Methanol is a widely used organic alcohol in many commercial products including inks, dyes, chemical synthesis, and transportation fuel. Methanol poisoning is a significant issue in many regions, particularly affecting lower socioeconomic groups and leading to mass poisoning outbreaks. 

These outbreaks often happen when methanol, which is inexpensive and easily accessible, is added to alcoholic beverages to dilute them. Methanol poisoning outbreaks are a global issue, with hundreds, if not thousands, of fatalities each year. Groups of people died due to methanol poisoning in Sri Lanka, with incidents reported in both 2006 and last year (2024).

Methanol itself is not toxic, but it is metabolised into the highly dangerous formic acid/formate complex, which can lead to metabolic acidosis, neurological complications (including blindness), and even death. Formic acid is the main toxic metabolite responsible for the metabolic disturbances, vision problems, and brain damage seen in methanol poisoning. 

The toxicity of formic acid/formate worsens as acidosis increases. Poisoning can result from oral ingestion, inhalation, or even skin absorption. As little as 30 millilitres (ml) of pure methanol has been known to be fatal, and just 10 ml can cause blindness. It feels and tastes just like alcohol, and at first, it can make you feel tipsy or even a bit unwell. In those initial moments, you might not suspect that anything is wrong. The real danger however, unfolds hours later as your body works hard to clear it out, breaking it down in the liver. This process produces toxic byproducts like formaldehyde, formate, and formic acid. These toxic compounds begin to build up, causing significant damage to your nerves and organs. The damage can be severe, leading to symptoms like blindness, slipping into a coma, and even death. 

Formate, the primary toxin produced, behaves much like cyanide by halting energy production in cells. The brain is especially susceptible to this toxin, and as a result, specific areas of the brain can suffer damage. The eyes are also particularly vulnerable, often leading to blindness in many individuals exposed to high levels of methanol.

Treatment focuses on inhibiting the enzyme alcohol dehydrogenase (ADH) using either ethanol or fomepizole, buffering the metabolic acidosis with bicarbonate, and, when possible, utilising renal replacement therapy to remove methanol and formate while correcting the acidosis. Additionally, folic acid or folinic acid should be administered to boost the body's natural metabolism of formate. 

Poisoning is a serious medical emergency that requires immediate hospital treatment. Medications are available to counteract the effects, and dialysis can be used to cleanse the blood. Ethanol works as a competitive inhibitor, significantly slowing down the breakdown of methanol. This delay gives the body more time to eliminate methanol through the lungs, kidneys, and even a bit through sweat.

The quantitative measurement and identification of methanol levels are essential in both clinical and forensic toxicology. Gas chromatography-headspace is a reliable method for determining methanol concentrations in various biological fluids such as blood, urine, and vitreous humour. Detecting ethanol and methanol requires less than 1 ml of sample, along with the addition of an internal standard. Formic acid can be detected using ion chromatography or a colourimetric method by forming a colour complex with chromotropic acid.

Chemically, ethanol has an extra methylene (CH2) group compared to methanol, making them distinct substances. Interestingly, methanol has one extra letter at the beginning compared to ethanol, but this small difference has significant implications. It is crucial to never drink methanol instead of ethanol, as consuming methanol can be fatal. Understanding the effects of methanol poisoning is vital in preventing such risks. Being informed about these differences can help safeguard against accidental poisoning and its severe consequences.

(The writer is a Senior Assistant Government Analyst attached to the Government Analyst’s Department) 

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The views and opinions expressed in this article are those of the author, and do not necessarily reflect those of this publication