Final answer:
The legal BAC limit for drivers over 21 in the U.S. is 0.08%. This limit is consistent across almost all states, imposing legal consequences for those who exceed it. Factors such as age, weight, and health affect individual alcohol metabolism rates.
Step-by-step explanation:
The legal limit of blood alcohol content (BAC) for a driver over the age of 21 in the United States is 0.08%. This limit is set to define the point at which a driver is considered legally impaired and unable to safely operate a motor vehicle. The 0.08% BAC threshold is standard across almost all states, as a result of the influence of the National Minimum Drinking Age Act of 1984, which tied the establishment of this BAC limit to federal highway funds.
If a person is found driving with a BAC above this limit they are at risk of legal consequences due to driving under the influence (DUI) or driving while intoxicated (DWI). It is important to understand that alcohol affects each person differently, and factors like age, sex weight and overall health can influence how quickly someone becomes impaired. The body metabolizes alcohol at a rate of about 15 mg/dL per hour which means it can take several hours for someone who has reached the legal intoxication limit to completely sober up.