A review of available sources identified acute toxicity data (LC50, LD50) for copper hydroxide. In addition, analysts evaluated available exposure limits for inorganic copper compounds (Cu, CASRN: 7440-50-8). 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. Analysts evaluated the rat LC50; the resultant TEEL-3 (25 mg/m3) appears overly conservative, when compared with the TEEL-3 values for copper compounds with similar valence and solubility, such as cupric chloride (CASRN: 7447-39-4, TEEL-3 = 120 mg/m3) or cupric nitrate (CASRN: 3251-23-8, TEEL-3 = 160 mg/m3). Considering this, analysts instead selected a rat oral LD50 as the TEEL-3 basis. The TEEL-2 was derived according to Table 3.5. An OEL-STEL for inorganic copper compounds (Latvia, inhalable fraction, 15-minute) 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-STEL (inorganic copper compounds, CASRN: 7440-50-8; 1 mg/m3)
• PAC-2 = TEEL-2 = TEEL-3/6
• PAC-3 = TEEL-3 = Rat oral LD50 (489 mg/kg)
This review generated PAC values inconsistent with Rev. 29A. The Rev 29A TEEL-3 basis was a rat oral LD50 not identified during this review; 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 basis was a weight adjusted TLV-TWA, while the current TEEL-1 basis is an OEL-STEL for inorganic copper compounds (Table 3.5, see Note).