United States
Environmental Protection
Agency
Office of
Solid Waste and
Emergency Response
Publication 9345.0-11FSI
EPA 540/F-95/037
PB95-963323
January 1996
SERA
ECO Update
Office of Emergency and Remedial Response
Intermittent Bulletin
Volume 3, Number 1
Ecological Significance and
Selection of Candidate
Assessment Endpoints
This Bulletin provides
guidance to Superfund risk
assessors and risk
managers on planning
ecological risk
assessments (ERAs) at
Superfund sites. This
guidance is based on the
experience of the Regional
Biological Technical
Advisory Groups (BTAGs).
Following the concepts
advocated in this Bulletin
should result in ERAs that
will meet the needs of
Superfund program.
IN THIS BULLETIN
Background
1
Ecological Significance and the
Risk Assessment Process 2
Ecological Significance and
Candidate Assessment Endpoint
Selection 3
Conclusion 4
Reference 5
Glossary 5
Background
In a 1994 OSWER Directive (No.
9285.7-17), Assistant Administrator Elliott Laws
stressed the importance of protecting ecological
receptors at Superfund sites through the
Ecological Risk Assessment (ERA) process. The
purpose for conducting the ERA was described
as characterizing threats from chemical
contaminants to the environment and identifying
clean-up levels that will protect the ecological
receptors atrisk. The information provided in the
ERA and the Human Health Risk Assessment
complete the Baseline Risk Assessment
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conducted during the Remedial Investigation It
is important to note ihat Superfimd ERAs may be
more focused than ERAs conducted by other
programs, in that only chemical stressors are
evaluated during the baseline risk assessment
process. Superfund risk managers, however, do
consider both chemical and non-chemical (e.g.,
habitat loss due to physical disturbances)
stressors when selecting a remedial alternative
that will be ecologically protective.
A critical element in the ERA process
requires distinguishing important environmental
responses to chemical releases from those that
are inconsequential to the ecosystem in which the
site resides: in other words, determining the
ecological significance of past, current,
or projected site-related effects. Failure to make
this distinction may result in a risk assessment that
brings little value to the decision-making process.
For the purpose of a Superfund ERA,
investigations should focus on endpoints most
likely to be affected given the fate and transport
mechanisms of the contaminants involved, the
ecotoxicological properties of the contaminants,
the habitats at the site, and the potential
ecological receptors. Additional endpoints may
be added to assist in risk communication. The
challenge then, for the risk assessor and the risk
manager, is to structure the ERA in such a
manner that potentially ecologically significant
risks will be addressed.
Ecological Significance and The
Ecological Risk Assessment Procesjs
The Superfund program accepts the
approach described in the Framework for
Ecological RiskAssessment(EPA/630/R-
92/001) as an appropriate conceptual model for
the ERA process. Superfund-specific guidance
is being prepared by both the Office of
Emergency and Remedial Response (OERR) and
some Regions that will complement this generic
Agency Framework. However, the OERR
guidance is a process document that does not
address issues such as the ecological significance
of an observed or expected effect. Due to
inherent complexities in developing site-specific
ERAs, risk managers (e.g., Remedial Project
Managers and On-Scene Coordinators) should
coordinate with Regional ecological risk
assessment teams (BTAGs).
The issue of ecological significance must
be addressed in at least two phases of the risk
assessment process. First, during the Problem
Formulation phase, the risk assessor and the risk
Ecological Significance must be
addressed during two phases of a
Superfund ERA:
• Problem Formulation, and
• Risk Characterization.
manager should discuss and identify ecological
attributes associated with the site that may
function as assessment endpoints, which are
defined as explicit expressions of the
environmental value that is to be protected (EPA,
1992). During these planning discussions, it is
important to keep in mind the objectives of the
risk assessment and what it seeks to achieve. A
pertinent question to ask at this juncture is how
an assessment of the proposed ecological
endpoints will help determine whether or not to
remediate the site, and if so, to what level.
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ECO Update
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The issue of ecological significance arises
again during the Risk Characterization step. At
this time, the risk assessor presents the results of
the assessment to the risk manager and the results
are in turn presented to the general public. The
risk assessor must provide an interpretation of the
assessment in the context of the questions raised
intheProblemFormulation what is ihe nature of
the risk (likelihood, duration andmagnitude) to
the receptor(s) represented by the assessment
endpoint(s), what is the anticipated
spatial/temporal extent of the threads), and at
what chemical concentration would the
contaminant(s) of concern no longer pose a
threat.
Ecological Significance and Candidate
Assessment Endpoint Selection
During Problem Formulation, the
significance of adverse toxicological, biological,
and ecological effects to receptors is considered
as part of the process in the selection of
assessment endpoints. The BTAG considers
individual, population, and community level
assessment endpoints appropriate at Superfund
sites. Examples of receptors at these levels of
organization include:
Individual Level
• Endangered or threatened species
known to be present (e.g., bald eagle,
spotted owl, gopher tortoise)
Population Level
A sensitive fish population
Bird populations exposed
contaminants of concern
to
Community Level -
• Distribution and abundance of:
- fish and avian communities
- benthic community
- wetland plant community
- soil invertebrate communities
This list does not encompass the
complete array of potential ecological structural
and functional attributes that could be assessed.
Given the state of current ecosystem models and
the relatively small physical size of most
Superfund sites, however, the utility of
ecosystem-type assessments is questionable for
Superfund ERAs.
For Superfund ERAs, at the population
level of organization, "lite-table" parameters (e.g.,
mortality, fecundity, age class distributions) are
recommended as appropriate measures of
response. It is suggested that community
assessment endpoints should focus on structural
characteristics such as productivity and diversity.
Distinguishing potential and current
adverse effects due to releases of contaminants
from normal fluctuations in measurable
population- and community-level parameters is
the most contentious and complicating issue in the
ERA. Natural variability (e.g., population
During a Superfund ERA, natural
variability inherent in the ecosystem at
a site must be addressed as an
uncertainty, and factored into the risk
characterization.
fluctuations, changes in presence/absence of
ECO Update
January 1996 • Vol. 3, No. 1
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species, abundance, diversity, biomass) is a
factor that must be addressed when selecting
assessment endpoints. Due to time constraints in
the Superfund process, it is unlikely that site-
specific studies will be conducted to determine
natural variability inherent in populations
associated with Superfund sites. Consideration
of whether the observed or estimated effect is
within the range of normal variability should be
addressed as an imcertainty, and factored into Ihe
risk characterization.
Candidate assessment endpoints Ihat are
consistent with the Superfund ERA process
include (but are not limited to) the following
Population Level Assessment
Endpoints
• Survival and reproduction of fish
• Survival, growth, and reproduction of
fish-eating birds and mammals
Level Assessment
Community
Endpoints
• Stream benthic invertebrate species
diversity and abundance
• Survival of soil invertebrates
• Productivity of wetland vegetation
• Maintenance of song-bird population^
Additionally, candidate assessment endpoints for
endangered or threatened species, individuals, or
populations should include impacts on the
following:
Physiological status
Reproduction
Growth
Development
Morbidity and mortality
Conclusion
Choosing from candidate endpoints is a
challengingprocess that requires site-specific
information on species, communities, and
functions; the mode of action (both direct and
indirect) of the released contaminants; and
exposure and sensitivity of the response of the
receptors. It is important that Superfund ERAs
address risks that are ecologically significant and
relevant to the site. Decisions to remediate sites
based upon poorly-designed ERAs that do not
clearly define site-specific needs are
contradictory to the intent of CERCLA and
compromise the integrity of the Superfund
Program.
It may be argued that any discussion
regarding the significance of an effect, the
significance of a specific receptor, and the
societal value of remediation all fall within the
purview of risk management rather than risk
assessment. While it is important to not allow
Regional BTAG Coordinators can
work with Superfund RPMs and other
project managers to select appropriate
assessment endpoints for ERAs. This
process will increase the chance that
the ERA will address risks that are
ecologically significant and relevant to
the site.
the risk management process to force the
assessment process in any predetermined
direction (and thus compromise the integrity of
the assessment), the risk assessor and risk
manager must reach agreement on the issue of
assessment endpoints prior to beginning any date
January 1996 • Vol. 3, No. 1
ECO Update
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collection activities to confirm the projected
effects. When the results of the ERA are
provided to the risk manager, the significance of
the risks to the ecosystem should be discussed,
and die role of societal value can Ihen be weighed
as an aspect of risk management. Without this
coordination, there is no way to assure that the
ERA will be useful to the risk management
decision-making process.
The Regional BTAG Coordinators can
work with the project manager to select the
appropriate assessment endpoints for the ERA.
Establishing explicit assessment endpoints very
early in the process greatly increases the
likelihood that a successful ERA will be
accomplished.
Reference
U.S. Environmental Protection Agency, 1992.
Framework for Ecological Risk Assessment.
EPA/63O/R-92/001. Risk Assessment Forum,
U.S. Environmental Protection Agency,
Washington, DC.
GlOSSary (adapted from EPA, 1992)
assessment endpoint - An explicit expression of
the environmental value that is to be protected.
community - An assemblage of populations of
different species within a specified location in
space or time.
direct effect - An effect where the stressor acts
on the ecological component of interest itself, not
through effects on other components of the
ecosystem (compare with definition for indirect
effect).
ecological risk assessment - The process that
evaluates the likelihood that adverse ecological
effects may occur or are occurring as a result of
exposure to one or more stressors.
ecosystem - The biotic community and abiotic
environment within a specified location in space
and time.
exposure - Co-occurrence of or contact between
a stressor and an ecological component.
indirect effect - An effect where the stressor
acts on supporting components of the ecosystem,
which in turn have an effect on the ecological
component of interest.
measurement endpoint - A measurable
ecological characteristic that is related to the
valued characteristic chosen as the assessment
endpoint. Measurement endpoints are often
expressed as the statistical or arithmetic
summaries of the observations that comprise the
measurement.
population - An aggregate of individuals of a
species within a specified location in space and
time.
risk characterization - A phase of ecological risk
assessment that integrates the results of the
exposure and ecological effects analyses to
evaluate the likelihood of adverse ecological
effects associated with exposure to stressor. The
ecological significance of the adverse effects is
discussed, including consideration of the types and
magnitudes of the effects, their spatial and
temporal patterns, and the likelihood of recovery.
stressor - Any physical, chemical, or biological
entity that can induce an adverse response.
xenobiotic - A chemical or other stressor that
does not occur naturally in the environment.
Xenobiotics occur as a result of anthropogenic
activities such as the application of pesticides and
the discharge of industrial chemicals to air, land, or
water.
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