English: Airborne PM may enter the brain, inducing neurotoxic effects in the brain and is associated with increased risk of neurodegeneration. Firstly, the airborne PM can enter the brain via either the olfactory route which involves the olfactory system or the trigeminal nerve, or the passing through BBB after enter the circulation. Then the deposited PM can induce neurotoxicity, oxidative stress, neuroinflammation, and BBB and NVU damage. These adverse effects in the brain may result in neurodegenerative pathology, such as brain structural abnormality and pathological hallmarks for neurodegenerative diseases. Epidemiological studies has associated PM exposure with cognitive impairment and increased risk of developing neurodegenerative diseases such as AD. (AD Alzheimer’s disease, BBB blood–brain barrier, NVU neurovascular units, PM Particulate matter.)

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8862284/figure/Fig1/

Ran You, Yuen-Shan Ho, and Raymond Chuen-Chung Chang