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This photo combo shows a general view of people visiting Tiananmen Square during a heavily polluted day on December 1, 2015 (LOWER) and two days later when the smog cleared on December 3 (TOP) in Beijing. The skies cleared in Beijing on December 2 and 3, after being swathed in choking smog that was nearly 24 times safe levels earlier in the week. AFP PHOTO / WANG ZHAO / AFP / WANG ZHAO (Photo credit should read WANG ZHAO/AFP/Getty Images)

This photo combo shows a general view of people visiting Tiananmen Square during a heavily polluted day on December 1, 2015 (LOWER) and two days later when the smog cleared on December 3 (TOP) in Beijing. The skies cleared in Beijing on December 2 and 3, after being swathed in choking smog that was nearly 24 times safe levels earlier in the week. AFP PHOTO / WANG ZHAO / AFP / WANG ZHAO (Photo credit should read WANG ZHAO/AFP/Getty Images)
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AFP WANG ZHAO