It is generally well-accepted that mesothelioma is almost always associated with asbestos exposure. The fact that, in such cases, the disease usually only occurs between 20-40 years after exposure to asbestos, however, has lead to very real difficulties in unambiguous quantitative diagnoses and to much controversy regarding compensation and liability disputes. (It has a very poor prognosis, with most patients dying within 2-4 years of diagnosis)
There is no scientific consensus as to whether there does indeed exist a threshold of exposure to asbestos below which a person is at zero risk of developing mesothelioma. The HSE does not assume that such a threshold exists, since they consider that it cannot currently be quantified for practical purposes; they cite evidence from epidemiological studies of asbestos exposed groups to argue that any such threshold for mesothelioma must be at a very low level.
Care should be taken to distinguish between several forms of relevant diseases. According to the World Health Organisation (WHO), these may defined as:-
asbestosis (which is a slowly developing fibrosis of the lung caused by the inhalation of high concentrations of asbestos dust and/or long exposure),
lung cancer, or “bronchial carcinoma” which can result from occupational exposures to certain substances, including asbestos fibres (even without co-existing asbestosis) and,
mesothelioma which is a malignant tumour of the pleura or peritoneum.
The latter is normally a very rare type of cancer (typically less than 0.04% of all deaths in the general population). A higher incidence of mesothelioma has nearly always been related to the inhalation of mineral fibres, and in the majority of cases to occupational asbestos exposure.
In order to not present an over-long article here, currently only specific examples regarding the situation in Britain and the USA are included. (links to resources regarding the situation in other countries are listed below).