What is methanol and what happened in the Laos poisonings?

Six tourists including a British lawyer have died in Laos after suspected methanol poisoning. Simone White, 28, from Orpington, Kent, was among a number of people taken to hospital following the incident in the popular backpacking town of Vang Vieng last week.

Five others known to have died include two Australian teenagers, an American and two Danish tourists.

An officer at Vang Vieng’s Tourism Police office said no charges have been filed but a “number of people” have been detained in connection with the case.

Staff at the Nana Backpacker Hostel, which is still operating but not accepting new guests, confirmed the manager and owner were among those taken in for questioning.

Those poisoned in the tragic incident are believed to have been served drinks tainted with methanol, which is sometimes used by disreputable bars as a cheaper alternative to ethanol, but can cause severe poisoning or death.

What is methanol?

Methanol, also known as wood alcohol (CH3OH), is often used to make solvents, pesticides, paint thinners and alternative fuels. Common products containing it include antifreeze, brake fluid and window cleaning solutions.

It’s sometimes used by disreputable bars as a cheaper alternative to ethanol and those poisoned in the incident are believed to have been served tainted drinks. The two are similar but methanol is toxic to humans.

Dr Wayne Carter, associate professor at the University of Nottingham, said it should not be present in standard alcoholic drinks but its presence can be masked by mixing it with alcohol.

He added: “Drinks spiked with methanol can cause blindness as well as damage to organs by metabolic acidosis.”

Methanol is a colourless liquid with a faintly sweet smell that’s hard to detect at low levels. It can be produced from produced from natural gas, renewable sources such as biomass, and fossil fuels.

Why is methanol toxic to humans?

When methanol is broken down in the body it produces toxic compounds including formic acid, formate and formaldehyde.

Professor Alastair Hay, emeritus professor of environmental toxicology at the University of Leeds, explained: “The formic acid upsets the acid /base balance in blood and the major consequence is initially the effect on someone’s breathing.

“There are effects on many other organs the kidney being one. The disturbance of acid/base balance and disrupted breathing will eventually affect the heart and it will stop functioning.”

Formate can cause the pH of the body to drop, damaging organs and potentially leading to organ failure. Meanwhile, formaldehyde attacks the nerves – particularly the optic nerve, causing risk of blindness.

One study suggested that ingesting just 15ml, or one tablespoon, of a 40% methanol solution could prove fatal, however people have been reported to survive drinking 500ml.

What are the symptoms of methanol poisoning?

People who have ingested methanol may at first just appear drunk. Early symptoms include drowsiness, reduced level of consciousness, dizziness, headache, confusion and the inability to coordinate muscle movement.

Vomiting and visual problems including sensitivity to light and blurred or snowy vision may also occur.

Professor Sir Colin Berry, emeritus professor of pathology at Queen Mary University of London, said: “In later stages, generally developing between 18 and 48 hours after methanol ingestion, drowsiness may progress to coma.

“Convulsions may occur, generally as a complication of the metabolic upset – there is formic acidaemia and an uncompensated metabolic acidosis.”

How is methanol poisoning treated?

Patients are often given ethanol or a drug to stop enzymes breaking down the methanol. Professor Hay explained:“The principle behind administering ethanol is quite simple; it delays methanol metabolism.

“Both alcohols are broken down by the same liver enzyme alcohol dehydrogenase. But the enzyme prefers ethanol.

“So ethanol acts as a competitive inhibitor largely preventing methanol breakdown, but markedly slowing it down, allowing the body to vent methanol from the lungs and some through the kidneys, and a little through sweat. Avoiding the formation of toxic levels of formaldehyde is key.”

Methanol can also be removed from the blood via dialysis, which involves using a machine to filter the blood.

Professor Oliver Jones, an expert in chemistry at RMIT University, said: “While thankfully rare, methanol poisoning is very serious, and treatment should be given at a hospital.”