Sciencemadness Discussion Board - How toxic is methanol actually?

How toxic is methanol actually?

CobaltChloride - 21-4-2018 at 09:19

Sorry if this has been asked before, but how toxic is methanol actually? It is said to be highly toxic, but the LD50 is said to be 5628 mg/kg, which is far higher than other common organic solvents. Also it is only a 1 on the NFPA health scale. So how dangerous is it to take a few strong whiffs of methanol vapors if you're distilling it (outside, of course, but taking a few whiffs is inevitable), how dangerous is it if you spill a bit on your hand, but you immediately wash your hands and how dangerous would it be to use it at room temperature in a room with an open window? Is there any serious danger of being harmed (besides the dangers posed by its property of being very flammable) in these situations?

aga - 21-4-2018 at 10:14

LD50 5.6g/kg means i need to drink about half a pint of the stuff before expecting to die, although the body is severely damaged before the amount required to cause death is ingested.

Drinking even a small amount can cause blindness.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1771266/

A single whiff is inconsequential. Sustained whiffing would be Bad.

A small spill on the hand has never caused me any problem.

Edit:

As with ALL chemicals, care when handling them to Prevent the chemical entering your body is vitally important, via the skin, ingestion or inhalation.

[Edited on 21-4-2018 by aga]

CobaltChloride - 21-4-2018 at 10:36

Thanks! I have one more question I forgot to ask: Is the odor of the methanol a good warning sign of potentially dangerous acute exposure? I smelled it before and it has a much fainter smell than either ethanol or isopropanol even though it is more volatile.

[Edited on 21-4-2018 by CobaltChloride]

WangleSpong5000 - 21-4-2018 at 10:59

Quote: Originally posted by CobaltChloride

Thanks! I have one more question I forgot to ask: Is the odor of the methanol a good warning sign of potentially dangerous acute exposure? I smelled it before and it has a much fainter smell than either ethanol or isopropanol even though it is more volatile.

[Edited on 21-4-2018 by CobaltChloride]

As said above a small amount can cause blindness if ingested.

I don't think the odor of a substance can be a reliable metric of toxicity. For example Trichloromethane smells like pine lime ice blocks (imo) while dichloromethane smells like something I would clean a large filthy engine block with... DCM is considered safer than chloroform as it is less carcinogenic. I have no idea what the LD50 of either is but I know which one I'd prefer to use... not the nice smelling one unfortunately...

CobaltChloride - 21-4-2018 at 11:07

My question was more like this: Is a dangerous concentration of methanol detectable by smell? Its smell is very faint so I'm not sure whether a dangerous concentration is detectable by smell, like it is for toluene, xylene, hydrochloric acid, chlorine, DCM etc. I wasn't asking whether bad smell equals toxicity. Sorry if it wasn't properly formulated, but as you can see from my location, English is not my native language.

aga - 21-4-2018 at 11:08

Man cannot live by Smell alone.

Edit:

If you smell something you are not accustomed to, and can positively identify, do an Elvis ASAP (leave the building)

[Edited on 21-4-2018 by aga]

WangleSpong5000 - 21-4-2018 at 11:31

Quote: Originally posted by CobaltChloride

My question was more like this: Is a dangerous concentration of methanol detectable by smell? Its smell is very faint so I'm not sure whether a dangerous concentration is detectable by smell, like it is for toluene, xylene, hydrochloric acid, chlorine, DCM etc. I wasn't asking whether bad smell equals toxicity. Sorry if it wasn't properly formulated, but as you can see from my location, English is not my native language.

Sorry. I probably misunderstood your original post... sounds like me.

Good question though... I would say that if a group of substances, ie alcohols in this case, become more noticeabley toxic as concentration increases by default. EtOH is a good example of something that lets you know how nasty it really is and the higher the conc the more obvious this becomes. I'd say methanol works in a similar fashion yet I don't think there is any precise sensory point that matches any meaningful level/metric of toxicity.

Tsjerk - 21-4-2018 at 11:33

As long as you don't drink the stuff you should be fine. On your hands the worst it can do is give you a dry skin, it doesn't penetrate the skin.

You shouldn't be working in a badly ventilated area where large amount are being spilled/boiled off or something, but a besides that you don't have to worry.

As with most chemicals: As long as you don't ingest them, they are pretty harmless.

LearnedAmateur - 21-4-2018 at 11:50

To me, methanol smells pretty much identical to ethanol, as it does with other lower MW alcohols although it tends to get more ‘solventy’ with more carbon atoms - for instance, isopropanol, to me, smells like halfway between ethanol and acetone. The sweetish odour is good for determining the presence of alcohols but distinguishing between them is almost impossible unless you are quite heavily trained to do so.

aga - 21-4-2018 at 12:04

Hence the 'heavy training' pays off, if you ever need it

Edit:

Personally ethanol and methanol smell distinctly different.

[Edited on 21-4-2018 by aga]

CobaltChloride - 21-4-2018 at 12:15

For me, methanol, ethanol and isopropanol smell quite differently. Methanol has a faint, sweet, alcoholic smell, ethanol has a sharp alcoholic smell and isopropanol is somewhat similar to both acetone and ethanol, but a bit sharper than both. I think this is attributed to the fact that the I never smelled any isopropanol until about 6 months ago and noses tend to be more wary of newer smells.

WangleSpong5000 - 21-4-2018 at 14:06

So if EtOH and MeOH smell similar and share the distinct 'moonshine' smell and isopropyl alcohol smells somewhere between that odor and the sharp, sweet 'chemical' smell of acetone (i agree with that observation) is it because your iso as Propan-2-ol is so close to acetone being propan-2-one as to be in the middle structurally as well as in the olfactory sense?

I wonder what the isomer of iso smells like? Being a primary alcohol and what not...

LearnedAmateur - 21-4-2018 at 14:08

I’ve noticed that ethanol is slightly sharper as well, having used both at >99% during high school OC (methanol is more like a vodka smell IMO) but it’s not a reliable way to tell the difference at the end of the day, as even slight contamination may spoil the odour. I’ve used isopropanol and been around acetone nail varnish remover quite a bit, they’re all quite characteristic odours to be fair and it’s unlikely that you’ll forget them in the long run, especially with a whiff every now and again.

happyfooddance - 21-4-2018 at 16:48

Although I hesitate to respond for fear of being aga'd... I will share my experience.

Methanol, contrary to what you would expect, is less detectable than ethanol. They smell almost identical in certain concentrations. I can tell subtle differences between substances, by smell and taste, usually. But I cannot distinguish MeOH and EtOH mixtures by smell or taste, at all.

If they are pure, ethanol is more pungent... But if they are not pure, and are mixtures with water... Damn, it is hard to tell. If you can't separate it via distillation, then don't mess with it, in this case.

DavidJR - 21-4-2018 at 18:07

Honestly even taking a big whiff from my bottle of dry methanol I can barely smell it at all. Much, much weaker odour than ethanol or isopropanol, to me at least. So I definitely don't think it's wise to rely on your sense of smell to indicate safe concentration. I wouldn't worry about a brief exposure to high concentration of the vapours though.

JJay - 21-4-2018 at 22:16

In my limited understanding of the subject, methanol is metabolized into formaldehyde, which is directly toxic. The body preferentially metabolizes ethanol, so it is sometimes used as an antidote for methanol ingestion.

Deathunter88 - 21-4-2018 at 23:44

Like some of the others, I can't really smell methanol as well. I have to practically stick my nose into a container of it to get a good whiff. However, when using it there is always a slightly sweet smell that I do notice.

As long as you don't ingest it, you can pretty much treat methanol like ethanol. Worst you will get is a headache, which means it's time to stop.

[Edited on 22-4-2018 by Deathunter88]

LearnedAmateur - 22-4-2018 at 01:57

Quote: Originally posted by JJay

In my limited understanding of the subject, methanol is metabolized into formaldehyde, which is directly toxic. The body preferentially metabolizes ethanol, so it is sometimes used as an antidote for methanol ingestion.

I think the main hazard is metabolism to formic acid, which attacks the optical nerve to cause blindness at teaspoon quantities of methanol (IIRC 10-20mL MeOH is the minimum dose to do so). I’ve never heard of ethanol being used as an antidote but it’s an interesting concept - however, I am skeptical because moonshine and cheap ‘substitute alcohol’ (commercial products and industrial chemicals) have caused many a case of methanol toxicity despite the high ethanol content.

https://www.google.co.uk/amp/s/gizmodo.com/at-least-48-dead-...

https://www.hri.global/files/2011/07/21/02.2_McKee_-_Composition_of_Surrogate_Alcohols_(Russia)_.pdf

https://www.google.co.uk/amp/s/amp.ibtimes.co.uk/drinking-bo...

ninhydric1 - 22-4-2018 at 07:20

Ethanol is NOT a cure to methanol poisoning; instead, it delays the onset of methanol poisoning. Alcohol dehydrogenase in our liver has a preference towards oxidizing ethanol over methanol and will first convert ethanol to acetaldehyde before it converts methanol. Depending on how much ethanol you consume, the onset of methanol poisoning can be delayed but NOT cured.

Melgar - 22-4-2018 at 07:53

Ah! Misinformation! I used to have a still for making ethanol, so I do know some stuff about this.

Methanol, like ethylene glycol, is toxic via "metabolic acidosis". If you're curious about methanol's toxicity, then type "metabolic acidosis" into Google, and you'll be able to find all the information you could ever want. The gist of it is, some alcohols are metabolized into acids that the human body can use for energy, and then exhale in the form of carbon dioxide. Acetic acid is one of those acids. Citric acid is another. Propylene glycol is another, since it's metabolized into pyruvic acid. So all these alcohols are pretty harmless to your body, because even though they're metabolized into acids, your mitochondria just immediately use those acids to produce CO2 and energy, so it's not a problem.

Metabolic acidosis happens when an alcohol is metabolized into an acid that your body CAN'T use for energy. As a result, it just sits around lowering the ambient pH. If that pH gets too low, bad things happen. Now, your kidneys can flush out these useless layabout acids, but it takes some time. This is why it helps to consume ethanol in the event of methanol poisoning. It keeps your enzymes busy metabolizing ethanol into acetic acid, which can be immediately metabolized for energy, as opposed to formic acid, which cannot.

I've heard that methanol is perhaps 5-10 times as toxic as ethanol though, so the answer to your question is "not very". You can even taste a drop or two with no ill effects, and the fumes from it would present a fire hazard before they'd present a health hazard.

Tsjerk - 22-4-2018 at 08:44

Alcohol dehydrogenase doesn't have a preference for either ethanol or methanol or whatever alcohol... It just oxidizes the first alcohol that comes along and needs a certain time to do that. How would anyone imaging an enzyme to have a preference? Like it will pick one molecule over another, but only if the preferred molecule is around? If the nicer one comes along it will throw the less nice molecule away?

What ethanol as an antidote (yes, antidote) will do is slow down methanol oxidation, and that way give the body more time to get rid of the formic acid.

[Edited on 22-4-2018 by Tsjerk]

PirateDocBrown - 22-4-2018 at 09:14

Don't get methanol into your eyes. It can be absorbed directly into the optic nerve, where it does the most damage. Even a tiny amount can blind you. Always wear your goggles.

Morgan - 22-4-2018 at 10:59

Tidbits
Alcohol Dehydrogenase
"Our bodies create at least nine different forms of alcohol dehydrogenase, each with slightly different properties."
http://pdb101.rcsb.org/motm/13

Melgar - 22-4-2018 at 12:03

Quote: Originally posted by PirateDocBrown

Don't get methanol into your eyes. It can be absorbed directly into the optic nerve, where it does the most damage. Even a tiny amount can blind you. Always wear your goggles.

Getting any alcohol in your eye is a bad idea, but there are quite a few barriers protecting your optic nerve from anything that might get into your eye. So basically what you wrote is complete bullshit.

The only way it can blind you accidentally is if you drink it. Or maybe go swimming in it.

LearnedAmateur - 22-4-2018 at 13:20

I’ll have to go with Melgar on this one (maybe not the ‘complete bullshit’ part since that’s a bit strong and we all share a bit of misinformation here and there), like I mentioned it’s the formic acid that does the damage hence requires metabolism first. Same goes for ethylene glycol, fairly benign in itself but it metabolises to oxalic acid in vivo which is quite toxic as most of us know.

aga - 22-4-2018 at 13:28

Quote: Originally posted by happyfooddance

Although I hesitate to respond for fear of being aga'd...

Fear Not !

The rod in my ass was removed yesterday by a team from AmateurAssRod.com.

They got a lot to learn those guys.

There was absolutely no need for the gimp suit, nor the Camel.

Melgar - 22-4-2018 at 13:33

Quote: Originally posted by LearnedAmateur

I’ll have to go with Melgar on this one (maybe not the ‘complete bullshit’ part since that’s a bit strong and we all share a bit of misinformation here and there), like I mentioned it’s the formic acid that does the damage hence requires metabolism first. Same goes for ethylene glycol, fairly benign in itself but it metabolises to oxalic acid in vivo which is quite toxic as most of us know.

Growing up, Nicodem was my role model.

woelen - 22-4-2018 at 23:12

I work with methanol quite comfotably. It indeed is not that dangerous. Just use common sense, do not ingest it and try to avoid excessive inhaling or excessive skin contact. An occasional whiff or occasional wetting of e.g. part of your hand is not a problem.

When it comes to smell:
- Methanol is nearly odorless to me, but what I can smell of it comes quite close to the smell of ethanol.
- Ethanol is a little more pungent, pure ethanol has a somewhat sweet, but also pungent smell. Not unpleasant.
- Iso-propanol has a very distinct smell, its smell is much stronger than that of ethanol and it is more 'chemical'. I do not dislike its smell, nor do I particularly like it.
- n-Propanol smells a lot like ethanol, but a little stronger. Besides that, it has a faint rancid 'side-smell'. This effect is weak, but it makes smelling n-propanol somewhat unpleasant.

MrHomeScientist - 23-4-2018 at 07:56

If I ever spill methanol on my skin, I go take a shot of rum just in case

LearnedAmateur - 23-4-2018 at 08:30

How about taking a shot of rum if there’s even the remotest chance you’ll be working with methanol

zed - 25-4-2018 at 13:53

In my neck of the woods, we used to call them MFOs. Multifunctional Oxidases.

Convert Ethanol into Acetaldehyde etc... Convert Methanol into first Formaldehyde, then Formic Acid.

To me, Methanol has a "Sweet" odor. Whereas, Ethanol has some "Bite" to it.

The chemical properties and uses of Ethanol

AK02 - 25-4-2018 at 16:01

Quote: Originally posted by ninhydric1

Ethanol is NOT a cure to methanol poisoning; instead, it delays the onset of methanol poisoning. Alcohol dehydrogenase in our liver has a preference towards oxidizing ethanol over methanol and will first convert ethanol to acetaldehyde before it converts methanol. Depending on how much ethanol you consume, the onset of methanol poisoning can be delayed but NOT cured.

Well Ian Chen, when refering to the treatment/cure for methanol poisoning, we can first use fomepizole as a precursor to the use of Ethanol. It serves to block the formation of toxic metabolite in toxic alcohol or drug ingestions by having a higher affinity to the enzyme Alcohol Dehydrogenase which works most efficiently at 101° F. By working the body to a higher temperature through physical exertion, we can promote the perfect conditions for the amino acids to function in the restoration of epicyllin bonds. So before making such bold statements as to what the properties of Ethanol consist of, do your research ahead of time.

AK

[Edited on 26-4-2018 by AK02]