Risk Assessment Presentation


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Risk Assessment presentation given by Claire Marcussen, June 2010 at a Protect Gainesville's Citizens Community Information Session.

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Risk Assessment Presentation

  1. 1. Use of Risk Assessment to Support Cleanup at Superfund Sites Presented By: Claire Marcussen Senior Environmental Consultant June 24, 2010 1
  2. 2. Overview* • What is Risk Assessment? • Uses • Risk Assessment Process • When are Risk Assessments Conducted? • Determining when Cleanup/Controls are Needed * Interject opinions on the Koppers Risk Assessment and Feasibility Study 2
  3. 3. What is Risk Assessment? • A systematic approach to determine the human health effect and environmental impacts associated with actual or threatened releases: – Chemicals – Radionuclides • A required component to support cleanup decisions at Superfund sites • Must follow regulatory protocols 3
  4. 4. Uses • To support cleanup decisions • Identifies chemicals and media requiring cleanup • Prioritizes areas for cleanup • Allows owners/operators to make focused decisions • Supports property transactions/due diligence • Develop cleanup levels • Aids in site re-use 4
  5. 5. Types of Risk Assessments • Deterministic (most common) – Calculations straightforward; not resource intensive – Use of point estimates to come up with a risk values – Use of established default assumptions – Easier to describe and communicate • Probabilistic (uncommon) – Much more complex approach – Used when simpler methods do not clearly support need for action (so why did they use it??) – Uses statistically derived distributions of exposure factors and toxicity values to calculate risks – Provides more detailed understanding of variability of risks (i.e., identifies what factors impact risks most) – Difficult to communicate in a transparent manner. 5
  6. 6. Risk Assessment Process Hazard Identification Hazard Identification Exposure Assessment Exposure Assessment Toxicity Assessment Toxicity Assessment Risk Characterization Risk Characterization 6
  7. 7. Hazard Identification • Conceptual Site Model = Road map – Describes the sources, release and transport pathways, human and ecological receptors – Ensures risk evaluation is focused on the right issues – Koppers: continue to discover new sources (drums?) • Data Evaluation – Identifies useable data – Is data complete (e.g., data gaps?) – Koppers: for years never sampled for dioxin (risk driver requiring more delineation) • Chemical Screening Step – Reduce list of chemicals to those likely to drive risks at site (focuses risk assessment) 7
  8. 8. Conceptual Site Model Dust ace urf il S o s Garden Groundwater Leaching to Groundwater Discharge
  9. 9. Data Evaluation • Ensure that relevant data are available: – To evaluate current and future exposures (on/offsite) – Direct contact to surface soils (e.g., current 0-6”; future 0-6 ft to address site rework) – Inhalation exposure (e.g., dust concentrations or modeled dust concentrations) • Ensure analytical methods are adequate – Sensitivity: Can detect levels below “safe” levels – Complete: Include methods that can detect site-related chemicals (e.g. PAHs, metals, dioxins)
  10. 10. Chemical Screening Step • Standardized approach • Compare maximum site concentration to a conservative health-based screening value – Florida’s Soil Cleanup Target Level (SCTL) – EPA’s Regional Screening Level (RSL) – Residential exposure assumptions • 10-6 cancer risk level, • Noncancer hazard of 0.1 • Contributions from Natural Background • Koppers: used commercial screening levels!
  11. 11. Example Chemical Screening Step Chemical Maximum Residential Natural COPC? Screening Background Level (RSL/SCTL) Arsenic 25 mg/kg 0.39 mg/kg 14 mg/kg Yes Chromium 100 mg/kg 210 mg/kg 34 mg/kg No Copper 160 mg/kg 150 mg/kg 170 mg/kg No PAHs 39 mg/kg 0.015 mg/kg NA Yes Dioxin 45 ng/kg 4.5 ng/kg NA Yes NA = not applicable
  12. 12. Screening Levels versus Cleanup Levels (Default Residential Level – Arsenic) Site-specific Response action No further study cleanup clearly warranted goal/level warranted 0.39 mg/kg Response/ Very high (10-6 risk) Cleanup level concentration “Zero” Screening concentration Level 3.9 or 39 mg/kg 100 mg/kg (10-5 - 10-4 risk) (2x10-3 risk) 14 mg/kg = Background (3.5x10-5)
  13. 13. Risk Assessment Process Hazard Identification Hazard Identification Exposure Assessment Exposure Assessment Toxicity Assessment Toxicity Assessment Risk Characterization Risk Characterization 13
  14. 14. Exposure Assessment • Cornerstone- - “no exposure/contact = no risk” • Components – Identify Completed Exposure Pathways – Estimate Exposure Concentrations – Calculate Chemical Intake/Dose 14
  15. 15. Exposure Pathways • Completed Exposure Pathway – Chemical source and chemical release(s) – Receptor point – Exposure route 15
  16. 16. Exposure Point Concentration • Daily concentration you are exposed to • Must address current and future likely exposure scenarios – Future outdoor industrial worker (widespread exposure) • Area-wide average exposure concentration – Future commercial or residential development (localized exposures) • Source Area exposure concentrations – Offsite residential/commercial areas (localized) • Koppers diluted exposure concentrations assuming all receptors are exposed to the entire site 16
  17. 17. Exposure Point Concentration • Exposure point concentration – Maximum detection (for screening) – Average concentration (most common for risk assess.) – Area-weighting (not commonly used) Commercial/Industrial Exposure Areas Residential Exposure X X X X Areas X X X X 0.5 acre . . . . . X 5 acres X X . . . . . X X . . . . . . . . . . . . . . . . . . . . X X 17
  18. 18. Chemical Intake • Amount of chemical that enters the body – Behavioral factors: frequency and duration of exposure – Physical factors: body weight, skin surface area, ingestion/inhalation/dermal contact rates – Biological factors: bioavailability, absorption – Koppers RA: used nonstandard absorption factors which lowers risk and HI; ignored future residential use • Intake (mg/kg/day) = Csoil x Contact Rate x ED x EF BW x AT 18
  19. 19. Chemical Intake • Default Exposure Assumptions* Exposure Factor Residential Residential Industrial/ Adult Child Commercial Body weight (kg) 70 15 70 (71.5) Soil Ingestion rate (mg/day) 100 200 50/100 Inhalation rate (m3/day) 20 10 17 (20) Skin Surface Area (cm) 5700 2800 3300 (2373) Soil adherence factor 0.07 0.2 0.2 (mg/cm2) Exposure Frequency (days/yr) 350 350 250 Exposure Duration (years) 24 6 25 *Probabilistic risk assessment uses a range of values; Koppers evaluated recreational and worker exposure and not future residential risk 19
  20. 20. Risk Assessment Process Hazard Identification Hazard Identification Exposure Assessment Exposure Assessment Toxicity Assessment Toxicity Assessment Risk Characterization Risk Characterization 20
  21. 21. Toxicity Assessment • Use EPA and FDEP approved toxicity values to evaluate cancer and noncancer health effects • Rely on chronic (long term) exposures over time - – Chronic = Lower doses cause long-term health effects – Acute = Higher doses cause short-term health effects • Cleanup for chronic effects is more stringent and is protective of acute effects • EPA and FDEP Toxicity values have undergone peer review • Koppers: used nonstandard toxicity values in the PRA (tend to be much lower than standard values) 21
  22. 22. Toxicity Assessment • Noncancer = reference doses; chronic target organ effect – Many different “safe” dose levels based on different organs – Use lowest “safe” dose to ensure protection for all effects • Cancer = cancer slope factors* – Many slope factors based on different types of cancer – Use the most stringent slope factor to cover all types • Special cases – Toxicity equivalency factors (TEFs)-- polycyclic aromatic hydrocarbons (PAHs) and dioxins * Carcinogens must also be evaluated for noncancer effects as well. 22
  23. 23. Toxicity Assessment • Toxicity Equivalency: Some chemicals are members of the same family and exhibit similar toxicological effects; however, they differ in the degree of toxicity – Applies to PAHs and Dioxins – TEF applied to adjust the measured concentrations of individual PAHs and dioxins as a fraction of the toxicity of benzo(a)pyrene for PAHs and 2378-TCDD for dioxins. – TEF x soil concentration = toxicity equivalent concentration (TEQ)
  24. 24. Kopper’s Toxicity Assessment • Deterministic used EPA established CSF value for dioxin • PRA used a range of toxicity factors (lowers risk/HI) • PRA ran a second dioxin risk calculation without the EPA dioxin CSF reducing risk by factor of 60 • EPA has a noncancer RfD value for dioxin; Koppers did not evaluate noncancer effects to dioxin. Receptor EPA Regional Site-wide Risk HI Group Screening Levels Exposure (ppt)* Weighted (HI=1/Risk=1E-06) Conc. (ppt) Residential 4.5 (72) 9200 2E-03 128 Commercial 18 (850) 9200 5E-04 11 * EPA May 2010 Regional Screening Level Table (value in parentheses is noncancer based).
  25. 25. Risk Assessment Process Hazard Identification Hazard Identification Exposure Assessment Exposure Assessment Toxicity Assessment Toxicity Assessment Risk Characterization Risk Characterization 25
  26. 26. Risk Characterization R Exposure i s Toxicity k Evaluate two effects: Cancer Risks versus Noncancer Hazards
  27. 27. Carcinogenic Risk • Carcinogens = cancer risk • Cancer risk = cancer slope factor x dose – Probability of an individual developing cancer over a lifetime – Expressed as 1 in one million, 0.000001, or 10-6 – Risks from each chemical are additive to arrive at a total site risk for each exposure scenario Risk chem1 + Risk chem2 + Risk chem3 27
  28. 28. Why Use Risk Numbers to Identify Problems? • Superfund and State regulations require to clean up sites to levels that do not contribute “significantly” above the risk that occurs from all other causes of cancer in the general population. • American Cancer Society indicates that 1 in 2 men and 1 and 3 women will develop some type of cancer in their lifetime based on studies in the general population* * www.cancer.org/docroot/PRO/content/PRO_1_1_Cancer_Statistics_2009_Presentation.asp 28
  29. 29. Why Use Risk Numbers? • EPA Regulation requires managing site risk within a range 10-6 to 10-4 • FDEP manages site risk > 1 x 10-6 * • General population risk is 5 x10-1 and 3 x10-1 for men and women. • Ideally we would like 0 risk but not realistic • EPA/FDEP Goal do not let site risks contribute significantly above general population risks FDEP Target Lower risk Higher risk EPA Target 10-6 10-5 10-4 10-1 * Unless background is above cleanup level 29
  30. 30. Noncancer Hazards • Noncarcinogens = noncancer hazard quotient (HQ) – Ratio of site chemical intake/safe dose – mg/kg/day site = Hazard quotient (HQ) mg/kg/day safe dose – HQchem1+HQchem2+HQchem3 = total HI – FDEP and EPA threshold = 1.0
  31. 31. Summarizing Risks/HIs • To prioritize what areas require cleanup at large sites, risks and HIs should be segregated by: – Exposure Areas onsite and offsite – Exposure population (residential, commercial, etc.) • Should identify chemicals driving risk and hazards onsite and offsite – Chemicals contribution > 10-6 risk – Chemicals contributing > 1 HI • Koppers: did not break site down into smaller areas for risk assessment – Assumed entire site was the exposure area – They only segregated ditch area 31
  32. 32. Koppers Deterministic Risk/HIs Summary Scenario HI Risk*+ Chemicals of Concern Onsite Trespasser-Soil 0.01 2E-05 Dioxin Onsite Trespasser-Ditch 0.02 4E-06 Dioxin and arsenic Outdoor Worker 0.2 5E-04 (8E-05) Dioxin, arsenic, PAH Indoor Worker 0.09 3E-04 (4E-05) Dioxin, arsenic, PAH Recreational Older 0.04 9E-05 Dioxin, arsenic, PAH Child Utility Worker (0-6 ft) 0.02 2E-05 Dioxin Construction Worker 0.3 1E-05 Dioxin (0-6 ft) *Residential onsite risks would be greater than the receptor risk with most frequent exposure (e.g., worker risks); thus, site-wide residential risks would >1E-04 which is above FDEP and EPA thresholds. +Parentheses = PRA risk result
  33. 33. Koppers Risk/HIs Summary • Koppers did not evaluate future residential, worker, or recreational risks to 0-6 feet soils – Typically done for sites expected to be redeveloped – Exposure concentrations higher in 0-6 ft for arsenic, PAHs, and PCP; dioxin similar – Risks/HIs will be slightly higher using 0-6 ft for these scenarios. • Even without calculating residential risk, since worker risk unacceptable so would residential risks (e.g., higher frequency and longer duration) • Subsurface soils concentrations are higher or the same, so surface soil risk conclusions would also apply to subsurface soil.
  34. 34. When Risk Assessments Occur Feasibility Study Remedial Remedial Detailed Remedial Design/ Investigation Action Analysis of Implementation (RI) Objectives Alternatives Baseline Risk Refine Risk evaluation Evaluate: Assessment * Preliminary of remedial Residual risk Cleanup goals alternatives Demonstrate based on risk attainment and legal levels 5-year review * Note that the baseline conditions have changed since the RI, as the site is no longer an active industrial facility. Thus, a risk assessment has been recently revisited and submitted again with the FS. Needs careful review!
  35. 35. When are Cleanup/Controls Needed? • Cancer Risks > Threshold (varies EPA vs FDEP) – Risk > 10-4 generally require cleanup or controls (EPA) – Risk < 10-6 generally do not require cleanup (FDEP) – Risk > 10-6 and <10-4 case-by-case basis (EPA and FDEP) • Case b ase (target 10-6, 10-5, or 10-4) - - C y – Contribution from natural background or other sources not related to the site • FDEP and EPA will not cleanup below background – Environmental Setting (industrial versus residential) 35
  36. 36. When are Cleanup/Controls Needed? • Noncancer HI > 1.0 – Thresholds are consistent across EPA and States – Can be no action if background metals are higher than noncancer-based screening level • Uncertainties – Risks are only as good as the data – Importance of delineating contamination (lack of data does not mean “no risk”) 36
  37. 37. Developing Cleanup Levels • Typically conducted as part of the FS – Considers background levels • FDEP and EPA will not cleanup below background • Arsenic frequently is cleaned up to background levels and not the 1E-06 level in Florida and other States – Considers noncancer effects (e.g., make sure final cancer risk-based level is also protective of noncancer effects) – Considers cumulative exposure to all site chemicals of concern
  38. 38. Developing Cleanup Levels • Koppers FS did not calculate cleanup levels for surface soil COCs (dioxin, arsenic, PAHs, PCP) – Need risk or HI-based cleanup goals for remedies to achieve; to know how much soil needs to be cleaned up • Koppers Risk Assessment did not calculate risks to 0-6 ft soil for site-redevelopment (e.g., soils reworked for site re-use) – Exposure Concentrations are higher for arsenic, pentachlorophenol and much higher for PAHs; dioxins similar to surface soil concentrations – Risks for subsurface soils would also be unacceptable for the same scenarios as surface soil. – Need health-based cleanup goals for subsurface soil
  39. 39. Questions? 39