A review of available sources identified exposure limits (IDLH, LOC, ceiling limit, TWAs) and acute animal toxicity data (LC50, LD50, 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. The 1990 and 1994 IDLH were evaluated; both values were derived from animal acute inhalation toxicity data, however the 1994 IDLH includes additional data. Considering this, analysts selected the 1994 IDLH as the TEEL-3. The LOC was selected as the TEEL-2. The TLV-TWA was selected as the TEEL-1 basis.
• PAC-1 = TEEL-1 = TLV-TWA (0.1 ppm, 0.53 mg/m3) x 3
• PAC-2 = TEEL-2 = LOC (0.045 g/m3)
• PAC-3 = TEEL-3 = IDLH (1994, 10 ppm)
This review generated PAC-3 and PAC-1 values inconsistent with Rev. 29A, and a consistent PAC-2 value. The Rev. 29A TEEL-3 was the 1990 IDLH, while the current TEEL-3 is the revised 1994 IDLH which includes additional inhalation acute toxicity data. The Rev. 29A TEEL-1 was derived from the TEEL-2, while the current TEEL-1 basis is a TLV-TWA. The Rev. 29A and current TEEL-2 values, source, and methodology are consistent.