What is methanol poisoning? Everything you need to know about the silent killer in alcoholic drinks

Alcohol tainted with methanol is suspected to be the cause of death of four foreign tourists at the popular backpacker destination of Vang Vieng in Laos.

Here are some facts:

What is methanol poisoning?

Methanol is a toxic alcohol used in industrial and household products like antifreeze, photocopier fluids, de-icers, paint thinner, varnish, and windshield wiper fluid. Colourless, flammable, and with a similar smell, it can be easily confused with its molecular cousin ethanol, which is usually found in alcoholic drinks. But methanol is toxic to humans, with exposure or ingestion being extremely dangerous if left untreated.

Drinking just 25-90 millilitres of it can be lethal, according to the Methanol Institute, a global trade association for the industry. It is absorbed by the gut in less than 10 minutes, but patients may appear normal for the first 12 to 24 hours after ingestion. It will then cause nausea, vomiting and severe abdominal pain, followed by hyperventilation and difficulty breathing.

Partial or complete blindness from methanol poisoning is common, and if left untreated, it can lead to a coma and even death. However, in smaller amounts, rapid diagnosis — within 10-30 hours of ingestion — and treatment can reduce the severest symptoms. People with suspected methanol poisoning should immediately consult a medical toxicologist or poison centre.

So far, an Australian woman, two Danish citizens and an American have been confirmed dead after a suspected methanol poisoning from drinking tainted alcohol.

How does it get into drinks?

Accidental poisonings may occur after drinking cheaply made home brew or contaminated alcohol. But methanol is often deliberately added to alcoholic beverages as a cheaper alternative to ethanol. This happens especially in countries where the price or taxes on legitimate alcoholic drinks may be considered too high.

Unscrupulous businesses or individuals may add industrial methanol into alcoholic drinks to increase their potency. Buying and consuming canned or bottled alcoholic beverages from trusted retailers tend to be safer and less likely to be adulterated than mixed drinks at bars.

How common is it in Asia?

It is difficult to estimate the number of victims poisoned alcohol, or “methanol cocktails”, claim each year. On their travel advice websites for Laos, the United Kingdom and Australia authorities warn their citizens to beware of methanol poisoning while consuming alcohol in Laos. In neighbouring Thailand at least six people died and more than 20 were hospitalised after drinking methanol-laced bootleg alcohol in August.

In India, which has a thriving moonshine industry, a batch of illegal alcohol laced with methanol killed 63 people and blinded several others in southern town in June. Popular tourist destinations in Malaysia and Indonesia have also seen mass deaths from methanol poisoning in recent years, with most reported victims being foreigners. Alcohol consumption is increasing across Asia and the world, with Laos, Cambodia and Vietnam seeing increases of 40-90 percent between 2010 and 2017, according to a study in The Lancet.