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Risk, Smoking, and Prevention

Most lung cancer is preventable. We look honestly at smoking and the pack-year, at radon, asbestos, and air pollution, at why never-smokers still get it, and at the single most powerful thing anyone can do for their lungs: quit.

The biggest cause, by far

Around 8 in 10 lung cancer deaths are linked to cigarette smoking. Tobacco smoke carries dozens of substances that damage the DNA of airway cells; each cigarette is a small genetic insult, and over years the injuries accumulate until a cell breaks free. This is not about blame — nicotine is one of the most addictive substances known — but it is the central, honest fact of the disease. The risk rises with how much and how long a person has smoked.

To compare smoking histories fairly, doctors use the pack-year: packs smoked per day multiplied by years smoked. One pack a day for 20 years, or two packs a day for 10 years, both equal 20 pack-years. This single number summarises a lifetime of exposure and, as you will see, it is the threshold that decides who is offered screening.

Pack-years = (cigarettes per day ÷ 20) × years smoked

Example A: 15 cigarettes/day for 30 years
  = (15 ÷ 20) × 30 = 0.75 × 30 = 22.5 pack-years

Example B: 1 pack/day for 40 years, quit 5 years ago
  = 1 × 40 = 40 pack-years
  (former smoker; years-since-quitting also matters for screening)

A pack = 20 cigarettes. Higher pack-years = higher risk.
Working out pack-years from a smoking history.

Other risks worth naming

Smoking is the giant, but it is not alone. Secondhand smoke raises the risk of those who live with smokers. Radon — an odourless radioactive gas that seeps from the ground into homes — is the leading cause of lung cancer in people who never smoked. Asbestos fibres, breathed in old buildings or certain trades, damage the lung over decades and multiply risk dramatically when combined with smoking. And air pollution, especially fine particulate matter from traffic and burning fuel, adds a real if smaller share.

This is why some people who never touched a cigarette still develop lung cancer — and why never-smokers deserve to be taken seriously when they have lung symptoms. Family history, prior lung disease, and certain inherited gene changes also tilt the odds. Risk is a sum of many factors, not a single switch.

Quitting is never too late

The single most powerful action for the lungs is quitting smoking, and the benefit begins quickly. Risk starts falling within a few years of quitting and keeps falling for decades. Even someone who already has lung cancer heals better, tolerates treatment better, and lives longer after stopping. It is genuinely never too late.

  1. Set a quit date and tell someone — a plan you say out loud is harder to abandon.
  2. Ask about nicotine replacement (patches, gum) or prescription medicines that ease cravings and roughly double success rates.
  3. Expect a few hard weeks; cravings come in waves that pass in minutes, and each lapse is data, not failure.
  4. Use counselling or a quitline alongside medicine — combining behavioural and drug support works best.