Asbestosis Causes

Lung Cancer

Asbestosis is caused by the accumulation of asbestos fibers in the lungs resulting in pulmonary fibrosis. The disease is caused by inhaling these toxic fibers, which leads to scarring of the lung tissue. Asbestosis is considered a progressive and sometimes fatal lung condition that typically develops after five or more years of consistent exposure

Historically, exposure most often occurred in occupational settings where asbestos-containing materials were used. The first asbestosis case was diagnosed in 1899. The patient was the only survivor of 10 men who had worked together in a carding room of an asbestos factory. By 1918, the causal relationship between exposure and asbestosis was so strong that the Prudential Insurance Company refused to issue life insurance policies to asbestos workers because of early mortality.

Where Does Exposure Occur?

Exposure to the toxic fibers that cause asbestosis primarily occurs in three ways: occupationally, environmentally or secondarily (through contact with someone who is consistently exposed).

  • Occupational Exposure

    There are many occupations that have earned a reputation for asbestos exposure. Some of the most common jobs affiliated with exposure include those in the construction, shipyard, manufacturing and automotive industries. In fact, most asbestosis cases develop in those who were exposed while on the job. Numerous studies indicate that people who work in an environment where exposure occurs for more than 10 years are at a much higher risk for developing asbestosis.

    Undamaged or new asbestos products are usually not harmful when intact (loose-fill insulation is an exception, as its composition readily leads to exposure). Asbestos products are most harmful when they age or when they are disturbed or damaged. Once these products are no longer intact, the toxic fibers can become airborne.

  • Other Types of Exposure

    Environmental exposure can occur when someone lives near naturally occurring deposits or near a landfill that is contaminated by asbestos. It can also occur if someone lives in an older residence that contains contaminated products like insulation, drywall, ceiling or floor tiles. Environmental exposure is typically low and is not considered a risk for asbestosis.

    Secondary exposure happens when someone contaminated with asbestos fibers transfers those fibers to another person. For example, a spouse can be exposed by washing work clothes. This type of exposure does not typically lead to asbestosis.

How Does Asbestosis Develop?

Inhaling Asbestos

Asbestosis develops from inhaling airbone fibers over a period of many years. Asbestos is a naturally ocurring mineral that has been mined, processed, and integrated into a wide variety of products, especially before the 1980s in the United States. Because of their microscopic size and shape, these fibers can become lodged in the lungs, eventually causing scarring and a buildup of scar tissue around the lungs' air sacs. As this scar tissue continues to build, pleural thickening develops and restricts the lungs from expanding to their normal capacity.

Smoking and Asbestosis

Although the causal relationship between asbestosis and cigarette smoking is unclear, many studies have indicated that smoking influences the development of the disease. In a study of 1,479 asbestos-exposed workers among a variety of industries in Barcelona, Spain, 912 of those who smoked showed significantly higher incidences of asbestosis than non-smokers. Most studies indicate the combination of smoking and asbestos exposure increases the risk of asbestosis.

Cigarette Smoking

The earliest symptoms of asbestosis include coughing and shortness of breath. These symptoms occur because the lungs are unable to expand to their normal capacity. Other symptoms may include chest pain and exhaustion during exercise. In the later stages of development, asbestosis patients can experience a finger deformity symptom called "clubbed finger," which causes bulging of the fingertips and misshapen fingernails. This develops from a lack of proper blood flow to the extremities.

Latency Period

Symptoms of asbestosis generally take 20 to 30 years to develop from the time someone is initially exposed to asbestos. In this regard, asbestosis arises faster than any related disease. Mesothelioma, a cancer with similar symptoms that is caused almost exclusively by exposure, has a latency period of up to 50 years.

Imaging Scans

Even though asbestosis has a long latency period before symptoms arise, imaging scans and other clinical testing can detect signs of asbestosis development between five and 15 years after exposure. The latency period associated with asbestosis is dependent on the duration and intensity of exposure. For heavy exposure, the latency period typically lies between 12 and 20 years after initial exposure occurs. At lower doses of exposure, a longer latency period is expected. In one study, 27 percent of mill workers developed asbestosis after five to nine years of heavy exposure.

Are You At Risk?

If you have been exposed to asbestos and begin to feel out of breath on occasion, make sure to get checked out by a doctor with experience in detecting these diseases. There are several treatment options for people with asbestosis. While there is no proven cure, many therapies can relieve symptoms and improve quality of life.

Additional Resources

  1. Dodson, R. and Hammar, S. (2011). Asbestos: Risk Assessment, Epidemiology, and Health Effects. Boca Raton: Taylor & Francis.
  2. Asbestosis: A Medical Dictionary, Bibliography, and Annotated Research Guide To Internet References. San Diego, Calif.: Icon Health Publications. 2004. ISBN 0-597-84339-2.
  3. Craighead, J. E., Gibbs, A. R. (2008). Asbestos and Its Diseases. New York: Oxford University Press.
  4. Dugdale, D., Hadjiliadis, D., Zieve, D. (2011, June 10) Asbestosis. Retrieved from
  5. Agency for Toxic Substances and Disease Registry. (2008, Apr. 1) Asbestos Health Effects. Retrieved from:
  6. Asbestos Toxicity: Respiratory Effects. Retrieved from:

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