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Chinese officials have shut down factories and ordered cars off the roads to try and save their capital city after spending three straight days under a cloud of toxic smog. Visibility has been as low as 100 yards in some parts of the city, as an increase in winter coal burning, combined with low wind conditions pushed the nation's already crushing pollution problems to dangerous levels.

To put the current crisis in perspective, the World Health Organization considers an acceptable level of airborne particulates to be 25 micrograms per cubic meter (μg/m3). On Saturday, readings in Beijing reached 993 μg/m3. The head of cardiology at Peking University People’s Hospital said "The number of people coming into our emergency room suffering heart attacks has roughly doubled since Friday."

The severe pollution has had a ripple effect throughout the economy. Car factories and construction sites have been shut down, airports have had to cancel flights, and all government vehicles have been ordered to stay off the roads until the crisis passes. (Though it has led to a surge in air purifier sales.) However, it won't solve China's underlying problem, which is massive unchecked growth and poor regulation that have made whole swathes of the country a dangerous place for citizens and visitors. Of the 20 most-polluted cities in the world, 16 are in China.