India, May 31 -- Mechanistically, the lungs function like a highly sophisticated air filter and gas-exchange system - every breath brings in oxygen and expels carbon dioxide (CO2). Tobacco smoke damages all the major defence mechanisms of the lungs. On average, a single puff of smoke contains more than 7,000 chemicals, of which at least 70 are known carcinogens. The primary culprits responsible for lung damage include tar, nicotine, carbon monoxide and various cancer-causing chemicals. Smoking begins to cause harmful effects within minutes to hours of exposure. Chronic cough may develop within days to months. Over time, smoking can lead to chronic obstructive pulmonary disease (COPD), including chronic bronchitis, characterised by persistent cough and phlegm production, and emphysema, which involves destruction of the alveolar walls and progressive breathlessness. Smoking also significantly increases the risk of developing lung cancer. Cigarettes, bidis, hookahs, cigars and even second-hand (passive) smoke exposure harm the lungs in similar ways. E-cigarettes (vaping) are also unsafe, as they can damage cilia, cause airway inflammation and lead to conditions such as 'popcorn lung'. Chewing tobacco affects the lungs indirectly and also increases the risk of cancers of the mouth and throat. The good news is that the lungs begin to recover after quitting tobacco. Health risks decline progressively over time. Although damaged alveoli do not fully regenerate, inflammation decreases, mucus clearance improves and the remaining healthy lung tissue functions more efficiently. In summary, tobacco transforms the lungs from a clean and efficient air-exchange system into an inflamed, mucus-filled and damaged organ. However, the lungs are remarkably resilient, and healing begins within hours of quitting. The longer a person smokes, the greater the risk of permanent damage. Yet it is never too late to quit. Stopping tobacco use at any age can add years to life and significantly reduce breathlessness. The author of this article is an MBBS, DNB, DM pulmonary and critical care medicine (PGI Chandigarh), FCCP, consultant pulmonologist, Jindal Clinics, Centre for Interventional Pulmonology and Sleep Medicine, SCO 21, Sector 20-D, Chandigarh. He can be contacted for appointments and consultations at 958-246-9429...