A review of available sources identified exposure limits (IDLH, 60-minute EEGL, ceiling limits, STELs, TWAs) and abundant acute toxicity data (LC50, LCLo, LDLo) for several species and routes. 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. Inhalation exposures were scaled to 60-minute equivalents using the ten Berge equation (Section 3.3.4). The 1990 and 1994 IDLHs were evaluated; the 1994 IDLH includes both human and animal acute inhalation toxicity. Additionally, analyst evaluations of acute toxicity indicate a more conservative IDLH is appropriate. As such, analysts selected the 1994 IDLH as the TEEL-3. The 60-minute EEGL was selected as the TEEL-2. The REL-STEL was selected as the TEEL-1.
• TEEL-1 = REL-STEL (0.30 ppm/0.60 mg/m3)
• TEEL-2 = EEGL (60-minute, 1 ppm)
• TEEL-3 = IDLH (1994, 5 ppm)
This review generated TEEL-3 and TEEL-1 values inconsistent with Rev. 29A. The Rev. 29A TEEL-3 was the 1990 IDLH, while the current TEEL-3 is the 1994 IDLH. The 1994 IDLH was used according to Handbook guidelines (Section 4.2-4.3). The Rev. 29A TEEL-1 basis was a TLV-TWA, while the current TEEL-1 is an REL-STEL, a more preferred source (Table 3.1). The Rev. 29A and current TEEL-2 values, source, and methodology are consistent.