Effects of smoking

Close-up of an open packet of cigarettes showing 'smoking kills' warning
Warnings such as 'Smoking kills' are used to deter people from smoking

Smoking can cause lung disease, heart disease and certain cancers.

Nicotine is the addictive substance in tobacco. It quickly reaches the brain and creates a dependency so that smokers become addicted.

Effects on the air passages

Sticky mucus in the lungs traps pathogens. The mucus is normally swept out of the lungs by the cilia on the epithelial cells lining the trachea, bronchi and bronchioles. However, cigarette smoke contains harmful chemicals that damage these cells, leading to a build-up of mucus and a smoker’s cough. Smoke irritates the bronchi, causing bronchitis.

Effects on the alveoli

Smoke damages the walls of the alveoli. The alveoli walls break down and join together, forming larger air spaces than normal. This reduces the efficiency of gas exchange, so people with the lung disease emphysema (a type of COPD or chronic obstructive pulmonary disease) carry less oxygen in their blood and find even mild exercise difficult.

Carbon monoxide

Carbon monoxide, CO, combines with the haemoglobin in red blood cells. This reduces the ability of the blood to carry oxygen, putting strain on the circulatory system and increasing the risk of coronary heart disease and strokes.

Lung cancer

Carcinogens are substances that cause cancer. Tobacco smoke contains many carcinogens, including tar. Smoking increases the risk of lung cancer, and cancer of the mouth, throat and oesophagus.

Sections of a healthy lung and a smoker's lung, showing tar deposits.
Section through a healthy lung and section through a smoker's lung, with tar deposits visible
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