When a cigarette burns, it does not simply deliver nicotine. Burning tobacco creates smoke — a mixture of more than 7,000 chemicals, about 70 of which can cause cancer (US Surgeon General, 2010). It is these chemicals, not nicotine, that are linked to most of the cancer, lung disease and heart disease attributed to smoking.
What actually reaches the lungs: tar, carbon monoxide, formaldehyde, benzene and dozens of other compounds. Tar settles in the airways; carbon monoxide binds to haemoglobin and makes it harder for blood to carry oxygen. That is where the morning cough, the heaviness on the stairs and slower wound healing come from.
Smoke does not stay with the smoker. Second-hand smoke is breathed in by people nearby — at home, in a car, on a stairwell. Opening a window or running an extractor reduces the smell, but does not remove the harmful substances.
Hence the main point: the harm comes first of all from burning. Stopping completely remains the lowest-risk option for health.
A useful question for tonight. How much of my day do I spend around smoke — my own or someone else's?
When to see a doctor. If a cough lasts more than three weeks, if you cough up blood, or if everyday exertion leaves you breathless — do not postpone the visit. For urgent symptoms call 103 or 112.