This review did not identify exposure limits or acute toxicity data for tellurous acid. Instead, exposure limits for elemental tellurium (CASRN: 13494-80-9, TLV-TWA and IDLH) and a similar chemical (potassium tellurite, CASRN: 7790-58-1) were evaluated as TEELs. Data sources were selected according to the hierarchy listed in Table 3.1. As reported, “The toxicity of tellurium is dependent on the oxidation state. The tellurites (TeO3)2-, are the most toxic compared to tellurates (TeO4)2−, or elemental tellurium.” Tellurous acid contains the tellurite ion (TeO3)2- ion. Given what little information is available for this chemical, assuming that it will demonstrate toxicity comparable to other tellurites is a conservative approach; therefore, the potassium tellurite human TDLo was selected as the TEEL-2 basis for tellurous acid. The TEEL-3 was derived according to Table 3.5. The tellurium TLV-TWA was selected as the TEEL-1 basis and a compound adjustment factor was applied (Section 3.4.3.2).
• TEEL-1 = MW-adjusted TLV-TWA (tellurium, CASRN: 13494-80-9, 0.1 mg/m3) x 3
• TEEL-2 = Human (male) oral TDLo (potassium tellurite, CASRN: 7790-58-1, 40 mg/kg/7D; toxicity endpoints reported as: sleep, nausea or vomiting)
• TEEL-3 = TEEL-2 x 6
This review generated TEEL-2 and TEEL-3 values inconsistent with Rev. 29A. The Rev. 29A and current TEEL-1 basis and values are consistent. The Rev. 29A TEEL-2 and TEEL-3 were derived from the TEEL-1, while the current values are based on the human TDLo for a similar chemical.