Nitrogen Oxide Levels Rise Dramatically As Economic Expansion Continues

CHONGQING, CHINA - MAY 14: Taxis travel along a street on May 14, 2009 in the center of Chongqing, China. Traffic congestion and pollution have worsened dramatically in Chinese cities because of the country's long-running economic expansion. For many years, Chongqing's main air pollution problem was caused by sulfur dioxide (SO2), primarily from coal burning. However, air quality monitoring data revealed that average nitrogen oxide (NOx) concentrations have doubled in the past five years, an indication that vehicle emissions have increased rapidly during this period. (Photo by Feng Li/Getty Images)

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