Rethinking the [Alcohol] Limit
The Case for Stricter BAC Standards
Co-authored by Sarah Scheinman, Michelle Bridenbaker, and Jess Steier
Dana G Smith, a science writer known for exploring the intersection of science and society, recently published an eye-opening article in the New York Times. In her piece, she delved into statistics on drunk driving and compared blood alcohol concentration (BAC) limits across different countries. The findings were astonishing, not just to Smith herself, but to us as well. Her investigation into this topic revealed surprising facts about how BAC limits vary internationally, challenging common assumptions about drunk driving regulations. Let’s discuss…
Summary:
Most countries set their legal BAC limit for driving at 0.05% or lower.
The United States has a higher limit of 0.08%, which is believed to contribute to the high number of drunk driving deaths (13,500 annually).
Studies show that driving ability is impaired at or even below 0.05% BAC, with one study reporting a 38% higher crash risk at 0.05% BAC compared to sober drivers.
The 0.08% limit in the US was established in 2000 as a compromise, with some experts believing it was too high even then.
Lowering the limit to 0.05% could potentially save nearly 1,800 lives per year, based on a 2017 analysis.
Utah lowered its limit to 0.05% in 2018, resulting in a 20% drop in fatal car crashes the following year.
Other states are considering similar legislation, and some national groups support the change.
The hospitality industry is seen as the main opponent to lowering the limit, fearing impacts on alcohol sales and business.
However, data from Utah shows no negative effect on alcohol, restaurant, or tourism revenue after lowering the limit.
The article suggests that instead of drinking less, people are more likely to find alternative transportation when stricter limits are in place.
Why does this matter?
In 2022 alone, 13,524 lives were tragically lost in alcohol-impaired driving crashes on American roads. That's an average of 37 lives extinguished each day, one every 39 minutes—a chilling reminder of the devastating toll of drunk driving. While progress has been made over the past three decades, with a 35% decrease in the rate of drunk driving fatalities per 100,000 population since 1991, the problem persists. This epidemic doesn't discriminate; it affects people of all ages, including the most vulnerable. In 2022, over 280 children were killed in drunk driving crashes, a heartbreaking reminder of the innocence lost to this preventable tragedy.
The economic impact is staggering, exceeding $58 billion annually in deaths and damages. But beyond the financial burden, the human cost is immeasurable. Every 79 seconds, someone is killed or injured in a drunk-driving crash, leaving families shattered and communities grieving. It's a stark reality that underscores the urgent need for continued efforts to combat drunk driving through education, awareness, and stricter enforcement. Remember, these aren't just statistics; they represent real lives forever changed by a choice that could have been avoided.
BAC Limits:
In the United States, the legal limit for blood alcohol concentration (BAC) for drivers aged 21 and over is 0.08%. This means that it is illegal to drive with a BAC of 0.08% or higher. For commercial drivers, the limit is lower at 0.04%, and for drivers under 21, there is a zero-tolerance policy, meaning any detectable amount of alcohol is illegal.
The 0.08% BAC limit was not established arbitrarily. It was based on extensive research and data analysis conducted by various organizations, including the National Highway Traffic Safety Administration (NHTSA) and the National Transportation Safety Board (NTSB).
These studies demonstrated that at a BAC of 0.08%, a driver's abilities are significantly impaired, including:
Reaction time: Slower reaction time to unexpected events on the road.
Coordination: Reduced hand-eye coordination, making it difficult to control the vehicle.
Vision: Impaired vision, including difficulty focusing and tracking moving objects.
Judgment: Impaired judgment and decision-making, increasing the likelihood of risky behaviors.
The research also showed that the risk of being involved in a fatal crash increases exponentially as BAC levels rise. 1 For example, at 0.08% BAC, the risk of a fatal crash is about four times higher than for a sober driver.
The 0.08% BAC limit was adopted as a national standard in 2000 through federal legislation. Before that, states had different BAC limits, ranging from 0.10% to 0.08%.
Note: As we travel to other countries around the world, we should make sure we know local BAC limits– popular spots like Hungary, Brazil, and the UAE have zero tolerance levels.
What Does 0.8% Look Like in a Night Out?
The same dose of alcohol per unit of body weight can produce very different blood alcohol concentrations in different individuals because of the large variations in the proportions of fat and water in their bodies. Women generally have a smaller volume of distribution (alcohol's tendency to either remain in the plasma or redistribute to other tissues or organs) than men because of their higher percentage of body fat. Women will have higher peak blood alcohol levels compared to men when given the same dose of alcohol as g per kg body weight. First pass metabolism of alcohol by the stomach, which may be greater in males, may also contribute to the higher blood alcohol levels found in women (Alcohol Metabolism Study 2012).
Other factors can impact alcohol absorption and metabolism
The higher the concentration of alcohol, the more rapid the absorption.
Alcohol has irritant properties and high concentrations can cause superficial erosions, hemorrhages, and paralysis of the stomach's smooth muscle. This will decrease alcohol absorption.
Peak blood alcohol levels are higher if alcohol is ingested as a single dose rather than several smaller doses
In general, blood ethanol concentration is not significantly influenced by the type of alcoholic beverage consumed, but the data on this is conflicting as some studies say beer is absorbed more slowly than some other spirits like whiskey or brandy.
The presence of food in the stomach retards gastric emptying and thus will reduce the absorption of alcohol - the “don't drink on an empty stomach” concept. Meals high in either fat, carbohydrate, or protein are equally effective in retarding gastric emptying. The major factor governing the absorption rate of alcohol is whether the drink is taken on an empty stomach or together with or after a meal.
Heavy drinking/alcoholism increases the metabolic rate of alcohol absorption.
Advanced liver disease will decrease the rate of ethanol metabolism.
Although rates vary widely, the “average” metabolic capacity to remove alcohol is about 170 to 240g per day for a person with a body weight of 70kg (154 pounds). This would be equivalent to an average metabolic rate of about 7 g/hr which translates to about one drink per hr. Since alcoholics may consume 200 to 300 g of ethanol per day, equivalent to 1400 to 2100 kcal, consumption of normal nutrients is usually significantly decreased (typically, 2000–3000 kcal consumed per day in the absence of alcohol).
In other words, a BAC of 0.05% can be achieved in a 154-pound female by consuming 2 drinks in two hours and three drinks in two hours for a 200-pound man.
Visual created by Derek Saunders. Adapted from:
What Is A Standard Drink? | National Institute on Alcohol Abuse and Alcoholism (NIAAA). https://www.niaaa.nih.gov/alcohols-effects-health/overview-alcohol-consumption/what-standard-drink. Accessed 14 Aug. 2024.
A few notes:
In the U.S., 12 oz (355 ml) is the most common size for beer bottles and cans. Some craft beers come in 16 oz (473 ml) or 22 oz (650 ml) bottles. In bars, draft beer is often served in 16 oz pints.
In a typical restaurant wine glass, 5 oz will fill the glass to about 1/2 to 1/3 full, depending on the size of the glass.
1.5 oz is the standard size of a shot glass.
In the U.S., an 8–10 oz serving of hard seltzer is considered a standard drink, or alcoholic drink equivalent, if it contains 0.6 fluid ounces, or 14 grams, of pure alcohol. This amount is roughly equivalent to 12 fluid ounces of regular beer, 5 fluid ounces of table wine, or 1.5 fluid ounces of distilled spirits.
How Do the Breath Alcohol Testing Devices Work?
There are three major types of breath alcohol testing devices, and they're based on different principles (more details are here):
Breathalyzer - Uses a chemical reaction involving alcohol that produces a color change
Intoxilyzer - Detects alcohol by infrared (IR) spectroscopy
Alcosensor III or IV - Detects a chemical reaction of alcohol in a fuel cell
Regardless of the type, each device has a mouthpiece, a tube through which the suspect blows air, and a sample chamber where the air goes. The rest of the device varies with the type.
It is estimated that <10 % alcohol is excreted in breath, sweat, and urine. Alcohol is volatile meaning it evaporates at room temperature. To estimate blood alcohol concentrations it is dependent on the diffusion of ethanol from pulmonary arterial blood into the alveolar air (the smallest sacs and blood-rich parts of the lungs). The ethanol vapor in the breath is in equilibrium with the ethanol dissolved in the water of the blood at a blood-to-breath partition coefficient of about 2100:1.
Modern breathalyzers are fairly accurate, but they're not perfect. They do have a margin of error, as any device can, and can be off as much as 0.01 percent. When in a legal situation like impaired driving a blood test is likely to be used in conjunction with the breath test to confirm the BAC of the individual.
Current Efforts to Lower the BAC Limit:
The NTSB and other organizations advocate for lowering the BAC limit to 0.05%, arguing that even at this level, driving abilities are impaired, and the risk of crashes is significantly increased. Utah became the first state to lower the BAC limit to 0.05% in 2018, and other states are considering following suit.
Why is it so dangerous to drink and drive?
So, why is it so dangerous to drink and drive? What exactly does alcohol do to the brain that makes it so detrimental to reaction time, coordination, and judgment?
Alcohol begins affecting the body rapidly but has a half-life of up to 5 hours. Although alcohol passes through the digestive system, it does not undergo substantial digestion in the same way that food does. Rather, it is absorbed through the stomach lining directly into the bloodstream, where it is carried throughout the body and reaches the brain in as little as 5 minutes.
While alcohol impacts many organ systems including the heart, pancreas, and liver, it takes the greatest toll on the brain. This is because ethanol (also known as “ethyl alcohol”), the biologically active ingredient in all alcoholic beverages, is a psychoactive chemical that fundamentally alters brain function, resulting in changes in mood, perception, cognition, behavior, and consciousness.
Ethanol is produced by the fermentation of carbohydrates by yeast and is broadly classified as a central nervous system depressant, which means that it slows down brain activity by acting primarily on the receptors of two specific neurotransmitters: GABA and Glutamate. GABA (gamma-aminobutyric acid) is an inhibitory neurotransmitter, a chemical messenger in the brain that reduces neuronal excitability, whereas glutamate is an excitatory neurotransmitter that promotes nervous system plasticity. Healthy and consistent communication between neurons (known as “synaptic transmission”) depends on a highly regulated homeostatic balance of both excitatory and inhibitory neurotransmitters in the brain.
One of the reasons that alcohol slows down the brain so much is that it both increases GABA (inhibitory) activity, while simultaneously decreasing glutamate (excitatory) activity, leading to less efficient and dysregulated synaptic transmission and the large-scale behavioral and cognitive effects associated with alcohol consumption. Alcohol also stimulates the release of dopamine in the brain’s reward center, a mechanism that is associated with the euphoric effects of alcohol, including feelings of relaxation and increased confidence, further lowering inhibitions and increasing the likelihood of engaging in risky behaviors. Studies show that even a single drink can impact brain function including blurred vision, slurred speech, and impaired decision-making, although sex, age, body weight, and tolerance, all play a role.
Ultimately, even in relatively low quantities, alcohol impairs brain systems responsible for balance, coordination, memory, speech, and judgment, increasing the risk of injuries and other adverse effects during driving, and other activities that require high levels of executive functioning. The graphic below describes generally what happens at the various BACs - remember each person can react differently to alcohol as they may have underlying health conditions and take medications that can drastically make alcohol intoxication worse.
The effects of differing BACs on the body
Created by Derek Saunders. Adapted from “Blood Alcohol Concentration (BAC): BAC Levels & Effects.” Alcohol.Org, https://alcohol.org/health-effects/blood-alcohol-concentration/. Accessed 14 Aug. 2024.
As we continue to grapple with the devastating effects of drunk driving, the evidence presented here underscores the potential benefits of stricter BAC limits. By understanding the science behind alcohol's effects on the body and considering international perspectives, we can work towards more effective policies to save lives and prevent tragedies on our roads.
P.S. Unbiased Science recently did a post on the health risks of alcohol consumption. You can read more here (be sure to click through all slides):
About the co-authors:
Sarah Scheinman, PhD, is a Chicago-based neurobiologist with expertise in basic science, preclinical, and translational biomedical research. Her primary focus is on the molecular mechanisms of aging and neurodegenerative diseases, but she also has subject-matter expertise in cell biology, genetics, epigenetics, and psychology. She received her PhD in neuroscience from the University of Illinois College of Medicine and is currently an NIH-funded research fellow at Northwestern University. Sarah is also passionate about scientific education and serves as an adjunct faculty member at The Erikson Institute in Chicago.
Michelle Bridenbaker, RN, BSN, MS, MBA, is an accomplished and patient-focused senior leader with extensive experience operationalizing, executing, optimizing, and digitally transforming aspects of medical/scientific affairs, health communication, and multichannel engagement across industry and healthcare. She is the Chief Operating Officer of VSC. With a healthcare, toxicology, and communications background, Michelle has worked tirelessly to ensure patient safety and improved health outcomes and empower healthcare professionals with vital information. She is active on scientific boards and volunteers as a consultant for various tech firms supporting healthcare, not-for-profit organizations, and public health. With over 20 years of experience, she has overseen quality assurance for multichannel medical and scientific content as a copy editor for Windover Publishing (now MedPage today) and Medscape and the past 15 years supporting multilingual, multichannel medical and scientific communications around the world.