A review of available sources identified exposure limits (TWAs, STELs) and acute toxicity data (LC50, LD50, TCLo) for several species and routes. 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 rat LC50 was considered as a TEEL-3 basis; however, it did not report the dose duration. Instead, a mouse LCLo¬ was selected as the TEEL-3 basis, and it was scaled to a 60-minute equivalent using the ten Berge equation (Section 3.3.4). The human TCLo was considered as a TEEL-2, but this resulted in a TEEL-2 > TEEL-3; instead, the TEEL-2 was derived according to Table 3.5. The OEL-STEL (15-minute, Poland) was selected as the TEEL-1.
• TEEL-1 = OEL-STEL (1.5 mg/m3)
• TEEL-2 = TEEL-3/6
• TEEL-3 = Mouse inhalation LCLo (3200 mg/m3/2H)
This review generated TEEL-3 and TEEL-2 values inconsistent with Rev. 29A. The Rev. 29A TEEL-3 basis was a rat oral LD50, while the current TEEL-3 basis is a mouse LCLo, a more preferred route (inhalation, Section 3.3.2). The Rev. 29A and current TEEL-2 use the same methodology, with differences due to the change in TEEL-3. The TEEL-1 value is consistent; however, the Rev. 29A TEEL-1 basis was derived from the TEEL-2 and the current TEEL-1 is an OEL-STEL.