Blood alcohol content

Blood alcohol content
Ethanol
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 the legal name for BAC but Blood Alcohol Concentration is sometimes used for simpler description.

Blood alcohol concentration is usually expressed as a percentage of ethanol in the blood in units of mass of alcohol per volume of blood or mass of alcohol per mass of blood, depending on the country. For instance, in North America a BAC of 0.1 (0.1% or one tenth of one percent) means that there is 0.10 g of alcohol for every dL of blood.

Effects by blood alcohol content

See also: Short-term effects of alcohol

Progressive effects of alcohol
BAC (% by vol.)	Behavior	Impairment
0.001–0.029	Average individual appears normal	Subtle effects that can be detected with special tests
0.030–0.059	Mild euphoria Relaxation Joyousness Talkativeness Decreased inhibition	Concentration
0.060–0.099	Blunted feelings Reduced sensitivity to pain Euphoria Disinhibition Extraversion	Reasoning Depth perception Peripheral vision Glare recovery
0.100–0.199	Over-expression Boisterousness Possibility of nausea and vomiting	Reflexes Reaction time Gross motor control Staggering Slurred speech Temporary erectile dysfunction
0.200–0.299	Nausea Vomiting Emotional swings Anger or sadness Partial loss of understanding Impaired sensations Decreased libido Possibility of stupor	Severe motor impairment Loss of consciousness Memory blackout
0.300–0.399	Stupor Central nervous system depression Loss of understanding Lapses in and out of consciousness Low possibility of death	Bladder function Breathing Dysequilibrium Heart rate
0.400–0.500	Severe central nervous system depression Coma Possibility of death	Breathing Heart rate Positional alcohol nystagmus
>0.50	High possibility of death

Estimated blood alcohol content by intake

Further information: Alcohol equivalence

To calculate estimated peak blood alcohol concentration (EBAC), a variation, including drinking period in hours, of the Widmark formula was used. The formula is:

$EBAC=\left({\frac {0.806\times SD\times 1.2}{BW\times Wt}}-MR\cdot DP\right)\times 10$

where :

• 0.806 is a constant for body water in the blood (mean 80.6%),
• 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 (0.58 for men and 0.49 for women),
• Wt is body weight (kilogram),
• MR is the metabolism constant (0.017) and
• DP is the drinking period in hours.
• 10 converts the result to permillage of alcohol

Regarding metabolism (MR) 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%). 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. A study conducted at the University of Surrey in the United Kingdom gave subjects equal amounts of flat and sparkling Champagne which contained the same levels of alcohol. After 5 minutes following consumption, the group that had the sparkling wine had 54 milligrams of alcohol in their blood while the group that had the same sparkling wine, only flat, had 39 milligrams.

Examples:

• 80 kg male drinking 3 standard drinks in two hours:

$EBAC=(0.806\cdot 3\cdot 1.2)/(0.58\cdot 80)-(0.015\cdot 2)=0.032534483\approx 0.033g/dL$

• 70 kg woman drinking 2.5 standard drinks in two hours:

$EBAC=(0.806\cdot 2.5\cdot 1.2)/(0.49\cdot 70)-(0.017\cdot 2)=0.036495627\approx 0.036g/dL$

Standard drink chart (U.S.)
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/bottle	5	0.6 US fl oz (18 ml)

Note: This chart defines a drink as 14g of ethanol, while the formula defines a drink as 10g of ethanol.

Male Female	Approximate blood alcohol percentage (by vol.) One drink has 0.5 US fl oz (15 ml) alcohol by volume
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.

Binge drinking

See also: Binge drinking

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.

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 (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/10dL, 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 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
	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
	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
	1 permille (‰)	1/1000 g/g = 1 mg/g	1.06 mg/mL, 23 mmol/L	Finland, Norway, Sweden, Denmark, Germany, Ireland, Russian Federation
	1 part per million (ppm)	1/1,000,000 g/g = 1 μg/g	1.06 μg/mL, 23 μmol/L

Legal limits

Further information: Drunk driving law by country

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 are 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.

Zero effective tolerance

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. None are jurisdictions where a majority of people of legal driving age are licensed drivers who own their own motor vehicles subject to DUI laws. They also have relatively small police presences relative to western countries in general and the United States in particular and police agencies and officers are typically very limited in their rights, duties and abilities to stop, question, investigate, detain and arrest suspected drunk drivers. Many police forces have more of their officers patrolling on foot or bicycles than on motorcycles or in 4-wheeled patrol cars.

• Australia—Learner drivers or those drivers with a Provisional/Probationary Licence
• Bangladesh
• Brazil
• Brunei
• Canada—new drivers undergoing graduated licensing in Ontario, British Columbia and Newfoundland and Labrador; drivers under the age of 22 in Manitoba, New Brunswick, Northwest Territories, Nova Scotia, Ontario, Saskatchewan, Quebec and in Alberta receive a 30-day suspension and 7-day vehicle seizure.
• Colombia —Zero Alcohol Tolerance law is effective since December 2013
• Czech Republic
• Estonia
• Fiji
• Hungary
• Israel—24 µg per 100 ml (0.024%) of breath (penalties only apply above 26 µg per 100 ml (0.026%) of breath due to lawsuits about sensitivity of devices used). New drivers, drivers under 24 years of age and commercial drivers 5 µg per 100 ml of breath.(0,005%)
• Italy—drivers under the age of 21
• Japan—drivers under the age of 20 because of not reaching legal drinking age.
• New Zealand—drivers under the age of 20 and convicted drivers required to gain a zero-limit license.
• Nepal
• Oman
• 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

0.02%

• China
• Netherlands (for drivers in their first five years after gaining a driving license)
• Norway (road vehicles and sea vessels over 15 m), alternatively 0.1 mg/L of breath.
• Poland
• Puerto Rico
• Sweden
• Ukraine

0.03%

• Belarus
• Bosnia and Herzegovina (0.031%)
• Chile
• India (note: In the state of Kerala, a policy of zero tolerance has developed.)
• Serbia
• Japan
• Russia (since September 2013)

0.04%

• Lithuania (0.00% for car drivers in their first two years after gaining a driving license, motorcycle and truck drivers)

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 (changed down from 0.02% on December 1, 2010), 0.02% for truck/bus/taxi, 0.00% for learner drivers, provisional/probationary drivers (regardless of age), truck and bus drivers, driving instructors and DUI drivers in all other states)
• Austria – no limit for pedestrians; 0.08% for cycling; 0.05% generally for cars <7,5 t (driving licence B) and motorbikes (A); but 0,01% during learning (for driver and teacher or L17-assistant), during probation period (at least the first 2 years) or up to the age of 20 (A1, AM, L17, F), trucks (C >7,5 t), bus (D), drivers of taxi and public transport
• Belgium (also for cyclists)
• 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 (0.0% for learner drivers, all drivers 18–21 and newly licensed drivers of any age for first two years of licence; also, if the BAC exceeds 0.03%, driving is illegal if the driver is showing changes in behavior ("Relative Fahruntüchtigkeit"))
• Greece
• Hong Kong
• Iceland
• Ireland (0.02% for learner drivers and professional drivers)
• Israel 24 µg per 100 ml (0.024%) of breath (penalties only apply above 26 µg per 100 ml (0.026%) of breath due to lawsuits about sensitivity of devices used). 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
• Macedonia (0.00% for drivers in their first two years after gaining a driving license)
• Netherlands (0.02% for drivers in their first five years after gaining a driving license)
• New Zealand
• 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
• 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
• Spain (0.03% for drivers in their first two years after gaining a driving license and common carriers, such as buses, trucks...)
• Switzerland (0.01% for drivers in their first three years after gaining a drivers licence and for driving instructors)
• 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 Quebec (provincial law)
• England and Wales (0.02% for operators of fixed-wing aircraft).
• Malaysia (0.00 for Probationary Driving Licence holders)
• Malta
• 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 21 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 (e.g., in Arizona driving impairment to any degree caused by alcohol consumption can be a civil or criminal offense in addition to other offenses at higher blood alcohol content levels). Drivers under 21 (the most common U.S. legal drinking age) 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.

0.1%

• Cayman Islands

Limits by country (BrAC: breath alcohol content)

In certain countries, alcohol limits are determined by the breath alcohol content (BrAC), not to be confused with blood alcohol content (BAC).

• In Greece, the BrAC limit is 250 microgrammes 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 microgrammes per litre of breath.
  • BrAC 250–400 = €200 fine.
  • BrAC 400–600 = €700 fine, plus suspension of driving license for 90 days (introduced in 2007)
  • 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 microgrammes per litre of breath (as well as other defined limits)
• In The Netherlands and Finland, the BrAC limit is 220 microgrammes of alcohol per litre of breath (μg/l, colloquially known as "Ugl").
• In New Zealand, the BrAC limit is 250 microgrammes of alcohol per litre of breath for those aged 20 years or over, and zero (meaning illegal to have any measurable breath alcohol content) for those aged under 20 years.
• In Singapore, the BrAC limit is 350 microgrammes of alcohol per litre of breath.
• In Spain the BrAC limit is 250 microgrammes of alcohol per litre of breath and 150 microgrammes 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 microgrammes of alcohol per litre of breath (as well as the above defined blood alcohol content).
• In Scotland the BrAC limit is 220 microgrammes of alcohol per litre of breath (as well as the above defined blood alcohol content).
• In Trinidad and Tobago the BrAC limit is 35 microgrammes of alcohol per 100 millilitres of breath (as well as the above defined blood alcohol content).

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

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.

Metabolism and excretion

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. The relative proportion disposed of in each way varies from person to person, but typically about 95% is metabolized by the liver. The remainder of the alcohol is eliminated through excretion in breath, urine, sweat, feces, milk and saliva. 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 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 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 (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 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. 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 thus decrease the hangover.

Carbonated beverages

See also: Carbonated water § Metabolism and excretion

Alcohol in carbonated beverages is absorbed faster than alcohol in non-carbonated drinks. Another study also confirmed this, conducted at the University of Surrey in the United Kingdom gave subjects equal amounts of flat and sparkling champagne which contained the same levels of alcohol. After 5 minutes following consumption, the group that had the sparkling wine had 54 milligrams of alcohol in their blood while the group that had the same wine, only flat, had 39 milligrams.

Stress

Being under stress causes alcohol to metabolize faster.

Retrograde 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 (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 prosecution has to prove beyond a reasonable doubt to the jury or presiding judge multi-variable "extrapolation" is possible. Because the supposed "retrograde" BAC level has to be determined and above the legal limit before it can be declared the "extrapolated" value based upon a measured level at an actual specific time, there are only two values to extrapolate from and they are two unrelated factors.

What time a test is conducted has nothing to do with the result. The result is calculated using known factors and there are no variables. So-called "extrapolation" from actual test results and inconsequential time of testing to "prove" that an indefinite period of time before the actual test the driver's BAC was identical to the measured result at a known time is impossible. Legitimate extrapolation involves determining the value of or at a midpoint between two known data points measured at two points in time.

A unit of measure and corresponding values are located on the vertical axis of the graph while a horizontal timeline is on the horizontal axis. The line connects the first measurement and the second measurement on the timeline. Any point in time between the first and second tests can be selected on the timeline and the value on the vertical measurement axis which is located on the graphed line itself is presumed to be the value that would have been observed had an actual measurement been taken at that time. However, using only two points in time indicates nothing but an increase or decrease in measured values at those two points in time, and nothing can be assumed or claimed as far as the ACTUAL relationship between value and time. The rate of increase or decrease will automatically look constant. The graph does not prove the rate remained constant or that at some point between there wasn't a rapid spike or drop in the value that if measured at the same given time would have put the reading well above or well below either or both measured values.

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.

Regardless of the existence of laws supposedly "permitting" retrograde or forward "extrapolation" of BAC levels based upon measured values made at but completely unrelated to specific times, before any prosecutor can begin to open that can of worms, he or she has to prove that the driver was actually driving a motor vehicle at the precise time the prosecutor claims an "assumed" BAC can legitimately, legally and scientifically be "extrapolated" for. The reality is that extrapolation is simply a psuedo-scientific mathematical "equation" specifically created for a unique and theoretical attempt to more comfortably and confidently make an important decision or estimate with insufficient data to make a scientific or at least informed approximation that would make the important decision easier to make and justify.

Extrapolation has been used by many handloaders and reloaders of ammunition to determine a "safe" load using existing published or measured ballistics data to estimate the performance of an bullet weight between two published weights using an identical powder charge or type, to estimate a "safe" powder charge using a powder no published data is possessed for based upon where it falls on a "powder burn rate chart" between two powders load data is available for, etc. While such extrapolation often "works out", many unfortunate loaders unwilling to contact a manufacturer of said bullet or powder to get expert opinion and facts have pressed ahead with extrapolation and catastrophic failures resulted.

For unknown reasons even to expert ballisticians working for major ammunition manufacturers, occasionally a certain powder/charge/bullet combo that by extrapolation and all known information and estimates should fall somewhere between two known loads with two variables in common will produce a massive pressure spike well above the much "hotter" load it has no logical or explicable reason for exceeding in pressure and velocity firing a identical bullet with less powder. When the manufactures of bullets or powders that have exhibited that "interesting" tendency or characteristics are contacted after a catastrophic failure or scary "near miss" overpressure event when the shooter is completely flabbergasted, convinced he did nothing wrong and wants answers, the manufacturer usually has the answer.

They have no explanation for why it occurred, but during THEIR tests a specific powder very commonly used by other ammunition and bullet manufacturers in their published loads for a certain cartridge with a wide range of bullet weights will be ABSENT from their load date or absent from the load data for as specific bullet because during testing they had the exact same thing happen. There is no published load data for that bullet and powder because it inexplicably caused severe pressure spikes at mild charge levels with a certain bullet while lighter and heavier charges were well within safe pressures. Many times, rather than risk someone playing the "extrapolation" game and publishing what safe data they have for a popular powder/bullet combo, they'll drop that powder entirely from the load data and results for that bullet. And when asked why there's no data, that's what their answer will be.

Extrapolating anything where serious damage or danger to life, limb or liberty can be the result of an extreme excursion from the "extrapolation curve" is a very dangerous activity. Shooters have discovered that at the shooting range and prosecutors have discovered that in courtrooms.

Highest recorded blood alcohol level/content

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

• 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.
• 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.
• 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 Wrocław caused a car accident near his hometown. He had a blood alcohol content of 1.48% ; he was tested five times but all results were the same. He died a few days later of injuries from the accident.
• In 2013, on July 26 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 there was recorded that the man had a blood alcohol content of 1.374%. The man survived.
• 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 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.
• 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.
• 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%. He was not injured in the accident but received a custodial sentence and his driving license was canceled.
• 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%. The man was treated for serious injuries sustained in the crash and survived.

References

Bibliography

• Carnegie Library of Pittsburgh. Science and Technology Department. The Handy Science Answer Book. Pittsburgh: The Carnegie Library, 1997. ISBN 978-0-7876-1013-5.
• Perham, Nick; Moore, Simon C.; Shepherd, Jonathan; Cusens, Bryany (2007). "Identifying drunkenness in the night-time economy". Addiction. 102 (3): 377–80. doi:10.1111/j.1360-0443.2006.01699.x. 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.

External links

• Blood Alcohol Concentration BAC Limits
• Blood Alcohol levels with practical exercises
• Comprehensive International BAC (Blood Alcohol Content) Limits Prescribed legal driving limits for over 250 jurisdictions