Microbial aerosol particles in four seasons of sanitary landfill site: Molecular approaches, traceability and risk assessment

Diffusion behavior and transport risk of bioaerosol particles in a domestic waste landfill site in an arid and cold region of northwestern China

Bioaerosols have attracted increasing attention as novel contaminants because of their potential role in the spread of disease. In this study, sampling sites were established in a landfill in northwestern China with the aim of investigating the emission and diffusion characteristics of bioaerosols. The results revealed that the counts of airborne bacteria released by landfill cover area (LCA) and waste dumping area (WDA) located in the landfill area reached 18 193 ± 30 CFU/m3 and 10 948 ± 105 CFU/m3, respectively. These two aeras were the main sources of bioaerosol generation. Meanwhile, Corynebacterium spp., Bacteroidetes spp., and Pseudomonas spp. were identified as potential pathogens. A Gaussian model was applied to simulate the diffusion of the bioaerosols; the influence distance was calculated as 12 km from the boundary of the landfill site. The potential health risks of bioaerosol exposure to on-site workers and nearby residents were calculated and evaluated in terms of aerosol concentration, particle size, and pathogenic bacteria. The present study promotes the recognition of the emission behavior of microorganisms in aerosol particles and provides a basis for controlling bioaerosol contamination from landfill sites, particularly those located in cold and arid northwestern regions of China.

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.

Distribution and survival of pathogens from different waste components and bioaerosol traceability analysis in household garbage room

Household garbage rooms release abundant bioaerosols and are an important source of pathogens; however, information on the distribution and survival patterns of pathogens in different waste components is limited. In this study, a culture method and 16S rRNA high-throughput sequencing were used to determine bacterial communities, culturable pathogens, and human bacterial pathogens (HBPs). The results showed that abundant culturable bacteria were detected in all waste types, and a large number of S. aureus was detected on the surface of recyclable wastes, whereas S. aureus, total coliforms, Salmonella, Enterococcus, and hemolytic bacteria were detected in food waste and other waste. The activities of these detected pathogenic bacteria decreased after 24 h of storage but re-activated within one week. Factors affecting the emergence of pathogens varied with different waste components. Sequencing results showed that Pseudomonas, Acinetobacter, and Burkholderia were abundant in the waste samples, whereas Achromobacter, Exiguobacteriums, Bordetella, and Corynebacterium were the primary pathogens in the bioaerosol and wall attachment. The results of traceability analysis showed that bioaerosol microbes were mainly derived from raw kitchen waste (5.98%) and plastic and paper contaminated with food waste (19.93%) in garbage rooms. In addition, bioaerosols were the main source of microflora in the wall attachment, which possessed high HBP diversity and required more attention. These findings will help in understanding the microbial hazards in different waste components and provide guidance for the control and risk reduction of bioaerosols during waste management and recycling.

Transport and risk of airborne pathogenic microorganisms in the process of decentralized sewage discharge and treatment

Sewage treatment processes are a critical anthropogenic source of bioaerosols and may present significant health risks to plant workers. Compared with the specialization and scale of urban sewage treatment, many decentralized treatment models are flexible and extensive. These treatment facilities are usually close to residential areas owing to the pipe network layout and other restrictions. Bioaerosols generated by these facilities may present a serious and widespread occupational and non-occupational exposure risk to nearby residents, particularly the elderly and children. An understanding of the characteristics and exposure risks of bioaerosols produced during decentralized sewage treatment is lacking. We compared bioaerosol emission characteristics and potential exposure risks under four decentralized sewage discharge methods and treatment models: small container collection (SCC), open-channel discharge (OCD), single household/combined treatment (SHCT), and centralized treatment (CT) in northwest China. The OCD mode had the highest bioaerosol production, whereas the CT mode had the lowest. The OCD model contained the most pathogenic bacterial species, up to 43 species, including Sphingomonas, Pseudomonas, Cladosporium, and Alternaria. Risk assessments indicated bioaerosol exposure was lower in the models with sewage treatment (SHCT and CT) than in those without (SCC and OCD). Different populations exhibited large variations in potential risks owing to differences in time spent indoors and outdoors. The highest risk was observed in males exposed to the SCC model. This study provides a theoretical basis and theories for the future joint prevention and control of the bioaerosol exposure risk from decentralized sewage treatment.

Disruption and recovery of outdoor bioaerosols before, during, and after the COVID-19 outbreak at a campus in Central China: pathogen composition, particle size distribution, influencing factors, and exposure risk

Before (2019), during (2020), and after (2021) the COVID-19 outbreak, different response methods and measures were taken on campuses to control the spread of COVID-19 within schools. These response methods may have changed the outdoor bioaerosol characteristics, which may affect staff and student health. Therefore, we analyzed the bacterial concentrations, particle size distribution, microbial populations, exposure risks, and environmental influences of bioaerosols at a campus before, during, and after the COVID-19 outbreak. This study used eight-stage Andersen samplers to collect and analyze culturable bacteria in bioaerosols from various locations, high-throughput sequencing to analyze microbial species, principal component analysis to compare differences in samples, RDA to investigate the effects of environmental factors on bioaerosols, and hazard quotient (HQ) and BugBase to evaluate human health risks. The study findings revealed that average bacterial concentrations before, during, and after COVID-19 were 75 CFU m-3, 136 CFU m-3, and 78 CFU m-3, respectively. Moreover, the average percentage of bacteria attached to PM2.5 was 49.2%, 42.7%, and 29.9%, respectively. High-throughput sequencing revealed that species composition changed significantly during the three years of COVID-19. The proportion of Pantoea and Bacillus increased with the development of COVID-19 and these became the dominant strains after COVID-19, whereas Pseudomonas had the maximum proportion during COVID-19. Both risk assessment and BugBase phenotype prediction results indicated that the potential pathogenic risk was the highest in the outdoor environment of the campus during COVID-19 and that bioaerosol contamination was the most severe compared to the outdoor bioaerosol characteristics of the campus recovered after COVID-19.

Seasonal variations of airborne microbial diversity in waste transfer stations and preventive effect on Streptococcus pneumoniae induced pulmonary inflammation

Environment, location, and season are important factors that influence the microbiological community, yet, little research on airborne microorganisms in waste transfer stations (WTSs). Here, the airborne bacterial and fungal communities at four WTSs during different seasons were analyzed by high-throughput sequencing. The bacteria were isolated by cultural method and screened bacterium alleviate inflammation induced by Streptococcus pneumoniae (Spn) by regulating gut microbiome. The results revealed that collected bioaerosols from the WTSs varied significantly by location and season. Proteobacteria and Pseudomonadota are prevalent in summer and winter, respectively. Ascomycota was predominant in two seasons. Hazard quotients for adults from four WTSs were below one. Three selected potential probiotics were formulated into a microbial preparation with a carrier that effectively prevented inflammation in bacterial and animal experiments. The expression levels of interleukin-1β, interleukin-6, and tumor necrosis factor-α in Pre group (0.11, 0.17, and 0.48-fold) were significantly lower than Spn group (2.75, 1.71, and 5.01-fold). These mechanisms are associated with changes in gut microbiota composition and short-chain fatty acids (SCFAs) levels, such as affecting Lachnospiraceae lachnospira abundance and acetic acid content. This study provides insights into the potential application of probiotics derived from WTSs as an alternative approach to preventing respiratory infections.

Dispersion characteristics of bioaerosols during treatment of rural solid waste in northwest China

In rural China, the release of bioaerosols containing pathogens from solid waste dumps poses a potential health risk to the local population. Here, we sampled bioaerosols from rural solid waste-treatment in four provinces of northwest China to investigate their emission and dispersion characteristics in order to provide a scientific basis for control and risk reduction of bioaerosols released from rural sanitation facilities. The airborne bioaerosol concentrations and particle size distributions were calculated using an Anderson six-stage airborne microbial sampler and counting with its internal Petri dish culture. High-throughput sequencing was used to characterize the microbial composition at different sampling sites and to explore possible influencing factors, while the health risk associated with exposure was estimated based on average daily dose-rate. The highest concentration point values of bacteria and fungi in bioaerosols near the solid waste were 63,617 ± 15,007 and 8044 ± 893 CFU/m³, respectively. Furthermore, the highest concentration point values of Enterobacteriaceae was 502 ± 35 CFU/m³. Most bioaerosols were coarse particles larger than 3.3 μm. Potentially pathogenic genera of winter-indicator species detected in the air were primarily Delftia, Rhodococcus and Aspergillus. The composition of solid waste and environmental conditions are important factors in determining the characteristics of bioaerosols. Local residents are exposed to bioaerosols mainly through inhalation. Children are at a particularly high risk of exposure through both inhalation and skin contact. The results of this study show that bioaerosols in the vicinity of rural solid waste dumps pose a health risk to the surrounding population. More suitable risk assessment criteria for rural areas should be established, and corresponding control and protection measures should be taken from three aspects: generation source and transmission pathway, as well as the recipient.

What's New in Prevention of Invasive Fungal Diseases during Hospital Construction and Renovation Work: An Overview

The goal of the overview was to give insight into the recent data of invasive fungal diseases (IFDs) associated with construction and renovation in healthcare settings as well as the recent evidence about available prevention and infection control measures. The number of studies describing IFD outbreaks associated with construction or renovation is on the rise again. Applying adequate prevention measures is still a challenge not just for healthcare workers but also for architects and construction workers as well. The role of multidisciplinary teams in the planning and monitoring of prevention measures cannot be overemphasized. Dust control is an inevitable part of every prevention plan. HEPA filters are helpful in the prevention of fungal outbreaks in hematologic patients, but further studies are needed to clarify the extent in which they contribute as specific control measures. The cut-off value for a "threating" level of fungal spore contamination still remains to be defined. The value of antifungal prophylaxis is difficult to assess because other preventive measures are simultaneously applied. Recommendations are still based on few meta-analyses, a large number of descriptive reports, and the opinion of respective authorities. Outbreak reports in the literature are a valuable resource and should be used for education as well as for preparing outbreak investigations.

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.

Assessment of rotavirus and norovirus emitted from water spray park: QMRA, diseases burden and sensitivity analysis

A quantitative model on exposure to pathogenic viruses in air of recreational area and their corresponding health effects is necessary to provide mitigation actions in content of emergency response plans (ERP). Here, the health risk associated with exposure to two pathogenic viruses of concern: Rotavirus (RoV) and Norovirus (NoV) in air of water spray park were estimated using a quantitative microbial risk assessment (QMRA) model. To this end, real-time Reverse Transcriptase polymerase chain reaction (real-time RT-PCR) was employed to measure the concentration levels of RoV and NoV over a twelve-month period. The probability of infection, illness and diseases burden of gastrointestinal illness (GI) caused by RoV and NoV for both workers and visitors were estimated using QMRA and Monto-Carlo simulation technique. The annual mean concentration for RoV and NoV in sampling air of water spray park were 20and 1754, respectively. The %95 confidence interval (CI) calculated annual DALY indicator for RoV (Workers: 2.62 × 10-4-2.62 × 10-1, Visitors: 1.50 × 10-5-2.42 × 10-1) and NoV (Workers: 5.54 × 10-3-2.53 × 10-1; Visitors: 5.18 × 10-4-2.54 × 10-1) were significantly higher the recommended values by WHO and US EPA (10-6-10-4 DALY pppy). According to sensitivity analysis, exposure dose and disease burden per case (DBPC) were found as the most influencing factors on disease burden as a consequences of exposure to RoV and NoV, respectively. The comprehensive information on DALY and QMRA can aid authorities involved in risk assessment and recreational actions to adopt proper approach and mitigation actions to minimize the health risk.

Municipal solid waste landfill: Evidence of the effect of applied landfill management on vegetation composition

Proper management of municipal solid waste (MSW) is crucial to avoid pollution, environmental impacts and threat to public health. The problem of MSW is mainly arising from inadequate landfill site management. The objective of this study was to evaluate the impact of management practices and environmental risks at two landfill sites. The landfills were subject to long-term (10 years) vegetation monitoring. The vegetation was assessed using a floristic survey of identified plant species. The vegetation analysis showed that significant differences existed between the two landfill locations, with neophytes, invasive and expansive species dominating on one of the landfill sites, which may be attributed to climatic and geomorphological differences between the two sites, but also to variations in landfill management. These environmentally problematic species can potentially spread from the landfill into adjacent ecosystems, displace native plants and degrade adjacent farmland areas. The study of vegetation monitoring data suggests that, in addition to other types of monitoring, landfills should be subjected to regular vegetation biomonitoring, too. Landfill management practices should target the regulation of unwanted species, create conditions that are favourable to native plant species and provide as early as possible the restoration of filled cells.

The changing pattern of bioaerosol characteristics, source and risk under diversity brush aerator speed

Bioaerosols containing pathogens released from wastewater treatment plants (WWTP) may pose potential health risks to workers on-site and residents downwind. In this study, sampling points were set up in the wastewater treatment facility to investigate the generation pattern of bioaerosols in the aeration tank section. High-throughput sequencing was utilized to assay the intestinal bacteria population, while the health risks associated with airborne bacteria were estimated based on average daily dose rates. The contribution of wastewater to bioaerosols was evaluated using the traceability analysis. As the rotational speed increased from 200 rpm to 800 rpm, the concentration of culturable bacteria increased from 397 CFU/m³ to 1611 CFU/m³, the proportion of bacteria attached to particles with an aerodynamic diameter larger than 4.7 µm increased from 30.41% to 48.44%, and the Shannon index of air samples increased from 1.032485 to 1.282065. Microbial composition, sources, and health risks of bioaerosols also changed as the rotational speed increased. The results showed that the predominant bacteria in the air at 200 rpm were Bacillus (78.78%), Paenibacillus (11.77%) and Lysinibacillus (1.40%). When the rotating speed reached 800 rpm, the dominant bacteria became Bacillus (55.50%), Acinetobacter (31.01%), and Paenarthrobacter (13.17%). The contribution of the wastewater to bioaerosols increased from 46.49% to 65.10%, in which surface water was the main source of bioaerosols (34.64% on average). Although the contribution of bottom water was lower than that of surface water, its contribution increased more, from 15.36% to 29.31%. The health risk of bioaerosols was 1.28 × 10^-2 on average, which increased with the increase of rotational speed. At the same exposure concentration, children (2.31 × 10^-2) have a higher exposure risk than adults (7.67 × 10^-3). This study is aimed at exploring the variation law of bioaerosols discharged from WWTP with oxidation ditch process and providing preliminary data for reducing its risk.