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Background: Development of methodologies to quantify airborne micro-organisms is needed for the prevention and control of infections. It is difficult to conclude which is the most efficient and sensitive strategy to assess airborne SARS-CoV-2 RNA levels due to the disparity of results reported in clinical settings.Aim: To improve our previously reported protocol of measuring SARS-CoV-2 RNA levels, which was based on bioaerosol collection with a liquid impinger and RNA quantification with droplet digital polymerase chain reaction (ddPCR).Methods: Air samples were collected in COVID-19 patient rooms to assess efficiency and/or sensitivity of different air samplers, liquid collection media, and reverse transcriptases (RT).Findings: Mineral oil retains airborne RNA better than does hydrophilic media without impairing integrity. SARS-CoV-2 ORF1ab target was detected in 80% of the air samples using BioSampler with mineral oil. No significant differences in effectiveness were obtained with MD8 sampler equipped with gelatine membrane filters, but the SARS-CoV-2 copies/m3 air obtained with the latter were lower (28.4 ± 6.1 vs 9 ± 1.7). SuperScript II RT allows the detection of a single SARS-CoV-2 genome RNA molecule by ddPCR with high efficiency. This was the only RT that allowed the detection of SARS-CoV-2 N1 target in air samples.Conclusion: The collection efficiency and detection sensivity of a protocol to quantify SARS-CoV-2 RNA levels in indoor air has been improved in the present study. Such optimization is important to improve our understanding of the microbiological safety of indoor air. [ABSTRACT FROM AUTHOR]

Bioaerosols have received widespread attention since the outbreak of Coronavirus Disease 2019 owing to their harmful effect on public health. To deal with indoor bioaerosols in an energy-saving method, an air filtration and sterilization PV-Trombe wall was proposed in this study. An experiment rig concerning thermal sterilization of aerosolized Klebsiella pneumoniae was set up to test its feasibility and effectiveness at different exposure temperature and residence time. With the experimental data, an inactivation model was derived based on the first kinetic model and Arrhenius equation. Besides, a mathematic model concerning heat and mass transfer was established for simulating the system performance at different conditions. The results reveal that: (1) The survival ratio of bioaerosols was 0.848, 0.689, 0.493 and 0.257 for the exposure temperature of 45 °C, 60 °C, 73 °C and 85 °C at the residence time of 6.5 s (2) the survival ratio predicted by the inactivation model corresponded well with the experimental results and the root mean square error was 0.041. (3) The electrical and thermal efficiencies were 0.134 and 0.218 while the indoor bacterial concentration was reduced by over 60 % with bacterial quantity of filter maintained at a low level. (4) The increase of air velocity could significantly improve the purification performance. [Display omitted] • Proposal of a novel air filtration and sterilization PV-Trombe wall system. • Experiments on the thermal sterilization of aerosolized Klebsiella pneumoniae. • Over 70 % of the aerosolized bacteria was inactivated at 85 °C for 6.5 s. • Combination of sterilization and filtration contributed to a better performance. [ABSTRACT FROM AUTHOR]

Among extreme environments, bioaerosol includes a wide range of primary atmospheric organic particles associated with and emitted by living and dead organisms. Bioaerosol samples were collected along two transects at a subArctic Atlantic spatial scale, including the eastern Fram Strait and the Greenland, Norwegian, and North Seas. This study was aimed at first estimating microscopically the prokaryotic abundance, biomass and phenotypic traits, along with the number of potential viable and respiring cells. Moreover, physiological profiles at community level were assessed. Prokaryotic abundance ranged from 104 to 107 cells m−3, with the predominance of small sized cells (0.1 μm3). Prokaryotic biomass reached higher values (mean value 233 μg C m−3) in relation to the occurrence of large sized rods. Overall, the percentage of the viable cells was lower than the dead ones, while respiring cells were in lower abundance than total cells. The physiological profiles revealed various potential metabolic pathways among the samples, highlighting the utilization of phosphate-carbon, carboxylic and amino acids. These first results on the metabolism and physiology of microbes, which survived transport in the atmosphere of the Northern Hemisphere, suggest that bioaerosol constitutes an extremely dynamic environment of remarkable ecological interest, also considering future global warming scenarios. [ABSTRACT FROM AUTHOR]

The effects of the surrounding environment on the bacterial composition of bioaerosol were well documented for polluted and contaminated sites. However, there is limited data on the impact of plant species, especially those that produce aromas, on bioaerosol composition at agricultural sites. Hence, the aim of this study is to evaluate the variability in bacterial communities present in bioaerosol samples collected from agricultural sites with aroma-producing crops. For this, PM 2.5 , PM 10, and bioaerosol samples were collected from agricultural fields growing Ocimum [two varieties of O. sanctum (CIM-Aayu and CIM-Angana)] and O. kilimandscharicum (Kapoor), nearby traffic junctions and suburban areas. PM 2.5 and PM 10 concentrations at the agricultural site were in between the other two polluted sites. However, bioaerosol concentration was lower at agricultural sites than at other sites. The culturable bacteria Bacillus subtilis , Bacillus tequilensis , and Staphylococcus saprophyticus were more prevalent in agricultural sites than in other areas. However, the composition of non-culturable bacteria varied between sites and differed in three fields where Ocimum was cultivated. The CIM-Aayu cultivated area showed a high bacterial richness, lower Simpson and Shannon indices, and a distinctive metabolic profile. The sites CIM-Angana and CIM-Kapoor had a higher abundance of Aeromonas , while Pantoea and Pseudomonas were present at CIM-Aayu. Acinetobacter, Staphylococcus , and Bacillus were the dominant genera at the other two sites. Metabolic profiling showed that the CIM-Aayu site had a higher prevalence of pathways related to amino acid and carbohydrate metabolism and environmental information processing compared to other sites. The composition of bioaerosol among the three different Ocimum sites could be due to variations in the plant volatile and cross-feeding nature of bacterial isolates, which further needs to be explored. [Display omitted] • The particulate matter and bacterial bioaerosol were analyzed at different sites. • High bioaerosol and particulate matter were observed at traffic junction. • The bacterial genera present in each sample exhibited limited inter-site correlation. • The phyllosphere and rhizopshere contributed to bioaerosol at agricultural site. • Distinct bacterial communities were observed site with different Ocimum varieties. [ABSTRACT FROM AUTHOR]

Disinfection of shared spaces has become essential to minimize the spread of various diseases. An efficient disinfection device that can simultaneously inactivate airborne bacteria and surface-adhered bacteria in an enclosed space is required. An air-passable plasma filter (APF) was developed and applied to a chamber model to evaluate the efficacy of zone disinfection. The 60 L chamber consisted of a nebulizer, circulation fans, temperature and humidity monitors, an air-sampling port with a sealed gate, airborne bacteria-trapping media, and a built-in fan for evaluation. After spraying each bacterial strain (Escherichia coli , Staphylococcus epidermidis , and Mycobacterium smegmatis) as a bioaerosol, airborne and surface-attached bacteria were quantified simultaneously to evaluate the zone-disinfection effect of APF. The operation of APF in the 60 L chamber showed a complete zone-disinfection effect for E. coli (10 min), S. epidermidis (10 min), and M. smegmatis (60 min) present in the air and on the walls at various locations. The time required to completely disinfect each of the airborne bacteria and surface-attached bacteria within the same space was different. APF has the potential to exhibit significant germicidal effects on various micro-organisms and can be an effective alternative for disinfection of enclosed spaces. [ABSTRACT FROM AUTHOR]

Background: Disinfection of shared spaces has become essential to minimize the spread of various diseases. An efficient disinfection device that can simultaneously inactivate airborne bacteria and surface-adhered bacteria in an enclosed space is required.Aim: An air-passable plasma filter (APF) was developed and applied to a chamber model to evaluate the efficacy of zone disinfection.Methods: The 60 L chamber consisted of a nebulizer, circulation fans, temperature and humidity monitors, an air-sampling port with a sealed gate, airborne bacteria-trapping media, and a built-in fan for evaluation. After spraying each bacterial strain (Escherichia coli, Staphylococcus epidermidis, and Mycobacterium smegmatis) as a bioaerosol, airborne and surface-attached bacteria were quantified simultaneously to evaluate the zone-disinfection effect of APF.Findings: The operation of APF in the 60 L chamber showed a complete zone-disinfection effect for E. coli (10 min), S. epidermidis (10 min), and M. smegmatis (60 min) present in the air and on the walls at various locations. The time required to completely disinfect each of the airborne bacteria and surface-attached bacteria within the same space was different.Conclusion: APF has the potential to exhibit significant germicidal effects on various micro-organisms and can be an effective alternative for disinfection of enclosed spaces. [ABSTRACT FROM AUTHOR]

Air quality considerably affects bioaerosol dynamics within the atmosphere. Frequent haze events, with their associated alterations in bioaerosol composition, may pose potential health risks. This study investigated the microbial diversity, community structure, and factors of PM 2.5 within an urban environment. We further examined the impact of haze on potentially pathogenic bacteria in bioaerosols, and analyzed the sources of haze pollution. Key findings revealed that the highest levels of microbial richness and diversity were associated with lightly polluted air conditions. While the overall bacterial community structure remained relatively consistent across different air quality levels, the relative abundance of specific bacterial taxa exhibited variations. Meteorological and environmental conditions, particularly sulfur dioxide, nitrogen dioxide, and carbon monoxide, exerted a greater influence on bacterial diversity and community structure compared to the physicochemical properties of the PM 2.5 particles themselves. Notably, haze events were observed to strengthen interactions among airborne pathogens. Stable carbon isotope analysis suggested that coal combustion and automobile exhaust were likely to represent the primary source of haze during winter months. These findings indicate that adoption of clean energy alternatives such as natural gas and electricity, and the use of public transportation, is crucial to mitigate particle and harmful pollutant emissions, thereby protecting public health. [Display omitted] • Air quality considerably impacted bioaerosol characteristics in the atmosphere. • Microbial growth was inhibited under poor air quality. • Air composition greatly shaped bacterial diversity and community structure. • Haze strengthened the interactions between pathogens. • Coal combustion and automobile exhaust may be the main causes of haze in winter. [ABSTRACT FROM AUTHOR]

Biological particles are ubiquitous in nature and can transmit diseases to humans, animals and plants. Moreover, they play a significant role in influencing both regional and global climates and hydrological cycles by serving as nuclei for water droplets or ice crystals. Fluorescent biological aerosol particles (FBAPs) were observed by a wideband integrated bioaerosol spectrometer (WIBS) at an urban site in Beijing, China during spring season with highly variable weather conditions. The average of number (N F), surface area (S F) and mass concentrations (M F) of FBAPs over the spring was 0.34 cm−3, 2.0 μm2 cm−3, 1.56 μg m−3, respectively. N F was barely fluctuated throughout the clean and haze periods, but revealed pronounced variations during rain period. During the dusty period, FBAPs size distributions shifted towards larger sizes (∼ 4.0 μm), suggesting that dust-storms may introduce biological particles with larger sizes. Different from total particles, FBAPs size distribution during rain period, all exhibited a unique undulant tail on the right side, which obviously increased when D a > 10.0 μm, indicating that there should be external biological particles with large size were emitted during the rain event. Overall, these results furthered our understanding on characteristic changes of FBAPs in Beijing during distinct weather conditions. [Display omitted] • Fluorescent biological aerosol particles constitute a significant proportion of total aerosol loading in Beijing. • Air quality conditions affect the size distribution of fluorescent biological aerosol particles. • Dust events contribute more significantly to the mass of FBAPs than to their number concentration. • Rain events caused most pronounced variations in FBAPs characteristics. [ABSTRACT FROM AUTHOR]

Among the components of fine particulate matter (PM 2.5), the contributions of airborne microorganisms and antibiotic resistance genes (ARGs) to health risks have been overlooked. Airborne microbial dynamics exhibit a unique diurnal cycle due to environmental influences. However, the specific roles of PM 2.5 chemical properties resulting from fossil fuel combustion in driving circadian fluctuations in microbial populations and ARGs remain unclear. This study explored the interactions between toxic components and microbial communities during the heating period to understand the variations in ARGs. Bacterial and fungal communities showed a higher susceptibility to diel variations in PM 2.5 compared to their chemical properties. Mantel tests revealed that chemical properties and microbial community interactions contribute differently to ARG variations, both directly and indirectly, during circadian fluctuations. Our findings highlight that, during the daytime, the enrichment of pathogenic microorganisms and ARGs increases the risk of PM 2.5 toxicity. Conversely, during the nighttime, the utilization of water-soluble ions by the fungal community increased, leading to a significant increase in fungal biomass. Notably, Aspergillus exhibited a significant correlation with mobile genetic elements and ARGs, implying that this genus is a crucial driver of airborne ARGs. This study provides novel insights into the interplay between the chemical composition, microbial communities, and ARGs in PM, underscoring the urgent need for a comprehensive understanding of effective air pollution control strategies. [Display omitted] • The diurnal enriching of antibiotic resistance genes (ARGs) elevated PM 2.5 toxicity. • The nocturnal fungal community was positively correlated with NH 4 + and NO 3 −. • The fungal community emerges as a crucial driver of ARG patterns in PM 2.5. [ABSTRACT FROM AUTHOR]

This investigation used portable air cleaners (PACs) and quantitative filter forensics (QFF) to assess week-long average airborne concentrations of SARS-CoV-2 RNA in homes occupied with COVID-symptomatic individuals, classrooms, and dining locations throughout Toronto, Canada. PACs were deployed for one week each, and dust from filters was collected via vacuuming. SARS-CoV-2 RNA from filter dust was quantified using reverse transcription-polymerase chain reaction (RT-PCR). RNA quantities and PAC metadata were used to estimate airborne concentrations of SARS-CoV-2 RNA. The highest concentrations of RNA were found in isolation rooms (median concentration = 8.68 RNA copies/m3). Classrooms had lower concentrations during summer than in fall and winter (median concentration of sampling weeks when RNA was present = 0.02 RNA copies/m3 and 0.11 RNA copies/m3, respectively), which may be attributed to differences in classroom occupancy among other factors. Limitations include unknown recovery efficiency of RNA from filters and the dynamics of concentrations due to the temporal averaging of QFF. Our results are consistent with previous research highlighting the effectiveness of isolation in preventing distribution of high concentrations of SARS-CoV-2 RNA throughout a home. Overall, QFF is a beneficial tool for environmental sampling of respiratory airborne viral RNA such as SARS-CoV-2 RNA, that can be implemented for long-term sampling in mixed-occupancy environments. [Display omitted] • Quantitative filter forensics provides week-long estimates of airborne SARS-CoV-2 RNA. • Isolation rooms have the highest SARS-CoV-2 RNA concentrations in homes. • Classrooms have seasonal differences in concentrations of SARS-CoV-2 RNA. • No significant difference in RNA quantification between RT-dPCR and RT-dPCR. [ABSTRACT FROM AUTHOR]

Bioaerosols produced during animal production have potential adverse effects on the health of workers and animals. Our objective was to investigate characteristics, antibiotic-resistance genes (ARGs), and health risks of bioaerosols in various animal barns. Poultry and swine barns had high concentrations of airborne bacteria (11156 and 10917 CFU/m3, respectively). Acinetobacter , Clostridium sensu stricto , Corynebacterium , Pseudomonas , Psychrobacter , Streptococcus , and Staphylococcus were dominant pathogenic bacteria in animal barns, with Firmicutes being the most abundant bacterial phylum. Based on linear discriminant analysis effect size (LEfSe), there were more discriminative biomarkers in cattle barns than in poultry or swine barns, although the latter had the highest abundance of bacterial pathogens and high abundances of ARGs (including tet M, tet O, tet Q, tet W sul 1, sul 2, erm A, erm B) and intI 1). Based on network analyses, there were higher co-occurrence patterns between bacteria and ARGs in bioaerosol from swine barns. Furthermore, in these barns, relative abundance of bacteria in bioaerosol samples was greatly affected by environmental factors, mainly temperature, relative humidity, and concentrations of CO 2 , NH 3 , and PM 2.5. This study provided novel data regarding airborne bio-contaminants in animal enclosures and an impetus to improve management to reduce potential health impacts on humans and animals. [Display omitted] • Bioaerosol types and levels differ by barn species: poultry, swine, cattle. • Identified 24 pathogen genera vary across barn bioaerosols. • Swine barns had high ARGs and pathogen levels. • Environmental conditions drive bioaerosol diversity in barns. • Health risks in cattle barns were lower than in poultry and swine barns. [ABSTRACT FROM AUTHOR]

The development of a rapid and sensitive method for the enrichment and direct detection of airborne viruses has become urgently needed to prevent their spread. We have developed a dual-functional, label-free platform for the enrichment and optical identification of airborne viruses. This platform allows for the on-site enrichment and identification of airborne viruses through a virus enrichment component combined with surface-enhanced Raman scattering (SERS). In this work, we created an Au-porous anodic alumina (PAA) composite film, by ion sputtering Au nanoparticles (Au NPs) on a porous structure. The Au-PAA serves as a dual-functional sensor: it combines ultrafiltration through the vertical nanopores in the PAA for virus enrichment and constitutes a plasmonic substrate due to the surface plasmon near-field enhancements within the nanochannel structure. This sensor demonstrates an extraordinary enrichment efficiency (about 98 %) of obtained bioaerosols and enables simultaneous, sensitive detection at the single-virus level. Finite-difference time-domain (FDTD) simulations evidenced the electric field intensity and charge distribution of the Au-PAA. This Au-PAA composite film offers a powerful system for on-site, label-free viral particle enrichment and SERS detection. Contaminated air containing viruses can be collected in a few minutes and analyzed immediately by our platform, which is particularly beneficial for timely monitoring of viruses in the air of large public spaces. Additionally, this platform can be applied to evaluate the indoor air quality. • A potential system for enrichment and label-free on-site detection of airborne virus was designed. • Comprehensive explanation of electromagnetic enhancement mechanism. • The mechanism of the enrichment and detection of virus is demonstrated. [ABSTRACT FROM AUTHOR]

[Display omitted] The COVID-19 pandemic affected universities and institutions and caused campus shutdowns with a transition to online teaching models. To detect infections that might spread on campus, we pursued research towards detecting SARS-CoV-2 in air samples inside student dorms. We sampled air in 2 large dormitories for 3.5 months and a separate isolation suite containing a student who had tested positive for COVID-19. We developed novel techniques employing 4 methods to collect air samples: Filter Cassettes, Button Sampler, BioSampler, and AerosolSense sampler combined with direct qRT-PCR SARS-CoV-2 analysis. For the 2 large dorms with the normal student population, we detected SARS-CoV-2 in 11 samples. When compared with student nasal swab qRT-PCR testing, we detected SARS-CoV-2 in air samples when a PCR positive COVID-19 student was living on the same floor of the sampling location with a detection rate of 75%. For the isolation dorm, we had a 100% SARS-CoV-2 detection rate with AerosolSense sampler. Our data suggest air sampling may be an important SARS-CoV-2 surveillance technique, especially for buildings with congregant living settings (dorms, correctional facilities, barracks). Future building designs and public health policies should consider implementation of Heating, Ventilation, and Air Conditioning surveillance. [ABSTRACT FROM AUTHOR]

Landfill is a huge pathogen reservoir and needs special attention. Herein, the distribution and spread risk of pathogen were assessed in excavated landfill scenario. The results show that landfill excavation will greatly increase the risk of environmental microbial contamination. The highest total concentration of culturable bacteria among landfill refuse, topsoil and plant leaves was found to be as high as 1010 CFU g−1. Total coliforms , Hemolytic bacteria , Staphylococcus aureus , Salmonella , Enterococci , and Fecal coliforms were detected in the landfill surrounding environment. Notably, pathogens were more likely to adhere to plant leaves, making it an important source of secondary pathogens. The culturable bacteria concentration in the air samples differed with the landfill zone with different operation status, and the highest culturable bacteria concentration was found in the excavated area of the landfill (3.3 × 104 CFU m−3), which was the main source of bioaerosol release. The distribution of bioaerosols in the downwind outside of the landfill showed a tendency of increasing and then decreasing, and the highest concentration of bioaerosols outside of the landfill (6.56 × 104 CFU m−3) was significantly higher than that in the excavated area of the landfill. The risk of respiratory inhalation was the main pathway leading to infection, whereas the HQ in (population inhalation hazardous quotient) at 500 m downwind the excavation landfill was still higher than 1, indicating that the neighboring residents were exposed to airborne microbial pollutants. The results of the study provide evidence for bioaerosols control protective measures taken to reduce health risk from the excavated landfill. [Display omitted] • Microbe from landfill are more likely to attach to wood, paper, and plastic. • Landfill surrounding plants are greater barrier for microbial containment. • Excavation process will increase the emission of microbial. • Aerosol dispersion model shows effectively simulation results. [ABSTRACT FROM AUTHOR]

As a large-scale, temporary hospital designed to accommodate a substantial number of infected patients, Fangcang shelter hospitals carry a significant risk of infection between healthcare workers and patients. Controlling pathogen transmission through rational placement of infected patients is crucial, yet there is a lack of research, particularly on-site investigations. We used on-site experiments with numerical analysis to perform a full-scale, well-characterized, quantitative modeling of the aerodynamics by bioaerosols released from different sources in a Fangcang shelter hospital. The aim was to elucidate the impact of changes in the release source location on the transmission of bioaerosols. We observed the airborne transmission of bioaerosols within a Fangcang shelter hospital and noted the significant impact of release locations on their transmission and distribution characteristics. We highlighted the significant accumulation of remotely transported bioaerosols in the medical staff area (MSA), with a maximum concentration of 1650 copies/m3, and the largest contribution to contamination by patients with patient shelter room (PSR) 6#. Moreover, surface deposition levels on the medical workbench exceeded 1000 copies/m2. Our findings expose the crucial issues that Fangcang shelter hospitals should address in practical usage, thus providing designers and managers with innovative ideas for improvement. • An experiment using tracer bacteria was conducted in Fangcang shelter hospital. • Release location and spatial layout impact airborne transmission of bioaerosols. • Medical staff area accumulated bioaerosol concentrations in excess of 1650 copies/m3. • Surface deposition level on the medical worktable exceeds 1100 copies/m2. [ABSTRACT FROM AUTHOR]

Concerns about contaminants dispersed by seasonal precipitation have grown due to their potential hazards to outdoor environments and human health. However, studies on the crucial environmental factors influencing dispersion changes in bacterial communities are limited. This research adopted four-season in situ monitoring and sequencing techniques to examine the regional distribution profiles of bioaerosols, bacterial communities, and risks associated with extreme snowfall versus rainfall events in two monsoon cities. In the early-hours of winter snowfall, airborne cultivable bioaerosol concentrations were 4.1 times higher than the reference exposure limit (500 CFU/m3). The concentration of ambient particles (2.5 μm) exceeded 24,910 particles/L (97 μg/m3), positively correlating with the prevalence of cultivable bioaerosols. These bioaerosols contained cultivable bacterial species such as pathogenic Staphylococcus aureus , Staphylococcus epidermidis , Streptococcus pneumoniae , and Escherichia coli. Bioaerosol concentrations increased by 53.0% during 50-mm snow extremes. Taxonomic analysis revealed that Pseudomonas, Staphylococcus, and Veillonella were the most abundant bacterial taxa in the initial snowmelt samples during winter precipitation. However, their abundance decreased by 87.6% as snowing continued (24 h). Reduced water base cation concentration also led to a 1.15-fold increase in the Shannon index, indicating a similar yet heightened bacterial diversity. Seasonally, Pedobacter and Massilia showed higher relative abundance (25% and 18%, respectively), presenting increased bacterial transmission to the soil. Furthermore, Pseudomonas was identified in 60% of spring snowstorm samples, suggesting long-distance dispersal of pathogenic bacteria. When these atmospheric aerosol particles carrying biological entities (0.65–1.1 μm) penetrated human alveoli, the calculated hazard ratio was 0.55, which as observed in inhalation exposures. Consequently, this study underscores the risk of seasonal precipitation-enhanced ambient bacterial transmission. [Display omitted] • A wide bacterial diversity and 0.65–3.3 μm bioaerosol dispersion were detected. • Extreme precipitation events could alter bacteria diversity and abundance in water. • Bioaerosol concentration correlated positively with PM 1.0‒10 during snowstorms. • Bioprecipitation temporarily predominated the relative abundance of Pseudomonas. • Inhalation risks of outdoor bioaerosols in hydrologic cycles are higher in cities. [ABSTRACT FROM AUTHOR]

Allergic respiratory diseases are considered to be among the most important public health concerns, and pollen is the main cause of allergic respiratory diseases worldwide. However, the biological component of air quality is largely underestimated, and there is an important gap in the legislation in this area. The aims of this study were to characterise the occurrence and incidence of pollen exposure in relation to potential pollen sources and to delineate the main areas of aerobiological risk in the Madrid Autonomous Region based on homogeneous patterns of pollen exposure. This study uses the historical aerobiological database of the Madrid Region Palynological Network (central Spain) from ten pollen stations from 1994 to 2022, and the land-use information from the Corine Land Cover. Multiple clustering approaches were followed to group the sampling stations and subsequently all the 1 × 1km pixels for the Madrid Autonomous Region. The clustering dendrogram for land-use distribution was compared to the dendrogram for historical airborne pollen data. The two dendrograms showed a good alignment with a very high correlation (0.95) and very low entanglement (0.15), which indicates a close correspondence between the distribution of the potential pollen sources and the airborne pollen dynamics. Based on this knowledge, the Madrid Autonomous Region was divided into six aerobiological risk areas following a clear anthropogenic gradient in terms of the potential pollen sources that determine pollen exposure in the Madrid Region. Spatial regionalisation is a common practice in environmental risk assessment to improve the application of management plans and optimise the air quality monitoring networks. The risk areas proposed by scientific criteria in the Madrid Autonomous Region can be adjusted to other operational criteria following a framework equivalent to other air quality networks. [Display omitted] • Aerobiological risk areas were delineated in the Madrid Autonomous Region. • Distribution of sources and airborne pollen exposure show a close correspondence. • Six aerobiological risk areas were defined following a clear anthropogenic gradient. • Pollen exposure was studied in urban areas, agricultural lands and forestry areas. • Spatial regionalisation is a common practice in environmental risk assessment. [ABSTRACT FROM AUTHOR]

Introduction: Money is the most common item with which we have daily contact. Circulated banknotes and coins can become microbiologically contaminated and act as both a source and a means of spreading such pollutants. Material and methods: The study was carried out in three money sorting facilities in Poland. Bioaerosol samples were collected using a 6-stage Andersen impactor, and microorganisms deposited on tabletop surfaces were sampled using the swab method. Bacterial and fungal concentrations were calculated and all isolated species were taxonomically identified. Results: The study confirmed that means of payment are active sources of microbial emission in money sorting facilities. The bioaerosol concentrations did not exceed the threshold limit values proposed for this type of office premises. It confirms that ventilation systems in these facilities worked efficiently, protecting them from the migration of microbial contaminants present in both indoor and outdoor (atmospheric) background air. On the other hand, the average concentrations of bacteria and fungi on tabletop surfaces in banknote and coin sorting rooms were above the proposed purity levels for indoor surfaces and should be treated as microbiologically contaminated. Microbiota isolated from the air and surfaces were very diverse and among those strains were bacterial and fungal pathogens that can pose a health threat to exposed individuals. Conclusions: The results showed that employees in money sorting facilities were exposed to microorganisms that may contribute to the development of adverse health outcomes. To protect them, highly efficient hygienic measures should be introduced in this working environment, to prevent both unwanted pollution and subsequent secondary emission of microbial contaminants from sorted means of payment and tabletop surfaces. [ABSTRACT FROM AUTHOR]

This study assessed the effects of bioaerosol pollution on community health across six urban and residential communities located in Ho Chi Minh megacity, Vietnam. A questionnaire survey was performed on 300 respondents to record health complaints from exposure to bioaerosols. The health symptoms (i.e. flu and cough) were highest in those items with means equal to 6.518 (SD=2.5068) and 6.555 (SD=2.6696), whereas the lowest item was "chest tightness" with mean equal to 3.334 (SD = 2.7001). The results showed that the questionnaire retained good internal consistency with Cronbach's alpha was 0.613. Using principle component analysis, we have identified 12 questions related to health complaints that could be grouped into five main clusters: PC1 named "nose symptoms"; PC2 named "throat (respiratory symptoms)"; PC3 named "fever symptoms"; PC4 named "flu (flu-like symptoms)"; and PC5 named "cough symptoms", respectively. The results indicated the potential effects of bioaerosols on human health, with the PCs have accounted for 63.2 percent of the overall total variance and with eigenvalues equal to 1.502 >1. Using multiple linear regression models, this study found that latent factors (i.e. daily habit, living environment, and medical history) such as duration from last pain, residential duration, duration staying at home, home time, distance to street can explain the effect of bioaerosols on health symptoms at the 0.05 significance level. The findings are helpful and significant reference for urban planning, policy making and the community health protection in Ho Chi Minh megacity. [ABSTRACT FROM AUTHOR]

Introduction. Money is the most common item with which we have daily contact. Circulated banknotes and coins can become microbiologically contaminated and act as both a source and a means of spreading such pollutants. Materials and method. The study was carried out in three money sorting facilities in Poland. Bioaerosol samples were collected using a 6-stage Andersen impactor, and microorganisms deposited on tabletop surfaces were sampled using the swab method. Bacterial and fungal concentrations were calculated and all isolated species were taxonomically identified. Results. The study confirmed that means of payment are active sources of microbial emission in money sorting facilities. The bioaerosol concentrations did not exceed the threshold limit values proposed for this type of office premises. It confirms that ventilation systems in these facilities worked efficiently, protecting them from the migration of microbial contaminants present in both indoor and outdoor (atmospheric) background air. On the other hand, the average concentrations of bacteria and fungi on tabletop surfaces in banknote and coin sorting rooms were above the proposed purity levels for indoor surfaces and should be treated as microbiologically contaminated. Microbiota isolated from the air and surfaces were very diverse and among those strains were bacterial and fungal pathogens that can pose a health threat to exposed individuals. Conclusions. The results showed that employees in money sorting facilities were exposed to microorganisms that may contribute to the development of adverse health outcomes. To protect them, highly efficient hygienic measures should be introduced in this working environment, to prevent both unwanted pollution and subsequent secondary emission of microbial contaminants from sorted means of payment and tabletop surfaces. [ABSTRACT FROM AUTHOR]

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Introduction. Workers of pellet production facilities (WPPF) are exposed to high concentrations of wood dust and microbial pollutants. Such stimulation may lead to numerous allergic and toxic reactions, infections, and other non-specific syndromes. Objective. To check the influence of individual traits of workers and characteristic features / factors of their living and working environments on the probability of adverse outcomes’ appearance. Materials and Method. The questionnaire study assessing adverse health effects resulting from individual exposure was conducted among 28 workers of 10 Polish WPPF. The logistic regression (for dichotomous variables) was used to determine the appearance probability (given as odds ratio) of adverse symptoms or diseases. Results and Conclusions. WPPF workers may have an increased risk of developing work-related adverse health outcomes. Both the individual traits and environmental exposure factors significantly influence the probability of their occurrence. [ABSTRACT FROM AUTHOR]

The study's primary focus lies in examining the relationship between respiratory and deposition doses of bacterial aerosols in urban kindergarten, providing valuable insights into the specific doses absorbed by individuals in different sections of their respiratory systems based on the aerodynamic diameter of bacterial particles. Samples were collected twice a week, using by an Andersen cascade impactor during autumn and winter seasons 2018/2019 resulting in a total of 1152 Petri dishes analyzed. The highest average concentration of bacterial aerosol was observed during autumn (1698 ± 663 CFU/m3) in comparison to winter months (723 ± 134 CFU/m3). Respirable doses for children and staff were 2945 and 2441 CFU/day during winter and 5988 and 4964 CFU/day during autumn, respectively. Deposition doses incorporated from empirical models for regional deposition in the respiratory tract showed that children in kindergarten absorb 33% less of bacteria into alveolar region if breath by nose instead of mouth. Additionally, risk assessment results indicate that the hazard indices for children attending kindergartens for 3 years and for staff working 25 years are below 1, suggesting minor risks associated with the inhalation of bioaerosols during autumn and winter. HI was <1, so the non-carcinogenic effects are on an acceptable level, but the indoor/outdoor ratio were 3.5 and 2.4 for autumn and winter, respectively, indicating children's and adult's exposure to bacterial aerosol should be reduced. [Display omitted] • Concentration and daily dose of bacteria were measured in Polish kindergarten. • The highest concentration of bacterial aerosol in indoor was 1698 CFU/m3. • The bacterial aerosol in indoor was relatively fresh and mostly of human origin. • The highest inhaled dose of respirable bacteria was observed during autumn. • Health risk from the exposure to bacterial aerosol is on acceptable level. [ABSTRACT FROM AUTHOR]

Toilet flushing can produce pathogen-laden aerosols and may pose a serious concern for the transmission of diseases. The emission of bioaerosols from flushing a squat toilet has not been thoroughly examined in the literature. In this study, we conducted pilot measurements to quantify the emission of airborne microorganisms during the flushing of a squat toilet. A full-scale custom-built squat toilet with a typical flushing system was designed and built. The aerosolized droplets and microbes emitted after a single flushing were measured and quantified. Three bacteria (Escherichia coli , Pseudomonas alcaligenes , and Salmonella enterica) and two viruses (bacteriophage MS2 and P22) were tested. The results suggest that a single flush can generate a large number of small droplets in the air. The total emission number of droplets within 0.3–10 μm per flush was 5.72 × 105±1.93 × 105 of which 96 % were smaller than 2 μm. We observed a linear correlation between the number of emitted bioaerosols and the amount of microorganisms introduced into the toilet bowl. The quantified data also shows that flushing-induced airborne microorganism emission strength (a normalized parameter) varied significantly with the sizes of microorganisms. Overall, the emission strengths of viruses were significantly higher than those of the tested bacteria. The mean emission strength of P22 and MS2 per flush was 33.5 times higher than the average emission strength of the three tested bacteria. This work provides valuable data on the bioaerosol emission by flushing a squat toilet, which is essential for developing control measures and evaluating the risk of pathogen exposure. • Aerosolized droplets and microbes after flushing a squat toilet were quantified. • The emission strengths of three bacteria and two viruses were determined. • 96 % of droplets produced by flushing were smaller than 2 μm. • The emission strength of flushing-generated viruses was much higher than that of bacteria. [ABSTRACT FROM AUTHOR]

Developing air filters with biocidal ability is important to protect the public from infectious respiratory diseases. A simple spray-coating approach was devised to fabricate antimicrobial air filters to remove bioaerosols. The commercial antimicrobial agent Goldshield 75 was coated on the air filters through covalent immobilization, endowing the fabricated filter with long-lasting biocidal ability. All coated filters significantly inhibited both Gram-positive bacteria (Micrococcus luteus) and Gram-negative bacteria (Escherichia coli). The antibacterial ability of the coated filters is similar to the commercial AeraSafe antibacterial filter. The coated filter showed over 99.9 % antibacterial efficiency 3 months after the application of the coating. Both bacterial and virus filtration efficiencies of coated charged polypropylene filter were higher than 99.9 %. The coating did not have much effect on the NaCl aerosol filtration efficiency of the filters. This simple spray-coating strategy is a practical method for producing antimicrobial air filters for the prevention of infectious respiratory diseases. [Display omitted] • An antimicrobial polypropylene filter was prepared using spray coating. • The antimicrobial filter had high filtration efficiency against particles, bacteria, and viruses. • The antimicrobial filter maintains its high antibacterial ability after three months. • This study provides a simple strategy for developing antibacterial filters to improve indoor air quality. [ABSTRACT FROM AUTHOR]

Infectious diseases are a part of everyday life, and acute respiratory diseases are the most common. Many agents carrying out respiratory infections are transmitted as bioaerosols through the air, usually, particulate matter containing living organisms. The purpose of the study is to conduct a systematic review and meta-analysis to assess the likelihood that people exposed to bioaerosols may experience severe respiratory diseases. Nine digital databases and bibliographies were assessed for papers conducted between January 1960 and April 2021. A total of 35 health and exposure studies were included from 825 studies for the systematic review, while only 17 contented the meta-inclusion analysis's criteria. This systematic review found higher bacterial bioaerosol concentrations in poultry farms, waste dumpsites, composting plants, and paper industries. The meta-analysis's Standard Mean Difference (SMD) measurement indicates a substantially positive association between bioaerosol exposure and respiratory disease outcomes in targeted populations. The value is 0.955 [95% CI, range 0.673–1.238; p < 0.001]. As per the Risk of Bias (ROB) findings, most of findings (30 out of 35 [85.71%]) were judged to have low ROB. From the random effect probit model, the total relative risk is 1.477 (95% CI, range 0.987–2.211), indicating a higher risk of respiratory diseases from bioaerosol exposure than the control groups. The total risk difference is 0.121 (95% CI, −0.0229 to 0.264), which means intervention groups may have a higher risk of respiratory diseases from continuous bioaerosol exposure than the control groups. The dose-response relationship revealed a strong positive linear coefficient correlation between bacterial & fungal bioaerosol exposure to respiratory health. Based on self-reported outcomes in those studies, The systematic review and meta-analysis stated that bioaerosol exposure had an effect on pulmonary health. [Display omitted] • Poultry farms, dumpsites & damp houses has higher bioaerosol concentrations. • People in/near damp houses, landfills, and animal farms face higher health risks. • Studies found cough, wheezing, pneumonia & asthma as major respiratory diseases. • As Per RE model, subject group had higher respiratory disease risk than control group. • 39.62% sample had positive respiratory health effects linked to bioaerosol exposure. [ABSTRACT FROM AUTHOR]

Depending on their concentrations, sizes, and types, particulate matters of biological origins (bioPM) significantly affect human health. However, for different air environments, they are not well characterized and can vary considerably. As an example, we investigated the bioPM differences at an urban (Beijing) site and a rural (Wangdu) site in the North China Plain (NCP) using an online monitoring instrument, an ultraviolet aerodynamic particle sizer (UV-APS), the limulus amebocyte lysate (LAL) assay, and a high-throughput sequencing method. Generally, lower concentrations of viable bioPM (hourly mean: 1.3 × 103 ± 1.6 × 103 m−3) and endotoxin (0.66 ± 0.16 EU/m3) in Beijing were observed compared to viable bioPM (0.79 × 105 ± 1.4 × 105 m−3) and endotoxin (15.1 ± 23.96 EU/m3) at the Wangdu site. The percentage of viable bioPM number concentration in the total PM was 3.1% in Beijing and 6.4% in Wangdu. Approximately 80% of viable bioPM was found to be in the range from 1 to 2.5 μm. Nevertheless, the size distribution patterns for viable bioPM at the Beijing and Wangdu sites differed and were affected by PM pollution, leading to distinct lung deposition profiles. Moreover, the distinct diurnal variations in viable bioPM on clean days were dimmed by the PM pollution at both sites. Distinct bacterial community structures were found in the air from the Beijing and Wangdu sites. The bacterial community in urban Beijing was dominated by genus Lactococcus (49.5%) and Pseudomonas (15.1%), while the rural Wangdu site was dominated by Enterococcus (65%) and Paenibacillus (10%). Human-derived genera, including Myroides , Streptococcus , Propionibacterium , Dietzia , Helcococcus , and Facklamia , were higher in Beijing, suggesting bacterial emission from humans in the urban air environment. Our results show that different air harbors different biological species, and people residing in different environments thus could have very different biological particle exposure. Image 1 • The PM of biological origins (bioPM) in urban Beijing and rural Wangdu were compared. • Viable bioPM in Beijing peaked around ∼2 μm, while below 2 μm in Wangdu. • Particulate air pollution dimmed the diurnal variation of viable bioPM. • The airborne bacterial communities showed large disparities between Beijing and Wangdu. • Human-derived bacterial genera contributed more to the air of urban Beijing. Urban and rural populations are exposed to distinct ambient bioPM communities. Humans themselves play a role in shaping the structure of bioPM in densely populated urban areas. [ABSTRACT FROM AUTHOR]

From a health prospective, it is critical to provide a comprehensive model which integrates all the parameters involved in virus transmission and its consequences on human body. In order to estimate the health risks, for workers and residents, associated with an exposure airborne viruses emitted from a wastewater treatment (WWTP), the concentration levels of viruses in emitted bioaerosols over a twelve-month period were measured by real-time polymerase chain reaction (RT-PCR). A combined Gaussian plum dispersion model and quantitative microbial risk assessment (QMRA) with Monte-Carlo simulation served as suitable explanatory tools to estimate the risk of acquiring gastrointestinal illness (GI) due to exposure to air containing Rotavirus (RoV) and Norovirus (NoV) bioaerosols. Additionally, DALY metric was applied to quantify the disability and mortality for workers and residents. RoV and NoV were detected above aeration tank with annual mean concentration 27 and 3099 (Viruses/m3.h), respectively. The medium calculated DALY indicator based on viral loads in contaminant source (RoV:5.76 × 10−2 and NoV:1.23 × 10−1) and estimated in different distances away (300–1000 m) (RoV:2.87 × 10−2- 2.75 × 10−2 and NoV:1.14 × 10−1-1.13 × 10−1) were markedly higher than the threshold values recommended by US EPA (10−4 DALY pppy) and WHO (10−6 DALY pppy). The sensitivity analysis highlighted dose exposure and disease burden per case (DBPC) as two most influential factors for both workers and residents following exposure to two pathogens of concern. Due to high resistance and high concentration in the environment, the presence of RoV and NoV can intensify the consequences of diarrhea especially for children under five years of age; A comprehensible and transparent presentation of DALYs and QMRA can help decision makers and responsibilities to justify the priorities of exposure to wastewater in comparison with other risks of daily life. Image 1 • RoV and NoV were monitored with annual mean concentration 27 and 3099 (Viruses/m3h), respectively. • Pinf for RoV(8.3 × 10−3-2.3 × 10−3) and NoV(9.8 × 10−2-9.4 × 10−2) decreased at distances 300–1000 m. • The medium DALY for workers for exposure to RoV and NoV were 5.7 × 10−2 and1.2 × 10−1. Capsule: Proposing a comprehensive model for measured RoV and NoV in WWTP air and their atmospheric dispersion to calculate corresponding QMRA and DALY for workers and residents. [ABSTRACT FROM AUTHOR]

Abstract The North China Plain is the agricultural heartland in China. High PM 2.5 levels and elevated chemical pollutants have been observed during crop harvest seasons due to open biomass burning. Biomass burning in the wheat-harvest season may significantly deteriorate the regional air quality. The harmful ingredients in smoke particles also have severe implications for toxicity and health effects. Previous studies have illustrated the potential role of bioaerosols as ice-nuclei and cloud condensation nuclei and highlighted their influence on biochemical cycles and human health effects. In a monthly field observation campaign of biomass burning conducted at the summit of Mount Tai in July 2015, we reported the composition, potential role, size distribution of microorganisms in particulate matters PM 1.0 , PM 2.5 , and estimated their contribution to particles. The wide-range particle spectrometer suggested that the predominant particles were distributed in submicron particles (PM 1.0), which resulted in a similar community structure for bacteria and fungi in PM 1.0 and PM 2.5. Among bacteria, the predominant Pseudomonas accounted for 18.06% and 21.29% in PM 1.0 and PM 2.5 , respectively. Alternaria covered up to 69.01% and 72.76% of the fungal community in PM 1.0 and PM 2.5 , respectively. A disparity between bacterial communities was identified by the abundance of rare species, such as Bacilli being higher in PM 1.0 (2.4%) than in PM 2.5 (1.8%), and Defluviicoccus being higher in PM 2.5 (2.5%) than in PM 1.0 (0.5%), which may be related to cell size and cell growth patterns. Quantitative PCR revealed that microbial cell numbers in PM 2.5 were higher than in PM 1.0 , and that the bacterial cell number was about an order of magnitude greater than the fungal cell number. However, the mass concentration and contribution of fungi to particulate matter was much higher than that of bacteria, suggesting the underestimated role of fungi in atmospheric aerosols. Airborne microorganisms in alpine areas remained less characterized. The findings presented here illustrated the potentially important impacts on air quality and bioaerosol pollution by biomass burning, which provides an essential reference for understanding the transmission and health effects of bioaerosols. Highlights • Elevated bioaerosols were affected by biomass burning disturbance. • Similar bacterial and fungal community structures identified in PM 1.0 and PM 2.5. • The microbial community included potential plants and human pathogens. • Fungi had a greater contribution to particle mass concentration than bacteria. [ABSTRACT FROM AUTHOR]

Abstract Jumping on the bed is a favorite behavior of children; however, no study has investigated the increased air pollutants resulting from jumping on the bed. Therefore, we aimed to investigate the elevated concentrations of particulate matter (PM) and bioaerosols from jumping on the bed and making the bed. Simulation of jumping on the bed and making the bed was performed at sixty schoolchildren's houses in Taiwan. PM 10 , PM 2.5 , PM 1 (PM with aerodynamic diameter less than 10, 2.5, and 1 μm, respectively) and airborne bacteria, fungi and endotoxin concentrations were simultaneously measured over simulation and background periods. Our results show the increase of PM 10 , PM 2.5 , PM 1 , airborne bacteria and fungi through the behavior of jumping on the bed (by 414 μg m-3, 353 μg m-3, 349 μg m-3, 6569 CFU m-3 and 978 CFU m-3, respectively). When making the bed, the PM 10 , PM 2.5 , PM 1 , airborne bacteria and fungi also significantly increased by 4.69 μg m-3, 4.09 μg m-3, 4.15 μg m-3, 8569 CFU m-3, and 779 CFU m-3, respectively. Airborne endotoxin concentrations significantly increased by 21.76 EU m-3 following jumping on the bed and making the bed. Moreover, when jumping on the bed, higher PM 2.5 and PM 1 concentrations in houses with furry pets rather than no furry pets, and less airborne fungi in apartments than in townhouses were found. For making the bed, lower airborne fungi was found in houses using essential oils rather than no essential oils using. The airborne endotoxin concentrations were positively associated with furry pets and smokers in the homes and negatively correlated to the home with window opening with a statistical significance during the periods of jumping on the bed and making the bed. In conclusion, significant increases of PM and bioaerosols during jumping on the bed and making the bed may need to be concerned. Graphical abstract Image 1 Highlights • First study to reveal increased PM and bioaerosols levels when jumping on the bed. • PM and bioaerosols up to 4 and 7 times background levels when jumping on the bed. • During jumping on the bed and making the bed, endotoxin was increased by 22 EU/m3. • PM significantly associated with fungi during jumping on the bed & making the bed. • Window opening reduced endotoxin exposure when jumping on the bed & making the bed. Jumping on the bed significantly increased the concentration of PM, airborne bacteria, fungi, and endotoxin. [ABSTRACT FROM AUTHOR]

Abstract Bacteria are ubiquitous in the near-surface atmosphere where they constitute an important component of aerosols with the potential to affect climate change, ecosystems, atmospheric process and human health. Limitation in tracking bacterial diversity accurately has thus far prevented the knowledge of airborne bacteria and their pathogenic properties. We performed a comprehensive assessment of bacterial abundance and diverse community in PM 2.5 collected at Mt. Tai, via high-throughput sequencing and real-time PCR. The samples exhibited a high microbial biodiversity and complex chemical composition. The dominating populations were gram-negative bacteria including Burkholderia , Delftia , Bradyrhizobium , and Methylobacterium. The PM mass concentration, chemical composition, bacterial concentration and community structure varied under the influence of different air-mass trajectories. The highest mass concentration of PM 2.5 (61 μg m−3) and major chemical components were recorded during periods when marine southeasterly air masses were dominant. The local terrestrial air masses from Shandong peninsula and its adjacent areas harbored highest bacterial concentration loading (602 cells m−3) and more potential pathogens at the site. In contrast, samples influenced by the long-distance air flow from Siberia and Outer Mongolia were found to have a highest richness and diversity as an average, which was also marked by the increase of dust-associated bacteria (Brevibacillus and Staphylococcus). The primary research may serve as an important reference for the environmental microbiologist, health workers, and city planners. Graphical abstract fx1 Highlights • PM 2.5 samples exhibited a high microbial biodiversity and complex chemical composition. • Relationships between bacterial populations and PM composition were investigated. • The highest bacterial concentration and more potential pathogens were recorded under the influence of local air pollutants. • The long-range transported air mass exhibited highest richness and diversity with an increased abundance of dust-borne bacteria. [ABSTRACT FROM AUTHOR]

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Antimicrobial resistance (AMR) is a serious issue that is continuously growing and spreading, leading to a dwindling number of effective treatments for infections that were easily treatable with antibiotics in the past. Animal farms are a major hotspot for AMR, where antimicrobials are often overused, misused, and abused, in addition to overcrowding of animals. In this study, we investigated the risk of AMR transmission from a farm to nearby residential areas by examining the overall occurrence of endotoxins, antibiotic resistance genes (ARGs), and mobile genetic elements (MGEs) in the air of a cattle farm. We assessed various factors, including the season and year, day and nighttime, and different locations within the farm building and its vicinity. The most abundant ARGs detected were tetW , aadA1, and sul2 , genes that encode for resistances towards antibiotics commonly used in veterinary medicine. While there was a clear concentration gradient for endotoxin from the middle of the farm building to the outside areas, the abundance of ARGs and MGEs was relatively uniform among all locations within the farm and its vicinity. This suggests that endotoxins preferentially accumulated in the coarse particle fraction, which deposited quickly, as opposed to the ARGs and MGEs, which might concentrate in the fine particle fraction and remain longer in the aerosol phase. The occurrence of the same genes found in the air samples and in the manure indicated that ARGs and MGEs in the air mostly originated from the cows, continuously being released from the manure to the air. Although our atmospheric dispersion model indicated a relatively low risk for nearby residential areas, farm workers might be at greater risk of getting infected with resistant bacteria and experiencing overall respiratory tract issues due to continuous exposure to elevated concentrations of endotoxins, ARGs and MGEs in the air of the farm. [Display omitted] • Endotoxins could not remain airborne for a long time • Antibiotic resistance genes & mobile genetic elements were abundant in fine aerosol • The same ARGs & MGEs were found in the air and manure • Farmworkers might be at risk of developing respiratory health issues [ABSTRACT FROM AUTHOR]

Ozone, a prevalent pollutant in enclosed spaces, can pose health risks even at low levels. Despite its widespread use for disinfection, the efficacy in neutralizing airborne pathogens in confined settings remains uncertain. A study was conducted to investigate the disinfection capabilities of low-concentration ozone (several dozen parts per billion, ppb), within an isolation ward. Serratia marcescens and phi-X174 were used as tracer bioaerosols. The study examined two scenarios of applying low-concentration ozone in closed environments: direct introduction of low-concentration ozone into the ward and comparison of air disinfection effects of ozone-producing and non-ozone-producing UVC lamps. The UVC lamps chosen for this study were of 185 nm and 254 nm, which cannot coexist with humans when turned on. The results revealed that ozone concentrations below 60 ppb did not significantly impact air disinfection regarding Serratia marcescens and there was no noteworthy difference in effectiveness between the two types of UVC lamps for both Serratia marcescens and phi-X174. However, using UVC lamp resulted in a significantly higher air disinfection effect compared to the absence of a UVC lamp. For Serratia marcescens , the inclusion of ozone-producing and non-ozone producing UVC lamps (k = 49.8 ± 9.2 h−1, 52.9 ± 8.6 h−1, mean ± SD) significantly enhanced the decay rate by 29.6 h−1 and 32.7 h−1 respectively, compared with the absence of UVC lamps (k = 20.2 ± 2.3 h−1, mean ± SD). These findings highlight the limited potential of low-concentration ozone for air disinfection and emphasize the need for cautious utilization in enclosed environments. [Display omitted] • The air disinfection effect of low-concentration ozone introduced directly in the range of dozens of ppb was investigated. • The air disinfection effect of low-concentration ozone produced by UVC lamps was confirmed. • The decay rate of bioaerosols in isolation wards under mechanical ventilation was clarified. [ABSTRACT FROM AUTHOR]

Abstract Operating rooms (ORs) in hospitals are sensitive wards because patients can get infections. This work aimed to characterize the type and concentration of bioaerosols in nine ORs of an educational hospital before and after sterilization and disinfection. During 2017, fungal samples were incubated at 25–28 °C for 3–7 days and bacterial samples at 37 °C for 24–48 h. The study results showed that the concentrations of fungi before cleaning procedures (for both of disinfection and sterilization) were limited from 4.83 to 18.40 CFU/m3 and after cleaning procedures ranged from 1.90 to 8.90 CFU/m3. In addition, the concentrations of bacteria before cleaning procedures were limited 14.65–167.40 CFU/m3 and after cleaning procedures ranged from 9.50 to 38.40 CFU/m3. The difference between the mean concentrations of airborne bioaerosols before and after sterilization was significantly different than the suggested value of 30 CFU/m3 (p ≤ 0.05). The bacterial concentration was higher than the recommended value (30 CFU/m3) in 41% of the ORs. The main fungal species identified in the indoor air of ORs (before vs. after sterilization) were A. fumigatus (25.6 vs. 18.3%), A. Niger (11.6 vs. 5.8%), Penicillium spp. (5.5 vs. 3.3%), Alternaria spp. (2.8 vs. 0.7%), Fusarium spp. (9.7 vs. 3.7%), Mucor spp. (15 vs. 12.7%), Cephalotrichum spp. (1.7 vs. 0.8%), A. Flavus (24.6 vs. 18.5%), Cladosporium spp. (2.6 vs. 0.8%), and Trichoderma spp. (0 vs. 0.9%). The growth of biological species even after sterilization and disinfection likely resulted from factors including poor ventilation, sweeping of OR floors, inadequate HVAC filtration, high humidity, and also lack of optimum management of infectious waste after surgery. Designing well-constructed ventilation and air-conditioning systems, replacing HEPA filters, implementing more stringent, frequent, and comprehensive disinfection procedures, and controlling temperature and humidity can help decrease bioaerosols in ORs. Graphical abstract fx1 Highlights • Bioaerosol composition measurements inside of hospital operating rooms (ORs) in Shiraz, Iran. • Bacterial concentration was higher than the recommended value (30 CFU/m3) in the ORs. • Gram-positive bacteria concentrations higher than Gram-negative bacteria in all ORs. • The concentration of bioaerosol decreased slightly after sterilization and disinfection. • The main fungal species in indoor air of ORs were A. fumigatus , Penicillium spp., Alternaria spp. , and Cephalotrichum spp. [ABSTRACT FROM AUTHOR]

Air in concentrated animal feeding operations contains antibiotic resistance genes and airborne pathogens, with potential threat to human and animal health. In this study, air was sampled in the living area, outside, and inside of a fattening pig house in a pig farm for 24 and 48 hours. Feedstuffs, drinking water additives, and feces in the pig house were collected. Three kinds of antibiotic resistance genes (macrolide, β-lactam, and tetracycline) and seven pathogenic microorganisms (Campylobacter, Clostridium perfringens, Enterococcus, Escherichia coli, Yersinia enterocolitica, Staphylococcus spp., and Streptococcus suis) were detected by polymerase chain reaction (PCR). Six genes with high detection rates were selected, with their concentrations being determined by real-time quantitative PCR (qPCR). Results showed that three macrolide and two tetracycline resistance genes were detected in all air samples. Enterococcus, Escherichia coli, Yersinia enterocolitica, and Staphylococcus spp. were detected in air samples and drinking water additive. The concentrations of most target genes were above 104 copies·m-3. The gene concentrations near the pig house were much higher than those in the living area. Main sources of antibiotic resistance genes and pathogens in the air were pig manure and drinking water additive. Sampling time of 24 h in the pig farm met the requirements for PCR detection. Sampling time of 48 h had a higher sampling efficiency than that of 24 h in the living area of the pig farm, whereas sampling time of 24 h was more appropriate than that of 48 h in high bioaerosol concentration area such as the pig house. [ABSTRACT FROM AUTHOR]

Introduction and objective. The goal of the study was a microbiological, qualitative and quantitative analysis of bioaerosol at the workplace of medical personnel (Health Emergency Departments (HEDs), ambulances), and comparative administration offices with an expected neutral occupational exposure to biological agents measured with individual Button Sampler. Materials and method. Personal sampling was performed with Button Sampler instrument loaded with gelatine filters in 10 HEDs, in 9 ambulances and in 9 offices to assess the occupational biological agents’ exposure in air. Sampling was conducted from March until April 2016. Samples were quantitatively assessed for viable and total number of bacteria and fungi. Routine procedures for microbiological diagnostics were implemented. Data were analysed using Kruskal–Wallis and Mann-Whitney statistical tests with α=0.05. P value less than 0.05 were considered significant. Results. At the workplaces assessed, the concentrations of viable microorganisms in HEDs were 1.3 × 102 – 4.2 × 103 CFU/m3 for bacteria, 3.4 × 100 – 8.1 × 101 CFU/m3 for fungi; in ambulances 1.3 × 102 – 1.4 × 103 CFU/m3 (bacteria), 6.7 × 100 – 6.5 × 102 CFU/m3 (fungi) and in offices 4.2 × 101 – 5.0 × 103 CFU/m3 (bacteria), 0 – 7.9 × 102 CFU/m3 (fungi). In outdoor air, the number of microorganisms reached the level: 1.0 × 102 – 5.9 × 102 CFU/m3 for bacteria and 1.5 × 102 – 8.2 × 102 CFU/m3 for fungi. The predominant isolated bacteria were Gram-positive cocci. The prevalent fungi species belonged to the genus Aspergillus and Penicillium. Conclusions. The quantitative assessment of examined indoor air was similar to control outdoor air, and were relatively low. The level of microbiological contamination did not exceed 5 × 103 CFU/m3 which is recommended as an admissible level in public spaces in Poland. [ABSTRACT FROM AUTHOR]

Ozone exacerbates allergy symptoms to certain pollens. The molecular mechanisms by which ozone affects pollen grains (PGs) and allergies are not fully understood, especially as the effects of pollutants may vary depending on the type of pollen. In this work, pollens of 22 different taxa were exposed under laboratory conditions to ozone (100 ppb) to quantify the ozone uptake by the PGs. The ozone uptake was highly variable among the 22 taxa tested. The highest ozone uptake per PG was measured on Acer negundo PGs (2.5 ± 0.2 pg∙PG−1). On average, tree pollens captured significantly more ozone than herbaceous pollens (average values of 0.5 and 0.02 pg∙PG−1, respectively). No single parameter (such as the number of apertures, pollen season, pollen size, or lipid fraction) could predict a pollen's ability to take up ozone. Lipids seem to act as a barrier to ozone uptake and play a protective role for some taxa. After inhalation of PGs, pollen-transported ozone could be transferred to mucous membranes and exacerbate symptoms through oxidative stress and local inflammation. Although the amount of ozone transported is small in absolute terms, it is significant compared to the antioxidant capacity of nasal mucus at a microscale. This mechanism of pollen-induced oxidative stress could explain the aggravation of allergic symptoms during ozone pollution episodes. [Display omitted] • Ozone uptake was measured on 22 different pollen taxa. • Acernegundo pollen has the greatest ozone capture (2.5 pg per pollen grain). • Tree pollens uptook significantly more ozone than herbaceous pollens. • Lipids seem to play a protective role for pollen against ozone. • Transfer of transported ozone to the mucous membranes could lead to oxidative stress. [ABSTRACT FROM AUTHOR]

The environment of underground hard coal mines, due to high humidity and temperature, combined with the presence of organic substances and very high dust content, provides optimal conditions for the growth and development of microorganisms, including pathogens. The presented research was aimed at determining the quantitative and qualitative diversity of air in underground mining excavations. Microbiological tests of air samples were carried out according to standard microbiological techniques. The study of microbial communities made it possible to determine the unit concentrations of microorganisms, identify potential pathogens, and analyze the manner of their spread in the air of an underground mine. A large number and variety of microorganisms were observed in the bioaerosol, including pathogenic ones (e.g., Staphylococcus aureus , Aspergillus flavus) that may pose a potential threat to humans by causing lung and skin diseases. Due to the insufficient state of global knowledge in this area of research the obtained results are helpful in the modernization of existing and designing new mining excavation ventilation systems, as well as in refreshing particularly hazardous places. • Saprophytic microflora dominated in the mine bioaerosol. • There were pathogens among the isolated microorganisms. • Spread of microorganisms was related to certain air parameters. • Structure of the ventilation network affected the concentration of microorganisms. [ABSTRACT FROM AUTHOR]

Legionella is a genus of pathogenic Gram-negative bacteria responsible for a serious disease known as legionellosis, which is transmitted via inhalation of this pathogen in aerosol form. There are two forms of legionellosis: Legionnaires' disease, which causes pneumonia-like symptoms, and Pontiac fever, which causes influenza-like symptoms. Legionella can be aerosolized from various water sources in the built environment including showers, faucets, hot tubs/swimming pools, cooling towers, and fountains. Incidence of the disease is higher in the summertime, possibly because of increased use of cooling towers for air conditioning systems and differences in water chemistry when outdoor temperatures are higher. Although there have been decades of research related to Legionella transmission, many knowledge gaps remain. While conventional wisdom suggests that showering is an important source of exposure in buildings, existing measurements do not provide strong support for this idea. There has been limited research on the potential for Legionella transmission through heating, ventilation, and air conditioning (HVAC) systems. Epidemiological data suggest a large proportion of legionellosis cases go unreported, as most people who are infected do not seek medical attention. Additionally, controlled laboratory studies examining water-to-air transfer and source tracking are still needed. Herein, we discuss ten questions that spotlight current knowledge about Legionella transmission in the built environment, engineering controls that might prevent future disease outbreaks, and future research that is needed to advance understanding of transmission and control of legionellosis. [ABSTRACT FROM AUTHOR]

In this pilot study, exposure to airborne microorganisms in solid recovered fuel (SRF) plants has been measured. Different steps in SRF production processes such as separation and size reduction can cause generation of airborne microorganisms. Exposure to these biological agents can cause some health problems, so their levels should be measured to assess the potential risks. Therefore, exposure to airborne total bacteria, Gram-negative bacteria, actinomycetes and fungi were measured in the running SRF plant. Sample locations were chosen considering work areas and wind direction in the plant. Airborne microorganisms were collected via AES Sampl’air Lite on particular agar plates and incubated for microorganism growth. No thermophilic actinomycetes were obtained from the samples. The measured concentrations of mesophilic heterotrophic bacteria were almost similar at each point throughout the SRF plant (ranged from 920 to 1750 CFU/m³) except the spare waste stock area (427 CFU/m³) and the monitoring room (ranged from 420 to 770 CFU/m3). The highest concentrations were measured near the pre shredder (1750 CFU/m³) and in the manual sorting unit (1610 CFU/m³). However, the concentrations of Gram-negative bacteria varied at each point (28 to 700 CFU/m³). Fungi concentrations varied from 280 to 1750 CFU/m³ and were high near the sorting unit, the ballistic separator, the fine shredder, the end-product stock area and the monitoring room (1750 CFU/m³). The concentrations of mesophilic heterotrophic bacteria, Gram-negative bacteria and fungi did not exceed the recommended limit values. [ABSTRACT FROM AUTHOR]

Didymella species are common plant pathogens affecting mainly cereal crops in countries with temperate climates, and their airborne spores are also a potential human allergen. A 5-y monitoring study was carried out at an urban site in the UK to establish the most likely exposure time in order to alert people sensitised to spores of this genus. Didymella ascospores occurred in air with a bimodal pattern, with peak concentrations occurring at 03:00 and 22:00. The majority of ascospores were observed from 20:30 to 07:30 according to a multivariate regression tree analysis. Similarly, circular tests indicated that the maximum hourly concentrations occurred in the morning hours. The highest ascospore concentrations were observed in very humid conditions occurring after rainfall. The observations taken from an urban site were delayed in relation to the time of ascospore release previously reported from field sites. Thus, there is a high possibility of regional transport of ascospores in the atmosphere from remote sources. [ABSTRACT FROM AUTHOR]

Walking and other human activities resuspend deposited pathogens from surfaces into the air, potentially leading to infection through inhaling the bioaerosols. We performed experiments in a laboratory chamber to quantify the pathogen resuspension from a human stepping on pathogen-seeded flooring. Three common flooring materials were chosen: carpet, vinyl tile, and hard wood. Three different types of bacteria were tested: Escherichia coli , Pseudomonas alcaligenes, and Staphylococcus epidermidis. The bacteria were first aerosolized into an experimental chamber and allowed to deposit onto the clean flooring materials, followed by a single human step on the flooring performed to resuspend the bacteria. The result showed that the resuspension emission factor (normalized parameter for the ratio of resuspended mass in the air to the mass available for resuspension on the surface during a resuspension event) of tested bacteria ranged from 3.4 × 10−5 to 2.1 × 10−4. For this study, because the resuspension mechanism is one footstep, the resuspension emission factor is also equivalent to the resuspension fraction (fraction of settled particles resuspended per footstep). The carpet consistently resulted in the highest emission factor of biological material resuspended from the surface to the air. In addition, the resuspension emission factor for Gram positive, S. epidermidis , was higher than that of the other two Gram negative bacteria for all floorings. The findings from this study provide valuable estimates for the emission of biological particles by resuspension and comparison to non-biological particles for estimating the risk of pathogen exposure in occupied environments. • Resuspension of different bacteria from stepping on flooring was quantified for the first time. • Resuspensions of E. coli , P. alcaligenes , and S. epidermidis were measured. • Resuspension emission factors were measured for carpet, vinyl tile, and hard wood. • S. epidermidis always gave the highest resuspension among the three bacteria. [ABSTRACT FROM AUTHOR]

Municipal solid waste (MSW) landfills, constituting the third largest anthropogenic sources of bioaerosols, are suspected to be one of the major contributors to adverse health outcomes. A regional modeling of aerosol trajectories based on wind-tunnel observations and on-site monitoring was newly-developed to uncover the impacts of a typical MSW landfill on ambient bioaerosol pollution. Results showed that the horizontal diffusion velocity of bioaerosols reached 4.33 times higher than the vertical velocity under surface calm winds. On-site monitoring revealed that the concentrations of particulate matter (PM) with a diameter of 10 μm were 3.05 times higher than those of PM1.0 in the 2.8-km downwind residential regions near the MSW landfill. With the increase in PM concentration, higher-abundance microorganisms were detected. A number of cultivable bacterial species (Micrococcus endophyticus , Micrococcus flavus , Bacillus sporothermodurans , Salmonella enterica serovar typhi , Rhodococcus hoagie , Blastococcups) and fungal species (Aspergillus niger , Penicillium , Microascus cirrosus , Cochliobolus , Stemphylium vesicarium) were identified in these bioaerosols. Furthermore, distinguished by transmission electron microscopy, a longer-range transported microorganism (E. coli) clinging onto suspended PM was observed, signifying higher exposure risks. Human health risk assessments demonstrate that the residents and occupational workers in the vicinity of MSW landfill endured atmospheric diffusion-induced bioaerosol exposure risks due to open dumping activities in MSW landfill. This study clearly indicates bioaerosol pollution from landfills, and people particularly living nearby the MSW facilities, must decrease outdoor activities during dusty days. [Display omitted] • Diffusion tube is used to qualitatively/quantitatively observe bioaerosol transfer. • Ambient bioaerosol adhered on lighter biomass particles soar diffuse concentration. • Cultivable E. coli confirms a long-range diffusion at a distance of ≥1.5 m. • 50-m-resolution model predict >10 Km transfer trajectory of aerosol in the air. • Downwind of MSW landfill derives high human exposures of pathogens in dusty days. [ABSTRACT FROM AUTHOR]

Cooling towers (CTs) are used to dissipate excess heat from water by evaporation, common in large facilities as hospital, companies, and hotels. The main risk attributed to CTs is represented by Legionella , a Gram-negative bacterium associated with a severe form of pneumonia known as Legionnaires' disease (LD). The infection route is by inhalation of aerosols reaching the lower respiratory tract. Despite several events associated with CTs, the knowledge in this field is still limited. The aim of this study was to develop a predictive model of bioaerosol dispersion using PM 10 particles as a proxy, to generate risk maps of Legionella spread in the surrounding area in several weather and microbiological conditions. The Legionella contamination in the CT basin was 40938 ± 24523 cfu/L, with four peaks independent of the season, associated with an increase in air minimum temperature values (+1–2 °C) and a high relative humidity (66–100%) preceded by rainfall (0.2–30.6 mm/day). The model revealed that the most extensive bioaerosol spread is predicted in winter and summer, with an increase in Legionella risk at a distance of up to 1.5 km from the CT. This method represents a novel integrated approach for the prevention and management of LD risk in CTs. • The environmental impact of cooling tower (CT) on Legionellosis was investigated. • The CT microbiome was correlated to meteorological conditions and seasonality. • A map of Legionella risk was developed using a preventive dispersion model. [ABSTRACT FROM AUTHOR]

We developed a high-speed filterless airflow multistage photocatalytic elbow aerosol removal system for the treatment of bioaerosols such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Human-generated bioaerosols that diffuse into indoor spaces are 1–10 μm in size, and their selective and rapid treatment can reduce the risk of SARS-CoV-2 infection. A high-speed airflow is necessary to treat large volumes of indoor air over a short period. The proposed system can be used to eliminate viruses in aerosols by forcibly depositing aerosols in a high-speed airflow onto a photocatalyst placed inside the system through inertial force and turbulent diffusion. Because the main component of the deposited bioaerosol is water, it evaporates after colliding with the photocatalyst, and the nonvolatile virus remains on the photocatalytic channel wall. The residual virus on the photocatalytic channel wall is mineralized via photocatalytic oxidation with UVA-LED irradiation in the channel. When this system was operated in a 4.5 m3 aerosol chamber, over 99.8% aerosols in the size range of 1–10 μm were removed within 15 min. The system continued delivering such performance with the continuous introduction of aerosols. Because this system exhibits excellent aerosol removal ability at a flow velocity of 5 m/s or higher, it is more suitable than other reactive air purification systems for treating large-volume spaces. [Display omitted] • >We developed a photocatalytic multi-stage elbow system for bioaerosol elimination. • >99.8% of 1–10 μm aerosol particles in a 4.5 m3 chamber were immediately removed. • >The system performance was equivalent to 1-h ventilation of a school classroom. • The photocatalyst used in the system almost completely inactivated SARS-CoV-2. [ABSTRACT FROM AUTHOR]

Desert dust intrusions cause the transport of airborne particulate matter from natural sources, with important consequences for climate regulation, biodiversity, ecosystem functioning and dynamics, human health, and socio-economic activities. Some effects of desert intrusions are reinforced or aggravated by the bioaerosol content of the air during these episodes. The influence of desert intrusions on airborne bioaerosol content has been very little studied from a scientific point of view. In this study, a systematic review of scientific literature during 1970–2021 was carried out following the standard protocol Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA). After this literature review, only 6% of the articles on airborne transport from desert areas published in the last 50 years are in some way associated with airborne pollen, and of these, only a small proportion focus on the study of pollen-related parameters. The Iberian Peninsula is affected by Saharan intrusions due to its proximity to the African continent and is seeing an increasing trend the number of intrusion events. There is a close relationship among the conditions favouring the occurrence of intrusion episodes, the transport of particulate matter, and the transport of bioaerosols such as pollen grains, spores, or bacteria. The lack of linearity in this relationship and the different seasonal patterns in the occurrence of intrusion events and the pollen season of most plants hinders the study of the correspondence between both phenomena. It is therefore important to analyse the proportion of pollen that comes from regional sources and the proportion that travels over long distances, and the atmospheric conditions that cause greater pollen emission during dust episodes. Current advances in aerobiological techniques make it possible to identify bioaerosols such as pollen and spores that serve as indicators of long-distance transport from remote areas belonging to other bioclimatic and biogeographical units. A greater incidence of desert intrusion episodes may pose a challenge for both traditional systems and for the calibration and correct validation of automatic aerobiological monitoring methods. [Display omitted] • A comprehensive literature review was carried out based on 50 years of publications. • Long-distance dust from desert areas has received greater interest since the late 90s. • Very little research has been carried out on bioaerosols co-transported by dust events. • Last researches evidenced an influence of intrusions on the airborne biological content. • Desert dust intrusions have remarkable effects on climate, health, biodiversity and economy. [ABSTRACT FROM AUTHOR]

The relationship between atmospheric bioaerosols and ecosystems is currently of global importance. Antarctica has an extreme climate, meaning that ecosystem behavior in this region is relatively simple. Direct sampling of atmospheric bioaerosols was performed at an Adélie penguin ( Pygoscelis adeliae ) colony at Hukuro Cove, Langhovde, Antarctica on 22 January 2013. The aim of the sampling was to reveal the effect of the penguins on the Antarctic ecosystem within the atmospheric bioaerosols. Samples were bio-analyzed using a next-generation sequencing method. Biomass concentrations of Bacilli-class bacteria were 19.4 times higher when sampled leeward of the penguin colony compared with windward sampling. The source of these bacteria was the feces of the penguins. Predicted atmospheric trajectories indicate that the bacteria disperse towards the Southern Ocean. The largest biomass concentration in the windward bacteria was of the Gammaproteobacteria class, which decreased markedly with distance through the penguin colony, being deposited on soil, surface water, and ocean. It is concluded that bioaerosols and ecosystems near the penguin colony strongly influence each other. [ABSTRACT FROM AUTHOR]

There are many species among the Alternaria genus, which hosts on economically important crops causing significant yield losses. Less attention has been paid to fungi hosting on plants constituting substantial components of pastures and meadows. Alternaria spp. spores are also recognised as important allergens. A 7-day volumetric spore trap was used to monitor the concentration of airborne fungal spores. Air samples were collected in Worcester, England (2006–2010). Days with a high spore count were then selected. The longest episode that occurred within a five year study was chosen for modelling. Two source maps presenting distribution of crops under rotation and pastures in the UK were produced. Back trajectories were calculated using the HYSPLIT model. In ArcGIS clusters of trajectories were studied in connection with source maps by including the height above ground level and the speed of the air masses. During the episode no evidence for a long distance transport from the continent of Alternaria spp. spores was detected. The overall direction of the air masses fell within the range from South-West to North. The back trajectories indicated that the most important sources of Alternaria spp. spores were located in the West Midlands of England. [ABSTRACT FROM AUTHOR]