Particle Concentration Levels Research Articles

The influence of ventilation modes on oil mist particles diffusion in a machining workshop

Mechanical processing and operations are widely involved in modern industry. Large amount of oil mist is tended to be produced and will diffuse in the processing workshop when metalworking fluids are applied on the high temperature workpiece. The ventilation modes and air distributions can influence the air pollutants dilution in machining workshops. Therefore, this paper presents both experimental investigation and simulation study on the oil mist particles diffusion under different ventilation modes. The results identified PM2.5 as the primary component among different oil mist particles generated during a typical machining process. The distribution of oil mist particles in a full-scale machining workshop laboratory was investigated under two ventilation modes: high-sidewall nozzle air supply and low-sidewall air supply. Results revealed obvious influences of both air supply modes on the distribution of oil mist particles. Under the high-sidewall-nozzle air supply mode, the airflow and the oil mist distribution in the workshop was relatively uniform; while the low-sidewall-vent air supply mode led to an uneven distribution of oil mist particles, and the maximum oil mist concentration appeared at the height of 3 m. Under both modes, the attempts to increase the airflow rate are not always successful. Compared with low-sidewall-vent air supply mode, the high-sidewall-nozzle air supply mode presents better performance in achieving lower overall particle concentration level. Overall, the results of this study give useful reference to improve the air quality of industrial plant by properly designing the ventilation mode of machining workshop.

High-frequency electric knife smoke particles: An experimental study on factors influencing emission characteristics

During surgery, the use of a high-frequency electric knife produces smoke, which can be harmful to the health of indoor medical staff and patients. The quantity and particle size distribution of smoke particles produced by different tissues may vary. Understanding the release characteristics of these smoke particles is necessary to clarify their impact on the surgical environment and to seek effective smoke control methods. A previous comparative analysis of human and pig tissues revealed that they share similar water and fat compositions in certain anatomical regions. In this study, we investigated the emission characteristics of smoke particles from various tissues of pigs (skeletal muscle, liver, kidney, skin, and subcutaneous fat) under different operating powers of an electric knife. We measured the indoor particle number concentration (particle concentration), and estimated the PM2.5 mass concentration (PM2.5 concentration), particle size distribution, and emission rate of the smoke particles. The study obtained the particle emission rates of different tissues under different electric knife operating powers, results of which showed that (1) during the operation of the electric knife, mainly small particles below 1 μm are produced. Among them, particles of 0.3 μm were the most abundant, with a particle concentration level of up to 109 particles/m3, accounting for 85.17–97.64% of the total particle number, and as the particle size increased, the particle concentration and percentage decreased significantly. (2) The water and fat compositions of different tissues influenced the indoor particle concentration and emission rate of the smoke emitted by the electric knife. Among different tissues, subcutaneous fat tissue had the lowest particle concentration and emission rate. (3) The electric knife operating power mainly affected particles below 1 μm, and except for kidney tissue, the indoor concentration and emission rate of these particle sizes were positively correlated with the power. The experimental results can provide data reference for the use of high-frequency electric knives in surgeries involving different human tissues in the operating room.

Reduction by air purifier of particulate concentration during orthodontic procedures: a pilot study

BackgroundThe SARS-CoV-2 pandemic has raised awareness of the importance of air quality. This pilot study arose from the need to reduce the concentration of particulate matter in the dental office during orthodontic procedures. To evaluate the efficacy of using an air purifier during orthodontic care in the dental office to reduce the concentration of ambient particulate matter.ResultsSignificant reductions in particle numbers were obtained for all particle sizes except the largest particles counted (10 μm) through use of the air filter. A marked association between higher humidity levels and higher particle counts was also observed.ConclusionsUsing an air purifier during dental care achieves a significant reduction in the concentration of ambient particles in the dental office. There is a correlation between higher relative humidity and higher particle concentration. The probability of obtaining a maximum particulate concentration level of 0.3 and 0.5 μm is 1000 times lower when using an air purifier.

Computer simulation-based nanothermal field and tissue damage analysis for cardiac tumor ablation.

Radiofrequency ablation is a nominally invasive technique to eradicate cancerous or non-cancerous cells by heating. However, it is still hampered to acquire a successful cell destruction process due to inappropriate RF intensities that will not entirely obliterate tumorous tissues, causing in treatment failure. In this study, we are acquainted with a nanoassisted RF ablation procedure of cardiac tumor to provide better outcomes for long-term survival rate without any recurrences. A three-dimensional thermo-electric energy model is employed to investigate nanothermal field and ablation efficiency into the left atrium tumor. The cell death model is adopted to quantify the degree of tissue injury while injecting the Fe3O4 nanoparticles concentrations up to 20% into the target tissue. The results reveal that when nanothermal field extents as a function of tissue depth (10mm) from the electrode tip, the increasing thermal rates were approximately 0.54362%, 3.17039%, and 7.27397% for the particle concentration levels of 7%, 10%, and 15% compared with no-particle case. In the 7% Fe3O4 nanoparticles, 100% fractional damage index is achieved after ablation time of 18s whereas tissue annihilation approach proceeds longer to complete for no-particle case. The outcomes indicate that injecting nanoparticles may lessen ablation time in surgeries and prevent damage to adjacent healthy tissue.

Safe by process design (SbPD) strategies based on proper measures to mitigate nanoparticle exposure in industrial settings

Due to its potential to develop new added value products, a staggering number of nanoparticles (NPs) is already available on the market. Moreover, this increase is expected to continue in the future. However, there is a lack of knowledge on the level of exposure to nanoparticles, and the information related to possible adverse health effects is scarce. Furthermore, there is very little studies concerning the effect of risk management measures (RMMs) on the levels of exposure to nanoparticles at workplaces, compared to the number of exposure situations that can be distinguished.This study focuses on 5 case studies covering different types of materials, assessing the effectiveness of targeted mitigation strategies applied during the production process. Customized mitigation measures were applied in each industrial scenario to minimize exposure levels. The effects on the particle concentration levels using source enclosure, partial or full, combined with local exhaust ventilation systems (LEVs), was evaluated to generate new knowledge to support the definition of informed safe by process design approaches when dealing with NPs. This study demonstrates that technological advancements can significantly reduce work-related exposures. The findings underscore the importance of tailored mitigation measures due to the diverse range of potential sources and activities in industrial scenarios.

Influence of effluent particles and particle-bound micropollutants on the removal of micropollutants and UVA254 in wastewater effluent ozonation

This study systematically investigated the influence of effluent particles and activated sludge (AS) particles on the removal of micropollutants via wastewater effluent ozonation within typical effluent total suspended solids (TSS) concentrations. A series of batch experiments revealed that particle concentrations up to 30 mg/L had a minor impact on the removal of organic micropollutants (OMPs) in the aqueous phase. Moreover, the reduction of UV absorbance at 254 nm (UVA254) was negatively correlated to the level of particle concentration at ozone doses higher than 0.5 gO3/gDOC. It indicates that UVA254 abatement was more sensitive to the presence of particles compared to OMP removal. Organic micropollutants (OMPs) sorbed on effluent particles and sludge particles were extracted before and after ozonation. OMP sorption in effluent particles was 2–5 times higher than that in sludge particles. During the ozonation of raw secondary effluent, particle-bound micropollutants were removed comparably to the micropollutants in the aqueous phase. This suggests that the boundary layer surrounding the particle didn’t affect the removal of OMPs in the particle phase. Furthermore, the removal of existing OMPs (irbesartan, sulfamethoxazole, and metoprolol) in the effluent was used to assess the ozone and •OH exposure. In water samples with and without particles, the elimination of OMPs could be reliably predicted (R² > 0.95) by calculated ozone and •OH exposures.

Stable COPD Picture through Exhaled Breath Condensate, Questionnaires and Tests. A Proof of Concept Study

Background: Changes in lung structures persist in stable Chronic Obstructive Pulmonary Disease (COPD), but their correlation with the clinical picture remains unclear. The purpose of this study was to assess the stable COPD picture via the relationship between exhaled breath condensate (EBC) particle concentration and the Saint George Respiratory Questionnaire (SGRQ), COPD Assessment Test (CAT), and six-minute walking test (6 MWT). Methods: 12 stable COPD and 12 healthy subjects participated in the study. The EBC was collected with Rtube and analyzed using the Accusizer FxNano. Particle concentration was measured and correlated with the findings of the tools used to assess the health status and functional profile of COPD. The results’ analysis was performed with the Spearman’s test and the Mann-Whitney U - test. Results: The COPD group presented a worse picture of health status and functional profile compared to the healthy group. Correlations were observed between components of the SGRQ and CAT. The two groups presented similar levels of EBC particle concentrations, but the number of small particles was higher in COPD subjects. A correlation of the EBC particle concentration with the activity and total score of the SGRQ was only observed in the healthy group. Conclusion: The total particle number was similar in the COPD and healthy groups. A few correlations between the EBC particles and tools used were also observed. The use of EBC particle concentration to monitor COPD status cannot be claimed with confidence because of the small sample size. Further research is necessary, particularly in large-scale groups.

Monitoring and Control of Particulate Matter in Urban Area in Douala-Cameroon Town

This study focused on the content of fine particle air pollution in the city of Douala. Several studies have analyzed pollution problems due to road traffic in Douala, Cameroon. Particle concentration levels are higher in heavy traffic than in light traffic. The population’s exposure to air pollution in cities is higher near roads. Several studies have analyzed pollution problems due to road traffic in Douala, Cameroon. In this city, the traffic density at the intersections is indeed higher. Thus, the question is as follows: Are these traffic areas hotspots of increased PM exposure levels? To determine it, four particle size fractions (PM10, PM2.5, PM5, and PM1) were collected using an “OC300 Gas and Dust Particle Laser Detector” for three months at different traffic locations (roundabouts or/and crossroads). Statistical analysis of the data shows very high concentrations at most measurement sites. PM concentrations at the different measurement sites are around 35.69-68.08 µg m−3 for PM1, 50.72-99.13 µg m−3 for PM2.5, 54.11-111.22 µg m−3 for PM5, and 57.97-119.25 µg m−3 for PM10. Exceedances of WHO daily guidelines for PM2.5 (45 µg m−3) and PM10 (15 µg m−3) were found during the measurement campaign, indicating that crossroads are the pollution hotspots in urban areas. Occupation of the roadsides for various economic activities (painting, restaurants, donut shops, etc.) is common in Cameroon, increasing health risks for people working around the roadside. Thus, crossroad locations are areas where the level of exposure to PMx is the highest on road traffics.

An Improved Method to Enrich Large Extracellular Vesicles Derived from Giardia intestinalis through Differential Centrifugation.

Giardia intestinalis is a flagellated unicellular protozoan that colonizes the small intestine, causing the diarrheal disease called giardiasis. The production of extracellular vesicles (EVs) by G. intestinalis and the role of these EVs in the parasite's interaction with the host have been described. According to biogenesis, EVs are grouped mainly into large (microvesicles-derived from the plasma membrane) and small (exosomes-derived from multivesicular bodies). Populations of EVs are heterogeneous, and improved methods to separate and study them are needed to understand their roles in cell physiology and pathologies. This work aimed to enrich the large extracellular vesicles (LEVs) of G. intestinalis in order to better understand the roles of these vesicles in the interaction of the parasite with the host. To achieve the enrichment of the LEVs, we have modified our previously described method and compared it by protein dosage and using Nano tracking analysis. Giardia intestinalis vesiculation was induced by incubation in a TYI-S-33 medium without serum, to which 1 mM of CaCl2 was added at 37 °C for 1 h. Then, the supernatant was centrifuged at 15,000× g for 1 h (15 K 1 h pellet), 15,000× g for 4 h (15 K 4 h pellet) and 100,000× g for 1.5 h (100 K 1h30 pellet). The pellet (containing EVs) was resuspended in 1× PBS and stored at 4 °C for later analysis. The EVs were quantified based on their protein concentrations using the Pierce BCA assay, and by nanoparticle tracking analysis (NTA), which reports the concentration and size distribution of the particles. The NTA showed that direct ultracentrifugation at 100,000× g for 1.5 h and centrifugation at 15,000× g for 4 h concentrated more EVs compared to centrifugation at 15,000× g for 1 h. Additionally, it revealed that centrifugation at 15,000× g 4 h was able to concentrate at the same particle concentration levels as a direct ultracentrifugation at 100,000× g for 1.5 h. As for the enrichment of LEVs, the NTA has shown a higher concentration of LEVs in direct ultracentrifugation at 100,000× g for 1.5 h, and in centrifugation at 15,000× g for 4 h, compared to centrifugation at 15,000× g for 1 h. Our results have shown that the most used method at 15,000× g for 1 h is not enough to obtain a representative population of large EVs, and we suggest that LEVs released by G. intestinalis can be better enriched by direct ultracentrifugation at 100,000× g for 1.5 h, or by centrifugation at 15,000× g for 4 h.

Exposure Assessment and Risk Characterization of Carbon-Based Nanomaterials at Different Production Scales

Data on the potential impact on human health of engineered nanomaterials are still scarce, with an evident lack of knowledge on the exposure levels at all stages of the life cycle. By prioritizing the responsible handling of engineered nanomaterials (ENMs), companies can promote sustainability by minimizing the risks of occupational exposure, protecting employee well-being, reducing liability, and avoiding costly environmental remediation efforts. This research aims to evaluate the risk in real scenarios involving the use of carbon-based nanomaterials in research laboratories, pilot-scale facilities, and industrial settings. Several online and offline instruments have been employed to characterize the particulate matter present in these environments, including particles in the nanometer range and relevant fractions for risk assessment purposes. Samples collected on polycarbonate filters were analyzed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Exposure estimation has been performed by applying a decision based on tier 2 from the nanoGEM methodology, with the weighing and transferring of reduced graphene oxide (RGO) in a pilot plant being the most liberating processes, which are the activities with the highest risk of exposure. In addition, high levels of particle concentration, with peaks up to 1.7 × 105 and 4.7 × 105 part/cm3, have been found for the dispersion of carbon nanotubes (CNTs) and incorporation of carbonaceous nanoparticles into resins, respectively.

The impact of high background particle concentration on the spatiotemporal distribution of Serratia marcescens bioaerosol

Airborne transmission is a well-established mode of dissemination for infectious diseases, particularly in closed environments. However, previous research has often overlooked the potential impact of background particle concentration on bioaerosol characteristics. We compared the spatial and temporal distributions of bioaerosols under two levels of background particle concentration: heavily polluted (150–250 μg/m3) and excellent (0–35 μg/m3) in a typical ward. Serratia marcescens bioaerosol was adopted as a bioaerosol tracer, and the bioaerosol concentrations were quantified using six-stage Andersen cascade impactors. The results showed a significant reduction (over at least 62.9%) in bioaerosol concentration under heavily polluted levels compared to excellent levels at all sampling points. The temporal analysis also revealed that the decay rate of bioaerosols was higher (at least 0.654 min-1) under heavily polluted levels compared to excellent levels. These findings suggest that background particles can facilitate bioaerosol removal, contradicting the assumption made in previous research that background particle has no effect on bioaerosol characteristics. Furthermore, we observed differences in the size distribution of bioaerosols between the two levels of background particle concentration. The average bioaerosols size under heavily polluted levels was found to be higher than that under excellent levels, and the average particle size under heavily polluted levels gradually increased with time. In conclusion, these results highlight the importance of considering background particle concentration in future research on bioaerosol characteristics.

Road traffic-induced particle matter dispersion in a calm wind environment at the main roundabout in Douala, central Africa


 
 
 
 Introduction: Road traffic emissions are among the most significant sources of pollution in Douala, Cameroon's economic town, alongside industrial operations. The morning and the evening are two times of the day when traffic is heavier and the winds are also at their calmest. The majority of the non-exhaust Particulate Matters (PMs) produced by autos is re-suspended road contaminants. The purpose of this research is to estimate fine particle dispersion in conditions of calm winds.
 Materials and methods: In one of Douala's roundabouts, the Gaussian Plume model is employed to calculate the PM concentration under calm winds conditions. Different vehicle classes (HDV: Heavy Duty Vehicles, LDV: Light Duty Vehicles, PC: Passenger Cars) are used to figure out the amount of PMs they produce. Measurements of ambient fine particle concentrations are made with the OC-300 laser dust particle detector.
 Results: The results made it possible to compare actual measurements of PM2.5, PM10 (300±150 μg/m3 and 650±150 μg/m3, respectively) with simulated values (PM2.5, PM10: 310 μg/m3 and 631 μg/m3, respectively). The difference between in-situ and computed values can range from 10 to 132 μg/m3. From 6 to 10 AM, the population's exposure to PM pollution is more severe. It has also been demonstrated that there is a significant association between traffic flow and PM Concentration during the dry season (R2=0.921). With increased traffic flow intensity, particle concentration levels rise.
 Conclusion: The concentration threshold stays above the World Health Organization (WHO) limits regardless of the approach. Furthermore, this paper provides important information about Douala's pollution levels.
 
 
 

Magnetorheological fluids subjected to non-uniform magnetic fields: experimental characterization

Magnetorheological (MR) fluids are suspensions of fine, low-coercivity, high-magnetizable particles in a continuous liquid phase. When subjected to magnetic field, the material exhibits a rapid change in the apparent viscosity of several orders of magnitude. This unique capability has been successfully exploited in automotive semi-active suspensions systems or systems for manufacturing high quality optics. In a majority of the existing systems, the rheology of MR fluids is controlled by an external uniform field oriented perpendicularly to the fluid flow direction. In general, it is an inherent feature of MR systems operating in flow, shear or squeeze modes, respectively. There is an experimental evidence that the behavior of MR fluids in the so-called pinch-mode (in which the fluid is subjected to non-uniform magnetic field distributions) clearly stands out against the remaining three operating modes. With the predecessors, the flow through the channel occurs once a pressure across it exceeds the field-dependent threshold pressure. For comparison, in pinch mode valves the magnetic flux energizes mostly the layers of the materials near the channel walls. The outcome is a change in the channel’s effective diameter achieved solely via material means without changing its geometry. To study the fluid’s unique behaviour in the pinch mode, the authors designed a prototype valve assembly and examined several fluid formulations of various particle concentration levels across a wide range of external (velocity, magnetic field density) stimuli in an organized effort to further comprehend the phenomenon. The obtained data indicate that the magnitude of the particular effect does not only depend on the magnitudes of the magnetic stimuli but also on the particle concentration; the smaller the concentration of particles the more pronounced the pinch mode like behavior is. In general, the authors believe that the study may provide guidelines as to the selection of fluid formulations for developing novel valveless actuators utilizing MR fluids operating in pinch mode.

Methods for the detection and characterization of boat paint microplastics in the marine environment

Microplastics in the marine environment have been the focus of intense research recently, however little attention has been given to boat paint sources, despite its direct influence on the marine ecosystem. This is largely due to the lack of established analytical methods. Microplastics from boating sources may originate from antifouling paints on the underwater body, surface coatings on the top sides, deck, and superstructure, as well as plastic parts of the boat construction. Their release can occur during construction, operation (leisure boats and commercial ships), service, and maintenance, from the materials themselves or used chemicals (e.g., abrasive detergents). Most importantly, boat paint microplastics containing biocides, such as the metals copper and zinc, and particles containing tin (residues from old or current use of tributyl-tin ship hull paints) should raise higher concern on potential environmental impacts. This study aims to provide practical insight on methods for the quantification of boat paint microplastics in marine waters and provide a baseline survey on their occurrence. Sampling and analysis methods are applied on case studies, i.e., marinas on the Swedish coast. A multi-method approach for identifying and characterizing boat paint microplastics based on visual and chemical characteristics is presented. In general, the measured content of biocide-containing microplastics was remarkably high in all marinas, with concentration levels of copper-rich particles >10 μm between 400 and 1400 particles per L. Given that biocide paint particles are manufactured to be toxic, it is particularly important to take into account field measurements in future environmental status assessments. This work underlines the importance of monitoring data in the action work between relevant authorities and stakeholders.

Levels of Fine Particle Concentrations in Schools and Postexercise Pulmonary Function Disorders in Schoolchildren in Brazzaville

Context: Fine particles (PM2.5 and PM10) can accumulate in classrooms and in schoolyards located near urban roads. PM2.5 and PM10 can initiate, develop and exacerbate exercise-induced bronchospasm (EIB). This study aimed to assess the concentration levels of PM2.5 and PM10 in schools and to determine the rate of sensitivity to EIB among schoolchildren. Methods: A total of 128 students (67 girls and 61 boys) with an average age of 11 participated in this study. An ISAAC II questionnaire on respiratory symptoms was administered. PM2.5 and PM10 were measured. A 6-minute stress test was performed. Spirometry was performed. The ratio (I/O) of the concentrations of PM2.5 and PM10 recorded inside (I) the classrooms to those obtained outside (O) the classrooms was equal to 1 (I/O = 1). Results: The concentrations of PM2.5 and PM10 recorded inside the classrooms and those obtained outside the classrooms were higher than the values recommended by the WHO. 29 students out of 128 were diagnosed as sensitive to EIB [EIB (+)], i.e., a rate of sensitivity to EIB of 22.66%. A drop in postexercise PEF of 17.396% was observed among EIB (+) students. Conclusion: Schoolchildren in schools located near highways are exposed to high levels of PM2.5 and PM10 concentrations. Exposure to PM2.5 and PM10 played an important role in the initiation and exacerbation of exercise-induced bronchospasm in schoolchildren from schools located near highways. Effective programs for improving air quality in schools must be put in place to reduce the effects of particulate pollution on the respiratory health of school children.

Influence of the ventilation strategy on the respiratory droplets dispersion inside a coach bus: CFD approach

The airborne transmission of the COVID-19 virus was considered the main cause of infection. The increasing concern about the virus spread in confined spaces, characterized by high crowding indexes and an often-inadequate air exchange system, pushes the scientific community to the design of many studies aimed at improving indoor air quality. The risk of transmission depends on several factors such as droplet properties, virus characteristics, and indoor airflow patterns. The main transmission route of the SARS-CoV-2 virus to humans is the respiratory route through small (<100 μm) and large droplets. In an indoor environment, the air exchange plays a fundamental role on the dispersion of the droplets. In this study, an integrated approach was developed to evaluate the influence of the ventilation strategy on the dispersion of respiratory droplets emitted inside a coach bus. There are no specific guidelines and standards on the air exchange rate (AER) values to be respected in indoor environments such as coach buses. The aim of this work is to analyse the influence of ventilation strategy on the respiratory droplet concentration and distribution emitted in a coach bus. Ansys FLUENT was used to numerically solve the well-known transient Navier-Stokes equations (URANS equations), the energy equation and using the Lagrangian Discrete Phase Model (DPM) approach to construct the droplet trajectories. The geometry is representative of an intercity bus, a vehicle constructed exclusively for the carriage of seated passengers. The 3D CAD model represented a coach bus with an HVAC system, within which an infected subject was present. The positions of exhaust vents and air-conditioning vents were chosen to ensure complete air circulation throughout the bus. The infected subject emitted droplets with a well-defined size distribution and mass through the mouth. The air exchange is provided in two different ways: general ventilation (from air intakes positioned along the bus windows and top side of central corridor) and personal ventilation (with air intakes for each passenger). For the general ventilation a single AER value was set (0.3 m3 s−1). The first results obtained showed a slight particle dispersion in the computational domain due to the airflow rate entered through the HVAC system, but a still elevated level of particle concentration tended to accumulate on the area near to infected subject. Additional analysis was executed to evaluate the beneficial effects linked to further addition of airflow through personal air-conditioning vents placed above every passenger’s head. The results show the importance of the use of the ventilation system inside a coach bus, highlighting how the contribution linked to of the personal air exchange rate can lead to a significant reduction of droplet concentration exposure and consequently a reduction of the risk of infection from airborne diseases.

US Embassy air-quality tweets led to global health benefits

The World Health Organization estimates that over 90% of the world's population is exposed to hazardous levels of local air pollution. Air pollution is markedly worse in low- and middle-income countries, yet air-quality monitoring is typically sparse. In 2008, the US Embassy in Beijing began tweeting hourly air-quality information from a newly installed pollution monitor, dramatically improving the information on air quality available to Beijing residents. Since then, the United States has installed over 50 monitors around the world, tweeting real-time reports on air quality in those locations. Using spatially granular measurements of local air pollution from satellite data that span the globe, we employ variation in whether and when US embassies installed monitors to evaluate the impact of air-quality information on pollution. We estimate that embassy monitors led to reductions in fine particulate concentration levels in host countries of 2 to 4 µg/m3. Our central estimate of the annual monetized benefit of the decrease in premature mortality due to this reduction in pollution is $127 million for the median city in 2019. Our findings point to the substantial benefits of improving the availability and salience of air-quality information in low- and middle-income countries.

Impact of COVID-19 lockdown on the ambient air-pollutants over the Arabian Peninsula

Lockdowns imposed across the world to combat the spread of the COVID-19 pandemic also reduced the anthropogenic emissions. This study investigates the changes in the anthropogenic and natural pollution levels during the lockdown over the Arabian Peninsula (AP), a region where natural pollutants (mineral dust) dominate. In-situ and satellite observations, reanalysis products, and Weather Research and Forecasting model (WRF) coupled with Chemistry module (WRF-Chem) simulations were analyzed to investigate the influence of COVID−19 lockdown on the aerosols (PM2.5, PM10, and AOD) and trace gases (NO2 and SO2). WRF-Chem reasonably reproduced the satellite and in-situ measurements during the study period, with correlation coefficients varying between 0.6–0.8 (0.3–0.8) for PM10 (NO2 and SO2) at 95% confidence levels. During the lockdown, WRF-Chem simulations indicate a significant reduction (50–60%) in the trace gas concentrations over the entire AP compared to the pre-lockdown period. This is shown to be mostly due to a significant reduction in the emissions and an increase in the boundary layer height. An increase in the aerosol concentrations over the central and northern parts of the AP, and a decrease over the north-west AP, Red Sea, and Gulf of Aden regions are noticeable during the lockdown. WRF-Chem simulations suggest that the increase in particulate concentrations over the central and northern AP during the lockdown is mainly due to an increase in dust concentrations, manifested by the stronger convergence and upliftment of winds and warmer surface temperatures (15–25%) over the desert regions. The restricted anthropogenic activities drastically reduced the trace gas concentrations, however, the reduction in particulate concentration levels is offset by the increase in the natural processes (dust emissions).

Metabolomics profile of 5649 users and nonusers of hormonal intrauterine devices in Finland

Use of hormonal intrauterine devices has grown during the last decades. Although hormonal intrauterine devices act mostly via local effects on the uterus, measurable concentrations of levonorgestrel are absorbed into the systemic circulation. The possible metabolic changes and large-scale biomarker profiles associated with hormonal intrauterine devices have not yet been studied in detail. To examine through the metabolomics approach the metabolic profile of patients using hormonal intrauterine devices and how this metabolic profile is affected by duration and discontinuation of use. The study consisted of cross-sectional analyses of 5 population-based surveys (FINRISK and FinHealth studies), spanning from 1997 to 2017. All fertile-aged participants (18-49 years) in the surveys with available information on hormonal contraceptive use and metabolomics data (n=5649) were included in the study. Altogether, 211 metabolic measures of users of hormonal intrauterine devices (n=1006) were compared with those of nonusers of hormonal contraception (n=4643) via multivariable linear regression models. To allow comparison across multiple measures, association magnitudes were reported in standard deviation units of difference in biomarker concentration compared with the reference group. After adjustment for covariates, levels of 141 metabolites differed in current users of hormonal intrauterine devices compared with nonusers of hormonal contraception (median difference in biomarker concentration, 0.09 standard deviation): lower levels of particle concentration of larger lipoprotein subclasses, triglycerides, cholesterol and derivatives, apolipoproteins A and B, fatty acids, glycoprotein acetyls, and aromatic amino acids. The metabolic pattern of hormonal intrauterine device use did not change according to duration of use. When comparing previous users and never-users of hormonal intrauterine devices, no significant metabolic differences were observed. The use of hormonal intrauterine devices was associated with several moderate metabolic changes previously associated with reduced arterial cardiometabolic risk. The metabolic effects were independent of duration of use of the hormonal intrauterine devices. Moreover, the metabolic profiles were similar after discontinuation of hormonal intrauterine device use and in never-users.

Occupant behavior and indoor particulate concentrations in daycare centers

‘Occupant behavior’ is the primary mechanism determining indoor particulate concentrations. Various indoor human activities generate particulate matter. Human-building interactions, such as window opening behavior, change the number of outdoor particulate matter introduces to the building. ‘Daycare center’ where young children spend considerable time has an occupant schedule distinguished from other types of buildings. In the study, we analyzed the effects of occupant behavior on indoor particle concentrations in daycare centers by on-site monitoring. The measurements were performed in four daycare centers located in Gyeonggi-do, South Korea. Optical particle counters(OPS, model 3330, TSI Inc., Shoreview, MN, USA) were used for particulate concentration monitoring. The source strengths of particles resuspended by each human activity were calculated, and their contributions to indoor particle concentrations were evaluated. Further, characteristics of human-building interactions and their corresponding impacts on indoor air quality were also analyzed. Results showed that particle resuspension was greater when occupants were awake (mean, 41.0 particles·min−1) than when they were asleep (mean, 9.2 particles·min−1), and the contribution of occupant status was also higher when awake (37–70% vs. 8–18%) for particles sized (0.3–10.0 μm). Analyzing five detailed human activities, vacuuming (9.8·107 particles·min−1) emitted the highest amount of particulate matter per person, followed by physical activity (4.8·107 particles·min−1), sedentary activity (1.9·107 particles· min−1), meals (1.9·107 particles·min−1), and nap time (8.1·106 particles·min−1). The study suggests that vacuuming should be avoided while children are occupied. This research also shows that children could be exposed to high daily average indoor particulate concentration (up to 1217 particles·cm−3) when windows were opened for an extended period of time while poor outdoor air quality. These results indicate that indoor air quality can be severely degraded by opening windows without considering the level of outdoor particle concentration.