Blind drunk – or dead drunk?
Methanol, methyl alcohol or wood alcohol (CH3OH) is one of the chemicals well known by lay people. Its risks in poorly distilled moonshine whiskies and similar products of regular alcohol or ethanol have become quite clear over decades. Methanol is added in many countries into technical alcohols on purpose: to denature alcohol to make it unfit for human consumption. This practice may also be criticized. My pharmacology professor Armas Vartiainen once stated that this practice should be subject to similar legislative process as the death penalty, because in fact it is a death penalty issued to anybody drinking these technical alcohols.
Methanol poisoning is an example of the unexpected consequences caused by unification of standards between countries with different cultures and traditions. Free trade throughout Europe was interpreted to suffer from restrictions on methanol use, and methanol was reintroduced into markets in countries where it had not been used for decades. It is used in windshield washers, where its main advantage is its lower price compared with competing products; it is also quite effective at removing dirt. The proposal to add ethanol/methanol to petrol or to design automobile motors using these products as the sole fuel will cause an even more massive increase in methanol use.
The hazards of methanol include both acute poisonings and long term adverse effects. Acute poisoning is usually caused by intentional or inadvertent consumption of technical products in place of alcohol. For example in Finland, acute deaths from methanol poisoning reached epidemic proportions after 1995 when the windshield washer products were introduced to the market due to the European Union ruling, and they started to decrease only after the year 2000 when warning labels with skull and crossbones were placed on the products to emphasize the deadly nature of these products. The problem still exists although at a somewhat lower level.
The fatal dose is 80–150 ml of 40% methanol, but occasionally even 15 ml dose has caused death. Even 5 ml (a teaspoonful) can cause blindness. The blindness is caused by the metabolism of methanol in the body to formaldehyde and formic acid. Formaldehyde is so rapidly metabolised further to formic acid that it is usually not detected in the body, but formic acid concentrations may be high enough to evoke metabolic acidosis, and this causes damage to the eyes and brain. Permanent blindness can develop in 48 hours.
Exposure via respiratory tract
Part of the washer liquid components can also evaporate and enter the car interior via the ventilation system. Long-term exposure to methanol can then lead to a variety of central nervous system symptoms, headache, visual disturbances, tiredness and decreased vigilance. These can cause traffic safety problems. Exposure levels will depend on the ventilation system of the car. The risks of methanol fumes in cars require clarification, but it is already apparent that in some conditions they represent a serious hazard. In particular, any use leading to exposure of pregnant women and small children should be restricted.
Methanol is a good example of double standards in the attitudes toward chemicals. The introduction of a clearly hazardous chemical for everyday use has been justified because of economic arguments, even though there are many safer chemicals. One could claim that the most common victims (skid-row alcoholics) do not arouse the sympathy of the public.
Notes and references
- Metabolic acidosis means decrease of pH of the body due to acids formed in metabolic processes.
One level up: Is man defiled by what goes to his mouth?
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