Sources, pathways and concentrations of potentially toxic trace metals in home environments.

Despite ongoing concerns about trace metal and metalloid (trace metals) exposure risks from indoor dust, there has been limited research examining their sources and relationship to outdoor soils. Here we determine the concentrations and sources for potentially toxic trace metals arsenic (As), chromium (Cr), copper (Cu), manganese (Mn), lead (Pb) and zinc (Zn) and their pathways into homes in Sydney, Australia, using home-matched indoor dust (n = 166), garden soil (n = 166), and road dust samples (n = 51). All trace metals were more elevated indoors versus their matched garden soil counterparts. Indoor Cu and Zn dust concentrations were significantly more enriched than outdoor dusts and soils, indicating indoor sources were more relevant for these elements. By contrast, even though Pb was elevated in indoor dust, garden soil concentrations were correspondingly high, indicating that it remains an important source and pathway for indoor contamination. Elevated concentrations of As, Pb and Zn in garden soil and indoor dust were associated with home age (>50 years), construction materials, recent renovations and deteriorating interior paint. Significant correlations (p < 0.05) between road dust and garden soil Cu concentrations, and those of As and Zn in soil and indoor dust, and Pb across all three media suggest common sources. Scanning electron microscopy (SEM) analysis of indoor dust samples (n = 6) showed that 57% of particles were derived from outdoor sources. Lead isotopic compositions of soil (n = 21) and indoor dust (n = 21) were moderately correlated, confirming the relevance of outdoor contaminants to indoor environments. This study illustrates the source, relationship and fate of trace metals between outdoor and indoor environments. The findings provide insight into understanding and responding to potentially toxic trace metal exposures in the home environment.

Portable X-ray fluorescence spectrometry: a cost-effective method for analysing trace metals in deposited dust.

For projects requiring extensive environmental sampling and rapid decision-making to identify trace metal contamination using dust wipes, the cost and time required for wet chemistry analysis can be prohibitive. Under such circumstances there is a need for a suitable screening method that is cost-effective, efficient, and portable. To address this need, this study investigated the utility of portable X-ray fluorescence (pXRF) for the analysis of trace metals in dust wipes. Here, 316 dust wipe samples from three different geographical settings co-located with mining and smelting operations were investigated for their trace metal loadings (µg m-2) of arsenic (As), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn) using pXRF. Results collected using pXRF were compared against inductively coupled plasma mass spectrometry (ICP-MS) concentrations using matched dust wipes (n = 87) to assess reproducibility. A subset of dust wipes (n = 4) were subject to different pXRF analytical scenarios (ranging from 1 to 12 pXRF measurements) using a standardised test duration of 30 seconds to identify the most efficient number of tests for analytical precision. Conducting four pXRF tests on a single wipe (total exposure time of 120 seconds) returned comparable results to ICP-MS and was adopted for analysis of all samples. Results from dust wipes analysed with both ICP-MS and pXRF (n = 87) showed moderate to strong Spearman Rho correlations (rs = 0.489-0.956, p < 0.01) and linear regression coefficients of variation demonstrated good agreement between methods (R2 = 0.432-0.989, p < 0.05). Linear regression equations were used to correct pXRF data to the ICP-MS dust wipe data for samples analysed by both approaches, and applied to pXRF data that were not subject to ICP-MS analysis (n = 229). Application of the correction formula resulted in a substantial improvement of pXRF's accuracy and precision, confirming its effectiveness for assessing trace metals in dust wipes.