A review of available sources identified several rat oral acute toxicity data (LD50). In addition, analysts evaluated exposure limits for the structurally similar chemical chlorodiphenyl - 42% chlorine (CASRN: 53469-21-9) for TEEL development. 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 determined that the use of the IDLH, which reports a combined value for polychlorinated biphenyls (PCBs) with 42% and 54% chlorine, is not advised considering that 54% PCBs are uniquely toxic among PCB congeners. Analysts observed that 1) animal strain and species influence toxic effects and 2) Aroclor 1260 is more toxic to immature rats than to adults. Considering this, analysts selected the lowest, adult rat oral LD50 as the TEEL-3 basis. The TEEL-2 was derived according to Table 3.5. The TLV-TWA for chlorodiphenyl – 42% chlorine (CASRN: 53469-21-9) was selected as the TEEL-1 basis (Section 3.4.6).
• PAC-1 = TEEL-1 = TLV-TWA (chlorodiphenyl – 42% chlorine, CASRN: 53469-21-9; 1 mg/m3) x 3
• PAC-2 = TEEL-2 = TEEL-3/6
• PAC-3 = TEEL-3 = Rat oral LD50 (10000 mg/kg)
This review generated PAC values inconsistent with Rev. 29A. The Rev. 29A TEEL-3 source was based on Aloclor 1262 oral LD50 toxicity in weanling rats; the current TEEL-3 is instead based on toxicity for adult rats. The Rev. 29A TEEL-2 basis was a rat TDLo not found during the current review; instead, the TEEL-2 was derived from the TEEL-3. The Rev. 29A TEEL-1 was derived from the TEEL-2, while the current TEEL-1 basis is a TLV-TWA for a similar chemical (chlorodiphenyl – 42% chlorine, CASRN: 53469-21-9, Section 3.4.6).