IGCSE Biology glossary
Tar
Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Definition
A sticky brown substance in tobacco smoke that accumulates in the lungs, damaging cilia on airway cells and increasing mucus production. Tar also contains carcinogens that can cause mutations in lung cells, leading to lung cancer.
What to include in an exam answer
Link tar to two effects: damage to cilia (leading to chronic bronchitis/smoker's cough as mucus builds up) and carcinogenic effect (causing lung cancer). These are separate marking points.
Example in context
Explain how tar in cigarette smoke can lead to lung cancer (2 marks): Tar contains carcinogens that cause mutations in the DNA of lung cells. The mutations may lead to uncontrolled cell division, forming a tumour (lung cancer).
Related syllabus topic
Gas exchange in humans