Keller, Alejandro

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Keller
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Alejandro
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Keller, Alejandro

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2017 - 201922020 - 20221
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Thema: 660 - Technische Chemie ×

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Gerade angezeigt 1 - 3 von 3
  • Vorschaubild
    Publikation
    Responses of reconstituted human bronchial epithelia from normal and health-compromised donors to non-volatile particulate matter emissions from an aircraft turbofan engine
    (Elsevier, 15.08.2022) Delaval, Mathilde N.; Jonsdottir, Hulda R.; Leni, Zaira; Keller, Alejandro; Brem, Benjamin T.; Siegerist, Frithjof; Schönenberger, David; Durdina, Lukas; Elser, Miriam; Salathe, Matthias; Baumlin, Nathalie; Lobo, Prem; Burtscher, Heinz; Liati, Anthi; Geiser, Marianne [in: Environmental Pollution]
    Health effects of particulate matter (PM) from aircraft engines have not been adequately studied since controlled laboratory studies reflecting realistic conditions regarding aerosols, target tissue, particle exposure and deposited particle dose are logistically challenging. Due to the important contributions of aircraft engine emissions to air pollution, we employed a unique experimental setup to deposit exhaust particles directly from an aircraft engine onto reconstituted human bronchial epithelia (HBE) at air-liquid interface under conditions similar to in vivo airways to mimic realistic human exposure. The toxicity of non-volatile PM (nvPM) from a CFM56-7B26 aircraft engine was evaluated under realistic engine conditions by sampling and exposing HBE derived from donors of normal and compromised health status to exhaust for 1 h followed by biomarker analysis 24 h post exposure. Particle deposition varied depending on the engine thrust levels with 85% thrust producing the highest nvPM mass and number emissions with estimated surface deposition of 3.17 × 109 particles cm−2 or 337.1 ng cm−2. Transient increase in cytotoxicity was observed after exposure to nvPM in epithelia derived from a normal donor as well as a decrease in the secretion of interleukin 6 and monocyte chemotactic protein 1. Non-replicated multiple exposures of epithelia derived from a normal donor to nvPM primarily led to a pro-inflammatory response, while both cytotoxicity and oxidative stress induction remained unaffected. This raises concerns for the long-term implications of aircraft nvPM for human pulmonary health, especially in occupational settings.
    01A - Beitrag in wissenschaftlicher Zeitschrift
  • Vorschaubild
    Publikation
    Non-volatile particle emissions from aircraft turbine engines at ground-idle induce oxidative stress in bronchial cells
    (Nature, 05.03.2019) Jonsdottir, Hulda R.; Delaval, Mathilde; Leni, Zaira; Keller, Alejandro; Brem, Benjamin T.; Siegerist, Frithjof; Schönenberger, David; Durdina, Lukas; Elser, Miriam; Burtscher, Heinz; Liati, Anthi; Geiser, Marianne [in: Communications Biology]
    Aircraft emissions contribute to local and global air pollution. Health effects of particulate matter (PM) from aircraft engines are largely unknown, since controlled cell exposures at relevant conditions are challenging. We examined the toxicity of non-volatile PM (nvPM) emissions from a CFM56-7B26 turbofan, the world’s most used aircraft turbine using an unprecedented exposure setup. We combined direct turbine-exhaust sampling under realistic engine operating conditions and the Nano-Aerosol Chamber for In vitro Toxicity to deposit particles onto air–liquid-interface cultures of human bronchial epithelial cells (BEAS-2B) at physiological conditions. We evaluated acute cellular responses after 1-h exposures to diluted exhaust from conventional or alternative fuel combustion. We show that single, short-term exposures to nvPM impair bronchial epithelial cells, and PM from conventional fuel at ground-idle conditions is the most hazardous. Electron microscopy of soot reveals varying reactivity matching the observed cellular responses. Stronger responses at lower mass concentrations suggest that additional metrics are necessary to evaluate health risks of this increasingly important emission source.
    01A - Beitrag in wissenschaftlicher Zeitschrift
  • Vorschaubild nicht verfügbar
    Publikation
    Characterizing particulate emissions from wood burning appliances including secondary organic aerosol formation potential
    (Elsevier, 31.08.2017) Keller, Alejandro; Burtscher, Heinz [in: Journal of Aerosol Science]
    Biomass burning is a major contributor to environmental particulate matter pollution and should therefore be contemplated by emission control legislation. However, policy decisions for improving air quality by imposing emission limits are only as good as the selected metric. We discuss an approach that incorporates recent scientific results and is compatible with type-approval testing and field measurements. We include potential secondary organic aerosol (SOA) by aging emissions in an oxidation flow reactor. Quantification is done by particle-bound total carbon analysis. Total carbon is the fraction relevant to combustion quality and a better marker for toxicity than total particulate matter, which also includes salts and ashes. The data is complemented by on-line size distribution measurements. We exemplify our approach by showing measurements performed on a variety of appliances. Our measurements suggest that non-methane hydrocarbons (NMHC) species with very low volatility are responsible for most of the SOA. Condensing and precipitating this fraction significantly reduces SOA potential but has no noticeable impact on total NMHC. Thus, key precursors of SOA may be a much smaller subset than previously thought. Targeting this fraction could be a straightforward SOA mitigation strategy. These results could not have been derived using the current standard emission control metrics.
    01A - Beitrag in wissenschaftlicher Zeitschrift