This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: An increase in pollution from wildfires and heat waves risks undermining international efforts to improve air quality and protect human and ecosystem health, according to a new report from the World Meteorological Organization (WMO), which traces the complex interrelationships between air quality and climate. The WMO report highlights the need for improved atmospheric observations of air pollutants such as fine particulate matter and ground-level ozone, as well as aerosols such as black carbon and microplastics, which are not sufficiently monitored even though they are widespread and potentially harmful to ecosystems.
It stresses the importance of complementary and coordinated policies on air quality and climate because they cannot be dealt with in isolation. The annual Air Quality and Climate Bulletin sheds light on the negative impacts of aerosols, including particulate matter, and surface ozone on human health. The report, which features a series of articles written by the scientific community advising WMO on air quality, was released for International Day of Clean Air for Blue Skies on Sept. 7.
It is based on data and information from WMO's Global Atmosphere Watch network, reflecting its philosophy of science for services for the public good. Particulate matter, PM2.5, is composed of microscopic particles and droplets less than 2.5 micrometers (μm) in diameter, which pose a health hazard because they can penetrate deep into the lungs and bloodstream. It is emitted by many different sources, such as industrial activities, agriculture, residential heating and transportation, as well as wildfires and dust storms.
In keeping with trends in recent years, PM2.5 concentrations in 2025 were above the long-term average in northern Canada, parts of the Russian Federation and west-central Africa because of increased fire activity. Northwestern Spain was also a hotspot because of exceptional fires in late summer 2025. In South America's Amazonia, burning was relatively lower in 2025 than in previous years.
PM2.5 levels continued to be below the long-term average in China in 2025, reflecting a decline in emissions from human activities. India continued to have above-average levels because of biomass burning and other pollution, according to the bulletin, which for the first time used models from four different sources. Despite differences in the models and inputs, the results are comparable and, for the most part, consistent, indicating a robust understanding of atmospheric processes.
Extreme wildfires are increasing, leading to significant health consequences because of the high toxicity of smoke. While regulations in Europe and North America have reduced industrial and transportation PM2.5 emissions, exposure to fire-related PM2.5 has increased. One study cited by the WMO Bulletin indicates that extreme fire-smoke events have tripled globally since the 1990s, contributing to nearly 100,000 additional deaths per year between 2010–2018—although this may well be an underestimate.
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