There are mainly five categories of air pollutants namely carbon monoxide, particulates, sulfur oxide, nitrogen oxide and hydrocarbons.
Carbon monoxide is a toxic but colorless and odorless gas generated by the combustion of carbon in fuels. Motor vehicle emissions are a source of this poisonous gas amongst many others.
Industrial processes and stationary fuel combustion release both solid and liquid particulates into the air.
Sulfur oxide is a corrosive and poisonous gas generated by burning of fuel containing sulfur. Its main sources include power and industrial plants.
Burning of fuel at very high temparature generates nitrogen oxide, as in motor vehicles and stationary combustion plants. Nitrogen oxide released into the air gets converted into pollutants such as sulfates and nitrates through oxidation and thereafter mixing with rain or snow returns to the earth as precipitation or acid rain.
Hydrocarbons, generated by power plants, car, motorboat etc., react with nitrogen oxide in the atmosphere under the influence of sunlight to form smog.
Air pollutants cause respiratory and cardiac disorders including bronchitis, emphysema, lung cancer etc.
Clean Air Act and its amendments is the federal law concerned with regulating air pollution, which requires the Environment Protection Authority (EPA) to set National Ambient Air Quality Standards (NAAQS) for different air pollutants in order to protect public health.
States have the primary responsibility of assuring air quality within their territorial limits. By virtue of the obligations under the aforesaid National Ambient Air Quality Standards (NAAQS), every state must furnish to the Environment Protection Authority (EPA) a State Implementation Plan for air quality standards within its own areas. However, state laws can provide for higher air quality standards than set by the federal government. In any case states must maintain the minimum national air quality standards set under the Clean Air Act.
Not only state and federal governments but also private parties including citizens can take recourse to the provisions of the Clean Air Act for redress against the offender in case of violation of norms to prevent air pollution.
There is international concern over the alarming manifestations of air pollution in the form of global warming and climate changes, ozone layer depletion and acid rain.
