Air pollution is a mix of particles and gases from both manmade and natural sources that can reach harmful concentrations both outside and indoors. Its effects can range from higher disease risks to rising temperatures. Pollution enters the Earth’s atmosphere in different ways. Most manmade pollution is the result of factory and vehicle emissions while naturally occurring air pollution can come from wildfires or volcano ash.   

Particulate matter (PM) and nitrogen dioxide (NO2) are both major components of urban air pollution. NO2 is a gas that is produced by combustion processes. The Department for Environment, Food & Rural Affairs (Defra) estimates that 80% of NO2 emissions in areas where the UK is exceeding NO2 limits are due to transport.  PM is a generic term used to describe a complex mixture of solid and liquid particles of varying size, shape, and composition. The main sources of man-made PM are the combustion of fuels (by vehicles, industry and domestic properties) and other physical processes such as tyre and brake wear. 

Air pollution affects everyone. The health effects of air pollution are complex, and range in severity of impact. In some cases, damage can be gradual and may not become apparent for many years. The 3 main conditions associated with air pollution are respiratory conditions (such as asthma), cardiovascular disease, and lung cancer, and there is emerging evidence for associations with dementia, low birth weight and Type 2 diabetes. 

Improving air quality is crucial to reduce the health impacts discussed above and, in turn, help people live longer, healthier lives. A study in 2006 found that reducing PM by 10µg/m3 would extend lifespan in the UK by 5 times more than eliminating casualties on the roads, or 3 times more than eliminating passive smoking.