CONTRA COSTA COUNTY SIERRA-CRETE TASK FORCE HUMAN HEALTH RISK ASSESSMENT OF SIERRA-CRETE

Transcription

1 CONTRA COSTA COUNTY SIERRA-CRETE TASK FORCE HUMAN HEALTH RISK ASSESSMENT OF SIERRA-CRETE Volume IX. Supporting Technical Information Prepared by: ENVIRON International Corporation Marketplace Tower 6001 Shellmound Street, Suite 700 Emeryville, California Prepared for: Contra Costa County Sierra-Crete Task Force* * The Contra Costa County Sierra-Crete Task Force includes representatives from the Contra Costa County Health Department, Contra Costa County Public Works Department, Contra Costa County Office of the County Administrator, Contra Costa County District V Office, Contra Costa County District III Office, California Department of Toxic Substances Control, California Department of Health Services, Central Valley Regional Water Quality Control Board, the Cities of Antioch, Brentwood, Oakley, and Pittsburg, DuPont, and other interested parties. February 28, 2003 i

2 HUMAN HEALTH RISK ASSESSMENT OF SIERRA-CRETE i Preface Contents Background Organization of this Report Acronyms and Abbreviations Page v v vi viii Volume I. Introduction and Overview Introduction and Background Task Force Interest in Dioxins Summary of Environmental Testing Overview of the HHRA Methods Summary and Conclusions Volume II. Exposures to Current and Future Residents Living Along Streets Where Sierra-Crete was Used as a Road Base or Sub-Base Summary Conceptual Exposure Model Relevant Environmental Data Exposure Pathways and Assumptions Results and Interpretations Volume III. Exposures to Current and Future Children Playing on Streets Where Sierra-Crete was Used as a Road Base or Sub-Base Summary Conceptual Exposure Model Relevant Environmental Data Exposure Pathways and Assumptions Results and Interpretations Volume IV. Exposures to Current and Future Road Utility Maintenance Workers Summary Conceptual Exposure Model Relevant Environmental Data Exposure Pathways and Assumptions Results and Interpretations

3 Volume V. Exposures to Current and Future Residents During Road Maintenance Summary Conceptual Exposure Model Relevant Environmental Data Exposure Pathways and Assumptions Results and Interpretations ii Volume VI. Exposures to Past Road Construction Workers Summary Conceptual Exposure Model Relevant Environmental Data Exposure Pathways and Assumptions Results and Interpretations Volume VII. Exposures to Past Trespassers at Former Road Construction Sites Summary Conceptual Exposure Model Relevant Environmental Data Exposure Pathways and Assumptions Results and Interpretations Volume VIII. Environmental Evaluation Summary Conceptual Approach Screening Model and Assumptions Theoretical Levels in Surface Water Theoretical Levels in Fish Conclusions Volume IX. Supporting Technical Information 1 East County Environmental Data 1 Hazard Identification for Dioxins 14 Overview of Methods for Calculating Theoretical Exposures and Health Risks 18 Methods for Calculating Theoretical Exposures to Road Surfaces 22 Methods for Calculating Theoretical Exposures During Road Maintenance 31 Methods for Calculating Theoretical Exposures During Road Construction 39 Uncertainties 45 References 49

4 Volume X. Appendices A. Contra Costa County Task Force September 2002 Sampling and Analysis Plan B. Summary of Road Surface Sampling Conducted by the Contra Costa County Task Force in September 2002 C. Summary of Dioxin Testing Results on Roads in the Cities of Antioch, Bay Point, Brentwood, Oakley, and Pittsburg D. Spreadsheet Risk Assessment Calculations for the Road Surface Scenario E. Spreadsheet Risk Assessment Calculations for the Road Maintenance and Utility Repair Scenario F. Spreadsheet Risk Assessment Calculations for the Road Construction Scenario G. Dioxin: Environmental Occurrence, Exposure, & Effects on Human Health, Fact Sheet iii List of Tables Table 1. Summary of the number of environmental samples used to support the HHRA. Table 2. Summary of total and respirable air particulate measurements performed during the construction of a test road at DuPont s former Oakley facility in November 1988 and the construction of a parking lot in August Table 3. Summary of dioxin TEQ WHO levels on road or asphalt pavement surfaces in the Cities of Antioch, Bay Point, Oakley, and Pittsburg where Sierra-Crete was used as a base or sub-base material. Table 4. Summary of dioxin TEQ WHO97 on road surfaces from the Cities of Martinez, Clayton, Bay Point, Pittsburg, Antioch and Oakley where Sierra-Crete was not used in the construction of roads. Table 5. Summary of the concentrations of dioxin TEQ WHO97 in Sierra-Crete. Table 6. Concentrations (mg/kg) of semivolatile organic chemicals (SVOCs), polyaromatic hydrocarbons (PAHs), and metals in Sierra-Crete. Table 7. Summary of the concentrations of dioxin TEQ WHO97 in subsurface soil collected from beneath Sierra-Crete and from beneath roads where Sierra-Crete was not used. Table 8. Summary of the concentrations of dioxin TEQ WHO97 in road particulate collected from cracks in the asphalt pavement. Table 9. Cancer slope factors used to evaluate theoretical incremental cancer risks posed by exposure to dioxin TEQ WHO97 and metals in Sierra-Crete. Table 10. Non-cancer toxicity values used to evaluate theoretical exposure to dioxin TEQ WHO97 and metals in Sierra-Crete. Table 11. Exposure variables and their definitions used in the exposure model for the road construction scenario. Table 12. Exposure variables and their definitions used in the exposure model for the road construction scenario.

5 Table 13. Summary of the possible sources of uncertainty in the HHRA. iv List of Figures Figure 1. Average profile of dioxins in 61 stained and 43 unstained road surfaces samples collected from white and dark stained and unstained surfaces of East Contra Costa County roads where Sierra-Crete was used. The profile of dioxins in eleven road surface samples collected to represent background conditions in the Cities of Martinez, Clayton, Bay Point, Pittsburg, Antioch and Oakley where Sierra-Crete was not used is shown for comparison. Figure 2. The profile of dioxins in 27 samples of Sierra-Crete and 16 samples of subsurface soils collected from beneath residential roads where Sierra- Crete was used in construction. The profile of dioxins in four subsurface soil samples where Sierra-Crete was not used in construction are presented for comparison.

6 Preface v Background In early 2002, DuPont, using an independent qualified laboratory, established that Sierra-Crete contained trace levels of dioxins. Sierra-Crete is a structural road-base material that was manufactured at the former DuPont facility located in Oakley, California, between 1988 and During that period, Sierra-Crete was sold commercially to construction companies and used as an aggregate base or sub-base material beneath asphalt during the construction of approximately 36 miles of roads, and a few parking lots in East Contra Costa County, California. In April 2002, trace levels of dioxins were detected in white and dark stains that appear on road surfaces along cracks in asphalt pavement in a significant but small percentage of roads where Sierra-Crete was used. Upon making this discovery, DuPont shared the results of environmental testing conducted in April/May 2002 and a human health risk assessment (HHRA) completed in June with the Contra Costa County Health Department and the California Department of Toxic Substances Control (DTSC). The risk assessment report titled, Human Health Risk Assessment of Sierra-Crete, provided a conservative estimate of the nature and extent of the health risks associated with potential pathways of exposure by road construction workers and residents. The environmental sampling and HHRA were performed in accordance with both United States Environmental Protection Agency (U.S. EPA) and California DTSC guidance. Using the data generated from April/May 2002 environmental sampling in the City of Antioch, the June 2002 HHRA concluded that the use of Sierra-Crete during the construction of roads did not pose a significant health risk to road construction workers. Further, exposure to dioxins on white and dark stained and unstained road surfaces in residential neighborhoods in the City of Antioch where Sierra-Crete was used did not pose a significant health risk to residents. For both road construction workers and residents, the theoretical health risks posed by potential exposure to dioxins through dermal, inhalation, and incidental ingestion pathways were within regulatory limits. To further evaluate and verify the information provided by DuPont, the Contra Costa County Health Department convened a Sierra-Crete Task Force (Task Force) under the direction of Health Department Director Dr. Wendell Brunner. The Contra Costa County Sierra-Crete Task Force included representatives from the Contra Costa County Health Department, interested residents, Contra Costa County Public Works Department, Contra Costa County Office of the County Administrator, Contra Costa County Counsel s Office, Contra Costa County District V Office, Contra Costa County District III Office, California DTSC, California Department of Health Services, Central Valley Regional Water Quality Control Board, the Cities of Antioch, Bay Point, Brentwood, Oakley, and Pittsburg, DuPont, and other interested parties. The purposes of the Task Force were to: 1. Evaluate the technical methods and assumptions used by DuPont in the June 7, 2002 HHRA; 1 The June 7, 2002 human health risk assessment and addenda can be found on the Internet at and

7 2. Perform additional environmental sampling in the Cities of Antioch, Bay Point, Brentwood, Oakley, and Pittsburg to further understand and evaluate the occurrence of dioxins on stained road surfaces and in Sierra-Crete ; vi 3. Prepare an updated HHRA that incorporates all of the available information pertaining to the use of Sierra-Crete in East Contra Costa County and further evaluates the potential for exposure and adverse health impacts on road workers and residents; and, 4. Provide recommendations to County and State authorities on actions that will protect public health and assure the continued well-being of residents in East Contra Costa County. Organization of this Report This document represents the final Sierra-Crete HHRA. It incorporates changes as a result of technical comments received on the June 7, 2002 HHRA from several members of the Task Force, as well as new information on the use of Sierra-Crete in East Contra Costa County and environmental sampling conducted in September The core of this document are six volumes that present the exposure and risk assessments for each of the six human exposure scenarios included in the HHRA. The intent is to provide all of the relevant information in each volume in a relatively straightforward manner that will assist the lay reader with understanding the significance of the environmental test data and results of the HHRA. Additional and more technical information that may be of particular interest to experienced risk assessors has been relegated to the last volume of the HHRA. Also included is an environmental evaluation as well as a number of supporting appendices. A synopsis of these volumes is as follows: Volume I Introduction and Overview The information provided in Volume I includes a description of the use of Sierra-Crete in East Contra Costa County and a summary of the results of extensive environmental sampling conducted in February and April/May by DuPont and September 2002 by the Contra Costa County Task Force. Volume I also includes an overview of the methods used to perform the HHRA and a summary of the results of the HHRA. Volume II through VII Exposure and Risk Assessments Volumes II through VII present the individual HHRAs for each of five different potentially exposed populations residents, children, road maintenance and utility workers, road construction workers, and road construction site trespassers. Each volume contains a non-technical summary of the assessment, a discussion of the relevant environmental data and the methods and assumptions used to calculate theoretical exposures. Each volume also includes a discussion of the exposure results, theoretical cancer and non-cancer health risks, a comparison to U.S. EPA s estimate of the typical background intake of dioxins from various environmental sources, and a brief discussion of the uncertainties in the assessment. Volume VIII Environmental Evaluation The information provided in Volume VIII addresses the potential for dioxins on road surfaces to migrate to groundwater or to nearby creeks, reservoirs, and the San Joaquin River. The results of soil, surface water, and sediment sampling are presented in conjunction with a discussion of the results of screening models used to estimate

8 environmental levels. The evaluation includes consideration of uptake by fish and comparisons to levels reported in fish from Contra Costa County s San Pablo Dam Reservoir and San Francisco Bay. vii Volume IX Supporting Technical information The information in Volume IX includes additional supporting information describing the environmental sampling data set used to derive the exposure point concentrations used in the HHRA and the mathematical equations associated with the different exposure pathways that were considered. The volume also includes a brief review of the scientific information regarding the hazards posed by dioxins and a discussion of the uncertainties inherent in the HHRA process. Volume X Appendices Additional information, including the environmental data set from sampling conducted in September 2002 and risk assessment equations, are presented as appendices to this report.

9 Acronyms and Abbreviations viii ASTM atm ATSDR BAAQMD BCF BW Cal/EPA CARB o C CDI Cl Cl 2 cm CRWQCB DHHS DL DTSC e.g. EPC ft ft 3 g GC-ECD GC-MS HEAST HHRA HI HQ Hr i.e. IARC IRIS kg L LADD lb LOQ MCL µg Microgram Me x Cl y Metal chlorides mg Milligram mg/day mg/kg mg/kg-day mm M 2 M 3 NA ng ND American Society for Testing and Materials Atmosphere Agency for Toxic Substances and Disease Registry Bay Area Air Quality Management District Bioconcentration Factor Body weight California Environmental Protection Agency California Air Resources Board Degree Celsius Chronic daily intake Chloride Dichloride Centimeters California Regional Water Quality Control Board U.S. Department of Health and Human Services Detection Limit California Department of Toxic Substances Control For example Exposure point concentration Feet Cubic Feet Gram Gas Chromatography/Electron Capture Detector Gas Chromatography/Mass Spectrometry Health Effects Assessment Summary Tables Human health risk assessment Hazard index Hazard quotient Hour That Is International Agency for Research on Cancer Integrated Risk Information System Kilogram Liter Lifetime average daily dose Pound Limits of Quantitation Maximum Contaminant Level Milligram per day Milligram per kilogram Milligram per kilogram per day Millimeter Square Meter Cubic Meter Not Applicable Nanogram Not Detected

10 NR NTP OCDD OCDF OPP PAH Pb PCBs PCDDs PCDFs PEA pg PM ppb ppm ppmv pg pg/cm 2 ppt ppt/v QA/QC RfC RfD RT SAB sec SF SFRWQCB sq TCDD TCDF TEF TEQ TiCl 4 TiO 2 TRI UCL 95 U.S. EPA USFDA VOC WHO yr 2,3,7,8-TCDD Not Reported National Toxicology Program Octachlorinated dibenzo-p-dioxins Octachlorinated dibenzofurans Office of Pesticide Programs Polycyclic Aromatic Hydrocarbons Lead Polychlorinated Biphenyls Polychlorinated Dibenzo-p-dioxins Polychlorinated Dibenzofurans Preliminary Endangerment Assessment Picogram Particulate Matter Parts Per Billion Parts Per Million Parts Per Million (Chapter Basis) Picograms Picograms per square centimeter Parts Per Trillion Parts Per Trillion (Chapter Basis) Quality Assurance/Quality Control Reference Concentration Reference Dose Residence Time Science Advisory Board Second Slope Factor (also Cancer Potency Factor) San Francisco Regional Water Quality Control Board Square 2,3,7,8-tetrachlorodibenzo-p-dioxin 2,3,7,8-tetrachlorodibenzofuran Toxicity Equivalency Factor Toxicity Equivalents Titanium Tetrachloride Titanium dioxide Toxics Release Inventory 95 percent upper confidence limit on the mean United States Environmental Protection Agency U.S. Food and Drug Administration Volatile Organic Chemical World Health Organization Year 2,3,7,8-tetrachlorodibenzo-p-dioxin ix

11 Volume IX. Supporting Technical Information 1 East County Environmental Data Summary In early 2002, DuPont, using an independent qualified laboratory, established that Sierra-Crete contained trace levels of dioxins. The results of testing ten samples of Sierra-Crete from beneath asphalt pavement on test roads at DuPont s Oakley facility and one sample collected from beneath a road in the City of Antioch indicated an average concentration of dioxins of 200 parts per trillion (ppt) TEQ WHO97 2. The range of dioxin concentrations in these 11 samples ranged between 66 and 314 ppt TEQ WHO97. In April 2002, DuPont implemented a test program in the City of Antioch, and determined that trace levels of dioxins occurred in stains that appear on road surfaces along cracks in the asphalt pavement in a significant, but small percentage of roads, where Sierra-Crete was used. The results of dioxin testing of Sierra-Crete at the Oakley facility and road surfaces in the City of Antioch were used in the draft HHRA submitted to Contra Costa County and California on June 7, In September 2002, additional environmental sampling was conducted by the Contra Costa County Sierra-Crete Task Force (the Task Force ) to supplement previously collected information pertaining to Sierra-Crete. The Task Force implemented an expanded sampling and analysis plan to further characterize dioxin levels on and beneath roads throughout East Contra Costa County. A summary of the total numbers and types of environmental samples collected to support the HHRA is presented in Table 1. The exposure assessments described in Volumes II through VII and the environmental evaluation in Volume VIII were performed using the combined environmental data generated from sampling in April/May and September In total, 104 road surface wipe samples from both stained and nonstained road surfaces were collected and analyzed for dioxins. This involved wiping a standard surface area of the road with a specially-treated gauze pad to remove the dioxins. The results of this testing showed that the average concentration of dioxins on East Contra Costa County roadways where Sierra-Crete had been used was picograms (trillions of a gram) dioxin TEQ WHO97 per square centimeter of road surface. In order to be able to compare the dioxin concentrations on the surfaces of roads where Sierra- Crete was used to background conditions, a total of 11 road wipe samples were collected from roads in residential communities where Sierra-Crete was not used. The average concentration on these background roads was picograms dioxin TEQ WHO97 per square centimeter of road surface. In addition to the 10 Sierra-Crete samples collected from the DuPont facility in Oakley in early 2002, the Task Force also collected and analyzed an additional 19 samples of Sierra- Crete in September 2002, bringing the total number of samples of the material to 29. However, two of these samples were found not to be Sierra-Crete. The average concentration of dioxins in the Sierra-Crete was 233 ppt (trillions of a gram per gram) dioxin TEQ WHO97. In addition, the Task Force collected 16 samples of soil from a depth of approximately 3 feet below the Sierra- 2 Dioxin concentrations are typically described in terms of toxicity equivalents (or TEQ WHO97 ) relative to the most toxic form of the dioxins, regardless of which specific dioxins are present in an environmental sample. The TEQ WHO97 method used throughout this assessment was developed by the World Health Organization (WHO) in 1997 and endorsed by both the U.S. EPA and California DTSC.

12 Crete. Dioxin testing revealed only trace levels of dioxins consistent with background soil and unrelated to the occurrence of dioxins in Sierra-Crete. 2 Table 1. Summary of the number of environmental samples used to support the HHRA. Media Number of Samples Tested Sierra-Crete samples [1] Subsurface soil boring samples from underneath Sierra-Crete roads Surface solid samples from cracks in road pavement Road surface samples from stained surfaces Road surface samples from unstained surfaces Subsurface soil boring sample from underneath non-sierra-crete roads 27 discrete samples 16 discrete samples 4 fragmented asphalt samples 2 crack particulate samples 41 discrete samples 20 composite samples 22 discrete samples 21 composite samples 4 discrete samples Road surface samples from non-sierra- 4 discrete samples Crete roads 7 composite samples [1] Data include samples collected from beneath asphalt pavement in April/May and September 2002, including the former DuPont Oakley plant, residential roads, one school and a youth sports complex parking lot. Two samples found not to be Sierra- Crete were excluded. The exposure assessments described in Volumes II through VII and the environmental evaluation in Volume VIII were performed using the combined environmental data generated from sampling in April/May and September In total, 104 road surface wipe samples from both stained and nonstained road surfaces were collected and analyzed for dioxins. This involved wiping a standard surface area of the road with a specially-treated gauze pad to remove the dioxins. The results of this testing showed that the average concentration of dioxins on East Contra Costa County roadways where Sierra-Crete had been used was picograms (trillions of a gram) dioxin TEQ WHO97 per square centimeter of road surface. In order to be able to compare the dioxin concentrations on the surfaces of roads where Sierra- Crete was used to background conditions, a total of 11 road wipe samples were collected from roads in residential communities where Sierra-Crete was not used. The average concentration of dioxins in these background roads was picograms dioxin TEQ WHO97 per square centimeter of road surface. In addition to the 10 Sierra-Crete samples collected from the DuPont facility in Oakley in early 2002, the Task Force also collected and analyzed an additional 19 samples of Sierra-Crete in September 2002, bringing the total number of samples of the material to 29. However, two of these samples were found not to be Sierra-Crete. The average concentration of dioxins in the Sierra-Crete was 233 ppt (trillions of a gram per gram) dioxin TEQ WHO97. In addition, the Task Force collected 16 samples of soil from a depth of approximately 3 feet below the Sierra-Crete. Dioxin testing revealed only trace levels of dioxins consistent with background soil and unrelated to the occurrence of dioxins in Sierra-Crete.

13 Chemical Laboratory Test Methods Dioxin testing was performed by Alta Analytical Laboratory (El Dorado Hills, CA) using U.S. EPA Method 1613A for high-resolution gas chromatography / mass spectroscopy. Chemical testing for polyaromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in the April/ May 2002 wipe samples also was conducted by Alta Analytical Laboratory. Chemical testing for semi-volatile organic chemicals (SVOCs), polyaromatic hydrocarbons (PAHs) and 17 metals in the September 2002 solid samples was conducted by STL-Denver (Denver, CO) using the appropriate U.S. EPA analytical methods. SVOCs were analyzed using U.S. EPA Method 8270C; PAHs were analyzed using U.S. EPA Method 8310; and the 17 metals were analyzed using U.S. EPA Methods 6010B, 7471 and Additional metal analysis for Chromium VI was conducted by STL-Los Angeles (Los Angeles, CA) using U.S. EPA Method The supporting laboratory and sample collection documentation is provided in Volume X. 3 Total and Respirable Particulate in Air The concentrations of total particulate and respirable particulate in air at road construction sites were extrapolated from the results of two air sampling events conducted in 1988 and In November 1988, air sampling was conducted during the construction of a 400-foot test road involving the installation of Sierra-Crete as an aggregate sub-base at DuPont s former Oakley facility. A second air sampling event was conducted during the construction of a parking lot in Antioch in August In both cases, air sampling included area-wide measurements at stationary monitoring stations and breathing zone measurements of laborers and road equipment operators using personal air monitors. Total particulate and respirable (10 micron diameter or less) particulate levels were determined in all samples. A summary of the air sampling results is presented in Table 2. Exposure levels to dust during the construction of the test road were below 0.4 milligram per cubic meter (mg/m 3 ), which is approximately 10% of the Occupational Safety and Health Administration (OSHA) standard. Exposure levels to dust were found to be below analytical detection limits during the construction of the parking lot. These data were used in the HHRA to support exposure modeling of the inhalation pathway in the road construction scenarios.

14 4 Table 2. Summary of total and respirable air particulate measurements performed during the construction of a test road at DuPont s former Oakley facility in November 1988 and the construction of a parking lot in August Sample Respirable Dust Concentration (mg/m 3 ) Total Dust Concentration (mg/m 3 ) Test Road Construction, November 1988 All Area Samples ND ND All Field Blanks ND ND Supervisor Blade Operator s Cab Front End Loader Driver Blade Operator -- ND Soil Density Tester -- ND Front Loader Cab Compactor Operator -- ND Parking Lot Construction, August 1990 Skiploader Operator, morning -- ND Skiploader Operator, afternoon Laborer, morning Laborer, afternoon -- ND An ND indicates that levels were non-detect by the air monitoring instrument. Road Surface Sampling Road surface samples were collected on four occasions during April, May and September During the first sampling effort, which was conducted on April 8, 2002, surface wipe sampling was found to be not only the most practical, but also the most relevant sampling method. Dark and white residues appearing on road surfaces were comparable to water stains on a fabric surface. There was no texture to the residue; it was not granular or powdery, nor could material be scraped from the pavement surface using a stainless steel spoon or sharp knife. Pavement surface conditions, with respect to presence or absence of cracking, were generally comparable in all locations where white or dark staining was evident on the pavement surface. The same surface wipe sampling method was used during each of the four pavement surface sampling events. At each road surface wipe sampling location, a rectangular piece of Teflon framing a 10-cm by 30-cm opening was placed directly on the asphalt pavement as a sampling template. The entire surface area within the rectangular area was wiped with an approximately two inch by two inch square gauze pad soaked in acetone. The gauze pad was folded in half with the clean surface facing outwards, and the area wiped a second time using the folded gauze pad. After the second wipe, the gauze pad was deposited into a 500-ml amber glass bottle and sealed with a Teflon -lined cap. The bottle was labeled and stored on ice in a cooler for shipment to the designated chemical testing laboratory. Samples were shipped to the laboratory under chain-ofcustody procedures following each day of sampling. The gauze pad and 500-ml amber glass

15 sampling bottles were supplied by Alta Analytical Laboratory. The Teflon template and stainless steel spatulas were decontaminated using gauze pads soaked in ethanol or methanol between each sampling event. Quality control samples, including trip blanks and decontamination wipe samples, were collected throughout the sampling period. 5 Four surface wipe samples were collected on April 8, The post-sampling report describing the sampling method and locations of road surface samples is provided in the June 7, 2002 HHRA. Sampling was intended as a preliminary screening-level effort to understand road surface conditions in areas where Sierra Crete was used. Three surface wipe samples were collected at locations where road staining appeared most pronounced based on visual inspection of road conditions in different neighborhoods conducted that same day. In addition, one surface wipe sample was collected from a road located in a neighborhood where Sierra-Crete was not used in road construction. To further evaluate road surface conditions in affected neighborhoods, a second and more extensive sampling effort was conducted between April 24 and May 1, The post-sampling report describing the sampling method and locations of road surface samples is provided in the June 7, 2002 HHRA. Surface wipe samples were collected from both stained and unstained road surfaces at approximately 125 locations in each of fifteen neighborhoods in the City of Antioch where Sierra-Crete was used. Twenty-three samples representing the visually worst looking stained surface in each neighborhood were tested individually for dioxins. The remaining road surface wipe samples (either stained or unstained) collected in each neighborhood were composited by the laboratory. To represent each neighborhood, one composited stained sample and one composited unstained sample were tested for dioxins. A third road surface sampling event was conducted on May 16, The post-sampling report describing the sampling method and locations of road surface samples is provided the June 7, 2002 HHRA. Sampling was conducted to determine whether residues on road surfaces appearing after a period of hot weather contained dioxins. Sampling was conducted on two roads within one neighborhood. Two samples, one from each road, were tested for dioxins. The fourth road surface sampling was conducted by the Task Force between September 11 and 26, Sampling was conducted during a prolonged period of hot and dry weather when daytime high temperatures in East Contra Costa County reached approximately 100 o F or hotter. This sampling event included a more extensive area of East Contra Costa County than previous sampling events and included residential neighborhoods in the Cities of Antioch, Bay Point, Oakley, and Pittsburg. In addition, surface wipe samples were collected from the parking lots of one commercial site located in the City of Brentwood and a sports field located in the City of Antioch. Surface wipe samples also were collected from a bus turnaround lane, a paved trash enclosure area, and paved playground area at a school located in the City of Pittsburg and from a small parking lot at a school located in the City of Oakley. The sampling and analysis plan (SAP) prepared by the Task Force and post-sampling report describing the sampling methods and locations of pavement surface samples are provided in Volume X of this report. During the September 2002 sampling event, surface wipe samples were collected from both stained and unstained portions of roads at 37 locations in residential neighborhoods where Sierra- Crete was used during road construction. Thirty-one samples representing the visually worstlooking stained surfaces in each residential neighborhood were tested individually for dioxins. The remaining surface wipe samples (either stained or unstained) collected in each neighborhood were composited by the laboratory. In nearly all cases, each composite sample represented surface wipe samples collected from three different pavement surfaces. In each city, one composite stained sample and one composite unstained sample were tested for dioxins. One composite stained sample and one composite unstained sample were collected from the

16 commercial parking lot located in the City of Brentwood. Six discrete stained samples, six discrete unstained samples, one composite stained sample, and one composite unstained sample were collected from the paved areas at the sports field and two schools. 6 A summary of the results of dioxin testing of all stained and unstained road or pavement surfaces is presented in Table 3 and Figure 1. Because statistical testing for the difference between the stained and unstained data sets indicated there was no statistical difference between the two data sets, the combined data set representing the level of dioxins on all road and pavement surfaces was used in the HHRA. A statistical evaluation of the data set and the supporting laboratory data for all of the sampling events are provided in Volume X of this report. A shown in Table 3, total dioxin TEQ WHO97 levels in wipe samples ranged between and picograms dioxin TEQ WHO97 /cm 2 (mean of pg TEQ WHO97 /cm 2 and 95 th UCL of pg TEQ WHO97 /cm 2 ). Dioxin TEQ WHO97 were calculated using World Health Organization (WHO) toxic equivalency factors (TEFs; van den Berg, 1998) and assumed that dioxin congener concentrations reported by the laboratory as non-detect were present in a sample at one-half of the laboratory-reported detection limit. Table 3. Summary of dioxin TEQ WHO levels on road or asphalt pavement surfaces in the Cities of Antioch, Bay Point, Oakley, and Pittsburg where Sierra-Crete was used as a base or sub-base material. Stained Road Surfaces Non-Stained Road Surfaces All Road Surfaces Sample Size Total Dioxin TEQ WHO97 (pg per cm 2 ) Minimum Maximum Arithmetic Mean th UCL of the Mean The profile of dioxins on stained and unstained road surfaces is presented in Figure 1. The results of dioxin testing of a total of 61 samples from stained pavement surfaces and 43 samples from unstained pavement surfaces indicated the presence of primarily octachlorinated dioxin and furan (OCDD and OCDF). Heptachlorinated dioxins and tetra- through hepta- chlorinated furans were also present, but at lower levels than OCDD and OCDF. The tetra- through heptachlorinated dioxins, including the most toxic of the dioxin congeners, 2,3,7,8-TCDD, was not found in pavement surface samples. The same four predominant congeners found on pavement surfaces (1,2,3,4,6,7,8-HpCDD, OCDD, 1,2,3,4,7,8-HxCDF, and OCDF) also were found in background road surface samples collected from road surfaces where Sierra-Crete was not used. Background Road Surface Data During sampling events conducted in April/May 2002 and September 2002, surface wipe samples were collected from roads in residential neighborhoods in the Cities of Martinez, Clayton, Bay Point, Pittsburg, Antioch and Oakley where Sierra-Crete was not used during road construction.

17 The purpose of this environmental sampling was to characterize background concentrations of dioxins on road surfaces in East Contra Costa County. The post-sampling report for September 2002 describing the sampling method and each sampling location is provided in Volume X of this report. The locations of background samples collected prior to September 2002 are described in post-sampling reports in the June 7, 2002 HHRA. 7 One background road surface sample was collected on April 8, During the April 24 to May 1, 2002 sampling, surface wipe samples were collected from six locations in Antioch, three locations in Clayton and three locations in Martinez. Sets of three samples were composited for dioxin testing by the laboratory and one sample representing each city was tested for dioxins. In addition, road surface samples from three different roads in Antioch were tested as discrete samples for dioxins. During sampling in September, background road surface wipe samples were collected from three different roads in each of the Cities of Antioch, Bay Point, Oakley, and Pittsburg. Altogether, the background road surface data set included 11 samples from East Contra Costa County.

18 Figure 1. Average profile of dioxins in 61 stained and 43 unstained road surfaces samples collected from white and dark stained and unstained surfaces of East Contra Costa County roads where Sierra-Crete was used. The profile of dioxins in eleven road surface samples collected to represent background conditions in the Cities of Martinez, Clayton, Bay Point, Pittsburg, Antioch and Oakley where Sierra- Crete was not used is shown for comparison. 8 Percent of Total Mass Percent of Total Mass Percent of Total Mass 80% 60% 40% 20% 0% 80% 60% 40% 20% 0% 80% 60% 40% 20% 0% Stained Pavement Surfaces N = 64 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 N = 43 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 N = 11 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 Unstained Pavement Surfaces 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 Background Pavement Surfaces 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 1,2,3,6,7,8-HxCDF 2,3,4,6,7,8-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 1,2,3,7,8,9-HxCDF 1,2,3,4,6,7,8-HpCDF 1,2,3,4,7,8,9-HpCDF 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 OCDF OCDF

19 A summary of the dioxin testing results of background road surface sampling is presented in Table 4. The profile of dioxins on road surfaces where Sierra-Crete was not used is presented in Figure 1 and compared to the profile representing stained and unstained road surfaces. The supporting laboratory data are provided in Volume X of this report. 9 The dioxin TEQ WHO97 levels in 11 surface wipe samples collected from road surfaces in East Contra Costa County where Sierra-Crete was not used ranged between and pg TEQ WHO97 /cm 2 (mean of pg TEQ WHO97 /cm 2 and 95% UCL of pg TEQ WHO97 /cm 2 ). Dioxin TEQ WHO97 were calculated using World Health Organization (WHO) toxic equivalency factors (TEFs; van den Berg, 1998) and assumed that dioxin congener concentrations reported by the laboratory as non-detect were present in a sample at one-half of the laboratory-reported detection limit. Table 4. Summary of dioxin TEQ WHO97 on road surfaces from the Cities of Martinez, Clayton, Bay Point, Pittsburg, Antioch and Oakley where Sierra-Crete was not used in the construction of roads. Background Road Surfaces Sample Size 11 Total Dioxin TEQ WHO97 (pg per cm 2 ) Minimum Maximum Arithmetic Mean th UCL of the Mean Sierra-Crete Data Review of DuPont sales records indicated that Sierra-Crete was used as a base or sub-base material beneath asphalt pavement in several residential neighborhoods in the Cities of Antioch, Bay Point, Oakley, and Pittsburg. In addition, Sierra-Crete was used beneath the asphalt pavement of a parking lot at one commercial site in the City of Brentwood. Sierra-Crete was used beneath paved areas at a sports field in the City of Antioch and at two schools in the Cities of Oakley and Pittsburg. Twenty-seven samples of Sierra-Crete were collected for dioxin testing in April/May and September The concentrations of dioxin in Sierra-Crete were determined in 10 samples collected from test roads at DuPont s former Oakley facility, 16 samples collected from beneath roads in 16 East Contra Costa County neighborhoods, and two samples collected from beneath the pavement of a bus turnaround lane and a parking lot at schools located in the Cities of Oakley and Pittsburg.

20 Altogether, 27 samples of Sierra-Crete were tested for dioxins; two of the 27 samples were tested for SVOCs, PAHs, and 17 metals 3. The concentrations of dioxin TEQ WHO97 in Sierra- Crete are summarized in Table 5. Dioxin TEQ WHO97 were calculated using World Health Organization (WHO) toxic equivalency factors (TEFs; van den Berg, 1998) and assumed that dioxin congener concentrations reported by the laboratory as non-detect were present in a sample at one-half of the laboratory-reported detection limit. The supporting laboratory data are provided in Volume X of this report. 10 A shown in Table 5, the average and 95% upper confidence level (UCL) concentrations of dioxin TEQ WHO97 in Sierra-Crete were 233 and 293pg TEQ WHO97 /g, respectively. Table 5. Summary of the concentrations of dioxin TEQ WHO97 in Sierra-Crete. Sierra-Crete Sample Size 27 Total Dioxin TEQ WHO97 (pg per g) Minimum 66 Maximum 1,004 Arithmetic Mean th UCL on the Mean 293 The profile of dioxins in Sierra-Crete and in subsurface soil collected from beneath Sierra- Crete and from beneath roads where Sierra-Crete was not used are shown in Figure 2. The profile of dioxins in Sierra-Crete is characterized by the occurrence of primarily OCDD and OCDF and several furan congeners. The concentrations of tetra- through hepta- chlorinated dioxins were below laboratory detection limits in all samples. The most toxic dioxin congener, 2,3,7,8-TCDD, was not found in Sierra-Crete. The results of dioxin testing of subsurface soil (representing 16 samples collected from beneath residential roads) indicated the presence of primarily octachlorinated dioxin and furan (OCDD and OCDF). The heptachlorinated congeners were also present at lower percentages, while the remaining congeners were present at very low percentages. The most toxic dioxin congener, 2,3,7,8-TCDD, was not found in subsurface soil samples. The average and 95% UCL concentrations in the 16 subsurface soil samples were 1.1 and 1.7 picograms TEQ WHO97/g, respectively. 3 In addition, two samples of Sierra-Crete collected from a road in Antioch in February and September 2002 and one sample of Sierra-Crete collected at the O Hara Park Middle School in Oakley in September 2002 were tested for dioxins with test results shown to be significantly lower than those from all other samples of Sierra-Crete. The results, along with the results of testing for SVOCs, PAHs and 17 metals on the O Hara Middle School sample, suggest that these materials were not Sierra-Crete. Consequently, the test results from these samples were excluded from the Sierra-Crete data set and were not considered in the HHRA.

21 Figure 2. The profile of dioxins in 27 samples of Sierra-Crete and 16 samples of subsurface soils collected from beneath residential roads where Sierra-Crete was used in construction. The profile of dioxins in four subsurface soil samples where Sierra-Crete was not used in construction are presented for comparison. 11 Percent of Total Mass 80% 60% 40% 20% 0% N = 27 Sierra-Crete 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 Percent of Total Mass 80% 60% N = 16 40% 20% 0% 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 Subsurface Soil Under Sierra-Crete Roads 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 Percent of Total Mass 80% 60% N = 4 40% 20% 0% 2,3,7,8-TCDD 1,2,3,7,8-PeCDD 1,2,3,4,7,8-HxCDD Subsurface Soil Under Background Roads 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

22 In addition to dioxin testing, six samples of Sierra-Crete were tested for SVOCs, PAHs, and 17 metals. These results are summarized in Table 6. The supporting laboratory data are provided in Volume X of this report. 12 Table 6. Concentrations (mg/kg) of semivolatile organic chemicals (SVOCs), polyaromatic hydrocarbons (PAHs), and metals in Sierra-Crete. Chemical LOV-Z-SC Stoneman Elementary School, Pittsburg [1] Sierra-Crete YOU-Z-SC Antioch Youth Sports Complex, Antioch Percent Moisture 44 % 35% All SVOCs Not Detected Not Detected All PAHs Not Detected Not Detected Antimony <1.0 <0.975 Arsenic Barium Beryllium <0.5 <0.5 Cadmium < Chromium, total Chromium, hexavalent Cobalt Copper Lead Mercury <0.03 <0.03 Molybdenum Nickel Selenium <1.3 <1.3 Silver Thallium <1.2 <1.2 Vanadium 1,200 1,800 Zinc [1] Samples were collected and tested by the Task Force in September Subsurface Soil Data In September 2002 at each of the 16 boring locations where Sierra-Crete was collected from beneath the asphalt pavement, a subsurface soil sample also was collected from approximately three feet below the Sierra-Crete. Subsurface soil samples were also collected from four different boring locations in residential neighborhoods in the Cities of Antioch, Bay Point, Oakley, and Pittsburg where Sierra-Crete was not used in road construction. The purpose of this environmental sampling was to characterize background concentrations of dioxins in subsurface soils in East Contra Costa County. A summary of the dioxin TEQ WHO results in subsurface soil is presented in Table 7. The profile of dioxins in subsurface soil is shown in Figure 2. Post-sampling reports describing the sampling method and each sampling location are provided in Volume X of this report. The supporting laboratory data also are provided in Volume X of this report. Dioxin TEQ WHO were calculated using World Health Organization (WHO) toxic equivalency factors (TEFs; van den Berg, 1998) and assumed that dioxin congener concentrations reported by the laboratory as non-detect were present in a sample at one-half of the laboratory-reported detection limit. The supporting laboratory data are provided in Volume X of this report.

23 As shown in Table 7, the average and 95% UCL concentrations in the 16 subsurface soil samples collected from three feet beneath Sierra-Crete were 1.1 and 1.7 picograms dioxin TEQ WHO /g, respectively. Lower dioxin TEQ WHO concentrations were found in background subsurface soil samples. Statistical testing for difference between the two subsurface soil data sets indicated there was no statistical difference between the two data sets. A statistical evaluation of the data set is included in Volume X of this report. 13 As shown in Figure 2, the profiles of dioxins in subsurface soil beneath Sierra-Crete and from beneath roads where Sierra-Crete was not used are different from the profile of dioxins in Sierra-Crete. The profile of dioxins in Sierra-Crete was characterized by the occurrence of primarily OCDD and OCDF and several furan congeners. The concentrations of tetra- through hepta- chlorinated dioxins were below laboratory detection limits in all samples. Similar to Sierra-Crete, the profile of dioxins in subsurface soils was characterized primarily by OCDD, OCDF, 1,2,3,4,7,8-HXCDF, and 1,2,3,4,5,7,8-HpCDF. The levels of other furan congeners in subsurface soils were lower than the levels found in Sierra-Crete. Dioxin congeners found in subsurface soils did not occur in Sierra-Crete. Table 7. Summary of the concentrations of dioxin TEQ WHO97 in subsurface soil collected from beneath Sierra-Crete and from beneath roads where Sierra-Crete was not used. Subsurface Soils Beneath Sierra- Crete Subsurface Soils Beneath Roads with no Sierra-Crete Sample Size 16 4 Total Dioxin TEQ WHO97 (pg per g) Minimum Maximum Arithmetic Mean th UCL on the Mean Road Particulate Sampling Environmental sampling in East Contra Costa County in April/May and September 2002 also included an effort to collect particulate samples from cracks in the asphalt pavement on roads where Sierra-Crete was used. However, little or no particulate material was found in the majority of pavement cracks. In some cases, the amount of particulate material was not sufficient for dioxin testing (approximately 10 grams was needed for dioxin testing by the laboratory). Consequently, road particulate samples were limited to four samples collected in April/May and two samples collected in September. The dioxin testing results for these samples are summarized in Table 8. The post-sampling report describing the sampling method and locations of pavement crack samples is provided in Volume X of this report. Dioxin TEQ WHO97 were calculated using World Health Organization (WHO) toxic equivalency factors (TEFs; van den Berg, 1998) and assumed that dioxin congener concentrations reported by the laboratory as non-detect were present in a sample at one-half of the laboratory-reported detection limit.

24 Table 8. Summary of the concentrations of dioxin TEQ WHO97 in road particulate collected from cracks in the asphalt pavement. 14 Dirt in Pavement Cracks [1] Sample Size 6 Total Dioxin TEQ WHO97 (pg per g) Minimum 7 Maximum 113 Arithmetic Mean th UCL of the Mean 62 [1] Samples were collected in May 2002 from four roads in residential neighborhoods in Antioch and in September 2002 from two roads in residential neighborhoods in Bay Point and Antioch. As shown in Table 8, the concentrations of dioxin TEQ WHO97 in six samples ranged widely. The average concentration in dirt from pavement cracks was approximately 97 picograms TEQ WHO97 per gram. The profile of dioxins indicated the presence of primarily OCDD and OCDF and low percentages of several furan congeners. The concentrations of tetra- through hepta- chlorinated dioxins were below laboratory detection limits in all samples. The most toxic dioxin congener, 2,3,7,8-TCDD, was not found in the pavement crack particulate. Hazard Identification for Dioxins Dioxins have received considerable attention over the past two decades because of their widespread occurrence in the environment and potential health effects associated with occupational exposure in certain industrial environments (U.S. EPA, 2000a, 2000b). The name dioxin is commonly used for the family of structurally related chemicals called polychlorinated dibenzo-para-dioxins (sometimes referred to as PCDDs, chlorinated dioxins, or dioxins) and polychlorinated dibenzofurans (sometimes referred to as PCDFs, chlorinated furans, or furans). This family includes 75 individual compounds referred to as dioxin congeners and 135 individual compounds referred to as furan congeners. The most toxic chemical in this family, called 2,3,7,8- tetrachlorodibenzo-p-dioxin (typically referred to as 2,3,7,8-TCDD or TCDD), is widely recognized as the most toxic of the 210 individual dioxin congeners. Dioxins are generated by both man-made and natural processes. Dioxins are by-products of a wide range of industrial processes, and are typically formed when thermal processes produce chlorine-containing organic substances. Industrial processes identified by the U.S. EPA (2000a, 2000b) as capable of generating dioxins include waste incineration, bleaching of paper pulp, and the manufacturing of some herbicides and pesticides. Other major sources include the production of iron and steel, backyard burning of household waste, wood burning, burning fuel for home heating, automobile engines, and electrical power generation. In terms of dioxin release into the environment, municipal solid waste incinerators are among the largest sources. Relatively small amounts of dioxins are formed during wastewater and drinking water treatment. Dioxins also result from natural processes, such as volcanic eruptions and forest fires.