDLo; TDLo data was found during this review however, none of the reported toxicity endpoints were appropriate for TEEL development (Section 3.3.2). Instead, the TEEL-2 was derived from the TEEL-3. The Rev. 29A TEEL-1 basis was a TLV-TWA, while the current value is a 15-minute STEL, a more preferred source.