The 338 cities of China have experienced good air quality on 88.1 percent of days in July, with a clear reduction in some major airborne pollutants last month. Many northern cities have seen more days with excessive ground-level ozone concentration.

The Ministry of Environmental Protection has released its monthly report on the air quality in the 338 Chinese cities on Thursday, showing the concentration of PM2.5 in July was reduced by 19.4 percent year-on-year, and the PM10 reduced by 18.8 percent.

The PM2.5 and PM10 refer to the fine particulate matter, measured in micrograms in diameter, and pose a risk to human health.

Among the 338 cities being monitored, eight cities from Hebei province were in the top ten with the worst air pollution, of which, Xingtai ranked first in air pollution in July. Beijing and Jinan of Shandong province were also listed in the top ten, the ministry said.

Compared to the reduction in PM2.5 and PM10, some northern cities have seen increasing ground-level ozone concentration in July, "because of the more days with strong sunshine and high temperature,"said Luo Yi, head of environmental monitoring department under the ministry on Thursday.

In the Beijing-Tianjin-Hebei region, 13 cities have 54.4 percent of days meeting the national air quality standards, mainly because of the increased concentration of ground-level ozone, a year-on-year increase of 9.4 percent.

In addition, the 34 cities in the Yangtze River Delta and Pearl River Delta, also major industrial zones in China, have seen the readings of PM2.5 and PM10 meeting the national standards in July, making these regions closer to meeting annual goals for air quality improvement.