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Recent research has revealed that passive smoking, even over short periods of time, can temporarily damage a non-smoker's heart. Experts have been warning for some time of the health risks caused by inhaling the smoke from other people's cigarettes, but the average person does not yet seem to be very aware of such risks. People in most countries know, for example, that smoking can lead to respiratory diseases, including serious diseases, such as lung cancer. However, their knowledge of the consequences of passive smoking seems very limited. Most people who do not smoke regard smoking as an "antisocial" habit which causes them some discomfort, rather than as a danger to their health. They may always sit, when possible, in the no-smoking areas of restaurants or other public places. Still, many of them do not yet realise that being in the company of smokers can make them actually ill.