What is Air Pollution?

Background to air pollution

Air pollution is where emissions into the air, such as chemicals and dust particles, make it less healthy for us to breathe. The sources of this pollution can be both local and distant, man-made and natural. Different pollutants have different health effects, and some pollutants are worse for health than others, and those such as particulates from combustion processes such as road vehicles are amongst the worst for health.

People often ask, 'What is the difference between air pollution and CO₂?'

• Air pollution affects the local air we breathe and can affect our health.

• CO₂ emissions increase climate change, which is where the earth is getting gradually warmer and level of the sea is rising.

Both are a problem, and measures to reduce one, such as energy efficiency, will often reduce the other. LEZs are focused on reducing air quality emissions, and are likely in general, to have less impact on CO₂ emissions. In some cases they may also have an impact on CO₂ if they lead to more efficient use of vehicles to do the same journeys and new EU rules on CO₂ emissions of new vehicles may also help LEZs to lead to CO₂ reductions.

The pollutants (or chemicals) that are of particular concern to health in Europe are fine particles, nitrogen dioxide (NO₂) and ozone (O₃).

Fine particles are far too small to be seen with the naked eye. They are classified into different sizes, including PM₁₀ (which are less than 10 millionths of a metre in diameter (or µm)), PM_2.5 (less than 2.5 µm), PM₁ or ultrafine particles (generally less than 0.1 µm diameter).

Particles are generally the pollutant which has greatest impact on our health. Within those particles, it is the very smallest particles, and particularly those from burning processes such as motor vehicles that are of most concern for health.

If you read German, French or Italian, www.pm10.ch  gives more information on PM₁₀.

Nitrogen dioxide (NO₂) causes health impacts. It is mostly (but not entirely) emitted  the form of nitrogen monoxide (NO), which is converted to NO₂ in the atmosphere after combining with ozone (O₃). This is why the pollutant of concern in the air is referred to as NO₂, but the emissions are referred to as nitrogen oxides (NOx).

Ozone is what is called a  'secondary pollutant', since it is, it is formed over a considerable period of time by other pollutants reacting together (in fact nitrogen oxides reacting with hydrocarbons and sunlight). This time delay means that while high levels of other pollutants are mainly in towns or industrial areas, high levels of ozone are mainly in the countryside. LEZs do therefore not reduce ozone directly, but reduce some of the emissions that form ozone.

The 'Encyclopedia of the Atmospheric Enviroment' is a good source of further information on air quality. The US government AirNow website gives a good overview of air quality, and its world air quality page can help you find out what the air quality is like near you.  This EU Commission page gives links to many environment ministries across the EU.