Blood Alcohol Level

What is BAL?

Blood Alcohol Level - BAL (also known as blood alcohol concentration - BAC) represents the amount of alcohol in the bloodstream as you drink. BAL is usually represented in percentages and it’s calculated by determining how many milligrams of ethanol are present in 100 milliliters of blood. For example, a BAL of .10 means that 1/10 of 1 percent (or 1/1000) of your total blood content is alcohol.

BAL and effects on drinking

When you drink, alcohol goes directly from the stomach into the bloodstream and then to liver, heart and brain. Because alcohol is not digested but absorbed fast in your blood, you typically feel the effects of alcohol quite quickly, especially if you haven’t eaten in a while. The more alcohol you drink, the higher your blood alcohol levels will rise. The BAC limit for drivers age 21 and older in most countries is 0.10 percent, and 0.08 percent in the US . To understand the effects of alcohol on driving, look at the following levels of alcohol intoxication:

  • 0.02% - relaxation, the ability to divide attention between two or more sources of visual information can be impaired, capacity of correctly judge the speed and distance is affected;
  • 0.05% - mild intoxication, inhibitions go away, visual perception is affected, reaction time grows, problems with responding quickly to traffic stimuli;
  • 0.10% - obvious intoxication on most people, attention and control are getting more impaired, slowing of reflexes, slowed thinking and coordination; driving skills are significantly impaired;
  • 0.20% - double vision, memory loss, not able to walk, vomiting, incontinence, high risk of accidents;
  • 0.30% - extreme intoxication, cool body temperature, tremors, not able to drive;
  • 0.40% - coma, unconsciousness, little response to stimuli, poor respiration, clammy skin;
  • 0.50% - possible death.

The risk of a fatal crash for drivers with positive BAL increases with increasing BAC, and the risks increase more steeply for drivers younger than age 21 than for older drivers. Between 0.08 and 0.10 percent BAL, the relative risk of a fatal single-vehicle crash varies between 11 percent (for drivers age 35 and older) and 52 percent (for male drivers ages 16-20).

Factors that influence the alcohol induced impairment

  • Age - for an older adult a drink raises the BAL 20% more than it does for a young adult;
  • The presence of food in your stomach slows down the absorption rate; the blood alcohol concentration will be higher if you do not eat before or during drinking;
  • Number of drinks per hour; as you increase the number of drinks per hour, your blood alcohol concentration steadily increases;
  • Tolerance to alcohol, or learned tolerance - an “experienced” drinker may need larger amount of alcohol to get to the same BAL compared with a person with low tolerance to alcohol;
  • Weight - the more you weigh, the more water you have in your body, which dilutes the alcohol and lowers the blood alcohol concentration;
  • Gender- women's bodies have less water and more fat than men's bodies. Alcohol does not go into fat cells as well as other cells, so women tend to retain more alcohol in their blood than men do. Women are also more affected by alcohol during menstruation;
  • Drinker's expectation – people who drink with the intention to get drunk, will experience faster impairment with a smaller amount of alcohol;
  • Other drugs – Combining medications with alcohol impair driving skills;
  • Emotional and physical state –when tired, ill or under stress, people tend to get more impaired with drinking smaller quantities of alcohol.

See an alcohol breath testing system that can accurately test blood alcohol level.