Search Results (26)

The characterization of airborne submicrometric composite structures’ debris is a challenge in the field of environmental monitoring and control. The work presented here aims to develop a new quantitative method to measure elemental mass concentrations via particle sampling and Transmission Electron Microscopy—Energy-Dispersive X-ray Spectroscopy (TEM-EDS). The principle is to collect airborne particles on a porous TEM grid, then add a certain mass of reference particles, and compare the relative mass percentages of elements from reference and sample particles via EDS. Diverse pairs of airborne particles (RbCl, CsCl, NaCl, SrCl₂, Ga(NO₃)₃, braking particles) were deposited on one TEM grid, and the experimental elemental mass ratios were measured by EDS and compared with the theoretical values. Results show that the quantitative and homogeneous collection of reference particles, such as RbCl, on the TEM grid could be suitable. For all the tested conditions, the absolute deviations between the theoretical elemental mass ratios and the experimental ratios remain lower than 8%. Thus, the mass concentration of Fe from the braking aerosol is calculated as 107 µg/m³. Compared to the cumbersome real-time instrument, this new method for mass characterization appears to be convenient, and requires a short time of aerosol sampling at the workplace. This approach ensures safety and practicability when assessing, e.g., the exposure risk of hazardous materials. Full article

Rural villages function as relatively self-sustained production and living units with well-developed infrastructure. In this setting, investigating the transmission pathways of airborne biological particles, including pathogenic microorganisms, is pivotal for ensuring the health of residents. This study investigated the sources and dispersion of biogenic particulate matter in rural ambient air and factors influencing their behavior. Potential bioaerosol sources including livestock farming areas, composting sites, garbage dumps, and sewage treatment facilities were investigated using a calibrated portable bioaerosol detector to collect and analyze the dispersion of bioaerosol particles. The dispersal characteristics of Enterobacteriaceae were explored using an Andersen six-stage sampler. Livestock farming areas were the primary source of bioparticles. The distribution of the bioparticles varied significantly with environmental conditions. Key factors influencing their distribution included the dispersal capabilities due to wind speed and the processes of aggregation and coagulation of particles. The dispersal pathway of Enterobacteriaceae indicated that the inhabitants of residences near the dispersion source might be exposed to health risks from pathogenic bacteria present in bioparticles indoors. Understanding such characteristics and transmission patterns of bioparticles in rural environments provides a scientific basis for risk assessment and management strategies, with important implications for improving air-quality monitoring, public health policies, and environmental management in rural areas. Full article

Bioaerosols have risen as pivotal constituents of airborne particles. Closely intertwined with the agricultural domain, these particles exert a significant influence on crops through the dissemination of various microorganisms that modulate crop growth dynamics, adaptive responses to environmental stimuli, and the nutritional profile of agricultural products. As the main vector, airborne particles are at the forefront in the transmission of plant pathogens. Therefore, this review explains the main factors influencing their composition in agricultural settings and their spreading. Furthermore, it elucidates the complex bioaerosol-based communication networks, including bacteria–bacteria, bacteria–plant, and plant–plant interactions, mediated by specialized volatile organic compounds (VOCs) released by plants and bacterial volatile compounds (BVCs) produced by bacteria. These compounds play a crucial role in synchronizing stress responses and facilitating adaptive processes. They serve as a pathway for influencing and regulating the behavior of both plants and microorganisms. Delving into their origin and dispersion, we assess the key methods for their collection and analysis while also comparing the strengths and weaknesses of various sampling techniques. The discussion also extends to delineating the roles of such particles in the formation of biodiversity. Central to this discourse is an in-depth exploration of their role in the agricultural context, particularly focusing on their potential utility in forecasting pathogen transmission and subsequent plant diseases. This review also highlights the importance of applying bioaerosol-based strategies in the promotion of sustainable agricultural practices, thus contributing to the advancement of ecological balance and food security, which remains a neglected area in scientific research. Full article

Emissions from domestic coal burning are generally recognized as the cause of the lung cancer epidemic in Xuanwei City, Yunnan Province, China. To examine the physicochemical characteristics of airborne particles emitted from burning this locally sourced coal, PM_2.5 samples were collected from Hutou village which has high levels of lung cancer, and Xize village located approximately 30 km from Hutou without lung cancer cases. Transmission Electron Microscopy-Energy Dispersive X-ray (TEM-EDX) analysis was employed to study the physiochemical features and chemistry of individual particles. Sulfur and silica are the most abundant elements found in the airborne particles in both of the two villages. Fewer elements in aerosol particles were found in Xize village compared with Hutou village. Based on the morphologies and chemical compositions, the particles in Xuanwei can be classified into five types including composite particles (38.6%); organic, soot, tar balls, and biologicals (28.3%); sulfate (14.1%); fly ash (9.8%); and minerals (9.2%). The particles in Hutou village are abundant in the size range of 0.4–0.8 μm while that in Xize is 0.7–0.8 μm. Composite particles are the most common types in all the size ranges. The percentage of composite particles shows two peaks in the small size range (0.1–0.2 μm) and the large size ranges (2–2.3 μm) in Hutou village while that shows an even distribution in all size ranges in Xize village. Core-shell particles are typical types of composite particles, with the solid ‘core’ consisting of materials such as fly ash or mineral grains, and the shell or surface layer being an adhering soluble compound such as sulfates or organics. The heterogeneous reactions of particles with acidic liquid layers produce the core-shell structures. Typically, the equivalent diameter of the core-shell particles is in the range of 0.5–2.5 μm, averaging 1.6 μm, and the core-shell ratio is usually between 0.4 and 0.8, with an average of 0.6. Regardless of the sizes of the particles, the relatively high core-shell ratios imply a less aging state, which suggests that the core-shell particles were relatively recently formed. Once the coal-burning particles are inhaled into the human deep lung, they can cause damage to lung cells and harm to human health. Full article

Recently, there has been a growing interest in understanding how respiratory particles spread within passenger cars, especially in light of ongoing challenges posed by infectious diseases. This study experimentally investigates dispersion patterns of respiratory airborne particles (<1 µm) within these confined spaces. The main objective is to introduce a manikin-based method for studying particle dispersion and assessing in-cabin air quality. To achieve this, a respiratory manikin as a particle source has been developed and tested under various use-cases, including variations in source emission (breathing vs. speaking), the HVAC ventilation mode (fresh and recirculation), and the blower level of the HVAC system (low and high). The findings reveal that for an infection source on the first row of the vehicle when cabin airflow originates from the front panel, the seat directly behind the particle source is associated with the highest particle exposure, while the seat adjacent to the source offers the lowest exposure. Among the tested configurations, the recirculation mode with an active HEPA filter and high blower level shows the lowest particle concentration at recipients’ breath levels during both breathing and speaking. These findings can be used to enhance the design of passenger cars to reduce the transmission of potentially pathogen-laden particles. Full article

Resuspended particles from human activities can contribute to pathogen exposure via airborne fomite contamination in built environments. Studies investigating the dissemination of resuspended viruses are limited. The goal of this study was to explore viral dissemination after aerosolized resuspension via human activities on indoor flooring. Nylon carpet or wood flooring was seeded with virus (MS2) or virus laden dust then evaluated after activities, i.e., walking and vacuuming. Statistically significant differences were found in dispersal of virus laden dust after vacuuming carpet (p-value = 5.8 × 10⁻⁶) and wood (p-value = 0.003, distance > 12 in/30 cm). Significant differences were also found between floor materials and virus laden dust dispersal vacuuming (p = 2.09 × 10⁻⁵) and walking (p = 2.68 × 10⁻²). A quantitative microbial risk assessment (QMRA) scenario using Norovirus and a single fomite touch followed by a single hand-to-mouth touch indicated a statistically significant difference associated with virus laden dust particles and vacuuming carpet(p < 0.001). Infection risks were 1 to 5 log₁₀ greater for dust exposure. The greatest risk reductions from fomites were seen across vacuuming carpet no-dust scenarios for surfaces <30 cm from flooring. More research is needed to determine the role resuspension plays in exposure and transmission of potentially infectious agents. Full article

The COVID-19 pandemic has underscored the urgency of understanding virus transmission dynamics, particularly in indoor environments characterized by high occupancy and suboptimal ventilation systems. Airborne transmission, recognized by the World Health Organization (WHO), poses a significant risk, influenced by various factors, including contact duration, individual susceptibility, and environmental conditions. Respiratory particles play a pivotal role in viral spread, remaining suspended in the air for varying durations and distances. Experimental studies provide insights into particle dispersion characteristics, especially in indoor environments where ventilation systems may be inadequate. However, experimental challenges necessitate complementary numerical modeling approaches. Zero-dimensional models offer simplified estimations but lack spatial and temporal resolution, whereas Computational Fluid Dynamics, particularly with the Discrete Phase Model, overcomes these limitations by simulating airflow and particle dispersion comprehensively. This paper employs CFD-DPM to simulate airflow and particle dispersion in a coach bus, offering insights into virus transmission dynamics. This study evaluates the COVID-19 risk of infection for vulnerable individuals sharing space with an infected passenger and investigates the efficacy of personal ventilation in reducing infection risk. Indeed, the CFD simulations revealed the crucial role of ventilation systems in reducing COVID-19 transmission risk within coach buses: increasing clean airflow rate and implementing personal ventilation significantly decreased particle concentration. Overall, infection risk was negligible for scenarios involving only breathing but significant for prolonged exposure to a speaking infected individual. The findings contribute to understanding infection risk in public transportation, emphasizing the need for optimal ventilation strategies to ensure passenger safety and mitigate virus transmission. Full article

The COVID-19 pandemic has caused major disruptions to workplace safety and productivity. A browser-based interactive disease transmission simulation was developed to enable managers and individuals (agents) to optimize safe office work activities during pandemic conditions. The application provides a user interface to evaluate the impact of non-pharmaceutical interventions (NPIs) policies on airborne disease exposure based on agents’ meeting patterns and room properties. Exposure is empirically calibrated using CO₂ as a proxy for viral aerosol dispersion. For the building studied, the major findings are that the cubicles during low occupancy produce unexpectedly high exposure, upgrading meetings to larger rooms reduces total average exposure by 44%, and when all meetings are conducted in large rooms, a 79% exposure reduction is realized. Full article

The COVID-19 pandemic has focused attention on the importance of understanding and mitigating the airborne transmission of pathogens in indoor environments. This study investigated the aerosol distribution in different indoor venues with varying ventilation concepts, including displacement, mixed, and natural ventilation. A measurement system was developed to investigate venue-specific aerosol distribution patterns using a sodium chloride solution as a tracer. To analyse the spatial dispersion of aerosols, Computational Fluid Dynamics (CFD) simulations were conducted in addition to experimental investigations. The investigations indicated the lowest aerosol load for the venue with displacement ventilation and the highest for the naturally ventilated venue. The measurement system developed in this study provides a useful tool for assessing the effectiveness of ventilation measures in reducing airborne transmission of pathogens in indoor environments. It also proved its wide range of applications, as it can be used in variously sized and shaped indoor environments, with or without an audience. Full article

Droplet transmission is a critical pathway for the spread of respiratory infectious viruses. A thorough understanding of the mechanisms of droplet dispersion within subway carriages is crucial to curb the widespread transmission of the virus. This study utilizes computational fluid dynamics (CFD) to establish a full-scale numerical model of a subway carriage. The numerical model and droplet evaporation behavior are validated using experimental data and literature. The impact of primary parameters such as the initial droplet size, release velocity, release position, relative humidity, and passenger density on the droplet diffusion and probability of infection for passengers is investigated. The results indicate that large droplets (100 μm) are deposited on the carriage floor before complete evaporation, while tiny droplets (10 μm) evaporate rapidly, leading to a longer suspension time in the air within the carriage. The infected passenger’s position influences the ventilation system’s efficiency in removing the droplets; removal takes significantly longer when the infected passenger is closer to the carriage end. Additionally, a low relative humidity (35%) and high passenger density (4 p/m²) result in more droplets being trapped by passengers’ bodies. The infection probability for passengers depends on the initial size and quantity of droplets trapped by their bodies. Maintaining higher relative humidity levels and limiting the passenger numbers within the subway carriage can reduce the number of droplets captured by passengers’ bodies, thus helping to reduce the infection probability of fellow passengers. Full article

Highway buses are used in a wide range of commuting services and in the tourist industry. The demand for highway bus transportation has dramatically increased in the recent post-pandemic world, and airborne transmission risks may increase alongside the demand for highway buses, owing to a higher passenger density in bus cabins. We developed a numerical prediction method for the spatial distribution of airborne transmission risks inside bus cabins. For a computational fluid dynamics analyses, targeting two types of bus cabins, sophisticated geometries of bus cabins with realistic heating, ventilation, and air-conditioning were reproduced. The passengers in bus cabins were reproduced using computer-simulated persons. Airflow, heat, and moisture transfer analysis were conducted based on computational fluid dynamics, to predict the microclimate around passengers and the interaction between the cabin climate and passengers. Finally, droplet dispersion analysis using the Eulerian–Lagrangian method and an investigation of the spatial distribution of infection/spread risks, assuming SARS-CoV-2 infection, were performed. Through parametric analyses of passive and individual countermeasures to reduce airborne infection risks, the effectiveness of countermeasures for airborne infection was discussed. Partition installation as a passive countermeasure had an impact on the human microclimate, which decreased infection risks. The individual countermeasure, mask-wearing, almost completely prevented airborne infection. Full article

Modeling the windborne transmission of aerosolized pathogens is challenging. We adapted an atmospheric dispersion model named the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model to simulate the windborne dispersion of porcine reproductive and respiratory syndrome virus (PRRSv) between swine farms and incorporated the findings into an outbreak investigation. The risk was estimated semi-quantitatively based on the cumulative daily deposition of windborne particles and the distance to the closest emitting farm with an ongoing outbreak. Five years of data (2014:2018) were used to study the seasonal differences of the deposition thresholds of the airborne particles containing PRRSv and to evaluate the model in relation to risk prediction and barn air filtration. When the 14-day cumulative deposition was considered, in winter, above-threshold particle depositions would reach up to 30 km from emitting farms with 84% of them being within 10 km. Long-distance pathogen transmission was highest in winter and fall, lower in spring, and least in summer. The model successfully replicated the observed seasonality of PRRSv, where fall and winter posed a higher risk for outbreaks. Reaching the humidity and temperature thresholds tolerated by the virus in spring and summer reduced the survival and infectivity of aerosols beyond 10–20 km. Within the data limitations of voluntary participation, when wind was assumed to be the sole route of PRRSv transmission, the predictive performance of the model was fair with >0.64 AUC. Barn air filtration was associated with fewer outbreaks, particularly when exposed to high levels of viral particles. This study confirms the usefulness of the HYSPLIT model as a tool when determining seasonal effects and distances and informs the near real-time risk of windborne PRRSv transmission that can be useful in future outbreak investigations and for implementing timely control measures. Full article

In the present work, we investigate the possibility that long-range airborne transport of infectious aerosols could initiate an epidemic outbreak at distances downwind beyond one hundred kilometers. For this, we have developed a simple atmospheric transport box model, which, for a hypothetical case of a COVID-19 outbreak, was compared to a more sophisticated three-dimensional transport-dispersion model (HYSPLIT) calculation. Coupled with an extended Wells–Riley description of infection airborne spread, it shows that the very low probability of outdoor transmission can be compensated for by high numbers and densities of infected and susceptible people in the source upwind and in the target downwind, respectively, such as occur in large urban areas. This may result in the creation of a few primary cases. It is worth pointing out that the probability of being infected remains very small at the individual level. Therefore, this process alone, which depends on population sizes, geography, seasonality, and meteorology, can only “trigger” an epidemic, which could then spread via the standard infection routes. Full article

Some of the most devastating crop diseases and insect pests can be transmitted by wind over extremely long distances. These low-probability but high-impact events can have severe consequences for crop production and food security by causing epidemic outbreaks or devastating insect infestations in previously uninfected geographic areas. Two prominent examples that have recently caused substantial damage to agricultural production are novel strains of wheat rusts and desert locust swarm infestations. Whilst quantitative estimates of long-range atmospheric transport events can be obtained using meteorological transport simulations, the exact characteristics of three-dimensional spatiotemporal dynamics of crop pathogen transport and insect flight on extremely large spatial scales, over entire regions and continents, remain largely unknown. Here, we investigate the feasibility and usefulness of new advanced geospatial data visualization methods for studying extremely long-distance airborne transmission of crop pathogens and insect pests. We combine field surveillance data and a Lagrangian Particle Dispersion Model with novel techniques from computer graphics to obtain, for the first time, detailed three-dimensional visual insights into airborne crop pathogen and insect pest transport on regional and continental scales. Visual insights into long-distance dispersal of pests and pathogens are presented as a series of short 3D movies. We use interactive three-dimensional visual data analysis for explorative examination of long-range atmospheric transport events from a selection of outbreak and infestation sites in East Africa and South East Asia. The practical usefulness of advanced 3D visualization methods for improving risk estimates and early warning is discussed in the context of two operational crop disease and insect pest management systems (for wheat rusts and desert locusts). The tools and methods introduced here can be applied to other pathogens, pests, and geographical areas and can improve understanding of risks posed to agricultural production by crop disease and insect pest transmission caused by meteorological extreme events. Full article

The COVID-19 pandemic highlighted the importance of indoor air quality (IAQ) and ventilation, which researchers have been warning about for years. During the pandemic, researchers studied several indicators using different approaches to assess IAQ and diverse ventilation systems in indoor spaces. To provide an overview of these indicators and approaches in the case of airborne transmission through aerosols, we conducted a literature review, which covered studies both from before and during the COVID-19 pandemic. We searched online databases for six concepts: aerosol dispersion, ventilation, air quality, schools or offices, indicators, and assessment approaches. The indicators found in the literature can be divided into three categories: dose-, building-, and occupant-related indicators. These indicators can be measured in real physical spaces, in a controlled laboratory, or modeled and analyzed using numerical approaches. Rather than organizing this paper according to these approaches, the assessment methods used are grouped according to the following themes they cover: aerosol dispersion, ventilation, infection risk, design parameters, and human behavior. The first finding of the review is that dose-related indicators are the predominant indicators used in the selected studies, whereas building- and occupant-related indicators are only used in specific studies. Moreover, for a better understanding of airborne transmission, there is a need for a more holistic definition of IAQ indicators. The second finding is that although different design assessment tools and setups are presented in the literature, an optimization tool for a room’s design parameters seems to be missing. Finally, to efficiently limit aerosol dispersion in indoor spaces, better coordination between different fields is needed. Full article