Blood alcohol content

Blood alcohol content (BAC), also called blood alcohol concentration or blood alcohol level, is a measurement of alcohol intoxication used for legal or medical purposes; it is expressed as mass of alcohol per volume or mass of blood. For example, a BAC of 0.10 by (0.10% or one tenth of one percent) means that there is 0.10 g of alcohol for every 100 () of blood, which is the same as 21.7 (). A BAC of 0.10 by (0.10%) is 0.10 g of alcohol per 100 g of blood (23 mmol/L). A BAC of 0.0 is sober; in different countries the maximum permitted BAC when driving ranges from about 0.02% to 0.08%; BAC levels over 0.08% are considered impaired; above 0.40% is potentially fatal. As BAC increases, the short-term effects of alcohol become more perceptible. At low levels of impairment (BAC 0.01–0.05%), people may experience mild relaxation and reduced social inhibition, along with impaired judgment and coordination. At moderate levels of impairment (BAC 0.06–0.20%), effects can include emotional swings, impaired vision, hearing, speech, and motor skills. Beginning at a BAC greater than 0.2%, people may experience urinary incontinence, vomiting, and symptoms of alcohol intoxication. At a BAC greater than 0.3%, people may experience total loss of consciousness and show signs of severe alcohol intoxication. A BAC of 0.4% or higher is potentially fatal and can result in a coma or respiratory failure. Blood alcohol content can be estimated by a method developed by Swedish professor Erik Widmark in the 1920s: where: A is the mass of alcohol consumed. r is the ratio of body water to total weight. It varies between individuals but averages about 0.68 for men and 0.55 for women, since women tend to have a higher percentage of fat. Wt is body weight. β is the rate at which alcohol is metabolized. It is approximately 0.017% per hour. T is the amount time during which alcohol was present in the blood (usually time since consumption began). Sometimes the above is multiplied by 1.055 g/mL, the density of blood.