Final answer:
A person is legally considered impaired with a BAC of 0.08% or higher in most jurisdictions, including the US. This is the legal threshold for intoxication and affects legal activities such as driving. Metabolism rates of alcohol by the human body play a role in how long it takes for BAC to decrease after drinking.
Step-by-step explanation:
The minimum blood alcohol content (BAC) at which a person is legally considered impaired in most places, including the United States, is 0.08%. This level of BAC signifies intoxication and is often the threshold for legal impairment, making activities such as driving illegal. It's important to understand that even small amounts of alcohol can affect driving ability, and the effects of alcohol can vary based on factors such as body weight, gender, and how quickly the drinks were consumed. The human body metabolizes alcohol at a rate of about 3.3 mmol/L (15 mg/dL) per hour, so once drinking stops, it may take several hours for a person's BAC to fall below the legal limit.