An environmental information system (EIS) was developed by HydroQual for several government agencies in Bolivia (Vice Ministry of Mining and Metallurgy, VMMM; Corporación Minera de Bolivia, COMIBOL; and Bolivian Geological and Mining Service, SERGEOMIN). The purpose of the system is to support the administration of mining activities on a country wide scale. It is designed to assist in the development of environmental impact assessments. The EIS is a tool for data storage and visualization, contaminant transport analysis, and computation of human health risk and associated cost. The system has a graphical user interface (GUI) that is bilingual (English and Spanish). The EIS structure follows that of a pyramid as shown in Figure 1. At the base os the pyramid is the Geographic Database which is managed using ArcView. At the next level are three fate and transport models for surface water (SWMOD), air (AIRMOD) and groundwater (GWMOD). The output of these models can be used as input to RISKMOD. At the top of the pyramid is the cost/benefit analysis module.

RISKMOD is a screening-level tool for estimating the human health risks from long-term exposures to metals in environmental media resulting from mining operations. The module is capable of performing risk calculations for a limited number of exposure scenarios and environmental media. The module is linked to the environmental information system using the ArcView Avenue programming language. The user communicates with the program via pop-up dialog boxes. Input data for the module are automatically extracted from the geographic information system (GIS) database. Calculation results are stored in the GIS database. Exposure scenarios can be examined based on both existing and predicted future exposure pathways, within the set of defined exposure scenarios and concentrations of metals in environmental media.

The risk assessment approach used in this module is based on the dose-response and exposure relationships developed by the United States Environmental Protection Agency (USEPA) and the US National Academy of Sciences (NAS) (NAS 1983, USEPA 1989, USEPA 1989a, UPEPA 1989b). This approach estimates the risk of an individual excess cancer over a lifetime and/or the potential for non-cancer effects from exposures to concentrations of metals in environmental media. For exposures to lead in environmental media, separate algorithms are used because the toxic effects of lead on humans are understood to affect humans differently than other metals.

RISKMOD performs screening level calculations for a number of exposure pathways based on generalized and conservative assumptions for child and adult residents and workers. The exposure pathways included in the risk assessment module represent many of the common exposure pathways that may be encountered, however, it is not an exhaustive list of potential exposure pathways.

RISKMOD runs inside the ArcView GIS environment on the Microsoft Windows platform and works as an ArcView extension (e.g. plug-in). It requires Esri ArcView version 3.0 (or higher) (Esri, 1998) and the Spatial Analyst extension.

Risk assessment provides an understanding of the potential risks or hazards to humans and ecological receptors from exposure to chemicals in environmental media, and provides quantitative measures of those risks or hazards to decision-makers so that protection alternatives may be evaluated (Hay Wilson, et.al., 1998). Risk is defined as the potential for adverse consequences. In terms of environmental exposures, risk can be quantified using the toxicity (i.e., the measure of response to a dose) and the exposure (i.e., the absorbed, effective dose) NAS (1983). For chronic or long-term exposures to carcinogenic chemicals, risk is a measure of the increase in the probability of cancer effects over background incidence levels. For non-carcinogenic effects the absorbed, effective dose is compared to a reference dose (i.e., one that is not expected to cause the adverse effects). If the estimated dose is smaller than the reference dose then the effects are not expected to occur. The probability of effects is not quantified by the reference dose, so the magnitude of the difference is not a measure of the magnitude of the effect. Risk is expressed as individual lifetime excess cancer probability for carcinogenic metals. A hazard quotient for non-carcinogenic metals and a hazard index is used for multiple non-carcinogenic metals. For lead exposure, risk is expressed as blood lead levels compared to a reference blood lead level .

The humans and animals that might be affected by a particular environmental condition are referred to as receptors. Toxicity, in the evaluation of chemicals, is a measure of specific adverse effects to the receptor at different dose levels. The source of chemicals is the physical structure or process equipment from which a release occurs. It is not usually possible to identify all of the specific sources and releases, so the source areas related to the sources are identified through environmental sampling or other methods (e.g. environmental models). The source area is the location of highest concentrations in environmental media. Exposure assessment identifies all of the potential exposure pathways by which a receptor may be exposed and provides an estimate of the concentration of chemicals at a point of exposure. The point of exposure is the location where receptors may come in contact with the chemicals. The process of exposure assessment provides predictions of the fate and transport of chemicals in the environment, identification of the pathways from the source or source area to the receptors. Exposure pathways can be thought of as being either cross media exposure pathways, where chemicals are transferred from one media to another (e.g., a chemical in soil leaching into the groundwater), or media specific, where the chemicals are transported within a single environmental media (e.g., a chemical dissolved in groundwater moves with the groundwater flow). The fate of a compound describes the chemical and physical reactions and changes that the chemical undergoes in environmental media. The groundwater, surface water and air dispersion fate and transport models developed within the *MOD suite of models provide the input data (e.g., concentrations of chemicals in environmental media at the points of exposure) for the risk assessment calculations as shown in Figure 2. These calculations can thereafter be used to estimate the costs and benefits of making decisions.

The general equation for determining carcinogenic risk is:

The general non-carcinogenic hazard equation is:

The exposure scenario is a description of the receptor, the receptor's activity and the frequency and duration of the activity. For any risk assessment there are many potential exposure scenarios for which risks and hazard quotients could be calculated. An evaluation usually begins with the identification of the possible exposure scenarios for the current and future land uses of the area or property where concentrations of chemicals may be present. Risk calculations are generally implemented for those exposure scenarios that are considered likely or probable, with other scenarios being calculated based on the results of the initial analyses. Figure 3 shows an example of a risk calculation for Arsenic.

The risk assessment calculations for an individual chemical estimate the potential for adverse effects if a receptor is exposed to only that chemical (e.g. Arsenic). If there are multiple chemicals to which the receptor may be exposed then the consequences of the multiple exposures can be quantified, within some limitations. For carcinogenic chemicals the cumulative risk of exposure to multiple chemicals can be calculated for each exposure pathway by summing the individual lifetime excess cancer risks for each chemical associated with the exposure pathway. For non-carcinogenic chemicals, the hazard quotients for each exposure pathway can be summed to develop a hazard index for that exposure pathway.

RISKMOD addresses the carcinogenic cumulative risk and the non-carcinogenic additive effects separately for all carcinogenic and all non-carcinogenic metals for each exposure pathway, excluding lead in order to avoid high levels of complexity or conversely overly simplifying assumptions that are not technically defensible. Adding across exposure pathways is not recommended because it includes assumptions about receptor habits that go beyond the formulation of the exposure scenarios included in this risk assessment module and therefore may not be valid. Risk is first calculated for each metal for each pathway that has been chosen to be analyzed and then a cumulative risk calculation is implemented as an additional step.

The exposure pathways included in the risk assessment module represent many of the common exposure pathways that may be encountered as shown in Figure 4, however, it is not an exhaustive list of potential exposure pathways.

It should be noted that the fore-going discussion of the calculation of risks applies to all of the metals identified in RISKMOD associated with mining operations with the exception of human exposures to lead. Lead has been included on a limited basis as a screening calculation for adult, worker exposures to lead in soil. The USEPA recommends that residential exposures to lead be evaluated using the Integrated Exposure Uptake Biokinetic (IEUBK) Model based on exposure of children to lead in environmental media (USEPA, 1994). The model is a sophisticated, complex compartmental model that simulates the transport and transfer processes of lead within the human system. This model is not a screening model and therefore is not suitable for the RISKMOD.

This section describes the user interface of RISKMOD. The user interface of the module is embedded in the ArcView graphical user interface (GUI). Figure 5 shows the ArcView GUI with the buttons for the risk assessment module. Each of the buttons is described in detail below. The risk assessment module buttons are accessed from the View.

RISKMOD is executed from the View using the "risk calculation tool." The exposure concentration theme or data layer must be included in the active View. If there is more than one exposure concentration data layer in the View, then the desired chemical data results must be selected. If there are no exposure concentration results in the View a non-spatial (e.g., point estimate) risk estimate will be calculated. When the user selects the R-button, the chemical selection dialog box is displayed. Figure 6 shows the chemical selection box.

Once the user chooses a chemical, the exposure pathway selection dialog box is displayed. Figure 7 shows the exposure pathway selection dialog box. The available exposure pathways for the risk assessment module are pre-set.

Once the user chooses an exposure pathway, the receptor selection dialog box is displayed. Figure 8 shows the receptor selection dialog box. The combined Adult/Child Resident is only applicable to carcinogenic risk calculations.

After selecting a receptor, the scenario selection dialog box is displayed. Since some chemicals exhibit both carcinogenic and non-carcinogenic effects, the user is given the option of calculating carcinogenic risk or hazard quotients. Figure 9 shows the scenario selection dialog box.

Once the scenario is selected, the chemical data input dialog box is displayed. Based on the selected chemical, exposure pathway, receptor, and toxicological effects the risk calculations are uniquely identified. Figure 10 shows the chemical data input dialog box.

The exposure parameter input dialog box is displayed next. Figure 11 shows the exposure parameter input dialog box. Depending on the pathway, scenario and receptor the parameter input screens vary.

Figure 12 shows the concentration input data dialog box. The user then selects the exposure concentration data layer.

Figure 13 shows the run name input dialog box. The user then enters a run name for the output file.

The model will assemble the data from the GIS database and make the risk calculations. The model calculation is executed in Avenue within ArcView. The output of the risk assessment module is a file of estimated carcinogenic risk or hazard quotient values. The data files are of the same form as the input exposure concentration data file (e.g., if a grid file of concentrations is used as the input file then the risk estimates will be generated as a grid file). The new data layer will be added to the active View and it will visible. The data layer will be named RUN NAME" - Results."

RISKMOD can do both spatial and non-spatial risk calculations, depending to the available input data and format. Figure 14 shows the data types supported by RISKMOD to perform spatial calculations. If the input is non-spatial, the output or result will be non-spatial.

Once the user chooses the first risk calculation output file and selects OK on the risk calculation output file selection dialog box, the additive risk calculation output file selection dialog box is displayed. The user then chooses an additional risk calculation output file. These processes are repeated until all applicable output files are selected and the user selects CANCEL on the additive risk calculation output file selection dialog box.

The module will assemble the data from the GIS database and make the cumulative risk or additive effects calculations. The model calculation is executed in Avenue within ArcView. The output of the cumulative risk or additive effects module is a file of estimated cumulative carcinogenic risk or hazard index values. The new data layer will be added to the active View and it will be visible. The data layer will be named RUN NAME" - Results."

If the user selects to calculate the risk from lead, the exposure pathway, receptor and medium are pre-set within the risk assessment module. The user will be prompted accept the default pathway, receptor and medium.

Figure 15 shows the chemical data input dialog box and Figure 16 shows the exposure parameters for lead.

RISKMOD calculates the risk as estimated lead exposure index values.

This section shows an application of RISKMOD in the mining town of Oruro in Bolivia (Figure 17). Oruro is a major mining center in Bolivia, with a population of nearly 200 000.

The example addresses the exposure pathway for air inhalation for Arsenic and Cadmium due to smelter emissions. As input data, RISKMOD uses the results of air dispersion modeling results shown in Figure 18.

The Vinto metallurgical complex is in the vicinity of Oruro as shoyn in Figure 17. The industrial activities in Oruro impact the air quality of the area occurring mainly through atmospheric deposition of trace metals emitted by four primary stacks.

The chemical of interest (As) and the scenario are chosen

Input data:

The results are presented as ArcView grids.

The A-button executes the selection box that displays all of the available risk assessment module runs. In this case we are selecting the Arsenic and Cadmium risk values

Once all of the desired risk or hazard quotient results output files have been selected, the module returns summary values for the combined effects (See Figure 20).

RISKMOD was used to estimate the potential risks (i.e., estimated incremental excess cancer risk values) from inhalation of cadmium and arsenic for an adult resident. The results indicate that potential air inhalation risks for cadmium are generally higher than the air inhalation risks for arsenic. The cumulative risk of air inhalation for cadmium and arsenic is greatest northwest of the source.

Environmental Systems Research Institute (Esri), 1998. ArcView GIS, Version 3.1,

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Hay Wilson, L. L. N. Koerner, A. P. Romanek, J. R. Rocco, R. B. Gilbert, 1998. Critical

Success Factors for Implementing Risk-Based Decision Making at a Large

Refinery Site. Proceedings of the Contaminated Sites Remediation Conference:

Challenges Posed by Urban & Industrial Sites, Fremantle, Western Australia,

Australia, March 22-24, 1999. CSIRO, Australia.

National Academy of Sciences (NAS), 1983. Risk Assessment in the Federal

Government. Managing the Process. National Academy Press, Washington, D.C.

USEPA, 1989a. Risk Assessment Guidance for Superfund, Volume 2: Environmental

Evaluation Manual, EPA/540/1-89/001, NTIS No. PB90155599, March 1989.

USEPA, 1989b. Risk Assessment Guidance for Superfund, Volume 1, Human Health

Evaluation Manual, Part A, EPA/540/1-89/002, December 1989.

USEPA, 1994. Guidance Manual for the Integrated Exposure Uptake Biokinetic Model for

Lead in Children. Office of Emergency and Remedial Response, Washington,

D.C. EPA/540/R-93/081, PB93-963510, 1994.

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