Can Occupational Ethanol Exposure Produce a Positive Breath Test After a Horse Ultrasound?

Yes. A small experiment found positive breath results after operators used ethanol during horse ultrasound without drinking an alcoholic beverage. But it did not measure blood ethanol, so it could not determine how much of the signal reflected inhaled systemic alcohol versus contamination of breath or the testing environment.

The participants were people, not the horse

Vitale and colleagues enrolled six healthy veterinary students aged 22–26, five women and one man. Each performed six abdominal ultrasound examinations on the same mare, producing 36 examination sessions.

Operators applied 90% ethanol by pouring or spraying it during examinations lasting ten, thirty or sixty minutes. Amounts ranged from 100 to 2,500 milliliters. The room was closed during ultrasound and opened for ventilation afterward. Operators wore gloves.

An evidential breath analyzer was used immediately after the procedure and at five-minute intervals until the study’s negative category was reached. Testing occurred in the same room near its open door, rather than in a separate vapor-free testing room.

“Negative” meant below a defined category, not necessarily zero

The device displayed blood-alcohol-equivalent percentages calculated using a 2,000:1 blood-to-breath ratio. These were not measured blood concentrations.

The investigators defined their negative category as a displayed value below 0.019%. Immediately after ultrasound, 30 of 36 sessions were above that cutoff, including eleven above a displayed 0.050%.

Time to fall below 0.019% ranged from zero to sixty minutes, with a median of 7.5 minutes. Results above 0.050% persisted for up to thirty-five minutes in this experiment. These are observations under the protocol, not universal waiting periods or current legal rules.

Ethanol amount mattered more clearly than application method

The amount used was significantly associated with the immediate reading and persistence categories. The highest-volume group generally had higher readings or longer persistence.

Application by jar versus spray and examination duration did not show significant effects in the adjusted analysis. Raw averages by duration therefore should not be presented as proof that a longer examination independently caused the result.

The 36 sessions were repeated observations from only six people, not a 36-person sample. That small participant base limits precision and generalization.

The mechanism remained unresolved

The authors suspected some absorption through the lungs, particularly for prolonged results. They acknowledged that no blood measurements tested that explanation. Residual ethanol in room air was another unresolved influence.

A positive breath signal after external exposure should not automatically be called a false-positive ethanol detection: ethanol may really be present in the sampled air. The unresolved issue is whether the result accurately represents systemic concentration.

The experiment measured neither impairment nor driving. It cannot prove that an exposed individual was safe to drive, or that an occupational-exposure explanation accounts for a particular roadside result. The exposure amounts, ventilation, elapsed time, testing location and actual test records would all matter to assessing applicability.

The site’s three-case analysis of mouth-alcohol detection addresses another potential source of breath-result distortion. It should be evaluated on its own evidence rather than assumed to share this experiment’s mechanism or timeline.

Primary source

Vitale V, Nocera I, van Galen G, Sgorbini M, Conte G, Aliboni B, Verwilghen D. Breath Alcohol Test Results in Equine Veterinarians after Performing an Abdominal Ultrasound with Ethanol. Veterinary Sciences. 2023;10:222. https://doi.org/10.3390/vetsci10030222.