Methanol Poisoning from Alcoholic Drinks
This article explains how methanol kills, and how methanol gets into alcoholic drinks, killing or blinding drinkers in many countries (most frequently in Asia).
In summary, methanol does not find its way into alcoholic drinks in Asia due to improper distillation, as is often claimed, but because bootleggers do not distil at all, instead buying “ethanol” from suppliers. These suppliers frequently supply contaminated ethanol, or pure methanol, instead of the purchased product.
Methanol and Ethanol
‘Alcohol’ usually refers to ethanol, also known as ethyl alcohol. However, in chemistry, there are many alcohols. An alcohol that frequently kills humans as a contaminant in alcoholic beverages is methanol, also known as methyl alcohol.
This diagram (source) shows the metabolism of ethanol, methanol, and ethylene glycol in the human body:
There are multiple classes of both alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) enzymes in the human body. For example, Class I ADH oxidizes ethanol into acetaldehyde, and methanol into formaldehyde. Formaldehyde is oxidized by Class III ADH (formaldehyde dehydrogenase) into formic acid. Acetaldehyde, on the other hand, is oxidized by ALDH.
Ethanol’s primary short-term effects are to depress the central nervous system, causing increasing drunkenness with consumption, and possible death, and leaving a possible hangover from the acetaldehyde, as well as long-term risks due to the carcinogenic effects of acetaldehyde. Methanol, meanwhile, also causes drunkenness/CNS depression, but its metabolite, formic acid is much more dangerous, causing optic nerve damage, and acidosis leading to brain damage and death.
Methanol and ethanol production during fermentation
Ethanol is typically produced by fermenting a sweet liquid, such as sugar cane juice. This can be done by adding a pure yeast, by adding a material such as tree bark (which will have natural yeasts present on it), or by spontaneous fermentation, where yeasts from the air make their way into the liquid.
It is normal for fruit to contain some ethanol, as a result of fermentation of sugars during ripening (e.g., a ripe banana may be 0.2% ethanol).
Fruit and plants contain pectin. Pectin is a complex polysaccharide. During pectin synthesis in the plant, some of the pectin will be esterified, usually methyl-esterified, but sometimes acetyl-esterified. Plants also contain enzymes that de-esterify pectin in the presence of water. Methyl-esterified pectin de-esterifies into methanol and pectic acid.
As a result of this, typical fruit juices contain up to around 0.01% free methanol, and overall 0.04% potential methanol (methyl-esterified pectin):
The process of fermentation will release some of the bound methanol. In some cases, pectinase is further added, which can further increase methanol content. The OIV (link) sets a limit of 0.04% (400mg/L) for red wine. Methanol content is likely to be lower in white wine, as the skins are not used.
Even if very poorly made, it’s implausible that fermented drinks, such as wine, could contain dangerous levels of methanol. In particular, since formic acid is always in the human body, low levels of methanol are non-toxic, and an adult can safely metabolize around 1500mg/hour of methanol.(See https://www.bio-conferences.org/articles/bioconf/full_html/2017/02/bioconf-oiv2017_02028/bioconf-oiv2017_02028.html)
However, in 1986 an Italian producer added more than 2.5 tons of methanol to cheap table wine, to increase profits, resulting in the deaths of 18 people. (See https://it.wikipedia.org/wiki/Scandalo_del_vino_al_metanolo_in_Italia)
Methanol concentration during distillation
Distillation is the process of distilling (boiling) an alcoholic beverage to concentrate the alcohol, as well, perhaps, as other flavours.
Some of the main distilled drinks are:
- whisk(e)y, distilled from a fermented grain mash (essentially beer)
- brandy, distilled from ‘wine’, including apple cider, red wine, champagne, or any other fruit wine
- rum, distilled from fermented sugar
- vodka, which is pure alcohol with water
- gin, which is pure alcohol (vodka) flavoured with juniper berries
The distillation process may be repeated resulting in a higher alcohol content, and allowing flavours to be isolated/heightened. The resulting distillate may then be further aged (typical for whisky, brandy, and gin). The distillate is diluted with water for bottling. A vodka is therefore essentially pure ethanol, which can be produced cheaply in an industrial process, plus water. The cost of vodka production is likely to be under $1/bottle, with the rest of the price marketing and tax (which in most countries is over $10/bottle). The alcohol content of distilled drinks may be set to a legal minimum of 35%, 37.5% or 40%, depending on the country. Taxation is typically then linked to alcohol content.
The alcoholic products made by fermenting and/or distilling fruits, vegetables, and/or grains, are often used to make further beverages. For example, Bailey’s Irish cream is a combination of cream, distilled alcohol (‘vodka’), and whiskey.
The process of distillation, as mentioned, converts a liquid ferment into gases. Wine, to make brandy, will contain numerous compounds, each with different boiling points. Just a few of them:
- acetaldehyde 20 °C
- methanol 65 °C
- ethanol 78 °C
- amyl alcohols (fusel oils) >100 °C
Distillation is considered to produce ‘heads’, being the first distillate, ‘hearts’ (typically the commercially valuable part), following the heads, and ‘tails’, the last drops as the distillation comes to an end. Despite its lower boiling point, methanol remains present throughout, while ethanol concentration is reduced during the end.
For distilled drinks, methanol is usually expressed in terms of its % of pure ethanol. This graph for distillation of pear brandy shows that it can reach 6% of alcohol:
When tails are reused for subsequent distillations, methanol concentration is likely to increase.
Studies have shown that plum brandy contains the highest levels of methanol. For example, a study in Romania found up to 2.4% methanol in a 40% ethanol plum brandy.
Although these levels of methanol are harmful to human health, and could lead to blindness or even death if large amounts of the worst distils are consumed, this implies consumption of typically >1 litre of brandy, which would be associated with chronic alcoholism, and unlikely to occur outside of specific communities such as in Romania, where Țuică (plum brandy) is the national drink.
Methanol deaths in Asia
Deaths due to methanol poisoning occur frequently in Asia, often affecting tourists, in countries such as Indonesia, Laos, Thailand, and Vietnam.
The traditionally distilled drinks popular in Asia include:
- Fermented sap of the aren, fishtail, nipa, palmyra or coconut palms, e.g., arak (Indonesia)
- Fermented glutinous rice, e.g., arak (Indonesia)
- Fermented molasses, e.g., Mekong whisky (actually a rum), or lao khao
- Fermented sorghum or other grains, e.g., baijiu (China)
In general, sugar cane and grain ferments will be low in pectin and methanol, when compared to wine made from fruit.
Although the use of spontaneous fermentation or the addition of tree bark containing unknown yeasts/fungi and bacteria means that there is potential for traditionally produced fermented products to contain harmful compounds, it doesn’t appear that this could result in a toxic level of methanol.
A number of mass poisonings due to methanol poisoning have occurred in Africa. It is suggested that no cases occurred prior to 2015 in Nigeria,(source) making it likely that methanol has become cheaper/more available/mixed into the industrial alcohol distribution in that country.
A 2019 study in Vietnam showed that home-distilled liquor made from rice contained very low levels of methanol. This shows that methanol-related deaths in that country are not the result of improper distillation, but instead are likely to result from illegal producers producing drinks using alcohol from chemical suppliers.
The question is then:
- did the producers deliberately use methanol to make their drinks, or
- did they buy in ‘ethanol’ which was actually methanol or partly so
In Spain in 1963 more than 50 people died when a producer switched ethanol at 30 pesetas/litre, for methanol, at 10 pesetas/litre.
In Indonesia a 200 litre drum of methanol delivered to your home, no questions asked, costs around $80:
This is around 35% cheaper than ethanol. Note that neither ethanol nor methanol is expensive, as a litre of vodka works out at around $0.25 for real ethanol, compared to a taxed selling price of at least $13. Besides the lower cost, which may be much lower in some countries, some producers may add methanol under the belief that it is ‘stronger’, and produces a better quality product. We cannot be certain whether producers are trying to save $0.05 on their fake product selling for $5, or whether they are ignorant of the risks of methanol, or finally whether they purchased an mislabelled/adulterated raw material from their supplier (who has a bigger profit motivation to switch ethanol for methanol).
We can be certain that many producers do no distilling, but simply buy in industrial alcohol, before mixing it with colourings and flavourings, and placing it into typically fake packaging.
In 2021 and 2022 more than 200 Indonesian babies died after a cough syrup manufacturer ordered propylene glycol from a supplier but instead received the cheaper ethylene glycol.
In 2020, the FDA ordered the destruction of hand sanitizer made in Mexico for the US market, when it was found to contain in various samples 0.2 ethanol to 74% methanol and 7% ethanol to 70% methanol. This killed at least one alcoholic man, who drank the product, believing it to contain ethanol as per its label. In 2024 an Indiana man was sentenced to 4 years in prison for selling “ethanol extraction”, which he advertised as 95% ethanol, 5% water, but was in fact up to 40% methanol, which caused several deaths. It is not completely clear how this occurred, except that his company, Glycerin Traders, dealt in waste methanol, and may have attempted to separate ethanol from methanol.
This minor 2020 court case in Jakarta Indonesia, one of many hundreds or thousands of cases, shows they confiscated:
- around 600 empty boxes and bottles of Hennessy, Martel VSOP and other brands
- around 1000 further empty bottles of Chivas Regal, Hennessy, Red Label, Black Label
- several dozen filled bottles of fake Cointreau, Imperial Black, and Hennessy
The alcohol was found to have between 31% and 34% methanol, and zero ethanol. For selling these deadly poisons, a sentence of 17 months was imposed for ‘selling a product that does not meet the required standards’. In this case the methanol content was 41.3%, and no prison sentence was imposed. In other cases drinks have been found to contain a mix of ethanol and methanol, and in others little or no methanol.
In Indonesia it is generally illegal to produce alcohol, except for big licensed producers, or as a traditional livelihood. The production of traditional distilled beverages can be done using bamboo pipes as shown below:
This process is almost certainly not going to create toxic levels of methanol, but there is nothing to stop a ‘traditional producer’ or retailer selling what purports to be a traditional product but is in fact simply alcohol supplied by a chemical company.
In 2009, 25 died, including foreign tourists, in Bali following the consumption of arak. The local ‘traditional arak’ producer added methanol from a supplier in Surabaya to his product, apparently for ‘flavour’, although it’s not clear the real reason (it seems the company did own a traditional distillery, but it is likely cheaper to use industrial ethanol or methanol, so we cannot be certain how much of their output they actually distil themselves).
Death due to supplier sending methanol instead of “food-grade ethanol”
In December 2024 it was a reported that a foreigner had died after making a herbal liqueur from “food-grade ethanol” he had purchased online, via the Indonesian Ebay-like marketplace Tokopedia.
A lab analysis showed that the “ethanol” was in fact 80% methanol:
The product was sold as follows:
It says “foodgrade”, “pure grain”, 96%, “for 21+ only”. 21 is the drinking age in Indonesia, showing that the seller intended the product to be used to make alcoholic beverages.
After the fact of the supposed “ethanol” actually being methanol was reported, the seller updated the description replacing the words “product for 21+ only” with “not for consumption”, and “alcohol commonly used in perfume, antiseptic, mouthwash, deodorant, cosmetics”, and “the alcohol most commonly used in daily life”. These claims remain fraudulent, not least because the product is not in fact ethanol at all.
Toxicity and treatment
As discussed above, it’s likely that in many cases that illegal alcoholic drinks contain only methanol, with no ethanol. This means two things:
- the product is much more likely to be deadly, since the body’s alcohol dehydrogenase has a 10x greater affinity to ethanol than methanol, and if sufficient ethanol is present, it will slow the metabolism of methanol to formic acid sufficiently to prevent formic acid’s toxic effects
- the quantity of methanol ingested may be be much higher than expected — a median deadly dose of 56g is estimated, with permanent blindness at around 15ml. Several shots of booze containing 10ml of methanol would be sufficient to kill a significant proportion of drinkers, and if drinking more than this, death is certain.
Treatment for methanol poisoning is fomepizole, a rather expensive medication, or ethanol. In both cases haemodialysis is usual.
Conclusions
As noted above, some fake alcohol in Asia has no ethanol it at all, just pure poison — methanol. Although it is sometimes suggested in the media that methanol in Asian moonshine might result from poor distillation, this does not appeal to be the case at all.
It is not possible to detect whether a drink contains methanol by any convenient means, nor is it obvious while drinking it. The concentration of methanol in alcoholic drinks which have been adulterated with methanol to an unsafe degree can range from around 2% to 75%.
Counterfeiters typically focus on making fake distilled drinks. Some of these, such as aged whisky, are likely to be difficult to replicate, however when mixed into cocktails it would be hard to tell. Bartenders may also refill empty bottles.
Although grape wine has been adulterated with methanol in the past, wine and beer both appear to be safe to drink across Asia, as do alcopops. On the other hand, cocktails/mixed drinks, at bars across Asia, carry a significant risk of fatal poisoning.
Counterfeit ingredients are common in many parts of the world, so we cannot be certain whether a small-scale producer of alcoholic beverages ordered a drum of ethanol but was sent mislabelled methanol instead, whether they chose to add methanol alongside to their product for ‘flavour’ or to cut costs, or whether they chose to use pure methanol from the outset.
