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Tittabawassee River Aquatic Ecological Risk Assessment – Results PowerPoint Presentation
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Tittabawassee River Aquatic Ecological Risk Assessment – Results

Tittabawassee River Aquatic Ecological Risk Assessment – Results

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Tittabawassee River Aquatic Ecological Risk Assessment – Results

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  1. Tittabawassee River Aquatic Ecological Risk Assessment – Results Hector Galbraith Galbraith Environmental Sciences Newfane, Vermont October 2003

  2. Background • Contamination of Tittabawassee River sediments by dioxins and furans known since 1980s • Between 2000 and 2003 intensive sampling efforts by MDEQ and USFWS characterized magnitude and spatial distribution of contaminants • Based on these data ERA determined to be necessary.

  3. Tittabawassee River Aquatic Ecological Risk Assessment (ERA) - Objectives Overall objectives of ERA: • To evaluate extent to which dioxins and furans in sediments of Tittabawassee River and downriver areas pose risks to ecological receptors • To characterize spatial variability of risk and to determine whether risk “hotspots” exist

  4. Tittabawassee River Ecological Risk Assessment - Objectives Objectives of presentation: • Provide overview of approaches used • Describe how models and parameters were selected • Evaluate magnitude and distribution of risk to receptors • Discuss implications for risk management

  5. Tittabawassee River Ecological Risk Assessment – Presentation Structure • Overview of toxicity, environmental behavior of dioxins and furans and their presence in study area • Overall ERA approach • TCDD-EQ approach • USEPA ERA Framework • ERA model parameter identification • Evaluation of risk • Spatial distribution of risk

  6. Tittabawassee River Ecological Risk Assessment Dioxin/furan toxicity – overview • Intrinsic toxicity - thresholds in biological tissues can be in low ppt (e.g., <10 pg/g, wet weight in chicken eggs – embryo mortality) • Environmentally persistent • Lipophilic, bioaccumulate and biomagnify in food chains • Pose risks to top predators (especially early life-stages)

  7. Tittabawassee River Ecological Risk Assessment Dioxin/furan toxicity – complications: • Structures highly variable and large numbers of isomers (congeners) possible: dioxins – 75 (dioxins) furans – 135 (furans) • Congeners differ in intrinsic toxicity (across 4 orders of magnitude) and environmental behavior • Environmental media typically contain complex mixtures of congeners – ERA should focus at level of congeners

  8. Tittabawassee River Ecological Risk Assessment Contaminants in Tittabawassee River: • Dioxins, furans, and PCBs all present in sediments • Other contaminants may also be present but have not been evaluated • Most of potential toxicity driven by dioxins and furans • Relatively little potential toxicity due to PCBs • This ERA focuses on dioxins and furans

  9. Tittabawassee River Ecological Risk Assessment Toxicity Equivalence (TEQ) approach: • Dioxins/furans exist in study area as complex mixtures • Because of intrinsic differences in toxicity, complex mixtures complicate assessment of toxicity • Toxicity of each congener relative to 2,3,7,8-TCDD can be expressed using a Toxicity Equivalence Factor (TEF) • A number of TEF categorizations exist – most recent (and most widely accepted for ERA) is WHO • By multiplying environmental concentration of each congener by TEF, then adding products, we get estimation of toxicity of mix relative to 2,3,7,8-TCDD - TCDD-EQ • Approach has limitations, is best method available with relatively wide acceptance

  10. Selected WHO TEFs: Birds Fish Mammals 2,3,4,7,8-PeCDF 1 0.5 0.5 2,3,7,8-TCDF 1 0.05 0.1 1,2,3,4,7,8-HxCDF 0.1 0.1 0.1 1,2,3,7,8-PeCDF 0.1 0.05 0.05 Differences across taxa Differences within taxa Tittabawassee River Ecological Risk Assessment

  11. Tittabawassee River Ecological Risk Assessment Congener Environmental Behavior: Congeners differ also in: • Abilities of organisms to metabolize and excrete them • Efficiencies of biological uptake • Propensities to bioaccumulate Knowing intrinsic toxicity is not enough – also have to estimate congener-specific exposure

  12. Tittabawassee River Ecological Risk Assessment – USEPA 1998 Framework • 1. Problem Formulation: • Conceptual model • Assessment endpoints • Analysis plan • 2. Analysis: • Exposure characterization • Effects characterization Communication to Risk Managers • 3. Risk Characterization: • Risk estimation • Risk distribution • Risk description

  13. Tittabawassee River Ecological Risk Assessment Overall approach: • Use data from site and parameters from scientific literature to evaluate exposure to piscivorous (fish-eating) wildlife • Use data from scientific literature to evaluate sensitivity of receptors • Combine above in risk characterization • Use sediment toxicity thresholds (STCs) to map distribution of risk

  14. Tittabawassee River Ecological Risk Assessment IN OUT • Environmental data • From site: • Sediment PCH conc. • Degree of Risk: • How Much? • Biological data • from site • PCHs in fish tissues • PCHs in bird eggs Ecological Risk Assessment Model • Spatial Extent of Risk: • Where? Literature Values

  15. Tittabawassee River Ecological Risk Assessment – Exposure Model Toxicity Reference Values (TRVs) • Piscivorous • Wildlife • Mink • Birds Biomagnification Factors (BMFs) Biomagnification Factors (BMFs) • Bottom-feeding • Fish Benthos Water Column Fish Plankton Sediment PCDDs PCDFs Floodplain Water column

  16. Tittabawassee River Ecological Risk Assessment Definition of terms: • Biomagnification Factor (BMF): ratio between contaminant concentration in prey and in tissues of predators. • Toxicity Reference Values (TRVs): Greatest TCDD-EQ in diet or eggs protective of organism viability (e.g., embryo survival) Functions are to translate media contaminant concentrations into exposures and risks to ecological receptors. Need to be congener-specific

  17. Steps In Aquatic ERA Estimate of risk to avian embryos Estimate of risk to mink and otter Compare with Egg TRVs Compare with Dietary TRVs Estimate bird egg TCDD-EQ BMFs TCDD-EQ Concentrations in prey of mink and otter Fish Tissue TCDD-EQ Concentrations

  18. Tittabawassee River Ecological Risk Assessment – Bird Egg TRVs TRVs for bird embryo survival exist for: Wood duck Mallard Great blue heron Eastern bluebird Forster’s tern Black-headed gull Common tern Chicken Double-crested cormorant Rock dove Pheasant Herring gull Turkey Domestic goose Bobwhite American kestrel

  19. Tittabawassee River Ecological Risk Assessment – Bird Egg TRVs

  20. Bird Egg TCDD-EQ TRVs Most sensitive species: 5-50 pg/g, ww Less sensitive species: 50-100 pg/g, ww Least sensitive species: >100 pg/g, ww

  21. Avian Egg TRVs Used In Previous Risk Assessments

  22. Mammalian Piscivore TRVs *LOAEC – lowest observed adverse effects concentration *NOAEC – No observed adverse effects concentration

  23. Mammalian Piscivore TRVs • 1 pg/g TCDD-EQ in diet assumed to be mink TRV • Very similar to values used in previous Great Lakes ERA • 1 pg/g TCDD-EQ also assumed to be TRV for river otter

  24. TCDD-EQ TRV - Summary Birds: 5 pg/g, ww in egg 50 pg/g, ww in egg 100 pg/g, ww in egg Mink and River Otter: 1 pg/g, ww in diet

  25. Steps In Aquatic ERA Estimate of risk to avian embryos Estimate of risk to mink and otter Compare with Egg TRVs Compare with Dietary TRVs Estimate bird egg TCDD-EQ BMFs TCDD-EQ Concentrations in prey of mink and otter Fish Tissue TCDD-EQ Concentrations

  26. Fish – Bird Egg BMFs: PCDDs

  27. Fish – bird egg BMFs: PCDFs

  28. Fish – bird egg BMFs

  29. TCDD-EQ in Fish Tissues

  30. Avian and Mammalian TRVs USEPA 1993 Sediment thresholds:

  31. Estimated TCDD-EQ in Bird Eggs

  32. Actual TCDD-EQ in Bird Eggs From Assessment and Reference Areas

  33. Bird Egg Hazard Indices (HI)

  34. Congeners in Bird Eggs

  35. Mink HIs

  36. Mink HIs

  37. River Otter HIs

  38. Mink and Saginaw Bay Carp • Saginaw Bay carp fed to captive mink • TCDD-EQ in carp – 78 pg/g, ww (WHO mammalian TEFs) • Majority of TCDD-EQ from dioxins and furans • 10% carp in diet resulted in reproductive impairments • Tittabawassee River carp have 128 pg/g, ww TCDD-EQ Giesy et al. (1994); Heaton et al. (1995); Tillitt et al. (1996)

  39. Congeners in Fish Prey of Mammals

  40. Hazard Indices - Summary

  41. Sediment Threshold Concentrations (STCs) • STCs are estimated TCDD-EQ concentrations in sediment that would result in HIs equal to or less than 1 • STCs calculated using existing sediment TCDD-EQ data, and estimated bird egg and mammalian HIs

  42. Sediment Threshold Concentrations (STCs) 5 pg/g egg TRV: HI of 206 results from sediment mean TCDD-EQ conc. of 2,109 pg/g HI of 1 would result from sediment mean TCDD-EQ conc. of 2,109/206 = 10 pg/g

  43. Avian and Mammalian STCs

  44. Avian and Mammalian STCs

  45. Sediment Threshold Concentration Exceedences

  46. Sediment Threshold Concentration Exceedences

  47. Sediment Threshold Concentration Exceedences

  48. Sediment Threshold Concentration Exceedences

  49. Sediment Threshold Concentration Exceedences

  50. Sediment Threshold Concentration Exceedences • No sample sites except those upriver and immediately downriver of Midland had HI <1 • At spatial scale of sampling and emphasis on depositional areas, risk not clumped into “hotspots” but is pervasive