Inhalation of nanoplastics in the mouse model: Tissue bio-distribution and effects on the olfactory system

The impact of plastic fragments on human health is currently under investigation, with nanoplastics (NPs) being particularly concerning due to their small size. This allows them to be inhaled, pass through blood barriers, and reach various organs. In this study, we evaluated the effects of airborne NPs on the mouse olfactory system, which is a primary target of NPs inhalation. Adult mice were exposed to an aerosol solution containing synthetic polystyrene nanoplastics (PS-NPs) labelled with a red fluorophore for 5 h a day over 7 days. Biodistribution analysis revealed that PS-NPs accumulated in tissues, such as brain, lung, adipose tissue, and testicles, but were cleared after one month. This study is the first to investigate the effects of inhaled PS-NPs on the olfactory bulb (OB) and subventricular neurogenesis in adult mice. We observed long-term impairments in olfactory discrimination, decreased neuronal functionality, and pro-inflammatory activation in microglia in OB following PS-NPs exposure. Surprisingly, we noted a compensatory increase in olfactory neurogenesis, although insufficient to counteract the olfaction impairment induced by the PS-NPs. These results provide novel insights into the potential neurotoxic effects of inhaled PS-NPs and emphasize the importance of assessing occupational and environmental exposure to these pollutants.