Air pollution has become an adverse consequence of modern-day living. The causes of air pollution vary considerably between countries. Much of the increasing severity of the problem is caused by rapid industrialization, urbanization, increasing use of energy (mostly derived from fossil fuels), and emissions from automobiles particularly in developed countries.
Globally, air pollution may be either natural (biogenic) and/or anthropogenic (man-made) in its origin. Natural sources include evaporated sea spray, windblown soil and dust, bio-aerosols, volcanic or other geothermal eruptions, and forest fires. Man-made sources originate from incineration, construction and mining activities, metal smelting and processing, power generation, heating and household cooking, diesel-fuel engine combustion, motorcycles and agricultural burning. Most particulates from natural sources tend to be coarse, while most of the emissions from anthropogenic sources tend to be in fine fractions.
An important aspect of air pollution is the distinction between primary and secondary pollutants. Primary pollutants are those emitted directly from the sources without undergoing any chemical transformations. Secondary pollutants are those generated in the atmosphere by chemical reactions of certain primary pollutants. These include those generated as part of photochemical smog formation, sulphate aerosol from Sulfur Dioxide (SO2) emission and particulate nitrates.
Air pollution has captured world attention because of its impacts on local and regional climate and the concern of possible enhanced greenhouse warming. In many towns and cities of the world, exposure to air pollution is the main environmental threat to human health. According to World Resources Institute, the three most important pollutants affecting human health in developing countries are lead, dust and soot. Previous research has provided overwhelming evidence that high levels of some air pollutants can be fatal to very young children, the elderly and those suffering from cardiovascular or respiratory ailments such as chronic bronchitis, pneumonia, respiratory disorders, emphysema and asthmatic problem.
