A review of available sources identified an OEL-TWA (Latvia) and acute toxicity data (LC50, LD50, LDLo) 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. Inhalation exposures were scaled to 60-minute equivalents using the ten Berge equation (Section 3.3.4). The most preferred species and route, a 4-hour rat LC50, was selected as the TEEL-3 basis. The TEEL-2 value was derived according to Table 3.5. The OEL-TWA was selected as the TEEL-1 basis.
• TEEL-1 = OEL-TWA x 3 (0.1 mg/m3; Latvia)
• TEEL-2 = TEEL-3/6
• TEEL-3 = LC50 rat inhalation (0.046 mg/L/4H)
This review generated TEEL values inconsistent with Rev. 29A. The Rev. 29A TEEL-3 basis was rat oral LD50, while the current basis is a more preferred route (Table 3.1, LC50 > LD50). The Rev. 29A and current TEEL-2 values were derived using the same methodology (Table 3.5), with differences due to the change in TEEL-3. The Rev. 29A TEEL-1 was derived from the TEEL-2, while the current TEEL-1 basis is an exposure limit (OEL-TWA, Latvia).