A review of available sources identified mouse and rat acute toxicity data (LD50, LC50) for various routes (oral, inhalation, intravenous, intraperitoneal). 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 inhalation is the most preferred route, the acute inhalation data (LC50) could not be verified and resulted in a TEEL-3 value that was the least conservative of the available sources (52 mg/m3); therefore, this data was not selected for TEEL development (Section 3.3.1). As such, the next most preferred species and route data, a rat oral LD50, was selected as the TEEL-3 basis. 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 LD50 oral (120 mg/kg)
This review generated TEEL values that are inconsistent with Rev. 29A. The Rev. 29A TEEL-3 basis was a mouse oral LD50, but the recommended value is based on a more preferred species (rat > mouse). The Rev. 29A and current methodology used to derive TEEL-2 and TEEL-1 are consistent, with difference in values due to the change in TEEL-3.