Smokers should be encouraged to use e-cigarettes as a safer alternative, Britain's Royal College of Physicians says in a sharp departure from other public health advice.
Thursday's report is based on expert opinion and concludes the hazards to health from inhaling e-cigarette vapours are likely less than the harms from smoking tobacco.
The authors of "Nicotine without smoke: tobacco harm reduction" say people smoke because they are addicted to nicotine but are harmed by the tar and cancer-causing chemicals. It calls smoking the biggest avoidable cause of death and disability and social inequalities in health in the U.K.
E-cigarettes heat liquid, often containing nicotine, into vapour. Use of e-cigarettes or vaping is proposed as a lower-risk alternative to smoking.
"E-cigarettes represent an important means to reduce the harm to individuals and society from tobacco use," epidemiology Prof. John Britton of the Royal College of Physicians and his co-authors said in a summary of the published in the BMJ. "This is an opportunity that should be managed and taken."
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But the long-term risks of e-cigarette use remain unknown and are likely associated with an increased risk of chronic obstructive pulmonary disease, lung cancer and possibly cardiovascular disease, the authors of the 200-page said.
On the question of how e-cigarettes could lure young people to smoke, the British group said there hasn't been "demonstrated evidence of significant progression into smoking among young people."
But in a U.S study of those aged 16 to 26 years suggested use of e-cigarettes was associated with eight times higher odds of taking up traditional cigarette smoking.
The ideal is for people to use nothing. - Linda Bauld
The global market for "vaping" products was estimated at around $7 billion US in 2015.
Tobacco smoking kills half of all smokers, plus at least another 600,000 people a year non-smokers through second-hand smoke.
This makes it the world's biggest preventable killer, with a predicted death toll of a billion by the end of the century, according to the World Health Organization (WHO).
E-cigarettes with nicotine have not been approved for sale by Health Canada but are readily available.
Many provinces ban sales of electronic cigarettes to minors.
The Canadian Cancer Society says seven provinces, (B.C., Manitoba, Ontario, Quebec, New Brunswick, N.S. and P.E.I.) have adopted legislation to regulate e-cigarettes by banning sales to minors, prohibiting e-cigarette use in public places and workplaces where smoking is banned, restricting advertising and promotion and other measures.
Ontario's law on sales to minors is in effect and it has proposed a ban on the use of e-cigarettes in enclosed public places and plans to limit where sales are prohibited.
Some municipalities including Vancouver, Edmonton, Calgary and Toronto have also adopted measures to restrict e-cigarette use in public places.
The World Health Organization has also called for bans on indoor use, advertising and sales to minors.
The Canadian Cancer Society holds a similar view.
"This is a product category that needs appropriate regulation, to prevent use by minors, and to prevent industry marketing strategies that would impede smokers from quitting altogether. We support legislation adopted to date by seven provinces that prohibits sales to minors, that prohibits use in places where smoking is banned, and that restricts promotional activities," Rob Cunningham, senior policy analyst with the Canadian Cancer Society in Ottawa, said in an emailed general comment on the U.K. report.
Dr. Peter Selby, an addictions researcher at the Centre for Addiction and Mental Health in Toronto, wonders why the British team is promoting e-cigarettes when there are proven alternatives, such as quit smoking programs, counselling programs and nicotine replacement patches, inhalers and lozenges.
Other questions remain about the long-term safety of e-cigarettes. For example, e-liquid contains propylene glycol, a common food additive and flavouring. The health risks of inhaling it deep into the lungs is unknown.
Nicotine delivered in 'cleaner form'
"The ideal is for people to use nothing," said Linda Bauld, a professor at Stirling University, deputy director of the U.K. Centre for Tobacco and Alcohol Studies and a co-author of the RCP report. But when the alternative is smoking, people should be encouraged to use nicotine "delivered in a cleaner form than in deadly cigarettes."
"This is what tobacco harm reduction is — it reduces the harm from tobacco while recognizing that some people will still use nicotine in other safer forms."
The anti-smoking group ASH UK welcomed the report, saying it showed "that switching to vaping is a positive and sensible life choice" for smokers.
"Electronic cigarette vapour does not contain smoke, which is why vaping is much less harmful," said Deborah Arnott, ASH's chief executive.