The Guangdong-Hong Kong-Macao Pearl River Delta recorded prominent air quality improvements in 2025, with the concentrations of five major air pollutants maintaining a sustained downward trend over the past two decades, a report showed on Friday.

Jointly released by Guangdong province and the Hong Kong and Macao special administrative regions, the report showed the 2025 annual average concentrations of sulphur dioxide (SO₂), nitrogen dioxide (NO₂), carbon monoxide (CO), respirable suspended particulates (PM₁₀) and fine suspended particulates (PM_2.5) declined by between 23 percent and 86 percent compared with 20 years ago.

Specifically, the annual average concentration of PM_2.5 dropped 34 percent from 29 per cubic meter (μg/m³) in 2015 to 19 μg/m³ in 2025, reaching a leading level nationwide and demonstrating the effectiveness of the emission reduction measures across the three places.

The most notable improvement was recorded in SO₂, whose annual average concentration fell 86 percent from 44 μg/m³ in 2006 to 6 μg/m³ in 2025.

Meanwhile, annual concentrations of NO₂ and PM₁₀ each declined by an average of 48 percent over their respective tracking periods, while that of CO fell 23 percent.

READ MORE: Pearl River Delta sees continuous air quality improvement

In recent years, the governments of Guangdong and the two SARs introduced a range of clean-air measures, including popularization of electric vehicles, management of volatile organic compounds (VOCs) and the phasing out of high-pollution vehicles.

The Guangdong-Hong Kong-Macao Pearl River Delta Regional Air Quality Monitoring Network comprises a total of 23 air monitoring stations in Guangdong, the Hong Kong and Macao SARs. Their respective environmental protection authorities are responsible for the coordination, management and operation of the stations in the three places and the release of quarterly and annual monitoring results.