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

Health Risks from Inhaled Polychlorinated Biphenyls

Evaluating Health Risks from Inhaled Polychlorinated Biphenyls: Research Needs for Addressing Uncertainty

A recent article published in Environ Health Perspect by Lehmann et al. DOI:10.1289/ehp.1408564 describes some common sources of PCBs in indoor air and estimate the contribution of inhalation exposure to total PCB exposure for select age groups and identified some critical areas of research needed to improve assessment of exposure and exposure response for inhaled PCBs.

Air concentrations of polychlorinated biphenyls (PCBs) in some buildings can be orders of magnitude higher than background levels. The potential health risk posed by PCBs from indoor environment need to be assessed. To assess such risk we need to face some uncertainty.

Previous assessments of exposure and risk associated with PCBs primarily focused on dietary intake of contaminated food. With many recent studies suggested the importance of indoor PCB exposure, this article points out one important uncertainty for risk assessment of PCBs from indoor exposure.

The distributions of  PCB congeners in food and in indoor air are quite different. As such, toxicity of of PCB mixtures from indoor environment is likely to be different from toxicity due to dietary intake.

In addition to the uncertainty mentioned in the article, I think another uncertainty we need to face lies in the pathway from external exposure to internal exposure. Bioavailability/toxicokinetics of PCBs from inhalation would be quite different from dietary intake and need to be addressed.