Chemicals associated with E-Cigarettes

Electronic cigarette is also referred as e-cig or e-cigarette, which is a battery-powered vaporizer which has a similar feel to tobacco smoking.

Third generation of e-cigarette that have organic light-emitting diode displays and buttons to adjust wattage or voltage.

Credit: Shutterstock/C&EN

Electronic cigarettes do not contain tobacco, although they do use nicotine from tobacco plants. They do not produce cigarette smoke but rather an aerosol. In general, they have a heating element that atomizes a liquid solution known as e-liquid.  E-liquid, also referred as e-juice or simply "juice", is a liquid solution that when heated by an atomizer produces vapor. The main ingredients of e-liquids are usually a mix of
propylene glycol (PG),

glycerin (G)

and/or polyethylene glycol 400 (PEG400),

sometimes with differing levels of alcohol mixed with concentrated or extracted flavourings;

E-cigarette fluid or “e-juice” comes in thousands of flavors, including pineapple custard and Scooby snack.

Credit: Associated Press

and optionally, a variable concentration of tobacco-derived nicotine.ingredients but without nicotine.

The solution is often sold in bottles or pre-filled disposable cartridges, or as a kit for consumers to make their own eJuices. Components are also available to modify or boost their flavour, nicotine strength, or concentration of e-liquid. Pre-made e-liquids are manufactured with various tobacco, fruit, and other flavors, as well as variable nicotine concentrations (including nicotine-free versions). Surveys suggested that the most liked e-liquids had a nicotine content of 18 mg/ml, and largely the favorite flavors were tobacco, mint and fruit. The flavorings may be natural or artificial.

Flavoring substances not identified in a natural product intended for human consumption, whether or not the product is processed. These are typically produced by fractional distillation and additional chemical manipulation of naturally sourced chemicals, crude oil or coal tar.

Most artificial flavors are specific and often complex mixtures of singular naturally occurring flavor compounds combined together to either imitate or enhance a natural flavor. These mixtures are formulated by flavorists to give a food product a unique flavor and to maintain flavor consistency between different product batches or after recipe changes. The list of known flavoring agents includes thousands of molecular compounds, and the flavor chemist (flavorist) can often mix these together to produce many of the common flavors.

Chemical	Odor
Diacetyl	Buttery
Isoamyl acetate	Banana
Benzaldehyde	Bitter almond
Cinnamaldehyde	Cinnamon
Ethyl propionate	Fruity
Methyl anthranilate	Grape
Limonene	Orange
Ethyl decadienoate	Pear
Allyl hexanoate	Pineapple
Ethyl maltol	Sugar, Cotton candy
Ethylvanillin	Vanilla
Methyl salicylate	Wintergreen

References and more to read:
http://cen.acs.org/articles/93/i7/Boom-E-Cigarettes-Sparks-Calls.html
http://en.wikipedia.org/wiki/Electronic_cigarette#Atomizer
http://health.howstuffworks.com/wellness/smoking-cessation/10-facts-about-e-cigarettes.htm
http://en.wikipedia.org/wiki/Flavor

Roles of the human occupant in indoor chemistry

"Human occupants, through the reactive chemicals that they emit, have a large influence on
the atmospheric chemistry that occurs around them, ultimately impacting their own chemical
exposures and their health" --A recent article published in the journal Indoor Air by Charles J. Weschler from the Environmental and Occupational Health Sciences Institute, Rutgers University gives an overview on roles of the human occupant in indoor chemistry.

As summarized by Weschler, a number of evidences suggested that there are pronounced influences of humans on chemistry within the indoor spaces they inhabit.

Occupants leave behind skin flakes, skin oils and body effluents on indoor surfaces and on their clothing. These human generated long-chain hydrocarbon involve unsaturated carbon bonds, which will react with indoor ozone and thus affect indoor chemical reactions involving ozone.

This review article also summarized the potential role of occupants on the levels of semivolatile organic compounds from indoor sources, which is based on a human uptake and exposure model coupled with an indoor chemical fate mass balance model that suggests human intake and elimination of a chemical (e.g., biotransformation, renal excretion, fecal egestion, hand washing, bathing)
influences its fate indoors. Such an impact varies according to chemicals properties (volatility, degradation, etc) as well as environmental characteristic (e.g., ventilation) and human behaviors (e.g. the frequency of cleaning. As mentioned by Wescler, this is an area that is potentially rich
for further exploration. Refer to this modeling study for more information.

Some facts summarized in the article:

• lipids on skin surface of human are a combination of sebum secreted by sebaceous glands and lesser amounts of lipids from the stratum corneum
• The chemicals that constitute skin surface lipids include triacyl glycerols (~25%), unesterfied fatty acids (~25%), wax esters (~22%), squalene (~10%), mono- and diacyl glycerols (~10%) and lesser amounts of sterol esters, sterols, phospholipids and other species 
• squalene is responsible for roughly 50% of the unsaturated carbon bonds in skin surface lipids

Finally, the review article by Weschler provides a summary on the roles of the human occupant in indoor chemistry- "We have read the early pages of what promises to be a long and interesting book –interesting, in part, because the subject is us. This unfolding story promises to inform strategies designed to protect our health, our technical devices and our cultural artifacts"

References and more to read: 

http://dx.doi.org/10.1111/ina.12185

http://dx.doi.org/10.1021/es502718k