Knowing about long-term risks though may not be enough to nudge you to quit, especially if you're young. It can be hard to feel truly frightened by illnesses that may strike decades later.
So, if you carry on smoking, what could be the effects on your body?
Smoking is harmful because there are many ingredients in tobacco smoke that can harm your body.
The main health risks from smoking are lung cancer, heart disease and stroke. Smoking causes almost 90% of deaths from lung cancer, around 80% of deaths from COPD, and around 17% of deaths from heart disease.
However, smoking also affects other parts of the body too.
One study on smoking found that, on average, men who smoked throughout their lives died 10 years younger than those who had never smoked.
As well as nicotine, there are more than 4,000 chemicals in tobacco smoke, of which many are poisons. At least 60 of these chemicals cause cancer.
Among some of the most dangerous components are:
Tar: When you breathe in tobacco smoke, some tar is deposited in the lungs. Your lungs are lined with tiny hairs that help 'sweep' germs and other things out of your lungs. It is harder for these hairs to move if your lungs are coated with tar.
The tar in cigarette smoke contains chemicals called carcinogens, which encourage the development of cancer cells in the body.
Carbon monoxide: Carbon monoxide binds itself to haemoglobin in the bloodstream and prevents it from carrying enough oxygen around the body. This means that someone who smokes is likely to get out of breath and get tired more easily.
Eventually, you can get a lung disease called chronic obstructive pulmonary disease (COPD). If you have this, it gets harder and harder to breathe.
Oxidant gases: Oxidant gases are gases that react with oxygen. They make blood more likely to clot, increasing the risk of heart attack or stroke.
Benzene: Exposure to benzene can cause cell damage at the genetic level, and has been linked to a range of different cancers, such as leukaemia and kidney cancer.
Benzene used to be added to petrol, but the practice was stopped because of health concerns.
One of the most dangerous effects of smoking is the increased risk of lung cancer.
Chemicals in tobacco smoke damage cells in the lungs and these then become cancer cells.
The chances of developing lung cancer are affected by how much an individual smokes and for how long.
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