The chemistry behind hooch tragedies

Over the last month alone, over 50 people have died in a series of hooch tragedies in Bihar (last month) and at two locations in Tamil Nadu (last week). Countless such tragedies over the decades beg the question: what makes hooch more lethal than alcoholic beverages sold legally?

The alcohols they use are different, as are the biochemical reactions triggered when either kind of alcohol is consumed. The key ingredient of an alcoholic beverage should be ethyl alcohol, also known as ethanol, but hooch usually contains methyl alcohol (methanol) in its place.

The human body breaks down both ethanol and methanol into compounds that can be harmful to health.

The difference is that compounds arising out of ethanol affect the body over time, while those arising out of methanol can kill instantly. If not death, consumption of methanol can damage the optic nerve and cause blindness.

Ethanol and methanol

Methanol is the simplest in the family of compounds called alcohols, while the ethanol molecule is only slightly more complex. Both are colourless liquids, similar in taste and smell, which enables dealers of spurious liquor to mix methanol in it rather than ethanol. The reason they prefer methanol is that it is cheaper.

Ethanol, used in alcoholic beverages as well as various drug preparations, is prepared by the fermentation of food crops. Methanol is manufactured mainly by synthetic processes, and its uses are largely industrial.

Methanol is used in acrylic plastics, synthetic fabrics, paints and various other preparations. It is present in hand sanitisers, which is why consuming sanitisers is a serious risk. Being low in carbon content, methanol is also a potential fuel; the NITI Aayog has a ‘Methanol Economy’ programme and describes the compound as “the best pathway for meeting India’s commitment to COP 21”. When consumed, however, even a small amount of methanol can be toxic. The Food Safety and Standards (Alcoholic Beverages Standards) Regulation, 2018, prescribes limits for how much methanol can be used in various alcoholic beverages. For country liquor, the limit is just 50gm per 100 litres.

It should be noted, however, that it is not methanol directly that causes eye damage, blindness and death. These effects are caused by new compounds that are formed when the body responds to methanol.

The science of getting drunk

When a person consumes alcohol, there are two broad effects. One, the body’s enzymes break down the alcohol into different compounds, each of which has a different effect on health. Two, when a person drinks too much, meaning a higher quantity than the digestive enzymes can process, some of the alcohol escapes into the bloodstream, and eventually reaches the brain.

The second is what “being drunk” means. Alcohol interferes with the central nervous system and communication networks, effectively slowing the brain’s functioning. As is well known, it is easier to get drunk on an empty stomach, and the reason lies in the same mechanism. If there is food in the stomach, acids will already be digesting the food and will, therefore, also start breaking down the alcohol. On the other hand, on an empty stomach, the alcohol will get into the small intestine. Because the small intestine has a larger surface area than the stomach, the alcohol will move into the bloodstream that much faster.

All this is true when one consumes ethanol. Can methanol cause intoxication the same way? The question to ask, rather, is whether a person can consume enough methanol to get drunk, because even a small amount can kill a person before it reaches the brain.

The body’s response

Whether a person has consumed ethanol or methanol, the same enzymes act on the alcohol. The primary enzymes at work are called ADH and ALDH. The resultant compounds are different, as are the effects.

Take methanol first. Its chemical breakdown is a two-step process: ADH reacts with methanol to create formaldehyde, and ALDH subsequently reacts with formaldehyde to create formic acid. Both are toxic.

Among effects listed by the US Centers for Disease Control and Prevention, formaldehyde can corrode the oesophagus and stomach, and cause ulcers, vomiting, diarrhoea, and inflammation of the stomach. Formaldehyde is harmful even when inhaled: the vapour can cause dizziness or suffocation. Even contact with a formaldehyde solution may cause severe burns to the eyes and skin. Formic acid, on the other hand, can burn the skin and eyes; damage to the optic nerve can cause blindness. It may also cause fluid to build up in the lungs. Like formaldehyde, formic acid too can be harmful through contact alone.

What happens with ethanol

When one consumes an ethanolbased beverage, ADH reacts with it to form acetaldehyde. This can cause headaches and nausea, increase one’s heart rate, and lead to a hangover. Among long-term effects, a build-up of too much acetaldehyde can cause cancer in the stomach and intestine, Duke University notes on its website.

The risk is, however, reduced by the second stage of metabolism. The ALDH enzyme reacts with acetaldehyde to form acetic acid, which is not toxic. In some people, the ability to metabolise acetaldehyde is low, so they are considered more at risk.