The major human sources of air pollution are the combustion of fuels for heat, electricity and transport. Road transport accounts for 31% of nitrogen oxides (NOx), 19.5% of PM2.5 and 18% of PM10 UK emissions. It frequently accounts for more than 64% of air pollution at urban monitoring sites (Road traffic's contribution to air quality in European cities European Topic Centre on Air Pollution and Climate Change Mitigation). This comes from exhausts and other sources such as the wear of tyres, brakes and the road.
Non-exhaust sources account for around 21% of PM2.5 from vehicles. As exhaust emissions are reduced, the relative contribution from other sources becomes more significant.
In 2008, the effect of human-produced (anthropogenic) particulate air pollution on mortality in the UK was estimated as equivalent to nearly 29,000 deaths at typical ages, and an associated loss of total life of 340,000 life years (COMEAP: mortality effects of long-term exposure to particulate air pollution in the United Kingdom Public Health England).
In 2010 the total mortality burden of anthropogenic PM2.5 in London was 52,630 life years lost and of long-term exposure to NO2 was up to 88,113 life years lost (Understanding the health impacts of air pollution in London King's College London). This figure assumes the World Health Organization value of up to a 30% overlap between the effects of PM2.5 and NO2. The authors note that the figure for NO2 is much less certain than that for PM2.5.
The health impact of PM2.5 pollution from human activities in the UK is estimated to cost between £8.5 billion and £18.6 billion a year (Ambient air quality UK Parliament).
Over recent decades air pollutant emissions have reduced. But in 2013, UK levels of nitrogen dioxide (NO2) exceeded the EU directive limit in 38 of 43 geographical zones (Directive 2008/50/EC European Commission).
The way air pollution is distributed is not straightforward. Pollutant concentrations vary:
The most deprived areas tend to have higher concentrations of NO2 and PM10.
Regardless of socioeconomic status, urban areas tend to have higher pollutant levels than rural areas, which often have larger populations in the mid-range of deprivation.
The national trend shows high average concentrations in both the most and least deprived areas, and lower concentrations in the (predominantly rural) mid-decile areas.
Children (14 and under) and older people (65 and older) are more susceptible to the effects of air pollution (Air quality and social deprivation in the UK: an environmental inequalities analysis Department of Environment, Food and Rural Affairs).
Addressing air pollution by encouraging people to walk and cycle rather than drive, can help people to become fitter and healthier. Changing the way we travel can also help reduce emissions of greenhouse gases that contribute to climate change. Climate change is linked to increased risk of extreme weather and other events that have an adverse effect on health, such as floods, heatwaves and the spread of some infectious diseases (Climate change 2013: the physical science basis Intergovernmental Panel on Climate Change Working Group I).
You can also see this guideline in the NICE pathway on air pollution.
 Particulate matter is produced by, among other things, combustion of fossil fuels or abrasion of tyres and brakes. Particles are classified by size, described using the abbreviation PM with a suffix (commonly 2.5 or 10) that gives the maximum particle size in micrometres. The mass concentration of particles is usually expressed in micrograms per m3 of air.
 The UK is divided into 43 zones for assessing air quality and reporting compliance with EU targets. These zones generally include more than 1 local authority (Air quality plan for the achievement of EU air quality limit values for nitrogen dioxide (NO2) in the UK, 2015 Department for Environment, Food and Rural Affairs.)