A review of available sources identified the following: mouse and rat acute toxicity data (LD50, LC50) and exposure limits for mixed isomers of dinitrotoluene (CASRN: 25321-14-6). 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. Inhalation concentrations were scaled to 60-minute equivalents using the ten Berge equation (Section 3.3.4). Although an IDLH is a more preferred source, analysts determined that 2,6-dinitrotoluene is more toxic than its isomer 2,4-dinitrotoluene (CASRN: 121-14-2) by comparing available acute toxicity for both chemicals. Vernot et al. (1977) report lower single oral LD50 doses for 2,6-dinitrotoluene than for 2,4-dinitrotoleune in rats (unspecified route, LD50 = 180 mg/kg vs. 270 mg/kg) and mice (unspecified LD50 = 1000 mg/kg vs. 1630 mg/kg). A similar study by La and Froines (1992) investigated the toxicity of 2,4-dinitrotoluene and 2,6-dinitrotoluene; all rats administered 2,6-dinitrotoluene (intraperitoneal or oral dose of 150 mg/kg) died within 24 hours, whereas no deaths were observed for the group administered 2,4-dinitrotoluene (375 mg/kg). Considering these differences, it was determined that 2,6-dinitrotoluene is more toxic than a mixture of dinitrotoluene isomers. Therefore, the most preferred route toxicity data, a rat LC50 (240 mg/m3/6H) was selected as the TEEL-3 basis (Table 3.1) and it was scaled to 60-minute equivalent using the ten Berge equation (Section 3.3.4). 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 = Rat LC50 (240 mg/m3/6H)
This review generated TEELs that are significantly more conservative than Rev. 29A. The Rev. 29A TEEL-3 values were based on exposure limits (TLV-TWA, IDLH) and dog oral TDLo toxicity data for a mixture of dinitrotoluene isomers (CASRN: 25321-14-6). However, it was determined that 2,6-dinitrotoluene is more toxic than these mixtures account for and a rat LC50 was selected as the TEEL-3 basis.