The cooperative agreement on Exposure-Dose Reconstruction Project (EDRP) was awarded towards the end of September 1993. Since then our efforts focused on several tasks of the research program in order to start the project in a most efficient and cost effective manner. A description of these activities and the progress made in each activity are given below.
Development of the analytical framework for the prediction of contaminant migration scenarios in multiple exposure pathways:
It is anticipated that the contaminant migration analysis (the forward pathway calculation environment) will include several analytical tools to evaluate the contaminant concentration levels in multiple and interactive pathways. These pathways, at a minimum, will include the following:
(i) air pathway;
(ii) ground-water pathway;
(iii)surface water pathway; and,
(iv) soil pathway.
According to the proposed schedule of the research program, the analytic tools for these pathways will be developed throughout the duration of the project. However, during the first project year, it was extremely important to conceptualize the overall system and develop a unified analytical structure and a user friendly framework for this computational environment. As parts of the overall system are developed, and several analytical tools are put together, this unified structure will provide the framework necessary for a user friendly computational environment. This approach will also minimize the revisions that will be necessary during the later stages of the research program. This task, although may not be in its final form, is completed and initial computational tools developed for the ground-water pathway is submitted to ATSDR/CDC within this framework.
In the next stage of the computational tool development, the conceptualization developed above needs to be integrated in a practical and user friendly analytical computational tool. This can only be accomplished if the complex analytical exposure pathway analysis methods can be integrated in a seamless computational environment. This environment should also provide tools for graphical presentation of results, for immediate interpretation of the analytical solutions. The preliminary computational software tool submitted to ATSDR/CDC for the ground-water pathway, during the first period of the research program, may describe our line of thought in this effort. In this tool several analytic solutions for the ground-water pathway was developed along with a graphical and text output format interphase which may be used to interpret the results. This software will be updated throughout the project period to include analytical tools for other pathways as well as other revisions that may be recommended by ATSDR/CDC. In its present form the computational tool submitted to ATSDR/CDC can be used to evaluate concentration distributions in site specific cases for the ground-water pathway. The software developed can be installed in ATSDR/CDC's network system for immediate access by all health professionals. At the present this computational tool is tested and used successfully in several site specific applications by ATSDR/CDC professionals.
It is our understanding that ATSDR/CDC's needs for computational tools in the area of health assessment is multilevel. The range of complexity of these tools may vary between screening tools, similar to the analytical computational environment described above, to the sophisticated GIS integrated multimedia modeling tools which may be used to analyze more complex cases. Given the number of sites that needs to be analyzed by ATSDR/CDC periodically and given the variability in complexity of the contaminant migration pathways in these sites, there would be a need for sophisticated approaches as well as the screening tools. Thus, in addition to the analytical tool development phase of the project, we are also in the process of developing user friendly GIS interface programs to simplify the analysis steps necessary in these complex cases. Our initial efforts in this phase of the study was concentrated towards the development of a shell structure for the GISPlus software which is presently used by ATSDR/CDC. This shell program will simplify the manipulation of data structures within a GIS integrated computation and the interaction of the complex simulation tools with the GIS system. The preliminary shell structure submitted to ATSDR/CDC during the first period of the project may describe our line of thought in this effort. Although this shell program will be updated throughout the project period, in its present form it is being tested and used to evaluate site specific conditions for the ground-water pathway at ATSDR/CDC and Ga. Tech. In this effort, in addition to the general shell structure submitted to ATSDR/CDC, certain coordinate transformation routines and data base generation routines, compatible with the existing ground-water flow and contaminant transport models, has been developed and submitted to ATSDR/CDC for beta testing. These codes were tested and used successfully in six site specific applications by ATSDR/CDC professionals during the first year of the research program.
The most important and also the most time consuming component of application of the finite element method to site specific case studies is the development of a suitable mesh to idealize the analysis region. To accomplish this task in a most efficient way, a GIS integrated mesh generation routine was developed and submitted to ATSDR/CDC during the first phase of the research program. This mesh generation routine is now in use by professionals at ATSDR/CDC to analyze ground-water pathway problems.
The PC-based GIS system in use at ATSDR/CDC is the GISPlus system. The implementation of existing ground-water pathway analysis tools required substantial revision of these codes to make them compatible with the GISPlus system. Although this is an ongoing task, our initial efforts provided ATSDR/CDC with these tools which are now in use in predicting ground-water flow patterns in several sites of interest to ATSDR/CDC. These codes were tested and used in six site specific applications by ATSDR/CDC professionals during the first period of the research program and the results are shared with several federal and state agencies involved in the program.
The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), as amended by the Superfund Amendments and Reauthorization Act (SARA), establishes certain Requirements for ATSDR/CDC and EPA with regard to hazardous substances which are most commonly found at facilities on the CERCLA National Priorities List (NPL). Section 104(i)(2) of CERCLA, as amended (42 U.S.C. 9604(i)(2), required that the two agencies prepare a list, in order of priority, of at least 100 hazardous substances that are most commonly found at facilities on the NPL and which, in their sole discretion, are determined to pose the most significant potential threat to human health. CERCLA also required the agencies to revise the priority list to include 100 or more additional hazardous substances, and to include at least 25 additional hazardous substances in each of the three successive years following the 1988 revision. The computational procedures used in this analysis is described in the document "Support Document for the CERCLA 104 Priority List of Hazardous Substances that will be the Subject of Toxicological Profiles," [ATSDR, 1992]. In the computational tool prepared and submitted to ATSDR/CDC on January 1993, this process is automated in a user friendly environment. Using this tool new chemicals can be added to the list, prioritized and ordered with relative ease.
During the first year of the cooperative agreement the following computational software were submitted to ATSDR/CDC for their evaluation and beta testing. Some of this software are still in development stage and should not be considered to be a final product. All of these products are presently used by ATSDR/CDC health assessors in evaluating health consequences of contaminants released to subsurface pathways.
(i) Site Ranking System (SRS Version 1.10)
(ii) Analytical Contaminant Transport analysis System (ACTS Version 1.10)
(iii) HAZardous Substance Database Analysis Tool (HAZDAT Version 1.10)
(iv) GIS Interphase SYStem (GIS-SYS Version 1.10)
The cooperative agreement on Exposure-Dose Reconstruction Project (EDRP) was awarded to Dr. M. M. Aral, School of Civil and Environmental Engineering, Georgia Institute of Technology, towards the end of September 1993. Since then our efforts focused on several tasks of the research program in order to start the project in a most efficient and cost effective manner. We have successfully completed the first project period during the 1993-1994 academic year. The progress made during the first year of the research program was submitted to ATSDR/CDC, USDHHS, in an Annual Progress Report on June 27, 1994. We are now in the second project period (1994-1995) of the research program. A description of research activities and the progress made in each activity during the second year of the research program are described below.
It is anticipated that the contaminant migration analysis (the forward pathway calculation environment) will include several analytical tools to evaluate the contaminant concentration levels in multiple and interactive pathways. These pathways, at a minimum, will include the following:
(i) air pathway;
(ii) ground-water pathway;
(iii) surface water pathway; and,
(iv) soil pathway.
According to the proposed schedule of the research program, the analytic tools for these pathways will be developed throughout the duration of the project. During the first project year, it was extremely important to conceptualize the overall system and develop a unified analytical structure and a user friendly framework for this computational environment. As parts of the overall system are developed, and several analytical tools are put together, this unified structure will provide the framework necessary for a user friendly computational environment. This approach will also minimize the revisions that will be necessary during the later stages of the research program. Major portion of this task was completed during the first project year. Although this software development effort may not be in its final form, the initial computational tool developed for the ground-water pathway and submitted to ATSDR/CDC during the first project period, indicate our line of taught for the general computational environment we are developing in this effort. During the second project period, the first years initial effort was modified significantly resulting in a major upgrade of the overall product. The new version of the software was submitted to ATSDR/CDC for beta testing during April 1995 (ACTS version 1.2). This version of the software is now more user friendly and more computationally efficient. In this tool several analytic solutions for the ground-water pathway and also the air pathway was developed along with a graphical and text output format interphase which may be used to interpret the results. This version now also includes the Monte Carlo simulations for the air pathway analysis as described in more detail below. This is an essential component of this pathway since the inherent uncertainties of the computations in the air pathway is much more pronounced. This software will be updated throughout the project period to include analytical tools for other pathways mentioned above as well as other revisions that may be recommended by ATSDR/CDC.
In it's present form the computational tool submitted to ATSDR/CDC can be used to evaluate concentration distributions in site specific cases for the ground-water pathway and air pathway. This software can be installed in ATSDR/CDC's network system for immediate access by all health professionals. At the present this computational tool is tested and used successfully in several site specific applications by ATSDR/CDC professionals.
As proposed in our first year progress report, an important component of the second project period effort was the incorporation of evaluation of the uncertainties involved in analytic contaminant migration simulations. Evaluation of the effect of these uncertainties on the numerical results generated can be accomplished using Monte Carlo methods.
Implementation of analytical tools in all pathways requires a number of input parameters including source-specific, media-specific, and chemical-specific variables. Typically, the values of these parameters are not known exactly due to measurement errors and/or inherent spatial and temporal variability. Therefore, it is often more appropriate to express these parameter values in terms of a probability distribution rather than a single deterministic value and use an uncertainty propagation model to assess the effect of the variability on the output of the models. Most suitable method that can be employed for this purpose is the Monte Carlo method. Based on the principles of this approach, the following procedure is incorporated to the software developed for ATSDR/CDC.
Whatever the source of the parameter uncertainty, the uncertainty can be quantified using a cumulative probability distribution. Thus, for each parameter to be analyzed as an uncertain variable, the user may select and assign a probability distribution (normal, lognormal, uniform, exponential, triangular) for the variable and specify the parameters that describe the distribution. In Monte Carlo simulations, data sets randomly generated from these distributions form the basis of the data sets that will be used in deterministic models which in turn will generate a population of model outputs. This series of outputs can than be analyzed to yield a cumulative probability distribution of expected model results. This distribution quantitatively describes the uncertainty in the model output and can be used in decision making.
During the second project year, considerable effort was devoted to introduce Monte Carlo simulation tools into the overall computational framework developed in the first project year. With this component added to the system, users will have the choice to select between direct calculations (deterministic mode computations) and Monte Carlo simulations in pathway analysis exercises based on the confidence they have on the parameters they are using in their applications. With the addition of Monte Carlo methods, the flexibility and reliability of the computational system is improved and the applicability of the overall system is enhanced. At the present this computational system is included into the air pathway calculations.
ATSDR/CDC and the Connecticut Department of Health Services (CDHS) are collaborating in a study of cancer incidence in the Town of Southington, Hartford County, Connecticut. As part of the study, ATSDR/CDC is determining population exposure to contaminated groundwater that was distributed in the town's water distribution system. To address the complex engineering issues associated with exposure assessment, ATSDR/CDC relied on the resources of EDRP project. The project was completed in time and the results were submitted to ATSDR/CDC in a final report titled "A Public Health Analysis of Exposure to Contaminated Municipal Water Supplies at Southington, Hartford County, Connecticut."
This research effort, was not included to the initial research program proposed by the principal investigator, and was undertaken as an additional effort at the request of ATSDR/CDC project officers. Since the problem posed to ATSDR/CDC by the CDHS is an extremely important health assessment problem with nationwide applications and the engineering analysis provided by Ga. Tech is an extremely useful and practical but preliminary solution to the problem at hand, the Ga Tech principal investigator recommends that ATSDR/CDC may like to pursue this research in the future.
It is our understanding that ATSDR/CDC's needs for computational tools in the area of health assessment is multilevel. The range of complexity of these tools may vary between screening tools, similar to the analytical computational environment described above, to the sophisticated GIS integrated multimedia modeling tools which may be used to analyze more complex cases. Given the number of sites that needs to be analyzed by ATSDR/CDC periodically and given the variability in complexity of the contaminant migration pathways in these sites, there would be a need for sophisticated approaches as well as the screening tools. Thus, in addition to the analytical tool development phase of the project, we are also in the process of developing user friendly GIS interface programs to simplify the analysis steps necessary in these complex cases. Our initial efforts in category was concentrated towards the development of a shell structure for the GISPlus software which is presently used by ATSDR/CDC. This shell program will simplify the manipulation of data structures within a GIS integrated computation and the interaction of the complex simulation tools with the GIS system. The preliminary shell structure submitted to ATSDR/CDC during the first period of the project may describe our line of thought in this effort. Although this shell program will be updated throughout the project period, in its present form it is being tested and used to evaluate site specific conditions for the ground-water pathway at ATSDR/CDC and Ga. Tech. In this effort, in addition to the general shell structure submitted to ATSDR/CDC, certain coordinate transformation routines and data base generation routines, compatible with the existing ground-water flow and contaminant transport models, has been developed and submitted to ATSDR/CDC for beta testing. These codes were tested and used successfully in site specific applications by ATSDR/CDC professionals. This aspect of the research program is still under development and revisions to the code will be supplied to ATSDR/CDC for their beta testing.
The PC-based GIS system in use at ATSDR/CDC is the GISPlus system. The implementation of existing ground-water pathway analysis tools required substantial revision of these codes to make them compatible with the GISPlus system. Although this is an ongoing task, our initial efforts provided ATSDR/CDC with these tools which are now in use in predicting ground-water flow patterns in several sites of interest to ATSDR/CDC. We are in the process of adding contaminant transport models to this system in the area of subsurface analysis. These codes were tested and used in site specific applications by ATSDR/CDC professionals during the second period of the research program and the results are shared with several federal and state agencies involved in the program.
During the second year of the cooperative agreement the following computational software were submitted to ATSDR/CDC for their evaluation and beta testing. Some of this software are still in development stage and should not be considered to be a final product. All of these products are presently used by ATSDR/CDC health assessors in evaluating health consequences of contaminants released to subsurface pathways.
(i) Analytical Contaminant Transport analysis System (ACTS Version 5.20)
(ii) GIS Interphase SYStem (GIS-SYS Version 2.20)
The cooperative agreement on Exposure-Dose Reconstruction Project (EDRP) was awarded to Dr. M. M. Aral, School of Civil and Environmental Engineering, Georgia Institute of Technology, towards the end of September 1993. Since then our efforts focused on several tasks of the research program in order to start the project in a most efficient and cost effective manner. We have successfully completed the first project period during the 1993-1996 academic year. The progress made during this period of the research program was submitted to ATSDR/CDC, USDHHS, in an Annual Progress Reports. We are now in the project period (2001-2004) of the research program. A description of research activities and the progress made in each activity during the period 1996-2001 are described below.
An epidemiologic study of childhood leukemia and central nervous system cancers that occurred during the period 1979 through 1996 in Dover Township, N.J., is under study. This study is exploring a wide variety of possible risk factors, one being the exposure to groundwater contaminants that occurred through private and community water supplies (i.e., the water-distribution system serving the area). For this purpose, a model of the complex water-distribution system has been developed and calibrated through an extensive field investigation. The components of this water-distribution system, such as number of pipes, number of tanks, and number of supply wells in the network, have changed significantly over a 35-year period (1962 through 1996) - the time frame established for the epidemiologic investigation. For the completion of the epidemiologic study, information on monthly distribution of water in the network, based on a management strategy is necessary for the period 1962 through 1996. For certain months of the study period, some data are available to estimate the operational characteristics and the management strategy employed to operate the water-distribution system. For other months, there are no data to predict the characteristics of this management system. Further complicating the study is that within a given month of any year, the water-distribution system may have operated under peak-, winter-, or average-demand conditions. Manual reconstruction of this management system is time consuming, labor intensive, and costly, given the complexity of the system and the time constraints imposed on the study. In an effort to reduce the required computational time, the problem was formulated as an optimization problem. For each month of the investigation, the management strategy was arrived at by obtaining a solution to the optimization problem. Thus, in this study, it is assumed that the water-distribution system was operated in an optimum manner at all times to satisfy the minimum and maximum pressure constraints and tank level constraints of the system. Given these assumptions, Genetic Algorithms along with the EPANET water-distribution network solver, is used to solve the optimization problem and to develop the historical management strategy used in the water-distribution system, serving the Dover Township area, NJ. This process reduced the required solution time significantly and generated a historically consistent management strategy for the system. The viewer may also connect to MESL research pages for further information on this activity.
During the second year of the cooperative agreement the following computational software were submitted to ATSDR/CDC for their evaluation and beta testing. Some of this software are still in development stage and should not be considered to be a final product. All of these products are presently used by ATSDR/CDC health assessors in evaluating health consequences of contaminants released to subsurface pathways.
(i) Analytical Contaminant Transport analysis System (ACTS Version 6.20)
(ii) GIS Interphase SYStem (GIS-SYS Version 3.20)