Smoking and Cancer Risk: Which Cancers Are Linked and by How Much

Lung cancer gets most of the attention when smoking and cancer are discussed. But the CDC says tobacco use can cause cancer almost anywhere in your body. Understanding the full picture changes how you think about the stakes of quitting.

The Overall Cancer Burden

In the US, the National Cancer Institute says smoking and exposure to tobacco smoke cause about 480,000 premature deaths a year, about 36% of them from cancer. The CDC says smoking cigarettes and breathing other people's smoke cause almost 9 of every 10 lung cancer deaths.

The Carcinogen Mechanism

The National Cancer Institute counts at least 69 cancer-causing chemicals in tobacco smoke; see the cigarette chemicals list. The main groups:

Polycyclic aromatic hydrocarbons (PAHs): including benzo[a]pyrene. These bind to DNA and, if the damage isn't repaired, can cause mutations — including in the TP53 tumour-suppressor gene, which is commonly mutated in smokers' lung tumours.

Tobacco-specific nitrosamines (NNK, NNN): strong carcinogens found only in tobacco.

Polonium-210: a radioactive element in smoke.

Formaldehyde and acetaldehyde: reactive aldehydes, both on the NCI's list.

Cancer Risk by Site

The CDC and the National Cancer Institute list the cancers smoking causes: lung, mouth and throat, voice box (larynx), oesophagus, stomach, pancreas, liver, kidney, bladder, colon and rectum, cervix, and acute myeloid leukaemia (NCI). The size of the risk varies a lot by site and by how much and how long someone smoked. We give a number only where a health body publishes one.

Lung Cancer

The dominant smoking-related cancer. The CDC says people who smoke are 15 to 30 times more likely to get or die from lung cancer than people who do not smoke, and that even a few cigarettes a day or occasional smoking raises the risk.

Risk after quitting: the NHS says your risk of dying from lung cancer halves after 10 years; the CDC and the 2020 Surgeon General's report put the halving at 10 to 15 years. It keeps falling but stays above a never-smoker's even after 30 years.

Mouth, Throat and Voice Box

Smoke comes into direct contact with these tissues. Drinking alcohol as well raises the risk further. The CDC says the added risk of mouth, throat and voice-box cancer drops by half 5 to 10 years after quitting, and to close to a non-smoker's at 20 years.

Oesophagus, Bladder and Kidney

The CDC says risk of these cancers decreases about 10 years after quitting. Bladder cancer is linked to carcinogens that are filtered out through the urine.

Pancreas

The CDC says risk of pancreatic cancer drops to close to a non-smoker's about 20 years after quitting.

Cervix

The CDC says the added risk of cervical cancer drops by about half 20 years after quitting.

Stomach, Liver, Colon and Rectum, and Leukaemia

All are on the CDC's and the NCI's lists of cancers smoking causes. Leukaemia risk is linked to benzene, a known cause of leukaemia found in smoke.

How Quickly Does Cancer Risk Drop After Quitting?

The National Cancer Institute says that within a few years of quitting, people have lower risks of cancer than if they had continued to smoke, and that the benefit is greatest for people who quit younger. The CDC's timeline, compared with continuing to smoke:

Cancer	After quitting (CDC)
Mouth, throat, voice box	Added risk halves at 5–10 years; close to a non-smoker's at 20 years
Lung	Added risk halves at 10–15 years
Bladder, oesophagus, kidney	Risk decreases at about 10 years
Pancreas	Close to a non-smoker's at about 20 years
Cervix	Added risk halves at about 20 years

Source: CDC, "Benefits of Quitting Smoking". We could find no source for the claim that pre-cancerous cells are "cleared" after quitting, so it isn't here.

Already diagnosed? The NCI says that for some cancers, quitting at the time of diagnosis may reduce the risk of dying by 30% to 40%, and that quitting helps the body heal and respond to treatment. It's worth quitting at any point.

The Dose-Response Relationship

Cancer risk rises with both how many cigarettes a day and how many years someone smoked. The CDC notes that even a few cigarettes a day or occasional smoking increases lung cancer risk — there is no safe level.

FAQ

What percentage of smokers get cancer?

We couldn't find a reliable single figure to give you — lifetime risk depends heavily on how much and how long someone smoked, and on when they quit. What is clear: the CDC says smokers are 15 to 30 times more likely to get or die from lung cancer than non-smokers, and the NCI says about 36% of the premature deaths smoking causes in the US are from cancer. Not every smoker gets cancer, but the risk builds with every year of smoking.

What is the biggest cancer risk from smoking?

Lung cancer — the CDC puts smokers' risk at 15 to 30 times a non-smoker's, and smoking causes almost 9 in 10 lung cancer deaths. But smoking causes cancers in at least a dozen other parts of the body, and together they add up.

Does switching to e-cigarettes reduce cancer risk?

Probably, for smokers who switch completely, though it hasn't been measured directly. E-cigarettes don't burn anything, and the UK's 2022 evidence review found vapers' exposure to toxicants linked to cancer far lower than smokers'. But the NHS says vaping hasn't been around long enough to know its long-term risks. Stopping all nicotine products remains the safest option.