Passive smoking is the cause of 600,000 deaths a year - or one in 100 deaths worldwide, a survey said.
Women and children were the groups most affected by second-hand smoke, according to the study conducted by researchers from Sweden's Karolinska Institute and the World Health Organisation (WHO).
Children were "more heavily exposed to second-hand smoke than any other age-group, and they are not able to avoid the main source of exposure as it is mainly their close relatives who smoke at home," the researchers said.
Worldwide, the researchers estimated that 40% of children, and about one in three adult non-smokers were exposed to second-hand smoke in 2004, the most recent year to have comprehensive data from the 192 countries studied.
Exposure to second-hand smoke was estimated to have caused 379,000 deaths from heart disease, 165,000 from lower respiratory infection2s, 36,900 from asthma, and 21,400 from lung cancer.
"Enforcing complete smoke-free laws could probably substantially reduce the number of deaths attributable to exposure to second-hand smoke within a few years of its implementation," said co-author Mattias Oberg of the Institute of Environmental Medicine at the Karolinska Institute.
Full details of the study, Global burden of disease from second hand smoke, are available from the online edition of the journal, The Lancet: www.thelancet.com (Sapa/ November 2010)
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