How dangerous is methanol poisoning?

Last Updated22/06/2024

At least 38 people had died after consuming spurious liquor in the Kallakurichi district of Tamil Nadu while as many as 82 others were receiving treatment in hospitals.

In the beverages consumed for recreational purposes, the alcohol in question is almost always ethanol.
In this context, ethanol is technically a psychoactive drug that, in low doses, reduces the level of neurotransmission in the body, leading to its typical intoxicating effects.
Contrary to popular belief, the World Health Organisation has found “no level of [its] consumption is safe for our health”.
Long-term use leads to dependence, heightens the risk of some cancers and heart disease, and may eventually cause death.
Ethanol (C2H5OH) is one carbon atom bonded to three hydrogen atoms and one more carbon atom; the second carbon atom is also bonded to two hydrogen atoms and the hydroxyl group, also known as the ion OH.
Inside the body, ethanol is metabolised in the liver and the stomach by alcohol dehydrogenase (ADH) enzymes to acetaldehyde.
Then, acetaldehyde is transformed into acetate by aldehyde dehydrogenase (ALDH) enzymes.
The adverse effects of alcohol consumption, from the hangover to a cancer, are due to acetaldehyde.

Spurious liquor is characterised by the liquid mixture containing methanol as well.
In many older cases, spurious liquor has typically been a homemade liquor to which methanol was added to strengthen the intoxicating effects
The Food Safety and Standards (Alcoholic Beverages) Regulations 2018 stipulate the maximum permissible quantity of methanol in different liquors.

The methanol molecule (CH3OH) consists of one carbon atom bonded with three hydrogen atoms and one hydroxyl group.
Schedule I of the Manufacture, Storage and Import of Hazardous Chemical Rules, 1989 includes methanol.
The Indian Standard IS 517 applies to how the quality of methanol is to be ascertained and, together with the Tamil Nadu Denatured Spirit, Methyl Alcohol, and Varnish (French Polish) Rules 1959, what signage methanol packaging should carry.
The most common way to produce methanol is to combine carbon monoxide and hydrogen in the presence of copper and zinc oxides as catalysts at 50-100 atm of pressure and 250° C.
In the pre-industrial era, going back to ancient Egypt, people made methanol (together with several other byproducts) by heating wood to a very high temperature.
Methanol has several industrial applications, including as a precursor to acetic acid, formaldehyde, and aromatic hydrocarbons. It is also used as a solvent and as antifreeze.
In Tamil Nadu, the manufacture, trade, storage, and sale of methanol requires licences under the 1959 Rules.

Once ingested, ADH enzymes metabolise methanol in the liver to form formaldehyde (H-CHO).
Then ALDH enzymes convert formaldehyde to formic acid (HCOOH).
The accumulation of formic acid over time leads to a condition called metabolic acidosis, which can lead to acidaemia: when the blood’s pH drops below its normal value of 7.35, becoming increasingly acidic.
The ‘metabolic’ in ‘metabolic acidosis’ means the concentration of the bicarbonate ion is dropping, leading to the acid gaining the upper hand.
Formic acid also interferes with an enzyme called cytochrome oxidase, disrupting cells’ ability to use oxygen and leading to the build-up of lactic acid and contributing to acidosis.

Once methanol is ingested, the body takes some time to completely eliminate it.
There are two immediate ways to treat methanol poisoning. One is to administer pharmaceutical-grade ethanol.
The other option is to administer an antidote called fomepizole, which has a similar mechanism: it slows the action of the ADH enzymes, causing the body to produce formaldehyde at a rate the body can quickly excrete, preventing the deadlier effects from kicking in.
Healthcare workers may also have the individual undergo a dialysis to remove methanol and formic acid salts from the blood, and mitigate damage to the kidneys and the retina
They may also administer folinic acid, which encourages the formic acid to break up into carbon dioxide and water.
Both fomepizole and folinic acid are in the WHO’s list of essential medicines.