A review of available sources did not identify exposure limits or acute toxicity data for anhydrous potassium metaborate. The GHS health hazards indicate a mid- to high level hazard level (H319, Category 2A), approximately equivalent to an HHR between 3 and 2 (PAC-3 = TEEL-3 = 79 and 790 mg/m3, respectively; Section 3.4.5). Analysts also evaluated acute toxicity data for sodium metaborate (CASRN: 7775-19-1). Analysts selected a rat oral LD50 for sodium metaborate as the TEEL-3 basis and evaluated it using factors in Tables 3.2, 3.3, and 3.4 (Section 3.4.6). This TEEL value is within the range indicated by GHS hazards. TEEL-2 and TEEL-1 values were derived according to Table 3.5.
• PAC-1 = TEEL-1 = TEEL-2/11
• PAC-2 = TEEL-2 = TEEL-3/6
• PAC-3 = TEEL-3 = Rat oral LD50 (sodium metaborate, CASRN: 7775-19-1, 2330 mg/kg)
This review generated PAC-3 and PAC-2 values consistent with Rev. 29A, and a PAC-1 value inconsistent with Rev. 29A. The Rev. 29A TEEL-1 basis is a weight adjusted TLV-STEL, reportedly for "inorganic borate compounds“; analysts determined this value is restricted to specific borates containing BO3, BO4 and BO5, and is not applicable to general inorganic borate compound. Instead, analysts derived the TEEL-1 from the TEEL-2 (Table 3.5).