BEIJING - The air quality of Yanqing district in Beijing, one of the competition zones of 2022 Winter Olympic Games and Paralympic Winter Games, ranked first in the city in the first half of this year, authorities said.

The suburban district's cumulative concentration of PM2.5, a main gauge of air pollution, was 37 micrograms per cubic meter during the period, the lowest among all city districts, the Yanqing bureau of ecology and environment said.

Fu Tiefeng, deputy director of the bureau, said, to prepare for the 2022 Games, Yanqing has covered the entire district under a smart environment monitoring system and used big data to analyze pollution trends and more accurately locate pollution sources.

This year, the district focuses on heavy trucks, kitchens, dusty construction sites, and other key sources of air pollution, having inspected projects under construction 56 times and checked about 230,000 heavy-duty diesel vehicles, Fu said.

The authority will continue to crack down on illegal air pollution to ensure good air quality during the Winter Olympics, Fu added.