A review of available sources identified acute toxicity data (LCLo, LD50) for several 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 inhalation is a preferred route, the rat LCLo was not selected as the TEEL-3 basis 1) its original RTECS record is no longer available for verification at the NIOSH/CDC site, 2) it resulted in a TEEL value that was several orders of magnitude higher than other toxicity data, and 3) it is less statistically relevant (Appendix A). Instead, a rat oral LD50, was selected as the TEEL-3 basis. 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 LD50 oral (50 mg/kg)
This review generated TEEL values inconsistent with Rev. 29A. The Rev. 29A basis was a rat LCLo identified during the current review, but was not selected; instead, analysts determine a rat oral LD50 to be a more appropriate source, resulting in less conservative TEEL values. The Rev. 29A and current TEEL-2/TEEL-1 were derived using the same methodology (Table 3.5), with differences due to the change in TEEL-3.