| Blood alcohol content | |
|---|---|
| Diagnostics | |
Ethanol |
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| LOINC | 5639-0, 5640-8, 15120-9, 56478-1 |
Blood alcohol content (BAC), also called blood alcohol concentration, blood ethanol concentration, or blood alcohol level is most commonly used as a metric of alcohol intoxication for legal or medical purposes.
Blood alcohol content is usually expressed as a percentage of alcohol in the blood. For instance, a BAC of 0.10 means that 0.10% (one tenth of one percent) of a person's blood, by volume, is alcohol.
Contents |
| Progressive effects of alcohol[1] | ||
|---|---|---|
| BAC (% by vol.) | Behavior | Impairment |
| 0.010–0.029 |
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| 0.030–0.059 |
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| 0.06–0.09 |
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| 0.10–0.19 |
|
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| 0.20–0.29 |
|
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| 0.30–0.39 |
|
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| 0.40–0.50 |
|
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| ≥0.50 |
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| Standard drink chart (U.S.)[2] | |||||
|---|---|---|---|---|---|
| Alcohol | Amount (ml) | Amount (fl oz) | Serving size | Alcohol (% by vol.) | Alcohol |
| 80 proof liquor | 44 | 1.5 | One shot | 40 | 0.6 US fl oz (18 ml) |
| Table wine | 148 | 5 | One glass | 12 | 0.6 US fl oz (18 ml) |
| Beer | 355 | 12 | One can | 5 | 0.6 US fl oz (18 ml) |
| Male Female |
Approximate blood alcohol percentage (by vol.)[3] One drink has 0.5 US fl oz (15 ml) alcohol by volume |
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|---|---|---|---|---|---|---|---|---|---|
| Drinks | Body weight | ||||||||
| 40 kg | 45 kg | 55 kg | 64 kg | 73 kg | 82 kg | 91 kg | 100 kg | 109 kg | |
| 90 lb | 100 lb | 120 lb | 140 lb | 160 lb | 180 lb | 200 lb | 220 lb | 240 lb | |
| 1 | – 0.05 |
0.04 0.05 |
0.03 0.04 |
0.03 0.03 |
0.02 0.03 |
0.02 0.03 |
0.02 0.02 |
0.02 0.02 |
0.02 0.02 |
| 2 | – 0.10 |
0.08 0.09 |
0.06 0.08 |
0.05 0.07 |
0.05 0.06 |
0.04 0.05 |
0.04 0.05 |
0.03 0.04 |
0.03 0.04 |
| 3 | – 0.15 |
0.11 0.14 |
0.09 0.11 |
0.08 0.10 |
0.07 0.09 |
0.06 0.08 |
0.06 0.07 |
0.05 0.06 |
0.05 0.06 |
| 4 | – 0.20 |
0.15 0.18 |
0.12 0.15 |
0.11 0.13 |
0.09 0.11 |
0.08 0.10 |
0.08 0.09 |
0.07 0.08 |
0.06 0.08 |
| 5 | – 0.25 |
0.19 0.23 |
0.16 0.19 |
0.13 0.16 |
0.12 0.14 |
0.11 0.13 |
0.09 0.11 |
0.09 0.10 |
0.08 0.09 |
| 6 | – 0.30 |
0.23 0.27 |
0.19 0.23 |
0.16 0.19 |
0.14 0.17 |
0.13 0.15 |
0.11 0.14 |
0.10 0.12 |
0.09 0.11 |
| 7 | – 0.35 |
0.26 0.32 |
0.22 0.27 |
0.19 0.23 |
0.16 0.20 |
0.15 0.18 |
0.13 0.16 |
0.12 0.14 |
0.11 0.13 |
| 8 | – 0.40 |
0.30 0.36 |
0.25 0.30 |
0.21 0.26 |
0.19 0.23 |
0.17 0.20 |
0.15 0.18 |
0.14 0.17 |
0.13 0.15 |
| 9 | – 0.45 |
0.34 0.41 |
0.28 0.34 |
0.24 0.29 |
0.21 0.26 |
0.19 0.23 |
0.17 0.20 |
0.15 0.19 |
0.14 0.17 |
| 10 | – 0.51 |
0.38 0.45 |
0.31 0.38 |
0.27 0.32 |
0.23 0.28 |
0.21 0.25 |
0.19 0.23 |
0.17 0.21 |
0.16 0.19 |
| Subtract approximately 0.01 every 40 minutes after drinking. | |||||||||
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 is approximately equivalent to 1.06 grams of blood. 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 weight/volume, equivalent to 10g/l or 1 g per 100 ml) is in use.[4] 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 to be 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 0.021 g/210L of breath alcohol, or 0.021 g/dL of blood alcohol (the units of the BAC in the United States). While a variety of units (or sometimes lack thereof) is used throughout the world, many countries use the g/L unit, which do not create confusion as percentages do. Usual units are highlighted in the table below.
| Reference | Unit | Dimensions | Equivalent to | Used in |
|---|---|---|---|---|
| BAC by volume | 1 percent (%) | 1/100 g/mL = 1 g/dL | 9.43 mg/g, 217.4 mmol/L | United States, Australia, Canada |
| 1 permille (‰) | 1/1000 g/mL = 1 g/L | 0.943 mg/g, 21.7 mmol/L | Austria, France, Latvia, Lithuania, Netherlands, Poland, Romania, Spain, Switzerland, Turkey | |
| 1 basis point (‱) | 1/10,000 g/mL = 10 mg/100 mL | 94.3 ppm, 2.17 mmol/L | Great Britain | |
| BAC by mass | 1 percent (%) | 1/100 g/g = 1 cg/g | 1.06 cg/mL, 230 mmol/L | |
| 1 permille (‰) | 1/1000 g/g = 1 mg/g | 1.06 mg/mL, 23 mmol/L | Finland, Norway, Sweden, Denmark, Germany | |
| 1 part per million (ppm) | 1/1,000,000 g/g = 1 μg/g | 1.06 μg/mL, 23 μmol/L |
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 are also regulated.
The alcohol level at which a person is considered to be 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. In the United States, the legal limit can vary by state but for all states as of 2011 is 0.08% blood alcohol content as measured by a breath device, urinalysis or blood test. This legal limit is down from 0.15% just a few decades previously.[5]
Since there is always some amount of alcohol even in non-drinkers' bodies, they have to have some legal guidelines for determining what behavior is illegal. Often that guideline is something like impairment in driving to any degree that can be shown to be probably caused by recent alcohol consumption.
In certain countries, alcohol limits are determined by the Breath Alcohol Content (BrAC), not to be confused with blood alcohol content (BAC).
"0.01" Blood alcohol content is the hundredth decimal part of the one thousandth part of a liter. (Please note that this "0.01" is measured in permille and not percentage as the "0.1" example in inroduction and numbers in 1 Effects at different levels.)
In digesting these numbers it must be remembered that one milliliter is the thousandth part of a liter. Therefore 1% of a milliliter is 0.00001-Liter. Expressing blood-alcohol concentration as "0.01" is naming the hundredth part of a thousandth part.
As final example, a blood-alcohol concentration of 0.08, being the 0.08 "part" of a milliliter (ITSELF the thousandth part of a Liter) therefore names an absolute blood-alcohol volume of 0.00008-Liter (within every liter of blood).
Each country or state may define BAC differently. For example, the state of California in the United States legally defines BAC as a ratio of grams of alcohol per 100 milliliters of blood,[25] which is equal to grams of alcohol per deciliter of blood.
Since measurement must be accurate and inexpensive, several measurement techniques are used as proxies to approximate the true parts per million measure. Some of the most common are listed here: (1) Mass of alcohol per volume of exhaled breath (for example, 0.38 mg/L; see also breath gas analysis), (2) Mass per volume of blood in the body (for example, 0.08 g/dL), and (3) Mass of alcohol per mass of the body (for example, 0.0013 g/Kg).
The number of alcoholic beverages (drinks) consumed is often a poor measure of blood alcohol content because of variations in sex, body weight, and body fat.
An ethanol level of 0.10% is equal to 22 mmol/l or 100 mg/dl of blood alcohol.[26][27] This same 0.10% BAC also equates to 0.10 g/dL of blood alcohol or 0.10 g/210L of exhaled breath alcohol or 0.476 mg/L of exhaled breath alcohol. Likewise, 0.10 mg/L of exhaled breath alcohol converts to 0.02% BAC, 0.022 g/dL of blood alcohol or 0.022 g/210L of exhaled breath alcohol.
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. 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. A similar assumption is made in urinalysis. When urine is analyzed for alcohol, the assumption is that there are 1.3 parts of alcohol in the urine for every 1 part in the blood, even though the actual ratio can vary greatly.
Breath alcohol testing further assumes that the test is post-absorptive—that is, that the absorption of alcohol in the subject's body is complete. If the subject is still actively absorbing alcohol, their body has not reached a state of equilibrium where the concentration of alcohol is uniform throughout the body. Most forensic alcohol experts reject test results during this period as the amounts of alcohol in the breath will not accurately reflect a true concentration in the blood.
Alcohol is removed from the bloodstream by a combination of metabolism, excretion, and evaporation. The relative proportion disposed of in each way varies from person to person, but typically about 95% is metabolised by the liver. The remainder of the alcohol is eliminated through excretion in breath, urine, sweat, feces, milk and saliva.[28] Excretion into urine typically begins after about 40 minutes, whereas metabolisation commences as soon as the alcohol is absorbed, and even before alcohol levels have risen in the brain.
Alcohol is metabolised mainly by the group of six enzymes collectively called alcohol dehydrogenase. These convert the ethanol into acetaldehyde (an intermediate that is actually 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. Persons below the age of 25, women[29] persons of certain ethnicities, and persons with liver disease may process alcohol more slowly. Many East Asians (for example, about half of Japanese) have impaired acetaldehyde dehydrogenase; this 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 brew 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 (Tagamet), ranitidine (Zantac), and acetaminophen (Tylenol) (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 100g dose of fructose has been shown to increase alcohol metabolism by an average of 80%.[30]
Alcohol absorption can be slowed by ingesting alcohol on a full stomach. Spreading the total absorption of alcohol over a greater period of time decreases the maximum alcohol level, decreasing the hangover effect. Thus, drinking on a full stomach or drinking while ingesting drugs which slow the breakdown of ethanol into acetaldehyde, will reduce the maximum blood levels of this substance, and decrease the hangover. Alcohol in non-carbonated beverages is absorbed more slowly than alcohol in carbonated drinks.[31]
Retrograde extrapolation is the mathematical process by which someone's blood alcohol concentration at the time of driving is estimated by projecting backwards from a later chemical test. This involves estimating the absorption and elimination of alcohol in the interim between driving and testing. The rate of elimination in the average person is commonly estimated at .015 to .020 grams per deciliter per hour (g/dl/h), although again this can vary from person to person and in a given person from one moment to another. Metabolism can be affected by numerous factors, including such things as body temperature, the type of alcoholic beverage consumed, and the amount and type of food consumed.
In an increasing number of states, laws have been enacted to facilitate this speculative task: the blood alcohol content at the time of driving is legally presumed to be the same as when later tested. There are usually time limits put on this presumption, commonly two or three hours, and the defendant is permitted to offer evidence to rebut this presumption.
Forward extrapolation can also be attempted. If the amount of alcohol consumed is known, along with such variables as the weight and sex of the subject and period and rate of consumption, the blood alcohol level can be estimated by extrapolating forward. Although subject to the same infirmities as retrograde extrapolation—guessing based upon averages and unknown variables—this can be relevant in estimating BAC when driving and/or corroborating or contradicting the results of a later chemical test.
Blood alcohol content can be roughly estimated using a mathematical approach. Mathematical estimations can be useful for calculating a blood alcohol content level that is not currently testable, or a level that may be present in the future. While there are several ways to calculate it, one of the most effective ways is to simply measure the total amount of alcohol consumed divided by the total amount of water in the body—effectively giving the percent alcohol per volume water in the blood.
Sex plays an important role in the total amount of water that a person has. In general, men have a higher percent of water (58%) than women (49%). This fact alone strongly contributes to the generalization that men require more alcohol than women to achieve the same blood alcohol content level. Additionally, men are, on average, heavier than women. The more water a person has, the more alcohol is required to achieve the same alcohol:blood ratio, or blood alcohol content level. Further, studies have shown that women's alcohol metabolism varies from that of men due to such biochemical factors as different levels of alcohol dehydrogenase (the enzyme which breaks down alcohol) and the effects of oral contraceptives.[32]
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 water content.
In November 2007, a driver was found passed out in her car in Oregon in the United States. A blood test showed her blood alcohol level was 0.550%. She was charged with several offenses, including two counts of driving under the influence of an intoxicant, reckless endangerment of a person, criminal mischief and driving with a suspended license. Her bail was later set at USD 50,000, since she had several previous convictions for similar offenses.[33][34][35]
In December 2007, a driver was arrested in Klamath County, Oregon, after she was found unconscious in her car which was stuck in a snow bank with its engine running. Police were forced to break a car window to remove her. After realizing she was in alcohol-induced coma, they rushed her to the hospital where a blood test showed her blood alcohol level was 0.720%. She reportedly was released from the hospital the next day.[33][36] She was subsequently charged with drunk driving.[37]
In July 2008, a driver was arrested after he ran into a highway message board on Interstate 95 in Providence, Rhode Island. A breath test showed his blood alcohol level was at 0.491% and he was raced to the hospital where he was sedated and placed in a detoxification unit. He was subsequently charged with driving while intoxicated and resisting arrest.[38][39] He was later sentenced to one year probation, a $500 fine, 40 hours of community service and a one-year loss of his driver's license. The police later stated that his blood alcohol level was the highest they had ever seen for someone who hadn't died of alcohol poisoning.[40] It was later estimated that the driver had consumed 10–14 drinks over the course of 1–2 hours,[33] based on the standard levels of elimination which as documented previously can vary by up to 300%.
In December 2009, a South Dakota woman was found behind the wheel of a stolen car with a measured blood alcohol content of .708%, almost nine times the state's limit of .08%, thus becoming the highest recorded level of alcohol toxicity for the state. After she was hospitalized, she was released on bond and subsequently found in another stolen automobile while under the influence.[41]
In 1995, a man in Wrocław, Poland, had a car accident. At the hospital, his BAC was determined to be 1.48%. Concerned that their equipment was malfunctioning, doctors also performed five separate lab tests, all of which confirmed the man's blood alcohol content. He died a few days later from wounds from the car accident. Police were baffled as to how an individual could attain such a high blood alcohol. Later, police discussions with his brother in-law revealed that he had "beer bonged" pure grain alcohol allegedly stolen from his place of work, a chemical plant.[42]
In December 2004, a man was admitted to the hospital in Plovdiv, Bulgaria, after being struck by a car. After detecting a strong alcohol odor, doctors at a hospital conducted a breath test which displayed the man's blood alcohol content at 0.914.[43] The man was treated for serious injuries sustained in the crash and survived.[44]
In February 2005, French gendarmes from Bourg-en-Bresse, France, conducted a breath test on a man who had lost control of his car. He had an alcohol content of 0.976.[45] He was not injured in the accident but was charged with a €150 fine and his driving license was canceled.
There have been reported cases of blood alcohol content higher than 1.00. In March 2009, a 45-year-old man was admitted to the hospital in Skierniewice, Poland, after being struck by a car. The blood test showed blood alcohol content at 1.23. The man survived but did not remember either the accident or the circumstances of his alcohol consumption.[46] One such case was reported by O'Neil, and others in 1984. They report on a 30-year-old man who survived a blood alcohol concentration of 1,500 mg/100 ml blood after vigorous medical intervention.[47]
In 1982, a 24-year-old woman was admitted to the UCLA emergency room with a serum alcohol concentration of 1.5 (1510 mg/dL). She was alert and oriented to person and place (reported in The Lancet, Dec 18, 1982, p. 1394). Serum Alcohol Concentration is not equal to nor calculated in the same way as Blood Alcohol Content.[48] (By conversion using BAC=SAC/1.14, this would correspond to a BAC of 1.33.[49])
In South Africa, a man driving a Mercedes-Benz Vito 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 g/100 ml. Also in the vehicle were five boys and a woman who were also arrested.[50]
In Poland, a homeless man was found sleeping half-naked on January 28, 2011, in Cieszyn. His blood had an alcohol level of 1.024%. Despite the temperature of −10 °C and extremely high blood alcohol content the man survived.[51]
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