Asbestos lung cancer is linked to 4,800 deaths a year but it is not clear how many of those are also connected to tobacco use.

While many studies have only examined the risk of lung cancer for asbestos-exposed populations, such as shipyard workers, they have failed to investigate the criteria for linking an individual’s lung cancer to asbestos exposure due to tobacco.

Most studies have demonstrated that certain occupations and populations of workers commonly have higher asbestos exposures and greater risks of asbestos-related diseases and further suggests that the volume of asbestos lung cancers caused by tobacco may be underestimated.

In 2004, researchers reviewed new study results that had emerged since the first criteria about linking lung cancer to asbestos exposure were formed. Researchers amended the criteria to:

• Diagnosis of asbestosis.
• Higher than normal asbestos fibers in the lung tissue.
• Higher than normal exposure to asbestos, typical of shipbuilding and construction work.

Researchers more closely considered the role of smoking in asbestos-related lung cancer, stating that a second cause of cancer complicates the issue. Most lung cancer cases are linked to smoking, and some are further linked to asbestos.

Because asbestos and smoking work together, researchers suggest it is especially difficult to distinguish smoking-related cases from those caused by both smoking and asbestos.

How Asbestos Causes Lung Cancer

Companies and manufacturers have mined and used asbestos, a naturally occurring mineral, for commercial purposes in North America since the late 1800s. It is now highly regulated and a number of countries classify it as a human carcinogen.

When someone disturbs an asbestos-containing product, they release the microscopic fibers into the air. If inhaled, these thin fibers can become trapped in the lungs. Over long periods of time, they can accumulate and cause inflammation, scarring and other critical health problems. In some cases, the fibers can even trigger the development of lung cancer.

Researchers report the duration and concentration of asbestos exposure plays a role in the risk of developing lung cancer. The implications of asbestos exposure are not apparent immediately following exposure.

When asbestos fibers are first inhaled, they can become lodged in the lining of the lungs. The size of asbestos fibers affects where they become lodged, having implications on whether lung cancer develops.

After many years, sometimes decades, these fibers cause enough irritation and cellular damage to generate tumor formation. Whether someone develops lung cancer, mesothelioma or asbestosis will depend on a person’s health, genetics, habits and the duration and concentration of exposure.

One reason to identify the lung cancers caused by asbestos exposure is for establishing occupational and public health policies regarding asbestos or for investigation of lung cancer that lead to new treatment therapies.