US EPA

89253 

Journal Article 

Translocation of inhaled ultrafine manganese oxide particles to the central nervous system 

Elder, A; Gelein, R; Silva, V; Feikert, T; Opanashuk, L; Carter, J; Potter, R; Maynard, A; Ito, Y; Finkelstein, J; Oberdörster, G 

2006 

Yes 

Environmental Health Perspectives
ISSN: 0091-6765
EISSN: 1552-9924 

114 

8 

1172-1178 

English 

16882521 

10.1289/ehp.9030 

WOS:000239468000037 

Background: Studies in monkeys with intranasally instilled gold ultrafine particles (UFPs; < 100 nm) and in rats with inhaled carbon UFPs suggested that solid UFPs deposited in the nose travel along the olfactory nerve to the olfactory bulb.
Methods: To determine if olfactory translocation occurs for other solid metal UFPs and assess potential health effects, we exposed groups of rats to manganese (Mn) oxide UFPs (30 nm; ~ 500 μg/m3) with either both nostrils patent or the right nostril occluded. We analyzed Mn in lung, liver, olfactory bulb, and other brain regions, and we performed gene and protein analyses.
Results: After 12 days of exposure with both nostrils patent, Mn concentrations in the olfactory bulb increased 3.5-fold, whereas lung Mn concentrations doubled; there were also increases in striatum, frontal cortex, and cerebellum. Lung lavage analysis showed no indications of lung inflammation, whereas increases in olfactory bulb tumor necrosis factor-α mRNA (~ 8-fold) and protein (~ 30-fold) were found after 11 days of exposure and, to a lesser degree, in other brain regions with increased Mn levels. Macrophage inflammatory protein-2, glial fibrillary acidic protein, and neuronal cell adhesion molecule mRNA were also increased in olfactory bulb. With the right nostril occluded for a 2-day exposure, Mn accumulated only in the left olfactory bulb. Solubilization of the Mn oxide UFPs was < 1.5% per day.
Conclusions: We conclude that the olfactory neuronal pathway is efficient for translocating inhaled Mn oxide as solid UFPs to the central nervous system and that this can result in inflammatory changes. We suggest that despite differences between human and rodent olfactory systems, this pathway is relevant in humans. 

brain; central nervous system; CNS; inhalation; intranasal instillation; manganese; metals; nose; olfactory bulb; respiratory tract