Blood alcohol content#Effects by alcohol level

BAC is generally defined as a fraction of weight of alcohol per volume of blood, with an SI coherent derived unit of kg/m³ or equivalently grams per liter (g/L). Countries differ in how this quantity is normally expressed. Common formats are listed in the table below. For example, the US and many international publications present BAC as a percentage, such as 0.05%. This would be interpreted as 0.05 grams per deciliter of blood. This same concentration could be expressed as 0.5‰ or 50 mg% in other countries.{{cite web |title=BAC Formats |url=http://www.mecinca.net/ALCOHOLIMETROS_Alcosim/BAC%20BrAC%20conversion%20table[1].pdf |access-date=3 November 2023}}

It is also possible to use other units. For example, in the 1930s Widmark measured alcohol and blood by mass, and thus reported his concentrations in units of g/kg or mg/g, weight alcohol per weight blood. Blood is denser than water and 1 mL of blood has a mass of approximately 1.055 grams, thus a mass-volume BAC of 1 g/L corresponds to a mass-mass BAC of 0.948 mg/g. Sweden, Denmark, Norway, Finland, Germany, and Switzerland use mass-mass concentrations in their laws, but this distinction is often skipped over in public materials,{{cite web |title=Drink-driving: What are the rules? |url=https://www.ch.ch/en/vehicles-and-traffic/how-to-behave-in-road-traffic/traffic-regulations/alcohol-in-road-traffic-and-navigation/#how-much-wine-or-beer-can-i-drink |website=www.ch.ch |language=en}} implicitly assuming that 1 L of blood weighs 1 kg.{{cite news |last1=Nager |first1=Anna |title=Alkoholpromille, beräkning|trans-title=Calculation of alcohol per mille |url=https://www.netdoktor.se/psykiatri/missbruk-beroende/sjukdomar/alkoholpromille-berakning/ |access-date=13 April 2024 |work=Netdoktor |date=4 May 2020 |language=sv-SE|quote=I detta sammanhang räknar man med att 1 liter blod väger 1 kilo.|trans-quote=In this context, it is assumed that 1 liter of blood weighs 1 kilogram.}}

In pharmacokinetics, it is common to use the amount of substance, in moles, to quantify the dose. As the molar mass of ethanol is 46.07 g/mol, a BAC of 1 g/L is 21.706 mmol/L (21.706 mM).{{cite web |title=Ethanol |url=https://pubchem.ncbi.nlm.nih.gov/compound/Ethanol |access-date=3 November 2023 |website=pubchem.ncbi.nlm.nih.gov |language=en}}

{{Further|Short-term effects of alcohol consumption}}

The magnitude of sensory impairment may vary in people of differing weights.{{Cite journal |last1=Dunn |first1=Richard A. |last2=Tefft |first2=Nathan W. |date=2014 |title=Has Increased Body Weight Made Driving Safer? |journal=Health Economics |language=en |volume=23 |issue=11 |pages=1374–1389 |doi=10.1002/hec.2991 |pmc=4135023 |pmid=24038409}} The NIAAA defines 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."Quick Stats: Binge Drinking." The Centers for Disease Control and Prevention. April 2008.[https://www.cdc.gov/alcohol/quickstats/binge_drinking.htm].

Blood samples for BAC analysis are typically obtained by taking a venous blood sample from the arm. A variety of methods exist for determining blood-alcohol concentration in a blood sample.{{cite journal |last1=Dubowski |first1=Kurt M. |title=Alcohol Determination in the Clinical Laboratory |journal=American Journal of Clinical Pathology |date=1 November 1980 |volume=74 |issue=5 |pages=747–750 |doi=10.1093/ajcp/74.5.747 |pmid=7446484 |url=https://www.researchgate.net/publication/15751585}} Forensic laboratories typically use headspace-gas chromatography combined with mass spectrometry or flame ionization detection,{{cite journal |last1=Zamengo |first1=Luca |last2=Tedeschi |first2=Gianpaola |last3=Frison |first3=Giampietro |last4=Griffoni |first4=Carlo |last5=Ponzin |first5=Diego |last6=Jones |first6=Alan Wayne |title=Inter-laboratory proficiency results of blood alcohol determinations at clinical and forensic laboratories in Italy |journal=Forensic Science International |date=1 February 2019 |volume=295 |pages=213–218 |doi=10.1016/j.forsciint.2018.12.018 |pmid=30611561 |s2cid=58591654 |issn=0379-0738}} as this method is accurate and efficient. Hospitals typically use enzyme multiplied immunoassay, which measures the co-enzyme NADH. This method is more subject to error but may be performed rapidly in parallel with other blood sample measurements.{{cite web |title=Hospital Blood Alcohol Lab Results: Are They Forensically Reliable? |url=https://www.new-jersey-dui-defense.com/hospital-blood-alcohol-lab-results-are-they-forensically-reliable.aspx |website=Law Offices of Christopher L. Baxter |date=30 April 2020}}

In Germany, BAC is determined by measuring the serum level and then converting to whole blood by dividing by the factor 1.236. This calculation underestimates BAC by 4% to 10% compared to other methods.{{cite journal |last1=Jones |first1=Alan Wayne |title=Concentration units used to report blood- and breath-alcohol concentration for legal purposes differ between countries which is important to consider when blood/breath ratios of alcohol are compared and contrasted |journal=Journal of Forensic Sciences |date=22 March 2024 |volume=69 |issue=4 |pages=1473–1480 |doi=10.1111/1556-4029.15511|pmid=38520069 }}

File:Breathalyser 'pint' glass - 2023-03-27 - Andy Mabbett.jpgs in the United Kingdom, in 1967]]

{{Main|Breathalyzer}}

The amount of alcohol on the breath can be measured, without requiring drawing blood, by blowing into a breathalyzer, resulting in a breath alcohol content (BrAC). The BrAC specifically correlates with the concentration of alcohol in arterial blood, satisfying the equation {{math|1=BAC_arterial = BrAC × 2251 ± 46}}. Its correlation with the standard BAC found by drawing venous blood is less strong.{{cite journal |last1=Lindberg |first1=L. |last2=Brauer |first2=S. |last3=Wollmer |first3=P. |last4=Goldberg |first4=L. |last5=Jones |first5=A.W. |last6=Olsson |first6=S.G. |title=Breath alcohol concentration determined with a new analyzer using free exhalation predicts almost precisely the arterial blood alcohol concentration |journal=Forensic Science International |date=May 2007 |volume=168 |issue=2–3 |pages=200–207 |doi=10.1016/j.forsciint.2006.07.018|pmid=16978819 }} Jurisdictions vary in the statutory conversion factor from BrAC to BAC, from 2000 to 2400. Many factors may affect the accuracy of a breathalyzer test,{{cite journal |last1=Jones |first1=AW |last2=Cowan |first2=JM |title=Reflections on variability in the blood-breath ratio of ethanol and its importance when evidential breath-alcohol instruments are used in law enforcement. |journal=Forensic Sciences Research |date=3 August 2020 |volume=5 |issue=4 |pages=300–308 |doi=10.1080/20961790.2020.1780720 |pmid=33457048|pmc=7782040 |doi-access=free }} but they are the most common method for measuring alcohol concentrations in most jurisdictions.{{cite journal |last1=Williams |first1=Paul M. |title=Current defence strategies in some contested drink-drive prosecutions: Is it now time for some additional statutory assumptions? |journal=Forensic Science International |date=1 December 2018 |volume=293 |pages=e5–e9 |doi=10.1016/j.forsciint.2018.09.030|pmid=30342920 |doi-access=free }}

{{Main|Pharmacology of ethanol#Modeling}}

Blood alcohol content can be quickly estimated by a model developed by Swedish professor Erik Widmark in the 1920s.{{cite web |last1=Ed Kuwatch |title=Fast Eddie's 8/10 Method of Hand Calculating Blood Alcohol Concentration: A Simple Method For Using Widmark's Formula |url=http://www.dui-law.com/810art.htm|archive-url=https://web.archive.org/web/20031202155933/http://www.dui-law.com/810art.htm |archive-date=2003-12-02 }} The model corresponds to a pharmacokinetic single-compartment model with instantaneous absorption and zero-order kinetics for elimination. The model is most accurate when used to estimate BAC a few hours after drinking a single dose of alcohol in a fasted state, and can be within 20% CV of the true value.{{cite conference |last1=Zuba |first1=Dariusz |last2=Piekoszewski |first2=Wojciech |title=Uncertainty in Theoretical Calculations of Alcohol Concentration |book-title=Proc. 17th Internat. Conf. on Alcohol, Drugs and Traffic Safety |date=2004 |url=https://www.researchgate.net/publication/255499090}}{{cite journal |last1=Gullberg |first1=Rod G. |title=Estimating the uncertainty associated with Widmark's equation as commonly applied in forensic toxicology |journal=Forensic Science International |date=October 2007 |volume=172 |issue=1 |pages=33–39 |doi=10.1016/j.forsciint.2006.11.010 |pmid=17210238}} It is not at all realistic for the absorption phase, and is not accurate for BAC levels below 0.2 g/L (alcohol is not eliminated as quickly as predicted) and consumption with food (overestimating the peak BAC and time to return to zero).{{cite journal |last1=Searle |first1=John |title=Alcohol calculations and their uncertainty |journal=Medicine, Science and the Law |date=January 2015 |volume=55 |issue=1 |pages=58–64 |doi=10.1177/0025802414524385 |pmid=24644224|pmc=4361698 }}{{cite journal |last1=Jones |first1=AW |title=Pharmacokinetics of Ethanol - Issues of Forensic Importance. |journal=Forensic Science Review |date=July 2011 |volume=23 |issue=2 |pages=91–136 |pmid=26231237 |url=https://www.researchgate.net/publication/280602837}} The equation varies depending on the units and approximations used, but in its simplest form is given by:{{cite journal |last1=Maskell |first1=Peter D. |last2=Jones |first2=A. Wayne |last3=Heymsfield |first3=Steven B. |last4=Shapses |first4=Sue |last5=Johnston |first5=Atholl |title=Total body water is the preferred method to use in forensic blood-alcohol calculations rather than ethanol's volume of distribution |journal=Forensic Science International |date=November 2020 |volume=316 |pages=110532 |doi=10.1016/j.forsciint.2020.110532|pmid=33099270 |s2cid=224966411 }}

:$EBAC\; =\; \backslash frac\{A\}\{V\_d\}-\backslash beta\backslash times\; T$

where:

• {{mvar|EBAC}} is the estimated blood alcohol concentration (in g/L)
• {{mvar|A}} is the mass of alcohol consumed (g).
• {{mvar|T}} is the amount of time during which alcohol was present in the blood (usually time since consumption began), in hours.
• {{mvar|β}} is the rate at which alcohol is eliminated, averaging around 0.15 g/L/hr.{{cite journal |last1=Jones |first1=Alan Wayne |title=Evidence-based survey of the elimination rates of ethanol from blood with applications in forensic casework |journal=Forensic Science International |date=July 2010 |volume=200 |issue=1–3 |pages=1–20 |doi=10.1016/j.forsciint.2010.02.021|pmid=20304569 }}
• {{mvar|V_d}} is the volume of distribution (L); typically body weight (kg) multiplied by 0.71 L/kg for men and 0.58 L/kg for women{{cite journal |last1=Maskell |first1=Peter D. |last2=Heymsfield |first2=Steven B. |last3=Shapses |first3=Sue |last4=Limoges |first4=Jennifer F. |title=Population ranges for the volume of distribution ( V_d ) of alcohol for use in forensic alcohol calculations |journal=Journal of Forensic Sciences |date=September 2023 |volume=68 |issue=5 |pages=1843–1845 |doi=10.1111/1556-4029.15317|pmid=37345356 |doi-access=free }}{{cite journal |last1=Maskell |first1=Peter D. |last2=Cooper |first2=Gail A. A. |title=The Contribution of Body Mass and Volume of Distribution to the Estimated Uncertainty Associated with the Widmark Equation |journal=Journal of Forensic Sciences |date=September 2020 |volume=65 |issue=5 |pages=1676–1684 |doi=10.1111/1556-4029.14447|pmid=32421216 |s2cid=218677989 }} although estimation using TBW is more accurate.{{cite journal |last1=Maskell |first1=Peter D. |last2=Jones |first2=A. Wayne |last3=Heymsfield |first3=Steven B. |last4=Shapses |first4=Sue |last5=Johnston |first5=Atholl |title=Total body water is the preferred method to use in forensic blood-alcohol calculations rather than ethanol's volume of distribution |journal=Forensic Science International |date=November 2020 |volume=316 |pages=110532 |doi=10.1016/j.forsciint.2020.110532|pmid=33099270 |s2cid=224966411 }}

A standard drink, defined by the WHO as 10 grams of pure alcohol,{{Cite web|url=https://apps.who.int/iris/bitstream/handle/10665/67205/WHO_MSD_MSB_01.6a.pdf?sequence=1&isAllowed=y|title=AUDIT The Alcohol Use Disorders Identification Test (Second Edition)|date=2001|website=WHO|format=pdf|access-date=2020-01-02}} is the most frequently used measure in many countries. Examples:

• An 80 kg man drinks 20 grams ethanol. After one hour:

$$EBAC\; =\; 20/(0.71\; \backslash cdot\; 80)\; -\; (0.148\; \backslash cdot\; 1)\; \backslash approx\; 0.204\; \backslash text\{g/L\}\; =\; 0.0204\%\; \backslash text\{BAC\}$$

• A 70 kg woman drinks 10 grams of ethanol. After one hour:

$$EBAC\; =\; 10/(0.58\; \backslash cdot\; 70)\; -\; (0.156\; \backslash cdot\; 1)\; \backslash approx\; 0.090\; \backslash text\{g/L\}\; =\; 0.0090\%\; \backslash text\{BAC\}$$

In terms of fluid ounces of alcohol consumed and weight in pounds, Widmark's formula can be simply approximated as

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

for a man or

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

for a woman, where EBAC and {{mvar|β}} factors are given as g/dL (% BAC), such as a {{mvar|β}} factor of 0.015% BAC per hour.

{{Main|Standard drink}}

File:NIH standard drink comparison.jpg, malt liquor, wine, and spirits compared. Each contains about 14 grams or 17.7 mL of ethanol.]]

This assumes a US standard drink, i.e. {{convert|0.6|USfloz|mL|1|abbr=on}} or {{convert|14|g|oz|1|abbr=on}} of ethanol, whereas other definitions exist, for example 10 grams of ethanol.

If individuals are asked to estimate their BAC, then given accurate feedback via a breathalyzer, and this procedure is repeated a number of times during a drinking session, studies show that these individuals can learn to discriminate their BAC, to within a mean error of 9 mg/100 mL (0.009% BAC).{{cite journal |last1=Huber |first1=H |last2=Karlin |first2=R |last3=Nathan |first3=P E |title=Blood alcohol level discrimination by nonalcoholics. The role of internal and external cues. |journal=Journal of Studies on Alcohol |date=January 1976 |volume=37 |issue=1 |pages=27–39 |doi=10.15288/jsa.1976.37.27|pmid=2811 }} The ability is robust to different types of alcohol, different drink quantities, and drinks with unknown levels of alcohol. Trained individuals can even drink alcoholic drinks so as to adjust or maintain their BAC at a desired level.{{cite journal |last1=Rowan |first1=D. C. |title=The Role of Blood Alcohol Level Estimation in Training Alcoholics to become Controlled Drinkers |journal=British Journal of Addiction to Alcohol & Other Drugs |date=March 1978 |volume=73 |issue=3 |pages=316–318 |doi=10.1111/j.1360-0443.1978.tb00159.x|pmid=280356 }} Training the ability does not appear to require any information or procedure besides breathalyzer feedback, although most studies have provided information such as intoxication symptoms at different BAC levels. Subjects continue to retain the ability one month after training.{{cite journal |last1=Kelly |first1=Alexandra R. |last2=Fillmore |first2=Mark T. |title=Use of mindfulness training to improve BAC self-estimation during a drinking episode. |journal=Psychology of Addictive Behaviors |date=24 August 2023 |volume=38 |issue=3 |pages=305–314 |doi=10.1037/adb0000955|pmid=37616096 |pmc=10907993 |s2cid=261098937 }}

After fatal accidents, it is common to check the blood alcohol levels of involved persons. However, soon after death, the body begins to putrefy, a biological process which produces ethanol. This can make it difficult to conclusively determine the blood alcohol content in autopsies, particularly in bodies recovered from water.{{Cite journal |last1=Kugelberg |first1=Fredrik C. |last2=Jones |first2=Alan Wayne |date=5 January 2007 |title=Interpreting results of ethanol analysis in postmortem specimens: A review of the literature |url=https://www.sciencedirect.com/science/article/pii/S0379073806002891 |journal=Forensic Science International |volume=165 |issue=1 |pages=10–27 |doi=10.1016/j.forsciint.2006.05.004 |pmid=16782292 |access-date=20 May 2020}}{{Cite journal|url=https://pubmed.ncbi.nlm.nih.gov/20232748/|pmid = 20232748|year = 2010|last1 = Xie|first1 = Y.|last2 = Deng|first2 = Z. H.|title = Analysis of alcohol mass concentration in corpse blood|journal = Fa Yi Xue Za Zhi|volume = 26|issue = 1|pages = 59–63}}{{Cite journal|url=https://pubmed.ncbi.nlm.nih.gov/8373563/|pmid = 8373563|year = 1993|last1 = Felby|first1 = S.|last2 = Nielsen|first2 = E.|title = Postmortem blood alcohol concentration|journal = Blutalkohol|volume = 30|issue = 4|pages = 244–250}}{{Cite journal|url=https://doi.org/10.1016/j.yrtph.2016.03.020|doi = 10.1016/j.yrtph.2016.03.020|title = Best-practices approach to determination of blood alcohol concentration (BAC) at specific time points: Combination of ante-mortem alcohol pharmacokinetic modeling and post-mortem alcohol generation and transport considerations|year = 2016|last1 = Cowan|first1 = Dallas M.|last2 = Maskrey|first2 = Joshua R.|last3 = Fung|first3 = Ernest S.|last4 = Woods|first4 = Tyler A.|last5 = Stabryla|first5 = Lisa M.|last6 = Scott|first6 = Paul K.|last7 = Finley|first7 = Brent L.|journal = Regulatory Toxicology and Pharmacology|volume = 78|pages = 24–36|pmid = 27041394}} For instance, following the 1975 Moorgate tube crash, the driver's kidneys had a blood alcohol concentration of 80 mg/100 mL, but it could not be established how much of this could be attributed to natural decomposition.{{cite news|title=Moorgate Alcohol Finding|work=The Guardian|date=16 April 1975|page=24}} Newer research has shown that vitreous (eye) fluid provides an accurate estimate of blood alcohol concentration that is less subject to the effects of decomposition or contamination.{{cite journal |last1=Savini |first1=F |last2=Tartaglia |first2=A |last3=Coccia |first3=L |last4=Palestini |first4=D |last5=D'Ovidio |first5=C |last6=de Grazia |first6=U |last7=Merone |first7=GM |last8=Bassotti |first8=E |last9=Locatelli |first9=M |title=Ethanol Determination in Post-Mortem Samples: Correlation between Blood and Vitreous Humor Concentration. |journal=Molecules (Basel, Switzerland) |date=12 June 2020 |volume=25 |issue=12 |page=2724 |doi=10.3390/molecules25122724|doi-access=free |pmid=32545471|pmc=7355602 }}

{{Main|Drunk driving law by country}}

File:Map of European countries by maximum blood alcohol level.svg

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 forbid operation of motor vehicles and heavy machinery above prescribed levels of blood alcohol content. Operation of boats and aircraft is also regulated. Some jurisdictions also regulate bicycling under the influence. The alcohol level at which a person is considered legally impaired to drive varies by country.

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 0.015 to 0.020 grams per deciliter per hour (g/dL/h),{{cite journal |doi=10.1080/15287399209531639 |title=Retrograde extrapolation of blood alcohol data: An applied approach |year=1992 |last1=Montgomery |first1=Mark R. |last2=Reasor |first2=Mark J. |journal=Journal of Toxicology and Environmental Health |volume=36 |issue=4 |pages=281–92 |pmid=1507264|bibcode=1992JTEHA..36..281M }} 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.

{{Main|Pharmacology of ethanol#Pharmacokinetics}}

The pharmacokinetics of ethanol are well characterized by the ADME acronym (absorption, distribution, metabolism, excretion). Besides the dose ingested, factors such as the person's total body water, speed of drinking, the drink's nutritional content, and the contents of the stomach all influence the profile of blood alcohol content (BAC) over time. Breath alcohol content (BrAC) and BAC have similar profile shapes, so most forensic pharmacokinetic calculations can be done with either. Relatively few studies directly compare BrAC and BAC within subjects and characterize the difference in pharmacokinetic parameters. Comparing arterial and venous BAC, arterial BAC is higher during the absorption phase and lower in the postabsorptive declining phase.{{cite journal |last1=Jones |first1=Alan W. |title=Alcohol, its absorption, distribution, metabolism, and excretion in the body and pharmacokinetic calculations |journal=WIREs Forensic Science |date=September 2019 |volume=1 |issue=5 |doi=10.1002/wfs2.1340|doi-access=free}}

{{See also|List of deaths through alcohol}}

According to Guinness World Records, the 2013 incident where a BAC of 1.374% (13.74 g/L) was recorded is the highest BAC recorded in a human who survived the ordeal.{{Cite web |title=Highest blood alcohol level |url=https://www.guinnessworldrecords.com/world-records/118837-highest-blood-alcohol-level |url-status=live |archive-url=https://web.archive.org/web/20241207045311/https://www.guinnessworldrecords.com/world-records/118837-highest-blood-alcohol-level |archive-date=7 December 2024 |access-date=2024-12-06 |website=Guinness World Records}}

{{notelist}}

{{Reflist}}

• Carnegie Library of Pittsburgh. Science and Technology Department. The Handy Science Answer Book. Pittsburgh: The Carnegie Library, 1997. {{ISBN|978-0-7876-1013-5}}.
• {{cite journal |doi=10.1111/j.1360-0443.2006.01699.x |title=Identifying drunkenness in the night-time economy |year=2007 |last1=Perham |first1=Nick |last2=Moore |first2=Simon C. |last3=Shepherd |first3=Jonathan |last4=Cusens |first4=Bryany |journal=Addiction |volume=102 |issue=3 |pages=377–80 |pmid=17298644}}
• Taylor, L., and S. Oberman. Drunk Driving Defense, 6th edition. New York: Aspen Law and Business, 2006. {{ISBN|978-0-7355-5429-0}}.

{{Commons category|Blood alcohol content statistics}}

• [https://www.mdcalc.com/estimated-ethanol-toxic-alcohol-serum-concentration-based-ingestion Estimated alcohol]

{{Alcohol and health}}

{{Authority control}}

Category:Alcohol law

Category:Alcohol policy

Category:Concentration indicators

Category:Driving under the influence

Category:Metabolism