How smoking causes cancer

Smoking is by far the biggest preventable cause of cancer. Thanks to years of research, the links between smoking and cancer are now very clear. Smoking accounts for more than 1 in 4 UK cancer deaths, and nearly a fifth of all cancer cases.

Tobacco was responsible for more than 100 million deaths worldwide in the 20th Century. The World Health Organisation has estimated that, if current trends continue, tobacco could cause a billion deaths in the 21st Century.

The good news is that most of these deaths are preventable, by giving up smoking. Speak to your GP or pharmacist, or visit NHS Smokefree for free advice and support.

Which cancers are caused by smoking?

cancers caused by smoking

Smoking causes more than 4 in 5 cases of lung cancer. Lung cancer has one of the lowest survival rates of all cancers, and is the most common cause of cancer death in the UK.

Smoking also increases the risk of at least 13 other cancers including cancers of the larynx (voice box), oesophagus (gullet), mouth and pharynx (throat), bladder, pancreas, kidney, liver, stomach, bowel, cervix, ovary, nose and sinuses and some types of leukaemia. There is also some evidence that smoking could increase the risk of breast cancer.

More information about different cancer types.

Why is smoking so addictive?

Smoking is very addictive because tobacco contains a powerful drug called nicotine. Cigarettes are deliberately designed to give you a fast nicotine hit. It takes less than 20 seconds for the drug to reach your brain from inhaled cigarette smoke.

Nicotine causes addiction in much the same way as heroin or cocaine. It is just as addictive as these ‘harder’ drugs.

This is the reason why most smokers say they want to quit but find it so difficult. If you start smoking, you may find it very hard to stop later on.

What parts of your body does smoking affect?

Chemicals in cigarette smoke enter our blood stream and can then affect the entire body. This is why smoking causes so many diseases, including at least 14 types of cancer, heart disease and various lung diseases.

How does smoking cause cancer?

The main way that smoking causes cancer is by damaging our DNA, including key genes that protect us against cancer. Many of the chemicals found in cigarettes have been shown to cause DNA damage, including benzene, polonium-210, benzo(a)pyrene and nitrosamines.

This is already bad news, but it’s made worse by other chemicals in cigarettes. For example chromium makes poisons like benzo(a)pyrene stick more strongly to DNA, increasing the chances of serious damage. And chemicals like arsenic and nickel interfere with pathways for repairing damaged DNA. This makes it even more likely that damaged cells will eventually turn cancerous.

How long does it take for smoking to cause cancer?

It usually takes many years, or decades, for the DNA damage from smoking to cause cancer. Our bodies are designed to deal with a bit of damage but it’s hard for the body to cope with the number of harmful chemicals in tobacco smoke.

Each cigarette can damage DNA in many lung cells, but it is the build up of damage in the same cell that can lead to cancer. However research has shown that for every 15 cigarettes smoked there is a DNA change which could cause a cell to become cancerous. This is why it’s better to give up smoking sooner rather than later.

How does smoking weaken the body’s defences?

Smokers are also less able to handle toxic chemicals than those with healthy lungs and blood.

We all have special cleaner proteins called ‘detoxification enzymes’ that mop up harmful chemicals and convert them into harmless ones. But the chemicals in smoke, such as cadmium, can overwhelm these cleaners.

Other chemicals like formaldehyde and acrolein kill cilia, the small hairs that clean toxins from your airways.

Cigarette smoke also impacts the immune system – increasing cells which can encourage tumour growth in the lungs and suppressing the ones which kill cancer cells.

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