Ozone overtook PM2.5 to become the main air pollutant in 74 Chinese cities in August, according to a ranking released by the Ministry of Environmental Protection on Wednesday.
More than 45 percent of August days in Beijing had pollution, with two days of heavy pollution, and the main pollutants were ozone and PM2.5, according to the monthly report, which reviews air quality in 74 cities.
Harder to detect than PM2.5, ozone is also more harmful and has been linked to respiratory, eye and immune problems. Crops can also be affected by ozone.
According to the report, the main pollutants in 25 cities in the Yangtze River Delta region were ozone and PM 2.5 in August, while the major pollutants in nine cities in the Pearl River Delta region were ozone and sulfur dioxide.
The two delta regions have high levels of economic development and encompass the cities of Shanghai in eastern China and Guangzhou in the south.
Seven cities in Beijing's neighboring province of Hebei, including Handan, Xingtai, Tangshan, Baoding, Hengshui, Langfang and Shijiazhuang, were among the ten most polluted, together with Zhengzhou in Henan Province, Jinan in Shandong Province, and the southwestern city of Chengdu.
The report also named ten cities with the best air quality, including Haikou in Hainan Province, Zhoushan in Zhejiang Province, Fuzhou in Fujian Province and Lhasa in Tibet.
