Ten questions concerning indoor dust

Dust is ubiquitous but heterogeneous and can be viewed through various lenses. Indoor dust commonly refers to particles in building interiors that have settled onto surfaces, albeit without a consensus scientific definition. Dust contains a myriad of chemicals and microbes in a complex mixture originating from multiple sources. Indoor dust thus serves as both an indicator of the constituents in an indoor environment and a source of exposure through ingestion, dermal contact, and/or inhalation of resuspended dust. The mass and composition of settled dust within a building varies by location. This variability and complexity of dust manifests in different physical and chemical properties on macro-, micro- and nanoscales, which in turn influences occupant exposure pathways and outcomes. For example, resuspension of allergens (e.g., by walking) may exacerbate asthma. Sampling via methods such as vacuuming or surface wiping allows for quantitative measurement of components to assess possible exposures. However, through collection or measurements, results may be biased, e.g., size. With large variations in dust composition and study methods, it can be difficult to compare studies. This heterogeneity impedes understanding the fate and transport of dust and, importantly, how dust impacts health. A standardized system to better define, sample, and characterize dust would help develop a more comprehensive understanding of dust across indoor environments. This paper aims to address outstanding questions regarding the chemical and biological characteristics of dust, how the characterization of dust is affected by sampling methods, and how design of indoor spaces affects the amount and qualities of accumulated dust.