There is no safe level of use. Quitting smoking at any age reduces risk; the benefit begins within hours and grows with the years without smoking.
Smoking is the leading preventable cause of cancer: it causes the vast majority of lung cancers and contributes to cancers of the mouth, pharynx, larynx, esophagus, stomach, pancreas, liver, kidney, bladder, cervix and myeloid leukemia (US Surgeon General's Report, 2014).
View the source (scientific report) →It is the main cause of COPD and of decline in lung function; it damages the airways and alveoli and multiplies the risk of chronic respiratory disease.
View the source (scientific report) →It accelerates atherosclerosis and increases the risk of heart attack, stroke, aneurysm and peripheral artery disease; vascular damage begins at low levels of exposure, including secondhand smoke.
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Smoking is the leading preventable cause of disease and premature death in the world. Tobacco smoke contains thousands of chemicals, of which hundreds are toxic and about 70 are known carcinogens. Five decades of evidence, synthesized in the reports of the U.S. Surgeon General, have established that smoking damages almost every organ in the body.
Smoking causes most lung cancers and increases the risk of cancer of the mouth, throat, larynx, esophagus, stomach, pancreas, liver, kidney, ureter, bladder, colorectum, cervix, and of acute myeloid leukemia. The risk increases with the amount and the years of smoking, and decreases on quitting.
It is a major cause of myocardial infarction, stroke, aortic aneurysm, and peripheral arterial disease, through acceleration of atherosclerosis, inflammation, and endothelial dysfunction. In the lungs it is the leading cause of COPD (emphysema and chronic bronchitis) and aggravates asthma and respiratory infections.
Smoking harms reproduction and pregnancy, bone health, wound healing, diabetes, and the immune system, and accelerates aging. Secondhand smoke causes cardiovascular disease and lung cancer in nonsmokers and harms children. There is no risk-free level of exposure.
Quitting smoking is the health intervention with the greatest impact: after 24 hours the acute cardiovascular risk already drops, and over the years the risk of heart attack, stroke, and several cancers approaches that of someone who never smoked. Tools with proven efficacy include behavioral support and smoking cessation treatments; it is advisable to seek professional help.
Information, not medical advice. Scientific evidence reflects the quality of the studies.