Abstract
Within the framework of the project “Integrated Evaluation of Indoor Particulate Exposure”, we carried out a 4-week field study to determine indoor bioaerosol, and its contribution to particulate matter (PM)10 and organic matter. The study was carried out in university classrooms, where most of the common indoor sources of atmospheric particles are missing. Bioaerosol was determined by a method based on propidium iodide staining, observation by fluorescence microscopy, and image analysis. Indoor bioaerosol concentrations were compared with outdoor values, which were determined simultaneously. The samplings periods were scheduled to divide weekday hours, when the students were inside, from night-time hours and weekends. Very high bioaerosol concentrations were detected inside the classrooms with respect to outdoor values. The mean difference was 49 μg/m3 when the students were inside, 5.4 μg/m3 during the night, and it became negative during the weekends. Indoor-to-outdoor ratios were 6.0, 4.2, and 0.7, respectively. Bioaerosol contributed 26% to organics and 10% to PM10. In indoor samples collected during the day, the microscope images showed numerous skin fragments, which were mostly responsible for the increase in the bioaerosol mass. People’s presence proved to be responsible for a significant increase in bioaerosol concentration in crowded indoor environments.
Highlights
Among the main objectives of the project “Integrated Evaluation of Indoor ParticulateExposure” (VIEPI) there was the chemical characterization of particulate matter (PM)suspended in the atmosphere of indoor environments, and the evaluation of its infiltration dynamics [1]
Indoor concentrations were much higher than the corresponding outdoor values. These differences, 49 μg/m3 as a mean value, significantly reduced at night (5.4 μg/m3 ), and became negative during the weekend (−6.1 μg/m3 ). These results highlight the presence of important indoor sources of PM, which add to the infiltration from outside, and indicate that these sources were active during the daytime hours of weekdays
The source that may be responsible for the increase in PM concentration during day hours may be identified as students and teachers
Summary
Among the main objectives of the project “Integrated Evaluation of Indoor ParticulateExposure” (VIEPI) there was the chemical characterization of particulate matter (PM)suspended in the atmosphere of indoor environments, and the evaluation of its infiltration dynamics [1]. Among the main objectives of the project “Integrated Evaluation of Indoor Particulate. One of the PM components taken into account by this objective was the fraction of organic particulate matter attributable to bioaerosol. Bioaerosol, include all types of particles derived from biological organisms, namely viruses, bacteria, fungi and fungal spores, pollen, and fragments of animal and plant organisms [2]. Bioaerosol constitutes a fraction of atmospheric particulate matter still poorly investigated from an environmental point of view, as these measurements have long been mainly carried out by cultivation methods, and aimed at assessing species potentially dangerous to human health. Cultivation methods, neglect most of the environmental bioaerosols, which are non-viable or non-culturable. Methods providing information about bioaerosol as a whole
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