Review of Existing Evidence Confirms No Risk From E-Cig Vapor

By Lindsay Fox Posted August 29, 2013

You’ve heard it all before. “E-cigs contain diethylene glycol,” “there are carcinogens in e-cigs,” “the liquid contains formaldehyde” and “nobody really knows what’s in the vapor.” These arguments are so frequently repeated that they become meaningless white noise – a continuous rallying cry for anti-smoking and anti-e-cig campaigners, readily repeated despite existing evidence to the contrary.


A new study, funded by CASAA (Consumer Advocates for Smoke-free Alternatives Association), has looked at the existing data on the contents of e-liquids and the vapor from e-cigs, and – unsurprisingly – found no evidence of risk to vapers, even under “worst case” scenarios. The odds were stacked against e-cigs purposefully, and they still come out looking positively angelic.


The Study


The research – available in full for free – comes from Igor Burstyn, PhD, and reviews the existing research on the chemistry of e-cigs and the vapor produced. The main aim was to compare the exposure to various components by vapers to pre-established occupational exposure standards.


One key point raised in the paper is that there is a difference between the standards set for occupational exposure (which is generally unintended) and reasonable standards for intentional exposure. For example, in an occupational setting, exposure to e-cig-like levels of nicotine would be a cause for (admittedly minor) concern, but since vapers actively choose to consume nicotine (as well as propylene glycol and vegetable glycerin), the occupational exposure levels aren’t a valid yardstick to measure it against. Generally speaking, up-to-date (2013) established safe threshold limits were used and all uncertainties in the evidence were resolved by using the “worst case” scenario.




Tobacco-specific nitrosamines are present in both e-cigs and FDA-approved products such as nicotine patches. Although specific threshold values aren’t available, it was calculated that if a liquid contained ten parts per billion of nitrosamines (as determined from research), the user would inhale around 0.000025 to 0.00005 μg (in micro-grams – one millionth of a gram) per day, and that’s if they consumed 5ml of liquid. The risk of cancer from smokeless tobacco is known to be absolutely minimal, and under this worst case scenario, the exposure from vaping would be between 160 and 320 times less than smokeless tobacco.


Volatile Organic Compounds


Acrolein and formaldehyde are two volatile organic compounds present in the highest quantities in e-cig vapor, with all of the others being found in less than one percent of safe threshold limits. Under worst case scenarios, acrolein was found in concentrations of around two percent of safe threshold limits and formaldehyde in concentrations of around four percent of accepted safe limits (both calculated as an average over 150 measurements).


Diethylene Glycol


The FDA famously detected diethylene glycol in a batch of tested e-cig liquid, but very few researchers have been able to replicate that result. Even using the (obviously anomalous) FDA result, the detected quantities were less than one percent of accepted safety thresholds.




The presence of metals in e-cig vapor is another often-cited reason for concern. Firstly, it’s pointed out in the paper that the detection method for these chemicals destroys the “parent” compound, thus making them difficult to translate to direct risk. For example, sodium has been detected, but since it’s highly reactive it literally couldn’t form part of the liquid, and is most likely present in the form of ordinary salt (and in a day of use, your exposure would be around 10,000 times less than safe limits). On the whole, metals were only ever found in trace amounts, the majority being less than one percent of the threshold for safe exposure.




Anybody reading the results of the study can clearly see that there is very little, if any, risk to the user from the oft-cited toxic components of e-cig vapor. This also means that risk to bystanders is even lower­, because the components of the vapor would be “diluted” when they’re exhaled into a room full of air. In fact, the biggest concern raised in the study was related to propylene glycol, which was still in notably lower levels (6mg per m3) than recommended occupational exposure limits (50mg per m3). Even in this area, Burstyn argues that in an occupational setting (meaning involuntary exposure) it would be “prudent” (not necessary) to investigate ways it could be reduced.


For vapers, this study has a very simple conclusion. The component which is also used in theatrical smoke machines is the biggest risk to your health, and even that is extremely negligible. This study offers significant reason to believe you aren’t at risk from vaping, and if anything the situation will improve even more in the future.


SEE ALSO: Top 10 E-Cig Studies You Need to Know About