A large area in northern China, including Beijing, Tianjin and the rest of Hebei province, has been shrouded in heavy smog since November 13. Beijing has issued a yellow alert for smog, the least severe in its current three-tier warning system. It triggers measures such as halting outdoor construction operations, vehicles that cause heavy pollution on the road and production in smokestack industries. Experts say the main cause of the air pollution is coal burning as heating has started for these cities. The Beijing-Tianjin-Hebei region is forecast to see moderate to severe air pollution until November 15.
