Asbestos is a group of minerals that occur naturally as bundles of fibers. These fibers are found naturally in soil and rocks in many parts of the world. They are made mainly of silicon and oxygen, but also contain other elements. There are 2 main types of asbestos:
Chrysotile asbestos, also known as white asbestos, is the most common type of asbestos in industrial applications. When looked at under the microscope, chrysotile asbestos fibers wrap around themselves as a spiral, that is why this form of asbestos has also been called curly or serpentine asbestos.
Amphibole asbestos fibers are needle-like and straight. There are several types of amphibole fibers, including amosite (brown asbestos), crocidolite (blue asbestos), anthophyllite, actinolite, and tremolite.
Both types of asbestos cause cancer. Amphibole asbestos does seem to be more potent in causing a rare type of cancer called mesothelioma
Asbestos fibers are strong, resistant to heat and to many chemicals, and do not conduct electricity. As a result, asbestos has been used as an insulating material since ancient times. Since the industrial revolution, asbestos has been used to insulate factories, homes, schools, and ships, and to make automobile brake and clutch parts, roofing shingles, ceiling and floor tiles, cement, textiles, and hundreds of other products.
During the first half of the 1900s, growing evidence showed that breathing in asbestos caused scarring of the lungs. In the early 1900s, exposure to asbestos dust in the workplace was not controlled. Beginning in England in the 1930s, steps were taken to protect workers in the asbestos industry by installing ventilation and exhaust systems. In the huge shipbuilding effort during World War II, large numbers of workers were exposed to high levels of asbestos.
As asbestos-related cancers became better recognized in the second half of the 20th century, measures were taken to reduce exposure, including establishing exposure standards and laws that banned the use of asbestos in construction materials. There has been a dramatic decrease in importing and using asbestos since the mid-1970s, and alternative insulating materials have been developed. As a result, asbestos exposure has dropped dramatically in the United States. It is still used in some products, and it is still possible to be exposed to asbestos in older buildings, water pipes, and other settings. Asbestos has been banned in the European Union for several years, although the ban did not require removal of asbestos that was already in place. Still, heavy asbestos use continues in certain countries.
How are people exposed to asbestos?
People are exposed to asbestos mainly by inhaling fibers in the air they breathe. In any of these situations, asbestos fibers tend to create a dust composed of tiny particles that can float in the air.
In addition, asbestos fibers can be swallowed. This may happen when people consume contaminated food or liquids (such as water that flows through asbestos cement pipes). It may also occur when people cough up asbestos they have inhaled, and then swallow their saliva.
Many people are exposed to very low levels of naturally occurring asbestos in outdoor air as a result of erosion of asbestos-bearing rocks. The potential for such exposure is higher in areas where rocks have higher asbestos content. In some areas, asbestos may be detected in the water supply as well as in the air. It may be released into the water through several sources, such as erosion or natural deposits, corrosion from asbestos cement pipes, and the breakdown of roofing materials containing asbestos that are then transported into sewers.
However, the people with the heaviest exposure are those who worked in asbestos industries, such as shipbuilding and insulation. Many of these people recall working in thick clouds of asbestos dust, day after day.
Family members of asbestos workers can also be exposed to higher levels of asbestos because the fibers can be carried home on the workers' clothing, and can then be inhaled by others in the household.
Asbestos exposure is also a concern in older buildings. If building materials like insulation and ceiling and floor tiles begin to decompose over time, asbestos fibers can be found in indoor air and may pose a health threat. There is no health risk if the asbestos is bonded into intact finished products, such as walls and tiles. As long as the material is not damaged or disturbed (for example, by drilling or remodeling), the fibers are not released into the air. Maintenance workers who sweep up and dispose of the asbestos dust or handle damaged asbestos-containing materials are often exposed to higher levels than other occupants of these buildings. Removing asbestos from homes and other buildings can also cause some exposure, although modern asbestos abatement workers are trained to use appropriate protective equipment to minimize exposure.
Although use of asbestos has declined in the United States, people are still exposed to asbestos in the workplace. In 2008, the Occupational Health and Safety Administration estimated that over a million employees in construction and general industries face significant asbestos exposure on the job.
The mining and use of asbestos is also still a health hazard in some other parts of the world. Mining in the Russian Federation, China, Kazakhstan, Brazil, Canada, and Zimbabwe accounted for almost all of the world production of asbestos in 2006. Much of what is produced is used in the Russian Federation (and other countries in the former Soviet Union) and Asia, and its use is on the rise in some areas. In 2005, the World Health Organization estimated that 125 million people worldwide were exposed to asbestos at work, despite the known links to cancer and other lung diseases for more than 60 years.
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