Drinking and Driving

Knowing your Blood Alcohol Content (BAC)

Blood Alcohol Content (BAC) is the amount of alcohol in the bloodstream. It is measured in percentages. For instance, having a BAC of .10 percent means that person has 1 part alcohol per 1,000 parts blood on the body. BAC can be measured by breath, blood or urine tests. BAC measurement is especially important for determining the role alcohol in crashes, falls, fires, crime, family violence, suicide and other forms of intentional and unintentional injury.

In review of studies of alcohol-related crashes, reaction time, tracking ability, concentrated attention ability, divided attention performance, information process capability, visual functions, perceptions, and psycho-motor performance, impairment in all these areas was significant at blood concentrations of .05 percent. Impairment first appeared in many of these areas of performance at BACs of .02 percent, substantially below the legal standard of .08 percent.

Most people associate BAC with drunk driving. But it is more accurate to refer to it as alcohol-impaired driving because one does not have to be drunk or intoxicated to be impaired. Driving skills, especially judgment, are impaired in most people long before they show any visible signs of intoxication.

While Virginia defines legal intoxication for purposes of driving at a BAC of .08 percent or higher, alcohol may cause deterioration in driving skills at .05 percent or even lower. Deterioration progresses rapidly with rising BAC. Alcohol depresses the central nervous system, causing slowed reactions, and one’s ability to drive is affected long before a BAC of .08 percent is reached.

What is a drink?

A standard drink is:

• One 12-ounce of beer* at 4% alcohol
• One 4-ounce glass of wine at 12% alcohol
• 1 ounce of 100-proof distilled spirits or 50% alcohol

*Different beers have different alcohol content. Malt liquor has a higher alcohol content than most other brewed beverages.

12-ounce of beer at 4 % alcohol	4-ounce glass of wine at 12% alcohol	100-proof distilled spirits or 50% alcohol

Factors that will affect the BAC:

• If you are male or female.
  Women reach higher BAC’s faster because they have less water in their bodies and more fat tissue, which is not easily penetrated by alcohol. Therefore, a man and woman, with all other factors equal, both drinking the same amount of alcohol will have different BAC levels. Hers will be higher. A woman’s menstrual cycle will also affect her rate of absorption. They will experience their highest BAC’s prior to their menstrual cycle. In addition, there is also evidence that a woman taking birth control pills will absorb alcohol faster, resulting in higher BAC levels.

• The rate of drinking.
  The quicker a person drinks, the higher the peak BAC will be. The liver gets rid of alcohol at the average rate of one drink per hour (12 oz beer at 4% alcohol, 4 oz glass of wine at 12% alcohol, 1 oz of distilled spirits at 100% alcohol). If a person drinks faster than this, the remainder will circulate in the blood stream until the liver can get rid of it.

• Body weight.
  Heavier people will be less affected by the same amount of alcohol than lighter people. They have more blood and water in their bodies in which to dilute the alcohol.

• Food in the stomach.
  When there is food in the stomach, alcohol is absorbed more slowly into the blood stream. The BAC rises more rapidly in those who drink on an empty stomach, because there is no food in which to dilute the alcohol.

• The size of the drink.
  Most times alcohol is not served as a standard drink. Many mixed drinks have more than 1 oz of distilled spirits, and wine may be poured at more than 4 oz. The stronger the drink the more quickly it will be absorbed.

• Type of mixer used.
  Water and fruit juices mixed with alcohol slow the absorption process, while carbonated beverages will speed it up. Carbon dioxide speeds the alcohol through the stomach and intestine into the bloodstream, creating a rapid rise in BAC.

• Temperature of the drink.
  Warm alcohol is absorbed quicker than cold alcohol.

Knowing your Blood Alcohol Content

Understand BAC is key to understanding how alcohol affects your body. To calculate your BAC, select the appropriate chart—for males or for females find the column with your approximate weight. Then select the number of drinks consumed. This BAC figure would result if the total number of drinks were consumed in one hour. The Time Factor table can be used to calculate BAC more than one hour. Impairment Charts

Time Factor

Hours since first drink Subtract this from BAC

• 1 .015
• 2 .030
• 3 .045
• 4 .060
• 5 .075
• 6 .090

Note: These charts give you good general guidelines, but there are many factors involved in a person’s reaction to alcohol, including body composition, use of medication or other drugs, mood changes, and metabolism.

Blood Alcohol Educator
http://www.b4udrink.org/bae/program/

Blood Alcohol Educator is a fun, interactive way to look at BAC levels. You input your gender and weight and choose the time of drink, how quickly you drink it. Then you can compare yourself to friends of different weights and genders.

BAC and Impairment for driving

Understanding
.10
.09
.08		Concentrated attention, speed control
.07
.06		Information processing, judgment
.05		Coordination
.04		Eye movement control, standing steadiness, emergency responses
.03		Tracking and steering
.02		Divided attention, choice reaction time, visual function
.01
BAC

Effect of blood alcohol content on thinking, feeling, and behavior: