A review of available sources identified the following: a TLV-TWA, a REL-C, and animal (guinea pig, mouse, rat) acute toxicity data for several routes. Additionally, GHS ratings of this chemical were considered to estimate appropriate TEEL magnitudes. Data sources were selected according to the hierarchy listed in Table 3.1. Toxicity data were based on the 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 TLV-TWA was selected as the TEEL-1 basis. A REL-C exposure limit was considered as a TEEL-2; however, it would have generated a value that was lower than the TEEL-1. Considering the GHS classification of this chemical as toxic to inhale (Category 3,) this chemical could conservatively be assumed to have an equivalent of a rat LC50 (1000 mg/m3/4H, see Table D-1 of The Overview of the GHS Classification Scheme in Hazard Classification Appendix D), corresponding to a TEEL-2 of 7 mg/m3 and TEEL-1 of 0.67 mg/m3. These values support deriving a TEEL-2 from the TEEL-3 value (Table 3.5,) instead of the overly conservative REL-C. The most preferred species, route, and most current source, a rat LC50, was selected as the TEEL-3 basis and scaled to 60-minute equivalent using the ten Berge equation (Section 3.3.4).
• TEEL-1 = TLV-TWA (0.005 ppm) x 3
• TEEL-2 = TEEL-3/6
• TEEL-3 = Rat LC50 (434 mg/m3/4H)
This review generated TEEL values comparable to those in Rev. 29A. Although values are nearly identical, the Rev. 29A basis was a rat LCLo while the current TEEL-3 basis in a rat LC50, a more preferred route (LC50 > LCLo). The Rev. 29A and TEEL-2 were both derived from the TEEL-3, with difference due to the change in TEEL-3. The Rev. 29A and current TEEL-1 values were derived using the same methodology.