By Abbas Nazil
A study has revealed that sunlight significantly worsens the pollution caused by wildfire smoke, providing an explanation for why atmospheric models have consistently underestimated its impact.
Researchers from King Abdullah University of Science and Technology (KAUST) and the Chinese Academy of Sciences found that smoke particles behave like chemical factories under sunlight, producing harmful oxidants such as peroxides.
The study, published in *Science Advances*, shows that wildfire smoke particles bypass the usual suppression of oxidant formation by nitrogen oxides, which are abundant in polluted urban environments.
Professor Chak Chan, co-author and dean of KAUST’s Physical Science and Engineering Division, explained that the process is unexpectedly efficient, occurring at rates far faster than traditional chemical pathways.
The team discovered that colored organic molecules within biomass-burning aerosols act as photosensitizers.
When exposed to sunlight, these molecules trigger chains of reactions that generate peroxy radicals and peroxides within the particles.
Although peroxides are not greenhouse gases, they influence atmospheric chemistry in ways that promote haze, secondary particle formation, and health risks.
By serving as radical reservoirs, they also contribute to long-term climate and air quality dynamics.
This finding highlights that wildfire smoke not only directly releases particulate matter but also indirectly creates more pollutants, amplifying its impact on urban air pollution.
The implications are significant as wildfires continue to expand in frequency and intensity worldwide.
In the western United States, fire sizes have quadrupled since the 1980s, while Mediterranean regions have experienced more than a doubling of burned areas in just two decades.
As these events grow, wildfire smoke is increasingly turning into a hidden source of pollution, intensified by sunlight-driven chemistry.
Chan emphasized that updating climate and air-quality models to account for this overlooked pathway is critical.
Without such updates, policymakers and communities may underestimate the health threats and environmental impacts, particularly in regions like Saudi Arabia that are already grappling with climate change.
