Thick, choking smog enveloped cities in northeast China for a second day Tuesday, snarling traffic and closing schools, airports and highways. In some places, visibility was reduced to a few yards.
Oct. 22, 2013 Buildings and streets are seen under heavy smog in Harbin, an industrial city in northeast China's Heilongjiang province that is home to more than 10 million people. The PM 2.5 level of fine particulate matter in the air reached 1,000 micrograms per cubic meter in parts of the city Monday, 50 times above what the World Health Organization considers safe. AFP/Getty Images