The file photo shows a wind power plant in Zhangjiakou, North China's Hebei province. [Photo/Xinhua]

China's air quality and surface water quality has continued to improve in the first three quarters of this year, the Ministry of Ecology and Environment announced on Tuesday.

In 339 cities at the prefecture level and above nationwide, four out of the six major pollutant indicators — PM2.5, PM10, ozone, nitrogen dioxide — decreased; while the other two — sulfur dioxide and carbon monoxide — remained stable, Pei Xiaofei, a spokesman of the ministry said during a news conference in Beijing.

Among them, the average concentration of PM2.5 was 27 micrograms per cubic meter, a year-on-year decrease of 3.6 percent; the average concentration of PM10 was 47 micrograms per cubic meter, a year-on-year decrease of 7.8 percent.

In these cities, the proportion of days with good air quality averaged 85.8 percent, an increase of 1.6 percentage points year-on-year; the proportion of days with heavy pollution or worse averaged 1.1 percent, a decrease of 0.7 percentage points year-on-year.

Regarding surface water quality, among over 3,600 national assessment sections, the proportion of sections with excellent water quality was 88.5 percent, an increase of 1.4 percentage points compared to the previous year, according to the ministry.