A review of limited sources identified mouse and rat acute toxicity data (LC50, LD50). 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. Inhalation exposures were scaled to 60-minute equivalents using the ten Berge equation (Section 3.3.4). The rat LC50 was considered as a TEEL-3 basis but was not selected because 1) the source could not be verified, and 2) the dose range was very large; instead, a mouse intraperitoneal LDLo 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 = Mouse intraperitoneal LDLo (20 mg/kg)
This review generated TEEL values inconsistent with Rev. 29A. The Rev. 29A TEEL-3 basis was a rat intravenous LD50 for a similar chemical (isometamidium, CASRN: 20483-03-3); instead, the current TEEL-3 basis is a rat intraperitoneal LDLo for ethidium bromide. The Rev. 29A and current TEEL-2 andTEEL-1 were derived from using the same methodology (3.5) with differences due to the change in TEEL-3.