How does smoking cause cancer?

  • Smoking is the biggest preventable cause of cancer in the UK
  • Chemicals in cigarette smoke enter our blood stream and can then affect the entire body, this is why smoking causes so many different types of cancer
  • Stopping smoking completely is the best thing you can do for your health, and there are many ways you can do it

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.

What types of cancer does smoking cause?

The link between smoking and cancer is very clear. It causes at least 15 different types of cancer.

Smoking causes around 7 in 10 lung cancer cases in the UK, which is also the most common cause of cancer death.

It causes other cancers including mouth, pharynx (upper throat), nose and sinuses, larynx (voice box), oesophagus (food pipe), liver, pancreas, stomach, kidney, bowel, ovary, bladder, cervix, and some types of leukaemia.

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

What’s my cancer risk from smoking?

The number of years you spend smoking affects your cancer risk most strongly. For example, smoking one pack a day for 40 years is even more dangerous than smoking two packs a day for 20 years.

So, it’s never too late to stop. Speak to your GP or pharmacist, or visit NHS Smokefree for free support to help you stop for good.

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

Research has shown that for every 15 cigarettes smoked, there is a DNA change which could cause a cell in the body to become cancerous. But the best way to reduce your risk is to stop smoking completely.

Find out more about how to stop smoking here.

There are many ways that the combination of harmful chemicals in tobacco smoke can cause damage in the body:

  • Some have been found to damage DNA.

The DNA in all our cells controls how they behave. If DNA is damaged, things can go wrong. For example, a chemical, benzo(a)pyrene causes damage specifically at a part of the DNA that normally protects our cells from cancer.

  • This is already bad news for our bodies, but the cocktail of chemicals in tobacco smoke is even more dangerous as a mix.

For example, chromium can make other harmful chemicals stick more strongly to DNA. So, it is even more likely that damaged cells will eventually turn cancerous.

  • Chemicals in tobacco smoke harm the cleaning system that our bodies use to remove toxins, so smokers are less able to handle toxic chemicals than those with healthy lungs and blood.

Each cigarette can damage DNA, and it is the build up of damage in the same cell that can lead to cancer.
 

  • Alcohol is another well-established cause of cancer. But, together, the cancer-causing effects of alcohol and tobacco are worse than for either one of them by itself.
  • Studies show those who smoke and drink alcohol are at a higher risk of cancer of the mouth and upper throat.

A review found that people who only drank alcohol increased their risk by a third compared to non-drinkers. Whereas those who smoke or used to smoke, and also drank alcohol were around 3 times more likely to develop cancer than those who did neither.

  • There are multiple ways the harm from smoking cigarettes and drinking alcohol may combine to increase a person’s risk of cancer.

Alcohol may make it easier for harmful chemicals from tobacco smoke to pass through the mouth and throat into the blood stream. Alcohol may also change how the toxic chemicals from tobacco smoke are broken down in the body, making them even more harmful.  

Find out more about alcohol as a cause of cancer here

Smokeless tobacco includes many products which can be used in different ways - chewed (‘dry chewing tobacco’), sucked (‘moist oral tobacco’) or inhaled (‘nasal snuff’).

Smokeless tobacco also causes cancer. For example, users can take in similar, if not higher, levels of cancer-causing tobacco-specific nitrosamines (TSNAs) than cigarette smokers.

‘Betel quid’ or ‘paan’ is a mixture of betel nut (or areca nut), slaked lime, herbs and spices, wrapped in betel leaf and is most popular in South Asian communities. Betel nut itself can cause cancer, so chewing betel quids can cause mouth cancer, even if no tobacco is added.

Snus is a moist powder tobacco product originating in Sweden. It is banned in most European countries, including the UK. Snus is processed so that it contains lower levels of harmful, tobacco-specific chemicals. Unlike other forms of smokeless tobacco, evidence linking snus use to cancer is unclear, but it has been linked to some types, particularly pancreatic cancer.

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. Cruk.org/health-professional/cancer-statistics/statistics-by-cancer-type/lung-cancer [Accessed November 2018]

Flanders, W. D. et al. Lung cancer mortality in relation to age, duration of smoking, and daily cigarette consumption: results from Cancer Prevention Study II. Cancer Res. 63, 6556–6562 (2003).

Gandini S, Botteri E, Iodice S,  et al. Tobacco smoking and cancer: a meta-analysis. Int J Cancer.  1, 155–164 (2008).

International Agency for Research on Cancer. Smokeless Tobacco and Some Tobacco-specific N -Nitrosamines. Vol 89 (2007).

International Agency for Research on Cancer. Tobacco smoke and involuntary smoking. Vol 83, 1–1413 (2004).
 

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