The term “
particulate Matter (PM)” refers to the mixture of small-sized solid particles and liquid droplets floating in the
air, and is referred to as PM₁₀ ( < 10 µm), PM(2.5) ( < 2.5 µm) and PM(1.0). Much PM is an anthropogenic substance generated by
transportation or industrial activities, which is transformed into a second toxic substance by
chemical reactions in the
atmosphere. PM reaches the
brain directly through olfactory transport, or through the
blood-brain barrier during systemic circulation. PM that enters the local
cerebral circulation causes
neuroinflammation through
microglial cells and
endotoxins. According to previous studies, greater PM exposure results in lower
brain volume, especially
white matter. Among
neurodevelopmental disorders, the correlation between the occurrence of
autism spectrum disorder and exposure to PM is widely known. Other studies have found that exposure to PM was associated with low
cognitive function and increased rate of
cognitive aging. PM can also cause
pathology of early
Alzheimer's disease and increases the
risk of Alzheimer's
dementia and
mild cognitive impairment.