Blood alcohol concentration (BAC) refers to the percentage of alcohol (ethyl alcohol or ethanol) in a person’s bloodstream at any given time. Law enforcement frequently use this measurement to determine if an individual is legally intoxicated.
Health providers also use BAC to calculate health risks linked to alcohol poisoning. Understanding BAC necessitates knowledge of ethanol’s characteristics and how it affects the body as levels rise.
Basics of Ethyl Alcohol
Ethyl alcohol (ethanol) is produced from a chemical process known as fermentation, which occurs when sugar is contained in various types of grains, fruit, honey, or other substances broken down by microorganisms known as yeasts. Alcohol is a byproduct generated by yeasts during sugar’s breakdown.
There are four primary types of alcoholic beverages produced by the fermentation process: beer, malt liquor, wine, and spirits (distilled liquor). A number of other alcoholic drinks have emerged in recent years that also include hard seltzer and cider but commonly into the category of beer due to alcohol content.
Each method of fermentation yields ethyl alcohol at a different rate, meaning that each alcoholic beverage has a different average alcohol content. As an overall comparison of alcohol content, experts use a measurement referred to as a “standard drink,” equivalent to about 0.6 oz. of ethyl alcohol, which is as follows:
- Beer has the lowest ABV (alcohol content by volume), with 0.6 ounces in a 12-ounce serving
- Malt liquor contains 0.6 ounces of ethyl alcohol per 8-ounce serving
- Wine contains 0.6 ounces of alcohol per 5-ounce serving
- Distilled spirits (e.g., gin, whiskey, rum, or vodka) that are 80-proof contain 0.6 ounces of alcohol in each 1.5- ounce serving.
These numbers are equivalent to an ABV percentage of about 5 percent for beer, 12 percent for wine, and 40 percent for liquor, but this can vary widely. For example, extremely light beers can contain as little as 2.5-3 percent ABV, and it’s relatively common for modern craft beers to contain as much as 8 percent alcohol or more. Wine can range between 5-20 percent alcohol.
Intoxication and BAC
Although it isn’t often thought of this way, alcohol consumption is actually a kind of poisoning. The body confronts this poisoning by moving the ethanol in the bloodstream to the liver. This organ then gradually breaks down the alcohol, rendering it less harmful.
However, the liver can only process one standard drink per hour, and if an individual ingests more, this will begin to overwhelm its efficient but moderately limited capabilities. Intoxication starts to occur when the liver can no longer process the alcohol as fast as it’s being ingested. As it backs up, alcohol, which is a central nervous system depressant, begins accumulating in the bloodstream.
BAC and Effects
BAC is measured by the weight of ethanol contained in a given blood volume.
A BAC of .02-.04 percent may produce mild relaxation and lightheadedness.
At .06 percent, effects can include relaxation, increased sociability, talkativeness, feelings of well-being, and the beginning of judgment impairment.
A BAC of .08 percent is the standard for legal intoxication in all fifty states. This level can be achieved by drinking two standard drinks in two hours or less. Typical effects of this level include clear impairments in judgment, vision, and motor coordination, in addition to reduced inhibitions.
A BAC from .10-.20 percent reveals increasing intoxication accompanied by increasingly impaired motor skills function, balance, judgment, and memory.
As BAC nears or surpasses .20 percent, the poisonous nature of ethanol begins to reveal itself. Effects associated with this degree of intoxication can include intense vomiting, blacking out, memory loss, and reduced pain sensations, possibly resulting in a failure to notice or respond to injuries.
When BAC reaches .30 percent, passing out is common, and it may be challenging to arouse an individual who has reached this point. Someone with this much alcohol in their system can potentially die from acute alcohol poisoning.
When BAC climbs to .35 percent, the affected individual may stop breathing entirely. Percentages of .40 or higher can easily result in coma and death in many persons, especially those without a high tolerance. However, some people have been reported to survive BACs significantly higher, likely due to personal factors.
Symptoms of Alcohol Poisoning
Being able to identify symptoms of alcohol poisoning is vital. If a person you know has been drinking excessively and is experiencing this condition, he or she will be in no condition to help themselves and could incur severe injuries and complications as a result, up to and including death.
Warning signs of alcohol poisoning include the following:
- Impaired coordination
- Nausea and vomiting
- Slow, shallow breathing
- Bluish or pale skin
- Low body temperature
- Coma and death
Acute alcohol poisoning is considered to be a life-threatening medical emergency. If you suspect someone you know is suffering from alcohol poisoning, do not assume they will merely “sleep it off.” Call 911 or visit the nearest emergency department immediately.
In the meantime, do not attempt to make the individual walk around due to the risk of falling, or place them in a cold bath or shower as this can result in hypothermia. Please do not try to induce vomiting or offer them food, as they may be at a high risk of choking. Do not offer the person caffeinated beverages such as coffee, as this can lead to further dehydration.
Instead, try to keep the person conscious. If you cannot, keep them propped up or lay them on their side to ensure they do not aspirate on their own vomit—this is more common than one might think due to alcohol’s ability to impair a person’s gag reflex significantly.
Factors that Influence Blood Alcohol Concentration
In addition to the total amount of alcohol ingested and the rate at which it was consumed, several other factors can affect a person’s BAC level. These include sex (whether male or female), weight, and the amount and type of food in the stomach.
In general, women produce a higher BAC than men for any given level/rate of alcohol consumption. Part of this equation is a person’s body fat amount, not just one’s overall size. The presence of fat permits alcohol to more easily enter the bloodstream, and individuals with higher body fat amounts tend to get drunk more rapidly than some others who are leaner. It goes without saying that women typically have more body fat than men.
Also, alcohol consumption being roughly equal, persons with a relatively low body weight will likely incur higher BAC levels than individuals with a higher body weight.
Food in the stomach can help lower a person’s blood alcohol concentration by impeding alcohol’s entry into the bloodstream. In particular, fatty foods and protein help to delay alcohol absorption.
One misconception is that an individual’s tolerance may affect their BAC. This is not the case, however, and instead, among those with a higher tolerance, the liver tends to become more efficient at breaking down alcohol. This fact would suggest it may take more alcohol to produce obvious signs of intoxication.
Treatment for Alcoholism
Long-term and excessive drinking can lead to devastating consequences and wreak havoc on a person’s physical and emotional health and well-being. Those who engage in problematic drinking patterns, such as binge-drinking or drinking every day, are urged to seek professional help before the situation worsens.
Just Believe Recovery offers specialized substance abuse treatment in both partial-hospitalization and outpatient formats, including a variety of evidence-based approaches proven beneficial for recovery. These services include psychotherapy, individual and family counseling, group support, relapse prevention, aftercare planning, and more.