3 November 2026 Punjab Khabarnama Bureau : Smoking is one of the leading causes of lung cancer worldwide. Every cigarette exposes the lungs to a mixture of toxic and cancer-causing chemicals that can gradually damage healthy cells, alter their DNA and disrupt the body’s natural defence mechanisms. Over time, these changes can allow abnormal cells to multiply uncontrollably and develop into cancer.
According to the World Health Organization (WHO), lung cancer was responsible for an estimated 2.5 million new cases and 1.8 million deaths worldwide in 2022. Tobacco smoking remains its primary risk factor, although air pollution, secondhand smoke and occupational exposures also contribute to the disease.
Understanding how smoking damages the lungs helps explain why the risk increases with continued tobacco use and why quitting is important at every stage of life.
What Happens When Cigarette Smoke Enters the Lungs?
Cigarette smoke contains thousands of chemicals, including dozens known to cause cancer. These include tobacco-specific nitrosamines, polycyclic aromatic hydrocarbons, benzene and other toxic substances.
When a person inhales cigarette smoke, these chemicals enter the respiratory system and reach the delicate tissues lining the airways and lungs. Some harmful substances can also enter the bloodstream and travel to other organs.
The lungs have a natural cleaning system made up partly of tiny hair-like structures called cilia. These structures help remove mucus, dust and harmful particles from the respiratory tract.
Smoking damages these cilia and reduces their ability to clear harmful substances. As a result, toxic particles and mucus can accumulate in the airways, increasing irritation and inflammation.
How Smoking Damages DNA
One of the most important ways smoking contributes to lung cancer is through DNA damage.
DNA contains the instructions that control how cells grow, divide and repair themselves. Certain chemicals in tobacco smoke can attach themselves to DNA, forming structures known as DNA adducts.
These changes can interfere with the normal process of copying genetic information when cells divide. If the damage is not repaired correctly, permanent genetic mutations can develop.
Some mutations affect genes responsible for controlling cell growth and preventing abnormal cells from multiplying. Changes in genes such as TP53 and KRAS have been associated with smoking-related lung cancers.
The accumulation of several genetic changes over time can transform a normal lung cell into a cancerous one.
Why Damaged Cells Start Growing Uncontrollably
Healthy cells follow a carefully regulated process. They grow when required, divide to replace damaged or old cells and undergo programmed cell death when they become too damaged.
Tobacco smoke can interfere with these protective mechanisms.
Some harmful chemicals damage genes that normally act as brakes on cell growth. Others activate biological pathways that encourage abnormal cells to survive and multiply.
When these protective systems stop functioning properly, damaged cells may continue dividing instead of being removed by the body.
Over many years, additional genetic and cellular changes can allow these abnormal cells to form a tumour. The tumour may grow into surrounding lung tissue and, in advanced cases, spread to other parts of the body.
Does Every Smoker Develop Lung Cancer?
Not everyone who smokes develops lung cancer, but smoking significantly increases the risk. The likelihood of developing the disease generally increases with the number of cigarettes smoked and the duration of smoking.
Other factors, including genetic susceptibility, age, exposure to air pollution and workplace chemicals, can also influence an individual’s risk.
People who have never smoked can also develop lung cancer. Exposure to secondhand smoke, radon, asbestos, diesel exhaust and outdoor or household air pollution are among the recognised risk factors.
The WHO identifies tobacco smoking as the primary risk factor, but lung cancer is not exclusively a smokers’ disease.
Secondhand Smoke Also Poses a Risk
The health effects of tobacco smoke are not limited to people who actively smoke. People who regularly breathe in smoke from cigarettes smoked by others are exposed to many of the same harmful chemicals.
This is known as secondhand smoke exposure. It can increase the risk of lung cancer in non-smokers, including people living with smokers and those exposed to tobacco smoke at workplaces or other public settings.
Children and other vulnerable individuals can also be affected by exposure to tobacco smoke in indoor environments.
Can Quitting Smoking Reduce the Risk?
Quitting smoking is one of the most important steps a person can take to reduce the risk of lung cancer and other serious diseases.
The body begins recovering after tobacco exposure stops. Over time, lung function and the natural cleaning mechanisms of the airways can improve, although some damage may not be completely reversible.
The risk of lung cancer also decreases after quitting compared with continuing to smoke. However, it does not immediately return to the level of someone who has never smoked.
People who find it difficult to quit can seek medical guidance, counselling and evidence-based cessation support. Nicotine replacement therapy and certain prescribed medicines may help manage withdrawal symptoms and reduce cravings.
Symptoms That Should Not Be Ignored
Lung cancer may not cause noticeable symptoms during its early stages. As the disease progresses, some people may experience:
- A persistent cough that does not improve.
- Coughing up blood.
- Chest pain or discomfort.
- Shortness of breath.
- Unexplained weight loss.
- Persistent tiredness.
- Repeated chest infections.
These symptoms can occur due to conditions other than cancer, but persistent or unusual symptoms should be evaluated by a healthcare professional.
Doctors may recommend imaging tests, such as a CT scan, followed by further investigations or a biopsy when necessary. Screening with low-dose CT may also be considered for eligible people at high risk, depending on clinical guidelines and individual circumstances.
Conclusion
Smoking does not cause lung cancer overnight. It gradually exposes lung cells to harmful chemicals that damage DNA, interfere with normal cell functions and increase the possibility of cancerous changes.
Although genetics and environmental exposures also influence lung cancer risk, avoiding tobacco and quitting smoking remain important ways to prevent the disease. The earlier a person stops smoking, the sooner they can begin reducing the health risks associated with tobacco exposure.