Diode laser devices are commonly applied in equine upper airway surgeries, such as vocal cordectomy, palatoplasty, and aryepiglottic fold excision, as they can be transmitted through a quartz fiber endoscopically, allowing minimally invasive and controlled excision of tissues.1–3 Smoke plumes are readily visible during exhalation in horses undergoing upper airway laser surgery under sedation. Diode laser application to tissues results in absorption, heat generation, and expelled gaseous vapors and char in the form of smoke, which can be measured by its particulate matter components. Particulate matter suspended in air contains a mixture of compounds that could cause deleterious effects on humans upon inhalation.4,5 Animal models document that the inhalation of plumes generated by surgical lasers results in chronic lung diseases, including emphysema, bronchiolitis, and congestive interstitial pneumonia.6,7 Surgical smoke is irritating to the lungs, risks of inhalation are cumulative, and personnel closest to the site of generation have the highest exposure.8 Despite the known toxic characteristics of surgical plumes, inhalation hazards posed to hospital personnel conducting equine upper airway procedures have not been evaluated.
The objective of this study was to evaluate the composition of surgical plumes generated from diode laser application to equine upper airway tissues during the simulation of common surgical procedures. The specific plume components evaluated included the concentration of particulate matter under 2.5 μm (PM2.5), carbon analysis, and volatile organic compound (VOC) analysis.
Methods
Experiments were performed on 6 horse heads explanted within 2 hours following humane euthanasia. Horses were euthanized for reasons unrelated to the present study. The median age of the donor horses was 15 years (range, 11 to 22 years). Heads were vertically split on the midline to expose the upper airway regions. Laser tissue excision was randomized to be performed in 1 of 3 laryngeal or pharyngeal locations relevant to a specific clinical application and included vocal cordectomy, palatoplasty, and aryepiglottic fold excision (Supplementary Table S1). Vocal cordectomy, palatoplasty (staphylectomy), and aryepiglottic fold excision were performed as previously described utilizing a diode laser and modified as a transnasal endoscopic approach was not required.3,9,10 A 980-nm-wavelength surgical diode laser (Ceralas D 50; Biolitec) and 600-μm quartz fiber were utilized. For all procedures, a laser setting of 24 W in continuous mode was applied with contact, and activation time and energy were recorded as well as total procedure time. During laser activation, plume samples were collected as described below within 2.5 cm of the tissue. The order of sample collection and surgical site was randomized. Control samples were obtained via sample collection within the operating room prior to laser activation.
Particulate matter under 2.5 μm
Surgical plumes were collected via plastic tubing connected to an aerosol monitor (DustTrak Pro model 8520; TSI Inc) with a flow rate of 1.7 L/min to record real-time PM2.5 during laser procedures. Concentrations were recorded every 5 seconds throughout each laser procedure and logged using internal monitor software (TrakPro Data Analysis Software, Version 4.4.0.5; TSI Inc). A total of 6 surgical plume samples were collected, in addition to a control sample, specifically for PM2.5 analysis utilizing this described methodology. Sample collection time was measured in seconds.
Organic carbon and EC
Organic carbon (OC) and elemental carbon (EC) were measured using the National Institute for Occupational Safety and Health Method 5040.11 Surgical plumes were collected with a 0.25-inch-outer-diameter copper tube and a PM2.5 size-cut cyclone (URG Corp) onto a 47-mm quartz filter. To prevent contamination prior to sampling, wrapped filters were stored in plastic bags in a sealed box until loaded into the filter holder. A vacuum pump pulled air samples into the system at a flow rate of 17.84 L/min throughout the surgical procedure, with sample time recorded. A total of 6 surgical plume samples were collected, in addition to 2 control samples, specifically for EC and OC analysis utilizing this described methodology. Quartz filter samples were stored at −20 °C prior to analysis. The OC and EC concentrations for each filter sample were determined by thermal/optical transmission (Lab OC-EC Aerosol Analyzer; Sunset Laboratory Inc).12 For each filter, a 2.27-cm3 filter punch was used for analysis. The final concentration was corrected for collection time and flow rate.
Volatile organic compounds
Surgical plumes were collected in 1.4-L canisters for VOC determination. Samples were collected from each laser procedure in triplicate in evacuated 1.4-L canisters, with less than 1 minute between sampling events. A total of 18 surgical plume samples were collected, in addition to a control sample, specifically for VOC analysis utilizing this described methodology. The canisters were analyzed using a gas chromatograph analytical system with 3 flame ionization detectors (FIDs), 1 electron capture detector, and 1 mass spectrometer (Shimadzu GC17-A; Shimadzu Corp). Ninety individual VOCs were investigated and quantified in ppb, including C2 through C10 nonmethane hydrocarbons (NMHCs), C1 and C2 halocarbons, C1 through C5 alkyl nitrates, reduced sulfur compounds, and oxygenated VOCs (OVOCs), similar to previous studies.13,14 In brief, for each sample a 1,363-cm3 (standard temperature and pressure) aliquot of air was trapped on a glass-bead-filled loop immersed in liquid nitrogen. The loop was then isolated, warmed to 80 °C, and injected. Ultra-high purity helium carrier gas then flushed the loop contents, and the stream was split into 5, with each substream feeding a separate gas chromatograph column/detector pair as follows: (1) a CP-Al2O3/Na2SO4 PLOT column (50 m X 0.53-mm internal diameter, 10-μm film thickness; Varian-Chrompack) connected to a FID to measure C2 through C7 NMHCs, (2) a VF-1ms column (60 m X 0.32-mm internal diameter, 1-μm film thickness; Varian-Chrompack) connected to a FID to measure C4 through C10 NMHCs, (3) a CP-PoraBond Q column (25 m X 0.25-mm internal diameter, 3-μm thickness; Varian-Chrompack) coupled to a Restek XTI-5 column (30 m X 0.25-mm internal diameter, 0.25-μm film thickness; Restek) connected to a FID to measure selected OVOCs, (4) an OV-1701 column (60 m X 0.25-mm internal diameter 1-μm thickness; Ohio Valley Specialty Chemical) connected to an electron capture detector to measure C1 through C5 alkyl nitrates and C1 and C2 halocarbons, and (5) an OV-624 column (60 m X 0.25-mm internal diameter, 1.4-μm thickness; Ohio Valley Specialty Chemical) connected to a mass spectrometer to measure C6 through C10 NMHCs, C1 and C2 halocarbons, selected OVOCs, and reduced sulfur compounds. Standards were analyzed at 10 sample intervals.
Statistical analysis
Analyses were performed using commercial software (Prism, version 10; GraphPad Software LLC). Particulate matter under 2.5 μm sample collection time underwent Shapiro-Wilk normality testing and was reported as mean ± SD. Particulate matter concentrations under 2.5 μm data were reported as mean, median, and quartiles.15 A mixed-effects model was used to compare the PM2.5 of plume samples and control, with P < .05 considered statistically significant. Organic carbon and EC concentration and OC/EC ratios were reported as median and quartiles. Each VOC identified was reported as mean, minimum, and maximum.
Results
Surgical plumes from ex vivo diode laser excision applied to laryngeal and pharyngeal tissues were collected and analyzed in addition to control samples. Visible smoke was encountered during all surgical plume sample collection procedures. Diode laser median activation time was 326 seconds (IQR, 116 to 387 seconds), and median energy was 8,099 J (IQR, 2,721 to 9,110 J). Median surgical procedure duration was 486 seconds (IQR, 388 to 639 seconds).
Particulate matter under 2.5 μm
The mean sample collection time was 98 ± 13 seconds. The mean real-time PM2.5 concentrations measured at 5-second intervals fluctuated over sampling the periods in both laser procedures and control, and the PM2.5 exceeded 5 mg/m3 throughout the laser procedures, which is the permissible exposure limit set by the Occupational Safety and Health Administration (Figure 1).16 The PM2.5 concentration measured during laser procedures (mean, 142.2 mg/m3; median, 147.3 mg/m3; IQR, 120.0 to 169.9 mg/m3) exceeded control (mean, 0.006 mg/m3; median, 0.005 mg/m3; IQR, 0.005 to 0.006 mg/m3; P < .001).
A 980-nm diode laser fiber was applied in continuous-wave mode in contact with laryngeal and pharyngeal tissues of 6 equine cadaver heads and real-time concentration of particulate matter under the size of 2.5 μm (PM2.5) was measured from resulting surgical plumes. Real-time PM2.5 concentrations measured at 5-second intervals are illustrated graphically. The yellow line indicates the mean PM2.5 concentration at each time point throughout the laser procedures, with an overall mean of 142.2 mg/m3 represented by the black line. The purple line indicates control concentrations, with an overall mean of 0.006 mg/m3. The permissible exposure limit (PEL) set by the Occupational Safety and Health Administration (OSHA) is 5 mg/m3 and is represented by the red line.
Citation: American Journal of Veterinary Research 2025; 10.2460/ajvr.24.11.0338
Organic carbon and EC
Surgical plume collection on quartz filters resulted in visible discoloration following sample collection (Figure 2). The results from our analysis revealed higher OC concentrations within the surgical plume when compared to EC, with a median OC of 847 µg·C/m3 (IQR, 527 to 950 µg·C/m3), median EC of 1.83 µg·C/m3 (IQR, 1.40 to 2.26 µg·C/m3), and median OC:EC ratio of 422 (IQR, 264 to 555). Median control concentrations of OC (2.81 µg·C/m3; IQR, 2.33 to 3.28 µg·C/m3) and EC (0 µg·C/m3; IQR, 0 to 0.004 µg·C/m3) were well below sample concentrations (Figure 3).
A 980-nm diode laser fiber was applied in continuous-wave mode in contact with laryngeal and pharyngeal tissues of 6 equine cadaver heads, and resultant plumes were collected onto quartz filters for analysis organic carbon (OC) and elemental carbon (EC) composition. This is a photograph of a quartz filter following sample collection of the diode laser plume resulting from vocal cordectomy.
Citation: American Journal of Veterinary Research 2025; 10.2460/ajvr.24.11.0338
Surgical plumes collected onto quartz filters, an example of which is shown in Figure 2, were further analyzed. Median concentrations of OC and EC components of laser surgical plumes compared with control are illustrated in µg·C/m3 using logarithmic scaling, with error bars signifying IQR. Control samples are indicated in blue and surgical plume samples in tan.
Citation: American Journal of Veterinary Research 2025; 10.2460/ajvr.24.11.0338
Volatile organic compounds
Surgical plumes and corresponding controls were sampled, and VOC concentrations were analyzed. Fifty-five individual VOCs were identified, and the mean, minimum, maximum, and control concentrations of these VOCs are reported in Supplementary Table S2 along with recommended daily exposure limits. Figure 4 illustrates the VOC concentrations from each sample in logarithmic scale, with all mean concentrations increased relative to controls.
A 980-nm diode laser fiber was applied in continuous-wave mode in contact with laryngeal and pharyngeal tissues of 6 equine cadaver heads, and resultant plumes were collected into evacuated canisters for analysis of volatile organic compounds (VOCs). Concentrations of 55 VOCs identified from diode laser plume samples collected during simulated upper airway surgical procedures are illustrated graphically. Individual sample VOC concentrations are indicated in log10 scale in tan, with control sample results represented in blue.
Citation: American Journal of Veterinary Research 2025; 10.2460/ajvr.24.11.0338
Discussion
In this study, we evaluated laser surgical plumes to determine plume components and identify the potential harm of hospital staff exposure. Specifically, we determined that plume components generated using a 980-nm diode applied and activated upon upper airway tissues of the horse in a manner similar to common operative procedures in this species. We examined exposure concentrations for 3 pollutant categories used extensively to catalog known hazardous material inhalation exposure potential to humans and selected to detect the presence of adverse components of surgical laser plumes. Documented levels of all measured components, including PM2.5, OC/EC, and VOCs, indicate procedural or cumulative exposure hazards associated with the inhalation of surgical laser plumes during upper respiratory surgery in horses.
Fine particle pollution, such as PM2.5, accumulates within the small airways and has been linked to lung disease and other serious disorders.17 Reactive oxygen species production following the application of PM2.5 to alveolar epithelial cells leads to oxidative stress and subsequent DNA and mitochondrial structural damage, which can result in tissue remodeling, apoptosis, accelerated aging, and cancerogenesis.5,18–21 In fact, according to the WHO, ambient air particulate matter is responsible for 4.2 million deaths each year.22 Due to the broad health implications, the measurement of PM2.5 within surgical plumes was considered essential to identify inhaled exposure risk. The PM2.5 exposure in the present study was 30-fold higher than the Occupational Safety and Health Administration's 8-hour permissible exposure limit for particulates of 5 mg/m3 and exceeds the WHO's recommended annual mean ambient PM2.5 of 0.01 mg/m3.22 In the present study, PM2.5 surpassed background concentrations (0.006 mg/m3), and concentrations of 200 mg/m3 were measured within seconds of diode laser application. These data show a sustained increase of PM2.5 upon commencing surgery, highlighting the importance of further investigation into the health implications of exposure to plumes generated from surgical devices regardless of procedure length.
Carbonaceous material found in particulate matter is composed of OC and EC.23 Elemental carbon is a stable chemical that derives from incomplete combustion of carbonaceous matter and is notable as a significant atmosphere absorber of solar radiation and trigger of reduced atmospheric visibility,24 whereas OC is a complex and harmful substance made up of primary OC and other subspecies of secondary OC, such as mutagenic polyaromatic hydrocarbons, that are formed via photochemical reactions from pollutants.23 In the present study, the measured values in surgical plumes far exceeded background control OC/EC measurements. Additionally, OC concentrations within surgical laser plumes exceeded elemental concentrations 400-fold. The plume carbon composition observed in the present study was similar to those associated with wood burning, meat cooking, and cigarettes.25,26 The present study is the first to report OC/EC in plumes generated from surgical devices in veterinary and human applications. Carbon content analysis could be used to characterize and compare plumes from different surgical devices applied to various tissues in order to better understand the implications of exposure on human health.
Volatile organic compounds have been extensively studied in smoke, from sources such as cigarettes and fires, due to their potential to cause respiratory disease, cancer, bone marrow depletion, and brain damage.27 Among VOCs, benzene, toluene, ethylbenzene, and xylene, or the BTEX complex, are of particular concern due to their potential to cause noncancer health effects via acute and chronic exposure as well as their activity as carcinogens. All 55 VOCs measured within laser surgical plumes in the present study exceeded control background concentrations. Mean concentrations of benzene, a Category A known human carcinogen, were near daily exposure limits, though concentrations exceeding these values were measured during procedures. Concentrations of the remaining compounds were within acceptable daily exposure ranges. As samples were collected from specimens over a maximum time period of 3 minutes, it is likely that collection over longer periods would show higher concentrations due to cumulative effects and increased tissue temperature from extended laser contact time resulting in further release of chemical pollutants.27 Additionally, due to the transient nature of smoke, sample concentrations vary, and measured quantities may not be adequately representative. More samples over a longer time period are needed to determine representative surgical staff exposure levels. Despite most of the observed concentrations being lower than exposure limit requirements, the effect of long-term, low-dose, and cumulative effects of these VOCs is largely unknown. Individual factors should also be considered. For example, if a person is taking aspirin while exposed to toluene, they have prolonged exposure times in the body due to a decreased clearance.28 Furthermore, when exposed to both benzene and toluene simultaneously, benzene levels are increased in the body due to the inhibitory effect of toluene on benzene metabolism. 29
Utilizing explanted cadaveric upper airway tissues is an appropriate first step to better understand surgical plumes resulting from diode laser application and tissue ablation in a controlled environment. Although there are obvious limitations to the model utilized in the present study, such as variations in soft tissues ex vivo in comparison to perfused tissue in vivo, the data are useful in better understanding components of surgical laser plumes resulting from the application to equine upper airway tissue. Lower hydration levels observed in ex vivo models can result in hastened laser excision and have been shown to underestimate the amount of tissue char and necrotic zones following diode laser tissue interaction when compared with in vivo models.30 Further study in a perfusing animal model would overcome the limitations of an ex vivo model and yield further information to inform exposure risks.
This study represents the first comprehensive testing of surgical laser plumes in veterinary medicine. Inhalation exposure of equine hospital staff to laser plumes associated with upper airway surgery could have safety implications. Identification of potential hazards to veterinarians and staff could be utilized to further understand exposure risk and evaluate protections in a clinical setting. This information provides insight into levels of toxic materials and how they relate to the physical properties of laser plumes. Laser plume characteristics associated with equine upper airway surgical procedures pose a potential risk to exposed personnel, indicating the need for appropriate mitigation and protection from laser plumes. While there are no occupational safety requirements at present, these data highlight the potential for exhaust ventilation and respirator application to decrease plume exposure. It is prudent to further evaluate operating room exposures of laser-generated plumes in veterinary medicine.
Supplementary Materials
Supplementary materials are posted online at the journal website: avmajournals.avma.org.
Acknowledgments
None reported.
Disclosures
The authors have nothing to disclose. No AI-assisted technologies were used in the composition of this manuscript.
Funding
The authors have nothing to disclose.
ORCID
D. W. Koch https://orcid.org/0000-0001-9267-2995
E. S. Hackett https://orcid.org/0000-0001-6559-9585
References
- 1.↑
Henderson CE, Sullins KE, Brown JA. Transendoscopic, laser-assisted ventriculocordectomy for treatment of left laryngeal hemiplegia in horses: 22 cases (1999–2005). J Am Vet Med Assoc. 2007;231(12):1868–1872. doi:10.2460/javma.231.12.1868
- 2.
Alkabes KC, Hawkins JF, Miller MA, et al. Evaluation of the effects of transendoscopic diode laser palatoplasty on clinical, histologic, magnetic resonance imaging, and biomechanical findings in horses. Am J Vet Res. 2010;71(5):575–582. doi:10.2460/ajvr.71.5.575
- 3.↑
King DS, Tulleners E, Martin BB Jr, Parente EJ, Boston R. Clinical experiences with axial deviation of the aryepiglottic folds in 52 racehorses. Vet Surg. 2001;30(2):151–160. doi:10.1053/jvet.2001.21389
- 4.↑
Piao MJ, Ahn MJ, Kang KA, et al. Particulate matter 2.5 damages skin cells by inducing oxidative stress, subcellular organelle dysfunction, and apoptosis. Arch Toxicol. 2018;92(6):2077–2091. doi:10.1007/s00204-018-2197-9
- 5.↑
Valavanidis A, Vlachogianni T, Fiotakis K, Loridas S. Pulmonary oxidative stress, inflammation and cancer: respirable particulate matter, fibrous dusts and ozone as major causes of lung carcinogenesis through reactive oxygen species mechanisms. Int J Environ Res Public Health. 2013;10(9):3886–3907. doi:10.3390/ijerph10093886
- 6.↑
Baggish MS, Elbakry M. The effects of laser smoke on the lungs of rats. Am J Obstet Gynecol. 1987;156(5):1260–1265. doi:10.1016/0002-9378(87)90158-X
- 7.↑
Wenig BL, Stenson KM, Wenig BM, Tracey D. Effects of plume produced by the Nd:YAG laser and electrocautery on the respiratory system. Lasers Surg Med. 1993;13(2):242–245. doi:10.1002/lsm.1900130213
- 8.↑
Barrett WL, Garber SM. Surgical smoke: a review of the literature. Is this just a lot of hot air? Surg Endosc. 2003;17(6):979–987.
- 9.↑
Kidd JA, Slone DE. Treatment of laryngeal hemiplegia in horses by prosthetic laryngoplasty, ventriculectomy and vocal cordectomy. Vet Rec. 2002;150(15):481–484. doi:10.1136/vr.150.15.481
- 10.↑
Smith JJ, Embertson RM. Sternothyroideus myotomy, staphylectomy, and oral caudal soft palate photothermoplasty for treatment of dorsal displacement of the soft palate in 102 Thoroughbred racehorses. Vet Surg. 2005;34(1):5–10. doi:10.1111/j.1532-950X.2005.00002.x
- 11.↑
Eller PM, Cassinelli ME, eds. NIOSH Manual of Analytical Methods. 4th ed. National Institute for Occupational Safety and Health; 1996.
- 12.↑
Birch ME, Cary RA. Elemental carbon-based method for occupational monitoring of particulate diesel exhaust: methodology and exposure issues. Analyst. 1996;121(9):1183–1190. doi:10.1039/an9962101183
- 13.↑
Zhou Y, Shively D, Mao H, et al. Air toxic emissions from snowmobiles in Yellowstone National Park. Environ Sci Technol. 2010;44(1):222–228. doi:10.1021/es9018578
- 14.↑
Russo RS, Zhou Y, White ML, Mao H, Talbot R, Sive BC. Multi-year (2004–2008) record of nonmethane hydrocarbons and halocarbons in New England: seasonal variations and regional sources. Atmos Chem Phys. 2010;10(10):4909–4929. doi:10.5194/acp-10-4909-2010
- 15.↑
Nguyen GTH, Hoang-Cong H, La LT. Statistical analysis for understanding PM2.5 air quality and the impacts of COVID-19 social distancing in several provinces and cities in Vietnam. Water Air Soil Pollut. 2023;234(2):85. doi:10.1007/s11270-023-06113-1
- 16.↑
Permissible exposure limits – annotated tables. Occupational Safety and Health Administration. Accessed April 24, 2024. https://www.osha.gov/annotated-pels/table-z-1
- 17.↑
Behinaein P, Hutchings H, Knapp T, Okereke IC. The growing impact of air quality on lung-related illness: a narrative review. J Thorac Dis. 2023;15(9):5055–5063. doi:10.21037/jtd-23-544
- 18.↑
Upadhyay D, Panduri V, Ghio A, Kamp DW. Particulate matter induces alveolar epithelial cell DNA damage and apoptosis: role of free radicals and the mitochondria. Am J Respir Cell Mol Biol. 2003;29(2):180–187. doi:10.1165/rcmb.2002-0269OC
- 19.
Soberanes S, Panduri V, Mutlu GM, Ghio A, Bundinger GRS, Kamp DW. p53 mediates particulate matter-induced alveolar epithelial cell mitochondria-regulated apoptosis. Am J Respir Crit Care Med. 2006;174(11):1229–1238. doi:10.1164/rccm.200602-203OC
- 20.
Sahin E, DePinho RA. Axis of ageing: telomeres, p53 and mitochondria. Nat Rev Mol Cell Biol. 2012;13(6):397–404. doi:10.1038/nrm3352
- 21.↑
Mehta M, Chen LC, Gordon T, Rom W, Tang MS. Particulate matter inhibits DNA repair and enhances mutagenesis. Mutat Res. 2008;657(2):116–121. doi:10.1016/j.mrgentox.2008.08.015
- 22.↑
Ambient (outdoor) air quality and health. WHO. Accessed June 21, 2019. https://www.who.int/news-room/fact-sheets/detail/ambient-(outdoor)-air-quality-and-health
- 23.↑
Qi M, Jiang L, Liu Y, et al. Analysis of the characteristics and sources of carbonaceous aerosols in PM2.5 in the Beijing, Tianjin, and Langfang region, China. Int J Environ Res Public Health. 2018;15(7):1483.
- 24.↑
Marvel SJ, Hafez A, Monnet E. Thoracoscopic treatment of persistent right aortic arch in dogs with and without one lung ventilation. Vet Surg. 2022;51(suppl 1):O107–O117.
- 25.↑
Kleeman MJ, Schauer JJ, Cass GR. Size and composition distribution of fine particulate matter emitted from wood burning, meat charbroiling, and cigarettes. Environ Sci Technol. 1999;33(20):3516–3523. doi:10.1021/es981277q
- 26.↑
McDonald JD, Zielinska B, Fujita EM, Sagebiel JC, Chow JC, Watson JG. Emissions from charbroiling and grilling of chicken and beef. J Air Waste Manag Assoc. 2003;53(2):185–194. doi:10.1080/10473289.2003.10466141
- 27.↑
Bratu AM, Petrus M, Patachia M, et al. Quantitative analysis of laser surgical smoke: targeted study on six toxic compounds. Rom Journ Phys. 2015;60(1):215–227.
- 28.↑
Tramontini CC, Galvao CM, Claudio CV, et al. [Composition of the electrocautery smoke: integrative literature review]. Rev Esc Enferm USP. 2016;50(1):148–157. doi:10.1590/S0080-623420160000100019
- 29.↑
Inoue O, Seiji K, Watanabe T, et al. Mutual metabolic suppression between benzene and toluene in man. Int Arch Occup Environ Health. 1988;60(1):15–20. doi:10.1007/BF00409373
- 30.↑
Fornaini C, Merigo E, Sozzi M, et al. Four different diode lasers comparison on soft tissues surgery: a preliminary ex vivo study. Laser Ther. 2016;25(2):105–114. doi:10.5978/islsm.16-OR-08
