A powerful preventive against pneumonia, influenza and other respiratory diseases may be promised by a brilliant series of experiments conducted during the last three years at the University of Chicago's Billings Hospital. Dr. Oswald Hope Robertson last week was making final tests with a new germicidal vapor—propylene glycol—to sterilize air. If the results so far obtained are confirmed, one of the age-old searches of man will finally achieve its goal.

The idea of sterilizing the air is not new —London's great fire of 1666, for example, was touched off by the countless fires which townsmen lit to purge the air of plague. Use of chemical sprays to control air contamination was first attempted in 1928 by three doctors who tried a fine mist of sea water containing sodium hypochlorite. This venture gave promising results, but all such research lapsed for another decade. Within the last few years, several research groups (notably the University of Pennsylvania's new Air-Borne Disease Laboratories) again began testing various sprays. Many chemicals were found to kill airborne micro-organisms quickly, even in concentrations as low as one gram of chemical per 500 cu. ft. of air. Trouble was that all these air germicides smelled bad, or were toxic, or irritated the respiratory tract. Dr. Robertson's propylene glycol vapor is odorless, tasteless, nontoxic, non-irritating, cheap, highly bactericidal.

Its discovery was accidental. Dr. Robertson and his colleagues were trying out another possible germicide—a detergent or "soapless soap" (similar to Dreft, Aerosol and other products widely sold for household and industrial use). Water solutions of the detergent were only mildly effective, so the researchers tried solutions of detergents in propylene glycol, which is a sort of thin glycerine. Results were much better. Then the researchers found that the propylene glycol itself was a potent germicide. One part of glycol in 2,000,000 parts of air would—within a few seconds—kill concentrations of air-suspended pneumococci, streptococci and other bacteria numbering millions to the cubic foot.

How did it work? Respiratory disease bacteria float about in tiny droplets of water breathed, sneezed and coughed from human beings. The germicidal glycol also floats in infinitesimally small particles. Calculations showed that if droplet had to hit droplet, it would take two to 200 hours for sterilization of sprayed air to take place. Since sterilization took place in seconds, Dr. Robertson concluded that the glycol droplets must give off gas molecules which dissolve in the water droplets and kill the germs within them.

Dr. Robertson placed groups of mice in a chamber and sprayed its air first with propylene glycol, then with influenza virus. All the mice lived. Then he sprayed the chamber with virus alone. All the mice died.

Propylene glycol is harmless to man when swallowed or injected into the veins. It is also harmless to mice who have breathed it for long periods. But medical science is cautious—there was still a remote chance that glycol might accumulate harmfully in the erect human lungs which, unlike those of mice, do not drain themselves. So last June Dr. Robertson began studying the effect of glycol vapor on monkeys imported from the University of Puerto Rico's School of Tropical Medicine. So far, after many months' exposure to the vapor, the monkeys are happy and fatter than ever. Dr. Robertson does not expect mankind to live, like his monkeys, continuously in an atmosphere of glycol vapor; but it should be most valuable in such crowded places as schools and theaters, where most respiratory diseases are picked up.

Ref: http://www.time.com/time/magazine/article/0,9171,932876-2,00.html

Clinical trials on electronic cigarettes containing propylene glycol were carried out in New Zealand by Dr. Murray Laugeson of Health New Zealand and can be found on the website of SS Choice LLC at http://www.eCigarettesChoice.com under the tab "Media Coverage." Far from posing a threat to our health, the propylene glycol in e cigarettes might just keep us healthy. Further studies should be done on the effects of propylene glycol to determine if it can be used successfully as a virus prevention tool. Wouldn't it be wonderful if the best flu preventative was right under our noses all this time?

Ref: http://www.news-medical.net/news/20091104/Propylene-glycol-in-e-cigarettes-might-keep-us-healthy-says-researchers.aspx?page=2

Propylene glycol, also called 1,2-propanediol or propane-1,2-diol, is an organic compound (a diol or double alcohol) with formula C3H8O2 or HO-CH2-CHOH-CH3. It is a colorless, nearly odorless, clear, viscous liquid with a faintly sweet taste, hygroscopic and miscible with water, acetone, and chloroform.

The compound is sometimes called α-propylene glycol to distinguish it from the isomer propane-1,3-diol HO-(CH2)3-OH, also called β-propylene glycol.

Industrially propylene glycol is produced from propylene oxide .[3] Different manufacturers use either non-catalytic high-temperature process at 200 °C (392 °F) to 220 °C (428 °F), or a catalytic method, which proceeds at 150 °C (302 °F) to 180 °C (356 °F) in the presence of ion exchange resin or a small amount of sulfuric acid or alkali.

Final products contain 20% 1,2-propanediol, 1.5% of dipropylene glycol and small amounts of other polypropylene glycols.[4] Propylene glycol can also be converted from glycerol, a biodiesel byproduct.

Applications
Propylene glycol is used:

* As a solvent in many pharmaceuticals, including oral, injectable and topical formulations. Notably, diazepam, which is insoluble in water, uses propylene glycol as its solvent in its clinical, injectable form.[5]
* As a humectant food additive, labeled as E number E1520
* As an emulsification agent in Angostura and orange bitters
* As a moisturizer in medicines, cosmetics, food, toothpaste, mouth wash, hair care and tobacco products
* As a carrier in fragrance oils
* As an ingredient in massage oils
* In hand sanitizers, antibacterial lotions, and saline solutions
* In smoke machines to make artificial smoke for use in firefighters' training and theatrical productions
* In electronic cigarettes, as a vaporizable base for diluting the nicotine liquid
* As a solvent for food colors and flavorings
* As an ingredient, along with wax and gelatin, in the production of paintballs
* As a moisture stabilizer (humectant) for snus (Swedish style snuff).
* As a cooling agent for beer and wine glycol jacketed fermentation tanks
* As a non-toxic antifreeze for winterizing drinking water systems, and in applications where the used antifreeze eventually will be drained into the soil, water, or a septic system.[6]
* As a less-toxic antifreeze in solar water heating systems
* As a solvent used in mixing photographic chemicals, such as film developers
* In cryonics
* As a working fluid in hydraulic presses
* As a coolant in liquid cooling systems
* To regulate humidity in a cigar humidor
* As the killing and preserving agent in pitfall traps, usually used to capture ground beetles
* As an additive to pipe tobacco to prevent dehydration.
* To treat livestock ketosis
* As the main ingredient in deodorant sticks.
* To de-ice aircraft.[7]
* As an ingredient in UV or blacklight tattoo ink
* As a lubricant in Air Conditioning compressors.

Propylene glycol has properties similar to those of ethylene glycol (monoethylene glycol, or MEG). (Note: Infrequently propylene glycol may also use the acronym MEG, but as an abbreviation of methyl ethyl glycol- the industry standard acronym for propylene glycol is PG or MPG (monopropylene glycol)). The industrial norm is to replace ethylene glycol with propylene glycol when safer properties are desired.

Safety
Humans
The acute oral toxicity of propylene glycol is very low, and large quantities are required to cause perceptible health damage in humans; propylene glycol is metabolized in the human body into pyruvic acid (a normal part of the glucose-metabolism process, readily converted to energy), acetic acid (handled by ethanol-metabolism), lactic acid (a normal acid generally abundant during digestion) [9] , and propionaldehyde [10] [11].

Serious toxicity generally occurs only at plasma concentrations over 1 g/L, which requires extremely high intake over a relatively short period of time.[12] It would be nearly impossible to reach toxic levels by consuming foods or supplements, which contain at most 1 g/kg of PG. Cases of propylene glycol poisoning are usually related to either inappropriate intravenous administration or accidental ingestion of large quantities by children.[13] The potential for long-term oral toxicity is also low. In one study, rats were provided with feed containing as much as 5% PG in feed over a period of 104 weeks and they showed no apparent ill effects.[14] Because of its low chronic oral toxicity, propylene glycol was classified by the U. S. Food and Drug Administration as "generally recognized as safe" (GRAS) for use as a direct food additive.

Prolonged contact with propylene glycol is essentially non-irritating to the skin. Undiluted propylene glycol is minimally irritating to the eye, and can produce slight transient conjunctivitis (the eye recovers after the exposure is removed). Exposure to mists may cause eye irritation, as well as upper respiratory tract irritation. Inhalation of the propylene glycol vapors appears to present no significant hazard in ordinary applications. However, limited human experience indicates that inhalation of propylene glycol mists could be irritating to some individuals. Therefore inhalation exposure to mists of these materials should be avoided. Some research has suggested that propylene glycol not be used in applications where inhalation exposure or human eye contact with the spray mists of these materials is likely, such as fogs for theatrical productions or antifreeze solutions for emergency eye wash stations.[15]

Propylene glycol does not cause sensitization and it shows no evidence of being a carcinogen or of being genotoxic.[16][17]

Adverse responses to intravenous administration of drugs which use PG as an excipient have been seen in a number of people, particularly with large dosages thereof. Responses may include "hypotension[,] bradycardia... QRS and T abnormalities on the ECG[,] arrhythmia[,] cardiac arrest[,] serum hyperosmolality[,] lactic acidosis[,] and haemolysis." [18] A high percentage (12% to 42%) of directly-injected propylene glycol is eliminated/secreted in urine unaltered depending on dosage, with the remainder appearing in its glucuronide-form. The speed of renal filtration decreases as dosage increases [19], which may be due to propylene glycol's mild anesthetic / CNS-depressant -properties as an alcohol [20]. In one case, administration via IV of PG-suspended nitroglycerin to an elderly man may have induced coma and acidosis [21].

Animals
Propylene glycol is an approved food additive for dog food under the category of animal feed and is generally recognized as safe (GRAS[22]) for dogs [23]. Similarly propylene glycol is an approved food additive for human food as well[24]. The exception is that it is prohibited for use in food for cats because of a species-specific reaction in the body, as noted in 21 CFR 582.1666.

Veterinary data indicate that propylene glycol is toxic to dogs with a 50% chance of being lethal at doses of 9mL/kg, although the figure is higher for most laboratory animals (LD50 at levels of 20mL/kg).[25]

However, propylene glycol may be toxic to cats in ways not seen in other animals. The U.S. Food and Drug Administration has determined that its presence in or on cat food has not been shown by adequate scientific data to be safe for use. Any such use is considered an adulteration of the cat food and a violation of the Federal Food, Drug, and Cosmetic Act.[26]

Allergic reaction

Research has suggested that individuals who cannot tolerate propylene glycol probably experience a special form of irritation, but that they only rarely develop allergic contact dermatitis. Other investigators believe that the incidence of allergic contact dermatitis to propylene glycol may be greater than 2% in patients with eczema.[27]

Patients with vulvodynia and interstitial cystitis may be especially sensitive to propylene glycol. Women struggling with yeast infections may also notice that some OTC creams can cause intense burning.[28] Post menopausal women who require the use of an estrogen cream may notice that brand name creams made with propylene glycol often create extreme, uncomfortable burning along the vulva and perianal area. In these cases, patients can request that a local compounding pharmacy make a "propylene glycol free" cream.

Additionally, some electronic cigarette users who inhale propylene glycol vapor may experience dryness of the throat or shortness of breath . As an alternative, some suppliers will put Vegetable Glycerin in the "e-liquid" for those who are allergic (or have bad reactions) to propylene glycol.
[edit] Possible air germicide

Studies conducted in 1942 by Dr. Oswald Hope Robertson of University of Chicago's Billings Hospital showed vaporized propylene glycol inhalation in laboratory mice may prevent pneumonia, influenza, and other respiratory diseases. Additional studies in monkeys and other animals were undertaken to determine longterm effects, especially the potential for accumulation in the lungs. After a few months of treatment, no ill effects were discovered.[29]

Environmental

Propylene glycol is known to exert high levels of biochemical oxygen demand (BOD) during degradation in surface waters. This process can adversely affect aquatic life by consuming oxygen aquatic organisms need to survive. Large quantities of dissolved oxygen (DO) in the water column are consumed when microbial populations decompose ethylene glycol.

The oxygen depletion potential of airport deicing operation discharges is many times greater than that of raw sewage. For example, before application, Type I propylene glycol-based deicing fluid is generally diluted to a mixture containing approximately 50% propylene glycol. Pure propylene glycol has a five-day biochemical oxygen demand (BOD5) concentration of approximately 1,000,000 mg/L. A typical diluted propylene-based deicing fluid could therefore have a BOD5 concentration of approximately 500,000 mg/L. In comparison, raw sewage typically has a BOD5 concentration of approximately 200 mg/L. The amount of fluid used to deice a single jet depends on the nature of the precipitation event and the size of the aircraft but can range from a couple hundred to several thousand gallons. Therefore, deicing a single jet can generate a BOD5 load greater than that of one million gallons of raw sewage. A large hub airport often has several hundred flights each day.

Sufficient DO levels in surface waters are critical for the survival of fish, macroinvertebrates, and other aquatic organisms. If oxygen concentrations drop below a minimum level, organisms emigrate, if able and possible, to areas with higher oxygen levels or eventually die. This effect can drastically reduce the amount of usable aquatic habitat. Reductions in DO levels can reduce or eliminate bottom-feeder populations, create conditions that favor a change in a community’s species profile, or alter critical food-web interactions.[30]

Ref: http://en.wikipedia.org/wiki/Propylene_glycol

WOW...cool article.

I like it! See we be healthy lol


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Great post....great info! My OCD approves

Very nice.