Find out what causes mesothelioma and who is more likely to get it.

Who gets mesothelioma

In the UK more than 2,600 people are diagnosed with mesothelioma each year. About 5 times more men than women get it. This is probably because mesothelioma is often caused by exposure to asbestos at work.

Mesothelioma is quite a rare cancer, but it is becoming more common. Mesothelioma in the chest (pleural mesothelioma) is much more common than mesothelioma in the abdomen (peritoneal mesothelioma).

What a risk factor is

Anything that can increase your risk of getting a disease is called a risk factor.

Different cancers have different risk factors.­ Having one or more of these risk factors doesn't mean you will definitely get that cancer.

The risk factors for mesothelioma are explained below. 

Asbestos

We know that asbestos causes most cases of pleural mesothelioma. The risk is greater if you were exposed to large amounts of it from an early age for a very long period of time. Many people with peritoneal mesothelioma have also 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 for the next few years. This is because of the heavy use of asbestos in industry from the end of the second world war up until the mid 1970s.

It is estimated that in the UK more than 9 out of 10 men with mesothelioma and more than 8 out of 10 women have been in contact with asbestos. But some people say they have no history of any exposure to asbestos.

What asbestos is

Asbestos is an insulating material that’s heat and fire resistant. It was widely used in:

• building industry
• shipbuilding
• manufacturing of household appliances
• motor industry
• power stations
• telephone exchanges

There are three main types of asbestos – blue, brown and white. Blue and brown asbestos are strongly linked with mesothelioma and have been banned in the UK since the late 1980s. White asbestos is now also thought to be harmful. The use of any 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 may cause gene changes (mutations) that lead to the growth of cancer. Some of the fibres 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. The families of people exposed to asbestos also have a higher risk of developing mesothelioma.

Highest risk groups

Mesothelioma is most common in men who have: 

• worked in manufacturing using asbestos
• used asbestos products, particularly in construction or engineering

Risks are particularly high for metal plate workers (mainly in shipbuilding) and carpenters.

The risk is higher in people exposed to asbestos before the age of 30. An estimated 1 out of 17 (nearly 6%) of British men born in the 1940s who worked in carpentry for more than 10 years before the age of 30 get mesothelioma.

People who worked as plumbers or mechanics also have an increased risk.

Asbestos was widely used in the years after the war (after 1945). Mesothelioma may not develop until 15 to 60 years after you have been exposed to asbestos, which is why we have seen an increase in cases in recent years. The number of people dying from mesothelioma each year is expected to peak around 2020 and then start to go down.

SV40 virus

Research has looked into a virus called SV40 (the SV stands for simian virus).

In people who have been exposed to asbestos, contact with the SV40 virus could make it more likely that they will develop mesothelioma. So SV40 is thought of as a possible co factor. But this is not completely clear.

Some people in the UK and elsewhere were exposed to polio vaccines contaminated with SV40 virus between 1955 and 1963.

Radiation

Pleural and peritoneal mesothelioma has been shown to develop after exposure to radiation from the chemical thorium dioxide (Thorotrast). This chemical was used until the 1950s in some x-ray tests.

Some research 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 happen only in a very small number of people.

Other chemicals

A mineral found in Turkey called erionite (a type of Zeolite fibre) has been shown to cause mesothelioma. 

Working as a painter has been linked with an increased risk of mesothelioma, possibly due to chemicals in the paint.

Other possible causes

Stories about potential causes of cancer are often in the media. It isn’t always clear which ideas are supported by good evidence.

You might hear about possible causes we haven’t included here. This is because there is no evidence about them or because the evidence isn’t clear.