Alcohol & BAC

Alcohol Facts

To understand the basic theory of alcohol testing in human body (which is based on certain well-established physical and physiological principles), we should first consider some of the basic facts about the passage of alcohol through the human body.

Alcohol is highly water soluble, so alcoholic beverages can diffuse rapidly through body membranes into the various tissues of the body. Let us start with its initial consumption and proceed, through its absorption into the blood supply, to its breakdown (metabolism) in the liver.

Alcohol Absorption and Metabolism

When an alcohol is first consumed, it passes down the esophagus through the stomach and into the small intestine. Only small amount of alcohol is absorbed into the bloodstream through the mucous membrane, the vast majority of alcohol enters the bloodstream through the walls of the small intestine. As alcohol is highly water soluble and the bloodstream rapidly transports the ethanol throughout the body where it is absorbed into the body tissues in proportion to their water content.

Metabolism is the body's process of converting ingested substances to other compounds. Metabolism involves a number of processes, one of which is referred to as oxidation. Through oxidation in the liver, alcohol is detoxified and removed from the blood through breath, in the sweat and in urine, preventing the alcohol from accumulating and destroying cells and organs. Until all the alcohol consumed has been metabolized, it is distributed throughout the body, affecting the brain and other tissues.

The rate of alcohol metabolism depends, in part, on the amount of metabolizing enzymes in the liver, which varies among individuals and. In general, after the consumption of one standard drink, the amount of alcohol in the drinker's blood peaks within 30 to 45 minutes. (A standard drink is defined as 12 ounces of beer, 6 ounces of wine, or 1.5 ounces of 80-proof distilled spirits, all of which contain the same amount of alcohol.) Alcohol is metabolized more slowly than it is absorbed. Since the metabolism of alcohol is slow, consumption needs to be controlled to prevent accumulation in the body and intoxication.

An Explanation of Blood Alcohol Concentrations (BAC)

The legal definition of whether someone is intoxicated is the measurement of alcohol concentration in his or her blood.

Blood alcohol concentrations are determined by testing the level of alcohol present in a person's blood. Alcohol is testable because it is not processed like other food products. When alcohol is ingested it is absorbed into the bloodstream. This absorption is what causes the alcoholic effect we call intoxication.

The blood-alcohol concentration (BAC) is expressed as a percentage. Here's an example:

A BAC of 0.05% means that out of 10,000 blood component parts, five parts are alcohol.
Three types of tests are commonly used in determining blood alcohol concentrations: blood test, urine test and breath test.