Comparison of Gastric versus Gastrointestinal PBET Extractions for Estimating Oral Bioaccessibility of Metals in House Dust

Carcinogenic metal(loid)s in house dust compared to soil: Concentrations and gastric bioaccessibility

As a sink and a source of chemicals, house dust represents a relevant medium to assess indoor exposure to metal(loid)s via incidental ingestion or inhalation. However, nationally representative indoor data are scarce. Results from the Canadian House Dust Study (CHDS, 2007-2010; n = 1025) provide nationally representative mean, median and 95th percentile concentrations for 38 elements in typical urban house dust, along with their gastric bioaccessibility. Total concentrations (median/95th percentile) of carcinogenic metal(loid)s in Canadian house dust (μg g-1) are as follows: As (9.0/40), Be (0.4/0.9), Cd (3.5/17), Co (5.6/19), Cr (99/214), Ni (62/322) and Pb (100/760). Total As and Pb concentrations in house dust exceed residential soil guidelines for the protection of human health in about one-third of Canadian homes. Percent bioaccessibilities (median) are: Cd (65%) > Pb (63%) > Be ∼ Ni (36%) > Co (35%) > As (20%) > Cr (15%). Lead, Cd and Co concentrations are significantly greater in older houses (< 1976). Data from two pilot studies (n = 66 + 51) further demonstrate the distinct geochemistry of house dust compared to soils, notably enrichment of carcinogenic metal(loid)s and their increased bioaccessibility. These results provide essential baseline values to refine risk assessment and inform on health risk at contaminated sites.

Human Health and Ecological Risks Associated with Total and Bioaccessible Concentrations of Cadmium and Lead in Urban Park Soils

This study investigated the total and bioaccessible concentrations of cadmium (Cd) and lead (Pb) in urban soils and their associated human health and ecological risk. Total and bioaccessible metal concentrations were found within the safe limits except for Cd, surpassing the State Environmental Protection Administration (SEPA) China limit in 9.5% of parks. Bioaccessible concentrations were higher in the gastric (G) phase than the intestinal (I) phase, while Cd showed more bioaccessibility compared to Pb. Bioaccessible concentrations reduced Hazard Quotient (HQ_ing) values by 2-22 times and 0-2 times for children and adults, respectively, while hazard index (HI) declined by 1.7 times, and the mean total bioaccessible risk of Pb decreased by 20.8 times. Further, the study revealed a low level of contamination factor (CF < 1) and a low degree of contamination (CD < 6), and Potential Ecological Risk Index (PERI) values for all the cities were less than 150, indicating low ecological risk.

Estimating the proportion of bioaccessible lead (BaPb) in household dust wipe samples: a comparison of IVBA and PBET methods

Established methods for using standardized dust wipes to collect and measure total lead in household dust are readily available but the use of dust wipes to measure bioaccessible lead (BaPb) is less clear. This study compared two in vitro methods for estimating the proportion of BaPb in dust collected into dust wipes including the US-EPA's in-vitro bioaccessible assay (IVBA) method at two pH (1.5 and 2.5) values; and the physiologically based extraction test (PBET 2.5 pH). Two types of simulated household dust samples (Pb-soil contaminated and Pb-paint contaminated) each with three Pb concentrations were created. Equal amounts of simulated dust were applied to a smooth surface and collected following the standard EPA dust wipe protocol and were analyzed for BaPb and total Pb (ASTM-E1644-17, ICP-OES). Estimated BaPb levels differed significantly by the method of extraction. Mean percent BaPb were IVBA pH 1.5, > 90% (Pb-paint) and 59-63% (Pb-soil); IVBA pH 2.5 78-86% (Pb-paint) and 45-50% (Pb-soil); PBET pH 2.5 56 to 61% (Pb-paint) and 41-50% Pb-soil). Particularly for lead-paint contaminated dust, PBET showed significantly greater discrimination as suggested by the broader range of BaPb values and closer approximation to total lead concentrations in simulated household dust samples.

Human health risk assessment and geochemical mobility of rare earth elements in Amazon soils

Rare earth elements (REEs) are a grouping of elements that encompasses lanthanides, yttrium and scandium due to their similar chemical properties and occurrence in ore deposits. Over the past few decades, economic interest in REEs has increased due to their use in several types of industries such as high-tech, medicine and agriculture. Extraction of REEs has been followed, in general, by incorrect disposal of tailing and waste, creating hazardous conditions in several countries. However, the magnitude of the possible impacts on ecosystem and human health are relatively unknown, especially in tropical systems. Thus, the objectives of this study were to assess the geochemical mobility and the bioaccessibility of REEs based on a series of chemical extractions and in vitro essay. We also tested two promising simple protocols (0.01 mol L^-1 CaCl₂ and 0.43 mol L^-1 HNO₃) for measuring REE bioaccessible fractions through a single extraction. Our findings show that the bioavailable fractions represent less than 20% of the ΣREEs fraction in all soil samples examine. Similarly, the oral bioaccessibility obtained by two in vitro methods (Gastric protocol and Gastric-Intestinal protocol) and by the single extraction tests represented less than 20% of the ΣREE contents. The non-carcinogenic risks and the carcinogenic risks associated to REEs oral exposure were low for children and adults. The extractions with 0.01 mol L^-1 CaCl₂ showed great potential as a method for measuring the REEs bioaccessible fraction.

Oral and inhalation bioaccessibility of potentially toxic elements in household dust from former Hg mining district, Idrija, Slovenia

One of the main sources of potential chronic exposure to potentially toxic elements is household dust, especially in an environment with known point sources of PTE pollution. The literature review clearly shows that the total concentrations of an element in the environment do not provide information to predict its bioavailability. The aim of the present study was to evaluate the oral and inhalation bioaccessibility of PTE present in household dust in the small town of Idrija, the site of the former mercury mine. Unified bioaccessibility method was used to assess oral bioaccessibility of PTE in the stomach and intestine, while inhalation bioaccessibility was assessed by extraction of household dust samples with two synthetic extraction solutions-Gamble's solution (GS) and artificial lysosomal fluid (ALF). A low bioaccessibility of mercury was observed in all synthetic solutions (less than 3%). The highest bioaccessibility of PTE was observed in ALF solution, especially for Zn, Pb and Cd. Only a slightly lower bioaccessibility of these three elements was also observed in the stomach, while the bioaccessibility of other elements in the gastric phase was less than 40%. In general, the bioaccessibility of all elements decreased in the intestine. With the exception of Cr, the lowest bioaccessibility of the elements was observed in GS. Daily ingestion and inhalation doses of PTE from household dust were calculated and their values were below the available recommended or tolerable daily intakes of PTE from food according to the European Food Safety Authority.

Tracing the sources of bioaccessible metal(loid)s in urban environments: A multidisciplinary approach

Understanding the links between sources of magnetic particles and bioaccessibility of metal(loids) in environmental sampling media is crucial for better evaluating human health risks, although relevant information in the scientific literature is scarce. Here, soil, road and house dust samples from a heavy industrial area in Greece were characterized in a multidisciplinary study combining magnetic measurements, SEM/EDS analyses, bioaccessibility measurements and Pb isotopic analyses of bioaccessible Pb. The oral and inhalable bioaccessible fractions of As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn were assessed by applying simulated gastric and lung solutions. SEM/EDS analysis revealed the abundant presence of anthropogenic Fe-containing spherules of industrial origin in all sampling media, often containing minor contents of Cr, Cu, Mn, Pb and Zn. The inhalation bioaccessibility (%) in all environmental compartments was higher than the oral one for most elements analyzed in the present study. Clear associations between magnetic susceptibility and bioaccessible amounts of most of analyzed elements were encountered for the soil and road dust. The isotopic analyses of bioaccessible Pb showed that there are significant differences in the isotopic ratios between total and bioaccessible Pb. We conclude that Pb solubilized by the simulated gastric and lung extractions is principally anthropogenic, representing a mixture of industrial Pb and Pb related to the past usage of leaded petrol. Low values of ²⁰⁶Pb/²⁰⁷Pb were accompanied by high bioaccessible contents of Cd, Pb and Zn indicating that anthropogenic (mostly industrial) sources exert influence on the bioaccessible forms of these metals. Coupling magnetic and bioaccessibility measurements with stable isotopic technique of bioaccessible Pb is more reliable for determining Pb and other metal sources with high oral and inhalation bioaccessibility.

Thoracic Fraction (PM10) of Resuspended Urban Dust: Geochemistry, Particle Size Distribution and Lung Bioaccessibility

A fluidized bed aerosol generator was connected to a 13-stage cascade impactor (nanoMOUDI) for the size fractionation of urban dust (<10 µm), followed by the gravimetric analysis of loaded PTFE filter samples. This method was used to characterize the PM10 (thoracic) fraction of road dust sampled from expressways, arterial roads and local roads in Toronto, Canada. The fine particle fractions (<1.8 µm) of all the studied samples accounted for 51–72% of the resuspended PM10 (by weight). Elemental analysis using ICP-MS and ICP-OES revealed an overall trend of element enrichment in the <1.8 µm fraction compared to the coarse fraction (1.8–10 µm) of the road dust. By contrast, archived house dust samples displayed the reverse trend for most elements. The lung bioaccessibility of target elements (Al, B, Ba, Co, Cr, Fe, La, Mn, Mo, Sb, Sr, Ti, V and Zn) was assessed for each road dust fraction using 0.1 M ammonium citrate (pH 4.4) to simulate intracellular fluid and Gamble solution (pH 7.2) to simulate interstitial lung fluid. The <1.8 µm fraction of local road dust displayed significantly higher bioaccessibility (p < 0.05) for Zn when using Gamble solution, and for seven out of the 14 target elements when using ammonium citrate. These results show the importance of characterizing the fine fraction of road dust.

Biogeochemistry of Household Dust Samples Collected from Private Homes of a Portuguese Industrial City

The main objectives of the present study were to (i) investigate the effects of mineralogy and solid-phase distribution on element bioaccessibility and (ii) perform a risk assessment to calculate the risks to human health via the ingestion pathway. Multiple discriminant analysis showed that the dust chemistry discriminates between indoor and outdoor samples. The solid-phase distribution of the elements in indoor dust indicated that a large proportion of zinc, nickel, lead, copper, and cobalt is associated with an aluminum oxy-hydroxides component, formed by the weathering of aluminum silicates. This component, which seems to influence the mobility of many trace elements, was identified for a group of indoor dust samples that probably had a considerable contribution from outdoor dust. An iron oxide component consisted of the highest percentage of chromium, arsenic, antimony, and tin, indicating low mobility for these elements. The bioaccessible fraction in the stomach phase from the unified BARGE method was generally high in zinc, cadmium, and lead and low in nickel, cobalt, copper, chromium, and antimony. Unlike other potentially toxic elements, copper and nickel associated with aluminum oxy-hydroxides and calcium carbonates were not extracted by the stomach solutions. These trace elements possibly form stable complexes with gastric fluid constituents such as pepsin and amino acid. Lead had a hazard quotient >1, which indicates the risk of non-carcinogenic health effects, especially for children.

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.

Opportunities for evaluating chemical exposures and child health in the United States: the Environmental influences on Child Health Outcomes (ECHO) Program

The Environmental Influences on Child Health Outcomes (ECHO) Program will evaluate environmental factors affecting children's health (perinatal, neurodevelopmental, obesity, respiratory, and positive health outcomes) by pooling cohorts composed of >50,000 children in the largest US study of its kind. Our objective was to identify opportunities for studying chemicals and child health using existing or future ECHO chemical exposure data. We described chemical-related information collected by ECHO cohorts and reviewed ECHO-relevant literature on exposure routes, sources, and environmental and human monitoring. Fifty-six ECHO cohorts have existing or planned chemical biomonitoring data for mothers or children. Environmental phenols/parabens, phthalates, metals/metalloids, and tobacco biomarkers are each being measured by ≥15 cohorts, predominantly during pregnancy and childhood, indicating ample opportunities to study child health outcomes. Cohorts are collecting questionnaire data on multiple exposure sources and conducting environmental monitoring including air, dust, and water sample collection that could be used for exposure assessment studies. To supplement existing chemical data, we recommend biomonitoring of emerging chemicals, nontargeted analysis to identify novel chemicals, and expanded measurement of chemicals in alternative biological matrices and dust samples. ECHO's rich data and samples represent an unprecedented opportunity to accelerate environmental chemical research to improve the health of US children.

Bioaccessibility and relative oral bioavailability of cobalt and nickel in residential soil and dust affected by metal grinding operations

Including measures of relative bioavailability (RBA) improves the accuracy of site-specific risk assessment when evaluating metals bound in matrices that resist acid digestion (alloys, slag, tailings). In vitro gastrointestinal bioaccessibility and in vivo RBA assessments were conducted using baghouse dust, surface dust, and soil collected in a neighborhood near a metal forge, which emitted metals in the form of corrosion resistant alloys. The study objective was to characterize the in vitro bioaccessibility and relative bioavailability (RBA) of cobalt and nickel when ingested as freely soluble forms (ionic salts used as the basis for oral toxicity criteria), compared to when incidentally ingested in the forms found in the environment. Test materials and standard reference materials-cobalt chloride and nickel sulfate-were administered daily for 14 or 21 days, twice daily, to juvenile swine. Daily intake doses for cobalt were ≤229 μg/kg-day, and for nickel, ≤1419 μg/kg-day. Concentrations of cobalt and nickel were measured in various tissues; 24-hour urinary excretion of each metal was also measured. Multiple linear regression modeling was performed for tissue concentration or urinary excretion vs. dose in each material, with weighting as inverse variance in each dose group. Liver, urine, and kidney provided the optimal data. Although RBA values were affected by limited absolute bioavailability of cobalt and nickel in reference materials, trends across the different biological matrices consistently showed significantly reduced bioavailability of cobalt and nickel in soil and dust, with RBAs ranging from 0.2% to 12%. Bioaccessibility of cobalt and nickel in soil and dust were 1% to 5%, and similar results were found for baghouse dust. The data demonstrate that cobalt and nickel in soil and dust affected by alloys are resistant to bioelution and absorption. This study provides useful information for site-specific risk assessments and insights for planning future research.

Assessment of oral and lung bioaccessibility of Cd and Pb from smelter-impacted dust

Soil and dust contamination by metals engenders significant environmental and health problems in northern France where a lead smelter was in activity for more than a century. This study aims to examine the long-term effects of the smelter, 10 years after its closedown, on the presence of metal in sidewalk dust for a better assessment of the local population's exposure to Cd and Pb. The investigation included: (i) the metal distribution in different dust particle sizes and (ii) the assessment of metal bioaccessibility via ingestion and inhalation of dust. Seventy-two sidewalk dust samples were collected using a dust-sampling vacuum. The samples were sieved to collect different particle sizes from 0.3 to 1000 μm. The unified bioaccessibility method (UBM) was employed to evaluate the oral bioaccessibility of metals in the different particle sizes. The pulmonary bioaccessible fraction of Cd and Pb via the finest particles was extracted with lung-simulating solution (artificial lysosomal fluid). Ten years after the smelter closedown, (i) a strong relationship was observed between the concentrations of metals in dust and the distance to the former smelter, whatever the particle size; (ii) both total and oral bioaccessible concentrations of metals were high in the finest fraction (0.3-5 μm) and decreased when the particle size increased; (iii) a higher oral bioaccessibility of Cd and Pb was measured in the gastric phase (on average 43% for both metals for all particle sizes) and compared to the gastrointestinal phase (on average 16% for both metals for all particle sizes); and (iv) metal bioaccessibility via inhalation of dust was relatively high (on average 74 and 69%, for Cd and Pb, respectively). The results of the present study suggest that this environmental compartment may be a sensitive and effective indicator of anthropogenic metal contamination and the human exposure in urban areas.