While much is still unknown about the health risks of e-cigarettes, here’s what we do know: E-cigarettes are addicting. And while they may not be as harmful as tobacco cigarettes, critics like the British Medical Association and the World Health Organisation are wary of the trend and warn of the dangers that may be associated with the smoking devices.

Here's what we do know about e-cigarettes:

1. E-cigarettes contain toxic chemicals.

A 2009 FDA analysis of e-cigarettes from two leading brands found that the samples contained carcinogens and other hazardous chemicals, including diethylene glycol, which is found in antifreeze. Last year, a report from Greek researchers found that using e-cigarettes increased breathing difficulty in both smokers and non-smokers, according to Medical News Today. A more recent study funded by a smoking-cessation advocacy group concluded that:

"There is no evidence that vaping produces inhalable exposures to contaminants of the aerosol that would warrant health concerns by the standards that are used to ensure safety of workplaces. However, the aerosol generated during vaping as a whole (contaminants plus declared ingredients), if it were an emission from industrial process, creates personal exposures that would justify surveillance of health among exposed persons."

2. Kids and teens can buy them.

Unlike other tobacco products, e-cigarettes can be sold to minors in many places throughout the country. The smoking devices can also be bought legally online, according to the Wall Street Journal.

4. Laws regulating cigarette ads don't yet apply to e-cigarettes.

TV commercials for cigarettes may be banned, but ones for e-cigarettes sure aren't, Adage points out. (The above ad for Blu eCigs features Jenny McCarthy.)

5. And e-cigarette companies are spending a TON on advertising.

Industry advertising spending increased to $20.8 million in 2012 from just $2.7 million in 2010, according to The New York Times.

6. E-cigarettes can be used in many places where smoking is banned.

Even though some studies suggest that secondhand vapor poses health risks, many lawmakers have yet to determine whether smoking rules apply to e-cigarettes, according to USA Today.

7. People think e-cigarettes can help them quit smoking.

Research published in the American Journal of Public Health indicates that 53 percent of young adults in the U.S. who have heard of e-cigarettes believe they are healthier than traditional cigarettes and 45 percent believe they could help them quit smoking -- though there is little evidence to support either of these claims.

Even though cigarette consumption fell significantly as taxes went up.

9. Despite unknown health consequences, e-cigarettes are poised to make inroads with a new generation of young people.

Half of young adults say they would try e-cigarettes if a friend offered them one, according a study cited by USA Today.