What is air pollution?
Air pollution is anything in the air that causes harm, but the pollutants of biggest current concern in the UK are particulate matter (PM) and the gas nitrogen dioxide (No2).
Particulate matter is all solid and liquid particles suspended in the air. These are both man-made (such as diesel, soot) and natural (such as sea spray, dust and pollen).
The size of particles in the air varies. PM 10 has a diameter of 10 micrometers or less, whereas PM 2.5 has a diameter of 2.5 micrometers or less – and is often described as ‘fine particles’. These finer particles are the biggest concern, because they’re small enough to be breathed deep into our lungs.
By way of comparison, a human hair is about 100 micrometres, so roughly 40 fine particles make up the width of one strand of hair!