Even as the use of e-cigarette continues to grow phenomenally as as an alternative to a regular cigarette for habitual smokers, doctors have never been sure if the use of the former is as good as quitting smoking itself. Now a research has shown that the vapor from electronic cigarette contains two carcinogenic chemicals. Researchers at the Lawrence baerkeley National Laboratory found that the vapor contains propylene oxide, which is a "possible" carcinogen and respiratory irritant. Moreover, aerosol produced with vaporisers contains another carcinogen, glycidol, which is also a powerful respiratory irritant. The research said the principal constituent of refill "e-liquid" were - propylene glycol (PG), glycerin, nicotine, ethanol, acetol, and propylene oxide, while the aerosol had up to 31 compounds. The research published in Environmental Science & Technology said glycidol was not identified earlier in the vapor. The researchers stimulated vaping at different battery power settings with two separate e-cigarettes. It was found that the vaporisers released 31 harmful chemicals and amount of the chemcials produced varied as per the temperature at which the liquids are "vaporised" by the device, a report in The Verge says. According to the report, studies had shown earlier that e-cigarettes contain harmful chemicals. A 2015 study showed that aerosols contained, formaldehyde, a carcinogen. While advocates of e-cigarettes claim that one can be safe with its use as emissions are "much lower" than the conventional cigarettes, the researchers said that may be true for "long time smokers that cannot quit" but that doesn't mean they are healthy, The Verge reported.