Blood alcohol content

Blood alcohol content can be estimated by a method developed by Swedish professor Erik Widmark in the 1920s:[4]

${\displaystyle EBAC=A/(r\times Wt)-\beta \times T}$

where:

• A is the mass of alcohol consumed.
• r is the ratio of body water to total weight. It varies between individuals but averages about 0.68 for men and 0.55 for women, since women tend to a higher percentage of fat.
• Wt is body weight.
• β is the rate at which alcohol is metabolized. It is approximately 0.017% per hour.
• T is the amount time during which alcohol was present in the blood (usually time since consuption began).

Sometimes the above is multiplied by 1.055 g/mL, the density of blood.[4]

In terms of fluid ounces of alcohol consumed and weight in pounds, the formula can be written as

${\displaystyle EBAC=8\times {\text{fl oz}}/{\text{weight in pounds}}-\beta \times T}$

for a man or

${\displaystyle EBAC=10\times {\text{fl oz}}/{\text{weight in pounds}}-\beta \times T}$

for a woman.[4]

Regarding metabolism (β) in the formula; females demonstrated a higher average rate of elimination (mean, 0.017; range, 0.014–0.021 g/210 L) than males (mean, 0.015; range, 0.013–0.017 g/210 L). Female subjects on average had a higher percentage of body fat (mean, 26.0; range, 16.7–36.8%) than males (mean, 18.0; range, 10.2–25.3%).[5] Additionally, men are, on average, heavier than women but it is not strictly accurate to say that the water content of a person alone is responsible for the dissolution of alcohol within the body, because alcohol does dissolve in fatty tissue as well. When it does, a certain amount of alcohol is temporarily taken out of the blood and briefly stored in the fat. For this reason, most calculations of alcohol to body mass simply use the weight of the individual, and not specifically his/her water content. Finally, it is speculated that the bubbles in sparkling wine may speed up alcohol intoxication by helping the alcohol to reach the bloodstream faster.

Examples:

• 80 kg male drinking 3 drinks of 10 grams each, in two hours:

${\displaystyle EBAC=(0.030{\text{kg}})/(0.68\cdot 80{\text{kg}})\times 1.055{\text{g/mL}}-(0.015\cdot 2)\approx 0.025{\text{ g/dL}}}$

• 70 kg woman drinking 2.5 drinks of 10 grams each, in two hours:

${\displaystyle EBAC=0.025/(0.55\cdot 70)-(0.017\cdot 2)\approx 0.035g/dL}$

Note: This chart defines a standard drink as 0.6 fluid ounces (14 g) of ethanol, whereas other definitions exist, for example 10 grams of ethanol.

Standard drink sizes (Australia)

• 375 ml can of light beer (2.7% alcohol) = 0.8 standard drinks
• 375 ml can of mid-strength beer (3.5% alcohol) = 1 standard drink
• 375 ml can of full strength beer (4.8% alcohol) = 1.4 standard drinks
• 100 ml glass of wine (13.5% alcohol) = 1 standard drink
• 150 ml glass of wine (13.5% alcohol) = 1.5 standard drinks
• 30 ml shot of spirits (40% alcohol) = 0.95 standard drinks
• 440 ml can of pre-mix spirits (approx. 5% alcohol) = 1.7 standard drinks
• 440 ml can pre-mix spirits (approx. 7% alcohol) = 2.4 standard drinks

The National Institute on Alcohol Abuse and Alcoholism (NIAAA) define the term "binge drinking" as a pattern of drinking that brings a person's blood alcohol concentration (BAC) to 0.08 grams percent or above. This typically happens when men consume 5 or more drinks, and when women consume 4 or more drinks, in about 2 hours.[8]

There are several different units in use around the world for defining blood alcohol concentration. Each is defined as either a mass of alcohol per volume of blood or a mass of alcohol per mass of blood (never a volume per volume). 1 milliliter of blood has a mass of approximately 1.06 grams. Because of this, units by volume are similar but not identical to units by mass. In the U.S. the concentration unit 1% w/v (percent mass/volume, equivalent to 10 g/l or 1 g per 100 ml) is in use.

This is not to be confused with the amount of alcohol measured on the breath, as with a breathalyzer. The amount of alcohol measured on the breath is generally accepted as proportional to the amount of alcohol present in the blood at a rate of 1:2100. Therefore, a breathalyzer measurement of 0.10 mg/L of breath alcohol converts to 0.0001×2100 g/L, or 0.21 g/L of blood alcohol (the units of the BAC in the United States, this is equivalent to 0.21 permille). While a variety of units (or sometimes lack thereof) is used throughout the world, many countries use the g/L unit, which does not create confusion as percentages do. Usual units are highlighted in the table below.

Map of Europe showing countries' blood alcohol limits as defined in g/dl for the general population.

For purposes of law enforcement, blood alcohol content is used to define intoxication and provides a rough measure of impairment. Although the degree of impairment may vary among individuals with the same blood alcohol content, it can be measured objectively and is therefore legally useful and difficult to contest in court. Most countries disallow operation of motor vehicles and heavy machinery above prescribed levels of blood alcohol content. Operation of boats and aircraft is also regulated.

The alcohol level at which a person is considered legally impaired varies by country. The list below gives limits by country. These are typically blood alcohol content limits for the operation of a vehicle.

Blood alcohol tests assume the individual being tested is average in various ways. For example, on average the ratio of blood alcohol content to breath alcohol content (the partition ratio) is 2100 to 1. In other words, there are 2100 parts of alcohol in the blood for every part in the breath. However, the actual ratio in any given individual can vary from 1300:1 to 3100:1, or even more widely.[47] This ratio varies not only from person to person, but within one person from moment to moment. Thus a person with a true blood alcohol level of .08% but a partition ratio of 1700:1 at the time of testing would have a .10 reading on a Breathalyzer calibrated for the average 2100:1 ratio.

Alcohol is absorbed throughout the gastrointestinal tract, but more slowly in the stomach than in the small or large intestine. For this reason, alcohol consumed with food is absorbed more slowly, because it spends a longer time in the stomach. Furthermore, alcohol dehydrogenase is present in the stomach lining. After absorption, the alcohol passes to the liver through the hepatic portal vein, where it undergoes a first pass of metabolism before entering the general bloodstream.[49]

Alcohol is removed from the bloodstream by a combination of metabolism, excretion, and evaporation.

Alcohol is metabolized mainly by the group of six enzymes collectively called alcohol dehydrogenase. These convert the ethanol into acetaldehyde (an intermediate more toxic than ethanol). The enzyme acetaldehyde dehydrogenase then converts the acetaldehyde into non-toxic acetic acid.

Many physiologically active materials are removed from the bloodstream (whether by metabolism or excretion) at a rate proportional to the current concentration, so that they exhibit exponential decay with a characteristic halflife (see pharmacokinetics). This is not true for alcohol, however. Typical doses of alcohol actually saturate the enzymes' capacity, so that alcohol is removed from the bloodstream at an approximately constant rate. This rate varies considerably between individuals. Another sex based difference is in the elimination of alcohol. People under 25, women[50] or with liver disease may process alcohol more slowly. False High (BAC) readings are related to patients with proteinuria and hematuria, due to kidney-liver metabolism and failure (for example, Hematuria 1+ protenuria 1+ )

Such persons have impaired acetaldehyde dehydrogenase, which causes acetaldehyde levels to peak higher, producing more severe hangovers and other effects such as flushing and tachycardia. Conversely, members of certain ethnicities that traditionally did not use alcoholic beverages have lower levels of alcohol dehydrogenases and thus "sober up" very slowly, but reach lower aldehyde concentrations and have milder hangovers. Rate of detoxification of alcohol can also be slowed by certain drugs which interfere with the action of alcohol dehydrogenases, notably aspirin, furfural (which may be found in fusel alcohol), fumes of certain solvents, many heavy metals, and some pyrazole compounds. Also suspected of having this effect are cimetidine, ranitidine, and acetaminophen (paracetamol).

Currently, the only known substance that can increase the rate of metabolism of alcohol is fructose. The effect can vary significantly from person to person, but a 100 g dose of fructose has been shown to increase alcohol metabolism by an average of 80%. Fructose also increases false positives of high BAC ratio readings in anyone with proteinuria and hematuria, due to kidney-liver metabolism.[51]

There have been reported cases of blood alcohol content higher than 1%:

• In 1982, a 24-year-old woman was admitted to the UCLA emergency room with a serum alcohol content of 1.51%, corresponding to a BAC of 1.33%. She was alert and oriented to person and place.[53] Serum alcohol concentration is not equal to nor calculated in the same way as blood alcohol content.[54]
• In 1984, a 30-year-old man survived a blood alcohol concentration of 1.5% after vigorous medical intervention that included dialysis and intravenous therapy with fructose.[55]
• In 1995, a man from Wrocław, Poland, caused a car accident near his hometown. He had a blood alcohol content of 1.48% ; he was tested five times, with each test returning the same reading. He died a few days later of injuries from the accident.[56]
• In 2004, an unidentified Taiwanese woman died of alcohol intoxication after immersion for twelve hours in a bathtub filled with 40% ethanol. Her blood alcohol content was 1.35%. It was believed that she had immersed herself as a response to the SARS epidemic.[57]
• In South Africa, a man driving a Mercedes-Benz Vito light van containing 15 sheep allegedly stolen from nearby farms was arrested on December 22, 2010, near Queenstown in Eastern Cape. His blood had an alcohol content of 1.6%. Also in the vehicle were five boys and a woman, who were also arrested.[58]
• On 26 October 2012, a man from Gmina Olszewo-Borki, Poland, who died in a car accident, recorded a blood alcohol content of 2.23%; however, the blood sample was collected from a wound and thus possibly contaminated.[56]
• On 26 July 2013 a 40-year-old man from Alfredówka, Poland, was found by Municipal Police Patrol from Nowa Dęba lying in the ditch along the road in Tarnowska Wola. At the hospital, it was recorded that the man had a blood alcohol content of 1.374%. The man survived.[59][60]

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