Sources and mechanisms of bioaerosol generation in occupational environments

The abundance and pathogenicity of microbes in automobile air conditioning filters across the typical cities of China and Europe

Bioaerosols are widely distributed in urban air and can be transmitted across the atmosphere, biosphere, and anthroposphere, resulting in infectious diseases. Automobile air conditioning (AAC) filters can trap airborne microbes. In this study, AAC filters were used to investigate the abundance and pathogenicity of airborne microorganisms in typical Chinese and European cities. Culturable bacteria and fungi concentrations were determined using microbial culturing. High-throughput sequencing was employed to analyze microbial community structures. The levels of culturable bioaerosols in Chinese and European cities exhibited disparities (Analysis of Variance, P < 0.01). The most dominant pathogenic bacteria and fungi were similar in Chinese (Mycobacterium: 18.2-18.9 %; Cladosporium: 23.0-30.2 %) and European cities (Mycobacterium: 15.4-37.7 %; Cladosporium: 18.1-29.3 %). Bartonella, Bordetella, Alternaria, and Aspergillus were also widely identified. BugBase analysis showed that microbiomes in China exhibited higher abundances of mobile genetic elements (MGEs) and biofilm formation capacity than those in Europe, indicating higher health risks. Through co-occurrence network analysis, heavy metals such as zinc were found to correlate with microorganism abundance; most bacteria were inversely associated, while fungi exhibited greater tolerance, indicating that heavy metals affect the growth and reproduction of bioaerosol microorganisms. This study elucidates the influence of social and environmental factors on shaping microbial community structures, offering practical insights for preventing and controlling regional bioaerosol pollution.

Assessing environmental exposure to viruses in wastewater treatment plant and swine farm scenarios with next-generation sequencing and occupational risk approaches

Occupational exposure to pathogens can pose health risks. This study investigates the viral exposure of workers in a wastewater treatment plant (WWTP) and a swine farm by analyzing aerosol and surfaces samples. Viral contamination was evaluated using quantitative polymerase chain reaction (qPCR) assays, and target enrichment sequencing (TES) was performed to identify the vertebrate viruses to which workers might be exposed. Additionally, Quantitative Microbial Risk Assessment (QMRA) was conducted to estimate the occupational risk associated with viral exposure for WWTP workers, choosing Human Adenovirus (HAdV) as the reference pathogen. In the swine farm, QMRA was performed as an extrapolation, considering a hypothetical zoonotic virus with characteristics similar to Porcine Adenovirus (PAdV). The modelled exposure routes included aerosol inhalation and oral ingestion through contaminated surfaces and hand-to-mouth contact. HAdV and PAdV were widespread viruses in the WWTP and the swine farm, respectively, by qPCR assays. TES identified human and other vertebrate viruses WWTP samples, including viruses from families such as Adenoviridae, Circoviridae, Orthoherpesviridae, Papillomaviridae, and Parvoviridae. In the swine farm, most of the identified vertebrate viruses were porcine viruses belonging to Adenoviridae, Astroviridae, Circoviridae, Herpesviridae, Papillomaviridae, Parvoviridae, Picornaviridae, and Retroviridae. QMRA analysis revealed noteworthy risks of viral infections for WWTP workers if safety measures are not taken. The probability of illness due to HAdV inhalation was higher in summer compared to winter, while the greatest risk from oral ingestion was observed in workspaces during winter. Swine farm QMRA simulation suggested a potential occupational risk in the case of exposure to a hypothetical zoonotic virus. This study provides valuable insights into WWTP and swine farm worker's occupational exposure to human and other vertebrate viruses. QMRA and NGS analyses conducted in this study will assist managers in making evidence-based decisions, facilitating the implementation of protection measures, and risk mitigation practices for workers.

Temporal variations of antimicrobial resistance genes in aerosols: A one-year monitoring at the puy de Dôme summit (Central France)

The recent characterization of antibiotic resistance genes (ARGs) in clouds evidenced that the atmosphere actively partakes in the global spreading of antibiotic resistance worldwide. Indeed, the outdoor atmosphere continuously receives large quantities of particles of biological origins, emitted from both anthropogenic or natural sources at the near Earth's surface. Nonetheless, our understanding of the composition of the atmospheric resistome, especially at mid-altitude (i.e. above 1000 m a.s.l.), remains largely limited. The atmosphere is vast and highly dynamic, so that the diversity and abundance of ARGs are expected to fluctuate both spatially and temporally. In this work, the abundance and diversity of ARGs were assessed in atmospheric aerosol samples collected weekly between July 2016 and August 2017 at the mountain site of puy de Dôme (1465 m a.s.l., central France). Our results evidence the presence of 33 different subtypes of ARGs in atmospheric aerosols, out of 34 assessed, whose total concentration fluctuated seasonally from 59 to 1.1 × 105 copies m-3 of air. These were heavily dominated by genes from the quinolone resistance family, notably the qepA gene encoding efflux pump mechanisms, which represented >95 % of total ARGs concentration. Its abundance positively correlated with that of bacteria affiliated with the genera Kineococcus, Neorhizobium, Devosia or Massilia, ubiquitous in soils. This, along with the high abundance of Sphingomonas species, points toward a large contribution of natural sources to the airborne ARGs. Nonetheless, the increased contribution of macrolide resistance (notably the erm35 gene) during winter suggests a sporadic diffusion of ARGs from human activities. Our observations depict the atmosphere as an important vector of ARGs from terrestrial sources. Therefore, monitoring ARGs in airborne microorganisms appears necessary to fully understand the dynamics of antimicrobial resistances in the environment and mitigate the threats they may represent.

Effect of forceful suction and air disinfection machines on aerosol removal

BACKGROUNDS

Dental procedures involving drilling and grinding can produce a significant amount of suspended aerosol particles (PM) and bioaerosols. This study aims to analyze the size and concentration of aerosol particles generated during drilling and to investigate the effectiveness of two air exchange systems, namely forceful suction (FS) and air disinfection machines (DM), in removing PM.

METHODS

For this study, 100 extracted permanent teeth were collected and divided into three groups: without suction (n = 50), suction with forceful suction (n = 25), and suction with air disinfection machines (n = 25). The removal rate of suspended aerosol particles was analyzed using particle counters and air data multimeter.

RESULTS

When drilling and grinding were performed without vacuum, 0.75% of the aerosol particles generated were PM2.5-10, 78.25% of total suspended aerosol particles (TSP) were PM2.5, and 98.68% of TSP were PM1. The nanoanalyzer measurements revealed that the aerodynamic diameter of most aerosol particles was below 60 nm, with an average particle diameter of 52.61 nm and an average concentration of 2.6*1011 ultrafine aerosol particles. The air change per hour (ACH) was significantly lower in the air disinfection machines group compared to the forceful suction group. Additionally, the number of aerosol particles and mass concentration was significantly lower in the air disinfection machines group compared to the forceful suction group in terms of PM2.5 levels. However, the forceful suction group also reduced the mass concentration in PM10 level than the air disinfection machines group.

CONCLUSION

In conclusion, the air exchange system can reduce the aerosol particles generated during drilling and grinding. Comparing the two air exchange systems, it was found that the air disinfection machines group reduces the number of aerosol particles and mass concentration in PM2.5 levels, while the forceful suction group reduces the mass concentration in PM10 level.

Environmental Stability and Transmissibility of Enveloped Viruses at Varied Animate and Inanimate Interfaces

Enveloped viruses have been the leading causative agents of viral epidemics in the past decade, including the ongoing coronavirus disease 2019 outbreak. In epidemics caused by enveloped viruses, direct contact is a common route of infection, while indirect transmissions through the environment also contribute to the spread of the disease, although their significance remains controversial. Bridging the knowledge gap regarding the influence of interfacial interactions on the persistence of enveloped viruses in the environment reveals the transmission mechanisms when the virus undergoes mutations and prevents excessive disinfection during viral epidemics. Herein, from the perspective of the driving force, partition efficiency, and viral survivability at interfaces, we summarize the viral and environmental characteristics that affect the environmental transmission of viruses. We expect to provide insights for virus detection, environmental surveillance, and disinfection to limit the spread of severe acute respiratory syndrome coronavirus 2.

Critical review of antibiotic resistance genes in the atmosphere

We conducted a critical review to establish what is known about the sources, characteristics, and dissemination of ARGs in the atmosphere. We identified 52 papers that reported direct measurements of bacterial ARGs in air samples and met other inclusion criteria. The settings of the studies fell into the following categories: urban, rural, hospital, industrial, wastewater treatment plants (WWTPs), composting and landfill sites, and indoor environments. Certain genes were commonly studied and generally abundant: sul1, intI1, β-lactam ARGs, and tetracycline ARGs. Abundances of total ARGs varied by season and setting, with air in urban areas having higher ARG abundance than rural areas during the summer and vice versa during the winter. There was greater consistency in the types and abundances of ARGs throughout the seasons in urban areas. Human activity within indoor environments was also linked to increased ARG content (abundance, diversity, and concentration) in the air. Several studies found that human exposure to ARGs through inhalation was comparable to exposure through drinking water or ingesting soil. Detection of ARGs in air is a developing field, and differences in sampling and analysis methods reflect the many possible approaches to studying ARGs in air and make direct comparisons between studies difficult. Methodologies need to be standardized to facilitate identification of the dominant ARGs in the air, determine their major sources, and quantify the role of atmospheric transport in dissemination of ARGs in the environment. With such knowledge we can develop better policies and guidelines to limit the spread of antimicrobial resistance.

Coronavirus in water media: Analysis, fate, disinfection and epidemiological applications

Considerable attention has been recently given to possible transmission of SARS-CoV-2 via water media. This review addresses this issue and examines the fate of coronaviruses (CoVs) in water systems, with particular attention to the recently available information on the novel SARS-CoV-2. The methods for the determination of viable virus particles and quantification of CoVs and, in particular, of SARS-CoV-2 in water and wastewater are discussed with particular regard to the methods of concentration and to the emerging methods of detection. The analysis of the environmental stability of CoVs, with particular regard of SARS-CoV-2, and the efficacy of the disinfection methods are extensively reviewed as well. This information provides a broad view of the state-of-the-art for researchers involved in the investigation of CoVs in aquatic systems, and poses the basis for further analyses and discussions on the risk associated to the presence of SARS-CoV-2 in water media. The examined data indicates that detection of the virus in wastewater and natural water bodies provides a potentially powerful tool for quantitative microbiological risk assessment (QMRA) and for wastewater-based epidemiology (WBE) for the evaluation of the level of circulation of the virus in a population. Assays of the viable virions in water media provide information on the integrity, capability of replication (in suitable host species) and on the potential infectivity. Challenges and critical issues relevant to the detection of coronaviruses in different water matrixes with both direct and surrogate methods as well as in the implementation of epidemiological tools are presented and critically discussed.

Advances on the immunotoxicity of outdoor particulate matter: A focus on physical and chemical properties and respiratory defence mechanisms

Particulate matter (PM) is acknowledged to have multiple detrimental effects on human health. In this review, we report literature results on the possible link between outdoor PM and health outcomes with a focus on pulmonary infections and the mechanisms responsible for observed negative effects. PM physical and chemical properties, such as size and chemical composition, as well as major emission sources are described for a more comprehensive view about the role played by atmospheric PM in the observed adverse health effects; to this aim, major processes leading to the deposition of PM in the respiratory tract and how this can pave the way to the onset of pathologies are also presented. From the literature works here reviewed, two ways in which PM can threaten human health promoting respiratory infectious diseases are mostly taken into account. The first pathway is related to an enhanced susceptibility and here we will also report on molecular mechanisms in the lung immune system responsible for the augmented susceptibility to pathogens, such as the damage of mechanical defensive barriers, the alteration of the innate immune response, and the generation of oxidative stress. The second one deals with the relationship between infectious agents and PM; here we recall that viruses and bacteria (BioPM) are themselves part of atmospheric PM and are collected during sampling together with particles of different origin; so, data should be analysed with caution in order to avoid any false cause-effect relation. To face these issues a multidisciplinary approach is mandatory as also evident from the ongoing research about the mechanisms hypothesized for the SARS-CoV-2 airborne spreading, which is still controversial and claims for further investigation. Therefore, we preferred not to include papers dealing with SARS-CoV-2.

Recent Advances on Bioaerosol Collection and Detection in Microfluidic Chips

Bioaerosols containing pathogenic microorganisms have posed a great threat to human and animal health. Effective monitoring of bioaerosols containing pathogenic viruses and bacteria is of great significance to prevent and control infectious diseases. This Feature summarizes recent advances on bioaerosol collection and detection based on microfluidic chips. Besides, the challenges and trends for bioaerosol collection and detection were also discussed.

Recent developments in antimicrobial and antifouling coatings to reduce or prevent contamination and cross-contamination of food contact surfaces by bacteria

Illness as the result of ingesting bacterially contaminated foodstuffs represents a significant annual loss of human quality of life and economic impact globally. Significant research investment has recently been made in developing new materials that can be used to construct food contacting tools and surfaces that might minimize the risk of cross-contamination of bacteria from one food item to another. This is done to mitigate the spread of bacterial contamination and resultant foodborne illness. Internet-based literature search tools such as Web of Science, Google Scholar, and Scopus were utilized to investigate publishing trends within the last 10 years related to the development of antimicrobial and antifouling surfaces with potential use in food processing applications. Technologies investigated were categorized into four major groups: antimicrobial agent-releasing coatings, contact-based antimicrobial coatings, superhydrophobic antifouling coatings, and repulsion-based antifouling coatings. The advantages for each group and technical challenges remaining before wide-scale implementation were compared. A diverse array of emerging antimicrobial and antifouling technologies were identified, designed to suit a wide range of food contact applications. Although each poses distinct and promising advantages, significant further research investment will likely be required to reliably produce effective materials economically and safely enough to equip large-scale operations such as farms, food processing facilities, and kitchens.

Insight Into Microbial Community Aerosols Associated With Electronic Waste Handling Facilities by Culture-Dependent and Culture-Independent Methods

Airborne microorganisms in the waste associated environments are more active and complex compared to other places. However, the diversity and structure of airborne bacteria in waste-associated environments are still not clearly understood. The purpose of this study was to assess airborne bacterial community in electronic waste dismantling site and a waste transfer station based on culture-dependent and culture-independent methods. A total of 229 isolates were obtained from four airborne sites collected from residential area, electronic industrial park, and office area in or near an electronic waste dismantling site and a waste transfer station in Southern China in the morning, afternoon, and evening. Most of the isolates were isolated from air for the first time and 14 potentially novel species were identified by Sanger sequencing. Bacterial communities in waste-associated bioaerosols were predominated by Proteobacteria and Bacteroidetes. Abundant genera (>1%) included Paracaedibacteraceae (uncultured EF667926), Ralstonia, Chroococcidiopsis, Chitinophagaceae (uncultured FN428761), Sphingobium, and Heliimonas. One-third of the species in these genera were uncultured approximately. Differences community structure existed in airborne bacterial diversity among different sampling sites. These results showed that waste-associated environments have unique bacterial diversity. Further studies on such environments could provide new insights into bacterial community.

Pollen and Fungal Spores Evaluation in Relation to Occupants and Microclimate in Indoor Workplaces

Indoor air quality depends on many internal or external factors mutually interacting in a dynamic and complex system, which also includes indoor workplaces, where subjects are exposed to many pollutants, including biocontaminants such as pollen and fungal spores. In this context, the occupants interact actively with their environment through actions, modifying indoor environmental conditions to achieve their own thermal comfort. Actions such as opening/closing doors and windows and turning on/off air conditioning could have effects on workers’ health. The present study explored the contribution of human occupants to pollen and fungal spore levels in indoor workplaces, combining aerobiological, microclimate, and worker monitoring during summer and winter campaigns. We evaluated the overall time spent by the workers in the office, the workers’ actions regarding non-working days and working days, and non-working hours and working hours, during two campaigns of pollen and fungal spore monitoring. Our results showed that the biocontaminant values depend on many mutually interacting factors; hence, the role of all of the factors involved should be investigated. In this regard, aerobiological monitoring should be a valid tool for the management of occupational allergies, providing additional information to improve occupational health protection strategies.

The bioaerosols emitted from toilet and wastewater treatment plant: a literature review

The aerosols harboring microorganisms and viruses released from the wastewater system into the air have greatly threatened the health and safety of human beings. The wastewater systems, including toilet and wastewater treatment plant (WWTP), are the major locations of epidemic infections due to the extensive sources of aerosols, as well as multifarious germs and microorganisms. Viruses and microorganisms may transport from both toilet and hospital into municipal pipes and subsequently into WWTP, which accounts for the main source of bioaerosols dispersed in the air of the wastewater system. This review aims to elaborate the generation, transmission, and diffusion processes of bioaerosols at toilet and WWTP. Moreover, the main factors affecting bioaerosol transmission and the corresponding prevention strategies for the airborne and inhaled bioaerosols are also discussed. Collectively, this review highlights the importance of managing bioaerosol occurrence in the wastewater system, which has aroused increasing concern from the public.

Pollution profiles of antibiotic resistance genes associated with airborne opportunistic pathogens from typical area, Pearl River Estuary and their exposure risk to human

To reveal the selective pressures of near-shore human activities on marine and continental bioaerosols, the pollution profile and potential exposure risk of airborne pathogens and antibiotic-resistance genes (ARGs) in Pearl River Estuaries (113.52 ^oE, 22.69 ^oN), a transitional zone between marine and continental environments, were fully explored. The results showed that the total bacteria among bioaerosols varied largely with average pollution levels of 1.86 × 10⁵ and 4.35 × 10⁴ cfu m^-3 in spring and summer, respectively, and were high than those of airborne fungi. The predominant aerodynamic diameters of bioaerosols were in respirable size range (<4.7 µm), and the microbes communities' diversity and abundance varied significantly. Besides, many opportunistic pathogenic bacteria (Burkholderia-Paraburkholderia, Staphylococcus and Acinetobacter) and fungi (Alternaria, Penicillium and Cladosporium) were dominant in bioaerosol samples. Of 21 ARGs subtypes detected, the tetracycline resistance gene tetA was the most abundant, followed by aminoglycoside resistance gene and mobile genetic elements. Correlation analysis revealed that the changes of pathogens community contributed significantly to the prevalence of ARGs in bioaerosol. Based on the average daily dose rates of microorganisms and human direct intake of ARGs, health risk of bioaerosols from the Pearl River Estuaries were also evaluated. In summary, the presence of opportunistic pathogens and diversity of ARGs strengthens the call to consider the bioaerosol in air quality monitoring and risk assessment in the future.

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.

Field sampling of indoor bioaerosols

Because bioaerosols are related to adverse health effects in exposed humans and indoor environments represent a unique framework of exposure, concerns about indoor bioaerosols have risen over recent years. One of the major issues in indoor bioaerosol research is the lack of standardization in the methodology, from air sampling strategies and sample treatment to the analytical methods applied. The main characteristics to consider in the choice of indoor sampling methods for bioaerosols are the sampler performance, the representativeness of the sampling, and the concordance with the analytical methods to be used. The selection of bioaerosol collection methods is directly dependent on the analytical methods, which are chosen to answer specific questions raised while designing a study for exposure assessment. In this review, the authors present current practices in the analytical methods and the sampling strategies, with specificity for each type of microbe (fungi, bacteria, archaea and viruses). In addition, common problems and errors to be avoided are discussed. Based on this work, recommendations are made for future efforts towards the development of viable bioaerosol samplers, standards for bioaerosol exposure limits, and making association studies to optimize the use of the big data provided by high-throughput sequencing methods.