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Blood Alcohol Content Information
Blood alcohol content (or blood alcohol concentration), often
abbreviated Blood Alcohol Content, is the concentration of alcohol in blood,
measured, by volume, as a percentage. For example, a Blood Alcohol Content
rating of 0.20 means 1 part per 500 in an individual's blood is alcohol. In many
countries, the Blood Alcohol Content is measured and reported as milligrams of
alcohol per 100 milliliters of blood (mg/100ml).
Number of drinks consumed is a poor measure of intoxication, because of
variation according to body weight. One drink (unit of alcohol) will increase
the average person's Blood Alcohol Content to roughly 0.04, but there is much
variation according to body weight, gender and body fat percentage. Furthermore,
neither Blood Alcohol Content nor the number of drinks consumed are necessarily
accurate indicators of the level of impairment. Individual alcohol tolerance
varies, and can be affected by genetic or nutritional factors, drugs, other
degrees of impairment, and long-term heavy drinking.
Alcohol content in blood can be directly measured by a hospital laboratory. More
commonly, for law enforcement purposes, Blood Alcohol Content is estimated from
breath ethanol content measured with a machine commonly referred to as a
Breathalyzer (even though that is just the trademark of one manufacturer of the
devices).
For purposes of law enforcement, Blood Alcohol Content is used to define
intoxication and provides a rough measure of impairment. Although degree of
impairment may vary among individuals with the same Blood Alcohol Content, the
Blood Alcohol Content has the advantage of being simpler to measure objectively,
and therefore harder to contest, than impairment of driving.
Most countries disallow operation of motor vehicles and heavy machinery at
prescribed levels of Blood Alcohol Content, which vary both by country and by
situation. In Sweden, driving with a Blood Alcohol Content rate of over 0.02 is
illegal. By contrast, the policies of the United States are much more liberal:
In one state, a Blood Alcohol Content rating as high as .099 is considered not
intoxicated, though the federal government is pushing for a reduction of the
limit to 0.08. In some states, drivers under 21 (the American drinking age) are
considered legally impaired at lower levels (perhaps 0.02, or even a mere trace)
as part of a zero tolerance policy.
In Australia, the limit is 0.05 in most states and territories, and either 0.02
or zero for inexperienced drivers (learner drivers or those on probationary
licenses). It is enforced by random breath testing.
Despite the liberal intoxication limits of many countries, one should not assume
that driving with a Blood Alcohol Content rating of, say, .079 is as safe as
driving while sober. At a Blood Alcohol Content rating of 0.05, the probability
of a driver having an accident is more than four times its base level. Despite
this, some drivers believe their driving actually improves with small amounts of
alcohol. This assertion is false, because their ability to accurately judge the
quality of their driving (measured by actual motor competence) deteriorates.
Unless a person has developed a high tolerance, a Blood Alcohol Content rating
of 0.20 represents very serious intoxication (most first-time drinkers would be
passed out by about 0.15), 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 Blood Alcohol Content ratings as high as 0.914,
but only with medical attention.
For more free legal information on Blood Alcohol Contents, please use the
links below:
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