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  • Barath, Stefan, et al. (författare)
  • Impaired vascular function after exposure to diesel exhaust generated at urban transient running conditions
  • 2010
  • Ingår i: Particle and fibre toxicology. - : BioMed Central. - 1743-8977. ; 7:1, s. 19-
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Traffic emissions including diesel engine exhaust are associated with increased respiratory and cardiovascular morbidity and mortality. Controlled human exposure studies have demonstrated impaired vascular function after inhalation of exhaust generated by a diesel engine under idling conditions. OBJECTIVES: To assess the vascular and fibrinolytic effects of exposure to diesel exhaust generated during urban-cycle running conditions that mimic ambient 'real-world' exposures. METHODS: In a randomised double-blind crossover study, eighteen healthy male volunteers were exposed to diesel exhaust (approximately 250 mug/m3) or filtered air for one hour during intermittent exercise. Diesel exhaust was generated during the urban part of the standardized European Transient Cycle. Six hours post-exposure, vascular vasomotor and fibrinolytic function was assessed during venous occlusion plethysmography with intra-arterial agonist infusions. MEASUREMENTS AND MAIN RESULTS: Forearm blood flow increased in a dose-dependent manner with both endothelial-dependent (acetylcholine and bradykinin) and endothelial-independent (sodium nitroprusside and verapamil) vasodilators. Diesel exhaust exposure attenuated the vasodilatation to acetylcholine (P < 0.001), bradykinin (P < 0.05), sodium nitroprusside (P < 0.05) and verapamil (P < 0.001). In addition, the net release of tissue plasminogen activator during bradykinin infusion was impaired following diesel exhaust exposure (P < 0.05). CONCLUSION: Exposure to diesel exhaust generated under transient running conditions, as a relevant model of urban air pollution, impairs vasomotor function and endogenous fibrinolysis in a similar way as exposure to diesel exhaust generated at idling. This indicates that adverse vascular effects of diesel exhaust inhalation occur over different running conditions with varying exhaust composition and concentrations as well as physicochemical particle properties. Importantly, exposure to diesel exhaust under ETC conditions was also associated with a novel finding of impaired of calcium channel-dependent vasomotor function. This implies that certain cardiovascular endpoints seem to be related to general diesel exhaust properties, whereas the novel calcium flux-related effect may be associated with exhaust properties more specific for the ETC condition, for example a higher content of diesel soot particles along with their adsorbed organic compounds.
  • Rissler, Jenny, et al. (författare)
  • Deposition efficiency of inhaled particles (15-5000 nm) related to breathing pattern and lung function : An experimental study in healthy children and adults
  • 2017
  • Ingår i: Particle and Fibre Toxicology. - : BioMed Central (BMC). - 1743-8977 .- 1743-8977. ; 14:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Exposure to airborne particles has a major impact on global health. The probability of these particles to deposit in the respiratory tract during breathing is essential for their toxic effects. Observations have shown that there is a substantial variability in deposition between subjects, not only due to respiratory diseases, but also among individuals with healthy lungs. The factors determining this variability are, however, not fully understood. Method: In this study we experimentally investigate factors that determine individual differences in the respiratory tract depositions of inhaled particles for healthy subjects at relaxed breathing. The study covers particles of diameters 15-5000 nm and includes 67 subjects aged 7-70 years. A comprehensive examination of lung function was performed for all subjects. Principal component analyses and multiple regression analyses were used to explore the relationships between subject characteristics and particle deposition. Results: A large individual variability in respiratory tract deposition efficiency was found. Individuals with high deposition of a certain particle size generally had high deposition for all particles <3500 nm. The individual variability was explained by two factors: breathing pattern, and lung structural and functional properties. The most important predictors were found to be breathing frequency and anatomical airway dead space. We also present a linear regression model describing the deposition based on four variables: tidal volume, breathing frequency, anatomical dead space and resistance of the respiratory system (the latter measured with impulse oscillometry). Conclusions: To understand why some individuals are more susceptible to airborne particles we must understand, and take into account, the individual variability in the probability of particles to deposit in the respiratory tract by considering not only breathing patterns but also adequate measures of relevant structural and functional properties.
  • Sehlstedt, Maria, et al. (författare)
  • Antioxidant airway responses following experimental exposure to wood smoke in man
  • 2010
  • Ingår i: Particle and Fibre Toxicology. - : BioMed Central (BMC). - 1743-8977. ; 7
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Biomass combustion contributes to the production of ambient particulate matter (PM) in rural environments as well as urban settings, but relatively little is known about the health effects of these emissions. The aim of this study was therefore to characterize airway responses in humans exposed to wood smoke PM under controlled conditions. Nineteen healthy volunteers were exposed to both wood smoke, at a particulate matter (PM2.5) concentration of 224 +/- 22 mu g/m(3), and filtered air for three hours with intermittent exercise. The wood smoke was generated employing an experimental set-up with an adjustable wood pellet boiler system under incomplete combustion. Symptoms, lung function, and exhaled NO were measured over exposures, with bronchoscopy performed 24 h post-exposure for characterisation of airway inflammatory and antioxidant responses in airway lavages. Results: Glutathione (GSH) concentrations were enhanced in bronchoalveolar lavage (BAL) after wood smoke exposure vs. air (p = 0.025), together with an increase in upper airway symptoms. Neither lung function, exhaled NO nor systemic nor airway inflammatory parameters in BAL and bronchial mucosal biopsies were significantly affected. Conclusions: Exposure of healthy subjects to wood smoke, derived from an experimental wood pellet boiler operating under incomplete combustion conditions with PM emissions dominated by organic matter, caused an increase in mucosal symptoms and GSH in the alveolar respiratory tract lining fluids but no acute airway inflammatory responses. We contend that this response reflects a mobilisation of GSH to the air-lung interface, consistent with a protective adaptation to the investigated wood smoke exposure.
  • Ahlberg, Erik, et al. (författare)
  • "Vi klimatforskare stödjer Greta och skolungdomarna"
  • Ingår i: Dagens nyheter (DN debatt). - 1101-2447.
  • Tidskriftsartikel (populärvet., debatt m.m.)abstract
    • DN DEBATT 15/3. Sedan industrialiseringens början har vi använt omkring fyra femtedelar av den mängd fossilt kol som får förbrännas för att vi ska klara Parisavtalet. Vi har bara en femtedel kvar och det är bråttom att kraftigt reducera utsläppen. Det har Greta Thunberg och de strejkande ungdomarna förstått. Därför stödjer vi deras krav, skriver 270 klimatforskare.
  • Alsved, Malin, et al. (författare)
  • Aerosolization and recovery of viable murine norovirus in an experimental setup
  • 2020
  • Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 10:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Noroviruses are the major cause for viral acute gastroenteritis in the world. Despite the existing infection prevention strategies in hospitals, the disease continues to spread and causes extensive and numerous outbreaks. Hence, there is a need to investigate the possibility of airborne transmission of norovirus. In this study, we developed an experimental setup for studies on the infectivity of aerosolized murine norovirus (MNV), a model for the human norovirus. Two aerosol generation principles were evaluated: bubble bursting, a common natural aerosolization mechanism, and nebulization, a common aerosolization technique in laboratory studies. The aerosolization setup was characterized by physical and viral dilution factors, generated aerosol particle size distributions, and the viral infectivity after aerosolization. We found a lower physical dilution factor when using the nebulization generator than with the bubble bursting generator. The viral dilution factor of the system was higher than the physical dilution; however, when comparing the physical and viral dilution factors, bubble bursting generation was more efficient. The infectivity per virus was similar using either generation principle, suggesting that the generation itself had a minor impact on MNV infectivity and that instead, the effect of drying in air could be a major reason for infectivity losses.
  • Alsved, Malin, et al. (författare)
  • Effect of Aerosolization and Drying on the Viability of Pseudomonas syringae Cells
  • Ingår i: Frontiers in Microbiology. - : Frontiers Media S. A.. - 1664-302X. ; 9
  • Tidskriftsartikel (refereegranskat)abstract
    • Airborne dispersal of microorganisms influences their biogeography, gene flow, atmospheric processes, human health and transmission of pathogens that affect humans, plants and animals. The extent of their impact depends essentially on cell-survival rates during the process of aerosolization. A central factor for cell-survival is water availability prior to and upon aerosolization. Also, the ability of cells to successfully cope with stress induced by drying determines their chances of survival. In this study, we used the ice-nucleation active, plant pathogenic Pseudomonas syringae strain R10.79 as a model organism to investigate the effect of drying on cell survival. Two forms of drying were simulated: drying of cells in small droplets aerosolized from a wet environment by bubble bursting and drying of cells in large droplets deposited on a surface. For drying of cells both in aerosol and surface droplets, the relative humidity (RH) was varied in the range between 10 and 90%. The fraction of surviving cells was determined by live/dead staining followed by flow cytometry. We also evaluated the effect of salt concentration in the water droplets on the survival of drying cells by varying the ionic strength between 0 and 700 mM using NaCl and sea salt. For both aerosol and surface drying, cell survival increased with decreasing RH (p < 0.01), and for surface drying, survival was correlated with increasing salt concentration (p < 0.001). Imaging cells with TEM showed shrunk cytoplasm and cell wall damage for a large fraction of aerosolized cells. Ultimately, we observed a 10-fold higher fraction of surviving cells when dried as aerosol compared to when dried on a surface. We conclude that the conditions, under which cells dry, significantly affect their survival and thus their success to spread through the atmosphere and colonize new environments as well as their ability to affect atmospheric processes.
  • Alsved, Malin, et al. (författare)
  • Experimental and computational evaluation of airborne bacteria in hospital operating rooms with high airflows
  • 2018
  • Ingår i: Proceedings of The 5<sup>th</sup> Working &amp; Indoor Aerosols Conference 18-20 April 2018; Cassino, Italy.
  • Konferensbidrag (refereegranskat)abstract
    • Post-operative infections after surgery can be decreased by the use of efficient ventilation with clean air. In this study, we investigated three types of operating room ventilation: turbulent mixed airflow(TMA), laminar airflow (LAF) and a new type of ventilation named temperature controlled airflow(TcAF). Measurements of airborne bacteria were made during surgery and compared with values calculated by computational fluid dynamics (CFD). The results show that LAF and TcAF are most efficient in removing bacteria around the patient. With LAF, there are large differences in bacterial loads, depending on location in the room.
  • Alsved, Malin, et al. (författare)
  • Natural sources and experimental generation of bioaerosols : Challenges and perspectives
  • Ingår i: Aerosol Science and Technology. - : Taylor & Francis. - 0278-6826.
  • Forskningsöversikt (refereegranskat)abstract
    • Experimental aerosol generation methods aim to represent natural processes; however, the complexity is not always captured and unforeseen variability may be introduced into the data. The current practices for natural and experimental aerosol generation techniques are reviewed here. Recommendations for best practice are presented, and include characterization of starting material and spray fluid, rational selection of appropriate aerosol generators, and physical and biological characterization of the output aerosol. Reporting of bioaerosol research should capture sufficient detail to aid data interpretation, reduce variation, and facilitate comparison between research laboratories. Finally, future directions and challenges in bioaerosol generation are discussed.
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