International Analysis of Sources and Human Health Risk Associated with Trace Metal Contaminants in Residential Indoor Dust.

People spend increasing amounts of time at home, yet the indoor home environment remains understudied in terms of potential exposure to toxic trace metals. We evaluated trace metal (and metalloid) concentrations (As, Cu, Cr, Mn, Ni, Pb, and Zn) and health risks in indoor dust from homes from 35 countries, along with a suite of potentially contributory residential characteristics. The objective was to determine trace metal source inputs and home environment conditions associated with increasing exposure risk across a range of international communities. For all countries, enrichments compared to global crustal values were Zn > Pb > Cu > As > Cr > Ni; with the greatest health risk from Cr, followed by As > Pb > Mn > Cu > Ni > Zn. Three main indoor dust sources were identified, with a Pb-Zn-As factor related to legacy Pb sources, a Zn-Cu factor reflecting building materials, and a Mn factor indicative of natural soil sources. Increasing home age was associated with greater Pb and As concentrations (5.0 and 0.48 mg/kg per year of home age, respectively), as were peeling paint and garden access. Therefore, these factors form important considerations for the development of evidence-based management strategies to reduce potential risks posed by indoor house dust. Recent findings indicate neurocognitive effects from low concentrations of metal exposures; hence, an understanding of the home exposome is vital.

The relevance of particle size distribution and bioaccessibility on human health risk assessment for trace elements measured in indoor dust.

Trace metal contaminants in indoor dust pose a significant potential exposure risk to people because of the time spent indoors and the readily ingested and inhaled fine-grained composition of indoor dusts. However, there is limited trace metal data available on the specific interaction of dust particle size fraction and their respective bioaccessibility/bioavailability and its consequent effect on health risk assessment. This study addresses this knowledge gap by examining bioaccessible and bioavailable trace element concentrations (As, Cr, Cu, Mn, Ni, Pb, Zn) in 152 discrete size fractions from 38 indoor vacuum samples from a larger dataset (n = 376) of indoor dust from Sydney, Australia. Arsenic, Cu, Ni, Pb and Zn were most concentrated in the 90-150 µm fraction with Cr and Mn being more concentrated in < 45 µm fraction. Dust particle size fractions < 45 µm, 45-90 µm, 90-150 µm and 150-250 µm were analysed for their individual gastric phase (G-alone) in vitro trace element bioaccessibilities. Lead exposure risk was estimated using the United States Environmental Protection Agency's Integrated Exposure Uptake Biokinetic (IEUBK) children's model. Mean Pb bioaccessibility was 59.6%, 42%, 62% and 62.2% for < 45 µm, 45-90 µm, 90-150 µm, and 150-250 µm, respectively. Mean Pb absolute bioavailability (ABA) was lower at 26.2%, 18.4%, 27.2% and 27.3% for size fractions < 45 µm, 45-90 µm, 90-150 µm, and 150-250 µm, respectively. The predicted blood Pb (PbB) levels for a hypothetical child aged 1 to 3 years for each of the dust particle size fractions was > 5 µg/dL. Lead concentrations measured in the selected dust samples show a potential for adverse health impacts on young children with the greatest risk being from indoor dust sized 90-150 µm.

Human exposure and risk associated with trace element concentrations in indoor dust from Australian homes.

This study examines residential indoor dust from 224 homes in Sydney, Australia for trace element concentrations measured using portable X-ray Fluorescence (pXRF) and their potential risk of harm. Samples were collected as part of a citizen science program involving public participation via collection and submission of vacuum dust samples for analysis of their As, Cr, Cu, Mn, Ni, Pb and Zn concentrations. The upper 95% confidence level of the mean values for 224 samples (sieved to <250 µm) were 20.2 mg/kg As, 99.8 mg/kg Cr, 298 mg/kg Cu, 247 mg/kg Mn, 56.7 mg/kg Ni, 364 mg/kg Pb and 2437 mg/kg Zn. The spatial patterns and variations of the metals indicate high homogeneity across Sydney, but with noticeably higher Pb values in the older areas of the city. Potential hazard levels were assessed using United States Environmental Protection Agency's (US EPA) carcinogenic, non-carcinogenic and Integrated Exposure Uptake Biokinetic (IEUBK) model human health risk assessment tools for children and adults. US EPA hazard indexes (HI) for Cr and Pb were higher than the safe level of 1.0 for children. HI > 1 suggests potential non-carcinogenic health effects. Carcinogenic risks were estimated for As, Cr and Pb whose carcinogenic slope factors (CSF) were available. Only the risk factor for Cr exceeded the US EPA's carcinogenic threshold (1 × 10-4) for children. Children aged 1-2 years had the highest predicted mean child blood lead (PbB) of 4.6 µg/dL, with 19.2% potentially having PbB exceeding 5 µg/dL and 5.80% exceeding 10 µg/dL. The Cr and Pb levels measured in indoor dust therefore pose potentially significant adverse health risks to children.