A review of available sources did not identify exposure limits, acute toxicity data, or health hazard ratings for alkyl benzenes (C8-C9), a mixture of compounds. Instead, analysts evaluated exposure limits and acute toxicity for C8 and C9 benzenes, including: 1) 1,2,3-trimethylbenzene (C9H12, CASRN: 526-73-8; rat LDLo), 2) 1,2,4-trimethylbenzene (C9H12, CASRN: 95-63-6; AEGLs), 3) xylene (C8H10, CASRN: 1330-20-7, AEGLs), and ethylbenzene (C8C10, CASRN: 100-41-4; rat LD50, mouse LCLo). 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 most conservative AEGLs, AEGL-1 and AEGL-2 for 1,2,4-trimethylbenzene, were selected due to their priority among Protective Action Criteria (Section 3.4.6, Section 1). The toxicity data for ethylbenzene (LD50, LCLo) were considered as a TEEL-3 bases, however these resulted in TEEL-3 values < TEEL-2. Instead, analysts selected the rat LDLo for 1,2,3-trimethylbenzene as the TEEL-3 basis (Section 3.4.6). The dose is reported in units of mL/kg; therefore, the reported density of 1,2,3-trimethylbenzene (0.894 g/m3 at 25°C) was used to convert the dose to mg/kg.
· PAC-1 = AEGL-1 (1,2,4-trimethylbenzene, CASRN: 95-63-6)
· PAC-2 = AEGL-2 (1,2,4-trimethylbenzene, CASRN: 95-63-6)
· PAC-3 = TEEL-3 = Rat oral LDLo (1,2,3-trimethylbenzene, CASRN: 526-73-8. 10 mL/kg converted to 8940 mg/kg with density = 0.894 g/m3)
This review generated PAC values that are inconsistent with Rev. 29A. The Rev. 29A TEEL-1 basis was a TLV-TWA for particles not otherwise specified (Section 3.5.2), from which the TEEL-2 and TEEL-3 were derived (Table 3.5). The current PAC-1 and PAC-2 are AEGL-1 and AEGL-2, respectively, for a C9 benzene (1,2,4-trimethylbenzene, CASRN: 95-63-6). The current TEEL-3 basis is acute toxicity data (rat LDLo) for a C9 benzene compound (1,2,3-trimethylbenzene, CASRN: 526-73-8).