Introduction Air pollution is nothing new. Ever since the discovery of fire, less-than-desirable substances have been vented into the air. One of the first air-pollution regulations dates back to the fourteenth century, when King Edward I banned the burning of sea coal in lime kilns. U.S. air-pollution regulations have their roots in British Common Law. But regardless of those efforts, air pollution continues to be a serious local and world-wide problem.
Pollution is the pressure within the air of one or more substances that are harmful to human health, welfare, animal or plant life, or property. In the past with air pollution we included mainly the outdoor pollutants, although in recent years this is not the case. Today we separate pollutants in to two categories. Primary pollutants, because they come directly from various sources, and secondary which are by-products of chemical interactions of the primary pollutants within the atmosphere. Particulates Although air pollution might be thought of as unwanted gases in the atmosphere, two of five primary pollutants are really solid substances called particulates. Soot has always been a sure indicator of a polluted atmosphere, but other than soiling and a negative psychological effect, soot can’t settle into the lungs and cause serious diseases.
Thick ,black smoke coming out of a stack is that what we think causes the pollution, but what really creates the damage is what we can’t see. Particles like this are called suspended particles. They come from many incomplete burning and can consist a variety of substances. The most harmful type of particulate is so small that that it is microscopic. All the particulates are harmful for several reasons.
When inhaled, they can damage the interior of the lung; they can also be poisonous. Sometimes gases will glue to their surfaces and in a process called adsorption they can reach the lungs. All these particles are mainly products of combustion. The major sources include industrial processes, power plants that are both coal and oil-fired, residential heating, and transportation. But coal burning is the greatest source. Table 1 below shows estimates of U.S. particulate emissions from various sources.
TABLE 1 National U.S. Emissions Estimates-1990 (Million metric tons/year) SOURCE PARTICULATES SULFUR OXIDES CARBON MONOXIDES Transportation Highway 1.3 0.6 30.3 Aircraft 0.1 0 1.1 Rail&Sea 0 0.3 1.9 Off-Highway equipment 0.1 0.1 4.4 TOTAL 1.5 1 37.7 Stationary fuel combustion Electric utilities 0.4 14.2 0.3 Indusrial furnaces 0.3 2.3 0.7 Commercial 0 0.4 0.1 Residential 1 0.3 6.4 TOTAL 1.7 17.2 7.5 Industrial processes 2.8 3.1 4.7 Solid waste disposal 0.3 0 1.7 Miacellaneous Forest fires 1.1 0 8.1 Other burning 0.1 0 0.6 Misc. Organic solvents 0 0 0 TOTAL 1.2 0 8.7 OVERALL TOTAL 7.5 21.3 60.3 Only 13% of the total is generated by transportation. Industrial sources account for nearly three times as much as 37%. Fires account for just about as much particulate emissions as transportation.
That amount is matched by combustion from sources, which include the generation of all heat and electricity. Emissions When coal was the main source to generate energy, power plants and homes accounted for much greater contribution. The switch to oil and nuclear power has lowered those concentrations, but it hasn’t been without its own problems. In addition to health-related problems, particles can damage materials through corrosion and erosion, as well as soiling. Particles can also impact the weather, through changes in visibility, and even in enhancing precipitation.
Studies around major urban areas show an increase in precipitation and in thunderstorms with hail downwind from downtown areas. The weather modification is localizes but definite, and may be related to an increase in the large condensation nuclei that the particles provide. Lead particulates are brutal primary pollutant. Their presence in the atmosphere has diminished sharply during the past 29 years. Since 1975, the concentration of lead has decreased by more than 90%, which can be directly linked to the elimination of lead from gasoline.
The following table shows that huge drop. TABLE 2 Gas Another primary group of pollutants consists of the surfur oxides(Sox), and the major contributor is SO2, a sulfur dioxide. This is generated whenever sulfur is burned, most often where fuel with a high sulfur content is used. Coal can have very high sulfur concentrations, as can some oil. Overall, coal and oil are the major sources for sulfur oxide pollution.
The vast majority of this type of air pollution comes from generation of heat and electricity. These stationary sources account about 80% of all sulfur oxides. Transportation’s contribution is minor, about 5%. The rest comes from industry. Sulfur dioxides cause damage to vegetation and material.
Plants lose their chlorophyll which is the plants food factory. But the most damage appears when sulfur oxides combine with other substances. Because of its solubility, sulfur dioxide becomes a major contributor to acid deposition. Leaves are bleached and show damage. Tree growth is stunted and vegetation dies. Damage to vegetation occurs at concentrations lower than what is harmful to people.
Carbon monoxide (CO) Carbon monoxide is colorless, odorless , tasteless,non-corrosive, highly poisonous gas of about the same density as that of air. It is very flammable, burns in air with bright blue flame. Its melting point is at-205.0 C and boiling point is at -191.5 C. There is no way to know if it is around, except we may no feel so well. When a fire burns in an enclosed space, oxygen is gradually depleted and carbon dioxide is increased. The changes in both of the these gases increasingly cause the combustion process to change from one of complete combustion to one of incomplete combustion, resulting in the release of increasing amounts of CO.
Thus, even a perfectly designed and adjusted furnace or water heater (or any kind of combustion device) will eventually begin producing toxic/lethal amounts of CO if it operates in a closed space and/or where insufficient fresh air is available. Table three lists some of the effects of CO to humans. TABLE 3 CO concentration in Parts Per Million or as as percentage of air % of CO in air Inhalation time and toxic symptoms developed 0.0001% Normal background levels 0.0009% Maximum allowable concentration short term in living area 0.0025% Maximum exposure TWA (Time Weighted Average) in the workplace. 0.005% Maximum exposure allowed (OSHA) in the workplace. 0.02% Mild headache, fatigue, nausea and dizziness. 0.04% Serious headache – other symptoms intensify. Life threatening after 3 hours.
0.08% Dizziness, nausea and convulsions Dead within 2 to 3 hours 0.16% Headache, dizziness and nausea. Death within 1 – 2 hours. 0.32% Headache, dizziness and nausea. Death within 1 hour. 0.64% Headache, dizziness and nausea. Death within 25 – 30 minutes.
1.28% Death within 1 – 3 minutes. Control of Air Pollution The Regulations The early air pollution laws were passed within small communities and concerned the color and density of the smoke that comes out from the stacks. They first appeared in Chicago and Cincinnati and later on began to show up also in other communities. A special chart determined the level of smoke. The chart showed smoke with different shades of gray and black.
At a particular level violations would be set. No natio …