UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
OFFICE OF THE ADMINISTRATOR
EPA-SAB-EPEC-ADV-94-001 SCIENCE ADVISORY BOARD
September 26, 1994
Honorable Carol M. Browner
Administrator
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
Subject: Advisory on the Development of a National Wildlife Criteria
Program
Dear Ms. Browner:
On April 27-28, 1994, the Wildlife Criteria Subcommittee of the Ecological
Processes and Effects Committee (EPEC) of the Science Advisory Board (SAB) met
in Washington, D.C. to hear briefings and engage in a consultation with Agency
representatives on plans for the development of a national methodology for
developing wildlife criteria. Although SAB consultations typically last only a few
hours and do not result in a formal report, at the request of Agency staff from the
Office of Water, we spent nearly seven hours in briefings and discussion with
Agency staff on this topic. Our sense from Agency staff was that a proposed
national methodology was unlikely to come to the SAB for another year or so.
Therefore, based on these discussions and our review of the background materials
provided to the Subcommittee, we would like to provide you with our assessment
of the overall program and the approaches being considered for developing wildlife
criteria.
We congratulate the Agency managers and researchers for assembling
thoughtful and concise background materials to facilitate our discussions. The
presenters were enthusiastic about the topic of wildlife criteria, prepared insightful
questions to guide our consultation, and assembled a well-organized set of briefing
materials. Clearly, a main strength of the wildlife criteria development effort is
ths multidisciplinary nature of the Agency staff and contractors involved. In large
part, the future success of the program will relate to how well the group
maintains communication as the chemical, physical and biological elements
necessary to develop relevant criteria are assembled.
Recycled/Recyclable
PrtnMd on p«p«r that contain*
at toatt 75% ncydad Oxr
-------
Prior to the consultation in April, the Subcommittee was provided with. ~.
set of 34 specific questions (enclosed) regarding the development of wildlife
criteria. Although we have not attempted to answer each of these, our comme:..
are grouped in seven major categories which summarize the questions posed.
1. ECOLOGICAL RISK ASSESSMENT AND THE DEVELOPMENT OF
WILDLIFE CRITERIA
Recommendation: The wildlife criteria program should be guided by the
Agency's Ecorisk Assessment Framework, which provides a paradigm for
considering integrated risks to wildlife populations from both chemical and
non-chemical stressors and multiple routes of exposure. In particular,
questions arising from the problem formulation phase of ecorisk assessment
should be addressed.
In 1992, several committees of the SAB reviewed technical documents
supporting the Great Lakes Water Quality Initiative (GLWQI), including those
portions which related to wildlife criteria for the Great Lakes. A number of the
recommendations in the final report (EPA-SAB-EPEC/DWC-93-005) are relevant to
the national wildlife criteria program (e.g., the relationship of wildlife criteria to
ecological risk assessment, protection of populations vs. individuals, and the need
to consider additional wildlife species) and are reiterated by the current
Subcommittee in this letter.
The SAB report on the GLWQI recommended that wildlife criteria based on
aquatic routes of exposure should be considered in the broader context of
ecological risk assessment. In other words, the GLWQI, which focuses on point
sources of pollution, should be related to an ecosystem management approach
which incorporates multiple pathways of exposure and additional endpoints of
effects for wildlife.
- We recognize that the Agency staff associated with the wildlife criteria
program are operationally familiar with the Agency's landmark document,
Framework for Ecological Risk Assessment (EPA/630/R-92/001), commonly referrei
to as the Ecorisk Framework. Although Agency staff made reference to evolving
linkages between the Ecorisk Framework and the national wildlife criteria effort,
we urge that the Framework be used more directly.
The Ecorisk Framework provides the essential and most relevant outline for
development of science-based wildlife criteria. The current phase of the national
wildlife criteria program is directly analogous to the initial problem formulation
phase of ecorisk assessment. Careful initial scoping of relevant issues and
-------
questions, through a thorough review of available toxicological field data for
wildlife populations, will focus subsequent assessments of exposure and effects "• y
clarifying issues of uncertainty, prioritizing long-term research needs, and
providing the framework for integration of laboratory and field data. Such an
exercise will also address external criticism of the need for wildlife criteria.
The Agency's guidance for developing wildlife criteria should discuss the
relative risk of chemical and non-chemical stresses on wildlife populations. In
keeping with the tenets of the problem formulation phase of the Ecorisk
Framework, the Agency needs to clearly indicate where and when wildlife
populations remain at risk when existing criteria for aquatic life are met. A
critical review of real-world case studies should be conducted in the future to
identify examples where wildlife populations are at incremental risk. Considering
wildlife criteria in the context of ecorisk assessment automatically provides a
framework for considering that chemical stressors are but one stress imposed on
wildlife populations. Additional stressors may include habitat loss/fragmentation,
introduction of exotic species, and various biological and physical stressors. In
cases where these non-chemical stressors are more significant than chemical
stressors, wildlife criteria values based on chemical stressors may be insufficient ;o
protect wildlife populations.
Preliminary knowledge of the properties of the perturbation or chemical of
concern can be used to decide which endpoints are likely to be most relevant (e.g.,
hydrophobic, tightly-sorbed, non-persistent chemicals are not likely to be
significant for exposure via aquatic prey species and non-bioaccumulative
compounds are unlikely to impact higher trophic levels).
In addition, chemical stressors for wildlife may have multi-media routes of
exposure (e.g., soil and atmospheric routes, as well as water). For example,
researchers have found PCB/DDT/DDE loadings in the forest soil at Hubbard
Brook Experimental Forest in New Hampshire to be higher than sediment and
water-column loadings to Long Island Sound . In areas with important non-
water exposure of wildlife to toxic chemicals, exclusive examination of water-based
wildlife screening could seriously underestimate wildlife population risks.
W.H., R.C. Hale, J. Greaves, and R.J. Huggett. 1993. Trace
Organochlorine Contamination of the Forest Floor of the White Mountain National
Forest, New Hampshire. Environmental Science and Technology, vol. 27, pp. 2244-
2246.
-------
2. ALTERNATE APPROACHES AND METHODS FOR DERIVING WILDLCF I1,
CRITERIA
Recommendation: Both approaches proposed by the Agency for deriving
wildlife criteria, 1) an adaptation of the human health non-cancer approach
proposed in the GLWQI and 2) a modification of the aquatic life criteria
approach, are in the early stages of development, but each holds promise
and should be pursued further.
The primary approach presented to the Subcommittee is based largely on
the proposed GLWQI and is an adaptation of the human health non-cancer
approach with an uncertainty factor to account for interspecies variability. The
majority of our comments relate to that approach, which, while clearly in the early
stages of development, promises to be an innovative and valuable new method for
understanding the fate and effects of contaminants in the environment. An
alternate method based on modification of the aquatic life criteria approach was
also presented to the Subcommittee and appeared worthy of further research. At
this early stage in methodology development, we encourage the Agency to continue
pursuing both options.
While the research staff involved in the wildlife criteria program are aware
of the regulatory framework into which this approach must ultimately be
coordinated, we think it is important to explicitly state how this developmental
effort will evolve into the determination of criteria and enforceable standards. For
example, the Agency should decide up-front on the level of uncertainty (i.e.,
variability in the data sets and level of statistical confidence) which is acceptable
for specific uses of the methodology. This information in turn will help define
data requirements and research needs.
Another option discussed at the meeting involved the use of egg-injection
studies to assess the effects of chemicals on the avian embryo. In most cases,
embryonic development represents the most sensitive stage in reproduction.
However, extreme care must be taken in interpreting data on embryo toxicity
derived from such studies. Egg-injection studies ignore many important
physiological and behavioral factors which affect exposure (e.g., fertility and
nesting behavior). In addition, the female may incorporate the chemical of
concern into the egg in a different manner from that used in the egg-injection
study. For example, fat-soluble chemicals are deposited into the yolk portion of
the egg which has a metabolic regime different from that of the albumen. In
short, experimental results may not accurately reflect reponses that would occur in
nature. Other sources of experimental error include excess mortality in the
embryos due to poor injection technique and adverse effects caused by the vehicle
-------
employed as a carrier. In summary, we do not recommend the use of these
studies since more valid data on effects can usually be obtained by using natural
transfer of the chemical of concern from the female to the embryo and using
residue analysis to quantify exposure.
3. NATIONAL VS. REGIONAL WILDLIFE CRITERIA
Recommendation: The objective of the Agency's wildlife criteria program
should be to develop a national methodology which can hi turn be used to
derive regional or site-specific wildlife criteria.
Development of national criteria per se would not be defensible given the
many factors affecting regional and local wildlife populations. For example,
feeding ecology and behavior of a particular species can vary markedly in different
geographic locations and may exceed interspecies variability in some instances.
The natural history work included in the Agency's proposed long-term research
strategy will be important to define appropriate geographic areas for given wildlife
criteria. This effort should be coordinated with the activities of the National
Biological Survey. In addition, although one tends to think of regional or
geographically-based criteria, protection of some species requires consideration of
migratory patterns and home ranges. This may result in a need for criteria
specific to species groups in some circumstances.
4. MODEL VALIDATION
Recommendation: The Agency should consider the use of hind-cast testing
or case studies using existing data for well-studied chemicals of interest to
validate the models and methodologies and to focus future research needs.
Many of the proposed models and algorithms for developing wildlife criteria,
and indeed the entire approach, can be fully evaluated using existing toxicology
data. _An initial focus on data-rich scenarios (e.g., the well-studied effects of
DDT/DDE on eagle reproduction and the effects of selenium on waterfowl
reproduction) would allow the theoretical basis of the model to be evaluated, as
well as its applicability to real-world events. Also, this use of case studies should
help focus future research needs for the development of wildlife criteria. As noted
by Agency researchers, however, data cannot always be used directly from peer-
reviewed literature, but instead must be reviewed for quality assurance and quality
control. Many published toxicological studies do not fully confirm or measure dose
to the organism, relying instead on unconfirmed estimates of exposure. We
recommend direct consultation with authors of published studies when possible to
double-check accuracy of data prior to its use by the Agency.
-------
5. CHARACTERIZATION OF TOXIC EFFECTS
Recommendation: The focus of the wildlife criteria program should remain
on the protection of wildlife populations (as opposed to individuals) from the
direct effects of stressors, although consideration of indirect effects should
be added hi the future. Methods to refine both the benchmark dose and
calculated NOAEL should proceed. Wildlife criteria approaches should
consider both chemical and biological transformations of chemicals when
characterizing toxic effects.
The Subcommittee strongly endorses the focus on population rather than
individual organism effects, except in special cases such as endangered species.
This emphasis was also recommended in the previous SAB review of the GLWQI
(EPA-SAB-EPEC/DWC-93-005). We recognize, however, that due to the difficulty
of measuring wildlife population effects, it is sometimes necessary to measure
effects on individuals and extrapolate to population-level effects.
One method of protecting wildlife populations within the human non-cancer
risk assessment paradigm is to use toxicological endpoints which can be related to
population effects. Of the potential endpoints under consideration by the Agency,
reproductive endpoints (e.g., number of viable young per female) are clearly the
most relevant and most readily related to population effects and are therefore the
clear first choice when data are available or are being generated. Mortality, while
also a useful endpoint, is not always related to the response of a population to a
stress. Growth and development endpoints are even harder to relate to population
effects, and published data are often not comparable due to differences in
experimental design. Growth and development endpoints, therefore, are not
recommended for use when other alternatives exist.
Given the early stage of wildlife criteria development, we agree with the
Agency's initial emphasis on direct effects of chemicals on wildlife versus indirect
effects. Due to the better data sets available on direct vs. indirect effects, this
focus should improve the chances for success in initial model development.
However, indirect effects of chemicals on wildlife (e.g., via impacts on habitat) are
extremely important and should be considered in the context of the ecorisk
assessment paradigm as model development becomes more sophisticated.
With regard to the use of no observed adverse effect level (NOAEL) or
lowest observed adverse effect level (LOAEL) values to establish criteria, the SAB
previously recommended that the Agency develop guidance for the selection of
NOAELs appropriate for protection of wildlife populations as distinct from the
protection of individuals and cautioned that uncertainty factors relating LOAEL to
-------
NOAEL are highly dependent on the dosage-spacing used in the chronic
studies (EPA-SAB-EPEC/DWC-93-005). In other words, NOAEL values are
sometimes extrapolated from effects data, rather than being based on direct
observations. LOAEL or benchmark dose values, if based on actual measured
effects, represent an adverse effect level, but provide a value with minimal
uncertainty. Since no clear preference for a benchmark dose vs. a calculated
NOAEL currently exists among human and ecological toxicologists, methods to
refine both approaches should proceed.
The methodologies presented by the Agency (the human health non-cancer
algorithm and the aquatic life criteria-derived method) use effects terms whica
characterize the animal's response to a chemical insult. Missing from both
methods is an explicit factor acknowledging chemical and biological
transformations of the chemical that may occur between the time the chemical
enters the environment and the time the organism is exposed. Such
transformations may substantially alter the severity and nature of the effect and/or
the bioavailability of the compound. Selenium and mercury are cases in point: in
aquatic environments, both are naturally transformed from inorganic to organic
forms which are far more toxic. We recommend that these potential pathways be
recognized explicitly within the effects and exposure terms for both methodologies;
when the approach is broadened to include non-bioaccumulating chemicals, the
bioaccumulation factor (BAF) term will not serve this purpose. Other
transformations which should be included in the physiologically-based toxicokinetv;
(PB/TK) models, are those occurring within the animal that produce metabolites
whose effects may differ from those of the parent compound. In the 1992 review
of the GLWQI, the SAB referred to the need to consider chemical speciation,
bioavailability, and persistence in the environment when establishing criteria;
these considerations remain valid in the development of a national wildlife criteri .
methodology.
The uncertainty factors included in the exposure term represent at least two
qualitatively different types of uncertainty. One type, exemplified by the
interspecies uncertainty factor, will be relevant to any methodology and therefore
deserves considerable attention. The current attempts to establish a range of
uncertainty and guidance for deriving an uncertainty factor for specific chemicals
should be considerably refined and augmented. Another type, exemplified by the
LOAEL to NOAEL uncertainty factor, is necessary only where there is a paucity
of relevant data. In this case, a large uncertainty factor probably renders the
resulting criterion indefensible, and suggests that the Agency is better served
improving the data set rather than expending substantial resources bounding the
uncertainty factor.
-------
Allometric relationships can provide useful ways to analyze data but should
not be the sole basis for selection of an interspecies uncertainty factor. Many
examples can be proffered that render such an approach invalid. For example,
animals with similar body weight can exhibit very different sensitivities to a
chemical, as seen in the case of hamsters, which are very resistant to dioxin, and
guinea pigs, which are very sensitive to dioxin. We recommend that the Agency
collect toxicological data on a greater number of wildlife species to improve the
ecological relevance of an interspecies uncertainty factor.
6. CHARACTERIZATION OF WILDLIFE EXPOSURE
Recom mendation: While we agree with the initial focus on persistent,
bioaccumulative, organic contaminants, we recommend that the wildlife
criteria methodology be developed and tested for other chemical groups, in
other ecosystems and regions than the Great Lakes, and for additional
wildlife species.
During the initial stages of wildlife exposure characterization, it is
imperative that expert opinion and professional judgement be used to determine,
to the extent practical, what exposure will dominate, which species are likely to be
maximally exposed, and which endpoints will be most ecologically meaningful at
the population level. As mentioned previously, chemical, physical, and biological
transformations which may alter either the fate of the compound or its biological
effects must also be considered. We note that the Agency is focusing its initial
' wildlife criteria efforts on persistent organic contaminants that are bioaccumulated
by wildlife primarily through trophic transfer through aquatic systems. While this
is an appropriate place to begin, the wildlife criteria methodology should be
developed and tested on other chemical groups as well, since exposure pathways,
chemical forms, and primary impacted species may differ with other categories of
contaminants. The methodology should also be tested in ecosystems and regions
other than the Great Lakes. Specifically, trace element exposure in a western
ecosystem might be used to test the robustness of the models on a qualitatively
different system.
The wildlife criteria program is currently focusing exclusively on avian and
mammalian species due to the lack of toxicological data for reptiles and
amphibians. We agree that development of wildlife criteria at this time should
focus on species which have substantial databases and upon which considerable
toxicological understanding already is available. However, as stated in the SAB
report on the GLWQI, the Agency should consider incorporating reptiles and
amphibians into the program in the future so that wildlife criteria derived with
the national methodology will adequately protect these species. The importance of
-------
developing empirical databases for these species should be recognized in the
Agency's long-term research agenda.
7. LONG-TERM RESEARCH NEEDS
Recommendation: In addition to continuing Agency research in the
identified high-priority areas, the Agency should take greater advantage of
wildlife toxicology expertise in professional societies and at other federal
agencies.
The Subcommittee strongly endorses the Agency's four proposed research
areas to support development of science-based water quality criteria to protect
wildlife:
a) Integrated Wildlife Population and Toxicology Research
b) Species and Exposure Extrapolation Research
c) Watershed Characterization and Diagnosis Research
d) Natural History Surveys
These research areas are consistent with recommendations made at a recent
conference and book sponsored by the Society of Environmental Toxicology and
Chemistry (SETAC) on the need to integrate wildlife population and toxicology
research . As noted previously, we urge that model development and wildlife
criteria promulgation be consistent with the Agency's ecorisk assessment paradigm.
In order to define the need for additional research on toxicological endpoirv. j
and on the relevance of test species to target wildlife species, we urge the Agency
to establish criteria for judging a priori the level of variability in the data sets
which is acceptable for various policy and regulatory applications of the wildlife
criteria methodology. As mentioned, we also recommend research on additional
types of chemicals and ecosystems other than Great Lakes, as well as research to
develop toxicological data on amphibians and reptiles.
Finally, since wildlife biology/toxicology expertise within the Agency is
limited, we encourage the Agency to take greater advantage of the professional
expertise that is available outside the Agency. In particular, professional societies
can work in partnership with the Agency to define critical scientific issues, develop
research needs and strategies, plan and prioritize research goals, and provide
"Kendall, R.J. and T.E. Lacher, Jr., Editors. 1994. Wildlife Toxicology and
Population Modeling: Integrated Studies of Agroecosystems. CRC Press/Lewis
Publishing, Boca Raton, Florida. 579 pp.
-------
external peer review. These services are often available at nominal or no cost to
the Agency. Relevant professional societies include SETAC (ecotoxicology), Society
for Toxicology (toxicology), American Society for Microbiology (biogeochemistry,
bio transformation), and the American Chemical Society (analysis, chemical
reactions).
Additionally, we encourage EPA scientists and managers to coordinate their
programs with scientists in other federal agencies; science relevant to the
development of wildlife criteria is also taking place at the U.S. Fish and Wildlife
Service, NOAA, Department of Defense, Department of Energy, U.S. Forest
Service, National Institute of Environmental Health Science, and U.S. Department
of Agriculture.
We appreciate the opportunity to hear about the Agency's progress in
developing a national methodology for deriving wildlife criteria, and we hope our
comments will assist the Agency in that effort. We look forward to your response
on the issues raised and to further review of the Agency's national methodology
for wildlife criteria as it develops.
Sincerely,
Dr. Genevieve M. Matanoski, Chair
Executive Committee
Dr. Kenneth L. Dickson, Chair Dr. Alan W. Maki, Chair
Ecological Processes and Wildlife Criteria Subcommittee
Effects Committee
Enclosure
10
-------
U.S. ENVIRONMENTAL PROTECTION AGENCY
SCIENCE ADVISORY BOARD
ECOLOGICAL PROCESSES AND EFFECTS COMMITTEE
WILDLIFE CRITERIA SUBCOMMITTEE
April 27-28, 1994
ROSTER
CHAIR
Dr. Alan W. Maki, Exxon Company, USA, Houston, Texas
MEMBERS/CONSULTANTS
Dr. Ronald J. Kendall, Institute of Wildlife and Environmental Toxicology,
Clemson University, Pendleton, SC
Dr. Anne McElroy, State University of New York at Stony Brook, Stony
Brook, New York
Dr. Frederic K. Pfaender, Carolina Federation for Environmental Studies,
University of North Carolina, Chapel Hill, North Carolina
Dr. Robert Ringer, Institute for Environmental Toxicology, Michigan State
University, East Lansing, MI
Dr. William H. Smith, School of Forestry and Environmental Studies, Yale
University, New Haven, Connecticut
Dr. Terry F. Young, Environmental Defense Fund, Oakland, California
SCIENCE ADVISORY BOARD STAFF
Ms. Stephanie Sanzone, Designated Federal Officer, US EPA, Science
Advisory Board (HOOF), 401 M Street, SW, Washington, DC 20460.
Ms. Mary Winston, Staff Secretary, US EPA, Science Advisory Board
(1400F), 401 M Street, SW, Washington, DC 20460.
-------
U.S. Environmental Protection Agency
NOTICE
This report has been written as part of the activities of the Science
Advisory Board, a public advisory group providing extramural scientific
information and advice to the Administrator and other officials of the
Environmental Protection Agency. The Board is structured to provide balanced,
expert assessment of scientific matters related to problems facing the Agency.
This report has not been reviewed for approval by the Agency and, hence, the
contents of this report do not necessarily represent the views and policies of the
Environmental Protection Agency, nor of other agencies in the Executive Branch
of the Federal government, nor does mention of trade names or commercial
products constitute a recommendation for use.
-------
DISTRIBUTION LIST
Administrator
Deputy Administrator
Assistant Administrators
Deputy Assistant Administrator for Research and Development
Deputy Assistant Administrator for Water
EPA Regional Administrators
EPA Laboratory Directors
EPA Regional Libraries
EPA Laboratory Libraries
-------
Questions to Focus SAB Discussion at
SAB Commentary on
National Wildlife Criteria
3/31/94 DRAFT
Agenda Item: Characterization of Toxic Effects
Population vs. Individual Level Assessments
Wildlife criteria are intended to support risk assessments for populations of wildlife exposed
to chemical pollutants. These criteria are intended to address the direct effects of chemicau
on wildlife populations. They are not intended to protect individual organisms (except in
special cases where that is desired) or to provide protection for wildlife habitat and associate;"!
biological communities. Used in conjunction with other criteria and diagnostic approaches,
wildlife criteria provide an essential component for carrying out risk assessments at the
watershed scale.
1) Given the objective of protecting wildlife populations, do you think toxicological
endpoints such as mortality, growth, reproduction, and development, are appropriate
for deriving criteria because they can be related, at least qualitatively, to density-
independent factors which influence populations?
2) Should other endpoints such as biochemical or histopathological changes be used :o
support criteria development as well? Should use of these types of endpoints be
restricted to cases where they can be causally-linked to mortality rates, fecundity
rates, etc.?
3) Currently toxicological effects are extrapolated from NOAELs because of lack of
certainty concerning the amount of increased mortality or decreased fecundity that cr.n
be absorbed in different populations and because dosing regimes in most bioassays
result in very steep (i.e., "all or nothing") dose-response curves. Are you aware of
any credible population dynamic models that can be used to guide selection of effect
thresholds from toxicological studies?
Effects Analyses
Given the initial goal of deriving water-based wildlife criteria, a paradigm adapted from the
human health non-cancer approach was generally endorsed in two separate national
workshops and proposed in the Great Lakes Water Quality Initiative (GLWQI). Although
based on the human health paradigm, there are significant differences between the human
health and wildlife approach. Because the wildlife approach is designed to prptect
populations and not individuals, the wildlife paradigm does not include an intraspecies
uncertainty factor (although exceptions can be made in special cases where protection of
individuals is desired) and wildlife assessments are typically restricted to a smaller set of
more gross endpoints. This last point is illustrated in the GLWQI assessment for DDT
where the NOAELs used to calculate the mammalian wildlife value and the human health
-------
Questions for SAB Commentary on Wildlife Criteria
criteria were from the same rodent bioassay. However, in the wildlife assessment the
endpoint was the number of viable young per female while in the human health assessment
the more sensitive endpoint of impacts on liver pathology was used.
4) Because of the limited number of toxicity tests, what is a reasonable minimum
database? Should acute and/or chronic data be required?
5) Efforts are in progress to tabulate and analyze existing toxicity databases to further
evaluate interspecies differences and the type and nature of chronic endpoints tha. ^
available for criteria derivation. These analyses are designed to support the
development of guidance on the selection of interspecies, subchronic to chronic,
LOAEL to NOAEL, and intraspecies uncertainty factors. Do you have any
suggestions regarding this effort? Are you aware of additional data sources or
analyses that could be used?
Allometric Scaling
To date, decisions made concerning the selection of interspecies uncertainty factors have
been based on professional judgement concerning underlying toxicokinetic (i.e., absorption,
distribution, metabolism and excretion rates of chemicals) and toxicodynamic (i.e.,
modes/mechanisms of toxic action and associated physiological and biochemical processes)
principles and available empirical data. Allometric scaling (e.g.; based on surface area, m2/3;
or,physiological time, m3M) can be used to describe general toxicokinetic trends and
contribute to "weight-of-evidence" deliberations.
6) Should allometric relationships provide the basis for the selection of an interspecies
uncertainty factor or should toxicodynamic issues also be incorporated into
determining an interspecies uncertainty factor? If so, how?
7) Are you aware of any other mechanistically-based toxicokinetic and toxicodynamic
models that are currently available that can be employed to better predict interspecies
variability?
-------
Questions for SAB Commentary on Wildlife Criteria
Agenda Item: Characterization of Wildlife Exposure
Representative Species in the GLWQI Approach
One effort being conducted is to identify the most vulnerable (i.e., exposed and/or sensitive)
species to contaminants in the Great Lakes to compare with the initial five species (i.e., bald
eagle, osprey, kingfisher, mink, and otter) used to propose the wildlife criteria. The
approach is to identify those wildlife species for which adverse impacts due to toxic
contaminants have been documented in the Great Lakes region at one time or another over
the past three decades. In addition to the bald eagle, osprey, mink, and otter, which have
already been included in the analysis, species for which impacts have been documented
include, but may not be limited to, the Caspian tern, Forster's tern, common tern, ring-billed
gull, herring gull, double-crested cormorant, and black-crowned night heron. We will use
dietary information and allometric equations for food ingestion rates to determine if any of
these other species are likely to be more exposed to contaminants in aquatic food chains than
those already included in the criteria development.
S) Is this approach adequate for defending our selection of wildlife species to examine
for proposing criteria for the Great Lakes region?
9) Would this approach be appropriate for other regions of the country?
10) For areas for which adverse impacts have not yet occurred, what might be the most
appropriate alternative approach?
Exposure Assessments for National Wildlife Criteria
Efforts are underway to estimate the trophic level of wildlife species that may be at risk in
the Great Lakes region based on dietary studies of selected wildlife species in the Great
Lakes region and elsewhere. Information on both the species and size of aquatic prey taken
in specific locations is being compiled. To estimate the trophic level of the prey species,
data on the feeding habits of the aquatic prey species (and the prey species' prey or forage,
etc.) are~being compiled from the literature. These data will be used to estimate likely
trophic levels for the prey species and then for the wildlife that feed on them and to illustrate
how wildlife trophic level is likely to vary by location, season, and type of aquatic
ecosystem.
1
As part of this effort, trends in food web structure of aquatic ecosystems also are being
investigated. Food web structure and potential food chain length depend on many attributes
of the aquatic ecosystem and also on the history of introductions of new species to the
system. For example, lakes in which Mysis have been introduced to "improve" the forage
base for fish often have a food chain that is in effect one step longer than food chains in
similar lakes in which Mysis has not been introduced. Also, glaciated lakes tend to support
longer food chains than non-glaciated lakes in North America.
-------
Questions for SAB Commentary on Wildlife Criteria
These analyses will be used for three purposes:
a) To identify the potential range and central tendencies of trophic levels for ea-.'1.
selected species (e.g., bald eagle) in the Great Lakes Region and across the
US, as well as sources of uncertainty in these estimates (which include both
the wildlife feeding studies and knowledge of the aquatic food web).
b) To identify habitat attributes that are likely to influence trophic level for
wildlife species, which may help define appropriate geographical regions for
establishing wildlife criteria.
c) To iu^ntify key data gaps that contribu^ to the uncertainty in estimates of
wildlife trophic levels on a site- or region-specific basis to help identify which
studies (e.g., tissue residue monitoring for trout) might help most in improving
estimates of water quality criteria to protect wildlife.
11) Given the highly variable nature of aquatic food chains, is analysis of site-specific
wildlife diets and aquatic food webs suitable for the three purposes outlined above?
12) What other approaches should be examined to identify trophic levels for the model
used to estimate water quality criteria to protect piscivorous wildlife? On a regional
basis? On a more local basis?
Agenda Item: Adaptation of 1985 Aquatic Life Criteria Approach
13) We have concluded from our compilation and analysis of laboratory toxiciry data that
variability is so large as to made a purely statistical treatment highly uncertain and
probably overconservative. Do you agree with this conclusion?
-------
Questions for SAB Commentary on Wildlife Criteria
Agenda Item: U.S. Fish and Wildlife Service/National Biological Survey Approach :
Dioxin-like Compounds
Use of Field Data
14) The GLWQI allows for the use of field-derived data to take precedence over
laboratory data to develop a water quality criterion for a chemical. When should
field-derived data on species be used to develop a criterion? What type of specific
guidelines should be developed for the evaluation of field data for use in deriving
wildlife criteria?
15) Can the SAB suggest a mechanism whereby information from the field and specific
sites can be incorporated into the development of a wildlife criterion?
Egg-injection Studies
Egg-injection studies are useful in assessing potential reproductive/development effects, in
diagnosing responses in the field, and in deriving NOAELs for avian effects assessments. In
addition, many wildlife species can not be maintained in the laboratory making it impossib-2
to conduct reproductive studies yet direct injection of the chemical into the egg provides
important and relevant toxicity information. However, egg-injection studies do not
incorporate potential effects of metabolism or effects on the female/male reproductive
physiology or behavior. Therefore these studies could underestimate potential reproductive
hazards for some modes of toxic action.
16) Are egg-injection studies appropriate for deriving NOAELs for avian effects
assessments?
17) Should the use of egg-injection studies be limited to chemicals where evidence
indicates the chemicals direct effects are on the developing embryo?
18) Results from egg-injection studies are being considered for use in deriving NOAELs
m avian effects assessments. Although effects data from these studies can be useful
from a number of perspectives, do you agree that these data are currently problematic
in deriving water or sediment-based wildlife criteria because of limited
bioaccumulation and toxicokinetic data that relate chemical concentrations in bird eggs
to concentrations in the female bird and/or fish, sediments, or water associated with
the habitat?
Mode of Action Considerations
The best example of a class of compounds which are known to have the same mode of tcxic
action are the dioxin-like compounds. This class includes PCBs, PCDDs, and PCDFs. l"he
concept of assessing these using toxic equivalency factors and an additive model of toxicity
has been the topic of much discussion. The conclusions have generally been that this is a
-------
Questions for SAB Commentary on Wildlife Criteria Pa--- -
good concept, that there are examples where it has worked very well, but there are problems
related to a universally applicable set of toxic equivalence factors. These is, however, a
fairly large data set on avian related toxicity equivalency factors—particularly related to
embryo mortality. In most instances, we know that a multiplicity of compounds are acting in
concert and trying to assess them as individuals does not make sense.
Is the available data adequate to assess classes of compounds that act through the
same toxic mode of action?
-------
Questions for SAB Commentary on Wildlife Criteria
Agenda Item: General Discussion of Three Approaches
General Questions
20) Because of the paucity of data for amphibians and reptiles, wildlife criteria efforts
thus far have focused on avian and mammalian wildlife species. Given current
information concerning exposures and effects of bioaccumulative compounds on some
species of mammalian and avian wildlife, is it appropriate to proceed with credible
criteria for these taxonomic classes or should criteria/guidance be withheld until
empirical databases and predictive techniques can be created for amphibians and
reptiles?
21) Does the SAB have any suggestions on how best to incorporate effects on reptiles and
amphibians?
22) Are approaches other than these we have presented available to relate toxicity and
exposure data to derive criteria? If so, given the constraints on the availability of
wildlife toxicity data, is it feasible to apply any alternative approaches to deriving
wildlife criteria?
23) What is your assessment of the strengths and weaknesses of the three alternative
approaches presented?
Benchmark Dose Approach
Human health non-cancer assessments are considering using the benchmark dose approach
for developing RiDs for developmental endpoints in the near future. We recognize that the
benchmark dose approach may provide certain advantages to the current hypothesis-testing
approach (NOAEL), specifically, a LOAEL to a NOAEL uncertainty factor is no longer
applicable and intraspecies variability is incorporated in the dose-response curve.
24) Should the benchmark dose approach be pursued for future wildlife criteria derivation
'efforts?
25) Should EPA continue with the hypothesis testing methodology or wait until the
benchmark dose method is further developed?
Short-term Research Needs
In establishing a wildlife criteria approach, we have established efforts to address several
near-term research needs. This includes our efforts at quantifying wildlife exposures from
the aquatic food chain and compiling and analyzing wildlife toxicity data. These efforts are
essential for future criteria derivation, uncertainty factor analyses, and identification and
verification of critical data gaps for species-types, endpoints and modes of toxic action.
-------
, Questions for SAB Commentary on_Wild'ife Criteria 2SS.!,?.
26) Are there additional short-term research efforts which we should consider?
27) Do you have any suggestions for modifications to our research priorities?
28) Do you think there is sufficient scientific consensus concerning actual or potential
adverse effects of chemical stressors on wildlife to establish a formal wildlife criteria
approach for inclusion in ecological risk assessments. Why or why not?
•
29) Based on current information, it is scientifically credible to assume that aquatic life
and human health criteria for persistent bioaccumulative chemicals are necessarily
protective for wildlife? Why or why not?
Currently, development of criteria is not based on all possible mammalian and avian
populations, but rather on groups of avian and mammalian species which are likely to be
most at risk based on species' feeding habits (exposure analyses) and the properties of the
chemical, (e.g.; for highly bioaccumulative compounds which are not metabolized in
aquatic ecosystems, the most exposed species would be piscivorous species which feed at
higher trophic levels). If initial criteria development is based on species with the greatest
exposures, subsequent analyses can be undertaken to determine if less-exposed species would
be at risk based on greater sensitivity.
30) Should criteria be derived in this way, to protect populations identified as most at
risk, or, should they be derived to protect a percentage of all possible species, such as
is done with aquatic life criteria? (It should be noted that a percentage approach can
be applied in the GLWQI approach by using a distribution of exposures for wildlife
species. The toxicity database appeals too limited to enable developing distributions
of wildlife impacts considerate of both toxic effects and exposure assessments using
the GLWQI approach.
31) Should approaches for deriving wildlife criteria be premised on the bioaccumulative
potential and mode of action of the chemical of concern?
32) Should national criteria be developed based on exposure analyses of wildlife
populations in the entire U.S., or should analyses be derived for smaller geographical
settings in which the mammalian and avian populations most at risk can be identified
(e.g., ecoregions, classes of similar watersheds, individual watersheds)?
Geographical Considerations
An alternative to providing national wildlife criteria is to provide national guidance to
support criteria development in the context of specific ecoregions or smaller geographical
sites (e.g., watersheds). This strategy would require a national partnership to insure that
consistent approaches are used in developing criteria for similar watersheds, with similar
------- |