A review of available sources identified the following: a WEEL-STEL and rat LC50 and LCLo toxicity data. These sources were selected according to the hierarchy listed in Table 3.1. Toxicity data were evaluated using the type of exposure, species, and route preferability stated in Sections 3.3.1, and 3.3.2. The concentration is scaled to a 60-minute equivalent using the ten Berge equation (Section 3.3.4).
In the National Institute of Environmental Health Sciences (NIEHS) Review of Toxicological Literature for 3-Picoline (methyl pyridine, 3-), there are three rat inhalation exposures that may serve as starting points for TEEL-3: 300-min exposure of 11820 mg/m3 (purity unlisted, all died) from Monsanto Company (1972), 240-min exposure of 12570 mg/m3 (98.5% pure 3-picoline, all died) E. I. DuPont (1984a), and 120-min exposure of 33140 mg/m3 (purity unlisted, all died) Reinhardt and Brittelli (1981).
The first exposure (Monsanto) is also listed in PubChem as a LCLo, with source National Technical Information Service. Considering source age/credibility, conservatism, and concentration type preferences, the DuPont exposure was selected as the TEEL-3 basis. The TEEL-2 was derived according to Table 3.5. The WEEL-STEL was selected as the TEEL-1.
• TEEL-1 = WEEL-STEL
• TEEL-2 = TEEL-3/6
• TEEL-3 = Rat 240-min LC50 (3300 ppm)
This review generated TEEL-3 and TEEL-2 values inconsistent with those in Rev. 29A, while the TEEL-1 remained consistent. The Rev. 29A TEEL-3 basis was the Reinhardt and Brittelli concentration; although this is a shorter exposure (120 vs. 240 min), the concentration is unlisted, and it is therefore a less complete record. Additionally, when the Health Hazard Rating for 3-methyl pyridine is considered (HHR=3, a TEEL-3 of 79 mg/m3), a more conservative approach appears appropriate. The Rev. 29A and current TEEL-2 were both derived according to Table 3.5, with differences attributed to the change in TEEL-3 basis.