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which this article appears: Smoking
BMJ 2002;324:1544 ( 29 June )
News extra
Harm from smoking is even greater than previously thought
Owen Dyer London
Smoking is even more dangerous than previously believed, according to a major
review of epidemiological data by the World Health Organizations cancer agency.
The International Agency for Research on Cancer (IARC) also published the first
evidence to link conclusively second hand smoke with increased risk of cancer.
The agency convened 29 scientists from 12 countries to review all significant
published research on both active and passive smoking. They state unequivocally
that even an average degree of passive exposure to tobacco products can cause
lung cancer in people who have never smoked.
"Its been suspected for a long time," said Professor Richard Doll, one of
the reports authors, "but this is the first time weve had a clear scientific
consensus saying its definitely a cause."
Fifty years ago, Professor Doll was joint author of the first published paper
to suggest a link between tobacco and lung cancer.
The agencys report also implicates tobacco in five cancer sites not
previously shown to be associated with smokingthe stomach, liver, uterine
cervix, kidney (renal cell carcinoma), and myeloid leukaemia. "The additional
risk to these sites from smoking varies from about 30% to double," said
Professor Doll. "Some were previously suspected, but this is the first time
there is solid evidence."
"I myself was surprised to learn of a link between smoking and cervical
cancer," he said. "Its been hard to prove because smokers tend to be more
sexually active than non-smokers. But if you look just at people with HPV [human
papillomavirus] infection, youll find the smokers are more likely to develop
malignancies."
Cancers normally linked to hormonal causes seem to be unaffected by smoking.
In particular, the agency's working group rejected suggestions that passive
smoking can cause breast cancer. The agency was unable to provide a definitive
answer, however, to the question of whether passive smoke inhalation by children
in the home is linked to childhood cancers.
Overall, half of all smokers will die prematurely because of their habit.
Half of these deaths occur in middle age (35-69 years). Tobacco is the leading
cause of preventable cancers worldwide.
The current global trend towards people being younger when they start smoking
bodes ill for the future, says the report. Many young Britons and Americans will
have been committed smokers for 30 years by the time they reach the age of 40.
The WHO hopes that its report, which updates a previous survey from 1986,
will convince governments to act on controlling smoking in public places and to
encourage people to stop. "Smoking cessation, along with never starting to
smoke, will remain the best ways to prevent cancer around the world in the 21st
century," says the paper. "Any possible public health gains from changes in
cigarette composition would be minimal in comparison."
The report can be accessed at the agencys website (www.iarc.fr).
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