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Dangers of smoking
Tobacco smoke harms nearly every organ and is linked to cancer, cardiovascular disease and respiratory disease. Learn what strong evidence says and where uncertainty remains.
Nicotine, carbon monoxide, particles and the mixture called tar play different roles. Here is how to read the chemical numbers without losing the important distinction: smoke is a changing mixture created by combustion.
Dangers of smoking · Evidence guideIs nicotine the main cause of smoking-related cancer?Nicotine is central to dependence, while most smoking-related cancer risk comes from the toxic mixture produced when tobacco burns. That distinction does not mean nicotine is harmless.
Dangers of smoking · Evidence guideHow does smoking affect lung clearance and airflow?Smoke can impair the airway’s particle-clearing system, promote inflammation and contribute to narrowing or damage. Cough, mucus, airflow limitation and a medical diagnosis are related concepts, but they are not interchangeable.
Dangers of smoking · Evidence guideHow does smoking affect the heart and blood vessels?Smoking is not only a lung exposure. Smoke constituents enter the bloodstream and are linked with blood-vessel damage, inflammation, clotting changes and plaque formation, increasing population-level risk of heart disease and stroke.
Dangers of smoking · Evidence guideIs occasional or social smoking really low risk?Smoking less often usually means less cumulative exposure than heavy daily smoking, but it does not mean safe exposure. Non-daily smoking is associated with harm, and cardiovascular effects are not proportional to cigarette count in a simple straight line.
Dangers of smoking · Evidence guideAre ‘light,’ low-tar or filtered cigarettes safer?No combustible cigarette has been shown safe. Machine-measured tar or nicotine yields do not reliably describe what a person inhales, because puff size, frequency, ventilation holes and compensating behavior can change exposure.
Dangers of smoking · Evidence guideCan open windows, fans or air purifiers remove secondhand smoke?They may reduce odor or some airborne particles, but they do not eliminate secondhand-smoke exposure or make smoking indoors safe. The effective protection is a fully smoke-free indoor space and vehicle.
Dangers of smoking · Evidence guideWhat is thirdhand smoke, and what can the evidence show?Thirdhand smoke is tobacco-related contamination that remains on surfaces, in dust and in materials after visible smoke has cleared. Its chemistry and exposure routes are documented; the size of specific long-term human health risks is less certain than for active or secondhand smoke.
Dangers of smoking · Evidence guideHow does smoking affect gums, teeth and the mouth?Smoking is linked with gum disease, tooth loss, delayed oral healing and cancers of the mouth and throat. Tooth staining and bad breath are visible effects, but they are not the whole picture and cannot indicate an individual’s disease status.
Dangers of smoking · Evidence guideWhy are menthol cigarettes not safer?Menthol changes sensation, not the basic toxicology of combustion. Its cooling effect can make smoke feel less harsh or easier to inhale, but the cigarette still produces the same broad categories of toxic gases, particles and carcinogens.