Smoking and Lung Disease: COPD, Emphysema and Lung Cancer
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named review panel.
Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Key concept
Cigarette smoke contains tar (a carcinogen that damages cilia and causes lung cancer), nicotine (an addictive drug that raises heart rate and blood pressure), and carbon monoxide (which binds to haemoglobin, reducing oxygen-carrying capacity). Smoking causes chronic obstructive pulmonary disease (COPD), emphysema and lung cancer.
The smoking question is almost guaranteed to appear in some form. Key substances are tar, nicotine and carbon monoxide: each with specific harmful effects. Do not just say "smoking is bad for you"; name each substance and its specific consequence.
Harmful substances in cigarette smoke
Substance
Specific harmful effect
Tar
Carcinogen that triggers mutations in lung cells, potentially causing lung cancer. Also damages and paralyses cilia lining the airways.
Nicotine
Addictive stimulant that increases heart rate and blood pressure. Makes it difficult to stop smoking. Narrows blood vessels.
Carbon monoxide
Binds irreversibly to haemoglobin, forming carboxyhaemoglobin. This reduces the oxygen-carrying capacity of the blood.
Irritant particles
Stimulate excess mucus production in the airways and contribute to chronic bronchitis.
Emphysema and COPD
When tar damages and paralyses cilia, mucus and trapped pathogens are no longer swept away from the lungs. Infections become more frequent. The repeated inflammation and infection damage the delicate alveolar walls. In emphysema, alveolar walls break down, creating fewer, larger air spaces. This reduces the total surface area for gas exchange and makes breathing less efficient.
Patients with emphysema struggle to get enough oxygen into their blood and find it hard to exhale fully. Chronic bronchitis (persistent inflammation and mucus production in the bronchi) combined with emphysema is called chronic obstructive pulmonary disease (COPD).
Lung cancer
Tar is a carcinogen: it causes mutations in the DNA of lung cells. If mutations occur in genes controlling cell division, cells may divide uncontrollably, forming a tumour. If the tumour is malignant, it invades surrounding tissue and may spread to other parts of the body (metastasis).
Lung cancer is strongly linked to smoking: the longer and more heavily a person smokes, the greater their risk. Stopping smoking at any stage reduces the risk compared to continuing, though it remains higher than for someone who never smoked. Passive smoking (inhaling other people's smoke) also increases lung cancer risk.
Try a focused question (3 marks)
Explain how smoking reduces the oxygen-carrying capacity of the blood.
Show the answer and marking guidance
Cigarette smoke contains carbon monoxide.
Carbon monoxide binds to haemoglobin in red blood cells, forming carboxyhaemoglobin.
This prevents haemoglobin from carrying oxygen (forming oxyhaemoglobin), reducing the total amount of oxygen the blood can transport.
Original Cambridge-style practice written for this site. It is not an official Cambridge past-paper question.
Common mix-ups to avoid
Check these points against your own answer before moving on.
Saying smoking destroys red blood cells: carbon monoxide binds to haemoglobin, it does not destroy the cells.
Confusing nicotine (addictive) with tar (carcinogenic): each has a specific effect.
Describing emphysema as infection rather than destruction of alveolar walls reducing surface area.
Saying carbon monoxide reduces oxygen in the lungs rather than in the blood.