‘Dustsafe’: investigating the microbiome and potentially harmful contaminants in house dusts to characterise human exposures to hazardous agents in the home environment

Jabeen, Khadija (2023) ‘Dustsafe’: investigating the microbiome and potentially harmful contaminants in house dusts to characterise human exposures to hazardous agents in the home environment. Doctoral thesis, Northumbria University.

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Abstract

The present study represents the first scientific foray of its kind for 21st century Britain into the most intimate environment known to man – the home. The residential unit is the one type of built environment a human being is likely to interact with the most across their lifespan. Vacuum dust samples were collected from 258 households across the UK, which represented a mix of housing types and geographic regions including England, Scotland, Northern Ireland and Wales. Geomean concentrations of trace elements in settled dust (< 250 μm) were determined as follows: Zn (506 mg/kg), Mn (238 mg/kg), Cu (125 mg/kg), Pb (102 mg/kg), Cr (56.1 mg/kg), Ni (32.5 mg/kg) and As (5.9 mg/kg). Recent renovation (within the last 5 years), garden access, house type, engagement with soil-handling hobbies (e.g. gardening), occupant density and smoking status were found to be significant predictors of indoor metal(loid) content and hence the extent of pollution in residential environments. 16S amplicon sequencing revealed a dust-based core microbiome comprised of Proteobacteria, Firmicutes, Actinobacteria, Bacteroidota and Cyanobacteria was found. At the genus level, this core microbiome was dominated by Staphylococcus, Pseudomonas, Sphingomonas, Acinetobacter and Corynebacterium species. A mean bacterial load of 4.37 x 106 CFU/g was determined for settled floor dust from the UK’s residential environments by culture-based methods. The reduction in bacterial loads when dust samples were sieved was found to be statistically significant, rendering it an important experimental consideration for future dust surveys. Canonical correlation analysis (CCA) indicated the greatest sensitivity of bacterial genera native to the dust samples to the Cu and Mn content. This is the first national study to provide an evidence base for the formulation of national policies with regards to the need for healthy housing across the UK with data that could be used by local authorities and councils to improve housing infrastructure and citizen advice. Suggested best practice measures include the strict utilisation of separate gardening gear and removal of this external to the home environment prior to entry into it, washing hands and feet after contact with soil, ensuring pets do not enter directly into the home environment after contact with soil, installing a rug at the front door of the property for dust removal, not smoking anywhere on the property’s premises and ideally overcoming the habit altogether, introducing age-related dust screening of properties prior to sale and similar dust monitoring of properties that have undergone renovation works.

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