A review of available sources identified rat and mouse acute toxicity data (LD50) for oral and intraperitoneal exposures, and a Level of Concern (LOC). 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 data of the most preferred species and exposure, a rat oral LD50, was selected as the TEEL-3 basis. The LOC was evaluated as the TEEL-2 however it was not selected because 1) it resulted in a TEEL-2 > TEEL-3, and 2) LOCs are based on unspecified exposure limits from before the 1990s that appear to have been discontinued. TEEL-1 and TEEL-2 values were derived according to Table 3.5.
• TEEL-1 = TEEL-2/11
• TEEL-2 = TEEL-3/6
• TEEL-3 = Rat oral LD50 (5 mg/kg)
This review generated TEEL values that are inconsistent with Rev. 29A. The Rev. 29A TEEL-3 basis was also based on rat LD50 data; however, the recommended value is based on a more preferable route of exposure (oral > intraperitoneal). The recommended TEEL-2 was derived from the TEEL-3 (Table 3.5) instead of being based on the LOC. The Rev. 29A and current TEEL-1 methodology remain consistent, with differences due to the change in TEEL-2.