The World Health Organization (WHO) is the latest agency to speak up against electronic cigarettes, or e-cigarettes. In a report - Electronic Nicotine Delivery Systems (ENDS) - released on Tuesday, the United Nations health agency stressed the need for stringent regulation of e-cigarettes. It also urged a ban on indoor use as well as advertising and sales to minors.
Around the same time, the US Centres for Disease Control and Prevention (CDC) also released a report, highlighting its concern that that e-cigarettes encourage youths to take up smoking. The study, published in the Nicotine And Tobacco Research journal, was based on nationally representative surveys.
It revealed that more than a quarter-million non-smoking teens tried e-cigarettes in 2013. The figure is a threefold leap from 2011.
That's not all: According to the report, those who had experimented with e-cigarettes, compared with those who had never used an e-cigarette, were nearly two times more likely to say they would try a conventional cigarette within the next 12 months.
In March this year, the journal of the American Medical Association, published a study, concluding: "Use of e-cigarettes was associated with higher odds of ever or current cigarette smoking, higher odds of established smoking, higher odds of planning to quit smoking among current smokers, and, among experimenters, lower odds of abstinence from conventional cigarettes. Use of e-cigarettes does not discourage, and may encourage, conventional cigarette use among US adolescents."
Data from a recent US CDC study also showed that the number of calls to poison centres involving e-cigarette liquids containing nicotine rose from one per month in September 2010 to 215 per month in February 2014.
These are alarming numbers.
Equally distressing is that worldwide sales of e-cigarettes are expected to top US$10 billion (S$12.59 billion) by 2017, according to Wells Fargo, and will exceed those of traditional cigarettes by 2047, said Bloomberg Industries.
E-cigarettes are soaring in popularity globally, and the US Food and Drug Administration has already proposed a set of rules to regulate e-cigarettes.
In Singapore, under the Singapore Tobacco Act, the devices cannot be distributed, sold or imported.
Exactly how dangerous are e-cigarettes to health?
Supporters say there is no tobacco in e-cigarettes, so how can they be bad for health? Compared to normal cigarettes, e-cigarettes are definitely an alternative to tobacco. But studies on the side effects of inhaling pure liquid nicotine are inadequate to date, and therefore, unknown, warn health experts.
The caution then leads to the next point: Since the jury is still out on the effects of liquid nicotine inhalation, there is an equal chance of it being as harmful as it is safe, and if it is the former, the level of nicotine in an e-cigarette then becomes an issue, especially since users are able to choose cartridges filled with different quantities.
Also, liquid nicotine is just another form of nicotine, and it has long been acknowledged that nicotine is highly addictive.
And even if nicotine inhalation is eventually proven safe, there is still the question of quality control. Health experts say that some manufacturers may not list all the chemical ingredients used in e-cigarettes.
As with traditional cigarettes, there is second-hand smoke, or rather, vapour. Proponents protest that it is only water vapour and therefore innocuous - even as some users have complained of vomiting, nausea and eye irritation, from liquid nicotine ingestion - while opponents assert that there can be no certainty until conclusive research is done.
Gateway to tobacco use
Probably the greatest safety concern regarding e-cigarettes is not the physical harm to the user but to youths. In the US, e-cigarettes are marketed to children and teens in fruit and candy flavours - think chocolate, cherry and cotton candy - raising the worry among public health advocates that after e-cigarettes, which may glamourise smoking, come traditional cigarettes.
With so much unknown surrounding them, e-cigarettes are like the wild, wild west of living dangerously.