Tobacco smoking
Tobacco smoking, particularly the smoking of cigarettes, is believed to be by far the main cause of lung cancer, which in at least in theory makes it one of the easiest diseases to prevent. An estimated 80% of lung cancers result from smoking, due to the hundreds of known carcinogens, such as benzene, present in cigarette smoke. The length of time that a person continues to smoke as well as the amount smoked increases their chances of contracting lung cancer. However if someone stops smoking then these chances steadily decrease as the damage to their lungs is repaired.
Smoking also increases the chance of heart disease. Several ingredients of tobacco lead to the narrowing of bloodvessels, increasing the likelyhood of a block, and thus a heart attack. Others lead to high blood pressure. Also, some chemicals damage the inside of arteries, for example making it possible for cholesterol to adhere to the artery wall, possibly leading to a heart attack.
Passive smoking, whereby exhaled smoke is inhaled by other people, has recently been identified as a much larger cause of lung cancer in non-smokers than previously believed. The US Environmental Protection Agency (EPA) in 1993 concluded that about 3,000 lung-cancer related deaths in the US were caused by passive smoking every year, however the true extent is still being contested among scientists.
Smoking continues to be a major problem because of smokers' addiction to the nicotine in tobacco smoke, and the vigorous marketing of cigarettes by the tobacco industry.
In many countries smoking in public buildings is now prohibited. Many office buildings (are required by law to) contain specially ventilated smoking areas.
Nicotine is a powerful stimulant and is one of the main factors leading to the addictiveness of tobacco smoking. Although the amount of nicotine inhaled with tobacco smoke is quite small (most of the substance is destroyed by the heat) it is still sufficient to cause addiction. The amount of nicotine absorbed by the body from smoking depends on many factors, including the type of tobacco, whether the smoke is inhaled, and whether a filter is used. On average it takes about seven seconds for the substance to reach the brain.
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