Asbestos - Health risks

Significant Health Risks May Arise From the Inhalation of Airborne Asbestos Fibres

Significant health risks may arise from the inhalation of airborne asbestos fibres and their passage into the lungs. Small fibrous particles may become airborne and be inhaled. Fibres below three micrometres in diameter are referred to as respirable, meaning that they may enter the deepest parts of the lung. Most larger fibres are deposited in the nose and major airways, and are cleared by normal physiological processes; however, smaller fibres are generally deposited in the minor airways and airspaces (alveoli).

Inhalation of asbestos fibres may result in asbestosis, a progressive scarring of lung tissue. Further development of scar tissue (fibrosis) may occur after the cessation of exposure.

The two main forms of cancer associated with the inhalation of asbestos are lung cancer and mesothelioma. Generally, fibres below three micrometres in diameter and greater than eight micrometres in length are potentially carcinogenic, and the risk of cancer increases as fibre diameter decreases. The risk of cancer is also greater with increased exposure to asbestos, and vice versa. Cancer in the gastro-intestinal tract and other sites of the body have been noted in workers exposed to asbestos. Whether links exist between such cancers and asbestos exposure is still uncertain.

There is a long latency period which, in the great majority of cases, ranges from 10 to 50 years between exposure and the development of mesothelioma and lung disease, so asbestos-induced cancer will continue to occur in Australia long after asbestos exposure has been brought under control. Nevertheless, there should be continuing effort towards reducing the levels of asbestos exposure to workers.

All forms of asbestos have been found to cause lung cancer, both in a variety of experimental animals and in exposed humans. Cigarette smoking greatly increases the risk of lung cancer in people heavily exposed to asbestos.

Mesothelioma is a cancer of the lining of the chest cavity (the pleura) or less commonly, the lining of the abdominal cavity (the peritoneum). Crocidolite (blue asbestos) and amosite (brown or grey asbestos) have the most potent documented effects in producing this tumour, which is highly malignant. It has no known association with tobacco smoking. The most common cause of mesothelioma is occupational exposure to asbestos.

Pleural plaques (patches of thickening of the pleural membrane) may be associated with the inhalation of asbestos fibres. The appearance of pleural plaques on X-rays is not in itself an indication of cancer.

It should be noted that medical examinations of persons recently exposed to asbestos cannot reveal the presence or absence of health problems related to the exposure. In particular, X-rays are inappropriate for incidental or brief exposures and may pose an additional risk.

 'Asbestos in your home' GB149