Group 5 Central Portion of Areas III and IV RCRA Facility Investigation Report Santa Susana Field Laboratory, Ventura County, California

Transcription

1 Report Group 5 Central Portion of Areas III and IV RCRA Facility Investigation Report Santa Susana Field Laboratory, Ventura County, California Volume II Appendix A Human Health and Ecological Risk Assessment DRAFT IN PROGRESS Prepared for: The Boeing Company and United States Department of Energy November 2008 Jill Bensen Program Manager Dennis Shelton, DABT Risk Assessment Program Director Michael O. Bower, P.E. Project Manager SSFL RA REPORT_V09.DOC

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3 Contents Section Page Appendix A - Human Health and Ecological Risk Assessment Methodology...A-1 A.1 Introduction...A-1 A.1.1 Risk Assessment Guidance...A-2 A.2 Human Health Risk Assessment Methodology...A-4 A.2.1 Identification of Chemicals of Potential Concern for Human Health...A-4 A.2.2 Human Exposure Assessment...A-4 A Exposure Point Concentrations...A-6 A Human Exposure Assumptions...A-8 A Calculation of Chemical Intake...A-8 A.2.3 Human Health Toxicity Assessment...A-11 A Hazard Characterization...A-11 A Dose-Response Evaluation...A-11 A.2.4 Human Health Risk Characterization...A-13 A Cancer Risk Estimation Method...A-14 A Noncancer Risk Estimation Method...A-14 A Lead Risk Estimation...A-15 A Estimation of Risk for Chatsworth Groundwater...A-15 A.3 Ecological Risk Assessment Approach...A-16 A.3.1 Assumptions...A-16 A.3.2 Ecological Problem Formulation...A-17 A Ecological Management Goals, Assessment Endpoints, and Measures...A-17 A Ecological Conceptual Site Model...A-18 A.3.3 Ecological Analysis...A-22 A Exposure Characterization...A-23 A Ecological Effects Characterization...A-26 A.3.4 Ecological Risk Characterization...A-29 A Risk Characterization Process...A-29 A Risk Estimation...A-31 A Risk Description...A-32 A.4 Uncertainty Analysis...A-34 A.4.1 HRA Uncertainties and Limitations...A-34 A Environmental Sampling and Analysis...A-34 A Estimation of Fate and Transport...A-34 A Exposure Assessment...A-34 A Toxicity Assessment...A-36 A Risk Characterization...A-36 A.4.2 ERA Uncertainties and Limitations...A-36 SSFL RA REPORT_V09.DOC III

4 CONTENTS A Problem Formulation...A-37 A Exposure Characterization...A-37 A Ecological Effects Characterization...A-38 A Risk Characterization...A-38 A.5 References...A-40 SSFL RA REPORT_V09.DOC IV

5 CONTENTS List of Tables A.2-1 A.2-2 A.2-3 A.2-4 Summary of Human Exposure Assumptions Used in the Risk Assessment Summary of Toxicity Factors Used in the Risk Assessment Well-Specific Summary of Human Health Risk Estimates for Chatsworth Zone Groundwater; Reasonable Maximum Exposure - Hypothetical Future Residential Scenario Well-Specific Summary of Human Health Risk Estimates for Chatsworth Zone Groundwater; Central Tendency Exposure - Hypothetical Future Residential Scenario A.3-1 A.3-2 A.3-3 A.3-4 A.3-5 A.3-6 A.3-7 A.3-8 A.3-9 A.3-10 A.3-11 A.3-12 A.3-13 A.3-14 A.3-15 A.3-16 A.3-17 A.4-1 A.4-2 Ecological Assessment Endpoints and Measures Exposure Pathway Analyses for Group 5 RFI sites Representative Species for Terrestrial and Wetland Habitats Exposure Factors for Representative Species Area Use Factors for Group 5 RFI sites Bioaccumulation Factors for Plants, Soil Invertebrates, and Mammals Regression Models for Uptake by Plants, Soil Invertebrates, and Mammals Parameters for Soil Vapor Modeling Chemical Properties for VOCs Used in Soil Vapor Modeling ESLs for All Terrestrial and Aquatic Receptors Minimum ESLs Toxicity Reference Values for Terrestrial Plants Toxicity Reference Values for Soil Invertebrates Toxicity Reference Values for Birds Toxicity Reference Values for Mammals - Ingestion Toxicity Reference Values for Mammals - Inhalation of Soil Vapor Toxicity Reference Values for Aquatic Organisms - Exposure to Surface Water HRA Uncertainty Analysis ERA Uncertainty Analysis List of Figures A.3-1 Ecological Risk Assessment Process A.3-2 Generalized Ecological Conceptual Site Model A.3-3 Ecological Risk Characterization Process for Soil A.3-4 Ecological Risk Characterization Process for Burrowing Small Mammals A.3-5 Ecological Risk Characterization Process for Soil Vapor A.3-6 Ecological Risk Characterization Process for Surface Water SSFL RA REPORT_V09.DOC V

6 CONTENTS List of Attachments A1 Boeing Area IV Leach Field A2 Compound A Facility A3 Engineering Chemistry Laboratory A4 Environmental Effects Laboratory A5 Pond Dredge Area A6 Coal Gasification Process Development Unit A7 Area III Sewage Treatment Plant A8 Southeast Drum Storage Yard A9 System Test Laboratory IV A10 Building 65 Metals Laboratory Clarifier A11 Building 100 Trench A12 Department of Energy Leach Field 1 A13 Department of Energy Leach Field 2 A14 Department of Energy Leach Field 3 A15 Hazardous Material Storage Area A16 Rockwell International Hot Laboratory A17 Systems for Nuclear Auxiliary Power A18 Plant Surveys A19 Toxicity Reference Values for Ecological Receptors A20 Background Risk Calculations for Ecological Receptors A21 Ecological Risk Assessment for Wide Ranging Receptors A22 Background Risk Calculations for Human Health Receptors SSFL RA REPORT_V09.DOC VI

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8 Acronyms and Abbreviations ATSDR AUF BAF bgs Boeing BTAG Cal-EPA CF CFOU cm 2 CMS COEC COPC CPEC CSM CTE DDE Dioxins/Furans DioxinFuran_TEQ_Bird DioxinFuran_TEQ_Mammal DioxinFuranPCB_TEQ_Bird DioxinFuranPCB_TEQ_Mammal DTSC Agency for Toxic Substances and Disease Registry area use factor bioaccumulation factor below ground surface The Boeing Company Biological Technical Assistance Group California Environmental Protection Agency Chatsworth Formation Chatsworth Formation Operable Unit square centimeter Corrective Measures Study chemical of ecological concern chemical of potential concern chemical of potential ecological concern conceptual site model central tendency exposure dichlorodiphenyldichloroethylene (a) see table below 2,3,7,8-tetrachlorodibenzodioxin toxic equivalency (based on dioxins and furans for birds 2,3,7,8-tetrachlorodibenzodioxin toxic equivalency (based on dioxins and furans for mammals 2,3,7,8-tetrachlorodibenzodioxin toxic equivalency (based on dioxins, furans, and dioxin-like PCB congeners) for birds 2,3,7,8-tetrachlorodibenzodioxin toxic equivalency (based on dioxins, furans, and dioxin-like PCB congeners) for mammals Department of Toxic Substances Control SSFL RA REPORT_V09.DOC VIII

9 ACRONYMS AND ABBREVIATIONS EcoSSL EF EFA ELCR EPC ERA ESL HEAST HI HQ HRA ILCR IRIS kg LOAEL LOEL mg/kg mg/kg-day mg/l mg/m 3 ND NFA NOAEL NOEC NRWQC PAH PCB PCB_TEQ_Bird ecological soil screening level exposure frequency Engineering Field Activity excess lifetime cancer risk exposure point concentration ecological risk assessment ecological screening level Health Effects Assessment Summary Tables hazard index hazard quotient human health risk assessment incremental lifetime cancer risk Integrated Risk Information System kilogram lowest observed adverse effect level lowest observed effect concentration milligrams per kilogram milligrams of chemical per kilogram of body weight per day milligrams per liter milligrams per cubic meter nondetect no further action no observed adverse effect level no observed effect concentration national recommended water quality criteria polynuclear aromatic hydrocarbon polychlorinated biphenyl 2,3,7,8-tetrachlorodibenzodioxin toxic equivalency (based on dioxin-like PCB congeners) for birds SSFL RA REPORT_V09.DOC IX

10 ACRONYMS AND ABBREVIATIONS PCB_TEQ_Mammal PEF QA/QC RA RCRA RfD RFI RME sf SQL SRAM SSFL TEF TEQ TRV UCL USEPA μg/l μg/dl VF VOC WHO WRS 2,3,7,8-tetrachlorodibenzodioxin toxic equivalency (based on dioxin-like PCB congeners) for mammals particulate emission factor quality assurance/quality control risk assessment Resource Conservation and Recovery Act reference dose RCRA Facility Investigation reasonable maximum exposure slope factor sample quantitation limit Standardized Risk Assessment Methodology Work Plan Santa Susana Field Laboratory toxicity equivalency factor toxicity equivalency quotient toxicity reference value upper confidence limit United States Environmental Protection Agency micrograms per liter micrograms per deciliter volatilization factor volatile organic compound World Health Organization Wilcoxon Rank Sum SSFL RA REPORT_V09.DOC X

11 ACRONYMS AND ABBREVIATIONS (a) Definition of dioxin/furan congeners PCDD/PCDDs 2,3,7,8-TCDD 1,2,3,7,8-PeCDD 1,2,3,4,7,8-HxCDD 1,2,3,6,7,8-HxCDD 1,2,3,7,8,9-HxCDD 1,2,3,4,6,7,8-HpCDD OCDD 2,3,7,8-TCDF 1,2,3,7,8-PeCDF 2,3,4,7,8-PeCDF 1,2,3,4,7,8-HxCDF 1,2,3,6,7,8-HxCDF 2,3,4,6,7,8-HxCDF 1,2,3,7,8,9-HxCDF 1,2,3,4,6,7,8-HpCDF 1,2,3,4,7,8,9-HpCDF OCDF TEQ Polychlorinated dibenzo-p-dioxins/dibenzofurans 2,3,7,8-tetrachlorodibenzo-p-dioxin 1,2,3,7,8-pentachlorodibenzo-p-dioxin 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin 1,2,3,6,7,8-hexachlorodibenzo-p-dioxin 1,2,3,7,8,9-hexachlorodibenzo-p-dioxin 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin 1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin 2,3,7,8-tetrachlorodibenzofuran 1,2,3,7,8-pentachlorodibenzofuran 2,3,4,7,8-pentachlorodibenzofuran 1,2,3,4,7,8-hexachlorodibenzofuran 1,2,3,6,7,8-hexachlorodibenzofuran 2,3,4,6,7,8-hexachlorodibenzofuran 1,2,3,7,8,9-hexachlorodibenzofuran 1,2,3,4,6,7,8-heptachlorodibenzofuran 1,2,3,4,7,8,9-heptachlorodibenzofuran 1,2,3,4,6,7,8,9-octachlorodibenzofuran Toxic Equivalency Quotient (normalized to 2,3,7,8 TCDD) SSFL RA REPORT_V09.DOC XI

12 Appendix A - Human Health and Ecological Risk Assessment Methodology A.1 Introduction This appendix describes the approaches used in preparing the risk assessments (RA) for the Group 5 Resource Conservation Recovery Act (RCRA) Facility Investigation (RFI) Report. The RA for each Group 5 site has two components: a human health risk assessment (HRA) and an ecological risk assessment (ERA). Each RA for Group 5 was prepared as part of the RCRA Corrective Action Program at the Santa Susana Field Laboratory (SSFL), which is being conducted under the oversight of the California Environmental Protection Agency (Cal-EPA), Department of Toxic Substances Control (DTSC). The overall goal of each RA is to determine the nature, magnitude, and probability of actual or potential harm to public health or to the environment, posed by the threatened or actual release of hazardous substances at each site. This appendix provides an overview of RA methodologies that are common to all Group 5 RFI sites, including the exposure assumptions for human and ecological receptors, as well as the chemical-specific exposure and toxicity factors for assessing human and ecological risks. RAs for 17 RFI sites have been completed as part of the Group 5 RFI report. The RFI sitespecific RAs are included as Attachments A1 through A17 of this appendix. The site-specific HRAs and ERAs address pathways associated with potential exposure to site-related releases to soil, soil vapor, sediment, surface water, shallow groundwater and/or Chatsworth groundwater for estimating potential human and ecological health risks. Each RFI site-specific RA in Attachments A1 through A17 contains the following sections: Section 1.0 Introduction Section 2.0 Data Usability for Risk Assessment Section 3.0 Human Health Risk Assessment Section 4.0 Ecological Risk Assessment Section 5.0 References Supporting site-specific information for each RA is also provided in Attachments A18 through A22 as follows: Attachment A18 Plant Surveys Attachment A19 Toxicity Reference Values for Ecological Receptors Attachment A20 - Background Risk Calculations for Human Health and Ecological Receptors SSFL RA REPORT_V09.DOC A-1

13 Attachment A21 - Ecological Risk Assessment for Wide Ranging Receptors Key findings of each site-specific HRA and ERA are presented in the summary section of each respective attachment, as well as in Section 4 of the Site RFI Appendices (D through U). The RA results are used as the basis for site action recommendations: either recommendation for further action in the Corrective Measures Study (CMS) or No Further Action (NFA). Site action recommendations are presented in Section 5 of Appendices D through T and in Section 7 of the Group 5 RFI Report (Volume I). Supporting background information and data for the RAs are presented in the Group 5 RFI Report (Volume I) and in its appendices. Sections 1 through 5 of the Group RFI Report (Volume I) and Sections 1 through 3 of Appendices D through T (the RFI site appendices) provide the description of the characterization findings upon which these HRAs and ERAs are based. Note that Group 5 RFI site-specific sample locations are shown in figures in each of the RFI site appendices (Appendices D through T). Laboratory data for soil, sediment, and surface water samples are presented in Attachment 3 to each RFI site report appendix. A description of groundwater characterization for the Group 5 RFI Reporting Area is provided in Appendix B. A.1.1 Risk Assessment Guidance The RA for each Group 5 site was conducted following the methods and assumptions described in the Standardized Risk Assessment Methodology (SRAM) Work Plan, Revision 2 Final (SRAM) for SSFL (MWH, 2005). The approaches outlined in the SRAM include, in part, the guidance documents listed below: HRA Supplemental Guidance for Human Health Multimedia Risk Assessments of Hazardous Waste Sites and Permitted Facilities. (Cal-EPA, 1996) Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air. (Cal- EPA, 2004) Risk Assessment Guidance for Superfund (RAGS) Volume I: Human Health Evaluation Manual, Part A (Interim Final). (USEPA, 1989) Risk Assessment Guidance for Superfund (RAGS), Volume I: Human Health Evaluation Manual (Part E, Supplemental Guidance for Dermal Risk Assessment). (USEPA, 2004a) Software for Calculating Upper Confidence Limits (UCLs) ProUCL Version 4.0. (USEPA, 2008 [Online]) (USEPA, 2008a) ERA Guidance for Ecological Risk Assessment at Hazardous Waste Sites and Permitted Facilities. (DTSC, 1996) Ecological Risk Assessment Guidance for Superfund: Process for Designing and Conducting Ecological Risk Assessment. (Interim Final). (USEPA, 1997a) SSFL RA REPORT_V09.DOC A-2

14 ECO Updates, Volume 1, Numbers 1 through 5. (USEPA, 1991a, 1991b, 1992a, 1992b, and 1992c) ECO Updates, Volume 2, Numbers 1 through 4. (USEPA, 1994a, 1994b, 1994c, and 1994d) ECO Updates, Volume 3, Numbers 1 and 2. (USEPA, 1996a, and 1996b) Final Guidelines for Ecological Risk Assessment. (USEPA, 1998) Ecological Risk Assessment and Risk Management Principles for Superfund Sites. (USEPA, 1999a) The Role of Screening-Level Risk Assessments and Refining Contaminants of Concern in Baseline Ecological Risk Assessments. (USEPA, 2001) SSFL RA REPORT_V09.DOC A-3

15 A.2 Human Health Risk Assessment Methodology The site-specific HRAs present an analysis of the potential for adverse human health effects potentially associated with contaminants at each site. The HRA for each Group 5 RFI site includes the following components: Identification of chemicals of potential concern for human health. Identifies the chemicals detected at the site that are considered most important to the human health evaluation. Human exposure assessment. Describes the pathways by which potential human exposure could occur and estimates the magnitude, frequency, and duration of the exposure. Human health toxicity assessment. Summarizes the toxicity of the selected chemicals and the relationship between the magnitude of exposure and adverse human health effects. Human health risk characterization. Integrates the toxicity and exposure assessments to estimate the potential risks to public health from exposure to chemicals in environmental media. These components are completed as described in the following subsections. A.2.1 Identification of Chemicals of Potential Concern for Human Health In accordance with the processes outlined in the SRAM, available site data are reviewed to identify a set of data that is of acceptable quality for each HRA. Following a data usability evaluation, analytical data are screened to identify those constituents most important to the HRA. These constituents, called chemicals of potential concern (COPCs), are quantitatively addressed in the HRA. A.2.2 Human Exposure Assessment The exposure assessment component of the HRA identifies the means by which individuals at or near a Group 5 RFI Site may come into contact with constituents in exposure media. It addresses exposures that may result under reasonably anticipated potential uses of the site and the surrounding areas in the future. The exposure assessment also identifies the populations that may be exposed, the routes by which individuals may become exposed, and the magnitude, frequency, and duration of potential exposures. SSFL RA REPORT_V09.DOC A-4

16 Each HRA addresses residential exposure scenarios. However, a more likely future use of SSFL is for recreational purposes, and recreationists are the most plausible future human receptors. Therefore, risk estimates for recreational scenarios are quantified in the HRAs. Each RFI site-specific RA in Attachments A1 through A17 contains a figure that depicts the conceptual site model (CSM) for potential human exposures at each of the Group 5 RFI Sites. A generalized CSM for potential human exposures at the Group 5 Reporting Area is depicted in Figure A.2-1. The potential exposure scenarios considered for each HRA include the following: Hypothetical Future Urban Adult Residents: Potential exposure of urban adult residents to constituents in soil to 10 feet below ground surface (bgs) 1 by incidental ingestion, dermal contact, and inhalation of dust and vapors. Potential uptake of constituents in soil to 2 feet bgs into home-grown produce and consumption of produce by adult residents. Potential domestic use of groundwater. Potential inhalation exposure of adult residents to constituents volatilizing from soil vapor to indoor and ambient air. Hypothetical Future Urban Child Residents: Potential exposure of urban child residents to constituents in soil to 10 feet bgs by incidental ingestion, dermal contact, and inhalation of dust and vapors. Potential uptake of constituents in soil to 2 feet bgs into home-grown produce and consumption of produce by adult residents. Potential domestic use of groundwater. Potential inhalation exposure of child residents to constituents volatilizing from soil vapor to indoor and ambient air. Future Adult Recreationists: Potential exposure of adult recreationists to constituents in soil to 2 feet bgs by incidental ingestion, dermal contact, and inhalation of dust and vapors. Potential inhalation exposure of adult recreationists to constituents volatilizing from soil vapor to ambient air. Future Child Recreationists: Potential exposure of child recreationists to constituents in soil to 2 feet bgs by incidental ingestion, dermal contact, and inhalation of dust and vapors. Potential inhalation exposure of child recreationists to constituents volatilizing from soil vapor to ambient air. Each of these exposure scenarios is evaluated using both reasonable maximum exposure (RME) and central tendency exposure (CTE) assumptions, as discussed in Section A Although some hypothetical pathways of migration of COPCs to possible exposure points, such as volatilization of volatile organic compounds (VOCs) from groundwater or deep soil (more than 10 feet bgs) to ambient air, are considered very minor contributors to overall exposure to future residents at SSFL, these pathways are evaluated in the HRA. The exposure assessment component of the HRA includes the following tasks: Computation of exposure point concentrations (EPCs) Development of exposure assumptions for potentially complete exposure pathways Calculation of chemical intake for COPCs 1 In accordance with SRAM (MWH, 2005) (2005), risk estimates for residential scenarios were estimated for depth intervals that are 0 to 2 feet bgs and 0 to 10 feet bgs. The interval exhibiting the higher risk was reported for each RFI site in its respective Attachment (1 through 17). SSFL RA REPORT_V09.DOC A-5

17 The methodologies and results of these tasks are discussed in the following subsections. A Exposure Point Concentrations EPCs are estimated constituent concentrations with which a receptor may come into contact, and are specific to each exposure medium. For direct contact routes of exposure to soil and groundwater (incidental ingestion and dermal contact), EPCs are represented by concentrations directly measured in soil or groundwater samples collected from the Group 5 RFI Sites. For indoor air, ambient air, and homegrown produce, EPCs were estimated from other media using modeling approaches. EPCs for COPCs in soil, soil vapor, and groundwater are summarized for each Group 5 RFI site in Attachments A1 through A17, for the RME and CTE cases. EPC Approach for Ingestion of Soil or Groundwater The EPCs for exposure pathways associated with ingestion of soil and groundwater at the Group 5 RFI sites were estimated by aggregating concentration data from samples collected for each medium (and in the case of soil, for each depth interval of 0 to 2 feet or 0 to 10 feet bgs). For the RME case, the EPCs for risk estimation were calculated by using the best statistical estimate of an upper bound on the average exposure concentrations, in accordance with United States Environmental Protection Agency (USEPA) guidance for statistical analysis of monitoring data (USEPA, 1989, 1992d, 2002). The 95 percent UCL on the mean concentration is considered by these guidance documents as a conservative upper bound estimate that is not likely to underestimate the mean concentration and most likely overestimates that concentration. EPCs were calculated for each analyte using the USEPA statistical program ProUCL, Version 4.0 (USEPA, 2008a). This procedure identifies the statistical distribution type (that is, normal, lognormal, or non-parametric) for each constituent within the defined exposure area and computes the corresponding 95 percent UCL for the identified distribution type. The maximum detected concentration is used in place of the 95 percent UCL when the calculated 95 percent UCL is greater than the maximum detected value. Factors affecting the distribution of the data (resulting in the selection of the maximum detected value rather than the 95 percent UCL) include small sample size, low frequency of detection, and/or wide variability. Using maximum detected values for EPCs may contribute to overestimation of risk (this and other uncertainties are discussed in Section A.4). For the CTE case, the EPCs for risk estimation were calculated as the arithmetic mean concentration of the sample data for each medium and data group, in accordance with Section 6 of the SRAM (MWH, 2005). When the computed 95 percent UCL (based on sitespecific statistical distribution type) was lower than the arithmetic mean, the UCL was used. Dioxins/Furans EPCs for dioxin-like congeners of polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (PCBs) were adjusted in accordance with the 1998 and 2005 World Health Organization (WHO) toxicity equivalency factor (TEF) approach (Van den Berg et al., 1998 and 2006). The purpose of using the WHO TEF adjustment is to account for the relative toxic potencies of dioxin-like PCDDs, PCDFs, and PCBs relative to the most toxic congener 2,3,7,8-TCDD. TEF-adjusted SSFL RA REPORT_V09.DOC A-6

18 PCDDs, PCDFs, and PCBs were summed to derive a dioxin/furan toxicity equivalency quotient (TEQ) concentration for risk assessment. Separate TEQs were computed for birds (for use in the ERA) and mammals (for use in both the HRA and ERA) based on different TEFs for these receptor groups. TEQs are listed one of three ways in the individual site reports depending on the available site data as follows: DioxinFuran_TEQ site data included both dioxins and furans DioxinFuranPCB_TEQ site data included dioxins and furans as well as Aroclors (1254 and/or 1260) which were used to extrapolate dioxin-like PCBs. PCB_TEQ site data included only Aroclors (1254 and/or 1260) which were used to extrapolate the dioxin-like PCBs. Any of the above listings may be followed by _Bird to signify TEQs calculated using bird TEFs (used only in the ERA) or _Mammal to signify TEQs calculated using mammal TEFs (used in the HRA and ERA). Dioxin-Like Polychlorinated Biphenyls Dioxin-like polychlorinated biphenyls (PCBs) were not included in the analyses for Group 5 RFI sites. PCB congener concentrations in soil were estimated based on detected Aroclor 1254 and 1260 concentrations, using the extrapolation factor approach as described in SRAM (MWH, 2005). From this, PCB_TEQs were estimated from the WHO TEFs as described above for dioxins/furans. Extrapolation factors were developed in the SRAM (MWH, 2005) based on seven paired Aroclor 1254 and congener samples and two paired Aroclor 1260 and congener samples. Extrapolation factors were the maximum ratios of PCB congener to Aroclor concentration. Extrapolation factors were applied to the RME and CTE concentrations of Aroclor 1254 and/or Aroclor 1260 to derive a PCB_TEQ. If both Aroclor 1254 and 1260 were available for a site, the TEQs from each were summed. EPC Approach for Ingestion of Homegrown Produce EPCs in homegrown produce were estimated in accordance with Section 5.5 of the SRAM (MWH, 2005), using bio-uptake models to estimate transfer of COPCs from the top 2 feet of soil to both root-zone and aboveground (leaf and fruit) portions of edible plants. EPC Approach for Inhalation Route For the inhalation route, EPCs were estimated using modeling approaches consistent with SRAM (MWH, 2005). Soil-derived dust concentrations in ambient air were estimated using particulate emission factors (PEFs), as described in Section of SRAM (MWH, 2005). Soil gas concentrations of VOCs were either directly measured via soil vapor sampling, or estimated from subsurface soil and/or groundwater. When a VOC was detected in subsurface soil and/or groundwater at a site, but not analyzed for in soil vapor, the soil vapor concentration was estimated from levels found in the other media. Indoor air and ambient air concentrations were estimated for each VOC in soil vapor using the modeling approaches described in Section of SRAM (MWH, 2005). SSFL RA REPORT_V09.DOC A-7

19 A Human Exposure Assumptions The estimation of exposure requires numerous assumptions to describe potential exposure situations. Upper-bound exposure assumptions are used to estimate RME conditions to provide a bounding estimate on exposure. The RME case is defined as the highest exposure that is reasonably expected to occur at a site. The intent of the RME scenario is to estimate a conservative exposure case that is still within the range of possibilities. In addition to RME assumptions, average exposure assumptions are used to estimate CTE conditions to represent the typical case. The exposure assumptions used are specific to a hypothetical residential exposure scenario, consistent with assumed unrestricted future land use. The range of risk estimates bounded by the CTE and RME cases provides an indication of the most plausible range over which residential risks may occur under most conditions at the site. The exposure parameters used for generating RME and CTE risk estimates for the hypothetical residential and recreational adult and child exposure scenarios are listed in Table A.2-1. The exposure assumptions for ingestion, dermal contact, and inhalation are in accordance with Tables 5-2 through 5-5 of the SRAM (MWH, 2005), and are generally based on values provided in Cal-EPA and USEPA guidance documents, or best professional judgment. A Calculation of Chemical Intake Exposure that is normalized over time and body weight is termed intake (expressed as milligrams of chemical per kilogram body weight per day [mg/kg-day]). The method for computation of intake for the Group 5 RFI Sites exposure scenarios is described in the following subsections, and the intake results for each site are provided in the risk calculation tables in Attachments A1 through A17. Incidental Ingestion of Soil The following equation is used to calculate the intake associated with the incidental ingestion of constituents in soil for the recreational and hypothetical resident adult and child scenarios: C Intake = s IRS EF ED 10 BW AT 6 kg mg where: C S = Constituent concentration in soil (mg/kg) IRS = Soil ingestion rate (mg/day) EF = Exposure frequency (days/year) ED = Exposure duration (years) BW = Body weight (kilograms [kg]) AT = Averaging time (days) The exposure assumptions for estimating chemical intake from the ingestion of constituents in soil are listed in Table A.2-1. SSFL RA REPORT_V09.DOC A-8

20 Dermal Contact with Soil Chemical intake from dermal contact with soil for the recreational and hypothetical resident adult and child scenario is estimated using the following equation: C Intake = S SA ABS AF EF ED 10 BW AT 6 kg mg where: CS = Constituent concentration in soil (mg/kg) SA = Exposed skin surface area (square centimeters [cm 2 ]) ABS = Fraction of constituent absorbed from soil to skin (unitless) AF = Soil to skin adherence factor (mg/cm 2 ) EF = Exposure frequency (days/year) ED = Exposure duration (years) BW = Body weight (kg) AT = Averaging time (days) The exposure assumptions used to estimate exposure from dermal contact with soil are listed in Table A.2-1. Dermal absorption fractions (ABS) values are derived from the USEPA Supplemental Guidance for Dermal Risk Assessment (USEPA, 2004a), and are listed in Table A.2-2 for all COPCs detected at Group 5 RFI sites. Inhalation of Ambient Dust and Vapors from Surface Soil Chemical intake from inhalation of dust and vapors from ambient air for the recreational and hypothetical resident adult and child scenario is estimated using the following equation: Intake = C s INH PEF VF BW AT EF ED where: CS = Constituent concentration in soil (mg/kg) INH = Inhalation rate (m 3 /day) PEF = Particulate emissions factor (m 3 /kg) VF = Volatilization factor (m 3 /kg) EF = Exposure frequency (days/year) ED = Exposure duration (years) BW = Adult body weight (kg) AT = Averaging time (days) The exposure assumptions used to estimate exposure from inhalation are listed in Table A.2-1. The volatilization factors (VFs) for the VOCs identified as COPCs in soil at Group 5 RFI sites were calculated using the Jury Model as described in the USEPA Soil Screening Guidance: Users Guide (USEPA, 1996c) and are provided in Table A.2-2. The PEF used was the default value recommended by USEPA Region IX (USEPA, 2004b). SSFL RA REPORT_V09.DOC A-9

21 Ingestion of Groundwater The following equation is used to calculate the intake associated with ingestion of constituents in groundwater for the hypothetical resident adult and child scenarios: where: C Intake = w IRW EF ED BW AT Cw = Constituent concentration in groundwater (milligrams per liter [mg/l]) IRS = Water ingestion rate (L/day) EF = Exposure frequency (days/year) ED = Exposure duration (years) BW = Body weight (kg) AT = Averaging time (days) The exposure assumptions for estimating chemical intake from the ingestion of constituents in groundwater are listed in Table A.2-1. In accordance with the SRAM (MWH, 2005), intake of VOCs from the dermal and inhalation routes of exposure is assumed to be equivalent to the intake from the ingestion route. Ingestion of Homegrown Produce The following equation is used to calculate the intake associated with the ingestion of constituents in homegrown produce for the hypothetical resident adult and child scenarios: where: C Intake = p IRP EF ED BW AT C p = Constituent concentration in produce (mg/kg, wet weight basis) IRS = Produce ingestion rate (kg/day, wet weight basis) EF = Exposure frequency (days/year) ED = Exposure duration (years) BW = Body weight (kg) AT = Averaging time (days) The exposure assumptions for estimating chemical intake from the ingestion of constituents in homegrown fruits and vegetables are listed in Table A.2-1. The concentration term C p reflects COPC uptake from soil (0 to 2 feet bgs) to both aboveground (leaf and fruit) produce concentrations, as well as belowground (root) produce. The consumption rate data listed in Table A.2-1 for fruits and vegetables are not specific to above- and belowground produce. Therefore, it is conservatively assumed that one-half an individual s total produce consumption is associated with aboveground produce, and one-half is associated with belowground plants. This assumption is considered conservative because it is highly unlikely that most individuals consume a higher amount of belowground produce than aboveground produce, yet the biotransfer factors (used to estimate EPCs) for belowground produce are 35 times greater than those for aboveground produce. The biotransfer factors SSFL RA REPORT_V09.DOC A-10

22 used to estimate uptake into produce are listed in Table A.2-2 for all COPCs detected at Group 5 RFI sites. A.2.3 Human Health Toxicity Assessment The toxicity assessment identifies the types of toxicity that COPCs at the Group 5 RFI Sites could exhibit, and the relationship between the magnitude of exposure to a constituent and the likelihood of adverse health effects to potentially exposed populations. The toxicity assessment consists of two steps: hazard characterization and dose-response evaluation. These two steps are discussed in the following subsections. A Hazard Characterization Hazard characterization identifies the types of toxic effects a constituent can exert. Constituents can be divided into two broad groups on the basis of their effects on human health: noncarcinogens and carcinogens. This classification has been selected because health risks are calculated quite differently for carcinogenic and noncarcinogenic effects, and separate toxicity values have been developed for them. Carcinogens are those constituents suspected of causing cancer following exposure; noncarcinogenic effects cover a wide variety of systemic effects, such as liver toxicity or developmental effects. Some constituents (such as arsenic) are capable of eliciting both carcinogenic and noncarcinogenic responses; therefore, these carcinogens are also evaluated for systemic (noncarcinogenic) effects. For cancer effects, USEPA developed a carcinogen classification system (USEPA, 1986a) that was a weight-of-evidence approach to classify the likelihood that a constituent is a human carcinogen. Although this classification scheme has been superseded in more recent guidance, the Guidelines for Carcinogen Risk Assessment (USEPA, 2005a), it is used in this report because USEPA has not fully implemented the newer guidance for all chemicals. Information considered in developing the classification includes human studies of the association between cancer incidence and exposure, as well as long-term animal studies under controlled laboratory conditions. Other supporting evidence considered includes short-term tests for genotoxicity, metabolic and pharmacokinetic properties, toxicological effects other than cancer, structure-activity relationships, and physical and chemical properties of the constituent. For noncancer effects, toxicity values are derived on the basis of the critical toxic endpoint (that is, the most sensitive adverse effect following exposure). The USEPA classifications for each of the COPCs detected at Group 5 RFI sites are listed in Table A.2-2. For noncancer effects, toxicity values are derived on the basis of the critical toxic endpoint (that is, the most sensitive adverse effect following exposure). The Group 5 COPCs having documented systemic effects are listed in Table A.2-2. A Dose-Response Evaluation The magnitude of toxicity of a constituent depends on the dose to a receptor. Dose refers to exposure to a constituent concentration over a specified period of time. Human exposures are generally classified as acute (typically less than 2 weeks), sub-chronic (about 2 weeks to SSFL RA REPORT_V09.DOC A-11

23 7 years), or chronic (usually 7 years to a lifetime). The HRA addresses exposures that are considered chronic (for the hypothetical residential scenario). Acute exposures and risks are generally evaluated only when chronic exposure estimates pose a high risk. A doseresponse curve describes the relationship between the degree of exposure (the dose) and the incidence of the adverse effects (the response) in the exposed population. USEPA uses this dose-response information to establish toxicity values for particular constituents, as described in the following paragraphs. Toxicity Values for Human Health The hierarchy of sources of toxicity values (cancer slope factors and noncancer reference doses) used in the HRA is as follows: California Potency Factors: California Cancer Potency Values Table. Office of Environmental Health Hazard Assessment (OEHHA) (OEHHA, 2008). The Integrated Risk Information System (IRIS) database available through the USEPA Environmental Criteria and Assessments Office in Cincinnati, Ohio. IRIS, prepared and maintained by USEPA, is an electronic database containing health risk and USEPA regulatory information on specific chemicals (USEPA, 2008b). USEPA Provisional Peer Reviewed Toxicity Values (PPRTVs), provided by the Office of Research and Development/National Center for Environmental Assessment/Superfund Health Risk Technical Support Center, which develops these values on a chemicalspecific basis when requested under the USEPA Superfund program. The Health Effects Assessment Summary Tables (HEAST), provided by the USEPA Office of Solid Waste and Emergency Response, is a compilation of toxicity values published in various health-effects documents issued by USEPA (USEPA, 1997b). Reference Doses for Noncancer Effects The toxicity value describing the dose-response relationship for noncancer effects is the reference dose value, or RfD. For noncarcinogenic effects, the body s protective mechanisms must be overcome before an adverse effect is manifested. If exposure is high enough and these protective mechanisms (or thresholds) are exceeded, adverse health effects can occur. USEPA attempts to identify the upper bound of this tolerance range in the development of noncancer toxicity values. USEPA uses the apparent toxic threshold value, in conjunction with uncertainty factors based on the strength of the toxicological evidence, to derive an RfD. USEPA defines an RfD as follows (USEPA, 1989): In general, the RfD is an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime. The RfD is generally expressed in units of milligram per kilogram of body weight each day (mg/kg-day). In accordance with the SRAM (MWH, 2005), the HRA uses available chronic RfDs for the oral exposure route to evaluate toxicity for the dermal exposure route. The RfDs for the COPCs identified at Group 5 RFI sites are summarized in Table A.2-2. SSFL RA REPORT_V09.DOC A-12

24 Slope Factors for Cancer Effects The dose-response relationship for cancer effects is expressed as a cancer slope factor (SF) that converts estimated intake directly to excess lifetime cancer risk (ELCR). Slope factors are presented in units of risk per level of exposure (or intake). The data used for estimating the dose-response relationship are taken from lifetime animal studies or human occupational or epidemiological studies where excess cancer risk has been associated with exposure to the constituent. However, because risk at low intake levels cannot be directly measured in animal or human epidemiological studies, a number of mathematical models and procedures have been developed to extrapolate from the high doses used in the studies to the low doses typically associated with environmental exposures. The model choice leads to uncertainty. USEPA generally assumes linearity at low doses and uses the linearized multistage procedure when uncertainty exists about the mechanism of action of a carcinogen and when information suggesting nonlinearity is absent. It is assumed, therefore, that if a cancer response occurs at the dose levels used in the studies, there is some probability that a response will occur at all lower exposure levels (that is, a dose-response relationship with no threshold is assumed). Moreover, the dose-response slope chosen is usually the UCL on the dose-response curve observed in the laboratory studies. As a result, uncertainty and conservatism are built into the USEPA risk extrapolation approach. USEPA has stated that cancer risks estimated by this method produce estimates that provide a rough but plausible upper limit of risk. In other words, it is not likely that the true risk would be much more than the estimated risk, but the true value of the risk is unknown and may be as low as zero (USEPA, 1986a). In accordance with the SRAM (MWH, 2005), the HRA uses available cancer slope factors for the oral exposure route to evaluate toxicity for the dermal exposure route. The slope factors for the COPCs identified at Group 5 RFI sites are summarized in Table A.2-2. A.2.4 Human Health Risk Characterization This section summarizes the approach used to develop the quantitative risk characterization for environmental media, based on the results obtained from the analytical data collected at each Group 5 site. In the risk characterization component of the HRA process, quantification of risk is accomplished by combining the results of the exposure assessment (estimated chemical intakes) with the results of the dose-response assessment (toxicity values identified in the toxicity assessment) to provide numerical estimates of potential health risk. The quantification approach differs for potential noncancer and cancer effects, as described in the subsections below. Although the HRA produces numerical estimates of risk, it should be recognized that these numbers might not predict actual health outcomes because they are based largely on hypothetical assumptions. Their purpose is to provide a frame of reference for risk management decisionmaking. Any actual risks are likely to be lower than these estimates. Interpretation of the risk estimates provided should consider the nature and weight of evidence supporting these estimates, as well as the magnitude of uncertainty surrounding them, as described in Section A.4. SSFL RA REPORT_V09.DOC A-13

25 A Cancer Risk Estimation Method The potential for cancer effects is evaluated by estimating ELCR. This risk is the incremental increase in the probability of developing cancer during one s lifetime in addition to the background probability of developing cancer (that is, if no exposure to site constituents occurs). For example, a 2 x 10-6 ELCR means that, for every 1 million people exposed to the carcinogen throughout their lifetimes, the average incidence of cancer may increase by two cases of cancer. In the United States, the background probability of developing cancer for men is a little less than one in two, and for women a little more than one in three (American Cancer Society, 2008). As previously mentioned, cancer slope factors developed by USEPA represent upper-bound estimates, so any cancer risks generated in the HRA should be regarded as an upper bound on the potential cancer risks rather than accurate representations of true cancer risk. The true cancer risk is likely to be less than that predicted (USEPA, 1989). For each Group 5 RFI Site, ELCRs were estimated by using the following formula: where: Risk = Intake SF Risk = Excess lifetime cancer risk (unitless probability) Intake = Chronic daily intake averaged over a lifetime (mg/kg-day) SF = Cancer slope factor (mg/kg-day)-1 Although synergistic or antagonistic interactions might occur between cancer-causing constituents and other constituents, information is generally lacking in the toxicological literature to predict quantitatively the effects of these potential interactions. Therefore, cancer risks are treated as additive within an exposure route in the HRA. This is consistent with the USEPA guidance regarding risk assessment of chemical mixtures (USEPA, 1986b). For estimating the cancer risks from exposure to multiple carcinogens from a single exposure route, the following equation is used: where: N Risk T = Risk 1 i RiskT = Total cancer risk from route of exposure Riski = Cancer risk for the ith constituent N = Number of constituents A Noncancer Risk Estimation Method For noncancer effects, the likelihood that a receptor will develop an adverse effect is estimated by comparing the predicted level of exposure for a particular constituent with the highest level of exposure that is considered protective (that is, its RfD). The ratio of the intake divided by RfD is termed the hazard quotient (HQ): where: HQ = Intake RfD SSFL RA REPORT_V09.DOC A-14

26 HQ = Noncancer hazard quotient from route of exposure Intake = Chronic daily intake averaged over the exposure duration (mg/kg-day) RfD = Noncancer reference dose (mg/kg-day) When the HQ for a constituent exceeds 1 (that is, exposure exceeds RfD), there is a concern for potential noncancer health effects. To assess the potential for noncancer effects posed by exposure to multiple constituents, a hazard index (HI) approach was used according to USEPA guidance (USEPA, 1989). This approach assumes that the noncancer hazard associated with exposure to more than one constituent is additive; therefore, synergistic or antagonistic interactions between constituents are not accounted for. The HI may exceed 1.0 even if all the individual HQs are less than 1. In this case, the constituents may be segregated by similar mechanisms of toxicity and toxicological effects. Separate HIs may then be derived based on mechanism and effect. The HI is calculated as follows: where: HI N = 1 Intake i RfD HI = Noncancer hazard index Intake i = Chronic daily intake of the ith constituent (mg/kg-day) RfD i = Reference dose of the ith constituent (mg/kg-day) N = Number of constituents A Lead Risk Estimation Potential risks from lead concentrations are evaluated using methods different from those conventionally used for other carcinogens and noncarcinogens. Risks resulting from uptake of lead are evaluated using the DTSC LeadSpread 7 calculation spreadsheet from the Cal-EPA Web site (Cal-EPA, 2006). The model calculates blood lead levels from exposure to soil lead concentrations, in addition to other routes. A default blood lead level of 10 micrograms per deciliter (μg/dl) of blood is considered a level of concern that triggers intervention to reduce exposure. As recommended by DTSC, the 90th, 95th, 98th, and 99th percentile blood lead concentrations predicted by the model will be evaluated for both children and adults. If the lead concentrations in site media result in a calculated blood lead level below 10 μg/dl in 95 to 99 percent of the potentially exposed population, no unacceptable risk exists. A Estimation of Risk for Chatsworth Groundwater For each site HRA, risk estimates for Chatsworth Formation groundwater are based on the maximum risk well point within Group 5 Reporting Area, using the maximum concentrations detected over the last 3 years of available data. For Group 5, the maximum risk well point is at HAR-18. The Chatsworth groundwater well-specific (for the entire Group 5 Reporting Area) ELCR and HI estimates for the future resident adult and child exposure scenarios are provided in Attachment 22 for the RME and CTE cases. Tables A.2-3 and A.2-4 summarize the well-specific results for the RME and CTE cases, respectively. i SSFL RA REPORT_V09.DOC A-15

27 A.3 Ecological Risk Assessment Approach The ERA presents an analysis of the potential for adverse ecological effects that may be associated with contaminants at each site. The ERAs were conducted in accordance with the SRAM (MWH, 2005) and guidance documents listed previously in Section In addition to evaluations specified by the SRAM, additional evaluations were completed, resulting in more robust ERAs that would provide more information to risk managers for use in determining corrective actions. Additional evaluations are noted in the following sections. The ERA process includes three main components: Problem Formulation, Analysis, and Risk Characterization (as shown in Figure A.3-1). Information from each of these components that is common to all Group 5 RFI sites is presented as part of this Appendix. Site-specific information is presented in each of the Group 5 ERAs. Information included in each component is listed below. Ecological Problem Formulation. Describes the ecological setting of the site; identifies potentially complete exposure pathways, representative species, and chemicals of potential ecological concern (CPECs); and develops the ecological CSM. Ecological Analysis. Presents exposure characterization and ecological effects characterization including exposure factors, bioaccumulation factors/uptake models, area use factors (AUFs), EPCs, and toxicity reference values (TRVs). Ecological Risk Characterization. Integrates the Problem Formulation and the Analysis to estimate the likelihood of impacts to ecological receptors from exposure to site constituents, identifies chemicals of ecological concern (COECs), and summarizes uncertainties associated with the ERA. A.3.1 Assumptions The ERA is based on the following assumptions and constraints, which are typical for ERAs currently being performed: All evaluations of current exposures is based on existing conditions. Future land use is assumed to revert to native conditions. The abiotic media of primary ecological concern include soil, soil vapor, shallow groundwater, and surface water. Groundwater was only evaluated for potential ecological risks when there was potential for the groundwater to reach the surface (seeps, for example) or when depth to groundwater was within the top 6 feet bgs. Current chemical concentrations are present at a steady state and will not change over time. Chemicals not detected or analyzed are not present or evaluated. SSFL RA REPORT_V09.DOC A-16