Typical Vapor Content of an Electronic Cigarette

By John Madden Posted September 25, 2013

This article is part 7 of the Top 20 Rebuttals to Win an E-Cigarette Debate


For the most part, we know exactly what goes into the production of the liquid used in the majority of electronic cigarettes. E-liquid typically consists of four main ingredients: propylene glycol, vegetable glycerin, nicotine and flavoring. What isn’t exactly clear is what constituents make up the vapor e-cigs produce.


E-Cig Ingredients
Most e-liquid and e-cig cartridges list the ingredients on the label.


Key Points


  • Most e-liquids are made with propylene glycol, vegetable glycerine, USP grade nicotine, GRAS flavoring and, in some cases, distilled water.
  • A 2012 study published in the scientific journal Indoor Air found e-cigs vapor contains only 6 out of 20 chemicals found in cigarette smoke.
  • VOC levels in vapor were far below safety limits and up to 40 times lower than those of tobacco smoke.
  • 2nd hand nicotine inhalation is not a concern as only trace amounts were detected from vapor directly exhaled into a 10L glass chamber.


Chemical reactions produced by heat as well as components of the atomizer will often produce unexpected results in electronic cigarette vapor. That’s not to say the vapor is bad, it just simply has more than the four ingredients, on average, that make up the liquid that produces it.


Electronic Cigarette Ingredients


Fortunately, an increasing amount of evidence has shown the vapor produced by e-cigs to be far safer than cigarette smoke. Before we dive into what actually makes up the contents of electronic cigarette vapor, let’s break down each of the main ingredients used in the manufacturing of e-cig liquid.


Propylene Glycol


Propylene glycol is an organic compound generally recognized as safe (GRAS) by the FDA. It is used as an humectant, solvent, and preservative in food and tobacco products, and is one of the main ingredients in the liquid used in electronic cigarettes.


It is also used in pharmaceutical and personal care products. Propylene glycol is a solvent in many pharmaceuticals that are insoluble in water. While it won’t produce the amount of vapor that vegetable glycerin will, PG provides much of the throat hit in e-cig vapor that many smokers are accustomed to feeling in that of a cigarette.


Vegetable Glycerin


Like propylene glycol, vegetable glycerin is another base ingredient of e-liquids that produces the vapor of an e-cigarette. Also known as vegetable glycerol, VG is a considerably thicker liquid solution than PG and thus produces more vapor, albeit with a weaker throat hit.


Because of this, it will cause gunk to build up in atomizers, reducing their life span. However, it isn’t as allergenic and doesn’t cause irritation as often as propylene glycol does in sensitive users. Most e-cigarette liquids incorporate a combination of both PG and VG to give vapers a good throat hit as well as vapor production.




Contrary to popular misconception, nicotine is NOT the cancer causing agent found in most tobacco products. It is an addictive stimulant similar to caffeine that is produced from tobacco leaves.


Nicotine can then be used in the manufacturing of various pharmaceutical products like gums, patches and lozenges to help smokers wean off cigarettes. In the case of e-cigs, it is extracted into a liquid form, often combined with different mixes of propylene glycol and vegetable glycerin to dilute its strength.


Distilled Water


Sometimes distilled water is used in place of propylene glycol to thin out mixes that only use vegetable glycerin as a diluent. This is done to decrease the viscosity of the mix to ensure it wicks better in some atomizers and doesn’t gunk up as quick as 100% vegetable glycerin would.




  • Malic Acid: Malic acid is an organic compound made from living organisms that is used in fruit flavored e-liquids. It’s what gives green apples and grapes their sour, tarty taste and has been approved as a food additive in the USA, EU, Australia and New Zealand. Malic acid is also added to some cola drinks to lower their pH levels.


  • Acetylpyrazine: Acetylpyrazine occurs naturally in peanuts, corn and sesame oil. It is another commonly used food flavoring that is often used in tobacco, chocolate and coffee flavored eliquid.


  • Vanillin: As one might expect, vanillin is used in most vanilla and other desert flavored e-liquids. It is the primary component of vanilla bean extract. Vanillin may be extracted from vanilla pods or artificially made from lignin.


So What’s In the E-Cig Vapor?


The nitrosamine argument has been hotly contested for a while now. The electronic cigarette industry doesn’t claim e-cigs to be 100 percent healthy, as nothing we eat, drink or breathe is perfectly safe. We do know that the quantities of impurities found in e-juice are far lower and thus exponentially safer than those in tobacco cigarettes. But what is actually in the vapor and how safe is it?


A 2012 study published in the scientific journal Indoor Air compared the vapor of electronic cigarettes to that of conventional cigarette smoke. The German researchers analyzed volatile organic compounds after test subjects either smoked or vaped in an 8 cubic meter steel chamber. One 0mg and two 18mg nicotine liquids in apple and tobacco flavor were used during the experiment, along with a regular cigarette.


Out of 20 of the chemicals found in the tobacco, only six of which were present in the electronic cigarette vapor and at much lower concentration levels. Those chemicals included butanone, acetic acid, acetone, isoprene, formaldehyde and acetaldehyde.


Concentration of chemicals exhaled

Image by Elaine Keller


As the table above shows, the concentrations of the six VOCs found in the e-cig vapor were at levels far below the occupational safety limit. For comparison, levels found in cigarette smoke were anywhere from 2.5 to 40 times higher.


However, the researchers also examined the vapor contents of a direct exhale into a 10 liter glass chamber to get a clearer picture of what vapers actually inhale. Of the nine chemicals found in the chamber, five are not considered toxic for inhalation at any level. The other four were found to have at least a 90 percent safety margin.


Concentration of selected chemicals in e-cig vapor

Image by Elaine Keller


Another not of importance was the amount of nicotine found in the e-cigarette vapor. While it wasn’t detected in the 8 meter steel room, nicotine was found in the much smaller glass chamber but only at very low levels. According to Allvoices, bystanders would have to directly inhale the same amount of vapor that the user inhales for 300 puffs in order to receive as much nicotine as that of a piece of Nicorette gum contains.




In addition to knowing what the majority of manufacturers use to create their e-liquids, we also have scientific evidence of what typical electronic cigarette vapor contains. Some of the chemicals found are indeed toxic, but only at levels far lower than those detected in cigarette smoke. Next time your local politician goes on a misinformed tirade about the lack of knowledge for electronic cigarettes, just refer them to this evidence. The Indoor Air study further backs the fact that not only do we know what’s in e-cigarettes, but vapor they produce is far safer than cigarette smoke and is not a threat to bystanders.


Further reading:


Characteristics of Tested E-Cigarettes – Indoor Air

What’s in an E-Cigarette?

Levels of Carcinogens and Toxicants in Electronic Cigarette Vapor – Tobacco Control

Emission of Organic Compounds in E-Cigs is Lower than Cigarettes – Dr. Siegel