A review of available sources identified exposure limits (LOC, OEL-STEL, TWAs) and acute toxicity data (LC50, LD50, and TDLo) 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 LC50 did not specify a duration, therefore analysts instead selected a dog oral LD50 as the TEEL-3 basis (Section 3.3.1). The LOC was considered as a TEEL-2, however this resulted in a TEEL-2 > TEEL-3. Instead, analysts selected a human (female) oral TDLo as the TEEL-2 basis. An OEL-STEL (Austria, Denmark, Romania) was selected as the TEEL-1.
• PAC-1 = TEEL-1 = OEL-STEL (Austria, Denmark, Romania; 0.2 mg/m3)
• PAC-2 = TEEL-2 = Human female oral TDLo (0.8 mg/kg; Behavioral Effect: hallucinations, distorted perceptions, convulsions, or effect on seizure threshold)
• PAC-3 = TEEL-3 = Dog oral LD50 (5 mg/kg)
This review generated PAC values that are inconsistent with Rev. 29A. The Rev. 29A TEEL-3 basis was a rat LC50 with an assumed duration of 4H; the current TEEL-3 basis is a dog oral LD50, a more preferred approach given that the duration of the LC50 is not reported and there is other acute toxicity data from which to derive the TEEL-3 (Section 3.2.2). The Rev. 29A TEEL-2 was the LOC, while the current TEEL-2 basis is a human oral TDLo. The Rev. 29A TEEL-1 was derived from the TEEL-2, while the current TEEL-1 is an OEL-STEL, a more preferred source (see note in Table 3.5).