6Beijing, China

While China has made significant strides in reducing pollution in recent years, Beijing remains one of the dirtiest cities in terms of air quality. The city has long been plagued by severe smog, largely due to industrial emissions, coal-fired power plants, and vehicular traffic. Although government initiatives have reduced coal consumption and improved public transportation, the city still experiences dangerous levels of particulate matter, particularly in the winter when coal is burned for heating. Beijing also faces water pollution challenges, as its rivers and lakes have suffered from industrial contamination.