Ecological Assessment

Quest evaluation and execution of an ecological risk assessment includes three primary phases: Problem formulation, analysis and risk characterization.  In problem formulation, Quest as the risk assessor evaluates goals and selects assessment endpoints, prepares the conceptual model, and develops an analysis plan.  During the analysis phase, Quest evaluates exposure to stressors and the relationship between stressor levels and ecological effects.  In the third phase, risk characterization, Quest estimates risk through integration of exposure and stressor-response profiles, describes risk by discussing lines of evidence and determining ecological adversity, and prepares a report.  The interface among Quest, risk managers (including regulatory staff), and interested parties during planning at the beginning and communication of risk at the end of the risk assessment is critical to ensure that the results of the assessment can be used to support a management decision.  Because of the diverse expertise required (especially in complex ecological risk assessments), Quest frequently works in multidisciplinary teams.

Quest approaches each ecological assessment assignment utilizing the following criteria:

  • What scientific understanding is missing that would provide confidence in the use of bioavailability factors for different contaminant classes?  That is, what bioavailability mechanism and processes require better understanding?  What are the highest priority research needs?  For which contaminant classes, environmental setting, and organism classes are bioavailability assessments most important?
  • What tools (biological, chemical, and physical) are available to characterize and measure bioavailability for different contaminant classes, and what new tools are needed?  What criteria should be used to validate these tools?
  • How do treatment processes affect bioavailability for different contaminant classes?  How does bioavailability affect treatment processes that rely on microbial uptake and/or degradation of contaminants?
  • How and when should bioavailability information be used?  What are its implications for relevant regulations?  How can information on bioavailability be reliably communicated, especially to the public?

Both regulatory and client risk managers and Quest risk assessors bring valuable perspectives to the initial planning activities for an ecological risk assessment.  Risk managers charged with protecting the environment can identify information they need to develop their decision; Quest can ensure that science is effectively used to address ecological concerns, and together they can evaluate whether a risk assessment can address identified problems.  However, this planning process is distinct from the scientific conduct of an ecological risk assessment.  This distinction helps ensure that political and social issues, while helping to define the objectives for the risk assessment, do not introduce undue bias.

Problem formulation, which follows these planning discussions, provides a foundation upon which the entire risk assessment depends.  Successful completion of problem formulation depends upon the quality of three products: assessment endpoints, conceptual models, and an analysis plan.  Since problem formulation is an interactive, nonlinear process, substantial reevaluation is expected to occur during the development of all problem formulation products. 

The analysis phase includes two principal activities: characterization of exposure and characterization of ecological effects.  The process is flexible, and interaction between the two evaluations is essential.  Both activities evaluate available for scientific credibility and relevance to assessment endpoints and the conceptual model.  Exposure characterization describes sources of stressors, their distribution in the environment, and their contact or co-occurrence with ecological receptors.  Ecological effects characterization evaluates stressor-response relationships or evidence that exposure to stressors causes an observed response.  The bulk of quantitative uncertainty analysis is performed in the analysis phase, although uncertainty is an important consideration throughout the entire risk assessment.  The analysis phase products are summary profiles that describe exposure and the stressor-response relationships.

Risk characterization is the final phase of an ecological risk assessment.  During this phase, Quest estimates ecological risks, indicates the overall degree of confidence in the risk estimates, cites evidence supporting the risk estimates, and interprets the adversity of ecological effects.  To ensure mutual understanding between the Quest risk assessors and risk managers, a good risk characterization will express results clearly, articulate major assumptions and uncertainties, identify reasonable alternative interpretations, and separate scientific conclusions from policy judgments.  Regulatory risk managers use risk assessment results, along with other factors (e.g., economic or legal concerns), in making risk management decisions and as a basis for communicating risks to interested parties and the general public.

After completion of the risk assessment, regulatory risk managers may consider whether follow-up activities are required.  They may decide on risk mitigation measures, and then develop a monitoring plan to determine whether the selected procedures reduced risk or whether ecological recovery is occurring.  Regulatory risk managers may also elect to conduct another planned tier or iteration of the risk assessment is necessary to support a management decision. 















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