•EPA/600/D-89/069
ASSESSMENT OF ECOLOGIC RISKS RELATED TO CHEMICAL .EXPOSURE"
METHODS AND STRATEGIES USED IN THE UNITED STATES.
J. W. Falco
Office of Environmental Processes and Effects Research
United States Environmental Protection Agency
Washington, B.C.
R. V. Moraski
Office of Health and Environmental Assessment
United States Environmental Protection Agency
Washington, D.C.
1 CURRENT STATUS
At present, the United States has yet to develop government- or
agency-wide guidelines for conducting ecologic risk assessments; however,
various standard test methods have been developed to provide toxicologic
benchmarks. The earliest of these methods measured acute toxicologic ef-
fects, but as this field of science progressed, methods to measure chronic
effects were also developed. Most recently, research efforts have been
directed toward developing test methods that predict chronic and acute
toxicologic effects based on results of short-term exposure of organisms
during sensitive life stages.
The American Society for Testing and Materials (ASTM) has published
many of the earlier methods used in the United States for testing acute
and chronic effects. Depending on their scope and level of detail, test
procedures are published as ASTM guides, practices, or test methods. A
partial compilation of methods developed by the United States Environmen-
tal Protection Agency (EPA) or published by ASTM is presented in Tables
5.1, 5.2, and 5.3. These toxicologic methods are grouped according to
their use for measuring effects on terrestrial, freshwater, or saltwater
organisms,
" . Ecologic risk assessments performed by the EPA are done primarily by
the quotient or ratio method; less frequently used methods include ranking
techniques and application factors. The ratio method compares a- toxico-
logic benchmark such as an acute LC5Q value or a chronic no-effects con-
centration to a given exposure concentration to provide an estimate of
risk,.s "As the ratio for a given species approaches a critical value, a
high risk is inferred. Exposures of varying intensities and data on eco-
logic effects are evaluated depending on the purpose of the assessment and
the legal requirements that specify the scope of the assessment.
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Table 5.1. Methods for Estimating Toxicologic Effects on Terrestrial
Species and Birds of Exposure to Potentially Toxic Chemicals
Method Reference
Standard Method for Effective Bird Control ASTM, 1986a
Standard Method for Percutaneous Toxicity ASTM, 1986b
Standard Method for Subchronic Dermal Toxicity ASTM, 19860
Standard Practice for Determining Acute Oral LD5Q
for Testing Vertebrate Control Agents ASTM, 1986d
Table 5.2. Methods for Estimating Toxicologic Effects on Freshwater
Organisms of Exposure to Potentially Toxic Chemicals
Method Reference
Methods for ftcute Tests with Fish, Macroinvertebrates, U.S. EPA, 1975
and Amphibians - ASTM, 1986e
Method for Aquatic Multiple Species Toxicant Testing, Phipps and
Hoicombe, 1985
Methods for Conducting Effect Studies on Snail Holconbe et al.
(Aplexa hypnorum) Embryo through Adult Exposures 198^
Standard Practice for Conducting Static Acute Toxicity ASTM, 1986f
Tests on Wastewaters with Daphnia
Standard Guide for Assessing the Hazards of a Material ASTM, 1986g
to Aquatic Organisms and their Uses
2 FUTURE DIRECTIONS
State-of-the-art assessment of risk to the ecosystem is still evolv-
ing. Although the single-species tests listed in Tables 5.1, 5.2, and 5.3
have provided valuable information for the assessment of ecologic risk, it
is necessary to focus on ecosystems-level tests and analyses. The in-
creasing availability of predictive models makes assessment of risk to the
environment, rather than simply to a single species, more possible.
Predicting an ecosystem's response to pollutant stress is difficult
because of the large number of dependent and independent variables consti-
tuting and inherent to a natural ecosystem. These include population-
level factors such as density, immigration, growth, and mortality, and
community-level factors such as diversity, relative dominance, trophic
structure, and distribution.
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Table 5.3. Methods for Estimating Toxicologic Effects on Saltwater
Organisms of Exposure to Potentially Toxic Chemicals
Method
Reference
Sea Urchin DMA-Based Embryo Growth Toxicity Test
Sea Urchin Sperm Cell Toxicity Test
Bacterial Toxicity Test (Microtox®)
Phorocephalid Amphipod Bioassay
Rhodophyta Life Stages Toxicity Test
Atherinid Fish Early Life Stage Toxicity Test
Sheepshead Minnows Life Cycle Toxicity Test
Cytogenetic Model for Marine Genetic Toxicology
Method to Measure Scope for Growth Index
for Blue Mussels •
Method for Measuring AEC as a Test for Stress
in Mussels
Method for Measuring Bioaccumulation of
Chemicals in Mussels and Polychaetes
Method for Measuring Sister Chromatid Exchange
in Marine Polychaetes
System for Preliminary Evaluation of Infectivity
and Pathogenesis of Insect Virus in Shrimp
Tidewater Silversides (Menldia peninsulae)
Early Life Stage Toxicity Test
Early Life Stage Toxicity Test Using
California Grunion
Jackim and Nacci,
1984, 1986.
Dinnel et al., 1983
Beckman, 1982
Sectarian, 1982
Nacci, 1986
Swartz, 1985
Steele and Thursby,
1983
Goodman et al., 1985a
Hansen and Parrish,
1977
Pesch et al., 1981
Nelson et al., 1985
Zaroogi'an et al.,
1982
Lake et al., 1985
Pesch et al., 1984
Couch and Martin,
1984
Goodman et al,, 1983
Goodman et al,, 1985b
There are ways to simplify the complex structure of an ecosystem.
For example, determination and analysis of a key species may facilitate
prediction of the effects of pollutant stress on dependent species. In
addition, knowledge of physico-chemical parameters of pollutants may make
possible the analysis of pollutant fate and transport (see, for example,
Chapter 7 of this book). Nevertheless, ecosystem-level analysis is an
inherently complex undertaking. Ecosystems may modify the fate and trans-
port of environmental pollutants. In aquatic systems, for example, micro-
accumulation of
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neurotoxic methylmercury in fish. A number of the factors to be included
in any discussion of ecological risk assessment are discussed below.*
2.1 End Points
A variety of ecotoxicologic end points have been proposed to assess
the effects of pollutants on ecologic systems. Potential end points occur
at the level of the individual organism, the population, and the ecosys-
tem. In general, end points at lower levels of organization (organism or
suborganisra levels) have -been used more widely because they are simpler,
are more rapidly and inexpensively assessed, and are most useful in deter-
mining the mechanisms of toxicologic effects. End points at the popula-
tion or ecosystem levels of organization are more complex and difficult to
interpret but are probably ecologically more realistic, because they in-
corporate the complexity of interactions among organisms and between
organisms and their abiotic environment. A major, unresolved question is
the extent to which end points at lower levels of organization can be used
to predict pollutant impacts at higher levels of organization.
2. 1 . 1 Ecosystem Structure End Points. Measures of ecosystem struc-
ture can provide important data for ecosystem risk assessments. Structur-
al changes in stressed ecologic communities may be visualized as an infor-
mation network reflecting environmental conditions but not demonstrating
the external mechanisms or internal interactions that brought about a
reorganization in species composition or dominance patterns.
Structural end points such as abundance (McNaughton and Wolf, 1973)
and biomass (Clapham, 1973) of communities provide relatively simple,
gross measurements of ecosystem stress. Species richness has been shown
to be sensitive to the level of stress and can provide a partial picture
of changes in community composition which accompany stress (McNaughton and
Wolf, 1973).
Combined numerical indices such as similarity (Hellawell, 1977) and
ordination (Odum, 1971) measures may be used to track changes in community
structure which occur as pollutant concentrations change. Although diver-
sity indices (Odum, 1971; Herricks and Cairns, 1982) have been used widely
in hazard assessment studies (see, for example, Chapter 10 of this book),
these integrated measures are often insensitive to stress and provide data
that are difficult to interpret (Hellauell, 1977). The use of numerical
indices exclusive of the biologic data from which they are calculated
should be discouraged.
2,1,2 Ecosystem FunctionEnd Points. The analysis of functional re-
sponse end points can provide data on energy flow and nutrient cycles.
The functional capability of the ecosystem is, in fact, the ultimate cri-
terion of ecologic success. The effective use of end points in describing
impacts is dependent on a theoretical and practical knowledge of ecosys-
tems for proper interpretation, and on collection of sufficient baseline
data to establish normal process rates. A history of measuring functional
response variables will be necessary to establish threshold values for
unacceptable reductions in functional capability.
Primary productivity (McNaughton and Wolf, 1973) provides the energy
for the base of the food web. This process has been shown to be sensitive
to a variety of pollutants and other forms of stress. Reductions in pri-
mary productivity, which are of substantial magnitude and long duration,
*Some of the discussion that follows is talcen from material submitted by
Technical Resources, Inc., Rockville, MD, for work performed under EPA
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are unquestionably detrimental to energy processing in exposed ecosystems.
Disruptions in material cycles such as the nitrogen cycle (Westman,
1985; Cook, 198*1) can be critical if the effects on cycling processes
indirectly inhibit ecosystem production. Material cycles can be upset by
pollutant inhibition of the decomposition process, interference with the
functional links in specific nutrient cycles, or disruption of nutrient
conservation mechanisms. Effects on decomposition can be measured in ter-
restrial and aquatic ecosystems, and changes in decomposition rate and
completeness of mineralization can be related to the level of .pollution
stress. At present, few data are available on the long-term impacts of
reduced decomposition on ecosystem production.
Specific nutrient cycling processes are key to the production effi-
ciency of ecosystems. Identification of the critical cycles in specific
ecosystems will be necessary for the selection of appropriate monitoring
points.
Nutrient conservation is exceedingly important in terrestrial ecosys-
tems. Evidence of excessive leaching of essential nutrients is a sign of
stress. Leaching loss of nutrients has been correlated with reduced nu-
trient availability in the plant-root zone and reduced plant growth in
nutrient-deficient soil (Jackson et al., 1979).
A problem in the use of ecosystem function end points is their rela-
tive insensitivity to ecosystem structure. Shifts in species composition
to more pollutant-resistant species may or may not result in changes in
such functional processes as productivity or nutrient cycling. Thus, an
assessment of pollutant effects at the ecosystem level should include both
structure and function end points.
Because the factors controlling ecosystem structure and function are
numerous and poorly understood, it is difficult to distinguish ecosystem-
level effects of pollutants from naturally occurring processes. Many of
the ecosystem-level end points depend on the questionable assumption that
unpolluted ecosystems are at a stable, undisturbed state.
2.1.3 Population-Level End Points. At the population level, stress
response may be monitored in terms of changes in the abundance, distri-
bution, age structure, or gene makeup of exposed populations. The first
three end points can be related quite clearly to the overall success of
the exposed population. Changes in the gene pool may be related to future
adaptability of the population to similar types of stress.
Also in question is the selection of an appropriate population or
populations to be monitored in an impact assessment. Quite clearly, moni-
toring effects on commercially or aesthetically valuable species is impor-
tant for predicting impacts on those species. More valuable for predict-
ing higher level impacts are population response data on representative
and ecologically important species within exposed communities. Included
within this category are keystone species that strongly influence the
structure of the communities or the functioning of the ecosystem. If
there is interest in extrapolating population response to predict eco-
system-level impacts, emphasis should be placed on gathering data on popu-
lations from major functional groups, including primary producers, pri-
mary, secondary, and tertiary consumers, and decomposers.
A problem in using population-Level end points as indicators of the
effects of pollution is that the numerous factors regulating population
structure are, as yet, poorly understood. This makes it difficult to
discriminate pollutant effects from naturally occurring processes. As
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population structure is ' influenced by interactions among population
members, with other populations, and with the abiotic environment, it
becomes necessary to examine effects of pollutants at the ecosystem level.
2_. 1_. 14 _ Physiologic End Points. The physiologic end points most close-
ly related to individual fitness are acute mortality, growth and develop-
ment, and reproductive success. Acute lethality testing such as LD5Q or
LC5Q determination is widely used to provide minimal estimates of toxic-
ity. However, such testing is not sufficiently sensitive to assess sub-
lethal or chronic effects that occur at lower toxicant concentrations and
that may be of considerable ecologic importance.
Biochemical response end points may provide information on mechanisms
of toxic action. Since biochemical processes are in general particularly
sensitive to pollutants, biochemical response end points may provide early
warning of potential impacts on the individual. However, most biochemical
processes also respond to conditions other than pollutant stress, and the
response of these end points may be adjusted as an individual acclimates
to a stress. Correlations between biochemical response end points and
individual success need to be established to enhance the value of these
sensitive end points as predictors of higher level impacts.
Osmoregulatory activity is an appropriate end point for assessing im-
pacts on certain freshwater and estuarine fish and invertebrates. Again,
the ability of individual organisms to acclimate to osmoregulatory stress
must be considered in interpreting osmoregulatory response data. Musculo-
skeletal end points have also been used to monitor stress responses in
fish. Correlations need to be established between abnormalities and the
ecologic success of deformed fish.
Respiratory activity has been used as a response end point for a num-
ber of species. However, it is difficult to generalize about the patterns
of respiratory response to stress. Respiration, rates may be elevated or
inhibited by pollutants, and ventilation rates in exposed individuals may
adjust as acclimation occurs.
Behavioral alterations are appropriate end points for impact assess-
ments if the alterations act either to protect the individual from harm,
as in avoidance behavior, or to make the individual more vulnerable to the
stress, as in the loss of antipredator behavior. Although behavioral re-
sponses are not easy to demonstrate in the laboratory or in the field,
these end points, if demonstrated, may be easily extrapolated to .predict
potential population-level effects.
Genotoxicity and carcinogenicity are end points that provide early
warning of stress. Data must be gathered on the natural incidence of
mutations and tumors to aid in interpreting the importance of chemically
induced mutation and tumor incidence rates.
End points measuring growth, development, and reproductive success of
individuals are of most obvious utility in predicting population-level
impacts. Because these end points are directly related to population suc-
cess, their use is recommended in impact studies where single-species test
data are extrapolated to predict population-level impacts. These end
points have been used less frequently because of the time and expense
required to conduct full-life-cycle chronic toxicity tests. However, the
more frequently used short-term physiologic and biochemical end points
cannot be recommended until their relationships to organismal growth and
reproductive success are determined.
A number of studies (Babich and Stotzky, 1980; Lighthart, 1980;
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Reinert and.Spurr, 1972; Miles and Parker, 1980) have documented interac-
tions between effects of pollutants and abiotic and biotic factors in the
environment. These studies illustrate the inadequacy of using laboratory
single-species, single-factor testing to estimate all ecologic effects of
contaminants, and they point to the necessity of relating ecotoxicologic
effects on individual organisms to population- and ecosystem-level effects
of pollutants.
2.1.5 End Points and Ecological Risk Assessment. A multilevel eco-
logic risk assessment, which makes use of a combination of organism, popu-
.lation, and ecosystem-level end points, provides the most effective ap-
proach to examining ecosystem stress, Multilevel testing would both
enhance the sensitivity of a risk assessment and broaden its scope to in-
clude more complex levels of ecologic organization. In contrast, the
traditional approach of using only single-species testing is generally
inadequate to account for pollutant-induced effects on the complex organi-
zation of an ecosystem. Single-species measures can be greatly enhanced
by the use of population and ecosystem-level end points.
The precise choice of end points for use in an ecologic risk assess-
ment should be made on a case-by-case basis, depending on both the eco-
system being tested and the nature of the pollutant stressor. Various
population- and ecosystem-level end points are potential choices. Many of
these end points are readily measurable and are highly sensitive to low
levels of pollutant stress. Still inadequate, however, are field data
documenting the usefulness of population- and ecosystem-level end points
in ecosystem toxicity studies. Future research in this area would facil-
itate the development of the multilevel risk assessment approach.
2.2 Choice of Species
The choice of species to study in an ecosystem is also important;
typically, the focus is endangered or sensitive species. The selection of
ecosystem media and interaction of pollutants within these media further
complicate ecosystem assessment. Ecosystems incorporate processes that
operate on diverse spatial, structural, or temporal scales. The enmeshing
of these variables presents difficulties in calculating the effects of
localized versus general processes and in integrating key factors such as
primary production with seasonal climatic changes and geochemical cycling.
Intermediate between full field tests and single-species laboratory
bioassays are microcosm and mesocosm studies. Microcosms and intermediate
mesocosms are isolated parts of a naturally occurring system-that can be
modified to duplicate many features of an intact ecosystem. Microcosms
have many limitations including those of spatial scale, number of orga-
nisms, species diversity, and physical controlling variables.
2.3 Use of Models
Various models can be used to evaluate ecosystem risk. These include
models of fate, transport, exposure, and effects as well as integrative
models (see, for example, Chapter 7'of this book). Other ecosystem models
focus on population density, food chains, bioenergetics, and toxico-
kinetics. The diverse models for both individual species and population
groups have advantages and disadvantages that must be defined and tailored
to specific circumstances. This diversity provides for a wide variety of
approaches that can be applied to the problems encountered in ecologic
risk assessment.
Succession models take on a wide range of mathematical forms. Their
riohn'0" in formulation originates to an extent in the specific objectives
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and training of the model designer. These differences frequently imply
different theoretical constructs as to what is important In the function-
ing of a given ecosystem. In this sense, the models represent a complex
set of a priori hypotheses about the function and behavior of ecosystems.
Thus it is essential to use an orderly, justifiable process in devel-
oping and selecting an appropriate ecosystem model. Refining and improv-
ing available models are critical aspects of developing precise models for
each particular situation in nature.
One of the most pressing needs in environmental management is for
evaluation of models used routinely in assessment of environmental expo-
sure and impact. Many models are being used for situations where they are
of questionable validity, In particular, models should not be applied to
environments outside the range for which they have been calibrated and
tested. Although this may seem obvious, oftentimes models are used to
predict impacts for changing conditions that are appreciably different
from those for which the models were originally developed and calibrated.
With regard to population modeling, although current work on mathe-
matical models of individuals and populations shows great promise, insuf-
ficient scrutiny to date has precluded a general consensus on approach.
Most rudimentary population models have been developed from a retrospec-
tive viewpoint with biologic data, , but few biologic principles, as a
focus. Such models are useful for risk assessment only from a qualitative
perspective. However, discrete age- or stage-structured population models
offer a well-developed theory and a reasonable computational scheme.
Another significant problem in current ecosystem risk assessment is
the paucity of toxic effects models and of predictive methods. Validation
of methods to predict ecosystem response is difficult because of the ab-
sence of empirical data in many areas. Generation of data, development of
models, and validation of methods are current projects of the EPA's Office
of Environmental Processes and Effects Research.
2.1 Resilience and Recovery
Factors that influence recovery of an ecosystem from environmental
stress, include severity of the stress, reversibility of effects, rate and
effectiveness of stress removal, frequency and duration of ecosystem dis-
turbance, resilience of ecosystem structure and function, extent of alter-
ation, compensatory interaction of multiple species, kinetic balance of
the system, complexity of the system, temporal and spatial variability,
availability of regenerating units, and rate of reestablishment of the
biologic and physical habitat.
The resilience of ecologic systems and their resistance to natural
and anthropogenic forms of disturbance have been measured in field and
laboratory studies. Of necessity, these studies have been of long dura-
tion. In most cases, natural ecosystems have not been shown to be dis-
placed to the extent that recovery is not possible when the disturbance
abates (Sheehan, 1984). The availability of colonizers to the disturbed
ecosystem and the existence of biogeochemical feedback loops are cited as
factors important to the rapid recovery of disturbed ecosystems. Func-
tional redundancy of species is cited as important to the resistance of
ecosystems to disturbance. Loss of individual populations may not in it-
self be an adequate measure of the stability of the structure and function
of a disturbed ecosystem.
Resistance and resilience are appropriate response variables for im-
These stability criteria represent integrated measures of
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system breakdown and recovery. In future studies, measurement of amplitude
will be essential to establish measurable threshold levels of disturbance
which may be indicative of permanent changes in stressed ecosystems.
2.5 Development of Surrogate Systems
One potential tool for quantification of health and environmental ef-
fects is the classification of well-described ecosystem types for use as
surrogates for candidate ecosystems. Establishment of such surrogate sys-
tems would simplify evaluation without excessive loss of accuracy.
Screening methodologies can be used for certain classes of chemicals
to predict chemical persistence and the potential for bioaccumulaticn
based on physico-chemical properties and quantitative structure-activity
relationships. On the basis of screening results, biologic testing may be
recommended. Further assessment with integrated exposure/effects models,
microcosm/mesocosm experiments, or field studies are logical extensions of
such screening efforts.
2,6 Uncertainty
The uncertainty associated with ecosystem risk analysis can arise
from a variety of different sources and in a number of different ways that
affect the calculation of risk. Perhaps foremost among these is that the
response of ecosystems, or their components, to anthropogenic stress in-
volves numerous factors. Each of these factors incorporates physical or
biologic mechanisms that in turn vary in degree of scientific characteri-
zation, availability of data sets, and sources and levels of uncertainty.
Thus, natural complexity and stochasticity contribute to the uncertainty
associated with models. Because ecosystem risk analysis typically in-
cludes a mathematical or statistical model, lack of correspondence between
the model and the modeled ecosystem leads to model error. Errors in pa-
rameter estimates resulting from experimental measurement error, approx-
imation and extrapolation of experimental results, and solution techniques
also contribute uncertainties to ecologic risk assessment (see also Chap-
ter 2 of this book).
2.7 Integrated Strategy
An integrated strategy including single-species bioassays, microcosm
and mesocosm experiments, and models for exposure and toxic effects allows
an estimate of the biologic effects of a physical or chemical stress. If
model parameters can be obtained from actual test data, then model accu-
racy can be improved by stepwise calibration of models to microcosms and
mesocosms. Thus, variable natural conditions can be represented more re-
alistically and ecologic risk estimated with fewer uncertainties.
3 ECOLOGICAL RISK ASSESSMENT GUIDELINES
Ecosystem risk assessment appears to be a feasible undertaking when
its limitations are clearly delineated. The EPA's Office of Health and
Environmental Assessment is currently developing guidelines that will
provide a general approach for conducting ecologic risk assessments. The
guidelines will help the assessor identify the pathways and mechanisms by
which chemicals reach nonhuman populations; from an understanding of the
chemical effects, the assessor will then develop an assessment of risk.
The guidelines will help the assessor to determine which aspects of the
ecosystem to emphasize and whether available data are adequate to estimate
exposure and effects of concern. The risk manager will then have a basis
for deciding what constitutes an unreasonable ecologic risk.
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The guidelines will discuss the fundamental principles governing the
response of the environment to stress not only for individual organisms
but also for populations of organisms. Discussion will include current,
acceptable methods for testing effects of pollutants on single and multi-
ple species; biologic, molecular, and physiologic indicators of tcxicity;
pharmacodynamic and environmental mechanisms of toxic effects; and eco-
system-level functions such as nutrient processing, productivity, and di-
versity as indicators of toxic effects.
The guidelines will allow the risk assessor to consider the following
questions when developing an ecologic exposure assessment: how does the
ecosystem modify the fate and transport of the toxicant; how is the con-
taminant distributed within the ecosystem; what are the residence times;
what are the sites of retention or deposition; what fate and transport
models would be helpful in determining environmental concentrations; is it
possible to combine bioassay data with models, microcosm studies, and
field-study methods to determine transport, fate, and potential exposure;
what is known about the natural dynamics of the ecosystem; what is the
extent and duration of exposure for the biota; does the ecosystem recover
from the stress, and how is recovery measured; and are any sensitive or
endangered species, or species at vulnerable life stages, present in the
ecosystem being studied?
The guidelines will help the assessor develop an ecologic hazard
assessment. Elements that may contribute to a hazard assessment include
factors that affect the toxicity of the chemical; parent, metabolite, or
degradation products responsible for the toxic effects; selection of
models based on an intent to study effects on individual species, certain
population groups, or the ecosystem as a whole; comparison of changes that
occur in the environment in the absence of stress with changes that occur
in the presence of stress; identification of ecologically important spe-
cies; possible synergistic mechanisms; intent to study acute or chronic
effects or both; appropriateness of •laboratory-to-field extrapolations;
availability of appropriate benchmark compounds; availability of appli-
cable retrospective cases; appropriateness of an approach involving a sur-
rogate species or ecosystem; and presence of ecologic indicators in the
air, water, soil, and ecosystems.
The guidelines will help the assessor choose the best monitoring
system for the assessment, design the sampling plan, determine the role of
models, and decide whether a tiered testing approach is necessary to pre-
dict higher-order effects.
Finally, the guidelines will help the assessor to develop a risk
assessment that integrates the exposure and hazard assessments. Key ele-
ments that should be considered for inclusion in the risk assessment in-
clude selection of end points, description of the reference environment,
identification of sources, assessment of exposure and effects, integrated
risic assessment, and evaluation of uncertainty.
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TECHNICAL REPORT DATA
(Pfease read Instructions on the reverse before completing}
REPORT NO.
EPA/60Q/D-89/069
2,
OHEA-E-283
, TITLE ANDSUBTITLE
Assessment of Ecclcgic Risks Related to Chemical
Exposure: Methods and Strategies Used in the United
6. PERFORMING ORGANIZATION CODE
States
3. RECIPIENT'S ACCESSION NO.
S. REPORT DATE
May 1988
7, AUTHOPHS)
J.W. Falco
R.V. Horaski
8. PERFORMING ORGANIZATION REPORT NO.
S. PERFORMING ORGANIZATION NAME AND ADDRESS
10, PROGRAM ELEMENT NO.
It. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF F1EPORT AND PERIOD COVERED
Office of Health and Environmental Assessment
Exposure Assessment Group (RD-689)
U.S. Environmental Protection Agency
VJashington, DC 20460
book chapter
Id. SPONSORING AGENCY CODE
EPA/600/21
15. SUPPLEMENTARY NOTES
Published in Risk Management of Chemicals in the Environment, Vol. 12 of NATO:
Challenges of Modern Society. Hans M. Seip & Anders B. Heiberg, editors. January 1989
16. ABSTRACT
The state-of-the-art assessment of risk to the ecosystem in still evolving.
Although single-species tests have provided valuable information for the assessment
of ecologic risk, it is necessary to focus on ecosystems-level tests and analyses.
The increasing availability of predictive models makes assessment of risk to the
environment, rather than simply to a single species, more possible. The United
States has yet to develop government- or agency-wide guidelines for conducting
ecologic risk assessments although the U.S. Environmental Protection Agency currently
has efforts underway to develop such guidelines in the Office of Health and
Environmental Assessment. However, various standard test methods have been developed
to provide toxicologic benchmarks primarily for the measurement of acute
toxicological effects. Recent research efforts have been directed toward developing
test methods that predict chronic and acute toxicologic effects based on results of
short-term exposure to organisms during sensitive life stages. This paper presents a
partial compilation of methods used in performing ecological risk assessments
developed by the U.S. Environmental Protection Agency or published by the American
Society for Testing and Materials and looks at the future directions of the U.S. EPA
in the development of new ecological risk assessment methodologies and approaches. ..
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