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 ...
