Ginger Harris, age 13, of Lowell, Mass., for her question:
WHY IS WORKING WITH ASBESTOS DANGEROUS?
Scientific studies during the 1960s found that people who were exposed to small amounts of asbestos dust over many years were more likely than other people to get cancer of the lungs and other organs. For this reason, people working with asbestos must take special precautions.
Most industries that process asbestos make medical checks of their employees on a regular schedule. If there are any indications that problems may develop, the employees are transferred to other jobs. Federal, state and local regulations control worker exposure to asbestos.
Asbestos was first used by the ancient Greeks and Romans. The first factory for making asbestos cloth was operated in Russia in the 1700s. But widespread commercial use of asbestos didn't start until after the discovery of the huge Quebec deposits in 1878.
Asbestos is the fibrous form of various minerals. Its fibers are soft and flexible and can be spun into threads and woven into cloth. It is remarkable for its resistance to heat. Asbestos also resists acids, alkalies and other chemicals.
Often threads of asbestos are blended with cotton or rayon to add strength and then these threads are woven into cloth. Such fabrics are widely used for brake linings and clutch facings for cars, where friction causes intense heat. Other types of asbestos fabrics can be made into safety clothing, such as firemen's suits, gloves and helmets, theater curtains, awnings and conveyor belts for carrying hot materials.
Short fiber asbestos is often molded into sheets and then used to insulate pipes and wires, to line stoves and to coat boilers and furnaces. Molded asbestos is also used in automobile brake linings. Mixed with cement, short fiber asbestos is also used in shingles, wallboard and tiling. It is also used to waterproof paints, gas burners and water pipes.
Because of health risks that are posed by the use of asbestos, research into acceptable replacements is presently being conducted.
Doctors have known since the 1920s that asbestos particles can damage the lungs. Asbestos fibers pierce the tiny sacs in the lungs and accumulate there, causing a condition called asbestosis.
About 95 percent of the world supply of asbestos is of a type called chrysolite, and 75 percent of this comes from the Canadian province of Quebec. Other large deposits of chrysolite can be found in South Africa and the Soviet Union. Asbestos is also found in China, Italy Rhodesia and the United States.
A majority of the U.S. deposits of asbestos are of little commercial value, but deposits can be found in California, Vermont, Arizona and North Carolina.
Asbestos mining can be done from an open pit, as in a quarry, or it can be mined and blasted in tunnels, as in the mining of coal.