Chromate is an anion and the conjugate base of hydrogen chromate (CrHO4-). It is not well defined without its counterion; however, it is a Cr(VI) compound and a review of available sources identified exposure limits for chromic acid and chromates that were evaluated for TEEL development. A review of available sources identified an IDLH (1990), STELs (PEL, TLV), and TWAs (PEL, REL, TLV). Data sources were selected according to the hierarchy listed in Table 3.1. The IDLH (1990) was selected as the TEEL-3 and the TLV-STEL was selected as the TEEL-1. A compound adjustment factor was applied to these exposure limits (Section 3.2.2). The TEEL-2 values were derived according to Table 3.5.
• TEEL-1 = MW-adjusted TLV-STEL (chromic acid and chromates as CrO3, 0.0005 mg/m³)
• TEEL-2 = TEEL-2/6
• TEEL-3 = MW-adjusted IDLH (1990, chromic acid and chromates as CrO3, CASRN: 1333-82-0, 30 mg/m³)
This review generated TEEL values inconsistent with Rev. 29A. The Rev. 29A and current TEEL-3 sources are the same, the 1990 IDLH; however, the current TEEL-3 applies a compound adjustment factor to account for differences in molecular weight between the IDLH (CrO3) and chromates (CrO42-). The Rev. 29A and current TEEL-2 used the same methodology to derive a TEEL-2 (Table 3.5), with differences due to the change in TEEL-3. The Rev. 29A TEEL-1 basis was a TLV-TWA for chromates, while the current basis is a TLV-STEL, a more preferred basis (STEL > TWA, Table 3.1).