The London smog of 1952 killed thousands but gave many more lifelong health problems.
Beijing has announced it will add 50 miles of subway track by the end of next year, making the city's subway system bigger than New York's. But will the new additions alleviate the city's notorious traffic and pollution?
China's southeastern province of Fujian enjoys some of China's cleanest air. Provincial officials have launched a 'clean air tourism' campaign to court Chinese who live in cities like Beijing, where pollution levels have been at record highs this year.