About Air Quality
Air pollution is a substance or complex mixture of particles and gases in the air that cause harm to people’s health. Air pollutants are emitted from both natural and human sources.
Ambient air pollution originates from sources including transport, industrial processes, farming, energy generation and domestic heating. Concentrations of air pollutants can vary both temporally and spatially but are typically higher close to the source.
Nitrogen Oxides
Nitrogen oxides are gaseous air pollutants. Nitrogen oxide (NO) is mostly produced by road transport emissions and other combustion processes such as the energy supply. Once released into the atmosphere, NO is rapidly transformed to NO2 which is harmful to health. Both NO and NO2 are referred to as nitrogen oxides (NOx).
Fine Particles
Particulate matter (PM) consists of solid particles and liquid droplets small enough to be suspended in the air. Currently in the UK PM with a size -diameter of 10 micrometer (µM) or less (PM10) and 2.5 µM or less (PM2.5) are measured.
Particulate matter is composed of a wide range of materials, natural and human-made, including sources such as:
- Domestic combustion sources (heating; cooking)
- Industry
- Road traffic (such as tailpipe, tyre and break wear and road dust)
- Construction activities (such as demolition, earthworks, construction and track-out)
- Desert dust, pollen, volcano activity, forest fires
