Why is smoking so harmful?

Most people know that smoking is bad for us but why is it so damaging?

Smoking is to blame for nearly one fifth of all cancer cases and more than 1 in 4 cancer deaths in the UK are because of smoking. Most people know that smoking can cause lung cancer, but did you know that smoking can also increase the risk of at least 13 other types of cancers…? These are: mouth, upper throat, voice box (larynx), food pipe (oesophagus), liver, pancreas, stomach, kidney, bowel, bladder, leukaemia, ovaries, and cervix.

You may wonder what smoking has to do with all these other cancer types… The thing is that when people smoke cigarettes, there are chemicals in the smoke that get into the blood stream and because the blood circulates around the whole of our body, so do these chemicals. And because these chemicals travels to all parts of our body, they can cause damage in all these places. Some of the chemicals in cigarette smoke can cause cancer by damaging our DNA. It’s our DNA that contain the genes that carry the instructions for telling our cells what they need to do in order for the body to grow and work properly. (You can read more about how DNA and genes and cancer are connected in our section called “Genetics of cancer”). So if the genes in our DNA are damaged by the chemicals in the cigarette smoke, the damage can over time get so severe that what used to be healthy body cells can become cancerous. That means they start growing out of control and the damaged cells can no longer do their jobs.

So number one is that cigarette smoke can damage the control centre in our body cells (i.e. genes in our DNA). A second way that smoking can cause cancer to develop is that other chemicals in cigarettes interfere with the ‘repair system’ in our cells so that cells that get damaged by the smoke become harder for the body to repair. A third way is that chemicals can also affect our immune system and make it harder for the immune system to clean up the harmful chemicals and to kill cancer cells that starts developing. So basically, if the harmful chemicals keep coming into the body and damage our cells, the body’s ‘cleaning and repair system’ can be overwhelmed and the buildup of damage in our body cells can lead to cancer developing.

If you smoke and want to quit you may want to check out the NHS Under-18s guide to quitting smoking.

Page updated 13 July 2016