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PRELIMINARY FINDINGS OF THE ECOLOGICAL COMMITTEE ON FIFRA RISK ASSESSMENT METHODS (ECOFRAM): VII. AQUATIC RISK CHARACTERIZATION AND TIERED RISK ASSESSMENT PROCESS

ECOFRAM Aquatic Exposure and Effects Subcommittees

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Abstract

The Aquatic Exposure and Aquatic Effects Subcommittees of ECOFRAM have developed a tiered scheme for aquatic risk assessment of pesticides, consistent with the EPA's Framework for Risk Assessment, that integrates new developments in exposure and effects analysis. The lowest tier of the risk assessment process incorporates generic worst-case exposure modeling and a standard set of acute and chronic toxicity tests. Risk characterization at the lowest tier is based on risk quotients. At higher tiers, exposure is expressed probabilistically (see Poster V) and effects are expressed in terms of population- and community-level assessment endpoints as well as individual-based measurement endpoints (see Poster VI). Risk is characterized in the higher tiers as a function of probability of exposure and magnitude of ecological effect. Risk mitigation options (aimed at reducing exposure) are evaluated after each phase of the assessment. Results of risk characterization are conveyed to risk managers, who weigh the risks and benefits associated with each pesticide before making decisions on product registration.

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Aquatic Risk Assessment Process

Tier 1 Flow Diagram

Flow Diagram with 4 columns: Effects, Process, Exposure, and Scale. Three Rows: 1st Row says Problem Formulation with arrows to 2nd Row entries of Aquatic Effects in Effects and Aquatic Exposure (GENEEC, PRZM/EXAMS) in Exposure. Each of these points to Hazard Quotient in Process which points to 3rd Row entry of Criteria Exceeded? in Process having an arrow labeled NO that points to Minimal Aquatic Concern in Effects and another arrow labeled YES that points to the Tier 2 diagram. The scale for Tier 1 is labeled Edge-of-field / Pond.

Tier 2 Flow Diagram

Flow Diagram with 4 columns: Effects, Process, Exposure, and Scale. Three Rows: 1st Row says Problem Formulation with arrows to 2nd Row entries of Aquatic Effects in Effects and Aquatic Exposure (PRZM/EXAMS) in Exposure. Each of these points to Risk Characterization in Process which points to 3rd Row entry of Aquatic Risk Management Recommendation in Process with 3 outward arrows, one pointing to Aquatic Risk and Potential Mitigation Defined in Effects, another arrow pointing to Mitigation Options in Exposure (which itself points to Aquatic Exposure in the 2nd row) and a third arrow labeled More data required for aquatic risk assessment pointing to the Tier 3 diagram. The scale for Tier 2 is labeled Edge-of-field / Pond.

Tier 3 Flow Diagram

Flow Diagram with 4 columns: Effects, Process, Exposure, and Scale. Five Rows: 1st Row says Problem Formulation with arrows to 2nd Row entries of Aquatic Effects in Effects and Aquatic Exposure in Exposure. Each of the 2nd Row entries has 4 arrows pointing to 3rd row entries. From Aquatic Effects, arrows point to Effects column entries of: sediment toxicity, pulse dosing, acute toxicity, and chronic toxicity. From Aquatic Exposure, arrows point to Exposure column entries of: refined modeling, additional efate data, fate-o-cosm, and watershed landscape modeling. All of this 3rd Row points to 4th Row entry of Risk Characterization in Process which points to 5th Row entry of Aquatic Risk Management Recommendation in Process with three outward arrows of its own. One points to Aquatic Risk And Potential Mitigation Defined in Effects, another points to Mitigation Studies or Refinement in Exposure (which itself points back to Problem Formulation in Row 1) and the third labeled More data required for aquatic risk assessment points to the Tier 4 diagram. The scale for Tier 3 is labeled Edge-of-field / pond / and/or watershed.

Tier 4 Flow Diagram

Flow Diagram with 4 columns: Effects, Process, Exposure, and Scale. Five Rows: 1st Row says Problem Formulation with arrows to 2nd Row entries of Aquatic Effects in Effects and Aquatic Exposure in Exposure. Each of the 2nd Row entries has 4 arrows pointing to 3rd row entries. From Aquatic Effects, arrows point to Effects column entries of: microcosm/mesocosm, population modeling, PBPK modeliing, and behavioral tests. From Aquatic Exposure, arrows point to Exposure column entries of: microcosm/mesocosm, field monitoring, benchmark modeling, and refined watershed modeling. All of this 3rd Row points to 4th Row entry of Risk Characterization in Process which points to 5th Row entry of Aquatic Risk Management Recommendation in Process with two outward arrows of its own. One points to Aquatic Risk And Potential Mitigation Defined in Effects; the other points to Mitigation Development in Exposure, which in turn points back to Problem Formulation in Row 1. The scale for Tier 4 is labeled Edge-of-field / pond / and/or watershed.

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Risk Characterization

Integrating Exposure and Effects Distributions into a Joint Probability Curve

3 graphs: exposure distribution and dose-response which combine to create the third labeled Joint Probability Curve. Exposure Distribution has y-axis of frequency and x-axis of concentration and a line resembling stairs from upper left to lower right. Dose-Response has y-axis of mortality (%) and x-axis of concentration and a line curving in a slight S from lower left to upper right. Joint Probability Curve has y-axis of probability and x-axis of mortality(%) with a gentle U-shaped curve from upper left to lower right.

Integrating Exposure and Effects Distributions into a Joint Probability Curve

Using Joint Probability Curves to Evaluate Relative Risk

graph with y-axis labeled exceedence frequency and x-axis labeled magnitude of effect. arrow labeled decreasing risk pointing from upper right to lower left with lower left labeled more acceptable and upper right labeled less acceptable. 4 unlabeled parabolic lines also appear on the graph

Using Joint Probability Curves to Evaluate Relative Risk

Using Joint Probability Curves to Make Risk Management Decisions

graph with axes y labeled exceedence frequency and x labeled magnitude of effect. 3 areas of different colors and labels from lower left to upper right: C in green for risk judged acceptable, B in yellow for apply higher tiers or mitigation, and A in red for risk judged unacceptable.

Using Joint Probability Curves to Make Risk Management Decisions

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