Abstract
Introduction
During surgical operations, energy devices such as electric knives, lasers, and ultrasonic scalpels are commonly used to separate tissues and seal blood vessels. During this process, cell decomposition, rupture, and evaporation occur, releasing surgical smoke into the air. 1 Surgical smoke is composed of 95% water or steam and 5% particles. 2 These particles vary in size and can deposit onto different parts of the human respiratory system: particles with a size >5 µm deposit on the nasopharynx wall, those with a size between 2 and 5 µm enter the trachea and bronchi, and those smaller than 1 µm, similar to gas molecules, can penetrate downward into the alveoli and further transfer to cellular tissue and/or the circulatory system.3,4
Inhaling particulate matter (PM) may have adverse effects on human health due to the various toxic compounds attached to its surface, among which polycyclic aromatic hydrocarbons (PAHs) are considered to be the most cytotoxic, mutagenic, and carcinogenic organic chemicals. 5 Studies have shown that PAHs promote the production of large amounts of reactive oxygen species, leading to oxidative stress in the cardiovascular and pulmonary systems, and may cause DNA damage. 6 Short-term exposure to PAHs may lead to eye and skin irritation, nausea, and vomiting, whereas long-term exposure may lead to liver and kidney damage and increased risk of lung cancer, skin cancer, and bladder cancer as well as gene mutations, cell damage, and increased rates of cardiovascular and pulmonary mortality. 7 Epidemiological studies have shown that PAHs exert adverse effects on female reproduction and fetal development and are associated with several later childhood issues, such as low IQ, behavioral problems, allergies, or asthma.8,9
Although the toxic effects of surgical smoke are not typical, relevant studies have revealed that surgical smoke exhibits potential mutagenicity on standard Salmonella particles, embryotoxicity on human embryonic cells, and inhibitory effects on the differentiation of myocardial cells.10,11 Compared with open abdominal surgery, the surgical smoke generated from laparoscopic surgery is confined to the abdominal cavity and discharged when necessary, which results in even higher particle concentrations at the time of release. 12 This also indicates that healthcare workers near the operating table may be exposed to higher concentrations of toxic PAHs. However, there is still insufficient data to quantify the PAHs in laparoscopic surgical smoke and the potential carcinogenic risk they pose to healthcare workers. Therefore, the purpose of this study was to analyze the distribution and concentration of 16 PAHs adhering to particles in laparoscopic surgical smoke in the respiratory system, which have been listed as priority pollutants by the US Environmental Protection Agency. 13 The total toxic equivalent concentration (ΣTEQ) was calculated based on the toxicity equivalency factor (TEF) of each PAH to evaluate the potential cancer risk for the medical staff in the operating room. 14 Considering that the liver produces more particles than other tissues, 15 this study collected the smoke generated during laparoscopic liver resection as a sample. In addition to solid organs, we sought to understand the status of PAHs produced by hollow organs. Therefore, we also collected the smoke generated during laparoscopic rectal cancer surgery. This study has been approved by the Institutional Review Board (2022055) of the hospital, and the participants provided written informed consent.
Materials and methods
Study design
This is a cross-sectional study conducted in a large teaching hospital in northern China, which has been approved by the hospital's ethics committee. It was not possible to calculate the minimum sample size for this study, and the study was mainly terminated when the color of the sampler filter membrane changed visibly. This study serves as a pilot for further research. All patient details have been de-identified.
The study was conducted in accordance with the Helsinki Declaration.
Air sampling
The sampler (Model 20-800, Thermo-Andersen, Atlanta, GA, USA) used to collect laparoscopic surgical smoke was a multi-stage porous cascade impactor for nonbiological environmental sampling. It has eight impact plates, each with a diameter of 81 mm, and glass fiber filter membrane, as shown in Figure 1. The sampler classifies the particles collected based on the deposition of atmospheric particles in the human respiratory system through aerodynamic simulation. The cutoff diameters of each stage are 0.43, 0.65, 1.1, 2.1, 3.3, 4.7, 5.8, and 9 µm. The human respiratory system simulated by the sampler is shown in Figure 2. PM4.7–10 mainly exists in the nasal pharynx, whereas PM1.1–4.7 and PM < 1.1 can enter the tracheobronchial and alveolar regions of the human respiratory system, respectively. Surgical smoke enters the sampler and is collected on the surface of the filter membranes of each stage through small holes with different diameters on the impact plate. The sampler was disinfected with 75% alcohol and flow-calibrated before sampling. The sampling flow rate was set at 28.3 L/min, and the glass fiber filter membranes were heated at 480°C to remove possible contaminants.

Sampler and all levels of impact plate.

Particle size classification and deposition location in the human respiratory system.
Sample collection
All surgical samples were collected in the same operating room at the same cleanliness level of the hospital (level 7 cleanliness, with a dust particle count greater than 35,000 particles/m3 but less than or equal to 350,000 particles/m3 and a size ≥0.5 µm). The environment during surgery was maintained at a temperature of 21°C–24°C and humidity of 30%–40%.
Purpose sampling was used to select participants from a large teaching hospital between December 2022 and February 2023. The inclusion criteria were as follows: (a) patients underwent elective laparoscopic hepatectomy or laparoscopic rectal resection; (b) surgery involving general anesthesia; (c) provision of informed consent for study participation. The exclusion criteria were as follows: (a) patients converted to laparotomy during the operation; (b) occurrence of a life-threatening situation during the operation, such as massive bleeding; (c) the operation duration was >5 h.
The sampler was placed under the patient’s head on the surgical table. A disposable sterile straw was connected to the puncture needle exhaust port by the scrub nurse, whereas the other end was connected to the sampling line by the experimenter, as shown in Figure 3. After the surgery began, the surgeon opened the valve of the puncture needle by 1/2 to 2/3 to ensure that the surgical smoke could be drawn into the sampler and maintain the pneumoperitoneum pressure between 12 and 14 mmHg, collecting the smoke until the end of the surgery. This study was reported in accordance with the Strengthening the Reporting of Observational studies in Epidemiology (STROBE) guidelines. 16

Method of sampling.
PAH analysis
Sample preconditioning
The filter membranes were cut into small pieces using scissors and placed in 10-mL glass centrifuge tubes with stoppers. The tools used for cutting and transferring the membrane samples were rinsed with a mixture of n-hexane and dichloromethane. In each centrifuge tube, 9 mL of a mixed solution of n-hexane and dichloromethane (v/v: 1/3) and 100 μL of PAH surrogate standards (including naphthalene-d8, phenanthrene-d10, and pyrene-d10) at a concentration of 200 ng/mL were added sequentially, vigorously vortexed, and then subjected to ultrasonic extraction in the dark for 60 min. The two-stage filter membranes (0.43–0.65 and 0.65–1.1 µm) from the surgical samples were extracted twice using the same method. The tubes containing the extracts were subjected to centrifugation at 3500 rpm for 5 min, and the supernatant was filtered through a 0.45-µm nylon filter. Blank controls were set up by processing filter membranes that were placed in the sampler but not exposed to surgical smoke using the same method as for the samples to correct for any system errors.
After extraction, the sample solutions were transferred to a nitrogen blow tube and then evaporated until a volume of 100 μL under nitrogen gas. The extracted samples were stored in a −20°C freezer until they were analyzed using instrumental methods.
Sample testing
The samples were qualitatively and quantitatively analyzed using gas chromatography–mass spectrometry in the selected ion monitoring mode. The chromatographic column used was an HP-5 (30 m × 250 μm × 0.25 μm). The temperature program was initially set at 80°C for 3 min, after which the temperature was increased at a rate of 10°C/min to 200°C and held for 4 min, followed by an increase to 260°C at a rate of 12°C/min, where it was held for 1 min. Finally, the temperature was increased to 310°C at a rate of 15°C/min and held for 8 min. The PAH standard curves were prepared with concentrations of 5, 10, 50, 100, 200, and 500 ng/mL. The retention times and characteristic ions of PAHs are shown in Table 1. The collected filter membranes from rectal and liver surgeries were labeled as 1-1, 1-2…1-9, and 2-1, 2-2,…2-9, respectively. The chromatograms of the 500 ng/mL PAH standard and the actual sample (sample 2–9) are shown in Figures 4 and 5, respectively. The concentrations of the second extraction samples were lower than those of the first extraction samples by <30%, indicating good extraction efficiency. All sample concentrations were blank-corrected, and the final concentrations were expressed as absolute concentration (ng), air volume concentration (ng/m³), and per-operation concentration (ng/operation). The formulas for calculating the PAH air volume concentration (ng/m³) and per-operation PAH concentration (ng/operation) were as follows:
Retention time and characteristic ions of 16 polycyclic aromatic hydrocarbons.

TIC chromatogram of polycyclic aromatic hydrocarbon standard solution (500 ng/mL). TIC: total ion chromatogram.

TIC chromatogram of actual samples (2–9). TIC: total ion chromatogram.
In the above formulas, Ci, V, and N represent the absolute concentration of PAHs at the ith particle size level (ng), volume of collected air (m³), and number of surgical operations, respectively.
Results
Sample concentration analysis
The sampling period was from December 2020 to March 2021, during which surgical smoke generated from 16 laparoscopic colorectal resections and 19 laparoscopic liver resections was collected. The air volumes collected were 70.467 and 84.4189 m³, respectively. The concentrations of PAHs (ng/m³) in the two types of surgical smoke are shown in Table 2.
Concentrations of polycyclic aromatic hydrocarbons in laparoscopic surgical smoke.
ND: not detected; Nap: naphthalene; Acy: acenaphthylene; Ace: acenaphthene; Fl: fluorene; Phe: phenanthrene; Ant: anthracene; Fla: fluoranthene; Pyr: pyrene; BaA: benzo[a]anthracene; Chr: chrysene; BbF: benzo[b]fluoranthene; BkF: benzo[k]fluoranthene; BaP: benzo[a]pyrene; IDP: indeno[1,2,3-cd]pyrene; DBahA: dibenz[a,h]anthracene; BghiP: benzo[g,h,i]perylene.
With the exception of naphthalene and dibenz[a,h]anthracene, the remaining 14 PAHs were found in laparoscopic surgical smoke. In colorectal surgery, acenaphthene had the highest concentration (0.422 ng/m³), followed by fluoranthene (0.34757 ng/m³), pyrene (0.3107 ng/m³), benzo[b]fluoranthene (0.25436 ng/m³), anthracene (0.214 ng/m³), and phenanthrene (0.206873 ng/m³). In liver surgery, acenaphthene also had the highest concentration (1.249858 ng/m³), followed by chrysene (0.4469 ng/m³), benzo[b]fluoranthene (0.3367 ng/m³), pyrene (0.229018 ng/m³), and benzo[k]fluoranthene (0.1221 ng/m³). The total concentration of PAHs produced during colorectal surgery was 2.399 ng/m³, with concentrations in the nasal pharynx, tracheobronchial region, and alveoli of 0.448, 0.415, and 1.536 ng/m³, respectively. The total concentration of PAHs produced during liver surgery was 2.819 ng/m³, with concentrations in the nasal pharynx, tracheobronchial region, and alveoli of 0.796, 0.270, and 1.752 ng/m³, respectively. The deposition patterns of both types of laparoscopic surgical smoke in the human respiratory system were similar, with the highest concentration in the alveoli, followed by the nasal pharynx, and the lowest in the tracheobronchial region.
As shown in Figure 6, although PAHs generated during laparoscopic surgery were predominantly deposited in the alveoli, there were differences in their distribution across particle size ranges. During colorectal surgery, PAHs were mainly present in particles with a size of 0.43–0.65 µm, with lower concentrations observed in particles smaller than 0.43 µm. In contrast, PAHs produced during liver surgery were distributed in larger particle size ranges, with the peak concentration observed in particles with a size of 0.65–1.1 µm and significantly higher concentrations observed in particles smaller than 0.43 µm compared with those observed during colorectal surgery. Additionally, liver surgery exhibited higher concentrations of PAHs in particles with a size of 4.7–5.8 µm.

Characteristics of polycyclic aromatic hydrocarbon respiratory deposition in laparoscopic smoke.
As shown in Figure 7, the concentration of PAHs produced during liver surgery (12.5 ng/operation) was higher than that produced during colorectal surgery (11.3 ng/operation). The concentration of PAHs that can be deposited in the tracheobronchial region during colorectal surgery (1.83 ng/operation) was higher than that during liver surgery (1.20 ng/operation), whereas the concentration of PAHs that can be deposited in the nasal pharynx (3.54 ng/operation) and alveoli (7.79 ng/operation) during liver surgery was significantly higher than that during colorectal surgery (nasal pharynx (1.97 ng/operation) and alveoli (7.48 ng/operation)).

Concentration of polycyclic aromatic hydrocarbons produced per operation (ng per operation).
Carcinogenic toxicity equivalents
The TEF for each target compound was calculated relative to the carcinogenicity of benzo[a]pyrene, which was assigned a value of 1. The TEF data are shown in Table 3. Based on the TEF method, the total carcinogenic potential (ΣTEQ) of the PAHs in the surgical smoke particles was calculated according to the detected concentrations of each compound using the following formula:
Toxic equivalence factors of compounds.
The calculation results showed that the mean ΣTEQ of the 16 PAHs in rectal and liver surgeries were 0.0123 and 0.00726 ng/m³, respectively. These values were below the World Health Organization standard (1 ng/m³), indicating that the concentration of PAHs generated during these surgeries did not reach carcinogenic risk levels.
Discussion
In this pilot study, we collected the surgical smoke during laparoscopic hepatectomy or laparoscopic rectal resection as well as monitored the specific composition and amount of PAHs in surgical smoke. This is different from a previous study that focused on other composition in surgical smoke and surgery types. 17
Overall, 14 of the 16 monitored PAHs were detected in the smoke generated during the two laparoscopic surgeries, including benzo[a]pyrene and indeno[1,2,3-cd]pyrene, which have been listed as human carcinogens or potential carcinogens by the International Agency for Research on Cancer (IARC). 18 Although the concentrations of these compounds were below the carcinogenic risk level, healthcare workers must remain vigilant.
This study showed that after inhaling PAHs, they could be deposited in large amounts in the alveoli, indicating that they easily participate in the metabolism of pulmonary tissue and enter the bloodstream. As healthcare workers are exposed to surgical smoke for decades, this finding raises concerns about their health. A study based on breast surgery expressed the same view. According to their results, the risk of cancer in surgeons and anesthetists exposed to PAHs in surgical smoke for 70 years was 117 and 270 times higher than that in the general population, respectively. 19
In addition, although the health risks of exposure to surgical smoke are primarily determined by the toxicity of individual compounds, PAHs, especially low molecular weight PAHs (LMW-PAHs, containing 2–4 benzene rings) with high concentrations in the environment, may have synergistic effects on toxicity. These LMW-PAHs have not been given much attention because they are either nongenotoxic or have weak genotoxicity. Existing studies have indicated that LMW-PAHs such as anthracene and 1-methylanthracene can act as co-carcinogens with the carcinogenic PAH benzo[a]pyrene (B[a]P)20,21; a mixture of phenanthrene and fluorene can act synergistically to cause oxidative damage and induce cell toxicity. 22 In addition to malignant tumors, exposure to LMW-PAHs is associated with the development of lung diseases such as asthma and chronic obstructive pulmonary disease. 23
In this study, in both liver and colorectal surgeries, acenaphthene (containing three benzene rings) was the PAH with the highest concentration. A previous study reported that acenaphthene exerted mutagenic effects on
Furthermore, we found the existing studies analyzing the concentration of PAHs in smoke generated during open surgeries,12,19,26 where naphthalene was the PAH with the highest concentration. For example, Claudio et al. collected smoke from 50 abdominal surgeries and detected naphthalene in 48 of them, except for the 2 laparoscopic surgeries. 27 This was contradictory to our results, as naphthalene was not detected in our samples.
We speculate that the reason for this difference may be the different surgical methods, such as open and laparoscopic surgeries. In the current study, the concentration of PAHs in laparoscopic liver surgery was higher but less toxic than that in laparoscopic gastrointestinal surgery, which may be due to the significant difference in the concentration of individual PAHs produced by the two surgeries. This may be related to various factors such as the surgeon's technique, target tissue, amount of bleeding, type of energy used, power used, duration of surgery, and the patient's body mass index.3,26,28–30 As the current study is a pilot cross-sectional survey, we would control for some variables and analyze how they affect the surgical smoke production of PAHs in future studies, aiming to reduce the production of PAHs from the source.
This study also found that in rectal surgery, PAHs were mainly present in particles with a size of 0.43–0.65 µm, whereas in liver surgery, concentration peaks were observed in particles with a size of 0.65–1.1 and 4.7–5.8 µm, suggesting that PAHs in laparoscopic surgical smoke are more likely to adsorb on smaller particles and be deposited in the lower respiratory tract accompanied with respiratory movements, which may lead to occupational exposure for the medical staff during surgery, even though healthcare workers wear disposable surgical masks during surgeries. A study showed that the filtration efficiency of regular surgical masks for particles with a size of ≤4 µm was only 63.7%. 31 However, the concentration of PAHs attached to particles smaller than 4.7 µm was very high, indicating that most PAHs could still enter and be deposited in the lower respiratory tract along with surgical smoke particles.
This suggests that more strategies should be explored to reduce the medical staff's exposure to surgical smoke. The guideline from the Association of periOperative Registered Nurses (AORN) in the United States recommends ensuring at least 20 air changes per hour in operating rooms as well as equipping ultra-low particulate air filters and smoke evacuator systems specialized for minimally invasive surgeries. For high-risk surgeries that may have potential for aerosol transmission, N95 respirators are recommended. 32 However, there is no mandatory requirement for hospitals to use additional smoke evacuation devices; therefore, the decision of whether to purchase and use these devices depends only on hospitals.
In China, the relevant technical specifications stipulate that the operating room should guarantee 12–24 air changes per hour based on different levels of cleanliness, with a minimum fresh air volume of 15–20 m³/h per square meter; adjustments should be made according to whether electrosurgical devices are used during the surgery. 33 Many surgeons still use only the suction device as the sole smoke evacuation method, which involves using a general negative pressure suction device to suck smoke into another suction canister, which is not effective in removing surgical smoke. Some scholars have also attempted to use fixed-tube needles with balloons, maintaining the lowest possible intra-abdominal pressure and carbon dioxide levels during surgery, to reduce exposure risks34,35 from the gas leakage caused by the pressure needle of the insufflation device used in laparoscopic surgeries. However, these methods face limitations in both clinical implementation and practical efficacy. Therefore, it is necessary to conduct more studies urging healthcare institutions to pay more attention to surgery smoke exposure and explore the effect of different prevention techniques.
Implications for nursing and health policy
Role-specific training programs and continuous education are needed to enhance surgical smoke exposure-related knowledge and practices among medical professions in operating rooms. Policies must support educational efforts and measures, ensuring that the operating room medical staff could balance patient care responsibilities with surgical smoke protection measures.
Limitations
First, due to time and resource constraints, the sample size for collecting surgical smoke was not sufficiently large, and we did not measure gaseous PAHs, which may have an impact on the final study results. Second, the PAH concentrations in our data showed the amount of surgical smoke adsorbed on all inhalable particles, without considering the diffusion of smoke in the environment and the filtering effect of protective devices. Further research should increase the sample size and focus on the impact of gaseous and fine particulate PAHs on healthcare workers.
Conclusion
During laparoscopic hepatectomy and laparoscopic rectal resection, various low-level PAHs may be produced, among which naphthalene has been detected with the highest concentration. PAHs in surgical smoke during these surgeries tend to deposit in the alveoli of the respiratory system, followed by the nasopharynx and the trachea and bronchi. The concentration of PAHs is higher in laparoscopic hepatectomy than in laparoscopic rectal resection, but they are less toxic in laparoscopic hepatectomy. PAHs in surgical smoke may pose long-term potential hazards to the health of healthcare workers, and it is recommended to adopt reasonable protective measures to reduce the associated risk.
