Smoker's Lungs vs Healthy Lungs

Compared with healthy lungs, a smoker’s lungs have airways irritated by tobacco smoke, cilia that no longer clear mucus well, and, over years, lung tissue that can be destroyed. Health Canada attributes about 80% of COPD deaths to smoking. Some of the changes are permanent, but quitting lowers the risk and many symptoms ease within weeks.

What happens inside the lungs

Healthy lungs clear themselves. Tiny hair-like structures called cilia line the airways and sweep mucus and trapped particles upward so they can be coughed out. The lungs end in clusters of small air sacs where oxygen passes into the blood.

Tobacco smoke interferes at each of these steps. Health Canada explains that chemicals in the smoke irritate the cilia, and that this irritation impairs the body’s ability to clear mucus and foreign material from the lungs. Irritated airways also become inflamed, which is why a smoker’s cough and phlegm are so common.

Two conditions linked to long-term smoking

Chronic bronchitis. Health Canada describes it as inflammation of the main airways of the lungs that causes a long-term cough with phlegm.

Emphysema. Health Canada describes it as the gradual and irreversible damage of lung tissue, resulting in shortness of breath. The US National Heart, Lung, and Blood Institute adds that in COPD the air sacs lose their elasticity and the walls between many of them are destroyed, while the walls of the airways become thick and inflamed.

Together these conditions are called chronic obstructive pulmonary disease, or COPD. The World Health Organization defines COPD as a common lung disease that causes restricted airflow and breathing problems.

How strongly smoking is linked to COPD

Health Canada states that approximately 80% of deaths from COPD are due to smoking. The World Health Organization reports that tobacco smoking accounts for over 70% of COPD cases in high-income countries, and for 30 to 40% in low- and middle-income countries. These figures describe populations, not an individual’s risk.

Healthy lungs and smoker’s lungs side by side

	Healthy lungs	Lungs of a long-term smoker
Cilia	Sweep mucus and particles out of the airways	Irritated by smoke, so clearing mucus and foreign material is impaired
Airways	Open and thin-walled	Inflamed, with thick walls and a long-term cough with phlegm in chronic bronchitis
Air sacs	Elastic, with intact walls between them	In emphysema, tissue is damaged gradually and irreversibly; walls between air sacs can be destroyed
Breathing	Oxygen exchange without effort at rest	Shortness of breath as damage accumulates

What changes after quitting

Health Canada lists these milestones:

• Within 24 hours, the risk of a heart attack begins to drop.
• Within weeks, breathing gets easier and coughing lessens.
• After one year, the risk of coronary heart disease is half that of someone who smokes.
• After 10 to 15 years, the chance of getting cancer decreases by about half.

The UK’s NHS Wales gives a more detailed timeline, which is not Canadian but is consistent in direction: lung function improves by about 10% after 3 to 9 months, and the risk of lung cancer is halved after 10 years. Tissue lost to emphysema does not grow back, so the sooner someone quits, the more lung function is kept.

Second-hand smoke affects non-smokers too

Health Canada states that second-hand smoke causes premature death and disease in children and adults who do not smoke. Non-smokers living with a smoker have a 30% increased risk of lung cancer, heart disease and stroke. Health Canada estimates second-hand smoke causes nearly 1,000 deaths a year in Canada, and says there is no safe level of exposure.

Smoking in Canada today

The Canadian Tobacco and Nicotine Survey found that 10.9% of Canadians aged 15 and older currently smoked cigarettes in the 2022 survey period, ranging from 8.7% in British Columbia to 15.8% in New Brunswick. Health Canada estimates that about 48,000 people in Canada died from tobacco use each year based on 2017 data, and a later estimate is about 46,000 deaths in 2020.

What to do next

If you smoke and want help, see free quit-smoking help by province or work out how much you could save. To record your smoking history for a doctor, use the pack-year calculator. If you cough up blood, have chest pain or sudden trouble breathing, get medical help right away.