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HUMAN HEALTH AND ENVIRONMENT: SOURCES OF AIR POLLUTION
Sulfur Dioxide
Sulfur dioxide is a yellowish brown gas that is a by-product of burning fossil fuels. Electricity generating stations, smelters, refineries, and industrial boilers are the main source points. In humans, sulfur dioxide aggravates symptoms of heart and lung disease, obstructs breathing passages, and increases the incidence of respiratory diseases such as colds, asthma, bronchitis, and emphysema. It is toxic to plants, destroys some paint pigments, corrodes metals, impairs visibility, and is a precursor to acid rain.
Particulates
Particulates are tiny solid particles or liquid droplets that are suspended in the air. Cigarette smoke releases particulates. They are also by-products of some industrial processes and the internal combustion engine. Particulates can in and of themselves irritate the lungs and can additionally carry heavy metals and carcinogenic agent deep into the lungs. When combined with sulfur dioxide, they exacerbate respiratory diseases. Particulates can also corrode metals and obscure visibility. Numerous scientific studies have found significant links between exposure to air particulate concentrations at or below current standards and adverse health effects, including premature death.
Carbon Monoxide
Carbon monoxide is an odorless, colorless gas that originates primarily from motor vehicle emissions. Carbon monoxide interferes with the blood\'s ability to absorb and carry oxygen and can impair thinking, slow reflexes, and cause drowsiness, unconsciousness, and death. Many people have purchased home monitors to test for carbon monoxide.
Nitrogen Dioxide
Nitrogen dioxide is an amber-colored gas emitted by coal-powered electrical utility boilers and by motor vehicles. High concentrations of nitrogen dioxide can be fatal. Lower concentrations increase susceptibility to colds and flu, bronchitis, and pneumonia. Nitrogen dioxide is also toxic to plant life and causes a brown discoloration of the atmosphere. It is a precursor of ozone, and, along with sulfur dioxide, of acid rain.
Ozone
Ground-level ozone is a form of oxygen that is produced when nitrogen dioxide reacts with hydrogen chloride. These gases release oxygen, which is altered by sunlight to produce ozone. In the lower atmosphere, ozone irritates the mucous membranes of the respiratory system, causing coughing and choking. It can impair lung functioning, reduce resistance to colds and pneumonia, and aggravate heart disease, asthma, bronchitis, and pneumonia. This ozone corrodes rubber and paint and can injure or kill vegetation. It is also one of the irritants found in smog. The natural ozone found in the upper atmosphere (sometimes called \"good\" ozone), however, serves as a protective membrane against heat and radiation from the sun.
Lead
Lead is a metal pollutant that is found in paint, batteries, drinking water, pipes, and dishes with lead-glazed bases. The elimination of lead from gasoline and auto exhaust in the 1970s was one of the great public health accomplishments of all time. Although stricter standards for all of the above prevail, almost 1 million children in the United States had elevated blood lead levels in 1997. Lead affects the circulatory, reproductive, and nervous systems. It can also affect the blood and kidneys and can accumulate in bone and other tissues. Lead is particularly detrimental to children and fetuses. It can cause birth defects, behavioral abnormalities, and decreased learning abilities.
Hydrocarbons
Although not listed as one of the six major air pollutants in the Clean Air Act, hydrocarbons encompass a wide variety of chemical pollutants in the air. Sometimes known as volatile organic compounds (VOCs), hydrocarbons are chemical compounds containing different combinations of carbon and hydrogen. The principal source of polluting hydrocarbons is the internal combustion engine. Most automobile engines emit hundreds of different types of hydrocarbon compounds. By themselves, hydrocarbons seem to cause few problems, but when they combine with sunlight and other pollutants, they form such poisons as formaldehyde, various ketones, and peroxyacetylnitrate (PAN), all of which are respiratory irritants. Hydrocarbon combinations such as benzene and benzo(a)pyrene are carcinogenic. In addition, hydrocarbons play a major part in the formation of smog.
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GENERAL HEALTH
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