It's hard to separate fact from fiction from fear-mongering, when trying to understand the relationship between the Mexican agave-based spirit mezcal, and methanol poisoning resulting in blindness or death as the worst case scenarios. The purely physical science treatises are in large part beyond my level of comprehension. At the other end of the spectrum one finds lay literature without references backing up claims and allegations regarding the likelihood of hangovers, headaches and the much more serious harmful effects; it's all cloaked in words and phrases like "as little as," "likely" and "probably." And it ignores aspartame.
Is it appropriate to equate mezcal which has been produced essentially safely and without incident by families in the southern Mexico state of Oaxaca for generations, with American moonshine, with deaths due to deliberately adulterating a spirit for purely profit motive, with concoctions created by naive youth, or with reports from third world countries in which ignorance of safe spirit production results in imprudent means of production or the use of equipment which contaminates? It is suggested that the alarmists draw their data from such sources.
Otherwise all I have to rely on is my cursory review of online literature (sources are cited at the conclusion of this article, including but not restricted to International Center for Alcohol Policies, UPI, Methanol Institute, National Institute of Health / U.S. National Library of Medicine, World Health Organization), and my background in social anthropology. It was my Darwinian academic training which lead me to an internet search so that I might be able to prove what I considered to be a reasonable hypothesis, and put into perspective the tall tales I'd been reading. Regarding the latter, I have read that mezcal not certified by a regulatory agency is fake, illegitimate, results in hangovers, and may even lead to blindness or death from methanol poisoning. Have imbibers of agave-based spirits been extremely lucky all these years, decades and perhaps even millennia?
The two lines of thought regarding the origins of distillation in Mexico are that indigenous groups learned to distill long before the arrival of the Spanish, or, that the Spanish learned distillation from the Moors and so brought that knowledge with them in the first half of the 16th century. The former theory gives more credence to my thought process, although 450 years of trial and error and perfecting safe distillation is nothing to sneeze at.
Just like the early Zapoteco natives of Oaxaca learned to dye with the cochineal insect, and in due course presumably through trial and error that the mineral alum served as the best available mordent or fixer, it is suggested that so too did the invaders and the indigenous peoples of Mexico learn how to distill safely. Following the same analogy, it is likely that long ago wool dyed red with cochineal dramatically faded from the sun or through washing, until the best available mordent was found; and so perhaps dating back hundreds of years indeed native Mexicans (and Spanish) succumbed to unwise distillation practices. They have learned the benefit of using alum; and of taking off the methanol, and using predominantly clay or copper or other "safe" metal compounds during and for distillation respectively.
Even the healthiest among us, and that includes those who do not imbibe alcohol, have methanol in their bodies. Humans get it in small amount from eating fruits and vegetables. It is not only absorbed through the gastrointestinal tract, but also through the skin and by inhalation. Methanol is metabolized in the liver, converted first to formaldehyde, and then to formate (formic acid). As a building block for many biological molecules, formate is essential for our survival. On the other hand, high levels of formate buildup after excessive methanol intake can cause severe toxicity. An EPA assessment reported that methanol is considered a cumulative poison due to the low rate of excretion once it is absorbed.
The primary uses of methanol are for industrial and automotive purposes. It is found in antifreeze, canned heating sources, copy machine fluids, de-icing fluids, fuel additives, paint remover or thinner, shellac, varnish, windshield wiper fluid, and more. This is known as denatured alcohol. Government regulations in fact dictate the inclusion of high levels of methanol as a compound in such products, knowing its toxicity and wanting to ensure that the public buys its liquor (in which levels of methanol are controlled, as opposed to other alcohols), in order to maintain healthy tax revenue.
But Government dictates do not prevent the drinking of denatured alcohol or it being used to fortify other beverages. In fact the literature on non-commercial alcohol, which is sometimes referred to as unrecorded alcohol, cites these "surrogates" or non-beverage alcohols, as one of three categories of drinks which potentially create health risks. They are drunk alone (i.e. the classic skid row cases), and used as "cocktails" when they are added for example to fruit juices. The other two are "counterfeit" products and illicit mass-produced drinks, and traditional drinks produced for home consumption or limited local trade (licit or illicit). It is suggested that artisanal mezcal falls into the second part of this third category. So yes, there is the possibility of health problems arising as a consequence of consumers imbibing Mexican mezcal with higher than "safe" levels of methanol.
Spirits Health Risks in Mexico and Internationally
In central Mexico, as born out in the literature, much more than anything else the singular health problem related to mezcal and other traditional alcohol consumption is alcoholism resulting in liver cirrhosis.
In an article centering upon global methanol poisoning outbreaks, the World Health Organization cited examples of adulterated, counterfeit and informally produced spirits in Cambodia, Czech Republic, Ecuador, Estonia, India, Indonesia, Kenya, Libya, Nicaragua, Norway, Pakistan, Turkey and Uganda. Mexico is conspicuously absent from the list. In an article centering upon the quantification of selected volatile constituents in the Mexican spirits sotol, bacanora, tequila and mezcal, while methanol was the most problematic compound and at times the samples taken were far above the levels recommended by international as well as national standards, two points are particularly noteworthy: methanol levels were not of toxicological relevance; and, other legally obtained drinks such as German fruit spirits were found to have significantly higher methanol levels.
In an article entitled "Noncommercial Alcohol: Understanding the Informal Market," the International Center for Alcohol Policies reported that much of the perceived health risk stems from patterns of drinking such as chronic consumption and binging, use of low quality ingredients, adulteration, and lack of control during production or storage. In Russia and other republics in the former Soviet Union samagon is cheap and easy to make using household equipment. Kenya's poor fortifies its grain spirit, chang'aa, with surrogates. Brazil's national drink cachaca or pinga is sometimes fortified using industrial alcohols, some of which have been noted above.
And what about the United States' renowned moonshine, the usually high alcohol content spirit typically made using corn mash as the main ingredient? Poorly produced moonshine is contaminated mainly from materials used in still construction, such as employing car radiators as condensers (glycol from the antifreeze or lead from the connections). In addition, methanol can be added to the spirits to increase strength and improve profits.
The 1994 reported poisoning from ingesting mezcal produced in the Mexican state of Morelos cite the spirit having been spiked with methanol. It is suggested that this was an aberration, though of course is noteworthy. Somewhat surprisingly, there was relatively little reported about the incidents, and they have not to my knowledge received attention in the broader English literature centering upon methanol poisoning.
As suggested, methanol is not the only potentially harmful constituent. Lead as well as other toxic metals can poison not only as a consequence of employing unsuitable distillation equipment but also through the use of a contaminated water source. Volatile compounds such as acetaldehyde or higher alcohols can be produced in significant amounts due to fault in production technology or microbiological spoilage. There have been occurrences of certain fruit and sugarcane spirits containing the carcinogen urethane.
When is Methanol Safe?
Returning to methanol, one must now ask what is the safe maximum level of its ingestion. It was only in 1981 that the sugar substitute aspartame was approved for dry goods, and two years later for carbonated beverages. It is made up of three chemicals: aspartic acid, phenylalanine, and methanol which makes up a whopping 10% of its composition. The absorption of methanol into the body is sped up when "free methanol" is ingested, and this form of the chemical is created from aspartame when it is heated to above 86 degrees Fahrenheit (i.e. when making sugar-free Jello). In 1993 the FDA approved aspartame as an ingredient in numerous food items that would normally be heated to above that temperature. The EPA recommends consumption of no more than 7.8 grams of methanol daily. While the amount of aspartame in a diet soda can vary, it has been reported that a single can produces 20 mg of methanol in the body. It is no wonder that aspartame accounts for over 75% of the adverse reactions to food additives reported to the FDA. Chronic illnesses can be triggered or worsened by ingesting aspartame. The range of afflictions reported is alarming.
The current regulation for the maximum amount of methanol in mezcal is .3 of a gram per 100 ml. It is an arbitrary standard. Query how much mezcal one must ingest to reach the EPA maximum limit of methanol of 7.8 grams daily. The FDA states that as much as .5 of a gram per day of methanol is safe in an adult's diet. Should the Mexican standard be higher, or lower?
It is no wonder that the study referenced earlier identifying volatile constituents in Mexican spirits, did not find toxicological relevance in the face of analyzing samples far above recommended levels. Furthermore, as distinct from household foodstuffs and drink containing aspartame, ethanol (i.e. mezcal) serves as an antidote for methanol toxicity in humans.
There is indeed confusion in the literature regarding recommended maximum levels of methanol and at what level health risks kick in, both dealing specifically with Mexican spirits, and where they are noted merely tangentially or not at all. However there is also considerable consistency:
If there is a lesson to be learned, it is perhaps that one should never drink artisanal mezcal, commercial or otherwise, while consuming government authorized products containing aspartame.
Most of the foregoing has been drawn from the following references:
Alvin Starkman operates Mezcal Educational Excursions of Oaxaca (http://www.mezcaleducationaltours.com), a registered trademark. He is authorized to teach about the culture of mezcal and pre-Hispanic beverages by the Mexican government.