Editing Blood alcohol content (section)

== Estimation ==
=== Direct measurement ===
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.<ref name="Dubowski">{{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}}</ref> Forensic laboratories typically use [[Headspace gas chromatography for dissolved gas measurement|headspace-gas chromatography]] combined with mass spectrometry or flame ionization detection,<ref>{{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}}</ref> as this method is accurate and efficient.<ref name="Dubowski"/> Hospitals typically use [[enzyme multiplied immunoassay technique|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.<ref>{{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}}</ref>

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.<ref>{{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 }}</ref>

=== By breathalyzer ===
[[File:Breathalyser 'pint' glass - 2023-03-27 - Andy Mabbett.jpg|thumb|upright|Joke "Breathalyser 'pint{{'"}} beer glass, about 2 inches tall, dating from around the time of the introduction of [[breathalyzer]]s 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<sub>arterial</sub> = BrAC × 2251 ± 46}}. Its correlation with the standard BAC found by drawing venous blood is less strong.<ref>{{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 }}</ref> 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,<ref>{{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 }}</ref> but they are the most common method for measuring alcohol concentrations in most jurisdictions.<ref>{{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 }}</ref>

=== By intake ===
{{Main|Pharmacology of ethanol#Modeling}}
Blood alcohol content can be quickly estimated by a model developed by Swedish professor Erik Widmark in the 1920s.<ref name=Ed>{{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 }}</ref> 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% [[Coefficient of variation|CV]] of the true value.<ref>{{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}}</ref><ref>{{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}}</ref> 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).<ref>{{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 }}</ref><ref name="Jones2011">{{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}}</ref> The equation varies depending on the units and approximations used, but in its simplest form is given by:<ref>{{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 }}</ref>
:<math>EBAC = \frac{A}{V_d}-\beta\times T</math>
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 [[Elimination (pharmacology)|eliminated]], averaging around 0.15 g/L/hr.<ref>{{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 }}</ref>
*{{mvar|V<sub>d</sub>}} 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<ref name="MaskellVd">{{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 }}</ref><ref name="MaskellMass">{{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 }}</ref> although estimation using TBW is more accurate.<ref>{{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 }}</ref>

A standard drink, defined by the WHO as 10 grams of pure alcohol,<ref name="WHO_AUDIT_EN">{{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}}</ref> is the [[Standard_drink#Definitions_in_various_countries|most frequently used measure in many countries]]. Examples:
* An 80&nbsp;kg man drinks 20 grams ethanol. After one hour:
<math display="block"> EBAC = 20/(0.71 \cdot 80) - (0.148 \cdot 1) \approx 0.204 \text{g/L} = 0.0204% \text{BAC}</math>
* A 70&nbsp;kg woman drinks 10 grams of ethanol. After one hour:
<math display="block"> EBAC = 10/(0.58 \cdot 70) - (0.156 \cdot 1) \approx 0.090 \text{g/L} = 0.0090% \text{BAC}</math>

In terms of [[fluid ounce]]s of alcohol consumed and weight in pounds, Widmark's formula can be simply approximated as<ref name=Ed/>
:<math>EBAC=8\times\text{fl oz}/\text{weight in pounds}-\beta\times T</math>
for a man or
:<math>EBAC=10\times\text{fl oz}/\text{weight in pounds}-\beta\times T</math>
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.<ref name=Ed/>

===By standard drinks===
{{Main|Standard drink}}
[[File:NIH standard drink comparison.jpg|thumb|400x400px|United States standard drinks of [[beer]], [[malt liquor]], [[wine]], and [[Distilled beverage|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.

{| class="wikitable sortable" style="text-align: center"
|+ Approximate blood alcohol percentage (by volume)<ref>[http://www.alcohol.vt.edu/Students/alcoholEffects/estimatingBAC/index.htm BAC Charts] {{webarchive |url=https://web.archive.org/web/20070630210916/http://www.alcohol.vt.edu/Students/alcoholEffects/estimatingBAC/index.htm |date=June 30, 2007 }} from [[Virginia Polytechnic Institute and State University|Virginia Tech]]</ref><br /><small>Based on one drink having 17.7 mL alcohol by volume</small>
|-
! scope="col" rowspan="2" | Drinks
! scope="col" rowspan="2" | Sex
! scope="col" colspan="9" | Body weight
|-
! scope="col" class="nowrap" | 40&nbsp;kg<br />90&nbsp;lb
! scope="col" class="nowrap" | 45&nbsp;kg<br />100&nbsp;lb
! scope="col" class="nowrap" | 55&nbsp;kg<br />120&nbsp;lb
! scope="col" class="nowrap" | 64&nbsp;kg<br />140&nbsp;lb
! scope="col" class="nowrap" | 73&nbsp;kg<br />160&nbsp;lb
! scope="col" class="nowrap" | 82&nbsp;kg<br />180&nbsp;lb
! scope="col" class="nowrap" | 91&nbsp;kg<br />200&nbsp;lb
! scope="col" class="nowrap" | 100&nbsp;kg<br />220&nbsp;lb
! scope="col" class="nowrap" | 109&nbsp;kg<br />240&nbsp;lb
|-
| rowspan="2" | 1 || Male || – || 0.04 || 0.03 || 0.03 || 0.02 || 0.02 || 0.02 || 0.02 || 0.02
|-
| Female || 0.05 || 0.05 || 0.04 || 0.03 || 0.03 || 0.03 || 0.02 || 0.02 || 0.02
|-
| rowspan="2" | 2 || Male || – || 0.08 || 0.06 || 0.05 || 0.05 || 0.04 || 0.04 || 0.03 || 0.03
|-
| Female || 0.10 || 0.09 || 0.08 || 0.07 || 0.06 || 0.05 || 0.05 || 0.04 || 0.04
|-
| rowspan="2" | 3 || Male || – || 0.11 || 0.09 || 0.08 || 0.07 || 0.06 || 0.06 || 0.05 || 0.05
|-
| Female || 0.15 || 0.14 || 0.11 || 0.10 || 0.09 || 0.08 || 0.07 || 0.06 || 0.06
|-
| rowspan="2" | 4 || Male || – || 0.15 || 0.12 || 0.11 || 0.09 || 0.08 || 0.08 || 0.07 || 0.06
|-
| Female || 0.20 || 0.18 || 0.15 || 0.13 || 0.11 || 0.10 || 0.09 || 0.08 || 0.08
|-
| rowspan="2" | 5 || Male || – || 0.19 || 0.16 || 0.13 || 0.12 || 0.11 || 0.09 || 0.09 || 0.08
|-
| Female || 0.25 || 0.23 || 0.19 || 0.16 || 0.14 || 0.13 || 0.11 || 0.10 || 0.09
|-
| rowspan="2" | 6 || Male || – || 0.23 || 0.19 || 0.16 || 0.14 || 0.13 || 0.11 || 0.10 || 0.09
|-
| Female || 0.30 || 0.27 || 0.23 || 0.19 || 0.17 || 0.15 || 0.14 || 0.12 || 0.11
|-
| rowspan="2" | 7 || Male || – || 0.26 || 0.22 || 0.19 || 0.16 || 0.15 || 0.13 || 0.12 || 0.11
|-
| Female || 0.35 || 0.32 || 0.27 || 0.23 || 0.20 || 0.18 || 0.16 || 0.14 || 0.13
|-
| rowspan="2" | 8 || Male || – || 0.30 || 0.25 || 0.21 || 0.19 || 0.17 || 0.15 || 0.14 || 0.13
|-
| Female || 0.40 || 0.36 || 0.30 || 0.26 || 0.23 || 0.20 || 0.18 || 0.17 || 0.15
|-
| rowspan="2" | 9 || Male || – || 0.34 || 0.28 || 0.24 || 0.21 || 0.19 || 0.17 || 0.15 || 0.14
|-
| Female || 0.45 || 0.41 || 0.34 || 0.29 || 0.26 || 0.23 || 0.20 || 0.19 || 0.17
|-
| rowspan="2" | 10 || Male || – || 0.38 || 0.31 || 0.27 || 0.23 || 0.21 || 0.19 || 0.17 || 0.16
|-
| Female || 0.51 || 0.45 || 0.38 || 0.32 || 0.28 || 0.25 || 0.23 || 0.21 || 0.19
|- class="sortbottom"
| colspan="11" style="text-align: center" | Subtract approximately 0.01 every 40 minutes after drinking.
|}

===By training===
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&nbsp;mg/100 mL (0.009% BAC).<ref>{{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 }}</ref> 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.<ref>{{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 }}</ref> 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.<ref>{{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 }}</ref>

===Post-mortem===
After fatal accidents, it is common to check the blood alcohol levels of involved persons. However, soon after death, the body begins to [[Putrefaction|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.<ref>{{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}}</ref><ref>{{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}}</ref><ref>{{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}}</ref><ref>{{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}}</ref> For instance, following the 1975 [[Moorgate tube crash]], the driver's kidneys had a blood alcohol concentration of 80&nbsp;mg/100&nbsp;mL, but it could not be established how much of this could be attributed to natural decomposition.<ref>{{cite news|title=Moorgate Alcohol Finding|work=The Guardian|date=16 April 1975|page=24}}</ref> 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.<ref>{{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 }}</ref>