The Impact of PM(2.5) on the Host Defense of Respiratory System

The harm of fine particulate matter (PM(2.5)) to public health is the focus of attention around the world. The Global Burden of Disease (GBD) Study 2015 (GBD 2015 Risk Factors Collaborators, 2016) ranked PM(2.5) as the fifth leading risk factor for death, which caused 4.2 million deaths and 103.1 million disability-adjusted life-years (DALYs) loss, representing 7.6% of total global deaths and 4.2% of global DALYs. Epidemiological studies have confirmed that exposure to PM(2.5) increases the incidence and mortality of respiratory infections. The host defense dysfunction caused by PM(2.5) exposure may be the key to the susceptibility of respiratory system infection. Thus, this review aims to assess the impact of PM(2.5) on the host defense of respiratory system. Firstly, we elaborated the epidemiological evidence that exposure to PM(2.5) increases the risk of respiratory infections. Secondly, we summarized the experimental evidence that PM(2.5) exposure increases the susceptibility of different pathogens (including bacteria and viruses) in respiratory system. Furthermore, here we discussed the underlying host defense mechanisms by which PM(2.5) exposure increases the risk of respiratory infections as well as future perspectives.