The electronic cigarettes marketed as a safer alternative to the real thing produce immediate changes in users' airways, a small study suggests.
Researchers in Greece saw changes in the lung function of healthy smokers who puffed on an e-cigarette for just five minutes –although it's not clear what the long-term result of those responses might be in regular e-cigarette users, the team reports in the journal Chest.
"E-cigarettes" are battery-powered devices that allow users to inhale a vaporised liquid nicotine solution instead of tobacco smoke. They were designed as a way for smokers to get their nicotine fix without exposing themselves, or other people, to the toxins in tobacco smoke.
But some scientists, including officials at the US Food and Drug Administration (FDA), warn that too many questions remain about the safety of these products.
Acute physiological effects
"This is the first evidence that just one (e-cigarette) use can have acute physiologic effects," said lead researcher Constantine I. Vardavas, of the Centre for Global Tobacco Control at the Harvard School of Public Health.
For the new study, Vardavas and colleagues in Athens had 30 healthy smokers puff on an e-cigarette to see how it affected their airways.
The researchers found that after five minutes, users showed signs of airway constriction - as measured by several types of breathing tests - and of inflammation.
It is not known whether that short-term response could translate into health effects in the long run, including lung diseases like emphysema.
"More studies on the long-term effects are needed," said Vardavas.
But, he noted, if e-cigarettes trigger airway effects after just a few minutes, that raises concerns about repeated use of the products over time.
Any e-cigarette benefits?
"There are claims that e-cigarettes have no health effects," Vardavas said. "But that's not correct."
An industry spokesperson defended the products.
"This is a product that eliminates second-hand and third-hand smoke," said Ray Story, CEO of the Tobacco Vapour Electronic Cigarette Association.
Third-hand smoke refers to the toxic particles that remain on smokers' clothes, furniture and other surfaces long after second-hand smoke has cleared.
"We already know e-cigarettes are much safer than the conventional cigarette," Story said, "because you're not burning it, and you don't have the five or six thousand ingredients in cigarettes, which are mostly dangerous chemicals."
Story said that e-cigarettes contain only five main ingredients: nicotine, water, propylene glycol, glycerol and flavouring.
"These ingredients are all FDA-approved," Story said.
But the FDA says on its website that "e-cigarettes may contain ingredients that are known to be toxic to humans, and may contain other ingredients that may not be safe."
Indeed, the FDA and the e-cigarette industry have had a rocky relationship.
In 2010, the agency sent warnings to five makers of e-cigarettes for marketing them illegally as stop-smoking aids. The FDA also tried to regulate e-cigarettes as drugs - and thereby block their importation into the US - but a US court ruled that the FDA could only regulate the devices as tobacco products.
Vardavas said it's not clear why e-cigarettes increased airway constriction in this study. But when they had 10 of the study participants use "control" devices, e-cigarettes that had the cartridges removed, they did not see the same airway effects.
So one or more ingredients in the e-cigarette may be responsible, but it's not known which they are, Vardavas said.
The study was partly funded by the Hellenic Cancer Society in Greece. The researchers report no financial conflicts of interest.
It's possible, according to Vardavas, that if people used e-cigarettes as a temporary "bridge" to quitting smoking, any short-term effects of the products would be outweighed by the long-term health benefits.
But no one knows if e-cigarettes actually do help smokers kick the habit.
"If you're trying to quit," Vardavas advised, "stick to the methods that are known to work."
Those, he noted, include nicotine patches and gum, prescription medications like bupropion (Zyban) and varenicline (Chantix), and counseling.
(Reuters, Amy Norton, January 2012)