Definition: alcotest

When should you stop? When have you crossed the line? Although everyone reacts differently to alcohol, certain principles apply to everyone. Once you understand them, you will be better equipped to make informed and intelligent decisions about alcohol.

How breathalysers work:

When we talk about blood alcohol content, we are actually talking about the level of alcohol in the blood. In Canada, this level is generally expressed as the weight of alcohol in relation to a given volume of blood. Canadian law specifies that the maximum blood alcohol level permitted for drivers is 80 milligrams per 100 millilitres of blood, or 80 mg% or 0.8‰. In Switzerland, this standard was lowered to 0.5 on¹ January 2005.

Blood alcohol content can be easily measured from a person's breath using a breathalyser. As blood naturally flows through the lungs, the alcohol molecules it contains permeate the air in the lungs. When a person blows into the breathalyser, these molecules are expelled with the air. The blood alcohol level can then be measured. This measurement is almost as accurate as a blood test.

The more you drink, the higher your blood alcohol level will be. And the higher your blood alcohol level, the less control you will have over your physical and mental faculties. The risk of an accident is directly proportional to the impairment of your faculties. If you drive with a blood alcohol level above 0.8‰, you are drunk and breaking the law.

Alcohol and the body:

Many of us enjoy having a drink with a meal, when out with friends, or simply to relax. As ingrained as this habit is in our culture, we must not forget that alcohol should be consumed in full knowledge of the facts, in moderation, and only when the circumstances are right. Knowing the effects of alcohol is just as important as knowing how to read the instructions and warnings on a medicine label. Since prevention is better than cure, be aware of how your body reacts to alcohol.

Spirits, wines and beers do not have the same alcohol content. Most beers contain 5% alcohol, while wines contain 11 to 12% and spirits 40%. However, since the glasses in which these different types of drinks are usually served are of different sizes, they contain the same amount of alcohol—about 13.5 grams. It is important to know that some beers contain more than 5% alcohol and others contain less. Furthermore, if you do not use a measuring glass to measure your alcohol, you may be consuming more than you think.

Alcohol is absorbed:

When you drink a glass, the alcohol passes directly from your stomach and small intestine into your bloodstream. The more you drink, the more alcohol your body absorbs, and the higher your blood alcohol level rises. After a while, usually between 30 and 90 minutes or more, the alcohol is distributed evenly throughout your body.

Elimination:

Like most foods and drinks you consume, alcohol must be digested in order to be eliminated. However, it takes much longer to eliminate alcohol from your body than it does to drink it. Most alcohol is eliminated through a process called oxidation, which breaks it down into carbon dioxide and water. The liver alone oxidises more than 90% of the amount absorbed. The rest is eliminated without transformation by the kidneys and lungs. But the liver's ability to break down and eliminate alcohol is limited. It takes just under two hours to eliminate a standard dose of alcohol.

As you drink, alcohol is absorbed into your bloodstream and your blood alcohol level rises rapidly to a peak. If you stop drinking, your blood alcohol level stabilises and can remain at the same level for an hour or two. This means that alcohol is eliminated as quickly as it is absorbed into your bloodstream. Your blood alcohol level will then decrease steadily by about 0.15‰ per hour. But be careful, it is important to remember that blood alcohol levels rise much faster than they fall.

The myth of black coffee (and other useless remedies):

There is no point in dancing, jogging, singing, shouting or urinating to get rid of alcohol. Contrary to popular belief, drinking black coffee or taking a cold shower has no effect on blood alcohol levels. Only a very small amount of alcohol is eliminated through tears, saliva and sweat.

If you have a blood alcohol level of 0.9‰, it will take about six hours to eliminate all that alcohol from your blood. There is nothing you can do to speed up the process. Whether you are a heavy drinker or a novice, the elimination time will be virtually the same. Time is the only thing that matters.

Size matters:

Blood alcohol content is related to body weight, as this determines the volume of blood circulating in your veins (or more precisely, the volume of water in the body). When two people consume the same amount of alcohol, the one with the greater blood volume will have the lower blood alcohol content. Blood volume varies depending on two factors: body weight and body tissue composition. Taller people generally have a larger blood volume, which allows them to absorb more alcohol. After consuming the same amount of alcohol, a person weighing 68 kg will therefore have a higher blood alcohol level than a person of the same sex weighing 80 kg.

In addition, muscle tissue is better supplied with blood than fatty tissue. The more muscular or slender you are, the greater your body's water volume and the better the alcohol will be distributed. After consuming the same amount of alcohol, a person who weighs 80 kg but is overweight will have a higher blood alcohol level than a thin person of the same weight and gender.

Women generally have more fatty tissue than men and, as a result, a lower water volume. For the same amount of alcohol, a woman weighing 60 kg will have a higher blood alcohol level than a man of the same weight. As women are generally smaller than men, the differences in blood alcohol levels between the two sexes can be significant. Women should therefore not be under any illusions. Even if they consume less alcohol than men, they do not necessarily have a lower blood alcohol level.

How much alcohol can you consume before it is safe to drive?

Some suggest limiting consumption to one drink per hour. Unfortunately, this rule only applies in the early hours and generally only to men. When you drink alcohol, you lose the ability to recognise the signs of intoxication. Most people are unable to judge how impaired they are after drinking and cannot accurately estimate their own blood alcohol level without the aid of a breathalyser. Therefore, if in doubt, do not drive.

Your faculties begin to be impaired very shortly after you start drinking. However, you can reduce the risk of causing an accident by drinking moderately. A good rule of thumb is to limit your consumption to a maximum of two drinks in the evening, because the more you drink, the less in control you are and the more likely you are to put your life or safety at risk.

But it is by abstaining completely from drinking when you drive that you give yourself the best chance of staying safe.