BEIJING — Beijing saw primary air-pollution index readings fall 40 percent year-on-year in the first quarter of 2022, official data shows.

The city's average concentration of PM2.5 was 36 micrograms per cubic meter in the January-March period, according to the Beijing municipal ecology and environment bureau.

In the quarter, Beijing reported 81 days with an air quality index (AQI) reading at or below 100.

The city will improve its coordinated control of PM2.5 and ozone pollution as it works to further improve air quality, said Yu Jianhua, deputy director of the Beijing municipal ecology and environment bureau.

PM2.5 readings are a gauge monitoring airborne particles of 2.5 microns or below in diameter.

Beijing made a breakthrough in its air pollution control last year when the city reached the national air quality standard. The city's average concentration of PM2.5 was 33 micrograms per cubic meter in 2021, the lowest level since records began in 2013.