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Item Open Access ASSESSING THE IMPACT OF LOWER NATIONAL MERCURY AND LEAD REPORTING THRESHOLDS(2007-05) Fiffer, MelissaAfter a pair of toxic releases in Bhopal, India and Institute, West Virginia in the 1980s, environmental groups and members of the public demanded more information on toxic chemical releases into the community. As a result, United States facilities that manufacture, use, or process above-threshold amounts of one of 650 listed toxic chemicals must publicly report their releases and transfers via the annual Toxics Release Inventory (TRI). In 2000 and 2001, the EPA lowered the reporting thresholds for mercury and lead, respectively. This project assesses how the increased TRI reporting for mercury and lead changes our understanding of the geographic distribution and industry composition of mercury and lead-releasing facilities, as well as the demographic characteristics of the areas surrounding the facilities. Through a geospatial analysis of mercury and lead TRI reporting before and after the threshold changes, this project evaluates the effectiveness of the TRI program at achieving its founding purpose: to provide information to empower communities. The findings suggest evidence of an overall geographic and industry diversification across the threshold changes, but point to specific states and industry types that tend to account for larger than average portions of releases. Reporting was found to be concentrated in working poor block groups, with no change in income distribution across the threshold changes. Further geospatial and statistical analysis of income and other demographic variables is recommended in order to confirm reporting and release trends. Given the limitations to interpretation of TRI data, more outreach and education would be prudent in order to maximize communities’ utility of the increased mercury and lead data available after the threshold changes.Item Open Access Blood lead levels among pregnant women: historical versus contemporaneous exposures.(Int J Environ Res Public Health, 2010-04) Miranda, Marie Lynn; Edwards, Sharon E; Swamy, Geeta K; Paul, Christopher J; Neelon, BrianBlood lead among pregnant women, even at modest levels, may impair offspring cognitive development. We examine whether blood lead levels (BLLs) result from current versus historic exposures, among a cohort of pregnant women. Cumulative logit models were used to characterize the relationship between maternal risk factors and higher BLLs. Maternal blood lead levels more likely result from lead remobilization from historic versus contemporaneous exposures. Even if all lead sources were abated immediately, women and their fetuses would experience lead exposure for decades. This work emphasizes the importance of addressing sources of environmental lead exposure in the United States and internationally.Item Open Access Crumbling Infrastructure and Learning Impairment: A Call for Responsibility.(Environmental health perspectives, 2016-05) Levin, Edward DItem Open Access Effects of Toxic Metal Exposures and Their Mixtures on Adverse Health Outcomes in the Peruvian Amazon(2022) Berky, AxelNon-essential trace metals (lead, mercury, arsenic, and cadmium) are ubiquitous in our environment and have overlapping routes of exposure, yet mixed trace metal exposures are rarely considered in epidemiological studies. Instead, research often follows a single research question that focuses on a single trace metal of concern and does not incorporate potential co-exposures. The published literature of artisanal small-scale mining in the Amazon is a prime example as it has predominantly focused on mercury exposure, due to its use in the mining process. Once exposures of concern are identified, further studies evaluate health outcomes; however, the health effects cannot be accurately determined without accounting for co-exposures. This verification is becoming more important as there is a growing recognition that mixed trace metal exposures are more common than previously believed.To address the prevalence of mixed trace metal exposures and their health effects in the Peruvian Amazon region of Madre de Dios, I use epidemiological data from the COhorte de NAcimiento de MAdre de Dios (CONAMAD) birth cohort study (2018-Present), and two cross-sectional epidemiological studies (Amarakaeri Communal Reserve study (ACR, 2015), and Etiology and Toxic Metals study (EATM, 2018)). CONAMAD collected survey data along with maternal and cord blood samples at birth, which were processed for minerals and trace metals. The cross-sectional studies collected venous blood for trace metal analysis and hair samples for total hair mercury. Blood samples from the ACR were also processed for amino acids. In-depth demographic and health survey data were collected in all three studies. Structural equation models and random mixed effect models were used to evaluate research questions. The cross-sectional studies demonstrate a high correlation of lead and mercury exposure in communities that rely on wild fish and wild game as protein sources, which is prevalent throughout the Amazon. Consuming a meal of wild game resulted in an estimated lead dose of 500 µg, with those who eat wild game (Yes/No) associated with 1.41 µg/dL (95% CI: 1.20 – 1.70) higher blood lead levels compared to those who do not. This furthers the notion that mixed exposures are likely more common than previously believed. Mixed exposures target the same toxicological pathway, which may lead to synergistic or antagonistic effects. My research found that lead disrupts the arginine pathway and is associated with increased blood pressure. Mercury exposure was a modifier of the arginine pathway, with high blood mercury levels changing the effect of global arginine bioavailability from 17.16 (95% CI: 9.09 – 25.84) to -14.17 (95% CI: -31.88 - -0.33) on systolic blood pressure. Interestingly, mercury was not directly associated with the arginine pathway. Results from the birth cohort demonstrate the importance of nutrition and prenatal care for fetal development, which had a large positive effect on birthweight and gestational age. However, even low maternal lead exposure had detrimental effects on fetal health. A 1% increase in maternal blood lead was associated with a shorter gestational age of 0.05 days (β: -0.75, 95% CI: -1.51 - -0.13), even with the CONAMAD birth cohort having lower blood lead levels than other birth cohorts. There is a need for an integrated approach of nutritional and exposure assessments to better understand neonatal health outcomes.
Item Open Access Examining interactions of lead and repeated Rotavirus infection on infant cognitive development(2018-04-26) Reilly, DelaneyRotavirus is a major cause of severe childhood gastroenteritis globally. When children are frequently exposed to unsanitary conditions they are more likely to be repeatedly exposed to pathogens that cause diarrheal diseases and gut inflammation. This chronic inflammation can decrease cognitive function and generally stunt growth. Additionally, lead is well known to be neurodevelopmentally toxic, causing lower cognitive functioning at levels of 5ug/dL, the current CDC maximum acceptable blood lead level. Children in the developing world may be more likely to have a double burden of these growth stunting factors, disadvantaging them in global competition. Therefore, this project evaluated if the effects of repeated early life Rotavirus infection and elevated blood lead levels increase cognitive stunting beyond what might be expected of either threat individually. To understand these potential interactions, infants from Bangladesh, India, and Pakistan were assessed for cognition at 6 months using the Bayley’s Scales of Infant and Toddler Development. This score was evaluated in relation to the child’s blood lead level and incidence of Rotavirus infection while controlling for covariates such as home socioeconomic status, maternal reasoning abilities, nutrition, and other pathogenic burden. No relationship was found in this cohort, but it should be noted that the number of infants in this study with a non-zero Rota incidence was 43 of the 634 participants. Therefore, it is not able to be determined if the data is masking a potential reaction or if there is truly no interaction. It is possible that increased gut injury could be increasing lead uptake, as was hypothesized, but it may also be injuring the gut enough to decrease all absorption, thus decreasing lead uptake. Further study of this and other environmental health interactions are needed to evaluate if and how any stunting effects that may be seen are impacting these populations and potentially presenting a greater than additive risk.Item Open Access Genomic Signatures of Disease and Environmental Exposure in the Peripheral Blood(2011) LaBreche, Heather GarrenMy thesis research has centered on the concept of the peripheral blood cell (PBC) as an indicator of disease and environmental exposure. The PBC is not only easily accessible and constantly replenished, but it provides a snapshot of an individual's health. Doctors have long utilized PBCs as indicators of health based on count, morphology or the expression of particular cell surface markers. Using these methods, PBCs can serve as indicators of infection, inflammation or certain types of hematological malignancies. Now PBCs can be characterized as a function of their gene expression profiles in response to disease and toxicant exposure. Advances in cDNA microarray technology have made it possible to analyze global gene expression in small volumes of whole blood, or even in a sorted population of blood cells. The resulting gene expression data can serve as a molecular phenotype, or signature, of disease or toxicant exposure. These signatures serve a twofold purpose. First, they act as biological markers (biomarkers) that can indicate the presence of disease or aid monitoring the response to treatment. Second, they provide insight into the underlying biological mechanisms that are at work, by revealing genes, networks and pathways that are affected by the disease or toxin. This paradigm has been applied in a number of contexts, including infection, inflammation, leukemia, lymphoma, neurological disorders, cardiovascular disease, environmental exposures and solid tumors.
In the work presented here, we describe signatures of lead (Pb) exposure and breast cancer based on peripheral blood gene expression. Our objective in generating a blood-based signature of lead exposure was to develop a potential predictor of past and present exposure. This is particularly relevant because of continued widespread lead exposure through both environmental and occupational sources. Pb causes significant toxicities in a number of different organ systems including the hematological, endocrine, neurological and renal systems. Pb is considered a potential carcinogen due to evidence that it causes cancer in animal models and contributes to an elevated cancer risk in humans. Pb is thought to contribute to cancer risk indirectly through a variety of mechanisms, such as inhibition of DNA synthesis and repair, oxidative damage, interaction with DNA-binding proteins and tumor suppressor proteins, causing chromosomal aberrations and alterations to gene transcription. In addition, it has been shown to exacerbate the effects of other mutagens. Recent work also indicates that even low-level Pb exposure (defined here as levels below the threshold of detection of many common tests or below the level set by the CDC as an "elevated blood lead level" in children, or 10µg/dL) can impact health, especially in children, who are more susceptible to these negative health consequences.
We hypothesized that we could detect subtle and lasting changes in the PBC transcriptome that correlated to Pb exposure. We used a mouse model of per os Pb exposure to generate signatures corresponding to two different doses of Pb. One dose reflected a high-level exposure and the other a low-level exposure. We also analyzed the gene expression changes following removal of the Pb source. We were able to generate robust, dose-specific signatures of Pb exposure. This supports the growing body of evidence that even low levels of Pb exposure can have biological effects, and that there is likely no safe level of exposure. We also utilized a collection of pathway signatures to identify those pathways that were activated or repressed in response to Pb exposure compared to controls. We observed an increase in interferon-gamma pathway activity in response to low-level Pb exposure and an increase in E2F1 pathway activity in response to high-level Pb exposure. These results support previous findings that low-level Pb exposure can increase interferon-gamma production, whereas high-level Pb has been shown to increase DNA synthesis. The Pb signatures we report here were not predictive of a past lead exposure. These results suggest that the effect of Pb exposure on PBC gene expression is transient, perhaps due to the rapid turnover of blood cells and the absorption of Pb by the bones. We have proposed further studies to identify cells in the bone marrow that may serve as indicators of past Pb exposure based previous reports on the lasting effects of genotoxic stress on this tissue.
We also describe a predictor of human breast cancer based on peripheral blood gene expression. The objective of this study was to identify and characterize PBC gene expression patterns associated with the presence of a breast tumor. This work has the potential to make a significant impact on breast cancer screening and diagnosis. Despite the success of mammography in reducing mortality from breast cancer, many cancers go undetected due to factors such as breast density, age of the woman, or type of cancer. A blood-based breast tumor predictor would potentially offer an easy and noninvasive means of detecting primary breast cancer as well as monitoring patients for recurrences or metastases. In addition, the concept of using a blood-based biomarker for cancer detection would have positive implications for other types of cancer. For instance, patients with ovarian cancer are typically diagnosed at a late stage because of the absence of definitive symptoms and the lack of effective screenings methods.
We were able to successfully identify robust predictors of both mouse mammary tumors and human breast tumors based on PBC gene expression. The human breast tumor predictor exhibits a high level of sensitivity and specificity in distinguishing breast cancer patients and controls in an independent validation cohort. However, the true novelty in this study is that it integrates a factor modeling approach and a transgenic mouse model of breast cancer to identify biologically meaningful gene expression changes in the mouse PBC transcriptome. These genes were then used as the starting point for developing a human breast cancer predictor. This establishes an experimental system in which we can address questions that are inherently difficult to answer in human studies, such as whether this predictor is useful in detecting breast tumors early or in monitoring patients for recurrence or metastasis. In fact, our work suggests that tumor-associated gene expression changes in the PBCs can be detected in asymptomatic mice. Our results support those of previous studies, which identified blood gene expression profiles that are associated with a variety of solid tumors, including breast cancer. However, the sensitivity and specificity of our predictor are higher than that of the previously reported breast cancer signature. This may suggest that our strategy of using a mouse model to first identify informative genes allowed us to focus on those genes most relevant to the presence of a breast tumor and overcome the influence of the high degree of variation in blood gene expression in our human population. In order to be clinically useful, the predictor we report here would need to be tested in additional, large validation sets to establish its utility in an early detection setting and its specificity in distinguishing breast cancer from other cancer types as well as other potentially confounding conditions such as infection and inflammation. We describe some preliminary experiments in the mouse model intended to address these important questions.
Item Open Access Great Lakes Drinking Water: A Gaps Analysis of Policy Regulation and Funding Mechanisms Supporting Safe, Affordable and Equitable Access to Drinking Water in Michigan and Wisconsin(2023-04-27) Fleck, ErinThe Great Lakes, the world’s largest freshwater resource, provide abundant freshwater to the Midwest United States, despite record-setting drought throughout the Western United States. And yet situations like the lead poisoning crisis in Flint, Michigan, and the PFAS crisis affecting the entire country continue to threaten public health across the region. An analysis of federal, state, and local drinking water management policies focused on Michigan and Wisconsin will identify gaps and challenges that exist within the current management system that prevent all Midwesterners from enjoying safe, affordable and equitable access to drinking water. Through two case studies on either side of Lake Michigan, this analysis identifies specific opportunities for improvement in both funding and regulatory mechanisms that could be implemented to better guarantee safe drinking water in the region.Item Open Access Leadership for Thriving: A Framework to Lead the Business Community to Sustainable Behaviors(2023-04-25) Olivares, MagdalenaClimate change is a complex problem whose solution is still far from being on track. Although we have advanced a lot in terms of knowledge and awareness of the problem, we are struggling to transition to sustainable actions. Corporations have the key to unleash a substantial potential contribution to facing this challenge moving forward. Developing new business models that move their operations away from current environmental damage is needed. Their potential to leverage their connections with consumers and other stakeholders, educating and influencing them to be part of the solution, and joining efforts to adjust lifestyles and preferences for sustainable consumption also presents a huge opportunity. For these challenges, corporations need to face the transition from a technical to an adaptative approach. But corporations are not prepared to run this challenge on their own; integrating the environmental impact in the business model requires the support of environmental experts. This research is based on the hypothesis that there is an opportunity to enhance sustainable behavior transformation by improving communication and collaboration between business and environmental professionals. With this purpose, the research was done through a qualitative comparative analysis that looks to contrast the perspective and resources those professionals have with respect to climate change, looking for the interconnection of joint possibilities that can be approached in a more collaborative manner. The ecological self maturity, nature experience, and knowledge of environmental professionals make them the best candidates to support corporate change. But there is a learning challenge for environmental professionals as well, since technical acumen is not enough to lead such large and complex adaptative changes in human systems in the corporate world. This framework aims at providing a tool for environmental professionals to effectively hone their skills to lead and communicate with corporate audiences and guide them towards effective actions to tackle environmental change. Leadership for Thriving combines this perspective of leadership and inspiring storytelling with the optimistic approach of the breakthrough movement of thriving, which inspires the examples and reflections of this proposal.Item Open Access Legacies of Lead Paint Contamination in the Mineral Soils Adjacent to Historic Buildings(2023-04-28) Skinner, Adam; Lambert, CarsonFor hundreds of years, compounds containing the element lead (Pb) have been added to paint in order to improve the texture and weather resistance. Across the United States, millions of homes and buildings were painted with lead-based paints up through the 1970s, when lead paint was phased out following medical research confirming the link between lead and a variety of neurological and developmental disorders. Over 170 million Americans are estimated to have been exposed to lead levels above safe concentrations, many of whom were likely exposed to soil lead while playing in yards as children. Although the phase-out of lead in paint began over 50 years ago, the legacies of contamination from lead paint are still present in the soil in a meaningful way. This is largely due to the immobile nature of lead in the soil, tightly binding to clays and other particles, preventing it from being leached out of the soil. Previous soil lead studies have attempted to characterize spatial patterns of contamination at various scales, but this study is unique in the highly fine-scale sampling design around each structure. Up to 190 samples were taken around each structure, at a point density of 1 sample every 4-12 square meters, prioritizing areas closer to the base of the structure. Nine study sites were chosen in the vicinity of Durham, North Carolina, including 2 buildings that continue to be well-maintained, 5 dilapidated structures, and 2 footprints of buildings burned to the ground. For our study, we surveyed the top inch of the mineral soil using an Olympus Vanta portable X-ray Fluorescence Machine to get lead concentration in parts per million. At all nine of our study sites, we found evidence of elevated lead levels in the mineral soil that can reasonably be attributed to legacies of paint contamination. Sites varied in the intensity of lead contamination, ranging from maximum values below 300ppm to multiple samples above 5000ppm, and each had its own unique footprint of soil lead. Interpolations of lead concentration were created in ArcGIS from the point data. Despite the variation, we were able to draw a variety of conclusions about the state of soil lead around historic structures: • Concentrations are typically highest adjacent to the base of the structure, and often decline rapidly with distance. • Concentrations often decline back down to the geologic background within 4-12 meters of the structure, related to the maximum concentration. • The corners of buildings are often hotspots for lead contamination, likely due to weathering patterns of paint. • Topography and erosion of soil can affect concentrations and directionality of elevated lead plumes. • We did not find any direct pattern between lead levels and a building’s height, age, location, or level of maintenance. • Destroyed/burned structures can show very high hotspots even within the footprint of the former structure. • Mulch and other ground covers may either protect the soil from contamination or insulate the soil lead from loss. Statistical and geospatial analysis was used to help characterize the spatial patterns of the contamination at each site. For each structure, data of lead concentration versus distance from the building was used to generate a logarithmic regression that can be used to predict concentration at any given distance. For two structures, interpolations were georeferenced to estimate the area of spatial contamination at different thresholds. Other analyses were done on a site-specific basis, such as comparing concentrations at the different cardinal directions from one structure. All of our results were communicated and interpreted to the landowners to help inform their knowledge of their properties. This is especially important considering most of our sites are open to the public, and multiple have outdoor programs for children. For each site, we estimated a total health risk, based on the levels of lead contamination and the potential for human exposure. Considering the levels still present in soils even after 50+ years, more research is needed into soil remediation methods, as the high values we found in soils demonstrate that lead still poses a considerable risk to humans.Item Open Access Legacies of Lead Paint Contamination in the Mineral Soils Adjacent to Historic Buildings(2023-04-28)For hundreds of years, compounds containing the element lead (Pb) have been added to paint in order to improve the texture and weather resistance. Across the United States, millions of homes and buildings were painted with lead-based paints up through the 1970s, when lead paint was phased out following medical research confirming the link between lead and a variety of neurological and developmental disorders. Over 170 million Americans are estimated to have been exposed to lead levels above safe concentrations, many of whom were likely exposed to soil lead while playing in yards as children. Although the phase-out of lead in paint began over 50 years ago, the legacies of contamination from lead paint are still present in the soil in a meaningful way. This is largely due to the immobile nature of lead in the soil, tightly binding to clays and other particles, preventing it from being leached out of the soil. Previous soil lead studies have attempted to characterize spatial patterns of contamination at various scales, but this study is unique in the highly fine-scale sampling design around each structure. Up to 190 samples were taken around each structure, at a point density of 1 sample every 4-12 square meters, prioritizing areas closer to the base of the structure. Nine study sites were chosen in the vicinity of Durham, North Carolina, including 2 buildings that continue to be well-maintained, 5 dilapidated structures, and 2 footprints of buildings burned to the ground. For our study, we surveyed the top inch of the mineral soil using an Olympus Vanta portable X-ray Fluorescence Machine to get lead concentration in parts per million. At all nine of our study sites, we found evidence of elevated lead levels in the mineral soil that can reasonably be attributed to legacies of paint contamination. Sites varied in the intensity of lead contamination, ranging from maximum values below 300ppm to multiple samples above 5000ppm, and each had its own unique footprint of soil lead. Interpolations of lead concentration were created in ArcGIS from the point data. Despite the variation, we were able to draw a variety of conclusions about the state of soil lead around historic structures: • Concentrations are typically highest adjacent to the base of the structure, and often decline rapidly with distance. • Concentrations often decline back down to the geologic background within 4-12 meters of the structure, related to the maximum concentration. • The corners of buildings are often hotspots for lead contamination, likely due to weathering patterns of paint. • Topography and erosion of soil can affect concentrations and directionality of elevated lead plumes. • We did not find any direct pattern between lead levels and a building’s height, age, location, or level of maintenance. • Destroyed/burned structures can show very high hotspots even within the footprint of the former structure. • Mulch and other ground covers may either protect the soil from contamination or insulate the soil lead from loss. Statistical and geospatial analysis was used to help characterize the spatial patterns of the contamination at each site. For each structure, data of lead concentration versus distance from the building was used to generate a logarithmic regression that can be used to predict concentration at any given distance. For two structures, interpolations were georeferenced to estimate the area of spatial contamination at different thresholds. Other analyses were done on a site-specific basis, such as comparing concentrations at the different cardinal directions from one structure. All of our results were communicated and interpreted to the landowners to help inform their knowledge of their properties. This is especially important considering most of our sites are open to the public, and multiple have outdoor programs for children. For each site, we estimated a total health risk, based on the levels of lead contamination and the potential for human exposure. Considering the levels still present in soils even after 50+ years, more research is needed into soil remediation methods, as the high values we found in soils demonstrate that lead still poses a considerable risk to humans.Item Open Access Legacy Pb contamination in the soils of three Durham city parks: Do secondary forest organic horizons effectively blanket Pb in city park soils contaminated by historic waste incineration?(2022-12-16) Bihari, EnikoeLead (Pb) has historically been used in many products such as gasoline, paint, batteries, ceramics, pipes and plumbing, solders, and cosmetics, and Pb contamination from these materials and their waste streams is widespread around the world. Pb is a highly insoluble and persistent contaminant that accumulates in the environment, especially in urban soils; to this day, soil Pb concentrations remain high in many cities, posing a significant long-term public health and environmental risk. Some remediation options are available for Pb, with the most effective being removal and replacement of the contaminated soil. However, plants that can tolerate soil Pb may be effective at phytostabilization. In phytostabilization, soil Pb is immobilized both physically and chemically by the roots, while also being sequestered by new layers of organic matter and soil that accumulate on the surface. Throughout the early 1900s, the city of Durham, NC operated neighborhood municipal incinerators which combusted most of the city’s waste, including waste collected from homes, businesses, and public street cleaning. Around 1950, the four of the incinerator sites were closed and converted into public parks, with playgrounds, grass fields, picnic benches, sports facilities, and walking paths. These are now Walltown, East End, East Durham, and Lyon Parks. The parks currently contain streams and large areas of secondary forest cover, which have been largely unmanaged throughout the last century. From local newspaper articles, we have direct evidence for the disposal of incinerator refuse at these sites and other Durham parks. While historic news accounts describe the incinerator sites being covered with topsoil, until this study there has been no monitoring of the status of contaminant metals in the soils throughout the parks. We hypothesized that the surface soils of these parks had elevated Pb concentrations as the result of the parks’ history of incineration. Our primary objectives were to: 1. Measure total mineral surface soil Pb concentrations across three of Durham’s urban parks which were historically used for waste incineration (Walltown, East End, and East Durham Parks). 2. Assess whether secondary hardwood forests have accumulated organic horizons that were effective barriers to Pb-contaminated mineral soil below. We sampled mineral surface soil and organic horizon according to a stratified random sampling design, and the samples were measured for total Pb with an Olympus Vanta pXRF instrument. Data were analyzed using R and ArcGIS Pro, resulting in statistical models and spatial interpolations. Our main results were: 1. Mineral soil Pb concentrations across Walltown, East End, and East Durham Parks are elevated above both geologic background levels and several EPA hazard thresholds, especially in some highly-trafficked areas. 2. Hardwood forest organic horizons provide a blanket for highly Pb-contaminated mineral soil, but a significant amounts of surface soil Pb is mixed up into these O horizons. Thus, exposure risk is not eliminated and can remain quite high. Our results show that all three parks have total Pb in surface soils (0-2.5 cm) well above the geologic background (0-30 ppm), with many soils exceeding the US EPA’s hazard thresholds for gardening (100 ppm), residential play areas (400 ppm), and residential non-play areas (1200 ppm). For all three parks combined, mineral soil Pb ranged from 8 to 2342 ppm, with a mean of 201 ppm and a median of 93 ppm. A notable hotspot with extremely high Pb was mapped throughout the southeastern portion of East Durham Park north of East Main St., spanning a grassy field and part a secondary forest (Figure 12). Mineral soil Pb in this hotspot ranged from 694 to 2342 ppm. This is of particular concern because this field is adjacent to an apartment building, and residents appear to use this area to play, garden, and park their cars. Additionally, our study demonstrates that while hardwood O horizons provide a physical barrier to exposure for highly contaminated mineral soil, a significant amount of mineral soil Pb is mixed up into the O horizons. This relationship differed significantly between the upper O1/O2 and the lower O3 horizons. Pb concentration in the lower O3 horizon increased by 0.6 ppm for every 1 ppm increase in Pb increase in the mineral soil, with an adjusted R2 of 0.86. This means that the lower O3 horizon has about 60% of the Pb concentration of the mineral soil below. In contrast, Pb concentration in the upper O1/O2 horizon increased by 0.1 ppm for every 1 ppm increase in Pb increase in the mineral soil, with an adjusted R2 of 0.49. This means that the upper O1/O2 horizons have about 10% of the Pb concentration of the mineral soil below, Our results suggest limitations to phytostabilization as tool to reduce Pb exposure, particularly in hardwood forests where there is relatively rapid decomposition and bioturbation in the O horizons compared to many coniferous forests. Overall, the spatial distribution of soil Pb concentrations demonstrates the complicated land use history of these landscapes, pointing towards multiple sources of Pb inputs and outputs throughout the 20th century. Based on articles in historic newspapers from five cities across the USA, many municipalities may have public parks converted from historic waste incinerator sites; these sites may be contaminated with Pb and other metals that would have accumulated in ash and cinders, posing an exposure risk to residents who visit the parks.Item Open Access Potential health risks of trace elements in adobe brick houses in a historical mining town: Potosí, Bolivia(2015-04-21) McEwen, AbigailThe objectives of this study were to investigate trace elements in adobe houses and to characterize potential health risks from children’s exposure in Potosí, Bolivia. The city of Potosí sits at the base of the Cerro Rico Mountain, which has been mined heavily for its rich polymetallic deposits since the Spanish Colonial era in the 16th century, leaving a legacy of pollution that is not well understood. In this study, total trace elements were quantified in dirt floor, adobe brick, and surface dust samples from 49 houses. Mean concentrations of total mercury, lead, and arsenic in adobe bricks were significantly greater than concentrations in Sucre, Bolivia, a non-mining town used as a reference site, and exceeded US-based soil screening levels that are protective of human health. Adobe brick samples were further analyzed by simulated gastric fluid (GF) extraction, which approximates bioaccessibility. Mean GF extractable concentrations of mercury, arsenic, and lead were 0.841, 14.9, and 30.0 percent of the total concentration, respectively. Total and GF extractable concentrations of these elements were used to estimate exposure and potential health risks to one and six year old children following incidental ingestion of element enriched adobe brick particles. Although the majority of households have concentrations of total mercury and arsenic that represent a potential health risk, the percentage significantly decreases when GF extractable concentrations are considered. However, even when GF extractable lead is considered, the majority of the households have lead concentrations in adobe bricks that represent a potential health risk to children. This is the first study to quantify trace elements in adobe houses and the results show that the building materials in these houses are a source of exposure to potentially toxic trace elements in South American mining communities. Additional environmental sampling, biomonitoring, and exposure questionnaires are needed to fully characterize sources of exposure and to understand potential adverse health outcomes within the community.