Particulate Matter (PM)
PM is a complex mixture of non-gaseous particles of varied physical and chemical composition. It is categorised by the size of the particle (for example PM10 are particles with a diameter of less than 10 microns (μm)).
- PM10 can adhere to the lung walls causing irritation and some cancers
- PM2.5 can pass through the blood barrier in the lungs and affect arteries
- PM0.1 has been found to pass through the blood-brain barrier and lead to neurological disorders
Most PM emissions in urban environments are caused by road traffic including exhaust emission as well as tyre and brake wear. Construction sites, with high volumes of dust and emissions from machinery, are also a source of local PM pollution.
Poor air quality can be highly localised, especially in the urban realm as particles are trapped between buildings and re-suspended along major roads. The example map below shows a pollution profile for PM10 concentrations in central London – just a step away from a main road can reduce your exposure significantly.