Rats breathed an aerosol of uranium tetraoxide particles for 30 minutes and were examined 4 hours later. Uranium was higher in every brain region tested than in controls, with the highest levels in the olfactory bulbs and a front-to-back gradient, which the authors read as direct transfer along the olfactory nerve. Imaging located uranium in olfactory neuron dendrites, between epithelial cells and along nerve bundles.
Key numbers
- Mean aerosol concentration 218 mg/m3 (series 1) and 545 mg/m3 (series 2); aerodynamic mass median diameter 4.6 and 4.4 µm (p. 3).
- Olfactory bulb uranium: 1.51 ± 0.19 ng/g tissue in controls, 17.95 ± 13.34 (series 1) and 15.31 ± 4.60 ng/g (series 2); cerebellum 0.47 ± 0.05, 2.45 ± 0.47 and 5.25 ± 1.09 ng/g; n = 8 per group (Table 1, p. 5).
- Uranium-235 share 0.7% in controls and 0.4% in exposed animals, confirming the depleted test powder as the source (p. 5).
Methods (brief)
Nose-only inhalation exposure; brain structures microdissected and analyzed by ICP-MS; secondary ion mass spectrometry and transmission electron microscopy with energy-dispersive X-ray spectroscopy located uranium in tissue.
Evidence fitness
Supports a statement that inhaled uranium particles can reach the brain through the olfactory pathway in rats, relevant to occupational dust exposure. It does not support dietary exposure or toxicity claims and reports no functional neurological outcomes.
Limitations
Single acute exposure at high aerosol concentrations, one time point (4 hours), male rats only, and no behavioral or functional endpoints.
Related evidence
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