A review of available sources identified exposure limits (OELs) and acute toxicity data (LCLo, LD50, TDLo) 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). Of the available LCLo data, dog was determined the most preferred species; this record is also the most appropriate duration for TEEL development (Section 3.3.2). As such, analysts selected the 1-hour dog LCLo as the TEEL-3 basis. The human TDLo was considered as a TEEL-2 basis, but the record was incomplete (no reported duration or sex). Instead, the TEEL-2 value was derived according to Table 3.5. The MAK-STEL (Germany DFG, inhalable fraction, 15-minute) was selected as the TEEL-1.
• PAC-1 = TEEL-1 = MAK-STEL (Germany DFG, inhalable fraction, 15-minute, 0.2 mg/m3)
• PAC-2 = TEEL-2 = TEEL-3/6
• PAC-3 = TEEL-3 = Dog LCLo (110 mg/m3/1H)
This review generated PAC values inconsistent with Rev. 29A. The Rev. 29A TEEL-3 basis was a mouse intraperitoneal LD50 not found during the current review. Instead, the current TEEL-3 basis is a 1-hour dog LCLo; note that inhalation based TEELs from rat and dog, with varying durations, resulted in comparable TEEL-3 values. 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 (Table 3.5), while the current TEEL-1 is an exposure limit (OEL-STEL).