tittabawassee river aquatic ecological risk assessment results
Download
Skip this Video
Download Presentation
Tittabawassee River Aquatic Ecological Risk Assessment – Results

Loading in 2 Seconds...

play fullscreen
1 / 58

Tittabawassee River Aquatic Ecological Risk Assessment - PowerPoint PPT Presentation


  • 487 Views
  • Uploaded on

Tittabawassee River Aquatic Ecological Risk Assessment – Results. Hector Galbraith Galbraith Environmental Sciences Newfane, Vermont October 2003. Background. Contamination of Tittabawassee River sediments by dioxins and furans known since 1980s

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Tittabawassee River Aquatic Ecological Risk Assessment ' - LionelDale


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
tittabawassee river aquatic ecological risk assessment results

Tittabawassee River Aquatic Ecological Risk Assessment – Results

Hector Galbraith

Galbraith Environmental Sciences

Newfane, Vermont

October 2003

background
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.
tittabawassee river aquatic ecological risk assessment era objectives
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
tittabawassee river ecological risk assessment objectives
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
tittabawassee river ecological risk assessment presentation structure
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
tittabawassee river ecological risk assessment
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)
tittabawassee river ecological risk assessment7
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
tittabawassee river ecological risk assessment8
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
tittabawassee river ecological risk assessment9
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
tittabawassee river ecological risk assessment10
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
tittabawassee river ecological risk assessment11
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

tittabawassee river ecological risk assessment usepa 1998 framework
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
tittabawassee river ecological risk assessment13
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
tittabawassee river ecological risk assessment14
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

tittabawassee river ecological risk assessment exposure model
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

tittabawassee river ecological risk assessment16
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

steps in aquatic era
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

tittabawassee river ecological risk assessment bird egg trvs
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

bird egg tcdd eq trvs
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

mammalian piscivore trvs
Mammalian Piscivore TRVs

*LOAEC – lowest observed adverse effects concentration

*NOAEC – No observed adverse effects concentration

mammalian piscivore trvs23
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
tcdd eq trv summary
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

steps in aquatic era25
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

avian and mammalian trvs
Avian and Mammalian TRVs

USEPA 1993 Sediment thresholds:

mink and saginaw bay carp
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)

sediment threshold concentrations stcs
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
sediment threshold concentrations stcs42
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

sediment threshold concentration exceedences50
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
saginaw river and saginaw bay sediments
Saginaw River and Saginaw Bay Sediments

* STC corresponds to least protective TRV (100 pg/g ww in egg)

risk summary
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
uncertainty
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

uncertainty54
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
uncertainties in era
Uncertainties in ERA
  • Diets of piscivorous birds and mammals
  • Avian TRVs
  • Mammalian TRVs
  • Fish – Bird egg BMFs
uncertainty and robustness of results of era
Uncertainty and Robustness of Results of ERA
  • Even if <100% 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

era taxonomy spectrum
ERA “TaxonomySpectrum”

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

-

utility of era
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
ad