Two new ASH Wales/YouGov reports provide fresh evidence on tobacco and vape regulation and smoking-related inequalities in social housing in Wales.
Information / Smoking and cancer
Smoking and cancer
Tobacco smoke damages cells across the body, not just in the lungs. Smoking causes at least 16 types of cancer and is the biggest cause of cancer in the UK.
Stopping smoking lowers cancer risk. The sooner you stop, the more risk you avoid, yet people can benefit from quitting at any age.
Last reviewed: 24th September 2026
QUICK ANSWER
Smoking causes cancer throughout the body.
Cancer Research UK says tobacco is the biggest cause of cancer in the UK. Cigarette smoke contains thousands of chemicals, with at least 70 known to cause cancer.
What do you want to know?
Which cancers are linked to smoking?
Smoking causes at least 16 cancer types, including lung, bowel, mouth, throat, bladder, kidney, liver, pancreas, stomach and several others.
How does smoke cause cancer?
Cancer-causing chemicals in tobacco smoke damage DNA and make it harder for cells to repair that damage. Damage can build up over time.
Does light or social smoking count?
Yes. There is no safe level of smoking. Risk rises with the number of cigarettes smoked and the number of years someone smokes.
Does quitting reduce cancer risk?
Yes. Cancer risk falls after stopping smoking. Cancer Research UK says the sooner someone stops, the lower their risk becomes.
How smoking causes cancer
Tobacco smoke contains more than 5,000 chemicals. Cancer Research UK reports that at least 70 can cause cancer.
Those chemicals enter the lungs, then can reach tissues across the body. Some damage DNA directly. Others interfere with the systems cells use to repair DNA. Repeated damage can build up over time and lead to cancer.
Why the number of years matters
Cancer Research UK says both the amount smoked and the length of time someone smokes affect cancer risk. The number of years smoked has a particularly strong effect.
Cutting down can be a useful start, yet stopping completely gives the greatest reduction in risk.
Cancers caused by smoking
Cancer Research UK lists at least 16 cancer types caused by smoking:
nose and sinuses · mouth · pharynx · larynx · oesophagus · lung · breast · liver · stomach · kidney · pancreas · bowel · ovary · bladder · cervix · some types of leukaemia
Smoking causes more than 6 in 10 lung cancer cases in the UK. Existing ASH Wales guides cover lung cancer and oral cancer in more depth.
Second-hand smoke can cause cancer too
Breathing other people’s tobacco smoke can cause lung cancer. Keeping homes and cars smokefree protects people who do not smoke from tobacco smoke exposure.
There is no safe level of smoking
“Light”, occasional and social smoking still increase cancer risk. Smoking fewer cigarettes lowers exposure, yet it does not remove the risk.
Smoking fewer cigarettes
Reducing how much you smoke can be a useful first move, especially if it helps you reach a full quit attempt.
Stopping completely
Stopping gives cells a chance to recover from ongoing tobacco smoke exposure and lowers the chance of further DNA damage.
It is never too late
People who have smoked for many years can still lower their cancer risk by stopping. Cancer Research UK says everyone who smokes can benefit from quitting.
If you are worried about cancer symptoms
New, persistent or unexplained symptoms should be checked by a health professional. A symptom does not mean you have cancer, yet getting changes checked can help find the cause.
For lung symptoms, ASH Wales has a dedicated guide to cough, breathlessness, COPD and lung cancer risk.