A review of available sources identified rat oral LD50 toxicity data and GHS health hazard ratings for lanthanum oxide. 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. Reported GHS health hazard ratings (H315 and H319, Category 2; H335, Category 3) indicate a mid-level health hazard. Two rat oral doses were evaluated; however, no mortality was reported for the larger dose, so these were not selected for TEEL development. Considering this, and the physical properties of this compound, analysts determine the LD50 support a TEEL-3 less conservative than an HHR=2 (790 mg/m3). As such, analysts selected the PNOS as the TEEL-1 basis (Section 3.5.2). TEEL-3 and TEEL-2 values were derived according to Table 3.5.
• PAC-1 = TEEL-1 = TLV-TWA (PNOS, 10 mg/m3) x 3
• PAC-2 = TEEL-2 = TEEL-1 x 11
• PAC-3 = TEEL-3 = TEEL-2 x 6
This review generated PAC values inconsistent with Rev. 29A. The Rev. 29A TEEL-3 basis was a mouse oral LD50 not found in the current review, from which the TEEL-2 and TEEL-1 were derived (Table 3.5). The current TEEL-1 basis is the TLV-TWA for particles not otherwise specified (Section 3.5.2), from which the TEEL-2 and TEEL-3 were derived (Table 3.5).