Guangdong province will have more than 100 PM2.5 monitoring sites by the end of 2013, covering 21 cities, an official with the Guangdong Environment Monitoring Center (GEMC) told the Southern Daily on Sunday.

Zhong Liuju, an official with GEMC answered questions from residents and media regarding their recent activities in honor of the June 5 World Environment Day which was held in Guangzhou on Sunday.

None of the cities along the Pearl River Delta region in Guangdong, one of China's most developed areas, has met the national standard of PM2.5 or ozone in the past year, said Zhong.

"In the past year, the highest daily average of PM2.5 was 163 micrograms per cubic meters, among the 62 monitoring sites in the Pearl River Delta region. It was 2.2 times the national standard of 75 and reached Grade V heavy pollution," added Zhong.