blood alcohol concentration (BAC)

Definition

Amount of alcohol (ethanol) in bloodstream used as an indicator whether or not a person is legally intoxicated and, therefore, too impaired to drive. The legal limit varies among jurisdictions (typically, from 0.05 to 0.40). BAC of 0.05 means that one-twentieth of one percent (1/2000) of blood content is alcohol. In some jurisdiction it is expressed in milligram of alcohol per 100 milliliters of blood or 210 liters of breath, in other jurisdictions as millimoles per liter, one mmol/L being equal to 4.61 milligram per decaliter (mg/dL) or 0.00461 percent weight to volume (w/v). Since different bodies process alcohol at different rates, they show different percentages of alcohol in the blood for the same amount of alcohol consumed. In general, higher the bodyweight, higher the amount of alcohol required to reach the limit. For example, a 95 kilogram (210-pound) male may drink six beers and may still be legally sober; but a 68 kilogram (150-pound) male may cross the limit with just four of those beers. Gender also affects the BAL: for example, a 150-pound female would be ineligible to drive after only three bottles of that beer. When measured with a breathalyzer, BAC is referred to as breath alcohol concentration.