Ambient bioaerosol indices for indoor air quality assessments of flood reclamation

Abstract

An air quality study was conducted in arid-region residences that were cleaned and reoccupied following a major regional flood (Arkansas River, Colorado, USA). This demonstration study leveraged a suite of aerosol measurements to assess the effects of common flood reclamation practices on indoor air quality. These assays included (i) optical counting (OPC) of airborne particulate matter (0.3– 5 μ m optical diameter), (ii) composite observations of volatile organic compounds (VOC), (iii) culturing and direct microscopic counts of airborne bacteria and fungi, and (iv) air-exchange rate measurements. As judged by OPC, most of the flood damaged homes surveyed had higher concentrations of airborne particulate matter indoors than outdoors; the same trend was observed for selected VOC. When compared to large literature databases, culturing from air samples collected in houses reclaimed from flood damage had significantly higher airborne microorganism levels than in houses where no flood damage had occurred—in many cases this difference was between two and three orders of magnitude. As determined by direct epifluorescence microscopy, total airborne microorganism concentrations were 3–1000 times higher than those recovered by conventional culturing. In flood damaged homes, biological particles averaged 52% of the total particles measured indoors, and 18% of the total particles measured immediately outdoors. Relative differences between the indoor and outdoor concentrations of airborne particulate matter, microorganisms, and associated VOCs, suggested that flood-impacted building materials were sustaining high aerosol bioburdens and contributing to poor indoor air quality more than 3 months after the structures had been reclaimed from flood damage.