A review of available sources identified exposure (LOC) and acute toxicity data (TDLo, LD50) for various 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. Although dog is a more preferred species, analysts evaluated the rat oral LD50 because it was 1) a higher priority route, and 2) a more recent source (1973 vs. 1948). When compared, dog and rat doses resulted in comparable magnitude TEELs; as such, the most current and preferred route toxicity data, the rat oral LD50, was selected as the TEEL-3 basis. The LOC was evaluated, but not selected as a TEEL-2 because 1) the exposure limit source could not be verified, and 2) it resulted in a value greater than the TEEL-3. Similarly, the human TDLo was evaluated, but not selected as a TEEL-2 basis because 1) details of the study and toxicity endpoints could not be verified, and 2) it resulted in a value greater than TEEL-3. Instead, TEEL-2 and TEEL-1 values were derived according to Table 3.5.
• TEEL-1 = TEEL-2/11
• TEEL-2 = TEEL-3/6
• TEEL-3 = Rat oral LD50 (1.25 mg/kg)
This review generated TEEL values inconsistent with Rev. 29A. The Rev. 29A TEEL-3 basis, a dog intraperitoneal LD50; this source was evaluated in the current review, with analysts determining that more a recent (Section 3.2.2) and higher ranked route (oral > intraperitoneal) toxicity data, a rat LD50, was a more appropriate basis. The Rev. 29A and current TEEL-2/TEEL-1 values used the same methodology, with differences due to the change in TEEL-3.