Indoor bioaerosol dynamics

Nazaroff, William W

There are many reasons to be interested in the microbiology of the built environment. The context for this study derives from three primary concerns. First, exposure to bioaerosol material can cause or can contribute to many important diseases. Second, adverse respiratory symptoms correlate well with indicators of indoor dampness (Fisk et al., 2007) . It is a reasonable hypothesis, although not yet well established, that the underlying cause of these associations is microbial. Third, the microbiology of spaces we occupy may influence the human microbiome in ways that could confer health benefits. Evidence for this last point is admittedly thin. There is growing evidence that people influence the microbiology of the spaces they inhabit (e.g., Lax et al., 2014) . Emerging evidence also indicates that some aspects of the human microbiome are important for health (Grice and Segre, 2012) . We further know that aspects of our personal microbiome can be influenced by individual factors such as diet and illness. So, it is not a large stretch to imagine that elements of our personal microbiome that matter for health might in fact be influenced by attributes of the spaces we inhabit, including their microbiology generally and their bioaerosol aspects specifically. Hanski et al. (2012) reported evidence supporting an analogous suggestion: 'rapidly declining biodiversity may be a contributing factor to . . . the rapidly increasing prevalence of allergies and other chronic inflammatory diseases among urban populations. . .. ' Following the introduction, the study is organized into two main sections. In 'Framing the issues,' I define a framework for considering indoor bioaerosol dynamics. That section also defines the scope and limitations of this study. It presents some empirical evidence about indoor bioaerosols to help establish a context for studying dynamics. The section outlines the use of a material balance as a first-principles method for linking process to outcome for indoor bioaerosols. The size of particles is described as a primary variable of concern. Regional deposition of bioaerosol particles in the respiratory tract is described as a process linking concentrations and exposure to dose. Opportunities and limitations for progress in understanding indoor bioaerosol dynamics are strongly influenced by measurement technology, so some of the key measurement methods are summarized. Evidence regarding infectious disease transmission by airborne routes is also assembled.