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Many factors determine the extent of the health risk posed by asbestos exposure. These factors include:
Dose (how much you are exposed to)
Duration (how long you are exposed for)
Fiber type (Amphibole [Rod Shaped] or Chrysotile [Curly shaped])
Fiber size (Length and diameter)
Type of contact (inhalation, ingestion, skin)
You must also consider other chemicals you have been exposed to, your age, sex, diet, family traits, lifestyle (including whether you smoke tobacco), and overall state of health.
A fair amount of scientific debate exists concerning the differences in the extent of disease caused by different asbestos fiber types and sizes. Some of these differences may be due to the physical and chemical properties of the different fiber types. For example, several studies suggest that amphibole or rod-shaped asbestos types (tremolite, amosite, and especially crocidolite) may be more harmful than chrysotile, particularly as a cause of mesothelioma. Other data indicate that fiber size dimensions (length and diameter) are important factors for cancer-causing potential. Some data indicate that fibers with lengths greater than 5.0 micro-meter are more likely to cause injury than fibers with lengths less than 2.5 micro-meter (1 micro-meter is about 1/25,000 of an inch). Additional data indicate that short fibers can also contribute to injury such as mesothelioma, lung cancer, and asbestosis. Fibers thicker than 3.0 micro-meter are of lesser concern, because they have little chance of reaching the lower regions of the lung.
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While nearly everyone is exposed to asbestos at some time during her/his lifetime, most people do not become ill as a result of the exposure. People who become ill from exposure to asbestos are usually those who are exposed to it on a regular basis, most often in a job where they work directly with the material or through substantial environmental contact. Since the early 1940s, millions of American workers have been exposed to asbestos. Asbestos-related health hazards have been recognized in workers exposed in shipbuilding trades, asbestos mining and milling, manufacturing of asbestos textiles and other asbestos products, insulation work in the construction and building trades, brake repair, and a variety of other trades. Demolition workers, drywall removers, and firefighters also may be occupationally exposed to asbestos fibers. As a result of government regulations and improved work practices, today’s workers (those without previous exposure) are likely to face smaller risks than workers in the past. Although it is known that the risk to workers increases with heavier exposure and longer exposure time, investigators have also found asbestos-related diseases in individuals with only brief exposures. Generally, those who develop asbestos-related diseases show no signs of illness for a long time after their first exposure. It can take from 10 to 40 years for symptoms of an asbestos-related condition to appear. Some evidence shows that family members of workers heavily exposed to asbestos face an increased risk of developing mesothelioma. This risk is thought to result from exposure to asbestos fibers brought into the home on the shoes, clothing, skin, and hair of workers. In general, persons exposed only to naturally occurring, low levels of asbestos in the environment are not at significantly higher risk for contracting asbestos-related diseases.
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