SHANGHAI, Dec 21 (SMM) – All construction sites in Zhengzhou of Henan province were required to suspend as local environmental authorities raised the alert for air pollution to the highest level on CST 22:00 on Thursday December 20. 

This is the city's first, highest-level air pollution this winter. The highest level is a red alert in China's four-tiered warning system for severe weather. By the evening of December 20, all 18 cities in Henan have issued heavy air pollution warnings.

Local authorities forecasted heavy smog in the next four days in the provincial capital of Henan. General air quality index readings of the city surged to around 400 on Thursday.