Final answer:
In almost all US states, it is illegal for adults to drive with a BAC level of 0.08% or higher, which is the legal limit for intoxication.
Step-by-step explanation:
It is illegal for adults to drive when they have a blood alcohol concentration (BAC) level at or above 0.08% by volume. In the United States, this is the standard legal limit for intoxication across almost all states. Driving with a BAC at or above this level is considered driving under the influence (DUI) or driving while intoxicated (DWI), and it can lead to severe legal consequences. The liver metabolizes alcohol at a rate of about 0.015% BAC per hour, so it is crucial for individuals to wait an adequate amount of time after drinking before getting behind the wheel. This ensures their BAC falls well below the legal limit and they are not risking safety or breaking the law.