Size distributions of total airborne particles and bioaerosols in a municipal composting facility

Air sampling and ATP bioluminescence for quantitative detection of airborne microbes

Exposure to bioaerosol contamination has detrimental effects on human health. Recent advances in ATP bioluminescence provide more opportunities for the quantitative detection of bioaerosols. Since almost all active organisms can produce ATP, the amount of airborne microbes can be easily measured by detecting ATP-driven bioluminescence. The accurate evaluation of microorganisms mainly relies on following the four key steps: sampling and enrichment of airborne microbes, lysis for ATP extraction, enzymatic reaction, and measurement of luminescence intensity. To enhance the effectiveness of ATP bioluminescence, each step requires innovative strategies and continuous improvement. In this review, we summarized the recent advances in the quantitative detection of airborne microbes based on ATP bioluminescence, which focuses on the advanced strategies for improving sampling devices combined with ATP bioluminescence. Meanwhile, the optimized and innovative strategies for the remaining three key steps of the ATP bioluminescence assay are highlighted. The aim is to reawaken the prosperity of ATP bioluminescence and promote its wider utilization for efficient, real-time, and accurate detection of airborne microbes.

Online monitoring system for qualitative and quantitative analysis of bioaerosols by combined ATP bioluminescence assay with loop-mediated isothermal amplification

Rapid detection of airborne pathogens is crucial in preventing respiratory infections and allergies. However, technologies aiming to real-time analysis of microorganisms in air remain limited due to the sparse and complex nature of bioaerosols. Here, we introduced an online bioaerosol monitoring system (OBMS) comprised of integrated units including a rotatable stainless-steel sintered filter-based sampler, a lysis unit for extracting adenosine triphosphate (ATP), and a single photon detector-based fluorescence unit. Through optimization of the ATP bioluminescence method and establishment of standard curves between relative luminescence units (RLUs) and ATP as well as microbial concentration, we achieved simultaneous detection of bioaerosols' concentration and activity. Testing OBMS with four bacterial and two fungal aerosols at a sampling flow rate of 10 to 50 L/min revealed an outstanding collection efficiency of 95 % at 30 L/min. A single OBMS measurement takes only 8 min (sampling: 5 min; lysis and detection: 3 min) with detection limits of 3 Pcs/ms photons (2.9 × 103 and 292 CFU/m3 for Staphylococcus aureus and Candida albicans aerosol). In both laboratory and field tests, OBMS detected higher concentrations of bioaerosol compared to the traditional Andersen impactor and liquid biosampler. When combined OBMS with loop-mediated isothermal amplification (LAMP), the bioaerosol can be qualitative and quantitative analyzed within 40 min without the cumbersome procedures of sample pretreatment and DNA extraction. These results offer a high compressive and humidity resistance membrane filtration sampler and validate the potential of OBMS for online measurement of bioaerosol concentration and composition.

Advances in understanding bioaerosol release characteristics and potential hazards during aerobic composting

Bioaerosol emissions and their associated risks are attracting increasing attention. Bioaerosols are generated during the pretreatment, fermentation, and screening of mature compost when processing various types of solid waste at composting plants (e.g., municipal sludge and animal manure). In this review, we summarize research into bioaerosols at different types of composting plants by focusing on the methods used for sampling bioaerosols, stages when emissions potentially occur, major components of bioaerosols, survival and diffusion factors, and possible control strategies. The six-stage Andersen impactor is the main method used for sampling bioaerosols in composting plants. In addition, different composting management methods mainly affect bioaerosol emissions from composting plants. Studies of the components of bioaerosols produced by composting plants mainly focused on bacteria and fungi, whereas few considered others such as endotoxin. The survival and diffusion of bioaerosols are influenced by seasonal effects due to changes in environmental factors, such as temperature and relative humidity. Finally, three potential strategies have been proposed for controlling bioaerosols in composting plants. Improved policies are required for regulating bioaerosol emissions, as well as bioaerosol concentration diffusion models and measures to protect human health.

Pathogenic Bacteria Are the Primary Determinants Shaping PM2.5-Borne Resistomes in the Municipal Food Waste Treatment System

Bioaerosol pollution poses a substantial threat to human health during municipal food waste (FW) recycling. However, bioaerosol-borne antibiotic-resistant genes (ARGs) have received little attention. Herein, 48 metagenomic data were applied to study the prevalence of PM2.5-borne ARGs in and around full-scale food waste treatment plants (FWTPs). Overall, FWTP PM2.5 (2.82 ± 1.47 copies/16S rRNA gene) harbored comparable total abundance of ARGs to that of municipal wastewater treatment plant PM2.5 (WWTP), but was significantly enriched with the multidrug type (e.g., AdeC/I/J; p < 0.05), especially the abundant multidrug ARGs could serve as effective indicators to define resistome profiles of FWTPs (Random Forest accuracy >92%). FWTP PM2.5 exhibited a decreasing enrichment of total ARGs along the FWTP-downwind-boundary gradient, eventually reaching levels comparable to urban PM2.5 (1.46 ± 0.21 copies/16S rRNA gene, N = 12). The combined analysis of source-tracking, metagenome-assembled genomes (MAGs), and culture-based testing provides strong evidence that Acinetobacter johnsonii-dominated pathogens contributed significantly to shaping and disseminating multidrug ARGs, while abiotic factors (i.e., SO42-) indirectly participated in these processes, which deserves more attention in developing strategies to mitigate airborne ARGs. In addition, the exposure level of FWTP PM2.5-borne resistant pathogens was about 5-11 times higher than those in urban PM2.5, and could be more severe than hospital PM2.5 in certain scenarios (<41.53%). This work highlights the importance of FWTP in disseminating airborne multidrug ARGs and the need for re-evaluating the air pollution induced by municipal FWTP in public health terms.

Adenosine triphosphate (ATP) bioluminescence-based strategies for monitoring atmospheric bioaerosols

Bioaerosols play a momentous role in the transmission of human infectious diseases, so there has been increasing concern over their exposure in recent years. Bioaerosol monitor is crucial in environmental fields. Based on the universal existence of Adenosine triphosphate (ATP) in bioaerosols, ATP bioluminescence can be used as a powerful technique to detect bioaerosols without interference from non-bioaerosols. When ATP is released from bioaerosols, they can quantify microbial biomass by ATP bioluminescence. In this review, we provide the latest methodological improvements that enable more reliable quantification of bioaerosols in complex environmental samples, especially the use of ATP bioluminescence in this era of technological advancement via the following routes: lower sample content for the trace existence of bioaerosols in the atmosphere, higher sensitivity of ATP bioluminescence reaction system and shorter process times. We also highlight the new techniques in improving the efficiencies of these monitoring processes. The purpose of this paper is to make more people realize the great potential of the ATP bioluminescence system for monitoring airborne microorganisms. Additionally, the present work intends to increase people's awareness of developing novel technology combined with ATP bioluminescence reaction system to realize rapid, real-time, and sensitive sensing of bioaerosols.Implications: The ATP bioluminescence methodology can not only eliminate the interference of co-existing nonbiological (fluorescent or PM) but also significantly improve the efficiency of bioaerosol. Recent progresses, such as the application of ATP fluorescence technology in bioaerosol monitoring, indicating that the efficiency and sensitivity are possible to be further improved. Nevertheless, there is no reviews address these advances and deeply analyze the application of ATP fluorescence technology in this field. his contribution will attract wide attention from both academic and industrial communities of this field, as well as researchers engaging in environmental monitoring. Furthermore, the strategies and techniques of studying the ATP bioluminescence reviewed here is instructive for environment monitoring in various fields. Therefore, in view of significance and broad interest, we feel strongly that our critical review is very essential to the field of public health security, pharmaceutics, anti-bioterrorism, etc., and would like it to be published in Journal of the Air & Waste Management Association.

What are the disease burden and its sensitivity analysis of workers exposing to Staphylococcus aureus bioaerosol during warm and cold periods in a wastewater treatment plant?

Biological treatment in wastewater treatment plants releases high amounts of pathogenic bioaerosols. Quantitative microbial risk assessment is a framework commonly used for quantitative risk estimation for occupational exposure scenarios. However, the quantitative contributions of health-risk-estimate inputted parameters remain ambiguous. Therefore, this research aimed to study the disease burden of workers exposed to Staphylococcus aureus bioaerosol during warm and cold periods and strictly quantify the contributions of the inputted parameters by sensitivity analysis on the basis of Monte Carlo simulation. Results showed that the disease health risk burden of workers in the warm period was 1.15-6.11 times higher than that of workers in the cold period. The disease health risk burden of workers without personal protective equipment was 23.83-36.55 times higher than that of workers with personal protective equipment. Sensitivity analysis showed that exposure concentration and aerosol ingestion rate were the first and second predominant factors, respectively; the sensitivity partitioning coefficient of the former was 1.17-1.35 times the value of the latter. In addition, no remarkable differences were revealed in the sensitivity percentage ratio between warm and cold periods. The findings could contribute to the mitigation measures for the management of public health risks.

High-volume sampler for size-selective sampling of bioaerosols including viruses

Owing to the recent global spread of the new coronavirus SARS-CoV-2, the development of technology to effectively detect viruses in crowded public places is urgently needed. In this study, a three-stage high-volume bioaerosol sampler was developed for the size-selective sampling of bioaerosols through the suction of air at a high flow rate of 1000 L/min. In stage 1, an omnidirectional inlet cyclone separator that can draw air from all directions was applied to collect bioaerosols larger than 10 μm in the collection fluid. In stage 2, an axial flow cyclone separator was used to collect bioaerosols sized between 2.5 and 10 μm in the collection fluid. In stage 3, bioaerosols smaller than 2.5 μm were collected on a filter and extracted in a solution through an elution process using a sodium phosphate buffer. To simulate the suspension of bioparticles including viruses that are attached to other particles in the atmosphere, the aerosol samples were prepared by coagulating aerosolized bacteriophages with Arizona test dust. Then, the coagulated particles were collected for 30 min using the developed bioaerosol sampler, and the samples collected in each stage were analyzed via polymerase chain reaction (PCR) method. The PCR analysis results confirmed that the high-volume bioaerosol sampler enables size-selective bioaerosol sampling even at a high airflow rate of 1000 L/min. The developed high-volume bioaerosol sampler will be useful in detecting viruses through PCR analysis because it can collect bioaerosols within a specific size range.

Exposure Assessment of Airborne Bacteria Emitted from Swine Manure Composting Plant

This study was performed to investigate the distribution characteristics of airborne bacteria emitted from swine manure composting plants. The types of swine manure composting plants selected for the survey in this study were as follows: screw type, rotary type, and natural dry type. Mean levels of airborne bacteria in swine manure composting plants were 7428 (±1024) CFU m−3 for the screw type, 3246 (±1407) CFU m−3 for the rotary type, and 5232 (±1217) CFU m−3 for the natural dry type, respectively. Based on the results obtained from this study, the swine manure composting plant operated by screw type showed the highest concentration of airborne bacteria, followed by the natural dry type and rotary type. The monthly concentration of airborne bacteria was the highest in August and the lowest in November, regardless of the type of swine manure composting plant. The respirable size of airborne bacteria accounted for about 50% of the total. The ratio of respirable to the total quantity of airborne bacteria was 50%. The correlation relationships between airborne bacteria and environmental factors (temperature, relative humidity, particulate matters, and odor) were not found to be significant in the swine manure composting plants. The predominant genera of airborne bacteria identified were Micrococcus spp., Staphylococcus spp., Escherichia (E-coli) spp., Enterococcus spp., and Enterobacteriaceae spp.

Development of a size-selective sampler combined with an adenosine triphosphate bioluminescence assay for the rapid measurement of bioaerosols

In this study, a size-selective bioaerosol sampler was built and combined with adenosine triphosphate (ATP) bioluminescence assay for measuring the bioaerosol concentration more rapidly and easily. The ATP bioaerosol sampler consisted of a respirable cyclone, an impactor to collect bioaerosols onto the head of a swab used for ATP bioluminescence assay, a swab holder, and a sampling pump. The collection efficiency of the impactor was tested using aerosolized sodium chloride particles and then the particle diameter corresponding to the collection efficiency of 50% (cut-off diameter) was evaluated. The experimental cut-off diameter was 0.44 μm. The correlations between ATP bioluminescence (relative light unit; RLU) from commercially available swabs (UltraSnap and SuperSnap, Hygiena, LLC, U.S.A.) and colony forming unit (CFU) were examined using Escherichia coli (E. coli) suspension and then the conversion equations from RLU to CFU were obtained. From the correlation results, the R² values of UltraSnap and SuperSnap were 0.53 and 0.81, respectively. The conversion equations were the linear function and the slopes of UltraSnap and SuperSnap were 633.6 and 277.78, respectively. In the lab and field tests, the ATP bioaerosol sampler and a conventional Andersen impactor were tested and the results were compared. In the lab tests, concentrations of aerosolized E. coli collected using the sampler were highly correlated to those from the Anderson impactor (R² = 0.85). In the field tests, the concentrations measured using the ATP bioaerosol sampler were higher than those from the Andersen impactor due to the limitations of the colony counting method. These findings confirm the feasibility of developing a sampler for rapid measurement of bioaerosol concentrations, offering a compact device for measuring exposure to bioaerosols, and an easy-to-use methodological concept for efficient air quality management.

Emission characteristics of bioaerosol and quantitative microbiological risk assessment for equipping individuals with various personal protective equipment in a WWTP

Wastewater treatment plants (WWTPs) are a nonnegligible source of bioaerosols that can pose health risks to workers and nearby residents. Thus, this study systematically investigated the emission characteristics of the size distribution and concentration of Staphylococcus aureus bioaerosol in a WWTP. Then, the research focused on the quantitative microbiological risk assessment (QMRA) of workers and nearby residents for equipping them with various grades personal protective equipment (PPE). Results showed that the peak proportion of the size distributions of bioaerosol particles in the three sources all obtained a size range between 3.3 and 4.7 μm. In the residential building, the peak proportion was larger (>7.0 μm). Referring to the three sources, the average bioaerosol concentrations were in the following sequence: inverted umbrella aerator tank > residual sludge storage yard > microporous aerator tank. The health risks of residents were generally 1-2 orders of magnitude higher than the other two exposure scenarios and were clearly beyond the benchmarks. Meanwhile, the health risks of the field engineer were usually lower than those of the staff at the residual sludge storage yard. In general, equipping workers and residents with PPE could at least decrease the health risks by one order of magnitude, and higher-grade PPE could appropriately promote the reduction of health risks. This research systematically delivered a series of novel data about the emission characteristics of Staphylococcus aureus bioaerosol in a WWTP. It advanced the understanding of the quantitative health risks of equipping individuals with various PPE.

Size fractionation of bioaerosol emissions from green-waste composting

Particle size is a significant factor in determining the dispersal and inhalation risk from bioaerosols. Green-waste composting is a significant source of bioaerosols (including pathogens), but little is known about the distribution of specific taxa across size fractions. To characterise size fractionated bioaerosol emissions from a compost facility, we used a Spectral Intensity Bioaerosol Sensor (SIBS) to quantify total bioaerosols and qPCR and metabarcoding to quantify microbial bioaerosols. Overall, sub-micron bioaerosols predominated, but molecular analysis showed that most (>75%) of the airborne microorganisms were associated with the larger size fractions (>3.3 µm d_a). The microbial taxa varied significantly by size, with Bacilli dominating the larger, and Actinobacteria the smaller, size fractions. The human pathogen Aspergillus fumigatus dominated the intermediate size fractions (>50% d_a 1.1-4.7 µm), indicating that it has the potential to disperse widely and once inhaled may penetrate deep into the respiratory system. The abundance of Actinobacteria (>60% at d_a < 2.1 µm) and other sub-micron bioaerosols suggest that the main health effects from composting bioaerosols may come from allergenic respiratory sensitisation rather than directly via infection. These results emphasise the need to better understand the size distributions of bioaerosols across all taxa in order to model their dispersal and to inform risk assessments of human health related to composting facilities.

Assessment of airborne particles and bioaerosols concentrations in a waste recycling environment in Brazil

This study aims to assess the concentrations of size-fractioned particle mass (PM_1.0, PM_2.5, PM_4.0, PM₁₀) and number (PNC_0.3, PNC_0.5, PNC_1.0, PNC_2.5), bacteria, and fungi in a Materials Recycling Facility (MRF) in Brazil. The measurements were performed inside the waste processing shed (P1) and in the outdoor environment (P2) during working days in winter and spring of 2017, and summer of 2019. A total of 2,400 min of PM, 1,440 min of PNC, and 216 samples of bioaerosols were collected in the morning and afternoon. P1 has the strongest air contamination with mean values of 475.5 ± 563.7 µg m⁻³ for PM₁₀, 58.6 ± 36.0 cm⁻³ for PNC_0.3, 1,088.8 ± 825.2 colony-forming units per cubic meter (CFU m⁻³) for bacteria, and 2,738.3 ± 1,381.3 CFU m⁻³ for fungi. The indoor/outdoor ratios indicated the large influence of indoor sources due to the activities performed inside P1 that promote the generation and resuspension of pollutants. Gram-positive bacteria dominated with 58.6% of indoor samples. Overall, our results show a critical indoor air quality situation in a Brazilian MRF, which may cause several health risks for waste pickers. Finally, we call attention to the lack of occupational exposure limits for bioaerosols in industrial workplaces and mainly in MRFs.

Recent Advances in Monitoring, Sampling, and Sensing Techniques for Bioaerosols in the Atmosphere

Bioaerosols in the form of microscopic airborne particles pose pervasive risks to humans and livestock. As either fully active components (e.g., viruses, bacteria, and fungi) or as whole or part of inactive fragments, they are among the least investigated pollutants in nature. Their identification and quantification are essential to addressing related dangers and to establishing proper exposure thresholds. However, difficulties in the development (and selection) of detection techniques and an associated lack of standardized procedures make the sensing of bioaerosols challenging. Through a comprehensive literature search, this review examines the mechanisms of conventional and advanced bioaerosol detection methods. It also provides a roadmap for future research and development in the selection of suitable methodologies for bioaerosol detection. The development of sample collection and sensing technology make it possible for continuous and automated operation. However, intensive efforts should be put to overcome the limitations of current technology as most of the currently available options tend to suffer from lengthy sample acquisition times and/or nonspecificity of probe material.

Risk of respiratory hospital admission associated with modelled concentrations of Aspergillus fumigatus from composting facilities in England

Bioaerosols have been associated with adverse respiratory-related health effects and are emitted in elevated concentrations from composting facilities. We used modelled Aspergillus fumigatus concentrations, a good indicator for bioaerosol emissions, to assess associations with respiratory-related hospital admissions. Mean daily Aspergillus fumigatus concentrations were estimated for each composting site for first full year of permit issue from 2005 onwards to 2014 for Census Output Areas (COAs) within 4 km of 76 composting facilities in England, as previously described (Williams et al., 2019). We fitted a hierarchical generalized mixed model to examine the risk of hospital admission with a primary diagnosis of (i) any respiratory condition, (ii) respiratory infections, (iii) asthma, (iv) COPD, (v) diseases due to organic dust, and (vi) Cystic Fibrosis, in relation to quartiles of Aspergillus fumigatus concentrations. Models included a random intercept for each COA to account for over-dispersion, nested within composting facility, on which a random intercept was fitted to account for clustering of the data, with adjustments for age, sex, ethnicity, deprivation, tobacco sales (smoking proxy) and traffic load (as a proxy for traffic-related air pollution). We included 249,748 respiratory-related and 3163 Cystic Fibrosis hospital admissions in 9606 COAs with a population-weighted centroid within 4 km of the 76 included composting facilities. After adjustment for confounders, no statistically significant effect was observed for any respiratory-related (Relative Risk (RR) = 0.99; 95% Confidence Interval (CI) 0.96-1.01) or for Cystic Fibrosis (RR = 1.01; 95% CI 0.56-1.83) hospital admissions for COAs in the highest quartile of exposure. Similar results were observed across all respiratory disease sub-groups. This study does not provide evidence for increased risks of respiratory-related hospitalisations for those living near composting facilities. However, given the limitations in the dispersion modelling, risks cannot be completely ruled out. Hospital admissions represent severe respiratory episodes, so further study would be needed to investigate whether bioaerosols emitted from composting facilities have impacts on less severe episodes or respiratory symptoms.

Inhalable dust as a marker of exposure to airborne biological agents in composting facilities

OBJECTIVES

Industrial composting is associated with high levels of worker exposure to bioaerosols. Measurement of airborne microorganisms and endotoxin is complex and the related cost is high. The objective was therefore to examine whether dust measurement could be used as a marker of exposure to bioaerosols in composting facilities.

METHODS

A dataset of 110 measurements carried out in eight sludge composting plants was explored. Mixed-effects models were constructed to explain between-site and within-site variability in concentration of endotoxin and culturable mesophilic bacteria, mesophilic moulds and thermophilic actinomycetes in air. Fixed-effects variables were inhalable dust concentration, the season, the outdoor/indoor location of sampling and the process area.

RESULTS

The level of dust was a highly significant determinant of concentration for all biological agents. Within-site variability was always larger than between-site variability. The proportion of within-site variability explained by determinants was 68%, 65%, 56% and 60% for endotoxin, bacteria, moulds and actinomycetes, respectively. Inclusion of dust in the final model resulted in an increase of 24, 20, 12 and 17 points of percentage within-site variability, respectively. Inclusion of season resulted in an increase of 9, 12, 12 and 15 points, respectively. Within-site variability was less influenced by outdoor/indoor location and process area, except for moulds.

CONCLUSION

Dust was the factor that most influenced within-site variability in endotoxin and culturable bacteria concentration. Measurement of dust can efficiently assist decision making for prevention measures against endotoxin and bacteria in sludge composting plants. Our results are not as conclusive for actinomycetes and especially for moulds.

Fine particulate matter (PM2.5) in a compost facility: heavy metal contaminations and health risk assessment, Tehran, Iran

The aim of this study was to evaluate the concentration of PM_2.5 particles, potential sources, and determination of health risk assessment of heavy metals in various parts of composting facilities of Tehran's Kahrizak. A total of 60 PM_2.5 particle samples were collected every 3 days from January to March 2016. To analyze the heavy metals, inductively coupled plasma atomic emission spectroscopy (ICP-AES) was applied. SEM-EDX analysis indicated that metals of Al, Si, Mg, Na, Au, S, Ca, K, and Co were dominant in the structure of particles. The concentration of PM_2.5 was found to be the highest in the final processing site (c), followed by primary processing site (a) and the aerated site (b). The mean concentrations of Al and Fe in all sampling sites of a, b, and c were 7.46 ± 2.73, 1.48 ± 0.59, 24.30 ± 8.23 μg/m³ and 4.97 ± 2.83, 1.33 ± 0.48, 16.48 ± 7.36, respectively. The enrichment factor order of the trace elements was as follows: Cd > As > Pb > Zn > Cu > V > Cr > Ni > Mn > Fe > Al, with the highest EF value exceeding 10,000 for Cd at the a site. For all sampling sites in composting facilities, the cancer risk was more than > 1 × 10^-4 as posed by the total of five carcinogenic metals (Pb, Cr, As, Ni, and Cd), indicating that risk factors were not negligible.

Use of dispersion modelling for Environmental Impact Assessment of biological air pollution from composting: Progress, problems and prospects

With the increase in composting asa sustainable waste management option, biological air pollution (bioaerosols) from composting facilities have become a cause of increasing concern due to their potential health impacts. Estimating community exposure to bioaerosols is problematic due to limitations in current monitoring methods. Atmospheric dispersion modelling can be used to estimate exposure concentrations, however several issues arise from the lack of appropriate bioaerosol data to use as inputs into models, and the complexity of the emission sources at composting facilities. This paper analyses current progress in using dispersion models for bioaerosols, examines the remaining problems and provides recommendations for future prospects in this area. A key finding is the urgent need for guidance for model users to ensure consistent bioaerosol modelling practices.

Application of acoustic agglomeration to enhance air filtration efficiency in air-conditioning and mechanical ventilation (ACMV) systems

The recent episodes of haze in Southeast Asia have caused some of the worst regional atmospheric pollution ever recorded in history. In order to control the levels of airborne fine particulate matters (PM) indoors, filtration systems providing high PM capturing efficiency are often sought, which inadvertently also results in high airflow resistance (or pressure drop) that increases the energy consumption for air distribution. A pre-conditioning mechanism promoting the formation of particle clusters to enhance PM capturing efficiency without adding flow resistance in the air distribution ductwork could provide an energy-efficient solution. This pre-conditioning mechanism can be fulfilled by acoustic agglomeration, which is a phenomenon that promotes the coagulation of suspended particles by acoustic waves propagating in the fluid medium. This paper discusses the basic mechanisms of acoustic agglomeration along with influencing factors that could affect the agglomeration efficiency. The feasibility to apply acoustic agglomeration to improve filtration in air-conditioning and mechanical ventilation (ACMV) systems is investigated experimentally in a small-scale wind tunnel. Experimental results indicate that this novel application of acoustic pre-conditioning improves the PM_2.5 filtration efficiency of the test filters by up to 10% without introducing additional pressure drop. The fan energy savings from not having to switch to a high capturing efficiency filter largely outstrip the additional energy consumed by the acoustics system. This, as a whole, demonstrates potential energy savings from the combined acoustic-enhanced filtration system without compromising on PM capturing efficiency.

Continuous and real-time bioaerosol monitoring by combined aerosol-to-hydrosol sampling and ATP bioluminescence assay

We present a methodology for continuous and real-time bioaerosol monitoring wherein an aerosol-to-hydrosol sampler is integrated with a bioluminescence detector. Laboratory test was conducted by supplying an air flow with entrained test bacteria (Staphylococcus epidermidis) to the inlet of the sampler. High voltage was applied between the discharge electrode and the ground electrode of the sampler to generate air ions by corona discharge. The bacterial aerosols were charged by the air ions and sampled in a flowing liquid containing both a cell lysis buffer and adenosine triphosphate (ATP) bioluminescence reagents. While the liquid was delivered to the bioluminescence detector, sampled bacteria were dissolved by the cell lysis buffer and ATP was extracted. The ATP was reacted with the ATP bioluminescence reagents, causing light to be emitted. When the concentration of bacteria in the aerosols was varied, the ATP bioluminescence signal in relative light units (RLUs) closely tracked the concentration in particles per unit air volume (# cm^-3), as measured by an aerosol particle sizer. The total response time required for aerosol sampling and ATP bioluminescence detection increased from 30 s to 2 min for decreasing liquid sampling flow rate from 800 to 200 μLPM, respectively. However, lower concentration of S. epidermidis aerosols was able to be detected with lower liquid sampling flow rate (1 RLU corresponded to 6.5 # cm^-3 of S. epidermidis aerosols at 200 μLPM and 25.5 # cm^-3 at 800 μLPM). After obtaining all data sets of concentration of S. epidermidis aerosols and concentration of S. epidermidis particles collected in the flowing liquid, it was found that with our bioluminescence detector, 1 RLU corresponded to 1.8 × 10⁵ (±0.2 × 10⁵) # mL^-1 of S. epidermidis in liquid. After the lab-test with S. epidermidis, our bioaerosol monitoring device was located in the lobby of a building. Air sampling was conducted continuously for 90 min (air flow rate of 8 LPM, liquid flow rate of 200 μLPM) and the ATP bioluminescence signal of indoor bioaerosols was displayed with time. Air sampling was also carried out using the 6th stage of Andersen impactor in which a nutrient agar plate was used for the impaction plate. The sample was cultured at 37 °C for five days for colony counting. As a result, it was found that the variation of the bioluminescence signal closely followed the variation of indoor bioaerosol concentration in colony forming unit (CFU) and 1 RLU corresponded to 1.66 CFU m^-3 of indoor bioaerosols. Our method can be used as a trigger in biological air contamination alarm systems.

Emission of bacterial bioaerosols from a composting facility in Maharashtra, India

This study was undertaken to quantify and characterize size-segregated bacterial bioaerosols both on-site and off-site of a waste treatment facility (WTF) in Maharashtra employing windrow composting. Viable bacterial bioaerosols on nutrient agar (NA) and actinomycetes isolation agar (AIA) were quantified after sampling using Anderson-six stage impactor. Viable bacterial bioaerosols were identified based on 16S rDNA sequencing. Approximately, 16-34% of the total viable bacteria collected at the WTF were in the size range 0.65-2.1μm that can penetrate deep into the respiratory tract and also represents bacteria present in free form. Thus, 66-84% of bacterial bioaerosols were associated with coarse airborne particles greater than 2.1μm. A total of 24 bacterial species were isolated and characterized through gram staining. Among these 25% were gram negative and 75% were gram positive. The predominant bacterial genera were Bacillus, Streptococcus, Staphylococcus, Acinetobacter and Kocuria. The mean on-site concentration of total viable bacteria on NA and AIA and airborne particles (PM2.5 and PM10) were higher than the corresponding off-site values. The mean on-site concentration of viable bacteria on NA and AIA were in the range of 3.8×10(3) to 5.4×10(4)CFU/m(3) and 9.8×10(3) to 1.2×10(5)CFU/m(3), respectively, during activity period. Good correlation (R(2)=0.999) was observed between total bioaerosols and aerosols (PM10) collected using Anderson impactor and High volume sampler, respectively. Sampling size segregated aerosols using the Siotus personal cascade impactor indicated higher association of bacteria with the coarse fraction (greater than 2.5μm).

Fast monitoring of indoor bioaerosol concentrations with ATP bioluminescence assay using an electrostatic rod-type sampler

A culture-based colony counting method is the most widely used analytical technique for monitoring bioaerosols in both indoor and outdoor environments. However, this method requires several days for colony formation. In this study, our goal was fast monitoring (Sampling: 3 min, Detection: < 1 min) of indoor bioaerosol concentrations with ATP bioluminescence assay using a bioaerosol sampler. For this purpose, a novel hand-held electrostatic rod-type sampler (110 mm wide, 115 mm long, and 200 mm tall) was developed and used with a commercial luminometer, which employs the Adenosine triphosphate (ATP) bioluminescence method. The sampler consisted of a wire-rod type charger and a cylindrical collector, and was operated with an applied voltage of 4.5 kV and a sampling flow rate of 150.7 lpm. Its performance was tested using Staphylococcus epidermidis which was aerosolized with an atomizer. Bioaerosol concentrations were measured using ATP bioluminescence method with our sampler and compared with the culture-based method using Andersen cascade impactor under controlled laboratory conditions. Indoor bioaerosol concentrations were also measured using both methods in various indoor environments. A linear correlation was obtained between both methods in lab-tests and field-tests. Our proposed sampler with ATP bioluminescence method may be effective for fast monitoring of indoor bioaerosol concentrations.

Assessment of microbial contamination within working environments of different types of composting plants

The objective of the study was to determine the degree of microbiological contamination, type of microflora, bioaerosol particle size distribution, and concentration of endotoxins in dust in different types of composting plants. In addition, this study provides a list of indicator microorganisms that pose a biological threat in composting facilities, based on their prevalence within the workplace, source of isolation, and health hazards. We undertook microbiological analysis of the air, work surfaces, and compost, and assessed the particle size distribution of bioaerosols using a six-stage Andersen sampler. Endotoxins were determined using gas chromatography-mass spectrometry (GC-MS). Microbial identification was undertaken both microscopically and using biochemical tests. The predominant bacterial and fungal species were identified using 16S rRNA and ITS1/2 analysis, respectively. The number of mesophilic microorganisms in composting plants amounted to 6.9×10(2)-2.5×10(4) CFU/m3 in the air, 2.9×10(2)-3.3×10(3) CFU/100 cm2 on surfaces, and 2.2×10(5)-2.4×10(7) CFU/g in compost. Qualitative analysis revealed 75 microbial strains in composting plants, with filamentous fungi being the largest group of microorganisms, accounting for as many as 38 isolates. The total amount of endotoxins was 0.0062-0.0140 nmol/mg of dust. The dust fraction with aerodynamic particle diameter of 0.65-1.1 μm accounted for 28-39% of bacterial aerosols and 4-13% of fungal aerosols. We propose the following strains as indicators of harmful biological agent contamination: Bacillus cereus, Aspergillus fumigatus, Cladosporium cladosporioides, C. herbarum, Mucor hiemalis, and Rhizopus oryzae for both types of composting plants, and Bacillus pumilus, Mucor fragilis, Penicillium svalbardense, and P. crustosum for green waste composting plants. The biological hazards posed within these plants are due to the presence of potentially pathogenic microorganisms and the inhalation of respirable bioaerosol. Depending on the type of microorganism, these hazards may be aggravated or reduced after cleaning procedures.

IMPLICATIONS

This study assessed the microbial contamination in two categories of composting plants: (1) facilities producing substrates for industrial cultivation of button mushrooms, and (2) facilities for processing biodegradable waste. Both workplaces showed potentially pathogenic microorganisms, respirable bioaerosol, and endotoxin. These results are useful to determine the procedures to control harmful biological agents, and to disinfect workplaces in composting plants.

Exposures and health outcomes in relation to bioaerosol emissions from composting facilities: a systematic review of occupational and community studies

The number of composting sites in Europe is rapidly increasing, due to efforts to reduce the fraction of waste destined for landfill, but evidence on possible health impacts is limited. This article systematically reviews studies related to bioaerosol exposures within and near composting facilities and associated health effects in both community and occupational health settings. Six electronic databases and bibliographies from January 1960 to July 2014 were searched for studies reporting on health outcomes and/or bioaerosol emissions related to composting sites. Risk of bias was assessed using a customized score. Five hundred and thirty-six papers were identified and reviewed, and 66 articles met the inclusion criteria (48 exposure studies, 9 health studies, 9 health and exposure studies). Exposure information was limited, with most measurements taken in occupational settings and for limited time periods. Bioaerosol concentrations were highest on-site during agitation activities (turning, shredding, and screening). Six studies detected concentrations of either Aspergillus fumigatus or total bacteria above the English Environment Agency's recommended threshold levels beyond 250 m from the site. Occupational studies of compost workers suggested elevated risks of respiratory illnesses with higher bioaerosol exposures. Elevated airway irritation was reported in residents near composting sites, but this may have been affected by reporting bias. The evidence base on health effects of bioaerosol emissions from composting facilities is still limited, although there is sufficient evidence to support a precautionary approach for regulatory purposes. While data to date are suggestive of possible respiratory effects, further study is needed to confirm this and to explore other health outcomes.

Morphological classification of bioaerosols from composting using scanning electron microscopy

This research classifies the physical morphology (form and structure) of bioaerosols emitted from open windrow composting. Aggregation state, shape and size of the particles captured are reported alongside the implications for bioaerosol dispersal after release. Bioaerosol sampling took place at a composting facility using personal air filter samplers. Samples were analysed using scanning electron microscopy. Particles were released mainly as small (<1 μm) single, spherical cells, followed by larger (>1 μm) single cells, with aggregates occurring in smaller proportions. Most aggregates consisted of clusters of 2-3 particles as opposed to chains, and were <10 μm in size. No cells were attached to soil debris or wood particles. These small single cells or small aggregates are more likely to disperse further downwind from source, and cell viability may be reduced due to increased exposure to environmental factors.

Effect of temperature on bacterial emissions in composting of swine manure

Swine manure was subjected to laboratory scale composting in order to quantify bioaerosols, i.e., airborne culturable bacteria and endotoxin, in the exhaust gas, which provided details on the effect of temperature on bacterial emissions. The concentration of airborne bacteria reached 31,250 colony-forming units (CFU)/m(3) during the thermophilic stage of composting, and positively correlated with the temperature profile of the compost pile. Initially, the endotoxin concentration was 1820 endotoxin units (EU)/m(3), but it decreased exponentially as the composting process proceeded. The temperature can be an excellent indicator of bacterial emissions during the composting process, indicating that the composting process requires a consistently high temperature to ensure sanitization of both compost and bacterial emissions. The cumulative emission data showed that emission factors was 11.2-13.5 CFU/g dry swine manure and that of endotoxin was 0.5-0.9 EU/g dry swine manure. The bacterial diversity in the bioaerosol was analyzed by polymerase chain reaction-denaturing gradient gel electrophoresis, revealing the presence of various gram-negative bacterial consortia.

Bioaerosols from composting facilities--a review

Bioaerosols generated at composting plants are released during processes that involve the vigorous movement of material such as shredding, compost pile turning, or compost screening. Such bioaerosols are a cause of concern because of their potential impact on both occupational health and the public living in close proximity to such facilities. The biological hazards potentially associated with bioaerosol emissions from composting activities include fungi, bacteria, endotoxin, and 1-3 β-glucans. There is a major lack of knowledge concerning the dispersal of airborne microorganisms emitted by composting plants as well as the potential exposure of nearby residents. This is due in part to the difficulty of tracing specifically these microorganisms in air. In recent years, molecular tools have been used to develop new tracers which should help in risk assessments. This review summarizes current knowledge of microbial diversity in composting aerosols and of the associated risks to health. It also considers methodologies introduced recently to enhance understanding of bioaerosol dispersal, including new molecular indicators and modeling.

Real-time monitoring of bioaerosols via cell-lysis by air ion and ATP bioluminescence detection

In this study, we introduce a methodology for disrupting cell membranes with air ions coupled with ATP bioluminescence detection for real-time monitoring of bioaerosol concentrations. A carbon fiber ionizer was used to extract ATP from bacterial cells for generating ATP bioluminescence. Our methodology was tested using Staphylococcus epidermidis and Escherichia coli, which were aerosolized with an atomizer, and then indoor bioaerosols were also used for testing the methodology. Bioaerosol concentrations were estimated without culturing which requires several days for colony formation. Correlation equations were obtained for results acquired using our methodology (Relative Luminescent Unit (RLU)/m(3)) and a culture-based (Colony Forming Unit (CFU)/m(3)) method; CFU/m(3)=1.8 × measured RLU/m(3) for S. epidermidis and E. coli, and CFU/m(3)=1.1 × measured RLU/m(3) for indoor bioaerosols under the experimental conditions. Our methodology is an affordable solution for rapidly monitoring bioaerosols due to rapid detection time (cell-lysis time: 3 min; bioluminescence detection time: <1 min) and easy operation.

The effect of dust emissions from open storage piles to particle ambient concentration and human exposure

The current study focus on the determination of dust emissions from piles in open storage yards of a municipal solid waste (MSW) composting site and the subsequent atmospheric dust dispersion. The ISC3-ST (Industrial Source Complex Version 3 - Short Term) model was used for the evaluation of the PM(10) ambient concentrations associated with the dispersion of MSW compost dust emissions in air. Dust emission rates were calculated using the United States Environmental Protection Agency proposed dust resuspension formulation from open storage piles using local meteorological data. The dispersion modelling results on the spatial distribution of PM(10) source depletion showed that the maximum concentrations were observed at a distance 25-75 m downwind of the piles in the prevailing wind direction. Sensitivity calculations were performed also to reveal the effect of the compost pile height, the friction velocity and the receptor height on the ambient PM(10) concentration. It was observed that PM(10) concentrations (downwind in the prevailing wind direction) increased with increasing the friction velocity, increasing the pile height (for distances greater than 125 m from the source) and decreasing the receptor height (for distances greater than 125 m from the source). Furthermore, the results of ISC3-ST were analysed with the ExDoM (Exposure Dose Model) human exposure model. The ExDoM is a model for calculating the human exposure and the deposition dose, clearance, and finally retention of aerosol particles in the human respiratory tract (RT). PM(10) concentration at the composting site was calculated as the sum of the concentration from compost pile dust resuspension and the background concentration. It was found that the exposure to PM(10) and deposited lung dose for an adult Caucasian male who is not working at the composting site is less by 20-74% and 29-84%, respectively, compared to those for a worker exposed to PM concentrations at the composting site.

Protection of the vehicle cab environment against bacteria, fungi and endotoxins in composting facilities

Microbial quality of air inside vehicle cabs is a major occupational health risk management issue in composting facilities. Large differences and discrepancies in protection factors between vehicles and between biological agents have been reported. This study aimed at estimating the mean protection efficiency of the vehicle cab environment against bioaerosols with higher precision. In-cab measurement results were also analysed to ascertain whether or not these protection systems reduce workers' exposure to tolerable levels. Five front-end loaders, one mobile mixer and two agricultural tractors pulling windrow turners were investigated. Four vehicles were fitted with a pressurisation and high efficiency particulate air (HEPA) filtration system. The four others were only equipped with pleated paper filter without pressurisation. Bacteria, fungi and endotoxins were measured in 72 pairs of air samples, simultaneously collected inside the cab and on the outside of the cab with a CIP 10-M sampler. A front-end loader, purchased a few weeks previously, fitted with a pressurisation and high efficiency particulate air (HEPA) filtration system, and with a clean cab, exhibited a mean protection efficiency of between 99.47% CI 95% [98.58-99.97%] and 99.91% [99.78-99.98%] depending on the biological agent. It is likely that the lower protection efficiency demonstrated in other vehicles was caused by penetration through the only moderately efficient filters, by the absence of pressurisation, by leakage in the filter-sealing system, and by re-suspension of particles which accumulated in dirty cabs. Mean protection efficiency in regards to bacteria and endotoxins ranged between 92.64% [81.87-97.89%] and 98.61% [97.41-99.38%], and between 92.68% [88.11-96.08%] and 98.43% [97.44-99.22%], respectively. The mean protection efficiency was the lowest when confronted with fungal spores, from 59.76% [4.19-90.75%] to 94.71% [91.07-97.37%]. The probability that in-cab exposure to fungi exceeded the benchmark value for short-term respiratory effects suggests that front-end loaders and mobile mixers in composting facilities should be fitted with a pressurisation and HEPA filtration system, regardless of whether or not the facility is indoors or outdoors. Regarding the tractors, exposure inside the cabs was not significantly reduced. However, in this study, there was a less than 0.01% risk of exceeding the bench mark value associated with fungi related short-term respiratory effects during an 1-h per day windrow turning operation. Pressurisation and a HEPA filtration system can provide safe working conditions inside loaders and mobile mixer with regard to airborne bacteria, fungi and endotoxins in composting facilities. However, regular thorough cleaning of the vehicle cab, as well as overalls and shoes cleaning, and mitigation of leakage in the filter-sealing system are necessary to achieve high levels of protection efficiency.

Design and application of an inertial impactor in combination with an ATP bioluminescence detector for in situ rapid estimation of the efficacies of air controlling devices on removal of bioaerosols

We proposed a rapid method to estimate the efficacies of air controlling devices in situ using ATP bioluminescence in combination with an inertial impactor. The inertial impactor was designed to have 1 mum of cutoff diameter, and its performance was estimated analytically, numerically, and experimentally. The proposed method was characterized using Staphylococcus epidermidis, which was aerosolized with a nebulizer. The bioaerosol concentrations were estimated within 25 min using the proposed method without a culturing process, which requires several days for colony formation. A linear relationship was obtained between the results of the proposed ATP method (RLU/m(3)) and the conventional culture-based method (CFU/m(3)), with R(2) 0.9283. The proposed method was applied to estimate the concentration of indoor bioaerosols, which were identified as a mixture of various microbial species including bacteria, fungi, and actinomycetes, in an occupational indoor environment, controlled by mechanical ventilation and an air cleaner. Consequently, the proposed method showed a linearity with the culture-based method for indoor bioaerosols with R(2) 0.8189, even though various kinds of microorganisms existed in the indoor air. The proposed method may be effective in monitoring the changes of relative concentration of indoor bioaerosols and estimating the effectiveness of air control devices in indoor environments.