(Yicai Global) May 23 -- Air pollution is back in many places in China as life and business activities return to normal with the lifting of the country’s zero-Covid policy earlier this year, according to the latest research.

Local pollutants rebounded in 74 of the 113 cities surveyed last winter, according to a report by a research team led by Chen Songxi, professor at the Center for Statistical Science at Peking University. Pollutants PM2.5, PM10, sulfur dioxide and ozone all increased significantly last year, it said.

The concentration of PM2.5 thickened in Beijing as well as Shaanxi and Shanxi provinces, while that of PM10 rebounded in Beijing as well as Shanxi, Shaanxi, Henan and Hebei provinces and another 56 cities, it added.

Some 80.1 percent of the days in the first three months had good or excellent air quality, a drop of 3.7 percentage points from the same period last year, according to a study of 339 Chinese cities released by the Ministry of Ecology and Environment last month. And 3.3. percent of the days had heavy or worse pollution, a climb of 1.5 percentage point.

In March, due to four sandstorms, 2.6 percent of the days had heavy or worse pollution, a year-on-year gain of 1.3 percentage point.

Most places in the country will have good air quality or light pollution in the second half of May, although some places could experience moderate or worse pollution, the Ministry said.

Editors: Shi Yi, Kim Taylor