Authorities in Shenyang, capital of Liaoning province, have identified coal used for heating as the primary source of air pollution in the city.

The latest data from Shenyang Environmental Protection Bureau shows that coal used for heating makes up 30 percent of air pollution.

The city is expected to burn 16 million metric tons of coal this winter, eight million tons of which is for heating, according to the bureau.

Other main causes of air pollution are dust from construction sites (20 percent), urban vehicle exhaust (20 percent), industrial emissions (10 percent) and extraterritorial dust (20 percent).

According to the bureau, the overall air quality in Shenyang is gradually improving. However, the improvement over the past decade has been relatively small.

The local government is formulating an emergency plan to relieve air pollution, with measures imposed when pollution hits certain high levels.

Measures include an odd-and-even license plate rule for vehicles on the road, an injunction on the open-air burning of crops, straw and waste, and setting flexible work hours during heavily polluted days.

The local government is currently consulting the public on the plan.