A review of available sources identified the following: TWAs (PEL, REL, TLV), an IDLH, and LD50 (mouse, rabbit, rat) acute toxicity data for various routes. Data sources were evaluated 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. Although an IDLH is a highly preferred source, it was determined to be based on a 6-hour human TCLo also reported in PubChem; the TEELs results would generate conflicting TEEL-2 values, with either a TCLo based TEEL-2 (0.66 ppm) that would be less than 3-times the TLV-TWA (Section 3.4.2) or a TEEL-1 derived TEEL-2 (9 ppm) that is greater than the IDLH. Given the rejection of this TC¬Lo as a TEEL-2 basis, it is not appropriate to also accept an IDLH developed from this basis as the TEEL-3. As such, the next most preferred basis, a rat oral LD50, was selected to develop the TEEL-3. The TEEL-2 value was calculated according to Table 3.5. The TLV-TWA was selected as the TEEL-1 basis.
• TEEL-1 = TLV-TWA (0.5 ppm) x 3
• TEEL-2 = TEEL-3/6
• TEEL-3 = Rat oral LD50 (200 mg/kg)
This review generated TEEL values consistent with Rev. 29A.