ABSTRACT: The chemical composition of dust particles in typical urban homes has been the focus of a nationally representative study entitled “”The Canadian House Dust Study”. The study’s first priority was to quantify lead contamination in dust, which can be a significant source of exposure for toddlers and pre-schoolers who accidentally ingest dust through normal hand-to-mouth activities. Later the Canadian House Dust Study examined a host of other inorganic and organic chemical compounds that accumulate in dust after being released from consumer products, furniture, building materials, coatings, combustion products, tracked-in soil and infiltrated ambient particles. Results for hundreds of compounds have been reported in a series of publications which collectively show that the ability of settled house dust to accumulate chemical compounds makes it an excellent indicator of residential contamination.
This presentation focuses on the relationship between the chemical composition of indoor air particulate matter (PM) and settled house dust (1). There is abundant evidence in the literature that re-suspended house dust contributes to indoor airborne particulate matter (PM). Despite this evidence, usage of settled dust concentration data has been generally limited to estimating chemical exposures via the ingestion pathway, and not the inhalation pathway. Lab experiments using archived Canadian House Dust Study samples showed that resuspended dust particles in the <10 µm size range (known as PM10 or the “inhalable fraction”) tend to have higher trace element concentrations than the bulk dust samples (<80 µm size range) from which the PM10 was derived. The same trend was observed in a residential study in Windsor, Ontario which compared the elemental composition of dust collected from living room floors with airborne PM samples collected from the same rooms. Most importantly, the residential study showed significant correlations between elemental concentrations in the matched PM10 and settled house dust samples. These results provided strong evidence that resuspended dust significantly influences the composition of indoor air PM. Additionally, concentrations of many elements were elevated in the inhalable fraction (<10 µm) of settled dust from heavily carpeted homes compared to homes with little or no carpeting. This observation is particularly significant given that higher rates of resuspension are associated with carpets than with bare floors. It is concluded that house dust makes a very useful sampling medium for investigating inhalation exposures in indoor residential environments – not just exposures to metal compounds but also to the myriad of synthetic organic chemicals such as plasticizers, flame retardants, and pesticides that are found in house dust.
(1) Rasmussen, P.E., Levesque, C., M Chénier, M., Gardner, H.D. (2018) Contribution of metals in resuspended dust to indoor and personal inhalation exposures: Relationships between PM10 and settled dust. Building and Environment 143: 513-522. doi.org/10.1016/j.buildenv.2018.07.044
BRIEF BIO: Dr. Pat Rasmussen is a Research Scientist with Health Canada where she has focussed on indoor exposures to particle-bound contaminants for the past 20 years, and is the principle investigator of “The Canadian House Dust Study.” Pat obtained her MSc degree from U of Toronto, and her BSc and PhD degrees from U of Waterloo, and has been an Adjunct Professor at U of Ottawa since 1999.