A review of available sources identified acute toxicity data (LD50, LDLo) for several species and routes. In addition, analysts evaluated available exposure limits for palladium (Pd, CASRN: 7440-05-3) for TEEL development (Section 3.4.6). 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, a rat oral LD50, was selected as the TEEL-3 basis. The TEEL-2 was derived according to Table 3.5. The OEL-TWA for palladium was selected as the TEEL-1 basis and a compound adjustment factor was applied (Section 3.2.2).
• PAC-1 = TEEL-1 = MW-adjusted OEL-TWA x 3 (palladium, CASRN: 7440-05-3; 0.5 mg/m3)
• PAC-2 = TEEL-2 = TEEL-3/6
• PAC-3 = TEEL-3 = Rat oral LD50 (2704 mg/kg)
This review generated PAC-3 and PAC-2 values consistent with Rev. 29A and an inconsistent PAC-1 value. The Rev. 29A and current TEEL-3 and TEEL-2 use the same source and methodologies. The Rev. 29A TEEL-1 was derived from the TEEL-2, while the current TEEL-1 is a weight adjusted OEL-TWA (Section 3.2.2).