A review of the possible associations between ambient PM2.5 exposures and the development of Alzheimer's disease

PM2.5 particles in air pollution have been widely considered associated with respiratory and cardiovascular diseases. Recent studies have shown that PM2.5 can also cause central nervous system (CNS) diseases, including a variety of neurodegenerative diseases, such as Alzheimer's disease (AD). Activation of microglia in the central nervous system can lead to inflammatory and neurological damage. PM2.5 will reduce the methylation level of DNA and affect epigenetics. PM2.5 enters the human body through a variety of pathways to have pathological effects on CNS. For example, PM2.5 can destroy the integrity of the blood-brain barrier (BBB), so peripheral systemic inflammation easily crosses BBB and reaches CNS. The olfactory nerve is another way for PM2.5 particles to enter the brain. Surprisingly, PM2.5 can also enter the gastrointestinal tract, causing imbalances in the intestinal microecology to affect central nervous system diseases. The current work collected and discuss the mechanisms of PM2.5-induced CNS damage and PM2.5-induced neurodegenerative diseases.