Feasibility of Generating Peaks of Bioaerosols for Laboratory Experiments

Bioaerosol concentration peaks are frequently encountered in real-life atmospheres (indoor, outdoor, workplace, etc.), where they can be caused by several factors. However, evolution over time and variability of microbiological pollutant concentrations remain under-documented. The contribution of such peaks in the onset or the worsening of respiratory symptoms - in particular immuno-allergic reactions - has yet to be extensively studied. Although experimental bioaerosol generators are increasingly used, the intentional and controlled production of concentration peaks of biological agents has not yet been utilized in laboratory experiments. The main objective of this study was to show that it is possible to produce experimental bioaerosol concentration peaks with defined characteristics. Experiments were performed with a 'Liquid Sparging Aerosoliser'-type generator. With this system, peaks can be created by increasing the bubbling airflow through a film of bacterial (Escherichia coli) or fungal (Penicillium brevicompactum) liquid culture. The higher the set point value of the bubbling airflow, the greater the maximum bioaerosol concentration during the generated peak. Similarly, longer-lived peaks can be created by maintaining the increased airflow for a longer period of time. For both studied species, the relative size distribution was constant over time, regardless of modifications to the bubbling flow rate. The operator can monitor and control peak formation with this system thanks to real-time measurement of the number concentrations, targeting the appropriate particle size classes corresponding to diameters of the aerosolised microorganisms. This generator, characterized by gentle aerosolisation and a capacity to produce bioaerosol peaks, may contribute to enrich laboratory experiments for numerous applications.