Laser Particle Counter Research Articles

Longitudinal Analysis of Annual PM2.5 Concentration Variations in Blantyre City, Malawi

This study presents current levels of fine particulate matter, with aerodynamic diameter of less than 2.5 micrometre (PM2.5) in the city of Blantyre, Malawi measured between June 2021 to May 2022. PM2.5 measurements were done in 18 different locations (spanning greater than 2 km apart) using Dylos DC1100 PRO Laser Particle Counter (2018 model). The sampling points were; 3 school campuses, 3 hospitals, 3 industrial areas, 3 open markets, 3 residential areas, and 3 commercial/ business centres (CBC) of Blantyre. PM2.5 monitoring was conducted between 10:00-12:00 hours and 15:00-17:00 hours local time. The results showed that the hourly mean PM2.5 concentrations (µg/m3) for the 10:00-12:00 time period were; 43 ± 23 µg/m3 for school campuses, 35 ± 16 µg/m3 for hospitals, 62 ± 38 µg/m3 for industrial areas, 44 ± 26 µg/m3 for markets, 40 ± 21 µg/m3 for residential areas and 35 ± 16 µg/m3 for CBC. The results showed that the hourly mean PM2.5 concentrations (µg/m3) for the 15:00-17:00 time period were; 38 ± 22 µg/m3 for school campuses, 34 ± 18 µg/m3 for hospitals, 57 ± 37 µg/m3 for industrial areas, 42 ± 25 µg/m3 for markets, 36 ± 23 µg/m3 for residential areas and 34 ± 18 µg/m3 for CBC. Significant increases of PM2.5 levels were observed in school campuses, residential areas and CBC during the months of June-October, which are windy and drier. On the other hand, lowest concentration of PM2.5 was observed during the warm season (November-March) across the sampling locations over Blantyre. Based on these findings, this study recommends further investigation of long-term concentration of PM2.5 in Blantyre city because it is hazardous and likely to cause health implications to the local population. Furthermore, interventions should be sought to reduce PM2.5 concentration in the city.

Source Apportionment of Air Quality Parameters and Noise Levels in the Industrial Zones of Blantyre City

The increase in industrial activities has raised concerns regarding air quality in urban areas within Malawi. To assess the source apportionment of air quality parameters (AQPs) and noise levels, concentrations of AQPs (CO, TSP, PM 2.5, PM10) and noise levels were monitored at 15 sites in Makata, Limbe, Maselema, Chirimba, and Maone during dry and wet seasons, respectively. Active mobile multi-gas monitors and a Dylos DC1100 PRO Laser Particle Counter (2018 model) were used to monitor AQPs, while Integrated Sound Level Meters were used to measure noise levels. Monitoring and analysis were guided by the World Health Organization (WHO) and Malawi Standards (MS). A Positive Matrix Factorization (PMF) model was used to determine source apportionment of AQPs, and matrix trajectories analysed air mass movement. In the wet season, the average concentration values of CO, TSP, PM10, and PM2.5 were 0.49 ± 0.65 mg/m3, 85.03 ± 62.18 µg/m3, 14.65 ± 8.13 µg/m3, and 11.52 ± 7.19 µg/m3, respectively. Dry season average concentration values increased to 1.31 ± 0.81 mg/m3, 99.86± 30.06 µg/m3, 24.35 ± 9.53 µg/m3, and 18.28 ± 7.14 µg/m3. Noise levels remained below public MS and WHO standards (85 dB). Positive correlations between AQPs and noise levels were observed, strengthening from weak in the dry season to moderately strong in the wet season. PMF analysis identified key factors influencing AQPs accumulation, emphasizing the need for periodic sampling to monitor seasonal pollution trends, considering potential impacts on public health and environmental sustainability. Further studies should look at factors affecting the dynamics of PMF in Blantyre City.

Air quality assessment in (semi) liquid food packaging environments

This study aimed to assess the prevalence of airborne microorganisms within the packaging areas of (semi) liquid food product facilities, considering the impact of outdoor microbiological air, seasonal fluctuations, rural-urban differences and environmental parameters such as temperature and relative humidity. Additionally, the effectiveness of both natural ventilation and air handling units were evaluated against total viable and non-viable particulate matter.Air samples were collected from the packaging areas of fourteen diverse (semi) liquid food producers and the outdoor environment in Flanders, Belgium, over the course of four separate days from January to September 2022. Airborne microorganisms, including total mesophilic plate count (TMPC) and yeast and mould (Y&M) count, were sampled using impaction and settle plate methods on Plate Count Agar and Rose Bengal Chloramphenicol agar, respectively. Simultaneously, a laser particle counter was used to collect and categorise particles into six size-based channels, while environmental parameters were monitored using a hygrometer.The study revealed a wide range of concentrations of airborne microorganisms across various companies (indoor TMPC ranging from 1.35 ± 0.65 log cfu/m3 to 3.42 ± 0.16 log cfu/m3 and Y&M count ranging from 1.22 ± 0.65 log cfu/m3 to 3.10 ± 0.08 log cfu/m3), irrespective of outdoor air quality. Neither relative humidity nor temperature exhibited any influence on TMPC and Y&M count. Companies equipped with high-efficiency filter air handling unit showed decreased concentrations of airborne microorganisms, although this trend did not align with their total particle counts. Moreover, no correlation was observed between total particle count and either TMPC or Y&M count. Additionally, impaction and sedimentation methods demonstrated a strong correlation.In conclusion, the diversity in airborne microorganism concentrations within food packaging areas is influenced by multiple factors, with air handling unit filters playing a pivotal role. High-efficiency filters were found to reduce microorganism levels, but their impact on total particle counts was less pronounced.

Analysis of aerosol generation during Er:YAG laser-assisted caries treatment: A randomized clinical trial.

Maintaining biosafety in dental practice involves the effective elimination of aerosols produced during dental treatment. To assess the quantity of aerosols and aerobic bacteria in the air during the treatment of caries. The study involved 60 patients with a total of 60 molar teeth (n = 60) in the mandible who were divided into 2 groups based on caries treatment method. Group 1 (G1, n = 30) received treatment with a conventional dental turbine (W&H Synea TA-98LC; W&H, Burmoos, Austria), while group 2 (G2, n = 30) underwent treatment with an Er:YAG (erbium-doped yttrium aluminium garnet) laser (LightWalker, Fotona, Slovenia). Measurements of aerosol particles between 0.3 Ęm and 10.0 Ęm near the operatorfs mouth were taken using the PC200 laser particle counter (Trotec GmbH, Schwerin, Germany). The number of aerobic bacteria in the air was determined using 60 Petri plates with a microbiological medium (Columbia agar with 5% sheep blood) and the sedimentation method. A control group (G3) was established to measure initial aerosol levels and initial total number of bacteria colony-forming units (CFUs) before each treatment. In G1 (dental turbine), the median value of aerosol particles was 57,021 (42,564.67,568), while in G2 (Er:YAG laser), it was significantly lower at 33,318 (28,463.35,484) (p < 0.001). The median total bacteria count per cubic meter of air in G1 (conventional dental turbine + high volume evacuator (HVE)), G2 (Er:YAG laser + HVE) and G3 (control group before caries treatment) were 734 (420.988), 158 (96.288) and 48 (32.74), respectively, with a statistically significant difference between the groups (p < 0.001). The use of Er:YAG laser during caries treatment resulted in a 41.6% reduction in aerosol amounts and a 78.5% decrease in the total bacterial count (TBC) compared to treatment with a dental turbine.

Investigation of the Emission Rate of Particles when Musicians Play Wind, Woodwind, and Brass Instruments

In the context of the high risk of airborne transmission of COVID-19, the question of the production of particles while playing wind instruments is highly relevant. Therefore, in this study, 23 professional musicians played their instruments in a cleanroom in cleanroom-grade clothing. The most common orchestral wind instruments flute, oboe, clarinet, and trumpet were therefore chosen. Aerosol measurements using a laser particle counter were conducted to quantify the emission rate of respiratory particles. Orchestral excerpts as well as sustained tones in two dynamic levels were played. The emitted particles were mostly in a submicron size range. For all instruments besides the clarinet, an influence of the loudness of playing on the emission rate could be observed. The emission rates for all musical instruments were independent of the passages played. Flute and oboe showed similar emission rates but lower than the values for clarinet and trumpet. While playing a note with a small volume, the flute, oboe, and trumpet have a similar emission rate as found for speaking.

Design of a high counting efficiency sensor for 1.0 cubic feet per minute laser particle counter.

Based on the theory of Mie scattering, an optical sensor for a 1.0 cubic feet per minute laser particle counter is developed in this paper. First, an illumination optical path relying on aspherical lens and cylindrical lens for laser shaping was designed, and a narrow optical spot with the illumination in the vertical direction of the photosensitive area approximately distributed as a flat top was obtained. Second, the scattering light path was designed by using the theory of Mie scattering and geometric optics method. Then, the structure of the sampling air path was designed with reference to the principle of Laval nozzle, and the particle flow trajectory was verified by simulation using the fluid dynamics software Ansys Fluent. Finally, the performance of the optical sensor was measured with polystyrene latex (PSL) particles, and the results showed that the counting efficiency of the 0.3μm particle size channel met the requirement of 50% ± 20% and the 0.5μm particle size channel met the requirement of 100% ± 10%, which complied with the ISO 21501-4 standard.

Quantitative Evaluation of Aerosols Produced in the Dental Office during Caries Treatment: A Randomized Clinical Trial.

Effective removal of aerosols generated during dental treatment is crucial for maintaining biosafety in dental practice. This study aimed to measure the aerosol amount and the number of aerobic bacteria in the air during caries treatment. The study involved 50 molar teeth (n = 50) in the mandible in 50 patients divided into two groups based on the type of a high-volume evacuator (HVE); G1 (n = 25) conventional HVE (EM19 EVO, Monoart® Euronda, Vicenza, Italy) and G2 (n = 25) a new, wider, customized HVE. The PC200 laser particle counter (Trotec GmbH, Schwerin, Germany) was used to measure aerosol particles in a range of 0.3-10.0 μm near the operator's mouth. The study used 60 microbiological plates with a microbiological medium (Columbia Agar with 5% Sheep Blood) to check the number of aerobic bacteria in the air. The mean value of aerosol particles in the G1 group (conventional HVE) was 54,145 ± 7915, while in the G2 group (test, wider evacuator) was lower and amounted to 32,632 ± 1803. (p < 0.001). The median total bacteria count in the air per cubic meter in control, G1 (HVE), and G2 (NEW-HVE) groups were 50 [36-60]; 772 [643-881]; 120 [92-139], respectively. (p < 0.05). Gram-positive cocci were the predominant bacteria in the plates: Micrococcus sp. (50%), Bacillus species (36.4%), Staphylococcus epidermidis (3.8%), Staphylococcus saprophyticus (3.8%). the application of the wider high-volume evacuator increases the air purity during caries treatment as well as the biological safety of a dental office.

An experimental study on the resuspension characteristics of evaporation residues of human exhaled droplets on medical clothing

Resuspension of the evaporation residues of the human exhaled droplets deposited on medical clothing during the daily activities of medical staff poses the risk of aerosol transmission of respiratory infectious diseases. We built a resuspension experimental chamber and used vibration devices to simulate the motions of medical staff. A laser particle counter was used to make real-time measurements of resuspended particles in six size channels from 0.3 to 25 μm. The experimental results showed that the resuspension rate of particles under continuous high-intensity vibration ranged from 0.97 × 10−3 to 7.89 × 10−3 h−1 with a mean value of 4.07 × 10−3 h−1, which was at a quite low level. The mass fraction of the resuspension in the residues on the clothing was only 0.04–0.33%. The particles with an aerodynamic diameter of 10–25 μm accounted for approximately 83.2% of the total mass of the resuspension. The resuspension mass in the treatment groups was an average of 0.83 μg higher than that in the control groups. The results revealed that the residues of the exhaled droplets deposited on medical clothing are not prone to resuspension, and the chance of respiratory pathogens transmitting through evaporation residue resuspended from the medical clothing is low.

Effective use of an extraoral vacuum in preventing the dispersal of particulate matter from metal dental materials.

When dentists adjust prostheses at the dental chairside, particulate matter (PM) from the dental material is dispersed. Little is known about the effective use of an extraoral vacuum (EOV) in preventing PM dispersal. This study aimed to evaluate the effective use of an EOV in preventing the dispersal of metal PM in dental offices. The following experimental conditions were planned: the distance from the EOV to the metallic materials (50, 100, 150, and 200 mm), the horizontal angle between the long axis of the micromotor handpiece and EOV (0°, 45°, and 90°), and the operating time of the EOV (during grinding, during grinding and 1 min thereafter, during grinding and the preceding 1 min, 1 min before and after grinding, and during grinding). Carborundum and silicone points were used for grinding and PM dispersal. Diameters (0.3, 0.5, 1.0, and 3.0 μm) were measured using a laser particle counter. Depending on the instrument used to grind, there were undetectable PMs of different diameters (Carborundum point: 0.3 and 0.5 μm, Silicone point: 0.3 μm). PMNs were reduced as the distance from the EOV to metal materials decreased. Operating the EOV before grinding along the long axis of the micromotor handpiece was effective in reducing the PMNs. PMNs dispersed when grinding metals were effectively reduced by positioning the EOV closer to the grinding surface (within 150 mm) along the long axis of the micromotor handpiece and operating the EOV before grinding.

Measurements of Tire and Roadway Dust Particulates in Chelyabinsk

Harmful emissions from tire wear and roadway wear are released into the air during the operation of vehicles. Particulate road dust contains carcinogenic substances. The amount and dispersion of particulate matter in road dust was determined with a portable laser particle counter. On asphalt roads, 75% of the harmful emissions were 0.3 µm particulate matter. On dirt roads, 95% of emissions were from particles less than 1 µm. The amount of large fractions of harmful emissions did not exceed 1.5%, regardless of traffic intensity. 30 m from the roadway, the concentration of harmful substances reduced by five- to sevenfold. By 2030, the number of vehicles in Chelyabinsk will increase by 25%. This will increase the amount of harmful emissions from tire and roadway wear by 20 tons per year.

Automatically Controlled Dust Generation System Using Arduino.

A dust generator was developed to disperse and maintain a desired concentration of airborne dust in a controlled environment chamber to study poultry physiological response to sustained elevated levels of particulate matter. The goal was to maintain an indicated PM10 concentration of 50 µg/m3 of airborne dust in a 3.7 m × 4.3 m × 2.4 m (12 ft × 14 ft × 8 ft) controlled environment chamber. The chamber had a 1.5 m3/s (3200 cfm) filtered recirculation air handling system that regulated indoor temperature levels and a 0.06 m3/s (130 cfm) exhaust fan that exchanged indoor air for fresh outdoor air. Dry powdered red oak wood dust that passed through an 80-mesh screen cloth was used for the experiment. The dust generator metered dust from a rectangular feed hopper with a flat bottom belt to a 0.02 m3/s (46 cfm) centrifugal blower. A vibratory motor attached to the hopper ran only when the belt was operated to prevent bridging of powdered materials and to provide an even material feed rate. A laser particle counter was used to measure the concentration of airborne dust and provided feedback to an Arduino-based control system that operated the dust generator. The dust generator was operated using a duty cycle of one second on for every five seconds off to allow time for dispersed dust to mix with chamber air and reach the laser particle counter. The control system maintained an airborne PM10 dust concentration of 54.92 ± 6.42 µg/m3 in the controlled environment chamber during six weeks of continuous operation using red oak wood dust. An advantage of the automatically controlled dust generator was that it continued to operate to reach the setpoint concentration in response to changes in material flow due to humidity, partial blockages, and non-uniform composition of the material being dispersed. Challenges included dust being trapped by the recirculation filter and the exhaust fan removing airborne dust from the environmental chamber.

Air flow and sediment transport dynamics on a foredune with contrasting vegetation cover

AbstractWind flow and sediment transport across a northern California beach‐foredune system with two adjacent vegetation types are examined for the same incident wind conditions. The invasive Ammophila arenaria was taller (c. 1 m) with denser coverage than the neighbouring Elymus mollis alliance canopy (c. 0.65 m), which consisted of a variety of interspersed native plants. Wind flow was measured with rotating cup and sonic anemometry, while sediment transport was measured using laser particle counters. Wind speed profiles over the two canopies were significantly different because of differing vegetation height, coverage density, and stem stiffness. In both cases, there was a lower zone of semi‐stagnant air (below about 0.3 m) that transitioned upward to a shear zone comprising the upper part of the canopy and immediately above. The shear zone above the Elymus canopy was relatively thin (confined to 0.3–0.5 m above‐ground) whereas the shear zone in the Ammophila canopy was thicker extending from a height of about 0.5h (h is average plant height) to about 1.5h. Vertical profiles of Reynolds shear stress (RSS) and turbulence kinetic energy (TKE) are consistent with the shear layer structure over these two contrasting vegetation canopies. The degree of topographically‐forced and vegetation‐enhanced flow steering was significant, with Ammophila strongly shifting the highly oblique (55°) incident wind to essentially shore‐perpendicular trajectories. In comparison, the shore‐perpendicular steering effect was not as pronounced for the Elymus canopy. Sediment transport intensity on the beach was continuous, but decreased progressively to the dune toe, and then dropped to essentially zero once the vegetation canopy was encountered (on the stoss slope). Overall, the study illustrates the significant differences in wind flow and turbulence conditions that may occur in contrasting plant canopies on foredunes, suggesting that greater attention needs to be placed on vegetation roughness characteristics in models of foredune morphodynamics and sediment transport potential.

Pre-adolescent children exhibit lower aerosol particle volume emissions than adults for breathing, speaking, singing and shouting.

Speaking and singing are activities linked to increased aerosol particle emissions from the respiratory system, dependent on the utilized vocal intensity. As a result, these activities have experienced considerable restrictions in enclosed spaces since the onset of the COVID-19 pandemic due to the risk of infection from the SARS-CoV-2 virus, transmitted by virus-carrying aerosols. These constraints have affected public education and extracurricular activities for children as well, from in-person music instruction to children’s choirs. However, existing risk assessments for children have been based on emission measurements of adults. To address this, we measured the particle emission rates of 15 pre-adolescent children, all eight to ten years old, with a laser particle counter for the test conditions: breathing at rest, speaking, singing and shouting. Compared with values taken from 15 adults, emission rates for breathing, speaking and singing were significantly lower for children. Particle emission rates were reduced by a factor of 4.3 across all conditions, whereas emitted particle volume rates were reduced by a factor of 4.8. These data can supplement SARS-CoV-2 risk management scenarios for various school and extracurricular settings.

Detection of nanoparticles suspended in a light scattering medium

Intentionally intensifying the light scattering of medium molecules can allow the detection of suspended nanoparticles under conditions not suitable for conventional optical microscopies or laser particle counters. Here, we demonstrate how the collective light scattering of medium molecules and nanoparticles is imaged in response to the power, frequency, and oscillating direction of the incident light wave electric field, and how this response can be used to distinguish between nanoparticles and microparticles, such as viruses or bacteria. Under conditions that the medium light scattering is intensified, suspended nanoparticles appear as magnified shiny moving dots superimposed on the quasi-steady background of medium light scattering. Utilizing the visual enlargement resulted from the enhanced light scattering and possible light interference, we can detect directly suspended nanoparticles that are much smaller than visible light wavelengths even in unopened water bottles or other large containers. This suggests new approaches for detecting nanoparticles with many potential applications.

Aerosol emission in professional singing of classical music

In this study, emission rates of aerosols emitted by professional singers were measured with a laser particle counter under cleanroom conditions. The emission rates during singing varied between 753 and 6093 particles/sec with a median of 1537 particles/sec. Emission rates for singing were compared with data for breathing and speaking. Significantly higher emission rates were found for singing. The emission enhancements between singing and speaking were between 4.0 and 99.5 with a median of 17.4, largely due to higher sound pressure levels when singing. Further, significant effects of vocal loudness were found, whereas there were no significant differences between the investigated voice classifications. The present study supports the efforts to improve the risk management in cases of possible aerogenic virus transmission, especially for choir singing.

Potential health risks due to in-car aerosol exposure across ten global cities

Car microenvironments significantly contribute to the daily pollution exposure of commuters, yet health and socioeconomic studies focused on in-car exposure are rare. This study aims to assess the relationship between air pollution levels and socioeconomic indicators (fuel prices, city-specific GDP, road density, the value of statistical life (VSL), health burden and economic losses resulting from exposure to fine particulate matter ≤2.5 µm; PM2.5) during car journeys in ten cities: Dhaka (Bangladesh); Chennai (India); Guangzhou (China); Medellín (Colombia); São Paulo (Brazil); Cairo (Egypt); Sulaymaniyah (Iraq); Addis Ababa (Ethiopia); Blantyre (Malawi); and Dar-es-Salaam (Tanzania). Data collected by portable laser particle counters were used to develop a proxy of car-user exposure profiles. Hotspots on all city routes displayed higher PM2.5 concentrations and disproportionately high inhaled doses. For instance, the time spent at the hotspots in Guangzhou and Addis Ababa was 26% and 28% of total trip time, but corresponded to 54% and 56%, respectively, of the total PM2.5 inhaled dose. With the exception of Guangzhou, all the cities showed a decrease in per cent length of hotspots with an increase in GDP and VSL. Exposure levels were independent of fuel prices in most cities. The largest health burden related to in-car PM2.5 exposure was estimated for Dar-es-Salam (81.6 ± 39.3 μg m−3), Blantyre (82.9 ± 44.0) and Dhaka (62.3 ± 32.0) with deaths per 100,000 of the car commuting population per year of 2.46 (2.28–2.63), 1.11 (0.97–1.26) and 1.10 (1.05–1.15), respectively. However, the modest health burden of 0.07 (0.06–0.08), 0.10 (0.09–0.12) and 0.02 (0.02–0.03) deaths per 100,000 of the car commuting population per year were estimated for Medellin (23 ± 13.7 μg m−3), São Paulo (25.6 ± 11.7) and Sulaymaniyah (22.4 ± 15.0), respectively. Lower GDP was found to be associated with higher economic losses due to health burdens caused by air pollution in most cities, indicating a socioeconomic discrepancy. This assessment of health and socioeconomic parameters associated with in-car PM2.5 exposure highlights the importance of implementing plausible solutions to make a positive impact on peoples’ lives in these cities.

Health Risk Associated with Near-Road Ambient Air Concentration of Particulate Matter in Mukono Municipal Council, Uganda

More than 98% of urban centres exceeding 100,000 people in Low and Middle-Income Countries (LMICs), do not meet the WHO air quality limits. Data on air pollution from LMICs is scarce. We measured the mean concentrations of near-road PM2.5 in the period of Aug.-Dec. 2020, described the Mukono Municipality’s near-road populations’ exposure to PM2.5, and assessed the associated health risk. PurpleAir PA-II laser particle counters, measured near-road ambient air PM2.5 concentration in Mukono Municipality during the period of 09/1/20 to 12/04/20. Excel Toolpak was used for data analysis and the health risk assessed with the WHO AirQ+ tool. The mean ambient near–road PM2.5 in Mukono Municipality were 30.97, 33.84 and 47.74 ug/m3for background, near-unpaved and near-paved roads, respectively. Mukono Municipality’s population was exposed to ambient PM2.5 concentrations higher than the WHO annual limit of 10 ug/m3. This level of air pollution is associated with preventable annual premature deaths of up to 133.11 per 100,000 population. Vehicles were assumed to be the predominant source of near-road ambient air PM2.5 pollution. The Municipality’s population was exposed to near-road ambient air PM2.5 exceeding the WHO annual limit by as much as *4.7 for the paved roads, *3.3 for the unpaved roads and *3 for the background. This leads to increased risk of preventable premature deaths in the Municipality.Mukono Municipality could monitor PM2.5; guide developers to placebuildings more than 100 meters away from roadsides and should promotepolicies for newer vehicles on Ugandan roads.

Comparison of surgical smoke between open surgery and laparoscopic surgery for colorectal disease in the COVID-19 era.

BackgroundSurgical smoke during operation is a well-known health hazard for medical staff. This study aimed to investigate the dynamics of surgical smoke during open surgery or laparoscopic surgery for colorectal disease.MethodsThis study quantitated particulate matter (PM) counts as part of surgical smoke in 31 consecutive patients who underwent colectomy at the Niigata City General Hospital using a laser particle counter. Particles were graded by size as ≤ 2.5 μm PM (PM2.5) or > 2.5 μm PM (large PM). Operative procedures were categorized as either open surgery (n = 14) or laparoscopic surgery (n = 17).ResultsThe median patient age was 72 (range 41–89) years and 58.1% were male. The total PM2.5, PM2.5 per hour, and maximum PM2.5 per minute counts during operation were significantly higher in open surgery than in laparoscopic surgery (P = 0.001, P < 0.001, and P = 0.029, respectively). Large PM counts (total, per hour, and maximum per minute) were also higher in the open surgery group than in the laparoscopic surgery group. The maximum PM2.5 concentration recorded was 38.6 µm/m3, which is considered “unhealthy for sensitive groups” according to the U.S. Environment Protection Agency air quality index standards, if it was a 24-h period mean value.ConclusionExposure to surgical smoke is lower during laparoscopic surgery than during open surgery for colorectal diseases.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00464-021-08394-1.

Aerosol emission of adolescents voices during speaking, singing and shouting.

Since the outbreak of the COVID-19 pandemic, singing activities for children and young people have been strictly regulated with far-reaching consequences for music education in schools and ensemble and choir singing in some places. This is also due to the fact, that there has been no reliable data available on aerosol emissions from adolescents speaking, singing, and shouting. By utilizing a laser particle counter in cleanroom conditions we show, that adolescents emit fewer aerosol particles during singing than what has been known so far for adults. In our data, the emission rates ranged from 16 P/s to 267 P/s for speaking, 141 P/s to 1240 P/s for singing, and 683 P/s to 4332 P/s for shouting. The data advocate an adaptation of existing risk management strategies and rules of conduct for groups of singing adolescents, like gatherings in an educational context, e.g. singing lessons or choir rehearsals.

Field test of the accuracy of laser particle counters to measure aeolian sediment flux

Abstract In this study we tested to what extent grain count data from a laser particle counter, when enriched with granulometric data, can lead to accurate measurements of aeolian sediment fluxes in the field. Field experiments were conducted at Koksijde beach (Belgium) with a vertical array of five Wenglor fork sensors and co-located vertically stacked mesh sand traps. Sand collected in the traps was used to both obtain the reference values for sediment flux as well as to obtain granulometric data at the five Wenglor sensor elevations. Grain counts were transformed to sediment fluxes by combining the granulometric data with the grain size dependent, effective detection width concept. It was found that the limitation of the Wenglor sensor to have a minimum detectable grain size, well within the diameter range of sand grains in transport, could easily be corrected for through a linear relation of Wenglor detectable sediment flux with total sediment flux. However, we found that the Wenglor derived fluxes deviated from the sand trap derived fluxes in an inconsistent manner, both in the vertical and over time, which made us conclude that there is no uniform calibration possible to match the Wenglor data with the trap data. This suggests that further studies using optical aeolian transport sensors should focus on analysing the raw photoelectric signal rather than on internally processed count data.