Air Pollution
The air that surrounds us is a mixture of 78% nitrogen; 21% oxygen; less than 1% of carbon dioxide, argon, and other gases; and varying amounts of water vapor. Any other particles, gases or unoriginal constituents hanging in the air which are not part of its original composition are called 'Pollutants' and this kind of air is called Polluted Air. Even inhaling small amounts of such air pollutants can have serious effects on one's health and leads to environmental problems.
We can see some air pollutants such as the reddish-brown haze in smog; however, other air pollutants, including some of the most dangerous, are invisible.
Air pollution can be natural or human-made. Air pollution occurs naturally during volcano eruptions, forest fires, or dust storms. This has been an occasional problem for humans. However, during the past hundred years, air pollution created by humans has become a major, persistent problem.
Outdoor Air Pollution
Air pollution is a serious problem in the United States and many other industrialized countries. In the United States, the Environmental Protection Agency, is charged with identification and regulation of pollutants in the ambient air that may cause adverse Effects on Health. The current National Ambient Air Quality Standards are for six pollutants. Despite these federal and state regulations, many cities and regions in the United States currently do not meet these primary standards. Epidemiologic research, human clinical studies and animal toxicological studies continue to provide evidence for adverse Effects on Health of ambient air pollutants, even at exposure levels below the current standards. The major sources of air pollutants are:
Combustion of fossil fuels: These are divided into mobile sources such as motor vehicles, stationary sources such as power plants and factories, and other sources such as barbecues and fireplaces. Tailpipe emissions from motor vehicles are a complex mixture of carbon monoxide, oxides of nitrogen, hydrocarbons, diesel exhaust particles, and other particulates including lead oxide from tetraethyl lead contained in leaded gasoline.
Photochemical reactions: Oxides of nitrogen and hydrocarbons interact in the atmosphere to produce Ozone (O3) as a secondary pollutant.
Power Plant Emissions: These release Sulphur dioxide (SO2) and particulates in the atmosphere. Coal and oil contain sulphur, leading to atmospheric formation of sulfates. Automobiles release oxides of nitrogen, leading to atmospheric formation of nitrates. Aerosolized acid sulfates contribute to acid rain.
Waste incinerators, industry, smelters. These point sources release acid aerosols, metals and organic compounds that maybe hazardous for human health. One example of the numerous hazardous chemicals emitted by these sources is methyl isocyanides that was accidentally released at Bhopal in India in 1984, resulting in 3000 deaths due to pulmonary edema. Some of the air toxins, such as polycyclic aromatic hydrocarbons, are known carcinogens.
Lungs are the major target of common outdoor air pollutants; especially vulnerable are children, asthmatics, and people with chronic lung or heart disease. The serious toxicity associated with lead exposure is discussed subsequently under Industrial Exposures. The major air pollutants and the mechanisms responsible for their adverse Effects on Health are summarized briefly.
Ozone
Ozone is a major component of smog that accompanies summer heat waves over much of the United States. Exposure of exercising children and adults to as little as 0.08 ppm produces cough, chest discomfort, and inflammation in the lungs. Asthmatics are especially sensitive and require more frequent visits to emergency rooms and more hospitalizations during smog episodes. It is not known whether these acute changes lead to chronic, irreversible lung injury. Ozone is highly reactive and oxidizes polyunsaturated lipids to hydrogen peroxide and lipid aldehydes. These products act as irritants and induce release of inflammatory mediators, cause increased epithelial permeability and reactivity of the airways, and decrease ciliary clearance. The highest inhaled dose is delivered at the bronchoalveolar junction; however, ozone also causes inflammation of the upper respiratory tract.
Nature and Sources of Ozone sensitive and edgy gas which is in the shape of oxygen is O3 that is Ozone. This gas is the chief producer of smog, which is one of the constituent of Air pollution.
Ozone chemically reacts, by oxidizing internal tissues of the body with which it impinges; for example when it impinges with the lungs. It is also potent enough to break down other materials such as rubber compounds.
Formation of Ozone takes place when the sunlight impinges on carbon-based...
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