Blood alcohol content
Blood alcohol content is a measurement of alcohol intoxication used for legal or medical purposes. A BAC of 0.10 means that there are 0.10 g of alcohol for every 100 ml of blood which is the same as 21.7 mmol/l. A BAC of 0.0 is sober, while in the United States 0.08 is legally intoxicated, and above that is very impaired. BAC levels above 0.40 are potentially fatal.
Effects by alcohol level
Estimation by intake
To calculate estimated peak blood alcohol concentration, a variation, including drinking period in hours, of the Widmark formula was used. The formula is:where:
- 0.806 is a constant for body water in the blood,
- SD is the number of standard drinks, that being 10 grams of ethanol each,
- 1.2 is a factor to convert the amount in grams to Swedish standards set by The Swedish National Institute of Public Health,
- BW is a body water constant,
- Wt is body weight,
- MR is the metabolism constant and
- DP is the drinking period in hours.
- 10 converts the result to permillage of alcohol
Examples:
- 80 kg male drinking 3 standard drinks in two hours:
- 70 kg woman drinking 2.5 standard drinks in two hours:
| Alcohol | Amount | Amount | Serving size | Alcohol | Alcohol |
| 80 proof liquor | 44 | 1.5 | One shot | 40 | |
| Table wine | 148 | 5 | One glass | 12 | |
| Beer | 355 | 12 | One can/bottle | 5 |
Note: This chart defines a drink as 14 g of ethanol, while the formula defines a drink as 10 g of ethanol.
Standard drink sizes
- 375 ml can of light beer = 0.8 standard drinks
- 375 ml can of mid-strength beer = 1 standard drink
- 375 ml can of full strength beer = 1.4 standard drinks
- 100 ml glass of wine = 1 standard drink
- 150 ml glass of wine = 1.5 standard drinks
- 30 ml shot of spirits = 0.95 standard drinks
- 440 ml can of pre-mix spirits = 1.7 standard drinks
- 440 ml can pre-mix spirits = 2.4 standard drinks
Binge drinking
Units of measurement
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. 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 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/10dL, or 0.21 g/dL of blood alcohol. While a variety of units 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.
| 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 |
| BAC by volume | 1 permille | 1/1000 g/mL = 1 g/L | 0.943 mg/g, 21.7 mmol/L | Austria, Belgium, Bulgaria, France, Latvia, Lithuania, Netherlands, Poland, Romania, Spain, Switzerland, Turkey |
| BAC by volume | 1 basis point | 1/10,000 g/mL = 10 mg/100 mL | 94.3 ppm, 2.17 mmol/L | United Kingdom |
| BAC by mass | 1 percent | 1/100 g/g = 1 cg/g | 1.06 cg/mL, 230 mmol/L | - |
| BAC by mass | 1 permille | 1/1000 g/g = 1 mg/g | 1.06 mg/mL, 23 mmol/L | Finland, Norway, Sweden, Denmark, Germany, Ireland, Russian Federation |
| BAC by mass | 1 part per million | 1/1,000,000 g/g = 1 μg/g | 1.06 μg/mL, 23 μmol/L |
Legal limits
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.
0%
It is illegal to have any measurable alcohol in the blood while driving in these countries. Most jurisdictions have a tolerance slightly higher than zero to account for false positives and naturally occurring alcohol in the body. Some of the following jurisdictions have a general prohibition of alcohol.- Australia—Learner drivers or those drivers with a Provisional/Probationary Licence
- Bangladesh
- Brazil
- Brunei
- Canada—new drivers undergoing graduated licensing in Ontario, British Columbia, Newfoundland and Labrador and Alberta; drivers under the age of 22 in Manitoba, New Brunswick, Northwest Territories, Nova Scotia, Ontario, Saskatchewan and in Quebec receive a 30-day suspension and 7-day vehicle seizure. Drivers in Alberta who are in the graduated licensing program, regardless of age, are subject to the same 30-day/7-day suspensions/seizure policy.
- Colombia —Zero Alcohol Tolerance law is effective since December 2013
- Czech Republic
- Estonia
- Fiji
- Hungary
- Israel—24 µg per 100 ml of breath. New drivers, drivers under 24 years of age and commercial drivers 5 µg per 100 ml of breath.
- Italy—for drivers in their first three years after gaining a driving license
- Japan—drivers under the age of 20 because of not reaching legal drinking age.
- Kuwait
- New Zealand—drivers under the age of 20; drivers convicted of excess breath alcohol may be required to gain a zero-limit license.
- Nepal
- Oman
- Qatar
- Pakistan
- Paraguay
- Romania—beyond 0.08% drivers will not only receive a fine and have their license suspended, the offense will also be added to their criminal records.
- Russian Federation—0% introduced in 2010, but discontinued in September 2013
- Saudi Arabia
- Slovakia
- Uruguay
- United Arab Emirates
- Vietnam
0.02%
- China
- Netherlands
- Norway, alternatively 0.1 mg/L of breath.
- Poland
- Puerto Rico
- Russia
- Sweden 0.02
- Ukraine
- United States—drivers under the age of 21 must have 0.02% or less, on the federal level, however most states have Zero Tolerance laws emplaced. Otherwise the limit is 0.08%, except in Utah, where it is 0.05%.
0.03%
- Belarus
- Bosnia and Herzegovina
- Chile
- India
- Japan
- Korea
- Serbia
0.04%
- Lithuania
0.05%
- Argentina: 0.02% for motorbikes, 0.00% for truck, taxi, and bus drivers, 0.00% in the provinces of Cordoba and Salta)
- Australia: 0.00% for Australian Capital Territory learner, provisional and convicted DUI drivers, 0.02% for truck/bus/taxi, 0.00% for learner drivers, provisional/probationary drivers
- Austria: no limit for pedestrians; 0.08% for cycling; 0.05% generally for cars <7.5 t and motorbikes ; but 0,01% during learning. During probation period or up to the age of 21, when license was handed out after July 1, 2017, when older or up to the age of 20, trucks, bus, drivers of taxi and public transport
- Belgium
- Bulgaria
- Canada: Alberta, British Columbia, Ontario, Manitoba, Newfoundland, Nova Scotia, New Brunswick—provincial offence. Drivers have not committed a criminal offense, however a 3-day licence suspension and 3-day vehicle seizure occurs.
- Costa Rica
- Croatia: professional drivers, driving instructors and drivers of the vehicle categories C1, C1+E, C, C+E, D, D+E and H; the limit for other drivers is 0.50 mg/g, but they do get an additional separate fine if they cause an accident while having a blood alcohol level between 0 and 0,50 mg/g
- Denmark
- Finland
- France: 0.025% for bus drivers
- Germany
- Greece
- Hong Kong
- Iceland: New laws yet to take effect will change the limit to 0.02%.
- Ireland: 0.02% for learner drivers and professional drivers
- Israel: 24 µg per 100 ml of breath. This is equivalent to a BAC of 0.05. New drivers, drivers under 24 years of age and commercial drivers 5 µg per 100 ml of breath. This is equivalent to a BAC of 0.01.
- Italy: 0.00% for drivers in their first three years after gaining a driving license
- Latvia: 0.02% for drivers in their first two years after gaining a driving license
- Luxembourg
- Malta: 0.02% for drivers with a probationary driving licence and drivers of commercial vehicles, and 0.00% for drivers of buses, coaches and other passenger carrying vehicles.
- Mauritius
- Netherlands: 0.02% for drivers in their first five years after gaining a driving license
- New Zealand
- North Macedonia: 0.00% for drivers in their first two years after gaining a driving license
- Peru
- Philippines: 0.00% for taxicab and public transport drivers
- Portugal: 0.02% for drivers holding a driver's licence for less than three years, professional drivers, and drivers of taxis, heavy vehicles, emergency vehicles, public transport of children and carrying dangerous goods.
- Scotland: Scotland's drink-drive limit was reduced, by law, on 5 December 2014 from 0.08 to any of the following: 22 mcg of alcohol in 100 ml of breath, 50 mg of alcohol in 100 ml of blood, or 67 mg of alcohol in 100 ml of urine
- Slovenia: 0.00% for drivers in their first two years after gaining a drivers licence, drivers under 21 and professional drivers, such as buses, trucks.
- South Africa: 0.02% for professional drivers; to be changed for all to 0.00% by June 2020
- Spain
- Switzerland
- Thailand
- Taiwan: breath alcohol limit decreased from 0.25 to 0.15 from 13 June 2013
- Turkey
0.06%
- The Bahamas
0.07%
- Honduras
0.08%
- Canada
- England and Wales; 0.02% for operators of fixed-wing aircraft
- Malaysia: 0.00 for Probationary Driving Licence holders
- Mexico
- New Zealand: Criminal offence
- Norway: legal limit for sea vessels under 15 m
- Northern Ireland: The government of Northern Ireland intends to reduce the general limit to 0.05%.
- Puerto Rico: For drivers 18 years and older
- Singapore
- Trinidad and Tobago
- United States: All states impose penalties for driving with a BAC of 0.08% or greater. Even below those levels drivers can have civil liability and other criminal guilt. Drivers under 21 are held to stricter standards under zero tolerance laws adopted in varying forms in all states: commonly 0.01% to 0.05%. See Alcohol laws of the United States by state. Federal Motor Carrier Safety Administration: 0.04% for drivers of a commercial vehicle requiring a commercial driver's license and 0.01% for operators of common carriers, such as buses.
0.10%
- Cayman Islands
Breath alcohol content
- In Greece, the BrAC limit is 250 micrograms of alcohol per litre of breath. The limit in blood is 0.50 g/l. The BrAC limit for drivers in their first two years after gaining a driving license and common carriers are more restricted to 100 micrograms per litre of breath.
- * BrAC 250–400 = €200 fine.
- * BrAC 400–600 = €700 fine, plus suspension of driving license for 90 days
- * BrAC >600 = 2 months imprisonment, plus suspension of driving license for 180 days, plus €1,200 fine
- In Hong Kong, the BrAC limit is 220 micrograms per litre of breath
- In The Netherlands and Finland, the BrAC limit is 220 micrograms of alcohol per litre of breath.
- In New Zealand, the BrAC limit is 250 micrograms of alcohol per litre of breath for those aged 20 years or over, and zero for those aged under 20 years.
- In Singapore, the BrAC limit is 350 micrograms of alcohol per litre of breath.
- In Spain the BrAC limit is 250 micrograms of alcohol per litre of breath and 150 micrograms per litre of breath for drivers in their first two years after gaining a driving license and common carriers.
- In England and Wales the BrAC limit is 350 micrograms of alcohol per litre of breath.
- In Scotland the BrAC limit is 220 micrograms of alcohol per litre of breath.
- In Trinidad and Tobago the BrAC limit is 35 micrograms of alcohol per 100 millilitres of breath.
Other limitation schemes
- For South Korea, the penalties for different blood alcohol content levels include
- * 0.01–0.049 = No penalty
- * 0.05–0.09 = 100 days license suspension
- * >0.10 = Cancellation of car license.
Test assumptions
Extrapolation
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, 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.
Metabolism
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.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. The enzyme acetaldehyde dehydrogenase then converts the acetaldehyde into non-toxic acetic acid.
Many physiologically active materials are removed from the bloodstream at a rate proportional to the current concentration, so that they exhibit exponential decay with a characteristic halflife. 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 or with liver disease may process alcohol more slowly. False High readings are related to patients with proteinuria and hematuria, due to kidney-liver metabolism and failure
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, fumes of certain solvents, many heavy metals, and some pyrazole compounds. Also suspected of having this effect are cimetidine, ranitidine, and acetaminophen.
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.
Full stomachs
Alcohol absorption can be slowed by ingesting alcohol on a full stomach. The belief that the food absorbs the alcohol is a common misconception. Alcohol absorption is slowed because the stomach sphincter closes in order to break down the food. The alcohol cannot be absorbed through the stomach, thus cannot be absorbed until the sphincter is opened and the consumed alcohol can flow to the small intestine.Highest levels
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. Serum alcohol concentration is not equal to nor calculated in the same way as blood alcohol content.
- 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.
- In 1995, a man from Rzeszów, 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.
- 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.
- 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.
- 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.
- 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.