Columbia SRP 2012-2017

Overall Summary

This proposal is submitted in response to RFA-ES-10-010, entitled "Superfund Hazardous Substance Research and Training Program (P42).”  The proposed work involves substantial work at the single most seriously As-affected Superfund site in Vineland, NJ.  It also involves unique epidemiologic studies of As- and Mn-exposed adults and adolescents residing in Bangladesh as well as an important mechanistic investigation of As-induced epigenetic dysregulation.  As in the past, the Columbia University SRP includes a balance between biomedical and non-biomedical research.

The proposal includes three biomedical research projects: 1) Health Effects of As Longitudinal Study (HEALS); 2) Consequences of As and Mn Exposure on Children’s Health; and 3) Impact of Nutrition on Arsenic-Induced Epigenetic Dysregulation.  The biomedical research is intimately intertwined with three non-biomedical projects: 4) Arsenic, Iron, Sulfur and Organic Carbon Speciation, and Their Impact on Groundwater Arsenic; 5) Application of Enhanced Mitigation Methods for Groundwater As at US Superfund Sites; and 6) Defining the Sustainable Uses of Low-As Aquifers in Bangladesh.  The Projects are supported by four Research Support Core Laboratories:  8) Data Management; 9) Trace Metals; 10) Biogeochemistry; and 11) Hydrogeology.

A Research Translation Core (RTC) entitled, "Collaborating with government & the NIEHS SRP: As & Mn Exposure in Groundwater” works with several government agencies to help understand and solve their local groundwater problems.  Finally, our RTC will work closely with our Community Engagement Core (CEC) entitled “Promoting As Testing and Treatment to Reduce Health Risks for Residents in Maine.”  Our CEC has developed naturally from our past biomedical and geochemical As research in Maine.

Project 1 - Health Effects of As Longitudinal Study (HEALS)
PI - Habib Ahsan

Nearly 200 million people in the world, including ~57 million in Bangladesh and ~17 million in the United States (US), are chronically exposed to inorganic arsenic (As), a class I human carcinogen, and are at increased risk of mortality, cancers as well as cardiovascular, pulmonary and other non-malignant disorders.  As part of the Columbia University SRP, we established the 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 As from drinking water in Araihazar, Bangladesh. Over the past 12 years, using a population-based sampling frame, we recruited >24,000 men and women (with >95% response rates) and collected detailed questionnaires, clinical data, and biospecimen samples at baseline recruitment as well as every two years subsequently. Approximately 80% of participants are exposed to water As at low-to-moderate doses (0-150 µg/L) with nearly 75% exposed at <100 µg/L. Through a dedicated medical clinic established by Columbia University and The University of Chicago that exclusively serves the HEALS participants, we have also developed an effective mechanism of following the cohort, especially for detecting incidence of respiratory and cardiovascular disorders. In this proposal, with up to 17 years follow-up, we propose to prospectively evaluate the effects of various measures of As exposure and methylation capacity on: i) all-cause, chronic-disease and cancer-related mortalities; ii) incidence of total and subtypes of chronic non-malignant respiratory disease (CNRD) including chronic obstructive pulmonary disease, restrictive lung disease, and pulmonary tuberculosis; iii) incidence of total and subtypes of cardiovascular disease (CVD) including coronary heart disease and stroke and also CVD subclinical marker carotid artery intima-medial thickness; and, finally to identify iv) modifiable host factors that influence these associations. A combination of prospective study designs including cohort and efficient case-cohort studies 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 cohort will continue to support other biomedical research. Projects (including Projects 2, 3 and 6 of the proposed program).

Project 2 - Consequences of As and Mn Exposure on Children’s Health
PI - Joe Graziano

The goal of Project 2 is to address several questions concerning the health effects of exposure to arsenic and manganese in water (WAs and WMn, respectively) among adolescents.  First, does the As-induced respiratory disease observed in adults also manifest itself in adolescents, and what are possible physiologic mechanisms?  Second, to what extent do associations between WAs and both lung function brain function reflect the effects of exposure in utero and in infancy, periods of dramatic development for these systems? Third, are WAs and WMn associated with specific cognitive functions in addition to intelligence?

We will draw on an existing sample of 780 adolescents (15-17 years old) whose mothers are participants in the HEALS Study.  Based on mothers' well As, measured five times from 2000 until the present, we are able to define four groups of adolescents with varying levels and patterns of exposure to As.  Defined on the basis of WAs levels, four groups include adolescents with exposures that are: Group 1) consistently low (mean WAs = 3 ppb); Group 2) consistently moderate (mean WAs = 26 ppb); Group 3) consistently high (mean WAs = 146 ppb); and Group 4) high from conception through roughly age one (mean WAs = 201 ppb) but much lower thereafter (mean WAs =13 ppb).  Within each group, there is wide variation in WMn concentrations.   Three specific aims target As exposure and pulmonary function (FEV1 and FVC) as well as biomarkers of lung dysfunction in exhaled breath condensate.

Three additional aims expand our earlier work on As, Mn and neuropsychologic outcomes by considering components of Executive Function (planning, sustained attention, working memory) that have been mapped to brain regions thought to be affected by exposure to these elements. Components of Executive Function will be measured with the Cambridge Neuropsychological Test Automated Battery (CANTAB), a computerized and well-validated set of tests; intelligence will also be assessed.  We will examine adolescents, an understudied age group, because certain components of Executive Function and lung development do not mature until this age; studies with younger children would miss these health effects.

Project 3 - Impact of Nutrition on Arsenic-Induced Epigenetic Dysregulation
PI - Mary Gamble

The carcinogenic and non-carcinogenic mechanisms of As are incompletely understood, but an emerging body of evidence suggests that As exposure leads to epigenetic dysregulation.  In 4 independent studies in our Bangladesh cohort we have demonstrated that chronic As exposure is associated with increased global DNA methylation, contingent on adequate folate status.  We hypothesize that the mechanism underlying this relates to As-induced alterations in histone modifications.  Two potential mechanisms include a) in vitro, As induces G9a mRNA and protein expression; G9a is a central player in epigenetic regulation, and b) As is a very potent inhibitor of pyruvate dehydrogenase, an enzyme that catalyzes the final step in Acetyl CoA biosynthesis; inhibition of Acetyl CoA biosynthesis may decrease histone acetylation leading to chromatin condensation and increased DNA methylation.

Folate is a key regulator of one-carbon metabolism mediated methylation reactions, including methylation of DNA and histones.  A large randomized trial is currently underway in Bangladesh to evaluate the effects of folic acid (FA) supplementation on As methylation.  We propose a cross-disciplinary collaboration that will take advantage of a unique repository of samples collected from this trial to carry out a set of aims related to nutrition/environment interactions.  In these aims, we will characterize the influence of As exposure on histone modifications, relate changes in histone modifications to changes in DNA methylation, and characterize the impact of FA supplementation on these marks.  Finally, using the Infinium Human Methylation450 array, we will identify a set of genes that are differentially methylated by As exposure and determine gene-specific histone modifications at these loci.  Collectively, these aims will begin to elucidate the molecular events that underlie the effects of As and folate on DNA methylation.  The implications of identifying an influence of FA supplementation on histone modifications are considerable, as this represents a simple, low-cost, low-risk intervention as a potential therapeutic approach to reverse As-induced epigenetic dysregulation.

Project 4 - Arsenic, Iron, Sulfur & Organic Carbon Speciation, & Their Impact on Groundwater Arsenic
PI - Ben Bostick

Arsenic groundwater concentrations are determined in part by their sediment concentration but also by sediment mineralogy and the transformations that affect them. The first goal of this project is to examine the spatial distribution of aqueous As (and other analytes) within the comprehensive sampling efforts outlined in Projects 5 (Vineland), 6 (Bangladesh) and Cores  to link groundwater As levels to tangible aqueous and sediment properties (e.g., mineralogy, measured using state-of-the-art spectroscopic methods including Fe, As, and S X-ray spectroscopy) and the biological communities that transform them (with 16 rDNA community libraries and functional gene analysis). As part of this comprehensive effort, this project will characterize the Fe, As and S phases that regulate dissolved As concentrations, identify active redox processes in the aquifer that affect these phases and the bacteria that facilitate these processes, and determine which active carbon pools drive microbial respiration. The second overarching goal of this project is to examine the role of transformations in sediment mineralogy and aquifer geochemistry on arsenic levels. Within the simulated pond-village in Araihazar, and the Vineland Superfund Site, we will study the relationship between sediment mineralogy, redox status, microbial populations and arsenic levels, but we will also be able to monitor how those and other parameters change over time in controlled laboratory experiments. These batch and column studies will use natural sediments and will probe the effect of perturbations of geochemical conditions on sediment biogeochemical processes, Fe, S and As mineralogies, and As geochemistry.  These manipulations will directly probe the question of the effect of human activity on As contamination (applicable to Proj. 6 goals), and will allow us to examine the rates of relevant and fundamental environmental processes for the first time. The resulting data will then be used to develop and calibrate reactive transport models that more accurately capture the processes that affect As partitioning (Proj. 5, 6, Hydrogeology Core). These data also will be used to engineer improved remediation solutions at the Vineland Superfund site. 

Project 5 - Application of Enhanced Mitigation Methods for Groundwater As at US Superfund Sites
PI - Steve Chillrud

Our prior work has shown that injection of oxalic acid can substantially increase mobilization of arsenic from sediments at the Vineland Superfund site (from laboratory to pilot field scales), potentially showing a way to greatly enhance the pump and treatment (P&T) methodology currently in use there as well as at other sites. Here, our overall aim is to partner with site managers who are very interested in evaluating how to scale-up and determine what portions of the site are most amenable to our oxalic acid accelerated P&T approach.  Our primary hypothesis is that we can overcome spatial heterogeneities in both hydraulic flow-paths and arsenic geochemistry to allow the oxalic acid approach to dramatically increase the efficiency of P&T.  A series of aims focused on field, laboratory and modeling experiments to be carried out in partnership with USEPA&USACE scientists will be used to determine an optimized combination of injection well density, timing, and reactant composition to allow us to plan and carry out a medium scale pilot study, where a key aim will be the use of continuous, high resolution geophysical resistivity survey methods to determine in real-time the advection and dispersion of injected oxalic acid.  A recent Remedial Site Evaluation Review of the Vineland Superfund Site recommended that different approaches may be needed in different portions of the site and that remediation by in situ immobilization might provide cheaper and more effective strategies for some portions of the site. As such, we will also investigate immobilization approaches that focus on developing the in situ use of the mineral magnetite to immobilize arsenic; we hypothesize magnetite will be a good target mineral since it is stable under both oxic and reducing conditions found at many sites and has recently been shown to incorporate arsenic into its structure. Our aims here will be to carry out preliminary lab studies in order to predict when magnetite will form and when it will effectively result in a stable net sink of aqueous arsenic.  Then a small pilot field experiment testing As immobilization with magnetite will be carried out in years 4-5.  Finally we will use sediments collected from other Superfund sites (e.g. a landfill in Dover NH) to carry out preliminary laboratory studies on the transferability of the 2 methods.

Project 6 - Defining the Sustainable Uses of Low-As Aquifers in Bangladesh
PI - Lex van Geen

The first goal of this project is to continue to lower the exposure to arsenic (As) of a cohort of 24,000 men and women recruited under the Health Effects of Arsenic Longitudinal Study (HEALS). This will be achieved by testing the numerous household wells that continue to be installed within the study area of Araihazar, using both laboratory measurements and field kits with support from Core C. In addition, the 110 deep community wells installed in some of the most affected portions of the study area will continue to be monitored. Beyond the ethical motivation, lowering exposure will help define exposure estimates of the study population and, therefore, the dose-response relationships for various end-points studied under Projects 1, 2, and 3.

The second goal of the project is to improve our understanding of the processes that threaten the quality of groundwater in aquifers that are presently low in As in Bangladesh by conducting field investigations. To determine the vulnerability of shallow (<30 m) aquifers that are tapped by most household wells, a ~1 km2 open field area located between a high-As and a low-As village of Araihazar will be densely instrumented and monitored for an entire year. Four ponds will then be dug and a nearby area raised with the fill to simulate the rural development of the region. The impact of this perturbation on the local hydrology and biogeochemistry (including As) of the perturbed areas, as well as two unperturbed controls, will be monitored for three years. To determine the vulnerability of deeper (>100 m) low-As aquifers, the origin of the failure of a handful of community wells in Araihazar will be investigated using a combination of geophysical, hydrological, and biogeochemical approaches supported under Project 4 and Cores C and D. The potential for downward incursion of shallow high-As groundwater on a broader scale due to intensive deep pumping below the city of Dhaka will be evaluated and modeled. These investigations will be carried out in the country where the health impact of As release to groundwater is by far the largest worldwide.