A review of available sources identified exposure limits (OEL-STEL and TWA) and acute toxicity data (LC50, 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. Inhalation exposures were scaled to 60-minute equivalents using the ten Berge equation (Section 3.3.4). The most preferred species and route toxicity data, a rat oral LD50, was selected as the TEEL-3 basis. The TEEL-2 value was derived according to Table 3.5. Available OEL-STELs and TWAs were evaluated; those reported by Finland and Romania resulted in a TEEL-1 > TEEL-2. Considering this, analysts selected the OEL-TWA reported by Latvia as the TEEL-1 basis.
• PAC-1 = TEEL-1 = OEL-TWA (10 mg/m3) x 3
• PAC-2 = TEEL-2 = TEEL-3/6
• PAC-3 = TEEL-3 = Rat LC50 (21.5 mg/L/5H)
This review generated PAC values inconsistent with Rev. 29A. The Rev. 29A TEEL-3 basis was a rat oral LD50; the current TEEL-3 basis is a more preferred route, a rat LC50 (inhalation > oral, Section 3.3.2). The Rev. 29A and current TEEL-2 use the same methodology, 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 is an exposure limit (OEL-TWA).