ABSTRACT

A large number of pollutants are present in the environment, often in very large quantities. They arise from many sources and exposure to these pollutants may occur through a range of routes. For example, the ambient air in urban areas may contain sulfur dioxide (SO2), carbon monoxide (CO), and nitrogen oxides (NOx), as well as smoke and suspended particles containing metals and hydrocarbons produced mainly from coal or heavy-oil combustion by industries, power plants, and some households. Several pollutants are also found in the indoor environment. Some examples include CO arising from incomplete combustion of fossil fuels and tobacco smoke, lead (Pb) from paint used in old houses, and formaldehyde from insulation and wood preservatives and adhesives.