BEIJING, Nov. 10 (Xinhua) -- China has achieved preliminary results in preventing and controlling ozone pollution this summer, the top environment authority said Tuesday.

Ozone concentrations in key regions including Beijing, Tianjin, Hebei and Shanxi came down considerably in July, and the number of days of ozone levels crossing the standard declined significantly, said Li Tianwei, an official with the Ministry of Ecology and Environment.

The average concentration of ozone in 337 cities rose 6.5 percent year on year in 2019, Li added.

The official pledged more efforts to reduce the emission of volatile organic compounds, a key component of ozone and PM2.5, and further contain ozone pollution. Enditem