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Appendix C

How Alcohol Affects Us

Almost all of us have heard that alcohol is a drug, but many of us don’t think of the act of drinking alcohol as putting a drug into our bodies. It is important for people to understand that alcohol impairs their judgment and their peripheral and central nervous system.

Alcohol also affects different people in different ways. Some of the characteristics that determine the way alcohol affects you include:

  • Gender
  • Mood
  • Body Weight
  • Type of Alcohol
  • Full/Empty Stomach
  • Speed of Consumption
  • Use of Medication or Other Drugs

But for most people, the effects of alcohol are determined by simple volume.

How does impairment happen?
Let’s take a look.

When a person drinks alcohol, it can enter the blood-stream as soon as you begin to drink. The molecular structure of alcohol (chemically known as ethanol) is small, so the alcohol can be absorbed or transferred into the blood through the mouth, the walls of the stomach, and the small intestine.

The stomach actually has a relatively slow absorption rate; it is the small intestine that absorbs most of the alcohol. That’s why we want to keep the alcohol in the stomach as long as possible by eating food, which dilutes the alcohol and keeps it from entering the small intestine so quickly. Once alcohol gets into the bloodstream it moves through the body and comes into contact with virtually every organ. However, some of the highest concentrations, and certainly the highest impact, are caused by the alcohol that reaches the brain.

We need to know that the body is quite efficient when it comes to dealing with alcohol. The liver is designed to metabolize the alcohol as we drink it. Enzymes break down the alcohol into harmless products and then it is excreted. However, the liver can only handle so much alcohol at a time. For a person of average weight and body type, the liver and small intestine can handle alcohol at a rate of about one drink per hour.

If a person drinks at a faster rate than one drink per hour, the alcohol simply stays in the body, waiting its turn to
be metabolized. Since there is more alcohol in the body than can be metabolized, the result is increasing levels
of intoxication.

Blood Alcohol Concentration (BAC) Level Information and Chart

Of course, it’s important to define what we mean by a drink. Normally we think in terms of:

  • One beer;
  • One mixed drink;
  • One glass of wine; or
  • One shot of alcohol.

But it is important to understand that “one drink” equals:

  • a 12-ounce beer;
  • a 5-ounce glass of wine; or
  • 1.5 ounces of 80 proof (40% Ethanol) distilled spirits.

In other words, a 20-ounce mug of beer is considered more than a drink; it’s actually closer to a drink and a half. And, if a person ordered a mixed drink at a bar or at a party, it may be possible that whoever mixed the drink may have put in two or three ounces of alcohol.

All of these factors will determine the amount of alcohol in your body, which is measured by your BAC, or blood alcohol concentration. This is measured in grams per deciliter (g/dL).

The following chart contains some of the more common symptoms people exhibit at various BAC levels, and the probable effects on driving ability.

Concentration (BAC)1

Typical Effects

Predictable Effects on Driving

.02 g/dL

  • Judgment impaired
  • Muscles relaxed
  • Slight body warmth
  • Mood altered
  • Brain’s ability to control eye muscles declines
  • Ability to perform two tasks at the same time declines

.05 g/dL

  • Behavior/emotions exaggerated
  • Small loss of muscle control (e.g., focusing your eyes)
  • Judgment Impaired
  • Alertness lowered
  • Coordination reduces
  • Ability to track moving objects reduces
  • Ability to respond to emergency situations declines
  • Ability to steer vehicle declines

.08 g/dL

  • Muscle coordination diminished (e.g., balance, speech, vision, reaction time, and hearing)
  • Increased difficulty in detecting danger
  • Judgment, self-control, reasoning, and memory impaired • Ability to concentrate reduces
  • Ability to concentrate reduces
  • Short-term memory loss
  • Ability to control speed reduces
  • Recognition of traffic signals and signs slows
  • Ability to perceive traffic hazards diminishes

.10 g/dL

  • Reaction time delayed
  • Speech slurred, coordination is poor
  • Thinking slowed
  • Ability to maintain lane position and braking reduces

.15 g/dL

  • Loss of normal muscle control
  • Vomiting may occur
  • Major loss of balance
  • Ability to process information from sight and hearing slows
  • Substantial impairment and loss of vehicle control

1 Information in this table shows the BAC level at which the effect usually is first observed, and has been gathered from a variety of sources including NHTSA, the National Institute on Alcohol Abuse and Alcoholism, the American Medical Association, the National Commission Against Drunk Driving, and www.webMD.com.

It’s nearly impossible for a person to gage their BAC level without diagnostic testing. Before choosing to drink, individuals should understand the effects of alcohol and the associated risks of misuse.