WMO Air Quality and Climate Bulletin No. 5 - September 2025

It stresses the need for improved atmospheric monitoring and more integrated policies to safeguard human and environmental health and reduce agricultural and economic losses.

While regulatory action has reduced aerosol concentrations in parts of North America, Europe, and East Asia, levels remain high or are increasing in South Asia, South America, and high latitudes, largely due to wildfires and industrial activity.

PM2.5 pollution remains a major global health risk, causing millions of premature deaths annually. In 2024, levels declined in eastern China but stayed high in northern India and spiked in Canada, Siberia, central Africa, and the Amazon, where record wildfires spread pollution as far as Brazilian cities.

The Bulletin also reports worsening winter fog in the Indo-Gangetic Plain, now linked more to human activity than seasonal weather. Shipping rules cutting sulphur emissions improved health but slightly accelerated warming by reducing aerosol cooling.