A review of available sources did not identify exposure limits or acute toxicity data for 2,3-dihydro-4-methyl furan. In addition, analysts evaluated acute toxicity data for an isomer (3,4-dihydro-2H-pyran, CASRN: 110-87-2) for TEEL development (Section 3.4.6). 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. The rat LC50 for 3,4-dihydro-2H—pyran was not selected because it reported “no mortality”; instead, analysts selected a rat oral LD50 as the TEEL-3 basis. TEEL-2 and TEEL-1 values were derived according to Table 3.5.
• PAC-1 = TEEL-1 = TEEL-2/11
• PAC-2 = TEEL-2 = TEEL-3/6
• PAC-3 = TEEL-3 = Rat oral LD50 (3,4-Dihydro-2H-pyran, CASRN: 110-87-2; 4600 mg/kg)
This review generated PAC values inconsistent with Rev. 29A. The Rev. 29A TEEL-3 basis was rat oral LD50 for tetrahydromethylfuran (CASRN: 1320-94-1), while the current TEEL-3 basis is a rat oral LD50 for 3,4-dihydro-2H-pyran (Section 3.4.6, CASRN: 110-87-2). The Rev. 29A and current TEEL-2 and TEEL-1 use the same methodologies, with differences due to the change in TEEL-3.