Microplastics in settled indoor dust: Implications for human exposure

In recent years, microplastics (MPs) occurrence in indoor environments has raised significant concerns due to their distinctive physicochemical properties and potential toxicity. Indoor dust is well-documented as important vector for human exposure to emerging contaminants via inadvertent ingestion. Consequently, the main aim of the present study is to assess human exposure to MPs in settled indoor dust by determining concentrations, and characteristics (size, shape, and polymer type) of MPs in dust samples collected from houses (n = 30) and workplaces (n = 30) in Birmingham, UK. The average MPs concentrations were 155 ± 222 MP/mg in homes, and 125 ± 209 MP/mg in workplaces. Statistical analysis revealed the mean concentration of MPs in the studied homes was significantly higher than that in workplaces, which was attributed mainly to carpeting. In terms of morphology, various shapes of MPs (e.g., fiber, fragment, foam, foil) were identified, with fibres and fragments constituting ∼90 % of the identified MPs in all studied samples. Within the MPs particle size range (10–150 μm) investigated in the current study, the particle size fraction (50–100 μm) was predominant (>49 %) in all the studied samples, followed by particles >100 μm, with fibres having the largest average size (67 μm) among the detected MPs shapes. Polypropylene (PP) and Polyethylene Terephthalate (PET) were the most abundant polymer types in the studied samples, followed by Polyvinyl Chloride (PVC). Typical daily exposures of UK adults and toddlers to MPs through inadvertent ingestion of indoor dust were estimated at 56 and 103 MPs/day. The higher exposure of toddlers was exacerbated by their lower body weight with an estimated typical exposure of 9.7 MP/kg Bw/day, compared to 0.8 MP/kg Bw/day for adults. The higher ingestion exposure to MPs in toddlers raises concern over potential adverse health effects due to their incompletely developed immune and nervous systems.