China will start a massive environmental overhaul on June 11 to ensure the effective curb of air pollution in key regions, said sources with the Ministry of Ecology and Environment Saturday.

The inspection is expected to last until April 28, 2019, during which approximately 18,000 environmental supervisors will aim to discover environmental protection problems in the Beijing-Tianjin-Hebei region and the surrounding areas, the Yangtze River Delta, and the Fenhe and Weihe river plains.

A total of 28 cities will be targeted, including 11 cities in the provinces of Shanxi, Shaanxi and Henan situated in the river plains of Fenhe and Weihe, as well as the Shanghai Municipality, and the provinces of Jiangsu, Zhejiang and Anhui in the Yangtze River Delta.

Although air quality in these areas has continuously improved on the whole, pollution remains serious in individual regions, the sources said.

The Beijing-Tianjin-Hebei region is the worst, while in some provinces like Henan and Shandong, the annual share of days with good air quality is less than 60 percent.

In the Fenhe and Weihe river plains, air pollution has worsened in recent years, the sources said.

The supervisors will be professionals selected from local environment protection departments and the ministry to uncover structural problems in industrial development, energy use, transportation and land use that are detrimental to air pollution control.

The inspections will revolve around prominent public complaints, such as emergency responses to cases of heavy pollution, crop straw burning and coal-fired boilers.

Cities failing in their responsibilities will be openly questioned. When necessary, inspection teams at the central level will be sent to supervise local governments, according to the sources.