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 backpacker town of Vang Vieng last week.

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

An officer from the Vang Vieng Tourism Police Office said no charges had been laid but “a number of people” had been detained in connection with the case.

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

Those poisoned in the tragic incident are believed to have been served drinks contaminated with methanol, which is sometimes used by reputable 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 produce solvents, pesticides, paint thinners and alternative fuels. Common products that contain it include antifreeze, brake fluid, and window cleaners.

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

Dr. Wayne Carter, associate professor at the University of Nottingham, said it shouldn’t 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 organ damage through metabolic acidosis.”

Methanol is a colorless liquid with a faint sweet odor that is difficult to detect at low levels. It can be produced from natural gas products, 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: “Formic acid disrupts the acid/base balance in the blood and the major consequence is initially the effect on someone’s breathing.

“There are effects on many other organs, the kidney being one. Disturbance of acid/base balance and interrupted breathing will eventually damage the heart and it will stop working.”

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

One study suggested that ingesting as little as 15ml, or a 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 seem drunk at first. Early symptoms include drowsiness, reduced level of consciousness, dizziness, headache, confusion and inability to coordinate muscle movement.

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

Professor Sir Colin Berry, Emeritus Professor of Pathology at Queen Mary University of London, said: ‘In the later stages, which generally develop between 18 and 48 hours after methanol ingestion, drowsiness can progress to coma.

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

How is methanol poisoning treated?

Patients are often given ethanol or a drug to stop the enzymes that break down methanol. Professor Hay explained: “The principle behind ethanol administration is quite simple; 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 from breaking down, but slowing it down significantly, allowing the body to flush methanol out of the lungs and some through the kidneys and a little through sweat. Avoiding the formation of toxic levels of formaldehyde is essential.”

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

RMIT University chemistry expert Professor Oliver Jones said: “Although fortunately rare, methanol poisoning is very serious and should be treated in hospital.”