These two numbers represent the amount of alcohol in the blood stream. The two numbers represent different ways of reporting blood alcohol content.
See this website for a good explanation of why it is NOT correct to assume that 0.021% is equivalent to 210 (http://www.bookrags.com/research/blood-alcohol-concentration-measure-edaa-01/)
For example, a BAC of 0.021% means 0.21% (permille) or 0.021 grams of alcohol per 100 grams of individual's blood, or 0.21 grams of alcohol per 1000 grams of blood.
And, the legal limit in many states is 0.08% or 0.08 g/100 ml. The percentage can be produced from a "breathalyzer" test.
A number such as 210 usually represents 210 mmol/L in the United States. This type of number usually comes from a drawing a person's blood and represents the amount alcohol per unit volume in a person's blood.
~•~ Dr. Parks
This answer is not intended as and does not substitute for medical advice. The information presented in this posting is for patients’ education only. As always, I encourage you to see your personal health care provider for further evaluation of your individual case.
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