A review of available sources identified the following: a WEEL-TWA, rat LC50, and rat LD50 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. The most preferred species and route, a rat LC50, was selected as the TEEL-3 basis, and scaled to a 60-minute equivalent using the ten Berge equation (Section 3.3.4). TEEL-2 and TEEL-1 values were calculated according to Table 3.5.
• TEEL-1 = WEEL-TWA (7.45 mg/ m3) x 3
• TEEL-2 = TEEL-3/6
• TEEL-3 = Rat LC50 (>8817 mg/m3/4H)
This review generated TEEL values that are inconsistent with Rev. 29A. The current TEEL-2 and TEEL-1 recommendations are more conservative than those in Rev. 29A, while the TEEL-3 is less conservative. In Rev. 29A a rat oral LD50 was used as the TEEL-3 basis, however this review selected a more preferred route, inhalation, as the basis. The rat TCLo used as the TEEL-2 basis in Rev. 29A was not found during the current review, and instead was calculated from the fill gap adjustment factors. Additionally, this review found and used a WEEL-TWA for the TEEL-1 basis, instead of calculating from the fill gap adjustment factors.