The information below on the electronic cigarette, chemical change, physical change, propylene glycol, glycerol, flavorings, water, nicotine and other components of e-liquid is given to pose questions, not answers. We encourage all to read the linked articles and testing to form their own opinions. The information was compiled from online sources. We encourage readers, especially those with professional knowledge of the subject to comment, suggest, and correct any of the information presented below.
We know one thing for sure; combustion such as a burning cigarette, causes a chemical change. This means that although you start with tobacco, you end up with 4000+ chemicals due to the process of combustion.
Here is the definition of chemical change from about.com:
Chemical changes take place on the molecular level. A chemical change produces a new substance. Examples of chemical changes include combustion (burning), cooking an egg, rusting of an iron pan, and mixing hydrochloric acid and sodium hydroxide to make salt and water.
Electronic cigarettes don’t use combustion, they use vaporization which is, according to Wikipedia (I understand it is not the best source…..but it’ll have to do), is the same as evaporation.
Based on this, electronic cigarettes undergo a physical change, not a chemical change. Here is the definition of a physical change from about.com:
Physical changes are concerned with energy and states of matter. A physical change does not produce a new substance. Changes in state or phase (melting, freezing, vaporization, condensation, sublimation) are physical changes. Examples of physical changes include crushing a can, melting an ice cube, and breaking a bottle.
So, based on this, the vapor from an electronic cigarette is composed on what is found in the e-liquid. So what is in the e-liquid? Although exact formulations differ from manufacturer to manufacturer, the typical ingredients include: propylene glycol (PG), glycerin, water, flavorings, and sometimes nicotine. The vast majority of any e-liquid is comprised of propylene glycol and/or glycerin, as these are the substances that have the low vaporization point, making it possible to create the vapor in the first place. Any reputable manufacturer should be using food grade or pharmaceutical grade PG or glycerin. Next is water, then flavoring and nicotine. So what do we know about these substances? Follow the links below.
Propylene Glycol (aka PG)
EPA report on propylene glycol
NASA report on propylene glycol
CDC report on propylene glycol
Preclinical Safety Evaluation of Inhaled Cyclosporine in Propylene Glycol in the Journal of Aerosol Medicine
Tests for the Chronic Toxicity of Propylene Glycol and Triethylene Glycol on Monkeys and Rats by Vapor Inhalation and Oral Administration
Propylene Glycol is an additive for food, medicine, pharmaceuticals and personal care products
*Propylene Glycol is often found in tobacco cigarettes
Glycerin (aka Glycerol, Vegetable Glycerin, VG, Glycerine)
2-Week and 13-Week Inhalation Studies of Aerosolized Glycerol in Rats
United States Department of Labor information on Glycerin Mist
Glycerol is an additive for food, medicine, pharmaceuticals and personal care products
*Glycerol is often found in tobacco cigarettes
The flavorings in electronic cigarettes generally contain very small amounts of natural food flavorings such as citric acid and vinegar as well as artificial food flavorings.
Inhaling Nicotine Shows No Signs of Leading to Cancer
*Nicotine is often found in tobacco cigarettes, as well as a variety of FDA approved smoking cessation products such as inhalers, gums, patches, and lozenges
Anyone who has additional studies and testing (good or bad) on the contents of electronic cigarette e-liquid, please use the comment section below to note them.