A review of available sources identified an OEL-TWA for palladium. ECHA reports that the palladium it is not expect to “reach the lungs in appreciable quantities” and “...is considered to fall withing the scope of the read-across category 'Palladium, palladium monoxide and Palladium dihydroxide'.” Considering this, analysts evaluated acute toxicity data (LD50) for palladium monoxide (CASRN: 1314-08-5) 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. A rat oral LD50 for palladium monoxide was selected as the TEEL-3 basis (Section 3.4.6). The TEEL-2 was derived according to Table 3.5. The OEL-TWA (Finland) was selected as the TEEL-1 basis.
• PAC-1 = TEEL-1 = OEL-TWA (0.5 mg/m3) x 3
• PAC-2 = TEEL-2 = TEEL-3/6
• PAC-3 = TEEL-3 = Rat oral LD50 (palladium monoxide, CASRN: 1314-08-5, >4900 mg/kg)
This review generated PAC values inconsistent with Rev. 29A. The Rev. 29A TEEL-3 basis was a rat oral LD50 not found during the current review; instead, the current TEEL-3 basis is a rat oral LD50 for palladium monoxide (Section 3.4.6, CASRN: 1314-08-5). The Rev. 29A and current TEEL-2 methodology is consistent, 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 OEL-TWA for palladium.