A review of available sources did not identify exposure limits or acute toxicity data for potassium ferricyanide trihydrate. Considering this, analysts instead evaluated a structurally similar chemical, potassium ferricyanide (K3Fe(CN)6, CASRN: 13746-66-2) for TEEL development (Section 3.4.6). For potassium ferricyanide, analysts identified exposure limits (OEL-TWA) and acute toxicity data (LD50, LDLo) 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. From the review, analysts found that that ferrocyanides (calcium, potassium, and sodium) are “of low order toxicity” due to the strong bond between iron and cyanide. The most preferred source and route for potassium ferricyanide, a mouse oral LD50, was selected as the TEEL-3 basis (Section 3.4.6). TEEL-2 values were derived according to Table 3.5. The OEL-TWA for potassium ferricyanide was selected as the TEEL-1 basis.
• PAC-1 = TEEL-1 = OEL-TWA (potassium ferricyanide, CASRN: 13746-66-2; Latvia, 4 mg/m3) x 3
• PAC-2 = TEEL-2 = TEEL-3/6
• PAC-3 = TEEL-3 = Mouse oral LD50 (potassium ferricyanide, CASRN: 13746-66-2; 2970 mg/kg)
This review generated PAC values that are inconsistent with Rev. 29A. The Rev. 29A TEEL-3 basis was a weight adjusted 1990 IDLH for cyanides (CASRN: 57-12-5), while the current TEEL-3 is based on acute toxicity data for a structurally similar chemical, potassium ferricyanide (CASRN: 13746-66-2). 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 MAK-TWA for cyanides (CASRN: 57-12-5), while the current TEEL-1 is an OEL-TWA for potassium ferricyanide (Section 3.4.6).