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Technical Overview of Ecological Risk Assessment
Problem Formulation
Contents
About Problem Formulation
Before the risk assessment is conducted, risk assessors and risk managers engage in a planning dialogue. During the planning dialogue, which feeds into the problem formulation component of the risk assessment process, risk assessors and risk managers discuss the following items:
Management goals
- statements about the desired condition of ecological values of concern. For example, management goals may be to "prevent toxic levels of contamination in water, sediments, and biota" or to " maintain a sustainable aquatic community." Management goals drive the risk assessment and many times come from an enacted law, such as the Clean Water Act which has the goal to "protect and restore the chemical, physical, and biological integrity of the Nation's waters."
Management options to achieve goals
- risk management decisions that establish national policy across the county for specific chemicals, sites, or management concern that will achieve an environmental goal when implemented. Management options may range from cancelling a particular use of a pesticide to label restrictions for limiting the application of a pesticide in certain areas of the country. Management options define the scope, focus, and conduct of a risk assessment.
Scope and complexity of the risk assessment
- risk assessments are constrained by the availability of valid data, expertise, time, and financial resources. The scope and complexity of the risk assessment is partly based on the uncertainty that can be tolerated in a decision supporting the risk assessment. Risk assessments that are conducted in support of legal mandates and likely to be challenged in court will require more resources and attention than those based on a small area.
After planning agreements are reached, the problem formulation phase, which is the foundation for the risk assessment, begins. In this process, risk hypotheses or assumptions are generated about why ecological effects have occurred. Then the risk assessors and risk managers perform the following tasks:
Select assessment endpoints
These are based on management goals identified in the planning dialogue and are important because they provide direction and boundaries for the risk assessment. Assessment endpoint include two elements: identification of the specific ecological entity that is to be protected, such as a species, a community, an ecosystem, or other entity of concern and a characteristic about the entity of concern that is important to protect. In a screening-level pesticide ecological risk assessment, typical assessment endpoints are reduced survival and reproductive impairments for individual animal species. For plants, the assessment endpoints are typically concerned with maintenance and growth of non-target species. Although these assessment endpoints are measured at the individual level, they indicate potential risk to populations.
Evaluate the nature of the problem
This step includes defining the nature of the stressor (pesticide) and characterizing the pesticide use. In defining the nature of the stressor, risk assessors generally focus on the pesticide active ingredient although in some cases they may consider pesticide formulations, inert ingredients, or degradates based on available data. Risk assessors use the pesticide product labeling to characterize the nature of the pesticide use in the field. Characterization of pesticide use allows the risk assessors to focus the risk assessment on specific use patterns that are representative of a larger variety of use patterns. In this way, risk assessors can focus on use scenarios that reasonably represent the highest exposures.
Prepare a conceptual model
The conceptual model includes a set of risk hypotheses and a diagram that describe the predicted relationships among stressor, exposure, and assessment endpoints. Typical conceptual models are flow diagrams that contain boxes and arrows illustrating these relationships. Developing a conceptual model allows the risk assessor to identify the available information regarding the pesticide, justify the model, identify data and information gaps, and rank model components in terms of uncertainty.
Develop an analysis plan
This is the final stage of problem formulation in which risk assessors develop a plan for analyzing data and characterizing risk. The analysis plan summarizes what has been done during problem formulation and targets those hypotheses that are likely to contribute to the risk. It also evaluates the risk hypotheses to determine how they will be assessed, develops the assessment design, identifies data gaps and uncertainties, determines which measures will be used to evaluate the risk hypotheses (e.g., LC50, NOAEC, EEC's), and ensures that the planned analyses will meet the risk managers' needs.
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