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Blood alcohol content
Blood alcohol content (BAC), also called blood alcohol concentration or blood alcohol level, is a measurement of alcohol intoxication used for legal or medical purposes.
BAC is expressed as mass of alcohol per volume of blood. In US and many international publications, BAC levels are written as a percentage such as 0.08%, i.e. there is 0.8 grams of alcohol per liter of blood. In different countries, the maximum permitted BAC when driving ranges from the limit of detection (zero tolerance) to 0.08% (0.8 g/L). BAC levels above 0.40% (4 g/L) can be potentially fatal.
BAC is generally defined as a fraction of weight of alcohol per volume of blood, with an SI coherent derived unit of kg/m3 or equivalently grams per liter (g/L). Countries differ in how this quantity is normally expressed. Common formats are listed in the table below. For example, the US and many international publications present BAC as a percentage, such as 0.05%. This would be interpreted as 0.05 grams per deciliter of blood. This same concentration could be expressed as 0.5‰ or 50 mg% in other countries.
It is also possible to use other units. For example, in the 1930s Widmark measured alcohol and blood by mass, and thus reported his concentrations in units of g/kg or mg/g, weight alcohol per weight blood. Blood is denser than water and 1 mL of blood has a mass of approximately 1.055 grams, thus a mass-volume BAC of 1 g/L corresponds to a mass-mass BAC of 0.948 mg/g. Sweden, Denmark, Norway, Finland, Germany, and Switzerland use mass-mass concentrations in their laws, but this distinction is often skipped over in public materials, implicitly assuming that 1 L of blood weighs 1 kg.
In pharmacokinetics, it is common to use the amount of substance, in moles, to quantify the dose. As the molar mass of ethanol is 46.07 g/mol, a BAC of 1 g/L is 21.706 mmol/L (21.706 mM).
The magnitude of sensory impairment may vary in people of differing weights. The NIAAA defines the term "binge drinking" as a pattern of drinking that brings a person's blood alcohol concentration (BAC) to 0.08 grams percent or above.
Blood samples for BAC analysis are typically obtained by taking a venous blood sample from the arm. A variety of methods exist for determining blood-alcohol concentration in a blood sample. Forensic laboratories typically use headspace-gas chromatography combined with mass spectrometry or flame ionization detection, as this method is accurate and efficient. Hospitals typically use enzyme multiplied immunoassay, which measures the co-enzyme NADH. This method is more subject to error but may be performed rapidly in parallel with other blood sample measurements.
In Germany, BAC is determined by measuring the serum level and then converting to whole blood by dividing by the factor 1.236. This calculation underestimates BAC by 4% to 10% compared to other methods.
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Blood alcohol content
Blood alcohol content (BAC), also called blood alcohol concentration or blood alcohol level, is a measurement of alcohol intoxication used for legal or medical purposes.
BAC is expressed as mass of alcohol per volume of blood. In US and many international publications, BAC levels are written as a percentage such as 0.08%, i.e. there is 0.8 grams of alcohol per liter of blood. In different countries, the maximum permitted BAC when driving ranges from the limit of detection (zero tolerance) to 0.08% (0.8 g/L). BAC levels above 0.40% (4 g/L) can be potentially fatal.
BAC is generally defined as a fraction of weight of alcohol per volume of blood, with an SI coherent derived unit of kg/m3 or equivalently grams per liter (g/L). Countries differ in how this quantity is normally expressed. Common formats are listed in the table below. For example, the US and many international publications present BAC as a percentage, such as 0.05%. This would be interpreted as 0.05 grams per deciliter of blood. This same concentration could be expressed as 0.5‰ or 50 mg% in other countries.
It is also possible to use other units. For example, in the 1930s Widmark measured alcohol and blood by mass, and thus reported his concentrations in units of g/kg or mg/g, weight alcohol per weight blood. Blood is denser than water and 1 mL of blood has a mass of approximately 1.055 grams, thus a mass-volume BAC of 1 g/L corresponds to a mass-mass BAC of 0.948 mg/g. Sweden, Denmark, Norway, Finland, Germany, and Switzerland use mass-mass concentrations in their laws, but this distinction is often skipped over in public materials, implicitly assuming that 1 L of blood weighs 1 kg.
In pharmacokinetics, it is common to use the amount of substance, in moles, to quantify the dose. As the molar mass of ethanol is 46.07 g/mol, a BAC of 1 g/L is 21.706 mmol/L (21.706 mM).
The magnitude of sensory impairment may vary in people of differing weights. The NIAAA defines the term "binge drinking" as a pattern of drinking that brings a person's blood alcohol concentration (BAC) to 0.08 grams percent or above.
Blood samples for BAC analysis are typically obtained by taking a venous blood sample from the arm. A variety of methods exist for determining blood-alcohol concentration in a blood sample. Forensic laboratories typically use headspace-gas chromatography combined with mass spectrometry or flame ionization detection, as this method is accurate and efficient. Hospitals typically use enzyme multiplied immunoassay, which measures the co-enzyme NADH. This method is more subject to error but may be performed rapidly in parallel with other blood sample measurements.
In Germany, BAC is determined by measuring the serum level and then converting to whole blood by dividing by the factor 1.236. This calculation underestimates BAC by 4% to 10% compared to other methods.