Title: Blood alcohol content
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. For example, a BAC of 0.10 (0.10% or one tenth of one percent) means that there is 0.10 g of alcohol for every 100 ml of blood, which is the same as 21.7 mmol/l. A BAC of 0.0 is sober, while in the United States 0.08 is legally intoxicated, and above that is very impaired. BAC levels above 0.40 are potentially fatal.
Title: Blood alcohol content
Content:  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 has a mass of approximately 1.06 grams. 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 mass/volume, equivalent to 10 g/l or 1 g per 100 ml) is in use. This is not to be confused with the amount of alcohol measured on 
Title: Blood alcohol content
Content:  Blood alcohol tests assume the individual being tested is average in various ways. For example, on average the ratio of blood alcohol content to breath alcohol content (the partition ratio) is 2100 to 1. In other words, there are 2100 parts of alcohol in the blood for every part in the breath. However, the actual ratio in any given individual can vary from 1300:1 to 3100:1, or even more widely. This ratio varies not only from person to person, but within one person from moment to moment. Thus a person with a true blood alcohol level of 0.08% but a partition ratio of 1700:1 at the time of testing would have a 0.10 reading on a Breathalyzer calibrated for the average 2100:1 ratio.
Title: Blood alcohol content
Content:  breath, as with a breathalyzer. The amount of alcohol measured on the breath is generally accepted as 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 0.0001×2100 g/L, or 0.21 g/L of blood alcohol (the units of the BAC in the United States, this is equivalent to 0.21 permille). While a variety of units (or sometimes lack thereof) is used throughout the world, many countries use the g/L unit, which does not create confusion as percentages do. Usual units are highlighted in the table below.
Title: Alcohol abuse among college students
Content:  Binge drinking occurs when students drink large amounts of alcohol in a relatively short space of time in order to feel the full effects of alcohol consumption. The National Institute on Alcohol Abuse and Alcoholism (NIAAA) defines binge drinking as a pattern of drinking that brings a person's blood alcohol concentration (BAC) to 0.08 percent or above. BAC is the measure of alcohol in one's bloodstream; a BAC of 0.08, therefore, means that 0.08% of the bloodstream consists of alcohol. This is usually seen when men consume five or more drinks, and when women consume four or more drinks in a two-hour time period. Factors that can affect a person's BAC include body weight, biological sex, medications, the number of drinks consumed, and the time during which they have been consumed. Most people younger than age 21 who drink alcohol 
Title: Blood alcohol content
Content: In 1982, a 24-year-old woman was admitted to the UCLA emergency room with a serum alcohol content of 1.51%, corresponding to a BAC of 1.33%. She was alert and oriented to person and place. Serum alcohol concentration is not equal to nor calculated in the same way as blood alcohol content. ; In 1984, a 30-year-old man survived a blood alcohol concentration of 1.5% after vigorous medical intervention that included dialysis and intravenous therapy with fructose. ; In 1995, a man from Wrocław, Poland, caused a car accident near his hometown. He had a blood alcohol content of 1.48% ; he was tested five times, with 
Title: Breathalyzer
Content:  of 0.02/drink and a general elimination rate of 0.015/hour. (One drink is equal to 1.5 USoz of liquor, 12 USoz of beer, or 5 USoz of wine. ) Breath alcohol is a representation of the equilibrium of alcohol concentration as the blood gases (alcohol) pass from the (arterial) blood into the lungs to be expired in the breath. Arterial blood distributes oxygen throughout the body. Breath alcohol concentrations are generally lower than blood alcohol concentrations, because a true representation of blood alcohol concentration is only possible if the lungs were able to completely deflate. Vitreous (eye) fluid provides the most accurate account of blood alcohol concentration.
Title: Driving under the influence
Content:  simple percent of alcohol in the blood by weight. Research shows an exponential increase of the relative risk for a crash with a linear increase of BAC as shown BAC does not depend on any units of measurement. In Europe, it is usually expressed as milligrams of alcohol per 100 milliliters of blood. However, 100 milliliters of blood weighs essentially the same as 100 milliliters of water, which weighs precisely 100 grams. Thus, for all practical purposes, this is the same as the simple dimensionless BAC measured as a percent. The per mille (promille) measurement, which is equal to ten times the percentage value, is used 
Title: Short-term effects of alcohol consumption
Content:  The definition of a unit of alcohol ranges between 8 and 14 grams of pure alcohol/ethanol depending on the country. There is no agreement on definitions of a low, moderate or high dose of alcohol either. The U.S. National Institute on Alcohol Abuse and Alcoholism defines a moderate dose as alcohol intake up to two standard drinks or 28 grams for men and one standard drink or 14 grams for women. The immediate effect of alcohol depends on the drinker's blood alcohol concentration (BAC). BAC can be different for each person depending on their age, sex, pre-existing health condition, even if they drink the same amount of alcohol. Different BACs have different effects. The following lists describe the common effects of alcohol on the body depending on the BAC. However, tolerance varies considerably between individuals, as does individual response to a given dosage; the effects of alcohol differ widely between people. Hence in this context, BAC percentages are just estimates used for illustrative purposes. 
Title: Blood alcohol content
Content:   For purposes of law enforcement, blood alcohol content is used to define intoxication and provides a rough measure of impairment. Although the degree of impairment may vary among individuals with the same blood alcohol content, it can be measured objectively and is therefore legally useful and difficult to contest in court. Most countries disallow operation of motor vehicles and heavy machinery above prescribed levels of blood alcohol content. Operation of boats and aircraft is also regulated. The alcohol level at which a person is considered legally impaired varies by country. The list below gives limits by country. These are typically blood alcohol content limits for the operation of a vehicle.

Question: blood alcohol concentration means the parts of alcohol in the blood in relation to what?
Answer: volume of blood.
ethanol.