Impacts of Floods on the Indoor Air Microbial Burden

Abstract

Floods create a conducive environment for the proliferation of microbes in the indoor air by providing nutrients and moisture and by introducing new microbes from outdoors to indoors. Thus, it is important to better understand the level of proliferation and the characteristics of microbes in the indoor air of flooded built environments. In this work, we address these aspects in a flooded environment in India and investigate the changes in the indoor air microbial burden by comparing with the control (non-flooded) houses. Flooded houses within one month of water recession were compared with control houses. Microbes (bacteria, fungi) were characterized and endotoxins were quantified. Microbial concentrations were significantly higher in flooded houses than the control houses ( p < 0.05). The potential infectious bacterial genera Pantoea , Acinetobacter , and fungal genera Aspergillus and Penicillium were found dominant in the indoor air of flooded houses. Though these fungal genera were also present in the control houses, concentrations were higher ( p < 0.05) in the flooded houses. Multivariable regression analysis revealed that indoor air microbial burden was significantly and positively associated with outdoor air and outdoor soil. Further, antibiotic resistant bacteria (ARB) were found in both indoor air, and outdoor water sources (wells) of flooded houses. In our chlorine tests, the bacteria showed resistance to concentrations above 100 ppm, far exceeding those found in national and international guidelines. Bacteria were resistant to common antibiotics such as penicillin and ciprofloxacin.