A review of available sources did not identify exposure limits or acute toxicity data for cobalt(II) sulfate hydrate. Instead, exposure limits for cobalt (CASRN: 7440-48-4, TLV-TWA and IDLH) and acute toxicity data for a similar chemical, cobalt(II) sulfate (CASRN: 10124-43-3), were evaluated for TEEL development. Data sources were selected according to the hierarchy listed in Table 3.1. Although an IDLH is a preferred source, the corrosivity of cobalt(II) sulfate hydrate may be better represented by the acute toxicity data for cobalt(II) sulfate. The most preferred species and current source, a rat intraperitoneal LD50, was selected as the TEEL-3 basis and a molecular weight adjustment applied (Section 3.4.3.2). The TEEL-2 was derived according to Table 3.5. The TLV-TWA was selected as the TEEL-1 basis and a compound adjustment factor was applied (Section 3.2.2); this methodology resulted in a slightly more conservative TEEL-1 value than derivation from the TEEL-2 (0.18 mg/m3 vs. 0.21 mg/m3).
• TEEL-1 = MW-adjusted TLV-TWA (0.02 mg/m3) x 3
• TEEL-2 = TEEL-3/6
• TEEL-3 = MW-adjusted Rat intraperitoneal LD50 (cobalt sulfate, CASRN: 10124-43-3, 31600 ug/kg)
This review generated TEEL-3 and TEEL-2 values that are inconsistent with Rev. 29A. The Rev. 29A and current TEEL-1 value, source, and methodology are consistent. The Rev. 29A TEEL-3 and TEEL-2 were derived from this TEEL-1. Instead, the current TEEL-3 basis is a molecular weight adjusted rat LD50 for a similar chemical (cobalt(II) sulfate) that is comparable in magnitude. The TEEL-2 was derived according to Table 3.5, with differences due to the change in TEEL-3.