Cigarettes contain many dangerous chemicals. Some occur naturally in tobacco, and others are formed when processing tobacco into cigarettes. When a cigarette is burnt, it releases thousands more chemicals in tobacco smoke.

Many of these chemicals are harmful to people who smoke and also to people who breathe in second-hand smoke. We know that at least 70 of these chemicals cause cancer.

Roll-up tobacco cigarettes are not safer. They contain the same cancer-causing chemicals as manufactured cigarettes. Smoking using a filter, and smoking ‘low-tar’ or ‘light’ cigarettes also doesn’t reduce the risk of disease from smoking.

Cigarettes are the most common type of tobacco used in the UK. But tobacco comes in many different forms. These include cigars, pipes, shisha and smokeless tobacco, such as paan or snus. All forms of tobacco are addictive and cause cancer, so there is no safe way to use tobacco.
What’s in tobacco smoke?
Tar
Tar is a sticky-brown substance that collects in the lungs when tobacco smoke is breathed in. It can stain fingers and teeth a yellow-brown colour.

Tar contains cancer-causing chemicals. It also increases the risk of lung diseases, such as emphysema and chronic obstructive pulmonary disease (COPD).
Carbon Monoxide
Tobacco smoke contains a poisonous gas called carbon monoxide. You can’t smell it, see it or taste it.

Carbon monoxide stops the blood from carrying as much oxygen. This means organs of the body don’t get the amount of oxygen they need, and the heart must work harder to supply the body with oxygen. This increases the risk of heart disease and stroke.
Nicotine
Nicotine is a very addictive chemical. Most people who smoke don’t continue to do so out of choice – it’s because they have a nicotine addiction.

Nicotine does not cause cancer. People have used nicotine replacement therapy (NRT) safely for many years to help them stop smoking. NRT helps people deal with cravings and nicotine withdrawal symptoms.
Over 5,000 different chemicals
Tobacco smoke is made up of thousands of chemicals. These include toxic metals, poisonous gases and chemicals that are known to cause cancer.

The chemicals in tobacco smoke mix when they are inhaled together and cause greater damage to the body. Some chemicals help other cancer-causing chemicals to damage the cells of the body.
How do chemicals in tobacco smoke lead to cancer?
Chemicals in tobacco smoke damage DNA.
Our DNA controls how our cells grow and behave. DNA damage can cause cells to behave in ways they’re not supposed to, which can lead to cancer.

Chemicals in tobacco smoke damage DNA. This includes the parts of DNA that protect our cells from becoming cancerous. There are also chemicals in tobacco smoke that stop our cells from repairing damaged DNA. This makes it even more likely that cancer will develop.