E-cigarettes are harmful, according to a new study done by experts from the Australian National University (ANU).
Contrary to a popular view, vapes increase the risk of a range of bad effects, including some forms of poisoning and lung injury.
Many vapes have nicotine (and can only be used legally if they are prescribed by a doctor) while some don't and are more freely available.
The researchers say that both are dangerous.
Nicotine vapes make it more likely that vapers will move on to conventional cigarettes which are linked strongly to cancer, the research says.
"Young non-smokers who vape are around three times as likely to take up smoking than non-vapers," Professor Emily Banks from the ANU National Centre for Epidemiology and Population Health said.
She also said that addiction to one substance - like nicotine - increased the likelihood of addiction to other addictive substances.
"Nicotine use in children and adolescents can lead to lifelong addiction issues as well as difficulties in concentration and learning. Vaping is also illegal if it isn't on prescription."
The researchers at the ANU took three years to reach their conclusions. One of the findings is that the effect on the body of many of the chemicals in e-cigarettes is unknown, and so their dangers are also not known. "There is no quality control," as Professor Banks put it.
She is particularly dismayed by the way some products are marketed at young children, using bright colours and cartoon-like images.
"The evidence is there for some of the risks but for most major health outcomes, like cancer, cardiovascular disease and mental illness, we don't know what the impacts of e-cigarettes are. Their safety for these outcomes hasn't been established," Professor Banks said.
She said that there can be benefits to vaping for smokers who have tried all other ways of giving up smoking but failed however, she said, these cases were not usual.
"E-cigarettes may be beneficial in the small number of smokers who use them to quit smoking completely and promptly, but there is a huge uncertainty about their effectiveness and the overall balance of risks and benefits for quitting," Professor Banks said.
"Vapes deliver hundreds of chemicals - some of them known to be toxic and many others with unknown effects."
The Cancer Council welcomed the study as "the most comprehensive study of all the health impacts of e-cigarettes ever published worldwide and it sends an urgent message to Australian governments".
"Every week we're hearing growing community concern about e-cigarettes in schools, the health harms and the risks of smoking uptake among young people," Anita Dessaix, who chairs the Council's public health committee, said.
"Now we have the world's most authoritative independent scientific analysis showing us exactly why we're seeing those problems. A public health crisis is rapidly unfolding before our eyes."
