SHIJIAZHUANG, Sept. 11 (Xinhua) -- Hebei Province, which neighbors Beijing and is known for severe winter smog, recorded its best air quality levels in August since pollution control measures were implemented six years ago, according to the provincial department of ecology and environment.

The average density of PM 2.5 in August was 24 micrograms per cubic meter, down 11.1 percent year on year. PM 2.5 is a measure of the density of hazardous particulate in the air. The World Health Organization recommends an annual PM 2.5 level of 10 micrograms per cubic meter.

Hebei also recorded improvements in the density of other major pollutants, with sulfur dioxide and PM 10 registering at the lowest level since 2013 when China initiated a harsher air quality standard.

The number of good air days in the province was 27 in August, accounting for 87.1 percent of total days. No heavy pollution days were recorded.

From January to August, the average density of PM 2.5 was 50 micrograms per cubic meter, and 146 good air days were recorded, two more than the previous year.

The province has made efforts to fight smog by promoting clean energy, monitoring emissions from factories and vehicles as well as banning open-air burning, among a batch of regulations.

China has vowed to combat air pollution in recent years. According to an action plan released last year, by 2020, emissions of sulfur dioxide and nitrogen oxide should have dropped by more than 15 percent compared with 2015 levels, while cities that fail to meet the requirement of PM 2.5 density should see a decline of more than 18 percent from 2015 levels.

Meanwhile, cities at prefecture level and above should see their numbers of good air days reach 80 percent annually, and the percentage of heavily polluted days decrease by more than 25 percent from 2015 levels.