Lead Speciation, Bioaccessibility, and Sources for a Contaminated Subset of House Dust and Soils Collected from Similar United States Residences.

Residential lead (Pb) exposure is of critical concern to families globally as Pb promotes severe neurological effects in children, especially those less than 5 years old, and no blood lead level is deemed safe by the US Center for Disease Control. House dust and soils are commonly thought to be important sources of Pb exposure. Probing the relationship between house dust and soil Pb is critical to understanding residential exposure, as Pb bioavailability is highly influenced by Pb sources and/or species. We investigated paired house dust and soil collected from homes built before 1978 to determine Pb speciation, source, and bioaccessibility with the primary goal of assessing chemical factors driving Pb exposure in residential media. House dust was predominately found to contain (hydro)cerussite (i.e., Pb (hydroxy)carbonate) phases commonly used in Pb-based paint that, in-turn, promoted elevated bioaccessibility (>60%). Pb X-ray absorption spectroscopy, µ-XRF mapping, and Pb isotope ratio analysis for house dust and soils support house dust Pb as chemically unique compared to exterior soils, although paint Pb is expected to be a major source for both. Soil pedogenesis and increased protection from environmental conditions (e.g., weathering) in households is expected to greatly impact Pb phase differences between house dust and soils, subsequently dictating differences in Pb exposure.

United States house dust Pb concentrations are influenced by soil, paint, and house age: insights from a national survey.

BACKGROUND: Lead (Pb) in house dust contributes significantly to blood lead levels (BLLs) in children which may result in dire health consequences. Assessment of house dust Pb in the United States, relationships with Pb in soil and paint, and residential factors influencing Pb concentrations are essential to probing drivers of house dust Pb exposure. OBJECTIVE: Pb concentrations in vacuum-collected house dust are characterized across 346 homes participating in the American Health Homes Survey II (AHHS II), a US survey (2018-2019) evaluating residential Pb hazards. Connections between house dust Pb and soil Pb, paint Pb, and other residential factors are evaluated, and dust Pb concentration data are compared to paired loading data to understand Pb hazard standard implications. RESULTS: Mean and median vacuum dust Pb concentrations were 124 µg Pb g-1 and 34 µg Pb g-1, respectively. Vacuum-collected dust concentrations and dust wipe Pb loading rates were significantly correlated within homes (α < 0.001; r ≥ 0.4). At least one wipe sample exceeded current house dust Pb loading hazard standards (10 µg ft-2 or 100 µg Pb ft-2 for floors and windowsills, respectively) in 75 of 346 homes (22%). House dust Pb concentrations were correlated with soil Pb (r = 0.64) and Pb paint (r = 0.57). Soil Pb and paint Pb were also correlated (r = 0.6). IMPACT: The AHHS II provides a window into the current state of Pb in and around residences. We evaluated the relationship between house dust Pb concentrations and two common residential Pb sources: soil and Pb-based paint. Here, we identify relationships between Pb concentrations from vacuum-collected dust and paired Pb wipe loading data, enabling dust Pb concentrations to be evaluated in the context of hazard standards. This relationship, along with direct ties to Pb in soil and interior/exterior paint, provides a comprehensive assessment of dust Pb for US homes, crucial for formulating effective strategies to mitigate Pb exposure risks in households.

A national survey of lead and other metal(loids) in residential drinking water in the United States.

BACKGROUND: Exposure to lead (Pb), arsenic (As) and copper (Cu) may cause significant health issues including harmful neurological effects, cancer or organ damage. Determination of human exposure-relevant concentrations of these metal(loids) in drinking water, therefore, is critical. OBJECTIVE: We sought to characterize exposure-relevant Pb, As, and Cu concentrations in drinking water collected from homes participating in the American Healthy Homes Survey II, a national survey that monitors the prevalence of Pb and related hazards in United States homes. METHODS: Drinking water samples were collected from a national survey of 678 U.S. homes where children may live using an exposure-based composite sampling protocol. Relationships between metal(loid) concentration, water source and house age were evaluated. RESULTS: 18 of 678 (2.6%) of samples analyzed exceeded 5 µg Pb L-1 (Mean = 1.0 µg L-1). 1.5% of samples exceeded 10 µg As L-1 (Mean = 1.7 µg L-1) and 1,300 µg Cu L-1 (Mean = 125 µg L-1). Private well samples were more likely to exceed metal(loid) concentration thresholds than public water samples. Pb concentrations were correlated with Cu and Zn, indicative of brass as a common Pb source is samples analyzed. SIGNIFICANCE: Results represent the largest national-scale effort to date to inform exposure risks to Pb, As, and Cu in drinking water in U.S. homes using an exposure-based composite sampling approach. IMPACT STATEMENT: To date, there are no national-level estimates of Pb, As and Cu in US drinking water collected from household taps using an exposure-based sampling protocol. Therefore, assessing public health impacts from metal(loids) in drinking water remains challenging. Results presented in this study represent the largest effort to date to test for exposure-relevant concentrations of Pb, As and Cu in US household drinking water, providing a critical step toward improved understanding of metal(loid) exposure risk.

Interconnected soil iron and arsenic speciation effects on arsenic bioaccessibility and bioavailability: a scoping review.

Extensive research has examined arsenic (As) bioavailability in contaminated soils and is routinely assessed using in vitro bioaccessibility (IVBA) assays. Analysis of differences in bioaccessibility measurements across IVBA assays and phases is expected to provide valuable insights into geochemical mechanisms controlling soil As bioaccessibility and bioavailability. Soil iron (Fe) content and As speciation are expected to significantly influence IVBA gastric and intestinal phases due to fluctuations in precipitation-dissolution chemistry and sorption reactivity as pH and assay chemical complexity changes. The aim of this review was to examine these relationships by 1) conducting a meta-analysis (n = 47 soils) determining the influence of total Fe on As bioaccessibility measurements and 5 IVBA assays and 2) investigating the effect of As speciation on gastric/intestinal phase IVBA and in vitro-in vivo correlations. Our findings indicate that soil Fe content and As speciation heterogeneity are important in elucidating variability of bioaccessibility measurements across IVBA assays and gastrointestinal phases. Greater focus on coupled As speciation and Fe precipitation chemistry may (1) improve our understanding of soil geochemical factors and assay constituents that influence As in vitro-in vivo correlations and (2) resolve variability in the precision of oral relative bioavailability (RBA) estimated using IVBA assays for soils possessing heterogenous As speciation and Fe composition.

Bioavailable soil Pb minimized by in situ transformation to plumbojarosite.

Exposure to lead (Pb) during early life has persistent adverse health effects. During childhood, ingestion of bioavailable Pb in contaminated soils can be a major route of Pb absorption. Remediation to alter physiochemical properties of soil-borne Pb can reduce Pb bioavailability. Our laboratory-based approach for soil Pb remediation uses addition of iron (Fe) sulfate and application of heat to promote formation of plumbojarosite (PLJ), a sparingly soluble Pb-Fe hydroxysulfate mineral. We treated two soils with anthropogenic Pb contamination and samples of clean topsoil spiked with various Pb compounds (i.e., carbonate, chloride, phosphate [P], or sulfate) to convert native Pb species to PLJ and used a mouse assay to assess relative bioavailability (RBA) of Pb in untreated (U) and remediated soils. Bone and blood Pb levels were significantly lower (P < 0.001, Student's t test) in mice that consumed diets amended with remediated soils than with U soils. Estimated RBA for Pb in both remediated natural soils and Pb-mineral spiked soils were reduced by >90% relative to Pb RBA for U soils, which is substantially more effective than other soil amendments, including P. X-ray absorption spectroscopy showed that >90% of all Pb species in remediated soils were converted to PLJ, and ingested PLJ was not chemically transformed during gastrointestinal tract transit. Post treatment neutralization of soil pH did not affect PLJ stability, indicating the feasibility in field conditions. These results suggest that formation of PLJ in contaminated soils can reduce the RBA of Pb and minimize this medium's role as a source of Pb exposure for young children.

High Lead Bioavailability of Indoor Dust Contaminated with Paint Lead Species.

House dust and soils can be major sources of lead (Pb) exposure for children. The American Healthy Homes Survey (AHHS) was developed to estimate Pb exposure from house dust and soil, in addition to other potential household contaminants and allergens. We have combined X-ray absorption spectroscopic (XAS) fingerprinting and in vivo mouse relative bioavailability (RBA) measurements for a subset of house dust and residential soils collected in the AHHS, with the primary objective of gaining a better understanding of determinants of house dust Pb bioavailability. Lead speciation was well related to variations in RBA results and revealed that highly bioavailable Pb (hydroxy)carbonate (indicative of Pb-based paint) was the major Pb species present in house dusts. Measured Pb RBA was up to 100% and is likely driven by paint Pb. To our knowledge, this is the first report of in vivo Pb RBA for U.S. house dust contaminated in situ with paint Pb and corroborates results from a previous study that demonstrated high RBA of paint Pb added to soil. We also report a relatively low RBA (23%) in a residential soil where the major Pb species was found to be plumbojarosite, consistent with a previous report that plumbojarosite lowers Pb RBA in soils.

Arthroscopic Subscapularis Repair Using a Subacromial View.

As a result of the continued improvement in arthroscopic equipment and techniques, subscapularis tears are now more reliably identified and are being repaired at higher rates than previously reported. Whereas small upper-border subscapularis tears can usually be effectively managed using an intra-articular view, larger tears often cannot be fully visualized with a standard 30° arthroscope when viewed from the posterior portal. These tears may require either using a 70° arthroscope or viewing through the standard 30° arthroscope from a subacromial portal-site location to completely visualize the tear. This article illustrates and discusses the advantages of using a subacromial-space portal site to view and arthroscopically manage large subscapularis tears.

Elevated Arsenic and Lead Concentrations in Natural Healing Clay Applied Topically as a Treatment for Ulcerative Dermatitis in Mice.

Ulcerative dermatitis in laboratory mice remains an ongoing clinical problem and animal welfare issue. Many products have been used to treat dermatitis in mice, with varying success. Recently, the topical administration of healing clays, such as bentonite and green clays, has been explored as a viable, natural treatment. We found high concentrations of arsenic and lead in experimental samples of therapeutic clay. Given the known toxic effects of these environmental heavy metals, we sought to determine whether the topical administration of a clay product containing bioavailable arsenic and lead exerted a biologic effect in mice that potentially could introduce unwanted research variability. Two cohorts of 20 singly housed, shaved, dermatitis free, adult male CD1 mice were dosed daily for 2 wk by topical application of saline or green clay paste. Samples of liver, kidney and whole blood were collected and analyzed for total arsenic and lead concentrations. Hepatic and renal concentrations of arsenic were not different between treated and control mice in either cohort; however, hepatic and renal concentrations of lead were elevated in clay treated mice compared to controls in both cohorts. In addition, in both cohorts, the activity of δ-aminolevulinate acid dehydratase, an enzyme involved with heme biosynthesis and a marker of lead toxicity, did not differ significantly between the clay-treated mice and controls. We have demonstrated that these clay products contain high concentrations of arsenic and lead and that topical application can result in the accumulation of lead in the liver and kidneys; however, these concentrations did not result in measurable biologic effects. These products should be used with caution, especially in studies of lead toxicity, heme biosynthesis, and renal α2 microglobulin function.

Lead speciation, bioaccessibility and source attribution in Missouri's Big River watershed.

The Southeast Missouri Lead District is among the most productive lead deposits exploited in modern times. Intensive mining conducted prior to regulations resulted in a legacy of lead contaminated soil, large piles of mine tailings and elevated childhood blood lead levels. This study seeks to identify the source of the lead contamination in the Big River and inform risk to the public. Isotopic analysis indicated the mine tailing piles at the head of the Big River are the primary source of the lead contamination. The isotopic signature of the lead in these mine tailings matched the lead over 100 km downstream. All of the other potential lead sources investigated had different isotopic signatures. Lead concentrations in soils and sediments decrease with distance downstream of the mine tailings piles. Additionally, the speciation of the lead changes from predominantly mineralized forms, such as galena, to adsorbed lead. This is reflected in the in-vitro bioaccessibility assay (IVBA) analysis which shows higher bioaccessibility further downstream, demonstrating the importance of speciation in risk evaluation.

Dietary Lead and Phosphate Interactions Affect Oral Bioavailability of Soil Lead in the Mouse.

Effects of dietary P level on the oral bioavailability of Pb present in soil were examined in a mouse model. Adult female C57BL/6 mice had free access to AIN-93G purified rodent diet amended with Pb as a soluble salt, Pb acetate, or in a soil matrix (NIST SRM 2710a). In these studies, the basal diet contained P at a nutritionally sufficient level (0.3% w/w) and the modified diets contained P at a lower (0.15%) or a higher (1.2%) level. For either dietary Pb source (Pb acetate or NIST SRM 2710a), low dietary P level markedly increased accumulation of Pb in bone, blood, and kidney. Tissue Pb levels in mice fed a high P in diet were not different from mice fed the basal P diet. Dietary P and Pb interacted to affect body weight change and feed efficiency in mice. The relative contribution of different Pb species in diet and feces was also affected by dietary P level. Differences in Pb species between diet and feces indicated that transformation of Pb species can occur during gastrointestinal tract transit. These interactions between Pb and P that alter Pb speciation may be important determinants of the bioavailability of Pb ingested in soil.

Long-Term in Situ Reduction in Soil Lead Bioavailability Measured in a Mouse Model.

Effects of different treatments on the bioavailability of lead (Pb) in soil from a smelter emission contaminated site in Joplin, Missouri, were evaluated in a mouse model. Similar estimates of relative bioavailability for Pb in untreated or treated soil were obtained in mice and in the well-established juvenile swine model. In the mouse model, treatments that used phosphate (phosphoric acid or triple superphosphate) combined with iron oxide or biosolids compost significantly reduced soil Pb bioavailability. Notably, effects of these remediation procedures were persistent, given that up to 16 years had elapsed between soil treatment and sample collection. Remediation of soils was associated with changes in Pb species present in soil. Differences in Pb species in ingested soil and in feces from treated mice indicated that changes in Pb speciation occurred during transit through the gastrointestinal tract. Use of the mouse model facilitates evaluation of remediation procedures and allows monitoring of the performance of procedures under laboratory and field conditions.

Characterization of engineered nanoparticles in commercially available spray disinfectant products advertised to contain colloidal silver.

Given the potential for human exposure to silver nanoparticles from spray disinfectants and dietary supplements, we characterized the silver-containing nanoparticles in 22 commercial products that advertised the use of silver or colloidal silver as the active ingredient. Characterization parameters included: total silver, fractionated silver (particulate and dissolved), primary particle size distribution, hydrodynamic diameter, particle number, and plasmon resonance absorbance. A high degree of variability between claimed and measured values for total silver was observed. Only 7 of the products showed total silver concentrations within 20% of their nominally reported values. In addition, significant variations in the relative percentages of particulate vs. soluble silver were also measured in many of these products reporting to be colloidal. Primary silver particle size distributions by transmission electron microscopy (TEM) showed two populations of particles - smaller particles (<5nm) and larger particles between 20 and 40nm. Hydrodynamic diameter measurements using nanoparticle tracking analysis (NTA) correlated well with TEM analysis for the larger particles. Z-average (Z-Avg) values measured using dynamic light scattering (DLS); however, were typically larger than both NTA or TEM particle diameters. Plasmon resonance absorbance signatures (peak absorbance at around 400nm indicative of metallic silver nanoparticles) were only noted in 4 of the 9 yellow-brown colored suspensions. Although the total silver concentrations were variable among products, ranging from 0.54mg/L to 960mg/L, silver containing nanoparticles were identified in all of the product suspensions by TEM.

Total and Bioaccessible Soil Arsenic and Lead Levels and Plant Uptake in Three Urban Community Gardens in Puerto Rico.

Arsenic (As) and lead (Pb) are two contaminants of concern associated with urban gardening. In Puerto Rico, data currently is limited on As and Pb levels in urban garden soils, soil metal (loid) bioaccessibility, and uptake of As and Pb in soil by edible plants grown in the region. This study examined total and bioaccessible soil As and Pb concentrations and accumulation in 10 commonly grown garden plants collected from three urban community gardens in Puerto Rico. Bioavailability values were predicted using bioaccessibility data to compare site-specific bioavailability estimates to commonly used default exposure assumptions. Total and bioaccessible As levels in study soils ranged from 2 to 55 mg/kg and 1 to 18 mg/kg, respectively. Total and bioaccessible Pb levels ranged from 19 to 172 mg/kg and 17 to 97 mg/kg, respectively. Measured bioaccessibility values corresponded to 19 to 42% bioaccessible As and 61 to 100% bioaccessible Pb when expressed as a percent of total As and Pb respectively. Predicted relative percent bioavailability of soil As and Pb based on measured bioaccessibility values ranged from 18 to 36% and 51 to 85% for As and Pb respectively. Transfer factors (TFs) measuring uptake of As in plants from soil ranged from 0 to 0.073 in the edible flesh (fruit or vegetable) of plant tissues analyzed and 0.073 to 0.444 in edible leaves. Pb TFs ranged from 0.002 to 0.012 in flesh and 0.023 to 0.204 in leaves. Consistent with TF values, leaves accumulated higher concentrations of As and Pb than the flesh, with the highest tissue concentrations observed in the culantro leaf (3.2 mg/kg dw of As and 8.9 mg/kg dw of Pb). Leaves showed a general but not statistically-significant (α = 0.05) trend of increased As and Pb concentration with increased soil levels, while no trend was observed for flesh tissues. These findings provide critical data that can improve accuracy and reduce uncertainty when conducting site-specific risk determination of potential As and Pb exposure while gardening or consuming garden produce in the understudied region of Puerto Rico.

In vivo and in vitro methods for evaluating soil arsenic bioavailability: relevant to human health risk assessment.

Arsenic (As) is the most frequently occurring contaminant on the priority list of hazardous substances, which lists substances of greatest public health concern to people living at or near U.S. National Priorities List site. Accurate assessment of human health risks from exposure to As-contaminated soils depends on estimating its bioavailability, defined as the fraction of ingested As absorbed across the gastrointestinal barrier and available for systemic distribution and metabolism. Arsenic bioavailability varies among soils and is influenced by site-specific soil physical and chemical characteristics and internal biological factors. This review describes the state-of-the science that supports our understanding of oral bioavailability of soil As, the methods that are currently being explored for estimating soil As relative bioavailability (RBA), and future research areas that could improve our prediction of the oral RBA of soil As in humans. The following topics are addressed: (1) As soil geochemistry; (2) As toxicology; (3) in vivo models for estimating As RBA; (4) in vitro bioaccessibility methods; and (5) conclusions and research needs.

Five-year minimum clinical and radiographic outcomes of total shoulder arthroplasty using a hybrid glenoid component with a central porous titanium post.

BACKGROUND: To determine the effectiveness of hybrid glenoid components in reducing the frequency of glenoid component loosening, we evaluated clinical and radiographic outcomes at a minimum 5-year follow-up in 45 shoulders that underwent total shoulder arthroplasty (TSA) using a system with a central porous titanium post to augment the cemented peripheral pegs. METHODS: Function and pain were evaluated with the American Shoulder and Elbow Surgeons Standardized Shoulder Assessment score, visual analog scale, active shoulder range of motion, and strength. Postoperative radiographs were analyzed for radiolucent lines, progressive loosening, and at-risk signs. RESULTS: The mean American Shoulder and Elbow Surgeons score improved from 40.4 to 83.7 (P < .0001) and the mean visual analog scale from 5.9 to 0.8 (P < .0001). Forward elevation improved from 113° to 151° (P < .001), internal rotation from 49° to 60° (P = .035), and mean external rotation from 36° to 50° (P = .0006). Radiographs showed glenoid component radiolucency in 29 shoulders. Radiolucencies were confined to the area under the glenoid faceplate in 6 and were only around the central post in 13. Nine TSAs (20%) demonstrated 2 or more columns of involvement but were not judged to be at-risk. One implant (2.2%) had glenoid component failure and was revised to a hemiarthroplasty. CONCLUSION: Anatomic TSA using a hybrid glenoid component with a central porous titanium post demonstrated a low rate of mechanical failure and a rate of radiolucent lines comparable to reports of all polyethylene implants. Further evaluations are needed to demonstrate the long-term durability of these implants and to determine the significance and fate of the radiolucent lines, particularly relative to the central post.

Relating soil geochemical properties to arsenic bioaccessibility through hierarchical modeling.

Interest in improved understanding of relationships among soil properties and arsenic (As) bioaccessibility has motivated the use of regression models for As bioaccessibility prediction. However, limits in the numbers and types of soils included in previous studies restrict the usefulness of these models beyond the range of soil conditions evaluated, as evidenced by reduced predictive performance when applied to new data. In response, hierarchical models that consider variability in relationships among soil properties and As bioaccessibility across geographic locations and contaminant sources were developed to predict As bioaccessibility in 139 soils on both a mass fraction (mg/kg) and % basis. The hierarchical approach improved the estimation of As bioaccessibility in studied soils. In addition, the number of soil elements identified as statistically significant explanatory variables increased when compared to previous investigations. Specifically, total soil Fe, P, Ca, Co, and V were significant explanatory variables in both models, while total As, Cd, Cu, Ni, and Zn were also significant in the mass fraction model and Mg was significant in the % model. This developed hierarchical approach provides a novel tool to (1) explore relationships between soil properties and As bioaccessibility across a broad range of soil types and As contaminant sources encountered in the environment and (2) identify areas of future mechanistic research to better understand the complexity of interactions between soil properties and As bioaccessibility.

Relationship Between Total and Bioaccessible Lead on Children's Blood Lead Levels in Urban Residential Philadelphia Soils.

Relationships between total soil or bioaccessible lead (Pb), measured using an in vitro bioaccessibility assay, and children's blood lead levels (BLL) were investigated in an urban neighborhood in Philadelphia, PA, with a history of soil Pb contamination. Soil samples from 38 homes were analyzed to determine whether accounting for the bioaccessible Pb fraction improves statistical relationships with children's BLLs. Total soil Pb concentration ranged from 58 to 2821 mg/kg; the bioaccessible Pb concentration ranged from 47 to 2567 mg/kg. Children's BLLs ranged from 0.3 to 9.8 µg/dL. Hierarchical models were used to compare relationships between total or bioaccessible Pb in soil and children's BLLs. Total soil Pb concentration as the predictor accounted for 23% of the variability in child BLL; bioaccessible soil Pb concentration as the predictor accounted for 26% of BLL variability. A bootstrapping analysis confirmed a significant increase in R2 for the model using bioaccessible soil Pb concentration as the predictor with 99.0% of bootstraps showing a positive increase. Estimated increases of 1.3 µg/dL and 1.5 µg/dL in BLL per 1000 mg/kg Pb in soil were observed for this study area using total and bioaccessible Pb concentrations, respectively. Children's age did not contribute significantly to the prediction of BLLs.

In vitro bioaccessibility of copper azole following simulated dermal transfer from pressure-treated wood.

Micronized copper azole (MCA) and micronized copper quaternary (MCQ) are the latest wood preservatives to replace the liquid alkaline copper and chromated copper arsenate preservatives due to concerns over the toxicity or lack of effectiveness of the earlier formulations. Today, the use of MCA has become abundant in the wood preservative industry with approximately 38millionlbs of copper carbonate being used to treat lumber each year. Despite this widespread usage, little information is available on the bioaccessibility of this preservative upon gastrointestinal exposure. Using a simulated hand-to-mouth/gastric system exposure study we investigated several types of commercially available copper-treated lumber products as-purchased and after exposure to outdoor weathering conditions. Soluble and particulate fractions of copper were measured after transfer to and release from surface wipes passed along copper-treated lumber and exposed to synthetic stomach fluid (SSF, pH1.5) or deionized (DI) water. Wipes passed along new boards contained greater amounts of copper than wipes from weathered boards. The total copper recovered from the wipes after microwave extraction varied among the different wood types. For all wood types the copper released into SSF was more soluble than what was soluble in DI water. The data suggest that copper from treated wood is highly bioaccessible in SSF regardless of wood type and weathering condition.

Influences of Coal Ash Leachates and Emergent Macrophytes on Water Quality in Wetland Microcosms.

The storage of coal combustion residue (CCR) in surface water impoundments may have an impact on nearby water quality and aquatic ecosystems. CCR contains leachable trace elements that can enter nearby waters through spills and monitored discharge. It is important, therefore, to understand their environmental fate in affected systems. This experiment examined trace element leachability into freshwater from fly ash (FA), the most common form of CCR. The effects on water quality of FA derived from both high and low sulfur coal sources as well as the influences of two different emergent macrophytes, Juncus effusus and Eleocharis quadrangulata, were evaluated in wetland microcosms. FA leachate dosings increased water electric conductivity (EC), altered pH, and, most notably, elevated the concentrations of boron (B), molybdenum (Mo), and manganese (Mn). The presence of either macrophyte species helped reduce elevated EC, and B, Mo, and Mn concentrations over time, relative to microcosms containing no plants. B and Mo appeared to bioaccumulate in the plant tissue from the water when elevated by FA dosing, while Mn was not higher in plants dosed with FA leachates. The results of this study indicate that emergent macrophytes could help ameliorate downstream water contamination from CCR storage facilities and could potentially be utilized in wetland filtration systems to treat CCR wastewater before discharge. Additionally, measuring elevated B and Mo in aquatic plants may have potential as a monitoring tool for downstream CCR contamination.

Estimating relative bioavailability of soil lead in the mouse.

Lead (Pb) in soil is an important exposure source for children. Thus, determining bioavailability of Pb in soil is critical in evaluating risk and selecting appropriate strategies to minimize exposure. A mouse model was developed to estimate relative bioavailability of Pb in NIST SRM 2710a (Montana 1 Soil). Based on Pb levels in tissues, the mean relative bioavailability of this metal in this soil was 0.5. Estimates of relative bioavailabilities derived from mouse compared favorably with those obtained in juvenile swine. The mouse model is thus an efficient and inexpensive method to obtain estimates of relative bioavailability of soil Pb.