This study presents for the first time comprehensive measurements of the particle number size distribution (10 nm to 10 μm) together with next-generation sequencing analysis of airborne bacteria inside a dental clinic. A substantial enrichment of the indoor environment with new particles in all size classes was identified by both activities to background and indoor/outdoor (I/O) ratios. Grinding and drilling were the principal dental activities to produce new particles in the air, closely followed by polishing. Illumina MiSeq sequencing of 16S rRNA of bioaerosol collected indoors revealed the presence of 86 bacterial genera, 26 of them previously characterized as potential human pathogens. Bacterial species richness and concentration determined both by qPCR, and culture-dependent analysis were significantly higher in the treatment room. Bacterial load of the treatment room impacted in the nearby waiting room where no dental procedures took place. I/O ratio of bacterial concentration in the treatment room followed the fluctuation of I/O ratio of airborne particles in the biology-relevant size classes of 1-2.5, 2.5-5, and 5-10 μm. Exposure analysis revealed increased inhaled number of particles and microorganisms during dental procedures. These findings provide a detailed insight on airborne particles of both biotic and abiotic origin in a dental clinic.
Keywords: I/O ratio; airborne microorganisms; airborne particles; dental clinic; indoor sources; personal exposure.
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