In June 2022, as many as 21 teenagers lost their lives in a case of suspected methanol poisoning in East London. During the COVID-19 hard lockdown, numerous deaths were reported to be a result of the consumption of home- brewed alcohol, after the government restricted the purchase of alcohol. This is not new, a 2018 study published by the BMC Medicine journal revealed that 1 in 10 deaths in South Africa can be attributed to the abuse of alcohol in one way or the other. The recent spate of alcohol-related deaths in the country has been a subject of public interest and has seen increased calls for public awareness on the dangers of consuming impure alcoholic beverages.
Alcohol refers to a group of organic compounds, which contain at least one hydroxyl functional group (-OH) bound to a saturated hydrocarbon (CnH2n+1), such as methanol (CH3OH) and ethanol (C2H5OH). For alcoholic beverage production, yeast is typically used to produce ethanol, colloquially referred to as alcohol, from the fermentation of carbohydrates. Ethanol has other uses including as a fuel additive and, as the past two COVID-19 pandemic years have shown, as a disinfectant solvent. Each alcoholic “drink” typically contains about fifteen grams of ethanol. A “drink” can be a “shot” of 40% liquor, a glass of 12% wine, or a bottle of 5% v/v (alcohol by volume) beer. On the other hand, methanol is not used for alcoholic beverages but as a fuel additive and building block to produce fine chemicals. However, methanol occurs naturally at low levels in most alcoholic drinks. Occasionally, methanol concentrations may be up to 0.72% in beverages containing 40% ethanol. Industrially, alcohol manufacturers have dedicated quality assurance departments responsible for conducting quality tests on each batch of product they produce, to ensure that toxic compounds such as methanol are either not present or are at levels not harmful to consumers in the alcoholic drinks.
Dr Samkelo Malgas, "Biochemistry" Lecturer
Methanol poisoning via ingestion is mostly due to the consumption of surrogate alcohols (non-beverage alcohols such as antifreeze and window cleaner, and illegally- produced alcohols using industrial methylated spirits). It is noteworthy to mention that methanol doesn’t have the inebriating ability that ethanol has. Therefore, polluting one’s drink with methanol would not result in a heightened experience of drunkenness. In addition to ingestion, methanol poisoning can also result from exposure via inhalation or absorption through the skin. This means that methanol as an unlisted ingredient in alcohol-based hand sanitisers, which became popular during the COVID-19 pandemic, may pose health risks. Therefore, methanol should never be used in products to be consumed or applied to the body.
On consumption, methanol is metabolised in the liver and converted to formaldehyde which is further converted to formate. Unlike the metabolites from ethanol, formate can’t be cleared off our bodies upon methanol consumption. Instead, it ends up blocking metabolic reactions in cells, depriving the cells of adequate oxygen supply. This develops into end-organ damage and retinal toxicity due to oxidative stress, leading to potentially fatal complications. As little as 15 millilitres of pure methanol, about a full tablespoon, is toxic to humans and may be potentially fatal. About 2% methanol in a polluted 40% alcoholic drink is considered the maximum tolerable concentration (MTC) for humans. In a 2014 World Health Organisation (WHO) report, it stated fatality rates of over 30% in some cases of methanol poisoning.
In conclusion, the source of methanol contamination in alcoholic beverages is unlikely originating from commercial manufacturers, but probably from devious vendors or patrons who are experimenting and might deliberately spike their beverages with methanol. In the case of home-brewed beverages, it is likely that the methanol and congeners – substances, other than the desired type of alcohol – might be produced by contaminating microbes during traditional ethanol fermentation, as this is usually done under uncontrolled conditions. This increasing crisis in the consumption of hazardous alcohol calls for amplified public awareness interventions by numerous stakeholders such as health officials, teachers, scientists, brewers and breweries, about the lethal dangers of this practice.
Dr Samkelo Malgas is a Lecturer in the Division of Biochemistry at the Department of Biochemistry, Genetics and Microbiology (University of Pretoria).