Browsing by Author "Salonen, Heidi, Prof., Aalto University, Department of Civil Engineering, Finland"
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- Indoor air contaminants, symptoms and effects of mechanical ventilation in school buildings
School of Engineering | Doctoral dissertation (article-based)(2020) Vornanen-Winqvist, CamillaAccording to a recent national survey, significant indoor air quality (IAQ) problems occur in almost 20% of municipal school buildings in Finland. The causes of the problems are often difficult to detect, and this leads to ambiguous and challenging situations. Mechanical supply and exhaust ventilation plays a major role in maintaining the IAQ of highly occupied buildings, such as schools, but poorly functioning systems result in occupant discomfort and health problems. This study aimed to identify the differences in IAQ between schools with and without reported complaints. In addition, the effects of ventilation system interventions were monitored. Perceived and measured IAQ were studied in 40 classrooms in six mechanically ventilated comprehensive schools in the Helsinki metropolitan area. Schools were categorized as 'problematic' (n = 4) and 'comparison' (n = 2) schools, based on the known history of occupants' IAQ complaints. Occupant perceptions were recorded with a commonly used indoor air survey and a novel online questionnaire. Altogether, 14 parameters which contribute to the IAQ, such as gaseous, particulate matter (PM) and biological pollutants, were measured. As a new approach, indoor airborne fungi were identified from the exhaust air filter dust of the air handling units of the schools. In addition, the application of a moderate (5–7 Pa) positive differential pressure (dPa) and adjustments to a hybrid ventilation system were studied. A total of 105 teachers and 1268 students responded to the questionnaires. The responses to the two questionnaires were in agreement, and also corroborated the categorization of the schools as problematic or comparison schools. The online questionnaire showed significant differences between classrooms. Median relative humidity in the schools was 15–27%. Gaseous pollutant, PM and endotoxin levels were low, and there were no notable differences between the two types of schools. The sampling of airborne cultivable microorganisms and cultivation of settled and filter dust showed potential in identifying schools with a significant amount of occupant complaints. The total concentration of the airborne microbes exceeded the outdoor concentration in 58% of the samples in the four problematic schools, and in 8% of the samples in the two comparison ones. Representative species of the genus Trichoderma, including mycoparasitic, biocide-resistant species such as T. atroviride and T. trixiae, and potentially pathogenic, biocide-sensitive species as T. citrinoviride and T. longibrachiatum, were found only in the problematic schools. After ventilation interventions, a change in the indoor mycobiota composition was observed, and minor but indicative changes in symptoms were reported. Importantly, the positive dPa did not promote the transfer of moisture through the structure and the moisture excess was kept low. Further, even a drying effect was observed during the measured moisture excess of 0.02 g/m3. - Microbiological effects of copper and other abiotic factors in drinking water and touch surface environments
School of Engineering | Doctoral dissertation (article-based)(2018) Inkinen, JenniHumans spend most of their time indoors. The built environment with its systems (e.g. water system) should be designed and operated in a way that it is microbiologically safe in all stages of operation. Copper is a widely used material within indoor environments and may aid to maintain low bacterial counts in drinking water and touch surface environments depending on the surroun- ding circumstances e.g. water/air interface, biofilm formation or soiling. Basic knowledge of the composition of drinking water bacteria has been earlier limited only to a small cultivable fraction of bacteria. Next-generation sequencing (NGS) technologies help to reveal entire microbial communities and to date these approaches are also extended to cover studies on drinking water systems. This thesis focuses on the unique microbiological niches of drinking water and touch surface indoor environments utilizing up-to-date technologies and real-life environments with emphasis on environmental factors that shape such microbiota. The role of copper in both water and air interfaces is of special interest. NGS approach was utilised to evaluate the effect of copper pipelines on biofilm or water micro-biota under real-life circumstances (full-scale water system) and under controlled conditions (pilot-scale system). Copper was compared to another commonly used pipeline material, cross-linked polyethylene (PEX). Environmental conditions i.e. the effect of cold and hot water systems with different flow regimes and temperatures (full-scale), and disinfection and magnetic water treat- ment (pilot-scale) were studied by NGS or traditional analysis methods in which stagnated water represented the worst-case scenario for water quality. The microbiological effects of copper in touch surface environment were studied at different real-life facilities under varying environmental circumstances (e.g. usage profiles, cleaning). This thesis successfully revealed the active and dormant bacterial inhabitants of the drinking water system utilizing 16S ribosomal RNA gene amplicon sequencing and ribosomal RNA as a template. For public health relevance, Legionella spp. were suggested as inactive using the RNA approach. Operational conditions (stagnation, temperature) and increased disinfectant concen- tration were revealed as important environmental factors that shape drinking water bacterial populations. Moreover, the study emphasizes the importance of use of only fresh water for drinking water usage, in accordance with the current recommended practises. Based on this study, copper pipelines showed similar characteristics to PEX pipelines without antibacterial properties in drin- king water systems. At the air interface however, copper showed antibacterial properties with varying real-life circumstances. Thus, its usage as an antibacterial touch surface material can be recommended especially for small frequently touched items that were shown to possess the highest microbial counts. - Novel detection methods and knowledge of indoor emissions from building materials, fungi, and cleaning agents
School of Engineering | Doctoral dissertation (article-based)(2020) Castagnoli, EmmanuelleThe quality of the indoor air is paramount to guarantee occupants' health and comfort as they spend most of their time indoors. Yet, a proper understanding of emissions' mechanisms from moisture-damaged building materials and of suitable detection methods targeting harmful indoor air contaminants are lacking. This dissertation aims at providing new knowledge and methods for the detection of volatile organic compounds and microbial contaminants. The airborne emissions of C9-alcohols from DEHP-free PVC floor coverings were studied at 75, 85 and 95% RH. The aim was to determine whether C9-alcohols could be used as an indicator of the degradation of the DEHP-PVC floor coverings and of hidden underlying moisture damage. 2-ethylhexanol and TVOC emissions were also monitored. The C9-alcohols emissions were the highest at 95% RH but were also emitted at 75 and 85% RH. It was concluded that monitoring C9-alcohols alone were not a clear indicator of the hidden degradation of floor coverings. The toxin production of toxigenic Trichoderma strains isolated from buildings where occupants reported health symptoms was investigated. The toxicity profiles of the exudates and biomass extracts were similar to reference peptaibols (alamethicin and trilongins). The toxins were identified as trichorzianines, trilongins, trichostrigocins and trichostrigocin-like peptaibols using HPLC/ESI-MS/MS. Furthermore, the Trichoderma strains emitted the same toxic peptaibols in both their biomasses and exudates. The production of guttation droplets by indoor fungi may serve as a mechanism of aerosol formation for non-volatile metabolites in indoor air. A new computed motility inhibition (CMI) assay was developed to improve the screening of microbial contaminants. The CMI assay calculates objective toxicity values from digital micrographic videos of toxin-exposed boar spermatozoa experiments using a simple MATLAB® script. The results of the CMI assay were similar to the other established motility inhibition assays (BSMI and VMI assays). In addition, only the CMI assay was able to detect subtle changes in motility. The CMI assay was highly sensitive to the inhibition of mitochondrial function, glucose transport activity and the disruption of cellular cation homeostasis by ionophoric toxins. A new detection method for the airborne diffusion and toxicity of surfactants using two-compartment Petri dishes was developed. Genapol X-080, used in cleaning products, was selected as a model for polyethylene glycol monoalkyl ether surfactants. The airborne diffusion of Genapol X-080 was observed and evaluated as a change in the surface tension of water and the fluorescence of resazurin. The boar spermatozoa toxicity assays were the most sensitive to airborne Genapol X-080 than the inhibition of cell proliferation assays. The resazurin + Genapol X-080 test showed potential for developing a new and easy method to track the airborne diffusion of PEG monoalkyl ethers used in buildings.