As co-host of the 2022 Winter Olympic Games with Beijing, Zhangjiakou in Hebei province plans to plant 7 million mu (467,000 hectares) of trees and shut down 200 highly polluting companies in the next six years, according to the city's Party chief Hou Liang.

"We aim to lift the city's forest coverage rate to 50 percent by 2022 from the current 37 percent," Hou said, on the sidelines of the NPC session that concluded on Wednesday.

By 2022, all polluting coal, iron and open-pit mines around future Olympic venues in the city's Chongli county will be closed, he said.

Zhangjiakou has some of the best air quality in northern China, with an annual average PM 2.5 concentration of 34 micrograms per cubic meter last year.

PM 2.5 refers to airborne particulate matter with a diameter of 2.5 micrometers or less that is hazardous to human health.

The city is drawing up a seven year plan to reduce PM 2.5 concentrations to 25 mg per cubic meter by 2022 — the level considered safe by the World Health Organization, according to Xinhua News Agency.

During the last five years, around 7,000 hectares of trees have been planted around the future Olympic venues, according to the city's government work report.