A review of available sources identified exposure limits (OEL-TWAs) and acute toxicity data (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. 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 lowest reported OEL-TWA was selected as the TEEL-1 basis and a compound adjustment factor was applied (Section 3.2.2) because the reported basis for this TWA is copper.
• PAC-1 = TEEL-1 = MW-adjusted OEL-TWA (as Cu, 0.02 mg/m3)
• PAC-2 = TEEL-2 = TEEL-3/6
• PAC-3 = TEEL-3 = Rat oral LD50 (794 mg/kg)
This review generated PAC values inconsistent with Rev. 29A. The Rev. 29A TEEL-3 basis was a less conservative rat oral LD50 not found during the current review; instead, the current TEEL-3 basis is a lower dose rat oral LD50. 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 a weight adjusted TLV-TWA for copper, while the current TEEL-1 basis is a weight adjusted OEL-TWA for copper nitrate.