Short answer: In a small controlled veterinary-ultrasound study, breath-alcohol instruments produced positive readings after operators worked with large quantities of 90% ethanol solution, although the operators were instructed not to drink alcohol in the preceding 24 hours. Of 36 examination sessions involving just six people, 30 produced readings at or above the investigators’ positive threshold immediately after the procedure. In some sessions, readings remained above that threshold for as long as 60 minutes. The study did not measure blood alcohol, so it cannot establish whether a reading arose from ambient vapor, residual respiratory ethanol, systemic absorption, or some combination. It also does not establish intoxication, impairment, or what a particular roadside instrument would report.

The source is Vitale and colleagues’ peer-reviewed 2023 study, “Breath Alcohol Test Results in Equine Veterinarians after Performing an Abdominal Ultrasound with Ethanol”, published in Veterinary Sciences. The researchers studied an unusual but forensic-relevant occupational exposure: ethanol used to improve ultrasonic probe contact with a horse’s abdomen.

What exactly did the researchers test?

Six healthy fourth- and fifth-year veterinary students, five women and one man aged 22–26 years, each performed six abdominal ultrasound examinations on a single Standardbred mare. Each participant undertook three examinations using ethanol poured from a jar and three using a spray. Examinations lasted 10, 30, or 60 minutes. The participants reported habitual alcohol use of no more than two drinks weekly and were told not to consume alcoholic beverages for 24 hours beforehand. The researchers did not describe independent biological verification of that abstinence instruction.

The procedures took place indoors, in a roughly 35-square-meter room maintained near 21 °C. The ultrasound contact liquid was 90% ethanol; recorded volumes ranged from 100 to 2,500 mL, with a median of 500 mL. Researchers allowed at least 24 hours between each examination session for a given operator. Participants wore nitrile gloves during the procedure and changed to clean gloves before providing breath samples.

The instrument was a calibrated Dräger Alcotest 7110, a breath tester using infrared and electrochemical sensing. It was programmed to display an estimated blood-alcohol-equivalent percentage using a 2,000:1 blood-to-breath partition ratio. That display is not a laboratory measurement of whole-blood ethanol.

What did the 36 breath-test sessions actually show?

A breath sample was taken immediately after each ultrasound, within the same room but near an open doorway. When the instrument produced a reading above the study’s negative band, testing continued at five-minute intervals until the instrument returned a reading below 0.019% on its configured display.

These are 36 repeated sessions, not 36 independent human subjects. Every operator appeared in six sessions. Inferences about how frequently this occurs among veterinarians, other workers, or motorists must not treat the session count as an independent population sample.

Did the quantity of ethanol matter more than spray versus pouring?

The investigators grouped ultrasound sessions by the amount of 90% ethanol used: less than 300 mL, 300–1,000 mL, or more than 1,000 mL. In the reported analysis, higher volume was associated with a higher immediate instrument reading and longer time to the study’s negative category. The published Table 2 reports a p value of 0.02 for the amount-of-ethanol association with the immediate percentage reading. The study did not report statistically significant differences in that outcome by jar-versus-spray application or assigned examination duration.

That does not prove that exposure quantity was the only causal factor. Air exchange, position in the room, individual breathing, varying handling techniques, and correlations between duration and ethanol volume were not resolved. With six volunteers, even statistically significant associations deserve cautious application outside the study room.

Is a positive breath reading the same as an elevated blood-alcohol concentration?

No. The relevant analytical sequence matters. The instrument responded to a breath sample. It then used a programmed partition ratio to display a blood-alcohol-equivalent percentage. A contemporaneous venous or other blood specimen was not collected. Therefore, the study cannot validate its displayed percentages against blood-gas or laboratory blood-ethanol measurements, and it cannot establish any participant’s actual blood alcohol concentration.

A positive instrument signal can be consistent with ethanol present in the delivered breath sample, but the origin of that ethanol is a separate scientific question. Potential contributions include vapor present in the testing environment, alcohol temporarily present in the airways, and ethanol absorbed into circulation after inhalation. The authors specifically acknowledged that they could not confirm pulmonary uptake because no blood samples were measured. They also noted that residual ethanol vapor might have remained in the room, notwithstanding the open doorway.

Nor does a result from this protocol quantify psychomotor function. The study did not include standardized driving exercises, neurobehavioral testing, clinical impairment ratings, or actual roadside breath-test records.

Does the study prove a false-positive evidential breath test?

It establishes that a particular evidential-style instrument produced above-threshold readings after the described occupational procedure. Whether those results would be legally or scientifically characterized as “false positives” depends on the exact proposition being tested. An instrument detecting ethanol in a collected breath sample is not necessarily analytically mistaken. It could nonetheless be misleading to present its blood-equivalent display as proof that ethanol entered the body through drinking, that a particular blood concentration existed, or that a person was impaired.

The experiment also should not be used to assert that every workplace ethanol exposure generates a positive breath result. Exposure intensity was unusual: in some sessions, more than a liter of 90% ethanol was applied indoors to a horse. The study did not sample ambient ethanol concentrations, validate a general correction factor, or establish how readings would change after moving away from the exposure site and following a jurisdiction-specific breath-testing protocol.

Why does the observation period require case-specific analysis?

Some breath-testing programs use pretest observation procedures intended to reduce contamination by recently introduced mouth alcohol. Vitale and colleagues pointed out that a minority of their occupational-exposure sessions remained positive beyond a brief waiting period. But this experiment was not a controlled trial of U.S. police observation practices, nor did it test the legal adequacy of any specific waiting period.

The authors discussed their own recommendation that exposed practitioners delay driving after ultrasound work. That recommendation should not be converted into a universal number of minutes at which driving is safe or at which all forensic readings become trustworthy. The study’s longest time to a reading below its lower threshold was 60 minutes. A roadside investigation requires the exact timestamps, instrument model and software, collection conditions, observation and retest records, and any confirmatory blood test.

What records would matter in litigation or a laboratory review?

A scientifically focused review would identify the operator’s activity and exposure conditions: concentration and volume of ethanol, ventilation, time and location of exposure, when the worker left that environment, and elapsed time before each breath sample. It would then distinguish a device-indicated breath-derived value from any directly measured blood ethanol. Instrument maintenance, calibration/verification, sampling sequence, error flags, observation history, paired tests, raw result records, and case-specific jurisdictional procedures all matter.

Where competing interpretations are raised, the appropriate question is not simply whether ethanol vapor exists. It is whether the actual case has measurements sufficient to assess a causal explanation. A study of six repeated-exposure operators cannot assign the origin of ethanol in an unrelated individual’s breath result, demonstrate deliberate drinking, or determine fault in a specific prosecution.

What are the major scientific limitations?

The sample comprised six young veterinary students, not a representative population of practicing veterinarians, industrial workers, or motorists. The study used one horse and one room; ventilation and vapor levels were not quantified. No blood samples were analyzed and no blinded comparison with an exposure-free control session was reported. The participants’ abstinence instruction was reported, not biologically independently confirmed. The repeated-measures structure, small subject count, varying ethanol volumes, and categorical instrument thresholds further limit generalizability.

The most defensible conclusion is narrow: under these high-volume veterinary-ultrasound conditions, breath-alcohol-equivalent instrument readings may persist after occupational ethanol exposure even when drinking was not intended. Their physiological source, relationship to blood concentration, and significance for impairment were not resolved by this study.

Frequently asked questions

Can an equine veterinarian have a positive breath-alcohol reading after ultrasound without consuming a drink?

Yes, this was observed in controlled sessions involving operators instructed not to drink for 24 hours beforehand. The study did not independently assay blood alcohol or verify every possible alternative source of ethanol.

Did all six participants have positive tests?

The researchers reported that all participants tested positive in at least four of their six ultrasound sessions. That is not a population prevalence estimate because the same six people completed all 36 sessions.

Does a reported 0.06% after vapor exposure mean the person had a measured blood BAC of 0.06%?

No. The instrument presented a blood-equivalent percentage calculated using a programmed 2,000:1 blood-to-breath ratio. No blood ethanol was measured to confirm a corresponding BAC.

Does the study prove that alcohol vapors were absorbed into the blood?

No. The investigators considered pulmonary uptake possible, particularly with prolonged positive results, but explicitly recognized that without blood sampling they could not show systemic absorption.

Were spray applications more likely than pouring to produce positive readings?

The investigators did not identify a statistically significant effect of the application method in their reported comparisons. The volume of ethanol used showed the clearer association in this small dataset.

Is a 15-minute wait always sufficient or insufficient after ethanol-vapor exposure?

Neither proposition was established universally. Some sessions remained above the study threshold longer than 15 minutes, but this protocol is not a validation of roadside observation intervals across different equipment or environments.

Can the study determine whether an exposed driver was impaired?

No. Impairment testing was outside the experimental design. Breath-instrument responses after an unusual workplace exposure should not be used as a substitute for clinical, behavioral, laboratory, and case-specific evidence.

Primary source and interpretation boundary

Source: Vitale V, Nocera I, van Galen G, et al. Breath Alcohol Test Results in Equine Veterinarians after Performing an Abdominal Ultrasound with Ethanol. Veterinary Sciences. 2023;10(3):222. doi:10.3390/vetsci10030222 (open-access full text; see Methods, Tables 1–2, Results, Discussion, and Limitations). Study population and findings described here are limited to that publication and are not a case-specific forensic conclusion.