Asbestos fibres enter the body when people breathe in or swallow airborne particles. These particles can then become embedded in the tissues of the respiratory or digestive systems.
Asbestos is now recognised as a human carcinogen — a substance that can cause cancer. It can cause:
- asbestosis (lung scarring)
- mesothelioma (a cancer of the lining of the chest cavity)
- lung cancer.
Asbestos-related diseases take time to develop. They usually emerge at least 10 years after exposure, and sometimes as long as 50 years later. Currently there are no cures for these diseases.
What is the risk?
Asbestos is only a health risk when extremely fine particles — known as respirable fibres — become airborne and are inhaled. Respirable fibres are:
- less than 3 microns* in diameter and
- greater than 5 microns in length.
*(1 micron = 1/1000th of a millimetre)
These small fibres cannot be seen with the naked eye. They can enter the deepest parts of the lungs where they may stay, causing disease.
The presence of asbestos materials in a building does not necessarily create a health risk. While the materials are undisturbed and in sound condition, they will not generate airborne respirable fibres or create a health risk.
The likelihood of any particular person developing an asbestos-related illness depends on a number of factors, including:
- length of time a person is exposed to airborne asbestos fibres
- concentration or levels of asbestos in the air breathed
- individual susceptibility
- size and type of asbestos fibres
- influence of other factors, especially cigarette smoke. (Research has shown that smoking significantly increases the risk of lung cancer in people who have been exposed to asbestos.)
Asbestos materials should be repaired, cleaned up or removed if they are damaged or in poor condition, or could possibly be disturbed by building works. This will reduce the likelihood of asbestos fibres becoming airborne and creating a health risk.
- Asbestosis causes widespread interstitial fibrosis (scar tissue between the alveoli, spread over the lung).
- It is difficult to distinguish from other causes of interstitial fibrosis.
- Only confirmation of exposure to asbestos or detection of unusually high numbers of asbestos fibres in the lung is considered conclusive evidence of this disease.
- The rate of onset of asbestosis is not related to the level of exposure.
- However, the rate at which the disease progresses is related to the level of exposure.
- Mesothelioma is a tumour of the chest lining, abdominal lining and occasionally the heart lining.
- It is a very rare disease — incidence is 1 in every 100,000 for males and 0.3 in every 100,000 for females.
- Mesothelioma is not related to smoking.
- Asbestos is not the only cause of this disease, but it is the most important cause in modern times.
- Crocidolite is the most important asbestos-related factor, but amosite, chrysotile and tremolite are also linked.
- This disease takes 20-50 years to appear, with the highest risk around 30-35 years after exposure.
- It is typically dose-related, but in rare cases has been known to occur in patients with little known occupational exposure to asbestos.
- Lung cancer is relatively common among the general public and is the cancer most frequently associated with asbestos.
- Tumours grow and eventually obstruct airways.
- No characteristics specify a lung cancer as being caused by asbestos — we cannot distinguish a ‘cigarette’ lung cancer from an ‘asbestos’ lung cancer or ‘another’ lung cancer.
- Smoking multiplies by 10 the risk of death due to lung cancer for asbestos workers.