Praxichys
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Metabolism of Propylene Glycol
As far as I have found, rat, mouse, and rabbit oral LD50 for propylene glycol is in the order of 20g/kg.
Propylene glycol is used as antifreeze in potable water systems and is an ingredient in many of foods and beverages, albeit in small amounts. It also
finds use in cosmetics and lubricants.
How much propylene glycol is too much to ingest? I have yet to find any published effects short of nonhuman LD50 information. I am wondering about
whether it would be a smart demonstration to drink somewhere around 50mL of USP grade propylene glycol while talking about how its metabolites differ
from that of its toxic cousin ethylene glycol. (Various ketone bodies instead of oxalates) This is for a presentation in organic chemistry, and I
really want to do something dramatic.
That, and I wonder if I can pull off a positive result on a Ketostix test later that day as a result of this ingestion?
I am fairly certain this act will be inconsequential healthwise, but I would rather not end up in the hospital over a silly experiment. Good idea or
not?
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Morgan
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Some tidbits - maybe you will come away with some general impression.
http://toxnet.nlm.nih.gov/cgi-bin/sis/search/a?dbs+hsdb:@ter...
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bfesser
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I'm allergic to propylene glycol containing deodorants, and have to check the ingredients before buying different brands. You should check to be sure
that you don't have a similar allergy before swallowing the stuff—which I'd advise against, regardless.
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Finnnicus
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People vaporize propylene gycol in e-cigarettes all the time.
I'm not saying it's healthy, but they aren't all dead either.
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Morgan
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"Taste, fun and convenience"
http://www.propylene-glycol.com/propylene-glycol-ups-ep-phar...
"Propylene glycol is used professionally by manufacturers of consumer and industrial products, but it is not available to consumers as pure substance.
Under normal conditions it is therefore impossible to ingest propylene glycol in large amounts, and consumer exposure to propylene glycol via products
is extremely low. In addition, studies have shown that propylene glycol has a very low degree of toxicity. Actually, from a toxicological point of
view, alcohol is more toxic than propylene glycol. European legislation limits the presence of propylene glycol as food additive to 1-3 g/kg in the
final foodstuff (0.1-0.3%). A full acceptable daily intake (ADI) of 0 – 25 mg/kg bodyweight has been assigned for propylene glycol by the European
Commission´s Scientific Committee on Food.
"The producers of propylene glycol and members of Cefic’s PO/PG sector group do not support the use of propylene glycol in electronic cigarettes,
nor in artificial (theatrical) fogs due to possible effects on the eye, nose, throat, and respiratory tract membranes as well as the absence of
information on potential long term effects from prolonged inhalation of (fine) droplets of propylene glycol."
http://www.propylene-glycol.com/faq
http://www.accessdata.fda.gov/scripts/fcn/fcnDetailNavigatio...
Seems like they put it in too many things. The other day I recall reading it listed on a simple package of shredded coconut.
"a) Propylene glycol (C3H8O2, CAS Reg. No. 57-55-6) is known as 1,2-propanediol. It does not occur in nature. Propylene glycol is manufactured by
treating propylene with chlorinated water to form the chlorohydrin which is converted to the glycol by treatment with sodium carbonate solution. It is
also prepared by heating glyercol with sodium hydroxide."
http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/cfrs...
http://www.glycolallergy.com/Advice/tabid/63/articleType/Art...
Supplemental feeding with glycerol or propylene glycol of dairy cows in early lactation--effects on metabolic status, body condition, and milk yield.
http://www.ncbi.nlm.nih.gov/pubmed/22541468
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jwpa17
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I doubt that 50 mL (about 50 g) of propylene glycol would be dangerous to a healthy adult, but I question whether it is an effective "demonstration"
to an audience of any size. As I see it, you pour a water-white liquid into a glass, tell everyone what it is, and drink it. Several hours later,
you tell them your ketone levels are increased, as evidenced by a pee-stick? Sorry, it just doesn't seem engaging to me, so why do it?
Also note - according to Wikipedia, "Serious toxicity generally occurs only at plasma concentrations over 1 g/L, which requires extremely high intake
over a relatively short period of time.[19]" You're proposing to ingest about 50 g in a very short time. Assuming about 5L of plasma (a generous
assumption, I know), you might have a problem if your absorption efficiency is better than 10%.
Seem to me questionable safety and dubious merit as a demo...don't do it.
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Praxichys
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I guess what I had in mind was two clearly labeled glass vials, one with ethylene glycol and one with propylene glycol, which get passed around as I
talked about polyols, their history, manufacture, and industrial use. The audience would be told to examine the viscosity, color, and odor. A gallon
jug of ethylene glycol antifreeze and one of propylene glycol antifreeze would also be used as props, one green and the other pink. The contents of
the vials, of course, would simply be syrupy clear liquids.
After they had both gone around I would then explain alcohol dehydrogenase and its effect on both, and then drink the propylene glycol vial.
I think perhaps if I expanded the scope of this project I could increase safety to myself by instead consuming glycerol, mannitol, sorbitol,
erythritol, or some other less-digestible polyol, although the metabolites of these compounds (If the longer chains can even be altered at all) and
their uses outside of the food industry are much more difficult to explain, IMO, and might hurt the flow of the presentation. Propylene glycol was
chosen at first since since most people interested in chemistry already know that glycerol is safe for consumption. The remainder of the polyols are
solids and are more difficult to ingest in a dramatic fashion.
I would have a minute or two the next day of presentations to show that the ingestion of the propylene glycol induced acute ketonuria, using a
Ketostix test strip.
Anyway, it is probably a bad idea to drink propylene glycol. I think I should rewrite for glycerol, and plan for a potentially laxitive effect.
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bfesser
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Why are you so insistent on drinking anything? It seems like an ineffective and risky way of conveying your point, to me.
If you absolutely must; prepare two vials for the 'propylene glycol' with identical labelling and volumes of clear colorless viscous fluid. Hide one
filled with <a href="http://www.kinderproducts.ca/Drink_Thickeners.html" target="_blank">thickened water</a> <img
src="../scipics/_ext.png" /> and a drop of colorless flavoring (food-grade peppermint extract?) in your pocket (flavor so you know you're drinking
the guaranteed safe one). Pass the real propylene glycol vial around, but when you get it back use a little <a href="http://youtu.be/oXGr76CfoCs"
target="_blank">misdirection and sleight of hand</a> <img src="../scipics/_yt.png" /> to swap the two vials. Fudging the "Ketostix"
positive is trivial.
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Morgan
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Seems like if you pretended to drink the propylene glycol to prove that it was safe you would be defeating the purpose of the demonstration. And then
someone else might see the demonstration and decide 50 ml is safe because you appeared to drink it and nothing happened. And maybe nothing would but
maybe for some reason it would cause some transient malaise.
On the other hand if you did get sick it would be a good demonstration showing that it isn't always safe in the amount taken or maybe even by lesser
amounts over time.
How can you present something as true if you don't have faith enough in your own premise or if you read that it does have side effects in some cases
and mislead your audience?
What you risk is the truth, even if you are prudently erring on the side of caution.
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Paddywhacker
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There are enough idiots confusing ethanol and methanol without starting another such meme, but in the classroom the metabolism of methanol, ethanol,
ethylene glycol, propylene glycol and glycerol is an interesting subject for Biochem 101.
Some wag is sure to bring up 1,3-propandiol, so teacher, do your homework.
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Praxichys
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Speaking of confusing your alcohols, I think you mean 1,4-butanediol. But I get your point.
I think I am dropping this idea altogether. There is just too much that could go wrong.
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unionised
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Teaching students to drink lab chemicals is a bad idea.
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Chemosynthetic
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I feel the exact same way. I see too many professionals drinking and eating in labs that are intentionally using acutely toxic chemicals for research
as is, and would personally recommend against any demonstrations whereby the two activities of research and eating might get dangerously conflated.
Unfortunately, you have to keep a lowest common denominator approach... though I do fully support the concept of demonstrating valence and ligand
changes in bioavailability, receptor binding, etc. I have to tell people the equivalent of "different things are different" in regard to mercury
valence for vaccines all the time.
edit: not to bring controversy to the thread with my last line... though there shouldn't be controversy over vaccinations as a concept anyway in this
day and age.
[Edited on 15-2-2014 by Chemosynthetic]
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Morgan
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"A greater understanding..."
Ruminal Fermentation of Propylene Glycol and Glycerol
"The feeding of sugars and other polyols to ruminants for either therapeutic or nutritional purposes is a long-standing practice in the animal
production industry. Ketosis, a metabolic disorder affecting dairy cows that occurs during high-energy demand (milk synthesis) and insufficient
nutrient intake (late prepartum to early postpartum), is effectively treated with drenching of propylene glycol (5-8) and glycerol."
'Although propylene glycol can prevent and treat ketosis in
dairy cows, large doses (>500 g/day) can harm cattle (5, 11)
and other herbivores. Symptoms when such doses are fed
include depression, ataxia, and excessive salivation, as well as abnormal, malodorous, and foul breath and feces (12-14).
Anecdotal evidence suggests that the foul breath is sulfurous, and specifically garlicky and/or onion-like in odor. As large amounts of glycerol may
be fed to ruminants and as propylene glycol may be toxic to them, a greater understanding of how these compounds are metabolized in ruminants is
needed."
http://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1014&a...
I hope the salmon aren't getting depressed like the cows.
Effect of Dietary Propylene Glycol on Growth, Survival, Histology, and Carcass Composition of Atlantic Salmon
"Weight gain and feed conversion efficiency were better for fish fed the diets containing 5–15% propylene glycol than in those fed diets containing
either 0 (control) or 25% propylene glycol."
"These results indicate that propylene glycol can effectively be used to elevate moisture level in diets for Atlantic salmon and may enhance diet
palatability by improving texture, flavor, or moisture content."
http://www.tandfonline.com/doi/abs/10.1577/1548-8640(1988)050%3C0012%3AEODPGO%3E2.3.CO%3B2#.UwDsuvlRS_A
"It does not occur in nature." And yet it's everywhere.
"Current good manufacturing practice results in maximum levels, as served, of 5 percent for alcoholic beverages, as defined in 170.3(n)(2) of this
chapter; 24 percent for confections and frostings as defined in 170.3(n)(9) of this chapter; 2.5 percent for frozen dairy products as defined in
170.3(n)(20) of this chapter; 97 percent for seasonings and flavorings as defined in 170.3(n)(26) of this chapter; 5 percent for nuts and nut products
as defined in 170.3(n)(32) of this chapter; and 2.0 percent for all other food categories."
http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRS...
[Edited on 16-2-2014 by Morgan]
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Morgan
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"Beer treated with STABILFOAM forms an attractive, white and long-lasting lace on the glass as the beer is consumed."
"STABILFOAM helps to overcome fluctuations in wort composition due to seasonal variations in raw materials which adversely affect head retention."
http://www.cbsbrew.com/Fiches/Fiches_html/Stabilfoam.html
What exactly is in your beer?
"Fancy a refreshing pint of betaglucanase? Or maybe a thirst-quenching glass of propylene glycol alginate?"
TYPICAL BEER ADDITIVES
Betaglucanase
Ammonia caramel
Rhoiso-alpha acids
Sulphur dioxide
Protease
Amyloglucosidase
Propylene glycol alginate
Silicone
"Perhaps, then, it is hardly surprising that fans of German beers insist that they taste "cleaner" - and swear that they cause less of a hangover."
"You would only be tempted to start adding chemicals if you were producing on a vast scale and needed to speed things up - if you have that pressure
to be as quick and profitable as possible," he says.
"We are a small operation here, so we simply don't need to use any additives."
"Consumers deserve to know what goes into their [alcoholic] drink in the same way as they would any other product," says Camra research and
information manager Iain Loe.
"Brewers shouldn't have anything to hide."
http://news.bbc.co.uk/2/hi/business/4942262.stm
"I was also diagnosed with an allergy to propylene glycol 2 years ago. I was tested specifically for that in 2 types of tests so I am 100% certain
that's what it is. I was already a fairly all-natural kind of person but still had to make further modifications with everything that I consume or
absorb, etc. I was able to go off of asthma meds that I had taken for 20 years and no longer have chronic asthmatic bronchitis. I have been drinking
craft beer for quite some time now and "know my brewer." The issue of what to drink on the rare occasions that I go somewhere with friends that does
not have a decent beer selection. I know that if in doubt I can generally go with German beer due to the German Purity Law. It would be nice to have a
list of beers that use StabilFoam in their beer products the same way there are lists of vegan, vegetarian, gluten-free, etc. Or ingredients disclosed
on the packaging. Or something..."
"Also under suspicion are artificial flavorings and/or colorings. PG may lurk in there as artificial flavorings are proprietary and straight up food
coloring (not sure about dyes and lakes) is pure PG. Our brewer used real pumpkin (from a can) in their pumpkin ales last fall. The mass produced
kinds of pumpkin ale may be artificial flavor."
"Good luck and if you or anyone else discovers any good resources on which beers contain StabilFoam, I would greatly appreciate your passing the info
along. Thanks!"
http://thebrewingnetwork.com/forum/viewtopic.php?f=10&t=...
"Adverse responses to intravenous administration of drugs that 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".[27] 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,[28] which may be due to propylene glycol's mild anesthetic / CNS-depressant -properties as an alcohol.[29] In one case, intravenous
administration of propylene glycol-suspended nitroglycerin to an elderly man may have induced coma and acidosis.[30]"
http://en.wikipedia.org/wiki/Propylene_glycol
[Edited on 16-2-2014 by Morgan]
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Morgan
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"Propylene glycol is a related chemical that, like PEGs, functions as a penetration enhancer and can allow harmful ingredients to be absorbed more
readily through the skin. It can also cause allergic reactions. Health Canada categorized propylene glycol as a "moderate human health priority" and
flagged it future assessment under the government's Chemicals Management Plan."
http://davidsuzuki.org/issues/health/science/toxics/chemical...
Penetration enhancers.
http://www.ncbi.nlm.nih.gov/pubmed/15019749
Urea analogues in propylene glycol as penetration enhancers in human skin
http://www.sciencedirect.com/science/article/pii/03785173899...
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Paddywhacker
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Quote: Originally posted by Praxichys  | Speaking of confusing your alcohols, I think you mean 1,4-butanediol. But I get your point.
I think I am dropping this idea altogether. There is just too much that could go wrong. |
No, 1,3-propanediol
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bigmol
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The legal limit for propylene glycol in food is good manufacturing practice. The reason is that it is metabolised completely to carbon dioxide and
water by human. Other that the hyperosmolar effect on the gut of high concentrations the only other thing of concern is the calorific value of the
stuff. It is somewhere between that of carbohydrate and fat. But do not get it confused with ethylene glycol. The end product of ethylene glycol
metabolism is oxalic acid. The oxalic acid then precipitates out as calcium oxalate. The precipitated calcium oxalate then blocks kidneys. Only cure
dialysis or kidney transplant
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gregxy
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Some other interesting topics you could discuss:
The differences in alcohol metabolism in Asians and Europeans.
Compare the "therapeutic ratios" of alcohol and THC. Which drug would be most likely to be approved by the FDA?
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zed
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Yup. And based on the toxicity of oxalic acid formed via ethylene glycol metabolism, we might well imagine propylene glycol metabolism also produces
a very toxic by-product. Heck, glycerol too.
Doesn't seem to work that way. Good thing. If glycerol was a problem, I wouldn't live long enough to finish the french-fries I'm currently chomping
on.
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