China and Europe recorded below-average levels of hazardous PM2.5 particulate matter in 2023, attributable to declining human-caused emissions, according to a recent report by the World Meteorological Organization.

This continues a trend observed since the annual WMO Air Quality and Climate Bulletin was first published in 2021, according to a media release from the organization on Thursday.

Wildfires over North America caused exceptionally high PM2.5 emissions compared to the reference period from 2003 to 2023, the report said. Above-average PM2.5 levels were also measured in India, due to an increase in emissions from human and industrial activities.

The report also explored the intricate relationship between air quality and climate.

Chemicals that lead to a degradation of air quality are normally co-emitted with greenhouse gases. Thus, changes in one inevitably cause changes in the other, it said, adding that air quality in turn affects ecosystem health as air pollutants settle from the atmosphere on the Earth's surface.

"Climate change and air quality cannot be treated separately. They go hand-in-hand and must be tackled together," said WMO Deputy Secretary-General Ko Barrett.

"It would be a win-win situation for the health of our planet, its people and our economies, to recognize the interrelationship and act accordingly," Barrett was quoted as saying in the release.

Her remarks align perfectly with China's current strategy to tackle pollution and climate change, which is officially referred to as "synergizing the reduction of pollution and carbon emissions".

According to the bulletin, ambient air pollution causes more than 4.5 million premature deaths annually and wreaks a high economic and environmental cost.

The bulletin was released for Clean Air for Blue Skies Day, which falls this year on Saturday under the theme of "Invest in Clean Air Now".

In his video remarks for an event in Beijing on Thursday, Siddharth Chatterjee, the United Nations' development system resident coordinator in China, said "Air pollution is preventable and reversible" and "Beijing stands as a testament to the possibilities for reducing air pollution".

Last year, the average PM2.5 density in Beijing dropped to only 32 micrograms per cubic meter, compared with 89.5 mcg/cubic meter in 2013, the first year when Beijing started to monitor the pollutant, according to the Ministry of Ecology and Environment.

"This achievement did not happen by chance or luck. It was the result of a long and arduous journey, with many important lessons learned that can serve as examples and best practices for any nation, district or municipality that wishes to follow a similar path to reduce air pollution," Chatterjee said.