Nicotine, the addictive agent found in tobacco cigarettes, has been discovered in a number of e-cigarette liquids claiming to be free of it.

Key points: The sale of liquid nicotine in e-cigarettes is illegal across Australia

The sale of liquid nicotine in e-cigarettes is illegal across Australia Six varieties of "nicotine-free" e-liquids have been found to contain nicotine

Six varieties of "nicotine-free" e-liquids have been found to contain nicotine Health experts say the findings highlight the lack of regulation of vaping products in Australia

Australian researchers investigating the potential health impacts of e-cigarettes tested 10 varieties of "nicotine-free" e-liquids and found six to contain nicotine.

The e-liquid samples, purchased online and over the counter from Australian suppliers, were also found to contain a substance known as 2-chlorophenol, an "acutely toxic" chemical typically found in insecticides and disinfectants.

Lead researcher Alex Larcombe of the Telethon Kids Institute said the findings highlighted the risks of "little to no regulation" of vaping products in Australia.

"In a lot of cases, people who are using e-cigarettes are unaware of what they're breathing in," Associate Professor Larcombe said.

The sale of liquid nicotine is illegal in Australia, meaning vape stores are restricted to e-cigarette devices and "nicotine-free" e-liquids.

But inaccurate labelling means vape users may "unwittingly inhale this addictive substance" or retailers may sell incorrectly-labelled nicotine-containing e-liquids to willing customers, according to the study published today in the Medical Journal of Australia.

"There is little to no regulation of their manufacture, and potentially dangerous ingredients and incorrect nicotine levels have been identified," the authors wrote.

The nicotine found in three of the samples was at levels comparable to those found in low-dose nicotine e-liquids, and at trace levels in the other three samples in which it was present.

Potentially harmful ingredients identified

Associate Professor Larcombe said he was "surprised" by the discovery of 2-chlorophenol, a known respiratory and dermal irritant.

"It was only in there in small amounts, but it was found in all of the liquids that we looked at," he said.

"We also found other things — by-products of animal or human bodily functions — which indicates the process of making the e-liquids might not be as clean as you might hope."

The samples were also found to contain "relatively benign" chemicals commonly used in foodstuffs, soaps and detergents, as well as common e-liquid ingredients such as flavours and solvents.

"Most of these sorts of things are food additives qualified as 'safe to eat', but … it's unknown what the heating process does to the chemical composition of these ingredients, especially when it's being breathed into the lungs," Associate Professor Larcombe said.

A 'regulatory no-man's land'

Simon Chapman, emeritus professor of public health at Sydney University, said Australia was operating in a "regulatory no-man's land" when it came to e-cigarettes.

"Vaping retailing in Australia is a real cowboy … they say they can sell the juice without nicotine, but there's no specification about what can and can't be in it," said Professor Chapman, who was not involved in the study.

In Australia, nicotine is classified as a "schedule 7 dangerous poison", with exemptions made for certain nicotine replacement therapies and for tobacco used in smoking.

People who want nicotine in their e-cigarettes must order it in liquid form from overseas and add it to the devices themselves.

But Professor Chapman, who has been at the forefront of tobacco control in Australia, said it was an "open secret" that you could buy e-liquid containing nicotine, despite it being illegal.

"I've also been told there's a fair amount of amateur, backyard lab production of e-juices which are being sold," he said.

Last year, health inspectors from the New South Wales Department of Health visited 227 retailers selling e-liquids and found 63 per cent of e-liquids labelled "nicotine-free" actually contained nicotine.

How do e-cigarettes work? E-cigarettes are battery-operated devices that heat a cartridge of liquid nicotine into a mist to be vaporised

E-cigarettes are battery-operated devices that heat a cartridge of liquid nicotine into a mist to be vaporised They deliver nicotine (the addictive agent in cigarettes) without burning tobacco and producing harmful smoke

They deliver nicotine (the addictive agent in cigarettes) without burning tobacco and producing harmful smoke Smoking e-cigarettes is often referred to as vaping

Professor Chapman said the lack of regulation and mislabelling of nicotine was a particular concern when it came the use of e-cigarettes among young people.

"In the United States, the Food and Drug Administration is currently considering what they're going to do about the regulation of nicotine products … because they've seen an incredible spike in teenagers using e-cigarettes," he said.

"We hope that e-cigarettes are less harmful than smoking because they don't contain combusted material ... but there is no long-term evidence about the risks or the benefits of vaping."

Vaping as a harm reduction measure

Colin Mendelsohn, associate professor of public health at the University of New South Wales, said although more stringent vaping regulations were required, the findings of the research were "relatively unimportant" as a health issue.

"The labels are definitely misleading, and these products should certainly be legalised and regulated," he said.

"But the average dose of nicotine they found was trivial … and I doubt very much it would be addictive in any way."

Associate Professor Mendelsohn, who has long campaigned for the use of electronic cigarettes as a harm reduction measure, said the discovery of other potentially harmful chemicals was "not in itself a concern".

"There are chemicals everywhere — we are exposed to them all day long. The harm depends on the level of the chemical and the toxicity of that chemical," he said.

"Lots of studies have looked at the chemicals in vaping, and they're way below occupational health standards. I suspect these products would be down at that level."

Associate Professor Mendelsohn said the majority of regular vapers were smokers and ex-smokers, and that the health impacts of e-cigarettes should always be compared to those of smoking.

"We know vaping is dramatically less harmful than smoking," he said.

"I think nicotine liquids should be available for sale for smokers who are unable to quit, because the alternative for these people is to keep smoking — and two out of three will die from that."

Professor Chapman, however, said the evidence for people quitting smoking using e-cigarettes was "very poor".

"For every person who has a positive outcome, there are more than two people who have a negative one — meaning they switch back exclusively to cigarettes," he said.

"It will take decades before we know whether or not vaping is less dangerous than smoking, and by how much, if it all."