Airborne Particle Concentrations Research Articles

Operating Room Airborne Microbial Load: Nonscrubbed Staff Apparel Matters

BackgroundInfection is a leading cause of total joint arthroplasty failure. In previous studies, we found correlations between the level of contamination, concentrations of airborne particles, and the number of staff present. In this study, we focused on the apparel of nonscrubbed operating room (OR) staff to elucidate their contribution to the airborne microbial load. MethodsWe compared hospital-laundered scrubs to disposable coveralls using 2 methods. (1) Participants entered an isolation chamber with a controlled environment and completed tasks for 1 hour wearing both the approved and alternative OR attire. Settle plates collected viable contaminants that were shed by the participants during testing. (2) Lab members conducted standardized maneuvers in a functional OR that simulated typical movements of the nurse, anesthesiologist, implant representative, and entering/exiting staff. An airborne particle counter and settle plates were positioned throughout the OR. After 1 hour, the staff changed apparel and repeated the test. Each session of both phases consisted of 2 tests by the same individuals on the same day. ResultsThere was approximately a 10-fold difference in the settlement rate of viable particles between groups when employing the isolation chamber. The settle rate for scrubs was 5,519 ± 1,381 colony forming units (CFUs)/m2/h, while the settle rate for coveralls was 505 ± 55 CFUs/m2/h (P = .008). During testing in the OR, 218.7 ± 35 CFUs/m2/h were captured for scrubs, compared with 50.5 ± 13 CFUs/m2/h for the coverall (P < .01). The concentration of airborne particles collected for scrubs was 4,952.1 ± 495 particles/m3 and 1,065 ± 53 particles/m3 for the coveralls (P < .01). This was a 77% and 79% reduction for both measures, respectively. ConclusionsThe open nature of standard scrubs allows contaminated particles to escape into the OR environment, whereas the one-piece design of the coveralls restricts pathways of escape. The results of this study may be helpful when developing hospital infection prevention policies.

Advancing Methodologies for Investigating PM2.5 Removal Using Green Wall System.

Combustion processes are the primary source of fine particulate matter in indoor air. Since the 1970s, plants have been extensively studied for their potential to reduce indoor air pollution. Leaves can retain particles on their surfaces, influenced by factors such as wax content and the presence of hairs. This study introduces an innovative experimental approach using metal oxide particles in an office-like environment to evaluate the depolluting effect of plant walls. Two plant walls were installed in a controlled room, housing three plant species: Aglaonema commutatum 'Silver Bay', Dracaena fragrans, and Epipremnum aureum. Metal oxide particles were introduced via a compressed air blower positioned between the two walls. The concentration of these particles was monitored using PM2.5 sensors, and the deposition of iron (Fe) on the leaves was quantified through Inductively Coupled Plasma Mass Spectrometry (ICP-MS). This novel methodology effectively demonstrated the utility of both real-time sensors and ICP-MS in quantifying airborne particle concentrations and leaf deposition, respectively. The results revealed that Dracaena fragrans had a 44% higher Fe particle retention rate compared to the control (wallpaper). However, further validation through methodological replication is necessary to confirm the reproducibility of these findings.

Accumulation characteristics of precipitation static on rotating wind turbine blades and its influence on the lightning attachment characteristics

AbstractThe linear velocity at the tip of large wind turbine blades can reach 100 m/s, generating static electricity through friction with airborne particles. However, the accumulation characteristics of precipitation static on the blade surface and its impact on the lightning attachment characteristics are rarely reported. The authors constructed a platform for measuring charges on rotating wind turbine blades and employed the electrostatic probe method to obtain the accumulation characteristics of surface charges under different environmental conditions. The experimental results show that positive charges accumulate on the blade surfaces, peaking at 0.69 μC/m2 under experimental conditions. The charge density is positively correlated with airborne particle concentration and blade rotation speed, while it is negatively correlated with relative air humidity. Additionally, the authors developed a model of the electric field distribution on wind turbine blades considering the effects of precipitation static. Simulation results indicate that the electrostatic field induced by precipitation static weakens the field strength in the vicinity of receptors, reaching a minimum of only 38% of the original strength, thereby increasing the probability of lightning protection failure. The findings provide an effective supplement to the lightning attachment mechanism of rotating wind turbine blades.

Radiological complexity of nuclear facilities: an information complexity approach to workplace monitoring.

Nuclear energy is crucial for achieving net-zero carbon emissions. A big challenge in the nuclear sector is ensuring the safety of radiation workers and the environment, while being cost-effective. Workplace monitoring is key to protecting workers from risks of ionising radiation. Traditional monitoring involves radiological surveillance via installed radiation monitors, continuously recording measurements like radiation fields and airborne particulate radioactivity concentrations, especially where sudden radiation changes could significantly impact workers. However, this approach struggles to detect incremental changes over a long period of time in the radiological measurements of the facility. To address this limitation, we propose abstracting a nuclear facility as a complex system. We then quantify the information complexity of the facility's radiological measurements using an entropic metric. Our findings indicate that the inferences and interpretations from our abstraction have a firm basis for interpretation and can enhance current workplace monitoring systems. We suggest the implementation of a radiological complexity-based alarm system to complement existing radiation level-based systems. The abstraction synthesized here is independent of the type of nuclear facility, and hence is a general approach to workplace monitoring at a nuclear facility.

Conversion of a regular patient room to negative pressure at Ancona university hospital (Italy). A combined experimental and numerical investigation

Negative pressure isolation rooms are employed to prevent the spread of infectious diseases to surrounding spaces. This study reports a combined experimental and numerical analysis aimed at reliably assessing the performance of hospital ventilation systems and effectively reducing the risk of airborne infections. The study appraises the enhancement of the safety conditions by retrofitting an existing, positive pressure room ventilation system with a negative pressure and recirculation one. The assessment consisted in experimental measurements of airborne particle concentration and Computational Fluid Dynamics (CFD) simulations with Lagrangian particle tracking of respiratory droplets. The ventilation performance improvement was quantified in terms of recovery rate, contaminant removal effectiveness, particle transfer toward adjacent spaces and probability of infection.Two experimental campaigns were carried out: an ISO standard recovery assessment and a test in real operational conditions. The negative pressure configuration significantly improved the safety inside the patient ward: the recovery rate for droplets with diameter larger than 5 μm increased by a factor three, and the contaminant removal effectiveness after 15 min increased from 45% to 81%. The numerical model for Computational Fluid Dynamics simulation was successfully validated, confirming the ability of the approach to reproduce the undergoing Physics. The negative pressure design eliminated the particle transmission to surrounding spaces, while 2.5% of the emitted respiratory droplets escaped the room in the original existing scenario. The probability of infection after 15 min exposure was reduced by a factor three and peak values reaching 15% were limited to the immediate vicinity of the patients.

Estimating PM levels on an underground metro platform by exploring a new model-based factor research

Over recent decades, the adverse impacts of airborne particles on human health have received wide attention. Elevated PM concentrations on underground platforms might pose a significant public health issue within underground metro systems. This study explores the impact of introducing a new type of train on the concentration of airborne particles on an underground metro platform through statistical modelling, analyses interactions between various factors, and estimates air quality on underground platforms after introducing a new type of train. Based on the data from a long-term field measurement, a linear mixed model, the multi-factor interaction model, which is an expansion of a previous multi-factor model, explored the impacts of train operations, passenger flow, urban background PM levels, ventilation, nighttime maintenance work, and their interactions on hourly PM10, PM2.5, and PM1 values on the platform. The model results show a positive correlation between those factors and platform PM10, PM2.5 and PM1 values, with significant interactions among these factors. The new model has a higher estimate quality than the previous model. Based on the combination of the model and measurement results, the levels of underground PM decreased significantly after replacing the old type of trains with new ones.

Nonthermal plasma air disinfection for the inactivation of airborne microorganisms in an experimental chamber and indoor air.

Airborne transmission of diseases presents a serious threat to human health, so effective air disinfection technology to eliminate microorganisms in indoor air is very important. This study evaluated the effectiveness of a non-thermal plasma (NTP) air disinfector in both laboratory experiments and real environments. An experimental chamber was artificially polluted with a bioaerosol containing bacteria or viruses. Additionally, classroom environments with and without people present were used in field tests. Airborne microbial and particle concentrations were quantified. A 3.0 log10 reduction in the initial load was achieved when a virus-containing aerosol was disinfected for 60min and a bacteria-containing aerosol was disinfected for 90min. In the field test, when no people were present in the room, NTP disinfection decreased the airborne microbial and particle concentrations (P<0.05). When people were present in the room, their constant activity continuously contaminated the indoor air, but all airborne indicators decreased (P<0.05) except for planktonic bacteria (P=0.094). NTP effectively inactivated microorganisms and particles in indoor air.

Urban green spaces and their impact on environmental health: A Global Review

Urbanization has become an irreversible global phenomenon, with a majority of the world's population residing in cities. As urban areas expand, the significance of incorporating green spaces into these landscapes is paramount for environmental health. This study provides a concise overview of a global review that explores the multifaceted impact of urban green spaces on sustainability, well-being, and ecological balance. Urban green spaces play a crucial role in biodiversity preservation, acting as vital habitats for diverse plant and animal species. These spaces contribute to the maintenance of urban ecosystems, fostering ecological balance in densely populated areas. The presence of varied flora and fauna supports environmental health by enhancing biodiversity and promoting a more sustainable urban environment. One of the significant contributions of urban green spaces is their role in improving air quality. Through the natural process of photosynthesis, plants absorb pollutants and release oxygen, serving as an effective filtration system. Trees, in particular, act as natural air purifiers, reducing the concentration of airborne particles and pollutants. This contributes to enhanced air quality, mitigating the adverse effects of urban pollution on environmental health. Urban green spaces also play a pivotal role in temperature regulation, combating the phenomenon of urban heat islands. By providing shade and reducing surface temperatures, greenery helps create a cooler and more comfortable urban living environment. This temperature regulation not only contributes to the well-being of residents but also addresses the challenges posed by rising temperatures in urban areas. Beyond environmental considerations, access to urban green spaces has profound effects on the mental and physical well-being of urban dwellers. These spaces serve as outlets for recreation, exercise, and relaxation, contributing to stress reduction and improved mental health. Additionally, urban green spaces act as hubs for social interaction and community engagement, fostering a sense of belonging and strengthening social cohesion. In conclusion, this global review emphasizes the pivotal role of urban green spaces in promoting environmental health through biodiversity preservation, air quality improvement, temperature regulation, and enhancing overall well-being. Recognizing the multifaceted benefits of these spaces is crucial for guiding sustainable urban development practices worldwide.

Field testing of low-cost particulate matter sensors for Digital Twin applications in nanomanufacturing processes

The EU-project ASINA is testing Low-Cost Particulate Matter Sensors (LCPMS) for industrial monitoring of the concentration of airborne particles, with the purpose of integrating this sensor technology within the data collection layer of Digital Twins (DTs) for manufacturing.This paper shows the results of field performance evaluations carried out with five LCPMS from different manufacturers (Alphasense OPC-N3, Plantower 9003, Sensirion SPS30, Sensirion SEN55 and Tera Sensor NetxPM), during several field sampling campaigns, conducted in four pre-commercial and commercial pilot lines (PLs) that manufacture nano-enabled products, belonging to the ASINA and OASIS H2020 EU-projects [2,28]. Field tests consisted of deploying LCPMS in manufacturing process, measuring in parallel with collocated reference and informative instruments (OPS TSI 3330/CPC TSI 3007), to enable intercomparison.The results show the complexity and differential response of the LCPMS depending on the characteristics of the monitored scenario (PL). Overall, they exhibit uneven precision and linearity and significant bias, so their use in industrial digital systems without proper calibration can lead to uncertain and biased measurements. In this sense, simple linear models are not able to capture the complexity of the problem (non-linear systems) and advanced calibration schemes (e.g. based on machine learning), applied “scenario by scenario” and in operating conditions as close as possible to the final application, are suggested to achieve reliable measurements with the LCPMS.

On the concentration of radon in a polluted city of the Middle East: An insight into its association with PM levels, air properties, and risk assessment

This study was conducted in Ahvaz city, where the concentrations of radon and airborne particles in 10, 2.5, and 1 micrometers, along with meteorological parameters were measured. The measurements were performed in three educational and therapeutic sampling points at both ground and underground levels during cold and hot seasons. The results showed that in 3.17% of the samples, the concentration of radon exceeded the permissible limit recommended by the Environmental Protection Agency (EPA). Factors affecting the increase of radon concentration in indoor air included cold season, underground sampling points, the number of doors and windows as air dilution factor and air exchange, air pressure, and air humidity. The concentration of particles in the air did not have any effect on radon in the indoor air. The annual effective dose of exposure to radon (DR), the annual effective dose of lung (DE), and the risk of lung cancer cases (LCC) during both cold and hot seasons and at ground and underground levels were lower than the permissible values recommended by the International Committee on Radiological Protection (ICRP). We concluded that the increase of particles is neither the cause nor the source of increased indoor air radon. The findings of the present investigation recommend controlling physical indoor air parameters particularly temperature and relative humidity by proper ventilation systems to mitigate the impact of radon exposure on inhabitants.

Effects of triboelectric charging, flooring materials, relative humidity, and shoe sole materials on human walking-induced particle resuspension

Resuspension of settled particles via human activity is one of the primary sources of indoor aerosols. Previous studies have recognized the importance of electrostatic forces on particle resuspension, but the impact has not been well characterized. In this study, we measured the shoe sole electrostatic potential (static charge), airborne particle electrostatic charges, and airborne particle concentration during human stepping under different conditions to assess how these factors affect the resuspension rate of particle size ranging from 0.8 to 8 μm. Six flooring materials (aluminum with and without pattern, carpet, glass, polyvinyl chloride, Teflon, and tile) and three shoe sole materials (EVA, nylon, and rubber) under two relative humidity (RH) levels (normal RH: 60 ± 5% and high RH: 85 ± 5%) were tested. The measured surface static charges of different shoe sole materials before and after human stepping generally agreed with the material's tendency to gain or lose electrons in the triboelectric series. The results also showed that the resuspension rate consistently increased with the increase of particle sizes for all tested scenarios, while it decreased with the increase in RH. Besides, the carpet always gave the highest value for the resuspension rate, while the tile gave the lowest. The data indicated a positive correlation between the charge of resuspended particles and the resuspension rate. In addition, EVA shoe soles generally resulted in higher resuspension rates than shoe soles made of nylon and rubber. This study elucidates the role of electrostatic charge on walking-induced particle resuspension for common materials and helps to assess human exposure to particulate matter.

Air quality particulate-pollution prediction applying GAN network and the Neural Turing Machine

Urban areas in many countries face significant concerns over the presence of aerosol particles and their effects on human health. These particles, which range in size from 1 nanometer to 100 micrometers, can easily penetrate organic matter and transport toxic gas compounds and mineral substances such as carbon monoxide, ozone, nitrogen dioxide, and sulfur dioxide. High concentrations of airborne particles pose serious challenges to health, the economy, the environment, and society, and it is crucial to investigate ways to improve the quality of life for people. The main objective of this study is to develop a framework that accurately predicts aerosol and air quality index (AQI) values in advance by estimating missing data and predicting future data. To achieve this, we propose the DAerosol.GAN.NTM framework, which combines a neural Turing machine with a generative adversarial network (GAN) to address the limitations of previous studies. Our framework outperforms previous methods, including DAerosol.NTM (without GAN) and four baseline studies using Multilayer Perceptron (MLP), Deep Neural Networks (DNN), Long-short Term Memory (LSTM), and Deep LSTM (DLSTM) models, in terms of accuracy, precision, root mean square error (RMSE), mean absolute percentage error (MAPE), and the prediction of aerosol pollution surge hours in advance according to the Time Interval Before and After the Aerosol Event (TIBAAE) criterion.

Background concentrations of airborne, culturable fungi and dust particles in urban, rural and mountain regions

Geographic location and meteorological factors can affect the content of bioaerosol concentrations. This study was conducted to determine the natural background concentrations of culturable fungal spores and dust particles in three different geographical areas. Focus was given to the dominant airborne genera Cladosporium, Penicillium, Aspergillus and the species Aspergillus fumigatus. The influence of weather conditions on the microorganism concentrations in urban, rural and mountain regions were examined. Possible correlations between particle counts and culturable fungal spore concentrations were investigated.125 measurements of the air were conducted using the air sampler MAS–100NT® and the particle counter Alphasense OPC–N3. The analyses of the collected samples were based on culture methods using different media.The highest median of fungal spore concentrations was detected in the urban region and was of 2.0 × 103 CFU/m3 for xerophilic fungi and 1.7 × 103 CFU/m3 for the genus Cladosporium. The concentrations of fine and coarse particles in rural and urban regions were the highest of 1.9 × 107 pa/m3 and 1.3 × 107 pa/m3, respectively. Little cloud cover and slight wind had a positive influence on the concentration of fungal spores. Furthermore, correlations were observed between air temperature and the concentrations of xerophilic fungi as well as the genera Cladosporium. In contrast, relative humidity correlated negatively with total fungi and Cladosporium and no correlation was found with the other fungi. For the region of Styria in summer and early autumn, the natural background concentration for xerophilic fungi ranged between 3.5 × 102 and 4.7 × 103 CFU/m3 air. No significant differences were detected between the fungal spore concentrations in urban, rural and mountainous regions.The data of this study could be used as a reference to compare the natural background concentrations of airborne culturable fungi in further studies concerning air quality assessment.

Effects of portable air filtration on submicrometer- and micrometer-sized particle deposition and concentration in a natural ventilated skilled nursing facility

Older adults are highly vulnerable to respiratory diseases. Effective engineering controls are critical to reduce transmission risk via airborne particles, particularly in spaces where older adults reside (e.g., skilled nursing facilities; SNF). We thus investigated how recirculating portable air filtration (PAF) units and natural ventilation influenced airborne particle travel via the direct aerosol (i.e., representing airborne transmission) and indirect aerosol (i.e., representing fomite transmission) routes. A breathing simulator atomized fluorescein-tagged submicrometer- (0.6–0.7 μm) and micrometer-sized (2 μm) particles simultaneously utilizing a physiologically-correct inhalation-exhalation waveform, with the breathing simulator outlet connected to an anatomically-correct respiratory manikin. Experiments involved two SNF resident rooms, the ‘infector’ and ‘susceptible’ rooms, with the former room containing the breathing simulator (i.e., proxy infected resident) and the latter room representing a susceptible resident's room. Observations revealed that despite PAF units enhancing deposition velocities for submicrometer- and micrometer-sized particles, effective deposition fluxes of submicrometer-sized particles were significantly lower during PAF use versus the Baseline Condition. Further, PAF units increased the effective air exchange rate by ∼3.7–4.5x for submicrometer- and micrometer-sized particles, respectively, resulting in significantly lower particle concentrations (>60%) for these particle sizes versus the Baseline Condition. While natural ventilation significantly reduced submicrometer- and micrometer-sized particle concentration and deposition, cross contamination between rooms was identified when natural ventilation was the singular ventilation solution. Observations validated our previous studies in that particle deposition is non-negligible in smaller rooms with poor ventilation and that PAF units are recommended to supplement natural ventilation and best limit airborne particle concentration and deposition.

124 Laboratory Evaluation of Low-Cost Optical Particle Counters for Occupational Respirable Exposure Measurements

Abstract Direct-reading, time-resolved devices, such as optical particle counters (OPCs) and photometers, offer a unique insight into the temporal and spatial distribution of airborne particles. They can provide a comprehensive picture of changes in concentration of airborne particles in occupational settings and therefore can be used to investigate failures in engineering control systems as well as identify exposures driven by working procedures and methods. In recent years, new developments have led to the commercialisation of low- cost optical-based sensors, which provide particle matter (PM) mass concentrations including PM2.5 and PM10 for environmental monitoring. TNO, NIOSH, and HSE are investigating their application to occupational settings with the aim to produce guidelines for calibration and use. This study evaluated the performance and accuracy of six commercially available low-cost sensors (Airbeam 2, Airveda, Omni Awair, OPC-N3, OPC-R1 and PATS+), in calm air test chambers, against reference devices including an Aerodynamic Particle Sizer (APS 3320), GK2.69 respirable cyclones, and pDR-1500 photometers. Several factors were considered: type of dust (particles having different size distribution, shape and refractive index), within- and between-device variations and exposure pattern (peak and constant concentrations). The devices were subjected to relatively high respirable concentrations (greater than 1 mg/m3) in addition to low concentrations. This presentation will present the results of the laboratory testing with particular focus on their accuracy, response, and calibration for quantitative exposure measurements. The low-cost sensor devices are also being deployed in the workplace for further evaluation and practicality of use.

Critical aspects in occupational exposure assessment with different aerosol metrics in an industrial spray coating process

Engineered Nanomaterials (ENMs) have several uses in various industrial fields and are embedded in a myriad of consumer products. However, there is continued concern over the potential adverse health effects and environmental impacts of ENMs due to their unique physico-chemical characteristics. Currently, there are no specific international regulations for various ENMs. There are also no Occupational Exposure Limits (OEL) regulated by the European Union (EU) for nanomaterials in the form of nano-objects, their aggregates or agglomerates (NOAA). For ENMs the question of which metric to be used (i.e., mass, surface area, number concentrations) to determine the exposure is still not resolved. The aim of this work is to assess the worker exposure by inhalation in an industrial spray coating process by using all three metrics mentioned above. Two target ENMs (N-doped TiO2, TiO2N and AgNPs capped with a quaternized hydroxyethyl-cellulose, AgHEC) generated for industrial-scale spraying processes were considered. Results showed that the averaged particle number concentration (10–100 nm) was below 2.7 104 cm−3 for both materials. The Lung Deposited Surface Area (LDSA) was in the range between 73 and 98 μm2cm−3 and the particle mass concentration (obtained by means of ICP-EOS off-line analysis) resulted below 70 μg m−3 and 0.4 μg m−3 for TiO2 and Ag, respectively. Although, the airborne particles concentration compared well with the NIOSH Recommended Exposure Level (REL) limits the contribution to the background, according to EN 17058 (Annex E) was significant (particularly in the particle number and PM1 mass concentrations). We successfully evaluated the worker exposure by means of the different airborne particles' metrics (number, surface and mass concentrations). We concluded that worker exposure assessment involving ENMs is a complex procedure with requires both real time and off-line measurements and a deep investigation of the background.

The effect of airborne Palladium nanoparticles on human lung cells, endothelium and blood – A combinatory approach using three in vitro models

A better understanding of the mechanisms behind adverse health effects caused by airborne fine particles and nanoparticles (NP) is essential to improve risk assessment and identification the most critical particle exposures. While the use of automobile catalytic converters is decreasing the exhausts of harmful gases, concentrations of fine airborne particles and nanoparticles (NPs) from catalytic metals such as Palladium (Pd) are reaching their upper safe level. Here we used a combinatory approach with three in vitro model systems to study the toxicity of Pd particles, to infer their potential effects on human health upon inhalation. The three model systems are 1) a lung system with human lung cells (ALI), 2) an endothelial cell system and 3) a human whole blood loop system. All three model systems were exposed to the exact same type of Pd NPs. The ALI lung cell exposure system showed a clear reduction in cell growth from 24 h onwards and the effect persisted over a longer period of time. In the endothelial cell model, Pd NPs induced apoptosis, but not to the same extent as the most aggressive types of NPs such as TiO2. Similarly, Pd triggered clear coagulation and contact system activation but not as forcefully as the highly thrombogenic TiO2 NPs. In summary, we show that our 3-step in vitro model of the human lung and surrounding vessels can be a useful tool for studying pathological events triggered by airborne fine particles and NPs.

Determination of Particulate Matter in Dental Clinics: The Effectiveness of Different Air Purifiers and the Central Ventilation System

The purpose of this study was to measure the number and concentration of airborne particulates occurring in a dental clinic while performing dental procedures, with and without the simultaneous use of air purifier systems and a central ventilation system. The initial background concentrations of airborne particulates recorded during dental procedures, i.e., grinding of natural teeth and metals, without the use of air purifier systems, and with closed windows, reduced by 68% for ΡΜ10, 77% for ΡΜ2.5, and 81% for ΡΜ1 when the same procedures were carried out with the simultaneous use of air purifying systems. In addition, measurements taken during patient treatment showed that an operating central ventilation system contributes to the reduction of airborne particles by a significant 94% for ΡΜ10, 94% for ΡΜ2.5, and 88% for ΡΜ1 compared to dental procedures performed without the simultaneous use of air purifiers. Air purifying systems were also observed to contribute to the further reduction of airborne particulates when dental procedures were performed in combination with an operating central ventilation system. The majority of particles captured had diameters of 0.25-0.30 μm, 0.5 μm, and 1.0-4.0 μm, while particles with diameters of &gt;5.0 μm were the least commonly observed in all experiments. Finally, a statistically significant difference between concentrations of particulate matter was recorded during dental procedures carried out with and without the simultaneous operation of air purifiers and central ventilation system increasing the risk of SARS-CoV-2 virus contamination in dental clinics due to the aerosols emitted by the use of common dental instruments during standard treatments.

Contribution to the building of a weather information service for solar panel cleaning operations at Diass plant (Senegal, Western Sahel)

Abstract The accumulation of dust on the surface of solar panels reduces the amount of sunlight reaching the solar cells and results in a decrease in panel performance. To avoid this loss of production and thus, to improve the performance capacity, solar panels must be cleaned frequently. The West African region is well known for its high solar energy potential. However, this potential can be reduced by the high occurrence of dust storms during the year. This article aims to provide a contribution to the construction of a meteorological information service for solar panel cleaning operations at Diass solar plant in Senegal (Western Sahel). It is based on a full year in situ experiment comparing the power loss due to dust between solar panels cleaned at different frequencies and those not cleaned. The model to determine the cleaning frequencies is based on the deposition rate of airborne particles, the concentration of airborne particles, and the density of the dust that has a major impact on the power loss. Cleaning frequencies are presented at seasonal scale because in the study area, dust episodes differ according to the seasons. A cost–benefit analysis is also performed to demonstrate the advantage of using weather information service to support the dust cleaning operations at Diass plant. As results, it is found that cleaning every 3 weeks is required during the dry seasons, December–January–February and March–April–May. During the rainy season, cleaning every 5 weeks is recommended in June–July–August, while in September–October–November cleaning every 4 weeks is sufficient to maintain an optimal performance of the solar panel. The total costs of cleaning operations based on these results are reduced compared to the current costs of cleaning and the benefits are much higher than without cleaning action.

Evaluation of indoor environmental quality, personal cumulative exposure dose, and aerosol transmission risk levels inside urban buses in Dalian, China.

The transmission of pollutants in buses has an important impact on personal exposure to airborne particles and spread of the COVID-19 epidemic in enclosed spaces. We conducted the following real-time field measurements inside buses: CO2, airborne particle concentration, temperature, and relative humidity data during peak and off-peak hours in spring and autumn. Correlation analysis was adopted to evaluate the dominant factors influencing CO2 and particle mass concentrations in the vehicle. The cumulative personal exposure dose to particulate matter and reproduction number were calculated for passengers on a one-way trip. The results showed the in-cabin CO2 concentrations, with 22.11% and 21.27% of the total time exceeding 1000ppm in spring and autumn respectively. In-cabin PM2.5 mass concentration exceeded 35μm/m3 by 57.35% and 86.42% in spring and autumn, respectively. CO2 concentration and the cumulative number of passengers were approximately linearly correlated in both seasons, with R value up to 0.896. The cumulative number of passengers had the most impact on PM2.5 mass concentration among tested parameters. The cumulative personal exposure dose to PM2.5 during a one-way trip in autumn was up to 43.13μg. The average reproductive number throughout the one-way trip was 0.26; it was 0.57 under the assumed extreme environment. The results of this study provide an important basic theoretical guidance for the optimization of ventilation system design and operation strategies aimed at reducing multi-pollutant integrated health exposure and airborne particle infection (such as SARS-CoV-2) risks.