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Risks and causes

Find out about the possible causes chronic myeloid leukaemia (CML).

We don’t know what causes most chronic myeloid leukaemia. But there are some factors that may increase your risk of developing it.

Having any of these risk factors does not mean that you will definitely develop cancer.

CML is more common in men than women. As people get older their risk of CML increases. As CML is rare, the risk is still small.


We know radiation can increase risk because atomic bomb survivors had an increased risk of leukaemia. There’s a 20 year study of the workers who clean up after the Chernobyl nuclear power plant accident in 1986. It shows that even at low doses of radiation there’s an increased risk of all types of leukaemia. 

If you have had radiotherapy for another cancer previously, this could increase your risk of developing CML. This risk is very small, compared to the benefit of radiotherapy treating the cancer.

Low immunity

Studies have shown that people with low immunity due to HIV or AIDS are 3 times more likely to develop leukaemia than the general population.

People who take drugs that lower their immunity after an organ transplant are twice as likely to develop leukaemia.

Ulcerative colitis or Crohn's disease

Studies have shown that people with inflammatory bowel conditions, such as ulcerative colitis or Crohn's disease, have a higher risk of CML compared to the general population.


A review has looked at the evidence of men who are exposed to pesticides as part of their work (for example, farmers or agricultural workers) to find out if the exposure increases their risk of CML. This review found that the men had a 40% increase in their risk of CML compared to the general population.


Contact with the chemical benzene for some years may increase CML risk. Benzene is one of the chemicals in petrol. It’s also a solvent used in the rubber industry. Most people in the UK wouldn't come into contact with enough benzene for it to increase their risk at all.

Body weight

A combined review of 4 published studies shows the risk of CML increases by about a quarter (25%) for people who are overweight or obese. This is compared to people with a healthy bodyweight.

Electromagnetic fields

Electromagnetic fields are often talked about as a possible risk factor for developing leukaemia. We are all exposed to electromagnetic radiation.

No increase in the risk has ever been found in adults who are exposed to the normal background levels people generally have in their own homes.

Other possible causes

Stories about potential causes are often in the media and it isn’t always clear which ideas are supported by evidence. There might be things you have heard of that we haven’t included here. This is because either there is no evidence about them or it is less clear.

For detailed information on CML risks and causes

Information and help

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