Toxicology of Alcohol: The Role of Toxicologists in Social Host & Liquor Liability
Tuesday, December 14, 2021
by: Clara Chan, MSc, DABT, Bruce Kelman, PhD, DABT, ATS, ERT, Nadia Moore, PhD, DABT, CIH, ERT, and Allison Stock, PhD, MPH, MS

Section: Fall 2021

Clara Chan, MSc, DABT, Bruce Kelman, PhD, DABT, ATS, ERT, Nadia Moore, PhD, DABT, CIH, ERT, Annette Santamaria, PhD, MPH, DABT, Brandon Pressly, PhD, and Allison Stock, PhD, MPH, MS (Author bios located at the end of the article.)
Commercial establishments where alcoholic beverages are served (e.g., bars, restaurants) and social hosts who serve alcohol in non-commercial settings may find themselves potentially liable for damage, injury, and/or death caused by alcohol-related accidents involving individuals they have served. Critical issues addressed by toxicologists often involve interpretation and/or estimation of blood alcohol concentration (BAC) levels, associated clinical effects, and degrees of intoxication. This article outlines how toxicologists help resolve questions regarding liability in the alleged over-service of patrons or guests that has led to damage, injury, and/or death.
Clinical Effects of Alcohol
Alcohol consumption affects mental, cognitive, and other physical functions in a dose-related manner (e.g., more consumption is associated with greater effects). Toxicologists combine BACs with observed behavior to determine associated levels of impairment/intoxication. It is generally accepted by toxicologists that the degree of physical and mental impairment from alcohol correlates with BAC. In general, higher BACs produce increased impairment and greater degrees of intoxication. For example, the typical effects of a 0.02% (or 0.02 g/dL) BAC include some loss of judgment, decline in visual function, and divided attention.[1] At a 0.08% BAC, which is the current national limit for legally driving while intoxicated in the United States,[2] typical effects include poor reaction time, balance, speech, vision, hearing, perception, and judgment.[3]
People who are chronic alcohol drinkers, however, can develop a tolerance to the effects of alcohol and learn to compensate for impairment. Tolerance to alcohol means that alcohol produces less of an effect, including on behavior, than it would for non-tolerant individuals. These individuals may not exhibit gross signs or symptoms of impairment even when their BAC is above the legal limit, even though they are actually impaired.[3] A person who consumes alcohol does not appear “intoxicated” merely because he or she has consumed alcohol. Rather, intoxicated behavior occurs when the quantity of alcohol the person consumed has exceeded the individual’s tolerance for alcohol and produced mental, cognitive, or physical abnormalities. Whether an individual appears intoxicated depends on multiple factors other than alcohol consumption, including body weight, gender, race/ethnicity, the amount of food consumed before drinking, use of drugs or prescription medicines,[4] and social behavioral changes learned during multiple drinking episodes.[5]
Interpretation of Alcohol Test Results
When interpreting alcohol test results to determine how much alcohol was consumed by an individual at an earlier time, the toxicologist considers the quality of the sample collected and the analysis method used.
The “gold standard” tissue sample collection for measuring BAC is a peripheral venous sample of blood or serum. Alternatively, a breathalyzer test is a non-invasive method to obtain an immediate result of the individual’s breath alcohol concentration.[5] Interpretation of postmortem samples can be complex as discussed later in this article. Forensic analyses for BAC analyze whole blood samples using gas chromatographic (GC) methods, which provide accurate and selective alcohol (i.e., ethanol) quantitation. In clinical settings (e.g., hospitals, emergency rooms), BAC is generally evaluated in serum or plasma samples using enzymatic methodologies with lesser accuracy but faster turnaround times (and lesser cost).[6] Due to the differences in the methodologies and the types of biological samples analyzed, BACs quantitated in clinical settings using enzymatic methodologies are generally higher than the same samples quantitated using forensic GC analyses.[7] Toxicologists guide the interpretation of results considering the various factors from the different assays.
The appropriateness of using BAC from postmortem samples to reflect BAC levels prior to death (i.e., antemortem) can be complex due to after-death redistribution and the potential for decomposition-related alcohol production. Each assessment to determine postmortem sample suitability (i.e., correlation to the concentration at time of death) is unique. One approach is to compare the postmortem BAC to alcohol concentrations measured in other biological fluid/tissue samples that are inherently less influenced by redistribution and decomposition-related issues (e.g., vitreous humor fluid of the eye, urine); correlation between the different assessments increases confidence that the postmortem BAC accurately reflects the antemortem level.[4]
An assessment for proper sample storage conditions may occur as improper storage may alter samples such that alcohol levels may no longer reflect an individual’s BAC at the time of collection. For example, it is well known that loss of alcohol from biological specimens may result from evaporation and/or oxidation. Alcohol is volatile and will evaporate from blood samples if the specimen containers are not properly sealed, resulting in loss of alcohol by evaporation. Loss of alcohol can also result from oxidation of alcohol (ethanol) to acetaldehyde in stored biological specimens. Alcohol concentrations in biological specimens may increase when sterility is lost, as alcohol (ethanol) production can occur as a byproduct of biological growth. Under sterile conditions, the concentration of alcohol in blood specimens would not be expected to increase.[4]
Blood Alcohol Concentration Calculation
Toxicologists estimate BAC for individuals based on the known pharmacokinetics of alcohol (i.e., the time and dose-profile for how it is absorbed, distributed, metabolized, and excreted) together with specific attributes of the individual and the drinking event under consideration. BAC assessments are generated to assess different parameters important for the evaluated issue, such as:
  • Was the reported consumption profile and timing (e.g., what and when drinks were served and consumed) consistent with the measured BAC?
  • How much alcohol would the individual have needed to consume to generate the measured BAC?
  • Given the BAC was measured at a later timepoint, what was the individual’s BAC when leaving the serving establishment and/or when the accident occurred?
  • When assessing the BAC at the time of the accident (and if appropriate), what was the contribution of alcohol intake from the service event under consideration compared to additional alcohol consumed by the individual (either before arriving and/or after leaving the serving establishment)?
The tool toxicologists generally use for BAC extrapolations is the Widmark equation.[8] The equation uses a set of variables to mathematically describe alcohol pharmacokinetics in the human body. Specifically, the equation incorporates a uniform distribution of alcohol (a one-compartment model) and a constant elimination/metabolism rate per unit time (zero-order elimination kinetics), together with human-specific factors (e.g., body weight and distribution volume) and time-specific variables (e.g., time elapsed since drinking began, time of accident, and/or time of BAC measurement). The resulting equation describes BAC as a function of an individual’s human factors together with the timing and amount of alcohol consumed.[9] The accuracy of estimates associated with the Widmark equation depends on the reliability of input parameters. Uncertainties arise with the number of assumptions made regarding an individual’s body weight, the type and alcohol content of consumed beverages, and the individual’s alcohol elimination/metabolism rate.
Social host liability issues generally hinge on the alleged over-service of guests subsequently involved in incidents resulting in damage, injury, and/or death. Key issues in these matters hinge on the amount of alcohol served by the establishment, the resulting BAC of the consuming individual, and the associated clinical effects and degree of intoxication.
Toxicologists can address these issues and more, including assessments of sample validity and methodology; extrapolations of BAC to earlier timepoints; assessments to determine whether the service profile (i.e., what and when) correspond with the measured BAC; and, if appropriate, assessments to determine the contribution of alcohol from the service event under consideration to the BAC at the time of the accident.
Clara Chan, MSc, DABT
Clara Chan is a Project Manager and Senior Toxicologist at J.S. Held LLC.  She has a Master of Science in toxicology from Queen’s University, Canada, and a Bachelor of Science in pharmacology from the University of Toronto. She is certified in toxicology by the American Board of Toxicology. Clara has been working in the field of toxicology since 2003, evaluating chemical toxicities and health effects. She provides technical support and serves as a consultant for projects in areas of toxicology, risk assessment, personal injury litigation, consumer product safety, and indoor air quality/mold assessment. She has provided support to clients composing safety data sheets and deriving of occupational exposure limits and permissible daily exposure limits. She has supervised client-sponsored laboratory testing of consumer products in North America and in Hong Kong. She has experience with analysis and interpretation of consumer product safety testing results. Clara’s native language is English and she is fluent in Chinese (Cantonese).
Bruce Kelman, PhD, DABT, ATS, ERT
Dr. Bruce Kelman is Senior Vice President and Principal Toxicologist at J.S. Held LLC. He has more than 40 years of experience in toxicology and has served as a consultant and expert in numerous investigations across North America, South Korea, and the United Kingdom. He has evaluated numerous claims of personal injury and health impacts from many chemicals and drugs, and has presented a variety of health risk concepts to policy makers, government regulators, citizen groups, and individuals. Dr. Kelman also regularly interprets standard and non-standard tests for drugs of abuse including ethanol, opioids, methamphetamine, cocaine, and cannabis.
Nadia Moore, PhD, DABT, CIH, ERT
Dr. Nadia Moore is Vice President and Principal Toxicologist at J.S. Held LLC. She has more than 25 years of multidisciplinary experience in toxicology, exposure science, regulatory compliance, molecular biology, and analytical chemistry. She has performed risk-based exposure and toxicology assessments for potential contaminants in workplaces, residential scenarios, and consumer products and has conducted short-term through 2-year carcinogenicity animal studies of inhaled vapors, aerosols, particulates, and complex mixtures. Her experience encompasses chemical and physical agents (including asbestos, pesticides, solvents, vapors, particulate matter, metals, and microbial agents), diverse exposure scenarios (including environmental, occupational, and residential), and all routes of exposure (including inhalation, oral/drinking water, and percutaneous). Nadia’s practice also includes the determination of whether exposure to a chemical or physical agent has caused an injury, exposure assessment in diverse scenarios, determination of acceptable impurity levels in consumer products, and weight-of-evidence analysis of historical scientific data to gauge present-day conclusions.
Allison Stock, PhD, MPH, MS
Dr. Allison Stock is Vice President, Environmental Health and Safety at J.S. Held LLC. She is an internationally known toxicologist with 25 years of toxicological, epidemiological, regulatory, and environmental experience. Her background is supported by experience in the federal and state government as well as private industry (small and Fortune 500 companies). Dr. Stock specializes in human health risk assessments combing both toxicological and epidemiological data. She has expertise in petrochemicals; pharmaceutical agents; environmental permitting; property transfer; environmental, social, and health impact assessments; inhalation toxicology; renal toxicology; drug and alcohol exposures; toxicological and epidemiological risk assessment; communicable and foodborne illnesses such as Legionella, Salmonellosis, and Pseudomonas infections; rapid needs assessments; emergency response; ambient and indoor air monitoring; occupational health and safety plans; and stakeholder communications. Dr. Stock has served on both federal and industry working groups on air pollution issues such as particulate matter (PM2.5), benzene, carbon monoxide, and low sulfur diesel exhaust. She has also served as a corporate representative and an expert witness for litigation support.
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