Blue sky framed by trees

The air pollution problem

Although vehicles and power stations in many countries are cleaner than they used to be, air pollution limits are still regularly exceeded in most large towns and cities worldwide. It is estimated that air pollution kills between one million and four million people worldwide every year, and causes many more to need hospital treatment or to take time off work or school.1 This costs the global economy billions of dollars in healthcare and lost productivity. On top of this, fossil fuel pollution acidifies rivers, lakes and soil, and releases toxic compounds such as mercury and dioxins into the environment.

The main pollutants are:

  • Particles of soot, dust, sulphates and nitrates, known as particulate matter (PM). This comes mainly from burning coal and oil, especially diesel fuel in vehicles. When people breathe in the particles, they can cause heart and lung diseases and cancer, especially since toxic chemicals often stick to the surfaces of the particles. Fine particles are worst, because they travel further in the air and penetrate further into the lungs. Vehicle emissions are the biggest problem because they are emitted directly into crowded streets where large numbers of people are exposed to traffic fumes. However, there is also a serious problem with indoor air pollution in countries where many people use open fires or stoves burning coal, kerosene, wood or dung for cooking and heating.

  • Sulphur dioxide (SO2). This comes mainly from burning coal and oil. It is an acidic gas that irritates the lungs and can also form fine sulphate particles. It can also dissolve into rainwater, causing the acidification of rivers, lakes and soil, damaging ecosystems and killing trees, fish and other plants and animals.

  • Nitrogen oxides (NOx). A mixture of nitrogen oxide (NO) and nitrogen dioxide (NO2), known together as NOx, is created during any high temperature combustion process, whether it involves burning coal, oil, gas or biomass. NOx is acidic, forms fine nitrate particles and contributes to nutrient overload in ecosystems. NO2 irritates the lungs, increases the risk of contracting diseases such as bronchitis and pneumonia, and also reacts with other air pollutants to form ozone.

  • Ozone (O3). This is a secondary pollutant, formed when nitrogen oxides react with volatile organic compounds, methane or carbon monoxide, especially in the presence of sunlight. It is a highly reactive gas that damages lung tissue, causing breathing difficulties including asthma attacks. It also damages crops and ecosystems.

  • Toxic compounds. Burning coal and oil releases heavy metals such as mercury, arsenic and cadmium, which damage the immune system and nervous system. Burning coal, oil, waste and biomass produces dioxins. Burning any carbon-based fuel releases polycyclic aromatic hydrocarbons (PAHs). All these pollutants are toxic to humans, livestock and wildlife, persist for a long time in the environment, can accumulate in the food chain and are thought to be carcinogenic (i.e. cause cancer).

How climate policy can help

Climate change and air pollution are both mainly caused by our use of fossil fuels, so climate policy based on cutting fossil fuel use can result in cleaner air, with benefits for health, ecosystems and the economy. In some cases, the air quality benefits can exceed the costs of climate action, so that climate policy pays for itself.

The most promising strategies are based on cutting energy consumption and switching to cleaner energy sources such as wind and solar. Cutting transport emissions is a priority, as traffic pollution causes severe health impacts. This can be done by making vehicles more fuel-efficient, by switching to gas or electric vehicles, and by making it easier for people to walk, cycle or use public transport instead of driving.Deaths from air pollution for different greenhouse gas reduction strategies

One study estimated that if global greenhouse gas emissions were halved from 2005 to 2050, premature deaths from exposure to particle pollution would be reduced by 42% compared to the business-as-usual case. This would avoid more than 5 million early deaths per year by 2050.2

An integrated strategy tackling climate change and air pollution together would be even more effective, achieving a 67% reduction in premature deaths.

Benefits would be highest in developing countries with low levels of pollution control. Meeting a target to limit the global temperature increase to 2°C by 2050 would save 29 million life years in China and 44 million life years in India. The resulting health benefits would be worth over €6 trillion per year in Europe, China and India. In Europe, the benefits would be worth €24 per tonne of CO2 abated.

Further co-benefits can be gained by controlling methane, black carbon and ozone, which contribute to both climate change and loss of air quality. Fast action to control these pollutants could avoid 2.4 million premature deaths from outdoor air pollution and save the loss of 32–52 million tonnes of crops through ozone damage every year. Key actions included reducing soot emissions from cooking stoves and diesel vehicles, and stopping methane leaks from landfill sites, coal mines and oil and gas infrastructure.3


Conflicts can arise between climate change and air quality. For example, switching to diesel for transport will cut carbon dioxide emissions but make air pollution worse. Other conflicts include air pollution from biofuel combustion, accidental release of radioactive pollution from nuclear power stations, and geo-engineering techniques that involve pumping sulphate into the atmosphere.  These conflicts require careful management.

Key messages

  • Saving energy and shifting to clean, low-carbon energy sources can save millions of lives worldwide every year, by cutting air pollution (fine particles, ozone and heavy metals). Damage to crops and ecosystems will also be avoided, and there will be large financial savings through avoided health care costs and a reduction in time taken off work and school.

  • An integrated strategy for addressing climate change and air quality can be cheaper and more cost-effective than separate strategies, because synergies can be exploited and conflicts avoided. For example, it can be cheaper and more effective to cut energy use than to build more coal-fired power stations with expensive pollution control equipment.

  • Reducing air pollution can provide a stronger motivation for cutting fossil fuel use than climate concern, because the benefits are immediate, local, and more easily quantified than climate benefits.

Links to other co-benefits pages