HUMAN HEALTH RISK ASSESSMENT FOR THE COEUR D' ALENE RIVER BASIN


This comprehensive assessment of human health issues and potential exposures and risks in the Coeur d’Alene Basin was conducted under a Memorandum of Agreement between the State of Idaho and EPA Region X. The Basin, located in northern Idaho, is the ancestral home of the Coeur d’Alene Indian Tribe. Since the late 19th century, this area known as the Silver Valley has been the center of one of the most productive mining districts in the world. During the last century, substantial quantities of industrial wastes were directly discharged to the environment from mining, mineral processing, and smelting activities. Public health investigations in the 1970s to 1980s resulted in the 1983 designation, of a 21 square mile area called the Bunker Hill Superfund Site (BHSS), surrounding the former smelter complex near Kellogg. Remedial activities and public health response activities have been ongoing in the BHSS for two decades. In 1998, a Remedial Investigation/Feasibility Study (RI/FS) was undertaken to characterize the degree and extent of the contaminant release in the Basin. Concurrent with the RI/FS, this baseline Human Health Risk Assessment (HHRA) addressed potential health risks associated with residual heavy metals contamination in the Basin for areas east of Harrison upstream from the mouth of the Coeur d’Alene River to the Idaho/Montana border. The main purpose of this HHRA was to determine the extent of heavy metal contamination in environmental media that may expose current or future residents or visitors to the Basin, to evaluate the potential human health risks associated with exposure to those contaminated media, and to provide information for risk managers to evaluate the need for remedial action and development of associated clean-up criteria. The HHRA was accomplished on an accelerated schedule paralleling the RI/FS to accommodate State and local community concerns. The project integrated existing data from State and federal health and exposure surveys, the RI/FS process, and the Natural Resource Damage Assessment ongoing in the Basin. Procedures were developed to combine data from these activities into a comprehensive, compatible data set. Data gaps were identified and supplemental sampling campaigns were designed and implemented to address areas of uncertainty. TerraGraphics performed the lead health RA while the EPA RAC contractor performed the non-lead RA. TerraGraphics combined these efforts into a draft document that was released in June of 2000, completing the entire effort in one year, several months ahead of the RI/FS. This document was extensively reviewed and critiqued by a variety of entities including the national EPA Technical Review Work Group for Lead that commended the HHRA as an innovative and comprehensive report.

Site Specific and USEPA Default Lead Risk Assessment: TerraGraphics conducted site-specific quantitative analysis of the relationship between observed blood lead levels and environmental variables and developed quantitative models relating blood lead levels to soil, house dust, and paint lead levels These were used to quantify baseline exposures and project risk reductions that might be achieved through source modifications. Residential baseline (everyday home life) blood lead predictions were estimated using four different applications of the IEUBK Model. Both the EPA Default Model (using national assumptions for soil and dust ingestion rates and bioavailability) and the Box Model (derived specifically for the BHSS) were employed. The Box Model uses a lower bioavailability estimate and includes a community-wide component for soil/dust exposure that is not included in the EPA Default Model. Paint Lead Assessment: The HHRA contained one of the most extensive evaluations of lead paint as an additional source of exposure in a CERCLA site investigation. Using data collected during the 1996 Coeur d'Alene River Basin Environmental Health Exposure Assessment, TerraGraphics created a database of over 33,000 records of paint XRF samples. Interior and exterior XRF readings and paint conditions were noted for every house sampled, were merged with the blood lead and other exposure source data, and analyzed contemporaneously. Adherence to USEPA Guidance for Lead Risk Assessment: The HHRA provides extensive discussion and is compliant with EPA and U.S. Public Health Service policies regarding lead health and risk assessment. The lead health criteria, the recommended health response actions, the policies and procedures and the methodologies applied including the IEUBK model have been extensively reviewed in open scientific forums and adopted pursuant to federal rules and regulations. Those policies are provided by reference, and in most cases in full text in the document and appendices. A clarification indicating how the policy has evolved and the importance of the risk considerations for individual properties was also included. Coeur d’Alene Tribe Subsistence Scenarios were also assessed in association with tribal representatives. These senarios pertain to children and adults engaged in traditional (aboriginal) or current subsistence lifestyles in the floodplain of the Coeur d'Alene River. Exposure pathways and lead intakes were estimated. Blood lead levels were not predicted for either the traditional or current subsistence scenarios because extremely high estimated intake rates coupled with cultural-specific dietary and behavioral considerations invalidate current blood lead models. Nevertheless, projected intake rates are sufficiently high to indicate that blood lead levels associated with subsistence activities in the floodplain of the Basin would exceed any current health criteria for children or adults in either scenario. The HHRA concluded that achieving appropriate levels of risk for subsistence lifestyles would require levels of environmental contamination comparable to background concentrations.

Stakeholder Involvement: TerraGraphics was tasked with producing a consensus risk assessment document in cooperation with State, federal, Tribal and mining industry representatives. In addition, we were responsible for all public information and stakeholder meetings held to solicit input and our staff publicly presented the results and findings of the HHRA. We reported regularly to the Governor's Task Force on Health and Risk Assessment in the Coeur d'Alene Basin. We conducted weekly conference calls among representatives of the Coeur d'Alene Tribe, Idaho State Agencies, federal Natural Resource Trustees, EPA Region X and their RAC contractor, EPA's National Criteria and Assessment Office, and ATSDR. Periodic conference calls were held to brief mining industry and PRP representatives, Spokane Tribe, Coeur d'Alene Basin Citizens Advisory Committee members, State of Washington, and Spokane County representatives. Every stakeholder was able to review and submit comments on each section of the HHRA during the draft stages. Several public meetings were held throughout the process and were well attended by vociferous advocates of divergent views. Hundreds of written comments and suggestions were received, addressed and incorporated in the planning stage. Substantial efforts were made to address the concerns and input from the local citizens.