Just one extra carbon atom makes the difference between life and death. Here lies the molecular divergence between methanol and ethanol. The first has just one carbon atom in its chemical formula and the second consists of two. But you can’t tell them apart with the naked eye.
They’re both alcohols used to make hand sanitizer gels, which have become particularly important during the current pandemic. However, only disinfectants based on ethanol are recommended, whereas those made from methanol can be lethal and are banned worldwide by health authorities.
The Center for Disease Control and Prevention (CDC) website says that methanol is a colorless liquid, also known as wood alcohol or methyl alcohol, which is legally used as an industrial solvent, pesticide, or fuel.
Its similarity to ethanol (a non-toxic alcohol) means that some party lovers use methanol to make alcoholic drinks or, recently, to make disinfectant gels. This is very dangerous.
The explanation from an expert
Paola Castillo Juárez, researcher and professor at the National School of Biological Sciences (ENCB) of the National Polytechnic Institute (IPN), delves deeper in an interview for Tec Review on this crucial public health matter.
She confirms that methanol-based gels are disinfectants which are made instead of those that should exclusively be based on ethanol, for the following reasons:
“Methanol is absorbed through the skin and mucous membranes. The danger of this is that when it’s metabolized, it produces products such as formaldehyde and formic acid, the latter being really dangerous because it gives rise to low oxygen levels in cells, i.e. they experience a state called hypoxia, which causes the death of cells,” explains this ENCB academic.
Small amounts of methanol are needed for the damage to begin to occur, according to Castillo Juárez. That’s why it’s completely forbidden for disinfectant gels to have even minimum contamination from methanol.
In the event of methanol ingestion (in adulterated alcoholic drinks), some of the consequences are vomiting and headache. Symptoms are similar when it’s absorbed through the skin.
It’s very difficult to identify methanol poisoning, because the time it takes for symptoms to develop varies greatly. According to Castillo, it can take up to 72 hours for symptoms to be noticed.
“Up to 50% of methanol poisoning cases end in death. The people who don’t die from it can develop long term outcomes affecting the central nervous system, permanent blindness, or seizures. There are also many cases of patients arriving at hospital in a coma,” she says.
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When sanitizer gels are made with ethanol, there’s no health risk. According to Castillo, this alcohol has low toxicity and is well assimilated by the body, as well as having a fairly effective bactericidal power.
“Sanitizer gels of between 60 and 90 per cent ethanol can be used. The side effects are minimal. It does dry out the skin and irritate mucous membranes, and consumption is obviously not recommended. Its toxicity is minimal compared to that of methanol, because unlike methanol, it doesn’t produce lethal metabolites,” says the IPN scientist.
SARS-CoV-2 is a virus with an envelope that’s part of its cellular membrane, which is rich in lipids, fats in other words. “Alcohol destroys the viral membrane and therefore destabilizes it. So, it’s effective in inactivating the virus,” mentions Castillo.
She says that ethanol, which is the base of hand sanitizer gels, can be used to disinfect hands, but simple soap works just as well. “Washing your hands for more than 20 seconds is completely effective, because the soap also breaks down the lipid layer that protects the virus.”
To achieve the same effect, Castillo states that chlorine can also be used, but in very low concentrations of about 1%.
In summary, soap, ethanol, and chlorine are the most advisable non-toxic products for disinfecting your hands, especially in these times of pandemic.