A review of available sources identified the following: TLV-TWA and IDLH for Copper (7440–50–8) and rat LD50 and LC50 for the chemical of interest. Sources were selected according to the hierarchy listed in Table 3.1. Toxicity data were evaluated using the type of exposure, species, and route preferability stated in Sections 3.3.1 and 3.3.2. The concentration was scaled to a 60-minute equivalent using the ten Berge equation (Section 3.3.4). The rat 4-hr LC50 was selected the TEEL-3 basis, as it is the more preferred route (inhalation). TEEL-2 values were derived according to Table 3.5. The TLV-TWA was selected as the TEEL-1 basis and a compound adjustment factor was applied.
• TEEL-1 = MW-adjusted TLV-TWA x 3 (Cu CASRN: 7440-50-8, 1.0 mg/m3)
• TEEL-2 =TEEL-3/6
• TEEL-3 =Rat 4-hr LC50 (2.92 mg/L)
This recommendation is inconsistent with Rev29A. A rat oral LD50 was previously selected for TEEL-3; inhalation data is preferable. For TEEL-1, the TLV-TWA for copper fume was adjusted in the past; it was determined that fume is not as representative of the copper component as copper dust, which was selected in the recommendation (valance considerations). TEEL-2 subsequently differed, although the same methodology was applied between revisions.