11 results on '"Diamond, Gary L."'
Search Results
2. Estimating relative bioavailability of soil lead in the mouse.
- Author
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Bradham KD, Green W, Hayes H, Nelson C, Alava P, Misenheimer J, Diamond GL, Thayer WC, and Thomas DJ
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- Animals, Biological Availability, Environmental Monitoring, Female, Mice, Mice, Inbred C57BL, Risk Assessment, Tissue Distribution, Lead pharmacokinetics, Soil Pollutants pharmacokinetics
- Abstract
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.
- Published
- 2016
- Full Text
- View/download PDF
3. Amending soils with phosphate as means to mitigate soil lead hazard: a critical review of the state of the science.
- Author
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Scheckel KG, Diamond GL, Burgess MF, Klotzbach JM, Maddaloni M, Miller BW, Partridge CR, and Serda SM
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- Animals, Biological Availability, Environmental Monitoring, Humans, Lead pharmacokinetics, Models, Animal, Soil Pollutants pharmacokinetics, Solubility, Environmental Restoration and Remediation, Lead chemistry, Phosphates chemistry, Soil chemistry, Soil Pollutants chemistry
- Abstract
Ingested soil and surface dust may be important contributors to elevated blood lead (Pb) levels in children exposed to Pb contaminated environments. Mitigation strategies have typically focused on excavation and removal of the contaminated soil. However, this is not always feasible for addressing widely disseminated contamination in populated areas often encountered in urban environments. The rationale for amending soils with phosphate is that phosphate will promote formation of highly insoluble Pb species (e.g., pyromorphite minerals) in soil, which will remain insoluble after ingestion and, therefore, inaccessible to absorption mechanisms in the gastrointestinal tract (GIT). Amending soil with phosphate might potentially be used in combination with other methods that reduce contact with or migration of contaminated soils, such as covering the soil with a green cap such as sod, clean soil with mulch, raised garden beds, or gravel. These remediation strategies may be less expensive and far less disruptive than excavation and removal of soil. This review evaluates evidence for efficacy of phosphate amendments for decreasing soil Pb bioavailability. Evidence is reviewed for (1) physical and chemical interactions of Pb and phosphate that would be expected to influence bioavailability, (2) effects of phosphate amendments on soil Pb bioaccessibility (i.e., predicted solubility of Pb in the GIT), and (3) results of bioavailability bioassays of amended soils conducted in humans and animal models. Practical implementation issues, such as criteria and methods for evaluating efficacy, and potential effects of phosphate on mobility and bioavailability of co-contaminants in soil are also discussed.
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- 2013
- Full Text
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4. Issues related to time averaging of exposure in modeling risks associated with intermittent exposures to lead.
- Author
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Lorenzana RM, Troast R, Klotzbach JM, Follansbee MH, and Diamond GL
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- Environmental Exposure, Humans, Models, Theoretical, Risk, Risk Assessment, Software, Time Factors, Environmental Monitoring methods, Lead pharmacokinetics, Lead Poisoning, Soil Pollutants analysis
- Abstract
Typical exposures to lead often involve a mix of long-term exposures to relatively constant exposure levels (e.g., residential yard soil and indoor dust) and highly intermittent exposures at other locations (e.g., seasonal recreational visits to a park). These types of exposures can be expected to result in blood lead concentrations that vary on a temporal scale with the intermittent exposure pattern. Prediction of short-term (or seasonal) blood lead concentrations arising from highly variable intermittent exposures requires a model that can reliably simulate lead exposures and biokinetics on a temporal scale that matches that of the exposure events of interest. If exposure model averaging times (EMATs) of the model exceed the shortest exposure duration that characterizes the intermittent exposure, uncertainties will be introduced into risk estimates because the exposure concentration used as input to the model must be time averaged to account for the intermittent nature of the exposure. We have used simulation as a means of determining the potential magnitude of these uncertainties. Simulations using models having various EMATs have allowed exploration of the strengths and weaknesses of various approaches to time averaging of exposures and impact on risk estimates associated with intermittent exposures to lead in soil. The International Commission of Radiological Protection (ICRP) model of lead pharmacokinetics in humans simulates lead intakes that can vary in intensity over time spans as small as one day, allowing for the simulation of intermittent exposures to lead as a series of discrete daily exposure events. The ICRP model was used to compare the outcomes (blood lead concentration) of various time-averaging adjustments for approximating the time-averaged intake of lead associated with various intermittent exposure patterns. Results of these analyses suggest that standard approaches to time averaging (e.g., U.S. EPA) that estimate the long-term daily exposure concentration can, in some cases, result in substantial underprediction of short-term variations in blood lead concentrations when used in models that operate with EMATs exceeding the shortest exposure duration that characterizes the intermittent exposure. Alternative time-averaging approaches recommended for use in lead risk assessment more reliably predict short-term periodic (e.g., seasonal) elevations in blood lead concentration that might result from intermittent exposures. In general, risk estimates will be improved by simulation on shorter time scales that more closely approximate the actual temporal dynamics of the exposure.
- Published
- 2005
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- View/download PDF
5. Lead intervention and pediatric blood lead levels at hazardous waste sites.
- Author
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Lorenzana RM, Troast R, Mastriano M, Follansbee MH, and Diamond GL
- Subjects
- Child, Environmental Exposure, Environmental Pollution prevention & control, Humans, Soil Pollutants analysis, Dust, Hazardous Waste, Lead blood, Lead Poisoning prevention & control
- Abstract
Lead intervention at Superfund sites typically seeks to reduce pediatric blood lead levels by disrupting the surface-to-hand-to-mouth pathway. This article presents the results of a survey of the publicly available literature on the effectiveness of lead intervention on pediatric blood lead levels at hazardous waste sites. The survey includes six hazardous waste sites located in Canada, Australia, and the United States at which intervention activities were conducted and pediatric blood lead levels were sampled both pre- and postintervention. Evaluation of the effectiveness of intervention on pediatric blood lead levels is often complicated due to confounding variables and statistical limitations. Nevertheless, the outcomes of the intervention studies reviewed in this report suggest that various approaches to the intervention of the dust ingestion pathway, alone or in combination, contributed to declines in blood lead levels in children living in areas heavily contaminated with lead.
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- 2003
- Full Text
- View/download PDF
6. Risks to children from exposure to lead in air during remedial or removal activities at Superfund sites: a case study of the RSR lead smelter Superfund site.
- Author
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Khoury GA and Diamond GL
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- Air Movements, Child, Dust, Environmental Monitoring, Facility Design and Construction, Humans, Industry, Lead adverse effects, Lead blood, Metallurgy, Models, Theoretical, Risk Assessment, Vehicle Emissions analysis, Air Pollutants analysis, Child Welfare, Environmental Exposure, Hazardous Waste, Inhalation Exposure, Lead analysis
- Abstract
Superfund sites that are contaminated with lead and undergoing remedial action generate lead-enriched dust that can be released into the air. Activities that can emit lead-enriched dust include demolition of lead smelter buildings, stacks, and baghouses; on-site traffic of heavy construction vehicles; and excavation of soil. Typically, air monitoring stations are placed around the perimeter of a site of an ongoing remediation to monitor air lead concentrations that might result from site emissions. The National Ambient Air Quality (NAAQ) standard, established in 1978 to be a quarterly average of 1.5 microg/m(3), is often used as a trigger level for corrective action to reduce emissions. This study explored modeling approaches for assessing potential risks to children from air lead emissions from the RSR Superfund site in West Dallas, TX, during demolition and removal of a smelter facility. The EPA Integrated Exposure Uptake Biokinetic (IEUBK) model and the International Commission of Radiologic Protection (ICRP) lead model were used to simulate blood lead concentrations in children, based on monitored air lead concentrations. Although air lead concentrations at monitoring stations located in the downwind community intermittently exceeded the NAAQ standard, both models indicated that exposures to children in the community areas did not pose a significant long-term or acute risk. Long-term risk was defined as greater than 5% probability of a child having a long-term blood lead concentration that exceeded 10 microg/dl, which is the CDC and the EPA blood lead concern level. Short-term or acute risk was defined as greater than 5% probability of a child having a blood lead concentration on any given day that exceeded 20 microg/dl, which is the CDC trigger level for medical evaluation (this is not intended to imply that 20 microg/dl is a threshold for health effects in children exposed acutely to airborne lead). The estimated potential long-term and short-term exposures at the downwind West Dallas community did not result in more than 5% of children exceeding the target blood lead levels. The models were also used to estimate air lead levels for short-term and long-term exposures that would not exceed specified levels of risk (risk-based concentrations, RBCs). RBCs were derived for various daily exposure durations (3 or 8 h/day) and frequencies (1-7 days/week). RBCs based on the ICRP model ranged from 0.3 (7 days/week, 8 h/day) to 4.4 microg/m(3) (1 day/week, 3 h/day) for long-term exposures and were lower than those based on the IEUBK model. For short-term exposures, the RBCs ranged from 3.5 to 29.0 microg/m(3). Recontamination of remediated residential yards from deposition of air lead emitted during remedial activities at the RSR Superfund site was also examined. The predicted increase in soil concentration due to lead deposition at the monitoring station, which represented the community at large, was 3.0 mg/kg. This potential increase in soil lead concentration was insignificant, less than 1% increase, when compared to the clean-up level of 500 mg/kg developed for residential yards at the site.
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- 2003
- Full Text
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7. Evaluation of the integrated exposure uptake biokinetic (IEUBK) model for lead in children
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Brown, James S., Spalinger, Susan M., Weppner, Sarah G., Hicks, Kynan J. Witters, Thorhaug, Mara, Thayer, William C., Follansbee, Mark H., and Diamond, Gary L.
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- 2023
- Full Text
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8. Dietary lead modulates the mouse intestinal microbiome: Subacute exposure to lead acetate and lead contaminated soil.
- Author
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George, S. Elizabeth, Devereux, Richard, James, Joseph, Wan, Yongshan, Diamond, Gary L., Bradham, Karen D., and Thomas, David J.
- Subjects
LEAD exposure ,GUT microbiome ,LEAD ,LEAD in soils ,ACETATES ,HEAVY metals ,SOILS - Abstract
The effect of dietary lead on the intestinal microbiome has not been fully elucidated. To determine if there was an association between microflora modulation, predicted functional genes, and Pb exposure, mice were provided diets amended with increasing concentrations of a single lead compound, lead acetate, or a well characterized complex reference soil containing lead, i.e. 6.25–25 mg/kg Pb acetate (PbOAc) or 7.5–30 mg/kg Pb in reference soil SRM 2710a having 0.552 % Pb among other heavy metals such as Cd. Feces and ceca were collected following 9 days of treatment and the microbiome analyzed by 16 S rRNA gene sequencing. Treatment effects on the microbiome were observed in both feces and ceca of mice. Changes in the cecal microbiomes of mice fed Pb as Pb acetate or as a constituent in SRM 2710a were statistically different except for a few exceptions regardless of dietary source. This was accompanied by increased average abundance of functional genes associated with metal resistance, including those related to siderophore synthesis and arsenic and/or mercury detoxification. Akkermansia , a common gut bacterium, was the highest ranked species in control microbiomes whereas Lactobacillus ranked highest in treated mice. Firmicutes/Bacteroidetes ratios in the ceca of SRM 2710a treated mice increased more than with PbOAc, suggestive of changes in gut microbiome metabolism that promotes obesity. Predicted functional gene average abundance related to carbohydrate, lipid, and/or fatty acid biosynthesis and degradation were greater in the cecal microbiome of SRM 2710a treated mice. Bacilli/Clostridia increased in the ceca of PbOAc treated mice and may be indicative of increased risk of host sepsis. Family Deferribacteraceae also was modulated by PbOAc or SRM 2710a possibly impacting inflammatory response. Understanding the relationship between microbiome composition, predicted functional genes, and Pb concentration, especially in soil, may provide new insights into the utility of various remediation methodologies that minimize dysbiosis and modulate health effects, thus assisting in the selection of an optimal treatment for contaminated sites. • Ingesting lead acetate or mining soil altered murine fecal and cecal microbiome differently. • Differences in cecal microflora were observed at different taxon levels. • Cecal Firmicutes/Bacteroidetes ratio was greater with exposure to soil than lead acetate. • Predicted cecal microbiome metabolism and detoxification genes were elevated. • Microbiome impacts in soil treated mice did not directly correlate with lead acetate. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
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9. Testing for lead: How important is it?
- Author
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Diamond, Gary L.
- Subjects
LEAD ,LEAD in the body ,HEALTH - Abstract
Comments on the utilization of lead in the United States that is estimated to be approximately one million tons per year. Recovery and recycling; Chemical non-degradability in the environment; Toxic levels; Vulnerability of children and infants to environmental lead; Importance of measuring blood lead levels for monitoring populations and individuals for lead-related health risks.
- Published
- 1996
10. Ingestion of remediated lead-contaminated soils affects the fecal microbiome of mice.
- Author
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George, S. Elizabeth, James, Joseph, Devereux, Richard, Wan, Yongshan, Diamond, Gary L., Bradham, Karen D., Scheckel, Kirk G., and Thomas, David J.
- Published
- 2022
- Full Text
- View/download PDF
11. Predicting oral relative bioavailability of arsenic in soil from in vitro bioaccessibility
- Author
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Karen D. Bradham, Clay Nelson, Gary Diamond, David J. Thomas, Yvette W. Lowney, Albert L. Juhasz, Julie M Klotzbach, William J. Brattin, Michele Burgess, Cheryl A Hawkins, Susan Griffin, Kirk G. Scheckel, Diamond, Gary L, Bradham, Karen D, Brattin, William J, Burgess, Michele, Griffin, Susan, Hawkins, Cheryl, Juhasz, Albert L, Klotzbach, Julie M, Nelson, Clay, Lowney, Yvette W, Scheckel, Kirk G, and Thomas, David J
- Subjects
Soil test ,cadmium ,Health, Toxicology and Mutagenesis ,contaminated soils ,Biological Availability ,010501 environmental sciences ,Toxicology ,01 natural sciences ,Models, Biological ,Arsenic ,Soil pH ,Linear regression ,errors ,Soil Pollutants ,Public, Environmental & Occupational Health ,0105 earth and related environmental sciences ,validation ,lead ,Pesticide residue ,Chemistry ,swine ,Soil classification ,04 agricultural and veterinary sciences ,assay ,Soil contamination ,Bioavailability ,Environmental chemistry ,Soil water ,040103 agronomy & agriculture ,Linear Models ,0401 agriculture, forestry, and fisheries ,regression ,Biological Assay ,Environmental Sciences - Abstract
Several investigations have been conducted to develop in vitro bioaccessibility (IVBA) assays that reliably predict in vivo oral relative bioavailability (RBA) of arsenic (As). This study describes a meta-regression model relating soil As RBA and IVBA that is based upon data combined from previous investigations that examined the relationship between As IVBA and RBA when IVBA was determined using an extraction of soil in 0.4 M glycine at pH 1.5. Data used to develop the model included paired IVBA and RBA estimates for 83 soils from various types of sites such as mining, smelting, and pesticide or herbicide application. The following linear regression model accounted for 87% of the observed variance in RBA (R2 = .87): RBA(%) = 0.79 × IVBA(%) + 3.0. This regression model is more robust than previously reported models because it includes a larger number of soil samples, and also accounts for variability in RBA and IVBA measurements made on samples collected from sites contaminated with different As sources and conducted in different labs that have utilized different experimental models for estimating RBA.
- Published
- 2016
- Full Text
- View/download PDF
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