Tobacco is smoked to obtain nicotine, principally to relieve symptoms of nicotine withdrawal. Although nicotine has few serious adverse effects on health, the smoker exposes themselves to serious harm from tar and gases including oxidant gases and carbon monoxide:

• Nicotine:
• Increases levels of circulating catecholamines resulting in modest increases in heart rate, blood pressure, and peripheral vascular tone. The most significant effects of this are to:
• Increase the risk of accelerated hypertension in people with severe hypertension.
• Delay wound healing in people with peripheral vascular disease.
• Increases the metabolic rate and suppress appetite, resulting in a lower average body weight.
• Tar is the principal source of carcinogens in cigarette smoke.
• Carbon monoxide binds to haemoglobin, reducing the oxygen-carrying capacity of the blood. In pregnancy, this causes fetal hypoxia and is thought to be the most important cause for the adverse effects of smoking on the fetus.
• Oxidant gases increase the tendency of the blood to clot by their effects on platelets and the endothelial lining of blood vessels. This increases the risk of myocardial infarction and stroke.
• Substances other than nicotine are thought to:
• Alter the lipid profile and accelerate the development of atheroma, causing cardiovascular disease.
• Increase gastric acidity and risk of peptic ulceration.

[RCP, 2000]