oEPA
United States
Environmental Protection
Agency
Environmental Research
Laboratory
Athens GA 30613
Research and Development
EPA/600/M-88/011 Aug. 1988
ENVIRONMENTAL
RESEARCH BRIEF
EPA's Ecological Risk Assessment Research Program
October 1985 - March 1988
Harvey W. Holm, Program Manager
By Congressional mandate, the U.S. Environmental
Protection Agency must determine whether individual
chemicals, either new or existing, can be manufactured
and sold in the United States. The evaluation process for
each chemical includes an ecological risk assessment.
The number of chemicals requiring review is large. In
1986, for exa mple, the Agency's Office of Toxic Substa nces
(OTS) had more than 60,000 existing chemicals on
inventory and also processed more than 1500 new
chemicals (Premanufacture Notices). The challenge for
OTS is to provide realistic, consistent evaluations within
short time frames when only a limited data set is provided.
Often, OTS must make screening level decisions when
only a chemical's structure, its proposed use pattern, and
two to three bioassay results (collected under only one
set of laboratory conditions) are available. It is very unusual
for OTS to have site-specific information on fate, exposure,
or effects for the premanufacture notice process.
EPA's Office of Pesticide Programs (OPP) also has a
gigantic problem. More than 50,000 existing pesticide
products must be evaluated, with new products being
developed each year. Although OPP can require submis-
sion of significant amounts of fate and effects information,
it still faces the challenge of extrapolating results from
one ecosystem to another and from a limited number of
test species and exposure scenarios to a myriad of natural
populations.
The Office of Pesticides and Toxic Substances (OPTS)
recognizes ecological risk assessment as a synthesis of
lexicological hazard and environmental exposure. Toxico-
logical hazard is the intrinsic quality of a chemical to cause
adverse effects, such as death (characterized by an LCso)
or a chronic effect (such as reproductive failure) when
exposure occurs. Environmental exposure is a function
of the amount of toxic chemical available to components
of ecosystems and the distribution and dynamics of
organisms within these ecosystem components. An
ecological risk assessment, then, involves systematically
combining results from exposure and hazard assessment.
Numerous techniques have been suggested and some-
times used by OPTS for ecological risk assessment. These
include fault tree analysis, safety factor evaluation,
ecosystem uncertainty analysis, and predictive ecosystem
modeling.
The most commonly used technique, however, is the
quotient method. This methodology compares a lexicolog-
ical benchmark (such as LC50, EC5o, etc.) to an anticipated
level of exposure. The closer the exposure and effects
numbers approach each other, the higher the risk value.
This technique is simple and straightforward. Its disad-
vantages are that it does not take into account dose-
response relationships, that it provides no basis for
predicting population or system-level responses, that it
does not account for ranges in hazard and exposure
estimates, and that it cannot address indirect effects of
chemicals.
To improve capabilities for assessing and predicting risk
to ecosystems, the Office of Research and Development
(ORD) initiated a comprehensive research program in
consultation with OPTS. The research, which began in
October 1986, was undertaken by the Office of Environ-
mental Processes and Effects Research's (OEPER's)
Environmental Research Laboratories in Athens, GA,
Corvallis, OR, Duluth, MN, and Gulf Breeze, FL The Athens
Laboratory was designated as the lead laboratory.
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OPTS and ORD established several goals for this research:
• Identify critical ecological components for assessment.
• Develop techniques for extrapolating laboratory and
limited field data to other systems.
• Provide systematic procedures to permit consistent
ecological evaluations among analysts.
• Provide insights into "so what" questions (e.g., "so
what" if primary productivity in lakes is decreased by
25%).
OEPER's approach to this problem is primarily one of
developing system-independent mathematical models and
protocols for exposure and hazard assessment and of
embedding them in a computer-based "Decision Support
System" that provides convenient access to these models,
protocols, and databases essential for completing
ecological risk assessments. The models and protocols
generated in this research have four characteristics in
common.
1. They are based on fundamental understanding of
primary ecotoxicological processes and, thus, may
require specific research to achieve the prerequisite
level of scientific knowledge for routine application.
2. They are formulated in "system-independent" terms
so that reliable extrapolations among systems are
possible; that is, the only use made of observed
datasets that are in the output domain of the models
is for validation studies.
3. They result in the generation of mathematical
formulations and computational algorithms that will
be encoded in computer programs, thus providing a
formal statement of methods that is objective,
reproducible, readily available, and accessible to
external peer evaluation and public appraisal.
4. They are linked to specific databases assembled (in
each project as appropriate) to provide the maximum
feasible geographic coverage; the databases will
contain virtually all the collateral (i.e., not specific to
the regulatory concern under analysis) data needed
to apply the models.
To achieve its goal, OEPER's Ecological Risk Assessment
Research Program relies heavily on results from EPA's
base chemical exposure and hazard assessment research
and development efforts. The major emphasis in the
current program is to integrate results from these two
areas to provide the scientific basis for assessing ecological
risks. The present state of the art of research in chemical
exposure and hazard evaluation has not adequately
covered all subject areas needed to provide tools for
ecological risk assessment. Existing research results,
ongoing research in the areas of chemical exposure and
hazard evaluation, and complementary new research
conducted in this program will provide a foundation for
developing a scientifically sound ecological risk assess-
ment capability for the Agency.
Three elements of any risk assessment (exposure analysis,
hazard analysis, and the integration of the two into a risk
analysis) are addressed in research involving six levels
of integration of individual projects. Aside from levels A
and B, each succeeding level of the project represents
a higher level of integration and, therefore, may derive
its mechanistic knowledge and summary descriptive
models from results at lower levels. For example, projects
at the level of population and ecosystems (level E) may
use some of the results of research on toxicological impacts
on individual organisms (research level D). The kinds of
research projects, their level of integration ("A" through
"F"), some correlative toxicological nomenclature, and
results to date are provided below.
(A) Decision Support Systems—computer software and
databases that allow an analyst to assemble and
deploy the specific array of analytical tools needed
for an ecological risk assessment. These "integra-
tion" projects assemble the executive software that
allows the user to interact with the models, access
databases, and provide service functions for all the
models eventually in the system.
(No published reports available)
(B) Exposure Analysis—release, transport, and transfor-
mation of xenobiotic chemicals in the physical
environment. This research plan does not initiate
significant new research m the transport and
transformation of pollutants in ecosystems, which
is a well-developed field in its own right. In the
Ecological Risk Assessment Research Program, we
intend to adapt existing models to the needs of the
dependent ecological models, and to sponsor such
remedial work as may be necessary to bring all the
exposure models in the project to a commensurate
state of sophistication.
Ambrose, R. B., T. A. Wool, J. P. Connolly, and R.
W. Schanz. 1987. WASP4, A Hydrodynamic and
Water Quality Model—Model Theory, User's
Manual, and Programmer's Guide. U.S.
Environmental Protection Agency, Athens, GA.
EPA/600/3-87/039.
Demonstration of the Terrestrial Environmental
Exposure Assessment Model (TEEAM), Office of
Pesticides and Toxic Substances, Washington, DC,
December 1987.
Demonstration of Pesticide Leaching Model and
Associated Soils/Climate Data Bases, Office of
Pesticides and Toxic Substances, Washington, DC,
March 1988.
(C) Toxicokinetics—exchange of xenobiotics between
individual organisms and their environment, and the
transport and transformation of xenobiotic chemicals
within the organism. These projects encompass the
area of mechanisms and processes that translate
an initial exposure into a realized tissue dose at a
target organ. In human studies, it would include
some aspects of both hazard identification and dose-
response assessment; wildlife biologists regard the
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behavioral response to initial contact with pollutants
as an aspect of exposure assessment.
Barber, M. C., L A. Suarez, and R. R. Lassiter. 1987.
FGETS (Food and Gill Exchange of Toxic
Substances): A Simulation Model for Predicting
Bioaccumulation of Nonpolar Organic Pollutants
by Fish. U.S. Environmental Protection Agency,
Athens, GA. EPA/600/3-87/038.
Barber, M. C., L. A. Suarez, and R. R. Lassiter. 1988.
Bioconcentration of nonpolar organic pollutants by
fish. Env. Tox. Chem. (accepted).
Barber, M. C., L. A. Suarez, and R. R. Lassiter. 1988.
Kinetic exchange of nonpolar organic pollutants
by fish. Env. Tox. Chem. (accepted).
Boersma, L., T. Lindstrom, C. McFarlane, and E. L.
McCoy. 1988. Uptake of organic chemicals by
plants: A theoretical model. Soil Sci. (accepted).
Boersma, L., T. Lindstrom, C. McFarlane, and E. L.
McCoy. 1988. Model of coupled transport of water
and solutes in plants. Oregon State University,
Corvallis, OR. Special Publication 818.
Boersma, L., C. McFarlane, and T. Lindstrom. 1987.
Uptake and transport of chemicals by plant. Three
leaf model. (Version 2.1) User Guide. Oregon State
University, Corvallis, OR. Special Publication 819.
Fletcher, J. S., A. Groeger, and C. McFarlane.
Metabolism of 2-chlorobiphenol by suspension
cultures of Paul's Scarlet Rose. Soc. for Envir. Tox.
and Chem. (submitted).
Fletcher, J. S., A. Groeger, J. McCrady, and C.
McFarlane. 1987. Polychlorobiphenyl (PCB) uptake
by plant cells. Biotechnology Letters 9(11):817-
820.
Groeger, A. and J. S. Fletcher. Influence of increasing
chlorine content on the accumulation and
metabolism of polychlorobiphenyls (PCBs) by plant
cultures. Plant Cell Reports (submitted).
Heitmuller, P. T. and J. R. Clark. Bioaccumulation
of 1,2,4-trichlorobenzene from food and water
sources by spot (Leiostomus xanthurus). Aquatic
toxicology and hazard assessment. American
Society for Testing and Materials, Philadephia, PA
(In Press).
Lindstrom, F. T., L. Boersma, and C. McFarlane.
1987. A steady state fluid transport model in
plants. In: James, L. G. and J. Marshall (eds.),
Irrigation Systems for the Twenty-First Century.
American Society of Civil Engineers, New York,
NY. 768 pages.
Link, S. 0., R. J. Fellows, D. A. Cataldo, J. G. Droppo,
and P. Van Voris. 1987. Estimation of Aerial
Deposition and Foliar Uptake of Xenobiotics:
Assessment of Current Models. PNL-6173/UC-
11, Battelle Pacific Northwest Laboratory,
Richland, WA 99352.
McCrady, J. K., C. McFarlane, and F. T. Lindstrom.
1987. The transport and affinity of substituted
benzenes in soybean stems. J. Exp. Bot.
38(196):1875-1890.
McFarlane, C., C. Nolt, C. Wickliff, T. Pfleeger, R.
Shimabuku, and M. McDowell. 1987. The uptake,
distribution and metabolism of four organic
chemicals by soybean plants and barley roots. Env.
Tox. & Chem. 6:847-856.
McFarlane, C., T. Pfleeger, and J. S. Fletcher. 1987.
Transpiration effect on the uptake and distribution
of bromacil, nitrobenzene and phenol in soybean
plants. J. Environ. Qual. 15(4):372-376.
McFarlane, C. andT. Pfleeger. 1986. Plant Exposure
Laboratory and Chambers. U.S. Environmental
Protection Agency, Corvalllis, OR. EPA/600/3-
86/007a,b.
Pace, C. M. 1987. Ion Source Surface Activity in
High Pressure Electron Capture Mass
Spectrometry. Masters Thesis. December.
Montana State University.
Randall, D. J., R. C. Russo, and R. V. Thurston. 1988.
Ammonia distribution in and excretion by fishes.
In: Fate and Effects of Pollutants on Aquatic
Organisms and Ecosystems: Proceedings of the
Ninth US-USSR Symposium, Athens, GA, October
19-21,1987. R. C. Ryans (ed.). U.S. Environmental
Protection Agency, Athens, GA. (In Press).
Russo, R. C., D. J. Randall, and R. V. Thurston. 1988.
Ammonia toxicity and metabolism in fishes. In:
Protection of River Basins, Lakes, and Estuaries:
Fifteen Years of Cooperation Toward Solving
Environmental Problems in the USSR and USA.
R. C. Ryans (ed.). Special Publication, American
Fisheries Society, Bethesda, MD. (In Press).
Suarez, L. A., M. C. Barber, and R. R. Lassiter. 1986.
GETS, A Simulation Model for Dynamic
Bioaccumulation of Nonpolar Organics by Gill
Exchange: A Users Guide. U.S. Environmental
Protection Agency, Athens, GA. EPA/600/3-86/
057.
Thurston, R. V. and D. J. Randall. A respirometer
with controlled water quality and computerized
data acquisition for experiments with swimming
fish, (submitted).
Wright, P. A., D. J. Randall, and S. E. Perry, II. Fish
gill water boundary layer: A site of linkage between
carbon dioxide and ammonia excretion. J. of Comp.
Physiology, (submitted).
Wright, P. A., D. J. Randall, and C. M. Wood. The
distribution of ammonia and H+ between tissue
components in Lemon Sole (Parophrys vetulus) at
rest, during hypercapnia, and following exercise.
J. Exp. Biology, (submitted).
(D) Biotic Effects Analysis—lethal and sublethal conse-
quences to individual organisms of a body burden
of xenobiotic chemicals. In public health terms, this
research corresponds most closely to dose-response
assessment, although the transition from adminis-
tered dose to tissue dose, i.e., direct study of the
consequences of a specific body burden on morbidity
and mortality, has not been accomplished. For
ecological studies, the body burden must be
computed because of the importance of food-chain
transmission of chemicals in some systems. Given
success in computation of body burden, the life-
history consequences of exposure can be given a
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significantly improved basis for modeling, prediction,
and understanding.
Fletcher, J. S., F. L. Johnson, and C. McFarlane.
Database assessment of phytotoxicity data
published on terrestrial vascular plants. Soc. for
Environ. Tox. and Chem. (submitted).
Johnson, F. L. and J. S. Fletcher. 1987. PHYTOTOX
User's Manual. University of Oklahoma, Norman,
OK.
Mayer, F. L., Jr. and M. R. Ellersieck. Experiences
with single-species tests for acute toxic effects on
freshwater organisms. Ambio. (accepted).
McFarlane, C. andT. Pfleeger. 1987. Plant exposure
chambers for study of toxic chemical/plant
interactions. J. Environ. Qual. 16(4):361-371.
(E) Population and Community Risk Assessment-
consequences of realized biotic effects for the
distribution and abundance of single-species
populations and coupled population systems. This
research draws, to some extent, on the results
obtained in (C) and (D). Projects (E) are exploring
diverse approaches to "Risk Characterization" for
biotic communities, encompassing classic popula-
tion matrices and birth/death process modeling
through novel approaches attempting direct mea-
sures of the impact of pollutants on interspecific
interactions.
De Luna, J. T. and T. G. Hallam. 1987. Effect of
toxicants on populations: A qualitative approach.
IV. Resource-consumer-toxicant models. Ecol.
Modelling. 35:249-273.
Emlen, J. M. Terrestrial community models for
ecological risk assessment: A state of the art
review. Environ. Tox. and Chem. (submitted).
Emlen, J. M. Terrestrial population models for
ecological risk assessment: A state of the art
review. Environ. Tox. and Chem. (submitted).
Hallam, T. G., R. R. Lassiter, J. Li, and W. McKinney.
1988. Physiologically structured population
models in risk assessment: In: Biomathematics
and Related Computational Problems. L. Riccardi
(ed.). Reidel, Hingham, MA.
Hallam, T. G., R. R. Lassiter, and S. A. L. M. Kooijman.
1988. Effects of toxicants on aquatic populations.
In: Mathematical Ecology; II. Applications. S. A.
Levin, T. G. Hallam, and L. J. Gross (eds.). Springer-
Verlag, New York.
Hallam, T. G., R. R. Lassiter, J. Li, and L. A. Suarez.
Modeling individuals employing an integrated
energy response: Application to Daphnia. Ecology
(submitted).
Hallam, T. G. and M. Zhien. 1987. On density and
extinction in continuous population models. J.
Math. Biol. 25:191-201.
Kelly, J. R. 1988. Ecotoxicology beyond sensitivity:
A case study involving "unreasonableness" of
environmental change. Chapter In: Ecotoxicology:
Problems and Approaches, S. A. Levin, M. A.
Harwell, J. R. Kelly, and K. D. Kimball (eds.),
Springer-Verlag, New York. (In Press).
Kelly, J. R., T. W. Duke, M. A. Harwell, and C. C.
Harwell. 1987. An ecosystem perspective on
potential impacts of drilling fluid charges on
seagrasses. Environ. Management 11(4):537-562.
Kelly, J. R. and M. A. Harwell. 1988. Indicators of
ecosystem response and recovery. Chapter 2 In:
Ecotoxicology: Problems and Approaches, S. A.
Levin, et al. (eds.), Springer-Verlag, New York. (In
Press).
Lassiter, R. R. and T. G. Hallam. Survival of the
fattest: A theory for assessing acute effects of
hydrophobic, reversibly acting chemicals on
populations. Env. Tox. Chem. (submitted).
Li, J. 1988. Persistence and extinction in continuous
age-structured population models. Int. J. Compt.
Appl. Math, (accepted).
Li, J. 1988. Persistence in discrete age-structured
population models. Bull. Math. Biol. (accepted).
Li, J. and T. G. Hallam. Survival in continuous
structured population models. J. Math. Biol.
(submitted).
Li, J., T. G. Hallam, and M. Zhien. 1987. Demographic
variation and survival in discrete population
models. IMA J. Math. Appl. in Med.and Biol. 4:237-
246.
Logan, J. A. Derivation and analysis of composite
models for insect populations. In: Estimation and
Analysis of Insect Populations. L. L. McDonald, J.
A. Lockwood, and J. A. Logan (eds.).
Morton, R. D. and S. O. Montgomery. 1988.
Microcosm studies on the effects of drilling fluids
on seagrass communities. In: 1988 International
Conference on Drilling Wastes, Calgary, Canada.
Elsevier. London. (In Press).
Wollkind, D. J., J. B. Codings, and J. A. Logan. 1988.
Metastabihty in a temperature dependent model
system for predator/prey mite outbreak
interactions on fruit trees. Bull, of Math. Biol.
(accepted).
Zhien, M. and T. G. Hallam. 1987. Effects of
parameter fluctuations on community survival.
Math. Biosci. 86:35-49.
(F) Ecosystem Risk Assessment—impacts of xenobiotic
chemicals on multi-population systems, including
processes expressed via their activities—primary and
secondary productivity, biogeochemical element
cycles, etc. These projects, like those of (E), can be
classed under the rubric of "Risk Characterization,"
specifically in (F) dealing with risk to the structure
and function of entire ecosystems.
Brezonik, P. L, L. A. Baker, J. R. Eaton, T. M. Frost,
P. Garrison, T. K. Kratz, J. J. Magnuson, W. J.
Rose, B. K. Shepard, W. A. Swenson, C. J. Watras,
and K. E. Webster. 1986. Experimental acidifi-
cation of Little Rock Lake, Wisconsin. Water, Air,
and Soil Poll. 31:115-121.
Flum, T. F. and L. J. Shannon. 1987. The effects
of three related amides on microecosystem
stability. Ecotox. and Envir. Safety 13:239-252.
Glass, G. E., J. A. Sorensen, B. W. Liukkonen, G.
R. Rapp, Jr., and 0. L. Loucks. 1986. Ionic
composition of acid lakes in relation to airborne
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inputs and watershed characteristics. Water, Air,
and Soil Poll. 31:1-15.
Niemi, G., S. Hedtke, R. Naiman, and J. Pastor. 1988.
Quantification of disturbance, resistance, and
resilience among ecological systems.
Rapp, G. Jr., B. Kiukkonen, J. D. Allert, J. A.
Sorensen, G. E. Glass, and 0. L. Loucks. 1987.
Geologic and atmospheric input factors affecting
watershed chemistry in upper Michigan. Environ.
Geol. Water Sci. 9:155-171.
Rygiewicz, P., S. L. Miller, and D. M. Durall. 1988.
A root-mycocosm for growing ectomycorrhizal
hyphae apart from host roots while maintaining
symbiotic integrity. Plant and Soil (accepted).
Shannon, L. J., M. C. Harrass, J. D Yount, and C.
T. Walbridge. 1986. A comparison of mixed flask
culture and standardized laboratory model
ecosystems for toxicity testing. Pages 135-1 57 in
J. Cairns, Jr. (ed.) Community toxicity testing,
ASTM STP 920, American Society for Testing and
Materials, Philadelphia.
Sorensen, J. A. and G. E. Glass. 1987. Ion and
temperature dependence of electrical conductance
for natural waters. Anal. Chem. 59:1594-1597.
Yount, J. D. and J. E. Richter. 1986. Effects of
pentachlorophenol on penphyton communities in
outdoor experimental streams. Arch. Environ.
Contam. Toxicol. 15:51-60.
Yount, J. D. and L. J. Shanon. 1987. Effects of aniline
and three derivatives on laboratory microeco-
systems. Environ. Toxicol. and Chem. 6:463-468.
Acknowledgment
Special assistance is provided to the Program Manager
by the Advisory Committee, which is comprised of the
research team leaders from all participating laboratories
and OEPER Headquarters. The Advisory Committee
includes Dr. Robert Swank, Athens Environmental
Research Laboratory; Dr. Bill Williams, Corvallis
Environmental Research Laboratory; Dr. Gerald Niemi,
Duluth Environmental Research Laboratory; Dr. Foster
Mayer, Gulf Breeze Environmental Research Laboratory;
and Dr. Frederick Kutz, OEPER Headquarters.
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