Kirk G Scheckel - Profile on Academia.edu (original) (raw)

Papers by Kirk G Scheckel

Journal of Toxicology and Environmental Health, Jan 16, 2018

Interest in improved understanding of relationships among soil properties and arsenic (As) bioacc... more 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 percent basis. The hierarchical approach improved the estimation of As bioaccessibility in study soils. Additionally, the number of soil elements identified as statistically significant explanatory variables increased when compared to previous studies. 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 percent model. The hierarchical approach developed in this study provides a novel tool to explore relationships between soil properties and As bioaccessibility across a broad range of soil types and As contaminant sources encountered in the environment and identifies areas of future mechanistic research to better understand the complexity of interactions between soil properties and As bioaccessibility.

Journal of Environmental Quality, 2013

2012 IJGGC-Hari-Dai-Christina-etal

Successful Conversion of Pb-Contaminated Soils to Low-Bioaccessibility Plumbojarosite Using Potassium-Jarosite at Ambient Temperature

Applied Geochemistry, 2020

The Southeast Missouri Lead District is among the most productive lead deposits exploited in mode... more 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.

Journal of Environmental Quality, 2012

Excessive Cu concentrations in water systems can negatively aff ect biological systems. Because C... more Excessive Cu concentrations in water systems can negatively aff ect biological systems. Because Cu can form strong associations with organic functional groups, we examined the ability of biochar (an O-C-enriched organic bioenergy by-product) to sorb Cu from solution. In a batch experiment, KOH steam-activated pecan shell biochar was shaken for 24 h in pH 6, 7, 8, or 9 buff ered solutions containing various Cu concentrations to identify the eff ect of pH on biochar Cu sorption. Afterward, all biochar solids from the 24-h shaking period were air-dried and analyzed using X-ray absorption fi ne structure (XAFS) spectroscopy to determine solid-phase Cu speciation. In a separate batch experiment, biochar was shaken for 30 d in pH 6 buff ered solution containing increasing Cu concentrations; the Cu sorption maximum was calculated based on the exponential rise to a maximum equation. Biochar sorbed increasing amounts of Cu as the solution pH decreased from 9 to 6. Th e XAFS spectroscopy revealed that Cu was predominantly sorbed onto a biochar organic phase at pH 6 in a molecular structure similar to Cu adsorbed on model humic acid (Cu-humic acid [HA]). Th e XAFS spectra at pH 7, 8, and 9 suggested that Cu was associated with the biochar as three phases: (i) a complex adsorbed on organic ligands similar to Cu-HA, (ii) carbonate phases similar to azurite (Cu 3 (CO 3) 2 (OH 2)), and (iii) a Cu oxide phase like tenorite (CuO). Th e exponential rise equation fi t to the incubated samples predicted a Cu sorption maximum of 42,300 mg Cu kg −1. Th e results showed that KOH steam-activated pecan shell biochar could be used as a material for sorbing excess Cu from water systems, potentially reducing the negative eff ects of Cu in the environment.

Plumbojarosite formation in contaminated soil to mitigate childhood exposure to lead, arsenic and antimony

Journal of Hazardous Materials, 2021

In this study, a novel method for lead (Pb) immobilization was developed in contaminated soils us... more In this study, a novel method for lead (Pb) immobilization was developed in contaminated soils using iron (III) (Fe3+) in conjunction with 0.05 M H2SO4. During method optimization, a range of microwave treatment times, solid to solution ratios, and Fe2(SO4)3/H2SO4 concentrations were assessed using a mining/smelting impacted soil (BHK2, Pb: 3031 mg/kg), followed by treatment of additional Pb contaminated soils (PP, Pb: 1506 mg/kg, G10, Pb: 2454 mg/kg and SoFC-1, Pb: 6340 mg/kg) using the optimized method. Pb bioaccessibility was assessed using USEPA Method 1340, with Pb speciation determined by X-ray Absorption (XAS) spectroscopy. Treatment efficacy was also validated using an in vivo mouse assay, where Pb accumulation in femur, kidney and liver was assessed to confirm in vitro bioaccessibility outcomes. Results showed that Pb bioaccessibility could be reduced by 77.4-97.0% following treatment of soil with Fe2(SO4)3 (0.4-1.0 M), H2SO4 (0.05 M) at 150 °C for 60 min in a closed microwave system. Results of bioavailability assessment demonstrated treatment effect ratio of 0.06-0.07 in femur, 0.06-0.27 in kidney and 0.06-0.11 in liver (bioavailability reduction between 73% and 93%). Formation of plumbojarosite in treated soils was confirmed by XAS analysis.

Critical Reviews in Environmental Science and Technology, 2017

Metal and metalloid contamination of soil and sediment is a widespread problem both in urban and ... more Metal and metalloid contamination of soil and sediment is a widespread problem both in urban and rural areas throughout the United States (U.S. EPA, 2014). Beneficial use of waste byproducts as amendments to remediate metal-contaminated soils and sediments can provide major economic and environmental advantages on both a site-specific and national scale. These waste by-products can also reduce our need to mine virgin materials or produce synthetic materials for amendments. Waste by-products must not be hazardous or pose unacceptable risk to human health and the environment, and should be a suitable replacement for virgin and synthetic materials. This review serves to present the state of science on in situ remediation of metal-contaminated soil and sediment and the potential for beneficial usage of waste by-product materials. Not all unintended consequences can be fully understood or predicted prior to implementing a treatment option, however some realized, and potentially unrealized, benefits and unintended consequences are explored.

Advances in assessing bioavailability of metal (loid) s in contaminated soils

... sound. A vast amount of knowledge clearly illustrates the decisive role of metal speciation w... more ... sound. A vast amount of knowledge clearly illustrates the decisive role of metal speciation when metal bioavailability and phytoavailability in the environment have to be assessed ( [McNear et al., 2007] and [Ryan et al., 2004] ). ...

2012 IJGGC-Hari-Dai-Christina-etal

Environmental Health Perspectives, 2021

Proceedings of the National Academy of Sciences, 2020

Exposure to lead (Pb) during early life has persistent adverse health effects. During childhood, ... more 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...

Environmental Science & Technology, 2019

Soil Systems, 2018

Arsenic (As) is one of the most widespread, toxic elements in the environment, and human activiti... more Arsenic (As) is one of the most widespread, toxic elements in the environment, and human activities have resulted in a large number of contaminated areas. However abundant, the potential of As toxicity from exposure to contaminated soils is limited to the fraction that will dissolve in the gastrointestinal system and be absorbed into systemic circulation or bioavailable species. In part, the release of As from contaminated soil to gastrointestinal fluid depends on the form of solid phase As, also termed "As speciation". In this study, 27 As-contaminated soils and solid wastes were analyzed using X-ray absorption spectroscopy (XAS) and results were compared to in vivo bioavailability values determined using the adult mouse and juvenile swine bioassays. Arsenic bioavailability was lowest for soils that contained large amounts of arsenopyrite and highest for materials that contained large amounts of ferric arsenates. Soil and solid waste type and properties rather than the contamination source had the greatest influence on As speciation. Principal component analysis determined that As(V) adsorbed and ferric arsenates were the dominant species that control As speciation in the selected materials. Multiple linear regression (MLR) was used to determine the ability of As speciation to predict bioavailability. Arsenic speciation was predictive of 27% and 16% of Relative Bioavailable (RBA) As determined using the juvenile swine and adult mouse models, respectively. Arsenic speciation can provide a conservative estimate of RBA As using MLR for the juvenile swine and adult mouse bioassays at 55% and 53%, respectively.

Environment International, 2019

An elementary scheme is detailed for introducing certain basic concepts in the solution of (espec... more An elementary scheme is detailed for introducing certain basic concepts in the solution of (especially) the basic second-order ordinary differential equations of classical mathematical physics. The method proposed, an integration/iteration process, allows the development of (generally Frobenius) power series, as well as exposing the rudiments of the Green function approach to solving linear ordinary differential equations. The method assumes only a background knowledge compatible with most introductory calculus courses.

Soil Systems, 2018

Soluble lead (Pb) can be immobilized in pure systems as pyromorphite through the addition of phos... more Soluble lead (Pb) can be immobilized in pure systems as pyromorphite through the addition of phosphorus (P) sources; however, uncertainties remain in natural systems. Knowledge of point zero charge (PZC) is important to predict the ionization of functional groups and their interaction with metal species in solution. This study utilized Pb-and As-contaminated soils to determine the combined effect of pH with respect to PZC and different rates of P-application on pyromorphite formation as well as Pb and arsenic (As) bioaccessibility as impacted by speciation changes. Solution chemistry analysis along with synchrotron-based Pb-and As-speciation as well as bioaccessibility treatment effect ratios (TERs) were conducted. Results indicated no significant effect of PZC on pyromorphite formation in P-amended soils; however, the TER Pb appeared significantly lower at pH > pH PZC and higher at pH < pH PZC (α = 0.05). In contrast, the TER As was significantly higher at pH > pH PZC compared to the other two treatments for the tested soils. The lack of conversion of soil Pb to pyromorphite may be attributed to several reasons including the presence of highly stable minerals, such as plumbojarosite, limiting soluble Pb availability to react with phosphates, high Fe and S content in IKS, high organic matter in BO, and high Ca content in NW.

Environmental science & technology, Jan 25, 2018

Effects of different soil amendment treatments on the bioavailability of lead (Pb) in soil from a... more Effects of different soil amendment 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, chemical and physical remediation strategies using 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 treatments 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...

Environmental health perspectives, Aug 1, 2018

The diet is emerging as the dominant source of arsenic exposure for most of the U.S. population. ... more The diet is emerging as the dominant source of arsenic exposure for most of the U.S. population. Despite this, limited regulatory efforts have been aimed at mitigating exposure, and the role of diet in arsenic exposure and disease processes remains understudied. In this brief, we discuss the evidence linking dietary arsenic intake to human disease and discuss challenges associated with exposure characterization and efforts to quantify risks. In light of these challenges, and in recognition of the potential longer-term process of establishing regulation, we introduce a framework for shorter-term interventions that employs a field-to-plate food supply chain model to identify monitoring, intervention, and communication opportunities as part of a multisector, multiagency, science-informed, public health systems approach to mitigation of dietary arsenic exposure. Such an approach is dependent on coordination across commodity producers, the food industry, nongovernmental organizations, he...

Journal of Toxicology and Environmental Health, Jan 16, 2018

Interest in improved understanding of relationships among soil properties and arsenic (As) bioacc... more 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 percent basis. The hierarchical approach improved the estimation of As bioaccessibility in study soils. Additionally, the number of soil elements identified as statistically significant explanatory variables increased when compared to previous studies. 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 percent model. The hierarchical approach developed in this study provides a novel tool to explore relationships between soil properties and As bioaccessibility across a broad range of soil types and As contaminant sources encountered in the environment and identifies areas of future mechanistic research to better understand the complexity of interactions between soil properties and As bioaccessibility.

Journal of Environmental Quality, 2013

2012 IJGGC-Hari-Dai-Christina-etal

Successful Conversion of Pb-Contaminated Soils to Low-Bioaccessibility Plumbojarosite Using Potassium-Jarosite at Ambient Temperature

Applied Geochemistry, 2020

The Southeast Missouri Lead District is among the most productive lead deposits exploited in mode... more 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.

Journal of Environmental Quality, 2012

Excessive Cu concentrations in water systems can negatively aff ect biological systems. Because C... more Excessive Cu concentrations in water systems can negatively aff ect biological systems. Because Cu can form strong associations with organic functional groups, we examined the ability of biochar (an O-C-enriched organic bioenergy by-product) to sorb Cu from solution. In a batch experiment, KOH steam-activated pecan shell biochar was shaken for 24 h in pH 6, 7, 8, or 9 buff ered solutions containing various Cu concentrations to identify the eff ect of pH on biochar Cu sorption. Afterward, all biochar solids from the 24-h shaking period were air-dried and analyzed using X-ray absorption fi ne structure (XAFS) spectroscopy to determine solid-phase Cu speciation. In a separate batch experiment, biochar was shaken for 30 d in pH 6 buff ered solution containing increasing Cu concentrations; the Cu sorption maximum was calculated based on the exponential rise to a maximum equation. Biochar sorbed increasing amounts of Cu as the solution pH decreased from 9 to 6. Th e XAFS spectroscopy revealed that Cu was predominantly sorbed onto a biochar organic phase at pH 6 in a molecular structure similar to Cu adsorbed on model humic acid (Cu-humic acid [HA]). Th e XAFS spectra at pH 7, 8, and 9 suggested that Cu was associated with the biochar as three phases: (i) a complex adsorbed on organic ligands similar to Cu-HA, (ii) carbonate phases similar to azurite (Cu 3 (CO 3) 2 (OH 2)), and (iii) a Cu oxide phase like tenorite (CuO). Th e exponential rise equation fi t to the incubated samples predicted a Cu sorption maximum of 42,300 mg Cu kg −1. Th e results showed that KOH steam-activated pecan shell biochar could be used as a material for sorbing excess Cu from water systems, potentially reducing the negative eff ects of Cu in the environment.

Plumbojarosite formation in contaminated soil to mitigate childhood exposure to lead, arsenic and antimony

Journal of Hazardous Materials, 2021

In this study, a novel method for lead (Pb) immobilization was developed in contaminated soils us... more In this study, a novel method for lead (Pb) immobilization was developed in contaminated soils using iron (III) (Fe3+) in conjunction with 0.05 M H2SO4. During method optimization, a range of microwave treatment times, solid to solution ratios, and Fe2(SO4)3/H2SO4 concentrations were assessed using a mining/smelting impacted soil (BHK2, Pb: 3031 mg/kg), followed by treatment of additional Pb contaminated soils (PP, Pb: 1506 mg/kg, G10, Pb: 2454 mg/kg and SoFC-1, Pb: 6340 mg/kg) using the optimized method. Pb bioaccessibility was assessed using USEPA Method 1340, with Pb speciation determined by X-ray Absorption (XAS) spectroscopy. Treatment efficacy was also validated using an in vivo mouse assay, where Pb accumulation in femur, kidney and liver was assessed to confirm in vitro bioaccessibility outcomes. Results showed that Pb bioaccessibility could be reduced by 77.4-97.0% following treatment of soil with Fe2(SO4)3 (0.4-1.0 M), H2SO4 (0.05 M) at 150 °C for 60 min in a closed microwave system. Results of bioavailability assessment demonstrated treatment effect ratio of 0.06-0.07 in femur, 0.06-0.27 in kidney and 0.06-0.11 in liver (bioavailability reduction between 73% and 93%). Formation of plumbojarosite in treated soils was confirmed by XAS analysis.

Critical Reviews in Environmental Science and Technology, 2017

Metal and metalloid contamination of soil and sediment is a widespread problem both in urban and ... more Metal and metalloid contamination of soil and sediment is a widespread problem both in urban and rural areas throughout the United States (U.S. EPA, 2014). Beneficial use of waste byproducts as amendments to remediate metal-contaminated soils and sediments can provide major economic and environmental advantages on both a site-specific and national scale. These waste by-products can also reduce our need to mine virgin materials or produce synthetic materials for amendments. Waste by-products must not be hazardous or pose unacceptable risk to human health and the environment, and should be a suitable replacement for virgin and synthetic materials. This review serves to present the state of science on in situ remediation of metal-contaminated soil and sediment and the potential for beneficial usage of waste by-product materials. Not all unintended consequences can be fully understood or predicted prior to implementing a treatment option, however some realized, and potentially unrealized, benefits and unintended consequences are explored.

Advances in assessing bioavailability of metal (loid) s in contaminated soils

... sound. A vast amount of knowledge clearly illustrates the decisive role of metal speciation w... more ... sound. A vast amount of knowledge clearly illustrates the decisive role of metal speciation when metal bioavailability and phytoavailability in the environment have to be assessed ( [McNear et al., 2007] and [Ryan et al., 2004] ). ...

2012 IJGGC-Hari-Dai-Christina-etal

Environmental Health Perspectives, 2021

Proceedings of the National Academy of Sciences, 2020

Exposure to lead (Pb) during early life has persistent adverse health effects. During childhood, ... more 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...

Environmental Science & Technology, 2019

Soil Systems, 2018

Arsenic (As) is one of the most widespread, toxic elements in the environment, and human activiti... more Arsenic (As) is one of the most widespread, toxic elements in the environment, and human activities have resulted in a large number of contaminated areas. However abundant, the potential of As toxicity from exposure to contaminated soils is limited to the fraction that will dissolve in the gastrointestinal system and be absorbed into systemic circulation or bioavailable species. In part, the release of As from contaminated soil to gastrointestinal fluid depends on the form of solid phase As, also termed "As speciation". In this study, 27 As-contaminated soils and solid wastes were analyzed using X-ray absorption spectroscopy (XAS) and results were compared to in vivo bioavailability values determined using the adult mouse and juvenile swine bioassays. Arsenic bioavailability was lowest for soils that contained large amounts of arsenopyrite and highest for materials that contained large amounts of ferric arsenates. Soil and solid waste type and properties rather than the contamination source had the greatest influence on As speciation. Principal component analysis determined that As(V) adsorbed and ferric arsenates were the dominant species that control As speciation in the selected materials. Multiple linear regression (MLR) was used to determine the ability of As speciation to predict bioavailability. Arsenic speciation was predictive of 27% and 16% of Relative Bioavailable (RBA) As determined using the juvenile swine and adult mouse models, respectively. Arsenic speciation can provide a conservative estimate of RBA As using MLR for the juvenile swine and adult mouse bioassays at 55% and 53%, respectively.

Environment International, 2019

An elementary scheme is detailed for introducing certain basic concepts in the solution of (espec... more An elementary scheme is detailed for introducing certain basic concepts in the solution of (especially) the basic second-order ordinary differential equations of classical mathematical physics. The method proposed, an integration/iteration process, allows the development of (generally Frobenius) power series, as well as exposing the rudiments of the Green function approach to solving linear ordinary differential equations. The method assumes only a background knowledge compatible with most introductory calculus courses.

Soil Systems, 2018

Soluble lead (Pb) can be immobilized in pure systems as pyromorphite through the addition of phos... more Soluble lead (Pb) can be immobilized in pure systems as pyromorphite through the addition of phosphorus (P) sources; however, uncertainties remain in natural systems. Knowledge of point zero charge (PZC) is important to predict the ionization of functional groups and their interaction with metal species in solution. This study utilized Pb-and As-contaminated soils to determine the combined effect of pH with respect to PZC and different rates of P-application on pyromorphite formation as well as Pb and arsenic (As) bioaccessibility as impacted by speciation changes. Solution chemistry analysis along with synchrotron-based Pb-and As-speciation as well as bioaccessibility treatment effect ratios (TERs) were conducted. Results indicated no significant effect of PZC on pyromorphite formation in P-amended soils; however, the TER Pb appeared significantly lower at pH > pH PZC and higher at pH < pH PZC (α = 0.05). In contrast, the TER As was significantly higher at pH > pH PZC compared to the other two treatments for the tested soils. The lack of conversion of soil Pb to pyromorphite may be attributed to several reasons including the presence of highly stable minerals, such as plumbojarosite, limiting soluble Pb availability to react with phosphates, high Fe and S content in IKS, high organic matter in BO, and high Ca content in NW.

Environmental science & technology, Jan 25, 2018

Effects of different soil amendment treatments on the bioavailability of lead (Pb) in soil from a... more Effects of different soil amendment 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, chemical and physical remediation strategies using 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 treatments 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...

Environmental health perspectives, Aug 1, 2018

The diet is emerging as the dominant source of arsenic exposure for most of the U.S. population. ... more The diet is emerging as the dominant source of arsenic exposure for most of the U.S. population. Despite this, limited regulatory efforts have been aimed at mitigating exposure, and the role of diet in arsenic exposure and disease processes remains understudied. In this brief, we discuss the evidence linking dietary arsenic intake to human disease and discuss challenges associated with exposure characterization and efforts to quantify risks. In light of these challenges, and in recognition of the potential longer-term process of establishing regulation, we introduce a framework for shorter-term interventions that employs a field-to-plate food supply chain model to identify monitoring, intervention, and communication opportunities as part of a multisector, multiagency, science-informed, public health systems approach to mitigation of dietary arsenic exposure. Such an approach is dependent on coordination across commodity producers, the food industry, nongovernmental organizations, he...