Particulate Matter and Respiratory Diseases: How Far Have We Gone?

Air pollution is a potential threat to public health worldwide, especially in South Asia. The Global Burden of Diseases, Injuries, and Risk Factors Study 2016 (GBD 2016) reported that most of global deaths attributable to ambient particulate matter occurred in China and India. Particulate matter (PM), as the main air pollutant, is receiving increasing attention due to its specific biological properties. PM is a complicated mixture and varies in sizes, compositions and sources. Increasing epidemiological studies have shown that both short- and long-term PM exposure are associated with the morbidity and mortality of respiratory diseases, including chronic obstructive pulmonary disease (COPD), asthma, lung cancer, and pneumonia, especially in the elderly and children. Several potential biological mechanisms have been proposed to explain the adverse effect of PM on the respiratory diseases, including oxidant stress, pro-inflammation, epigenetic modifications, DNA damage and carcinogenesis. However, there are still some contradictions with regard to the role of PM in the development of these respiratory diseases. Thus, this review made a summary of results from epidemiological studies about the association between PM and COPD, asthma, lung cancer, and pneumonia, and elucidated its potential biological mechanisms.