Urban air pollution is derived largely from the combustion process of fossil fuels. Vehicle emissions contain many toxic compounds, mainly carbon monoxide, nitrogen dioxide, sulphur dioxide, ozone, lead, polycyclic aromatic hydrocarbons, and particulate matter. Particulate matter is a complex mixture of microscopic particles and liquid droplets composed of all these polycyclic aromatic hydrocarbons, metals, and dust particles. These particles are usually classified according to their size, they can be either PM 10 or PM 2.5 – these particles have diameters of 10 and 2.5 micrometers respectively. If you compare the size of PM 2.5 to a grain of sand or an erythrocyte, a red blood cell, they are 40 times and 3 times bigger than PM 2.5.
The nature of air pollution:
