Rising heatwaves intensify air pollution risks across Sub-Saharan Africa

Across the globe, heatwaves are becoming more frequent and intense because of climate change. When extreme heat hits, it often makes air pollution worse. Increased temperatures speed up chemical reactions in the air, boosting levels of harmful pollutants and creating stagnant conditions that trap them close to the ground. This combination of heat and pollution poses serious dangers to human health.

Around the world, studies have shown that increased heat along with pollution can be deadly. In California, the risk of death nearly doubled on days when extreme heat and fine particle pollution occurred together. In Seoul, heatwaves drove up both ground-level ozone and particle levels, and in parts of China, the number of days with extreme heat and high ground-level ozone has sharply increased. In both India and China, extra power plant emissions during heatwaves (as air conditioning demand soars) add even more smog to already stressed cities.

Previous studies have linked these hazards to serious health implications, such as pre-term births, increases in blood pressure and worsening heart and lung disease.

While the links between heatwaves and pollution are well-documented in Europe, North America and parts of Asia, Sub-Saharan Africa remains largely overlooked, even as cities are growing hotter, more polluted, and more densely populated. New research focusing on Kigali, Rwanda’s capital city, shows how heatwaves are making already poor air quality even worse. Rapid urbanisation, heavy traffic from older diesel vehicles, reliance on wood and charcoal for cooking, and smoke from agricultural fires all contribute to high levels of air pollution.

The study found that fine particulate matter (tiny airborne particles such as those from vehicle exhausts) exceeds World Health Organisation guidelines, sometimes reaching more than eight times the recommended limit. These tiny particles can penetrate deep into the lungs, causing serious heart and breathing problems, particularly among children, the elderly and those with pre-existing health conditions. During heatwaves, levels of nitrogen dioxide (primarily caused by burning fossil fuels) and ground-level ozone (created when pollutants emitted by cars, power plants etc. chemically react in sunlight) also rise sharply, further adding to the risks.

What makes this worse for Kigali specifically is the mountainous terrain and humid climate, which traps polluted air close to the ground, prolonging periods of poor air quality.

Tackling the double threat of heat and air pollution requires a combination of practical solutions, long term planning and coordinated action between governments, health agencies and efforts within local communities.

Unlike many wealthy nations, systems for warning citizens of dangerous heat or poor air quality are not currently in place across much of Africa. This means residents often have no idea when the air they’re breathing has reached harmful levels. Expanding air quality monitoring with low-cost sensors would give local authorities real-time data to identify when air quality is poor and poses a hazard to health. This would then support them in putting in place measures such as traffic restrictions or higher enforcement of emissions regulations.

Further solutions also exist and can be implemented to promote climate resilience and reduce emissions. Nature-based measures such as planting more trees, restoring wetlands, and adding green roofs to buildings can help cool cities while also filtering the air. At the same time, measures such as investing in cleaner cooking fuels – thereby reducing the use of wood, charcoal or agricultural waste as a fuel source – and switching to cleaner transport would reduce harmful emissions at their source.

The research shows that heatwaves make Kigali’s already poor air quality even worse, creating a dangerous mix that threatens people’s health. 

Future aims are understand how pollution spreads under different conditions, identifying main sources of pollution and identifying communities most at risk. This can be achieved through longer-term monitoring across more Sub-Saharan locations, along with information on weather patterns like wind and sunlight. Linking this with information on traffic, cooking fuels, industry emissions and land use would help pinpoint the main sources of pollution and the communities most at risk.

Tackling the deadly combination of heat and air pollution isn’t just about protecting the environment. It’s also about protecting people’s health, while building cities that are safer, cooler, and more liveable in the future.

Heatwaves amplify air pollution risks in Sub-Saharan Africa Kalisa, E., Sudmant, A. Sci Rep 15, 26448 (2025).