Owen Guo, To Limit Disruption, Beijing Raises Threshold on Red Alerts for Air Polution; A city wants fewer emergencies as it confronts its problem. New York Times, Feb 23, 2016.
(first paragraph: "The first red alert over air pollution in the Chinese capital almost brought this city to a standstill in December, with schools shut, construction halted and driving restricted. Now, in a swift policy shift, Beijing plans to issue a red alert based on higher thresholds, despite government pledges to better address the toxic air")