Wednesday, August 24, 2011

E-Cigarettes - No Toxic Effects from Inhaled Propylene Glycol Aerosol

One of the key ingredients in many e-cigarette liquids is propylene glycol (PG), described by Wikipedia (here) as a “colorless, nearly odorless, clear, viscous liquid with a faintly sweet taste…” The entry also explains that PG is used “as a moisturizer in medicines, cosmetics, food, toothpaste, shampoo, mouth wash, hair care and tobacco products…, in smoke machines to make artificial smoke for use in firefighters' training and theatrical productions” and “as a moisture stabilizer (humectant) for snus” among many other applications.

A new study provides valuable information about the toxicological profile of inhaled PG aerosols in laboratory animals; it also provides an excellent general review of the agent. The authors are Michael Werley, a scientist at Altria, and colleagues from Charles River Laboratories (Scotland), WIL Research Laboratories, Battelle Memorial Institute and Virginia Commonwealth University. It was published in the journal Toxicology (abstract here).

The investigators exposed rats and dogs to high concentrations of PG aerosol for up to 28 days, followed by comprehensive systemic evaluations, especially involving the respiratory system.

They report, “In general, these studies confirmed the relatively low toxic potential of [aerosol] PG, administered by various dose routes, including the inhalation route…in the dog, no histopathological effects on the [larynx, trachea and lung] tissues were observed.” The investigators noted decreases in some assessments of red blood cells in dogs treated for 28 days, but “these effects were not clinically significant in the dog and had no effect upon their activity of health”, and “the values still within the normal historical ranges for dogs of this age, strain and sex.”

Werley and colleagues added that, “overall, PG inhalation exposure in rats and dogs produced quite limited toxicological findings, and allowed us to conclude that [aerosol] PG exposures could be conducted safely in man by the inhalation route…”

This study assessed the effects of short-term exposure to PG vapor, but the effects of long-term (months or years) exposure are unknown and unknowable. However, it provides valuable information for e-cigarette users and policy makers. First, even high concentrations of PG vapor don’t have any measurable harmful effects, which is fully consistent with its designation by the FDA as “generally recognized as safe” as a food additive for all food categories up to 2% (here). Just as important, there will be no impact on bystanders from “second-hand” exposure to e-cigarette vapor, if it occurs at all.


Anonymous said...

Propylene Glycol has been a common ingredient in all American made tobacco cigarettes for several decades. Propylene Glycol is used as a humectant and a mild sweetner.

Why would the very same ingredient found in a real cigarette be deemed too harmful in a fake one?

Fact is the FDA knows that propylene Glycol is safe. No new research is needed--it was completed a long time ago.

I might ad that PG is also found in many medical inhalers, Ozium Air Sanitizer, fog machines, skin lotions, cosmetics, even Betty Crocker Super Moist Carrot Cake.

Please review Philip Morris USA brand Marlboro ingredient list found in the link below.

Please cut and paste to your address bar:

Bob Cully said...

A recent NY Times article reveals the fallacy of arguments presented by the FDA and other e-cigarette critics. It is a positive article that shows light on the potential of e-cigarettes as a better alternative for smokers. =)

Libby Manning said...

Propylene glycol may be controversial but the FDA supports its safety. So, there's really no reason to ban e-cigs. Moreover, this alternative is way better than regular tobacco because it's free from the unnecessary and very harmful by-products.

Disposable said...

Please let common sense prevail...

Anonymous said...

After smoking cigarettes for 30 years, I have been using my ecig for over a year now, and if they ban them in the US i will order them online. Nothing, that is *NOTHING* anyone says will ever convince me that ecigs are anywhere near as bad as smoking cigarettes. Why? DUH my own body and the way i feel are all the proof i need! Some people are just not happy unless they are making life miserable for everyone else. There is NO second hand smoke with an ecig, NONE. What is exhaled is water vapor, also known as steam. So are we going to ban tea kettles and anything else that boils water next? Indeed. please do let common sense prevail!

Unknown said...

Be that as it may.. But... The effects of ingesting PG, as opposed to inhaling its vapour, are very different!

Unknown said...

Granted.. e-cigs are less harmful than tobacco-burning cigarettes, but that doesn't alter the fact that there are still many potential harmful effects from e-cigs, along with MANY as yet 'unknowns', as there were initially when the research into tobacco smoking first began! Sounds to me like you're still addicted to the inhalation(with or without nicotine) habit. Me too.. but I'm avoiding all those possible unknowns as well as the few 'knowns' regarding PG vapour inhalation. Not easy, but I'm coping so far. :-)

Paul Davies said...

There has been more about this in the news this month. I read an article where it said the inhalation of propylene glycol and vegetable glycerin could lead to bradycardia (slowing of the heart) however this has only been shown in rodents so the effects on humans are not known. That said, I vape after smoking for years and I feel a hell of a lot healthier than I did before.