As alcohol levels rise in a person’s system, the negative effects on the central nervous system increase, too. Alcohol is absorbed directly through the walls of the stomach and small intestine. Then it passes into the bloodstream where it accumulates until it is metabolized by the liver. Alcohol level is measured by the weight of the alcohol in a certain volume of blood. This is called Blood Alcohol Concentration, or BAC. At a BAC of .08 grams of alcohol per deciliter of blood (g/dL), crash risk increases exponentially. Because of this risk, it’s illegal in all 50 States, the District of Columbia and Puerto Rico to drive with a BAC of .08 or higher. However, even a small amount of alcohol can affect driving ability. In 2015, there were 1,809 people killed in alcohol-related crashes where drivers' BACs were less than .08 g/dL.