BEIJING — China's environment further improved last year, according to an official report on the environmental conditions and the achievement of environmental protection objectives in 2021.

Last year, the percentage of days with good air quality was 87.5 percent in cities at and above the prefecture-level, up 0.5 percentage points year-on-year, the report said, which was submitted on April 18 to the National People's Congress Standing Committee for review.

The average concentration of hazardous airborne particles PM2.5 was 30 micrograms per cubic meter, down 9.1 percent year-on-year, according to the report.

The proportion of surface water at or above Grade III in the country's five-tier water quality system increased 1.5 percentage points year-on-year to 84.9 percent in 2021, the report said.

Meanwhile, the proportion of surface water below Grade V, the lowest level, stood at 1.2 percent, the report added.

In 2022, more efforts will be made to eliminate heavily polluted weather, control ozone pollution and diesel truck pollution, protect the Yangtze River and the Yellow River, carry out comprehensive treatment of key marine areas, and map the sewage outlets and control the discharge of pollutants, the report said.