A hardline opponent of electronic cigarettes fears that rather than helping people to quit ordinary cigarettes, they may keep them hooked on a daily dose of tobacco smoke.
Professor Stanton Glantz, of the University of California at San Francisco, will speak in New Zealand next week at seminars organised by researchers trying to find ways to help the country become virtually smoke-free within 12 years.
Battery-powered e-cigarettes, which emit a vapour containing nicotine, are promoted as a "harm-reduction" device. "Vaping" on e-cigarettes is said to be safer than smoking ordinary cigarettes and is not covered by the Smoke-free Environments Act ban on smoking indoors at workplaces and schools.
Many people consider them to be a quit-smoking aid; other people use them to cut down smoking.
But Professor Glantz asserts e-cigarettes, now marketed in his country as "hip, sexy and modern", as tobacco once was, "are a triumph of wishful thinking over evidence".
"There is no scientific evidence that electronic cigarettes help people to quit smoking. There's a lot of people saying they do, but the world is filled with people who think treatments work when they didn't.
"There's a couple of population-based studies looking at dual use. This is the real problem. Very few people switch from conventional cigarettes to electronic cigarettes; they keep using both.
"While the people who use electronic cigarettes seem to smoke fewer conventional cigarettes than the people who don't use electronic cigarettes, it's not enough difference to matter, particularly for the heart-disease effects of smoking," said Professor Glantz. But he added that for lung cancer, the more someone smoked, the greater the risk.
He supports a bill before the California legislature which would ban vaping within indoor workplaces and many other places.
E-cigarettes and nicotine cartridges are sold at many New Zealand shops but this remains a legal grey area. There is no evidence they are effective in helping people quit, but regulator Medsafe says they are medicines when supplied with a nicotine cartridge, even if no quit-smoking claim is made.
It is illegal to sell a medicine that has not been licensed by the Health Minister and when no one has applied for a licence.
All eyes are on an Auckland University trial of 657 smokers to compare the quit-smoking effectiveness of three 12-week methods: using nicotine patches, a nicotine e-cigarette and a non-nicotine e-cigarette.
Researcher Dr Chris Bullen said he expected the findings would be presented in early September at a European Respiratory Society meeting in Spain.
The Cancer Society represents the cautious approach to e-cigarettes of many in tobacco control circles.
It says there is limited evidence of their safety and suitability as a quit-smoking aid; they could be a gateway to tobacco for youth; and vaping in areas where smoking is banned, such as indoor workplaces, might undermine the Smoke-free Environments Act and the efforts to denormalise smoking.
But Dr Murray Laugesen, a supporter of greater access to e-cigarettes, notes the paradox of Medsafe's opposition to nicotine cartridge sales, while nicotine in "deadly tobacco cigarettes" can legally be sold.
He appealed to the Health Ministry for a review of the policy.