A review of available sources could not identify exposure, toxicity, or health hazard ratings for 4-bis(2-methylstyryl) benzene. Instead, two structurally similar chemicals were investigated: the isomers p-terphenyl (CASRN: 92-94-4) and o-terphenyl (CASRN: 84-15-1). For these structurally similar chemicals a review of available sources identified the following: ceiling exposure limits (PEL, REL, TLV), an IDLH, and acute toxicity data. Data sources were selected according to the hierarchy listed in Table 3.1. An IDLH is the most preferred basis for a TEEL-3. The 1990 and 1994 IDLH use the same methodology, 500x Ceiling limit; different values arise from their bases. The 1990 basis is a PEC-C (9 mg/m3), while the 1994 basis is a REL-C (5 mg/m3). Given this, the more conservative REL-C based IDLH (1994) was selected as the TEEL-3. Although considered, the most preferred ceiling limits (TLV-C, REL-C: 0.5ppm/5 mg/m3) were determined to be too conservative for TEEL-2 values, considering they are one-to-two orders of magnitude less than other TEEL-2 estimates. Instead, TEEL-2 and TEEL-1 values were derived according to Table 3.5.
• TEEL-1 = TEEL-2/11
• TEEL-2 = TEEL-3/6
• TEEL-3 = IDLH (1994, terphenyl mixed isomers, CASRN: 26140–60–3, 500 mg/m3)
This review generated TEEL values inconsistent with Rev. 29A. The Rev. 29A TEELs were derived from an assumed HHR=2, while the current TEEL-3 is an IDLH, with TEEL-2 and TEEL-1 values derived according to Table 3.5. Use of the 1994 IDLH was reviewed by a panel, according to Sections 4.2-4.3