• COPD epidemiology

Worldwide, COPD is an important cause of morbidity and mortality. The condition is increasing in prevalence, it is a major public health problem and it will remain a challenge for clinicians within the 21st century.1 COPD has become the third leading cause of death,2 resulting in 2.9 million deaths globally in 2013.3 The Global Burden of Diseases Study estimated that around 1.2 million premature deaths and 25 million disability-adjusted life-years annually in China alone could be attributed to air pollution.3 In recent years, evidence is growing that the exposure to ambient air pollution may contribute to the growing global burden of COPD.4 In many Western countries, levels of ambient air pollution have been improved with the setting of upper limits and better urban planning. However, air pollution in low/middle-income countries with rapid industrialisation, such as China, has become a major global problem.5 Severe air pollution events, with levels of fine particulate matter (PM) exceeding 690 μg/m³,6 result in a health burden that has increased …