Risks and Causes
Exposure to asbestos is thought to be responsible for up to nine out of 10 cases of mesothelioma. There may be other causes of the disease such as exposure to certain types of radiation and other chemicals, however the evidence linking these to mesothelioma is limited and asbestos remains the main cause for the majority of cases.
The disease has been described in medical literature since 1870 although the first suspicion linking asbestos and mesothelioma did not appear in the UK until 1935 and a definite link was not reported until 1960.
It is now understood that changes in our genes can influence the development of cancers. In a very small number of people there may be a predisposition to developing mesothelioma due to a mutation in a gene called BAP1. This gene has several different functions and investigators have discovered that when someone has a germline (inherited) mutation in one copy of the BAP1 gene, they have an increased risk of developing certain cancers including mesothelioma. It is important to know that the presence of this mutation does not guarantee someone will develop mesothelioma in their lifetime. For more on BAP1 Tumour Predisposition Syndrome visit our resource section.
It is likely that everyone will breathe in asbestos fibres at some point as very low levels are present in the air around us. Some people have a much greater risk of developing mesothelioma because their exposure has been much higher; this is usually linked to occupational exposure. Certain industries are associated with heavy asbestos use or exposure. These include:
- Shipbuilding/shipyard workers
- Boiler/heating workers
- Armed forces
- Power station workers
- Asbestos manufacturing
This is not an exhaustive list and people in other industries may have had considerable exposure through their employment.
Asbestos remains present in many public buildings. People working in occupations not traditionally linked to asbestos exposure potentially have an increased risk due to the presence of asbestos in buildings. These include healthcare workers and school workers. Exposure can also be para-occupational and can occur through exposure to asbestos present on clothing from those working in environments with heavy use or from living near an asbestos manufacturing plant. Whilst other asbestos-related diseases only develop as a result of heavy asbestos exposure, there is no accepted safe level when it comes to mesothelioma.
How does asbestos cause cancer?
Asbestos is a naturally occurring mineral, It Is found in many countries worldwide including Russia and South Africa.
There are two main types of asbestos:
- Serpentine – Chrysotile – long and curled fibres
- Amphibole – Amosite (brown) & Crocidolite (blue) – straight, needle like fibres
Asbestos is resistant to heat, fire and chemicals, and for this reason, it was used in buildings and products worldwide. Asbestos was widely used in UK industry and was present in thousands of products, with the peak of its use in the 1960s and 1970s. Blue (Crocidolite) and brown (Amosite) asbestos were banned in the UK in 1985, White (Chrysotile) asbestos was banned in 1999. This ban made it illegal to supply and manufacture asbestos products in the UK.
Asbestos is made up of tiny fibres and when asbestos is damaged/exposed or broken up fibres are released, these fibres are invisible to the naked eye. When asbestos fibres are inhaled they can lodge in small airways and some of the fibres can penetrate the lining of the lung (pleura), the body finds it difficult to clear the fibres. Some fibres can also be swallowed and may be the reason some people develop mesothelioma in the abdominal lining (peritoneum). Over time, inflammation can occur, the DNA of the cells in the lining of the lung become damaged leading to mesothelioma development. This change often takes decades to occur; exposure to asbestos may have occurred 10-60 years before the development of mesothelioma.
Smoking and asbestos
The combination of smoking and asbestos exposure is known to be harmful. People who smoke and are exposed to asbestos have a much greater risk of developing lung cancer. Smoking and asbestos exposure does not seem to increase the risk of developing mesothelioma but as smoking can cause many other problems to health, it is always recommended that people should try to stop.