Air pollution

Air quality describes how clean or polluted the air is. Good air quality means the air contains low levels of pollutants and poses little risk to people or the environment, while poor air quality means pollution levels are high enough to affect health and ecosystems.

Air pollution is the presence of harmful gases, particles, and other substances in the atmosphere that can affect human health, ecosystems, and the climate. It is a local, regional, and global issue caused by emissions from sources such as transport, industry, agriculture, wildfires, heating, and cooking. Many forms of air pollution are invisible to the naked eye, including pollutants such as nitrogen dioxide, ozone, methane, and particulate matter.

Outdoor air pollution is the presence of harmful gases, particles, and other pollutants in the air outside. Common sources include transport, industry, agriculture, wildfires, and domestic activities such as heating. Outdoor air pollution can affect human health, ecosystems, and the climate, and it can also enter buildings and contribute to indoor air pollution.

Indoor air pollution is the presence of harmful gases, particles, and other pollutants inside buildings such as homes, schools, and workplaces. Common sources include cooking, heating, cleaning products, building materials, and outdoor pollution that enters indoors. Indoor air pollution can affect health, especially because people spend most of their time inside buildings.

Air pollution is caused by the release of harmful gases, particles, and other substances into the atmosphere from both human activities and natural sources. Major sources include transport, industry, agriculture, energy production, heating and cooking, as well as wildfires, dust storms, and volcanic eruptions. Pollutants can affect the outdoors, indoors, human health, ecosystems, and the climate.

Air pollution includes gases such as nitrogen dioxide, which is released from sources including vehicle exhausts and gas combustion in homes. It also includes chemicals known as volatile organic compounds (VOCs), which come from sources such as fuels, cleaning products, paints, and industrial processes.

Small particles, known as particulate matter (PM10 and PM2.5), are produced by activities such as road transport and wood burning, and can be inhaled deep into the lungs. Some pollutants are emitted directly into the atmosphere, while others form through chemical reactions in the air.

Air pollution is one of the biggest environmental risks to human health and the environment. It can affect people throughout their lives, from before birth through to old age, and is linked to a wide range of health and environmental impacts.

In the short term, air pollution can cause symptoms such as coughing, headaches, and eye irritation. Long-term exposure increases the risk of respiratory and cardiovascular diseases, including asthma, heart disease, stroke, and some cancers. It can also affect lung development in children and may contribute to conditions such as dementia and poor mental health.

Air pollution also damages the natural environment. Pollutants such as ozone and nitrogen dioxide can harm crops, forests, and ecosystems, while particulate matter can reduce visibility and affect local air quality. Some air pollutants also contribute to climate change, increasing the risk of extreme weather and other impacts on society and the environment.

Particulate matter (PM) is a mixture of tiny solid particles and liquid droplets suspended in the air. It comes from sources such as vehicle exhausts, tyre and brake wear, wood burning, agriculture, and wildfires. The smallest particles, known as PM10 and PM2.5, can be inhaled deep into the lungs, affecting air quality and increasing risks to human health.

Nitrogen oxides (NOx) are a group of air pollutants that are released when fuels are burned. They include nitrogen dioxide (NO₂), which is commonly produced by vehicle exhausts, gas heating and cooking, power generation and industrial processes. Nitrogen oxides contribute to the formation of other air pollutants, including ground-level ozone and particulate matter, affecting both air quality and human health.

Volatile organic compounds (VOCs) are a group of carbon-based chemicals that easily evaporate into the air. They come from sources such as fuels, paints, cleaning products, personal care products, industrial processes, and some plants.

VOCs can react with other pollutants in sunlight to form ground-level ozone and particulate matter, contributing to poor air quality and affecting human health and the environment.

Ozone pollution, also known as ground-level ozone, is a harmful air pollutant that forms when gases such as nitrogen oxides and volatile organic compounds (VOCs) react in sunlight. Unlike the ozone layer high in the atmosphere, ground-level ozone can damage human health and ecosystems.

Weather affects air quality by influencing how pollutants are dispersed or removed from the atmosphere. Wind can carry pollutants away, rain can wash them out of the air, and hot, still conditions can allow pollution to build up near the ground.

Air pollution and climate change are closely linked. Some air pollutants warm the atmosphere or can have a cooling effect on the climate, as they affect how much sunlight is absorbed or reflected. Because different pollutants can warm or cool the atmosphere in different ways, understanding their effects is important for improving climate predictions and identifying actions that benefit both air quality and the climate.

Climate change can also worsen air pollution by increasing the frequency of heatwaves and wildfires, leading to higher levels of pollutants such as ozone and particulate matter.

Air quality is measured by monitoring the concentration of pollutants in the air, including particulate matter, nitrogen oxides, ozone, and volatile organic compounds. Scientists use monitoring stations, sensors, satellites, and computer models to measure pollution levels and understand how they change over time and across different locations.