Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Crypto1980 on February 10, 2017, 09:01:21 AM
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I have recently moved to a new lab and I am being trained in certain protocols that involve the use of methanol, including ultra-sonication steps in this solvent. I have worked with methanol in the past and I have always used a fume hood to handle this chemical. However, in my new lab it is customary to work with methanol on the bench, outside of the fume hood. Last week I spent 3-4 hours per day washing slides with methanol on the bench, almost on a daily basis. Should I expect some long-term health effects as a result of last week’s work? I did not experience any acute symptoms. I am sorry if I am being too paranoid, but in my opinion chemicals such as this should always be handled in a fume hood. I am going to use a fume hood from now on, regardless of the way in which things are commonly done here in my new group. Thanks.
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Methanol is near the bottom of the list of chemicals I am concerned about spilling, breathing etc. You pretty much have to drink it, get totally doused in it, or purposefully inhale a lot to see issues. You can read the SDS for the most scardy-cat version of at what levels things can be dangerous.
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Methanol is very dangerous and can cause myopia and blindness after prolonged exposure.
Short term exposure can cause dizziness and drunk-like symptoms. Additionally, medium term exposure can cause liver malfunction.
Apart by respiration methanol can also be absorbed by eyes and skin because it is a very small molecule (≈ 6 Å long). Therefore, all appropriate safety measures must be taken (gloves, gas mask or fume hood).
Any accidental exposure must be accompanied by immediate washing of the contaminated body parts with water and installation in a well ventilated environment.
Of course, 3-4 hours exposure for a few days is not a significant heath disaster. So, be calm but take care in the future.
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Methanol is very dangerous and can cause myopia and blindness after prolonged exposure. [...]
Crypto1980 tells he did not experience any acute symptoms. Do you expect delayed effects then?
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No, not at all.
3-4 hours exposure to methanol, for a few days is not enough, even for acute symptoms (by exception, a possible slight dizziness and a slight drunkenness). Vison adverse effects need long time exposure, in order to happen.
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A couple of times in the past, about 20 years ago, I spilled Methanol over my hand.... completely soaked it. I was a little worried and also annoyed with myself for being so clumsy. So far so good - I seem to be OK. I think it is a cumulative poison. Drinking it is very bad.
I have also spilt acetone, IPA, THF and several other solvents onto me many times over the years - darn! Maybe I am way to clumsy to be a chemist after all! :-\ Thankfully I am still OK, but probably need to be more careful.
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Accidental spilling of solvents, might always happen, even to the most careful chemists. Whether acetone, IPA, THF, DCM and several other solvents, it doesn’t matter.
Exceptionally, methanol, benzene and CCl4 are very dangerous because they are cumulative poisons, as “P” has described above. But even so, accidental spilling is not important, if it does not often happen.
Also, avoid smoking a cigarette, in presence of halogenated hydrocarbons (DCM, CHCl3, CCl4), though not flammable, they are pyrolyzed in the cigarette’s flame and thus, drastic free radicals are inhaled.
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Many people use methylated spirits as a cleaning solvent without gloves. I've read no report of mass intoxication.
Acetone is sold as a solvent. Expect most users not to wear gloves.
I even know hospitals where they use IPA on patients' skin.
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Ingested methanol is oxidized first to formaldehyde, then formic acid, which is quite toxic. In theory one might be able to take in sufficient amounts by absorption through the skin, but (and this is not meant to be medical advice) my suspicion is that it is not easy to do so.
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1). Almost, all organic solvents pass across the skin. But exceptionally, the highly toxic methanol further passes into the systematic circulation because it is a very small molecule. Therefore and apart drinking and inhalation, systematic intoxication from methanol also occurs by skin and eye absorption.
As Babcock_Hall has descibed above, the toxicity of methanol is due to the liver microsomal oxidation, in vivo, to formaldehyde that causes tissue necrosis (mummy syndrome). Contrary, ethanol is oxidized to acetaldehyde that simply causes a “hungover” the next day.
Skin absorption is an equilibrium effect, meaning that a fraction of absorbed methanol is simultaneously skin excreted. As a consequence, systematic intoxication from methanol by the skin, demands high methanol amounts and long contact times.
2). Methylated spirits and other organic solvents dehydrate the skin and thus, rash, eczema and dermatitis might appear after prolonged (repeated) use. Therefore, solvent-resistant vinyl gloves must be used, while intensively working with these solvents.
3). But it’s not that all solvents are dangerous for the skin. Indicatively: ethanol, IPA, glycerol, polyethylene glycol, mineral oil (Nujol), paraffin oil (Vaseline) and many others are widely used in skin care and cosmetic formulations.
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Many people use methylated spirits as a cleaning solvent without gloves. I've read no report of mass intoxication.
Acetone is sold as a solvent. Expect most users not to wear gloves.
I even know hospitals where they use IPA on patients' skin.
I think you are right - but they shouldn't use the methanol without gloves really.. I still use acetone as a wiping solvent as it is strong, 'relatively' harmless compared to methanol and it evaporates quickly. With regard to mass intoxication, I seem to remember that the banning of the washing of hands in white spirit for engineers was due to a lot of them getting skin cancers.... I might look that up later to check when I get home and have more time.
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If it’s necessary to clean the hands with hydrocarbon solvents (e.g. removing lubricant oils), the best is to use white spirit or toluene or xylene, followed by ethanol (that can be the cheaper, denaturized one) and then soap and water for a couple of times. Do not use any skin softening or hydrating cream after washing, because these products help the skin absorption of reamaining lipophilic solvents.
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If it’s necessary to clean the hands with hydrocarbon solvents (e.g. removing lubricant oils), the best is to use white spirit or toluene or xylene, followed by ethanol (that can be the cheaper, denaturized one) and then soap and water for a couple of times.
Denatured ethanol has methanol in it ;D. I've been around plenty of methanol for rinsing and cleaning in the lab setting, and I recently got my liver function checked as part of a routine blood test. I'm fine. Reasonable handling of methanol (read: not drinking it or bathing in it or pouring it into a bag and huffing it) is safe. If I worked in a room where it was being handled in bulk and was saturating the air I may become concerned. Sitting on a lab bench using it in a squirt bottle is fine.
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In the past, yes!
Today, ethanol is denaturized mainly with acetate esters that form azeotropes and thus, pure ethanol cannot be distilled. But even if containing methanol, its content is too low, in order to be dangerous by skin absorption.
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If it’s necessary to clean the hands with hydrocarbon solvents (e.g. removing lubricant oils), the best is to use white spirit or toluene or xylene,
I don't think I agree - I am pretty certain you are NOT supposed to wash your hands with these solvents at all... people used to in industry and it was banned due to skin cancers. I think it is like smoking - not everyone who washes their hands in white spirit will get cancer... but some will.... so don't do it.
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I have done this. It’s the only way to remove polymers from the hands.
By the way, polar aprotic solvents (e.g. THF, DMSO, ethylene carbonate, etc.) must be avoided otherwise, severe dermatitis will occur.
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I have done it too when I have been lazy... I think I used acetone... but not methanol. I am not sure about acetone - I read that it can build in the kidneys or something.. anyway, I am not sure it is the only way. It can be slowly abraded off with something like swarfega, or just picked off slowly with the fingers. Best wear gloves to avoid it in getting on you in the first place, although after years and years of working with anything you will probably end up getting something on you.
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Guys, I am very grateful for your advice and commentaries. Thanks a lot!!!