BEIJING, July 13 -- Seven of China's top 10 cities with the worst air quality in June were in Hebei Province, which neighbors Beijing, the Ministry of Environmental Protection said in a monthly report.

The cities in Hebei included Tangshan, Baoding and Shijiazhuang. The cities outside Hebei were Zhengzhou, Henan Province; Jinan, Shangdong Province and Taiyuan, Shanxi Province.

Air quality in the Beijing-Tianjin-Hebei region in June was worse than the month before, although it had improved yea on year, the report said.

According to the report, polluted days accounted for more than half of the month in six cities in the region, including Beijing and Tianjin.

The main pollutants were ozone and PM2.5.

The monthly report, which reviews air quality in 74 cities, also named ten cities with the best air quality, including Haikou, Hainan Province; Shenzhen, Guangdong Province; and Kunming, Yunnan Province.

The Yangtze River Delta region witnessed improved air quality in June compared with the same period last year, but the results were slightly worse than May.

For the Pearl River Delta region, improved air quality was reported in June compared with both the previous month and the same period last year.

The two delta regions are economically-developed eastern and southern areas encompassing Shanghai and Guangzhou respectively.