Fig. 9
Model of the pathway and mechanism of brain damage due to exposure to PM2.5. Ambient PM2.5 particles in air pollution enter the human body mostly from the airway. They could penetrate deeply into the lung, irritate and corrode the alveolar wall. PM2.5 also enters the gastro-intestinal tract. Inflammation damage and oxidative stress are aroused in both pathways and toxic agents, such as cytokines are released into the systemic circulation. PM2.5 and related toxic agents would invade and damage the central nervous system (brain) via the systemic circulation, olfactory tract, direct gun-brain axis, and even the optic tract. Solid line presents the proved pathways and dotted line means the suggested new one