A review of available data sources identified the following: TLV-STEL, MAK-TWA, PEL-C, LDLo (human, male assumed), LD50 (monkey, dog,) and TDLo (human, male) toxicity data for oral and intraperitoneal 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. Of the available TEEL-3 starting points, the human data was the most preferred but was not selected because the sex of the subject was not reported. Instead, a monkey intraperitoneal LD50 was selected as the TEEL-3 basis. This LD50 is reported as a range (4400-5500 mg/kg), therefore the lower limit was used for TEEL calculations. The PEL-C was the most preferred source for the TEEL-2; its ratio to the lowest reported human male oral TDLo (15 g/kg; toxicity-to-exposure ratio = 91) indicates that scaling the PEL-C by a factor of 10 is appropriate to allow for a less restrictive value (Section 3.4.7.1). The TLV-STEL was selected as the TEEL-1.
• PAC-1 = TEEL-1 = TLV-STEL (vapor fraction, 50 ppm)
• PAC-2 = TEEL-2 = PEL-C (40 ppm/100 mg/m3) x 10
• PAC-3 = TEEL-3 = Monkey intraperitoneal LD50 (4400 mg/kg)
This review generated PAC values inconsistent with Rev. 29A. The Rev. 29A TEEL-3 basis was a dog oral LD50, while the current TEEL-3 basis is a monkey intraperitoneal (monkey > dog, Section 3.3.2). The Rev. 29A was derived from the TEEL-3, while the current TEEL-2 basis is a PEL-C that has been multiplied by a factor of ten to correct for conservatism, per Section 3.4.7.1. Use of this methodology was in accordance with Section 4.2-4.3. The Rev. 29A TEEL-1 basis was a MAK-TWA, while the current TEEL-1 is a higher priority source, a TLV-STEL (Table 3.1).