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Mesothelioma risks and causes

This page is about the risk factors and possible causes of mesothelioma.  There is information on

    * How common mesothelioma is   
    * Asbestos and mesothelioma   
    * What asbestos is   
    * How asbestos causes mesothelioma   
    * Radiation   
    * Other chemicals and mesothelioma   
    * The SV40 virus

How common mesothelioma is

Mesothelioma is quite a rare cancer, but it is becoming more common.  Just over 2,100 people are diagnosed with mesothelioma in the UK each year.  There are about 5 times as many cases in men as in women.  This is probably because many cases have been caused by exposure to asbestos at work.  Mesothelioma in the chest (pleural mesothelioma) is much more common than mesothelioma in the abdomen (peritoneal mesothelioma).

Asbestos and mesothelioma
We know what causes most cases of mesothelioma.  It is common in people who have been exposed to asbestos.  We have known of a link between asbestos and lung disease since the beginning of the 18th century.  But the link with mesothelioma has only been known since the 1960's.  Unfortunately, the number of cases of mesothelioma in the UK each year is expected to rise sharply over the next 20 years because of the heavy use of asbestos in industry from the end of the second world war up until the mid 1970s.

Between 7 and 8 out of every 10 people (70 to 80%) diagnosed with mesothelioma say they have been in contact with asbestos.  Your risk is greater if you were exposed to large amounts of it from an early age for a very long period of time.  But some people say they have no history of any heavy exposure to asbestos.

Remember – Many people who develop mesothelioma due to asbestos exposure may be able to claim compensation.  You should talk to a solicitor about this as early as possible.  Your specialist doctor or nurse may be able to give you some information on this from dealing with other mesothelioma patients.  Or some of the mesothelioma organisations in the help and support section should be able to advise you.

What asbestos is
Asbestos is an insulating material that is heat and fire resistant.  In the past, asbestos was used widely in the

    * Building industry   
    * Ship building industry   
    * Manufacture of household appliances   
    * Motor industry   
    * Power stations   
    * Telephone exchanges

So most cases of mesothelioma occur in men who have worked in manufacturing using asbestos or who have used asbestos products, particularly in construction or engineering.  A recent UK study showed that risks are particularly high for metal plate workers (mainly in shipbuilding) and carpenters, and risk is higher in people  exposed to asbestos before the age of 30.  This study estimated that 1 out of 17 British carpenters born in the 1940s and employed in carpentry for more than 10 years before the age of 30 would go on to develop mesothelioma.

Asbestos was widely used in the years after the war (after 1945).  Mesothelioma may not develop until 15 to 40 years after you have been exposed to asbestos, which is why we are now seeing an increase in cases.  The number of cases is expected to peak around 2020 and then start to go down.

There are three main types of asbestos – blue, brown and white.  Blue and brown asbestos are strongly linked with mesothelioma.  They have been banned since the late 1980's and cannot be imported into the UK.  White asbestos is now also thought to be harmful.  The use of all asbestos was banned in 1999 in the UK.

How asbestos causes mesothelioma

Asbestos is made up of tiny fibres.  You can breathe these fibres in when you come into contact with asbestos.  The fibres work their way into the pleura, lining the lung.  They irritate the pleura and damage the cells that the pleura are made of.  Some of the fibres that have been breathed in can be coughed up and swallowed.  This is probably the cause of peritoneal mesothelioma.

If you have been exposed to asbestos, your family may also have been exposed.  Asbestos fibres can be carried home on your clothes.  Research studies have confirmed that the families of people exposed to asbestos also have a higher risk of developing mesothelioma.

Radiation

Pleural and peritoneal mesothelioma has been known to develop after exposure to a type of radiation called thorium dioxide (Thorotast).  This was used until the 1950's in some X-ray tests.

Some studies show an increased risk of mesothelioma in people treated with radiotherapy for a previous cancer.  But other studies show no increased risk.  If radiotherapy does increase the risk of mesothelioma, this is likely to occur only in a very small number of people.

Other chemicals and mesothelioma

A mineral found in Turkey called Zeolite has been shown to cause mesothelioma.

The SV40 virus

There has been some research into a virus called SV40 (the SV stands for 'simian virus').  There is a lot of dispute amongst scientists about this and it isn't generally accepted as a cause.  It seems more likely that the virus doesn't cause mesothelioma.  It is possible that SV40 may help to increase risk if you've been exposed to another more major risk factor.  Doctors call this a 'co-factor'.  But SV40 certainly hasn't been proved to be a co-factor so far.  In any case, it is far less important a risk factor than asbestos.