Blood alcohol content

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Blood alcohol content (BAC) or blood alcohol concentration is the concentration of alcohol in blood. It is usually measured as mass per volume. For example, a BAC of 0.02% means 0.2 ‰ (permille) or 0.02 grams of alcohol per 100 grams of individual's blood, or 0.2 grams of alcohol per 1000 grams of blood. Blood alcohol concentration is measured in many different units and in many different fashions, but they are all relatively synonymous for each other.

Blood alcohol levels

In many countries, BAC is reported as grams of alcohol per liter of blood (g/L). Because the specific gravity of blood is close to 1, the numerical value of BAC measured as mass per volume and that of BAC measured as mass per mass do not differ to any consequential degree other than the placement of the decimal point. For example, 1 g/L is equivalent to 0.94 g/kg.

In the UK, BAC is reported as milligrams of alcohol per 100 millilitres of blood. For example, a BAC of 0.08% is legally given as a limit of 80 mg per 100 ml [1]. It is also reported in grams per litre, which is an equivalent measurement [2].

The number of drinks consumed is a very poor measure of intoxication largely because of variation in physiology and individual alcohol tolerance. However, it is generally accepted that the consumption from sober of two standard drinks (containing a total of 20 grams) of alcohol will increase the average person's BAC roughly 0.05% (a single standard drink consumed each hour after the first two will keep the BAC at approximately 0.05%), but there is much variation according to body weight, sex, and body fat percentage. Furthermore, neither BAC nor the number of drinks consumed are necessarily accurate indicators of the level of impairment. Tolerance to alcohol varies from one person to another, and can be affected by such factors as genetics, adaptation to chronic alcohol use, and synergistic effects of drugs.

Alcohol content in blood can be directly measured by a hospital laboratory. More commonly in law enforcement investigations, BAC is estimated from breath alcohol concentration (BrAC) measured with a machine commonly referred to as a Breathalyzer which is a genericized trademark.

Contents 1 Effects at different levels 2 Units of measurement 3 Legal limits 3.1 Limits by country (BAC: Blood Alcohol Content) 3.2 Limits by country (BrAC: Breath Alcohol Content) 3.3 Other limitation schemes 4 Test assumptions 5 Metabolism and excretion 5.1 Retrograde extrapolation 6 Blood alcohol content calculation 7 See also 8 References 9 External links

[edit] Effects at different levels

See also: Effects of alcohol on the body

Unless a person has developed a high tolerance for alcohol, a BAC rating of 0.20% represents very serious intoxication (most first-time drinkers would be unconscious by about 0.15%)^{[citation needed]}, and 0.35% represents potentially fatal alcohol poisoning. 0.40% is the accepted LD₅₀, or lethal dose for 50% of adult humans. For a long-time, heavy drinker, those numbers can at least double. In extreme cases, individuals have survived BACs as high as 0.914.

Progressive Effects of Alcohol[1]
BAC (%)	Behavior	Impairment
0.01–0.029	Avg. individual appears normal	Subtle effects that can be detected with special tests
0.03–0.059	Mild euphoria Sense of well-being Relaxation Talkativeness Joyous Decreased inhibition	Alertness Judgment Coordination Concentration
0.06–0.10	Blunted Feelings Disinhibition Extroversion Sexual Pleasure	Reflexes Reasoning Depth Perception Distance Acuity Peripheral Vision Glare Recovery
0.11–0.20	Over-Expression Emotional Swings Angry or Sad Boisterous	Reaction Time Gross Motor Control Staggering Slurred Speech
0.21–0.29	Stupor Lose Understanding Impaired Sensations	Severe Motor Impairment Loss of Consciousness Memory Blackout
0.30–0.39	Severe Depression Unconsciousness Death Possible	Bladder Function Breathing Heart Rate
>0.40	Unconsciousness Death	Breathing Heart Rate

Standard Drink Chart[2] See also: Alcohol equivalence
Alcohol	Amount in ml	Amount in fl. oz.	Colloquial amount	Alcohol % by vol.	Alcohol in ml
80 proof liquor	44 millilitres	1.25 oz	one small shot	40	18
beer	355 millilitres	12 oz	one can	4.5	18
table wine	148 millilitres	5 oz	one small glass	10	18

Male Female	Approximate Blood Alcohol Percentage[3]
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
	6 st 6 lb	7 st 2 lb	8 st 8 lb	10 st	11 st 6 lb	12 st 12 lb	14 st 4 lb	15 st 10 lb	17 st 2 lb
1	– .05	.04 .05	.03 .04	.03 .03	.02 .03	.02 .03	.02 .02	.02 .02	.02 .02
2	– .10	.08 .09	.06 .08	.05 .07	.05 .06	.04 .05	.04 .05	.03 .04	.03 .04
3	– .15	.11 .14	.09 .11	.08 .10	.07 .09	.06 .08	.06 .07	.05 .06	.05 .06
4	– .20	.15 .18	.12 .15	.11 .13	.09 .11	.08 .10	.08 .09	.07 .08	.06 .08
5	– .25	.19 .23	.16 .19	.13 .16	.12 .14	.11 .13	.09 .11	.09 .10	.08 .09
6	– .30	.23 .27	.19 .23	.16 .19	.14 .17	.13 .15	.11 .14	.10 .12	.09 .11
7	– .35	.26 .32	.22 .27	.19 .23	.16 .20	.15 .18	.13 .16	.12 .14	.11 .13
8	– .40	.30 .36	.25 .30	.21 .26	.19 .23	.17 .20	.15 .18	.14 .17	.13 .15
9	– .45	.34 .41	.28 .34	.24 .29	.21 .26	.19 .23	.17 .20	.15 .19	.14 .17
10	– .51	.38 .45	.31 .38	.27 .32	.23 .28	.21 .25	.19 .23	.17 .21	.16 .19
Subtract approximately .01% every 40 minutes after drinking.

To use a simple Blood Alcohol Content calculator from the Wisconsin Department of Public Safety, refer to the following link: Blood Alcohol Calculator

[edit] 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 is approximately equivalent to 1 gram of blood, 1.06 grams to be exact. Because of this, units by volume are similar but not identical to units by mass.

Unit	Dimensions	Equivalent to	Used in
1 percent BAC by volume	1/100 (%) g/mL = 1 cg/mL	9.43 mg/g, 217.4 mmol/L	United States
1 permille BAC by volume	1/1000 (‰) g/mL = 1 mg/mL	0.943 mg/g, 21.7 mmol/L	Netherlands, Lithuania, Poland
1 basis point BAC by volume	1/10,000 (‱) g/mL = 100 μg/mL	94.3 ppm, 2.17 mmol/L	Britain
1 permille BAC by mass	1/1000 (‰) g/g = 1 mg/g	1.06 mg/mL, 23 mmol/L	Finland, Norway, Sweden
1 part per million	1/1,000,000 (ppm) g/g = 1 μg/g	1.06 μg/mL, 23 μmol/L
1 thousandth Molarity	1 mmol/L	0.0046 cg/mL,[4] 4.34 cg/g	Medical personnel

[edit] Legal limits

For purposes of law enforcement, BAC is used to define intoxication and provides a rough measure of impairment. Although degree of impairment may vary among individuals with the same BAC, BAC 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 BAC. Operation of boats and aircraft are also regulated.

[edit] Limits by country (BAC: Blood Alcohol Content)

The alcohol level at which a person is considered to be legally impaired varies by country. The list below gives limits by country. These are typically BAC (blood alcohol content) limits for the operation of a vehicle.

BAC Country 0.05% Argentina 0.05% Australia =Zero= • learner drivers, provisional/probationary drivers and DUI drivers 0.02% • WA and ACT learner, probationary & convicted DUI drivers 0.05% Austria 0.05% Belgium 0.06% Brazil[5] 0.05% Bulgaria 0.08% Canada[3](except 0.05% in Manitoba)[6] =Zero= • drivers with class G1 or G2 licenses in Ontario, or class 7 or 5P in the Northwest Territories =Zero= Croatia =Zero= Czech Republic 0.05% Denmark 0.02% Estonia 0.05% Finland 0.05% France[7] 0.05% Germany =Zero= *Learner drivers,all drivers under 21 and new drivers for first two years of licence 0.05% Greece =Zero= Hungary 0.05% Iceland 0.03% India[8] 0.08% Ireland [4] 0.05% Israel 0.05% Italy 0.015% Japan 0.04% Lithuania 0.05% Luxembourg 0.08% Malaysia 0.08% Malta 0.08% Mexico

BAC Country 0.05% Netherlands 0.02% • drivers in their first five years after gaining a driving license 0.08% New Zealand 0.03% • drivers under 20 0.02% Norway 0.02% Poland 0.05% Portugal 0.05% Republic of Macedonia =Zero= Romania =Zero= Russia * up to 01.07.2008 0.03% Russia * from 01.07.2008 =Zero= Saudi Arabia 0.05% Serbia 0.08% Singapore [5] =Zero= Slovakia 0.05% Slovenia =Zero= • drivers in their first two years after gaining a drivers licence 0.025% Spain 0.05% • prior to 2003 for drivers and cyclists 0.015% • drivers in their first two years after gaining a driving licence 0.02% Sweden 0.05% Switzerland 0.05% Thailand 0.05% Turkey =Zero= United Arab Emirates 0.08% United Kingdom [6] 0.02% • operators of aeroplanes 0.08% United States[9] For further information on U.S. laws, see Alcohol laws of the United States by state. 0.01% • U.S. operators of common carriers, such as buses 0.04% • U.S. pilots, Federal Aviation Regulations[10] within eight hours of consumption 0.08% Uruguay

[edit] 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 BAC.

• In Greece, the BrAC limit is 25 micrograms of alcohol per 1000 millilitres of breath. The limit in blood is 0,50 g/l).

Brac 0,25 - 0,40=200 euros fine, Brac 0,40 - 0,60=700 euros fine, plus suspension of driving licence for 90 days, Brac>0,60=2 months imprisonment,plus suspension of driving licence for 180 days,plus 1200 euros fine

• In The Netherlands and Finland, the BrAC limit is 220 micrograms of alcohol per litre of breath (μg/l, colloquially known as "Ugl").

• In Singapore, the BrAC limit is 35 microgrammes of alcohol per 100 millilitres of breath. [7]

• In the United Kingdom the BrAC limit is 35 microgrammes of alcohol per 100 millilitres of breath (as well as the above defined BAC).

[edit] Other limitation schemes

• For South Korea, the penalties for different BAC levels include
  • 0.01–0.049 = No Penalty
  • 0.05–0.09 = 100 days of license cancellation
  • >0.10 = Cancellation of car license.
  • >0.36 = Arrest
  • Getting caught driving while drunk 3 times in 5 years; or 2 times in 3 years results in arrest.^{[citation needed]}

[edit] Test assumptions

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Blood alcohol tests assume the individual being tested is average in various ways. For example, on average the ratio of BAC 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, his 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.

[edit] Metabolism and excretion

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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 92 to 98% is metabolised, 1 to 3% is excreted in urine, and 1 to 5% evaporates through the breath. A very small proportion (less than 0.5%) is also excreted in the sweat, tears, etc. 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. (In fact, in some males, alcohol dehydrogenase levels in the stomach are high enough that some metabolization occurs even before the alcohol is absorbed.)

Metabolism is mainly by the group of six enzymes collectively called alcohol dehydrogenase. These convert the ethanol into acetaldehyde (an intermediate that is actually more toxic than ethanol). The enzyme acetaldehyde dehydrogenase then converts the acetaldehyde into non-toxic acetyl-CoA.

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; experienced male drinkers with a high body mass may process up to 30 grams (38 mL) per hour, but a more typical figure is 10 grams (12.7 mL) per hour. Persons below the age of 25, women, persons of certain ethnicities, and persons with liver disease may process alcohol more slowly. Many East Asians (e.g. about half of Japanese) have impaired acetaldehyde dehydrogenase; this causes acetaldehyde levels to peak higher, producing more severe hangovers and other effects such as flushing and tachycardia. Conversely, members of certain ethnicities that traditionally did not brew alcoholic beverages have lower levels of alcohol dehydrogenases and thus "sober up" very slowly, but reach lower aldehyde concentrations and have milder hangovers. Rate of detoxification of alcohol can also be slowed by certain drugs which interfere with the action of alcohol dehydrogenases, notably aspirin, furfural (which may be found in fusel oil), 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).

There are currently no known drugs or other ingestible agents which will accelerate alcohol metabolism. Alcohol ingestion 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 taking aspirin, furfural, or other drugs which slow the release of acetaldehyde, will reduce the maximum blood levels of this substance, and decrease the hangover. Alcohol in non-carbonated beverages is absorbed more slowly than alcohol in carbonated drinks.

[edit] 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 percent 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 BAC 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.

[edit] Blood alcohol content calculation

BAC can be roughly estimated using a mathematical approach. While a mathematical BAC estimation is not as accurate as a breathalyzer, it can be useful for calculating a BAC level that is not currently testable, or a level that may be present in the future. While there are several ways to calculate a BAC, one of the most effective ways is to simply measure the total amount of alcohol consumed divided by the total amount of water in the body—effectively giving the percent alcohol per volume water in the blood.

The total water weight of an individual can be calculated by multiplying his or her body weight by their percent water. For example, a 150 pound woman would have a total amount of water of 73.5 pounds (150 x .49). For easiest calculations, this weight should be in kilograms, which can be easily converted by dividing the total pounds by 2.205. 73.5 pounds of water is equivalent to 33.3 kilograms of water. 33.3 kilograms of water is equivalent to 33,300 mL of water (1 L of water weighs 1 kg, and 1 L = 1000 mL).

Gender plays an important role in the total amount of water that a person has. In general, men have a higher percent of water per pound (58%) than women (49%). This fact alone strongly contributes to the generalization that men require more alcohol than women to achieve the same BAC level. Additionally, men are, on average, heavier than women. The more water a person has, the more alcohol is required to achieve the same alcohol:blood ratio, or BAC level. Further, studies have shown that women's alcohol metabolism varies from that of men due to such biochemical factors as different levels of acetaldehyde dehydrogenase (the enzyme which breaks down alcohol) and the effects of oral contraceptives. [8]

It is not strictly accurate to say that the water content of a person alone is responsible for the dissolution of alcohol within the body, because alcohol does dissolve in fatty tissue as well. When it does, a certain amount of alcohol is temporarily taken out of the blood and briefly stored in the fat. For this reason, most calculations of alcohol to body mass simply use the weight of the individual, and not specifically his water content.

[edit] See also

• Alcoholic beverage
• Driving under the influence

[edit] References

• The Handy Science Answer Book. Pittsburgh: The Carnegie Library, 1997.
• Taylor, L. Drunk Driving Defense, 6th edition. New York: Aspen Law and Business, 2006.
• Perham, N. R., Moore, S. C., Shepherd, J. P. & Cusens, B. (2007). Identifying drunkenness in the night time economy. Addiction, 102(3), 377-380

[edit] External links

• Wisconsin DOT BAC calculator
• International Blood Alcohol Limits
• Blood Alcohol levels with practical exercises