smoking is harmful to the health of people . it not oilly pollutes air，brings about sufferings of other people such as children and nonsmokers，but also causes diseases of bronchitis，lung cancer，chest cancer and throat catcer.

　　smoking is associated with cancers.smoke is a mixture of gases，vaporized chemicals，minlute particles of ash，and other solids.there are also tar and nicotine，which are powerful poisons.as the smoke is breathed in，all these components from deposits the membranes of the lungs.one point of concentration where air tube，or bronchus divides.most lung cancer begins at this point.

　　world governments should conduct seriou campaigns against smoking.first，legislative step must be introduced.second，restrictions on cigarette advertisements must be imposed.third，public smoking in certain places such as theatres，cinemas，waiting roms at airports and railway stations should be banned.in this way，we may make the smokers feel increasingly uncomfortable about their bad habits.finally，cigarette price should be booste.

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