The Phoenix Open is back in full swing! Even if it rains today, we’re sure it will still be an exciting event, especially since Tiger Woods has finally put the orange incident behind him. Although we discussed it a year ago, we’d like to give you a few reminders about drinking and your blood alcohol concentration (BAC). If you went to the Open last year, you likely saw the “Know Your Limit” fliers providing BAC levels and “burnoff” times for various alcoholic drinks like beer, wine, and mixed drinks. These fliers won’t be handed out this year, but it provides an important lesson. The numbers provided on those fliers or from BAC calculator apps simply are not reliable for the vast majority of the population because they completely ignore the scientific intricacies that relate a person’s BAC to gender, weight, drinking history, food consumption, and elimination rates—especially for women.

The “Standard Drink”

A “standard drink” is anything that contains 0.6 fluid ounces of pure ethanol. This phrase is intended to give people an understanding as to the alcoholic equivalent from one kind of alcoholic beverage to the next. This is based on the amount of ethanol contained in a given quantity of a drink and can be determined by the volume of the drink when compared to the alcohol by volume (abv) figure,[1] which the Alcohol and Tobacco Tax and Trade Bureau (TTB) mandates must be listed on every alcoholic beverage container sold in the United States. In layman’s terms (and those used in forensic science), the general “equivalence” is that 12 ounces of 4.2%abv (beer) has the same amount of ethanol as 5 ounces of 12%abv (wine) as 1.2 ounces of 40%abv (“80 proof”) hard liquors.

Problems with the Standard Dink

When you grab your drink from a vendor, no one tells you “there are 2 standard drinks in this cup.” BAC calculators won’t help much. They will only ask you if you’re drinking beer, wine, or hard liquor, so they only provide a rough estimation of the number of standard drinks a person is consuming. Unfortunately, an accurate determination would require a calculator, an examination of the abv on a label, and someone accurately measuring out how much alcohol was going into your glass.

Beer, probably the most commonly consumed beverage at the Open, has an abv range anywhere from 3.5%abv up to 11%abv.  If you do some rough estimates, 12 ounces of a 3.5%abv beer is only 0.7 standard drinks, but 12 ounces of an 8%abv beer is almost 2 standard drinks.  There are many common beers served in the Valley well over the 4.2%abv of Coors Light: Blue Moon 5.4%, Stella Artois 5.2%, Kilt Lifter 6%, Sierra Nevada Torpedo IPA 7.2%, and Dogfish Head 15%.

Factors Affecting a Person’s BAC

Here’s a bit of basic physiology: alcohol is absorbed from the stomach and small intestine, and a person’s BAC is affected by many factors. The list below is not comprehensive because some factors, such as absorption rates, elimination rates, and medical problems, like diabetes, are individualized. In general, people can metabolize alcohol anywhere from .01 to .02 every hour. Researchers have concluded that the average elimination rate, however, was 0.015.[2] This means that if a person has a BAC of 0.10, it could take anywhere from 5 to 10 hours to fully metabolize the alcohol.   However, the factors listed below contribute to the absorption and elimination rates.

  1. Number of standard drinks consumed. Obviously, the more alcohol consumed, the higher a person’s BAC will be.
  2. Rate of consumption: the more someone drinks in a given amount of time, the higher his or her BAC will be (this is due to elimination rates, which will be discussed below).
  3. Weight: a 200 pound person has more water in the body than does a 120 pound person. It takes more alcohol to create a change in BAC for the 200 pound person than it does the 120 pound person because blood is largely composed of water.
  4. Gender: men’s and women’s bodies are generally not the same! Women tend to have more fat and less lean body tissue than men do. Alcohol is not absorbed into fat cells like it is in other cells in the body, so it takes the body longer to eliminate the alcohol. Women’s hormones can also slow the breakdown of alcohol.[3]
  5. Age: “one drink raises the blood alcohol level of an older adult 20% more than it does for a young adult.”[4]
  6. Food consumed: Food in the stomach absorbs alcohol. Drinking on an empty stomach results in higher BAC levels. High-fat and fried foods combined with alcohol result in lower alcohol elimination rates because the liver is having to do extra work to metabolize the fats, cholesterols, and the alcohol.
  7. Carbonation: carbon dioxide causes alcohol to be absorbed at an increased rate. Sparkling wines like champagne have high carbon dioxide levels. Carbonated sodas are also often mixed with hard liquors.[5]
  8. Medication: many medications can also cause slower elimination rates because, like fatty foods, the liver is having to metabolize both the medication and the alcohol.
  9. Personal genetic makeup: some individuals do not have aldehyde dehydrogenases (ALDH), enzymes which help break down alcohol in the body.[6]

So how does this all work together?

Let’s apply the actual science to a variety of beers one can consume. Consider a 120 lb.  woman consuming 1 Coors Light at 4.2% alcohol versus that same woman consuming a Kilt Lifter at 6.0% alcohol. At full absorption, the 120 lb. woman drinking the Coors Light would have a max BAC of roughly a .04, yet the same woman consuming a Kilt Lifter in the same fashion would be a .06. At one drink over 2 hours, the difference may not matter much, but consider the same 2 beverages consumed over a day at the Open.

The woman arrives at the Open at 10am, and at that time, has her first beer, drinking one beer every 2 hours (10am, noon, 2pm, and 4pm). According to the flier or BAC calculator, which states that the burn off time for one beer is 2 hours, she stays until 6pm and then drives home. Based upon the information provided on the pamphlet, the alcohol would be “burned off” by the time the woman leaves.

However, applying real facts and real science to the equation, we have a completely different story.  If the 120lb woman is consuming a 12 ounce Coors Light at the referenced pace (with NO FOOD) her BAC at 6pm would be roughly a .065, under the legal Arizona limit of a .08, but not by much. If that same woman is consuming a Kilt Lifter at the same pace, when she leaves the Open at 6pm, her BAC could be as much as a .15, which is the legal level of an EXTREME DUI.[7]

But the Scottsdale police are breathalyzing people as they leave, right?

In the past, the Scottsdale Police Department have brought in mobile field breathalyzers to catch people as they were leaving the Open to check their BACs and make sure they were safe to drive. Although this is a great preliminary measure, breathalyzers, especially the mobile, hand-held units that come up with preliminary BACs, are quite imprecise. This is exactly why the majority of the law enforcement departments here in the Valley require blood testing.

Additionally, from the information we have received, the officers are not necessarily breathalyzing everyone who leaves the event. With all of the events going on in the Phoenix and downtown Scottsdale areas, law enforcement doesn’t seem to have the manpower to have a concentrated presence in just one area.

At the end of the day, the lesson is simple: don’t drive impaired. If you have been drinking and could possibly be impaired, avoid a DUI and have a sober driver!

[1] Richard Mendelson, Wine in America, p. 128 (2011).

[2] E.M.P. Widmark, Principles and Applications of Medicolegal Alcohol Determination.

[3] Lawrence Taylor & Steven Oberman, Drunk Driving Defense, pp. 376-77.

[4] Creighton University, “Factors that Affect BAC Level,” http://www.creighton.edu/studentlife/officeoftheasstdeanofstudents/alcoholdrugeducation/alcoholbasics/whataffectsbaclevel/index.php

[5] Fran Ridout et. al., “The Effects of Carbon Dioxide in Champagne on Psychometric Performance and Blood-Alcohol Concentration,” available at http://alcalc.oxfordjournals.org/content/38/4/381.full

[6] Samir Zakhari, “Overview: How Is Alcohol Metabolized by the Body?” available at http://pubs.niaaa.nih.gov/publications/arh294/245-255.htm

[7] All of the calculations in this section were completed by Chester Flaxmayer, a local expert in the field of forensic sciences who has testified on multiple occasions in criminal trials in courtrooms throughout Arizona. He utilized an average elimination rate of .012 per hour, which would not be uncommon for a 120 lb. woman.