PARIS, June 30 (AFP) - Passive smoking is more perilous than previously estimated, according to the first major study to assess blood samples from people exposed to cigarette smoke in pubs, the workplace and home.
Past studies into the effects of passive smoking usually look at the health history of people who live with a smoker.
They have found that the passive smoker faces an increased risk of 25 to 30 percent of developing coronary heart disease when compared with someone of similar age and background whose home is smoke-free.
In the latest research, British scientists cast the net wider and examined blood levels of cotinine, a byproduct of nicotine, among more than 2,000 British men, who were also quizzed about their health, work and leisure activities.
Those with higher concentrations of cotinine faced a 50-60 percent increase in the risk of coronary heart disease.
There was no apparent risk of an increase of a stroke from passive smoking.
The researchers conclude that exposure to smoke at home may account for less than half of the nicotine that is inhaled by passive smokers if their workplace allows smoking or if they go to smokey bars and restaurants.
The study was carried out by a team from St. George's Hospital Medical School and the Royal Free University College London Medical School in London.
It was published online on Wednesday by the British Medical Journal (BMJ) (bmj.com).
The data comes from a major heart study that was carried out among 2,105 middle-aged non-smoking men, whose health was monitored for 20 years from the late 1970s.
Cotinine levels declined significantly during the course of this long study, mainly because of changes in smoking habits. People began to smoke less, and public places and workplaces began to enforce no-smoking rules.
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