Basic Mesothelioma Information, Part 2

Mesothelioma risks and causes

Mesothelioma is quite a rare cancer but it is becoming more common. Just over 2,100 people were diagnosed with mesothelioma in the UK in 2003. There are about 4 times as many cases in men as in women. This is probably because many cases have been caused by exposure to asbestos at work.

Asbestos and mesothelioma

Unusually for cancer, we do know what causes the majority of cases of mesothelioma. It is most often linked to exposure 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 (70–80%) 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 there are some patients that say they have no history of any heavy exposure to asbestos.

What is asbestos?

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 used asbestos products, particularly in construction or engineering. The use of asbestos was very heavy in the years after the war (after 1945). Mesothelioma may not develop until 15 - 40 years after you have been exposed to asbestos, which is why we are seeing an increase in cases now. The number of cases is expected to peak around 2020 and then start to decline.

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 does asbestos cause 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 family 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.

Other chemicals

A mineral found in Turkey called Zeolite may 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.