Indoor Air Quality and Potential Health Risk Impacts of Exposure to Antibiotic Resistant Bacteria in an Office Rooms in Southern Poland

Bioaerosols emission from source facilities in a wastewater treatment plant: Critical exposure time and sensitivity analysis

Overexposure of sewage workers to bioaerosol released from wastewater treatment plants (WWTPs) can cause serious infections, but practical method for controlling their health risk is lacking. In this study, reverse quantitative microbial risk assessment was used to estimate the daily critical exposure time (CET) of sewage workers exposing to Staphylococcus aureus bioaerosol emitted by three emission sources facilities in a WWTP based on either U.S. EPA or WHO benchmark, and sensitivity analysis was conducted to analyze the influence of various parameters on the outcomes of CET. The results showed that the CET of females was always 1.12-1.29 times that of males. In addition, the CET after wearing face masks was 28.28-52.37 times as long as before. The working time can be determined based on the CET results of male workers wearing face masks exposed to the inverted-umbrella aeration tank (14.73-550.98 min for U.S. EPA benchmark and 55.07-1972.24 min for WHO benchmark). In each scenario, the variable parameter exposure concentration (ec) always showed the most influence on the CET results. After wearing the face masks, the removal fraction by employing face masks also had a significant effect on the results, only second to ec. Therefore, the wearing of face mask is the most convenient and effective measure to prolong the CET. Furthermore, practical methods to reducing bioaerosol concentration in WWTPs exposure are also necessary to extend CET and safeguard worker health. This study enriches the application range of reverse quantitative microbial risk assessment framework and provides theoretical support for stakeholders to establish reasonable working time threshold guidelines, and practical method and novel perspective to protect the on-site health risks of sewage workers exposing to various facilities.

Aerosol-Mediated Spread of Antibiotic Resistance Genes: Biomonitoring Indoor and Outdoor Environments

Antimicrobial resistance (AMR) has emerged as a conspicuous global public health threat. The World Health Organization (WHO) has launched the "One-Health" approach, which encourages the assessment of antibiotic resistance genes (ARGs) within an environment to constrain and alleviate the development of AMR. The prolonged use and overuse of antibiotics in treating human and veterinary illnesses, and the inability of wastewater treatment plants to remove them have resulted in elevated concentrations of these metabolites in the surroundings. Microbes residing within these settings acquire resistance under selective pressure and circulate between the air-land interface. Initial evidence on the indoor environments of wastewater treatment plants, hospitals, and livestock-rearing facilities as channels of AMR has been documented. Long- and short-range transport in a downwind direction disseminate aerosols within urban communities. Inhalation of such aerosols poses a considerable occupational and public health risk. The horizontal gene transfer (HGT) is another plausible route of AMR spread. The characterization of ARGs in the atmosphere therefore calls for cutting-edge research. In the present review, we provide a succinct summary of the studies that demonstrated aerosols as a media of AMR transport in the atmosphere, strengthening the need to biomonitor these pernicious pollutants. This review will be a useful resource for environmental researchers, healthcare practitioners, and policymakers to issue related health advisories.

Assessment of personal deposited dose and particle size distribution of bacterial aerosol in kindergarten located in southern Poland

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.

A comprehensive review of microbial contamination in the indoor environment: sources, sampling, health risks, and mitigation strategies

The quality of the indoor environment significantly impacts human health and productivity, especially given the amount of time individuals spend indoors globally. While chemical pollutants have been a focus of indoor air quality research, microbial contaminants also have a significant bearing on indoor air quality. This review provides a comprehensive overview of microbial contamination in built environments, covering sources, sampling strategies, and analysis methods. Microbial contamination has various origins, including human occupants, pets, and the outdoor environment. Sampling strategies for indoor microbial contamination include air, surface, and dust sampling, and various analysis methods are used to assess microbial diversity and complexity in indoor environments. The review also discusses the health risks associated with microbial contaminants, including bacteria, fungi, and viruses, and their products in indoor air, highlighting the need for evidence-based studies that can relate to specific health conditions. The importance of indoor air quality is emphasized from the perspective of the COVID-19 pandemic. A section of the review highlights the knowledge gap related to microbiological burden in indoor environments in developing countries, using India as a representative example. Finally, potential mitigation strategies to improve microbiological indoor air quality are briefly reviewed.

Evaluating the threshold limit value of acceptable exposure concentration for exposure to bioaerosols in a wastewater treatment plant: Reverse-quantitative microbial risk assessment and sensitivity analysis

Agitation operations produce numerous pathogenic bioaerosols in WWTPs¹. QMRA² can determine risks of persons exposed to these bioaerosols. However, QMRA framework cannot help stakeholders in immediately deciding whether a risk is intolerable. Thus, evaluating threshold of acceptable exposure concentration is an urgent issue but is still rarely addressed in WWTPs. This study analyzed TLV³ benchmarks of E. coli and S. aureus bioaerosols emitted from a WWTP by reverse-QMRA. Furthermore, variance of input parameters was clarified by sensitivity analysis. Results showed that, under conservative and optimistic estimates, TLV of technicians was 1.52-2.06 and 1.26-1.68 times as large as those of workers, respectively; wearing mask drive TLV up to 1-2 orders of magnitude; TLV of M⁴ was at most 1.33 and 1.31 times as large as that of RD⁵, respectively. For sensitivity analysis, removal fraction by equipping PPE enlarge TLV for effortlessly obtaining an acceptable assessment result; exposure time was dominant when without PPE excepting the scenario of technicians exposed to E. coli bioaerosol. This study helps establish threshold guidelines for bioaerosols in WWTPs and contribute innovative perspectives for stakeholders.

Deciphering the distribution of microbial communities and potential pathogens in the household dust

The reliance of modern society on indoor environments increasing has made them crucial sites for human exposure to microbes. Extensive research has identified ecological drivers that influence indoor microbial assemblages. However, few studies have examined the dispersion of microbes in different locations of identical indoor environments. In this study, we employed PacBio Sequel full-length amplicon sequencing to examine the distribution of microbes at distinct locations in a single home and to identify the potential pathogens and microbial functions. Microbial communities differed considerably among the indoor sampling sites (P < 0.05). In addition, bacterial diversity was influenced by human activities and contact with the external environment at different sites, whereas fungal diversity did not significantly differ among the sites. Potential pathogens, including bacteria and fungi, were significantly enriched on the door handle (P < 0.05), suggesting that door handles may be hotpots for potential pathogens in the household. A high proportion of fungal allergens (34.37 %-56.50 %), which can cause skin diseases and asthma, were observed. Co-occurrence network analysis revealed the essential ecological role of microbial interactions in the development of a healthy immune system. Overall, we revealed the differences in microbial communities at different sampling sites within a single indoor environment, highlighting the distribution of potential pathogens and ecological functions of microbes, and providing a new perspective and information for assessing indoor health from a microbiological viewpoint.

Quantitative microbial risk assessment with nasal/oral breathing pattern for S. aureus bioaerosol emission from aeration tanks and residual sludge storage yard in a wastewater treatment plant

A large number of pathogenic bioaerosols are generated during the treatment process of wastewater treatment plants (WWTPs), and they can pose potential risks to human health. Therefore, this study systematically analyzed the emission characteristics of Staphylococcus aureus bioaerosols released from an inverted umbrella aeration tank, a microporous aeration tank, and a residual sludge storage yard in a WWTP, and quantitatively evaluated the health risks of four kinds of exposed populations with nasal/oral breathing patterns under optimistic and conservative estimations. The results displayed that the bioaerosol concentration in inverted umbrella aeration tank was higher than that in microporous aeration tank and residual sludge storage yard. Aerosolization ratio in residual sludge storage yard was an order of magnitude lower than that in aeration tanks. Sludge workers were at higher health risks than the other three exposed populations. The health risks of nasal breathers (infection risk: 1.62 × 10^-5-2.56 × 10^-3 pppy; disease burden: 4.24 × 10^-8-6.72 × 10^-6 DALYs pppy) were 0.61-0.63 times higher than those of oral breathers (infection risk: 9.95 × 10^-6-1.59 × 10^-3 pppy; disease burden: 2.61 × 10^-8-4.18 × 10^-6 DALYs pppy). For female field engineers using oral breathing, laboratory technicians, and researchers without personal protective equipment (PPE), infection risk and disease burden had the opposite results, which indicated that satisfying one certain benchmark did not mean absolute safety. In addition, health risks of exposed populations were reduced by an order of magnitude after wearing PPE. This study can provide a reliable theoretical basis for the risk prevention of bioaerosols and supply data support for the strategies of health risk control perspectives for local sewage utilities.

Distribution characteristics and potential risks of bacterial aerosol in waste transfer station

The waste transfer station (WTS) is an important link in the transfer of municipal solid waste (MSW) between the community and disposal terminals. While WTSs facilitate waste collection in communities, odorous gases and bioaerosols can escape from them, thereby negatively affecting their surroundings. In this study, the concentration, particle size distribution, pathogen population, and health risks of bioaerosols were analyzed at different locations in a transfer station. The results showed that the highest viable bacterial aerosol concentration was 10,353 ± 3701 CFU/m³, which was at 5 m from the disposal site. Fifty-three bacterial species, including pathogens, were detected. Of these, 39 were human pathogenic bacteria directly originating from the WTS. Furthermore, health risk assessments indicated unacceptable levels of non-carcinogenic risk for operational workers caused by bacterial aerosols of the WTS work area. In addition, bacterial aerosols may pose a severe health risk to children within a 15 m area of the WTS. The results of this study provide a scientific basis to control and reduce the risk associated with bioaerosol exposure in solid WTSs.

Leave No Trace? Ecological and anthropogenic determinants of antibiotic resistant bacteria in a recreational alpine environment

Antibiotic resistant bacteria (ARB) have been detected in remote environments, but the degree to which their presence is due to anthropogenic contamination remains unclear. Here, anthropogenic and ecological determinants of ARB were characterized in remote and highly visited areas of Rocky Mountain National Park in the United States. Soil and water samples were collected from 29 sites once a month for three months and measured for bacteria resistant to seven antibiotics with flow cytometry. A novel index of the likelihood of human presence (HPI) was generated for estimating human impact on ARB abundance. The HPI accounted for 44% of variation in ARB abundance in water samples (p < 0.0001) and 51% of variation in soil samples (p < 0.00001). Human presence index was illustrated as a reliable predictor of ARB abundance despite a tendency to underpredict at higher levels of human impact. Ecological determinants such as temperature, elevation, slope, and aspect were also found to be significantly associated with ARB abundance. These findings suggest that human presence drives the abundance of ARB in Rocky Mountain National Park, but ecological variables play a significant role in their presence and dispersal.

Impact of Different Air Pollutants (PM10, PM2.5, NO2, and Bacterial Aerosols) on COVID-19 Cases in Gliwice, Southern Poland

Many studies have shown that air pollution may be closely associated with increased morbidity and mortality due to COVID-19. It has been observed that exposure to air pollution leads to reduced immune response, thereby facilitating viral penetration and replication. In our study, we combined information on confirmed COVID-19 daily new cases (DNCs) in one of the most polluted regions in the European Union (EU) with air-quality monitoring data, including meteorological parameters (temperature, relative humidity, atmospheric pressure, wind speed, and direction) and concentrations of particulate matter (PM₁₀ and PM_2.5), sulfur dioxide (SO₂), nitrogen oxides (NO and NO₂), ozone (O₃), and carbon monoxide (CO). Additionally, the relationship between bacterial aerosol (BA) concentration and COVID-19 spread was analyzed. We confirmed a significant positive correlation (p < 0.05) between NO₂ concentrations and numbers of confirmed DNCs and observed positive correlations (p < 0.05) between BA concentrations and DNCs, which may point to coronavirus air transmission by surface deposits on bioaerosol particles. In addition, wind direction information was used to show that the highest numbers of DNCs were associated with the dominant wind directions in the region (southern and southwestern parts).

Spatio-temporal diversity of biological aerosols over Northeast India: a metagenomic approach

Northeast India is considered as one of the major biodiversity hotspots in the world, but the region is underexplored for their microbial biodiversity. Extensive characterization of biological aerosol (bioaerosol) samples collected from various locations of Northeast India was carried out for all four seasons in a year. These were characterized in terms of their constituents, such as pollens, fungal spores, animal debris, and non-biological components, and particulate matters, such as inhalable, thoracic, and alveolic, and finally, the bacterial diversity was determined by DNA-based metagenomic approach. The non-biological (non-viable) component of aerosols is found to vary from 30 to 89% in the pre-monsoon season, which coexists with pollens (4-20%), animal debris (1-24%), and fungal spores (1-17%). The highest number of culturable microbial populations in terms of CFU count was observed in the pre-monsoon samples (i.e., 125.24-632.45 CFU/m³), and the lowest CFU was observed in monsoon season (i.e., 20.83-319.0 CFU/m³). The metagenomic approach with the samples collected during pre-monsoon season showed a total of bacterial 184 OTUs (operational taxonomic units) with 28,028 abundance count comprising 7 major phylum, 6 classes, 10 orders, 15 families, 13 genus, and 8 species of bacteria. The species-level distribution clearly shows the presence of Gammaproteobacteria (52%) most abundantly, followed by Bacilli (21%), Alphaproteobacteria (14%), Betaproteobacteria (5%), Flavobacteria (5%), and Sphingobacteria (3%). It is the first report from the entire Northeast India to uncover spatio-temporal distribution of biological components and bacterial diversity in aerosol samples through a DNA-based metagenomic approach.

Microbiological contamination of indoor and outdoor environments in a desert climate

Microbiological air contamination in the desert environment is becoming an essential subject for the health of office building occupants and public health. In this study, the concentrations and compositions of airborne microorganisms (bacteria and fungi) were assessed in indoor and outdoor environments using a multistory building complex in Kuwait as a case study. Airborne microorganism samples were collected from 12 sites within the building complex containing nineteen stories over four seasons. Culturable airborne bacteria and fungi were impacted on selected media to determine their concentrations and compositions with a Biolog Omnilog GEN III system and Biolog MicroStation. The indoor mean airborne bacterial count concentrations ranged from 35 to 18,463 CFU/m³, concentrations that are higher than 2,000 CFU/m³, demonstrating high-very high contamination levels in all seasons. Fungal contamination was high in winter and summer, with detected concentrations > 2,000 CFU/m³. Indoor-to-outdoor (I/O) ratios showed that airborne microbial contamination inside building floors originated from indoor air contamination. All the building floors showed bacterial and fungal concentrations ranging from less than 2,000 to more than 2,000 CFU/m³, indicative of a high to very high air contamination level. Statistical analysis showed no correlation between bacterial and fungal concentrations, demonstrating that they originated from unrelated sources. In the indoor building air, the most prevalent bacterial isolate was Bacillus pseudomycoides/cereus, whereas the most dominant fungal isolate was Aspergillus spp. The low count for indoor air bacterial species suggested no particular health risk for the occupants. In contrast, the high count of indoor air fungal species in the winter samples and the presence of potentially allergenic genera detected may suggest possible health risks for the occupants. The results obtained are the basis for the recommendation that the maintenance activities of the HVAC system and the periodical cleaning operation program be revised and preplanned as protective measures.

Pathogen Control in the Built Environment: A Probiotic-Based System as a Remedy for the Spread of Antibiotic Resistance

The high and sometimes inappropriate use of disinfectants and antibiotics has led to alarming levels of Antimicrobial Resistance (AMR) and to high water and hearth pollution, which today represent major threats for public health. Furthermore, the current SARS-CoV-2 pandemic has deeply influenced our sanitization habits, imposing the massive use of chemical disinfectants potentially exacerbating both concerns. Moreover, super-sanitation can profoundly influence the environmental microbiome, potentially resulting counterproductive when trying to stably eliminate pathogens. Instead, environmentally friendly procedures based on microbiome balance principles, similar to what applied to living organisms, may be more effective, and probiotic-based eco-friendly sanitation has been consistently reported to provide stable reduction of both pathogens and AMR in treated-environments, compared to chemical disinfectants. Here, we summarize the results of the studies performed in healthcare settings, suggesting that such an approach may be applied successfully also to non-healthcare environments, including the domestic ones, based on its effectiveness, safety, and negligible environmental impact.

A review of the emergence of antibiotic resistance in bioaerosols and its monitoring methods

Despite significant public health concerns regarding infectious diseases in air environments, potentially harmful microbiological indicators, such as antibiotic resistance genes (ARGs) in bioaerosols, have not received significant attention. Traditionally, bioaerosol studies have focused on the characterization of microbial communities; however, a more serious problem has recently arisen due to the presence of ARGs in bioaerosols, leading to an increased prevalence of horizontal gene transfer (HGT). This constitutes a process by which bacteria transfer genes to other environmental media and consequently cause infectious disease. Antibiotic resistance in water and soil environments has been extensively investigated in the past few years by applying advanced molecular and biotechnological methods. However, ARGs in bioaerosols have not received much attention. In addition, ARG and HGT profiling in air environments is greatly limited in field studies due to the absence of suitable methodological approaches. Therefore, this study comprehensively describes recent findings from published studies and some of the appropriate molecular and biotechnological methods for monitoring antibiotic resistance in bioaerosols. In addition, this review discusses the main knowledge gaps regarding current methodological issues and future research directions.

Indoor Air Quality in Healthcare and Care Facilities: Chemical Pollutants and Microbiological Contaminants

The indoor air quality of healthcare and care facilities is poorly studied. The aim of this study was to qualitatively and quantitatively describe the chemical pollution and the microbiological contaminations of the indoor environment of these facilities. Methods: A wide range of chemical compounds (39 volatile and 13 semi-volatile organic compounds, carbon dioxide, fine particulate matter) and microorganisms (fungi and bacteria) were studied. Sampling campaigns were conducted in two French cities in summer 2018 and winter 2019 in six private healthcare facilities (general practitioner’s offices, dental offices, pharmacies) and four care facilities (nursing homes). Results: The highest median concentrations of chemical compounds (μg/m3) were measured for alcohols (ethanol: 378.9 and isopropanol: 23.6), ketones (acetone: 18.8), aldehydes (formaldehyde: 11.4 and acetaldehyde: 6.5) and terpenes (limonene: 4.3). The median concentration of PM2.5 was 9.0 µg/m3. The main bacteria of these indoor environments were Staphylococcus, Micrococcus and Bacillus genera, with median bacterial concentrations in the indoor air of 14 cfu/m3. The two major fungal genera were Cladosporium and Penicillium, with median fungal concentrations of 7 cfu/m3. Conclusions: Indoor air in healthcare and care facilities contains a complex mixture of many pollutants found in higher concentrations compared to the indoor air in French hospitals in a previous study.

Distribution of antibiotic resistance genes in the environment

The prevalence of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in the microbiome is a major public health concern globally. Many habitats in the environment are under threat due to excessive use of antibiotics and evolutionary changes occurring in the resistome. ARB and ARGs from farms, cities and hospitals, wastewater treatment plants (WWTPs) or as water runoffs, may accumulate in water, soil, and air. We present a global picture of the resistome by examining ARG-related papers retrieved from PubMed and published in the last 30 years (1990-2020). Natural Language Processing (NLP) was used to retrieve 496,640 papers, out of which 9374 passed the filtering test and were further analyzed to determine the distribution and diversity of ARG subtypes. The papers revealed seven major antibiotic families together with their respective ARG subtypes in different habitats on six continents. Asia, especially China, had the highest number of ARGs related papers compared to other countries/regions/continents. ARGs belonging to multidrug, glycopeptide, and β-lactam families were the most common in reports from hospitals and sulfonamide and tetracycline families were common in reports from farms, WWTPs, water and soil. We also highlight the 'omics' tools used in resistome research, describe some factors that shape the development of resistome, and suggest future work needed to better understand the resistome. The goal was to show the global nature of ARB and ARGs in order to encourage collaborate research efforts aimed at reducing the negative impacts of antibiotic resistance on the One Health concept.

Quantitative microbial risk assessment for occupational health of temporary entrants and staffs equipped with various grade PPE and exposed to microbial bioaerosols in two WWTPs

PURPOSE

This study was to evaluate the occupational health risks of infection from Gram-negative bacteria and Staphylococcus aureus bioaerosols to temporary entrants and staffs equipped with various grade personal protection equipment (PPE) related to wastewater treatment plants (WWTPs).

METHODS

This study determined the emission concentrations of Gram-negative bacteria and Staphylococcus aureus bioaerosols from two WWTPs under various aeration modes. Then, a strict quantitative microbial risk assessment (QMRA) was performed on several exposure scenarios associated with occupational health risks of temporary entrants (researchers, visitors, and inspectors) and staffs (field engineer and laboratory technician).

RESULTS

Although the bioaerosol concentrations were generally regarded as safe according to existing standards, these bioaerosols' health risks were still unacceptable. The microbial bioaerosols posed considerable infection health risks in WWTPs. These risks were generally above the WHO and US EPA benchmarks. The health risks of females were always smaller than those of male of grown-up age group. Staffs that had been exposed to bioaerosols for a long time were found to have higher health risks compared with temporary entrants. In addition, field engineers equipped with PPE rendered low health risks, thus revealing that wearing PPE could effectively reduce the occupational health risks.

CONCLUSION

This study provided novel data and enriched the knowledge of microbial bioaerosol emission's health risks from various aeration modes in WWTPs. Management decisions could be executed by authorities on the basis of the results of QMRA for field engineers equipped with PPE to reduce the related occupational health risks.

Ultrastructure of the Mycobacterium avium subsp. hominissuis Biofilm

Mycobacterium avium subsp. hominissuis (MAH) is one of the most common nontuberculous mycobacterial pathogens responsible for chronic lung disease in humans. It is widely distributed in biofilms in natural and living environments. It is considered to be transmitted from the environment. Despite its importance in public health, the ultrastructure of the MAH biofilm remains largely unknown. The ultrastructure of a MAH-containing multispecies biofilm that formed naturally in a bathtub inlet was herein reported along with those of monoculture biofilms developed from microcolonies and pellicles formed in the laboratory. Scanning electron microscopy revealed an essentially multilayered bathtub biofilm that was packed with cocci and short and long rods connected by an extracellular matrix (ECM). Scattered mycobacterium-like rod-shaped cells were observed around biofilm chunks. The MAH monoculture biofilms that developed from microcolonies in vitro exhibited an assembly of flat layers covered with thin film-like ECM membranes. Numerous small bacterial cells (0.76±0.19‍ ‍μm in length) were observed, but not embedded in ECM. A glycopeptidolipid-deficient strain did not develop the layered ECM membrane architecture, suggesting its essential role in the development of biofilms. The pellicle biofilm also consisted of flat layered cells covered with an ECM membrane and small cells. MAH alone generated a flat layered biofilm covered with an ECM membrane. This unique structure may be suitable for resistance to water flow and disinfectants and the exclusion of fast-growing competitors, and small cells in biofilms may contribute to the formation and transmission of bioaerosols.

Seasonal variation and size distribution in the airborne indoor microbial concentration of residential houses in Delhi and its impact on health

Exposure of microbial agents in the air of indoor dwellings is associated with effects on respiratory and general health. The current study was conducted in the urban area of Delhi Metropolis for the seasonal quantitative assessment of viable microbial indoor air quality. Bioaerosol measurement was conducted by using Anderson six stage impactor with cut-off diameters of 7.0, 4.7, 3.3, 2.1, 1.1, and 0.65 µm) throughout the all the seasons (April 2019 to March 2020). Meteorological parameters such as temperature and relative humidity were measured to check their effect on microbial survival. Air quality index data of the sampling area were recorded by DPCC air quality monitoring system, Ashok Vihar, Delhi. The highest (1654 ± 876.87 CFU/m3) and lowest (738 ± 443.59 CFU/m3) mean bacterial concentration in houses was recorded in August and December, respectively. Similarly, the highest fungal concentration (1275 ± 645.22 CFU/m3) was found in August and the lowest in (776 ± 462.46 CFU/m3) in January. Bacterial respirable fraction shows an irregular pattern in different seasons. In the case of fungi, the respirable fraction of 2.1 and 1.1 contributes more than 60% of total culturable bioaerosols in all seasons. Bacterial genera including Staphylococcus, Micrococcus, and Streptobacillus were most dominant, and Cladosporium, Aspergillus, Penicillium, and Alternaria were the most dominant fungal genera observed indoors. The results of this study suggest that higher respirable fungal fraction might penetrate deeper into the lungs and cause various health effects. A higher concentration of bioaerosols in outdoor areas than indoor shows that the source of indoor bioaerosols is outdoor air.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10453-021-09718-3.

Bacterial Contamination in Health Care Centers: Differences between Urban and Rural Settings

This study aims to assess the airborne bioburden of rural and urban Portuguese Primary Health Care Centers (PHCC) using active and passive sampling methods and identify the potential differences in airborne microbiota between both environments. The highest total aerobic mesophilic bacterial load in indoor air were found in the Vaccination Room (448 CFU.m−3) in the Rural PHCC and in the Waiting Room (420 CFU.m−3) for Urban PHCC. The total coliforms contamination level in indoor air was detected only in the Cleaning Supplies Room (4 CFU.m−3) in the Urban PHCC. The most frequent bacteria genera identified was Micrococcus (21% Rural PHCC; 31% Urban PHCC). The surface samples showed a highest total aerobic mesophilic bacterial contamination in the Treatment Room (86 × 103 CFU.m−2) from the Rural PHCC and in the Front Office (200 × 103 CFU.m−2) from the Urban PHCC. The electrostatic dust cloth (EDC) samples showed a highest bacterial load in the Urban PHCC. Total aerobic mesophilic bacterial load in settled dust and in the Heating, Ventilating and Air Conditioning (HVAC) filter samples in the Urban PHCC (8 CFU.g−1 and 6 × 103 CFU.m−2) presented higher values compared with the Rural PHCC (1 CFU.g−1 and 2.5 × 103 CFU.m−2). Urban PHCC presented higher bacterial airborne contamination compared with the Rural PHCC for the majority of sampling sites, and when compared with the indoor air quality (IAQ) Portuguese legislation it was the Rural PHCC in two sampling places who did not comply with the established criteria.

Microbial, environmental and anthropogenic factors influencing the indoor microbiome of the built environment

A built environment is a human-made environment providing surroundings for human occupancy, activities, and settlement. It is supposed to safeguard humans from all undesirable and harmful pollutants; however, indoor concentrations of some pollutants are much greater than that of the outdoors. Bioaerosols infiltrate from the outdoors in addition to many indoor sources of bioaerosols including the use of various chemicals as well as activities like cooking, smoking, cleaning, or even normal movement. They are also associated with a number of serious health concerns. Various ecological factors associated with the generation, the persistence as well as the dispersal of these microbial components of indoor bioaerosols, are discussed in this review, that have not been considered all together till now. The factors like microbial taxa, environmental factors, and anthropogenic activities (human occupancy, activities, and impact of urbanization) are addressed in the review. Effects of both indoor environmental factors like architectural design, lighting, ventilation, temperature, humidity, indoor/outdoor ratio, particulate matter, indoor chemistry as well as outdoor environmental factors like geography, seasons, and meteorology on the microbial concentrations have been discussed. Efforts are underway to design selective pressures for microbes to create a healthy symbiotic built microbiome as the "right" indoor microbiome is a "healthy" indoor microbiome.

Quantitative microbial risk assessment of bioaerosols in a wastewater treatment plant by using two aeration modes

Nonnegligible emission of bioaerosols usually occurs during aeration of wastewater in aerator tanks in wastewater treatment plants (WWTPs). Literature had shown that the respiratory and intestinal diseases of workers at WWTPs are related to bioaerosols. Thus, quantitative microbial risk assessment (QMRA) based on Monte Carlo simulation was utilized in this research to assess the health risks of Gram-negative bacteria bioaerosol (GNBB) and Staphylococcus aureus bioaerosol (SAB) among academic visitors and staffs. Results showed that the concentrations of GNBB and SAB in the inverted umbrella aeration mode were consistently higher than those in the microporous aeration mode under all six size distribution ranges of the Anderson six-stage impactor. Thus, GNBB and SAB can be highly threatening to the weasand and first bronchus (or alveoli and third bronchus) for the exposure populations. The health risks (annual probability of infection (P_y) and disease burden (DB)) of males were constantly higher than those of females for each certain exposure scenario. The health risks of staffs were higher than those of academic visitors when assessed by Monte Carlo simulation. The wearing of mask is an effective measure to minimize health risks through reducing the bioaerosol concentration intake. Especially, for the academic visitors and staffs exposed to GNBB, all their DB failed to meet the World Health Organization DB benchmark under various credible intervals when they were without a mask on. In a word, the results of health risk assessment in this research can be utilized as an educational tool and policy basis to facilitate the implementation of efficacious prevention measures to protect the public health from bioaerosol health threats in WWTPs.

Effectiveness and Eco-Costs of Air Cleaners in Terms of Improving Fungal Air Pollution in Dwellings Located in Southern Poland—A Preliminary Study

Epidemiological evidence shows that air pollution is responsible for several million premature deaths per year. By virtue of being responsible for these deaths, economic evidence shows that air pollution also imposes a so-called economic cost to society of several trillion dollars per year. The diseases caused by biological air pollutants are of primary global concern for both social and economic reasons, and given that people may spend more than 90% of their time in enclosed spaces, the investigation into methods to remove indoor air pollutants is of paramount importance. One of the methods to improve indoor air quality (IAQ) is to use air cleaners (ACLs) with high-efficiency particulate air filters (HEPA) that remove biological indoor air pollutants from indoor environments. This work presents the results of a study of fungal aerosol samples collected during the summer season from inside two dwellings (DG1 and DG2) before and after starting the use of ACLs. The fungal aerosol samples collected from each of the six stages of the sampler were incubated on agar plates at 26 °C, and the colony forming units (CFU) were manually counted and statistically corrected. The concentration of living airborne fungi was expressed as the CFU in the volume of air (CFU·m−3). The average concentration of fungal aerosol decreased the most when the ACLs were active for 24 min. The reduction was from 474 CFU·m−3 to 306 CFU·m−3, and from 582 CFU·m−3 to 338 CFU·m−3 in DG1 and DG2, respectively. The use of ACLs was assessed by the life cycle assessment (LCA) methodology. This study highlights the benefits of controlling biological air pollutants in order to keep occupants of buildings happy and healthy.

Diversity of Bioaerosols in Selected Rooms of Two Schools and Antibiotic Resistance of Isolated Staphylococcal Strains (Bydgoszcz, Poland): A Case Study

The present study is aimed at evaluating microbiological air pollution in libraries, cafeterias and selected classrooms of two schools in Bydgoszcz city, northern Poland and determining the antibiotic resistance of Staphylococcal strains isolated from the indoor air. One of the investigated schools (School A) is located in the very center of the city, in the vicinity of a park, among old houses and stone-lined streets, while the other (School B), among modern residential buildings, close to a street with heavy traffic. In each school, air samples were collected in the morning, always from all three sampling sites, using the MAS-100 sampler. Selective growth media were used for bacteria and mold isolation and quantifying analysis. The antibiotic resistance of the isolated mannitol-positive staphylococci was assessed using the disc diffusion method in accordance with EUCAST recommendations. The highest mean concentration of heterotrophic bacteria was recorded in the cafeterias: 884 CFU m−3 in School A and 1906 CFU m−3 in School B. Molds were the most abundant in the library and cafeteria in School B, where their average concentration exceeded 300 CFU m−3. Cladosporium and Penicillium species prevailed, while Fusarium, Acremonium and Aspergillus were less abundant. Airborne mannitol-positive staphylococci were recorded at low concentrations, ranging from 6 to 11 CFU m−3 on average. According to the taxonomic analysis, Staphylococcus aureus isolates were the most abundant in both schools, followed by S. xylosus, S. haemolyticus and S. saprophyticus. The antibiograms indicated that resistance to erythromycin was common in 62.5% of the isolated staphylococcal strains. Levofloxacin and gentamicin were the most effective antibiotics. No multidrug-resistant strains were identified.

Bioaerosols at plants processing materials of plant origin-a review

Due to the dynamic development of industry, related to the processing of plant materials and a subsequent significant increase in the number of employees working in this kind of industry, the indoor air quality is of great importance for the human health. The premises of plants processing plant materials are a specific environment, related to exposure to biological agents. The major sources of microbial contamination of premises are employees' activities and the operation of devices used in the production process, quality of plant materials, technological processes, construction materials, ventilation (air-conditioning) systems, and outdoor air. Biological agents (primarily bacteria and fungi) transported in the air can cause numerous adverse health outcomes in exposed workers.

Microbiological Air Quality in a Highschool Gym Located in an Urban Area of Southern Poland—Preliminary Research

The benefits of regular exercise include improved physical and mental health. The school gym is a particular micro-environment where students perform intensive physical training. The question is if there is an increased risk of microbiological contamination. This preliminary work studied the exposure of students to bacterial aerosol (BA) in a highschool gym located in an urban area of Southern Poland. A sampling of BA was undertaken with an Andersen six-stage impactor (ANDI). BA was identified using API (analytical profile index) tests. The BA concentrations were expressed as Colony Forming Units (CFU) per cubic metre of air. The results showed that before gym classes (BGC), the concentration of BA was 4.20 × 102 ± 49.19 CFU/m3, while during gym classes (DGC), the level of BA more than doubled (8.75 × 102 ± 121.39 CFU/m3). There was also an increase in the respirable fraction of BA (particles less than 3.3 µm). Before the start of the sports activities, respirable fraction accounted for 30% of the BA, while during physical education classes, this share increased to over 80%. Identification of BA species showed that the dominant group of bacteria in the indoor air of the gym BGC was Gram-positive rods (61%) and for DGC it was Gram-positive cocci (81%). We detected that one bacteria strain (Corynebacterium striatum) was classified into risk group 2 (RG2) according to Directive 2000/54/EC. Additionally, multi-antibiotic resistance (MAR) showed that among the isolated airborne bacteria, the highest antibiotic resistance was demonstrated by Staphylococcus epidermis (isolated DGC) and Pseudomonas sp. (isolated BGC). The quantitative and qualitative information on microbiological air quality (MIAQ) in the school gym indicates that the actions to improve indoor physical activity spaces are recommended.

Surgical Smoke and Airborne Microbial Contamination in Operating Theatres: Influence of Ventilation and Surgical Phases

Air cleanliness is a crucial factor in operating theatres (OTs), where the health of patients and staff must be preserved by controlling air contamination. Particular attention must be paid to ultrafine particles (UFPs) size range, generated for instance by electrosurgical instruments (ESTs). OT contamination is also affected by ventilation systems, medical staff and their gowning system, staff routines, instruments, etc. This comparative study is based on experimental measurements of airborne microbial contamination and UFPs carried out during real ongoing surgeries in two OTs equipped with upward displacement ventilation (UWD) and hybrid ventilation, with unidirectional airflow on the operating table and peripheral mixing (UDAF+Mixing) ventilation systems. Airborne contamination concentration at the exit grilles has been analyzed as function of four different surgical phases normally performed during an operation. Results highlight that airborne contamination is influenced by the activities carried out during the surgical phases. EST usage affects the contamination level more than staff size during operation observed. Colony forming unit (CFU) values in the protected area close to the patient’s wound are influenced more by the type of ventilation system than by surgical phases. CFU values decrease by 18 to 50 times from the UWD system to the hybrid one. The large airflow volumes supply together with high air velocities in OTs equipped with UDAF+Mixing systems guarantee a better and a safer airborne contamination control for patients and medical team in comparison with UWD systems.

Microbiological Air Quality and Drug Resistance in Airborne Bacteria Isolated from a Waste Sorting Plant Located in Poland-A Case Study

International interests in biological air pollutants have increased rapidly to broaden the pool of knowledge on their identification and health impacts (e.g., infectious, respiratory diseases and allergies). Antibiotic resistance and its wider implications present us with a growing healthcare crisis, and an increased understanding of antibiotic-resistant bacteria populations should enable better interpretation of bioaerosol exposure found in the air. Waste sorting plant (WSP) activities are a source of occupational bacterial exposures that are associated with many health disorders. The objectives of this study were (a) to assess bacterial air quality (BAQ) in two cabins of a WSP: preliminary manual sorting cabin (PSP) and purification manual sorting cabin (quality control) (QCSP), (b) determine the particle size distribution (PSD) of bacterial aerosol (BA) in PSP, QCSP, and in the outdoor air (OUT), and (c) determine the antibiotic resistance of isolated strains of bacteria. Bacterial strains were identified on a Biolog GEN III (Biolog, Hayward, CA, USA), and disc diffusion method for antimicrobial susceptibility testing was carried out according to the Kirby-Bauer Disk Diffusion Susceptibility Test Protocol. A large share of fecal bacteria, Enterococcus faecalis and Alcaligenes faecalis spp. feacalis, was found in the tested indoor air, which is a potential health hazard to the workers of the monitored WSP. Our results demonstrate the necessity to take into account fecal air pollution levels to avoid making erroneous assumptions regarding the environmental selection of antibiotic resistance. Total elimination of many anthropogenic sources is not possible, but important findings of this study can be used to develop realistic management policies methods to improve BAQ.

The Dose of Fungal Aerosol Inhaled by Workers in a Waste-Sorting Plant in Poland: A Case Study

Bioaerosol monitoring is a rapidly emerging area in the context of work environments because microbial pollution is a key element of indoor air pollution and plays an important role in certain infectious diseases and allergies. However, as yet, relatively little is known about inhaled doses of microorganisms in workplaces. Today, the important issue of social concern is due to waste management, transport, sorting, and processing of wastes and their environmental impact and effects on public health. In fact, waste management activities can have numerous adverse effects on human wellbeing. Health effects are generally linked to exposure (EX), defined as the concentration of a contaminant and the length of time a person is exposed to this concentration. Dose is an effective tool for evaluating the quantity of a contaminant that actually crosses the body’s boundaries and influences the goal tissue. This document presents an analysis of the fungal waste-sorting plant EX dose (FWSPED) inhaled by workers in a waste-sorting plant (WSP) in Poland in March 2019. The main purpose of this research was to assess FWSPED inhaled by workers in two cabins at the WSP: the preliminary manual sorting cabin (PSP) and the purification manual sorting cabin (quality control; QSP). It was found that the FWSPED inhaled by workers was 193 CFU/kg in the PSP and 185 CFU/kg in the QSP. Fungal particles were quantitatively evaluated and qualitatively identified by the GEN III Biolog system. During the research, it was found that isolates belonging to the Aspergilus flavus and Penicillum chrysogenum strains were detected most frequently in the WSP. The total elimination of many anthropogenic sources is not possible, but the important findings of this research can be used to develop realistic management policies and methods to improve the biological air quality of WSPs for effective protection of WSP workers.

Quantification of Airborne Resistant Organisms With Temporal and Spatial Diversity in Bangladesh: Protocol for a Cross-Sectional Study

BACKGROUND

Antimicrobial resistance is a widespread, alarming issue in global health and a significant contributor to human death and illness, especially in low and middle-income countries like Bangladesh. Despite extensive work conducted in environmental settings, there is a scarcity of knowledge about the presence of resistant organisms in the air.

OBJECTIVE

The objective of this protocol is to quantify and characterize the airborne resistomes in Bangladesh, which will be a guide to identify high-risk environments for multidrug-resistant pathogens with their spatiotemporal diversity.

METHODS

This is a cross-sectional study with an environmental, systematic, and grid sampling strategy focused on collecting air samples from different outdoor environments during the dry and wet seasons. The four environmental compartments are the frequent human exposure sites in both urban and rural settings: urban residential areas (n=20), live bird markets (n=20), rural households (n=20), and poultry farms (n=20). We obtained air samples from 80 locations in two seasons by using an active microbial air sampler. From each location, five air samples were collected in different media to yield the total bacterial count of 3rd generation cephalosporin (3GC) resistant Enterobacteriaceae, carbapenem-resistant Enterobacteriaceae, vancomycin-resistant Enterococci and methicillin-resistant Staphylococcus aureus.

RESULTS

The study started in January 2018, and the collection of air samples was completed in November 2018. We have received 800 air samples from 80 study locations in both dry and wet seasons. Currently, the laboratory analysis is ongoing, and we expect to receive the preliminary results by October 2019. We will publish the complete result as soon as we clean and analyze the data and draft the manuscript.

CONCLUSIONS

The existence of resistant bacteria in the air like those producing extended-spectrum beta-lactamases, carbapenem-resistant Enterobacteriaceae, vancomycin-resistant Enterococci, and methicillin-resistant Staphylococcus aureus will justify our hypothesis that the outdoor environment (air) in Bangladesh acts as a reservoir for bacteria that carry genes conferring resistance to antibiotics. To our knowledge, this is the first study to explore the presence of superbugs in the air in commonly exposed areas in Bangladesh.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/14574.

Efficiency and Eco-Costs of Air Purifiers in Terms of Improving Microbiological Indoor Air Quality in Dwellings—A Case Study

Air pollution, a by-product of economic growth, generates an enormous environmental cost in Poland. The issue of healthy living spaces and indoor air quality (IAQ) is a global concern because people spend approximately 90% of their time indoors. An increasingly popular method to improve IAQ is to use air purifiers (APs). Indoor air is often polluted by bioaerosols (e.g., viruses, bacteria, fungi), which are a major concern for public health. This work presents research on culturable bacterial aerosol (CBA) samples collected from dwellings with or without active APs during the 2019 summer season. The CBA samples were collected using a six-stage Andersen cascade impactor (ACI). The CBA concentrations were expressed as Colony Forming Units (CFU) per cubic metre of air. The average concentration of CBA in dwellings when the AP was active was 450–570 CFU/m3, whereas the average concentration when the AP was not active was 920–1000 CFU/m3. IAQ, when the APs were active, was on average almost 50% better than in cases where there were no procedures to decrease the concentration of air pollutants. Moreover, the obtained results of the particle size distribution (PSD) of CBA indicate that the use of APs reduced the proportion of the respirable fraction (the particles < 3.3 µm) by about 16%. Life cycle assessment (LCA) was used to assess the ecological cost of air purification. Our conceptual approach addresses the impact of indoor air pollution on human health and estimates the ecological cost of APs and air pollution prevention policies.

Temporal variation in indoor transfer of dirt-associated environmental bacteria in agricultural and urban areas

An agricultural environment and exposure to diverse environmental microbiota has been suggested to confer protection against immune-mediated disorders. As an agricultural environment may have a protective role, it is crucial to determine whether the limiting factors in the transfer of environmental microbiota indoors are the same in the agricultural and urban environments. We explored how sampling month, garden diversity and animal ownership affected the indoor-transfer of environmental microbial community. We collected litter from standardized doormats used for 2 weeks in June and August 2015 and February 2016 and identified bacterial phylotypes using 16S rRNA Illumina MiSeq sequencing. In February, the diversity and richness of the whole bacterial community and the relative abundance of environment-associated taxa were reduced, whereas human-associated taxa and genera containing opportunistic pathogens were enriched in the doormats. In summer, the relative abundances of several taxa associated previously with beneficial health effects were higher, particularly in agricultural areas. Surprisingly, the importance of vegetation on doormat microbiota was more observable in February, which may have resulted from snow cover that prevented contact with microbes in soil. Animal ownership increased the prevalence of genera Bacteroides and Acinetobacter in rural doormats. These findings underline the roles of season, living environment and lifestyle in the temporal variations in the environmental microbial community carried indoors. As reduced contact with diverse microbiota is a potential reason for immune system dysfunction, the results may have important implications in the etiology of immune-mediated, non-communicable diseases.

Exposure to Bacterial and Fungal Aerosols: Microorganism Indices in A Waste-Sorting Plant in Poland

An increased understanding of airborne microorganism populations should enable a better interpretation of bioaerosol exposure found in a working environment. An assessment of the contamination levels of mesophilic bacterial aerosol (MBA) and fungal aerosol (FA) was carried out using two evaluation indices for microbiological pollution—the total index of microbiological contamination per cubic meter (TIMC/m³) and the indoor–outdoor index (IOI). An advantage of selected indices is the inclusion of several co-existing factors that have an impact on the formation of bioaerosol. When properly used, they also highlight the low efficiency of the ventilation system caused by an insufficient air exchange. In this study, the microbial air quality (MAQ) of the working environment was assessed during the spring season at a sorting plant located in Southern Poland. Sampling was undertaken in the plant using an Andersen six-stage impactor which allows the obtainment of information about the size distribution of the air microflora. The value of average concentrations of MBA and the average concentration of FA collected in the preliminary cabin of the sorting plant (PCSP) and the cleaning cabin of the sorting plant (CCSP) were analyzed. The obtained values of MBA were 1.6 times higher indoors, compared to outdoors, while FA was 1.7 times higher outdoors than indoors. The maximum TIMC/m³ value was obtained in PCSP (2626). The calculated IOI in this study suggests that MBA concentrations are influenced by internal sources, as opposed to FA. The purpose of this work was to present the usefulness of using indices in assessing air quality.

Quantitative evaluation of bioaerosols in different particle size fractions in dust collected on the International Space Station (ISS)

Exposure to bioaerosols can adversely influence human health through respiratory tract, eye, and skin irritation. Bioaerosol composition is unique on the International Space Station (ISS), where the size distribution of particles in the air differs from those on Earth. This is due to the lack of gravitational settling and sources of biological particles. However, we do not understand how microbes are influenced by particle size in this environment. We analyzed two types of samples from the ISS: (1) vacuum bag debris which had been sieved into five different size fractions and (2) passively collected particles on a tape substrate with a passive aerosol sampler. Using quantitative polymerase chain reaction (qPCR), the highest concentration of fungal spores was found in the 106-150 μm-sized sieved dust particles, while the highest concentration of bacterial cells was found in the 150-250 μm-sized sieved dust particles. Illumina MiSeq DNA sequencing revealed that particle size was associated with bacterial and fungal communities and statistically significant (p = 0.035, p = 0.036 respectively). Similar fungal and bacterial species were found within the passive aerosol sample and the sieved dust samples. The most abundant fungal species identified in the aerosol and sieved samples are commonly found in food and plant material. Abundant bacterial species were most associated with the oral microbiome and human upper respiratory tract. One limitation to this study was the suboptimal storage conditions of the sieved samples prior to analysis. Overall, our results indicate that microbial exposure in space may depend on particle size. This has implications for ventilation and filtration system design for future space vehicles and habitats.

Air Quality and Potential Health Risk Impacts of Exposure to Bacterial Aerosol in a Waste Sorting Plant Located in the Mountain Region of Southern Poland, Around Which There Are Numerous Rural Areas

Many studies have shown an association between working in waste sorting plants (SP) and occupational health problems, such as skin irritation or pulmonary diseases. These symptoms have been related to biological aerosol exposure. The main goal of this work was to assess the levels of concentration and the characteristics of bacterial aerosols in waste sorting plants, based on measurements taken in a plant located in the mountain region of Southern Poland, around which there are numerous rural areas. The average concentrations of culturable bacterial aerosol (CCBA) collected in the unloading hall of the waste sorting plant (UHSP) and the outdoor air of the sorting plant (OSP) were 2687 CFU/m3 and 1138 CFU/m3, respectively. Sampling was undertaken in the plant using an Andersen six-stage impactor (with aerodynamic cut-off diameters of 7.0, 4.7, 3.3, 2.1, 1.1, and 0.65 μm), during the spring of 2019. Size distributions were unimodal, with a peak in particle bacterial aerodynamic diameters at less than 3.3 µm, increasing the potentially adverse health effects of their inhalation. An analysis was conducted to determine the antibiotic resistance of isolated strains of bacteria. During the study, it was found that isolates belonging to the genus Bacillus were most frequently detected in the waste sorting plant. Isolates with the highest resistance to antibiotics belonged to the genus Neisseria. This test indicates that the use of personal protective equipment is necessary.