Blood alcohol concentration (BAC) is a commonly used measure of alcohol intoxication, also known as drunkenness. It is typically expressed as a percentage of alcohol per volume of blood. For example, in the United States (US), a BAC of 0.08 (0.08%) would translate to 0.08 grams of alcohol per 100 mL of blood.
In the US, the legal limit for BAC when driving is 0.08%. Drivers who are over the age of 21 (the legal drinking age in the US), who have a BAC equal to or greater than 0.08%, can face penalties. Penalties for those under the age of 21 are stricter, but vary by state. For those under the age of 21, the legal limit ranges from 0.01% to 0.05%.
Alcohol and health
Alcohol consumption has a number of short-term, as well as long-term effects. Short term effects include dehydration and intoxication, while more long-term effects can include changes in the metabolism of the liver and brain. Alcohol consumption can also result in alcoholism, which is generally described as use of alcohol that results in problems with mental or physical health.
Many studies regarding the effects of alcohol on health have been performed. Although there are some studies that support the conventional wisdom that a glass of red wine a day can have potential health benefits, these claims have not been rigorously proven. While some people may experience certain health benefits as a result of consuming some alcohol daily, not all people will, and the benefits do not come without risk.
Although alcohol, in moderation, is not necessarily deleterious, and may even have some positive benefits, more recent studies recommend that alcohol should not be consumed for its potential health benefits. While light or moderate alcohol (~1 drink per day: 12 fl oz beer, 5 fl oz wine, 1.5 fl oz distilled spirits) drinkers can certainly remain healthy, and may experience some health benefits, it is not fully known whether these benefits are worth the potential risks, since the potential benefits are relatively small compared to the risks.
Some of the potential health benefits that light to moderate use of alcohol can provide include:
- Reducing risk of developing and dying from heart disease
- Reducing risk of ischemic stroke
- Reducing risk of diabetes
Again, these are only potential benefits, and consuming any amount of alcohol may not necessarily result in these benefits. Also, even light to moderate drinking can increase the risk of certain cancers, and of course, driving while intoxicated can have many severe consequences.
Furthermore, drinking can lead to alcoholism, and heavy alcohol use has no health benefits. Heavy drinking, as defined by the Mayo Clinic, is having more than three drinks a day for women and men over 65, and more than four drinks per day, or more than 14 drinks a week for men younger than 65. Excessive drinking can result in serious health issues including:
- Increased risk of certain cancers
- Sudden death as a result of pre-existing cardiovascular disease
- Heart muscle damage that leads to heart failure
- High blood pressure
- Liver disease
- Accidental serious injury or death
- Brain damage
Overall, a person should not begin drinking for potential health benefits. Those who already drink light to moderate amounts, who have not experienced negative health effects, can probably continue drinking moderately as long as they are not at risk for becoming heavy drinkers and continue to be healthy. Most importantly, a person should consult their doctor regarding their alcohol consumption to determine what is safe for their particular situation.
Effects by blood alcohol content
The degree of impairment caused by alcohol intoxication varies based on BAC, as shown in the table below. Impairments range from subtle effects that can only be detected with special tests at levels between 0.001-0.029%, to problems with concentration, reflexes, motor control, and more, including a serious possibility of death at 0.50% or more.