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By Richard J.
Wenning
At the
heart of the numerous technical discussions in the United
States, Europe, and elsewhere regarding assessment of
contaminated sediments is the role of ecological risk
assessment (ERA). The characterization of perceived or actual
impacts on fish, birds, and aquatic wildlife has often
generated heated debates among technical experts. Assessment
methods, measurement endpoints, toxicity testing, interspecies
extrapolation, the composition of food chains, population
effects, and effects on representative species are among the
debated technical issues.
This
may be due, in part, to the various ERA frameworks favored by
different state and federal environmental agencies. True,
there are several gaps, some substantial, in our understanding
of the environmental fate, bioaccumulation, and ecotoxicity of
chemicals in terrestrial and aquatic ecosystems. The science
behind ecological modeling continues to evolve at a rapid
pace. While there is widespread agreement that the USEPA’s
1992 Framework for Ecological Risk Assessment 1
provides the basic construct for conducting ERAs, different
regulatory agencies in the United States and elsewhere have
tailored the methodology to fit their regulatory
responsibilities.
CENR Report on
Ecological Risk Assessment
In May
1999 an interagency work group under the auspices of the
Committee on Environment and Natural Resources (CENR) released
an analysis of the major uses of ERA by Federal U.S. agencies
2. Eight task groups staffed by 32 scientists from
9 Federal agencies were convened to address the use of ERA in
eight different regulatory arenas. These were: the Federal
Insecticide, Fungicide, and Rodenticide Act (FIFRA); the Toxic
Substances Control Act (TSCA); the Comprehensive
Environmental Response, Compensation, and Liability Act (CERCLA);
non-indigenous species; ecosystem management; agricultural
ecosystems; the Endangered / Threatened Species Act; and,
accidental releases.
An on-going
issue in the U.S. concerns how to best evaluate the numerous
and varied ecological problems, ranging from potential global
climate change to loss of biodiversity, habitat destruction,
urban development pressures, and the effects of multiple
chemicals on ecological systems. Nearly a dozen Federal
agencies have different responsibilities for addressing these
problems. Some agencies have regulatory functions, others
serve as natural resource trustees, and some must address
ecological risks associated with their own activities. These
differing responsibilities highlight the need for flexible
problem-solving approaches.
To those
involved in management of contaminated sediments, this diverse
array of regulatory programs, concerns and stakeholders
probably sounds familiar. Increasingly, ERA has been
suggested as an intricate part of the overall framework for
addressing this same wide array of environmental challenges
and concerns at contaminated sediment sites. The CENR report,
only two years old, is worth a second look.
CENR Case Studies
To explore the
uses and applicability of ERA across the federal government,
CENR task groups compiled case studies representing the
diverse applications of ecological assessments commonly
conducted by different Federal agencies. The assessments
typically involved several Federal and State agencies, as well
as nongovernmental organizations and citizen’s groups, and
were conducted in response to different statutory and
non-statutory requirements.
The case
studies were intended to convey the unique aspects of the
ecological challenges facing different regulatory agencies,
and highlight how ERA is used, or could be used, to achieve
regulatory goals. Case studies compiled by CENR were divided
into three categories: established (current) uses of ERA,
potential uses of ERA, and related ecological assessment
methods.
Established Uses of ERA
Case studies
describing established uses of ERA in the TSCA, FIFRA, and
CERCLA regulatory programs generally conform to the major
elements of USEPA's 1992 ERA framework 1 and
subsequent 1998 guidance 3. The fourth regulatory
program included by CENR in this category addresses the
evaluation of nonindigenous species.
Each of these
regulatory programs illustrates the value of a tiered
assessment approach. The approach typically proceeds
step-wise from the use of simple, relatively inexpensive
assessment methods at the outset to more complex and costly
detailed assessments. Each successive tier proceeds when data
gaps and difficult issues remain unresolved.
Uncertainty
analysis is an integral part of the tiered process. The
uncertainties associated with the data compiled at the end of
each tier of investigation are examined closely to determine
whether more detailed investigations are required to answer
key questions, and whether the level of certainty is
sufficient to support risk management decision-making.
In some cases,
for example ERAs of hazardous waste sites at U.S. Department
of Energy facilities, the ERA includes a data quality
objective (DQO) process, which helps at the outset to
minimize, or avoid, unintended uncertainties (e.g.,
uncertainties associated with too few environmental samples,
or inadequate laboratory detection limits). The DQO process
becomes a component of the planning and problem formulation
stages. It emphasizes determination of investigation
boundaries (i.e., study goals and assessment endpoints), as
well as evaluation of the quality and quantity of the data
necessary to conduct a meaningful ecological study within
those prescribed boundaries.
ERA in TSCA
In the TSCA
premanufacture notification (PMN) program to evaluate new
chemical substances, an ERA is a prospective evaluation. The
TSCA program illustrates the value of a tiered ERA evaluation
process and the use of uncertainty analysis for prediction of
possible future consequences of chemical usage. For USEPA’s
Office of Pollution Prevention and Toxics, the approach to ERA
has proved to be very pragmatic for assessment of thousands of
new chemicals in a short time frame, often with minimal data.
Under TSCA,
the initial planning and problem formulation stage is similar
for most ecological assessments, because the assessments are
usually not site specific and similar models and endpoints can
be used for different chemicals. Analysis and risk
characterization phases become more chemical-specific in each
successive tier of investigation by using additional data and
fewer worst-case assumptions.
Because of the
paucity of data associated with new chemicals, the ERA relies
heavily on the use of structure-activity relationships to
predict environmental fate and ecotoxic effects. Uncertainty
factors are used to compensate for the lack of definitive data
when comparing known or predicted effects concentrations with
possible exposure levels.
ERA in FIFRA and CERCLA
ERA
methodologies under FIFRA and CERCLA represent the most
familiar applications of USEPA’s 1992 framework and subsequent
ERA guidance. Assessments in both regulatory programs can be
either retrospective or prospective, or both.
ERA in the
FIFRA program tends to emphasize effects and exposure
analyses. For effects analyses of pesticides, the tiered
approach moves from acute toxicity testing to subchronic and
chronic toxicity testing to field, farm, pond, and mesocosm
levels of study. In exposure analysis, the first tier uses
conservative assumptions in exposure models. These models are
refined at higher tiers of investigation with site-specific
data, pesticide use information, use of more complex
calculations, and the application of probability modeling.
ERA in the
CERCLA program emphasizes the collection of baseline
information to evaluate whether a clean-up should be
considered for ecological reasons, and whether remedial
alternatives will effectively reduce actual or suspected
adverse effects. A fundamental purpose for ERA at Superfund
sites is to determine if releases or potential releases of
hazardous substances resulted in, or are likely to result in,
unacceptable adverse effects. Responding to this
determination becomes the focus of Superfund response actions,
which strive to prevent adverse ecological effects from
occurring or to mitigate effects that have occurred.
Cost-benefit
analysis plays a role in both regulatory programs. But,
unlike CERCLA (philosophical arguments aside), FIFRA
explicitly embodies a cost-benefit statute that seeks to
balance no unreasonable adverse effects to human health or the
environment with economic, societal, political, and legal
concerns. In this regard, uncertainty analysis plays a very
important role in FIFRA risk management decision-making.
A related, and
highly controversial, aspect of the CERCLA program is the use
of ERA at hazardous waste sites by natural resource trustees.
Trustees apply a variation of ERA, referred to as a natural
resource damage assessment (NRDA), to quantify the value of
ecological impacts. NRDAs emphasize demonstrating actual,
rather than potential, ecological damages and establishing the
cost for replacing or restoring so-called injured resources.
In this regulatory context, ERA is focused on establishing
causal links between chemical contamination at a site and
adverse effects in fish, birds, and other wildlife.
Potential Uses of ERA
The CENR
report identified two regulatory programs, agricultural
ecosystems and endangered/threatened species, as representing
potential uses of ERA. The third category discussed in the
CENR report addresses the use of ERA-like scientific
assessments in ecosystem management and evaluations of
accidental chemical releases. Several of the case studies in
the CENR report are not ERAs, but merge USEPA guidance with
different, or unique, investigation methods.
ERA in Agriculture
The
application of ERA by the U.S. Department of Agriculture
(USDA) to agricultural ecosystems has been varied in scope and
extent. The Federal Crop Insurance Reform and Department of
Agriculture Reorganization Act of 1994 required risk
assessment and cost-benefit analysis of all proposed
regulations having an annual economic impact of $100 million
or more on human health, human safety, or the environment.
For some of USDA’s programs, the problem formulation and risk
characterization components of ERA were identified early on as
promising tools for environmental assessments.
However,
applying quantitative analysis to multiple stressors, multiple
receptors, and larger geographic scales in both the USDA’s
Environmental Quality Incentives and Conservation Reserve
programs have proven to be more difficult to implement. The
objectives of both programs are similar to those in other
Agency programs: identification of resources at potential risk
from agricultural activities and practices, characterizing
those activities that result in risk, characterizing the
magnitude and extent of the risks, and developing risk
management options.
Further
refinement and application of the ERA process to agricultural
ecosystem assessments, according to the CENR report, should
include greater use of ERA problem formulation and analysis
tools to identify strategies for minimizing adverse ecological
impacts while achieving other agricultural goals. The CENR
report also advocates establishing an iterative information
exchange process between risk assessors and risk managers.
Communication between these experts, as well as with other
stakeholders, is a common theme throughout the CENR report.
Endangered Species & Accidental
Releases
According to
the CENR report, ERA in the U.S. Fish & Wildlife’s endangered
and threatened species program typically focuses on the use of
population-level modeling tools to estimate the risks of
extinction of small populations of a particular species. Some
of the parameters in these models include characteristics that
influence the probability of extinction (e.g., random
demographic or environmental changes, loss of adaptive
variation, environmental catastrophes, accumulation of
deleterious genetic factors, or habitat fragmentation). These
parameters are important, but generally undeveloped, in
current more traditional ERA applications, particularly those
representing the established use category.
The CENR
report concludes that ERA refinement could incorporate
considerations of exposure to anthropogenic stressors (e.g.,
habitat loss or introduced species), more explicit assessment
endpoints and conceptual models, and a more complete risk
characterization. Surprisingly, uncertainty analysis, an
important component in other regulatory programs, appears to
be generally under-utilized in assessments for listing of
endangered and threatened species.
In a similar
population-level fashion, the potential application of ERA to
assessment of accidental chemical releases, according to the
CENR report, could lead to better emergency response and
greater protection of sensitive ecological resources. Using
the ERA process as a guide for developing spill contingency
plans (or, likewise, for protection of endangered or
threatened species), risk managers could become more
proactive, rather then reactive, in crisis. ERA, in this
context, becomes precautionary, and could advance to the point
of predicting adverse effects of reasonably possible
theoretical accidents; these predictions could be used as
guidance for planing and rapid response purposes during an
actual crisis.
The largest
challenge is the very short time frame required for
decision-making following an accidental spill. ERA problem
formulation provides the basis for a planning process, by
defining important ecological parameters, assessment
endpoints, and investigation methods, all of which could be
characterized up-front. Analysis and risk characterization
phases of the ERA become elements of the response process.
Ecosystem Management
Perhaps the
ultimate use of ERA is for management of whole ecosystems.
While ERAs in regulatory programs tend to focus on impacts
from specific chemicals and hazardous waste sites or the
protection of certain species, ultimately these efforts are
intended to preserve the environment or restore it to a
condition prior to human interference.
Ecosystem, and
watershed, management frequently identifies goals using terms
such as ecological sustainability, integrity, or health.
While these terms are useful as guiding principles, they must
be explicitly interpreted to support an ERA. The key aspects
that need to be specified include: definition of
sustainability, integrity, and health for a particular
ecosystem; identification of the resource(s) that must be
protected to meet these goals; selection of ecological
resources and processes that are to be sustained; and,
recognition of how and when stated goals have been achieved.
According to
the CENR report, the different Federal agency approaches to
managing watersheds and forest resources all take advantage of
the problem formulation process. However, comparisons to
USEPA’s 1992 ERA framework indicate considerably fewer
similarities to the exposure to risk portion of the paradigm.
Perhaps acknowledging some of the criticisms associated with
the use of ERA in ecosystem management, the CENR report
advocates an improved focus of ERA as a tool for capturing
scientific information and uncertainties.
Broadening the
1992 ERA Framework
Together, the
established and potential uses of ERA described in the CENR
report illustrate the potentially broad applications and
considerable benefits of ERA in the regulatory decision-making
process. The inherent flexibility of the paradigm provides
the means to address a wide range of environmental stressors,
habitats, and fish and wildlife species, temporal issues
(ranging from legacy industrial problems to sudden accidental
releases), and spatial scales.
Written two
years ago, the CENR report concluded that much remained to be
done to develop a unifying ERA framework and incorporate the
ERA paradigm into the decision-making process of the different
Federal agencies with environmental protection
responsibilities. The same aspiration for a coordinated
Agency approach to environmental decision-making holds true in
the contaminated sediment arena.
About the CENR
The Committee
on Environment and Natural Resources (CENR) is one of five
committees convened under the National Science and Technology
Council (NSTC). The NTSC is a cabinet-level council
established by President Clinton in 1993 to coordinate
science, space, and technology policies across the federal
government. The NSTC is chaired by the President. Membership
consists of the Vice President, the Assistant to the President
for Science and Technology, Cabinet Secretaries and Agency
Heads with significant science and technology
responsibilities, and other senior White House officials.
The CENR is
charged with improving coordination among Federal agencies
involved in environmental and natural resources research and
development, establishing a strong link between science and
policy, and developing a federal environment and natural
resources research and development strategy that responds to
national and international issues. The CENR sponsored
workshops in October 1994 and December 1995 to promote
information exchange on ERA within the federal government.
The information in the CENR’s May 1999 report, Ecological
Risk Assessment in the Federal Government (CENR/5-99/001),
was prepared as follow-on to these workshops.
To obtain
additional information regarding the NSTC, contact the NSTC
Executive Secretariat at (202) 456-6102. To obtain additional
information about the CENR, contact the CENR Executive
Secretary at (202) 482-5916
References
1. USEPA,
1992. Framework for Ecological Risk Assessment.
EPA/630/R-92/001. Risk Assessment Forum, Washington, D.C.
2. Committee
on Environment and Natural Resources (CENR), 1992.
Ecological Risk Assessment in the Federal Government.
National Oceanic and Atmospheric Administration, U.S.
Department of Commerce, Washington, D.C. May.
http://www.nnic.noaa.gov/CENR/cenr.html.
3. USEPA,
1998. Guidelines for Ecological Risk Assessment.
Federal Register, 63(93): 26,846 – 26,924, 14 May.
http://www.epa.gov/ncea/ecorsk.htm.
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