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Alcohol

image from Kimery Davis at Creative Commons, modified

The information on this page is adapted from toxipedia.org. To learn more about Toxipedia’s integration into our website, visit our Toxipedia webpage.

content from Toxipedia

Alcohol has several alternative names due to its various chemical structures and uses. On this page we will discuss ethanol, also called ethyl alcohol and many other names,1 and methanol, also known as methyl alcohol or wood alcohol.

Both ethanol and methanol are solvents, and both can be used as fuel, although ethanol is formed through fermentation of food crops, while methanol is created by chemical processes. Their chemical structures are slightly different.

Ethanol

ethanol structure

ethanol chemical structure

Ethanol is a component of alcoholic beverages:

  • Beer: approximately five percent alcohol
  • Wine: Between 12 and 15 percent alcohol
  • Distilled liquor: typically from 30 to 50 percent alcohol, but can be higher

Ethanol is also an antiseptic, a medicinal solvent, a chemical solvent, and an engine fuel. It can be used as a rocket fuel, for household heating and other uses.2

Routes of Exposure

Ethanol is typically consumed in alcoholic beverages, but exposures also happen through inhalation of ethanol vapor and through dermal (skin) absorption. Inhalation and dermal absorption are most significant in occupational settings.3

Health Impacts

Acute effects vary with blood alcohol concentration (BAC):4
  • .05 BAC: reduced inhibitions
  • .10 BAC: slurred speech
  • .20 BAC: euphoria and motor impairment
  • .30 BAC: confusion
  • .40 BAC: stupor
  • .50 BAC coma
  • Above .50 BAC: respiratory paralysis and death

Acute health effects. Toxicity symptoms from consumption of ethyl alcohol include memory loss, inebriation, dehydration and depression of the central nervous system. 

Longer-term health effects include these with strong (causal) evidence:5

In addition, good evidence connects ethanol to these health impacts:6

Other poor health outcomes due excessive drinking can include these:7

  • Unintentional injuries such as motor vehicle accidents, drowning, falls and burns
  • Violence, including child maltreatment, homicide and suicide
  • Alcohol abuse and dependency

Health benefits. If used moderately, ethanol may decrease the risk of heart disease and stroke, and it may possibly reduce the risk of diabetes. Moderate alcohol use may benefit older adults or those with existing risk factors for heart disease. The benefit to middle-aged or younger adults has not been shown to outweigh the harm.8

Examples of one drink for a typical healthy adult:
  • Beer: 12 fluid ounces
  • Wine: 5 fluid ounces
  • Distilled spirits (80 proof): 1.5 fluid ounces

Dose and age. Moderate ethyl alcohol use is defined as one drink a day for women of all ages and men older than age 65, and up to two drinks a day for men age 65 and younger.

Health effects of ethanol vary by the dose, so an adult much smaller or larger than the "typical" adult could experience different degrees of effects. Children are at greater risks from exposure because of their smaller size.

Gender. Women metabolize less of their alcohol in the intestine, which leads to higher absorption and higher blood alcohol concentration. Women also tend to have a higher body fat percentage per body weight, causing women have a lower volume of fluid by weight. Because women also tend to have lower average body weight than men, women will have a higher blood alcohol concentration on average than a man who consumes a comparable amount.

Vulnerable populations. Those highly sensitive to ethanol include pregnant women and fetuses. Fetal exposure to alcohol can lead to various complications, including fetal alcohol syndrome. Children in general, and especially the very young, are more susceptible to toxic effects because their organs are still rapidly developing, and growing organs are more vulnerable than mature organs and tissues to the effects of toxic chemicals such as alcohol. For example, the brain is not fully developed until the late teens, growing especially rapidly during the first seven years of life. A toxic hit to the brain while it is forming can have more serious effects than one later in life. In addition, the fetal liver eliminates alcohol very poorly, and so a fetus is subjected to alcohol's effects longer than its mother. At the other end of the life stage, there may be a small decline in alcohol elimination with aging.9

beer

image from Karen Neoh at Creative Commons

Variance in metabolism. Individuals vary in how they metabolize alcohol. In addition to age and gender, factors that can influence metabolism include physical condition, race or ethnicity and the rate of consumption.

Certain groups have genetic challenges metabolizing acetaldehyde, which is an intermediate in the metabolism of alcohol. Some individuals, especially of northeast Asian or of African heritage, have variants in genes which encode for ALDH, causing acetaldehyde blood levels to rise with consumption of ethanol and leading to toxic effects.10

Reducing Exposures

liquor

image from www.pvz.lt at Creative Commons

Purchasing or consuming alcoholic beverages. Regulation of ethyl alcohol varies by country.11 In the United States, the minimum age to purchase alcohol is 21 years. Regulations also address drinking and driving, with criminal classifications varying by country12 and state within the US,13 starting .08 percent blood alcohol concentration.

Recommendations for pregnant women are to avoid all alcohol during pregnancy.14 The 2015-2020 Dietary Guidelines for Americans recommend that the following groups avoid all alcohol:

  • Anyone under age 21
  • Women who are or may be pregnant
  • Anyone who is driving, planning to drive or participating in activities which require coordination, certain skills and alertness
  • Anyone taking certain prescription or over the counter medications, which interact with alcohol
  • Individuals with certain medical conditions
  • Those recovering from alcoholism or who are not able to control their drinking15

ethanol label

image from Michael Coté at Creative Commons

Occupational exposure. The US Occupational Safety and Health Administration (OSHA) permissible exposure limit for general industry is 1,000 ppm.16 Exposure limits are lower in some European countries.17 A 2009 review found no appreciable cancer risk from occupational exposures within these limits.18

Methanol

Methanol is a solvent and fuel, found in products such as these:19  

methanol in home products

graphic from the Methanol Institute showing home products containing methanol; click to open the PDF from that website

  • Plastics
  • Synthetic fibers
  • Paints
  • Resins
  • Magnetic film
  • Safety glass laminate
  • Adhesives
  • Solvents
  • Carpeting
  • Insulation
  • Refrigerants
  • Windshield washer fluid
  • Particle board
  • Pigments and dyes

Methanol is also used:

  • As a solvent for resins, fats and oils
  • In manufacturing of acetaldehyde, acetic acid, ethyl acetate, ethyl chloride, ethyl ether, butadiene, ethylene dibromide, soaps, cleaning preparations, dyes and explosives.
  • As a pharmaceutical, such as rubbing compounds

methanol structure

methanol chemical structure

Although methanol occurs naturally in fruits and vegetables, and also in our blood, urine, and breath in small amounts,20 it is a poison when ingested (consumed) or inhaled.

Routes of Exposure

Typical routes of exposure include inhalation, ingestion and skin or eye contact.

Health Impacts

Toxicity symptoms from methyl alcohol exposure or poisoning can include these:21

  • Irritation in eyes, skin and upper respiratory system
  • Headache
  • Drowsiness
  • Nausea
  • Vomiting
  • Dermatitis
  • Visual disturbance to severe vision impairment within 8-24 hours of exposure
  • Blindness
  • Metabolic acidosis
  • Alcoholic ketoacidosis
  • Diabetic ketoacidosis
  • Central nervous system depression
  • Death

Acute methanol poisoning can cause blindness and death. The minimal lethal oral dose in humans is believed to be 1mg/kg of body weight,22 or as little as one to three fluid ounces (30-100 milliliters). Most poisonings have occurred after ingestion, although methanol poisoning after inhalation or skin absorption in the workplace has been reported.23

Longer-term health effects include these with strong (causal) evidence:24

Good evidence links methanol to the following:25

Vulnerable populations. For the same reasons described above regarding ethanol, fetuses and children are more susceptible to the effects of methanol exposures than adults.

Sources of Exposure

Sources of exposure to methanol include home, manufacturing and industrial products. A list of products containing methanol is on the US Department of Health and Human Services Household Products Database.  

Methanol can often be found in various home-distilled spirits, such as moonshine. Commercial manufacturers of liquor use technologies specifically designed to ensure methanol is separated from the ethanol as the liquor is produced, but home distillers seldom have the technology and capability to do so.26

Reducing Exposures

windshield washer fluid

image from Ben Husmann at Creative Commons

OSHA's current permissible exposure limit is 200ppm.27 Prevention focuses on avoiding skin and eye contact with methanol. If skin contact does occur, washing the skin immediately is critical, flushing with water. First aid for other exposures involves immediately irrigating eyes, providing respiratory support after inhalation, and providing immediate medical attention if methanol is swallowed.28

Other regulations on methanol include limiting the amount of methanol in windshield washing fluids to three percent. Swallowing windshield wiper fluid can be lethal, especially for small children.29 More information about methanol poisoning in home settings is available on the MedlinePlus website.

Avoid home-distilled alcoholic beverages, even though the price may be appealing. Home-brewed beer and homemade wine are generally not a concern for methanol.

History & Ethics

costs of excessive alcohol use

Costs of excessive alcohol use; click to open the PDF from the CDC website

Ethanol has been produced for millennia, with evidence dating as far back as 7000 BC. Greek literature contains warnings against excessive drinking, and so problems associated with alcohol consumption are nothing new.30 However, some problems seem to be increasing. Compared to 2006, when excessive drinking in the United States was estimated to cost $223.5 billion ($1.90 per drink), by 2010 the costs had risen to $249 billion ($2.05 per drink). 77 percent of these costs were attributed to binge drinking, which is five or more drinks on one occasion for men or four or more drinks on one occasion for women. Most of these costs were due to reduced workplace productivity, crime, and the cost of treating people for health problems caused by excessive drinking.31 In the US, the annual cost of alcohol-related motor vehicle crashes totals more than $44 billion.32

Not only is excessive drinking draining our economy, but the 88,000 lives lost each year to excessive drinking in America—one in 10 deaths among working-aged Americans33 —is a social and ethical outrage. Alcohol abuse and the needless and permanent damage to innocents, including fetuses and children, are entirely preventable.

See more about alcohol and health in the list of CHE publications and Dig Deeper resources in the right sidebar.


This page was last revised by student intern Eva Bauer and Nancy Hepp in July 2016. Read more about Eva's internship, including her review summary

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