Columbia SRP 2006-2012

Overall Summary

This proposal is submitted in response to RFA-ES-05-01, entitled “Superfund Basic Research Program”. The contamination of groundwater and soils with As and Mn are associated with major public health, remedial, and environmental policy problems. Both Arsenic and manganese are found at numerous Superfund sites. This competitive renewal proposal seeks to obtain new knowledge, and train multidisciplinary pre- and post-doctoral students, concerning the health effects, geochemistry, and remediation of As and Mn, with particular focus on groundwater. The proposed work involves substantial work at the single most seriously As-affected Superfund site in Vineland, NJ. It also involves epidemiologic studies of As- and Mn-exposed adults and children residing in Bangladesh and New Hampshire. As in the past, the Columbia University SBRP includes a unique balance between biomedical and non-biomedical research.

The proposal includes four biomedical research projects: 1) Genotoxicity and Cell Signaling Pathways of As in Mammalian Cells; 2) Health Effects of Arsenic Cohort Study; 3) Consequences of As and Mn Exposure on Childhood Intelligence; and 4) One-Carbon Metabolism, Oxidative Stress, and Arsenic Toxicity. The biomedical research is intimately intertwined with three non-biomedical projects: 5) Mobilization of Natural Arsenic in Groundwater; 6) Mobilization of Anthropogenic Arsenic in Groundwater; and 7) Mitigation of Arsenic Mobilization in Groundwater. A Research Translation Core entitled, “Collaborating with government & the public: As & Mn exposure via groundwater” will work with several government agencies to help understand and solve their local groundwater problems. The Projects are supported by four Research Support Cores: 8) Data Management; 9) Trace Metals; 10) Biogeochemistry; and 11) Hydrogeology.  Finally, a Training Core coordinates multi-disciplinary education and interaction among pre- and post-doctoral trainees who benefit from participation in the major inter-disciplinary research program.

Project 1 - Genotoxic & Cell Signaling Pathways of As in Mammalian Cells

PI - Tom Hei

Arsenic is an important environmental carcinogen that affects millions of people worldwide through contaminated water supplies. Although arsenic induces various human cancers including skin, lung, bladder, kidney and liver, the carcinogenic mechanism remains unknown. With the funding support of this grant, the applicant has shown,  for the first time, that arsenic is a potent gene and chromosomal mutagen in mammalian cells and induces mostly multilocus deletions. These findings provide the first direct link between chromosomal abnormalities that have frequently been demonstrated in vitro and carcinogenicity in vivo. Furthermore, our recent data have shown that mitochondria are a primary target in mediating arsenic-induced genotoxicity. The overall goal of this application is to elucidate the contribution of mitochondrial DNA mutations and cell signaling pathways in mediating the genotoxicity and apoptosis of arsenic in mammalian cells. To achieve this goal, a series of eight inter-related specific aims are proposed to address the four testable hypotheses. The human-hamster hybrid (AL) cell assay will be used to ascertain the role of mitochondrial DNA mutations and mitochondrial functions in modulating arsenic (sodium arsenite and methylated arsenic species) induced mutations at the CD59 locus. Since mitochondrial damage is often associated with induction of cell death, human melanocytes and melanoma cells will be used to define the cell signaling pathways involved in mediating arsenic-induced apoptosis. There is a profound necessity to develop effective treatment strategy for this often fatal cancer. Furthermore, there is considerable interaction, both conceptually and in shared materials, between this project and that of Projects 2, 3 and 4.  A better understanding of the genotoxic and apoptotic mechanisms of arsenic will provide better interventional approach both in the treatment and prevention of arsenic-induced human diseases.

Project 2 - Health Effects of As Cohort Study

PI - Habib Ahsan

Nearly 100 million people in the world, including ~57 million in Bangladesh and ~15 million in the U.S., are chronically exposed to inorganic arsenic, a Class I human carcinogen, and are at increased risk of skin and other arsenic-induced cancers—as well as cardiovascular, pulmonary and other non-malignant disorders.   As part of the Columbia University Superfund Basic Research Program, we have established Health Effects of Arsenic Longitudinal Study (HEALS)—a large prospective cohort study based on individual level data among a population exposed to a wide range of inorganic arsenic (InAs) from drinking water in Araihazar, Bangladesh.  Over the past five years, using a population-based sampling frame, we recruited 11,754 men and women (with >99% response rates) and collected detailed questionnaires, clinical data, and biospecimen samples from them at baseline, two years and four years after recruitment.  Through a dedicated medical clinic established by Columbia University to exclusively serve the HEALS participants, we have also developed an effective mechanism of following the cohort, especially for detecting incidence and mortality of dermatological, pulmonary, and cardiovascular disorders (CVD).  In this proposal, we proposed to prospectively evaluate the effects of various measures of As exposure and metabolism on: i) incidence of skin lesions and skin cancer, ii) incidence and mortality from chronic lung disorders and mortality from lung cancers, iii) incidence and mortality from CVD, iv) serum levels of the epidermal growth factor receptor (as an early biomarker of As-induced skin carcinogenesis), v) serum levels of bronchial/alveolar cell-derived antioxidant Clara cell protein 16 (as an early biomarker of As-induced chronic lung damage and carcinogenesis), and vi) carotid artery intima-medial thickness (as early preclinical marker of As-induced vascular damage).  A combination of prospective cohort, case-cohort, cross-sectional and case-control study designs will be employed to address these Specific Aims in the most efficient manner.  In addition to investigating these novel research questions, as in the previous funding period, the HEALS will continue to support other biomedical research projects (including Projects 1 and 4 of the proposed program).  This will be the first prospective cohort study using individual level data on As exposure and metabolism, and findings from this study will be directly relevant for both research and policy issues pertaining to the health of millions of people around the world.

Project 3 - Consequences of Arsenic and Manganese Exposure on Childhood Intelligence

PI - Joseph Graziano

During the past grant cycle, working in Araihazar, Bangladesh, where both As and Mn levels in drinking water span a wide range, we have demonstrated that both As and Mn have adverse effects of child intelligence.  The current proposal seeks to further test and elaborate on the hypotheses that As and Mn exposures from drinking water are associated with deficits in intellectual function in two distinct population samples.  The first draws on a U.S. sample, for whom we are able to apply standardized scores to estimate the magnitude of association with IQ.  The second draws on a Bangladesh sample to examine whether or not the effects of As on intellectual function are reversible; it takes advantage of a Columbia Earth Institute initiative to provide As-free deep tube-well water to an exposed population in Araihazar, Bangladesh.

In New Hampshire (NH), we will conduct a cross-sectional study of 500 fourth-grade children in order to examine the relations between water As, water Mn and IQ.  We selected schools to yield a sample in which – based on USGS data - roughly 70% will consume water from wells with < 10 µg As/L, 20% from wells with 10-50 µg/L, and 10% from wells with > 50 µg/L.  The distribution of Mn in wells is less well characterized, but limited USGS data (5) indicates that roughly 10% of wells in this region will have Mn concentrations above the EPA Health Advisory Level of 300 µg/L.

In Bangladesh, we will test the hypothesis that the provision of deep tube-well water (essentially devoid of As and Mn) is associated with improved intellectual function.  We propose a two-year prospective study of 300 children (baseline ages 7-9) in a region of Araihazar, Bangladesh.  Children will be assessed before remediation and at 12- and 24-months post-remediation.  Seventy-five children will be recruited into each of the following four groups: a) low As, low Mn; b) low As, high Mn; c) high As, low Mn; d) high As, high Mn.  Based on EPA guidelines, the definition of “low As” will be ≤ 10µg/L, and “low Mn” will be ≤ 300 µg/L.  After their initial intellectual assessment, children with high As wells will be provided access to low As (and low Mn) community wells and education to promote their use.

Project 4 - One-carbon Metabolism, Oxidative Stress & As Toxicity in Bangladesh

PI - Mary Gamble

Two overarching themes of the biomedical research of this Superfund Program addressed in this project relate to a) the metabolism of arsenic (As) and b) As-induced oxidative stress.  There is significant variability in progression from As exposure to clinical manifestations of disease.  Several studies have led to the hypothesis that nutritional status may account for a substantial portion of this variability.  Inorganic As is methylated via one-carbon metabolism, a biochemical pathway that is dependent on folate for recruitment of one-carbon groups.  We wish to expand our studies, which have begun to characterize the impact of nutritional regulation of one-carbon metabolism on the inter-individual variability in As methylation.  Glutathione (GSH), a key component of the primary antioxidant defense mechanism, and the electron donor for As reduction, is synthesized from homocysteine, and this synthesis is regulated by intermediates of one-carbon metabolism.  A great deal of basic research, including salient work from members of our group, points to the growing belief that As depletes glutathione (GSH) and induces oxidative stress.  However, the relationship between As exposure and oxidative stress has not been rigorously examined in human populations. 

The first specific aim of this proposal will utilize the repository of biological samples established by the Cohort Study (Project #2) to conduct a nested case-control study to identify modifiable risk factors (e.g. oxidative stress and/or hyperhomocysteinemia) related to increased susceptibility to As-induced skin lesions.  The remaining specific aims will take advantage of the expansion of our study area (and installation of As-free tube wells) in Projects #3 and #7 to recruit 375 new adults who are currently exposed to As.  In Specific Aim 2, we will address a fundamental question: To what extent do urinary As metabolites reflect As metabolites in the circulation?  In Specific Aim 3, we will conduct a cross-sectional study to test the hypotheses that higher concentrations of s-adenosylhomocysteine (SAH) and lower concentrations of GSH are associated with reduced As methylation.  In Specific Aim 4, we propose to examine dose-response relationships between As exposure and oxidative stress.  Finally, we will test the hypothesis that reduction of As exposure alleviates oxidative stress.   The proposed studies have the potential to a) substantiate that As induces oxidative stress and depletes GSH in a human population, b) link As-induced oxidative stress and/or nutritional status to an arsenic-related clinical outcome, and c) expand our understanding of the mechanisms underlying these processes.  Such findings would have significant implications for the identification of potential targeted interventions for preventing As-toxicity.

Project 5 - Mobilization of Natural As & Mn in Groundwater

PI -  Yan Zheng

This project focuses on field studies designed to investigate the interactions between hydrology, mineralogy, geology and geochemistry that result in naturally-elevated As concentrations (> 10 mg/L) in reducing groundwater.  We will first seek to determine if a roughly linear relationship between groundwater As and groundwater age observed in Araihazar, Bangladesh, holds in New England.  This new relationship, corresponding to a steady rate of As mobilization of ~ 20 mg/L per year, implies that the rate of recharge of an aquifer plays an important -perhaps dominant- role in regulating the spatial distribution of As in groundwater.  Four areas in Maine and New Hampshire with known clusters of domestic wells with As concentrations up to 700 mg/L were selected for detailed study on the basis of bed-rock and surficial geology.  Two new areas of Bangladesh with very high and low groundwater As concentrations, respectively, were selected for detailed investigation, including groundwater dating.  Field observations from one site in New England and one site in Bangladesh will be synthesized with a reactive-transport model of a high-As plume along its flow path to a discharge area. 

There are striking similarities to the tectonic setting that led to the formation of the rocks that, eventually, produced the deposits of New England and Bangladesh where elevated groundwater As concentrations are observed.  We propose to explore the implication of this analogy by conducting experiments designed to elucidate the mechanisms leading to the formation of mobilizable As in sediment.  These experiments will include long-term laboratory and in situ incubations of model minerals (arsenopyrite and silicates), synthetic silicate glasses doped with arsenic, as well as rock specimens collected in the upland regions and river deposits from New England and Bangladesh.  Mineralogical changes will be monitored by selective extractions, XRD, SEM-EDX, XAS-XANES and –EXAFS; microbiological changes will be tracked as well.  We also propose to conduct push/pull experiments in the un-consolidated glacial-till aquifers tapped by the majority of public supply wells in New England to assess the mobility of As in response to changes in land use that could affect the subsurface hydrology or geochemistry.

Project 6 - Mobilization of Anthropogenic As in Groundwater

PI - Steve Chillrud

This project proposes a set of lab and field experiments to further the fundamental understanding of biogeochemical processes governing the behavior and transport of inorganic and organic Arsenic (As) species as well as contribute to the design and management of remediation activities of sites contaminated with As.  We have chosen the Vineland Chemical site in southern New Jersey as our primary field site because it offers a number of research opportunities. One primary focus will be on experiments that could help optimize pump and treat operations. These studies would include plume capture efficiency assessments through measurements of tracers of groundwater flow velocities and directions. They would also involve laboratory and field experiments to investigate whether manipulations of aquifer chemistry could enhance remediation of groundwater As, primarily through accelerating As mobilization from aquifer solids, thereby enabling pump and treat operations to decrease subsurface As inventories more rapidly. We will also collaborate with Project 7 on investigating the feasibility of using permeable reactive barriers of zero valent iron as an additional remediation strategy to the current pump and treat system.

Other field experiments will investigate fundamental transport and fate issues of As in two offsite areas highly contaminated with As, specifically the Blackwater Branch and Union Lake. We will further investigate As cycling in bottom sediments of both the stream (which runs adjacent to the Superfund site) and of Union Lake. Our prior work has shown that the sediments of these two surface water bodies have dramatically different As chemistries, with fine-grained sediments of the stream having As controlled largely by sulfur chemistry while As in the lake sediments appears to be primarily controlled by iron chemistry. Additional sediment-porewater research will be done in the Blackwater Branch to investigate whether As behavior changes as a function of streamflow/groundwater discharge rates and to investigate As porewater-sediment interactions in sandy sediments which represent >80% of the stream bottom. The role of storm events in transporting As in the Blackwater Branch will also be investigated. Finally, research in Union Lake will investigate the magnitude of As release from sediments during episodes of anoxia in bottom waters.

Project 7 - Mitigation of As Mobilization in Groundwater

PI - Lex van Geen

The research proposed for this project is intended to augment our fundamental understanding of arsenic (As) behavior in ways that lead directly to a reduction in human exposure in both the U.S. and in Bangladesh.  At the Vineland Chemical Superfund site in New Jersey, heavily contaminated with both inorganic As (InAs) and organic As (OrgAs), research will focus on reducing off-site transport of these contaminants in two ways.  The effort will first be directed at polishing effluent from the existing treatment plant using a treatment column containing zero-valent iron (Fe(0)) filings which, this project’s previous research has demonstrated, is capable of removing both InAs and OrgAs.  Second, the feasibility of reducing off-site transport of As will be explored by installing and monitoring a permeable-reactive barrier containing Fe(0) filings. 

In Bangladesh, we are ethically compelled to lower the As exposure of study participants in Projects 2, 3, and 4.  The proposed research will focus on the sustainability of continued withdrawals from those aquifers that are currently low in As.  The justification is that these aquifers are currently the only realistic alternative for the ~50 million inhabitants of the country who have been drinking well water with an As content that often exceeds the WHO guideline of 10 µg/L by one to two orders of magnitude.  Through detailed monitoring and targeted manipulations in the field and in the laboratory, the combination of hydrological, geochemical, and microbial processes that maintain As concentrations at low levels in both very shallow (<10 m) and deep (>30-150 m) aquifers will be investigated.  In a direct application of the approach to mitigation developed under the previous round of funding, the exposure to As and Mn of children and adults, participating in Project 3 and 4 and residing in 25 villages, will be rapidly reduced by targeting safe aquifers for the installation of community wells.  The timing of these interventions will be closely synchronized with parallel studies of their health impact, conducted under biomedical components of this application.