Tracing the Sources and Prevalence of Class 1 Integrons, Antimicrobial Resistance, and Trace Elements Using European Honey Bees.

Surveillance of antimicrobial resistance is essential for an effective One Health response. This study explores the efficacy of European honey bees (Apis mellifera) for biomonitoring antimicrobial resistance (AMR) in urban areas. Class 1 integrons (intI1) are investigated as a universal AMR indicator, as well as associated cassette arrays and trace element contaminants at a city-wide scale. Class 1 integrons were found to be pervasive across the urban environment, occurring in 52% (75/144) of the honey bees assessed. The area of waterbodies within the honey bee's foraging radius was associated with intI1 prevalence, indicating an exposure pathway for future investigation to address. Trace element concentrations in honey bees reflected urban sources, supporting the application of this biomonitoring approach. As the first study of intI1 in honey bees, we provide insights into the environmental transfer of bacterial DNA to a keystone species and demonstrate how intI1 biomonitoring can support the surveillance of AMR.

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.

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.

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.

Tracing nickel smelter emissions using European honey bees.

This study investigated trace element contamination in honey bees inhabiting urban areas around the South Pacific's largest and longest operating nickel smelter in Nouméa, New Caledonia. There remains a paucity of research on the environmental impact of nickel smelting, and to date, there has been no assessment of its effects on the popular practice of beekeeping, or whether honey bees are a suitable tracer for nickel smelting emissions. Honey bees and honey were sampled from 15 hives across Nouméa to ascertain linkages between nickel smelter emissions, environmental contamination, and trace element uptake by bees. Comparison of washed and unwashed bees revealed no significant difference in trace element concentrations, indicating trace elements bioaccumulate within the internal tissues of bees over time. Accordingly, trace element concentrations were higher in dead bees than those that were sampled live, with smelter related elements chromium, cobalt and nickel being significantly different at p < 0.05. Except for boron, trace element concentrations were consistently higher in bees than in honey, suggesting that the transfer of trace elements from bees during honey production is negligible. Elevated concentrations of potentially toxic trace elements including cobalt, chromium and nickel in bees declined with distance from smelting operations (Spearman's Rho, p < 0.05), indicating the relationship between environmental contamination and the uptake of trace elements by bees. The findings of this study emphasise potential environmental and human health risks associated with trace element contamination from nickel smelting operations and affirm the use of honey bees as a biomonitor of potentially harmful nickel smelting emissions.

Spatial distribution and composition of mine dispersed trace metals in residential soil and house dust: Implications for exposure assessment and human health.

Trace metal exposure from environmental sources remains a persistent global problem, particularly in communities residing adjacent to metal extraction and processing industries. This study examines front yard soil and house dust from 62 residences throughout the Australian Ag-Pb-Zn mining city of Broken Hill to better understand spatial variability in metal distributions, compositions and exposures across an industrially polluted urban environment. X-ray fluorescence analysis of paired soil/dust samples indicated that geomean concentrations (mg/kg) of Cu (32/113), Zn (996/1852), As (24/34) and Pb (408/587) were higher in house dust while Ti (4239/3660) and Mn (1895/1101) were higher in outdoor soil. Ore associated metals and metalloids (Mn, Zn, As, Pb) in soil and house dust were positively correlated and declined in concentration away from mining areas, the primary source of metalliferous emissions in Broken Hill. The rate of decline was not equivalent between soil and house dust, with the indoor/outdoor concentration ratio increasing with distance from mining areas for Zn/Pb (geomean = 1.25/1.05 (<1 km); 2.14/1.52 (1-2 km); 2.54/2.04 (>2 km)). House dust and Broken Hill ore Pb isotopic compositions (206Pb/207Pb; 208Pb/207Pb) were more similar in homes nearest to mining areas than those further away (geomean apportioned ore Pb = 88% (<1 km); 76% (1-2 km); 66% (>2 km)), reflecting spatial shifts in the balance of sources contributing to indoor contamination. Incorporation of house dust Pb reduced overestimation of IEUBK modelled blood Pb concentrations compared to when only soil Pb was used. These findings demonstrate that even in contexts where the source and environmental burden of metals are relatively apparent, geochemical relationships and exposures between outdoor and indoor environments are not always predictable, nor easily disaggregated.

Data for modelling vegetable uptake of trace metals in soil for the VegeSafe program.

Here we detail the soil to vegetable transfer factor (uptake) data and calculation procedures for vegetable trace metal uptake estimation that are presented in Taylor et al. (2021). Firstly, we present the literature review of trace metal uptake data, describing uptake from soil to vegetable produce determined in global experimental studies. After selecting the uptake factors most applicable to the VegeSafe dataset, using similar soil trace metal concentrations and studies that consider only the edible parts of plants, we applied these uptake factors to VegeSafe soils. Using this approach, we were able to estimate trace metal concentrations in home grown produce across the 3,609 homes included in our VegeSafe study. Using Australian and global food standards, we calculated the soil trace metal concentrations that would potentially result in exceedance of Australian and global food safety criteria. Our process followed the method detailed in the Australian soil guidelines (NEPM, 2013). Also presented are the numbers of individual samples and vegetable gardens that are likely to exceed food safety criteria in the three largest cities of Australia: Sydney, Melbourne and Brisbane. Individual household vegetable garden trace metal uptake data were aggregated across standarised geographic areas (Statistical Area Level 3) as established by the Australian Bureau of Statistics to visualise the geospatial distribution of potential trace metal risk from home produce. These modelled data provide the basis for prioritising locations, trace metals and soils for future empirically-based studies of trace metal contamination in home-grown produce.

A citizen science approach to identifying trace metal contamination risks in urban gardens.

We launched the VegeSafe program in 2013 to assist Australians concerned about exposure to contaminants in their soils and gardens. VegeSafe analyses garden soils provided by citizens for trace metals at our laboratory at little to no cost, with easy-to-follow guidance on any intervention required. The response was overwhelming-Australians submitted 17,256 soils from 3,609 homes, and in turn VegeSafe researchers now have unparalleled household-scale data, providing new insights into urban trace metal contamination. The results are sobering, with 35% of homes, particularly those that are older, painted and located in inner cities having soils above the Australian residential guideline (300 mg/kg) for the neurotoxic trace metal lead (Pb). Exposure pathway, blood Pb concentration and vegetable uptake modelling showed the communities in these locations were most at risk. VegeSafe is transformative: 94% of participants better understood contaminants, 83% felt safer in their home environment and 40% undertook remedial action based on their results. The two-way nature of this program enables education of citizens about environmental contaminants, advances public health, and delivers impactful science.

Anthropogenic contamination of residential environments from smelter As, Cu and Pb emissions: Implications for human health.

Communities in low-income and middle-income countries (LMIC) are disproportionally affected by industrial pollution compared to more developed nations. This study evaluates the dispersal and associated health risk of contaminant-laden soil and dust at a copper (Cu) smelter in Tsumeb, Namibia. It is Africa's only smelter capable of treating complex Cu ores that contain high arsenic (As) contents (<1%). The analyses focused on the primary trace elements associated with ore processing at the smelter: As, Cu, and lead (Pb). Portable X-Ray fluorescence spectrometry (pXRF) of trace elements in soils (n = 83) and surface dust wipes (n = 80) showed that elemental contamination was spatially associated with proximity to smelter operations. Soil concentrations were below US EPA soil guidelines. Dust wipe values were elevated relative to sites distal from the facility and similar to those at other international smelter locations (As = 1012 µg/m2 (95% CI 687-1337); Cu = 1838 µg/m2 (95% CI 1191-2485); Pb = 1624 µg/m2 (95% CI 862-2385)). Source apportionment for Pb contamination was assessed using Pb isotopic compositions (PbIC) of dust wipes (n = 22). These data revealed that the PbIC of 73% (n = 16/22) of these wipes corresponded to the PbIC of smelter slag and tailings, indicating contribution from industrial emissions to ongoing exposure risk. Modeling of carcinogenic risk showed that dust ingestion was the most important pathway, followed by inhalation, for both adults and children. Dermal contact to trace elements in dust was also determined to pose a carcinogenic risk for children, but not adults. Consequently, contemporary smelter operations remain an ongoing health risk to the surrounding community, in spite of recent efforts to improve emissions from the operations.