Browsing by Author "Garcia Alcega, Sonia"

Now showing 1 - 18 of 18
  • Thumbnail Image
    ItemOpen Access
    Bioaerosol biomonitoring: sampling optimisation for molecular microbial ecology
    (Wiley, 2019-02-08) Ferguson, Robert M. W.; Garcia Alcega, Sonia; Coulon, Frederic; Dumbrell, Alex J.; Whitby, Corinne; Colbeck, Ian
    Bioerosols (or biogenic aerosols) have largely been overlooked by molecular ecologists. However, this is rapidly changing as bioaerosols play key roles in public health, environmental chemistry and the dispersal ecology of microbes. Due to the low environmental concentrations of bioaerosols, collecting sufficient biomass for molecular methods is challenging. Currently, no standardized methods for bioaerosol collection for molecular ecology research exist. Each study requires a process of optimization, which greatly slows the advance of bioaerosol science. Here, we evaluated air filtration and liquid impingement for bioaerosol sampling across a range of environmental conditions. We also investigated the effect of sampling matrices, sample concentration strategies and sampling duration on DNA yield. Air filtration using polycarbonate filters gave the highest recovery, but due to the faster sampling rates possible with impingement, we recommend this method for fine ‐scale temporal/spatial ecological studies. To prevent bias for the recovery of Gram‐positive bacteria, we found that the matrix for impingement should be phosphate‐buffered saline. The optimal method for bioaerosol concentration from the liquid matrix was centrifugation. However, we also present a method using syringe filters for rapid in‐field recovery of bioaerosols from impingement samples, without compromising microbial diversity for high ‐throughput sequencing approaches. Finally, we provide a resource that enables molecular ecologists to select the most appropriate sampling strategy for their specific research question.
  • Thumbnail Image
    ItemOpen Access
    Bioaerosols emission characteristics from wastewater treatment aeration tanks and associated health risk exposure assessment during autumn and winter
    (Elsevier, 2022-08-22) Zhao, Xiao-yan; An, Dong-zi; Liu, Man-li; Ma, Jia-xin; Ali, Wajid; Zhu, Hao; Li, Ming; Ai, Xiao-jun; Nasir, Zaheer Ahmad; Garcia Alcega, Sonia; Coulon, Frederic; Yan, Cheng
    Aeration tanks from activated sludge wastewater treatment plants (WWTPs) can release a large amount of bioaerosols that can pose health risks. However, risk characterization of bioaerosols emissions form wastewater treatment plants is currently not systematically carried out and still in its infancy. Therefore, this study investigated emission characteristic of two indicator model bioaerosols Staphylococcus aureus and Escherichia coli, emitted from aeration tanks of a municipal WWTP. Monte Carlo simulation was then used to quantitatively assess microbial risk posed by different aeration modes under optimistic and conservative estimates. Further to this, two different exposure scenarios were considered during 3 days sampling campaign in autumn and winter. Results showed that the bioaerosol concentration from microporous aeration tank (20–262 CFU m−3) was one order of magnitude lower than rotating disc aeration tank. Average aerosolization rate was 7.5 times higher with mechanical aeration mode. Health risks of exposed populations were 0.4 and 9.6 times higher in winter than in autumn for E. coli and S. aureus bioaerosol, respectively. Health risks of staff members were 10 times higher than academic visitors. Interesting results were observed for academic visitors without personal protective equipment (PPE) respectively exposed to S. aureus and E. coli bioaerosol in autumn and winter: while the derived infection risk met the United States Environmental Protection Agency (U.S. EPA) benchmark under optimistic estimation, the disease risk burden was over the World Health Organization (WHO) benchmark under conservative estimation. These revealed that only satisfying one of the two benchmarks didn't mean absolute acceptable health risk. This study could facilitate the development of better understanding of bioaerosol quantitative assessment of risk characterizations and corresponding appropriate risk control strategies for wastewater utilities.
  • Thumbnail Image
    ItemOpen Access
    Can chemical and molecular biomarkers help discriminate between industrial, rural and urban environments?
    (Elsevier, 2018-03-16) Garcia Alcega, Sonia; Nasir, Zaheer A.; Ferguson, Robert M. W.; Noël, Cyril; Cravo-Laureau, Cristiana; Whitby, Corinne; Dumbrell, Alex J.; Colbeck, Ian; Tyrrel, Sean; Coulon, Frederic
    Air samples from four contrasting outdoor environments including a park, an arable farm, a waste water treatment plant and a composting facility were analysed during the summer and winter months. The aim of the research was to study the feasibility of differentiating microbial communities from urban, rural and industrial areas between seasons with chemical and molecular markers such as microbial volatile organic compounds (MVOCs) and phospholipid fatty acids (PLFAs). Air samples (3 l) were collected every 2 h for a total of 6 h in order to assess the temporal variations of MVOCs and PLFAs along the day. MVOCs and VOCs concentrations varied over the day, especially in the composting facility which was the site where more human activities were carried out. At this site, total VOC concentration varied between 80 and 170 μg m−3 in summer and 20–250 μg m−3 in winter. The composition of MVOCs varied between sites due to the different biological substrates including crops, waste water, green waste or grass. MVOCs composition also differed between seasons as in summer they are more likely to get modified by oxidation processes in the atmosphere and in winter by reduction processes. The composition of microbial communities identified by the analysis of PLFAs also varied among the different locations and between seasons. The location with higher concentrations of PLFAs in summer was the farm (7297 ng m−3) and in winter the park (11,724 ng m−3). A specific set of MVOCs and PLFAs that most represent each one of the locations was identified by principal component analyses (PCA) and canonical analyses. Further to this, concentrations of both total VOCs and PLFAs were at least three times higher in winter than in summer. The difference in concentrations between summer and winter suggest that seasonal variations should be considered when assessing the risk of exposure to these compounds.
  • No Thumbnail Available
    ItemOpen Access
    Can chemical and molecular biomarkers help discriminating industrial, rural and urban environments?
    (Cranfield University, 2018-02-05 10:48) Coulon, Frederic; Tyrrell, Sean; Garcia Alcega, Sonia
    Underlying data to study the feasibility of differentiate urban, rural and industrial areas between seasons with chemical and molecular markers such as MVOCs and PLFAs
  • Thumbnail Image
    ItemOpen Access
    Characterizing outdoor air using microbial volatile organic compounds (MVOCs)
    (Apple Academuc Press, 2018-11-02) Garcia Alcega, Sonia; Coulon, Frederic
    Exposure to bioaerosols containing airborne microorganisms and their by-products from outdoor environments such as industrial, urban or agricultural sites is of great concern as it is linked to adverse health effects in humans including respiratory diseases and infections. The risk exposure from outdoor emissions is difficult to quantify in real-time as the microbial concentration in air is low and varies depending on meteorological factors, anthropogenic activities, and sampling conditions. In addition, the collection of sufficient amount of sample to generate statistically distinguishable and reproducible patterns to characterize and quantify bioaerosols is still a challenge, and this analysis cannot be performed in real time yet. Microbial volatile organic compounds (MVOCs) can be used to chemically characterize ambient bioaerosols and identify pathogens early in air overcoming the inherent limitations of culturing. This book chapter aims to critically review the sampling techniques and analytical approaches that are currently available for the study of MVOCs from industrial, agricultural and rural emissions. Current challenges in MVOCs sample collection, analytical and speciation analysis are addressed, and recommendation for the implementation of a rapid, reproducible and sensitive analytical framework for fingerprinting bioaerosols is provided.
  • No Thumbnail Available
    ItemOpen Access
    Chemical fingerprint database of bioaerosols
    (Cranfield University, 2017-04-21 11:08) Garcia Alcega, Sonia; Coulon, Frederic; Tyrrel, Sean
    The impact of emissions from urban, agricultural and industrial scenarios on local air quality is of growing policy concern. Deleterious health effects can arise following exposure to infective microbes and the exposure risk to bioaerosols are difficult to quantify in real time. Current monitoring methods are labour intensive and a standardised protocol does not exist yet. Additionally, capturing sufficient amounts of material to generate distinguishable and reproducible patterns for bioaerosols identification and classification is still difficult. To overcome the inherent limitations of culturing, chemical fingerprint analysis of microbial biomarkers such as phospholipid fatty acids (PLFAs) and microbial volatile organic compounds (MVOCs) is proposed. Different air samples collection devices are currently being tested (Coriolis, Tenax® cartridges and polycarbonate filters) and each method will be evaluated depending on the complexity of the sampling, laboratory procedure, compounds identified and the limit of detection of the equipment.
  • Thumbnail Image
    ItemOpen Access
    A controlled study on the characterisation of bioaerosols emissions from compost
    (2018-09-28) Nasir, Zaheer A.; Rolph, Catherine A.; Collins, Samuel; Stevenson, David; Gladding, Toni L.; Hayes, Enda; Williams, Ben; Khera, Shagun; Jackson, Simon; Bennett, Allan; Parks, Simon; Kinnersley, Robert P.; Walsh, Kerry; Pollard, Simon J. T.; Drew, Gillian; Garcia Alcega, Sonia; Coulon, Frederic; Tyrrel, Sean
    Bioaerosol emissions arising from biowaste treatment are an issue of public concern. To better characterise the bioaerosols, and to assess a range of measurement methods, we aerosolised green waste compost under controlled conditions. Viable and non-viable Andersen samplers, cyclone samplers and a real time bioaerosol detection system (Spectral Intensity Bioaerosol Sensor (SIBS)) were deployed simultaneously. The number-weighted fraction of fluorescent particles was in the range 22–26% of all particles for low and high emission scenarios. Overall fluorescence spectral profiles seen by the SIBS exhibited several peaks across the 16 wavelength bands from 298 to 735 nm. The size-fractionated endotoxin profile showed most endotoxin resided in the 2.1–9 μm aerodynamic diameter fraction, though up to 27% was found in a finer size fraction. A range of microorganisms were detected through culture, Matrix Assisted Laser Desorption and Ionisation Time of Flight Mass Spectrometry (MALDI-TOF) and quantitative polymerase chain reaction (qPCR), including Legionella pneumophila serogroup 1. These findings contribute to our knowledge of the physico-chemical and biological characteristics of bioaerosols from composting sites, as well as informing future monitoring approaches and data interpretation for bioaerosol measurement.
  • Thumbnail Image
    ItemOpen Access
    Detection and characterization of bioaerosol emissions from wastewater treatment plants: Challenges and opportunities
    (Frontiers, 2022-11-10) Tian, Jianghan; Yan, Cheng; Garcia Alcega, Sonia; Hassard, Francis; Tyrrel, Sean; Coulon, Frederic; Ahmad Nasir, Zaheer
    Rapid population growth and urbanization process have led to increasing demand for wastewater treatment capacity resulting in a non-negligible increase of wastewater treatment plants (WWTPs) in several cities around the world. Bioaerosol emissions from WWTPs may pose adverse health risks to the sewage workers and nearby residents, which raises increasing public health concerns. However, there are still significant knowledge gaps on the interplay between process-based bioaerosol characteristics and exposures and the quantification of health risk which limit our ability to design effective risk assessment and management strategies. This review provides a critical overview of the existing knowledge of bioaerosol emissions from WWTPs including their nature, magnitude and size distribution, and highlights the shortcoming associated with existing sampling and analysis methods. The recent advancements made for rapid detection of bioaerosols are then discussed, especially the emerging real time detection methods to highlight the directions for future research needs to advance the knowledge on bioaerosol emissions from WWTPs.
  • Thumbnail Image
    ItemOpen Access
    Fingerprinting ambient air to understand bioaerosol profiles in three different environments in the South East of England
    (Elsevier, 2020-02-24) Garcia Alcega, Sonia; Nasir, Zaheer A.; Cipullo, Sabrina; Ferguson, Robert M. W.; Yan, Cheng; Whitby, Corinne; Dumbrell, Alex J.; Drew, Gillian; Colbeck, Ian; Tyrrel, Sean F.
    Molecular and chemical fingerprints from 10 contrasting outdoor air environments, including three agricultural farms, three urban parks and four industrial sites were investigated to advance our understanding of bioaerosol distribution and emissions. Both phospholipid fatty acids (PLFA) and microbial volatile organic compounds (MVOC) profiles showed a different distribution in summer compared to winter. Further to this, a strong positive correlation was found between the total concentration of MVOCs and PLFAs (r = 0.670, p = 0.004 in winter and r = 0.767, p = 0.001 in summer) demonstrating that either chemical or molecular fingerprints of outdoor environments can provide good insights into the sources and distribution of bioaerosols. Environment specific variables and most representative MVOCs were identified and linked to microbial species emissions via a MVOC database and PLFAs taxonomical classification. While similar MVOCs and PLFAs were identified across all the environments suggesting common microbial communities, specific MVOCs were identified for each contrasting environment. Specifically, 3,4-dimethylpent-1-yn-3-ol, ethoxyethane and propanal were identified as key MVOCs for the industrial areas (and were correlated to fungi, Staphylococcus aureus (Gram positive bacteria) and Gram negative bacteria, R = 0.863, R = 0.618 and R = 0.676, respectively) while phthalic acid, propene and isobutane were key for urban environments (correlated to Gram negative bacteria, fungi and bacteria, R = 0.874, R = 0.962 and R = 0.969 respectively); and ethanol, 2-methyl-2-propanol, 2-methyl-1-pentene, butane, isoprene and methyl acetate were key for farms (correlated to fungi, Gram positive bacteria and bacteria, R = 0.690 and 0.783, R = 0.706 and R = 0.790, 0.761 and 0.768). The combination of MVOCs and PLFAs markers can assist in rapid microbial fingerprinting of distinct environmental influences on ambient air quality.
  • No Thumbnail Available
    ItemOpen Access
    Fingerprinting ambient air to understand bioaerosol profiles in three different environments in the South East of England
    (Cranfield University, 2020-02-24 08:10) Coulon, Frederic; Garcia Alcega, Sonia; Tyrrel, Sean; Nasar, Zaheer; Drew, Gill; Cipullo, Sabrina; colbeck, ian; ferguson, Robert; Whitby, Corinne; J. Dumbrell, Alex; Yan, Cheng
    Raw data used and supporting the data and results presented in: "Fingerprinting ambient air to understand bioaerosol profiles in three different environments in the South East of England" Science of the Total Environment
  • Thumbnail Image
    ItemOpen Access
    Fingerprinting outdoor air environment using microbial volatile organic compounds (MVOCs) – A review
    (Elsevier, 2016-11-08) Garcia Alcega, Sonia; Nasir, Zaheer A.; Ferguson, Robert M. W.; Whitby, Corinne; Dumbrell, Alex J.; Colbeck, I.; Gomes, D. M.; Tyrrel, Sean F.; Coulon, Frederic
    The impact of bioaerosol emissions from urban, agricultural and industrial environments on local air quality is of growing policy concern. Yet the risk exposure from outdoor emissions is difficult to quantify in real-time as microbial concentration in air is low and varies depending on meteorological factors and land use types. While there is also a large number of sampling methods in use, there is yet no standardised protocol established. In this review, a critical insight into chemical fingerprint analysis of microbial volatile organic compounds (MVOC) is provided. The most suitable techniques for sampling and analysing MVOCs in outdoor environments are reviewed and the need for further studies on MVOCs from outdoor environments including background levels is highlighted. There is yet no rapid and portable technique that allows rapid detection and analysis of MVOCs on site. Further directions towards a portable GC–MS coupled with SPME or an electronic nose are discussed.
  • Thumbnail Image
    ItemOpen Access
    IMPACT Showcase: Bioaerosols monitoring
    (Cranfield University, 2017-04-21 11:08) Garcia Alcega, Sonia; Coulon, Frederic; Tyrrel, Sean
    Why shall we concern ourselves with bioaerosols in the environment? Poster showcasing work being conducting by Cranfield University
  • Thumbnail Image
    ItemOpen Access
    Quantitative SARS-CoV-2 exposure assessment for workers in wastewater treatment plants using Monte-Carlo simulation
    (Elsevier, 2023-11-16) Yan, Cheng; Hu, Yi-ning; Gui, Zi-cheng; Lai, Tian-nuo; Ali, Wajid; Wan, Nian-hong; He, Shan-shan; Liu, Sai; Li, Xiang; Jin, Ting-xu; Nasir, Zaheer Ahmad; Garcia Alcega, Sonia; Coulon, Frederic
    Several studies on COVID-19 pandemic have shown that the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) originating from human stool are detected in raw sewage for several days, leading to potential health risks for workers due to the production of bioaerosols and droplets during wastewater treatment process. In this study, data of SARS-CoV-2 concentrations in wastewater were gathered from literatures, and a quantitative microbial risk assessment with Monte Carlo simulation was used to estimate the daily probability of infection risk through exposure to viable infectious viral airborne particles of the workers during four seasons and under six environmental conditions. Inhalation of bioaerosols and direct ingestion of wastewater droplets were selected as exposure pathways. Spearman rank correlation coefficients were used for sensitivity analysis to identify the variables with the greatest influence on the infection risk probability. It was found that the daily probability of infection risk decreased with temperature (T) and relative humidity (RH) increase. The probability of direct droplet ingestion exposure pathway was higher than that of the bioaerosol inhalation pathway. The sensitivity analysis indicated that the most sensitive variable for both exposure pathways was the concentration of SARS-CoV-2 in stool. So, appropriate aeration systems, covering facilities, and effective ventilation are suggested to implement in wastewater treatment plants (WWTPs) to reduce emission concentration. Further to this, the exposure time (t) had a larger variance contribution than T and RH for the bioaerosol inhalation pathway. Implementing measures such as adding more work shifts, mandating personal protective equipment for all workers, and implementing coverage for treatment processes can significantly reduce the risk of infection among workers at WWTPs. These measures are particularly effective during environmental conditions with low temperatures and humidity levels.
  • Thumbnail Image
    ItemOpen Access
    Rapid Monitoring of Bioaerosols from industrial, rural and urban environments
    (Cranfield University, 2017-04-21 11:08) Garcia Alcega, Sonia; Coulon, Frederic; Tyrrel, Sean
    •Sampling at constant flow rate and varying sampling time: - does not affect in presence/absence of MVOCs (70% similarity) - There is large difference in abundance (ng.m-3), (20% similarity). • Sampling at different flow rates and varying sampling time affects both peak detection and concentration.
  • Thumbnail Image
    ItemOpen Access
    Sampling microbial volatile organic compounds: optimisation of flow rate and sampling time
    (WIT Press, 2017-08-06) Garcia Alcega, Sonia; Tyrrel, Sean; Coulon, Frederic
    The impact of bioaerosols emissions from urban, agricultural and industrial environments on local air quality is of growing policy concern. However, there is no standardised protocol established yet, despite a large number of bioaerosols sampling methods in use. Additionally, capturing sufficient amounts of material to allow reproducible separation and detection of molecular patterns is still difficult. Chemical fingerprint analysis of microbial volatile organic compounds (MVOC) is a potentially rapid and reproducible approach for the early detection and identification of outdoor contamination as it has been shown to be a successful approach for indoor environments and it can be done on a fine-scale, allowing the identification of species-specific volatiles that may serve as marker compounds for the selective detection of pathogens. In this study we have tested the number and concentration of MVOCs collected using different sampling conditions: 10 min sampling time with variable flow rate (100, 500 and 1000 ml min–1) and 100 ml min–1 flow rate during 10, 20 and 30 min using Tenax®-Carbotrap thermal desorption (TD) tubes attached to portable GilAir® air pumps. Our aim was to determine the best sampling conditions in order to get enough material allowing reproducible data of the microbial markers present in outdoor environments. Substantial loses (>50%) of MVOCs occurred when sampling at flow rates higher than 100 ml min–1. 10 min sampling time allowed the collection of most of the MVOCs present in the air (~96%). The optimal sampling settings that allowed the collection of higher concentrations of MVOCs without breakthrough was 10 min sampling at 100 ml min–1 flow rate. Ketones were the predominant group of MVOCs identified in the WWTP (34–42%), acetone being the compound present at higher concentration (6476–11731 ng m–3).
  • Thumbnail Image
    ItemOpen Access
    Scoping studies to establish the capability and utility of a real-time bioaerosol sensor to characterise emissions from environmental sources
    (Elsevier, 2018-08-09) Nasir, Zaheer A.; Hayes, Enda; Williams, Ben; Gladding, Toni; Rolph, Catherine A.; Khera, Shagun; Jackson, Simon; Bennett, Allan; Collins, Samuel; Parks, Simon; Attwood, Alexis; Kinnersley, Robert P.; Walsh, Kerry; Garcia Alcega, Sonia; Pollard, Simon J. T.; Drew, Gill; Coulon, Frederic; Tyrrel, Sean
    A novel dual excitation wavelength based bioaerosol sensor with multiple fluorescence bands called Spectral Intensity Bioaerosol Sensor (SIBS) has been assessed across five contrasting outdoor environments. The mean concentrations of total and fluorescent particles across the sites were highly variable being the highest at the agricultural farm (2.6 cm−3 and 0.48 cm−3, respectively) and the composting site (2.32 cm−3 and 0.46 cm−3, respectively) and the lowest at the dairy farm (1.03 cm−3 and 0.24 cm−3, respectively) and the sewage treatment works (1.03 cm−3 and 0.25 cm−3, respectively). In contrast, the number-weighted fluorescent fraction was lowest at the agricultural site (0.18) in comparison to the other sites indicating high variability in nature and magnitude of emissions from environmental sources. The fluorescence emissions data demonstrated that the spectra at different sites were multimodal with intensity differences largely at wavelengths located in secondary emission peaks for λex 280 and λex 370. This finding suggests differences in the molecular composition of emissions at these sites which can help to identify distinct fluorescence signature of different environmental sources. Overall this study demonstrated that SIBS provides additional spectral information compared to existing instruments and capability to resolve spectrally integrated signals from relevant biological fluorophores could improve selectivity and thus enhance discrimination and classification strategies for real-time characterisation of bioaerosols from environmental sources. However, detailed lab-based measurements in conjunction with real-world studies and improved numerical methods are required to optimise and validate these highly resolved spectral signatures with respect to the diverse atmospherically relevant biological fluorophores.
  • Thumbnail Image
    ItemOpen Access
    Seasonal variation of quantitative microbial risk assessment for three airborne enteric bacteria from wastewater treatment plant emissions
    (Elsevier, 2022-05-26) Gui, Zi-cheng; Li, Xiang; Peng, Zhang-di; Yan, Cheng; Nasir, Zaheer A.; Garcia Alcega, Sonia; Coulon, Frederic
    Airborne E. coli, fecal coliform, and Enterococcus are all related to sewage worker’s syndrome and therefore used as target enteric bioaerosols about researches in wastewater treatment plants (WWTPs). However, most of the studies are often inadequately carried out because they lack systematic studies reports bioaerosols emission characteristics and health risk assessments for these three enteric bacteria during seasonal variation. Therefore, quantitative microbial risk assessment based on Monte Carlo simulation was utilized in this research to assess the seasonal variations of health risks of the three enteric bioaerosols among exposure populations (academic visitors, field engineers, and office staffs) in a WWTP equipped with rotating-disc and microporous aeration modes. The results show that the concentrations of the three airborne bacteria from the rotating-disc aeration mode were 2–7 times higher than the microporous aeration mode. Field engineers had health risks 1.5 times higher than academic visitors due to higher exposure frequency. Health risks of airborne Enterococcus in summer were up to 3 times higher than those in spring and winter. Similarly, health risks associated to E. coli aerosol exposure were 0.3 times higher in summer compared to spring. In contrast, health risks associated with fecal coliform aerosol were between 2 and 19 times lower in summer compared to spring and winter seasons. Data further suggest that wearing of N95 mask could minimize health risks by 1–2 orders of magnitude. This research shed light on seasonal variation of health risks associated with bioaerosol emission from wastewater utilities.
  • Thumbnail Image
    ItemOpen Access
    Size fractionation of bioaerosol emissions from green waste composting
    (Elsevier, 2020-12-31) Ferguson, Robert M. W.; Neath, Charlotte E. E.; Nasir, Zaheer A.; Garcia Alcega, Sonia; Tyrrel, Sean F.; Coulon, Frederic; Dumbrell, Alex J.; Colbeck, Ian; Whitby, Corinne
    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 da). 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% da 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 da < 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