A review of available sources identified the following: mouse, rabbit, and rat LD50, and rat LC50 acute toxicity data. 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 two available inhalation acute toxicity doses, one did not list if it was a lowest lethal or 50% lethal dose, so it was removed from further consideration. The 4-hr rat LC50 was selected as the TEEL-3 basis was scaled to 60-minute equivalent using the ten Berge equation (Section 3.3.4). 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 LC50 (>12000 mg/m3/4H)
This review generated TEEL values inconsistent with those in Rev. 29A. The Rev. 29A TEEL-3 basis, a rat oral LD50, was not identified during the current review. Instead, the current TEEL-3 basis is an LC50, a more preferred route (LC > LD). The Rev. 29A and current TEEL-2 and TEEL-1 methodology remains unchanged (derived from TEEL-3, according to Table 3.5), with differences due to the change in TEEL-3 basis.