A review of available sources did not identify exposure limits or acute toxicity data for borate, an anionic compound. Instead, analysts identified exposure limits (STEL, TWA) and acute toxicity data (LCLo, LD50, LDLo, TDLo) for boric acid (H3BO3, CASRN: 10043-35-3) for TEEL development (Section 3.4.6). Boric acid was selected for evaluation since it was identified that inhalation toxicity data for boron typically relates to exposure to borate dusts such as boric acid, boron oxide, or various hydration states of borate salts (e.g., borax, sodium borate, calcium borate). 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. The rat LC50 was evaluated as a TEEL-3 basis but not selected because it resulted in a TEEL-3 value less than the reported STELs and TWAs. Instead, the most preferred route human toxicity data, a human (female) oral LDLo, was selected as the TEEL-3 basis. The TEEL-2 was derived according to Table 3.5. The TLV-STEL was selected as the TEEL-1 (Table 3.1).
• PAC-1 = TEEL-1 = TLV-STEL (boric acid, CASRN: 10043-35-3; 6 mg/m3)
• PAC-2 = TEEL-2 = TEEL-3/6
• PAC-3 = TEEL-3 = Human (female) oral LDLo (boric acid, CASRN: 10043-35-3; 200 mg/kg)
This review generated PAC-3 and PAC-2 values inconsistent with Rev. 29A, and a consistent PAC-1 value. The Rev. 29A and current TEEL-1 source, and methodologies are consistent. The Rev. 29A TEEL-2 and TEEL-3 values were derived from the TEEL-1 (Table 3.5). The current TEEL-3 basis is a human oral LDLo, from which the TEEL-2 was derived.