The Beijing Municipal Ecological Environment Bureau announced on Tuesday that the average concentration of PM2.5 - fine particulate matter that is hazardous to human health - in Beijing was 23 micrograms per cubic meter for the first nine months, a 10.6 percent drop year-on-year.

During the first three quarters, Beijing saw 165 days with good air quality. The number of days with severe air pollution was three, which was five days less than the same period last year.

Particularly, the index dropped to 23 micrograms per cubic meter in August, a record low since monitoring began.