Air pollution encompasses all types of pollution in the air. But much of the legislation, and subsequently the discussions in the media, refer to a few specific pollutants, due to their high prevalence and significant, negative health effects. These are Nitrogen Dioxide (NO2) and Patriculate Matter (PM).
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Air pollution does not respect administrative boundaries. Air pollution in London is a mixture of emissions created locally, and those from background concentrations. In particular, particles measuring between 0.1 μm and 1 μm in diameter can remain suspended for weeks and so can be transported long distances. Therefore local, national and international action is crucial to ensure that dangerous levels of air pollution are tackled.
There are various sources of NO2 and PM, transport is the main one, but others that contribute significantly include: energy production; industrial processes and construction.
Understanding where the different pollutants come from is important to guide effective policy formation.
The pollutants most widely referred to in air quality and pollution literature are:
- Particulate matter (these are usually split into 2 sizes: PM2.5 & PM10)
- Nitrogen dioxide (NO2)
- Sulphur dioxide (SO2)
- And occasionally, Carbon Monoxide (CO)
PM and NO2 are commonly seen as the most dangerous forms of air pollution due to their high concentrations and the negative health impacts they create. The sections below look to provide more detail on PM and NO2 but also some of the other air pollutants.