A review of available sources identified exposure limits (TWAs, REL-STEL, PEL-C, IDLH) and acute toxicity data (LD50) 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. Analysts evaluated the 1990 and 1994 IDLH. The 1990 IDLH basis is chronic animal toxicity and was calculated from the PEL-TWA (multiplied by protective factor). The 1994 IDLH was derived from an analogous chemical, nitroglycerine (CASRN: 55-63-0) which shares toxicity characteristics with ethylene glycol dinitrate (vasodilators). Analysts compared the magnitude of the 1994 IDLH (75 mg/m3) with a TEEL derived from rat oral LD50 (PAC-3 = TEEL-3 = 90 mg/m3), determining that they were comparable. As such, analysts selected the 1994 IDLH as the TEEL-3. The PEL-C was selected as the TEEL-2. The REL-STEL was selected as the TEEL-1.
• PAC-1 = TEEL-1 = REL-STEL (0.1 mg/m3)
• PAC-2 = TEEL-2 = PEL-C (0.2 ppm/1 mg/m3)
• PAC-3 = TEEL-3 = IDLH (1994, 75 mg/m3)
The review generated PAC-2 and PAC-1 sources consistent with Rev. 29A; differences in the values in mg/m3 may be due to conversion and rounding of the limits instead of as published (Section 3.4.7.2). The Rev. 29A and current PAC-3 values are inconsistent. The Rev. 29A TEEL-3 source was the 1990 IDLH, while the current TEEL-3 is the 1994 IDLH. The 1994 IDLH was used in accordance with handbook guidelines (Section 4.2-4.3).