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Phases of ERA - Planning and Problem Formulation

Planning

Planning and Problem FormulationAs described the Guidelines for Ecological Risk Assessment (U.S. EPA, 1998), planning is the initial phase of an ecological risk assessment (ERA). During planning, risk managers and risk assessors define the goals, scope, and timing of a risk assessment. These may include government officials, politicians, ecologists, toxicologists, wildlife biologists, chemists, statisticians, engineers. They also identify the resources that are available and necessary to achieve the goals. 

After the planning phase, problem formulation process begins.

Problem Formulation

Problem formulation is a process for generating and evaluating preliminary hypotheses about why ecological effects have occurred, or may occur, from human activities (U.S. EPA, 1998). During problem formulation,

  • the purpose for the assessment is articulated,
  • the problem is defined, and
  • a plan for analyzing and characterizing risk is determined.

As described in U.S. EPA’s Guidelines for Ecological Risk Assessment (U.S. EPA, 1998) problem formulation may include the integration of available information on sources, stressors, effects, and ecosystem and receptor characteristics. The table below summarizes information that may be considered during problem formulation.

Assessing the Available Information: Sources, Stressors, Exposures, and Receptors
Factor Considerations Example Questions
Stressors Types Chemical, physical, or biological? (Note that multiple contaminants and sources often impact a single site.)
Characteristics What effects are expected to be elicited by the stressor(s)?
Modes of Action How do the stressors act on organisms or ecosystem functions?
Toxicity AcuteHelpacuteAdverse effects that result from a single dose or single exposure of a chemical; any poisonous effect produced within a short period of time, usually less than 96 hours., chronicHelpchronicCauses an adverse effect in which symptoms recur frequently or develop slowly over a long period of time., bioaccumulativeHelpbioaccumulativeBioaccumulation is the general term describing a process by which chemicals are taken up by a plant or animal either directly from exposure to a contaminated medium (soil, sediment, water) or by eating food containing the chemical. Related terms are bioconcentration which chemicals are absorbed by an animal or plant to levels higher than the surrounding environment; and biomagnification, in which chemical levels in plants or animals increase from transfer through the food web (e.g., predators have greater concentrations of a particular chemical than their prey)., or nonpersistentHelpnonpersistentRefers to chemicals that break down quickly in the environment.?
Frequency of events Isolated, episodic, or continuous; is it subject to natural daily, seasonal, or annual periodicity? For biological stressors, is there an opportunity for repeated introduction or escape into the new environment?
Duration How long does it persist in the environment (e.g., for chemical, what is its half-lifeHelphalf-lifeThe length of time required for the mass, concentration, or activity of a chemical or physical agent to be reduced by one-half., does it bioaccumulateHelpbioaccumulateBioaccumulation is the general term describing a process by which chemicals are taken up by a plant or animal either directly from exposure to a contaminated medium (soil, sediment, water) or by eating food containing the chemical. Related terms are bioconcentration which chemicals are absorbed by an animal or plant to levels higher than the surrounding environment; and biomagnification, in which chemical levels in plants or animals increase from transfer through the food web (e.g., predators have greater concentrations of a particular chemical than their prey).; for physical, is habitat alteration sufficient to prevent recovery; for biological, will it reproduce and proliferate)?
Distribution How do the stressors move through the environment (e.g., for chemical, fate and transport; for physical, movement of physical structures; for biological, life-history dispersal characteristics)?
Intensity What is the dose or concentration of a chemical, the magnitude or extent of physical disruption, the density or population size of a biological stressor)?
Sources Status Is the source still active?
Background levels What are background or baseline conditions? 
Spatial scale What is the extent and delineation of the source? Is the extent or influence of the stressors local, regional, global, habitat-specific, or ecosystem-wide?
Exposure Media What environmental media (i.e., air, soil, water) first receive stressors? What are the potential exposure pathways to other media?
Timing When does exposure occur in relation to critical organism life cycles or ecosystem events (e.g., reproduction, lake overturnHelplake overturnLake overturn is the complete, wind-induced, top-to-bottom circulation of water in deep lakes. Also referred to as lake turnover.)?
Receptors Types, characteristics, life history What habitats are present? Which species are considered essential to, or indicative of, the healthy functioning of the habitat (e.g., stream invertebrates)? What types of water bodies are present? What species of plants and animals can be found at the site? What are the mobility patterns of the animals? Are any of the animal species migratory? Do any have large home ranges? Sensitive life stages?
Routes What are the exposure routes of the stressors (i.e., dermal, ingestion, or inhalation)?
Susceptibility,
SensitivityHelpsensitivityMore susceptible to the adverse effects of exposure to toxic chemicals, pesticides, and other pollutants.

Are there rare, endangeredHelpendangeredAnimals, plants, birds, fish, or other living organisms threatened with extinction by man-made or natural changes in the environment., or threatenedHelpthreatenedA plant or animal that is likely to become endangered if not protected. species on or near the affected area? Are there any species protected under Federal or State law (e.g., Migratory Bird Treaty Act, Marine Mammal Protection Act)? Are there any keystone speciesHelpkeystone speciesA species whose survival affects other organisms in an ecosystem. If a keystone species were removed from an ecosystem, the ecosystem would drastically change., sensitive speciesHelpsensitive speciesSpecies more susceptible to the adverse effects of exposure to toxic chemicals, pesticides, and other pollutants., or other species of concern?

Trophic levelsHelptrophic levelsEach step along a food chain; an organism's feeding level.? Predators can become more highly exposed through biomagnificationHelpbiomagnificationBioaccumulation is the general term describing a process by which chemicals are taken up by a plant or animal either directly from exposure to a contaminated medium (soil, sediment, water) or by eating food containing the chemical. Related terms are bioconcentration which chemicals are absorbed by an animal or plant to levels higher than the surrounding environment; and biomagnification, in which chemical levels in plants or animals increase from transfer through the food web (e.g., predators have greater concentrations of a particular chemical than their prey). in the food chainHelpfood chainA food chain is formed as one organism eats another. A food web is a system of interlocking and interdependent food chains, in which each organism supplies energy to another life form. or from feeding more often (or exclusively) on a specific type of prey that accumulates contaminants more easily than other prey types.

Sources: OSWER, 1997; U.S. EPA Region 5, 2011; U.S. EPA, 1991; 1998.

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Using this information risk assessors can develop: assessment endpoints and a conceptual model. These two products are needed to complete an analysis plan.

  • According to U.S. EPA’s Guidelines for Ecological Risk Assessment (U.S. EPA 1998) an assessment endpoint is “an explicit expression of the environmental value that is to be protected, operationally defined by an ecological entity and its attributes.” Assessment endpoints include two elements: identification of the specific receptor that is to be protected (e.g., species, community, ecosystem), and a characteristic about the receptor of concern that is important to protect (e.g., survival, growth, reproduction).
  • The Guidelines for Ecological Risk Assessment (U.S. EPA 1998) define a conceptual model as “a written description and visual representation of predicted relationships between ecological entities and the stressors to which they may be exposed.” The conceptual model consists of two components: a set of risk hypotheses that describe the predicted relationships among stressor, exposure, and assessment endpoint and a diagram that illustrates these relationships.
  • 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 and develops the assessment design. It identifies data gaps and uncertainties and determines which measures will be used to evaluate the risk hypotheses. It also ensures that the planned analyses will meet the risk managers' needs.

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Phase 1 of the ERA: Planning and Problem Formulation


The planning and problem formulation phase within the overall ecological risk assessment process is illustrated below (adapted from U.S. EPA, 1998). Analysis is directed by the products of problem formulation.

Problem Formulation

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References

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