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Advancing the Ecological Assessment Process for Pesticides
On this Page
- Why Revise the Assessment Process?
- What Are The Risk Management Questions?
- How Did We Go About It?
- What Happened Next?
- What Does This Assessment Scheme Look Like?
- What About Moving Between the Levels?
- Where Are We Now?
- What Does The Aquatic Model Look Like?
- What About the Aquatic Results for Acute Risk?
- What Does the Terrestrial Model Look Like?
- What About the Terrestrial Results?
- What Do the Regulators Say About the Models and Results?
- What Else Have We Been Doing?
- What Are the Next Steps?
- OPP EFED Implementation Team
Why Revise the Assessment Process?
Provide Agency regulators with:
Answers to risk management questions which could not be quantitatively addressed in the past, and
Improved risk characterizations, focusing on magnitude, probability, and certainty of predictions.
What Are The Risk Management Questions?
What are the magnitude and probability of effects and how certain are you?
Are these effects seen across different species?
Are there population or community impacts? Will the effects influence the density and diversity of the species?
How Did We Go About It?
Formed ECOFRAM (Ecological Committee on FIFRA Risk Assessment Methods), a stakeholder workgroup, in 1997.
Was charged with developing probabilistic tools and methods for use under the FIFRA regulatory framework.
Drew experts from national and international organizations such as government agencies, including USGS, Health Canada, UK MAFF, and others; industry, academia, consulting firms, ORD, and non-governmental organizations.
Participants selected based on expertise, affiliation, and availability.
Provided recommendations, which included a strategy for risk assessment refinement and a compendium of tools and methods for EPA consideration.
Held peer review workshops to review ECOFRAM recommendations (1999).
What Happened Next?
Formed OPP/EFED Implementation Team
Used ECOFRAM's recommendations and peer review comments as a starting point for developing a plan to incorporate probabilistic tools into the ecological assessment process, which includes a 4 level refined risk assessment scheme.
Plan peer reviewed by FIFRA SAP and strongly supported (2000).
What Does This Assessment Scheme Look Like?
Level I: Screening Level Assessment
Terrestrial
Dietary risk point estimates
Evaluation of dermal and inhalation significance
Aquatic - Point estimates of risk (1 in 10 year exposure; lowest toxicity value)
Level II: Preliminary assessment of probability and magnitude of effects
Multiple exposure routes (Terrestrial)
Distributions of critical exposure and effects variables
Generic scenarios
Levels III and IV: More refined assessments, representing increasingly focused biological and exposure scenarios
What About Moving Between the Levels?
Guidance will be developed for when to move to higher levels
Numerical criteria will be used for moving from Level I to II
Risk management factors, such as benefits, alternatives, economic and social considerations as well as Agency resources, will be used for moving to higher levels
Where Are We Now?
Developed pilot aquatic and terrestrial models to assess the pesticide carbofuran.
Peer reviewed and supported as "state-of-the-art" (2001).
Finalizing models, which will be used in Level II assessments.
What Does The Aquatic Model Look Like?
Aquatic Organisms and Endpoints
Freshwater fish and invertebrates and Estuarine fish and invertebrates
Acute and chronic effects
Spatial Scale
Small permanent water body dependent primarily on surface water runoff as its source
Drainage area and size of water body scenario specific
Acute Risk
Effects: Distributions based on D/R curve from lab acute toxicity data
Exposure: PRZM/EXAMS or monitoring data used to generate a distribution of exposures
Risk: Joint probability function
Chronic Risk
Based on estimates of the frequency of exceedences of the chronic benchmark level. Provides information on the probability that the chronic endpoint is exceeded, not the magnitude and probability of effect.
What About the Aquatic Results for Acute Risk?
Screening Level I assessment provides an acute risk quotient of 0.83 for daphnia and 5.2 for pink shrimp. What does this mean? The Level II assessment provides estimates of acute risk in terms of magnitude and probability and uncertainty in the risk estimates can be included. On average the pesticide is expected to reach surface water concentrations that result in 11% mortality of an exposed Daphnia population, confidence limits 2 - 27% mortality. Infrequently (one year out of twenty, 95th percentile), Daphnia would be expected to incur ∼ 41% mortality (5 - 89%). Nineteen out of twenty years (5th percentile) the pesticide is expected to reach surface water concentrations that will result in 94% mortality of exposed pink shrimp, 95% confidence limits of 86 - 99% mortality.
| Probability | Daphnia | Pink Shrimp |
|---|---|---|
| 5th percentile | 2 (<1-7) | 94 (86-99) |
| Median | 7 (1-22) | 98 (92-100) |
| Mean | 11 (2-27) | 96 (89-98) |
| 95th percentile | 41 (5-89) | 100 (99-100) |
What Does the Terrestrial Model Look Like?
Acute mortality to avian species
Oral exposure from food and water
Spatial scale at the field level
Temporal scale is for exposure at and following a single application
Effects Model
Uses distributions based on the dose/response curve to estimate and address
Intra-species toxicity variability
Inter-species toxicity variability
Exposure model: Incorporates distributions for parameter values, expressing exposure as a probability curve
Residue variables:
Application rate and method
Distribution of residues and degradation rates
Behavior variables:
Body weight
What, how much, and where a bird eats
How much and where the bird drinks
How much the bird breathes
How much foliage the bird contacts
Risk
Exposure and effects distributions combined using Monte Carlo sampling techniques
What About the Terrestrial Results?
95% probability that red-wing mortality will be greater than 9 out of 20 individuals (45% mortality) There is a 5% probability that mortality will be greater than 80%.
Red-Winged Blackbird Mortality
What Do the Regulators Say About the Models and Results?
General Comments
Strongly supported moving toward probabilistic analyses.
Appreciated scientific advancement.
Requested continuing and frequent dialogue to ensure they understand the models, assumptions, and limitations
Comments Related to Decision-making
Encouraged expanding assessments to evaluate mitigation options by
Providing a range of application rates,
Modifying timing and frequency of application methods, and
Evaluating alternative application methods and pesticide formulations.
Requested comparative analyses of alternatives using Level II assessments.
Encouraged providing "context" for results, such as
Indicating the importance of the species impacted,
Providing a link with reproductive impacts, such as whether birds reproduce quickly and can recover from acute impacts,
Identifying a reference point, such as a comparison to "normal" background mortality, and
Estimating population impacts.
What Else Have We Been Doing?
Collaboration:
To ensure we address risk management needs:
Risk management workshops and briefings
To ensure open and transparent process for stakeholders and the public
Peer review meetings and web site
To promote scientific exchange
National and international professional meetings
Training
Provide the foundation for refined risk assessments
Future courses on Level II model implementation
Research
To reduce uncertainty, develop population models, and provide other types of support
Extramural resources
ORD
What Are the Next Steps?
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OPP EFED Implementation Team
Chair
Ingrid Sunzenauer, M.S.
Aquatic Team
Donna Randall, M.S. (Lead)
Dirk Young, Ph.D.
Terrestrial Team
Ed Fite, M.S. (Lead)
Ed Odenkirchen, Ph.D.
EFED Technology Teams
Other Team Members
Tim Barry, Sc.D. (Office of the Administrator)
Stephanie Irene, Ph.D.
Douglas Urban, M.S.
Former Team Members
Kathryn Gallagher, Ph.D.
Les Touart, Ph.D.
Jim Lin, Ph.D.