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Analytical Chemistry

New chemicals add concern over e-cigarettes’ health impact

Two potential carcinogens detected for the first time in electronic cigarette vapor and liquid

by Deirdre Lockwood
August 2, 2016

Credit: Shutterstock
Vaporizing the solvents in e-cigarette liquid can produce harmful chemicals including glycidol, formaldehyde, and acrolein.
Credit: Shutterstock
Vaporizing the solvents in e-cigarette liquid can produce harmful chemicals including glycidol, formaldehyde, and acrolein.

Two new chemicals of concern have been connected to electronic cigarettes: Glycidol, a probable carcinogen, is found in e-cigarette vapor; and propylene oxide, a respiratory irritant and possible carcinogen, is found in the flavored liquid heated by the device to produce the vapor. Hugo Destaillats of Lawrence Berkeley National Laboratory and his colleagues also confirmed the presence of the probable carcinogens formaldehyde and acetaldehyde, as well as the strong respiratory and eye irritant acrolein, in the vapor (Environ. Sci. Technol., DOI: 10.1021/acs.est.6b01741).

Glycidol is a probable carcinogen found in e-cigarette vapor. Propylene oxide is a respiratory irritant and possible carcinogen found in e-cigarette liquid.
Glycidol is a probable carcinogen found in e-cigarette vapor. Propylene oxide is a respiratory irritant and possible carcinogen found in e-cigarette liquid.

Notably, the researchers conclude that several of these compounds come from heating the liquid’s solvents, propylene glycol and glycerin. Glycidol, acrolein, and formaldehyde are thermal by-products of glycerin, and propylene glycol degrades into acetaldehyde and formaldehyde.

The team tested two different brands of e-cigarettes with three different liquids, analyzing the liquid and vapor using gas chromatography-mass spectrometry and high-performance liquid chromatography. Propylene oxide was not detectable in the vapor in their HPLC analysis, but because it was found at relatively high levels in the liquid, the researchers speculate that it may be present in the vapor.

Several factors increased the amount of thermal degradation products delivered per puff, including repeated puffs within a half hour and increasing the e-cigarette voltage, both of which result in heating the liquid at a higher temperature. “As you increase the temperature, the amount of acrolein formed increases almost exponentially,” Destaillats says—by an order of magnitude for a voltage increase from 3.3 to 4.8 V. Minimizing the voltage could help e-cigarette users limit their exposure to these compounds, he says.

Most compounds of concern were detected at 0.3 to 70 μg per puff. The researchers estimate that e-cigarettes emit a quarter or less acrolein than a conventional cigarette for the equivalent number of puffs. However, the team’s calculations also indicate that at least two compounds in e-cigarette vapor exceed limits for chronic exposure—both secondhand and for vapers themselves—set by the California Office of Environmental Health Hazard Assessment by up to an order of magnitude or more, Destaillats says. The team’s conclusions on health implications will appear in a forthcoming paper.



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Glen Appleton (August 2, 2016 7:07 PM)
The methods used in this “study” are the same as those used in previous “research” that produced aldehydes (not actual formaldehyde). They chose products that were designed to be used at low power (CE4 style atomizers) and measured the results of power levels well above those within their design parameters. This type of “research” has been done twice before, and both times has been criticized by the scientific community for improper testing methods.

A quick analogy: There are those who would say that whole wheat bread is a relatively healthy food (definitely healthier than bleached flour white bread). However, if you put that same bread in the toaster too long and burn it, it then contains a chemical that is a known carcinogen (acrylamide). However, with the exception of the few who really like to live life dangerously and have a taste for burnt food, the vast majority of people are not going to eat that burnt toast because (to them) it just tastes terrible.

Now, given the analogy above, apply the same concept to vapor products. Yes, you can overheat and burn the contents of the liquid to produce undesirable and unhealthy results, but the resulting product would have an acrid taste that does not appeal to the vast majority of vapor product consumers. Anyone who thinks that people using vapor products would continue to just puff away once this state (overheating) is detected by sense of taste and smell must either think that these consumers have either lost those physical senses, or that they’re just incredibly stupid.

If you’re among those who think that vapor product users are just stupid or ignorant and being misled by “big vapor”, then you need to ask yourself if maybe you are the one that suffers from ignorance. The real information is available, although you won’t see it or read about it in major media outlets, which is the case for many unpopular issues. If you want to know the truth about why vapor products are being attacked and misrepresented by “studies” such as this one, you need to dig and follow the money.
Robert Strongin (August 7, 2016 5:59 AM)
It has always been standard practice and strategy of big tobacco to form grass roots organizations, use political consulting firms and lobbying groups, and to create doubt about any peer reviewed science that hinted of tobacco's harm. This is common knowledge, and the same tactics are now employed by many in the vaping industry. Also like big tobacco, the vaping industry has used harmful additives such as diacetyl and pyrazines to mask the harsh taste of carcinogens. There is also no strong evidence that users can safely detect carcinogens by taste. In fact, peer reviews research has shown that power settings on a e-cig affording levels of formaldehyde several-fold above safety levels were rated as sensorally pleasant by users. See International Journal of Hygiene and Health 2016, 258-227.
lana (August 16, 2016 9:47 AM)
@Apleton, you seem to be under the impression that there are clear industry standards ("design parameters"?) with design safety built into them and an informed and understanding consuming public. If that is the case please share with us the industry standards and evidence of the safety design parameters used by all manufacturers. Also please share with us evidence that the consuming public clearly understands which atomizers, 'clearomizers', cartonmizers, EVODs, are to be used with which wicks, tanks and liquid or 'juice'. Because from what I have seen, trying to navigate that seems to be a near full time job amongst the folks I know who vape.

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