asbestos 

Asbestos is a fibrous mineral that occurs naturally in SERPENTINE rock 
and can be mined and processed into a variety of materials that are 
uniquely resistant to fire, heat, and corrosion. Chrysolite rock is 
the most important asbestos source; it is mined principally in the 
Canadian province of Quebec, the USSR, and South Africa. 

Excavated, usually, from open-pit mines, asbestos rock is crushed to 
free the fibers. These can be spun and woven into fire-resistant 
safety textiles, matted into insulating materials, or used with other 
substances to make more than 2,500 products, including brake linings 
and clutch pads, roofing and flooring materials, cement, and 
insulation for electrical circuits. For many of these products, 
asbestos is almost irreplaceable. No other substance provides its 
stability, strength, and heat resistance so cheaply and efficiently. 

Asbestos roofing material is made by impregnating asbestos felt with 
asphalt or coal-tar pitch. Small asbestos fibers, combined under 
pressure with cement, are made into fireproof panels and used for 
building walls, partitions, and roofs. Because such panels are also 
corrosion-resistant, they are preferred by industries that produce 
corrosive fumes in the course of manufacturing. 

Asbestos fibers are often made into paper, which is corrugated and 
then glued together with flat asbestos paper to form a fireproof 
insulating covering for home heating systems. Asbestos paper is also 
used to fireproof areas of commercial and domestic structures and to 
insulate home appliances. Another common insulating material, used in 
both homes and industry, is made by mixing asbestos fiber with basic 
carbonate of magnesia. 

Well-documented health hazards are associated with long-term exposure 
to asbestos. Asbestos in the air can be responsible for both a lung 
disease known as asbestosis and lung cancer, especially when combined 
with cigarette smoking. Water polluted by asbestos fibers, either from 
running over rocks containing the mineral or from contact with water 
pipes made of asbestos cement, may be responsible for other cancers. 
Workers have successfully brought suit against companies for failing 
to warn them of asbestos hazards at the worksite. By the early 1980s, 
about 25,000 people had filed nearly 12,000 lawsuits against companies 
that manufacture, sell, or use asbestos. One such company, the 
Johns-Manville Co., filed bankruptcy in 1982 in order to seek 
protection from possible lawsuit settlements, which could total more 
than $2 billion dollars. The responsibility for asbestos-related 
health problems is clouded by the fact that for years the government 
required asbestos in several manufacturing processes and construction 
projects. Some steps have been taken to reduce the occupational hazard 
to asbestos workers and to reduce public exposure to asbestos 
particles released into the air from aging buildings or heavy traffic. 
Cements are now being produced that have no asbestos content. In some 
cases public facilities have been closed until exposed asbestos is 
removed. 

Bibliography: Michaels, L., and Chissick, S. S., Asbestos: Properties, 
Applications, and Hazards, vol. 1 (1979); Selikoff, Irving, and Lee, 
Douglas H., Asbestos and Disease (1978).