David Vernez | EPFL Graph Search

À propos de ce résultat

Cette page est générée automatiquement et peut contenir des informations qui ne sont pas correctes, complètes, à jour ou pertinentes par rapport à votre recherche. Il en va de même pour toutes les autres pages de ce site. Veillez à vérifier les informations auprès des sources officielles de l'EPFL.

Developing a UV climatology for public health purposes using satellite data

Athanasios Nenes, David Vernez

The effects of solar ultraviolet (UV) radiation on life on Earth differ greatly. While overexposure to UV rays is harmful, small amounts of exposure are necessary for the synthesis of Vitamin D and good health. To optimize individual exposure to solar UV, it is therefore crucial to use UV data sources representative for entire populations and realistically accounting for various influencing factors. A UV climatology for Switzerland based on satellite data has been developed to provide risk estimates at population level. An algorithm generating ground-based radiation estimate has been transformed from the visible to the UV wavelength domain by adapting both a clear-sky radiation transfer model and a cloud modification factor model using satellite imagery. The algorithm allows the computation of global UV erythemal irradiance at a spatial resolution of 1.5 – 2 km and an hourly temporal resolution over fifteen years. A validation, conducted with measurements from three meteorological stations over ten years, showed that the expanded uncertainty for low hourly UVI values (UVI < 3) is about ± 0.3, while for high hourly UVI values (UVI > 6) it can go up to ± 1.5. In clear-sky situation, the uncertainty is in the range of 10–15%. The climatology developed allows to visualise potential UV exposure at regional and national scale. National prevention intervention could use new strategies to better focus on populations at risk and better tailor available researches. The UV climatology allows a high versatility in adapting the data extraction to the goal of studies using it. Further tailored data extraction and analysis will be necessary to exploit this climatology in a wide range of environmental and occupational health applications. Its development was focused on Switzerland, but the techniques used can be extended globally.

2021

Satellite-Based Personal UV Dose Estimation

Athanasios Nenes, David Vernez

Epidemiology and public health research relating to solar ultraviolet (UV) exposure usually relies on dosimetry to measure UV doses received by individuals. However, measurement errors affect each dosimetry measurement by unknown amounts, complicating the analysis of such measurements and their relationship to the underlying population exposure and the associated health outcomes. This paper presents a new approach to estimate UV doses without the use of dosimeters. By combining new satellite-derived UV data to account for environmental factors and simulation-based exposure ratio (ER) modelling to account for individual factors, we are able to estimate doses for specific exposure periods. This is a significant step forward for alternative dosimetry techniques which have previously been limited to annual dose estimation. We compare our dose estimates with dosimeter measurements from skiers and builders in Switzerland. The dosimetry measurements are expected to be slightly below the true doses due to a variety of dosimeter-related measurement errors, mostly explaining why our estimates are greater than or equal to the corresponding dosimetry measurements. Our approach holds much promise as a low-cost way to either complement or substitute traditional dosimetry. It can be applied in a research context, but is also fundamentally well-suited to be used as the basis for a dose-estimating mobile app that does not require an external device.

2021

Reusability of filtering facepiece respirators after decontamination through drying and germicidal UV irradiation

Kiattisak Batsungnoen, Véronique Michaud, Guillaume Suarez, David Vernez

Introduction During pandemics, such as the SARS-CoV-2, filtering facepiece respirators plays an essential role in protecting healthcare personnel. The recycling of respirators is possible in case of critical shortage, but it raises the question of the effectiveness of decontamination as well as the performance of the reused respirators. Method Disposable respirators were subjected to ultraviolet germicidal irradiation (UVGI) treatment at single or successive doses of 60 mJ/cm2 after a short drying cycle (30 min, 70°C). The germicidal efficacy of this treatment was tested by spiking respirators with two staphylococcal bacteriophages (vB_HSa_2002 and P66 phages). The respirator performance was investigated by the following parameters: particle penetration (NaCl aerosol, 10–300 nm), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry and mechanical tensile tests. Results No viable phage particles were recovered from any of the respirators after decontamination (log reduction in virus titre >3), and no reduction in chemical or physical properties (SEM, particle penetrations

2020