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Ecological Committee on FIFRA Risk Assessment Methods (ECOFRAM)
Terrestrial Workgroup Report: VI. Preliminary Conclusions and General Recommendations

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Summary of the ECOFRAM Process

In response to the Scientific Advisory Panel's recommendations, the Ecological Committee on FIFRA Risk Assessment Methods was initiated to expand the pesticide risk assessment process to include probabilistic risk assessment tools and methods. In doing so, the ECOFRAM began by evaluating the primary goal of a pesticide ecological risk assessment and identifying the resources the assessment is designed to address. Assessment endpoints were identified which were obtainable and would provide a broad estimation of the ecological consequences of pesticide applications. Current EPA risk assessment methodology was discussed as to its strengths and limitations and a basis was formed for further discussion on approaches to explore for increasing the usefulness and validity of risk assessment outputs.

Early in the process, ECOFRAM realized the enormity of the task and consciously elected to focus on avian acute effects. Further refinement was conducted in that only the dietary route of exposure was addressed to any depth. The exposure subgroup focused on refining a dietary exposure equation developed by Pastorock (199?) by evaluating individual components of avian behavior and the physical environment which effect potential exposure. As presented in previous posters in this session, individual components were further subdivided to evaluate the potential for introducing distributions for variables that would allow for constructing probabilistic models. Through sensitivity analysis, the refined equation can be used to identify variables that will provide the basis for identifying variables that most affect the risk assessment thereby directing further research. However, this exercise also identified the poor quality of the data for use in probabilistic risk assessments and exposed areas where large improvements could be made in the quality of the data.

The Effects Subgroup began by identifying and evaluating the sources of uncertainty which effect the assessment output. Currently required toxicity and environmental fate data were evaluated for their applicability in probabilistic models and recommendations were identified which would reduce the uncertainty associated with extrapolations from the laboratory to the field. Dose-response models incorporating uncertainty factors were constructed for single and multiple species for predicting mortality to a given species or a range of species. Finally, the exposure subgroup produced a tiered approach for risk characterization through the integration of acute toxicity data distributions with estimates of exposure distributions.

ECOFRAM made a conscious decision to concentrate efforts on dietary exposure and to focus on birds. ECOFRAM made this decision because it was recognized that while dietary exposure may be the primary route of exposure for most species and exposure scenarios, other routes including dermal and inhalation could be equally important in some situations. ECOFRAM strongly recommends that further work be directed at additional exposure routes, perhaps using or modifying methods suggested by this workgroup.

The science of probabilistic risk assessments is still in its infancy with years of development before it. However, the methodology developed by the ECOFRAM will begin the process of providing probabilistic risk assessments to the risk manager, providing them an indication of the magnitude of predicted ecological effects of pesticide application.

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Levels of Refinement

The basic approach taken by the ECOFRAM is one of "Levels of Refinement." At every stage of the assessment process a hierarchical framework has emerged. The table illustrates the general refinement process throughout the risk assessment process identified by the ECOFRAM. The importance of population effects were recognized but not addressed in the process. It is important to note that these tiers may not be progressed through at the same rate. For instance, the data available for assessing exposure may be the quantity and quality for a level 3 assessment but the effects data may be lacking and only appropriate for level 1.

Levels of Refinement
Level 1Level 2Level 3Level 4
General Framework
  • Deterministic Inputs
  • Deterministic Outputs
  • Simple models
  • Conservative Assumptions
  • Ignore minor pathways and effects
  • Use only standard studies
  • Use only Existing Field Data
  
  • Probabilistic inputs
  • Probabilistic outputs
  • Complex models
  • Assumptions Replaced by data
  • Include all significant pathways and effects
  • Include special studies when needed
  • Include focused field studies when needed
Assessment EndpointsIndividual Survival & Reproduction
Measurement EndpointsLD50 and LC50 (with slope and confidence intervals), NOEL (clutch size, hatching success etc.) Quantity and quality of the data increase with successive tiers
Exposure Characterization Worst case based on means, generic species, existing data, gorging and non-gorging scenarios Hypothetical distributions for literature (or means if available), focal species Actual distributions from literature, focal species relevant to crop, relevant exposure scenario field studies, relevant species, temporal and spatial analysis
Effects Characterization Method Modified Pastorock Equation
Exposure Characterization Output Point estimates for acute toxicity in gorging and non-gorging scenarios Distribution of acute toxicity estimates in gorging and non-gorging scenarios Improved distributions of acute toxicity estimates in gorging and non-gorging scenarios based upon more data Field data on focal species and consideration of landscape factors in spatially explicit models
Effects Characterization Methods METHOD 1
Point Estimates
Quotients
METHOD 2
Comparison of distribution of exposure to a point estimate of effects with uncertainty factors
METHOD 3 Comparison of distributions of exposure and effects with uncertainty factors METHOD 5 Integration of exposure and effects distributions using Monte Carlo Analysis
Exposure Output Point estimates for acute toxicity in gorging and non-gorging scenarios Distribution of acute toxicity estimates in gorging and non-gorging scenarios Improved distributions of acute toxicity estimates in gorging and non-gorging scenarios based upon more data Field data on focal species and consideration of landscape factors in spatially explicit models
Effects Characterization Output
  • Acute: 1 LD50 dose-response*
  • Dietary: 2 LC50 U F *
  • Repro: 2 NOELs
  • Acute: 2-3 LD50 U F *
  • Dietary: 2 LC50 U F * , individual caging
  • Repro: 2 NOELs
  • Acute: 4+ LD50* U F
  • Dietary: 2 LC50* U F * , individual caging, vary exposure
  • Repro: 2 NOELs, vary exposure, aviary study
Field conditions but only in combination with exposure assessments
Risk Characterization
Spatial Treated Field (Pt = 1),
generic species,
generic crop,
gorging/non-gorging,
dietary and Repro.,
label maximum rate
Treated Field and Non-target Areas (Pt < 1), focal species, generic crop or linked to focal species, gorging/non-gorging, dietary and repro., label maximum rate Treated Field & Non-target Areas & Drift Zone (Pt < 1), focal species, generic crop or linked to focal species, gorging/non-gorging, dietary and Repro., label maximum and typical rates Landscape (clumping, explicit, sizes, pesticide market), focal species, crop linked to focal species, gorging/non-gorging, dietary and repro., label maximum and typical rates
Risk Characterization Method Deterministic Quotients
  • Acute: Methods 2, 3 and 5 as appropriate
  • Dietary: Methods 2, 3 and 5 as appropriate
  • Repro: Methods 2
Risk Characterization Output Quotient Probability distribution specific to method selected

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Recommendations

The Terrestrial ECOFRAM Work Group is still developing and discussing final recommendations and conclusions. The following points have been developed based on the draft report and discussion to date and are not inclusive. They are presented to provide some insight into the direction the work group is taking and to provide additional topics for the Interactive Session that follows this Poster Session.

ECOFRAM identified many areas that are critical to further development of probabilistic risk assessment methods. Recommendations for continuing this process were identified in the areas of problem formulation, study design, modeling and validation.

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Scope of Current Probabilistic Applications

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Test Suitability

Acute Oral Test

Acute Dietary Test

Avian Reproduction Test

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Proof of Concept

The workgroup acknowledges that none of the concepts or recommendations made as a result of the effort has been verified or validated. It is strongly recommended:

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