BEIJING - Beijing saw all its six major ambient air pollutants in 2021 reach the level-II national standard for the city's first time, said the Beijing municipal ecology and environment bureau on Wednesday.

The bureau released a report on the city's ecological environment situation in 2021 on Wednesday. According to the report, the city's average concentration of hazardous airborne particles PM2.5 last year was 33 micrograms per cubic meter, while the average concentration of PM10 was 55 micrograms per cubic meter.

The PM2.5 reading is a gauge monitoring airborne particles of 2.5 microns or less in diameter, which can penetrate deep into people's lungs.

Data released showed that other key air pollution readings, including sulfur dioxide, nitrogen dioxide, carbon monoxide and ozone, all reached the national standards during the period.

Besides the improving air quality, none of the total 97 sections of Beijing's major water systems were graded Class V in terms of their water quality in 2021. The proportion of surface water at or above Grade III in the country's five-tier water quality system reached 75.2 percent, up 11.4 percentage points compared to the prior year.

Meanwhile, about 116 kinds of phytoplankton, 195 kinds of zooplankton, 207 kinds of benthonic animals and 41 fish species were monitored in Beijing's main streams and tributaries, key lakes and large- and medium-sized reservoirs.

Notably, the city's carbon dioxide emission per 10,000 yuan ($1,486) of GDP last year fell by about 4 percent compared with 2020, said the report.