A review of available sources identified exposure limits (STELs, TWAs) and rat and human acute animal toxicity data (LCLo, TDLo) for inhalation and oral 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. The most preferred species and route toxicity data, a 4-hour rat LCLo, was selected as the TEEL-3 basis and it was scaled to 60-minute equivalent using the ten Berge equation (Section 3.3.4). The available TDLo were evaluated, however the durations were 1) intermittent and 2) for very long durations (> 6 months); therefore, these were not selected for TEEL-2 development. Instead, analysts derived the TEEL-2 according to Table 3.5. The OEL-STEL (Germany AGS, inhalable fraction, 15-minutes) was selected as the TEEL-1.
• PAC-1 = TEEL-1 = OEL-STEL (Germany AGS, 1.7 mg/m3)
• PAC-2 = TEEL-2 = TEEL-3/6
• PAC-3 = TEEL-3 = Rat LCLo (3860 mg/m3/4H)
This review generated a PAC-3 consistent with Rev. 29A, and inconsistent PAC-2 and PAC-1 values. The Rev. 29A and current TEEL-3 values, source, and methodology are consistent. The Rev. 29A TEEL-2 basis was a TCLo not found during this review. Instead, analysts derived the TEEL-2 from the TEEL-3 (Table 3.5). The Rev. 29A TEEL-1 was derived from the TEEL-2, while the current TEEL-1 is an exposure limit (OEL-STEL, Germany).