
Heavy smog suffocated northeast China for a fifth day Tuesday, with hundreds of flights cancelled and road and rail transport grinding to a halt under the low visibility conditions.
More than 20 cities have entered a state of red alert since Friday evening, implementing emergency measures aimed at cutting emissions and protecting public health from the toxic miasma.
Across the region, construction sites closed and authorities reduced the number of vehicles allowed on the roads in hopes of reducing the thick haze.
In Shijiazhuang, the capital of northern Hebei province, planes could not take off or land, according to a post on a verified social media account of the city's international airport.
Levels of PM 2.5 -- microscopic particles harmful to human health -- climbed to 844 in the area, according to the web site aqicn.org.
The number is almost 34 times the World Health Organization's recommended maximum exposure level of 25 over a 24-hour period.


