BEIJING, Jan. 17 -- China's air and water quality registered steady improvement in 2022, data from the Ministry of Ecology and Environment showed Tuesday.

The share of days with good air quality stood at 86.5 percent in Chinese cities at and above the prefecture-level, Jiang Huohua, an official with the ministry told a press conference.

The proportion of days with heavy air pollution was 0.9 percent last year, dropping to less than 1 percent for the first time, Jiang said.

The PM2.5 density, a key indicator of air pollution, dropped 3.3 percent year on year to 29 micrograms per cubic meter, falling below 30 micrograms per cubic meter for the first time since the data was first monitored.

The proportion of surface water at or above Grade III in the country's five-tier water quality system rose 3 percentage points year on year to 87.9 percent last year, while that of surface water below Grade V, the lowest level, stood at 0.7 percent, down 0.5 percentage points from 2021.

China will step up its efforts on pollution prevention and control in 2023, taking measures in various fields to fight against air, water and soil pollution, according to the ministry.