A review of available sources identified the following: OEL-STEL and multiple rat LC50 acute toxicity data. Data sources were selected according to the hierarchy listed in Table 3.1. Toxicity data were selected based on the type of exposure, species, and route according to the hierarchies stated in Sections 3.3.1, 3.3.2. These were evaluated using factors in Tables 3.2, 3.3, and 3.4. Inhalation doses were scaled to 60-minute equivalents using the ten Berge equation (Section 3.3.4). The chemical GHS acute toxicity classification was also evaluated; butanone oxime is classified as “harmful to the skin", with a Lowest Observed Adverse Effect Concentration of 108 mg/m3, (LOAEC, which is comparable to TEEL-2 by descriptions). From GHS health classifications, the primary hazard was determined to be skin exposure, not oral or inhalation exposures. Considering this, and considering the source credibility and age, the less conservative LC50 (ECHA) was selected as the TEEL-3 basis. The TEEL-2 was derived according to Table 3.5. The OEL-STEL (German) was selected as the TEEL-1.
• TEEL-1 = OEL-STEL (Germany (AGS), 8.0 mg/m3)
• TEEL-2 = TEEL-3/6
• TEEL-3 = Rat LC50 (20 mg/L/4H)
This review generated a TEEL-3 consistent with Rev. 29A. The Rev.29A TEEL-2 basis was a rat TCLo not found during the review; instead, the TEEL-2 was derived from the TEEL-3 (Table 3.5). The Rev. 29A TEEL-1 basis was WEEL-TWA, while the current TEEL-1 is an occupational short-term exposure limit (STEL), a more preferred source (Table 3.1).