Air quality improved in Chinese cities in the first five months of 2019, according to the Ministry of Ecology and Environment. 

Some 337 cities enjoyed good air quality on 80.3 percent of the days from January to May, up 0.6 percentage points from the same period last year. Nearly 120 cities met the air quality standards, including 20 cities joining this year, the ministry data showed. 

The average PM2.5 density, a key pollution indicator, remained unchanged at 44 micrograms per cubic meter over the period and the average density of PM10 and sulfur dioxide fell by 2.6 and 13.3 percent respectively year on year. 

Haikou, Lhasa and Shenzhen ranked top three on the list of 168 cities' air quality in the first five months while cities in the provinces of Hebei, Henan and Shanxi lagged behind. 

Several regions saw a decrease in PM2.5 in May 2019, with readings in the Beijing-Tianjin-Hebei region and the Yangtze River Delta down 16.7 and 8.6 percent year on year respectively. 

China has pledged to coordinate its efforts on environmental protection and economic development in 2019. 

The country has vowed to reduce imports of solid waste and push for better air quality with improved regional coordination and heavy-polluter revamps, according to the ministry.