What are the health risks of exposure to asbestos?

An x-ray of a healthy lung.		An x-ray of a lung affected by mesothelioma.

While the risk to health increases with the number of fibres inhaled and with frequency of exposure, no safe level of asbestos exposure for lung cancer or mesothelioma has been identified. All types of asbestos can break into fibres so small that once they are in the air, they can remain airborne and be inhaled into the lungs, making it difficult for the body to remove them. This has been known to cause asbestosis, mesothelioma, pleural plaques and lung cancer.

The first three of the following definitions have been extracted from the National Code of Practice for the Safe Removal of Asbestos 2nd Edition.

Asbestosis

Asbestosis is a form of lung disease (pneumoconiosis) directly caused by inhaling asbestos fibres, causing a scarring (fibrosis) of the lung tissue, which decreases the ability of the lungs to transfer oxygen to the blood. The time between first exposure to asbestos and the onset of illness is generally between 15 and 25 years.

Mesothelioma

Malignant mesothelioma is a cancer of the outer covering of the lung (the pleura) or the abdominal cavity (the peritoneum). The time between first exposure to asbestos and the onset of illness is generally between 35 and 40 years (but may be longer). Mesothelioma was once rare, but its incidence is increasing throughout the industrial world as a result of past exposures to asbestos. Australia has the highest incidence rate in the world. This disease is very difficult to detect before the onset of illness and is usually fatal.

Lung cancer

Lung cancer has been shown to be caused by all types of asbestos. The average time between first exposure to asbestos and the onset of illness generally ranges from 20 to 30 years. Lung cancer symptoms are rarely felt until the disease has developed to an advanced stage. Research has shown that smoking significantly increases the risk of lung cancer in people who have been exposed to asbestos.

Pleural plaques

Pleural plaques are the most common symptom of asbestos exposure. They are deposits of fibrous tissue that often become calcified over time. Pleural plaques are most commonly found on the inner surface of the diaphragm, the parietal (the membrane that lines the chest wall) and the peritoneal mesothelium (the membrane that lines the abdominal cavity wall). While pleural plaques themselves are not cancerous and do not turn cancerous, evidence shows that individuals who have pleural plaques have an increased risk of developing other asbestos related diseases (as mentioned above).