Tittabawassee River Aquatic Ecological Risk Assessment Results

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., lt10 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
Tittabawassee River Ecological Risk Assessment

• 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

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
Water column
Floodplain
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
Fish Tissue TCDD-EQ Concentrations
TCDD-EQ Concentrations in prey of mink and otter
18
Tittabawassee River Ecological Risk Assessment
Bird Egg TRVs

• TRVs for bird embryo survival exist for
• Wood duck Mallard
• Great blue heron Eastern bluebird
• Forsters 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 gt100 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
Fish Tissue TCDD-EQ Concentrations
TCDD-EQ Concentrations in prey of mink and otter
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 lt1
• At spatial scale of sampling and emphasis on
  depositional areas, risk not clumped into
  hotspots but is pervasive

51
Saginaw River and Saginaw Bay Sediments
STC corresponds to least protective TRV (100
pg/g ww in egg)
52
Risk Summary

• Furans and dioxins in sediments of Tittabawassee
  River pose risks to reproduction and early life
  stages of piscivorous birds and mammals
• Risks to wildlife pervasively distributed
  throughout the 22 miles of the Tittabawassee
  River below Midland
• Furans and dioxins in sediments of Saginaw River
  and Bay pose risks to reproduction and early life
  stages of piscivorous birds and mammals
• Experimental (mink feeding) and observational
  data (fish and bird egg contaminant data) confirm
  that dioxins and furans are bioaccumulated and
  pose risks to wildlife

53
Uncertainty

• All predictive scientific studies include
  uncertainty
• Uncertainty in ERA can result from (for example)
• site contaminant characterization
• parameter selection
• food chain specifics
• toxicity relationships

54
Uncertainty

• The job of an ecological risk assessor is to
  provide results that if used in remediation will
  be protective of environment
• Precautionary principle means that it is
  important that we guard against false negatives
• It is also important not to overstate risks (for
  financial and public perception reasons)
• In face of unresolvable uncertainty, Ideal ERA
  will shade slightly toward caution

55
Uncertainties in ERA

• Diets of piscivorous birds and mammals
• Avian TRVs
• Mammalian TRVs
• Fish Bird egg BMFs

56
Uncertainty and Robustness of Results of ERA

• Even if lt100 fish diet assumed HIs still exceed
  acceptable level for mammals and birds
• Even if less protective parameters used HIs still
  exceed acceptable level
• - Avian and mammalian TRVs
• - Bioaccumulation of TCDF

57
ERA Taxonomy Spectrum
Preliminary/Screening Few site-specific data Can
we confidently ignore the possibility of
unacceptable risk? Outcome - more study, clean-up

Uncertainty
Final/Definitive/Comprehensive Site-specific
data What is magnitude of risk? Which organisms
at risk? What is distribution of risk? Outcome -
risk management decisions
-
58
Utility of ERA

• Would further correctly collected site-specific
  data reduce uncertainty still further? YES
• Notwithstanding, do we know enough to make
  management decisions YES
• Can we identify important remediation
  sites YES
• Does this also address terrestrial
  environment? NO