A review of sources identified limited 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 route and species, 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-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 LC50 (200 mg/m3/4H)
This review generated TEEL values that are more conservative than those in Rev. 29A. The Rev. 29A TEEL-3 was a molecular-weight adjusted IDLH for chromates. The current TEEL-3 basis is an inhalation toxicity for ammonium dichromate that was determined more appropriate for TEEL development. The Rev. 29A and current TEEL-2 and TEEL-1 values were derived from consistently methodology (Table 3.5), with differences in value due to the change in TEEL-3 basis.