CHAPTER 1
1. INTRODUCTION
The air we respire contains mixture of natural and man-made chemical, physical and biological elements that modifies ambient air quality. Among all air pollutants, the most threatening for human health include particulate matter and gaseous pollutants such as carbon monoxide, ozone, nitrogen dioxide and sulfur dioxide (WHO). The movement of people into urban areas and the growth of industry within these areas has carried more people into contact with air pollution than any other time in recent memory. High concentrations of air pollutants can cause instant physical symptoms such as rapid pulse and restricted breathing but, even the presence of trace amounts is considered detrimental to health (Levy et al., 2000).
1.1. Particulate Matter Pollution
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Particulate matter is a complex combination of fine solid particles and liquid droplets comprising various types of dust, smoke, and soot, gaseous and biological contaminants that are suspended in air. The size of these particles ranges from few nanometers to around 100 micrometers. Mainly, coarser particulate matter PM10 with diameter less than equal to10 micrometers and fine particulate matter PM2.5 with diameters less than equal to 2.5 micrometers are significant. Particulate matter in air comes from both natural sources such as wildfires and dust storms and anthropogenic sources like power and industrial plants, fossil fuel burning, combustion of wood and other biomass fuels and automobiles. In Urban areas, vehicular traffic is one of the major sources of particulate matter pollution. Possible sources of particulate matter emissions from automobiles comprises fuel combustion, tire wear, lubricating oil combustion and road abrasion (US