How does smoking cause cancer?

  • Smoking is the biggest preventable cause of cancer in the UK, and worldwide.
  • Harmful chemicals in cigarette smoke affect the entire body – not just our lungs. And smoking causes at least 15 different cancer types.
  • There is no safe level of smoking - stopping completely is the best thing you can do for your health, and there are many support and quitting options available.


What’s my cancer risk from smoking?

Our bodies are designed to deal with a bit of damage, but they often can’t cope with the amount of harmful chemicals in tobacco smoke.

Both the amount you smoke, and the length of time you’ve been smoking for affect your cancer risk.

The more cigarettes you smoke a day, the higher your risk of cancer, so reducing the number of daily cigarettes you smoke can be a good first step.

But the number of years you spend smoking affects your cancer risk most strongly. So it’s important to make a plan to stop smoking completely.

Remember, the sooner you stop, the lower your risk of cancer. Everyone who smokes can benefit from stopping, and it’s never too late to stop- even if you’ve smoked for years . Speak to your GP or pharmacist, or visit NHS Smokefree for free support to help you stop for good.

Find out more about how to stop smoking.


Smoking, DNA damage and cancer

DNA is found in all our cells and controls how they behave. Even one cigarette can damage DNA.

  1. Cigarette smoke releases over 5000 chemicals and many of these are harmful - we know at least 70 can cause cancer.
  2. The harmful chemicals enter our lungs and spread around the entire body.
  3. Chemicals from cigarettes damage DNA.
  4. Cigarette chemicals make it harder for cells to repair any DNA damage. They also damage the parts of DNA that protect us from cancer.
  5. It’s the build-up of DNA damage in the same cell over time that leads to cancer.


Smoking is the leading cause of lung cancer

Smoking causes more than 7 in 10 lung cancer cases in the UK. Lung cancer is the most common cause of cancer death.

People who smoke sometimes have a cough. But coughing can also be a sign of lung cancer, as well as other conditions. So if you have any doubt, or a cough or other symptom that’s new, changing, or won’t go away, talk to your doctor.

And remember it’s never too late to stop smoking and reduce your lung cancer risk. The best way to reduce your risk is to stop smoking completely. Have a read of our tips and support to help you quit smoking for good.


What other types of cancer does smoking cause?

The link between smoking and cancer is very clear. It causes at least 15 different types of cancer, including two of the most common, lung and bowel cancer.

Other cancers caused by smoking include mouth, pharynx (upper throat), nose and sinuses, larynx (voice box), oesophagus (food pipe), liver, pancreas, stomach, kidney, ovary, bladder, cervix, and some types of leukaemia.

Smoking causes other diseases too, such as heart disease and various lung diseases.



Light, occasional and social smoking also cause cancer

There is no safe level of smoking.

Smoking 1-10 cigarettes per day increases the risk of getting smoking-related cancers and other diseases.

Even smoking less than one cigarette per day is harmful. One study found that it significantly increases the risk of dying early compared with people who have never smoked.

The best thing you can do for your health is to stop smoking completely. Find out about how to stop smoking.


Brown, K. F. et al. The fraction of cancer attributable to modifiable risk factors in England, Wales, Scotland, Northern Ireland, and the United Kingdom in 2015. Br. J. Cancer. 118, 1130–1141 (2018).

Cancer Research UK. Lung cancer statistics. [Accessed March 2021]

International Agency for Research on Cancer. Personal Habit and Indoor Combustion: Tobacco Smoking. 100 E, 377–504 (2012).

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