Exposure to asbestos causes 99% of mesotheliomas. Occupational exposure to asbestos is associated with the vast majority of mesotheliomas. How asbestos causes mesothelioma is not fully understood. Asbestos fibres are inhaled and travel through the upper passage ways, which include the throat, the windpipe and the large breathing tubes of the lungs (called large bronchi).
Many of these fibres are cleared by coughing or being swallowed. The asbestos fibres continue to travel in the respiratory tracts until they reach the small airways (called the alveoli). The body’s immune system is able to destroy the smaller fibres. However, the large long thin fibres cannot be cleared as easily by the body’s defences and eventually they reach the pleura (the lining of the lung and chest). Over time these fibres irate and injure the pleural cells and damage the cells. The latency period (the period between the ingestion of asbestos fibres and the onset of cancer) can be anything up to 50 years or even more. It is thought that it takes around 10 years for the mutation to take place from the beginnings of an abnormal cell to early tumour.