Units of Measurement
There are several different units in use around the world for defining blood alcohol concentration. Each is defined as either a mass of alcohol per volume of blood or a mass of alcohol per mass of blood (never a volume per volume). 1 milliliter of blood is approximately equivalent to 1.06 grams of blood. Because of this, units by volume are similar but not identical to units by mass. In the U.S. the concentration unit 1% w/v (percent weight/volume, equivalent to 10g/l or 1 g per 100 ml) is in use. This is not to be confused with the amount of alcohol measured on the breath, as with a breathalyzer. The amount of alcohol measured on the breath is generally accepted to be proportional to the amount of alcohol present in the blood at a rate of 1:2100. Therefore, a breathalyzer measurement of 0.10 mg/L of breath alcohol converts to 0.021 g/210L of breath alcohol, or 0.021 g/dL of blood alcohol (the units of the BAC in the United States). While a variety of units (or sometimes lack thereof) is used throughout the world, many countries use the g/L unit, which do not create confusion as percentages do. Usual units are highlighted in the table below.
| Reference | Unit | Dimensions | Equivalent to | Used in |
|---|---|---|---|---|
| BAC by volume | 1 percent (%) | 1/100 g/mL = 0.1 g/dL | 9.43 mg/g, 217.4 mmol/L | United States, Australia, Canada |
| 1 permille (‰) | 1/1000 g/mL = 1 g/L | 0.943 mg/g, 21.7 mmol/L | Austria, France, Latvia, Lithuania, Netherlands, Poland, Romania, Spain, Switzerland, Turkey | |
| 1 basis point (‱) | 1/10,000 g/mL = 10 mg/100 mL | 94.3 ppm, 2.17 mmol/L | Great Britain | |
| BAC by mass | 1 percent (%) | 1/100 g/g = 1 cg/g | 1.06 cg/mL, 230 mmol/L | |
| 1 permille (‰) | 1/1000 g/g = 1 mg/g | 1.06 mg/mL, 23 mmol/L | Finland, Norway, Sweden, Denmark, Germany | |
| 1 part per million (ppm) | 1/1,000,000 g/g = 1 μg/g | 1.06 μg/mL, 23 μmol/L |
Read more about this topic: Blood Alcohol Content
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