&EPA
United States
Environmental Protection
Agency
Office of Research and
Development
Washington DC 20460
EPA/600/R-96/100
September 1996
National Health and
Environmental Effects
Research Laboratory
1995 Annual Report
Advancing Knowledge for a Purpose
-------
United States Environmental Protection Agency
Office of Research and Development
Washington DC 20460
EPA/600/R-96/100
September 1996
National Health and Environmental
Effects Research Laboratory
1995 Annual Report
Advancing Knowledge for a Purpose
U.S. Environmental Protection Agency
Region 5, Library (PL-12J)
77 West Jackson Boulevard, 12th Floor
Chicago, IL 60604-3590
-------
FOREWORD
Safeguarding public health and the environment from the adverse consequences of
pollution is the fundamental goal of the U.S. Environmental Protection Agency (EPA). As a
regulatory agency, EPA is responsible for setting emission standards, for regulating toxic
contaminants and formulating sound environmental policy. Risk assessments and the ensuing
risk management decisions in each of these areas rely on sound scientific evidence linking
pollution sources, environmental exposures, and adverse effects. Such evidence is provided by
the Agency's Office of Research and Development (ORD), whose role is to strengthen the
scientific foundation for environmental decision making through mission-oriented research.
The National Health and Environmental Effects Research Laboratory (NHEERL), located
in Research Triangle Park, NC is the research arm of ORD that has the responsibility for the
conduct of a research program on the effects of contaminants and environmental stressors on
human health and ecosystem vitality. To convey the accomplishments of the NHEERL program,
the accompanying report provides summaries of the contributions made by the NHEERL to the
peer-reviewed literature during fiscal year 1995. A full listing of the scientific papers
published/accepted for publication is also provided.
A major component of NHEERL's mission is the conduct of peer-reviewed research that
improves the Agency's ability to assess human and ecological health risks. To achieve this
goal, the NHEERL risk-based research program has three major elements:
4 the development of state-of-the-art methods that facilitate the identification and
characterization of hazard;
* the development of predictive models for application to the quantitative assessment of
risk; and
* the application of these methods and models to collect scientific data (measurement) on
specific problems identified by the regulatory programs and other environmental
stakeholders.
Since NHEERL has the dual responsibilities of conducting research to support directly
the needs of the Agency's regulatory offices (e.g., Air, Water) and regions while also advancing
the science to improve the risk assessment process, in general, this report is complied along two
dimensions. The programmatic (media) sections summarize NHEERL's contributions to
programmatically relevant issues within EPA, discussing the ways in which the information is
useful to our client offices and risk assessment. The division-specific sections address the
NHEERL's research from disciplinary perspective based on the specialized fields of
environmental health or ecology research of its Divisions.
We hope that you will find the information presented here to be useful in understanding
the way in which NHEERL integrates Agency needs with scientific priorities while applying its
diverse scientific capabilities to advance scientific and technological progress in areas of
environmental and public health.
YI*> —
Lawrence W. Reiter, Ph.D.
Director, NHEERL
-------
NHEERL FY95 ANNUAL REPORT
National Health and Environmental Effects Research Laboratory I
Mission and Goals 3
Organizational Structure 5
Purpose of this Report 5
NHEERL Media Programs 7
Air Program 9
Air Toxics 12
Indoor Air 13
Global Change 14
Conclusions 16
Multimedia Research Program 17
Human Health Risk Assessment 18
Ecological Risk Assessment 21
Conclusion 23
Pesticides and Toxics Research Program 25
Methods 26
Models 27
Chemical-Specific Data 27
Conclusion 28
Waste Research Program 29
Bioremediation 30
Improved Risk Assessment at Waste Sites 31
Toxicity Evaluation of Agents Frequently Found at Waste Sites 31
Conclusion 33
Water Program 35
Water Quality 35
Drinking Water 39
NHEERL Ecology Divisions 41
Atlantic Ecology Division 43
Ecosystem Health and Integrity 44
Ecological Significance and Extrapolation Ecology 45
Ecological Risk Assessment 46
Biological Availability and Ecological Effects in Aquatic Systems 47
Global Change Issues (Ozone, UV-B, and the Carbon Cycle) 49
Gulf Ecology Division 53
Developing Test Methods 54
Biological Indicators of Ecological Condition 55
Development and Validation of Models 56
Microbial Ecology 58
Mid-Continent Ecology Division 63
Mechanisms of Toxicity 64
Dosimetry 65
Reproductive and Developmental Toxicology 66
Chemical Mixtures and Multiple Stressors 66
ADVANCING KNOWLEDGE FOR A PURPOSE i
-------
NHEERL FY95 ANNUAL REPORT
Measuring and Predicting the Responses of Aquatic Ecosystems 68
Watershed Characterization 69
Western Ecology Division 73
Ozone Considerations 74
Risk Assessment Issues 75
NHEERL Health Divisions 81
Environmental Carcinogenesis Division 83
Hazard Assessment 85
Biomarkers 85
Disinfection By-products, PAH, and Chemical Mixtures 86
Dose Response Assessment (BBDR Models) 87
Experimental Toxicology Division 91
Hazard Identification 93
Dose-Response Relationships 94
Quantitative Models 95
Human Studies Division 99
Sensitive Subpopulations (Asthmatics) 101
Respiratory Effects of Air Pollutants 102
Biomarkers of Human Exposure, Dose, and Early Molecular Effects 103
Dosimetry of Particles and Gases 104
Biologically Based Dose-Response (BBDR) Models 105
The Teplice Project 106
Sensitive Subpopulations (Asthmatics) 109
Neurotoxico/ogy Division Ill
Hazard Identification 112
Dose-Response Assessment 114
Chemical Specific Data 115
Hazard Identification 119
Reproductive Toxicology Division 123
Development of BBDR Models 125
Endocrine Disruption 127
Reproductive Effects of Drinking Water Disinfection By-Products 129
Improvements in Reproductive Toxicity Test Methods 130
Improvements in Noncancer Dose-Response Assessment 131
Developmental Toxicity of Complex Mixtures 132
References 135
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
INTRODUCTION
Introduction
Research conducted under the direction
of the agency's Office of Research and
Development (ORD) provides decision-
makers with a sound technical basis for
the formulation of environmental
policies and programs. ORD's National
Health and Environmental Effects
Research Laboratory, headquartered in
Research Triangle Park, NC, plays a vital
role in this mission.
NHEERL is the agency's focal point for
scientific research on the effects of
contaminants and environmental stressors
on human health and ecosystem integrity.
Its research helps the agency understand
the processes that cause pollution and
evaluate the risks that pollution poses to
humans and ecosystems. The impact of
its efforts is felt beyond the agency as
well, enabling state and local govern-
ments to implement more effective
environmental programs, assisting the
industrial sector in setting and achieving
environmental goals, and informing
international governments and organi
zations in issues of environmental
importance.
NHEERL's primary function is to
conduct research that supports the
agency's mandate, which includes
statutory obligations. It's more singular
role is to improve the agency's ability to
assess health and ecological risk by
strengthening the scientific basis for risk
assessment. To fulfill its responsibilities,
NHEERL maintains focused, yet diversi-
fied, research program that works to re-
duce the uncertainties inherent in
regulatory risk assessment. These
uncertainties vary in scope from
fundamental scientific questions (which
require the discipline of a sustained
research strategy) to Congressionally
mandated investigations (which demand
a more immediate response).
Accordingly, NHEERL strikes a balance
between long-term and short-term
studies, combining elements of both
basic and applied sciences to provide a
unique blend of research capabilities.
NHEERL's long-term studies confront
persistent and difficult issues, such as
global climate change or the relationship
between airborne particles and
increased rates of respiratory illness. It's
short-term projects, on the other hand,
are shaped by more pressing
imperatives; for example, when
complaints of illness coincided with the
use of oxygenated gasoline in certain
regions of the country, NHEERL quickly
initiated clinical studies of a fuel additive
suspected of causing the adverse effects.
Effective coordination of these
complementary capabilities enables
NHEERL to respond in a timely and
comprehensive manner to widely
divergent Agency needs. NHEERL is
organized into nine divisions, each of
which specializes in a different field of
environmental health or ecology
research (Figure I). NHEERL is able to
sustain a fluid program that offers
specialized skills in many distinct areas
while retaining sufficient flexibility to
adapt to changing research priorities.
National
Health and
Environmental
Effects
Research
Laboratory
(NHEERL)
The U.S. Environmental
Protection Agency (EPA) is one
of only a few federal
organizations that functions as
both a scientific and a
regulatory agency.
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
INTRODUCTION
The existence of such scientific diversity within a single
organization is unique, and it offers NHEERL a
competitive edge as it addresses emerging health and
ecological issues.
NHEERL has organized a cadre of nationally and
internationally recognized scientific experts who
pioneer innovative solutions to environmental
problems, provide leadership and guidance to the
scientific community, and lend technical advice in
national and international settings, often in crisis
situations. On issues ranging from disaster response
(e.g., the Exxon Valdez oil spill) to evaluations of health
and ecological effects (e.g., the toxicity of endocrine
disrupters) to risk assessment (e.g., the dioxin
reassessment), NHEERL scientists provide information
essential to effective decision-making. To augment its
in-house efforts, NHEERL administers an extramural
program through cooperative agreements, contracts,
and interagency agreements that draws upon the
expertise of pre-eminent researchers in academia,
industry, and government organizations. Collectively,
these efforts produce objective, reliable data that
provide the scientific foundation for the agency's risk
assessments and assist in resolving the most complex
environmental issues.
. , _
i National Exposure
i _ . , I
i Research Laboratory
NFRL
NERL
1
National Risk
Management Research
Laboratory
NRMRL
National Health and
Environmental Effects
Research Laboratory
NHEERL
Management
Coordination Division
Research and
Administrative Support
Division
Experimental
Carcinogenesis Division
Experimental
Toxicology Division
Human Studies Division
Neurotoxicology
Division
Reproductive Toxicology
Division
National Center for
Env ronmental Research
and Quality Assurance
NCEHQA
Research Planning and
Coordination Team
e Deputy
or for
EMENT
'-
!J;
»•
if
—
1
Office of the Associate
Director for
HEALTH
Office of the
Directc
ECOL(
Atlantic Ecology Division
Gulf Ecology Division
Mid-Continent Ecology
Division
Western Ecology
Division
Figure /. Organizational Structure of NHEERL and its Relationship to ORD.
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
INTRODUCTION
Mission and Goals
NHEERL's commitment to advance the current state of
knowledge surrounding the effects of contaminants and
other stressors on human health and ecosystem vitality
stems directly from a clear and strategic mission. The
mission statement, described below, embraces three
goals. Pursuit of these goals enables NHEERL to secure
and expand its position as a premier environmental
research institution.
NHEERL's mission is:
• to perform high quality, peer-reviewed Effects-
based Research that improves the Agency's
ability to make decisions about health and
ecological risk
• to provide Leadership in the area of
environmental science, research and assessment
• to provide scientific and technical Assistance at
local, state, regional, national and international
levels
Effects-based Research
Critical to the success of NHEERL's research is a
coherent research strategy. NHEERL's approach to
research, in accordance with ORD's landmark 1995
Strategic Plan, is founded on principles of risk
assessment. These principles bring cohesion to the
research, and they provide mechanism for setting
research priorities and for defining research goals. In
the area of health effects, NHEERL has adopted the risk
assessment paradigm described by the National
Academy of Sciences (NAS) in 1983 to guide its
research efforts. This paradigm consists of 4 steps
(hazard identification, dose-response assessment,
exposure assessment, and risk characterization) that
drive risk management decisions. For ecological effects,
NHEERL's research strategy follows the framework for
ecological risk assessment developed by EPA in 1992,
consisting of problem formulation, analysis
(characterization of exposure and effects), and risk
characterization.
NHEERL conducts risk-based research in three areas
aimed at improving the agency's ability to perform risk
assessments:
• hazard identification (or problem formulation), which
focuses on the development of methods that
demonstrate an association between exposure and
effects
• dose-response assessment, which seeks to under-
stand the cascade of events linking exposure to
effects and then incorporates this information into
predictive models that can reliably estimate risk
• problem-specific studies, which are designed to fill
gaps in knowledge on a particular chemical con-
taminant or environmental condition through
systematic collection and analysis of scientific
measurements.
The above efforts equip the agency with the scientific
knowledge and technical tools necessary for improved
evaluation of risk and for more informed regulatory and
policy decisions. For example, NHEERL has developed
neurotoxicity test guidelines as mandated by the Toxic
Substances and Control Act (TSCA) and toxicity tests
used to derive EPA's Water and Sediment Quality
Criteria; it has produced computer models that simulate
the response of ecosystems to climate change and
biologically based models that estimate human risks
from pollutants such as methanol; and it directs the
Environmental Monitoring and Assessment Program
(EMAP), in which measurements are gathered and
analyzed to document the status of ecosystems and to
depict ecologically relevant trends, such as land use
patterns or habitat fragmentation.
Central to research planning and scientific direction is
NHEERL's multi-disciplinary approach to problem-
solving. Assimilation and integration of information
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
INTRODUCTION
across environmental disciplines and across multiple
levels of biological organization (from molecular to the
whole organism, and from the organism to the
ecosystem levels) strengthens analyses of environmental
issues. Collaborations among scientists within and
outside the agency are encouraged, providing
opportunities for harmonization of research efforts.
Orchestrating research activities also leads to more
comprehensive analyses and more efficient expenditure
of resources.
Implicit to a multi-disciplinary approach to research is a
diverse and dynamic workforce. NHEERL retains a
highly trained mix of toxicologists, ecologists,
pathologists, biologists, physicians, clinicians, physical
scientists, statisticians, computer experts,
epidemiologists, chemists, oceanographers,
veterinarians, and support staff. These dedicated
scientists conduct cutting-edge research to address
effects-based issues. Microbiologists, for example, are
developing high-tech methods (such as gene probes and
immunoassay) to detect infection caused by pathogens
in drinking water, toxicologists are developing asthmatic
rodents that are helping to explain immune response to
indoor air pollutants, and climate modelers are
designing computer programs to predict fluctuations in
atmospheric carbon dioxide levels brought on by global
warming.
Also key to an effective research program are the
resources available to the scientists. Housed in
NHEERL's health and ecology research facilities are
chemistry, biology, toxicology, aquatic, and clinical
laboratories equipped with highly specialized and
technologically advanced instruments and computer
hardware and software. For testing especially
hazardous materials, NHEERL operates high hazard
containment facilities in Research Triangle Park, NC,
and in Duluth, MN, that boast advanced worker safety.
Often the equipment is designed exclusively by
NHEERL to meet individual research needs. For
example, NHEERL has developed state-of-the-art
inhalation exposure chambers for clinical research on air
pollutants, it has designed and operates programmable
growth chambers for studying the effects of
environmental stresses on plant and soil processes, and
it maintains specially outfitted research vessels for
marine and freshwater research.
Finally, and perhaps most importantly, NHEERL is
committed to scientific excellence in the execution of
its mission-oriented research. Rigorous peer review is
required for all major studies (as well as research
products, such as manuscripts) to ensure that research
output attains the highest possible scientific and
technical standards. Research protocols adhere to strict
EPA Quality Assurance (QA) guidelines, assuring the
quality and defensibility of methods and data.
Key scientific management positions are filled with the
help of committees that identify and recruit the most
highly qualified candidates. To optimize the quality of
its in-house program and to stimulate ingenuity among
NHEERL scientists, a competition for research
funds-similar in procedure to the system used to seek
federal grants-has been developed and instituted within
NHEERL. For this selection process, research
proposals are solicited from intramural investigators,
the submissions are peer reviewed for scientific merit
and programmatic relevancy, and the most deserving
projects are awarded funding.
Leadership
By virtue of their scientific acumen and their national
and international reputations, NHEERL scientists are
recognized as leaders in the environmental research
arena and are actively involved in the scientific
community. NHEERL scientists hold elected and
appointed positions in professional and scientific
societies; they are appointed to editorial review boards,
peer review committees, planning committees, and
advisory boards; they chair symposia and scientific
meetings; they author (and review) critical publications
and test guidelines; and they serve as mentors for
graduate students and as adjunct faculty members at
major universities across the nation. The collective
impact of these activities affords NHEERL the
opportunity to exert considerable influence on the
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
INTRODUCTION
direction and priorities of environmental research
around the world.
Assistance
NHEERL recognizes and embraces its duty to provide
assistance to agency programs and to the scientific
community at large. The expertise and agency-oriented
perspective of its scientists place NHEERL in a unique
position to respond to diverse requests for scientific
advice and technical consultation. NHEERL researchers
serve as advisors to EPA Program Offices and Regional
Offices, to other ORD laboratories, to other federal
agencies, and to interagency task forces; they provide
environmental guidance to local, state, native American,
and international governments; and they establish
partnerships with corporate, public, private, and
educational sectors to disseminate research results and
to provide technical training. By sharing its skills and
knowledge, NHEERL enhances the ability of other
organizations to safeguard public health and the
environment, and it serves as a catalyst for scientific and
technological progress.
Organizational Structure
NHEERL accomplishes its mission through the
integrated activity of nine research divisions, five of
which focus on human health issues and four of which
focus on ecological issues. The health divisions are
centrally located in Research Triangle Park, NC, while
the ecology divisions are strategically situated in
ecologically distinct geographic regions across the U.S.
Overall scientific direction is provided by the Office of
the Director for NHEERL. In addition to the Director,
who oversees and supervises the National Laboratory,
there exists within this Office
• a Deputy Director for Management, who is
responsible for oversight of Laboratory operations,
administrative support, and fiscal resource
accountability
Purpose of this Report
The remainder of this document focuses on some of
the scientific and programmatic accomplishments for
FY95, highlighting some of the more than 400
• an Associate Director for Health, who provides
leadership for the health effects research divisions;
• an Associate Director for Ecology, who provides
leadership for the ecology effects research divisions
• a Research Planning and Coordination Team,
whose members serve as liaisons between
• the Laboratory and the regulatory program offices
in headquarters and who are responsible for the
strategic planning of programmatically relevant
research (see Figure I).
These managers bring common direction to NHEERL's
research programs and ensure efficient use of limited
resources.
peer-reviewed publications produced by NHEERL
during FY95, and putting them in context of science and
agency programs.
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
Overview of NHEERL Media Programs
NHEERL FY95 ANNUAL REPORT
MEDIA PROGRAMS
There are five media research
programs, all located in Research
Triangle Park, NC. Each program
addresses a variety of issues within the
context of their media focus. Table I.
Health Programs Overview gives an
example of issues addressed by each
media program.
The media-specific sections of this
report highlight some of the
accomplishments of the media programs
that were published in the peer-
reviewed literature during FY95. The
sections reflect a "snapshot in time" and
focus on the state of the research at that
Table I. Media Programs Overview
particular time. NHEERL also provides
support to programs in terms of
technical consultation, review, sharing of
prepublication information, or other
support that may not be reflected in the
year's peer-reviewed publications.
NHEERL is preparing a series of reports
that are specific to each of the ORD
subcomponents under which NHEERL
research is performed. These subcom-
ponent reports will provide a chrono-
logical context to the research and
should complement this annual report.
MEDIA PROGRAM
Air
Multimedia
Pesticides and Toxics
Waste (i.e., Super-fund,
Hazardous Waste, and Oil
Spills)
Water
EXAMPLE OF ISSUES ADDRESSED
Sensitivity to ozone exposure: Who is most sensitive and why?
Research results that will lead to improved ecological risk
assessments and human health risk assessments across all media
programs.
Test method, model development, and chemical-specific
issues.
Research data supporting the additivity assumption used by
OSWER at waste site risk assessments
Effects of physical disturbances on urban wetlands quality
Media
Programs
The NHEERL media programs
perform important research
through all of EPA/ORD's
media-specific programs. The
summaries provided here
reflect the breadth of NHEERL
contributions to
programmatic issues
within EPA.
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
AIR PROGRAM
Introduction
the research activities of its
five health and four ecology
divisions, NHEERL's air program has
targeted four critical air quality
management issues for emphasis. These
significant air-related issues are: Criteria
Air Pollutants, Air Toxics, Indoor Air,
and Global Change. Findings from FY95
scientific air research on these issues are
discussed in the following sections.
fY 1995 Accomplishments
Air Pollutants
To protect public health and the
environment, the Clean Air Act requires
EPA to set National Ambient Air Quality
Standards for six pollutants (carbon
monoxide, particulate matter (PM), lead,
nitrogen dioxide, ozone, and sulfur
oxides), and to review and revise these
standards regularly. Agency decisions
about standards are based largely upon
criteria documents developed for each
pollutant. NHEERL's research focuses on
topics that will reduce uncertainties and
fill data gaps identified in previous
criteria documents. Our current
research emphasis is designed to
improve the scientific basis for regulation
of PM and ozone.
Particulate Matter (PM)
Recent epidemiological data have
suggested greater than expected human
morbidity and mortality from exposures
to particulate matter. Although
associated with considerable
uncertainties (Shy et al.), these
observations have elevated PM as a
priority research issue within NHEERL.
During FY95, ORD developed a strategic
research plan for PM. NHEERL defined its
research projects to complement ORD's
strategic vision, according to the categories
identified in Table 2. Particulate Matter
Research Focus.
Table 2. Particulate Matter Research Focus
Problem
characterization
Dosimetry
Causa)
mechanisms
Improve problem characterization by providing more detailed analysis of
epidemiology data.
Evaluate dosimetry (exposure-dose relationships) by measuring and
modeling particle deposition in the lungs.
Investigate causal mechanisms by determining the role of PM
Air
Program
The U.S. Environmental
Protection Agency (EPA) is
responsible for setting air
quality standards and
establishing regulations to
reduce air pollution. EPA's
National Health and Environ-
mental Effects Research
Laboratory (NHEERL)
supports this strategy by
conducting targeted research
to help the Office of Air and
Radiation make informed
decisions based upon the
best available science.
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
AIR PROGRAM
Problem Characterization
Environmental epidemiological studies have been limited
by the methods available to characterize accurately either
human exposures or biologically effective dose (Zenick
and Griffith, Lee et al.). NHEERL is conducting extensive
research to understand the links between exposure to
combustion-related particulates, biologically effective
dose, and various health effects. We are beginning to
develop powerful tools to study and understand the
effects of particulate exposures in human populations
(Mumford et al., in press).
Scientists from NHEERL and the Czech Republic have
been collaborating to study the health effects associated
with air pollution in heavily industrialized Northern
Bohemia, focusing on toxic components associated with
small respirable particles (PM2.5). During 1995, we
reported our observations that the prevalence and risk
for respiratory symptoms (Hnizdo et al.), but not
neurobehavioral dysfunction (Otto et al., in press) were
elevated in school children as a function of their
exposures to respirable particulates. In addition, we
found that personal exposure to PM2.5 was highly
correlated with exposures to carcinogenic polycyclic
aromatic hydrocarbons (PAHs) in the air (Binkova et al.).
These findings will help clarify the relationship between
PM exposures and various health effects (e.g., respiratory
disease, cardiovascular disease, and cancer).
Dosimetry
Understanding particle deposition is critical to assessing
the potential risks to humans. We have shown that
breathing pattern and airway resistance are the most
important factors affecting total lung deposition of fine
particles in normal subjects; age and gender had only
minor effects (Bennett et al.; Brown et al., in press).
However, preliminary findings indicate that preexisting
lung disease, such as Chronic Obstructive Pulmonary
Disease (COPD) may have substantial impact on
deposition.
Recent studies have challenged the traditional notion that
particles deposited in the ciliated airways were cleared
out from the lung within 24 hours, claiming that particles
persisted in the airways for some time. However, we
demonstrated complete clearance of particles from the
large airways of dogs following intrabronchial deposition,
thereby confirming the conventional understanding of
particle clearance kinetics (Lay et al.).
Causal Mechanisms
One of the most important questions about particle
toxicity is: What is it about particles that produces the
toxic effect? The answer to this question will allow policy
makers to predict which particles are most likely to
produce problems and why. In turn, they will ensure that
the appropriate sources of particle emissions are
targeted for regulation.
During FY95, we characterized and identified substances
present in particulate air pollution that are capable of
binding metals and demonstrated a relationship between
these substances and the amount of bound metal (Ghio
et al.). We also published our suggestion that soluble
metals on the surface of the particles may play a major
role in the observed toxicity. Comparisons of particles
from different emission sources have indicated that those
with higher concentrations of soluble metals are
associated with greater toxicity (Pritchard et al., in
press).
Tropospheric Ozone
Ozone is a reactive gas that produces irritation of the
lungs. Over the years NHEERL has provided data critical
to evaluating the ozone criteria set by EPA. A critical
remaining question about ozone toxicity is: How do
individuals differ in their responsiveness to ozone, and
what accounts for the differences? Or, put differently,
who is most susceptible to the effects of ozone, how
much more susceptible are they, and why? Answers to
these questions are multifaceted. During FY95, NHEERL
continued to build EPA's knowledge of ozone toxicity by
providing a response to key questions identified in Table
3. Key Research Questions on Susceptibility to Ozone
Toxicity.
The Clean Air Act requires EPA to protect the most
sensitive subpopulations from the potential adverse
10
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
AIR PROGRAM
effects of exposure to air pollutants. To improve our
understanding of how much variability exists among
individuals in response to ozone exposure, NHEERL
developed a model that describes the proportion of
individuals responding to ozone exposure as a function of
ozone concentration and exposure duration (McDonnell
et al.). This model is important because it can be used in
risk and benefit assessment for various regulatory
scenarios.
Because the predominant effects of ozone are
respiratory and asthma is a respiratory disease, EPA must
know whether asthmatics are more sensitive to ozone
than nonasthmatics. Reports by NHEERL in FY95
clarified the issue. Horstman et al. showed that more
severe asthmatics do indeed appear to be more
susceptfble to ozone than normal subjects, as measured
by lung function. Peden et al. demonstrated that allergic
asthmatics exposed to ozone experience a different kind
of inflammation (eosinophilic driven) than normal
Table 3. Key Research Questions on Susceptibility to Ozone
Toxicity
• How much variability exists between individuals in
their response to ozone?
• Are asthmatics more sensitive to ozone than
nonasthmatics?
• Do other common variables such as age,
socioeconomic status, or hormonal status (i.e., stage
of menstrua! cycle) alter ozone's effects on the
respiratory system?
• How can animal data best be used to elucidate risks to
humans?
subjects (neutrophil driven). Related studies by Ball et al.,
Noah' et al. and Seal et al. place boundaries on the
interpretation of these observations. For example, Seal
et al. showed that responsiveness to ozone was greatest
in young adults and decreased with increasing age.
The necessary and complete understanding of ozone's
toxic effects can only be achieved through a combination
of animal and human studies. Some important studies
cannot be carried out on humans. Yet, for animal studies
to be of value, we must know how ozone produces its
toxic effects and how best to extrapolate between animal
and human studies. Several NHEERL publications during
FY95 bring us closer to these goals. Gerrity et al. helped
identify potential sites of ozone damage in the airways.
Highfill and Costa developed exposure-response models
linking spirometric data and permeability of the lung in
humans and animals. Hatch et al. explored extrapolation
between rats and humans, comparing ozone dose and
effects and accounting for the species differences.
In addition to its effects on human health, tropospheric
ozone may have significant impact on terrestrial
ecosystems. During FY95 we showed that while ozone
is the most widespread air pollutant affecting vegetation
in the U.S., its effects on forests vary regionally. This
variation is the result of differences in wind patterns
carrying ozone from urban areas, differential sensitivity of
plant species, and differences in climate and soil
conditions (Hogsett et al.). We found that tropospheric
ozone has a profound effect on the rhizosphere (root
zone of the soil), where it depresses root growth and
mycorrhizal activity (symbiotic activity of fungal mycelium
with roots of a higher plant). Ozone often reduces the
amount of carbohydrate that is allocated to roots and
mycorrhizae, making seedlings more susceptible to
nutrient and moisture stress. By adversely affecting the
rhizosphere, ozone effects on forest ecosystems may be
more widespread than previously noted based on foliage
damage. Moreover, ozone stress may magnify the effects
on forests of increased temperatures and regional
drought predicted to result from global climate change
(Andersen and Rygiewicz, Rygiewicz et al., Wilson et al.).
ADVANCING KNOWLEDGE FOR A PURPOSE
II
-------
NHEERL FY95 ANNUAL REPORT
AIR PROGRAM
Air Toxics
The Clean Air Act Amendments of 1990 established a list
of 189 toxic air pollutants requiring regulation by EPA.
Initially the Agency must establish maximum achievable
control technologies for each of the toxic pollutants.
Then, EPA is required to evaluate residual risk for large
industrial sources of toxic air pollution and to identify and
control the chemicals that pose the greatest risks to
human health in urban areas. Performing these risk
assessments is difficult because of data gaps and
uncertainties. NHEERL's research is designed to improve
air toxics risk assessment as indicated in Table 4. Research
Objectives for Air Toxics. Although technically arduous,
solving many of the problems of quantitative risk
evaluation appears dependent upon development of
biologically based dose response models (BBDR).
Af a/or sources, urban areas, and risks
During FY95, NHEERL completed the data sets for three
prototype chemicals, a critical step in the development of
prototype models. The goal of this program is to develop
new approaches to air toxics risk assessment, in the
process addressing some of the most difficult assessment
issues faced by the Agency. The problematic risk
assessment issues include estimating exposure-response
relationships over a range of exposure concentrations
and durations, predicting the human health impacts of
these exposures, and estimating risk from common air
pollutant mixtures.
Table 4. Research Objectives for Air Toxics
Provide prototype data, methods, and models to improve
air toxics risk assessment. During FY95 NHEERL
addressed three major air toxic pollutant issues.
« Major sources and risks to public health
* Health risks from MTBE * Auto fuel oxygenate
» Health risks from MetharwJ
Efforts are focused on a list of chemicals and source
categories currently thought to pose the greatest risks
to public health. These are the following health effects
and chemicals classes:
I. Respiratory Toxicity - Irritant Gases (Selgrade et
al., Yang et al.)
2. Neurotoxicity - Solvents (Broadwell et at,
Croften)
3. Developmental Toxicity - Non-chlorinated
Hydrocarbons (Abbott et al., Andrews et al. (see
mobile sources discussion below)
4. Cancer - Polycyclic Organic Matter and
Atmospheric Transformation Products (Nesnow
et al., Ross et al.).
Mobile sources
The Clean Air Act mandates that those areas that do not
attain the NAAQS for carbon monoxide must add
oxygenates (e.g., MTBE) to auto fuels. The addition of
MTBE coincided with complaints of illness in some parts
of the country, especially in Alaska. Prah et al. demon-
strated that humans exposed to environmentally relevant
concentrations of MTBE in controlled chamber studies
did not report increased symptoms, changes in objective
cognitive measures, or physiological changes such as
respiratory tract inflammation. This work was key in
allaying some concerns about the potential risks posed by
MTBE and facilitated the continued use of MTBE to
control carbon monoxide and its adverse health effects.
Methanol
Methanol is an important chemical under the Clean Air
Act. It has been proposed as a cleaner burning alternative
fuel for current motor vehicles, it is a likely fuel for fuel
cell technology cars of the future, and it is listed among
the 189 toxic air pollutants. Previously, we showed that
methanol appears to be particularly toxic during fetal
development, therefore, evaluating the risk posed by
methanol is a high priority. During FY95, NHEERL
moved closer to achieving its scheduled development of
the Agency's first BBDR model for a developmental
toxicity of methanol. We completed work on the toxicity
12
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
AIR PROGRAM
of methanol's principal metabolite, formic acid, in
embryos exposed in an in vitro test system (Andrews et
al.,), and we described patterns of cell death in rat and
mouse embryos exposed to methanol in the same
culture system (Abbott et al.). The research
continues to indicate that methanol is the proximate
developmental toxicant, and to confirm the heightened
sensitivity of the mouse compared to the rat, in terms of
developmental toxicity. When completed, the BBDR
model will form a foundation for EPA to use in assessing
the health risks posed by methanol.
indoor Air
Indoor air pollution is often described as posing one of
the highest environmental risks to human health.
However, EPA's indoor air program is not regulatory.
The Office of Air and Radiation provides information on
indoor air quality for consumers, building owners and
managers, public health professionals, etc., based in large
part on ORD research results. In its indoor air research,
NHEERL emphasizes an improved understanding of the
health effects of indoor pollutants and pollutant mixtures,
as indicated in Table 5, with special attention to some of
the symptom-based conditions associated with indoor
air.
During FY95, NHEERL reported resolution of a
politically charged indoor air problem. Anecdotal reports
suggested an association between emissions from carpets
and a wide array of signs and symptoms. A private testing
firm reported finding an association between carpet
emissions and toxicity (respiratory and neurobehavioral)
in mice, which was claimed to validate the anecdotal
reports. However, NHEERL conducted a study of the
highest quality, marked by its extensive scrutiny from
both scientific peers and the public, Tepper et al. to
successfully defused this problem. Collaborative research
by NHEERL and other ORD scientists characterized the
chemistry and microbial emissions from three problem
carpets. Exposure of mice following a carefully controlled
experimental paradigm identical to that reported in the
press did not result in any significant adverse effects.
Increased asthma morbidity and mortality is a problem
that many scientists believe to be associated in part with
exposure of allergic individuals to house dust mites
and/or other characteristics of indoor environments. To
study this problem, NHEERL scientists have developed
an animal model for asthma. During FY95, Gilmour et al.
(in press) report that co-exposure of rats to house dust
mites and NO2, another common indoor pollutant,
enhances asthmatic responses, whereas exposure to
NO2 by itself does not trigger an asthmatic attack. While
the issue of asthma morbidity and mortality is far from
resolved, the study indicates that interactions between
common indoor pollutants may produce unexpectedly
severe adverse effects. This study also paved a new path
of scientific inquiry into mixture toxicity by evaluating
mixtures of biocontaminants with organic vapors.
Table 5. Understanding Health Effects of Indoor
Pollutants
• Understand the relationship between biocontaminants
and organic vapors and associated signs and
symptoms.
• Develop appropriate models and measurement tools
for symptom-based conditions.
* Develop strategies to study pollutant mixtures.
• Pevise approaches to identify susceptible pOftHtatej^gv;
ADVANCING KNOWLEDGE FOR A PURPOSE
13
-------
NHEERL FY95 ANNUAL REPORT
AIR PROGRAM
Global Change
Human activities are increasing the levels of carbon
dioxide and other gases in the atmosphere. Scientists
agree that these changes will lead to changes in climate-
driven conditions, such as temperature and sea level, and
decreases in stratospheric ozone. ORD must determine
the ecological and human health impacts of these changes
to inform the policy-making process. NHEERL research
is evaluating the potential ecological impact of climate
change and the potential health and ecological impact of
stratospheric ozone depletion.
Climate Change
Rising temperatures and rising sea level will likely shift the
composition and geographic distribution of ecosystems,
but the extent, rate, and interrelationships of these
effects are all unknown. NHEERL research is designed to
answer the three questions presented in Table 6. Key
Questions Related to Climate Change.
Indicators
During FY95, we reported on selected fish species
(Rivulus armoratus) distributions as a potential biological
indicator of global climate change to mangrove
ecosystems (e.g., Taylor et al.).
Effects
Redistribution of fish species may be a major impact of
climate change. In FY95, we reported our evaluation of
the potential effects of climate change on the distribution
of 57 species of freshwater fishes. The results indicated
Table 6. Key Questions Related to Climate Change
• What can be used as ecological indicators of global
change to help identify early warning signs that
climate-related damage to ecosystems may be
occurring?
• What are the long term ecological effects of global
change likely to be?
• How do ecosystems interact with atmospheric CO2 to
change climate?
that temperature shifts as predicted by a doubling of the
atmospheric carbon dioxide concentration would result
in a 50% reduction in the habitat for cold and cool water
fishes throughout the existing range of these species
(Eaton et al.; Eaton and Scheller).
Modulators
Level of atmospheric CO2 is a major driving force in
global climate change. Many interactive processes affect
the relationship between atmospheric CO2, global
change, and ecosystem vitality and productivity. NHEERL
is studying the dynamics of these processes, and during
FY95 we reported, as one of the major accomplishments
of the entire U.S. Global Change Research Program, that
net loss of carbon from the terrestrial biosphere may be
close to zero. Therefore, the carbon losses due to
deforestation must be offset by carbon accretion
elsewhere in the terrestrial biosphere (Bender et al.;
Keeling, in press; Keeling and Peng, in press)
Stratospheric Ozone Depletion
Stratospheric ozone depletion increases UV-B radiation
at the earth's surface. Increased UV-B is known to
increase risks of skin cancer and cataracts in humans.
During FY95, NHEERL conducted research onsseveral
potential impacts, identified in Table 6. Research on
Stratospheric Ozone Depletion, that are associated with
increased UV-B .
NHEERL research to date has shown that UV-B can
indeed suppress human immune function. NHEERL's
FY95 research begins to answer the question of what
would be the health impact of such suppression? Three
key questions which must be answered are I) what is the
impact of immune suppression on various classes of
infections (viral, bacterial, fungal, and parasitic), 2) what
is the window of susceptibility (temporal relationship)
between exposure to UV-B and altered immune
function, and 3) can UV-B affect hypersensitivity
responses (e.g., allergy/asthma). Selgrade et al. reported
on progress and identified the key problems and
14
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
AIR PROGRAM
opportunities for extrapolating between animal and
human studies on these issues.
The ozone hole in southern Chile presents a possible
opportunity to study the health effects of increased
ultraviolet exposure. Local reports had suggested that
there may be an effect on the eyes of animals. During
FY95, we reported (Schein et al.,) that it is possible to
perform standardized ocular, dermatologic, and
immunologic testing in the field in southern Chile.
Despite lay reports of blind sheep, we found no evidence
of short-term health effects produced by transient
fluctuations in ultraviolet exposure.
During FY95, NHEERL scientists resolved a critical
question about the effects of enhanced UV-B radiation on
rice, the world's most important crop species (Olszyk et
al., Olszyk). Previous studies had shown that UV-B has
significant effects on rice using exposures in greenhouses
and growth chambers. However, NHEERL scientists
found no consistent effect under field conditions. The
plants may be less susceptible to UV-B in the field due to
higher UV-A to UV-B ratios that stimulate cell repair.
Consequently, increased UV-B does not appear to pose
a major risk to rice production.
Table 7. Research on Stratospheric Ozone Depletion
NHEERL reported on the following suspected effects of
increased UV-B radiation:
)
• Suppressed immune function in humans
• Damage to marine phytoplankton
• Reduced rice production
* Increased toxicity of certain classes of chemicals
Oceanic phytoplankton are at the base of the oceanic
food chain. They are at particular risk from UV-B
exposure, because they inhabit the surface zones that are
most exposed to UV-B radiation. During FY95, reports
by NHEERL scientists clarified some of the relationships
between exposure to UV-B and marine phytoplankton.
For example, Vassiliev et al. demonstrated that even
100% increases in winter-time UV-B may not adversely
affect the light harvesting efficiency and phytoplankton
production in productive well-mixed coastal systems, but
even ambient UV-B levels may inhibit light harvesting
efficiency and phytoplankton production in clear waters
typical of the open sea. To assess maximum UV-B
impacts under field conditions, shipboard experiments
were conducted using Antarctic phytoplankton during
the period of the ozone hole (Sigleo and Neale, Sikorski
et al.). We found that increased UV-B alters pigment
composition, as expected from laboratory observations.
However, because the effect is mitigated by cloud cover
and mixing of the phytoplankton in the water column,
direct application of lab dose-responses to the Antarctic
may overestimate the actual effect.
During FY95, we reported that the toxicity of some
aromatic hydrocarbons can be increased by several
orders of magnitude in the presence of sunlight (Ankley
et al.; Moll et al.). Ultraviolet light activates some of these
compounds such that toxicity increases directly with the
increase in intensity and energy of the light. QSAR studies
have allowed us to predict the relationship between
structure of the chemical and the extent to which
sunlight will increase its toxicity (Mekenyan et al., Veith
et al.).
ADVANCING KNOWLEDGE FOR A PURPOSE
15
-------
NHEERL FY95 ANNUAL REPORT
AIR PROGRAM
Conclusions
NHEERL is charged with conducting air research to
support a wide range of topics of concern to the
nation, including criteria pollutants, toxic air pollutants,
indoor air quality, and global climate change. To meet
this charge successfully requires high quality research
over an exceptionally wide range of scientific disciplines
and an understanding of key regulatory and policy
issues. The accomplishments of NHEERL scientists
during FY95 have provided important contributions to
EPA's mission of protecting air quality and the
environment.
16
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
MULTIMEDIA RESEARCH PROGRAM
Introduction
NHEERL's Multimedia Research
Program focuses on addressing a
key question that is common to the use
of risk assessment by all regulatory
programs: How can we reduce
uncertainty in the extrapolations used in
risk assessment?
The risk assessment process relies upon
scientific data on the effects of contami-
nants on human and ecological health,
and models that extrapolate from
existing data to estimate effects where
data are lacking. Risk assessment-related
research strives to fill data gaps and build
models and methods for information
collection, interpretation, and extra-
polation. Ultimately, research informa-
tion is evaluated and used in risk
assessments to support National
Environmental Goals such as safe
drinking water, safe indoor environ-
ments, clean air, safe food, and healthy
sustainable ecosystems.
NHEERL's emphasis on issues of
multimedia importance complements its
regulatory program-specific research
activities. Decisions on multimedia
program organization and the nature,
direction, and priorities of the research
reflect recommendations of the EPA
Science Advisory Board, the National
Academy of Sciences, the U.S.
Congress's Office of Technology Assess-
ment, the Committee on Environment
and Natural Resources, the White
House Office of Science and Technology
Policy, and the EPA program offices.
The Multimedia Research Program is
separated into health and ecological risk
assessment components. In each of the
following sections, the key health or
ecological research questions are
identified, and examples of research
published in FY95 that addresses these
questions are summarized.
\\l//
Multi-
media
Research
Program
The US Environmental
Protection Agency (EPA) is
responsible for implementing
the nation's environmental
laws to protect human health
and the environment.
Decision-making to
implement these laws is
supported by the process of
risk assessment The
objective of the National
Health and Environmental
Effects Research Laboratory's
(NHEERL) Multimedia
Research Program is to
improve the scientific basis
for health and ecological risk
assessment.
ADVANCING KNOWLEDGE FOR A PURPOSE
17
-------
NHEERL FY95 ANNUAL REPORT
MULTIMEDIA RESEARCH PROGRAM
FY 1995 Accomplishments
Dl
Human Wea/fft
Health risk assessment, as defined by the National
Research Council in 1983, has four steps: hazard identi-
fication, dose-response assessment, exposure assess-
ment, and risk characterization. The Multimedia Re-
search Program emphasizes the uncertainties affecting
dose-response assessment. Some of the program's re-
search addresses hazard identification questions, but
most NHEERL work to improve hazard identification is
conducted by the Toxics and Pesticides Research
Program.
Quantitative risk assessment invariably involves
extrapolation from one set of conditions to another to
estimate risks to human health. In the dose-response
assessment step of risk assessment, quantitative
extrapolations are used to estimate the probability of
adverse effects in exposed humans. The key question is:
How can we reduce uncertainties in the following
extrapolations?
• High to low dose
• Interspecies (e.g., laboratory rodents to humans)
• Intraspecies (across the heterogeneous human
population)
• Inter-route of exposure (e.g., inhalation versus
ingestion)
• Across time (e.g., subchronic to chronic exposure
durations)
To address this question, the multimedia human health
research program has established a coordinated Research
to Improve Health Risk Assessments (RIHRA) Program,
that incorporates the three components identified in
Table 8. Research to Improve Health Risk Assessments Program.
The benefits of the RIHRA Program are that it increases
scientific knowledge of risk assessment parameters and
provides insight for the application of risk assessment
methods to critical human health issues, as illustrated in
Table 9. RIHRA Program Benefits.
Table 8. Research to Improve Health Risk
Assessments Program
• Development of quantitative models to estimate
target tissue dose (e.g., development of physiologically
based pharmacokinetic (PB-PK) models)
* Development of quantitative models to estimate
target tissue response as a function of target dose
(e.g., development of biologically based dose-response
(BBDR) models)
» Development of improved quantitative models to
utilize existing data better (e.g., development of the
benchmark dose (BMD) approach).
Table 9. RIHRA Program Benefits
PB-PK models enable more confident extrapolation
from results of high-dose studies in animals to predict
consequences of low-level exposure in humans. PB-PK
models can simultaneously address issues associated
with high-to-low dose, species-to-species, and route-
to-route extrapolations, and provide the time course
of toxicant dose at target tissues. f
BBDR models provide a key resource for
understanding the likelihood of a toxic response in
exposed individuals or populations. The/ are used
with PB-PK models to provide a sound scientific
estimate of tissue response including toxicity to
quantitative doses of toxicants. During FY9S, NHEERL
supported the development of BBDR models for
developmental toxicity, cancer, neurotoxicity, and
pulmonary toxicity.
Development and evaluation of a BMD approach to
improve noncancer risk assessment has been well
received by scientific peer groups as a replacement for
the traditional No Observed Adverse Effect Level
(NOAEL) technique. EPA is approaching the
development of a risk assessment guideline to
incorporate the implementation of BMD.
18
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
MULTIMEDIA RESEARCH PROGRAM
BBDR Models
Physiologically-based pharmacokinetic (PB-PK) models
represent a mathematical method to describe the
pharmacokinetics (absorption, distribution, metabolism,
and elimination) of chemicals in animals and humans. PB-
PK models are appealing because they can simultaneously
address issues associated with high-to-low dose, species-
to-species, and route-to-route extrapolations, and
provide the time course of toxicant dose at target tissues.
Specific FY95 accomplishments of NHEERL's Multimedia
Research Program address environmentally relevant
chemical exposures concurrent with development of
generic models for broader application. For example, a
study using O18 provided estimates of pulmonary ozone
dose in humans and animals. Quantitatively, this study
demonstrated that humans received a higher (about
fourfold) dose to pulmonary tissues at a given external
concentration than did rats, largely due to differences in
exercise levels and associated breathing rates. From a
risk assessment perspective, this study demonstrated the
quantitative relevance of studies in rats to human risk
estimation. Such information can be used to adjust
pulmonary dose levels quantitatively for gases of similar
reactivity in the majority of cases where human data are
not available (e.g., phosgene). In addition, these results
demonstrate the importance of exercise and breathing
patterns in interspecies extrapolation.
Other FY95 accomplishments address PB-PK model
development and application focused on route-to-route
extrapolation for phenol and carbon tetrachloride, and
on the metabolism of methyl mercury in humans. Each of
these chemicals, and the issue of data use from
alternative routes of exposure, is important to one or
more of the regulatory programs (e.g., Air, Superfund).
Coupled with sensitivity analyses of PB-PK model
parameters, which provide insights on study design and
identify the most critical model parameters, chemical-
specific data support generic PB-PK model development
and interpretation. The resulting advances in target dose
estimation will better enable the use of animal studies to
extrapolate to humans.
Research to improve the scientific basis for health risk
assessment has focused on developing quantitative
knowledge of the cascade of events linking exposure to
disease. The processes through which toxicants are
distributed from sites of exposure to target tissues and
the mechanisms by which toxic responses occur are
uncertain, yet central to understanding the likelihood of
a toxic response in exposed individuals or populations.
Together, PB-PK and biologically based dose-response
(BBDR) models are useful in that they support iterative
laboratory data collection and quantitative modeling,
ultimately leading to a better scientific basis for
quantitative dose-response estimation.
The Multimedia Research Program's FY95 accomplish-
ments related to development of BBDR dose-response
models began several years ago with theoretical
considerations regarding the development of BBDR
models, definition of a general framework for modeling
approaches, selection of agents for experimental work,
and, in an iterative fashion with data collection,
development of a mathematical framework that
describes the underlying biological processes.
These efforts involved experimental work on priority
chemicals, including persistent substances such as dioxin
and dioxin-like compounds, wherein exposure to these
chemicals was found to alter both male and female
reproductive function in offspring. These results provide
important information for both the reassessment of
dioxin by the Agency and for future BBDR modeling.
Research on the reproductive effects of another
persistent chemical, DDE, resulted in development of a
hypothetical model of a mechanism by which such
toxicity occurs. Studies of carcinogenesis provide data
needed to estimate critical model parameters in the
Moolgavkar-Venson-Knudson (MVK) model of
carcinogenesis and support development of a biological
model for the drinking water disinfection by-products
dichloroacetic acid and trichloroacetic acid. Other studies
of mechanisms of toxicity and/or repair include research
on the hazardous air pollutant phosgene and the
ADVANCING KNOWLEDGE FOR A PURPOSE
19
-------
NHEERL FY95 ANNUAL REPORT
MULTIMEDIA RESEARCH PROGRAM
fungicide vinclozolin. The research efforts for these
chemicals are at various stages, but the common goal is
to develop an understanding of the mechanisms that lead
to toxicity and thereby to improve the basis for
quantitative modeling at environmental levels.
As an expanded example of the type of efforts underway
on these agents, work on the model compound 5-FU
began with experimental efforts to link the postulated
mechanism of action, inhibition of thymidylate
synthetase, with alterations in the rate of DMA synthesis,
slowing of the cell cycle, and growth retardation that
would be related to the development of malformations.
Data published in FY95 indicate that one postulated
model of the events leading to malformations, fetal
anemia, is in fact not likely involved in the primary
cascade of events. This modeling, based on hypothesis
generation and testing, has allowed first-hand knowledge
of the quality and quantity of information needed to
construct a mechanistically based model. It has
demonstrated the need for careful evaluation of multiple
molecular, cellular, tissue, and organism responses in the
same or similar studies to tie together the progression of
events linking exposure to disease. It also demonstrates
the complexity and time course of this type of model
development and underscores the difficulty the Agency
may face in replacing default risk assessment approaches
with chemical-specific biological models.
The ultimate impact of these efforts on risk assessment
for a few specific chemicals will not be realized for some
time but certainly will form the foundation for
development of BBDR models for other chemicals.
These efforts also enhance EPA's science base for the
improvement of risk assessment and more firmly
establish EPA's leadership in the field of science-based
risk assessment modeling.
The development of mechanistic models, as described
above, is a long-term goal. In the near-term,
improvements to existing default risk assessment
procedures can result in better use of existing data and
more confident dose-response modeling. For the last
several years, there has been strong encouragement by
the Science Advisory Board and others for the Agency to
develop and evaluate the benchmark dose approach. In
the benchmark dose approach, the concept of NOAEL,
traditionally used in noncancer risk assessment, is
replaced by a benchmark dose (BMD), determined
through dose-response modeling.
Critical studies in support of BMD approach evaluation
were published in FY95. In these publications, the
application of the BMD approach to several hundred sets
of developmental toxicity data was reported, with an
evaluation of the consequences of selecting several
alternative benchmarks and model forms. This work was
cited in several conferences and workshops (e.g., Society
for Risk Analysis, International Life Sciences Institute
workshop) as essential and central to confident
incorporation of this method into the risk assessment
procedures used by EPA and others. The application of
this work has been immediate and substantial,
demonstrating EPA leadership in advancing
improvements in health risk assessment, and the Agency
is now approaching risk assessment guideline
implementation of this approach.
20
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
MULTIMEDIA RESEARCH PROGRAM
Ecological Risk Assessment
Ecological systems support the quality of human life and
represent an essential resource to be maintained or
restored. Through a multimedia ecological risk
assessment framework (illustrated in Table 10. EPA's
Multimedia Ecological Risk Assessment Framework), NHEERL
manages its research activities to understand, maintain,
and restore the condition, integrity, and sustainability of
ecosystems.
Table 10. EPA's Multimedia Ecological R/sk Assessment
Framework
Organizes research activities and supports environmental
management decision-making. The framework
encompasses research on
• The effects of stressors on ecological systems
* The multipathway exposure of key species and systems to
anthropogenic stressors
• The assessment of ecological condition and change
* The development and evaluation of resource iBonagwnef** and ,
mitigation options
Ecological degradation may be overt, as demonstrated by
declines of essential commercial fisheries; more subtle, as
suggested by declines in populations of migrating
songbirds; or not readily recognized when long-term
habitat degradation results in shifts in species
composition and reduced biodiversity. Change in
ecological systems may result from effects of multiple
stressors (e.g., pesticide exposures, stream flow
dynamics) across multiple scales (e.g., watershed sites,
ecoregions) and pathways (e.g., air, water). The
mechanisms and consequences of changes in the
biological, chemical, and physical attributes of ecosystems
are not well understood and represent significant
challenges to the research and environmental
management communities.
Research on the effects component of the multimedia
ecological risk assessment framework is conducted by
NHEERL. Specific FY95 NHEERL accomplishments
address six key questions, identified in Table II. Key
Questions of NHEERL's Ecological Risk Assessment Research.
NHEERL research published in FY95 will lead to more
effective and scientifically credible assessment of our
nation's ecological resources. Assessment of ecosystem
condition traditionally focuses on types or categories of
ecological resources, e.g., freshwater systems such as
lakes and streams, terrestrial resources such as forests
and grasslands, and marine systems such as coastal zone
ecosystems. Scientists at WED are evaluating the natural
variability of biological communities in lakes and streams.
Working with universities and State and Federal agencies
across the country, WED scientists have found that
Table 11. Key Questions of NHEERL's Ecological Rjsk Assessment Research
What is the condition of the ecosystems that comprise our natural biological resources? Research to address this question focuses on
development of indicators of ecological condition to identify affected or dysfunctional systems across a range of spatial and temporal scales.
What are the sources and stressors that affect ecological resources? Research to address this question focuses on developing methods to
identify and characterize sources and stressors and the means to measure ecological exposure to stressors.
What are the cause and effect associations between stressors and ecological response? Research to address this question focuses on
understanding cause/effect mechanisms and development of predictive models.
How rapidly is the condition of ecological systems changing? To distinguish normal fluctuation in condition from longer-term trends in
ecological degradation, the research to address this question focuses on development of distributed and intensive networks of study sites.
How can ecological condition be maintained, or mitigated when degraded? Research to address this question focuses on application of models
and methods to develop risk management options and predict the consequences of action.
Have ecological conditions improved fit response to management acaons*;Rere«xh to address this question focuses on identifying critical
indices to evaluate effectiveness of control strategies. , • ".''"• '^V, ' ,_
ADVANCING KNOWLEDGE FOR A PURPOSE
21
-------
NHEERL FY95 ANNUAL REPORT
MULTIMEDIA RESEARCH PROGRAM
biological measurements, while frequently more variable
than chemical or physical measurements, are sufficiently
robust to allow detection of trends and reliable
description of ecological condition. These findings will
translate into significant cost savings in monitoring
programs run by Federal and State governments.
NHEERL research demonstrated that temporal and
spatial variability in ecological parameters must be
considered in the design of studies of ecological
condition. Studies published by NHEERL in FY95
evaluated variability in the water quality of freshwater
wetlands as affected by wetlands characteristics and
surrounding land use. The implications of this variability
on study design were then assessed. Water quality
characteristics such as turbidity, and land use
characteristics such as degree of urbanization, were
found to influence the distribution of fish populations.
Fish populations are high on the trophic chain and,
therefore, are desirable as potential indicators of aquatic
ecosystem condition. This research will help ensure that
spatial and temporal variables that affect resources are
considered in design of monitoring studies.
NHEERL research in marine systems served as the basis
for the important assessment of the condition of the Gulf
of Mexico estuaries and the Florida Bay. This research
evaluated potential indicators of condition, which
included several scales of analysis, from physicochemical
properties (e.g., dissolved oxygen, nutrients) to
biochemistry in fish (e.g., vitellogenin, enzymes) to
community parameters (e.g., biodiversity and abundance
of target species). This evaluation of many potential
indicators provided the basis for assessing resource
changes over time.
NHEERL research improved the basis for evaluating
effects of stressors on ecological resources. Fish and
other aquatic organisms can accumulate stressors such as
dioxin directly from water or through ingestion of
contaminated food or sediment. An important
uncertainty in estimating effects of dioxin and similar
(e.g., PCB) contaminants is the relative amount of
accumulation through each route of exposure. In FY95,
NHEERL demonstrated a bioconcentration factor from
water for 2,3,7,8-TCDD of over 500,000, a number
considerably higher than previously reported. Other
research demonstrated that exposing fish eggs to dioxin
via either maternal, waterborne, or injection routes of
exposure results in very similar dose-response
relationships. Similar work distinguishing between lower
trophic levels of the food chain, such as filter-feeders
(Nelson, Bergen, et al., Peters et al.), and higher levels,
such as turtles, seals and dolphins (Lake, Haebler, et al.;
Lake, McKenney, et al.; Kuehl and Haebler) can be used
to estimate biomagnification factors.
Together, these NHEERL studies provide improved
estimates of bioconcentration and biomagnification
factors, which are needed for development of models to
estimate toxicant exposures in invertebrates, fish, and
mammalian species. Ultimately, these results support
improved assessment of population and ecosystem risks
from exposure to priority contaminants.
NHEERL research on the mechanisms by which
ecological effects occur has demonstrated that
laboratory-based estimates of the toxicity of pollutants
may underpredict ecosystem effects. Ecological effects of
pollutant exposures may result from changes in food web
dynamics. Such dynamics are not well characterized by
the fish toxicity tests commonly used to screen chemicals
for potential impacts of a pollutant on target populations.
NHEERL research has focused on understanding the
mechanisms leading to reduced bluegill growth following
exposure to diflubenzuron (a pesticide used to control
gypsy moths). Decreases in rates of fish growth were
associated with reduction or elimination of preferred
insect prey due to pesticide application, rather than to
direct toxicity of the pesticide to bluegill. This research
demonstrated that understanding mechanisms by which
ecological effects occur is important to interpreting fish
toxicity test results, and also that fish toxicity tests
provide limited ability to predict indirect ecological
effects.
NHEERL studies published in FY95 illustrated significant
changes in important ecological resources, such as the
22
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
Gulf of Mexico estuaries and Florida Bay. Based on
sampling 615 sites, approximately 30% of the estuarine
area in the Gulf of Mexico experienced some degree of
environmental degradation, with about 6% of the area
being seriously degraded. Most of the degraded
conditions appear to be related to sediment
contamination and toxicity rather than hypoxia. Research
was conducted to determine the change in condition of
submerged aquatic vegetation in Florida Bay, where it
was found that about 75% of the bottom sediments are
populated by vegetation. In the Chesapeake Bay area,
research quantified significant regional degradation from
hypoxia. These studies illustrate that ecological resources
are changing. Complementary research is targeted to
determine the causes of degradation in order to help risk
managers develop mitigation efforts.
NHEERL collaborative efforts with states, other
government agencies, and the private sector resulted in
additional large-scale, cost-effective analyses of ecological
condition. Multiyear, EMAP offshore demonstration
projects were completed in Lakes Michigan, Superior,
and Ontario, while monitoring was initiated in Lake
Michigan wetlands and in a Lake Superior estuary. An
EMAP study of the Southern California Bight was
completed with a ninefold matching contribution from
MULTIMEDIA RESEARCH PROGRAM
the State. Data collection and analysis continue from
these EMAP studies, with results from the Northeast
lakes study revealing a probable major loss in native
biodiversity. Almost no native minnows were found
where sportfish have been introduced and where
physical modifications to the surrounding landscape are
the greatest. These studies contribute to our
understanding of the status and changes of lakes and
streams potentially affected by stressors such as acid
deposition.
Understanding condition of ecosystems and mechanisms
by which stressors adversely effect species can lead to
improved targeting of mitigation efforts. For example,
NHEERL research implicated a parasite in the
appearance of withering syndrome in the black abalone
(Gardener et al.). These results suggest that alternative
mitigation strategies could be explored to alter the
progression of abalone destruction. The Northeast Lakes
assessment research findings also provide insights on
mitigation options by suggesting that lake restoration
techniques must focus on human perturbations other
than direct chemical contamination.
ft
>g"^ Conclusion
Concerns about environmental pollution and degradation
of human health and the environment result in
tremendous expenditures (over $ 100 billion) to reduce
pollution. Research to improve our ability to estimate the
consequences of environmental pollution is needed to
ensure adequate protection of health and the
environment, and also to ensure that we do not
misappropriate scarce resources to address insignificant
problems. Environmental problems are increasingly
viewed as multimedia; e.g., the research issues and
questions are of importance to more than one regulatory
program and/or multiple environmental media (e.g., air,
water) are involved in pollutant or stressor exposure or
effects. The multimedia research efforts highlighted
above demonstrate that NHEERL is improving the
scientific basis for risk assessment and management
activities.
ADVANCING KNOWLEDGE FOR A PURPOSE
23
-------
NHEERL FY95 ANNUAL REPORT
PESTICIDES AND TOXICS RESEARCH PROGRAM
Introduction
"T~he fundamental goal of the NHEERL
I Pesticides and Toxics research
program is to obtain and interpret
scientific data needed by the Office of
Prevention, Pesticides, and Toxic
Substances (OPPTS) and Regional
Offices to make informed regulatory
decisions. The U.S. Environmental
Protection Agency's (EPA's) mandate to
protect human health and the
environment from harmful effects of
pesticides and toxic substances is
authorized under two public laws.
• The Federal Insecticide, Fungicide,
and Rodenticide Act (FIFRA) gives
EPA the authority to regulate the
distribution and use of pesticides.
• The Toxic Substances Control Act
(TSCA) provides the authority to
regulate the manufacture,
distribution, use, and disposal of
industrial chemicals.
These statutes are implemented through
OPPTS and EPA's Regional Offices.
NHEERL provides science and research
support to OPPTS through the
development of standardized test
guidelines for end-points not previously
evaluated, revision to existing test
guidelines to reflect scientific advances,
assessment of the quantity and quality of
data required for responsible risk
management decisions, evaluation of the
need to review past regulatory decisions
in light of new scientific information,
evaluation of opportunities to reduce
the number of animals used in testing,
and consideration of increased reliance
on in vitro screening methods. NHEERL
accomplishes its goal and meets the
science needs of OPPTS and the Regions
by organizing its Pesticides and Toxics
research program around three themes,
described in Table 12. Pesticides and
Toxics Research Goals.
The NHEERL Pesticides and Toxics
research program is conducted by a
scientific staff of well-trained, highly
productive, nationally and internationally
recognized experts. Their work, while
directed toward specific regulatory
issues, contributes significantly to the
basic body of scientific knowledge. This
is evidenced by the number of instances
in which pesticides and toxic substances
research reports are shared with the
scientific community through publication
Table 12. Pesticides and Toxics Research Goals
Method This research includes efforts to develop and validate new methods to identify
Development human health and ecological hazards and to improve upon existing methods.
Model This research includes efforts to develop predictive models with broad hazard
Development identification and data extrapolation application.
Chemical- These studies are generally conducted as part of the development or
Specific Data validation efforts described above. They result from consultation with the
regulatory office regarding the selection of agents used for method and model
development and validation studies.
Pesticides
and Toxics
Research
Program
The objective ofNHEERL's
Pesticides and Toxics
Research Program is to
provide support for pro-
tecting human health and the
environment from risk posed
by exposure to pesticides
and industrial chemicals.
NHEERL assists the Agency's
risk assessors and risk man-
agers through the research
contributions of a scientific
staff, including experts in
ecotoxicology, microbial
ecology, terrestrial ecology,
developmental toxicology,
reproductive toxicology,
neurotoxicology, and genetic
toxicology.
ADVANCING KNOWLEDGE FOR A PURPOSE
25
-------
NHEERL FY95 ANNUAL REPORT
PESTICIDES AND TOXICS RESEARCH PROGRAM
in widely read scientific journals. In FY95, results of
NHEERL pesticides and toxics research projects were
reported in over 160 peer-reviewed publications. A
selected sample of these projects is briefly described
below to illustrate the nature of the work and its
contribution to the Agency's regulatory efforts.
FY 1995 Accomplishments
Methods
One of the fundamental elements of the OPPTS
regulatory program is the compendium of test
guidelines used to gather lexicological information on
pesticides and industrial chemicals. These guidelines are
provided to manufacturers to obtain data on both new
and existing chemicals, and for pesticide registration and
reregistration. OPPTS has historically relied on ORD
scientists to develop, validate, review, and revise test
guidelines.
NHEERL research programs provide the Agency access
to the most recent scientific advances. Through the
efforts of scientists in the health and ecology divisions,
improvements have been made to various components
Table 13. Pesticides and Toxics Research
Accomplishments
Method NHEERL research programs supported the
Development development of standardized ecological test
methods, standardized hazard identification
methods, and the interpretation of hazard
identification data.
Model
Development
Models developed through NHEERL scientific
research include: physiologically based models
to derive estimates for risk assessment,
ecological risk assessment models to evaluate
environmental stressors, and Quantitative
Structure Activity Models to evaluate new
Industrial chemicals and pesticides.
of the risk assessment process. In the area of hazard
identification, several projects have supported the needs
of OPPTS for standardized ecological test methods.
The scope of these ranges from review and evaluation
of general procedures for sediments and organic
chemicals to specific assays for an individual biomarker
of effect. Projects contributing to the development of
hazard identification methods for human health include
studies of sensory, reproductive, and developmental
processes, as well as studies of behavior, including
learning and memory. A related research focus is the
interpretation of hazard identification data. Ecological
research in this area included studies of the effects of
variables such as light, pH, and other aspects of water
chemistry on the outcome of toxicological evaluations.
Data extrapolation is another critical area in which the
NHEERL Pesticides and Toxics research program
provides methods development support to OPPTS and
the Regions. Ecological projects of this type include
studies that evaluate both acute and long-term effects
of chemicals in medaka. Human health studies evaluate
extrapolation of rat sensory evoked potential data to
humans and the relationship between developmental
exposures and effects in later stages of life.
reproductive toxtcity and neurotoxicity for
pesticides and several health and ecological
studies on the toxicity of PCBs and dioxins.
26
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
PESTICIDES AND TOXICS RESEARCH PROGRAM
Models
Several types of models are developed by NHEERL
scientists to support the requirements of OPPTS and the
Regions. Physiologically based models of specific
structures, such as the airway and lung, allow prediction
of actual target dose. This type of model reduces
uncertainty in the risk assessment process by providing
risk managers with realistic estimates of dose and
associated effect. Large scale models for ecological risk
assessment are also developed and greatly enhance the
ability of OPPTS and Regional assessors to compare the
effects of various stressors on the environment.
The number of new chemicals and pesticides developed
each year exceeds the annual review capacity of OPPTS.
Therefore, it is important to base chemical screening for
potential toxicity on the best available science, to ensure
that test requirements are appropriate. Extensive toxicity
data are required by FIFRA for all pesticide registrations.
In the case of industrial chemicals, regulated under
TSCA, testing requirements can vary. EPA has 90 days
from the time it is notified of intent to manufacture a
new chemical and provided with existing data to
demonstrate the need for additional toxicity data. The
decision process employed includes evaluation of the
chemical on the basis of its structure and physical
properties. Support for the development of Quantitative
Structure Activity Models to assist in this evaluation was
provided by NHEERL health scientists and ecologists in
FY95.
NHEERL scientists also continued to work on the
development of toxic equivalency factor models that
normalize toxicity across chemicals in terms of the
toxicity of a single standard, allowing a group of
chemicals to be ranked on the basis of relative risk. This
work helps OPPTS focus its regulatory activities on the
compounds of greatest concern from a risk perspective
and aids in decisions regarding acceptable substitutes for
regulated compounds.
Chemical-Specific
In some instances, NHEERL scientists provide OPPTS
and the Regional Offices with data on a specific chemical.
Information of this type usually focuses on a compound
of intense regulatory interest. Often this interest is
generated by controversy regarding the interpretation of
existing data on the chemical in question or the
appropriateness of the test(s) performed. In FY95,
NHEERL scientists provided expert advice to OPPTS
scientists concerning the interpretation of reproductive
toxicity and neurotoxicity data submitted to the Agency
in support of pesticide registrations.
In other instances, chemicals are selected for inclusion in
a basic research study because of their relevance to the
mission of OPPTS. For example, when NHEERL
scientists are designing a study to evaluate the
mechanisms underlying a particular effect, they routinely
consider the programmatic relevance of various available
prototype compounds. As a result, the data generated
are valuable from both a specific and a general
perspective.
In support of the Agency's continuing interest in the
toxicity of PCBs and dioxins, NHEERL scientists
conducted and published the results of several health and
ecology studies of these compounds. Related ecological
work concentrated on the effects of these and other
contaminants in marine species.
ADVANCING KNOWLEDGE FOR A PURPOSE
27
-------
NHEERL FY95 ANNUAL REPORT
PESTICIDES AND TOXICS RESEARCH PROGRAM
Conclusion
The NHEERL Pesticides and Toxics Research Program
provides support to OPPTS and the Regional Offices
primarily through development, validation, and
refinement of health and ecology test methods; the
development and validation of predictive health and
ecology models; and the development and interpretation
of data on the human health and ecological effects of
specific chemicals of intense interest. Applications of this
work include hazard identification, risk assessment, and
screening to determine relative risk. Protocols developed
within this program that become OPPTS test guidelines
are used to guide data collection by manufacturers of
pesticides and industrial chemicals. Thus, a relatively
small investment results in the generation of a large
volume of regulatory input.
28
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
WASTE RESEARCH PROGRAM
Introduction
NHEERL's waste research priorities
were established to address the
uncertainties of risk assessment (effects,
exposure, assessment, risk reduction)
and the ability of research to reduce
these uncertainties or to reduce the
risks themselves. The Waste Research
Program supports the three major
public laws administered by the Office of
Solid Waste and Emergency Response
(OSWER). ORD and NHEERL have
responded to the following legal
mandates by providing risk assessment
research, technical support, and
technology development to OSWER and
the Regional Offices.
• The Superfund Amendments and
Reauthorization Act of 1986
strengthened the Nation's program
to mitigate the health and
environmental hazards posed by
uncontrolled hazardous waste
dumps and contaminated plant sites.
It seeks permanent remedies at
waste sites and improved
assessments of the potential threats
to human health posed by each site.
Table 14. Waste Research FY95 Goals
• The Oil Pollution Act of 1990
expanded oil spill prevention
activities and established a new
federal authority to direct responses
to spills. It improved preparedness
and response capabilities, placed
financial responsibility for damages
from spills, and established an
expanded oil pollution research and
development program.
• The Resource Conservation and
Recovery Act of 1976, as revised by
the Hazardous and Solid Waste
Amendments of 1984, provided
legislation for a national program to
protect human health and the
environment from the risks of
improper management of hazardous
and solid wastes.
The Waste Research Program goals for
evaluating these three federal laws are
identified in Table 14. Waste Research
Goals. Research efforts conducted by
the program are concentrated among
three groups of applications:
bioremediation, improved risk
assessment, and toxicity evaluation of
agents found at waste sites.
Superfund
Oil
Spills
Hazardous
Waste
To provide guidance on how to evaluate the impact of an uncontrolled waste
site on human health and on the ecosystem. This goal is achieved by
developing improved methodologies, models, and chemical-specific data to
assess potential risks to human health and to the ecosystem.)
To assist in providing an effects-based evaluation of the risk management
options appropriate for remediating spilled oil based on health and ecological
risk assessment. Focus is on bioremediation of oil-contaminated shorelines
and the use of chemical counter-measures.
To provide the scientific and technical information needed by OSWER to
develop and Implement hazardous waste criteria and standards for
Waste
Research
Program
The objective of the National
Health and Environmental
Effects Research Laboratory's
(NHEERL) Waste Research
Program is to reduce
uncertainties in the risk
analyses used for environ-
mental management
decisions on wastes, waste
sites, or oil spills. The
Program seeks to balance
requirements for vigorous
longer-term effects research
needed to understand
emerging environmental
problems and the more
immediate short-term
research needs of the U.S.
Environmental Protection
Agency's (EPA) Program and
Regional Offices.
ADVANCING KNOWLEDGE FOR A PURPOSE
29
-------
NHEERL FY95 ANNUAL REPORT
WASTE RESEARCH PROGRAM
FY 1995 Accomplishments
Bioremediation
The bioremediation program determines the health and
ecological impacts of chemicals and microorganisms and
the impacts from their treatment residuals. In FY95
NHEERL ecologists completed numerous studies
designed to enhance bioremediation as an option for a
toxic chemical environmental cleanup. The focus of the
bioremediation program is identified in Table 15. Focus of
Bioremediation Research.
Protocols, to be used by the Agency in selecting
remediation options, are being developed and evaluated
for applicability in the laboratory and in the field. In order
to support protocol selection, microbial metabolic
pathways were characterized for several organisms and
chemical agents including fluorene (Grifoll et al.),
halobenzoates (Selifonov et al.), creosote polycyclic
aromatic hydrocarbons (Chapman et al.), and
naphthalene (Eaton). NHEERL completed protocols to
test the effectiveness of oil spill bioremediation products
and continues with the development and/or revision of
protocols for evaluating chemical countermeasures.
Table IS. Focus of Bioremediation Research
• Develop and test protocols to apply bioremediation
for toxic chemical environmental and oil spill cleanups
• Evaluate the effectiveness of commercial
bioremediation agents on open water, beach, and
marsh systems.
* Evaluate the toxicity of combinations of oil spill
pollutants and dispersants.
Research is continuing to focus on the influence of
environmental parameters on bacterial transformations.
Test systems and protocols are being developed and
evaluated to examine the efficacy and environmental
safety of commercial bioremediation agents (CBAs) on
estuarine organisms in open water, beach, and marsh
systems (Middaugh and Whiting). To date, eight CBAs
have been tested for efficacy and six for toxicity in open
water, two for efficacy in beach, and two for toxicity in
marsh microcosms, using the new protocols.
The toxicity of pollutants from oil spills in combination
with dispersants is also being evaluated. The surfactant
Triton X-100 was shown to enhance microbial
degradation of polycyclic aromatic hydrocarbons (PAH).
However, when fish embryos were exposed to the
water-soluble fraction of No. 2 fuel oil and two different
dispersants, toxicity was increased (Middaugh and
Whiting).
Several studies were published on attempts to test
whether the metabolism of mercury by genetically
engineered microorganisms could be exploited in
environmental bioremediation (Nazaret et al., Saouter et
al. "Development and Field Validation," Saouter et al.
"Evaluation of Ionic Mercury," Selifonova and Barkay).
Based on this research, it appears that the best use of
such organisms would be in pollution prevention (e.g., in
sewage bioreactors) where the microbes are contained.
In other work, a microcosm consisting of water,
sediment, and air components was used to simulate
mercury geochemical cycling in a mercury-contaminated
stream-pond system. This microcosm could be used to
test remedial treatments aimed at decreasing the amount
of mercury that is available for accumulation by biota
(Saouter et al. "Development and Field Validation").
30
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
WASTE RESEARCH PROGRAM
/mprovef/ jj/s|f Assessment at Waste Sites
Detailed and reliable databases are essential for assessing
and ranking ecological effects of waste chemicals to
aquatic life, wildlife, and plants. During FY95, NHEERL
released through the Internet an ecotoxicology database
(ECOTOX) and predictive quantitative structure-activity
relationship models (ASTER) to EPA, federal, and state
agencies for use in the assessment of ecological risks of
chemicals in wastes and at waste sites (Bradbury
"Quantitative structure," Bradbury et al., Bradbury
"Ecological risk assessment").
NHEERL scientists tested the additivity assumption used
to assess risks from mixtures of chemicals at waste sites.
Studies have shown that chemicals with similar modes of
action usually conform to this assumption. NHEERL
ecotoxicologists developed a joint toxic response
procedure to define the primary mode of action for
diverse industrial organic chemicals (Broderius et al.).
Also, NHEERL health scientists published a three-
chemical (diethylhexylphthalate, trichloroethylene, hepta-
chlor) mixture study on maternal and developmental
toxicity using five doses in a full factorial design (Narotsky
et al.). The three chemicals are known developmental
toxicants and occur frequently together at Superfund
sites. Individual dose-response data were reported for
the same chemicals in a companion paper (Narotsky and
Kavleck) that also addressed the neurotoxicity of the
agents.
Toxicity Evaluation of Agents Frequently Found at Waste
An extremely important category of hazardous wastes is
represented by the toxic bioaccumulating chemicals.
These chemicals must be carefully assessed for their
long-term and cumulative effects. A series of aquatic
full-life cycle and early-life stage toxicity studies were
completed, with associated toxicokinetic analyses, in
support of the ecological effects characterization of
2,3,7,8-TCDD (Schmieder et al., Walker et al.). During
FY95, NHEERL's Waste Research Program documented
several important research findings on toxicity, as
reported in Table 16. Research Findings from Toxicity
Evaluations.
Toxicity equivalency factors (TEFs) were developed for
pot/chlorinated biphenyl (PCB) congeners and the
assessment of TCDD and PCB mixtures in the rainbow
trout (Newsted et al., Zabel et al.). Such compounds are
Table 16. Research Findings from Toxicity
Evaluations
• Developed Toxicity Equivalency Factors (~TEFs) for
PCB congeners, TCDD and PCB mixtures, and several
dioxins, dibenzofurans, and PCBs.
• Demonstrated additive interactions for dioxin-like
chemicals acting through the Ah receptor and
nonadditive interactions when multiple mechanisms
are involved.
« Developed a model for pdycyclic aromatic
hydrocarbons to predict the probatiility <
sediment toxicity on marine and estuarinespie(«
ADVANCING KNOWLEDGE FOR A PURPOSE
31
-------
NHEERL FY95 ANNUAL REPORT
WASTE RESEARCH PROGRAM
very slowly metabolized by the human body and pose
varying degrees of relative risk. To gain a better
understanding of the human response to these chemicals,
the biliary elimination of TCDD in experimental animals
was characterized as an indirect measure of in vivo
metabolism. The effects of age, gender, and pharma-
cological manipulation on several hepatic enzyme systems
involved in metabolism of TCDD were studied (Dilberto
et al., DeVito et al.). Based upon this work, TEFs were
developed for three dioxins, three dibenzofurans, and six
PCBs to be used in estimating their toxicity relative to
that of TCDD (Birnbaum and DeVito).
NHEERL health scientists showed that additive
interactions occur for dioxin-like chemicals acting
through the arylhydrocarbon (Ah) receptor and that
nonadditive interactions occur when multiple
mechanisms of action are involved (Dejongh et al.).
Dioxins or dioxin-like PCBs plus nondioxin-like PCBs can
result in synergistic production of hepatic porphyries,
altered pharmacokinetic behaviors, and functional
antagonism of immunotoxicity at relatively high doses
(DeVito and Birnbaum, Burleson et al.). In studies with
TCDD, it was determined that doses that result in
developmental/reproductive effects in rats (permanent
decrease in sperm count, malformations of the external
genitals, premature reproductive senescence, etc.)
produce concentrations in target tissues of the embryo
that are within a factor of ten of background body levels
in the human population (Abbott et al., DeVito et al.).
Additional research focused on the developmental
neurotoxicity of PCBs: Aroclor 1254 caused persistent
hearing loss (Goldey et al. "Developmental exposure")
and reduction in regulated body temperature (Gordon et
al. "Temperature regulation and metabolism"). These
studies suggest that fundamental metabolic processes
may be altered by developmental exposure to dioxin,
with the hypothalamus and thyroid as possible target
sites. NHEERL neurotoxicologists also found that the
ortho-substituted PCBs, which have little or no Ah
receptor activity (and are thus considered to pose a low
risk relative to dioxin), affect calcium homeostasis with
adverse neurotoxic effects (Kodavanti et al.)
Through the use of knowledge bases and QSAR analysis
(Russom et al.), NHEERL scientists modeled chemical
substituents on polycyclic aromatic hydrocarbons
(PAH)'n order to predict photo-induced acute toxicity
(Veith et al. "A QSAR analysis," Veith et al. "A QSAR
evaluation"). To facilitate improved eco-risk assessments
for the class of PAHs, a model has been developed that
predicts the probability of acute sediment toxicity to
sensitive marine and estuarine species caused by the
combined stresses of 13 PAHs. The study reported an
86.6% correspondence between predicted and observed
toxicity at PAH-contaminated sites.
Key to the conduct of scientifically defensible risk
assessments is the development of relating exposure to
specific chemicals to their induced effects. NHEERL
health scientists demonstrated a mechanistic linkage
between DNA adducts induced by environmental
polycyclic aromatic hydrocarbons (PAHs), mutations in
oncogenes, and tumor formation, thereby paving the way
for the use of these biomarkers in relating environmental
exposures to induced health effects (Nesnow et al.
"Mechanistic linkage," Ross et al., You et al.). In addition-
al investigations, a relationship between adduct formation
and the mutagenicity of trinitrotoluene metabolites was
shown, and it was demonstrated that the pesticide
atrazine potentiates the mutagenicity of dinitrotoluene
(Chadwick et al. " Potential on," George et al.).
In health research on arsenic, NHEERL scientists
developed analytic strategies for the characterization of
arsenic metabolites in a variety of biological matrices
(Styblo et al. "Identification of methylated metabolites,"
"Mono- and Dimethylation of Arsenic"). This research
will provide needed information on arsenic metabolism
and target organ toxicity in support of health risk
assessment. In other research, arsenite, but not
cadmium, was shown to induce ornithine decarboxylase
and heme oxygenase in rat liver. These enzyme inductive
effects represent potentially important biomarkers in
arsenic carcinogenesis (Brown and Kitchen).
32
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
During FY95, NHEERL scientists completed and
published a great deal of research related to technical
support, and technology development. This research has
produced new protocols for bioremediation, more
accurate information for the assessment of risks to
humans from exposures to mixtures of waste chemicals,
NHEERL FY95 ANNUAL REPORT
WASTE RESEARCH PROGRAM
detailed and reliable databases on ecological effects of
waste chemicals, and data on the relative risks of the
toxic bioaccumulating chemicals.
ADVANCING KNOWLEDGE FOR A PURPOSE
33
-------
Introduction
NHEERL FY95 ANNUAL REPORT
WATER PROGRAM
The NHEERL water program
performs research to increase
scientific knowledge where major
uncertainties exist. This research pro-
vides critical scientific data, methods,
and models to help reduce major
uncertainties in environmental and
health risk assessments. These efforts
lead to more scientifically sound and
cost-effective regulations.
FY 1995 Acomplishments
a
Water Quality
The Clean Water Act authorizes the
EPA to develop regulations and guidance
to restore and maintain the physical,
chemical, and biological integrity of the
nation's waters. The Office of Water
supports this mandate through programs
designed to minimize the environmental
and human health risks associated with
pollutant discharges and other
environmental disturbances to fresh,
estuarine, and marine waters.
lntcgmte
-------
NHEERL FY95 ANNUAL REPORT
WATER PROGRAM
The NHEERL water quality research program is divided
into three interrelated research components: Aquatic
Ecocriteria, Contaminated Sediments, and Wetland
Protection.
Aquatic Ecacrfterl*
Broadly defined, aquatic ecocriteria are physical,
chemical, and/or biological parameters that are derived
for the protection of aquatic life and wildlife. Types of
criteria include those described in Table 18. Types of
Aquatic Ecocriteria. NHEERL scientists have conducted
extensive research to improve the scientific basis for
these criteria. NHEERL efforts have included research in
the area of ecosystem diagnostics which assist risk
assessors and managers in determining the most likely
causes of effects observed in aquatic systems and in
determining the best approach for watershed protection
(e.g., chemical-specific criteria versus biocriteria).
NHEERL research has also focused on hazard
identification studies or methods development research
to characterize the toxicity of single chemicals or
mixtures of contaminants in sediments, effluents, and
surface waters.
Specific examples of how NHEERL research has
advanced knowledge in the development of aquatic
ecocriteria include the following:
• Holcombe et al. and Cripe characterized the toxicity
of a number of individual chemicals by describing the
effects these single contaminants cause in different
aquatic species.
• Burgess et al. characterized the toxicity of a mixture of
contaminants by reporting the effects of contaminated
industrial and municipal effluents.
• NHEERL scientists developed useful techniques for
predicting acute (Sun, Kai, et al.) and chronic (Lee,
Gunher, et al.) toxicity of chemical contaminants from
different types of data sets.
• NHEERL scientists provided baseline information
concerning the influence of water temperature,
salinity, and starvation stress on the health of aquatic
organisms (Cripe, "Induction of maturation";
Behrenfeld, Lee, et al.; Ho, Mitchell, et al.; McKenney
and Celestial).
• NHEERL scientists described ecological conditions at
the regional/landscape level and the response of large
scale ecosystems to multiple environmental stresses
(Griffith, Omernik, et al.; Larsen et al.).
Table 18. Types of Aquatic Ecocriteria
ECOCRITERIA
Chemical-specific
DESCRIPTION
Numerical thresholds that, when exceeded, signal degradation of aquatic species condition
Quantitative values or narrative statements that describe the biological condition of aquatic
communities for a particular type of water fcody («.f,, river, estuary, wetlands) or use category (e.g.,
36
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
WATER PROGRAM
Ctmtamtnatetl Sediments.
Many toxic chemicals accumulate in the sediments of
coastal, estuarine, and freshwater ecosystems and thus
adversely affect benthic biota and other aquatic
communities. Bioaccummulation and biomagnification of
these sediment contaminants in the food chain may
ultimately threaten human health and wildlife.
NHEERL research efforts on contaminated sediments are
focused in the three general areas described in Table 19.
Contaminate Sediments Research Areas.
Certain physicochemical processes control the biological
availability of sediment-associated contaminants in
aquatic systems. Advancing knowledge of these
processes is key to improving estimates of contaminant
toxicity in sediments. Accordingly, Pesch et al. evaluated
the role of sulfide in determining the bioavailability of
cadmium and nickel in sediments.
NHEERL scientists also performed research that resulted
in advances in the use of predictive bioaccumulation
methods (Boese, Winsor, et al.) and equilibrium
partitioning (DiToro, Zarba, et al.; Hoke, Ankley, et al.)
for establishing more scientifically sound SQC for organic
contaminants in sediments.
A need also exists for better models and test systems to
assess the individual and aggregate toxicity of
contaminants in sediments. Swartz et al. developed an
innovative method to predict the toxicity of a mixture of
polyaromatic hydrocarbon mixtures in sediments
collected in the field. Burgess and Morrison and Phipps
et al. explored the use of different species for use in
sediment toxicity tests.
Table 19. Contaminated Sediments Research Areas
RESEARCH AREA
Support for the development of sediment quality
criteria (SQC).
Development of short- and tang-term toxidty
DESCRIPTION
SQC define safe levels of individual chemicals in sediment.
ADVANCING KNOWLEDGE FOR A PURPOSE
37
-------
NHEERL FY95 ANNUAL REPORT
WATER PROGRAM
Wetlands Protection
Loss or degradation of U.S. coastal and inland wetlands
in recent decades has been attributed primarily to the
environmental stresses that accompany population
growth and competing demands on aquatic resources.
To support sound management decisions designed to
protect these valuable resources at the local, regional,
and national levels, NHEERL researchers have
successfully addressed several critical issues. Table 20.
Wetland Science Issues and Accomplishments presents
three of these issues.
Table 20. Wetlands Science Issues and Accomplishments
ISSUE
ACCOMPLISHMENT
I. Characterization of the physical, chemical, and NHEERL scientists described the effects of physical disturbances on urban
biological stressors and their effects on wetland water quality (Detenbeck, numerous articles).
wetlands.
2. Understanding the Interactions of wetlands with Scientists studying Great lakes coastal wetlands identified important
other ecosystems within broad geographic regional and local factors that Influence ecosystem health (Brazner and
areas, such as ecoregions and watersheds.
Holland et al evaluated patterns and effects of wetlands loss and
38
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
WATER PROGRAM
Drinking Water
The Safe Drinking Water Act (SDWA) of 1974, as
amended in 1986, requires the EPA to identify and
regulate drinking water contaminants that may pose a
risk to human health. The SDWA also authorizes EPA to
carry out research to ensure that regulatory decisions are
based on sound scientific information.
NHEERL conducts research to reduce uncertainties in
the risk assessment process for priority contaminants in
drinking water. This research has provided
• Improved characterization of health risks posed by
drinking water contaminants.
• Support for development of contaminant or class-
specific Maximum Contaminant Level Goals
(MCLGs)/Maximum Contaminant Levels (MCLs).
Important long-term research at NHEERL includes
pharmacokinetic and mechanistic studies to evaluate
biological processes by which key drinking water
contaminants cause their effects. This information is used
to develop and evaluate biologically based dose-response
models, which facilitate the extrapolation of toxicity data
from animals to humans. These models represent a
significant improvement over conventional risk
assessment approaches, which generally rely upon a
number of default assumptions. Studies are also
conducted in the laboratory, clinic, and field to help
characterize toxic endpoints of concern (e.g., cancer,
adverse reproductive outcomes, gastrointestinal effects)
and the exposure levels at which these effects occur.
Disinfection By-Products
Widespread use of chlorine and other disinfectants in
drinking water has been highly effective in reducing
devastating waterborne disease outbreaks such as
cholera and typhoid. However, formation of low levels of
disinfection by-products (DBPs) during the treatment
process has raised questions about the risks of DBPs to
humans. A major objective of the drinking water research
program is to provide data to characterize the toxicity of
the DBPs that may be of greatest concern from a
regulatory perspective..
NHEERL scientists have provided key insights into the
carcinogenicity of dichloroacetic acid (a haloacid)
(Benane; Carter, J., Carter, H., et al.; Ferreira-Gonzalez
et al., Richmond et al.; Snyder et al.). Research by
Carter,]., Carter, H., et al. and Snyder et al., has helped
define critical parameters that are required for the
development of a biologically based dose-response
model for dichloroacetic acid.
Gao et al. discovered a novel metabolic pathway for
bromodichloromethane (a trihalomethane) that has
important implications for the development of a
physiologically based pharmacokinetic model and which
provides insights into the relative potencies of the
different members of that class of DBP.
Concern has been raised over the potential risks of
adverse reproductive outcomes following exposure to
DBPs in drinking water. Under et al. demonstrated
effects on the male reproductive system of rats exposed
to dibromoacetic acid, suggesting the need for additional
studies to define further the dose-response relationship
for this brominated by-product.
NHEERL scientists demonstrated the utility of a
quantitative structure-activity relationship (QSAR)
analysis for prioritizing compounds for in vivo study. They
used this approach to estimate the developmental
toxicity of a series of halogenated acids in vitro.
ADVANCING KNOWLEDGE FOR A PURPOSE
39
-------
NHEERL FY9S ANNUAL REPORT
WATER PROGRAM
Arsenic
Aluminum
Among the many naturally occurring and man-made
source water contaminants of potential concern, arsenic
is one of the most important from a regulatory and public
health perspective. Research at NHEERL is addressing
several key scientific issues that affect the risk assessment
for arsenic in drinking water. Publications by Styblo et
al., "Identification of methylated metabolites"; "Mono-
and dimethylation of arsenic" in FY95 on the metabolism
of arsenic provide important information on the role that
glutathione may play in the methylation and detoxification
of arsenic. These findings represent critical steps toward
a better understanding of the dose-response relationship
for arsenic toxic actions, the relationship of metabolism
to toxicity, and the important factors that can affect the
variable sensitivity of humans to arsenic.
Alum, or aluminum sulfate, is widely used as a coagulant
for removing nonsettleable solids in the water treatment
process. Although the low levels of aluminum in drinking
water are generally considered to be safe, concerns have
been raised about the possible relationship between
exposure to aluminum and the incidence of
neurodegenerative diseases such as Alzheimer's disease.
Research at NHEERL on aluminum is directed at
understanding the possible mechanisms by which
aluminum may be neurotoxic. Publications by Gilbert
and Shafer, "In Vitro Exposure to Aluminum" and Mundy
et al., "In Vitro Aluminum Inhibition" describe potential
cellular and molecular sites of action, and provide clues
as to the types of effects that aluminum may have on
brain function.
40
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
ECOLOGY DIVISIONS
Overview of NHEERL Ecology Divisions
There are four NHEERL ecology divisions.
Each division has a geographic and a
scientific focus, as described in Table 21.
Ecology Divisions Overview.
Table 21. Ecology Divisions Overview
DIVISION
Atlantic
Ecology
Division (AED)
LOCATION RESEARCH Focus
Narragansett,
Rl
Gulf Ecology
Division (GED)
Gulf Breeze,
FL
Mid-Continent
Ecology
Division (MiD)
Dutoth, HN
Gross* He, Ml
(field station)
Marine, coastal, and estuarine water quality.
Develop, and evaluate theory, methods, and data to
understand and quantify better the environmental
effects of anthropogenic stressors on the coastal waters
and watersheds of the Atlantic seaboard.
Areas of research specialization include modeling
cumulative effects of multiple anthropogenic stressors
on coastal ecosystems, development of methods for
assessing the ecological effects of contaminated marine
sediments, and geographic-based ecological
assessments for the Atlantic Coast.
Evaluate ecological conditions of gulf coastal wetlands,
bays, estuaries, and coral reefs,
Develop predictive models that consider the impact of
chemical contaminants, biotechnology products,
disease, nutrients, energy development, and global
warming.
The scale of investigation ranges from microorganism to
watershed/landscape, with particular expertise in
microbial ecology.
Develops methods for predicting and assessing the
effects of {joteiting activities on freshwater ecological
resources;
Ecology
Divisions
The NHEERL environmental
effects research program is
the responsibility of the four
ecology divisions. The
accomplishments of these
divisions reflect their
transition from an ecology-
oriented program to an
environmental effects
program that supports the
risk assessment paradigm.
This section provides a brief
overview of the strategic
context of this program.
ADVANCING KNOWLEDGE FOR A PURPOSE
41
-------
NHEERL FY95 ANNUAL REPORT
ECOLOGY DIVISIONS
EMAP
In addition to the nine research Divisions, NHEERL also
directs the Environmental Monitoring and Assessment Program
(EMAP). EMAP activities cut across the ecology divisions and
include designing a comprehensive environmental research and
monitoring program regarding the condition of ecological
resources; providing the science that enables Federal and State
monitoring data to be combined and extrapolated among and
within monitoring networks; and promoting extensive
involvement of other EPA laboratories, other Federal agencies,
Regional Offices, States, and interested international
communities to ensure a well-coordinated and maximally
leveraged research program.
Research Framework • -=': ,-'
As with all research in ORD, ecological research is focused on
the greatest scientific uncertainties in the risk assessment
process.
Ecological research is central to measuring, understanding, and
predicting the effects from chemicals in natural populations in
terrestrial and aquatic ecosystems. Each ecology division
continues to advance new and improved methods for
identification of chemicals that are potentially hazardous to the
important species of coastal and inland ecosystems.
Ecotoxicology
Advances in clinical risk assessment methods have led to
increased understanding of toxicity mechanisms and of the
extrapolation of effects among species. These advances have
enabled the ecotoxicology program (which requires
extrapolation of test effects to hundreds of important species)
to focus on the development of biological models for chemical
risk assessment. MED will continue the NHEERL emphasis in
ecotoxicology as the other divisions expand their research on
the effects of other anthropogenic stressors. However, as the
following divisional reports demonstrate, all divisions will have
to take advantage of the advancing body of knowledge and
expertise in ecotoxicology (e.g., effects of toxic chemicals in
studies of cumulative impacts of multiple stressors).
Ecological Risk Assessment
The performance of ecological risk assessment poses many
scientific questions that are not usually found in chemical risk
assessment. Regional/landscape ecology is central to providing
the answers to these questions by means of measuring,
understanding, and predicting the effects of nonchemical
stressors on natural populations. WED, GED, and AED
continue to advance and validate knowledge in these areas as
they address problems of ecosystem scale, and formulate and
characterize environmental risks.
The landscape ecology program is developing methods to
"take the pulse" of an ecosystem. These methods are designed
to assess the biodiversity, system integrity, and long-term
sustainability of an ecosystem. They take into account the
importance of temporal variation in extrapolating
experimental findings to real life situations and in predicting
environmental effects on a regional scale.
42
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
Important Scientific Issues
NHEERL FY95 ANNUAL REPORT
ATLANTIC ECOLOGY DIVISION
The AED mission and research acti-
vities support interagency research
priorities in:
• Ecosystem dynamics
• Resource use and management
• Ecosystem research
• Coastal and marine environments
AED scientists published 34 peer-
reviewed research articles, in FY95, that
directly contribute to ORD's primary
responsibility to provide the scientific
foundation for our nation's environ-
mental programs. Some of these
research accomplishments are
presented in this document with regard
to how they address current and
emerging environmental issues and
support EPA's goal of advancing the
science and technology of ecological risk
assessment.
The articles presented in this document
represent only a "moment in time"
owing to the dynamic nature of the
research in AED and elsewhere. Publi-
cation of these significant accomplish-
ments should provide a useful overview
concerning the direction AED is headed
as they work to advance knowledge in
the areas of:
• Ecosystem Health and Integrity
• Ecological Significance and
Extrapolation Ecology
• Integrated Ecological Effects
Assessment (methods and modeling)
• Biological Availability, and Global
Change considerations
Refer to Table 22. AED Issues and
Accomplishments Overview, for a quick
look at some of the major accomplish-
ments of Fiscal Year 1995.
Atlantic
Ecology
Division
The Atlantic Ecology Division
(AED), Narragansett, RI
conducts scientific research
to advance knowledge of the
environmental effects of
anthropogenic stresses on
the coastal waters and
watersheds of the Atlantic
seaboard.
ADVANCING KNOWLEDGE FOR A PURPOSE
43
-------
NHEERL FY95 ANNUAL REPORT
ATLANTIC ECOLOGY DIVISION
FY 1995 Research Accomplishments
Ecosystem Health and Integrity
An ecosystem is an intricate combination of organisms
that interact with their physical and chemical
environments, functioning together as an ecological
unit. The current functional and structural condition
("health" and "integrity") of an ecosystem is the result of
the cumulative effects of natural and anthropogenic
inputs to the system. Ecosystem health and integrity
are not currently well-defined attributes of coastal
systems. In order to better define these attributes,
AED (along with other divisions) has pursued the
development of biological criteria that may be used to
assess the biological integrity of aquatic communities—a
goal not addressed by the physical and chemical water
quality assessment approaches that have been
practiced for decades.
There is a need for research to enhance the process of
characterizing, understanding, and predicting physical,
chemical, and biological conditions caused by both natural
conditions and anthropogenic inputs.
*• Concerning physical conditions, AED scientists
developed an innovative device for characterizing
and predicting the entrainment of sediments
(Abdelrhman et al.).
*• AED scientists performed research to increase
understanding of nitrogen and phosphorus inputs
and cycling in Chesapeake Bay and several selected
tributaries (Boyton et al.).
A major focus of research in FY95 related to
characterizing the accumulation of anthropogenic con-
taminants at several trophic levels in the food chain.
*• AED scientists quantified contaminant
concentrations in two bivalve species (Nelson et al.)
and investigated histological effects of contaminants
in another bivalve (Peters et al.). These studies are
important because they provide a link between
characterizing chemical inputs and understanding
biological effects in lower trophic levels of the food
chain (i.e., water column filter-feeders).
^ AED scientists investigated the uptake of
anthropogenic contaminants at a higher trophic level
in turtles, seals, and dolphins, respectively (Lake et
al. 1994, Lake et al. 1995, Kuehl and Haebler). This
information is important because the accumulation
of contaminants in higher trophic levels provides
information that can be used to estimate the
biomagnification of contaminants that can have
potentially dramatic ecological effects. In addition,
examination of these higher trophic levels may
provide an indication of ecosystem health because
they integrate the effects of lower-level impacts.
44
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
ATLANTIC ECOLOGY DIVISION
Ecological Significance
Research supporting environmental regulation has
evolved from a single-contaminant perspective to one
addressing the ecological risks associated with a variety
of stressors at a number of levels of biological
organization. This evolution has brought environmental
research into the realm of ecology, and the questions
now being asked are of an ecological nature. Significant
uncertainty exists concerning the understanding and
interpretation of the effects of environmental stressors
on ecological systems.
As with other divisions, and their associated research
areas, extrapolation of findings is important in the
developing field of ecological risk assessment. In AED,
significant attention is being paid to questions of
extrapolation ecology. AED research accomplishments in
FY95 laid the groundwork for addressing the issues
surrounding both ecological significance and extrapolation
ecology.
* AED scientists have performed work to increase the
understanding and effectiveness of extrapolation
ecology (e.g., Suter and Vaughan 1984, Suter et al.
1985, Walker 1988, Barnthouse 1987, Gaylor et al.
1992, and others). This research lays the
groundwork for the extrapolation research to be
conducted in ecological significance. Similarly, a firm
foundation of theory and experimentation underlies
the process ecology aspects of this research.
Ecological significance research will advance our
understanding in these areas, thereby reducing
uncertainties currently associated with ecological
risk assessment.
*• AED scientists evaluated the mechanisms involved in
contaminant uptake by brown cells found in
commercially harvested hard clams, and evaluated
the sensitivities of these cells to organic and
inorganic chemicals (Zaroogian and Anderson 1995,
Zaroogian and Voyer, in press). This research
advances knowledge of the characterization of
mechanisms of stressor insult and development of
indicators of ecological effects.
*• AED scientists obtained information through an
analysis of stress protein accumulation in mussels,
which may help to identify tissue systems that are
most susceptible to damage caused by particular
chemical stressors (Sanders et al.). These efforts
support identification of inexpensive and rapid
indicators of biological impact and encourage
additional ecological significance research to
continue to improve the interpretation of such
indicators within an ecological context.
AED research also supported characterization of effects at
higher levels of ecological organization, in order to
strengthen our understanding of the causes and
significance of these higher level effects.
AED scientists found evidence implicating a prokaryotic
parasite in the symptomatic appearance of withering
syndrome, a devastating disease in California's black
abalone, (Gardner et al.). Such species interactions may
play significant roles in exacerbating or mediating the
effects of anthropogenic stressors.
^ AED scientists described some basic life history
traits for the inland silversides, a species of fish
commonly used to evaluate toxicity of marine and
estuarine waters (Gleason and Bengtson, in press).
Using information from that study, a population
dynamics model is being developed at AED with the
goal of understanding the ecological consequences
of endpoint responses observed in the standard
inland silversides toxicity test. This research will lead
to improved interpretive guidance for a number of
EPA and state regulatory programs.
^ AED scientists used population models to evaluate
ecological risks associated with disposal of municipal
sewage sludge at the 106-Mile Deepwater Dumpsite
ADVANCING KNOWLEDGE FOR A PURPOSE
45
-------
NHEERL FY95 ANNUAL REPORT
ATLANTIC ECOLOGY DIVISION
(Munns et al., in press). The results of this work
indicated the potential impacts of sludge disposal to
be minimal for upper-water column species at the
site.
By reducing the uncertainties in interpretation and
prediction of ecological effects, research products such
as these will improve EPA's ability to understand the
risks posed by stressors to coastal systems of the
United States.
Ecological Risk Assessment
The use of a systems approach and an ecological risk
assessment (ERA) perspective is not new to the
research conducted at AED. The ocean dumping
research program used both of these, calling it "hazard
assessment."
*• AED scientists have recently summarized the
research which was conducted during the 1980s as
applied to the disposal of sewage sludge at the
106-Mile Ocean Disposal Site, off the northeast
coast of the U.S. (Paul et al., in press). The research
was based on a risk assessment approach, evaluating
the likelihood of potential ecological and human
health impacts due to the disposal of sludge at the
site. Both exposure and effects assessments were
conducted using a systems approach to formulate
the models for the assessments conducted with
information that was available prior to initiation of
disposal activities. Numerous field studies were
conducted subsequently by EPA and NOAA,
providing information that was used by Paul et al. (in
press) to evaluate the original assessments. Overall
results confirmed the validity of the approach and
the assessments to predict impacts from disposal.
There is a need for ecologically relevant information that
can be used by environmental managers in making
important environmental decisions.
* Ecological risks associated with sewage sludge at the
106-Mile Site were also examined prospectively in a
case study focusing upon population-level responses
(Munns et al., in press). The case study was
described in terms of the EPA's Framework for
Ecological Risk Assessment. A conceptual model was
developed describing the nature of the stressor,
ecosystems potentially at risk, and ecological effects
on resident populations. Analysis procedures drew
upon modeling activities conducted before actual
disposal discussed in Paul et al. (in press). Risks to
the site, associated with the 1988 sludge loading
rate, were generally low, but increased dramatically
when loading was simulated at two orders of
magnitude above that rate. This research illustrates
how ecologically relevant information can be
generated for use by environmental managers in
order to make environmental decisions.
The need for research on ecological indicators is an
important aspect in developing tools for conducting
assessments. Contaminant-related indicators have been
traditionally the most studied ecological indicators.
Indicators of past contamination are important to put the
current condition in context and to estimate trends for
those indicators that have no historical data base.
* AED scientists examined the historical input of
organic contaminants to an urban estuary,
Narragansett Bay, by interpretation of the
sedimentary record (Latimer and Quinn, in press).
They constructed a mass balance model for the
system by comparing sedimentary flux estimates
with directly measured inputs to use as an
interpretive framework for assessing the current
inputs.
46
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
ATLANTIC ECOLOGY DIVISION
Eutrophication is a much discussed, broad-scale
environmental problem in estuarine systems. An
important aspect of developing conceptual models for
addressing this problem is specifying and quantifying the
causal links in the conceptual model along with input and
output across the system boundaries. Construction and
application of systems models permits identification of
major areas of uncertainties.
* AED scientists reported on experimental results
from large marine enclosures, addressing the
transition between phosphorus limitation of primary
production in freshwater and nitrogen limitation in
seawater Oviatt, et al.).
The work of Boyton et al. assembled and analyzed
annual input-export budgets for total nitrogen and
total phosphorus for Chesapeake Bay and three of
its tributaries. The results indicate that direct
relationships exist between annual rates of nutrient
input, water-column and sediment nutrient stocks,
and nutrient losses via burial in sediment and
denitrification. The identified sources of major
uncertainties were in estimates of atmospheric
deposition, contributions of nutrients via
groundwater, and sediment rates used to calculate
nutrient burial rates.
Accurate ecological risk assessments require that
substances causing adverse ecological impacts be
correctly identified and that concentration-response
relationships be based on bioavailable concentrations
for organisms in a community. By using bioavailable
concentrations, ecological impacts can be understood
across sediments and surface waters whose properties
vary spatially and temporally.
Substances that might be causing toxicity in sediments,
in effluents, or in nonpoint sources entering surface
waters can be identified using biologically directed
chemical fractionation (Toxicity Identification Evalu-
ation, TIEs) procedures, or predicted using equilibrium
partitioning-based (EqP) estimates of available
concentration coupled with concentration-response
relationships for organisms. Regulatory needs of EPA
Program Offices, Regional Offices, and states have
been linked to this long-standing research effort.
Publications include both scientific papers and
regulatory documents.
Research to develop and validate TIE procedures for the
marine environment has been in progress for five years. It
has resulted in publications and technical support
documents that permit application of TIE methodologies
to identify the cause of toxicity associated with sediments,
effluents, and surface waters.
* AED scientists describe the use of TIE procedures
developed at AED, using marine fish, invertebrates,
and a plant to identify metals and nonionic organic
chemicals as the cause of toxicity associated with an
industrial and a municipal effluent (Burgess, Ho et
al.). This study illustrates that marine toxicity tests,
TIE procedures, and historical data can be combined
to increase understanding of the ecological risks of
toxic effluents discharged into the marine
environment.
* One concern in conducting TIEs with effluents that
enter marine systems is that effluents consist of
freshwater while receiving waters are saline. Ho et
al. present data demonstrating that addition of brine
to effluents to achieve salinities of receiving waters,
or salinities tolerated by test species, should occur
after sampling, with TIE tests occurring soon
thereafter. Burgess and Morrison describe the utility
of marine clams as organisms for testing the
sublethal effects of sediment-associated contami-
nants. The procedures described in this paper are
ADVANCING KNOWLEDGE FOR A PURPOSE
47
-------
NHEERL FY95 ANNUAL REPORT
ATLANTIC ECOLOGY DIVISION
part of the overall effort to develop TIE test
metrologies for contaminated sediments.
Research on the biological availability ofnonionic organic
chemicals and metals in sediments, and the establishment
of acceptable sediment concentrations for ecological
protection, have been fundamental principal research
components of the sediment quality criteria (SQC)
program for about ten years. This program has produced
sediment quality criteria documents for five nonionic
organic chemicals and a large number of scientific papers
and technical support documents that have been
published by AED and other NHEERL scientists.
*• AED scientists describe the EqP approach as the
scientific basis that justifies the derivation of SQC,
and allows prediction of sediment toxicity for
nonionic organic chemicals (Di Toro et al.). Trace/
and Hansen (in press) also found that infaunal and
epibenthic organisms accumulate similar con-
centrations of nonionic organic chemicals regardless
of feeding habit. This finding is important because it
demonstrates that SQC must be derived to protect
all benthic species, not just infaunal deposit feeding
species. AED scientists have also observed that
metabolic alterations of PCBs in certain marine
organisms resulted in changes in the abundance of
individual coplanar or mono-ortho substituted
congeners (Lake, Haebler et al. 1995).
Recent scientific discoveries have resulted in a better
understanding of the environmental phases that control
the biological availability of environmentally important
metals. This research was detailed in a report in 1995 to
the EPA Science Advisory Board (SAB) on the technical
basis for predicting metal bioavailability in sediments and
deriving SQC for metals and was reviewed by the SAB this
year.
* AED scientists provided evidence to support
previously published EqP-based hypotheses that the
toxicity of metals-contaminated sediments can be
predicted using SEM/AVS ratios and interstitial
metals concentrations (Pesch et al.). These experi-
ments demonstrate that toxicity was absent when
SEM/AVS ratios were
-------
NHEERL FY95 ANNUAL REPORT
ATLANTIC ECOLOGY DIVISION
Global Change Issues (Ozone, UV-B, and the Carbon Cycle)
Ongoing global change research has successfully
addressed aspects of the probable effects of stratospheric
ozone loss resulting in UV-B increases and global warming
on marine ecosystems. This research has addressed how
changes in marine production could modulate changes in
the rate of atmospheric C02 increase (i.e., either amplify
or slow the rate of atmospheric CO2 increase) and thus
affect past and current rates of climate change.
* AED scientists have performed research to address
the issue of potential adverse effects of increased
UV-B due to stratospheric ozone loss, (Vassiliev et
al.). They have demonstrated that even 100%
increases in winter-time UV-B may not adversely
affect the light harvesting efficiency and phyto-
plankton production in productive well-mixed
coastal systems. However, even ambient UV-B
levels may inhibit light harvesting efficiency and
phytoplankton production in clear waters typical of
the open sea.
* NHEERL/AED collaborators have demonstrated that
carbon fixation in major regions of the open sea is
limited by low aeolian flux of iron; therefore past
and future changes in iron flux to the surface ocean
may affect atmospheric CO2 concentrations. Both
the scientific and policy aspects of this important
debate have been addressed (Chisholm).
Major uncertainties exist concerning the understanding of
the global carbon cycle.
* AED scientists have developed (e.g., Bender et al.)
and applied (Keeling, in press; Keeling and Peng, in
press) methods to reduce major uncertainties in the
global carbon cycle by more precisely estimating the
magnitude and trends in biologically mediated
carbon fluxes. This research has demonstrated that
recently the net loss of carbon from the terrestrial
biosphere may be close to zero; thus, carbon losses
due to deforestation must be offset by carbon
accretion elsewhere in the terrestrial biosphere.
Considerable uncertainties remain, but this finding is
recognized as one of the major FY95 accomplish-
ments of the entire U.S. Global Change Research
Program (USGCRP).
ADVANCING KNOWLEDGE FOR A PURPOSE
49
-------
NHEERL FY95 ANNUAL REPORT
ATLANTIC ECOLOGY DIVISION
Table 22. AED Issues and Accomplishments Overview
Ecosystem Health and Integrity
Issue
How may estuarine ecosystems be better
characterized in terms of their response to natural
and anthropogenic stressors?
• Developed an innovative device for characterizing and predicting the entrainment of
sediments.
• Demonstrated nutrient inputs and cycling with respect to nitrogen and phosphorus in
Chesapeake Bay and selected tributaries.
How may the accumulation of anthropogenic
contaminants at various trophic levels in the food
chain be characterized?
* Quantified contaminant concentrations in two bivalve species and provided information
concerning the histological effects of contaminants in another bivalve species.
• Provided information useful for estimating biomagnification of contaminants.
Ecological Significance and Extrapolation Ecology
Issue
What can be done to reduce uncertainty with
respect to the effects of environmental stressors on
ecological systems?
Addressed questions of extrapolation ecology to lay groundwork for extrapolation
research to be conducted in ecological significance.
Evaluated mechanisms involved in contaminant uptake and sensitivity of brown cells
found in commercially harvested hard clams.
Provided new information through analyzing stress protein accumulation in mussels to
help identity tissue systems most susceptible to chemical stressor damage.
How can we better understand the causes and
significance of effects at higher levels of ecological
organization?
Found evidence to indicate species interaction as a significant factor in appearance of
anthropogenic stressor related disease.
Provided life history traits for fish species to lay foundation for population dynamics
model.
Evaluated ecological risks to upper-water column species of municipal sewage
dumping.
Integrated Ecological Effects Assessment
Issue
What is the validity of a systems approach and an
Ecological Risk Assessment (ERA) perspective for
performing exposure and effects assessments to
evaluate potential ecological and human health
impacts?
Confirmed validity of original assessments that used ecological and human health
systems approach and ERA to predict effects of sludge dumping.
What is the relevance of conceptual modeling and
EPA's Framework for Ecological Risk Assessment
for predicting population-level responses?
• Illustrated how modeling and EPA's ERA Framework could be used to generate
ecologically relevant information useful to environmental managers.
How can contaminant-related ecological indicators
help us understand past contamination and estimate
future trends?
Examined historical input of organic contaminants to an urban estuary and constructed
a mass balance model.
How can we specify and quantify causal links and
input/output across system boundaries in developing
conceptual models to address eutrophication of
estuarine systems?
Reported on transition between phosphorus limitation (fresh water) and nitrogen
limitation (seawater).
Showed direct relationships between annual nutrient input rate, water column and
sediment nutrient stocks, and nutrient losses via burial in sediment and denitnfication.
Also identified areas of major uncertainty.
50
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
ATLANTIC ECOLOGY DIVISION
Ecological Risk Assessment
Issue
AED Accomplishment
How can toxicity identification evaluation (TIE)
approaches employing biologically directed chemical
fractionation and equilibrium partitioning (EqP) be
used to characterize risks to the marine
environment?
Showed that a combination of marine toxicity, TIE procedures, and historical data can
be used to increase understanding of ecological risks of toxic effluents.
Demonstrated the utility of marine clams for testing sublethal effects of sediment-
associated contaminants.
How can sediment quality criteria (SQC) be derived
to predict sediment toxicity for nonionic organic
chemicals?
Described EqP approach as scientific basis for derivation of SQC and prediction of
sediment toxicity for nonionic organic chemicals.
Demonstrated need to derive SQC to protect all benthic species.
What environmental conditions determine biological
availability of metals in sediments?
Provided evidence to support use of SEM/AVS ratios and interstitial metals
concentration to predict toxicity of metals-contaminated sediments.
Showed that toxicity of a trace metal (bioavailability) in surface waters is dependent on
the physical and chemical form of the metal.
How can changes in marine production modulate
changes in the rate of atmosphere CO2 increases
and thus affect past and current rates of climate
change?
Demonstrated that even 100% increases in winter UV-B may not adversely affect light
harvesting efficiency and phytoplankton production in productive, well-mixed coastal
systems. However, even ambient UV-B levels may inhibit production in clear open sea
waters.
Demonstrated that carbon fixation in major regions of the open sea is limited by low
aeolian flux of iron, thus, past and future changes in iron flux to the surface ocean may
affect atmospheric CO2 concentration.
How can we reduce major uncertainties in the
global carbon cycle?
More precisely estimated magnitude and trends in biologically mediated carbon fluxes.
Demonstrated that net loss of carbon from the terrestrial biosphere may be close to
zero, so that loss due to deforestation must be offset by carbon accretion elsewhere in
the terrestrial biosphere.
ADVANCING KNOWLEDGE FOR A PURPOSE
51
-------
NHEERL FY95 ANNUAL REPORT
GULF ECOLOGY DIVISION
Important Scientific Issues
The goal of GED is to protect and
preserve the living resources of the
Gulf of Mexico and similar environments
by developing scientific procedures to
characterize the ecological condition of
coastal areas, describing causes and
evaluating rates of decline, establishing
datasets and methods to predict future
conditions.
The Gulf of Mexico's ecosystem is large
and diverse. Information about this
system is provided below in Table 23.
Significant Aspects of the Gulf of Mexico.
Issues
Problems, such as the following, are
being identified in the Gulf area with
increasing frequency.
• Fish kills and toxic red tides and
brown tides have increased in number
and severity. More than half of the
shellfish-producing areas along the
Gulf Coast are permanently or
conditionally closed as a result of
contamination from increasing human
and animal populations in coastal
areas.
• Hypoxic zones have been docu-
mented off the Texas and Louisiana
coasts. The largest of these hypoxic
areas was estimated to be greater
than 9,000 km2.
• Gulf shorelines are eroding at rates as
rapidly as 30 m each year. Many of
the environmental quality problems
may result from natural processes as
well as from anthropogenic (human-
induced) pollution or combinations of
stressors, such as variations in climate
and pollution.
Refer to Table 24. GED Issues and
Accomplishments Overview for a quick
look at some of the major accomplish-
ments of Fiscal Year 1995.
Table 23. Significant Aspects of the Gulf of Mexico
Geographic The Gulf itself covers more than 1.6 million km2 and receives water from 33
Area major river systems, 207 estuaries, and the Mississippi River (approximately
two thirds of the contiguous U.S. land mass).
Contains coastal wetlands estimated at two million hectares and represent
about half of all wetlands in the United States.
Coastline is 2,609 km (longer than the Pacific coastline of CA, OR, and WA)
Significant Gulf of Mexico waters and coastal wetlands are essential habitats for many
Wildlife migratory waterfowl, as well as gulls, terns, and otfier shorebirds.,
Endangered and threatened species include:
• Five whale species (four baleen and one toothed whale species)
• Crocodile (loggerhead, green, leatherneck, tiawksblll) ..
• Kemp's Ridley turtles .
• West Indian Manatee - .';'" '," "
Annual fishing yields (over 1.7 billion pounds) of finfish,!
are greater than in South and Mid-Atlantic, Cl*
region combined.
In addition to commercial and
known for its vatu:
Gulf
Ecology
Division
The Gulf Ecology Division
(CED) is responsible for
studying the physical,
chemical, and biological
dynamics of coastal
wetlands, estuaries, bays,
and near-shore marine
environments.
Natural
Resources
ADVANCING KNOWLEDGE FOR A PURPOSE
53
-------
NHEERL FY95 ANNUAL REPORT
GULF ECOLOGY DIVISION
Uncertainties
Protecting unique Gulf resources is a difficult task that is
exacerbated by the lack of complete scientific •
information. In order to reduce these uncertainties and .
maintain public trust in EPA decisions, GED has
continued to provide national environmental scientific
leadership through the following four activities.
FY 1995 Accomplishments
Developing test methods
Identifying and applying biological indicators
Developing and validating predictive models
Investigating microbial ecology
The following pages present GED's accomplishments that address areas of uncertainty as they relate to important
national and regional issues.
Developing Test Methods
Biologically and ecologically meaningful test methods are
needed to reduce uncertainty in the use of single-species
toxicity tests concerning potential hazards of toxic
chemicals, pesticides, and genetically modified organisms.
Current test methods in marine systems rely on deter-
mining the effects of high-dose, short-time exposure to
chemicals on the mortality of a few selected species of
individual organisms during their most sensitive life
stages.
Methods are needed for determining the effects of complex
chemical mixtures, under chronic, intermittent, and other
exposure regimes. There is also a need for information on
the toxicities of novel stressors, such as microbial pest
control agents, on nonstandard test species and on
populations and communities of organisms are also needed
to provide realistic hazard assessments. Significant scientific
uncertainty exists when using such data to predict the
effects of exposure of aquatic organisms to complex
chemical mixtures, low concentrations of toxicants over long
periods of time, and effects at the population, community,
and ecosystem levels of biological organization. Similar, if
not greater, scientific uncertainties exist in conducting
hazard assessments of novel stressors, such as microbial
pest control agents, on marine systems.
* GED scientists developed and evaluated toxicity test
methods for estuarine organisms, which included
screening for adverse effects at the organism (survival
and reproduction), population (competition for space),
and community (recolonization) level.
*• GED scientists initiated development of a reproductive
bioassay based on immunochemical detection of P-
glycoprotein.
*• GED scientists studied the effects of scale (container
size as related to the toxicity of pesticides and benthic
community colonization) reporting that minimal size
requirements were necessary to ensure reliable
colonization to benthic community.
*• GED scientists provided information concerning
standard and innovative statistical techniques for the
extrapolation of limited toxicity data to alternate
species and alternative test concentrations of
contaminants.
Environment-modifying factors can have important effects
on the sensitivity and life history characteristics of the
important test species, marine mysids.
* GED scientists performed research to determine
optimal temperature and salinity ranges for the marine
mysid. This information will be used to increase the
54
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
GULF ECOLOGY DIVISION
efficiency of culturing and development of more
reliable test methods for this important test species.
*• In a similar study, GED scientists analyzed effects of
water temperature on shrimp maturation and
spawning in order to improve culture and testing
performance.
*• GED scientists emphasized the use of aquatic plants to
monitor environmental change. Use of plants is
important because animal test species are the focus of
most toxicity tests and can lead to incomplete hazard
assessments for toxicants.
*• GED scientists evaluated a new method to detect
Perkinsus marinus disease in oysters. This method may
be the most valuable of those that exist because it uses
all oyster tissues.
Results of the above studies have advanced knowledge in
the following areas.
• Application of current toxicity tests
• Productivity and reliability of laboratory toxicity tests
• Relevance of the results of environmental hazard
assessments
Biological Indicators of Ecological Condition
The selection and use of bioindicators is very important
because they will be used to quantify the health of a
population or community of aquatic vegetation-fish-shellfish
or of an entire ecosystem. They are useful in diagnosing the
most probable cause(s) of observed abnormalities. They also
provide a means to evaluate the ecological condition of bays,
estuaries, and wetlands of the Gulf of Mexico and similar
system, as well as to determine the sources and causes of
"stressed" systems. The goal is to identify and field-validate
biologically relevant measurements that quantify the health
of a population or community of aquatic vegetation-fish-
shellfish or of an entire ecosystem, with reasonable
certainty.
*• GED scientists monitored the physiological conditions
of oysters (in several studies) in response to
environmental conditions. Effects on digestive tubule
atrophy, defense-related hemocyte activity, and tissue
burdens were analyzed. Generally, histological and
physiological characteristics of oysters are reflective of
the quality of their habitat and can serve as effective
bioindicators.
*• GED scientists investigated the use of fish as sentinel
species, using blood serum collected from various fish
obtained from polluted and unpolluted areas. Studies
have emphasized vitellogenin as a bioindicator of
exposure to environmental estrogens as well as
immunohisto chemistry and serum chemistry tests to
relate chemical exposure to environmental effects.
3£ Future Effects: Results of the above research have been
promising, and » bioassay rnay soonbe developed.
GED scientists found that Rivulus and Medaka fish
appear to provide excellent physiological models for
studying the interacting factors that result in the
development of cardiac neoplasms. It was found that
development of germ cell neoplasms used in
carcinogenesis tests was due more to age than to
chemical exposure with Medaka. It is important to
develop non-mammalian models for elucidation of the
cancer process.
Research was performed by GED scientists to evaluate
selected bioindicator efficacy in large-scale monitoring
programs. Results demonstrated that macro-benthic
community parameters, fish blood chemistry,
eutrophication measures, fish community parameters,
ADVANCING KNOWLEDGE FOR A PURPOSE
55
-------
NHEERL FY95 ANNUAL REPORT
GULF ECOLOGY DIVISION
sediment chemistry and toxicity, stable isotopes, and
frequency and duration of hypoxic events can be used
effectively to indicate the condition of regional
estuarine resources. Numerous alternative bio-
indicators were rejected, at least for the present, as
having limited specificity, high levels of uncertainty
associated with the measurement, or an inability to be
rigorously interpreted.
GED scientists applied bioindicators to assess
environmental condition by using phytoplankton
productivity and dissolved oxygen patterns to evaluate
eutrophication potential in Perdido Bay, FU/AL
Selected fish species (Rivulus marmoratus) distri-
butions were used to examine damage to mangrove
ecosystems caused by global climate change.
Eutrophication is one of the major stressors affecting
coastal resources today. The development of strong
bioindicators that can mimic or predict the advent of
eutrophication through nutrient additions
(productivity) or process-mediated rate changes
(global climate change) provide important tools for our
understanding of the eutrophication process and,
subsequently, strategies to control it.
D!
|[] Development and Validation of Models
GED scientists have performed modeling research
designed to:
• Identify problem areas in the Gulf of Mexico
• Document the ecological effects at multiple levels of
biological organization
• Determine causal factors
• Provide research recommendations regarding the
source(s) of pollution and unacceptable pollution
stressors
• Predict future ecological conditions if circumstances
remain unchanged or if pollution loads are varied
The research effort is divided into the two areas of
effects models and assessment of ecological conditions
across spatial scales.
Effects Models
It is now possible to make reasonable assessments regarding
the direct effects of individual chemicals and pesticides on
a variety of representative aquatic organisms. The
interacting effects of dynamic changes in environmental
conditions, pollution load, and combinations of pollutants
and natural pathogens are largely unknown; and effects,
particularly indirect effects, at the population, community,
and ecosystem levels are difficult, if not impossible, to
predict. Research is directed to resolving some of these
uncertainties.
*• GED scientists developed and validated a new
statistical method to predict chronic toxicity from
acute toxicity data for aquatic life. Chronic toxicity
testing is time-consuming, tedious, and expensive.
Acute testing is rather short in duration, more
tractable, and less expensive. The development of
statistical tools to predict chronic effects from acute
testing will result in savings in time and money because
most toxic effects "observed" in nature are chronic.
These tools will make it easier to identify chronic toxic
effects in natural populations and to separate these
effects for natural variability.
*• GED scientists developed a method for
modelingaquatic toxicity data based on the theory of
accelerated life testing. Benefits of this method include
the integration of effects, dose, and exposure duration
56
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
GULF ECOLOGY DIVISION
in toxicity tests. The statistical procedures were
performed by computer and will reduce the amount of
toxicity testing necessary to characterize the chronicity
of chemicals. They will also provide scientists with a
more accurate procedure for analyzing chemical
effects.
* GED scientists performed research to determine
relative sensitivities of metals and pesticides on mysid
and penaeid shrimps. The scientists found that Mysids
were more sensitive in most cases, but the results
were contaminant-specific.
*• GED scientists performed research to determine the
effects of fungal weed and insect microbial pest
control agents for embryos, larvae and adults of
marine fish and shrimp. The effects, in some cases,
indicated probable negative environmental impact.
•£? Future Effects: Penaeid shrimp are of tremendous importance
to the commercial and ecological welfare of Gulf of Mexico!
ecosystems. Determining the relative toxicities of typical
concentrations of chemical stressors will permit our assessment of
important commercial species using tests that employ common,
easy-to-rear, inexpensive mysids. j
GED scientists demonstrated the relative toxicity of
fuel oil, fuel oil dispersant, and fuel oil-dispersant
mixture by exposing embryos of the inland silversides.
Oil dispersants were more toxic than oil itself when
tested separately, and the fuel oil-dispersant combi-
nation was more toxic than either the oil or the
dispersant alone (however, results were dispersant
specific). These studies illustrate the difficulty in
generalizing toxicity data without an appreciation of
environmental variables.
, this t)f»e of research souW Wcate
which oti aispersant, used alone or in combinations for control of oil
spills, '
Assessment of Ecological Condition
The Environmental Monitoring and Assessment-
Estuaries Program provided a regional assessment of the
health of bays and estuaries of the Gulf of Mexico
(Louisianian Province).
In order to advance the research of the Louisiana Province
study, GED scientists are continuing research to provide
assessments of individual bays and estuaries as well as
individual ecosystems and their components (e.g.,
submerged aquatic vegetation, benthic communities, etc.).
This has led to the emphasis of development, field
validation, and application of biological indicators for
identifying stressed populations, communities, and/or
ecosystems and for the establishment ofbiocriteria.
* GED scientists evaluated the effects of copper-treated
pilings on resident oysters. Results indicate that
copper-treated pilings are a significant stressor to
these bivalves.
*• GED scientists demonstrated that tumors of fish
collected from the Gulf of Mexico and from a
freshwater lake identified the first case of a liver
neoplasm for the common carp. These descriptions of
tumors resulted from the use of wide-scale sampling
to characterize population-level occurrences of
pathologies (Summers et al.). This description of a new
case of pathological incidence, like any first-reported
case, significantly advances our knowledge and
understanding of disease distribution and its
prevalence and importance at a population level rather
than simply at an individual level.
*• GED scientists compared serum chemistries for
brown bullheads collected from polluted and
unpolluted rivers. Of the 20 serum parameters
considered, seven were higher in fish collected from
the polluted area, thus demonstrating usefulness as
biomarkers of ecological condition.
ADVANCING KNOWLEDGE FOR A PURPOSE
57
-------
NHEERL FY95 ANNUAL REPORT
GULF ECOLOGY DIVISION
*• GED scientists were able to leverage the work of
ORD's Environmental Monitoring and Assessment
Program-Estuaries as they modified their approach to
examine the condition of a specific estuary in the Gulf
of Mexico (Perdido Bay) and to postulate designs for
other systems (Mobile Bay, Galveston Bay, Tampa
Bay). The regional assessments of condition provided
the first comparative assessment of estuarine condition
on large regional scales that utilized the same design,
indicators, methods, and assessment statistics.
Regional assessments that permit comparison at
common ecological and geographical scales, using
common indicators, allow us to look at the regional-
relative risk of estuarine resources throughout the
nation. This relative risk permits a baseline from which
to assess change and permits a reasoned process of
allocation of resources that is problem-driven.
Microbial Ecology
Microorganisms are critical to the cycling of C, N, P, S
and many other elements in the environment. The
balance of these cycles is, in turn, critical to supporting
the higher trophic levels composing our wetlands and
other coastal environments. Physical, chemical, or
biological stressors that can upset the balance of these
cycles can present a risk to a stable and productive
environment. Understanding the inter-relationships of
these cycles, the key organisms involved, the response of
organisms to environmental stress, and the effects of
nutrient and chemical cycling are vital to developing
sound measures of risk that can be used to evaluate
environmental problems.
Numerous naturally occurring, complex compounds and
chemicals exist in terrestrial, freshwater, and marine
systems. These natural chemicals and compounds, as well
as anthropogenic chemicals and compounds, undergo
transformation and are biogeochemically cycled within
the biosphere by microorganisms. Knowledge regarding
the rate of degradation, metabolic processes, and identity
of intermediate degradation products is generally lacking,
but is important for assessing the risk and burden of toxic
chemicals to ecological systems.
Elemental Cycling
Understanding the cycling of elements such as mercury in
the environment is essential to defining potential
environmental hazards. Research efforts have contributed
greatly to our understanding of the environmental effects of
mercury. Progress has been made at the environmental,
microorganism, and genetic levels.
+ Research by GED scientists has led to a method that
estimates the level of expression of the merA gene in
environments. This method can be used to estimate
how actively microorganisms are modifying the
chemical form of mercury in the environment and how
these organisms participate in the cycling of mercury.
to pathways for the degradation of hazardous organic chemicals will
revolutionize the study of biological activity in the environment. This
is because it allows us to measure benchmarks for degradation rates
to the actiyeiy-degradlrg organisms.
58
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
GULF ECOLOGY DIVISION
Biodegradation Processes
An understanding of the fate of toxic organic chemicals in
the environment advances research to evaluate the
potential for ecological effects from hazardous wastes.
GED scientists performed research to advance the
understanding of microbial communities and pathways
involved in the degradation of polycyclic aromatic
hydrocarbons (PAHs). Microbiological tools were developed
to investigate chemical availability which relates to both the
potential toxicity of these chemicals and their degradation
or transformation by microorganisms. Determining
bioavailability can result in better estimates of risk to the
environment.
* GED scientists developed a monoclonal antibody
technique to help track organisms that degrade
trichloroethylene. This tool can be used to understand
the environmental behavior of these organisms. In
some cases, the genetic composition of micro-
organisms must be altered to enhance the degradation
process. Detecting and enumerating these genetic
alterations requires very sophisticated procedures.
Chromogenic (color forming) reactions were
developed for monitoring the genetic transfer of
dioxygenase genes among different bacteria. This
enzyme is crucial to initial steps in the degradation of
many mutagenic PAHs.
*• GED scientists performed research to advance
understanding of the non-specific transformation of
chemical components that can occur when chemical
stressors are present as mixtures. In some cases, the
intermediates are more stable and more toxic than the
original mixture.
& Future Effects: Understanding the process leading to these
transformations and characterizing the microorganisms Involved, will
ultimately provide better toots for estimating the environment^ risk
posed by mixtures of hazardous chemicals.
Biotechnology Risk Assessment
Biochemical, physiological and environmental factors
influence survival, fitness, and competitive potential of
genetically engineered organisms (GEMs), introduced
nonendemic organisms, and viruses. Evaluating the
importance of these factors is critical to assessing and
predicting ecological impacts of these organisms.
*• GED scientists assessed the transfer of conjugal
plasmids from GEMs to indigenous microflora and
evaluated the effects of introduced microorganisms on
freshwater, marine, and terrestrial ecosystems in single
species, multispecies, and site-specific microcosms.
This research investigated the potential for transfer of
genes from introduced organisms to indigenous
organisms, environmental factors that can contribute
to the survival of organisms in the environment, and
the construction of suicide genes to limit the survival
of genetically engineered organisms in the
environment.
*• GED scientists developed a very efficient suicide
function based on a lethal E.coli gene. More than 7
orders of magnitude reduction in suicide bacteria has
been achieved in soil. Adding these genes to a
genetically engineered organism would greatly reduce
its ability to survive in the environment and would,
therefore, reduce the risk of using the organisms.
* GED scientists performed research using I6S rRNAto
characterize environmental communities. The
importance of this technique as it relates to under-
standing the composition of microbial communities is
only now becoming apparent. Using this technique,
GED scientists are investigating the composition of
microbial communities involved in nitrogen cycling in
anaerobic environments and how changes in these
communities affect nitrogen cycling and, ultimately, the
viability of submerged aquatic vegetation that inhabit
this environment.
ADVANCING KNOWLEDGE FOR A PURPOSE
59
-------
NHEERL FY95 ANNUAL REPORT
GULF ECOLOGY DIVISION
Table 24. CED Issues and Accomplishments Overview
Test Methods Development
Issue
GED Accomplishment
How may testing methods be advanced in order to
increase confidence in forecasts of potential
ecological hazards?
Developed and evaluated test methods with regard to contaminant effects on estuarine
organisms.
Developed initial steps for creation of a reproductive bioassay using immunochemical
detection of P-glycoprotein.
Increased information on effects of scale on toxicity of pesticides to benthic community
colonization.
Advanced knowledge of standard and innovative statistical techniques for extrapolation
of limited toxicity data to alternate species and various contaminant concentrations.
What are the effects of environment - modifying
factors on important toxicity test species?
• Determined optimal temperature and salinity ranges for increasing efficiency of
culturing and test methods development for the marine mysid.
• Increased information on water temperature effects on shrimp maturation and
spawning.
How may the use of new toxicity test results
enhance laboratory method productivity in
environmental risk assessments?
* Broadened application of toxic risk assessment process by using aquatic plants (instead
of animal species) to monitor environmental change.
* Increased knowledge of the value of a new method for detecting Perkinsus marmus
disease in oysters.
Biological Indicators of Ecological Condition
Issue
GEP Accomplishment
What reliable biological indicators are needed to
evaluate bays, estuaries, and wetlands and to
determine the sources and causes of "stressed"
systems?
Ecological Models for Spatial Scales
Demonstrated the value of oyster histological and physiological characteristics as
effective bioindicators.
Demonstrated the use of Rivulus and Medaka (fish) as excellent physiological models
for neoplasm development.
Demonstrated the value to large-scale monitoring programs of six specific groups of
bioindicators.
Demonstrated the utility of specific bioindicators in evaluating and predicting
eutrophication levels.
Issue
GED Accomplishment
Can effects models be advanced to predict chronic
effects from acute testing?
Developed and validated a new statistical method to predict chronic toxicity from acute
toxicity data.
Developed aquatic toxicity modeling method that reduces required toxicity testing for
chemical characterization and provides more accurate analysis of chemical effects.
Determined relative sensitivity data that allows for extrapolation of metals and
pesticides effects from inexpensive mysid shrimp to important commercial species.
Observed probable negative environmental impact of fungal weed and insect microbial
pest control agents.
Advanced knowledge of the environmental effects of oil dispersants (used for control of
oil spills).
What is being done to develop, field-validate, and
apply biological indicators to identify stressed
populations, communities, and/or ecosystems, and
to establish biocriteria?
Identified copper-treated pilings as stressors to oysters.
Characterized population-level occurrences and proof of the first case of a liver
neoplasm in common carp.
Examined condition of Perdido Bay estuary, building on work of EMAP-Estuanes in
Gulf, and provided first comparative assessment of estuarine condition on large regional
scales using same design, indicators, methods, and assessment statistics.
ADVANCING KNOWLEDGE FOR A PURPOSE
61
-------
NHEERL FY95 ANNUAL REPORT
GULF ECOLOGY DIVISION
Microbial Ecology
Issue
What work is underway to advance knowledge of
the cycling of elements such as mercury in order to
define the potential environmental hazard?
What is being done to advance understanding of
degradation pathways of PAHs in the environment
and to elucidate the chemical bioavailability of
these compounds?
• Developed method to estimate level of expression of merA gene in environments.
• Developed monoclonal antibody technique to help track organisms that degrade
trichloroethylene.
• Developed chromogenic reaction for monitoring transfer of dioxygenase genes among
different bacteria.
• Advanced knowledge of effects of mixtures of hazardous chemicals.
How can we evaluate the importance of
biochemical, physiological, and environmental
factors as a critical part of assessing and predicting
ecological impacts of genetically engineered
organisms (GEMs)?
Assessed transfer of conjugal plasmids from GEMs to indigenous microflora and
evaluated effects of "introduced" organisms to indigenous organisms.
Used 16S rRNA to characterize environmental communities.
Developed very efficient suicide function based on a lethal £. Coli gene.
62
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
MID-CONTINENT ECOLOGY DIVISION
Important Scientific Issues
MED-Duluth strives to develop
mechanistic understandings to
establish cause and effect relationships
for stressors already in the environment
and to predict potential responses of
stressors not yet present or released.
Research at MED-Duluth focuses on
ecotoxicological responses of aquatic life
and wildlife and effects of physical,
chemical, and biological stressors on
freshwater ecosystems. MED projects
range from the investigation of cellular
responses as a means of understanding
the mechanisms of toxic responses to
studies of the influence of watershed
characteristics on the sustainability of
aquatic ecosystems.
Table 25. MED Areas of Investigation lists
research areas of investigation at MED.
MED-Duluth pursues these research
areas to support both prospective and
retrospective risk assessments through
the development of sound methods,
models, and data to screen, diagnose,
and predict ecological effects.
Refer to Table 26. Issues and Accomplish-
ments Overview, for a quick look at some
of the major MED accomplishments of
Fiscal Year 1995.
Table 25. MED Areas of Investigation
Understanding and predicting basic biological and chemical mechanisms of toxicity
Measuring and predicting the uptake, distribution, and elimination of toxic chemicals in aquatic life
and wildlife
Predicting the reproductive and developmental effects of chemical stressors
Predicting the effects of mixtures and/or multiple stressors present in waters and sediments
Characterizing and predicting thes responses of aqumtte eeosysteias to MmttAm.
causes
degr^
Mid-
Continent
Ecology
Division
The Mid-Continent Ecology
Division (MED-Duluth)
provides scientific informa-
tion on ecotoxicological and
freshwater ecological effects
to reduce the uncertainty in
ecological risk assessments
and support risk
management option
selections.
ADVANCING KNOWLEDGE FOR A PURPOSE
63
-------
NHEERL FY95 ANNUAL REPORT
MID-CONTINENT ECOLOGY DIVISION
FY1995 Accomplishments
Mechanisms of Toxicity
Improved understanding of mechanisms of action and
xenobiotic metabolism of industrial chemicals is a critical
need in aquatic toxicology. Advances in these areas are
needed to improve prospective assessments where toxic
effects of untested chemicals must be predicted from
chemical structure and for extrapolating toxic effects
across species. Relationships of chemical structure and
properties to mechanisms of toxic action and xenobiotic
metabolism represent major areas of uncertainty in
ecological risk assessments.
EPA needs to advance its capability of predicting
ecotoxicological effects for risk assessments of new (i.e., the
premanufacturing notice process) and existing chemicals
under the Toxic Substances Control Act (TSCA), for
chemical listing-delisting actions under the Clean Air Act
(CAA) Amendments of 1990, and for identifying the relative
risk of compounds found at hazardous waste and Superfund
sites. EPA's Science Advisory Board has identified prediction
of ecotoxicological effects as essential to improving our
ability to forecast and interpret contaminant
bioaccumulation under regulatory mandates of the Clean
Water Act (CWA). Information and models developed
through such research can help determine appropriate
management and regulatory actions to prevent pollution or
to clean up chemical discharges and waste disposal sites.
*• One of the techniques used to assess modes of toxic
action involves investigations of the joint acute toxicity
of binary chemical mixtures where those chemicals
with similar modes of action should produce additive
responses when combined. MED scientists used this
technique to classify a diverse set of industrial
chemicals into several classes of narcotics and
uncouplers of oxidative phosphorylation (Broderius, et
al.).
Metabolism of a chemical in an organism can also be
critical when enzymatic processes result in by-
products that are more toxic than the original
chemical. Such chemicals can elicit their adverse
effects through a number of different mechanisms.
Recent research by MED scientists on the relationship
between the electronic structure of chemicals and
their activated metabolites is helping to improve our
ability to predict toxic effects. These studies have
addressed approaches to predicting the stability and
formation of reactive intermediates that can be
associated with electrophile reactivity (Mekenyen et al.
"Stability of organic cation intermediates") and
oxidative stress (Bradbury et al., numerous works).
Some chemicals can be activated by processes that do
not necessarily involve the organism's enzymes.
Several classes of chemicals display increased toxicity
in the presence of sunlight (Ankley et al., numerous
works; Monson et al.). MED scientists have
investigated relationships between the electronic
structure of chemicals and their photoinduced toxicity
(Mekenyen et al., numerous works; Veith et al.
"Photoinduced acute toxicity of PAHs"; Veith et al.
"Alph-terthienyl Phototoxicity"). These studies have
shown that "phototoxic" polycyclic aromatic hydro-
carbons (PAHs) can be identified when the energy of
the electrons in the structures is calculated and
interpreted in the context of environmentally relevant
ultraviolet light energies and intensities.
64
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
MID-CONTINENT ECOLOGY DIVISION
Bffja
ijrm Dosimetry
Ecological risk assessments for chemical stressors to
aquatic life and wildlife typically require extrapolating
toxic effects across species and exposure routes and
rates. Consequently, interspecies and dose-response
uncertainty factors must be employed to estimate
responses in the species of concern under varying
exposure conditions. Development of physiologically
based toxicokinetic models seeks to establish a
mechanistically based framework to identify first-order
uncertainties underlying interspecies differences. Such
models predict the uptake, disposition, and elimination of
chemicals based on anatomical, physiological, and
biochemical attributes that are species-specific. In turn,
these models provide important insights toward
improving the scientific credibility of species and dose-
response extrapolations in ecological risk assessments.
Ecological risk assessments for chemical stressors suffer
from a need to advance current interspecies extrapolation
techniques. Such approaches typically rely on the use of
interspecies uncertainty factors in screening level
assessments (e.g., new chemical evaluations under TSCA)
and/or statistical evaluations of relatively large sets of
toxicity data (e.g., aquatic criteria developed under the
CWA). With the increasing attention being placed on top
predators and wildlife, where reproductive and
developmental responses following chronic exposure are of
primary interest, there is a need for increased understanding
of the mechanistic basis underlying interspecies differences.
As a consequence, the need for better understanding of the
accumulation of contaminants and their relation to toxic
effects has been widely recognized. Because testing is not
possible for all relevant species and endpoints, the strategic
use of predictive toxicokinetic models has been identified
and endorsed by the CENR, ORD, the Office of Water, and
EPA's Science Advisory Board, as a sound approach to
reduce interspecies and dose extrapolations.
Mechanisms and rates of uptake, distribution, and
elimination of PCBs in tree swallows were studied by
Nichols et al. because the use of residues in these
organisms is being considered as an indicator of local
sediment contamination. Evaluation of a bioenergetics
model suggests that more research on dietary
composition and food consumption rates is required
before these organisms can be used successfully as a
monitor of sediment contamination levels.
Schmieder et al. evaluated the uptake and elimination
of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-
TCDD) in medaka, a small fish species. These studies
predicted a steady state bioconcentration factor from
water to fish tissue of over 500,000. This value is much
higher than those previously reported in the literature
and suggests a greater risk from accumulated 2,3,7,8-
TCDD than previously estimated.
Nichols et al. developed a technique for visualizing the
output of toxicokinetic models that employs
supercomputing capabilities to communicate the
massive amount of data produced through associated
experimental and modeling studies. This visualization
technique provides a rapid and easily understood
representation of complex toxicokinetic modeling
results.
ADVANCING KNOWLEDGE FOR A PURPOSE
65
-------
NHEERL FY95 ANNUAL REPORT
MID-CONTINENT ECOLOGY DIVISION
Reproductive and Developmental Toxicology
Understanding acute toxic effects of xenobiotics and
developing associated lexicological methods have
significantly improved the means to predict and interpret
the effects of chemicals on aquatic life and wildlife.
However, there is comparatively little information
concerning the responses of organisms during chronic
exposures. Ecological risk assessments are beset by
significant uncertainties in the extrapolation of effects at
the organism level to effects at the population or
community level. MED researchers are working on
development of chronic test methods and establishment
of properly characterized dose-response relationships for
representative species across mechanisms of toxic action.
These techniques and predictive tools will facilitate
extrapolation of ecological effects to higher levels of
biological organization and will provide a basis to assess
interspecies susceptibility.
Increased attention on reproductive and developmental
effects of chemical stressors on aquatic life and wildlife has
prompted ORD to establish a new program to address the
ability of certain classes of compounds to disrupt hormonal
control of reproduction and development. Increased
understanding in this area of ecotoxicology will be
particularly useful for development of water and sediment
quality criteria, registration of pesticides, and evaluation of
new and existing industrial chemicals.
The effects of 2,3,7,8-TCDD on the early life stage
development and subsequent fry survival of lake trout
embryos were investigated in the laboratory by
Walker et al. Routes of exposure included the
translocation of 2,3,7,8-TCDD from the adult female
to oocytes, exposure of fertilized eggs to waterborne
2,3,7,8-TCDD, and the injection of 2,3,7,8-TCDD into
fertilized eggs. Maternal transfer was sufficient to
cause dose-related effects, and there was little
difference in response based on the different routes of
exposure to the eggs.
The effects of several pesticides on the reproductive
success of bluegill sunfish were also investigated via
field methods for conducting and interpreting
reproductive studies using enclosures within portions
of a lake (Tanner and Knuth, Tanner and Moffett).
Tanner and Moffett found that the effects of
diflubenzuron on bluegill sunfish were not the result of
direct toxicity of the chemical but rather were caused
by a reduction in preferred food organisms that were
directly affected. This study demonstrated that
significant effects on aquatic organisms associated with
assessment endpoints in ecological risk assessments
may occur at chemical concentrations lower than
those expected based on laboratory toxicity data for
these species.
Chemical Mixtures And Multiple Stressors
Evaluation of ecological effects in aquatic systems often
includes an assessment of the effects of multiple
stressors. Aquatic life and wildlife are exposed to
complex chemical mixtures in water and sediments that
can cause synergistic, additive, or antagonistic responses.
Effects of chemical stressors can be enhanced or
moderated based on the habitat characteristics of the
organisms. Consequently, understanding the interaction
of chemical and nonchemical stressors is fundamental to
improving both prospective and retrospective ecological
risk assessments. The development and validation of
techniques to identify and characterize chemical-
mediated effects in aquatic ecosystems is also needed to
advance the conduct of scientifically sound retrospective
risk assessments.
66
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
MID-CONTINENT ECOLOGY DIVISION
One of the keys to understanding the effects of chemicals
on the environment lies in the development of
approaches for dealing with the potential effects of
bioaccumulative chemicals in sediments. A significant
research effort has been devoted to improving methods
for conducting and interpreting tests to assess the
ecological effects and bioaccumulation of chemical
contaminants on sediment-dwelling organisms and their
predators. The forthcoming information can be used by
EPA, other governmental agencies, and the regulated
community to help evaluate potential chemical
contamination of sediments and biota and to determine
whether mitigation action is indicated.
One application of these data is to identify acceptable
thresholds or benchmarks for sediment contamination.
These values can be used in prospective risk assessments
under the Clean Water Act to evaluate future and ongoing
chemical releases and in retrospective assessments where
the contribution of chemical contamination to an adverse
ecological condition must be evaluated and cleanup options
compared. For example, sediment quality criteria are being
used in the Superfund program as a component in site-
specific risk assessments.
*• Research conducted by MED scientists continues to
validate current methods of assessing the toxicity of
contaminated sediments. These studies include
comparisons of species sensitivity (Phipps et al.),
evaluations of the equilibrium partitioning method of
predicting responses based on water concentrations
(Hoke, Ankley et al.), and a general review of methods
available for sediment tests (Ingersoll et al. "A review
of methods and applications").
*• Sediment contaminant bioavailability is also critical to
understanding potential impacts. Methods for
measuring contaminants in sediment interstitial water
were developed and evaluated (Ankley and Schubauer-
Berigan "Comparison of the techniques"; Kosian et
al.), as was the role of acid volatile sulfide (AVS) in
binding with metals in sediments (Leonard et al.).
*• The bioavailability and bioaccumulation of chemicals in
sediments and surface waters are also important when
trying to interpret the potential effects of wastewater
discharges. A method to screen for the presence of
chemicals that bioaccumulate in freshwater organisms
was developed by Burkhard and Sheedy and found to
correlate extremely well with environmental samples.
Understanding and predicting the toxicity of chemical
mixtures is a challenge that is still in its infancy. The use of
toxic equivalency factors (TEFs), where the toxicities of
chemicals with a similar mode of action are assumed to be
additive, is being evaluated for chemicals thought to act
through the aryl hydrocarbon (Ah) receptor. These TEFs
provide numerical comparisons of the potency of individual
compounds to that of 2,3,7,8-TCDD. The need to advance
an understanding of the interactive effects of PCBs, dioxins,
and furans has long been recognized by both the scientific
community and regulatory agencies as a central issue in the
ability to assess the ecological risk of these compounds.
TEFs have been developed that are based on ecologically
relevant endpoints for representative species (e.g., embryo
mortality in salmonids). As a result, the means to advance
scientifically defensible techniques to diagnose and to
evaluate cause-effect hypotheses at existing contaminated
locations is now possible, and with it the means of
monitoring and ultimately controlling future point and
nonpoint releases.
*• Newsted et al. and Zabel et al. developed TEFs for
congeners of polychlorinated dibenzodioxins, furans,
and PCBs based on their effect on rainbow trout and
compared the values to those developed for
mammalian species. Although TEFs for dioxins and
furans were similar to those developed for mammals,
the relative potencies of some PCBs were lower in
fish.
Although toxic environmental matrices (i.e., toxic effluents
or sediments) inevitably contain mixtures of chemicals, not
all of these chemicals contribute to any toxicity that might
be expressed. Understanding which chemicals are
contributing to toxicity has been found to be a useful tool for
ADVANCING KNOWLEDGE FOR A PURPOSE
67
-------
NHEERL FY95 ANNUAL REPORT
MID-CONTINENT ECOLOGY DIVISION
EPA's Officer of Water, Regions, States and the regulated
community in evaluating pollution prevention and effluent
treatment options.
* Ankley and Schubauer-Berigan have described toxicity
identification evaluation (TIE) procedures to diagnose
the primary chemical causes of acute toxicity in
sediments (Ankley and Schubauer-Berigan "Sediment
toxicity identification evaluation procedures"). This
technique employs a toxicity-based fractionation
scheme to implicate specific contaminants as causative
toxicants.
The toxicity of some chemicals is also affected by
interactions with chemical and physical properties of the
aquatic environment. The absence of knowledge of these
interactions can confound predictions of chemical effects
and lead to greater uncertainties in pollution control
decisions. An increased understanding of the role these
properties play in determining toxic responses will lead to
better scientific decisions and management actions to
prevent undesirable environmental impacts. These
interactions have been particularly problematic in the
implementation of water and sediment quality criteria.
> The toxicity of some aromatic hydrocarbons is
increased by the presence of sunlight (Ankley et al.,
"Influence of ultraviolet light"; Ankley et al., "Effects of
light intensity"; Monson et al.). Ultraviolet light
activation can increase toxicity in direct proportion to
the intensity and energy of the light. As a result,
toxicity test results for chemicals that can be
photoactivated may be underestimated by several
orders of magnitude when the compounds are
evaluated under normal laboratory lighting.
The toxicity of ammonia can be affected by
temperature and pH because of their effect on the
chemical equilibrium between ionized and unionized
ammonia. Because ammonia is a common sediment
constituent, the influence of pH on the acute toxicity
of ammonia to benthic organisms has been studied
extensively (Ankley et al. "Influence of pH and
hardness"; Schubauer-Berigan et al.; Whiteman et
al.).These recent MED studies showed that, unlike
responses previously reported for other organisms,
the toxicity of total ammonia to a freshwater
amphipod (Hyalella azteca) in soft water was not
influenced by pH.
Water quality characteristics can also affect the toxicity
of metals. Erickson et al. reported the results of an
extensive investigation of factors influencing the
toxicity of copper. They found that while many
parameters (i.e., pH, hardness, dissolved organic
carbon) reduced toxicity, these effects were not solely
a function of copper speciation, as is often cited.
Measuring and
Current attempts at ecological risk assessments and
predictions of the effects of anthropogenic stressors on
natural ecosystems are often made with incomplete
knowledge of the system at risk. Such predictions of effects
that are based on laboratory test results do not include the
influences of habitat modifications or species interactions.
An improved understanding of ecosystem organization and
dynamics is necessary to reduce uncertainty in predicting
effects on aquatic ecosystems. Increased knowledge is also
needed of responses over various time and spatial scales;
of Aquatic Ecosystems
interactions within ecosystems that influence both direct
and indirect effects; and uncertainty associated with using
laboratory data to predict the response of aquatic systems
to chemical, biological, and physical stressors. Such
information is required to determine the degree of exposure
to chemicals that aquatic ecosystems can safely withstand
as well as to evaluate the relative contribution of various
potential stressors on these systems. With greater
knowledge, water resource managers can make decisions to
68
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
MID-CONTINENT ECOLOGY DIVISION
utilize mitigation procedures and resources efficiently where
they will provide the greatest environmental protection.
+ Much of the information currently available to predict
the responses of aquatic ecosystems to chemical
stressors comes from laboratory toxicity tests. Ankley
discussed some of the limitations in extrapolating from
laboratory-based sediment assessment techniques to
the field. Major drawbacks include the limited number
of methods for testing chronic effects and the lack of
a mechanistic understanding of the relationship of
single-species endpoints to population and community
endpoints.
* To investigate the effects of chemicals on freshwater
ecosystems, a method of enclosing portions of a lake
was developed and used to study two pesticides
(Knuth and Heinis, Stay and Jarvinen, Tanner and
Knuth, Tanner and Moffett). These studies related the
fate and distribution of the chemicals to effects on the
ecosystem. Effects occurred directly through toxic
responses as well as indirectly through changes in food
web dynamics.
Watershed Characterization
Ecological risk assessments have traditionally focused on
immediate impacts to single populations or ecosystems
from single chemical stressors. In reality, the sustainability
of aquatic ecosystems in relation to human impacts
depends on the ability of these systems to withstand
and/or recover from multiple anthropogenic and natural
stressors. Because aquatic ecosystems depend on the
exchange of materials and energy from terrestrial,
geologic, atmospheric, and other aquatic systems, the
protection of an aquatic ecosystem is intimately coupled
to protection of the surrounding watershed. Research is
being directed toward understanding the functional
linkages between ecosystem components within
watersheds, the degree to which spatial and temporal
landscape patterns influence aquatic ecosystems, and the
nature of cumulative impacts at the watershed scale.
In addition to chemical stressors, changes in
environmental conditions are important controlling
variables in determining the health of aquatic
ecosystems. A technique for determining the thermal
requirements for freshwater fish based on an extensive
database of field measurements was reported and then
used to evaluate the potential effects of global climate
change on the distribution of 57 species of fish (Eaton
et al. "Estimating fish temperature tolerance"; Eaton
and Scheller). The results indicate that temperature
shifts, as predicted by a doubling of the atmospheric
carbon dioxide concentration, would result in a 50%
reduction in the habitat for cold and cool water fish
throughout the existing range of these species. This
database was also used to help develop and validate a
model that simulates fish habitat in lakes and streams,
as defined by temperature and dissolved oxygen
concentrations (Sinokrot et al.; Stefan, Fang et al.;
Stefan et al. "Fish habitat model"; Stefan et al. "Fishes
in Minnesota lakes").
Wetlands are an important component of watersheds that
are often subject to physical, chemical, and biological
stresses. EPA is concerned with obtaining an improved
understanding of the roles that wetlands serve in
maintaining environmental quality as well as the relative
impacts that various stressors have on these roles.
*• Detenbeck and coworkers found the effects of
physical disturbances on urban wetland water quality
to be related to characteristics of the wetland as well
as to the surrounding land use (Detenbeck "Urban
wetlands"; Detenbeck "Prevention, minimization, and
monitoring"; Detenbeck et al.).
* A study of Great Lakes coastal wetlands by Brazner
and Magnuson found that a combination of regional
ADVANCING KNOWLEDGE FOR A PURPOSE
69
-------
NHEERL FY95 ANNUAL REPORT
MID-CONTINENT ECOLOGY DIVISION
factors (turbidity) and local factors (degree of human
development) influenced the patterns of fish
distribution that can be important to the health of fish
communities in the Great Lakes. Stable isotopes were
found to be useful for characterizing food webs in
these types of systems (Keough et al.).
Other physical and chemical characteristics are important
in aquatic ecosystems because of their impact on the
hydrologic regime of watersheds. For example, improved
knowledge on the extent and impact of extreme hydrologic
events can reduce uncertainties in assessing the risk of
chemical contaminants. The development and
implementation of a modeling approach provides the means
to establish a holistic perspective of a watershed response,
which then facilitates the integration of regulatory programs
to ensure that the most effective and efficient resource
management options are made available to responsible
parties.
*• Evaluation of a model developed as part of a study of
PCB transport from the Fox River (Wisconsin) found
that large storm events are predicted to cause
significant PCB resuspension from sediments with
subsequent export to Green Bay, Lake Michigan
(Velleux et al.).
70
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
MID-CONTINENT ECOLOGY DIVISION
Table 26. MED Issues and Accomplishments Overview
Mechanisms of Toxicity
Issue
•m
How can an understanding of the relationship
of chemical structure and properties to
mechanisms of toxic action and xenobiotic
metabolism be advanced?
Classified a diverse set of industrial chemicals into several classes of narcotics and oxidative
phosphorylation uncouplers using the method of joint acute toxicity of binary chemical
mixtures.
Addressed approaches to predicting stability and formation of reactive intermediates that can
be associated with electrophile reactivity and oxidative stress.
Described relationships between electronic structure of chemicals and their photoinduced
toxicity, and described method of identifying "phototoxic" PAHs.
Issue
How can interspecies extrapolation
techniques be advanced?
• Developed a predictive technique for visualizing the output of toxicokinetic models that
provides a rapid and easily understood representation of complex results.
• Evaluated the uptake and elimination of 2,3,7,8 - TCDD in medaka (small fish species),
revealing a much higher-than-expected bioconcentration factor from water to fish tissue.
• Modeled the uptake, distribution, and elimination of PCBs in tree swallows and used a
bioenergetics approach to evaluate uncertainties in using this species as a bioindicator of
effects in higher trophic levels.
Reproductive and Developmental Toxicology
Issue
MED Accomplishment
How can an understanding of scope and
nature of chemically mediated impacts on
reproduction and development be advanced?
Determined that 2,3,7,8 - TCDD effects on early life stage development and survival of lake
trout via various routes were dose-related, with little difference in response, based on
different exposure routes.
Demonstrated that effects of diflubenzuron on bluegill sunfish were caused by a reduction of
their preferred food source rather than by direct toxicity.
Chemical Mixtures and Multiple Stressors
Issue
How can current toxicity assessment methods
for contaminated sediments be validated?
Compared species sensitivity of benthic organisms.
Evaluated the equilibrium partitioning method of predicting responses based on water
concentrations.
Provided a general review of available sediment test methods.
How can an understanding of sediment
contaminant bioavailability be advanced?
Developed and evaluated methods for measuring contaminants in sediment interstitial water.
Evaluated the role of acid volatile sulfide (AVS) in binding with metals in sediments.
How can the potential effects of wastewater
discharge be interpreted?
Developed and evaluated a method to screen for the presence of chemicals that
bioaccumulate in freshwater organisms.
How can understanding of the interactive
effects of PCBs, dioxins, and furans be
advanced?
Developed toxic equivalency factors (TEFs) for congeners of polychlorinated dibenzodioxins,
furans, and PCBs based on their in vivo effect on rainbow trout and compared the values to
those developed for mammals.
How can methods be improved to identify
and quantify agents in toxic agents in complex
chemical mixtures?
Developed toxicity identification evaluation (TIE) procedure to implicate specific contaminants
as causative toxicants.
How can an understanding of interactions
between toxic chemicals and physical and
chemical properties of the aquatic
environment be advanced?
Found that toxicity of some aromatic hydrocarbons was increased by the presence of sunlight.
Found that toxicity of total ammonia to a freshwater amphipod (Hyalella ozteco) in soft water
was not influenced by pH.
Found that while many parameters reduced toxicity of copper, these effects were not solely a
function of copper speciation, as is often cited.
ADVANCING KNOWLEDGE FOR A PURPOSE
71
-------
NHEERL FY95 ANNUAL REPORT
MID-CONTINENT ECOLOGY DIVISION
Issue
How can the understanding of ecosystem
organization and dynamics, and time and
spatial scales advance the means to predict
aquatic system responses with laboratory
data?
MED Accomplishment
• Presented and discussed some of the limitations in extrapolating four laboratory-based
sediment assessment techniques to the field.
* Related fate and distribution of chemicals to effects on ecosystem in study of two pesticides in
an enclosed freshwater ecosystem.
• Presented a method for determining thermal requirements of freshwater fish. Used method
to evaluate potential effects of global climate change on distribution of 57 species.
* Developed and validated a model that simulates fish habitats in lakes and streams, as defined
by temperature and dissolved oxygen concentrations.
Watershed Characterization
Issue
How can understanding the role of wetlands
in environmental quality maintenance be
advanced?
How can knowledge of the extent and impact
of extreme hydrologic events be used to help
interpret and predict the movement of
chemical stressors?
MED Accomplishment
• Found physical disturbances on wetland water quality to be related to characteristics of the
wetland and to surrounding land use.
• Found that a combination of regional and local factors influenced patterns of fish distribution
that can be important to the health of Great Lakes fish communities.
* Found that large storm events are predicted to cause significant PCB resuspension from
sediments of the Fox River with subsequent export to Green Bay, in Lake Michigan.
72
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
WESTERN ECOLOGY DIVISION
Important Scientific Issues
Terrestrial vegetation
Terrestrial vegetation provides the
basic energy and structure for
terrestrial ecosystems, as well as serving
as our primary source of food, fiber, and
wood products. In the past, we have
considered vegetation to be an easily
regenerated natural resource that was
relatively insensitive to environmental
stress. However, our understanding and
concern for this basic component of the
biosphere is changing. There is increas-
ing concern over large-scale degradation
and loss of biotic diversity in terrestrial
ecosystems, owing partly to factors such
as:
• Regional-scale air pollution
• Climate change
• Large scale displacement of natural
terrestrial ecosystems
• Potential wide spread use of new
generations of highly phytotoxic
chemicals
Regional/landscape view
The focus is changing from the study of
relatively small, individual environmental
units, which were assumed to represent
"typical" classes of ecological systems, to
a closer consideration of the regional/
landscape ecology. Many key ecological
functions occur at interfaces or margins
between different types of ecosystems -
not just within a system. Some examples
include biological, nutrient, and energy
interchanges between estuaries and
their inland watersheds; between wet-
lands and their surrounding uplands; and
within riparian (riverbank) zones
surrounding lakes and streams. In
addition, at larger spatial scales, the
variation of responses within an
ecological unit can be more important
for risk assessment than the average
response of a "typical" system. The
question posed to scientists is often not
"how does a typical lake respond?" but
"which lakes are most sensitive?" or
"which watersheds offer the greatest
potential for wetland restoration?" Even
site-specific decisions, such as permis-
sible daily loadings for widely distributed
water pollutants such as sediments,
require a landscape or regional scale
understanding in order to determine
that action at a particular site will benefit
the watershed or ecosystem as a whole.
Issues .. ;.. . ;"•
Some of today's most important national
concerns also focus on larger and more
complex ecological issues, such as
regional acidification of lakes in the
Adirondacks, nutrient enrichment of
eastern coastal waters, viability of widely
distributed species such as the Northern
Spotted Owl, deterioration of major
waterfowl nurturing grounds areas (e.g.,
the Prairie Pothole region), loss of
biological diversity in the Everglades, etc.
In addition, some of the major social and
economic concerns of the WED region
include the old growth forest and
salmon declines in the Pacific northwest,
massive alteration of the coastal and
inland waters of California, and the
ever-increasing conflict among
competing uses of natural resources in
the intermountain west. All of these
Western
Ecology
Division
The Western Ecology
Division (WED) is responsible
for providing EPA with
national scientific leadership
in terrestrial/plant ecology
and regional/landscape
ecology, as well as a
geographic focus on
reducing uncertainty in the
assessment of risks to the
ecological resources of the
western United States and
the Pacific coast.
ADVANCING KNOWLEDGE FOR A PURPOSE
73
-------
NHEERL FY95 ANNUAL REPORT
WESTERN ECOLOGY DIVISION
issues go well beyond the boundaries of individual
ecosystem types and involve geographic mosaics of
ecosystems or clusters of similar ecosystems.
Uncertainties .
Issues on a larger scale include questions that highlight
the uncertainties in assessing environmental risks to
vegetation at individual and regional levels. Experience
with the National Acid Precipitation Assessment Program
has shown that measuring and predicting the impact of
environmental stresses on vegetative systems is full of
uncertainty. For example, plant responses to stress are
quite variable because of their high degree of genetic
variation and wide range of physiological responses to
environmental conditions. It cannot be assumed that
plants will behave the same under controlled conditions
as in the field. In addition, the long lifespan of some
species, such as trees, tends to mask early expression of
environmental stress and make the cumulative
interactions among multiple stresses more important.
Minor changes in competitive stresses can cause major
shifts in the species composition of vegetative systems.
The timing or sequence of extreme or intermittent
events such as droughts may have greater impact on
vegetation than average conditions. Natural cycles of
vegetative destruction (fire, pestilence, senescence, etc.)
and regeneration are hard to distinguish from
anthropogenic effects.
Scientific questions that derive from these uncertainties
are the target of WED's research efforts. National
scientific responsibilities combine with its geographical
focus to address these major questions that underlie the
protection, use, and restoration of the ecological
resources of the nation's West, including the Pacific
coast.
Refer to Table 27. Issues and Accomplishments Overview,
for a quick look at some of the major accomplishments
of Fiscal Year 1995.
FY 1995 Accomplishments
The following pages present a few of WED's accomplishments that address areas of uncertainty as they relate to
important national and regional issues.
Ozone Considerations
Consideration of the effects of ozone on terrestrial
systems includes issues of stratospheric ozone depletion
(with resultant increases in UV-B) as well as the effects of
increased tropospheric ozone (the most widespread air
pollutant affecting vegetation in the US). WED scientists
have addressed uncertainties in several ozone related
areas by advancing the knowledge of previous research.
Previous greenhouse and growth chamber studies have
shown that UV-B has significant effects on rice, the world's
most important crop species. In FY95 the culmination of
extensive research on the effects of climate change and
enhanced UV-B radiation addressed some of the
uncertainties that exist in the laboratory findings.
*• WED scientists (Olszyk et al.; Olszyk) showed that
enhanced UV-B had no consistent effects on rice yield
under field conditions. The plants may be less
susceptible to UV-B in the field because of the higher
UV-A to UV-B ratios that stimulate cell repair. This
finding suggests that increased UV-B does not pose a
major risk to rice production.
Oceanic phytoplankton are at the base of the oceanic food
chain and are particularly exposed to UV-B radiation
74
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
WESTERN ECOLOGY DIVISION
because of their surface zone habitat. Previous studies
(mostly conducted in laboratory conditions using
photosynthesis or carbon fixation as an indicator of effects)
have shown that UV-B affects phytoplankton.
* To assess maximum UV-B impacts under field
conditions, shipboard experiments were conducted
using Antarctic phytoplankton during the period of the
ozone hole (Sigleo and Neale, Sikorski et at.). Results
indicate that the increased UV-B alters pigment
composition, as expected from laboratory
observations. However, because the effect is mitigated
by cloud cover and mixing of the phytoplankton in the
water column, direct application of lab dose responses
to the Antarctic may overestimate the actual effect.'
The results also show that the primary degradation
product of chlorophyll constitutes up to 50% of the
chlorophyll at the end of a phytoplankton bloom.
Because this degradation product has a similar spectral
signature to chlorophyll, remote sensing may
substantially overestimate production, especially at the
end of blooms.
+ WED scientists (Behrenfeld et al.) tested the effects of
UV-B on nitrate and ammonium uptake by
phytoplankton. UV-B inhibited uptake of both nitrogen
compounds. Because of the specific wavelengths
having the effect, reductions in ammonium uptake will
occur deeper in the water column than reductions in
carbon fixation. Therefore, ecological assessments
based solely on short-term reductions in carbon
fixation may underestimate the extent of damage to
phytoplankton.
Tropospheric ozone also has profound effects on the
rhizosphere, but unlike carbon dioxide, it depresses root
growth and mycorrhizal activity.
*• Scientists at WED used a unique culturing system to
quantify carbon movement in plant systems, including
roots and mycorrhizal fungi, in order to understand
better the mechanisms of ozone effects on the
rhizosphere (Andersen and Rygiewicz; Rygiewicz,
Martin, et al.; Wilson et al.). Tropospheric ozone was
found to alter the movement of carbohydrates in
plants, often reducing the amount of carbohydrate that
is allocated to roots and mycorrhizae. As a result,
seedlings were more susceptible to nutrient and
moisture stress. By adversely affecting the
rhizosphere, ozone impacts on forest ecosystems may
be more widespread than previously noted based on
foliage damage. Moreover, ozone stress may magnify
the effects of predicted higher temperatures and
regional drought (due to global climate change).
Risk Assessment issues
WED scientists continue to advance knowledge in areas
that will reduce uncertainties regarding the ability to
extrapolate experimental findings to real life situations.
They have done this by providing data where gaps exist
and by developing and improving modeling and analysis
methods and indicators.
Uncertainties resulting from spatial variation in climate,
soils, and topography are significant factors limiting our
ability to extrapolate experimental findings to real life
situations and consequently, to predict environmental
impacts at regional scales. Distributed models of physical
and ecological processes are becoming widely used in
ecological research and assessments to account for this
spatial variation. These models often require data to be
interpolated from irregularly scattered measurement sites,
such as weather stations. Interpolation introduces spatially
varying errors that are compounded in model simulations.
ADVANCING KNOWLEDGE FOR A PURPOSE
75
-------
NHEERL FY95 ANNUAL REPORT
WESTERN ECOLOGY DIVISION
*• WED scientists used spatial analysis techniques to
develop a method for characterizing the risk of
tropospheric ozone to regional vegetation in the U.S.
(Hogsett et al. "Ecosystem exposure assessment").
Although ozone is the most widespread air pollutant
that affects U.S. vegetation, its effects on forests vary
regionally. This variation is the result of differences in
wind patterns that carry ozone from urban areas,
differential sensitivity of plant species, and differences
in climate and soil conditions. WED scientists also
developed a Geographic Information System
(GlS)-based technique that combined experimentally
derived response functions and regional environmental
and weather data to simulate long-term growth effects
at a regional scale.
* WED scientists applied spatial analysis techniques to
characterize the risk of global climate change to
forests and forest products. They combined regional
vegetation models and predicted human use of forest
resources to identify regions and timber products that
are vulnerable to global climate change (Cairns et al.
"Forests of Mexico"; Cairns et al. "Carbon dynamics";
Brown, Lennart et al.; Mo et al; Solomon, numerous
works; Silver et al. "Biodiversity and biogeochemical";
Brown). Much of this research was conducted in
support of the Intergovernmental Panel on Climate
Change.
Most contaminants that are released into aquatic habitats
eventually accumulate in sediments where they can
adversely affect benthic ecosystems and/or enter aquatic or
human food chains. Sediments can contain hundreds of
contaminants, but most risk assessments are based only on
the effects of single chemicals.
* WED scientists (Swartz et al.) developed and tested
the "IPAH Model" that predicts the probability of
mortality for mixtures of polynuclear aromatic
hydrocarbons by integrating models for equilibrium
partitioning, QSAR, and toxicity. Comparisons of
model predictions with observed toxicity in the field
showed over 86% correspondence. The model can be
expanded to include other neutral narcotic pollutants.
*• WED scientists tested the accuracy of an equilibrium
model that is widely used by EPA to predict
bioaccumulation of sediment-associated PCBs and
other neutral organics (Boese et al.). This model has
been criticized because it lacks an established degree
of uncertainty in its predictions. Test results indicated
that, while the model would underestimate the
bioaccumulation of certain PCB cogeners, the
differences between observed and predicted tissue
residues were within the range used by the agency and
that the model was sufficiently .accurate for agency
use.
Large-scale patterns in the distribution of habitat (e.g.,
fragmentation) are widely believed to be important for
maintenance of regional biodiversity. However, evidence
for these assumptions is lacking. Scientifically sound
techniques to deal effectively with regional scale ecological
resource questions are still in their early stages of
development.
* WED scientists examined patterns and effects of
wetland loss and degradation in rapidly urbanizing
areas to determine how wetland management impacts
wetland function. By using landscape scale analysis,
they showed that incremental loss of small, individual
wetlands caused a disproportionately large loss of
area-wide plant diversity. (Holland et al.)
Delineating geographic areas of ecological similarity based
on multiple landscape characteristics has become a powerful
tool for evaluating patterns of regional ecological response
and for extrapolating observations from individual sites to
regional scales.
* Continuing the refinement and application of
techniques for defining ecoregions at multiple scales
("Omernik ecoregions"), WED scientists developed a
classification for the western corn belt. This work
advances the scientific basis for establishing
environmental management goals such as water quality
standards. (Griffith et al.).
76
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
WESTERN ECOLOGY DIVISION
Over two-thirds of the carbon in forest ecosystems is
estimated to be in soils and peat deposits. Despite the
importance of forest soils in the global carbon cycle, our
understanding of carbon movement and sequestration in
soils is severely limited.
* WED scientists were among the first to measure
carbon flux directly through all major pools of a
mycorrhizal-coniferous tree system (Andersen and
Rygiewicz; Rygiewicz and Ingham; Rygiewicz and
Andersen). They found that mycorrhizal associations
(symbiotic associations of fungal mycelium with roots
of a higher plant) have a profound effect on the cycling
rate and size of forest carbon pools. The implications
are that if mycorrhizal colonization in forests is
affected by global climate change, the role of forests in
the global carbon cycle could be altered world-wide.
At regional scales, air pollutants-particularly
tropospheric ozone-could also alter rhizosphere
processes to the detriment of forest health.
Detection of trends in environmental conditions is critical for
effective environmental management both in terms of
evaluating the management decisions and in detecting
problems before they become widespread. To detect trends
it is necessary to develop and test indicators of ecological
condition.
+ Separating natural and induced variability of indicators
is a major scientific uncertainty in detecting trends.
Research by WED scientists identified a framework for
evaluating both natural and introduced variability and
their impact on trend detection. The results show
that the dominant forms of variability with which most
ecologists are familiar can be dealt with in a statistically
rigorous way and do not prevent us from effectively
detecting regional ecological trends. (Larsen, et al.)
*• Separating natural phenomena from anthropogenic
perturbations to ecological systems has always been a
challenge. Research by WED scientists demonstrates
that regional surveys using biological indicators can
detect and identify some types of natural events that
have very subtle ecological impacts. Ecological
condition indicators showed evidence of the impact of
the 1991 Mt. Pinatubo volcanic eruption on
temperature and zooplankton species richness in lakes
of the northeastern U.S. (Stemberger et al.)
Forests, grasslands, and agricultural fields are exposed to
increasing levels of anthropogenic stressors acting in
combination with each other. It is not enough to establish
dose-response data for specific stressors and apply them
in an additive fashion to assess risk to vegetation. In
order to predict responses to multiple stressors, we
need a mechanistic understanding of how species
interactions and ecosystem functioning are affected by
multiple stressors.
During fiscal year 1995, WED scientists addressed multiple
stress effects on vegetation associated with global climate
change, elevated atmospheric carbon dioxide, and
tropospheric ozone. Much of this work focused on the
rhizosphere (root zone of the soil), because many of the
processes controlling vegetation response originate there.
*• To determine the sensitivity of major vegetation types
to climate change, WED scientists developed, and
applied for the first time, "transient" models of global
vegetation redistribution (Solomon "Maximum natural
migration rates"; Solomon and Kirilenko; Bugmann and
Solomon). These models simulated the lags associated
with forest dieback, migration, and regrowth as the
earth's climate changes, revealing that over the next
100 years, increasing amounts of carbon could be
added to the atmosphere from accelerated changes in
the distribution of global vegetation. Redistribution
will likely be driven by forest dieback and wildfires.
While large-scale effects may take decades to become
visible, perhaps the most significant mechanism for
carbon release may be taking place in the near-term
changes in the rhizosphere.
Sulfonylurea (SU) compounds represent a new family of
chemical herbicides that work at extremely low application
rates and are rapidly replacing traditional chemicals such as
ADVANCING KNOWLEDGE FOR A PURPOSE
77
-------
NHEERL FY95 ANNUAL REPORT
WESTERN ECOLOGY DIVISION
atrazine and 2,4-D in major agricultural areas of the U.S.
While safer for humans, these chemicals are extremely toxic
to vegetation. Major concerns have arisen over their
potential effects on nontarget plants, both agricultural crops
and indigenous species.
* WED scientists conducted research to determine
vegetation effects of low levels of SU herbicides
(Fletcher et al. "Chlorsulfuron influence"; Fletcher et
al. "Low levels of chlorsulfuron") finding that a single
application of the SU herbicide "Glean" to cherry
trees, at I/100 of recommended field application rate,
caused a significant reduction in fruit production while
having no effect on leaves. Further experimentation
showed that SU herbicides had similar effects on a
range of annual plants, but that traditional herbicides
applied at the same rates had no adverse reproductive
effects.
78 ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY9S ANNUAL REPORT
WESTERN ECOLOGY DIVISION
Table 2 7. WED Issues and Accomplishments Overview
OZONE CONSIDERATIONS
issue
Does elevated UV-B radiation, caused by ozone
depletion, adversely affect rice production?
How can laboratory studies of UV radiation effects
on phytoplankton be extrapolated to assess UV
impact under field conditions?
What are effects of tropospheric ozone on the
rhizosphere?
RISK ASSESSMENT ISSUES
issue
How can experimental findings based on spatial
variation in climate, soils, and topography be
extrapolated to real-life situations?
How can risk assessments based on single-chemical
effects, be extrapolated to sediments that can
contain hundreds of contaminants?
How do patterns in distribution of habitat affect
regional biodiversity?
How can multiple landscape characteristics be used
to evaluate patterns of ecological response?
How can understanding of carbon movement and
sequestration in soil be increased?
What indicators of ecological condition can be
developed to detect problems before they become
widespread?
How are species interactions and ecosystem
functioning affected by multiple stressors?
What are the potential effects of Sulfonylurea
compounds on none-target plants?
•;• *F«iftf,;jf»wwfi'i,f|»iia>f,wif jw»ll*s» - - - . ",-"•:",•,
• Showed that increased UV-B had no consistent effect on rice production under field
conditions.
• Assessed UV-B impacts on Antarctic phytoplankton during the period of the ozone
hole.
• Tested effects of UV-B radiation on nitrate & ammonium uptake by phytoplankton.
• By quantifying carbon movement via a unique culturing system, showed that troposhere
ozone reduces the amount of carbohydrate allocated to roots and mycorrhizae and
thus makes seedlings more susceptible to nutrient and moisture stress.
l/t^iSM^'V*; ^3 ''' si^'« *~\^"^*S /'- '" .' .. " '•*••' • \
'wVKlnt A Jfc?&L»****iiMM*feitmMi'tt .
WtUACCOrnpllSIvM Vents
• Developed method for characterizing risk of tropospheric ozone to regional vegetation
in the U.S.
• Characterized risk of global climate change to forests and forest production.
• Developed/tested "ZPAH Model" that allows for assessment of mixtures of polynuclear
aromatic hydrocarbons.
* Validated accuracy range of a widely-used equilibrium model to predict
bioaccummulation of PCBs associated with sediment.
• Demonstrated use of landscape scale analysis to show regional loss of plant diversity.
• Developed a classification system for the western corn belt.
• By measuring carbon flux through all major pools of a mycorrhizal-coniferous tree
system, determined that mycorrhizal associations have a profound effect on the cycling
rate of forest carbon pools.
• Identified a framework for evaluating natural and induced variability and their impact on
trend detection.
• Demonstrated that regional surveys using biological indicators can detect & identify
some types of natural events.
• Developed and applied novel "transient" models of global vegetation redistribution to
determine multiple stress effects of global climate change and other factors.
How are species interactions and ecosystem functioning affected by multiple
stressors?
• Determined adverse reproductive effects of low level of Sulfonylurea herbicides on a
range of annual plants.
ADVANCING KNOWLEDGE FOR A PURPOSE
79
-------
NHEERL FY95 ANNUAL REPORT
HEALTH DIVISIONS
Overview of NHEERL Health Divisions
There are five health research divi-
sions, all located in Research
Triangle Park, NC. Each division has a
Table 28. Health Divisions Overview
particular focus, as described in Table
28. Health Divisions Overview.
Reproductive
Toxicology
Division
Environmental
Carcinogenesis
Division
Experimental
Toxicology
Division
Human Studies
Division
Neu rotoxrcology
Division
Performs research on the effects of environmental pollutants on
reproduction and development.
Develops biological indices for assessing damage (including germ cell
physiology, morphology, and function), reproductive function,
endocrine function related to reproduction, and teratogenesis.
Major research emphasis on the development of new and improved
methodologies and models for the assessment of male and female
reproductive toxicity, embryo and fetal toxicity, and postnatal
functional deficits.
Performs research on mutagenesis, Carcinogenesis, and related studies
in cellular toxicology including:
• Evaluation of the mutagenic and oncogenic potential of agents of
environmental concern. Includes evaluation of pure chemicals and complex
environmental mixtures through incremental application of bioassay
methodologies
• Development of improved risk assessment procedures
* Application of biomarkers to environmental health studies
• Application of structure activity methods (SAR) to environmental toxicology
Performs research to determine the health effects of inhaled
environmental pollutants, and cause and effects relationships at
pollutant concentrations that mimic those occurring in the
environment.
Intense investigations center on the pulmonary and cardiovascular
systems, the immune system, host defense mechanisms against
infectious and neoplastic disease, and other extrapulmonary systems
that are also susceptible to inhaled pollutants.
Conducts clinical and epidemidogJcat tnvestSgatfons to improve the
understanding of human health risks associated with environmental
animals or in vitro systems.
pulmonary,
other divisions.
means to enable the prediction of whether & environmental agent
will produce neurotoxicity in humans. Human neurotoxic disease is
modeled in laboratory animals, and data are collected in animals to
make predictions about possible neurotoxic risks in humans. Studies
range from the whole organism to the molecular level and include
neurobehavioral, neurochemtcal, neurophysiological, and
neuroanatomicaf approaches.
Health
Divisions
The NHEERL health effects
research program is the
responsibility of the five
health divisions. The
accomplishments of these
divisions reflect their support
of the risk assessment
paradigm. This section
provides a brief description
of the divisions and an
overview of the important
areas of focus and
coordination within the
health program.
ADVANCING KNOWLEDGE FOR A PURPOSE
81
-------
NHEERL FY95 ANNUAL REPORT
HEALTH DIVISIONS
NHEERL is recognized for its interdivisional, multi-
disciplinary approach to many research situations. The
unique expertise and facilities at NHEERL provide an
excellent opportunity for a three-pronged approach to
studying environmental health problems, encompassing
the following:
I. In vivo and in vitro laboratory studies
2. Clinical investigations (e.g., controlled human
exposures)
3. Epidemiological research
As an example, much of our understanding of respiratory
risks associated with ambient air pollution is the result of
application of this multidisciplinary approach. A variation
of this approach has been applied in each health division
and has resulted in improvements in animal-to-human
extrapolations (the "parallelogram" approach).
Research Framework
NHEERL health research is structured around the risk
assessment paradigm as applied in two ways. First,
research is conducted to address the generic data gaps
and limitations associated with various components of
the paradigm (e.g., hazard identification, and dose-
response assessment) and, as such, improve the overall
application of each of these components, irrespective of
the class of pollutants being addressed. Second, scientists
in NHEERL also apply the risk assessment paradigm in an
analytical manner to specific environmental problems of
high EPA priority. This analysis delineates the
component(s) for which the greatest uncertainties/data
gaps exist and allows research to be prioritized and
implemented accordingly.
The divisional reports will summarize the development
of a variety of methods, models and pollutant-specific
data that reflect progress in addressing both generic and
problem-specific risk assessment questions. Themes
repeatedly emphasized include the following:
Hazard Identification
Hazard identification research is directed toward the
following areas:
• Developing of better methods for identifying and
detecting adverse health affects
• Validating predictive biomarkers of adverse effects
• Better characterizing of the relationship of adverse
health effects to injury and disease (including the "at
risk" or most susceptible populations).
• Validating in vitro models and SAR approaches for
toxicity screening and identifying putative mechanisms
of toxicity
Dose-Response Assessment
Dose-response research investigates the nature of
normal, injured, or diseased processes. Information from
this research allows for the derivation of more
biologically based dose-response (BBDR) models that are
more relevant for quantifying human risk. Use of these
models reduces uncertainty in the assumptions that are
applied in the risk assessment process.
Pharmacokinetic data and models are important in BBDR
modeling because they delineate the processes and
factors that determine pollutant uptake and the
relationship between applied dose, target dose, and
target organ toxicity. Insights such as these often provide
a starting point for quantifying uncertainty between
species to species, route to route.and high to low dose
extrapolations.
Models of Environmentally-Related Diseases
For various problem areas investigated by the health
divisions, the transition from the hazard identification to
the dose-response assessment research has also been
accompanied by development of models for environ-
mentally-related diseases such as cancer, respiratory
allergies, neurodegenerative disease, and endometriosis.
In a similar manner, efforts have increased to better
identify, characterize and understand especially suscepti-
ble populations including asthmatics, immuno-
compromised individuals, children and the elderly.
82
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
ENVIRONMENTAL CARCINOGENESIS DIVISION
Important Scientific Issues
ECD research is directed toward
developing methods for detecting
cancer-causing agents (carcinogens) and
understanding the mechanisms of envi-
ronmental carcinogens.
EPA carcinogenesis research is con-
ducted within the Environmental Carcin-
ogenesis Division (ECD) of NHEERL.
ECD focuses its research program on
issues, assumptions, and uncertainties in
cancer risk assessment. Advances in
ECD's areas of research will improve
the risk assessment process and provide
a better scientific foundation for
decisions regarding potential environ-
mental carcinogens.
The division's research program includes
the following components:
• Evaluating the oncogenic potential of
environmental agents important to
regulatory offices
• Performing definitive studies on the
activation and detoxification of those
agents
• Improving models used in risk
assessment
• Developing and applying biomarkers
to health studies
• Developing and validating molecular
techniques and short-term tests for
evaluating carcinogenic potential
• Developing structure-activity
relationships (SAR) for predicting
cancer-causing potential and for
hypothesis generation
Refer to Table 30. Issues and Accomplish-
ments Overview, for a quick look at some
of the major ECD accomplishments of
Fiscal Year 1995.
Table 29. ECD Branches
ECD BRANCH Focus
Biochemistry and Development of mechanistically based dose-response models of
Pathology Branch chemical carcinogenesis using computational, chemical, biochemical,
(BPB) biological, and pathological endpoints.
Environmental
Carcinogenesis
Division
The Environmental
Carcinogenesis Division (ECD)
conducts mechanistically-
based research to advance
knowledge of how components
of environmental pollution
contribute to increased
incidence of cancer in the
human population.
Genetic and Cellular
To>tol
(OCTB)
biomarkers that can be used to both human arid :anJma!;s
ADVANCING KNOWLEDGE FOR A PURPOSE
83
-------
NHEERL FY95 ANNUAL REPORT
ENVIRONMENTAL CARCINOGENESIS DIVISION
Cancer is currently the second leading cause of death in
the United States, with over 500,000 cancer deaths
predicted annually. E.J. Sondik (NCI) estimates that the
incidence of cancer has increased by 18% since 1973,
even though the "cure rate" for certain cancers has also
increased dramatically during the same period. Research
over the past decade has provided significant evidence to
associate environmental factors with each of the
multistep processes involved in cancer. Cancer
prevention, therefore, concerns limiting human exposure
to environmental substances that induce or promote the
cancer process. EPA's cancer research is primarily a risk
assessment and cancer prevention program and not a
program targeted toward treatment.
The Agency is currently in the process of revising the
Guidelines for conducting cancer risk assessments and for
the presentation of those risk assessments. Scientists in
ECD have had substantive input into the revision of the
Guidelines. Because of advances in the understanding of
the etiology of cancer, the revised approach to cancer
risk assessment involves weighing all of the available
evidence (e.g., agent's properties, its structure-activity
relationships, its activities in studies related to the
carcinogenic processes, etc.). Thus, hazard identification
and mechanistic studies, like those done in ECD, are key
in weighing the evidence and determining the likelihood
that a particular chemical or environmental exposure will
be carcinogenic to humans. The insight gained from
mechanistic studies provides guidance in generating
further hypotheses for testing and in selecting models to
define the shape of the dose-response curve.
Using a research team-based approach, ECD has
selected a limited number of specific research problems
and focused the group's expertise on solving those
problems. The ECD research program is structured to
provide multi-level input into the risk assessment
process. Division research can be used in both the
hazard assessment and in the dose response evaluations.
The division conducts research that:
• provides techniques and approaches for hazard
assessment, with a particular focus on biomarkers that
can be used in animal models and in humans,
• provides insight into the mechanisms and activities of
specific chemicals, and
• allows for the development of biologically based
models.
In addition to providing information that helps define
approaches of general utility for the hazard and dose
response assessments, division scientists focus on
obtaining information on specific chemicals, classes of
chemicals, or specific environmental exposures that are
of high relevancy to the regulatory offices.
84
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
ENVIRONMENTAL CARCINOGENESIS DIVISION
IT 1995 Accomplishments
Hazard Assessment
As assays are continually being defined, combined, and
improved by research efforts, it is important that
scientifically sound methods for analyzing and interpreting
these assays are available to those responsible for risk
assessment, environmental monitoring, environmental and
resource management, and public policy. Ongoing ECD
research is designed to improve one's ability to interpret
data generated using specific assays.
* ECD scientists worked with national and international
scientists and organizations to define hazard identi-
fication strategies, protocols for the conduct of parti-
cular assays (Clive et al.), approaches to data analysis
(Claxton et al.) and interpretation (Clive et al.), and
approaches and considerations in the development of
risk assessment models (Allen et al.; Dearfield et al.).
*• ECD scientists joined two formal international
collaborations (involving the Commission of European
Communities, the US Environmental Protection
Agency, and the I PCS) that focused primarily on how
bioassay information, including recently developed
approaches, can be used for develop new techniques
to hazard and risk assessment (Allen et al.; Dearfield et
al.; Gichner et al.; Kanaya et al.; Ma et al.; Sandhu
"IPCS"; Sandhu "Results").
*• Because animals and cellular systems used in bioassays
differ in genetic characteristics, metabolism, and
lexicological response from humans, it is important to
clarify both the differences and similarities so that
more appropriate extrapolations and decisions can be
made when using toxicological bioassays. By
incorporating newly developed molecular techniques
with more conventional techniques, ECD researchers
continue to gain insight into assay performance and the
relevancy of specific test system information to the
etiology of cancer. In particular, significant information
has been obtained to improve understanding and
interpretation of SAR-based approaches (Lewis-Bevan
et al.; Richard), bacterial mutation assays (DeMarini et
al., numerous works; Shelton et al.), in vitro
mammalian mutation assays (Clive et al.), and
cytogenetic assays (Afshari et al.; Kligerman and King).
Biomarkers
ECD develops, validates, and interprets cancer bio-
markers of exposure, effect, and susceptibility in order to
detect or predict environmentally induced cancer in
human populations.
Biomarkers can be used prior to epidemiological efforts to
understand issues such as exposure levels, bioavailability,
and potential effects of known environmental carcinogens.
Biomarkers, of course, can also be used to enhance
epidemiological studies. The division has worked to identify
the structures of environmental carcinogenic polycyclic
aromatic hydrocarbon (PAH)-DNA adducts (biomarkers)
that are formed in rodent tissues and has related these
biomarkers to those identified in human populations.
* ECD scientists quantitated time course and dose
relationships in the formation and decay of each
ADVANCING KNOWLEDGE FOR A PURPOSE
85
-------
NHEERL FY95 ANNUAL REPORT
ENVIRONMENTAL CARCINOGENESIS DIVISION
biomarker in exposed rodents and related them to
tumorigenic potential (Ross et al.).
ECD scientists synthesized and chemically
characterized DNA adduct standards for the
commonly used herbicide alachlor for use in future
human biomarker studies of pesticide applicators
(Newsnow et al. "Synthesis and Characterization").
Disinfection By»*j>r«»*f»Ci$;:
In order to continue to provide scientific leadership
regarding safe drinking water, EPA must continue to
advance the knowledge of disinfection by-product
toxicity. ECD has focused on the disinfection by-products
that are known carcinogens, including the chlorinated
acids and dichloroacetic acid (DCA) in particular. The
following paragraphs describe some of the advances
made by ECD scientists in this area.
*• ECD scientists performed research to show that
chlorinated acids affect intercellular communication (in
an in vitro cell culture system) (Benane and House).
This finding suggests that these hepatocarcinogens
could also function as tumor promoters.
*• ECD scientists performed molecular analysis of
mutations induced by DCA in bacteria. This analysis
revealed that there may be some specificity in the type
of point mutations induced (DeMarini "Dichloro-
acetic"). Combined with studies on mutations induced
by DCA in mouse liver tumors, these efforts suggest a
possible genotoxic role for DCA in the cancer process.
* ECD scientists also found that in vivo administration of
DCA suppresses apoptosis in hepatocytes (Snyder et
al.), thus altering the number of cancer cells at risk.
MX ;s known to be a potent microbial mutagen that is
produced during water chlorination.
* ECD scientists showed that MX induced gene
mutations (predominantly of a chromosomal nature)
Biomarkers that identify interspecies sensitivities
(sister-chromatid-exchanges) were applied to
lymphocytes from three species including man
(Erexson et al.), thus providing additional scientific
information used in extrapolation models.
in mammalian cells (in vitro) (Brack et al.). This finding
strengthens the concern that MX may be a potential
mutagen/carcinogen and indicates that it has the
capability to induce multiple types of genetic
alterations.
*• In addition to chemical-specific work, research was
conducted to gain insight into the potential
mutagenicity of drinking water disinfected by
chlorination, chloramination, or ozonation. An
evaluation of relative potency and types of mutations
induced by these complex mixtures was completed
(DeMarini "Drinking Water"). These molecular
analyses indicate that much of the mutagenicity of the
samples could be accounted for by the mutagenicity of
MX, adding further evidence that MX is of potential
concern.
PAHs and their derivatives are toxic components of many
environmental contaminants, including combustion
emissions, creosote, crude oils, and most petroleum
products. ECD research continues to advance the
information available about PAHs.
*• Quantum mechanical studies of the structures and
reactivities of the diol-epoxides of benzo[c]phen-
anthrene were completed and published by ECD
scientists (Lewis-Bevan et al.). For many PAHs, such
products may be principal biologically active
metabolites. ECD scientists determined the relative
ability of dibenze[a,h]anthracene and its metabolites to
86
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
ENVIRONMENTAL CARCINOGENESIS DIVISION
form adducts and transform cells morphologically in
vitro (Nesnow et al. "Morphological Transformation").
ECD researchers also studied a series of environ-
mentally relevant PAHs, and derived a mechanistic
linkage between their ability to form DMA adducts,
mutate oncogenes, and induce tumors in mice.
Chemical Mixtures ,
Environmental exposures are rarely restricted to single
chemicals. Thus, it is imperative that a part of the ECD's
research effort be directed toward understanding and
prioritizing such exposures for human risk evaluation.
A large amount of research has been performed in the areas
of relative potency and complex mixtures using microbial
assays, primarily because of the relative ease of conducting
these experiments.
*• ECD scientists have made modifications and technical
advances directed toward making large numbers of
such comparisons possible (Taylor et al.).
*• Scientists in ECD have also performed molecular
analysis of mutations induced by complex mixtures and
have published results of the attempts to determine
the major mutagenic chemicals in the mixture
(DeMarini et al., numerous works). These studies help
demonstrate the usefulness of molecular mutational
analysis in identifying hazardous environmental
mixtures, identifying the active components, and in
understanding the mechanisms of the active
components.
In addition to using microbial mutagenesis studies to
understand the potential hazards of exposures to chemical
mixtures, ECD has made significant advances in
understanding chemical interactions in in vivo experiments.
Following, are some of the ECD accomplishments in this
area:
+ Demonstrated potentiation of 2,6-dinitro toluene
mutagenicity by coal tar creosote in rats (Chadwick et
al. "Fischer 344 Rats").
*• Demonstrated that the pesticide atrazine has also been
shown to increase the mutagenicity of urine from rats
coexposed to both the pesticide and 2,6-dinitro
toluene (George et al.).
DBI
• - •
Dose Response Assessment (BBDR Models)
ECD studies the chemical, biochemical, molecular, and
biological aspects of environmental carcinogenesis to
develop mechanistically based, biologically based dose
response (BBDR) animal cancer dose response models.
Carcinogens vary in how they initiate, alter, and affect the
stages of the cancer process. Because carcinogenesis is a
complex multistage biological process, chemicals can
increase the incidence of cancer via a variety of separate,
unrelated biochemical mechanisms.
One of the targets of carcinogens is the genes (DMA)
that control cell growth. Another target can be the
biochemical processes that are involved in cell growth,
cell growth regulation, cell signaling, and cell-to-cell
communication. Other targets of chemical carcinogens
may include processes involved in cell toxicity and death,
alterations in hormone levels, effects on receptors
involved in cell growth, effects on enzymes that
metabolize carcinogens, effects on the immune system,
and effects on the cellular repair systems that allow cells
to repair damage caused by carcinogens. Concomitant
ADVANCING KNOWLEDGE FOR A PURPOSE
87
-------
NHEERL FY95 ANNUAL REPORT
ENVIRONMENTAL CARCINOGENESIS DIVISION
with the recognition of these facts has been the
realization that the currently used statistically based
cancer risk assessment models (e.g., the linearized
multistage model) are probably not appropriate for all
types of chemical carcinogens.
DCA ••- ""•-' -'-Cj'.-^>'';'':-,---••:
In addition to the studies mentioned earlier, ECD has
focused on DCA and PAH pollutants for study of BBDR
modeling.
* From these studies, ECD has found that DCA is a
hepatocellular carcinogen in the male and female
B6C3FI mouse and in the male F344 rat.
*• This development has led to a BBDR model for DCA
using mouse tumor studies. ECD scientists have
generated biochemical, immunohistological (Richmond
et al.), and molecular mechanistic data (Snyder et al.)
on the progression of DCA-induced hepatic altered
foci, hyperplastic nodules, adenomas, and carcinomas.
Cell growth-cell proliferation (Carter et al.) and cell
death (apoptosis) parameters (Snyder et al.) were also
determined. This mechanistic data will be
incorporated with the tumor data into a multistage
dose response model for low dose extrapolation. In
order to create a BBDR model for DCA
hepatocarcinogenesis in the rat, ECD scientists
completed a series of studies in the rat with a
prototype carcinogen (Dragan et al., numerous
works).
These studies provide data on cell growth and death
parameters and genetic alterations that can be applied
to the DCA rat BBDR model.
PAH
One of the uncertainties used in the cancer risk assessment
ofPAHs is the assumption that all environmental PAHs are
of equal potency to benzo[a]pyrene (B[a]P).
* In order to reduce uncertainty in this area, ECD
scientists studied the lung tumorigenic potency of five
environmental PAHs in mice and found that the PAHs
ranged in potency from 0.6-1 18 times the activity of
B[a]P (Nesnow et al. "Mechanistic linkage"; You et al.).
*• ECD studies of the linkages between specific lung
DNA adducts, specific mutations in lung tumor
oncogenes, and lung tumorigenic potency induced by
PAHs have shown that there are direct linkages
between specific DNA adducts and induced mutations
in tumor oncogenes (Nesnow et al. "Mechanistic
Linkage") for specific PAHs. A set of DNA
adduct/tumor (dose/response) relationships has been
developed for these five PAHS that can be used in
their risk assessment (Ross et al.). This work provides
a good foundation for the understanding of PAH
carcinogenesis and its application to PAH risk
assessment.
88
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
ENVIRONMENTAL CARCINOGENESIS DIVISION
Table 30. LCD Issues and Accomplishments Overview
Hazard Assessment
issue
How may interpretations of specific
assay data be improved?
Helped to define national and international strategies and protocols to advance hazard identification,
data interpretation, and risk assessment modeling.
Collaborated with scientists at the national and international level to develop new approaches to
hazard and risk assessment using recent bioassay information.
Performed research to advance understanding and interpretation of structure-activity relationship
(SAR)-based approaches, bacterial mutation assays, in vitro mammalian assays, and cytogenic assays.
How can advanced knowledge of
biomarker usage improve the
detection and prediction of
environmentally induced cancer in
humans?
Quantified and related PAY-DMA adducts (biomarkers) in rodent tissue to tumorigenic potential in
terms of time course and dose relationships.
Synthesized and chemically characterized DNA adduct standards for alachlor herbicide.
Advanced knowledge available for extrapolation models (including humans) using interspecies
biomarker (sister-chromatid exchange).
Specific Chemical Information
Issue
What are the cancer-related risks of
water disinfection by products?
Demonstrated that chlorinated acids could function as tumor promoters.
Combined molecular analysis of bacterial mutations and mouse liver tumor research (both DCA-
induced) to suggest a possible genotoxic role for DCA in the cancer process.
Showed that DCA suppresses apoptosis in hepatocytes.
What potential risks are associated
with the chlorination by-product MX?
Showed that MX induces gene mutations in mammalian cells (in vitro).
Evaluated several complex drinking water disinfection mixtures and found that much of the
mutagenicity of these mixtures was attributable to MX.
How can the toxic effects of PAHs and
their derivatives be understood better?
Derived a mechanistic linkage between the ability of PAHs to form DNA adducts, mutate oncogenes,
and induce mice tumors.
What is the usefulness of molecular
mutational analysis in determining the
major mutagenic chemicals in chemical
mixtures?
Demonstrated usefulness of molecular mutational analysis in identifying hazardous mixtures and their
active components' mechanisms of action.
How may in vivo experiments advance
understanding of chemical interactions
that increase mutagenicity?
Demonstrated potentiation of 2,6-dinitrotoluene by coal tar creosote in rats.
Demonstrated increased mutagenicity in rat urine when were co-exposed to atrazine and 2,6-
dinitrotoluene.
ADVANCING KNOWLEDGE FOR A PURPOSE
89
-------
NHEERL FY95 ANNUAL REPORT
ENVIRONMENTAL CARCINOGENESIS DIVISION
Dose Response Assessment
What may be done to develop
biologically based dose response
(BBDR) models for chemical
carcinogens not suited to statistically
based risk assessment models?
• Performed research to provide data on the progression of dichloroacetic acid (DCA)-induced hepatic
altered foci, hyperplastic nodules, adenomas, and carcinomas as well as growth-cell proliferation and
apoptosis parameters.
* Performed studies with a prototype carcinogen that provided data for application to the DCA BBDR
model in rats.
How accurate is the assumption that
all environmental PAHs are equal in
potency to benzo[a]pyrene (B[a]P)?
• Determined potency of 5 PAHs, revealing a range from 0.6-118 times the activity of B[a]P.
Do direct linkages exist between
specific DMA adducts and induced
mutations in tumor oncogenes?
• Demonstrated direct linkage between specific DNA adducts and induced mutations in tumor
oncogenes and developed a set of adduct/tumor relationships for 5 PAHs for use in their risk
assessment.
90
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
EXPERIMENTAL TOXICOLOGY DIVISION
Important Scientific Issues
The Experimental Toxicology Divi-
sion comprises three branches: Pul-
monary Toxicology (PTB), Immunotoxi-
cology (ITB), and Pharmacokinetics
(PKB). Each branch works both inde-
pendently and collaboratively, not only
with the other branches in the Division,
but across divisions in NHEERL and with
scientists in other organizations. Refer to
Table 31. ETD Branch Objectives.
Background
PTB: The overall mission of the
Pulmonary Toxicology Branch is to
provide data derived from animal studies
that complement, extend, and clarify
pulmonary health issues associated with
human exposures to pollutants and
toxicants. These issues derive from the
need to understand better the nature of
injury or disease processes and to
establish a quantitative framework by
which animal data can be used in
assessing human risk.
Physiological approaches to pulmonary
toxicology involve all levels of biological
organization: morphological, cellular,
biochemical, and molecular. In addition,
much attention is paid to interactive
toxicities, both the effects of mixtures of
chemicals and results of combined
exposures to environmental pollutants
and altered host conditions, such as
concurrent infections. A major focus of
this branch has been the development of
animal models of lung disease.
Dosimetric issues have also been
addressed both for gases, such as ozone,
and for particles. Recent efforts have
focused on development of molecular
markers of tissue injury, the role of
endogenous oxidants and antioxidants in
tissue injury, and the development of
animal models for populations with
special sensitivity. Validation of quantita-
tive dosimetric models has also been a
high priority.
Table 31. ETD Branch Objectives
Branch
PTB
Major Objectives
• To investigate the mechanisms of gas and/or particle-induced lung toxicity
• To develop methods and models to improve extrapolation between animals and
humans, between acute and chronic exposures, and from high-dose experimental
scenarios to low-concentration environmentai exposures
from other institutions
ITB
Characterization of irnmunotoxic effects of various chemicals and mixtures
Examination of the mechanisms responsible for immunotoxidty
To understand and describe the f*» of chemkate In the bcdy'. =;.,
Experimental
Toxicology
Division
The Experimental Toxicology
Division (ETD) conducts
research to improve the
scientific basis of risk
assessment for pulmonary
toxicity and immunotoxidty
and to facilitate the use of
pharmacokinetic data in the
risk assessment process. In
addition, ETD assesses liver
and kidney toxicities. In all
cases, both mechanistic and
dosimetric information are
involved.
ADVANCING KNOWLEDGE FOR A PURPOSE
91
-------
NHEERL FY95 ANNUAL REPORT
EXPERIMENTAL TOXICOLOGY DIVISION
ITB: The Immunotoxicology Branch conducts research
directed toward detecting and interpreting the effects of
xenobiotics on the immune system. Suppression of the
immune system increases the risk of infectious and
neoplastic disease. On the other hand, stimulation of the
immune system can result in allergies or autoimmune
disease. There is evidence that a number of
environmental contaminants can modulate the immune
system as immunosuppressants, allergens, potentiators of
allergy, or inducers of autoimmunity. Approximately one-
third of the population suffer from respiratory allergies,
and a third of these have asthma. The incidence of
asthma has increased by 58% since 1970 for reasons that
are not entirely clear, although changes in the
environment have been implicated. Over 200 chemicals
in the workplace have been associated with respiratory
hypersensitivity disorders, and 25% of occupational skin
disease is attributed to allergic responses.
Infectious diseases are the most common illnesses in
man; they affect one out of four people in the U.S. each
year. The direct cost of one such disease, influenza, is
between 3-5 billion dollars annually, and infectious
disease accounts for lost work days in the billions. Several
environmental agents, including environmental tobacco
smoke, ozone, and UV radiation, have been shown to
enhance infections and/or affect immune function in
humans. Animal data suggest that many more agents may
have such effects. The public health and economic impact
of even small increases in infection or allergy could be
enormous.
Approaches to the ITB objectives (refer to Table 31)
involve the development of host defense models to
characterize the consequences of immunosuppression
and animal models for allergy and asthma associated with
exacerbation of an immune response. In addition, the
differential susceptibility of various animal models is being
examined to understand interspecies variability and to
improve our ability to extrapolate from animals to man.
To this end, comparisons have been made between
immune responses of humans and rodents following both
in vivo and in vitro exposure to selected immunotoxicants.
The effort to extrapolate from biochemical and cellular
responses to disease states leads to development of viral,
bacterial, parasitic, and allergic disease models in both
rats and mice, and the identification of biomarkers of
immune system dysfunction.
The exquisite sensitivity of the immune system of the
developing organism to chemical toxicants has been
examined, and efforts have begun to examine physical
stressors, such as UVB, as well. Experiments have been
initiated to determine the mechanisms of immunotoxicity
for selected agents. In assessing the health risk associated
with exposure to pollutants, toxicokinetic studies
examine the processes and controlling/modulating factors
that determine the uptake of a pollutant through the
portal organs, the relationship of the applied dose and
the dose delivered to target tissues, and the relationship
of delivered dose to target organ toxicity. These issues
include considerations of absorption, metabolism,
distribution among organs, storage in tissues, and
elimination. Better understanding of these factors is
needed to help reduce the uncertainty in risk assessment
associated with various extrapolations such as from
species to species, route to route, and low to high dose.
PBK: This group has taken a strongly iterative approach
to conducting disposition and metabolism studies
involving multiple routes of exposure (oral, dermal,
inhalation) that are closely integrated with computer
simulations. The focus has been on prototype classes of
chemicals such as the trihalomethanes, metals, and
dioxins/PCBs. Hazard identification and mechanistic
studies have been carried out on these chemical classes.
Effort has also been directed toward examining issues of
mixtures, including effects of various vehicles on
exposure. Interactive toxicity is being modeled to guide
experimental work better. Recent studies are exploring
the issue of differences in susceptibility between
individuals as well as between different populations.
The major scientific issues addressed and published in the
past year can be grouped into those addressing hazard
identification, dose/response relationships, and
quantitative models.
92
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
EXPERIMENTAL TOXICOLOGY DIVISION
FY 1995 Accomplishments
Hazard Identification
Based on anecdotal reports of human health impairments
and mortality in laboratory animals resulting from common
exposures to off-gassed carpet-derived vapors, a carefully
designed research effort using laboratory animals was
initiated to assess potential adverse effects from
commercially available carpets.
* This work (Tepper et al. "Carpet Samples") focused
on replication of the neurological, irritant, and
mortality effects noted in the anecdotal reports.
Collaborative research by NHEERL and other ORD
scientists characterized the chemistry and microbial
emissions from three "problem" carpets. Exposure of
mice following a carefully controlled experimental
paradigm identical to that reported in the press failed
to reveal any significant adverse effects. These negative
results fail to support the anecdotal reports of acute
toxicity of carpet emissions, but they do not address
the issue of delayed response or hypersensitization
associated with sick building syndrome.
While traditional toxicology focuses on the study of the
effects of exposure to single chemicals, it is clear that most
public exposures to environmental contamination involve
complex chemical mixtures. Both pharmacokinetic and
mechanistic approaches are necessary to disentangle the
issue of mixture toxicology. An example of one such air
pollutant issue of concern regards the conglomeration of
panicles residing in the air we breathe which derives from a
myriad of combustion and natural sources. For example,
mixtures of metals and organic matter associated with
particulate matter (PM) are purported to play an important
role in particle toxicity.
* Recent studies have demonstrated that inhalation of
very small particulate matter (PM 10) is associated with
enhanced morbidity and mortality. ETD researchers
have spent a great deal of effort developing appropri-
ate inhalation exposure systems for experimental
studies in rodents, as well as methods to characterize
the particles to which the animals are being exposed.
One of the most important questions concerning
particle toxicity is the mechanistic basis for the adverse
effects. ETD has suggested that the soluble metals on
the surface of the particles may play a major role in the
observed toxicity. Comparisons of particles from
different emission sources have indicated that those
with higher concentrations of soluble metals are
associated with greater toxicity (Pritchard et al.).
These particles appear to generate reactive oxygen
species that cause or exacerbate the lung damage.
Additionally, this recent work suggests that particulate
matter less than l.S^m in diameter carries more
bioavailable metals and is more toxic than larger
particles which are less likely to enter the deep lung.
The idea that active oxygen plays a causative role in
multiple types of toxicity is becoming generally
accepted. If the role of reactive oxygen species in lung
toxicity can be further substantiated, prophylactic use
and/or treatment with antioxidants has obvious
potential.
Another type of mixture exposure involves combination
of chemical and biological agents. Most asthmatic attacks
involve an allergic component whereby a sensitive
individual is exposed to an allergen that triggers the
classic asthmatic response, bronchoconstriction.
Both the incidence and mortality from asthma have
increased dramatically in the past twenty years, leading to
the suggestion that environmental factors may play a major
role. Because of the allergic nature of most asthma,
inflammation is a key component of the response. Dust
mites are a common allergen associated with asthmatic
attacks. ETD scientists have been able to develop a rat
model for human allergic asthma that mimics the pattern of
ADVANCING KNOWLEDGE FOR A PURPOSE
93
-------
NHEERL FY95 ANNUAL REPORT
EXPERIMENTAL TOXICOLOGY DIVISION
eosinophilic infiltration of the lungs, mucous secretion, and
hyperreactivity to antigens leading to constriction of the
airways.
> Using this model, ETD researchers have been able to
show that rats exposed to NO2, one of the criteria air
pollutants and an important indoor air contaminant,
exhibit enhanced asthmatic responses when exposed
to dust mites (Gilmour et al.). Thus, while exposure to
NO2 by itself does not trigger an asthmatic attack, co-
exposure to a common antigen and an air pollutant
does. Co-exposure to infectious agents and inhaled
chemicals can also lead to toxicity that would not
occur with one in the absence of the other.
* ETD scientists have previously demonstrated that
exposure to ozone increases sensitivity to Strepto-
coccus infection in rats and mice. This effect occurs
because of depression of the pulmonary macrophage
defense system, which allows time for the bacteria to
form protective capsules, thus increasing their
virulence. Pulmonary bacterial infections are a
common health problem that may be aggravated by
exposure to inhaled gases. In fact, phosgene, a highly
reactive toxic air pollutant, has also been shown to
enhance sensitivity to bacterial infection (Selgrade,
Gilmour et al.). This finding has proved crucial in the
current process of setting the Reference
Concentration (RfC) for phosgene.A comparison of
the effects of ozone on human and mouse pulmonary
macrophage activity following both in vivo and in vitro
exposure showed comparable sensitivity between the
two species, suggesting that humans, like mice
exposed to ozone and other air pollutants, may be at
increased risk for bacterial infection.
Dose-Response Relationships
To enable scientists to extrapolate data from animals to
humans, one must know the target dose to the affected
tissue. Ozone, a polluting oxidant to which 100 million
people are exposed at levels above the national standard,
has been difficult to study because it rapidly decays once it
touches biological tissue.
* Using a nonradiolabeled isotope for ozone (I8O), ETD
investigators have devised methods of generating,
sampling, and analyzing an ozone oxidation product in
tissues, cells, and fluids from both animals and humans.
>• ETD scientists (Hatch, Slade et al.) have used this
species-dependent dosimetry procedure to measure
the dose of ozone that affects the deep lung in both
humans and rats. A fourfold higher concentration of
ozone in air was required to achieve the same tissue
dose of ozone in rats as in humans. This discrepancy
apparently occurs because ozone exposure in clinical
studies generally involves a certain amount of exercise;
in contrast, rodents are normally sedentary during
inhalation exposures. In fact, if rats are exercised, the
dose of ozone in the deep lung dramatically increases.
These results imply that data generated from rodent
studies at concentrations higher than the ambient
ozone concentration are indeed relevant to human
exposure scenarios, and do not represent excessively
high levels of exposure.
»• A BBDR model developed by Highfill and Costa
demonstrates remarkable homology of response
between humans and animals over a range of
concentrations and durations. This effect of exercise
on deposition of inhaled materials is likely true for
other gases as well as for particles.
Metabolic constants are key parameters in many PBPK
models. These values are based on an understanding of
biotransformation and elimination pathways of the
chemicals that enter the body.
94
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
EXPERIMENTAL TOXICOLOGY DIVISION
*• Using a PBPK model, ETD scientists have discovered
a novel metabolic pathway involving conjugation of
bromodichloromethane, the most carcinogenic
trihalomethane (THM), with glutathione that leads to
the generation of genotoxic metabolites (Gao et al.).
This pathway has not been detected for chloroform.
This finding has major implications for comparative
toxicity and carcinogenicity of several THMs, which
are key disinfection products of drinking water. It also
supports the continued use of a linearized multistage
model for risk assessment for at least some of the
brominated compounds, while the weight of evidence
suggests that a nonlinear model might be more
appropriate for a nongenotoxic chemical such as
chloroform.
Arsenic is a natural toxic contaminant of drinking water of
concern mostly in Western states. The Agency is trying to
determine if it should establish a maximum contaminant
level (MCL) for arsenic in drinking water and, if so, whether
it should be set below the current interim level of 50 ppb.
Because metabolism of arsenic is the key to its toxicity and
carcinogenicity, ETD researchers are exploring the basis for
the methylation of arsenic, which leads to decreased toxicity
compared to the inorganic forms.
* ETD scientists have demonstrated that sulfur-
containing molecules such as glutathione are required
for the reduction of arsenic in intact cells and are also
required for methylation (Styblo et al. "Mono- and
dimethylation of arsenic"). The critical role of gluta-
thione in arsenic metabolism has major implications re-
garding the role of diet in arsenic toxicity, because diet
determines the availability of glutathione in the blood-
stream. These studies required the development of
analytical strategies for the characterization of arsenic
metabolites in a variety of biological matrices (Styblo
et al. "Methylated metabolites"). The need to speciate
arsenic in biological samples is currently leading to the
development of a PBPK model for arsenic exposure
which will be linked to a BBDR model with predictive
value for arsenic toxicity.
An intensive study has been aimed at estimating human
body burden of dioxins, dibenzofurans, and PCBs
(DeVito et al. "Estimated Human Body Burdens").
These chemicals, for which 2,3,7,8-tetrachloro-p-
dibenzodioxin (TCDD) is the prototype, have been
studied extensively in laboratory animals, fish, and
wildlife. Epidemiological investigations have been
consistent with findings from animal studies, which
indicate that dioxins are carcinogens and repro-
ductive/developmental immunotoxicants. ETD
scientists have explored dose/response relationships to
estimate relative potencies of major dioxin-like
congeners in biological specimens. Subchronic studies
at ETD have determined the relative potencies of 12
interacting congeners in laboratory animals and in
people from both exposed and background
populations. Results of this work have been
incorporated into EPA's Dioxin Reassessment to
calculate the risk posed by levels of dioxin exposure
experienced by the general population.
Quantitative Models
Structure-activity relationships can be extremely useful for
assessing how chemical structure contributes to toxicity.
*• ETD scientists have advanced the development of
quantitative structure-activity relationship (QSAR)
models for compounds that have the ability to bind to
steroid hormone receptors. Waller et al have used
advanced computer modeling techniques at ETD to
design a preliminary model that can predict estrogen
receptor binding affinities for structurally related, and,
recently, diverse compounds. Recently, ETD
researchers have also been able to describe the
structural parameters that underlie binding to the
androgen receptor. These approaches allow rapid
ADVANCING KNOWLEDGE FOR A PURPOSE
95
-------
NHEERL FY95 ANNUAL REPORT
EXPERIMENTAL TOXICOLOGY DIVISION
screening of a large data set to predict which
chemicals may function as endocrine disrupters, by
helping to clarify the relationship between chemical
structure and various possible molecular mechanisms
of action.
A key to developing quantitative models to describe
pharmacokinetic and pharmacodynamic biological processes
is the specification of relevant parameters, such as
organ/tissue weights and volumes, blood flows, chemical
solubility and partitioning properties, metabolic rates, etc.
While some of these parameters are measurable
experimentally or can be taken from the literature, others
must be assumed, based on the best scientific judgment and
the model specifications. Often there are more than twenty
parameters that must be set in a model, so it is critical to
know which are the most important for determining the
model predictions.
»• ETD scientists have demonstrated the use of sensitivity
analysis engineering principles to describe the most
important parameters for PBPK modeling (Evans and
Anderson) of carbon tetrachloride, trichlorethylene,
and more persistent organochlorines, such as dioxin.
ETD scientists have recently developed sophisticated and
predictive dosimetry models using a supercomputer.
Inter laboratory studies have been initiated to validate
immunological tests for use in risk assessment, and a
model to extrapolate from rodent immunotoxicity data
to human health effects has been developed. Interactive
toxicity studies conducted with various VOCs support
the use of the additivity assumption at low doses.
Selected populations of animals representative of the
elderly and the young have been examined for special
sensitivity to environmental chemicals. A state-of-the-art
exposure system has been developed to measure the in
vivo metabolism of volatile compounds. Other recent
ETD studies in the areas of pulmonary toxicology,
immunotoxicology, and pharmacokinetics are reflected
in the complete bibliography below.
96
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
EXPERIMENTAL TOXICOLOGY DIVISION
Table 32. ETD Issues and Accomplishments Overview
Hazard Identification
Issue
ETDAcconii
Can anecdotal reports of acute toxicity of carpet
emissions be supported scientifically?
Performed mouse exposure experiments in collaboration with other ORD scientists
that demonstrated no support for reports of acute toxicity of carpet fibers.
In complex chemical mixtures, what are the
mechanisms of adverse effects for toxic particulate
matter (PM) emissions?
Demonstrated the relationship of soluble metal concentration to toxicity levels in
emission sources, as well as the greater toxicity level of PM less than 2.5 [lm in
diameter.
Do environmental factors play a significant role in
the dramatic increase in asthma incidences and
mortality (co-exposure with antigens) and in
common pulmonary bacterial infections (co-
exposure with infectious agents)?
Dose Response Relationships
Issue
Developed rat model that demonstrated that co-exposure to NO2 and dust mites
caused enhanced asthmatic responses, while exposure to NO2 by itself does not trigger
an asthma attack.
Demonstrated that phosgene enhances sensitivity to bacterial infection and that ozone
exposure may also increase risk of bacterial infection.
ETD Accomplishment
How may the measurement of ozone deposition in
biological tissue be improved to enhance efforts to
extrapolate data and develop models for measuring
ozone effects on humans?
Developed method using "O to derive data to assess species-dependent dosimetry of
ozone and trace the product of its oxidant interaction with biological material.
Using the I8O method, measured dose of ozone that affects deep lung in humans and
rats and showed fourfold higher sensitivity to ozone in humans compared to rats.
Demonstrated through mechanistic studies that the difference in rat and human
sensitivity is due to clinical conditions (exercise during sampling) and that under similar
conditions remarkable homology of response exists between humans and animals over
a range of concentrations and durations.
How may physiologically based pharmacokinetic
(PBPK) modeling be improved through better
understanding of metabolic pathways?
Discovered novel metabolic pathway for bromodichloromethane involving con|ugation
with glutathione that leads to generation of genotoxic metabolites, thus supporting
continued use of linearized multistage risk assessment model for some brominated
compounds.
Characterized arsenic metabolites in a variety of biological matrices in order to
demonstrate that sulfur-containing molecules such as glutathione are required for
reduction of arsenic in intact cells and for methylation, thus providing information
leading to development of a PBPK model for arsenic exposure.
Estimated human body burdens of dioxin-like chemicals based on relative potencies in
subchronic studies in mice.
Quantitative Models
Issue
ETP Accomplishment
What can be done to improve the prediction of
chemicals that may function as endocrine disruptors
and to help clarify the chemical structure-molecular
mechanism relationship of these chemicals?
Developed a quantitative structure-activity relationship (QSAR) model for compounds
that can bind to steroid hormone receptors and described structural parameters that
underlie binding to the androgen receptor, thus providing information to allow rapid
data set screening.
In developing quantitative models, how are the most
relevant parameters specified?
Demonstrated sensitivity analysis engineering principles to describe the most important
parameters for PBPK modeling.
ADVANCING KNOWLEDGE FOR A PURPOSE
97
-------
NHEERL FY95 ANNUAL REPORT
HUMAN STUDIES DIVISION
Important Scientific Issues
A nimal toxicology studies provide the
j\primary means of evaluating the
mammalian toxicity of many environ-
mental pollutants, and provide data for
extrapolation of findings to humans.
However, humans differ from most
laboratory animals in ways that affect
these studies.
• The inter-individual variation within
the human species presents a much
wider range of response to pollutants
than is seen in animal studies.
• Humans have a relatively long life span
compared to laboratory animals and
exhibit a high incidence of chronic
diseases that are not common in
laboratory animals.
Some of these chronic diseases, such as
such as asthma, cancer, arteriosclerosis,
and emphysema, present major public
health concerns in the U.S. Epidemic-
logic studies show that individuals with
preexisting respiratory tract disease
constitute susceptible populations for a
wide variety of airborne ambient and in-
door air pollutants and toxics. There are
over 10 million asthmatics, over 10 mil-
lion chronic bronchitis cases, and several
million patients with emphysema in the
U.S. Next to cardiovascular diseases,
respiratory tract disease exacerbations
are the leading cause of noncancer
morbidity and mortality and account for
billions of dollars of medical expense and
lost productivity.
HSD consists of two branches, the
Clinical Research Branch and the
Epidemiology and Biomarker Branch, to
conduct clinical and epidemiological
investigations to advance the
understanding of human health risks
associated with environmental pollution.
The human studies research program
has excellent facilities at the University
of North Carolina, Chapel Hill, with
state of the art human exposure
chambers and supporting medical and
scientific resources. Through
cooperative agreements with UNC's
Center for Environmental Medicine and
Lung Biology (CEMLB) and Department
of Epidemiology, HSD is able to take
advantage of the school's critical
complementary expertise.
Table 33. HSD Branches, provides a brief
overview of the two HSD branches.
Human
Studies
Division
The Human Studies Division
(HSD) performs research to
provide critical data and
mechanistic information in
order to advance the
scientific basis for human
health risk assessments,
including extrapolation of
animal data to human risk
estimates.
ADVANCING KNOWLEDGE FOR A PURPOSE
99
-------
NHEERL FY95 ANNUAL REPORT
HUMAN STUDIES DIVISION
Table 33. HSD Branches
Clinical Research Branch
Primary Functions
• Monitor and administer exposures
on human subjects (under highly
controlled laboratory settings or
where the evaluation of effects
requires complex laboratory
procedures).
* Perform in vitro studies of human
cells and tissues to advance risk
assessment resources for human
study.
Goals
Determine direct effects of
pollutants on humans
Understand basis by which
pollutants exert their effects
Understand distribution and
kinetics of clearance of
pollutants, especially In the
human respiratory tract
Methods
Measure the deposition, fate, and biological effects of
inhaled gases and particles; pulmonary and
cardiovascular function; neurobehavioral function; and
pulmonary and systemic immunity and host defenses.
Epidemiology and Biomarker Branch
Primary Functions
Study humans in less rigid, more
natural settings, using field studies
Methods
approaches combined with emerging areas of
.
'
100
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
HUMAN STUDIES DIVISION
IT 1995 Accomplishments
Sensitive Subpopulatlons (Asthmatics)
Many environmental laws and public health laws explicitly
require that the most sensitive subpopulations be
protected. Asthmatics are potentially at increased risk for
many inhaled pollutants, especially those that cause
inflammation and cell damage in the airways (e.g., ozone
and particulate pollutants).
Controlled human exposure studies (published several years
ago) indicated that asthmatics are not more sensitive to
ozone than the general population. However, more recent
epidemiology studies suggest that there is a correlation
between increased hospital visits by asthmatics and
increased ozone concentration. This difference may be
because previous controlled exposure studies employed only
very mild asthmatics.
*• HSD scientists have reported that more severe
asthmatics appear to be more susceptible to 0.16 ppm
ozone than normal subjects, as measured by lung
function (Horstman et al.).
*• In addition, HSD scientists demonstrated that allergic
asthmatics exposed to relatively high (0.4 ppm)
concentrations of ozone experience an eosinophilic-
driven inflammation, as opposed to the neutrophil-
driven inflammation shown by normal subjects (Peden
et al.). This study also showed that the upper
respiratory passages of asthmatics who are exposed to
ozone become sensitized so that a subsequent allergen
challenge causes a more severe allergic reaction than
if the asthmatic subject had not been exposed to
ozone.
* In order to determine if this "sensitization" occurs only
at the high levels of ozone experienced in some areas
of the country during the summer (e.g., the southern
California basin), or if even moderate ozone
concentrations can put asthmatics at risk, HSD
performed further studies. Allergic asthmatics were
exposed to concentrations of ozone (0.10 ppm)
slightly below the current standard. There were no
observed ozone-induced decrements in lung function,
and no apparent sensitization in the lower airways to
a subsequent allergen challenge (Ball et al.).
*• HSD scientists demonstrated that asthmatic children
have elevated baseline levels of inflammatory cytokines
in upper respiratory passages, suggesting a reason for
their increased sensitivity to inhaled compounds
(Noah, Henderson, Henry et al.).
These studies provide important information to the Air
Program Office indicating that asthmatics may indeed be
more susceptible to ozone than the general population.
ADVANCING KNOWLEDGE FOR A PURPOSE
101
-------
NHEERL FY95 ANNUAL REPORT
HUMAN STUDIES DIVISION
Respiratory Effects of Ait Pollutants
Many pollutants of concern to EPA are airborne gases or
particles. These substances include "criteria pollutants"
(e.g., ozone, acidic aerosols, particulate pollution), indoor
air organic and biological pollutants, air toxics, and
oxyfuels. The majority of airborne pollutants affect the
respiratory tract primarily and interact with cells and fluid
lining the nasal passages, large and small airways, and gas
exchange region of the lung.
During the post year, HSD has focused on examining the
respiratory effects of three pollutants:
• Methyl tert-Butyl ether (MTBE)
• Particulate Matter < 10 microns (PM10)
• Ozone
MTBE
The 1990 Clean Air Act requires that those areas that do
not attain the National Ambient Air Quality Standard
(NAAQS) for CO must add oxygenates (e.g., MTBE) to
auto fuels. When MTBE-blended fuel was introduced into
Anchorage and Fairbanks, Alaska in November of 1992,
some citizens complained of acute symptoms (e.g.,
headache, nausea, sore throat, eye irritation, etc.), which
they attributed to the presence of MTBE in the gasoline.
HSD scientists performed studies in response to these
complaints (Prah et al.) that demonstrated that humans
exposed to likely ambient concentrations of MTBE in
controlled chamber studies did not report increased
symptoms, changes in objective or cognitive measures,
or physiological changes such as respiratory tract
inflammation. This important study, which won a bronze
medal, was cited by EPA as evidence that pure MTBE
does not cause overt changes in normal healthy
individuals.
PM10 (Particulate Matter <10 microns)
Recent epidemiological studies suggest that particulate air
pollution causes substantial increases in mortality and
morbidity every year in the U.S. However, there has
been no link established between mortality and morbidity
and a specific component of air pollution.
* HSD scientists and their colleagues have been testing
the hypothesis that transition metals (iron, nickel,
vanadium) present in urban air particulate pollution can
cause inflammation and lung cell damage, which, in
turn, contributes to observed morbidity and mortality.
HSD scientists demonstrated a relationship between
the amount of transition metal present on particulate
air pollution from several sources and the ability of
that particulate to generate free radicals and induce
lung damage in animals (Pritchard et al.).
* HSD scientists also characterized and identified
substances present in particulate air pollution that are
capable of binding metals and demonstrated a
relationship between their presence and the amount
of bound metal (Ghio et al.).
Ozone
Nearly all studies of humans exposed to ozone have
examined effects in healthy, young, white male subjects,
leaving open the question of whether this group is
representative of the population as a whole. HSD
scientists have demonstrated that gender and race do not
affect responsiveness to low levels of ozone for
moderate duration exposures (2.66 hours), and that
socioeconomic status and menstrual cycle phase did not
alter pulmonary response to ozone (Seal et al.).
However, this study showed that decreasing
responsiveness to ozone occurs with increasing age. This
"age factor" finding is very important in light of the Clean
Air Act requirement to protect the most sensitive
individuals in the population.
102
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
HUMAN STUDIES DIVISION
Ambient Exposures
In addition to conducting controlled exposure studies,
HSD researchers also investigated the respiratory effects
of pollutants in "real world" settings.
*• HSD scientists collaborated with scientists from
Harvard and Mexico City (Castillejos et al.) in a study
that measured lung function responses of Mexico City
school children who were exposed to ambient air
pollution. The observed magnitude of response of the
children was very similar to the response of young
adults exposed to similar levels of ozone in controlled
exposure studies. Data from such studies can be used
to predict the response of children living in areas with
high ambient levels of ozone.
A collaborative study by HSD, NERL, and UNC
scientists demonstrated that people living downwind
of hazardous waste incinerators in Charlotte, NC,
have neither decrements in lung function nor increased
upper respiratory tract inflammation compared to
matched control populations (Shy et al.). These
findings suggest that products of hazardous waste
incinerators do not cause acute respiratory effects in
nearby populations.
* Progress in environmental epidemiological studies has
been hampered by the lack of methods available for
accurately measuring human exposure and biologically
effective dose (Zenick and Griffith; Lee et al.).
Neither questionnaires nor environmental monitoring have
provided consistent quantitative assessment of pollutant
exposures on an individual or population level. In efforts to
advance epidemiological studies, biomarker methods have
been developed to separate, identify, and quantitate human
exposure to pollutants of concern to EPA, such as polycyclic
aromatic compounds and nitroaromatic compounds. The Air
Office has estimated that these two classes of compounds
contribute significantly to human genetic and cancer risk.
*• HSD scientists have developed biomarker methods for
these compounds, demonstrating that urine
metabolite analysis is a highly sensitive measure of
recent exposure to polycyclic aromatic hydrocarbons
(Mumford et al.). Advancements were also made in
the separation and identification of aromatic and nitro-
aromatic DNA adducts (Zhan et al.; Savela et al.).
Further development and validation of both urine
metabolite and DNA adduct analysis is essential for the
application of these methods in ongoing and future
epidemiological studies of environmental pollutants.
Development of these biomarker methods will provide
the tools necessary to quantitate human exposure and
dose in future air toxics epidemiologic studies.
DNA Adducts /: :
Because cardiovascular disease is one of the major causes
of death in the U.S., it is important to determine if
environmental pollutants are a contributing factor to its
development. In order to investigate the role of air
pollution in cardiovascular disease, we need to
understand molecular mechanisms in the disease process
that may be used to develop biomarkers of dose to the
heart and early molecular markers of damage to
cardiovascular cells.
Of particular interest in this area is the increasing evidence
of a possible link (DNA adducts) between cardiovascular
ADVANCING KNOWLEDGE FOR A PURPOSE
103
-------
NHEERL FY95 ANNUAL REPORT
HUMAN STUDIES DIVISION
disease and cancer. The evidence includes findings that
show that genetic damage and mutations initiate the
formation of both cancer (via alterations in oncogenes and
tumor suppressor genes) and cardiovascular disease (via the
formation of atherosclerotic plaques). The hypothesis that
DNA-adduct forming agents induce both mutations in
cancer-related genes and mutations in the arterial smooth
muscle cells that lead to the formation of atherosclerotic
plaques (pathogenetically comparable to the formation of
small benign tumors in the arteries that clog the blood
vessels) is under investigation.
*• Past HSD research has shown that DMA adduct levels
of smokers are exceptionally high in lung tissue and
even higher in the heart. HSD scientists have recently
found evidence of the presence of elevated levels of
DMA adducts in the smooth muscle layer of
atherosclerotic lesions from abdominal aorta samples
(Izotti et al. "Cancer Biomarkers"). These findings
support the future use of DMA adducts as a biomarker
of dose to the cardiovascular system and a biomarker
of genetic damage to the smooth muscle cells.
Dosimetry of Particles and Cases
Accurate determination of regional dose plays an
important role in understanding mechanisms of adverse
health effects of inhaled pollutants. Dose distribution of
inhaled gases and particles is heterogeneous in the lung,
causing certain local lung regions to receive more doses
than others. This effect is particularly pronounced in
subjects with lung disease, including asthmatics.
Consequently, enhanced local dose may become a
triggering point of biological responses even if the
average lung dose is within the acceptable range.
Although total uptake of ozone into the human lung has
been studied, very little is known about regional deposition
of ozone, which is important because cells residing in
different regions of the lung may have different sensitivities
to ozone. Regional deposition becomes more significant in
susceptible populations because of altered airway
structures.
* HSD scientists characterized ozone uptake in four
different airway regions in normal subjects in vivo
(Gerrity et al.). This characterization advances
knowledge of the dose-response relationship of
inhaled ozone, leading to improved identification of
the sites of potential ozone damage in the airways, and
to better understanding of potential toxic mechanisms.
Traditionally, lung function tests are used to measure
changes in airway caliber following pollutant exposure.
However, minor airway obstructions induced by pollutants
are difficult to detect by conventional lung function tests.
* In order to advance testing in this area, HSD scientists
studied a new aerosol bolus technique with respect to
lung volume, gender, and volume of bolus delivered
(Brown et al.). This study demonstrated the potential
use of this technique to measure small airway
obstructions in humans exposed to air pollutants.
Medical nebulizers are routinely used to deliver aerosolized
medications and challenging agents in human exposure
studies. However, actual aerosol dose delivered to the lung
is usually unknown.
* By measuring the actual dose of aerosol delivered
under a normal continuous operating mode, HSD
scientists demonstrated that the dose delivered to the
mouth was only 1.6% of total dose placed in the
nebulizer (Kim et al.). These findings are useful for
104
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
HUMAN STUDIES DIVISION
advancing the design of airway challenge protocols and
for interpreting bronchial challenge response data.
Certain epidemiology studies suggest that exposure to
paniculate pollution results in thousands of excess deaths
per year. One of the more important issues facing the Air
Office is deciding how much weight to put on these findings.
In order to assess the potential risk of paniculate pollution
to humans, it is critical to understand the deposition
patterns and rate of panicle clearance from the lungs. The
prevailing opinion has been that particles deposited in the
ciliated airways are cleared out from the lung within 24
hours. However, recent studies have challenged this notion
and claimed that particles persist in the large ciliated
airways for some time.
* HSD scientists demonstrated complete clearance of
particles from the large airways of dogs following
intrabronchial deposition, confirming the conventional
understanding of particle clearance kinetics (Lay et al.).
This finding is important for estimating particulate
toxic burden in the lungs of humans exposed to air
pollution.
In developing dose-response relationships, individual
variability factors such as breathing pattern, age, gender,
etc. are usually not accounted for because little is known
about how these factors affect deposition of particles in the
lung.
*• HSD scientists have demonstrated that breathing
pattern and airway resistance are the most significant
factors affecting total lung deposition of fine particles
in normal subjects (Bennet et al.). This study also
reported that age and gender had only minor effects,
which is helpful information for improving models that
predict particle deposition in the lungs of humans.
mgn Biologically Based Dose-Response (BBDR) Models
Information directly relating a particular exposure to
human response is often not available. Therefore,
regulatory standards or risk assessments must frequently
be based upon data from other species or exposure
regimens. BBDR models, which use physiological theory
and mechanistic understanding to characterize exposure-
response relationships, provide a means by which related
data can be used to generate the specific predictions of
human response required for standard setting or risk
assessment.
In particular, BBDR models facilitate general case
predictions, cross-species extrapolation, short-term to long-
term exposure extrapolation, and route-to-route extrapo-
lation. There is a large amount of individual variability in
acute response to ozone exposure, as well as to many other
toxicant exposures. Models that allow for this variability are
not well developed.
* In order to advance these modeling methods, HSD
scientists developed a model that allows description of
individuals responding to ozone exposure as a function
of ozone concentration and exposure duration
(McDonnell et al.). These results are important
because they provide risk models that describe the
number of individuals who are expected to respond
adversely to ozone exposure as a function of
concentration and duration. Such models can be used
in risk and benefit assessment for considering various
regulatory scenarios. In addition, the methods
developed using the available ozone response database
are likely to be useful for describing exposure-
response relationships for other inhaled toxicants.
Carboxyhemoglobin (COHb) formation resulting from CO
exposure can be accurately predicted using the
Coburn-Forster-Kane equation (CFKE), but only if a number
ADVANCING KNOWLEDGE FOR A PURPOSE
105
-------
NHEERL FY95 ANNUAL REPORT
HUMAN STUDIES DIVISION
of physiological parameters are known. These parameters
are usually estimated for static conditions from normative
tables, a laborious and sometimes impossible task.
Physiological parameters are interactively influenced by
exercise, age, body weight, gender, altitude, other
pollutants, and many other factors.
* In order to improve this method, HSD scientists
performed a study (Benignus) in which the CFKE was
incorporated into a pulmonary and blood gas
physiological model found in the literature. The
augmented model allows prediction of approximately
50 physiological and blood gas values (including
COHb), given a continuously changing mix of CO, O2,
and CO2. Exercise, altitude, and physiological
abnormalities are also simulated. This model runs on
desktop computers and permits extremely rapid
prediction of COHb (and some of its physiological
results) without having to resort to tables - even in
complicated exposure conditions.
In vitro toxicology helps to advance the understanding of
pollutant mechanisms and provides a means for animal to
human extrapolation. In humans, the primary target of most
inhaled pollutants is the lung epithelial cell. One of the
problems associated with using in vitro toxicology with these
cells is the difficulty of obtaining the cells on a regular basis.
HSD scientists have significantly diminished this
limitation by demonstrating that an immortalized
human airway epithelial cell line (BEAS2B) retains
many important properties in common with primary
human airway epithelial cells (Noah, Henderson,
Henry et al.). This research, coupled with previous
findings from HSD scientists, has validated the use of
this cell line for studies with air pollutants. Since the
initial reports from HSD, investigators from several
laboratories around the world have now begun using
this cell line for in vitro toxicology.
HSD scientists have also developed a qualitative
extrapolation model, which shows that a combination
of in vitro ozone exposure of animal and human
respiratory tract cells, coupled with in vivo animal
exposure studies, can accurately predict the response
of humans, as measured by host defense endpoints
(Selgrade et al.). A quantitative model is now being
developed that will (upon validation) enable the Air
Program Office to make better use of animal data in
assessing human risk, particularly of those pollutants
for which little, if any, human data are available.
Tepllce Projects Environmental Epidemiologic Studies in an Industrialized Region in Eastern Europe
Severe environmental pollution in the former Soviet
countries of Central and Eastern Europe led to an
international concern that human health in these
countries was at risk. Special funds were appropriated
through Congress to provide technological and scientific
assistance in the assessment and cleanup of the major
sources of pollution. NHEERL had a unique opportunity
to make a major contribution to one of these
environmental projects, the Northern Bohemia-Teplice
Project in the Czech Republic. EPA's objectives were to
assist the Czech Republic to develop a risk-based
approach to setting priorities for environmental
decisions. NHEERL's objectives were to characterize the
relationship between human exposure to environmental
pollution and health effects in adults, newborns, and
children in the Teplice District. Exceptionally high levels
of air pollution resulting from heavy industrialization in
Northern Bohemia had resulted in obvious adverse
effects on the ecosystem (e.g., deforestation) and a few
reports of unusually high incidences of cancer, birth
defects, and neurotoxicity in the population. These
reports had not been well documented or published in
peer-reviewed international journals prior to 1990.
NHEERL scientists from four of the health divisions have
collaborated with a multidisciplinary team of Czech
scientists to conduct a major long-term study of
106
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
HUMAN STUDIES DIVISION
respiratory, neurobehavioral, reproductive, and genetic
effects on the population in the Teplice District. The
research focused on the health effects of air pollution and
specifically on the toxic components associated with
respirable particles (PM2.5). EPA scientists organized the
first peer review of this program and have provided
training and guidance to the Czech scientists who have
organized two subsequent peer review panels. Members
of the Czech scientific team have all received training in
NHEERL laboratories and have increasingly participated
in the presentation and publication of studies, which have
contributed to a scientific assessment of human health
risk from airborne particulate matter in the Teplice
District, as follows:
• Elevated prevalence and risk for respiratory symptoms
in school children that were related to the air pollution
exposures (Hnizdo et al.).
• Neurobehavioral performance in the same population
of children was not consistently related to their air
pollution exposure (Broadwell et al.).
• Personal exposure to PM2.5 was highly correlated
with exposures to carcinogenic polycyclic aromatic
hydrocarbons (PAH) in the air (Watts et al.).
• DNA adducts in the white blood cells were also
significantly elevated and correlated with personal
exposures to carcinogenic PAH (Binkova et al.).
These findings have important implications for cancer and
reproductive risks from air pollution and have led to
additional biomarkers for the reproductive epidemiologic
studies that are in progress. These peer-reviewed
publications are the first scientifically well-documented
reports on the health effects of air pollution in this
region. This research program has also provided
NHEERL with an environmental laboratory to test and
validate measures of human exposure, uptake, dose, and
adverse respiratory and reproductive effects.
ADVANCING KNOWLEDGE FOR A PURPOSE
107
-------
NHEERL FY95 ANNUAL REPORT
HUMAN STUDIES DIVISION
Table 34. HSD Issues and Accomplishments Overview
Sensitive Subpopulations (Asthmatics)
Are asthmatics more susceptible to
ozone than the general population?
• More severe asthmatics are more susceptible to 0.16 ppm ozone than normal subjects.
• Allergic asthmatics exhibit eosinophil (rather than neutrophil) driven inflammation when exposed to
relatively high levels of ozone (0.4 ppm).
* Exposure to ozone sensitizes upper respiratory passages in asthmatics so that subsequent exposure
to allergens causes more severe allergic reaction.
* Lower level (. 10 ppm) exposure to ozone causes no ozone-induced asthma or increased sensitivity to
allergens in allergic asthmatics.
• Asthmatic children have elevated baseline levels of inflammatory cytokines in upper respiratory
passages, suggesting why they are more sensitive to inhaled compounds.
Respiratory Effects of Air Pollutants
Can scientific evidence be shown to
support claims that methyl tert butyl
ether (MTBE added to gasoline) causes
acute symptoms (e.g., headaches,
nausea, sore throat, eye irritation, etc.)
in exposed populations?
• In controlled chamber studies, demonstrated no evidence of detrimental effects from exposure to
MTBE.
Can links be shown between
mortality/morbidity (as reported in
epidemiological studies) and a specific
air pollution component?
• Demonstrated a relationship between amount of transition metal present on paniculate air pollution
(from several sources) and lung damage induced in animals.
• Characterized and identified substances in particulate air pollution capable of binding metals.
Do healthy, young white males
adequately represent the population as
a whole with respect to ozone
sensitivity?
Demonstrated that neither gender nor race affects responsiveness to low-level ozone exposure (2.66
hours) and neither socioeconomic status nor menstrual cycle phase affect pulmonary response to
ozone, but that age is a factor.
How does exposure to ambient ozone
air pollution compare to exposure to
ozone in controlled situations?
• Demonstrated that responses to ambient air pollution (high ozone) were similar to those in
controlled settings.
• Demonstrated that products of hazardous waste incinerators do not cause acute respiratory effects
in nearby populations.
What is the significance of biomarkers
and what evidence is there to support
the future use of DMA adducts as
biomarkers?
Showed that environmental epidemiological studies have been limited by methods available for
measuring human exposure or biologically effective dose.
Identified urine metabolite as a highly sensitive measure of recent exposure to PAHs and made
advancements in separation and identification of aromatic and nitroaromatic DNA adducts.
Showed evidence of the presence of DNA adduct levels in smooth muscle layer of atherosclerotic
lesions from abdominal aorta samples.
ADVANCING KNOWLEDGE FOR A PURPOSE
109
-------
NHEERL FY95 ANNUAL REPORT
HUMAN STUDIES DIVISION
Dosimetry of Particl.es and Gases
Issue
How can measurement of regional
deposition of ozone be improved?
Characterized ozone uptake in four different airway regions in normal subjects in vivo.
Demonstrated potential use of a new aerosol bolus technique for measuring small airway
obstructions in humans exposed to air pollutants.
Demonstrated that, using a nebulizer, aerosol dose delivered to the mouth was only 1.6% of total
dose placed in the nebulizer.
What weight should be given to recent
studies that claim that particles persist
in large ciliated airways for some time?
Demonstrated complete clearance of particles from the large airways of dogs following intrabronchial
deposition, the confirming conventional understanding of particle clearance kinetics.
What are the most significant factors
affecting total lung deposition of fine
particles?
Demonstrated that breathing patterns and airway resistance are most important in total lung
deposition of fine particles.
Biologically Based Dose Response (BBDR) Models
HSD Accomplishment
How can variability in acute response
to toxicant exposure be captured
better to provide improved risk
models?
• Developed model that predicts the proportion of individuals responding adversely to ozone exposure
as a function of ozone concentration and exposure duration.
What can be done to make the
Coburn-Foster-Kane equation (CFKE)
easier to use in predicting
Carboxyhemoglobin (COHb)
formation due to CO exposure?
• Incorporated the CFKE into an existing desktop computer-run model which allowed rapid prediction
of 50 physiological and blood gas values without resorting to tables.
How can human lung epithelial cells be
made more accessible for in vitro
toxicology study?
Validated the immortalized human airway epithelial cell line BEAS23 for use in studies of air
pollutants.
What can be done to make better use
of animal data in assessing human risk,
particularly where human data are
scarce?
The Teplice Project
Issue
Developed a qualitative extrapolation model that showed that a combination of in vitro animal and
human studies coupled with in vivo animal studies can accurately predict human response as
measured by host defense end points.
USD Accomplishment
What significant findings have come
from the Teplice Project, in terms of
assessing human health risk from
airborne particulate matter?
Air pollution exposure in school children was related to prevalence and risk for respiratory symptoms
but not for neurobehavioral performance.
Found that personal exposure to PM2.5 and elevated DMA adduct levels in white blood cells were
highly correlated with exposures to airborne carcinogenic PAHs.
110
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
NEUROTOXICOLOGY DIVISION
Important Scientific Issues
The full range of neurotoxic effects
reported in humans includes motor,
sensory, cognitive, and autonomic
disturbances, and these effects are
studied at the neurobehavioral,
neurophysiological, neurochemical, and
neuroanatomical levels of nervous
system organization. NTD consists of a
Cellular and Molecular Toxicology
Branch, a Neurophysiological Toxico-
logy Branch, and a Neurobehavioral
Toxicology Branch.
Most biological manifestations of
mammalian life, including muscular
movements, reproductive capability,
respiration, cardiac function, sensation,
perception, and learning/memory are
controlled by the nervous system, which
comprises the brain, spinal cord, and a
complex network of central and
peripheral nerves and supporting cells.
The proper functioning of the nervous
system is essential for good health and
productive life. One of the major
functions of the nervous system is to
transmit information or commands from
one component of the body to another;
this function is accomplished by a
complex interaction of various kinds of
nerve cells. Interruption of this process
can result in a variety of effects, such as
lowering of IQ scores in children; more
severe indications of neurological
dysfunction, such as paraesthesias in the
extremities, muscle weakness, or
seizures; or neurodegenerative-like
syndromes resembling naturally occur-
ring diseases such as Parkinson's and
Alzheimer's diseases.
Neurotoxicants are chemicals that
interfere adversely with the structure
and/or function of the nervous system.
The Agency receives approximately
1500 notices of intent to produce new
substances each year, and 65,000
chemicals are already listed in the EPA
inventory of chemicals. Estimates of how
many of these chemicals are neuro-
toxicants depend on the class of
chemical and the exposure scenario. For
example, of the more than 1,400 active
pesticides registered by the Agency,
more than half are considered to be
neurotoxic. Approximately 20% of the
chemicals in the Agency's Integrated Risk
Information System list neurotoxicity
either wholly or in part as the basis for
the reference dose or concentration.
Estimates of potential neurotoxicants in
the Agency's inventory range from 2,600
to over 18,000. Concern about expo-
sure to neurotoxicants has increased in
the last several years and has resulted in
several publications, including a 1990
report by the Office of Technology
Assessment (Neurotoxicology: Identifying
and Controlling Poisons of the Nervous
System) and a 1992 publication by the
National Research Council outlining the
principles of Environmental Neurotox/-
co/ogy. Developmental neurotoxicity was
a particular concern noted in the 1993
publication of the National Research
Council on Pesticides in the Diets of
Infants and Children. Neurological and
behavioral effects were noted in a recent
workshop sponsored by the Agency
concerning the influence of neuro-
Neuro-
toxicology
Division
The Neurotoxicology Division
(NTD) conducts research to
provide a scientific basis for
predicting whether an
environmental agent will
produce neurotoxicity. The
general approach for this
research acknowledges the
integrated nature and
complexity of the nervous
system, both structurally and
functionally, and uses
methodological and
conceptual advances in
neurology, experimental
psychology, and the
neurosciences to identify and
characterize chemicals
potentially neurotoxic to
humans.
ADVANCING KNOWLEDGE FOR A PURPOSE
III
-------
NHEERL FY95 ANNUAL REPORT
NEUROTOXICOLOGY DIVISION
endocrine disrupters in the environment. That the
Agency views neurotoxicity as a high priority is reflected
by the recent publication of the proposed neurotoxicity
risk assessment guidelines in the Federal Register in
October 1995.
Research in NTD is organized around the risk
assessment paradigm. Current studies focus on the
development and validation of methods to determine
whether or not exposure to a chemical produces an
adverse effect and whether an adverse effect can be
defined as neurotoxicity (hazard identification).
Estimating the association between the dose and effect
for various conditions of exposure (dose-response
assessment) helps provide information to the Agency
concerning chemicals of interest, using the best available
procedures and chemical-specific data strategies.
FY1995 Accomplishments
Hazard Identification
Premarket testing for pesticides is required by EPA
under the Federal Insecticide, Fungicide, and
Rodenticide Act. Evaluation of industrial chemicals may
also be required under the Toxic Substances Control
Act. Current research in NTD focuses on providing
data in support of existing neurotoxicity guidelines,
identifying areas where additional guidelines may be
needed, and assisting risk assessors in interpreting data
submitted to EPA by industry in response to the testing
guidelines.
Currently, NTD is focusing on the continuing validation of
the functional observational battery (FOB) and motor
activity, which are now used routinely in-house and by
industrial and contract laboratories to detect a wide range
ofneurotoxic agents.
*• The FOB and motor activity were used in a
comparative study along with measures of systemic
and developmental toxicity to assess the acute and
subacute effects of 10 industrial and agricultural
chemicals (Berman, et al.; MacPhail et al.; Moser,
Cheek et al.). Significant dose- and exposure
scenario-related effects were detected by the FOB,
and chemicals having different mechanisms of action
were found to produce different patterns of
neurotoxicity. Chemicals expected to have little or
no neurotoxicity affected some behavioral measures
at high doses.
Other NTD studies (Goldey, O'Callaghan et al.)
showed that a battery of tests for preweaning rats
was not sensitive to the neurotoxic effects of
prototypic developmental neurotoxicants. It has
been inferred from such results that testing for
developmental neurotoxicity may not be essential
because currently existing guidelines for teratology
studies may be sufficient to detect potential
developmental neurotoxicants.
However, a systematic literature review revealed
that the measures used in the Chernoff-Kavlock
teratology assay detected only about 60% of the
known developmental neurotoxicants included in a
survey (Goldey, Tilson et al.). This finding indicates
that additional work is needed to find cost-effective,
sensitive indicators of developmental neurotoxicity.
NTD has also helped to develop and validate
electrophysiological measures to detect and
characterize sensory deficits (Boyes). These studies
support the contention that sensory evoked
potentials in animal models are qualitatively similar to
those obtained in humans in terms of waveform
measurement, anatomical substrates, and
responsiveness to chemicals. Such information is
important because of a recently developed testing
guideline for evoked potentials, which is currently
under EPA review.
112
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
*• Procedures for assessing sensory function have also
been developed for studies involving humans
exposed to environmental chemicals (Anger et al.;
Broadwell et al.).
NTD has been developing mechanistically based tests to
identify generic neurochemical/neuroanatomical markers
of injury to the nervous system, such as glial fibrillary acidic
protein (CFAP).
* NTD researchers have recently studied the
expression of GFAP in transgenic mice (Miller, Bartke
et al.) and the possible role of cytokines as possible
markers of injury in the central nervous system
following chemical exposure (Maier et al.).
+ Dose- and time-dependent increases in the
expression of cytokine mRNAs in the hippocampus of
rats exposed to a prototypic neurotoxicant suggest
that increased expression of cytokines, like GFAP,
may also be an early indicator of injury to the brain
following chemical exposure.
*• Procedures involving tissue cultures are being used
with greater frequency in hazard identification, and
there is considerable interest in developing such
procedures for neurotoxicity testing (Atterwill et al.).
One area of promise concerns the use of tissue
culture techniques to measure changes in key
enzymes such as neuropathy target esterase (NTE)
associated with the manifestation of delayed
NEUROTOXICOLOGY DIVISION
peripheral neuropathy induced by cholinesterase-
inhibiting insecticides. Current testing guidelines
utilize neurological, neuropathological, and
neurochemical assessments of hens after acute and
repeated dosing with organophosphate compounds.
Work in NTD on potential use of in vitro preparations
to assay NTE (Ehrich, Correll et al.) showed good
agreement in response of cells from humans and
rodents to organophosphates that are known to
produce a delayed neuropathy in humans (Ehrich and
Veronesi et al.). Such information is crucial to
establishing appropriate conditions for using tissue
culture techniques and for determining the
appropriateness of extrapolating in vitro data derived
from rodents to humans.
Other NTD research has focused on identifying
potential endpoints that could be associated
mechanistically with chemical-induced neurotoxicity.
For example, it has been proposed that some
chemicals may produce neurotoxicity by interacting
with the immune system.
NTD researchers have found that neuropeptides may
be involved in mediating chemical-induced skin
irritation (Veronesi et al.), suggesting a neural
connection in this important response to toxicological
injury. Initial work is also underway to explore the
possible role of free radical/oxidative reactions in
environmentally related neurodegenerative diseases
such as Parkinson's disease (Sengstock et al.).
ADVANCING KNOWLEDGE FOR A PURPOSE
113
-------
NHEERL FY95 ANNUAL REPORT
NEUROTOXICOLOGY DIVISION
A large component of NTD's research program focuses
on reducing uncertainties in the risk assessment
process. For example, reference doses or
concentrations are derived from the following formula:
RfD=NOAEL (LOAEL)/UFs', where UFs are factors of
up to 10 for intrapopulation variability, animal-to-human
extrapolation, and less-than-lifetime exposures. NTD
research is designed to elucidate variables affecting the
quantitative estimate of risk, including factors that could
influence the estimation of the NOAEL or LOAEL.
Research to Reduce Uncertainties in the
NOAEL or LOAEL T ;
Calculation of the RfD begins with the determination of
the NOAEL or LOAEL based on results from a critical
study. It is important for the risk assessor to know that
the estimation of the NOAEL or LOAEL for some
neurotoxic endpoints can be shifted to the left or right
on the dose-response curve by a number of
environmental or dosing variables.
For example, it is generally known that the presence and
magnitude of neurotoxicity can be affected significantly by
environmental factors that alter the neuroendocrine status
of the organism. Stress has been shown to affect the
manifestation of chemical-induced neurotoxicity and can
have a significant effect on quantitative and qualitative
estimates of neurotoxic risk.
*• NTD researchers (Miller and O'Callaghan) have
shown that temperature stress significantly enhances
the expression of neurotoxicity produced by
prototypic neurotoxic agents.
RfD = Reference Dose
NOAEL = No Observed Adverse Effect Level
LOAEL = Low Observed Adverse Effect Level
UF = Uncertainty Factor
* Other studies at NTD have investigated the possible
contribution of route of administration to the
neurotoxicity of deltamethrin, which has been
reported in the literature to vary by as much as three
orders of magnitude. NTD research (Crofton, Kehn
et al.) showed that the potency of deltamethrin
depended on both the vehicle and route of
administration.
intrapopulation Variability
Differences in sensitivity to neurotoxic agents within a
population of exposed individuals can have very long-term
consequences (Barone, Stanton et al.).
* Recent studies have shown that early postnatal
exposure to triethyltin produced transient effects on
cognitive function in rats at the time of weaning.
However, as the animals matured and their cognitive
abilities started to decline, the animals that had
received triethyltin were more deficient in learning
than their age-matched controls. These data indicate
that developmental exposure to chemicals can
interact with normal aging and also caution against
dismissing transient changes following developmental
exposure as always being an indication of recovery.
Compensation for chemical exposure during
development may obscure neurological damage that
becomes evident only after the nervous system
begins to age.
* It has also been suggested that using different strains
of rats may affect the manifestation of neurotoxicity.
NTD studies comparing the responsiveness of Long-
Evans and Fischer-344 rats to a prototypic
neurotoxicant, trimethyl tin (Moser), have shown
significant baseline differences between rat strains,
but the qualitative response to trimethyl tin was the
same and the magnitude of the response varied only
by a factor of 2-3. Other experiments (Gordon and
Watkinson) compared the responses of four strains
114
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
NEUROTOXICOLOGY DIVISION
of rats (Sprague-Dawley, Long-Evans, Fischer-344,
and Wistar) to a cholinesterase-inhibiting chemical
and found that Fischer-344 rats were less susceptible
behaviorally and neurochemically. Differences
between rat strains, however, did not differ
qualitatively nor were the effects quantitatively
different by more than an order of magnitude. These
results suggest that rat strain is not an important
variable in determining the uncertainty factor for
intrapopulation differences.
Less-Than^Ufetlme Exposures
It is generally accepted that neurotoxidty for some
chemicals may be evident only following repeated
exposures. One explanation for this observation is that
repeated exposure to some agents may alter the sensitivity
or excitability of the nervous system, leading to increased
susceptibility to subsequent exposures and increased
incidence of seizure-related health effects. Repeated
presentations of subthreshold electrical stimuli in specific
brain regions can lead to enhanced seizure activity; this
phenomenon is known as kindling and is thought to
represent an experimental form of temporal lobe epilepsy.
* NTD studies have found that repeated exposure to
the pesticide lindane leads to a behavioral
sensitization that facilitates kindling (Gilbert) and that
seizure thresholds in kindled rats are reduced by
Chemical Specific Data
*• exposure to lindane and endosulfan (Gilbert and
Mack). These experiments underscore the possibility
that repeated low-level exposure to some chemicals
could alter the sensitivity of the CNS and lead to
epilepsy-like symptomatology.
*• Other NTD studies have focused on understanding
the cellular mechanisms associated with increased
sensitivity of the nervous system following repeated
exposure to neurotoxic agents (Qian et al.).
Interpretation of
Assessment
Data for Risk
EPA published the draft Neurotoxicity Risk Assessment
Guidelines in October of 1995.
* Papers written by NTD staff outlined the weight-of-
evidence approach used in the guidelines (Tilson et
al.) and special considerations that underlie risk
assessment following developmental exposures
(Tilson). These publications are intended to provide
peer-reviewed guidance to EPA personnel
concerning crucial procedural steps in the risk
assessment guidelines, and to address comments and
criticisms raised in the past concerning the issue of
neurotoxicity risk assessment.
NTD research employs validated methods and
procedures to address scientific questions raised by
program offices or the larger scientific community
concerning specific chemicals or chemical classes.
Aluminum
Over the last decade, there have been concerns that
aluminum in the drinking water may be associated with
the etiology of neurodegenerative diseases such as
Alzheimer's disease.
>• NTD's recent review of the literature on this issue
(Shafer and Mundy) concluded that the association
between aluminum and Alzheimer's disease was
weak.
*• However, the review did find consensus that
aluminum is a neurotoxic metal and that further
research was warranted. NTD research has shown
that aluminum alters signal transduction mechanisms
in brain tissue in vitro at relatively low concentrations
ADVANCING KNOWLEDGE FOR A PURPOSE
115
-------
NHEERL FY95 ANNUAL REPORT
NEUROTOXICOLOGY DIVISION
but revealed no age-dependent sensitivity to the
neurotoxic effects of aluminum (Mundy et al.).
*• Other NTD studies have shown that in vitro
exposure to aluminum does not alter long-term
potentiation or glutamate release in rat hippocampal
slices, indicating that aluminum may have general,
nonspecific effects on brain function (Gilbert and
Shafer).
3,3'-IminodIproprionitrlle (IDPN)
Nitrites are used in a number of industrial applications.
IDPN is a neurotoxic nitrite that adversely affects the
structure of both the peripheral and central nervous
systems. Until recently, little attention had been paid to
the possible functional effects of nitrites such as IDPN.
* Recent NTD studies have shown that IDPN appears
to have a direct effect on both neural and nonneural
structures in the eye and found a dose- and time-
dependent progressive histopathology (Barone, Herr
et al.). Functional studies with IDPN revealed
alterations in visual evoked potentials (Herr et al.).
*• Subsequent experiments showed that IDPN also
produced functional and morphological evidence of
cochlear damage and ototoxicity (Crofton, Janssen et
al.), as well as olfactory deficits in rats (Center et al.).
These data confirm that IDPN affects more than one
sensory system.
* Other NTD studies have shown that IDPN
significantly interferes with learning and performance
of a spatial task in rats, thus indicating that this
compound can also affect cognitive processing
(Llorens et al.).
Choltnesterase-Inhiblting Compounds
Research on cholinesterase-inhibiting pesticides is a major
component ofNTD's program. The main objectives of this
research are to address the adversity of cholinesterase
inhibition in animal models, the relative importance of
brain and blood cholinesterase inhibition, developmental
neurotoxicity, compensation following repeated exposure,
and ocular toxicity.
*• An NTD study has shown that a single exposure to
fenthion produced persistent neurochemical and
histopathological alterations in the rat eye (Boyes et
al.). This finding suggests that EPA should assess
directly the risk of ocular toxicity following exposure
to organophosphate insecticides.
*• NTD scientists have also reported a novel method
that markedly increases the sensitivity of the standard
erythrocyte acetylcholinesterase assay (Padilla et al.),
which will prove helpful for the hazard characteri-
zation of carbamates and organophosphates.
*• Chlorpyrifos is an organophosphate insecticide that
produces a persistent decrease in
acetylcholinesterase activity. Recovery from
chlorpyrifos is unusually slow compared to other
agents in this class, including parathion and methyl
parathion. NTD scientists (Chiappa et al.) have
shown that persistent decreases in brain
acetylcholinesterase activity after chlorpyrifos
exposure reflected a sustained inhibition of the
enzyme, not a loss of enzyme protein or suppression
of message of the enzyme. This information is
important because it provides the scientific basis for
understanding the persistent nature of chlorpyrifos's
inhibitory effect on brain acetylcholinesterase.
Cholinesterase inhibitors are frequently assessed on
the assumption that there will be a rapid and
complete recovery of function following acute
exposures.
116
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
NEUROTOXICOLOGY DIVISION
Risk assessment of the cholinesterase-inhibiting pesticides
depends heavily on characterization of their acute effects,
and it is generally believed that those effects are similar for
all compounds in this class.
*• NTD research (Moser "Cholinesterase Inhibitors")
compared the acute effects of two carbamates
(carbaryl and aldicarb) and five organophosphates
(chlorpyrifos, diazinon, parathion, fenthion, and DFP)
using the FOB and motor activity. The overall clinical
syndrome was similar for all compounds, but there
were compound-specific differences in the individual
measures, dose-response, and time-course of action.
These findings suggest that some differences may be
expected in the spectrum of effects produced by
compounds of the same chemical class having similar
mechanisms of action.
* Current guidelines for organophosphates require
testing of adult hens for delayed-onset neurotoxicity.
More frequently used laboratory animals such as the
rat are not recommended because they do not show
clear clinical impairment even in the presence of
histopathology.
* Recent NTD studies (Ehrich, Jornter et al.) examined
the relationship between inhibition of
acetylcholinesterase and neuropathy target esterase
(NTE, a biomarker of delayed neurotoxicity) in hens
and rats exposed to agents known to produce
neuropathy in the hen. The rat did not develop overt
and specific clinical signs, but the hens did. This
observation, combined with limited neuropathology
and difficulties in ensuring the survival of rats given
these agents, upholds the conclusion that the hen is
the more appropriate animal species for
organophosphate hazard identification.
Perturbations in homeostatic processes, including the
regulation of body temperature, are common effects in
experimental animals and humans exposed to
anticholinesterase pesticides.
NTD research has provided evidence for a
behaviorally mediated reduction in core temperature
in the rat following acute exposure to a prototypic
cholinesterase inhibitor, diisopropyl fluorophosphate
(DFP). Furthermore, during recovery from acute
DFP exposure, there was a persistent elevation in
core temperature lasting for several days (Gordon
"24-Hour Control"). These data indicate that not all
of the effects of acutely administered cholinesterase
inhibitors are transient; in addition, the hyperthermia
observed in rats may be similar to the fever that has
been frequently observed in humans exposed to
these agents.
Additional work (Gordon "Diisopropyl Fluoro-
phoshpate-induced Hypothermia") showed that the
hyperthermia produced by DFP was inversely related
to the baseline core temperature. These findings
indicate that some biologically significant adverse
effects following acutely administered cholinesterase
inhibitors could be diminished or obscured by testing
parameters.
Neurotoxicity is a primary concern after acute and
repeated spikes of exposure to VOCs and related
chemicals. Most previous studies of ototoxicity following
exposure to organic solvents have been restricted to low-
and mid-hearing frequencies.
*• NTD research has revealed that inhalation exposure
to styrene, mixed xylene, toluene, and 1, 1,2-
trichloroethylene caused hearing deficits only in the
mid-frequency range (2-20 KHz) and spared function
at lower and higher frequencies (Crofton, Lassiter et
al.). This information is useful because it indicates the
sensitive range of hearing frequencies that should be
assessed following exposure to solvents and suggests
a common mechanism for a number of environ-
mentally relevant solvents.
ADVANCING KNOWLEDGE FOR A PURPOSE
117
-------
NHEERL FY95 ANNUAL REPORT
NEUROTOXICOLOGY DIVISION
Polychlorinated
Dioxin
Risk assessments for dioxin and related PCBs are based on
the relative potency of the chemicals to bind to the
arylhydrocarbon (Ah) receptor. One class of PCBs, the
ortho-substituted congeners, has little or no Ah receptor
activity, and previous research has indicated that these
compounds may have adverse effects on the nervous
system.
*• NTD scientists have examined a number of
neurochemical measures in vitro and found that PCB
congeners with mono- and di-ortho- substitution
affect cellular calcium homeostasis, while coplanar
PCBs that bind to the Ah receptor do not affect
calcium homeostasis (Kodavanti, Ward, McKinney et
al.; Kodavanti, Ward, Tilson et al.). Characterization
of this effect using a prototypic ortho-substituted
PCB revealed a biphasic effect on receptor-mediated
phosphoinositide hydrolysis and translocation of
protein kinase-C in the nervous system of rats
(Kodavanti, Shafer et al.). These data provide a
neurochemical measure to use in performing
structure-activity modeling and suggest future studies
to identify the possible receptor target of neurotoxic
PCB congeners.
Additional NTD research focused on the
developmental neurotoxicity of PCBs. Recent
experiments showed that developmental exposure to
a mixture of PCBs (Aroclor 1254) caused persistent
hearing loss in animals tested as adults and that this
effect was associated with reduced circulating thyroid
hormone concentrations (Goldey, Kehn, Lav et al.).
This work also revealed that the hearing deficits
produced by developmental exposure to PCBs could
be attenuated by treatment with thyroxine. Hearing
loss was also demonstrated with propylthiouracil, an
agent known to produce hypothyroidism in the rat
(Goldey, Kehn, Rehnberg et al.). Because it is known
that the development of hearing depends on the
availability of circulating thyroid hormones, these data
suggest that evaluation of children exposed to PCBs
should include measures of auditory function.
Other NTD studies (Gordon, Gray et al.) showed
that developmental exposure of rats to dioxin
produced a persistent reduction in regulated body
temperature by decreasing the homeostatic set-
point. These data suggest that fundamental metabolic
processes may be altered by developmental exposure
to dioxin and suggest the hypothalamus and, possibly
the thyroid, as potential target sites for dioxin-
induced developmental toxicity.
us
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
NEUROTOXICOLOGY DIVISION
Table 35. NTD Issues and Accomplishments Overview
Hazard Identification
-,.y • ••
Issue
What are the validity, sensitivity, and cost-
effectiveness of various measures being
used to determine neurotoxicity?
What is being done about the lack of tests
for chemical-induced alterations in
cognitive function?
What is being done to develop more
mechanistically based tests to improve
identification of potential neurotoxicants?
NTD Accomplishment
• Demonstrated the sensitivity and reliability of the functional observational battery (FOB) for
assessing chemicals for potential neurotoxicity.
• Found that a battery of tests for preweaning rats was not sensitive to the neurotoxic effects of
prototypic developmental neurotoxicants.
• Found that measures used in the Chernoff-Kavlock assay detected only about 60% of the known
developmental neurotoxicants included in a survey, indicating that additional work is needed to
find better indicators.
• Supported studies that revealed qualitative similarity between animal models and humans in
terms of waveform measurement, anatomical substrates, and responsiveness to chemicals.
• Developed procedures for assessing sensory function in studies involving humans exposed to
environmental chemicals.
• Developed animal models to evaluate chemicals for their effects on cognitive function.
• Supported use of transgenic models by advancing research concerning expression of glial fibrillary
acidic protein (GFAP) in mice.
• Demonstrated possible role of cytokines as indicators of brain injury in rats exposed to
chemicals.
* Demonstrated similar responses in human and rodent cells that were exposed to
organophosphates, thus advancing basis for extrapolation of in vitro data from rodents to humans.
• Found evidence to suggest that neuropeptides may be involved (a neural connection) in
mediating chemical-induced skin irritation.
Dose-Response Assessment
Issue
What may be done to reduce uncertainties
in no observed adverse effect levels
(NOAEL) or low observed adverse effect
levels (LOAEL)?
What is the significance of intrapopulation
variability in terms of sensitivity to
neurotoxic agents?
What are the effects of repeated
neurotoxic exposure on nervous system
sensitivity?
NTD Accomplishment
• Demonstrated that temperature stress significantly enhanced the expression of neurotoxicity
from prototypic neurotoxic agents.
• Found that deltamethrin potency depended on both the vehicle and route of administration.
• Showed that developing organisms, relative to adults, are differentially sensitive to many
neurotoxic agents and that evidence of neurological damage may be obscured until after the
nervous system begins to age.
• Found that rat strain is not an important variable in determining the uncertainty factor for
intrapopulation differences.
• Found that repeated exposure to lindane leads to behavioral sensitization that facilitates
"kindling" and that seizure thresholds in kindled rats are reduced by exposure to lindane and
endosulfan.
• Advanced knowledge of cellular mechanisms associated with increased sensitivity of the nervous
system following repeated exposure to neurotoxic agents.
ADVANCING KNOWLEDGE FOR A PURPOSE
119
-------
NHEERL FY95 ANNUAL REPORT
NEUROTOXICOLOGY DIVISION
Chemical Specific Data
Issue
What scientific evidence can be provided
concerning reports of aluminum
neurotoxicity in vivo!
Concluded that there was no strong association between Al and Alzheimer's disease but found
consensus that Al is neurotoxic and warranted further study.
Found that relatively low concentrations of Al altered signal transduction mechanisms in brain
tissue in vitro but discovered no evidence of age-dependent sensitivity to neurotoxtc effects of Al.
Found evidence that Al may have general, nonspecific effects on brain function.
What is the environmental significance of
the class of chemicals known as nitriles?
Showed that 3,3'-iminodipropionitrile (IDPN) appears to have direct effects on both neural and
nonneural structures in the eye and found dose- and time-dependent progressive histopathology.
Demonstrated that IDPN affects more than one sensory system (alterations in visual evoked
potentials, cochlear damage and ototoxicity, and olfactory deficits in rats).
Found that IDPN can significantly affect cognitive processing.
Is ocular toxicity following exposure to
organophosphate insecticides an area of
concern?
Found that a single exposure to fenthion produced persistent neurochemical and
histopathological alterations in the rat eye.
Is rapid and complete recovery from acute
exposure to cholinesterase inhibitors to be
expected?
Found that persistent decreases in brain acetylcholinesterase activity after chloropyrifos exposure
reflected a sustained inhibition of the enzyme, not a loss of enzyme protein or suppression of
enzyme message.
Are differences in effects to be expected
from compounds of the same chemical
class that have similar mechanisms of
action?
Compared two carbamates and five organophosphates and demonstrated some differences in
the effects produced.
Are current requirements for use of adult
hens for organophosphate neurotoxicity
testing valid?
Affirmed current guidelines for organophosphates that require testing adult hens for delayed-
onset neurotoxicity.
How persistent are the adverse effects of
acutely administered cholinesterase
inhibitors in test animals?
Demonstrated that some effects of acutely administered cholinesterase inhibitors are not
transient and that observed rat hyperthermia may be similar to fever observed in humans
exposed to these agents.
Found that hyperthermia produced by diisopropyl fluorophosphate (DFP) exposure was inversely
related to animal baseline core temperature.
What is the most current methodology for
performing cholinesterase assays for
hazard characterization of carbamates and
organophosphates?
Reported a novel method that markedly increases the sensitivity of the standard erythrocyte
acetylcholinesterase assay.
120
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
NEUROTOXICOLOGY DIVISION
Organic Solvents
Issue
In ototoxicity studies, what range of
frequencies should be assessed following
exposure to solvents?
PCBs and Dioxins
Found hearing deficits only in the midrange frequencies (2-20 kHz) in rats exposed by inhalation
to styrene, mixed xylene, toluene, and 1, 1,2-trichloroethylene.
Is there evidence to suggest that evaluation
of children exposed to PCBs should
include measures of auditory function?
Found that developmental exposure to a mixture of PCBs caused persistent hearing loss
(associated with reduced circulatory thyroid hormone concentrations) in animals tested as adults
and that hearing deficits could be attenuated by treatment with thyroxine.
Demonstrated hearing loss with propylthiouracil (known to produce hypothyroidism in rats).
What effect does developmental exposure
to dioxin have on fundamental metabolic
processes?
Showed that developmental exposure of rats to dioxin decreased the homeostatic set-point,
causing a persistent reduction in regulated body temperature.
ADVANCING KNOWLEDGE FOR A PURPOSE
121
-------
NHEERL FY95 ANNUAL REPORT
REPRODUCTIVE TOXICOLOGY DIVISION
Important Scientific Issues
The production of healthy offspring is
a major concern in the human
population. In the United States, one out
of every ten couples seeks medical help
in achieving pregnancy. In addition, at
least 30 percent of all recognized human
pregnancies fail to culminate in a live
birth owing to spontaneous abortions.
An equal number of pregnancies are
believed to be lost before the time when
routine clinical indications of embryonic
growth can be detected.
While these spontaneous abortions
naturally end most abnormal pregnan-
cies, approximately 3 percent of babies
born in the United States suffer from
major malformations and roughly ano-
ther 3 percent are found to suffer from
subtle changes expressed during post-
natal development. Intrauterine growth
retardation of unknown etiology is a high
risk factor not only for structural mal-
formations but for later developmental
dysfunctions, including childhood
learning disabilities. Estimates by various
experts suggest that the cause(s) of
adverse reproductive outcomes in
Table 36. RTD Branches
humans are unknown for the over-
whelming majority of the cases.
Concern about potential environmentally
induced etiologies has increased
considerably in the last few years with
the 1993 publication of the National
Academy of Sciences report on
Pesticides in the Diets of Infants and
Children, and with the widely circulated
hypothesis that environmental
contaminants have influenced the
endocrine system and hence have
altered reproductive development and
function in a variety of species. For
example, several recent publications
have suggested alarming evidence of
marked declines in sperm counts and
semen quality, and increases in testicular
and genital abnormalities and testicular
cancer over the last several decades.
In order to address these vital issues, the
Reproductive Toxicology Division is
organized into three branches, as
shown in Table 36. RTD Branches,
below.
RTD BRANCH
Gamete and Early
Embryo Biology
Developmental
PRIMARY FUNCTION
Examine die processes of gamete formation and function
Focus on mechanisms responsible for birth defects
Explore dw impact of disturbances in endocrine systems on
Reproductive
Toxicology
Division
The Reproductive Toxicology
Division (RTD) is concerned
with the effects ofxeno-
biotics on the developmental
and reproductive processes
of humans. In order to
advance knowledge in this
area of concern, RTD
conducts research directed
toward detecting and
interpreting the effects of
xenobiotics on the develop-
mental and reproductive
processes of laboratory
animals. RTD then
extrapolates the data from
those models to the human
situation.
ADVANCING KNOWLEDGE FOR A PURPOSE
123
-------
NHEERL FY95 ANNUAL REPORT
REPRODUCTIVE TOXICOLOGY DIVISION
RTD has developed a cohesive research program that is Refer to Table 38. Issues and Accomplishments Overview,
designed around the five guiding organizational goals for a quick look at some of the major RTD accomplish-
shown in Table 37. RTD Goals. ments of Fiscal Year 1995.
Table 37. RTD Goals
EXAMPLE/COMMENT
Methanol, dioxin, atrazine, PCBs, and vinclozolin
Research on the predictiveness of measures of alterations in gonad and
reproductive tract function on fertility and the validation of the benchmark
RTD GOAL
I. Apply scientific knowledge to high priority
chemicals
2. Clarify assumptions in the risk assessment
guidelines.
3. Develop mechanistically basetl effect models, Work with 5-fl,uoro«racil (S-FU), methancd, dioxin, and vinclozolin. By
understanding mechanisms of toxlcity, we will reduce the urrceitawttie*
4. Conduct
5.
124
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
FT 1995 Accomplishments
NHEERL FY95 ANNUAL REPORT
REPRODUCTIVE TOXICOLOGY DIVISION
Development of BBDR Models
Biologically based dose response (BBDR) models begin
with an adverse effect and attempt to determine (to the
extent practical and feasible) the intervening steps
between administration of a chemical and a resulting
health effect. These knowledge-based formal
mathematical models of biological response facilitate
assimilation of relevant data and testing of model-derived
hypotheses.
BBDR models first gained prominence with the work of
Moolgavkar and coworkers who developed a multistage,
mathematically based description of carcinogenesis. Over
the last five years, RTD scientists have been active in
developing such models for noncancer endpoints. The
division's emphasis on development of BBDR models has
continued with iterative research on the 5-fluorouracil
(5-FU) model. Previously, we researched the effects of5-FU
on inhibition of thymidylate synthetase with subsequent
effects on DNA synthesis, cell cycle kinetics, growth
inhibition, and hindlimb defects in rats exposed to GDI4.
*• In the past year, predictions from a computer model
of the pharmacokinetics, nucleotide pool biosynthesis,
and cell cycle kinetics (developed in parallel with the in
vivo model by R.W. Setzer of the Biometry Branch)
were tested on the rat model.
In addition, other modes of action that might contribute to
developmental toxicity were pursued.
*• Maternal administration of 5-FU produced fetal anemia
as evidenced by decreases in cell counts, hematocrit,
and hemoglobin content of fetal blood (Zucker et al.).
A time course analysis indicated that the causative
effect was a delay in reticulocyte release from the fetal
liver. Because only a brief (3-6 hour) exposure to
5-FU is sufficient to induce limb malformations (Shuey
et al.), it does not appear that the anemia, which takes
about 48 hours to develop, is involved in the primary
pathogenetic cascade. However, it likely plays a role
in the overall growth retardation observed in treated
fetuses over the final several days of pregnancy. Thus,
even for the relatively well understood mechanism of
action that 5-FU afforded, by attempting to account
for the intervening steps in the induction of
developmental toxicity, new insights and alternative
modes of action have been uncovered.
& Future Effects: This year, efforts are being focused on
determining nucteotide poof tev«Js in exposed embryos w& on a
model cell culture system for comparison with some predictions
from the computer model.
Methanol has been proposed as a cleaner burning
alternative fuel for motor vehicles. In hazard identification
research conducted by the division several years ago, we
discovered that inhalation exposure of mice to methanol
resulted in multiple birth defects (exencephaly, cleft
palate, altered skeletal bones) at concentrations that
suggested concern for potentially exposed humans.
Therefore, in 1992 we proposed a 5-year plan to develop a
BBDR model for use in the upcoming methanol risk
assessment.
* This year we completed work on the toxicity of
methanol's principal metabolite, formic acid, in
embryos exposed in an in vitro test system (Andrews
et al.), and we described patterns of cell death in rat
and mouse embryos exposed to methanol in the
same culture system (Abbott, Ebron-McCoy et al.).
The in vitro embryo culture system allowed us to
ADVANCING KNOWLEDGE FOR A PURPOSE
125
-------
NHEERL FY95 ANNUAL REPORT
REPRODUCTIVE TOXICOLOGY DIVISION
examine the effects of exposure independent of
maternal metabolic influences, and to have precise
control over the concentration and duration of the
exposure. The research continues to indicate that
methanol is the proximate developmental toxicant
and confirms that the heightened sensitivity of the
mouse compared to the rat in terms of developm-
ental toxicity is due to an intrinsic property of the
embryo and not to differences in maternal meta-
bolism between the two species. This accumulated
evidence supports the relevancy of the mouse model
to the potential effects in humans exposed to
methanol in an environment that would not be
expected to cause buildup of formate levels in the
blood.
^Future Effects: tn the
search for early events in the
methanol, with specific attentiort
studies and quantitating
exposed embryos.
vw will be narrovwfjg the
of defects caused by
\"m concentration-time
An invited article (Kavlock and Setzer) reviewed the
background for quantitative dose-response modeling in
developmental toxicity, including the Benchmark Dose
Approach discussed below and the BBDR models and
suggested that a new concept, termed Embryologically
Based Dose Response (EBDR) models, is needed to
advance the use of mechanistic data in risk assessment.
»• EBDR models differ from BBDR models in that they
begin with a model of embryonic development of a
particular organ system (e.g., limbs, skeleton, palate),
attempt to cover normal development, and
secondarily factor in how development can be
perturbed. Thus, they can be considered "bottom
up" models in contrast to the "top down" BBDR
models. Because these models would be based upon
normal morphogenesis, they might be more
generically applicable across chemicals, and they
should be instructive as to the relevance of findings
across species. Development of these models will
require interplay between molecular embryologists,
developmental toxicologists, and biomathematicians,
and is currently in its initial stages.
126
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
REPRODUCTIVE TOXICOLOGY DIVISION
The ability of chemicals to mimic or interfere with the
function of the endocrine system during reproductive
development has been a focal point of the divisional
research program for nearly 15 years, but the
environmental significance of the program took on new
importance in the 1990s with reports of declining sperm
counts in humans over the last four decades; apparent
increased incidence of tumors with an endocrine basis
(testicular, breast, and prostatic); findings of increased
occurence and severity of endometriosis in primates
exposed to dioxin; and reports of a variety of effects in
fish, reptiles, birds, and sea mammals in areas where the
environment has been contaminated with
endocrine-disrupting chemicals.
Much of the focus on endocrine-disrupting chemicals has
been on those chemicals that mimic the action of the
female sex hormone estrogen (the so-called environmental
estrogens). Some have questioned whether the potency
and prevalence of environmental estrogens can account for
the plethora of effects being attributed to endocrine
disruption in different populations of exposed humans and
wildlife species. The endocrine disrupter issue expanded
well beyond the previous focus on environmental estrogens
with RTD's recent findings concerning p.p -DDE and
vinclozolin.
* p,p -ODE: RTD scientists reported that the major
and persistent DDT metabolite p.p.'-DDE has
surprisingly potent ability to bind to the androgen
receptor and block the action of endogenous
androgens in the body (Kelce et al.). The
concentration necessary to displace 50% of synthetic
androgen from its receptor was only one order of
magnitude higher than that necessary for a clinically
used anti-androgenic drug. Perinatal exposure of rats
to p,p'-DDE delayed the onset of puberty and
prolonged the retention of thoracic nipples in male
offspring—effects consistent with the proposed
mechanism of action.
*• Vinclozolin: RTD researchers demonstrated that
metabolites of this fungicide inhibit binding of the
androgen receptor to response elements on DNA
(Gray et al. "Developmental effects"; Wong et al.).
RTD research into endocrine disruption also included
study of the effects of dioxin.
*• Exposure of rats and hamsters early
in the third trimester of pregnancy '
to single dioxin doses as low as
l/Jg/kg permanently reduced
accessory sex gland weight and production of sperm
in male offspring in the absence of any evidence of
maternal toxicity (Gray et al. "Reproductive
morphology and function"; Gray et al. "Exposure to
TCDD"). Interestingly, the effects on sperm counts
were most severe when ejaculated counts were
obtained. The reductions were less severe in the
epididymis, and almost nonexistent when testicular
sperm production was assessed. These results
indicate that the primary developmental effect is
clearly post-testicular and point to the epididymis as
a primary target.
* In the female offspring of rats and hamsters, RTD
scientists observed a number of unusual and
previously reported effects, including a delay in
puberty, partial clefting of the phallus, abnormalities
of the vagina, and difficulties in mating.
Collectively, these findings heighten our concern over
the noncancer health effects of this ubiquitous
environmental contaminant, as noted in the draft Dioxin
Risk Assessment.
ADVANCING KNOWLEDGE FOR A PURPOSE
127
-------
NHEERL FY95 ANNUAL REPORT
REPRODUCTIVE TOXICOLOGY DIVISION
Endometrios/s is a painful reproductive disorder affecting
nearly five million women annually. Recently, it was
reported that primates exposed nearly a decade ago to
dioxin had dose-related increases in incidence and severity
of endometriosis. Unfortunately, there are few animal
models for study of causes of endometriosis.
> To help fill this void, we developed a surgically
induced model of endometriosis in the mouse based
upon earlier work in a rat model (Cummings and
Metcalf). The mouse was selected because of its
known sensitivity to dioxin, but difficulties created by
the small size of available uterine implants had to be
overcome and the model verified. In this model, slices
of the uterus were sutured to the intestinal
mesenteries and examined for growth in the
presence or absence of an estrogen. In control
females, the implants survived and grew to be
fluid-filled sacs within three weeks of surgery. In the
absence of estrogen (via ovariectomy) or its
supplementation (by silastic implants), the implants
responded as expected from other animal models
(i.e., their growth was estrogen-dependent).
The model is now being used to investigate the effects
of 2,3,7,8-tetrachlorodibenzo-f>-dioxin (TCDD) on the
growth of endometriotic implants.
One way to bridge the gap between species in extrapolating
data is to use a parallelogram approach with animal data
obtained from in vivo and in vitro models, and comparable
human data derived from an analogous in vitro system.
Predictions can then be made about what might be
expected in humans exposed in vivo.
*• RTD scientists were able to characterize the
expression patterns for the arylhydrocarbon (Ah)
receptor and its binding partner ARNT in human
embryonic palate shelves (Abbott, Probst et al.).
Both AhR and ARNT are expressed throughout the
developing palate, as well as numerous other
embryonic tissues. This accomplishment helps build
the basis for extrapolation of animal and in vitro test
data for TCDD to humans and contributes to the
understanding of the role of the Ah receptor in
normal development.
#Future Effects: This year, quantitative PCR (porynwase chain
reaction, a technique in which mRNA from cells is amplified millions
of times to Identify genes with low expression levels) is being used
to establish the expression of the respective mRNAs in both control
and exposed palates. Additional work is under-way to evaluate a
novel hypothesis for the marked synergism noted when developing
palates are exposed simultaneously to glucocorticoids and TCDD.
interaction with glucocorticoids & important because of the rote
that they play as a trophic factor in normal development and
because a variety of chemicals and environmental stimulations can
elevate the levels of this hormone in the blood by activating adrenal
128
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
REPRODUCTIVE TOXICOLOGY DIVISION
In response to concerns raised by several epidemiologi-
cal studies on adverse reproductive outcomes from
disinfectant by-products, RTD developed a comprehen-
sive research strategy in 1993 that consists of the
following three basic components:
• Hazard identification studies
• Mechanism of action studies
• Development of biomarkers of effect
Haloacetic acids formed during disinfection of water by
chlorination induce embryotoxicity and reproductive toxicity
in laboratory animal models.
*• RTD scientists, in conjunction with ECD scientists,
completed a Quantitative Structure Activity
Relationship (QSAR) study with a series of mono-, di-,
and tri- halo (bromo-, chloro-, iodo-, and fluoro-)
acetic acids using an in vitro mouse whole embryo
culture system (Richards and Hunter). These studies
showed that lipophilicity (log P) and electronic
properties (e lumo) were important determinants of
the ability to induce neural tube defects. The results
are being used to prioritize testing in in vivo models.
The potential health effects of bromoacetic acids are
becoming increasingly important because these acids are
formed at relatively high levels in source waters
containing bromide ion. Very little information on the
toxicity of brominated acetic acids is in the literature.
In the area of male reproductive effects, RTD scientists
observed that short-term exposure to dibromoacetic
acid alters sperm morphology and motility in adult male
rats (Under et al.). These findings were followed up
with dose-and time-course studies, in which the effects
were observed to occur in the absence of other
systemic effects and to persist at the highest dose levels
long after cessation of exposure. Significantly, fused
sperm (a rare finding in reproductive toxicity studies)
were found at doses as low as 50 mg/kg.
•$":• Future Effects: This information will likely affect the
establishment of the MCL for bromoacids and provide novel
markers for studies of mode of action as well as for studies of
biomarkers in highly exposed human populations.
RTD scientists collaborated with the cancer bioassay
program in ECD to evaluate reproductive function in
male rats receiving chronic exposure to
bromodichloromethane and chloral hydrate. The
results showed a significant impairment in sperm
motility for the former at a dose level (39 mg/kg)
which, at least after one year of exposure, was not
associated with increased tumor incidence (Klinefelter
et al.).
ADVANCING KNOWLEDGE FOR A PURPOSE
129
-------
NHEERl FY95 ANNUAL REPORT
REPRODUCTIVE TOXICOLOGY DIVISION
Improvements In Reproductive Toxlcity Test Methods
To cooperate with the development of internationally
harmonized toxicity testing guidelines, EPA has been
revising noncancer (including multigeneration) testing
guidelines. In addition to including endpoints sensitive to
disruption by chemicals that alter the function of the
endocrine system, more sensitive measures of gamete
production and function are also being incorporated into
the guidelines.
Newly incorporated endpoints for sperm motility and
morphology assessments require an understanding of the
relationship between motility and fertility for use in the risk
assessment process.
* RTD scientists developed a rodent model in which
sperm motility and fertilizing ability could be
evaluated in the same animal. This model was applied
after acute exposure to o/pho-chlorhydrin that
produced graded decrements in sperm motion
endpoints in both uterine and epididymal
spermatozoa as measured by computer-aided semen
analysis (Slott et al.). Analysis of the results using both
linear and logistic regression showed that uterine
sperm were more sensitive than epididymal sperm to
the effects of this model toxicant, and that the
combination of epididymal and uterine sperm
endpoints produced the best statistical model for the
prediction of fertility from sperm motion
characteristics.
RTD scientists demonstrated and characterized the
potential impact of acute toxicant exposure on female
reproduction in hamsters exposed to the fungicide
carbendazim during fertilization (Zuelke and
Perreault). Zygote morphology and zygote
chromosomes were evaluated after both in vivo and
in vitro exposures. Immunoflouresce microscopy
demonstrated chemically-induced abnormalities of
fertilization (altered meiotic spindle, multiple female
pronuclei, and fragmented polar bodies), while
chromosome analysis confirmed that these alterations
are associated with abnormal chromosome
partitioning (aneuploidy). The zygotic effects
correlated well with previously reported abnormal
pregnancy outcomes after the same treatment.
These results show that the fertilization process can
be severely affected by a single exposure, with
profound effects on developmental potential, and
demonstrate the utility of in vitro fertilization assays in
toxicology.
130
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
REPRODUCTIVE TOXICOLOGY DIVISION
To alleviate criticisms of No Observed Adverse Effect
Level (NOAEL)-based risk assessments for noncancer
endpoints, RTD completed analysis of a large database
of standard developmental toxicity bioassay results to
determine the feasibility of implementing the
"benchmark dose" (BMD) approach.
In the BMD approach, statistical dose response models
are used to calculate a preset level of risk near the low
end of the observable range, along with the 95% lower
confidence limit on that value. This approach has the
multiple advantages of using more of the experimental
data, of producing consistent potency calculations across
different studies and endpoints, and of making it
unnecessary to repeat studies that fail to determine a
NOAEL (Barnes et al.).
While the BMD models have generally been developed to
handle quanta/ (yes or no) data that derive from many
experiments, many other parameters are measured on
graded scales (i.e., continuous variable) such as effects on
body weight, motor activity, or serum enzyme levels.
* RTD recently showed how BMDs for reduced fetal
weight (often the most sensitive indicator of response
in developmental toxicity studies) could be obtained
and what effect levels were similar, on average, to
traditionally determined NOAEL (Kavlock, Allen et
al.).
One disadvantage of the NOAEL is that better study designs
(large sample sizes, more dose groups, greater statistical
power) can only yield more conservative risk estimates,
and, therefore, better experiments are in fact discouraged.
However, because current testing guidelines have been
optimized within resource and technical constraints to
generate NOAELs, it is important to determine how
experimental design might be modified to take advantage
of the strengths of the BMD approach.
*• RTD scientists performed simulation analyses to
determine the impact of study design (sample size
and dose spacing) on BMD calculations. These
analyses showed that optimal results were obtained
with designs that contained two nonzero responding
dose groups, with one dose preferably near the
estimated risk level (Kavlock, Schmid et al.). Designs
with only one positive dose group yielded results with
considerably wider (and hence more conservative)
confidence levels. We also showed that sample sizes
half those normally used were nearly as good for
calculating the BMD. Largely as result of this body of
research, the Agency is beginning to accept the BMD
as a replacement for the NOAEL in establishing
Reference Doses (RfDs) and Reference Concen-
trations (RfCs) for noncancer health effects, as
evidenced by 1995 risk assessments for methyl
mercury and boric acid.
The revised 1996 Cancer Risk Assessment Guidelines
have adopted a variation of the BMD approach as an
option in the dose-response assessment of some
carcinogens.
11>e BHE5 approach adds this Important
analysis to risk assessment study design, but
several years before sufficient experience and'
ADVANCING KNOWLEDGE FOR A PURPOSE
131
-------
NHEERL FY95 ANNUAL REPORT
REPRODUCTIVE TOXICOLOGY DIVISION
'xtures
Exposures in the real world are seldom to individual
chemicals, and risk assessments must often factor in
contact with multiple chemicals through multiple routes
of exposure.
In general, the additivity concept is adopted to make
predictions of how combinations of chemicals might act.
However, inadequate experimental work exists to verify
additivity assumptions beyond examining how simple binary
combinations of chemicals might interact.
*• RTD scientists published a major study that reported
the results of factorial design of the interactions of
three chemicals on developmental outcomes
(Narotsky, Weller et al.). This study employed three
chemicals (heptachlor, trichloroethylene, and
diethylhexylphthlate) known to be developmental
toxicants that occur together frequently at Superfund
sites. Individual dose-response data were reported in
a companion paper (Narotsky and Kavlock) that
resulted from a multidisciplinary effort with the
Neurotoxicology Division.
The interaction study investigated whether individual
effects would be additive or nonadditive across a
wide range of dose levels (30-fold difference between
the high and low dose). Five levels of each chemical
were combined with the other chemicals to yield a
design of 125 dose groups involving nearly 1500
pregnant rats. The study allowed for alternative,
more efficient, designs within the main body. The
main effects observed in the combination study were
consistent with known effects of the individual agents.
Of the nine endpoints examined, six had statistically
significant two-way interactions (some synergistic,
some antagonistic), but no three-way interactions
were detected.
future Effects: The study points out the difficulties of
design, execution, and interpretation of such
to explore alternative
132
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
REPRODUCTIVE TOXICOLOGY DIVISION
Table 38. RTD Issues and Accomplishments Overview
DEVELOPMENT OF BBDR MODELS
How are biologically based dose response (BBDR)
models helpful for assimilating relevant data and
testing model derived hypotheses?
• Tested predictions from computer model of pharmacokinetics, nucleotide pool
biosynthesis, and cell cycle kinetics on rat model.
• Demonstrated that maternal administration of 5-FU produced fetal anemia: uncovered
new insights and alternate modes of action for 5-FU.
How does methanol inhalation produce birth
defects in mice?
Completed work on toxicity of formic acid in embryos exposed in vitro.
Described patterns of cell death in rat and mouse embryos exposed to methanol.
Accumulated evidence to support relevancy of mouse model to potential effects in
humans exposed to methanol.
Accumulated evidence to support relevancy of mouse model to potential effects in
humans exposed to methanol in environment that is not expected to cause buildup of
formate levels in blood.
How may quantitative dose-response modeling in
developmental toxicity be advanced through use
of mechanistic data in risk assessment?
ENDOCRINE DISRUPTION
• Proposed an Embryologically Based Dose Response (EBDR) model that is likely to be
generically applicable across chemicals and instructive to findings across species.
How may concern over possible breadth of
chemicals responsible for endocrine disruption in
exposed human and wildlife populations be
addressed?
• Found p,p -DDE to have surprisingly potent ability to block endogenous androgens in
the body.
* Demonstrated that metabolites of vmclozolin inhibit binding of androgen to DNA
response elements.
• Found that low doses of dioxin permanently reduce accessory sex gland weight and
production of sperm in abscence of maternal toxicity.
How may animal models for study of the cause of
endometriosis be advanced?
Successfully developed surgically induced model of endometriosis in mice.
How may data extrapolation models be developed
without using in vitro data?
Characterized expression patterns for Ah receptor and ARm in human embryonic
palate shelves.
REPRODUCTIVE EFFECTS OF DRINKING WATER BY-PRODUCTS
RTD AcccofTfiplishments
How may continuing concern over disinfection by-
products, embryotoxicology and reproductive
toxicology be addressed?
• Showed that lipophilicity and electronic properties were important determinants of
ability to induce neural tube defects.
How may information on toxicity of brominated
acetic acids be advanced?
• Observed that short term exposure to dibromoacetic acid alters sperm morphology and
motility in adult male rats. Fused sperm found at low doses.
IMPROVEMENTS IN REPRODUCTIVE TOXICITY TEST METHODS
How may more sensitive measures of gamete
production and function be included in testing
guidelines?
Developed and applied rodent model for evaluating sperm motility and fertility in same
animal.
Demonstrated and characterized potential effect on female reproduction after acute
exposure to toxicant carbendazim.
ADVANCING KNOWLEDGE FOR A PURPOSE
133
-------
NHEERL FY95 ANNUAL REPORT
REPRODUCTIVE TOXICOLOGY DIVISION
IMPROVEMENTS IN NONCANCER DOSE-RESPONSE ASSESSMENT
Issue
RTD Acccomplishments
How may NOAEL-based risk assessment be applied
to noncancer endpoints?
Determined feasibility of implementing "benchmark dose" (BMD) approach.
Demonstrated how BMDs could be obtained for reduced fetal weight and showed
comparison to traditionally determined NOAELs.
Performed simulations to show how to design studies to obtain optimal results from
BMD approach.
DEVELOPMENTAL TOXICITY OF COMPLEX MIXTURES
Issue
RTD Acccompiishments
What experimental work exists to verify
assumptions of additivity concepts?
* Published results of largest and most comprehensive study of additivity concept for
developmental toxicity.
134
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
References
NHEERL FY95 ANNUAL REPORT
REFERENCES
Abbott, B.A., M.R. Probst, and G.H. Perdew. 1994. "Immuno-
histochemical Double-Staining for AH receptor and ARNT in
human embryonic palatal shelves." Teratology. 50:361 -366.
Abbott, B.A., M.T. Ebron-McCoy, and J.E. Andrews. 1995. "Cell
death in rat and mouse embryos exposed to methanol in whole
embryo culture." Toxicology. 97:159-171.
Abbott, B.D., L.S. Birnbaum, and G.H. Perdew. October, 1995.
Developmental Expression of Two Members of a New Class of
Transcriptional Factors: I. Expression of Aryl Hydrocarbon
Receptor in the C57BL/6N Mouse Embryo." Development
Dynamics. 204:133-143.
Afshari, A., et al. 1995. "Centromere Analysis of Micronuclei in 2-
Aminoanthraquinone in cultured mouse splenocytes using both a
gamma-satellite DMA probe and anti-kinetochore antibody."
Molecular and Environmental Mutagenesis. 24:96-102.
Allen, J., et al. 1995. "Germ-line Specific Factors in Chemical
Mutagenesis." Mutation Research. 330:219-231.
Andersen, Christian P., and Paul T. Rygiewicz. 1995. "Allocation of
carbon in mycorrhizal pinus ponderosa seedlings exposed to
ozone." The New Phytologist. 131:471 -480.
Andrews, J.A., M.T. Ebron-McCoy, R.J. Kavlock, and J.M. Rogers.
1995. "Developmental toxicity of formate and formic acid in whole
embryo culture: a comparative study with mouse and rat
embryos." Teratology. 51:243-251.
Andrews, S.J., j.H. Freeman, C.S. Carter, and M.E. Stanton. 1995.
"Ontogeny of Conditioning in the Rat: Auditory Frequency and
Discrimination Learning Effects." Developmental Psycho-
biology. 28(6):307-320.
Anger, W.K., R.E. Letz, D.W. Chrislip, H. Frumkin, H.K. Hudnell,
J.M. Russo, L. Chappell, and L. Hutchinson. 1994.
"Neurobehavioral Test Methods for Environmental Health Studies
of Adults." Neurotoxicology and Teratology. !6(5):489-497.
Ankley, G.T. 1996. "Laboratory versus field measurement endpoints:
A contaminated sediment perspective." Risk Assessment
Considerations for Contaminated Sediments. SETAC Pellston
Series.
Ankley, G.T., and M.K. Schubauer-Berigan. 1994. "Comparison of
the techniques for the isolation of pore water for sediment toxicity
testing." Archives of Environmental Contamination. 27:507-
512.
Ankley, G.T., and M.K. Schubauer-Berigan. 1995. "Background and
overview of sediment toxicity identification evaluation pro-
cedures." Journal of Aquatic Ecosystem Health. 4:133-149.
Ankley, G.T., and S.A. Collyard. 1995. "Influence of piperonyl
butoxide on the toxicity of organophosphate insecticides to three
species of freshwater benthic invertebrates." Comparative
Biochemistry and Physiology. I IOC: 149-155.
Ankley, G.T., M.K. Schubauer-Berigan, and P.O. Monson. 1995.
"Influence of pH and hardness on toxicity of ammonia to the
amphipod Hyalella azteca." Canadian Journal of Fisheries and
Aquatic Science. 52:2078-2083.
Ankley, G.T., R.S. Erickson, G.L. Phipps, V.R. Mattson, P.A. Kosian,
B.R. Sheedy, and J.S. Cox. 1995. "Effects of light intensity on the
phototoxicity of fluoranthene to a benthic microinvertebrate."
Environmental Science and Technology. 29(11):2828-2833.
Ankley, G.T., S.A. Collyard, P.O. Monson, and P.A. Kosian. 1994.
"Influence of ultraviolet light on the toxicity of sediments
contaminated with polycyclic aromatic hydrocarbons."
Environmental Toxicology and Chemistry. 13:1791 -1796.
Atterwill, C.K., A. Bruinink, J. Drejer, E. Duarte, E.M. Abdulla, C.
Meredith, P. Nicotera, and B. Veronesi. 1994. "In vitro
Neurotoxicity Testing: The Report and Recommendations of
ECVAM Workshop." ATLA. 22:350-362.
Baker, B., D.M. Olszyk, and D. Tingey. 1996. "Digital image analysis
to determine leaf area." Journal of Plant Physiology. 148:530-
535.
Ball, L.M., L Stocking, M.J. Kohan, S.H. Warren, and J. Lewtas. 1995.
"Metabolic Activation of the Genotoxic Environmental
Contaminants 2- and 3- Nitrofluoranthene in Variants of Salmonella
typhimurium TA98." Mutagenesis. 10(6):497-504.
Barkay, T., N. Kroer, L.D. Rasmussen, and S.J. Sorensen. 1995.
"Conjugal Transfer at Natural Population Densities in a Microcosm
Simulating an Estuarine Environment." FEMS (Federal European
Microbiological Society). Microbial Ecology. !6(l):43-54.
Barnes, D.G., G.P. Daston, J.S. Evans, A.M. Jarabek, R.J. Kavlock,
C.A. Kimmel, C. Park, and H.L Spitzer. 1995. "Benchmark dose
workshop: criteria for use of benchmark dose to estimate a
reference dose." Regulatory Toxicology and Pharmacology.
21:296-306.
Barone, S., D.W. Herr, and K.M. Crofton. 1995. "The Effects of 3,3'-
Iminodiproprionitrile on the Structure and Function of the Rat
Visual System." Neurotoxicology. 16:451-468.
Barone, S., M.E. Stanton, and W.R. Mundy. 1995. "Neurotoxic
Effects of Neonatal Triethyltin (TET) Are Exacerbated with
Aging." Neurobiology of Aging. !6(5):723-735.
ADVANCING KNOWLEDGE FOR A PURPOSE
135
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Bascom, R.B., P.A. Bromberg, D.A. Costa, R.B. Devlin, D.W.
Dockery, M.W. Frampton, W. Lambert, j.M. Samet, F.E. Speizer,
and M. Utell. 1996. "State of the art review: health effects of
outdoor pollutation." Respiratory Critical Care Medicine.
155:3-50.
Becker, S., R.B. Devlin, H.S. Koren, and LB. Roger. 1996. "Exposure
of humans to HNO3 causes alveolar macrophage activation."
Inhalation Toxicology. 8:185-200.
Behrenfeld, M., D. Lean, and H. Lee III. 1995. Journal of Phycology.
31:25-36.
Behrenfeld, M.J., D.R.S. Lean, and H. Lee II. 1995. "Ultraviolet-B
Radiation Effects on Inorganic Nitrogen Uptake by Natural
Assemblages of Oceanic Plankton." Journal of Phycology. 31:25-
36.
Behrenfeld, M.J., H. Lee II., LF. Small. 1994. "Interactions Between
Nutrition Status and Long-term Responses to Ultraviolet-B
Radiation Stress in a Marine Diatom." Marine Biology.
II8(3):523-530.
Benane, S., C. Blackman, C.F., House, D.E. 1996. "Effect of
perchloroethylene and its metoabolites on intercellular
communication in clone 9 rat liver cells." Journal of Toxicology
and Environmental Health. 48:427-438.
Bender, M.I., P.P. Tans, J.T. Ellis, j. Orchardo, and K. Habfast. 1994.
"A High Precision Isotope Ratio Mass Spectrometry Method for
Measuring the O2/N2 Ratio in Air." Geochimica and
Cosmochimica Acta. 58(21 ):4751 -4758.
Benignus, V. 1995. "A model to predict carboxyhemoglobin and
pulmonary parameters after exposure to O2, CQ and CO."
Journal of Aviation, Space and Environmental Medicine.
66:369-374.
Bennett, R.S., W.D. Edge, W.L. Griffis, A.C. Matz, J.O. Wolff, and
L.M. Ganio. 1994. "Temporal and Spatial Distribution of Azinphos-
methyl Applied to Alfalfa." Archives of Environmental
Contamination and Toxicology. 27:534-540.
Bennett, W.D., K.L Zeman, and C.S. Kim. 1996. "Variablity of fine
particle deposition in healthy adults: effect of age and gender."
American Journal of Respiratory Critical Care Medicine.
153:1641-1647.
Berman, E., M. Schlicht, V. Moser, and R.C. MacPhail. 1995. "A
Multidisciplinary Approach To Toxicological Screening. Systemic
Toxicity." Journal of Toxicology and Environvmental Health.
45:127-143.
Best, Louis B., Kathryn E. Freemark, James J. Dinsmore, and Martha
Camp. 1995. "A review and synthesis of breeding bird habitat use
in Iowa's agricultural landscape." American Midland Naturalist.
134(1): I-29.
Binkova, B.,J. Lewtas, I. MiskovaJ. Lenick, and R. Sram. 1995. "DNA
adducts and personal air monitoring of carcinogenic polycyclic
aromatic hydrocarbons in an environmentally exposed population."
Carcinogenesis. 16:1037-1046.
Birnbaum, L.S. December, 1995. "Developmental Effects of Dioxins
and Related Endocrine Disrupting Chemicals." Toxicology
Letters. 82/83:743-750.
Birnbaum, LS. February, 1995. "Workshop on Perinatal Exposure to
Dioxin-like Compounds. V. Immumologic Effects."
Environmental Health Perspectives. 103(2): 157-160.
Birnbaum, LS. November 1994. "The Mechanism of Dioxin Toxicity:
Relationship to Risk Assessment." Environmental Health
Perspectives. 102(9): 157-167.
Birnbaum, L.S. Re-evaluation of Dioxin. Great Lakes Water Quality
Board Meeting- 102nd Meeting, Chicago, IL.July 15, 1993.
Birnbaum, L.S., and B.D. Abbott. "Effect of Dioxin on Growth
Factor and Receptor Expression in Developing Palate."
Birnbaum, L.S., and M.J. DeVito. December 1995. "Use of Toxic
Equivalency Factors for Risk Assessment for Dioxins and Related
Compounds." Toxicology. 105:391 -401.
Bishop, G.D., and M.R. Church. 1992. "Automated approaches for
regional runoff mapping in the Northeastern United States."
Journal of Hydrology. 138:361 -383.
Bishop, G.D., and M.R. Church. 1995. "Mapping long-term regional
runoff in the Eastern United States using automated approaches."
Journal of Hydrology. 169:189-207.
Blackman, C., and S. Benane. 1996. "Frequency-dependent
Interference by Magentic Fields of Nerve-Growth-Factor-Induced
Neurite Outgrowth in PC-12 Cells." Bioelectromagnetics.
16:387-395.
Blanchard, J., D. House, and C. Blackman. 1995. "Evaluation of
Whole-Animal Data Using the Ion Parametric Resonance Model."
Bioelectromagnetics. 16:21 1-215.
Boese, B., H. Lee, D. Specht, J. Pelletier, and R. Randall.
Environmental Toxicology and Chemistry. In Press.
Boese, B.L, M. Winsor, H. Lee II., S. Echols, j. Pelletier, and R.
Randall. 1995. "PCB Congeners and Hexachlorobenzene Biota
Sediment Accumulation Factors for Macoma nasuta Exposed to
Sediments with Different Total Organic Carbon Contents."
Environmental Toxicology and Chemistry. 14(2):303-310.
Boyes, W.K. 1994. "Rat and Human Sensory Evoked Potentials and
the Predictability of Human Neurotoxicity from Rat Data."
Neurotoxicology. I5(3):569-S78.
136
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Boyes, W.K., P. Tandon, S. Barone, and S. Padilla. 1994. "Effects of
organophoshphates on the visual system of rats." Journal of
Applied Toxicology. 14:135-143.
Boyton, W.R., J.H. Garber, R. Summers, and W.M. Kemp. 1995.
"Inputs, Transformations, and Transports of Nitrogen and
Phosphorus in Chesapeake Bay and Selected Tributaries."
Estuaries. 18(1 B):285-3 14.
Bradbury, S.P. 1995. "Ecological risk assessment for chemical
stressors: Challenges in predictive ecotoxicology research."
Australian Journal of Ecotoxicology. 1:3-9.
Bradbury, S.P. 1995. "Quantitative structure activity relationships and
ecological risk assessmement: An overview of predictive aquatic
toxicology research." Toxicology Letters. 79:229-237.
Bradbury, S.P., O.G. Mekenyan, G.D. Veith, and N. Aaharieva. 1995.
"SAR models for futile metabolism: One electron reduction of
quinones, phenols and nitrobenzenes." SAR and QSAR
Environmental Research. 4:109-124.
Brazner, J.C., and J.J. Magnuson. 1994. "Patterns of fish species
richness and abundance in coastal marshes and other nearshore
habitats in Green Bay, Lake Michigan." International Association
of Theoritical and Applied Limnology. 25:2098-2104.
Brewer, A., UG. Ahlborg, LS. Birnbaum, and LE. Gray. September,
1995. "Functional Aspects of Developmental Toxicity of
Polyhalogenated Aromatic Hydrocarbons in Experimental Animals
and Human Infants." 293:1-40.
Broadwell, O.K., D. Darcey, H.K. Hudnell, D. Otto, and W. Boyes.
1995. "Worksite Clinical and Neurobehavioral Assessment of
Solvent Exposed Microelectronic Workers." American Journal
of Industrial Medicine. 27:677-698.
Broadwell, O.K., D.J. Darcey, H.K. Hudnell, W.K. Boyes, and D.A.
Otto. 1995. "Work-site Clinical and Neurobehavioral Assessment
of Solvent Exposed Microelectronics Workers." American
Journal of Industrial Medicine. 27:677-698.
Brock, K., C. Doerr, and M. Moore. 1995. "Mutagenicity and
Clastogenicity of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-
furanone (MX) in L5178Y/TK+/-3.7.2C Mouse Lymphoma Cells."
Mutation Research Letters. 348:105-1 10.
Broderius, S.J., M.D. Kahl, and M.D. Hoglund. 1995. "Use of joint
toxic response to define the primary mode of toxic action for
diverse industrial organic chemicals." Environmental Toxicology
and Chemistry. 14(9): 1591-1605.
Brooke, L.T., G.T. Ankley, D.J. Call, and P.M. Cook. 1996. "Gut
content weight and clearance rate for three species of freshwater
invertebrate." Environmental Toxicology and Chemistry.
15:223-228.
Brown, J., and K. Kitchin. 1995. "Arsenite, but not cadmium, induces
ornithine decarboxylase and heme oxygenase activity in rat liver:
relevance to arsenic carcinogenesis." Cancer Letters. 98:227-
231.
Brown, J.S., T.R. Gerrity, W.D. Bennett, C.S. Kim, and D. House.
1995. "Dispersion of aerosol boluses in the human lung:
dependence on lung volume, bolus volume, and gender." Journal
of Applied Physiology. 79:1787-1795.
Brown, S. 1996. "Present and potential future role of forests in the
global warming debate." Unasylva. In press.
Brown, S. 1996. "Tropical forests and the global carbon cycle:
estimating state and change in biomass density." The Role of
Forest Ecosystems and Forest Management in the Global
Carbon Cycle. Ed. M. Apps, D. Price. NATO Series, Springer
Verlag, NY.
Brown, Sandra, and Greg Gaston. 1995. "Estimates of biomass
density for tropical forests." Biomass Burning and Global
Change. Ed. Joel Levine. March 13-17. Williamsburg, VA.
Brown, Sandra, Jayant Sathaye, Melvin Cannell, and Pekka Kauppi.
1995. "Management of forest for mitigation of greenhouse gas
emissions." Second Assessment Report, Intergovernmental
Panel on Climate Change (IPCC), Working Group II.
Chap. 24, 48.
Brown, Sandra, Melanie Lenart, Jiangming Mo, Guohui Kong. 1995.
"Structure and organic matter dynamics of a human-impacted pine
forest in a MAB reserve of subtropical China." Biotropica.
27(3):276-289.
Bugmann, Harald K.M., Allen M. Solomon. 1995. "The use of a
European forest model in North America: A study of ecosystem
response to climate gradients." Journal of Biogeography.
22:477-484.
Bull, R.J., LS. Birnbaum, K.P. Cantor, J.B. Rose, B.E. Butterworth, R.
Pegram, and J. Tuomisto. October, 1995. "Water Chlorination:
Essential Process or Cancer Hazard?" Fundamental and Applied
Toxicology. 28:155-166.
Burgess, R.M., and G.E. Morrison. 1995. "Clams as a Species for
Sublethal Sediment Toxicity Studies." Quintessence-Excellence
in Environmental Contamination and Toxicology. I (l):48.
Burgess, R.M., K.T. Ho, M.D. Tagliabue, A. Kuhn, R. Comeleo, P.
Comeleo, G. Modica, and G.E. Morrison. 1995. "Toxicity
Characterization of an Industrial and Municipal Effluent Discharging
to the Marine Environment." Marine Pollution Bulletin.
30(8):524-535.
Burkhard, L.P., and B.R. Sheedy. 1995. "Evaluation of screening
procedures for bioconcentrable organic chemicals in effluents and
sediments." Environmental Toxicology and Chemistry.
14:697-711.
ADVANCING KNOWLEDGE FOR A PURPOSE
137
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Burleson, G.R. 1995. "Influenza Virus Host Resistance Model for
Assessment of Immunotoxicity, Immunostimulation, and Antiviral
Compounds." Wiley-Liss, Inc., (14). Ed. G.R. Burleson, J.H.
Dean, and A.E. Munson. A. John Wiley & Sons, Inc. 181 -202.
Burleson, G.R. "Pulmonary Immunocompetence and Pulmonary
Immunotoxicology." Experimental Immunotoxicology. Ed. M.
Hoisapple and R.J. Smialowicz. CRC Press.
Burleson, G.R., and J.H. Dean. 1995. "Immunotoxicology: Past,
Present, and Future." Wiley-Liss, Inc., (I). Ed. G.R. Burleson, J.H.
Dean, and A.E. Munson. A.John Wiley & Sons, Inc. 3-16.
Burleson, G.R., H. Lebrec, Y.G. Yang, and J.D. Ibanes, K.N.
Pennington, and LS. Birnbaum. January, 1996. "Effect of
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) on Influenza Virus
Host Resistance in Mice." Fundamental and Applied
Toxicology. 29:40-47.
Bushnell, P.J. 1995. "Overt Orienting in the Rat: Parametric Studies
of Cued Detection of Visual Targets." Behavioral Neuroscience.
109:1095-1 105.
Bushnell, P.J., and W.M. Oshiro. 1995. "2,4-Dithiobiuret in Rats:
Cognitive Facilitation After Acute Injection Precedes Motor
Impairment After Repeated Daily Injections."
Psychopharmacology. 123:267-279.
Bushnell, P.J., E.D. Levin, and D.H. Overstreet. 1995. "Spatial
Working and Reference Memory in Rats Bred for Autonomic
Sensitivity to Cholinergic Stimulation: Acquisition, Accuracy,
Speed, and Effects of Cholinergic Drugs." Neurobiology of
Learning and Memory. 63:1 16-132.
Cairns, Michael A., Jerry R. Barker, Ronald W. Shea, and Patricia K.
Haggerty. 1995. "Carbon dynamics of Mexican tropical evergreen
forests: influence of forest management options and refinement of
carbon-flux estimates." U.S. Country Studies Program
Regional Workshop on Greenhouse Gas Mitigation for Latin
American Countries. July 10-14. Cancun, Mexico. (Also,
Interciensia. 20(6):40I-408).
Cairns, Michael A., Rodolfo Dirzo, Frank Zadroga, and Omar Masera.
1995. "Forests of Mexico: A diminishing resource?" Journal of
Forestry. 93(7):21-24.
Carter, C.S., J.H. Freeman, and M.E. Stanton. 1995. "Neonatal
Medial Prefrontal Lesions and Recovery of Spatial Delayed
Alternation in the Rat: Effects of Delay Interval." Developmental
Psychobiology. 28(5):269-279.
Carter, J., H. Carter, and A. DeAngelo. 1995. "Biochemical, Patho-
logic and Morphometric Alterations Induced in Male B6C3FI
Mouse Liver by Short Term Exposure to Dichloroacetic Acid."
Toxicology Letters. 81:55-71.
Castillejos, M., D.R. Gold, A. Damokosh, P. Serrano, G. Allen, W.F.
McDonnell, D. Dockery, S. Ruiz Velasco, M. Hernandez, and C.
Hayes. "Acute effects of ozone on the pulmonary function of
exercising schoolchildren from Mexico City." 1966 American
Journal of Respiratory Critical Care Medicine. In press.
Chacko, R.J., G.J. Weidemann, D.O. TeBeest, and J.C. Correll. 1994.
"Use of Vegetative Compatibility and Heterokaryosis to
Determine Potential Asexual Gene Exchange in Colletotrichum
gloeosporioides." Biological Control. 4:382-389.
Chadwick, R., et al. 1995. "Possible errors in assay for beta-
Glycosidase activity within the Gl tract and its contents." Applied
and Environmental Microbiology. 61 (2):820-822.
Chadwick, R., et al. 1995. "Potentiation of 2,6-Dinitrotoluene
Genotoxicity in Fischer 344 Rats by Pretreatment with Coal Tar
Creosote." Journal of Toxicology and Environmental Health.
44:319-336.
Chadwick, R.W., S.E. George, M.J. Kohan, R.W. Williams, J.C.
Allison, D.L Talley, Y.O. Hayes, and J. Chang. 1995. "Potentiation
of 2,6-Dinitrotoluene genotoxicity in Fischer 344 rats by pretreat
with coal tar creosote." Journal of Toxicology and
Environmental Health. 44:319-336.
Chang, J., et al. 1995. "Microbial Succession and Intestinal Enzyme
Activities in the Developing Rat." Journal of Applied
Bacteriology. 77:709-718.
Chang, W.Y.B., and G.A. King. 1994. "Centennial Climate Changes
and their Global Associations in the Yangtze River (Chang Jiang)
Delta, China and Subtropical Asia." Climatic Research. 4:95-103.
Chapman, P.J., M. Shelton, Magda Grifoll, and S. Selifonov. 1995.
"Fossil Fuel Biodegradation: Laboratory Studies." Environmental
Health Perspectives. !03(Suppl):79-83.
Chen, J., and G. Henderson. 1994. "Marking Formosan Subterranean
Termites, Coptotermes formosanus, with Rubidium (Isoptera:
Rhinotermitidae)." Sociobiology. Vol. 23.
Cheng, P.W., T.F. Boat, S. Shaikh, O.L Wang, P.C. Hu, and D.L.
Costa. January, 1995. "Differential Effects of Ozone on Lung
Epithelial Lining Fluid Volume and Protein Content."
Experimental Lung Research. 21 (3):351 -365. 600/J-95/213.
Chiappa, S., S. Padilla, C. Koenignsberger, V. Moser, and S. Brimijoin.
1995. "Slow accumulation of acetylcholineseterase in rat brain
during enzyme inhibition by repeated dosing with chlorpyrifos."
Biochemical Pharmacology. 49:955-963.
Chisholm, S.W. 1995. "The Iron Hypothesis-Basic Research Meets
Environmental Policy." Reviews of Geophysics, Supplement, U.
S. National Report to International Union of Geodesy and
Geophysics 1991 -1994. 33:1277-1286.
138
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Church, MR., G.D. Bishop, D.L Cassell. 1995. "Maps of regional
evapotranspiration and runoff/precipitation ratios in the Northeast
United States." journal of Hydrology. 168:283-198.
Clark, C. Scott, J.A. Weber, E.H. Lee, and W.E. Hogsett. 1995.
"Accentuation of gas exchange gradients in ponderosa pine
exposed to ozone." Tree Physiology. 15:181 -189.
Claxton, L, et al. 1995. "Gene Tox Manager for Bacterial
Mutagenicity Assays: A Personal Computer and Minicomputer
System." Mutation Research. 342:87-94.
Clive, D., et al. 1995. "Consensus Agreement Regarding Protocol
Issues Discussed During the Mouse Lymphoma Workshop,
Portland, Oregon." Environmental and Molecular
Mutagenesis. 25:165-168.
Conn, J., and M.G. Paule. 1995. "Repeated Acquisition of Response
Sequences: The Analysis of Behavior in Transition." Neuroscience
& Biobehavioral Reviews. I9(3):397-406.
Connolly, J.P., and R.B. Coffin. 1995. "Model of Carbon Cycling in
the Planktonic Food Web." Journal of Environmental
Engineering. 121(10):682-690.
Couch, J.A. 1995. "Invading and Metastasizing Cardiac
Hemangioendothelial Neoplasms in a Cohort of the Fish Rivulus
marmoratus: Unusually High Prevalence, Histopathology, and
Possible Etiologies." Cancer Research. 55(1 l):2438-2447.
Courtney, Lee A. 1995. "Cholangioma in a Wild-Caught Sheepshead
Minnow (Cyprinodon variegatus) from the Northern Gulf of
Mexico." Gulf Research Report. 9(3):2I 1-213.
Cripe, G.M. 1994. "Comparative Acute Toxicities of Several
Pesticides and Metals to Mysidopsis bahia and Postlarval Penaeus
duorarum." Environmental Toxicology and Chemistry.
13(1 I): 1867-1872.
Cripe, G.M. 1994. "Induction of Maturation and Spawning of Pink
Shrimp, Penaeus duorarum, by Changing Water Temperature, and
Survival and Growth of Young." Aquaculture. 128(3-4):255-260.
Crofton, K.M., L.S. Kehn, and M.E. Gilbert. 1995. "Vehicle and Route
Dependent Effects of a Pyrethroid Insecticide, Deltamethrin, on
Motor Function in the Rat." Neurotoxicology and Teratology.
17(4):489-495.
Crofton, K.M., R. Janssen, j. Prazma, S. Pulvar, and S. Barone. 1994.
"The Ototoxicity of 3,3'-lminodipropionitrile: Functional and
Morphological Evidence of Cochlear Damage." Hearing
Research. 80(1): 129-140.
Crofton, K.M., T.L. Lassiter, and C.S. Rebert. 1994. "Solvent-Induced
Ototoxicity in Rats: An Atypical Selective Mid-frequency Hearing
Deficit." Hearing Research. 80(l):25-30.
Cummings, A.M., and j.L. Metcalf. 1995. "Induction of endometriosis
in mice: a new model sensitive to estrogen." Reproductive
Toxicology. 9:233-238.
Cummings, A.M., J.L Metcalf, and L.S. Birnbaum. 1995. "Promotion
of Endometriosis by 2,3,7,8-Tetrachlorodibenzo-p- dioxin in Rats
and Mice: Time-Dose Dependence and Species Comparison."
Toxicology and Applied Pharmacology.
Dai, Q., B.S. Vergara, A.Q. Chavez, and S. Peng. 1994. "Response of
Rice Plants from Different Regions to Ultraviolet-B Radiation."
International Rice Research Institute. 19(2): 15-16.
Dakalakis, K.D., and T.P. O'Connor. 1995. "Normalization and
Elemental Sediment Concentration in the Coastal United States."
Environmental Science and Technology. 29:470-477.
Daly, C., R.P. Neilson, and D.L. Phillips. 1994. "A statistical-
topographic model for mapping climatological precipitation over
mountainous terrain." Journal of Applied Meteorology. 33:140-
158.
Davis, W.P., D.S. Taylor, and B.J. Turner. 1995. "Does the
Autecology of the Mangrove Rivulus Fish (Rivulus armoratus)
Reflect a Paradigm for Mangrove Ecosystem Sensitivity?" Bulletin
of Marine Science. 57( I ):208-214.
Dearfield, K., et al. 1995. "Acrylamide: A Review of its Genotoxicity
and an Assessment of Heritable Genetic Risk." Mutagen
Research. 330:71-99.
Dejongh, J., M.J. DeVito, J.J. Diliberto, M. Van Den Berg, and L.S.
Birnbaum. October, 1995. "The Effects of
2,2',4,4',5,5'-hexachlorobiphenyl Cotreatment on the Disposition
of 2,3,7,8-tetra- chlorodibenzo-p-dioxin in Mice." Toxicology
Letters. 80:131 -137. 600/J-96/051.
Dejongh, J., M.J. DeVito, R. Nieboer, L.S. Birnbaum, and M. Van den
Berg. May, 1995. "Induction of Cytochrome P450 Isoenzymes
after Toxicokinetics Interactions Between 2,3,7,8-tetra-
chlorodibenzo-p-dioxin (TCDD) and 2,2',4,4'5,5'-hexa-
chlorobiphenyl (HxCB) in the Liver of the Mouse." Fundamental
and Applied Toxicology. 25:264-270.
Delnomdedieu, M., M. Styblo, and D.J. Thomas. August, 1995. "Time
Dependence of Accumulation and Binding of Inorganic and
Organic Arsenic Species in Rabbit Erythrocytes."
Chemico-Biological Interactions. 98:69-83. 600/J-95/560.
DeMarini, D. 1995. "Dichloroacetic acid and related compounds:
Induction of prophage in E. coli and mutagenicity and mutation
spectra in Salmonella TA100." Mutagenesis. 9:429-437.
DeMarini, D. 1995. "Induction of Mutation Spectra by Complex
Mixtures: Approaches, Problems and Possibilities." Environ-
mental Health Perspectives. 102(4): 127-130.
ADVANCING KNOWLEDGE FOR A PURPOSE
139
-------
NHEERL FY95 ANNUAL REPORt
REFERENCES
DeMarini, D., andj. Lewtas. 1995. "Mutagenicity and Carcinogenicity
of Complex Combustion Emissions: Emerging Molecular Data to
Improve Risk Assessment." Toxicology and Environmental
Chemistry. 49:157-166.
DeMarini, D., et ai. 1995. "Mutation spectra in Salmonella of
chlorinated, chloraminated, or ozonated drinking water extracts:
comparison to MX." Environmental and Molecular
Mutagenesis. 26:270-285.
DeMarini, D., M. Shelton, and D. Bell. 1995. "Mutation Spectra in
salmonella of Complex Mixtures: Comparison of Urban Air to
Benzo[a]pyrene." Environmental and Molecular Mutagenesis.
24:262-275.
DeMarini, D., M. Shelton, and D. Bell. 1996. "Mutation spectra of
chemical fractions of a complex mixture: role of nitroarenes in the
mutagenic specificity of municipal waste incinerator emissions."
Mutation Research. 349:1 -20.
DeMarini, D., M. Shelton, andj. Levine. 1995. "Mutation spectra of
cigarette smoke condensate in Salmonella: comparison to
mutations in smoking-associated tumors." Carcinogenesis.
16:2538-2542.
DeMarini, D., M. Shelton, and L Stankowski. 1995. "Mutation
Spectra in Salmonella of Sunlight, White Fluorescent Light, and
Light from Tanning Salon Beds: Induction of Tandem Mutations
and Role of DMA Repair." Mutation Research. 327:131 -149.
DeMarini, D.M., and J. Lewtas. 1995. "Mutagenicity and
carcmogenicity of complex combustion emissions: Emerging
molecular data to improve risk assessment." Toxicological and
Environmental Chemistry. 49:157-166.
Denslow, N.D., M.M. Chow, and LC. Folmar. 1995. "Isoforms of
Apolipoprotein A-l in the Serum of Brown Bullheads (Ameiurus
nebulosus) with Liver Cancer." Canadian Journal of Zoology.
72:1522-1527.
Detenbeck, N.E. 1994. "Ecological risk assessment case study:
Effects of physical disturbance on water quality status and water
quality improvement function of urban wetlands." In "A Review of
Ecological Assessment Case Studies from a Risk Assessment
Perspective. " U.S. EPA Risk Assessment Forum. Washington
DC. 2(4).
Detenbeck, N.E. 1994. "Prevention, minimization, and monitoring of
the impacts of physical disturbance to wetlands." In
"Transportation Solutions for Today, Tomorrow, and Beyond."
Proceedings, 4th National Conference for Small and
Medium-Sized Communities. National Transportation Research
Board, Duluth MN. May 25-27, 1994. 67-83.
Detenbeck, N.E., D.L Taylor, A. Lima, and C. Hagley. 1995.
"Temporal and spatial variability in the water quality of wetlands
in the Minneapolis/St.Paul, MN metropolitan area: Implications for
monitoring strategies and designs." Environmental Monitoring
and Assessment. 78:1 -30.
DeVito, E., and R.A. Yokel. November, 1994. "The Biological
Speciation and Toxicokinetics of Aluminum." Environmental
Health Perspectives. 102:940-951.
DeVito, M.J., and L.S. Birnbaum. 1994. "Toxicology of Dioxins and
Related Chemicals." Dioxins and Health. 5:139-162.
DeVito, M.J., and LS. Birnbaum. January, 1995. "The Importance of
Pharmacokinetics in Determining the Relative Potency of
2,3,7,8-tetrachlorodibenzo-p-dioxin and 2,3,7,8-tetra-
chlorodibenzofuran." Fundamental and Applied Toxicology.
24(1): 145-148.
DeVito, M.J., LE. Beebe, M. Menache, and L.S. Birnbaum. March
1996. "Relationship Between CYPIA Enzyme Activities and
Protein Levels in Rats Treated With 2,3,7,8-Tetrachlorodibenzo-p-
dioxin." 47:379-394.
DeVito, M.J., L.S. Birnbaum, W. Farland, and T. Gasiewicz.
September, 1995. "Comparisons of Estimated Human Body
Burdens of Dioxinlike Chemicals and TCDD Body Burdens in
Experimentally Exposed Animals." Environmental Health
Perspectives. I03(9):820-830. 600/J-95/480.
Di Tore, D.M., C.S. Zarba, D.J. Hansen, W.J. Berry, R.C. Swartz,
C.E. Cowan, S.P. Pavlou, H.E. Allen, N.A. Thomas, and P.R.
Paquin. 1995. "Equilibrium Partitioning in Setting Sediment Quality
Criteria." Quintessence-Excellence in Environmental
Contamination and Toxicology. I (3):45.
Dietert, R., A. Hedge, M.I. Luster, M.A. Qureshi, and M.J.K.
Selgrade. 1995. "Factors Influencing Indoor Air Quality Immunity
and Health." Inhalation Toxicology.
Diliberto, J.J., P.I. Akubue, R.W. Luebke, and LS. Birnbaum.
September, 1995. "Dose-Response Relationships of Tissue
Distribution and Induction of CYPIAI and CYPIA2 Enzymatic
Activities Following Acute Exposure to 2,3,7,8-Tetrachlorodi-
benzo-p- dioxin (TCDD) in Mice." Toxicology and Applied
Pharmacology. 130:197-208. 600/J-95/517.
DiToro, D., C.S. Zarba, D.J. Hansen, W.J. Berry, R.C. Swartz, C.E.
Cowan, S.P. Pavlou, H.E. Allen, N.A. Thomas, and P.R. Paquin.
1995. "Equilibrium partitioning in setting sediment quality criteria."
Quintessence. 1:45.
Dixon, R.K., J.K. Winjum, J.J. Lee, and P.E. Schroeder. 1994.
"Integrated land-use systems: Assessment of promising agroforest
and alternative land-use practices to enhance carbon conservation
and sequestration." Climate Change. 27:71-92.
Doering, P.H., CA Oviatt, B.L. Norwicki, E.G. Klos, and L.W. Reed.
1995. "Phosphorus and Nitrogen Limitation of Primary Production
in a Simulated Estuarine Gradient." Marine Ecology Progress
Series. 124:271-287.
140
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Donegan, K., C. Palm, V. Fieland, L Porteous, L Ganio, D. Harris,
L. Bucao, and R. Seidler. 1995. "Changes in levels, species and
DMA fingerprints of soil microorganisms associated with cotton
expressing the Bacillus thuringiensis var. kurstaki endotoxin."
Applied Soil Ecology. 2:1 I I -124.
Doyle, jack D., Guenther Stotzky, Gwendolyn McClung, Charles
W.Hendricks. 1995. "Effects of genetically engineered micro-
organisms on microbial populations and processes in natural
habitats." Advances in Applied Microbiology. 40:237-187.
Dragan, Y., et al. 1995. "Comparison of experimental and theoretical
parameters of the Moolgavkar-Venzon-Knudson incidence function
for the stages of initiation and promotion in rat hepato-
carcinogenesis." Toxicology. 102:161 -175.
Dragan, Y., et al. 1995. "Focal and Non-focal Hepatic Expression of
Placental Glutathione S-Transferase in Carcinogen-treated Rats."
Carcinogenesis. 15(1 I):2587-259I.
Dragan, Y., et al. 1995. "Incorporation of bromodeoxyuridine in
glutathione S-transferase-positive hepatocytes during rat
multistage hepatocarcinogenesis." Carcinogenesis. 15(9): 1939-
1947.
Driscoll, C. T., and R. Van Dreason. 1993. "Seasonal and Long-term
Temporal Patterns in the Chemistry of Adirondack Lakes."
Water, Air, and Soil Pollution. 67:3 19-344.
Due Vu, R.V., R. Poon, G. Josee, S. Bjarnason, M. Potvin, G.E. Hatch,
andj. Norwood. 1995. "Sensitivity of the Lungs of Aging Fischer
344 Rats to Ozone: Assessment by Broncho-Alveolar Lavage."
American Journal of Physiology.
Dunning, John B., Jr. 1994. "Tropical mass extinctions and the
scientific method." Bulletin of the Ecological Society of
America. 75(1 ):44-45.
Dunning, Jr., John B., David J. Stewart, Brent J. Danielson, Barry R.
Noon, Terry Root, Roland H. Lamberson, and Ted Stevens. 1995.
"Spatially-explicit population models: Current forms and future
uses." Ecological Applications. 5(l):3-l I.
Dutta, S., M. Verma, and C. Blackman. 1995. "Frequency-dependent
alterations in enolase activity in Escherichia coli caused by
exposure to electric and magnetic fields." Bioelectromagnetics.
!5(5):377-383.
Eaton, J.G., and R.M. Scheller. 1995. "Effects of climate warming on
fish thermal habitat in streams of the United States." Limnology
and Oceanography.
Eaton, J.G., J.H. McCormick, B.E. Goodno, D.G. O'Brien, K.E.
Hokanson, H.G. Stefan, and M. Hondzo. 1995. "A field
information-based system for estimating fish temperature
tolerance." Fisheries. 20(4): 10-18.
Eaton, J.G., J.H. McCormick, H.G. Stefan, and M. Hondzo. 1995.
"Extreme value analysis of a fish/temperature field database."
Ecological Engineering. 4(4):289-309.
Eaton, R.W. 1994. "Organization and Evolution of Naphthalene
Catabolic Pathways: Sequence of the DNA Encoding 2-
Hydroxychromene-2-Carboxylate Isomerase and trans-o-
Hydroxybenzylidenepyruvate Hydratase-Aldolase from the NAH7
Plasmid." Journal of Bacteriology. 176(24):7757-7762.
Eaton, Richard W., and Peter J. Chapman. 1995. "Formation of
Indigo and Related Compounds from Indolecarboxylic Acids by
Aromatic Acid-Degrading Bacteria: Chromogenic Reactions for
Cloning Genes Encoding Dioxygenases That Act on Aromatic
Acids." Journal of Bacteriology. 177(23):6983-6988.
Edge, W. Daniel, Jerry O. Wolff, and Robert L. Carey. 1995.
"Density-dependent response of gray-tailed voles to mowing."
Journal of Wildlife Management. 59(2):245-251.
Ehrich, M., and V. Veronesi. 1995. "Esterase Comparison in
Neuroblastoma Cells of Human and Rodent Origin." Clinical
Experimental Pharmacology and Physiology. 22:385-386.
Ehrich, M., B.S. Jornter, and S.J. Padilla. 1995. "Comparison of the
Relative Inhibition of Acetylcholinesterase and Neuropathy Target
Esterase in Rats and Hens Given Cholinesterase Inhibitors."
Fundamental and Applied Toxicology. 24:94-101.
Ehrich, M., L Correll, K. Carlson, J. Wilcke, and B. Veronesi. 1995.
"Examination of Culture Conditions on Esterase Activities in
Human and Mouse Neuroblastoma Cells." In Vitro Toxicology.
8(2): 199-207.
Erexson, G., et al. 1995. "Bleomycin sulfate-induced micronuclei in
human, rat, and mouse peripheral blood lymphocytes."
Environmental and Molecular Mutagenesis. 25:31-36.
Erickson, R.J., D.A. Benoit, V.R. Mattson, and H.P. Nelson Jr. 1995.
"The effects of water chemistry on the toxicity of copper to
fathead minnows." Environmental Toxicology and Chemistry.
15:181-193.
Erickson, R.J., T.D. Bills, J.R. Clark, D.J. Hansen.J. Knezovich, F.L.
Mayer, and A.E. McElroy. 1994. "Synopsis of Discussion Session on
Physicochemical Factors Affecting Toxicity." Bioavailability:
Physical, Chemical and Biological Interactions. Ed. P.F.
Landrum, H.L Bergman, and W.H. Benson. Lewis Publishers, Boca
Raton, FL Chapter 3,31 -38.
Ernst, Ted L, Nancy C. Leibowitz, Denis Roose, Steve Stehman, and
N. Scott Urquhart. 1995. "Evaluation of EMAP-Wetlands sampling
design and classification." Environmental Management.
ADVANCING KNOWLEDGE FOR A PURPOSE
141
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Eshleman, K.N., T.D. Davies, M. Tranter, and P.J. Wigington, Jr.
1995. "A two-component mixing model for predicting regional
episodic acidification of surface waters during spring snowmelt
periods." Water Resources Research. 31 (4): 1011 -1021.
Evans, M.V., and H.B. Mathews. December, 1995. "Session
Summary: Toxicokinetic Interactive Mechanisms." Toxicology.
105:209-210.
Evans, M.V., and J.E. Simmons. 1995. "Enhanced Bioactivation and
Hepatotoxicity of Carbon Tetrachloride in Methanol Pretreated
Rats." Toxicology and Applied Pharmacology.
Evans, M.V., and M.E. Andersen. October, 1995. "Sensitivity Analysis
and the Design of Gas Uptake Inhalation Studies." Inhalation
Toxicology. 7:1075-1094.
Farland, W.H., L.S. Birnbaum, and M.J. DeVito. The United States
Environmental Protection Agency (U.S. EPA) Approach to
Evaluating Dioxin Health Risks: Critical Issues. MS-95-I8I.
Ferraro, S.P., and F.A. Cole. 1995. "Taxonomic Level Sufficient For
Assessing Pollution Impacts on the Southern California Bight
Macrobenthos-Revisited." Environmental Toxicology and
Chemistry. 14(6): 1031 -1040.
Ferreira-Gonzalez, A., et al. 1995. "Ras Oncogene Activation During
Hepatocarcinogenesis in B6C3FI Male Mice by Dichloroacetic and
Trichloroacetic Acids." Carcinogenesis. I6(3):495-500.
Fisher, William S., and Leah M. Oliver. 1995. "Diagnosis of Perkinsus
marinus Disease in Whole Oysters Using Ray's Fluid Thioglycollate
Culture Medium." Journal of Shellfish Research. 15( I): 109-117.
Flemer, D.A., R.S. Stanley, B.F. Ruth, C.M. Bundrick, P.M. Moody,
and J.C. Moore. 1995. "Recolonization of Estuarine Organisms:
Effects of Microcosm Size and Pesticides." Hydrobiologia.
304:84-101.
Fleming, J.S., M. Nassim, A. Hashish, A. Bailey, J. Conway, S. Holgate,
P. Halson, E. Moore, and T.B. Martonen. 1995. "Description of
Pulmonary Deposition of Radiolabelled Aerosol By Airway
Generation Using a Conceptual Three Dimensional Model of Lung
Morphology." Journal of Aerosol Science.
Fleming, J.S., M. Nassim, A.H Hashish, A.G. Bailey, J. Conway, S.
Holgate, P. Halson, E. Moore, and T.B. Martonen. 1995. "Three
Dimensional Description of Deposition of Inhaled Aerosol in the
Lung Using a Hemispherical Transform of Data From
Multi-Modality Imaging." journal of Aerosol Medicine.
Fletcher, J.S., T.G. Pfleeger, and H.C. Ratsch. 1995. "Chlorsulfuron
influence on garden pea reproduction." Physiologia Plantarum.
94:261-267.
Fletcher, John S., James E. Nellessen, and Thomas G. Pfleeger. 1994.
"Literature review and evaluation of the EPA foodchain (Kenega)
nomogram, an instrument for estimating pesticide residues on
plants." Journal of Environmental Toxicology and Chemistry.
13(9): 1383-1391.
Fletcher, John S., Thomas G. Pfleeger, Hilman C. Ratsch, and Robert
Hayes. 1996. "Potential impact of low levels of chlorsulfuron and
other herbicides on growth and yield of nontarget plants."
Environmental Toxicology and Chemistry. 15(7).
Folmar, L.C., J. Harshbarger, P.C. Baumann, G. Gardner, and S.
Bonomelli. 1995. "Pathological and Serum Chemistry Profiles of
Brown Bullheads (Ameiurus nebulosus) from the Black River and
Old Woman Creek, Ohio." Bulletin of Environmental
Contamination and Toxicology. 54:50-59.
Folmar, L.C., J. Harshbarger, P.C. Baumann, G. Gardner, and S.
Bonomelli. 1995. "Pathological and Serum Chemistry Profiles of
Brown Bullheads (Ameiurus nebulosus) from the Black River and
Old Woman Creek, Ohio." Bulletin of Environmental
Contamination and Toxicology. 54( I ):50-59.
Folmar, L.C., N.D. Denslow, R.A. Wallace, G. LaFleur, S. Bonomelli,
and C.V. Sullivan. 1995. "Highly Conserved N-terminal Sequence
for Teleost Vitellogenin with Potential Value to the Biochemistry,
Molecular Biology and Pathology of Vitellogenesis." Journal of
Fish Biology. 46(2):255-263.
Ford, J., D. Landers, D. Kugler, B. Lasorsa, S. Allen-Gil, E. Crecelius,
andj. Martinson. 1995. "Inorganic contaminants in Arctic Alaskan
ecosystems: long-range atmospheric transport or local point
sources." The Science of the Total Environment. 160/161:323-
335.
Forschler, B.T., and G. Henderson. 1995. "Subterranean Termite
Behavioral Reaction to Water and Survival of Inundation:
Implications for Field Populations." Journal of Environmental
Entomology. 24(6): 1592-1597.
Fowles, J.R., A. Fairbrother, L. Baecher-Steppan, and N.I. Kerkvliet.
1994. "Immunologic and endocrine effects of the flame retardant
pentabromodiphenyl ether (DE-71) in C57BI/6J mice."
Toxicology. 86:49-61.
Fredericksen, T.S., J.M. Skelly, K.C. Steiner, T.E. Kolb, B.J. Joyce,
K.B. Kouterick, and J.E. Savage. 1994. "Ozone uptake of different-
sized black cherry trees in high- and low-light environments."
Proceedings IUFRO Workshop on Air Pollution and Multiple
Stresses. Fredericton, New Brunswick, Canada. September 7-9.
Freemark, Kathryn, and Celine Boutin. 1995. "Impacts of Agricultural
Herbicide Use on Terrestrial Wildlife: A Review." Agriculture,
Ecosystems, and Environment. 52:67-91.
Freemark, Kathryn. 1995. "Assessing effects of agriculture on
terrestrial wildlife: Developing a hierarchical approach for the US
EPA." Landscape and Urban Planning. 31:99-115.
142
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Frick, W.E., D.J. Baumgartner, and C.G. Fox. 1994. "Improved
Prediction of Bending Plumes." Journal of Hydraulic Research.
32(6):935-950.
Gao, P., J.R. Thornton-Manning, and R.A. Pegram. "Protective Effects
of Glutathione on Bromodichloromethane (n vivo Toxicity and In
vitro Macromolecular Binding." Journal of Toxicology and
Environmental Health.
Gardner, G.R., J.C. Harshbarger, J.L Lake, T.K. Sawyer, K.L Price,
M.D. Stephenson, P.L Haaker, and H.A. Togstad. 1995.
"Association of Prokaryotes with Symptomatic Appearance of
Withering Syndrome in Black Abalone Haliotis aacherodii."
Journal of Invertebrate Pathology. 66:1 I I -120.
Gaston, G.R., S.S. Brown, C.F. Rakocinski, R.W. Heard, and J.K.
Summers. 1995. "Trophic Structure of Macrobenthic
Communities in Northern Gulf of Mexico Estuaries." Gulf
Research Report. 9(2):I I l-l 16.
Gelatt, K.N., J.O. Matinic, J.L. Flaneig, O.D. Schein, B. Munoz, S.K.
West, D.D. Duncan, J.R. Nethercott, and H.S. Koren. 1995.
"Results of ophthalmic examinations of 29 alpacas." Journal of the
American Veterinary Medicine Association. 206:1204-1207.
Center, M.B., D.M. Owens, H.B. Carlone, and K.M. Crofton. 1996.
"Characterization of Olfactory Deficits in the Rat Following
Adminsitration of 2,6-Dichlorobenzonirile (Dichobenil),
3,3'-lminodipropionitrile (IDPN) or Methimazole." Fundamental
and Applied Toxicology. 29:7 \-77.
Genthner, F.J., and D.P. Middaugh. 1995. "Nontarget Testing of an
Insect Control Fungus: Effects of Metarhizium anisopliae on
Developing Embryos of the Inland Silverside Fish Menidia
beryllina." Diseases of Aquatic Organisms. 22(3): 163-171.
Genthner, F.J., D.P. Middaugh, and S.S. Foss. 1995. "Validation of
Embryo Tests for Determining Effects of Fungal Pest Control
Agents on Nontarget Aquatic Animals." Archives of Environ-
mental Contamination and Toxicology. 29(4):540-544.
Genthner, F.J., S.S. Foss, and W.S. Fisher. 1994. "Testing of the
Insect Pest Control Fungus Beauveria bassiana in Grass Shrimp,
Palaemonetes pugio." Diseases of Aquatic Organisms. 20:49-
57.
George, S., et al. 1995. "Atrazine Treatment Potentiates the
Excretion of Mutagenic Urine in 2,6-Dinitrotoluene-treated
Fischer 344 Rats." Environmental and Molecular Mutagenesis.
26:178-184.
George, S.E., R.W. Chadwick, M.J. Kohan, J.C. Allison, S.H. Warren,
and R.W. Williams. 1995. "Altrazine treatment potentiates
excretion of mutagenic urine in 2,6-Dinitrotoluene-treated Fischer
344 rats." Environmental Molecular Mutagenesis. 26:178-184.
Gerrity, T.R., F. Biscardi, A. Strong, A.R. Garlington, and P.A.
Bromberg. 1995. "Bronchoscopic determination of ozone uptake
in humans." Journal of Applied Physiology. 79:852-860.
Ghio, A.J., J. Stonehuemer, R.J. Pritchard, C.A. Piantadosi, D.R.
Quigley, K.L. Dreher, and D.L. Costa. "Humic-like Subtances in
Air Pollution Particulates Correlate with Concentrations of
Transition Metals and Oxidant Generation." 1996. Inhalation
Toxicology. 8:4479-494.
Ghio, A.J., R.H. Jaskot, and G.E. Hatch. December, 1994. "Lung
Injury after Silica Instillation Is Associated with an Accumulation of
Iron in Rats." American Journal of Physiology.
267(6): L686-L692.
Gichner, T., et al. 1995. "Arabidopsis Assay for Mutagenicity."
Mutation Research. 310(2):249-256.
Gilbert, M.E. 1995. "Repeated Exposure to Lindane Leads to
Behavioral Sensitization and Facilitates Electrical Kindling."
Neurotoxicology and Teratology. 17(2): 131-141.
Gilbert, M.E., and CM. Mack. 1995. "Seizure Thresholds in Kindled
Animals Are Reduced by the Pesticides Lindane and Endosulfan."
Neurotoxicology and Teratology. 17:143-150.
Gilbert, M.E., and T.J. Shafer. 1996. "In vitro Exposure to Aluminum
Does Not Alter Long-term Potentiation or Glutamate Release in
Rat Hippocampal Slices." Neurotoxicology and Teratology.
18:175-180.
Gilmour, M.I. 1995. "Interaction of Air Pollutants and Pulmonary
Allergic Responses in Experimental Animals." Toxicology.
105:335-342.
Gilmour, M.I., P. Park, and M.L.K. Selgrade. 1996. "Increased
Immune and Inflammatory Response to Dust Mite Antigen in Rats
Exposed to 5 ppm NO2." Fundamental and Applied
Toxicology. 31:65-70.
Glass, G.E., J.H. Sorenson, and K.W. Schmidt. 1994. "Regional
patterns of wet mercury deposition." Environmental Science
and Technology. 28(12):2025-2032.
Gleason, T.R., and D.A. Bengston. 1996. "Growth, survival and size-
selective predation mortality of larval and juvenile inland
silversides. Menidia beryllina (Pisces; Atherinidae)." Journal of
Experimental Marine Biology and Ecology. 199(2): 165-177.
Godshall, FA, H.A. Walker, and S.C. Cayula. 1995. "Scales of
Coastal Wind Variability Addressed by COADS Wind Summaries
in 2 Degree Square Areas. Proceedings of the International
COADs Wind Workshop." Kiel, Germany, May 31 -June 2, 1994.
Ed. H.F. Diaz and H-J. Isemer. Berichte aus dem Institut Fur
Meereskunde an der Christian-Albrecht-Univeritat Nr. 265.
U.S. Department of Commerce NOAA Environmental
Research Laboratories Climate Diagnostics Center. May
1995:187-211.
ADVANCING KNOWLEDGE FOR A PURPOSE
143
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Goldey, E.S., H.A. Tilson, and K.M. Crofton. 1995. "Implications of
the Use of Offspring Viability, Body Weight, and Survivorship Data
for Predicting Developmental Neurotoxicity: A Survey of the
Literature." Neurotoxicology and Teratology. 17(3):313-332.
Goldey, E.S., J.P. O'Callaghan, ME. Stanton, S. Barone, and K.M.
Crofton. 1994. "Developmental Neurotoxicity: Evaluation of
Testing Procedures with Methylazoxymethanol and
Methylmercury." Fundamental and Applied Toxicology.
23(3):447-464.
Goldey, E.S., LS. Kehn, C.S. Lau, G.L. Rehnberg, and K.M. Crofton.
1995. "Developmental Exposure to Polychlorinated Biphenyls
(Aroclor 1254) Causes Hypothyroidism and Hearing Deficits in
Rats." Toxicology and Applied Pharmacology. 135:77-88.
Goldey, E.S., L.S. Kehn, G.L Rehnberg, and K.M. Crofton. 1995.
"Effects of Development Hypothyroidism on Auditory and Motor
Function in the Rat." Toxicology and Applied Pharmacology.
135:67-76.
Gordon, C.J. 1994. "24-Hour Control of Body Temperature in the
Rat: II. Diisopropyl Fluorophosphate-lnduced Hypothermia and
Hyperthermia." Pharmacology Biochemistry & Behavior.
49(3):747-754.
Gordon, C.J. 1995. "Factors Influencing Diisopropyl
Fluorophosphate-lnduced Hypothermia and Hyperthemia in the
Rat." Neurotoxicology and Teratology. 17:679-683.
Gordon, C.J., and W.P. Watkinson. 1995. "Strain Differences in the
Laboratory Rat: Impact on the Autonomic, Behavioral,and
Biochemical Response to Cholinesterase Inhibition." Journal of
Toxicology and Environmental Health. 45:59-73.
Gordon, C.J., and W.P. Watkinson. May, 1995. "Strain Differences in
the Laboratory Rat: Impact on the Autonomic, Behavioral, and
Biochemical Response to Cholinesterase Inhibition." Journal of
Toxicology and Environmental Health. 45:59-73.
Gordon, C.J., L.E. Gray, N.A. Monteiro-Riviere, and D.B. Miller.
1995. "Temperature Regulation and Metabolism in Rats Exposed
Perinatally to Dioxin: Permanent Change in Regulated Body
Temperature." Toxicology and Applied Pharma-
cology. 133:172-176.
Graham, R.C., M.G. Menache, and J.H. Overton. March, 1996.
"Models of the Tracheobronchial Airways of the Dog Lung."
Inhalation Toxicology. 8:121 -142.
Gray, L.E., and J.S. Ostby. 1995. "In utero
2378-tetrachlorodibenzo-p-dioxin alters reproductive morphology
and function in female rat offspring." Toxicology and Applied
Pharmacology. 133:285-294.
Gray, L.E., J.S. Ostby, and W.R. Kelce. 1994. "Developmental effects
of an environmental anti-androgen: the fungicide vinclozolin alters
sex differentiation in male rat." Toxicology and Applied
Pharmacology. 129:46-52.
Gray, L.E., W.R. Kelce, E. Monosson, J.S. Ostby, and L.S. Birnbaum.
November, 1994. "Exposure to TCDD During Development
Permanently Alters Reproductive Function in Male LE Rats and
Hamsters: Reduced Ejaculated and Epididymal Sperm Numbers
and Sex Accessory Gland Weights in Offspring with Normal
Androgenic Status." Toxicology and Applied Pharmacology.
Gray, L.E., W.R. Kelce, E. Monosson, J.S. Ostby, and LS. Birnbaum.
1995. "Exposure to TCDD during development permanently
alters reproductive function in male Long Evans rats and hamsters:
Reduced ejaculated sperm numbers and sex accessory gland
weights in offspring with normal androgenic status." Toxicology
and Applied Pharmacology. 131:108-118.
Griffith, Glenn E, James M. Omernik, Thomas F. Wilton, and Suzanne
M. Pierson. 1994. "Ecoregions and subregions of Iowa: A
framework for water quality assessment and management."
Journal of the Iowa Academy of Science. 10( I ):5-13.
Grifoll, M., S.A. Selifonov, and P.J. Chapman. 1995. "Transformation
of Substituted Fluorenes and Fluorene Analogs by Pseudomonas
sp. Strain F274." Applied Environmental Microbiology.
6l(9):3490-3493.
Grifoll, Magdalena, Sergey A. Selifonov, Charylene V. Gatlin, and
Peter J. Chapman. 1995. "Actions of a Versatile Fluorene-
Degrading Bacterial Isolate on Polycyclic Aromatic Compounds."
Applied Environmental Microbiology. 61 (10): 3 711-3723.
Gubala, C.P., C. Branch, N. Roundy, and D.H. Landers. 1994.
"Automated global positioning system charting of environmental
attributes: A limnologic case study." Science of the Total
Environment. 148:83-92.
Gubala, C.P., D.H. Landers, M. Monetti, M. Heit, T. Wade, B.
Lasorsa, and S. Allen-Gil. 1995. "The rates of accumulation and
chronologies of atmospherically derived pollutants in Arctic Alaska,
USA." Science of the Total Environment. 160/161:347-361.
Hall, I.H., S.D. Wyrick, and C.L Waller. August, 1995. "The
Cytotoxicity of [(N-Alkyl-1H, 3H-l-oxisoindolin-5-yl-
oxylalkanoates and Related Benzamides in Murine and Human
Tissue Cultured Cell Lines." Anticancer Research.
15:1135-1140.
Hall, L.L., P.V. Allen, H.L. Fisher, and B.M. Most. 1995. "Kinetics
Models of Trace Element and Mineral Metabolism During
Development." Kinetic Models of Trace Element and Mineral
Metabolism during Development. Ed. M.E. Wastney and K.N.S.
Subramanian. 21:265-279.
Hatch, G.E.J.R. Harkema, C.G. Plopper, and L. Harris. November,
1994. "Ozone Dosimetry Studies in the Nose and Eye Using
Oxygen-18." Inhalation Toxicology. 6:125-134.
144
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Hatch, G.E., R. Slade, LP. Harris, W.F. McDonnell, R.B, Devlin, H.S.
Koren, D.L. Costa, and J. McKee. 1994. "Ozone Dose and Effect
in Humans and Rats." American journal of Respiratory Critical
Care Medicine. 150:676-83.
Hazucha, M.J., M. Madden, G. Rape, S. Becker, R.B. Devlin, H.S.
Koren, H. Kehrl, and P.A. Bromberg. 1996. "Effects of
cyclooxygenase inhibition on ozone-induced respiratory
inflammation and lung function changes." European Journal of
Applied Physiology. 73:17-27.
Hemmer, M.J., L.A. Courtney, and LS. Ortego. 1995.
"Immunohistochemical Detection of P-glycoprotein in Teleost
Tissues Using Mammalian Polyclonal and Monoclonal Antibodies."
Journal of Experimental Zoology. 272(l):69-77.
Henderson, G., and K.S. Delaplane. 1994. "Formosan Subterranean
Termite Swarming Behavior and Alate Sex-Ratio (Isoptera:
Rhinotermitidae)." Insect Society. 41:19-28.
Hendricks, Charles W. 1996. "The effects of toxic chemicals on
nutrient cycling processes in soil." Soil Ecotoxicology. Lewis
Publishers, Boca Raton, FL. 66.
Hendricks, Charles, Jack D. Doyle, and Bonnie Hugley. 1995. "A new
solid medium for enumerating cellulose-utilizing bacteria in soil."
Applied and Environmental Microbiology. 6I(5):20I6-2I09.
Heppell, Scott A., Nancy D. Denslow, Leroy C. Folmar, and Craig V.
Sullivan. 1995. "Universal Assay of Vitellogenin as a Biomarker for
Environmental Estrogens." Environmental Health Per-
spectives. I03(7):9-I5.
Herman, L.J. 1995. "Water-conditioning tank to control super-
saturation and temperature." Progressive Fish Culture. 57:164-
165.
Herr, D., D. King, S. Barone, and K.M. Crofton. 1996 "Alternations
in Flash Evoked Potentials (FEPs) in Rats Produced by
3,3'-lminodiproionitrile (IDPN)." Neurotoxicology and
Teratology. 17:645-656.
Highfill, J.W., and D.L. Costa. February, 1995. "Statistical Response
Models for Ozone Exposure: Their Generality, When Applied to
Human Spirometric and Animal Permeability Functions of the
Lung." Journal of the Air and Waste Management
Association. 45:95-102.
Highsmith, V.R., L. Cuppit, R. Zweidinger, J. Lewtas, W. Glen, and J.
Wu. 1996. "Characterizing the influence of residential wood
combustion and mobile source emissions on the indoor air quality
of selected Boise, Idaho, residence." Atmospheric Environment.
In press.
Hnizdo E., D.H. Horstman, N. Vitnerova, F. Kotesovec, and R. Sram.
1996. "Prevalence of and risk factors for respiratory symptoms,
bronchitis and asthma in school children exposed to high air
pollution in the Czech Republic." European Respiratory
Journal. In press
Ho, K.T., K. Mitchell, M. Zappala, and R.M. Burgess. 1995. "Effects
of Brine Addition on Effluent Toxicology and Marine Toxicity
Identification (TIE) Manipulations." Environmental Toxicology
and Chemistry. 14(2):245-249.
Hoch, Matthew P., Richard A. Snyder, Luis A. Cifuentes, and Richard
B. Coffin. 1995. "Stable Isotope Dynamics of Nitrogen Recycled
During Interactions Among Marine Bacteria and Protists." Marine
Ecology Progress Series. 132( I -3):229.
Hogsett, W.E., A. Herstrom,J.A. Laurence, J.E.Weber, E.H. Lee, D.
Tingey. 1996. "An approach for characterizing tropospheric ozone
risk to forests." Environmental Management. In press.
Hoke, R.A., G.T. Ankley, and J.F. Peters. 1995. "Use of a freshwater
sediment quality database in an evaluation of sediment quality
criteria based on equilibrium partitioning and screening level
concentrations." Environmental Toxicology and Chemistry.
14:451-459.
Hoke, R.A., P.A. Kosian, G.T. Ankley, A.M. Cotter, P.M.
VanderMeiden, G.L Phipps, and E.J. Durhan. 1995. "Check studies
with Hyalella azteca and Chironomus tentans in support of the
development of a sediment quality criterion for dieldrin."
Environmental Toxicology and Chemistry. 14:435-450.
Holcombe, G.W., DA. Benoit, D.E. Hammermeister, E.N. Leonard,
and R.D. Johnson. 1995. "Acute and long-term effects of nine
chemicals on the Japanese medaka Oryzias latipes." Archives of
Environmental Contamination and Toxicology. 28:287-297.
Holland, Cynthia, JoEllen Honea, Stephanie E. Gwin, and Mary
Kentula. 1995. "Wetland degradation and loss in the rapidly
urbanizing area of Portland, Oregon." Wetlands. 15(4):336-335.
Hood, M.A., and R.J. Seidler. "Design of microcosms to provide data
reflecting field trials of GEMs." Molecular Microbial Ecology
Manual. Kluwer Academic Publishers. Ed. J.D. van Elsa.
Horstman, D.H., B.A. Ball, J. Brown, T.R. Gerrity, and L.J. Folinsbee.
1995. "Comparison of pulmonary responses of asthmatic and
nonasthmatic subjects performing light exercise while exposed to
a low level of ozone." Toxicology and Industrial Health.
ll(4):369-385.
Hughes, James P., Dennis P. Lettenmaier, and Peter Guttorp. 1993.
"A stochastic approach for assessing the effect of changes in
regional circulation patterns on local precipitation." Water
Resources Research. 29(IO):3303-33I5.
ADVANCING KNOWLEDGE FOR A PURPOSE
145
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Hughes, M.F., and L.L. Hall. September, 1995. "Disposition of
Phenol in Rats After Oral, Dermal, Intravenous and IntratracheaJ
Administration." Xenobiotica. 25(8):873-883.
Hughes, M.F., C.T. Mitchell, B.C. Edwards, and M.S. Rahman.
February, 1995. "In Vitro Percutaneous Absorption of
Dimethylarsinic Acid in Mice." Journal of Toxicology and
Environmental Health. 45:101 -1 12.
Ibanes, J.D., K.T. Morgan, and G.R. Burleson. 1995.
"Histopathological Changes in the Upper and Lower Respiratory
Tract of Fischer-344 Rats Following Infection with a Rat-adapted
Influenza Virus." Journal of Computational Pathology.
XX-95-001.
Ingersoll, C, G. Ankley, R. Baudo, A. Burton, W. Lick, S. Luoma, D.
MacDonald, T. Reynoldson, K. Solomon, R. Swartz, and W.
Warren-Hicks. 1996. "Methodological uncertainty in conducting
risk assessment with contaminated sediments." Risk Assessment
Considerations for Contaminated Sediments. SETAC Pellston
Series.
Ingersoll, C.G., G.T. Ankley, D.A. Benoit, E.L. Brunson, G.A. Burton,
F.J. Dwyer, R.A. Hoke, P.F. Landrum, T.J. Norberg-King, and P.V.
Winger. 1995. "Toxicity and bioaccumulation of sediment-
associated contaminants using freshwater invertebrates: A review
of methods and applications." Environmental Toxicology and
Chemistry. 14(11): 1885-1894.
Israeli, Eitan, Brenda T. Shaffer, and Bruce Lighthart. 1993.
"Protection of freeze-dried Eschrichia coli by Trehalose upon
exposure to environmental conditions." Cryobiology. 30:519-512.
Israeli, Eitan, Brenda T. Shaffer, and Bruce Lighthart. 1994. "Survival
and enumeration of aerosolized and freeze-dried genetically
engineered £. coli, under controlled environmental conditions."
Aerobiologia. 10:167-173.
Izotti, A., S. DeFlora, G. Petrilli, J. Gallagher, M. Rojas, K.
Alexandrov, H. Bartsch, and j. Lewtas. 1995. "Cancer Biomarkers
in Human Atheroschlerotic Lesions: Detection of DMA adducts."
Cancer Epidemiology, Biomarkers and Prevention. 4:105-
110.
Izzotti, A., L. Scatolini, J. Lewtas, D. Walsh, and S. DeFlora. 1995.
"Enhanced levels of DMA adducts in the liver of woodchucks
infected with hepatitis virus." Chemico-Biological Interactions.
97:273-285.
Jakab, G.J., E.W. Spannhake, B.J. Canning, S.R. Kleeberger, and M.I.
Gilmour. February, 1995. "The Effects of Ozone on Immune
Function." Environmental Health Perspectives. !03(2):77-89.
Jeevan, A. 1994. "Final Report of Cooperative Agreement,
CR8I6748, with the University of Texas." USEPA HERL-0862.
Johnson, D.L., and T.B. Martonen. December, 1994. "Predicted and
Observed Behavior of Platelet Aerosols." Particulate Science
and Technology. 12:149-159.
Johnson, D.L, and T.B. Martonen. November, 1995. "Behavior of
Inhaled Fibers: Potential Applications to Medicinal Aerosols."
Particulate Science and Technology. 12:161 -173.
Johnson, Mark G. 1993. "The role of soil management in
sequestering soil carbon." Advances in Soil Science.
International Symposium on Soil Processes and Management
Systems; Greenhouse Gas Emissions and Carbon Sequestration.
Columbus, OH. April 5-9. Volume 2, 1995.
Johnson, Mark G., David T. Tingey, Majorie J. Storm, and Donald L.
Phillips. 1995. "Patterns of Ponderosa pine fine root growth and
turnover as affected by elevated CO2: Initial results."
"Proceedings: Belowground Responses to Rising Atmospheric
CO2: Implications for Plants, Soil Biota and Ecosystem Processes."
May 29-June 2, 1993. University of Michigan. Plant Physiology.
14:81-88.
Johnston, R.K., W.R. Munnsjr., FT. Short, and H.W. Walker (Ed).
December, 1994. Estuarine Ecological Assessment for
Portsmouth Naval Shipyard, Kittery Maine, Phase I:
Problem Formulation. Technical Report 1627, Naval Command,
Control an Ocean Surveillance Center, RDT&E Division, San
Diego, CA92152-5001.
Jorgensen, N.O.G., N. Kroer, and R.B. Coffin. 1994. Utilization of
Dissolved Nitrogen by Heterotrophic Bacterioplankton: Effect of
Substrate C/N Ratio." Applied Environmental Microbiology.
60(II):4I24-4I33.
Kahl, J.S., S.A. Norton, T.A. Haines, and R.B. Davis. 1993. "Recent
Trends in the Acid-base Status of Surface Waters in Maine, USA."
Water, Air, and Soil Pollution. 67:281-300.
Kanaya, N., et al. 1995. "Vicia Faba Chromosomal Aberration Assay."
Mutation Research. 310(2):231 -247.
Karentz, D., M.L Bothwell, R.B. Coffin, A. Hanson, G.J. Herndl, S.S.
Kilham, M.P. Lesser, M. Lindwell, R.E. Moeller, D.P. Morris, P.J.
Neale, R.W. Sanders, C.S. Weiler, and R.G. Wetzel. 1994. Impact
of UV-B Radiation on Pelagic Freshwater Ecosystems: Report of
Working Group on Bacteria and Phytoplankton. Archives of
Hydrobiology, Beih Ergebn. Limnology. 43:31-69.
Kavlock, R.J., and R.W. Setzer. March, 1996. "The road to
embtyologically based dose response models." Environmental
Health Perspectives. 104( I): 107-121.
Kavlock, R.J., B.C. Allen, E.F. Faustman, and C.A. Kimmel. 1995.
"Dose-response assessments for developmental toxicity IV.
Benchmark doses foe fetal weight changes." Fundamental and
Applied Toxicology. 26:211-222.
Kavlock, R.J.JA Schmid, and R.W. Setzer. 1996. "A simulation study
of the effects of study design on benchmark dose calculations for
developmental toxicity." Risk Analysis. 16(3)391 -403.
146
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Kawabata, T.T., G.R. Burleson, P.B. Ernst, S.E. Ullrich, and M.D.
Anderson. 1995. "Immunotoxicology of Regional Lymphoid tissue:
The Respiratory and Gastrointestinal Tract and Skin."
Fundamental and Applied Toxicology. 26:8-19.
Keeling, Ralph F. The atmospheric oxygen cycle: "The oxygen
isotopes of atmospheric CO2 and Q and the O /ty ratio."
Reviews of Geophysics, Supplement. 1253-1262, July 1995.
U.S. National Report to International Union of Geodesy and
Geophysics, 1991 -1994.
Keeling, Ralph F., Tsung-Hung Peng. 1995. "Transport of heat, CO2
and O2 by the Atlantic=s thermoline circulation." Phil. Trans. R.
Soc. Lond. B, 1995, 348, 133-142. Printed in Great Britain.
Kelce, W.R., C.R. Stone, S.C. Law, LE. Gray, J.A. Kemppainen, and
E.M. Wilson. 1995. "Persistent DDT metabolite pp'-DDE is a
potent androgen receptor antagonist." Nature. 375:581-585.
Kelly, C.A., C.S. Martens, and W. Ussier III. 1995. "Dynamics Across
a Tidally Flooded Riverbank Margin." Limnology and Ocean-
ography. 0(6): I 112-1129.
Kentula, Mary E. 1994. "Establishing Quantitative Criteria for
Wetland Restoration and Creation." Proceedings of the Fifth
Biennial Meeting of the Watershed Management Council.
November 16-18. Ashland, OR.
Keough, J.R., M.E. Sierszen, and C.A. Hagley. 1995. "Analysis of a
Lake Superior coastal food web using stable isotope techniques."
Limnology and Oceanography. 41:136-146.
Kern, Jeffrey S. 1995. "Evaluation of soil water retention models
based on basic soil physical properties." Soil Science Society of
America Journal. 59:1134-1141.
Kern, Jeffrey S. 1995. "Geographic patterns of soil water-holding
capacity in the contiguous United States." Soil Science Society
of America Journal. 59:1 126-1 133.
Kim, C.S., L. Garcia, and A. Wanner. 1995. "On the delivery of
pentamidine aerosol by Respigard II nebulizer." European
Respiratory Journal. 8:2178-2181.
King, George A., and Ronald P. Neilson. 1992. "The transient
response of vegetation to climate change: A potential source of
CO2 to the atmosphere." Water, Air and Soil Pollution.
64:365-383.
King, R.J., K.A. Short, and R.J. Seidler. 1995. "Assay for Detection and
Enumeration of Genetically Engineered Microorganisms Which is
Based on the Activity of a Deregulated 2,4-Dichloro-
phenoxyacetate Monooxygenase." Applied and Environmental
Microbiologia 57(6): 1790-1792.
Kitchen, K., and J. Brown. 1995. "Incorporation of 5-iodo-2'-
deoxyuridine and 5-bromo-2'-deoxyuridine into rodent DMA as
determined by neutron activation analysis." Analytical
Biochemistry. 228:180-187.
Kitchen, K., J. Brown, and A. Kulkarni. 1995. "Predicting rodent
carcinogenicity by in vivo biochemical parameters."
Environmental Carcinogenesis Review. CI2(l):63-88.
Kligerman, A., and S. King . 1995. "Frequency of micronucleated-
binucleated lymphocytes is not significantly affected by the harvest
time following Go exposure to X-radiation." International
Journal of Radiation Biology. 68( I): 19-23.
Kligerman, A., et al. 1995. "Cytogenetic and germ cell effects of
phosphine inhalation by rodents: II. Subacute exposures to rats and
mice." Environmental and Molecular Mutagenesis. 24:301-
306.
Kligerman, A., K. Mottus, and G. Erexson. 1995. "Cytogenetic
analyses of the in vitro and in vivo responses of murine cells to
peroxyacetyl nitrate (PAN)." Mutation Research. 341:199-206.
Klinefelter, G.R., J.D. Suarez, N.L. Roberts, and A.B. DeAngelo.
1995. "Preliminary screening for the potential of drinking water
disinfection to alter male reproduction." Reproductive
Toxicology. 9(6):57l-578.
Knudsen, S., P. Saasbye, L.H. Hansen, A. Collier, B.L. Jacobsen, J.
Schlundt, and O.H. Karlstrom. 1995. "Development and Testing
of Improved Suicide Functions for Biological Containment of
Bacteria." Applied Environmental Microbiology. 6I(3):985-
991.
Knuth, M.L., and L.J. Heinis. 1995. "Distribution and persistence of
diflubenzuron within littoral enclosure mesocosms." Agricultural
and Food Chemistry. 43:1087-1097.
Kodavanti, P.R.S., T.J. Shafer, T.R. Ward, W.R. Mundy, T.
Freudenrich, G.J. Harry, and H.A. Tilson. 1994. "Differential
Effects of Polychlorinated Biphenyl Congeners in Phosphoinositide
Hydrolysis and Protein Kinase C Translocation in Rat Cerebellar
Granule Cells." Brain Research. 662(l/2):75-82.
Kodavanti, P.R.S., T.R. Ward, H.A. Tilson, and J.D. McKinney. 1996.
"Inhibition of Intracellular Ca2+-Buffering Systems in Rat
Cerebellum by Polychlorinated Biphenyl Mixtures and Congeners:
Qualitative Structure-activity Relationships." Archives of
Toxicology. 70:150-157.
Kodavanti, P.R.S., T.R. Ward, J.D. McKinney, and H.A. Tilson. 1995.
"Increased [3H]-Phorbol Ester Binding in Rat Cerebellar Granule
Cells by Polychlorinated Biphenyl Mixtures and Congeners:
Qualitative Structure-Activity Relationships." Toxicology and
Applied Pharmacology. 130:140-148.
ADVANCING KNOWLEDGE FOR A PURPOSE
147
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Kodavanti, P.S., T.R. Ward, J.D. McKinney, C.L Waller, and HA
Tilson. 1995. "Increased [3H]Phorbol Ester Binding in Rat
Cerebellar Granule Cells and Inhibition of 45ca2+-Sequestration
in Rat Cerebellum by Polychlorinated diphenyl Ether Congeners
and Analogs: Structure-Activity Relationships." Toxicology and
Applied Pharmacology.
Kodavanti, U.P., D.L Costa, J. Richards, K.M. Crissman, R. Slade, and
G.E. Hatch. 1996. "Antioxidants in Bronchoalveolar Lavage Fluid
Cells Isolated From Ozone-Exposed Normal and
Ascorbate-Deficient Guinea Pigs." Experimental Lung
Research. In press..
Kodavanti, U.P., G.E. Hatch, B. Starcher, S.N. Giri, D.W. Winsett,
and D.L. Costa. February, 1995. "Ozone-induced Pulmonary
Functional, Pathological and Biochemical Changes in Normal and
Vitamin C-Deficient Guinea Pigs." Fundamental and Applied
Toxicology. 24:54-164.
Kodavanti, U.P., R.H. Jaskot, and K.L Dreher. 1996. "Eosinophilic
lung inflammation in paniculate-induced lung injury."
Experimental Lung Research. 22:541 -554.
Koren, H.S. 1995. "Associations between criteria air pollutants and
asthma." Environmental Health Perspectives. 66:369-374.
Koren, H.S., and P.A. Bromberg. 1995. "Is ozone a risk factor in
Environmental Asthma?" Allergo Journal. 4:215-218.
Koren, H.S., and P.A. Bromberg. 1995. "Respiratory responses of
asthmatics to ozone." International Archives of Allergy
Immunology. 107:236-238.
Kosian, PA, RA Hoke, G.T. Ankley, and P.M. VanderMeiden. 1995.
"Determination of dieldrin binding to dissolved organic material in
sediment pore water using a reverse phase technique."
Environmental Toxicology and Chemistry. 14:445-450.
Kroer, N., N.O.G. Jorgensen, and R.B. Coffin. 1994. "Utilization of
Dissolved Nitrogen by Heterotrophic Bacterioplankton: A
Comparison of Three Ecosystems." Applied Environmental
Microbiology. 60(1 I):4I 16-4123.
Kropff, M.J., K.G. Cassman, F.W.T. Penning de Vries, and H.H. van
Laar. 1993. "Increasing the Yield Plateau in Rice and the Role of
Global Climate Change." Journal of Agricultural Meteorology.
48(5):795-798.
Kuehl, D.W., and J. Serrano. 1994. "Identification of potentially
mutagenic contaminants in the aquatic environment by LC/TSP/MS
characterization of in vitro adducts". Journal of
Chromatography. 684:113-119.
Kuehl, D.W., and R. Haebler. 1995. "Organochlorine,
Organobromine, Metal, and Selenium Residues in Bottlenose
Dolphins (Tursiops truncates) Collected During an Unusual
Mortality Event in the Gulf of Mexico, 1990." Archives of
Environmental Contamination and Toxicology. 28:494-499.
Kuehl, D.W., and R. Haebler. 1995. "Organochlorine,
organobromine, metal, and selenium residues in bottlenose
dolphins Tursiops truncatus collected during an unusual mortality
event in the Gulf of Mexico, 1990." Archives of Environmental
Contamination and Toxicology. 28:494-499.
Lackey, R.T. 1993. "Ecological Risk Assessment." Fisheries Bulletin
of the American Fisheries Society. 19(9): 14-18.
Lake, CA.J.L Lake, R. Haebler, R. McKinney, W.S. Boothman, and
S.S. Sandove. 1995. "Contaminant Levels in Harbor Seals from the
Northeastern United States." Archives of Environmental
Contamination and Toxicology. 29:128-134.
Lake, J.L., R. Haebler, R. McKinney, CA. Lake, and S.S. Sadove.
1994. "PCBs and Other Chlorinated Organic Contaminants in
Tissues of Juvenile Kemp's Ridley Turtles (Lepi'doc/je/ys kempi)."
Marine Environmental Research. 38:313-327.
Lake, J.L., R. McKinney, CA. Lake, F.A. Osterman, and J. Heltshe.
1995. "Comparisons of Patterns of Polychlorinated Biphenyl
Congeners in Water, Sediment and Indigenous Organisms From
New Bedford Harbor, Massachusetts." Archives of
Environmental Contamination and Toxicology. 29:207-220.
Landers, D.H., G. Bangay, H. Sisula, T. Colborn, and L. LJjelund.
1995. "Airborne contaminants in the Arctic: What we need to
know." The Science of the Total Environment.
160/161:841-848.
Landers, D.H., J. Ford, C. Gubala, M. Monetti, Brenda K. Lasora, and
J. Martinson. 1995. "Mercury in vegetation and lake sediments
from the U.S. Arctic." Water, Air and Soil Pollution. 80:591 -
601.
Larsen, D. P. 1995. "The Role of Ecological Sample Surveys in the
Implementation of Biocriteria." Biological Assessment: Tools
for Water Resource Planning and Decision Making. Ed.
Wayne S. Davis and Thomas P. Simon. 287-300.
Larsen, D.P., N.S. Urquhart, and D.S. Kugler. 1995. "Regional scale
monitoring of indicators of trophic condition of lakes." Water
Resources Research. 31 (I): 117-140.
Latimer, J.S., and J.G. Quinn. 1996. "Historical Trends and Current
Inputs of Hydrophobic Organic Compounds in an Urban Estuary:
The Sedimentary Record." Environmental Science and
Technology. 30, 623-633.
Lay.J.C, C.R. Berry, C.S. Kim, and W.D. Bennett. 1995. "Retention
of insoluble particles following local intrabronchial deposition in
dogs." Journal of Applied Physiology. 79:1921 -1929.
Lebrec, H., K. Sarlo, and G. Burleson. 1995. "Effects of Influenza
Virus Infection on Ovalbumin-Species IgE Responses to Inhaled
Antigen in the Rat." Journal of Toxicology and Environmental
Health.
148
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERl FY95 ANNUAL REPORT
REFERENCES
Lee, E. Henry, William E. Hogsett, and David T. Tingey. 1994.
"Attainment and effects issues regarding alternative secondary
ozone air quality standards." Journal of Environmental Quality.
23(6): I 129-1 140.
Lee, G., M.R. Ellersieck, F.L Mayer and G.F. Krause. 1995.
"Predicting Chronic Lethality of Chemicals to Fishes from Acute
Toxicity Test Data: Multifactor Probit Analysis." Environmental
Toxicology and Chemistry. 14(2): 345-349.
Lee, K.M., J.V. Bruckner, S. Muralidhara, and J.M. Gallo. 1995.
"Characterization of Presystemic Elimination of Trichloroethylene
and Its Nonlinear Kinetics in Rats." XX-95-006.
Lee, K.M., S. Muralidhara, C.E. Dallas, and J.V. Bruckner. 1995.
"Does Orally Administered Trichloroethylene Volatilize and
Escape From the Gl Tract?" XX-95-007.
Lenihan, James M., and Ronald P. Neilson. 1993. "A rule-based
vegetation formation model for Canada." Journal of
Biogeography. 20:615-618.
Leonard, E.N., V.R. Mattson, and G.T. Ankley. 1995. "Horizon-
specific oxidation of acid volatile sulfide in relation to the toxicity
of cadmium spiked into a freshwater sediment." Archives of
Environmental Contamination and Toxicology. 28:78-84.
Lettenmaier, Dennis P., Kenneth L Brettman, Lance W. Vail, Steven
B. Yabusaki, and Michael J. Scott. 1992. "Sensitivity of Pacific
Northwest water resources to global warming." Northwest
Environmental Journal. 8:265-283.
Lewis, M.A. 1995. "Use of Freshwater Plants in Phytotoxicity
Testing: A Review." Environmental Pollution. 87(3):319-336.
Lewis-Sevan, L., S. Little, and J. Rabinowitz. 1995. "Quantum
Mechanical Studies of the Structure and Reactivities of the Diol-
Epoxides of Benzo[c]phenanthrene." Chemical Research in
Toxicology. 8:499-505.
Lighthart, B., and B.T. Shaffer. 1995. "Airborne bacteria in the
atmospheric surface layer; Temporal distribution above a grass
seed field." Applied & Environmental Microbiology.
64(4): 1492-1496.
Lighthart, B., B.T. Shaffer, B. Marthi, and L Ganio. 1993. "Artificial
wind-gust liberation of microbial bioaerosols previously deposited
on plants." Aerobiologia. 9:189-196.
Lighthart, Bruce, and Brenda Shaffer. 1995. "Viable bacterial aerosol
particle size distributions in the midsummer atmosphere at an
isolated location in the high desert chaparral." Aerobiologia.
11:29-25.
Lilly, P.O., J.E. Simmons, and R.A. Pegram. 1995. "Effect of
Subchronic Corn Oil Gavage on the Acute Toxicity of Orally
Administered Bromodichloromethane." Toxicology Letters.
MS-95-271.
Under. R.E., G.R. Klinefeter, LF. Strader, M.G. Narotsky, J.D.
Suarez, N.L Roberts, and S. Perreault. 1995. "Dibromoacetic acid
affects reproductive competence and sperm quality in male rat."
Fundamental and Applied Toxicology. 28:9-17.
LJpscomb, T.P., R.K. Harris, A.H. Rebar, B.E. Ballachey, and R.J.
Haebler. 1994. "Pathology of Sea Otters." Marine Mammals and
the Exxon Valdez. Ed. T.R. Loughlin. Academic Press, San Diego,
CA. Chapter 16, 265-279.
Liu, Jianguo, John B. Dunning, Jr., and H. Ronald Pulliam. 1995.
"Potential impacts of a forest management plan on Bachman's
sparrows (Aimophila aestivalis): Linking a spatially-explicit model
with CIS." Conservation Biology. 9(l):62-75.
Llorens, J., K.M. Crofton, and D.B. Peele. 1994. "Effects of
3,3'-lminodipropionitrile on Acquisition and Performance of Spatial
Tasks in Rats." Neurotoxicology and Teratology.
I6(6):583-59I.
Lowe, X., et al. 1995. "Aneuploidies and micronuclei in the germ
cells of male mice of advanced age." Mutation Research. 338:59-
76.
Lowrance, Richard, and George Vellidis. 1995. "A conceptual model
for assessing ecological risk to water quality function of bottomland
hardwood forests." Environmental Management.
I9(2):239-2S8.
Luebke, R.W. 1995. "Assessment of Host Resistance to Infection
with Malaria." Modern Methods in Immunotoxicology.
Wiley-Liss, Inc., 16:221-242.
Luebke, R.W. 1996. "Resistance to Trichinella Spiralis in Mice and
Rats Exposed to 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD):
Species Dependent Differences." in Modulators of Immune
responses Immunotoxicology: The Evolutionary Trail. (J.S.
Stolen, T.C. Fletcher. C.J. Zelikoff. LE. Twerdok, and D.P.
Anderson, eds). pp 491 -506.
Luebke, R.W., C.B. Copeland, and D.L. Andrews. January, 1995.
"Host Resistance to Trichinella Spiralis Infection in Rats Exposed
to 2,3,7,8,-Tetrachlorodibenzo-p-dioxin (TCDD)." Fundamental
and Applied Toxicology. 24:285-289.
Ma, T.-H., et al. 1995. "Tradescantia Micronucleus Bioassay."
Mutation Research. 3IO(2):22I-230.
Macauley, J.M., V.D. Engle, J.K. Summers. j.R. Clark, and DA.
Flemer. 1995. "Assessment of Water Quality and Primary
Productivity in Perdido Bay, a Northern Gulf of Mexico Estuary."
Environmental Monitoring and Assessment. 36(3): 191 -205.
MacPhail, R.C., E. Berman, JA Elder, R.J. Kavlock, V.C. Moser, M.G.
Narotsky, and M. Schlicht. 1995. "A Multidisciplinary Approach to
Toxicological Screening: IV. Comparison of Results." Journal of
Toxicology and Environmental Health. 45:211-220.
ADVANCING KNOWLEDGE FOR A PURPOSE
149
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Maier, W.E., H.W. Brown, HA Tilson, M.I. Luster, and G.J. Harry.
1995. "Trimethyltin increases IL-1, IL-6 and TNFa mRNA levels in
rat hippocampus." Journal of Neuroimmunology. 59:65-75.
Harden, B. Thomas, Anne Fairbrother, and Jewel K. Bennett. 1994.
"Interlaboratory comparison of cholinesterase assay measure-
ments." Environmental Toxicology & Chemistry.
I3(II):I76I-I768.
Marks, Danny, and Jeff Dozier. 1992. "Climate and energy exchange
at the snow surface in the Alpine region of the Sierra Nevada." "2.
Snow cover energy balance." Water Resources Research.
28(ll):3043-3054.
Marks, Danny, Jeff Dozier, and Robert E. Davis. 1992. "Climate and
energy exchange at the snow surface in the Alpine region of the
Sierra Nevada." " I. Meteorological measurements and monito-
ring." Water Resources Research. 28(11 ):3029-3042.
Marthi, Balkumar, Brenda T. Shaffer, Bruce LJghthait, and Lisa Ganio.
1991. "Resuscitation effects of catalase on airborne bacteria."
Applied and Environmental Microbiology. 57(9):2775-2776.
Martonen, T.B., and I.M.Katz. November, 1995. "Inter-related
Effects of Morphology and Ventilation on Drug Deposition
Patterns." Scientific and Technical Pharmacy
Pharmaceutical Sciences. 4( I): 11 -18.
Martonen, T.B., and IM Katz. 1996. "Thermodynamics of Inhaled
Hygroscopic Drugs," Aerosol Therapy.94:29-50.
Martonen, T.B., and Y. Yang. 1996. "Deposition Mechanics of
Pharmaceutical Particles in Human Airways." Aerosol Therapy.
94:3-27.
Martonen, T.B., I. Katz, and W. Cress. November, 1994. "Aerosol
Deposition as a Function of Airway Disease: Cystic Fibrosis."
Pharmaceutical Research. I2(I):96-I02.
Martonen, T.B., I. Katz, D. Hwang, and Y. Yang. Biomedical
Application of the Supercomputer Targeted Delivery of Inhaled
Pharmacuticals in Diseased Lungs. MS-95-268. In press.
Martonen, T.B., Y. Yang, and D. Hwang. November, 1994.
"Hygroscopic Behavior of Secondary Cigarette Smoke in Human
Nasal Passages." Pharma Sciences. 4(l):69-76.
Martonen, T.B., Y. Yang, and M. Dolovich. 1995. "Computer
Simulations of Lung Morphologies Within Planar Gamma Camera
Images." Journal of Nuclear Medicine. In press.
Martonen, T.B., Y. Yang, D. Hwang, and J.S. Fleming. May, 1995.
"Computer Model of Human Lung Morphology to Complement
SPECT Analyses." Computers in Biological Medicine. 40:5-16.
Martonen, T.B., Y. Yang, D. Hwang, and J.S. Fleming. September,
1995. "Computer Simulation of Human Lung Structures for
Medical Applications." Computers in Biological Medicine.
25(5).
Martonen, T.B., Y. Yang, Z.Q. Xue, and Z. Zhang. November, 1994.
"Motion of Air Within the Human Tracheobronchial Tree."
Particulate Science and Technology. 12:175-188.
Martonen, T.B., Z. Zhang, and Y. Yang. 1995. "Interspecies Modeling
of Inhaled Gases." Inhalation Toxicology. 7:1125-1139..
Martonen, T.B., Z. Zhang, and Y. Yang. 1995. "Particle Diffusion
From Developing Flows in Rough-Walled Tubes: A Closed Form
Solution." Journal of Mathematical Biology. In press..
Martonen, T.B., Z. Zhang, and Y. Yang. 1996. "Particle Diffusion
With Entrance Effects in a Smooth-Walled Cylinder." Journal of
Aerosol Science. 27:139-150.
Martonen, T.B., Z. Zhang, and Y. Yang. July, 1995. "Airway Surface
Irregularities Promote Particle Diffusion in the Human Lung."
Radiation Protection Dosimetry. 59(I):5-I4.
Martonen, T.B., Z. Zhang, Y. Yang, and G. Bottei. February, 1995.
"Gas Transport Processes in Human Airways." Inhalation
Toxicology. 7:303-318. 600/J-95/350.
Matthews, R.B., M.J. Kropff, D. Bachelet, T. Horie, Moon Hee Lee,
H.G.S. Centeno, J.C. Shin, D. Mohandass, Surjit Singh, and Zhu
Defeng. 1995. "Modeling the impact of climate change on rice
production in east and southeast Asia." Proceedings of the
International Symposium of Climate Change and Rice.
March 1994. Los BaZos, Phillipines.
McDonnell. W.F., P.W. Stewart, S. Andreoni, and M.V. Smith. 1995.
"Proportion of moderately exercising individuals responding to
low-level, multi-hour ozone exposure." American Journal of
Respiratory Critical Care Medicine. 152:589-596.
McErlean, A.J., E. Williams, and F. Wittwer. 1995. "Environmental
Education: A Blueprint for Serious Achievement?" Environmental
Professional. 17(3):263-270.
McGee, J.K., M.V. Evans, and W.D. Crank. October, 1995. "A
Versatile Gas Uptake Inhalation System Used in Pharmacokinetic
and Metabolic Studies of Volatile Organic Compounds."
Toxicology Methods. 5(4): 199-212.
McKelvey, Robert, and Joseph Apaloo. 1995. "The structure and
evolution of competition-organized ecological communities."
Rocky Mountain Journal of Mathematics. 25( I ):417-436.
McKenney, C.L.Jr., and D.M. Celestial. 1995. "Interactions Among
Salinity, Temperature, and Age on Growth of the Estuarine Mysid,
Mysidopsis bahia, Reared in the Laboratory Through a Complete
Life Cycle. I. Biomass and Age-Specific Growth Size." Journal of
Crustacean Biology. 15( I): 1269-178.
McKinneyJ., etal. 1995. "3,5-dinitro-4-(4-trifiuoromethylphenoxy)-
toluene, confromationally related to thyroid hormones." ACTA
Crystallographies. Chapter 51.
ISO
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
McKinney, J.D., and C.L Waller. 1995. "Molecular Determinants of
Hormone Mimicry, Halogenated Aromatic Hydrocarbon
Environmental Agents." Toxicology and Applied
Pharmacology.
McKinney, J.D., S.C. Agarwal, W.T. Padgett, G.R. Lambert, S. Phirtu,
and S. Nesnow. March, 1995.
"3,5-Dinitro-4-(4-trifluoromethylphenoxy)-toluene,
Conformationally Related to Thyroid Hormones." Acta
Crystallographica. C51.
McKinney, W.J., J.R. Lehmann, D.W. Winsett, D.L Doerfler, and
D.L Costa. 1995. "The Influence of b-Aminoproprionitrile (bAPN)
on Cadmium Chloride-induced Lung Fibrosis in the Rat and
Hamster." Inhalation Toxicology.
McMahon, T.F., M.A. Medinsky, and LS. Birnbaum. December,
1994. "Age-related Changes in Benzene Disposition in Male
C57BL/6N Mice Described by a Physiologically Based
Pharmacokinetic Model." Toxicology Letters. 74:241-253.
Mehrle, P.M., V. Kozlovskaya, and F.L. Mayer. 1994. "The Effect of
the Phosphororganic Herbicide DEF on Growth, Survival and
Activity of Acetylcholinesterase in Brain of Rainbow Trout (Salmo
gairdneri)." Russian Academy of Science and Biology Inland
Water Inform Bulletin. 97:53-57.
Mekenyan, O.G., G.D. Veith, S.P. Bradbury, and N. Aaharieva. 1995.
"SAR models for metabolic activation: Stability of organic cation
intermediates." Quantitative Structure - Activity
Relationship. !4(3):264-269.
Mekenyan, O.G., G.T. Ankley, G.D. Veith, and D.J. Call. 1994.
"QSARs for photoinduced toxicity. I.Acute lethality of polycyclic
aromatic hydrocarbons to Daphnia magna." Chemosphere.
28(3):367-382.
Mekenyan, O.G., G.T. Ankley, G.D. Veith, and D.J. Call. 1995.
"QSARs for photoinduced toxicity of aromatic hydrocarbons."
SAR QSAR Environmental Research. 4:139-145.
Mekenyan, O.G., G.T. Ankley, G.D. Veith, and D.J. Call. 1995.
"QSAR estimates of excited states and photoinduced toxicity of
polycyclic aromatic hydrocarbons." SAR QSAR Environmental
Research. 2:237-247.
Middaugh, D.P., and D.D. Whiting. 1995. "Responses of Embryonic
and Larval Inland Silver-sides, Menidia beryllina, to No. 2 Fuel
Oil and Oil Dispersants in Seawater." Archives of
Environmental Contamination and Toxicology. 29(4):535-
539.
Miller, D.B., A. Bartke, and J.P. O'Callaghan. 1995. "Increased Glial
Fibrillary Acidic Protein (GFAP) Levels in the Brains of Transgenic
Mice Expressing the Bovine Growth Hormone (bGH) Gene."
Experimental Gerontology. 30(3/4):383-400.
Miller, D.B., and J.P. O=Callaghan. 1995. "The role of temperature
stress and other factors in the neurotoxicity of the substituted
amphetamines: 3,4-methylenedioxymethamphetamine and
fenfluramine.'Joumal of Molecular Neurobiology. 11:177-192.
Mo, Jiangming, Sandra Brown, Melanie Lenart, Guohui Kong. 1995.
"Nutrient dynamics of a human-impacted pine forest in a MAB
reserve of subtropical China." Biotropica. 27(3):290-304.
Moll, R.A., D. Judd, R. Rossmann, G.V. Kantak.J. Barres, S. DeBoe,
j. Giesy, and M. Tuchman. 1995. "Movement and loadings of
inorganic contaminants through the lower Saginaw River." journal
of Great Lakes Research. 21:17-34.
Monnoson, E., and J.J. Stegeman. 1994. "Induced Cytochrome
P450IA in Winter Flounder, P/euronectes americanus. From
Offshore and Coastal Sites." Canadian Journal of Fisheries and
Aquatic Science. 51:933-941.
Monson, P.O., G.T. Ankley, and P.A. Kosian. 1995. "Phototoxic
response of Lumbriculus variegatus to sediments contaminated by
polycyclic aromatic hydrocarbons." Environmental Toxicology
and Chemistry. 14:891 -894.
Moser, V.C. 1996. "Rat Strain- and Gender-related Differences in
Neurobehavioral Screening: Acute Trimethyltin Neurotoxicity."
Journal of Toxicology and Environmental Health. 47:567-586.
Moser, V.C. "Comparisons of the Acute Effects of Cholinesterase
Inhibitors Using a Neurobehavioral Screening Battery in Rats."
1995. Neurotoxicology and Teratology. 17:617-626.
Moser, V.C., B.M. Cheek, and R.C. MacPhail. 1995. "A
Multidisciplinary Approach to Toxicological Screening: III.
Neurobehavioral Toxicity." Journal of Toxicology and
Environmental Health. 45:173-210.
Mumford, J.L, X. Li, F. Hu, X.B. Lu, and J.C. Chuang. 1996. "Human
exposure and dosimetry of polycylie aromatic hydrocarbons in
urine from Xuan Wei, China with high lung cancer mortality
associated with exposure to unvented coal smoke."
Carcinogenesis. 16:3031-3036.
Mundy, W.R., T.J. Shafer, T. Freudenrich, and A.C. Nostrandt. 1995.
"In Vitro Aluminum Inhibition of Brain Phosphoinositide
Metabolism Comparison of Neonatal and Adult Rats."
Neurotoxicology. !6(l):35-44.
Nacci, D., S. Cheer, E. Jackim, and A. Juinio. 1994. "Semiautomated
Fluorometric Analysis of Nucleic Acids in Tissue Homogenates."
Environmental Toxicology and Water Quality: An
International Journal. 9:123-130.
ADVANCING KNOWLEDGE FOR A PURPOSE
151
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Narasimham, T.R., A. Craig, L Arellano, N. Harper, L. Howie, M.
Menache, L.S. Birnbaum, and S. Safe. November, 1994. "Relative
Sensitivities of 2,3,7,8-tetrachlorodibenzo-p- dioxin
(TCDD)-induced Cypla-l and Cypla-2 Gene Expression and
Immunotoxicity in Female B6C3F1 Mice." Fundamental and
Applied Toxicology. 23(4):598-607.
Narotsky, M.G., and R.J. Kavlock. 1995. "A multidisciplinary approach
to toxicological screening. II. Developmental toxicity." Journal of
Toxicology and Environmental Health. 45:145-171.
Narotsky, M.G., E.A. Weller, V.M. Chinchilli, and R.J. Kavlock. 1995.
"Nonadditive developmental toxicity in mixtures of
trichloroethylene, di(2-ethylhexyl)phthlate, and heptachlor in a
5x5x5 design." Fundamental and Applied Toxicology.
27:203-207.
Nazaret, S., W.H. Jeffrey, E. Saouter, R. Von Haven, and T. Barkay.
1994. "merA Gene Expression in Aquatic Environments Measured
by mRNA Production and Hg(ll) Volatilization." Applied
Environmental Microbiology. 60(1 l):4059-4065.
Nebeker, A.V., G.S. Schuytema, and S.L Ott. 1994. "Effects of
Cadmium on Limb Regeneration in the Northwestern Salamander
Ambystoma gracile." Archives of Environmental Contami-
nation and Toxicology. 27:318-322.
Neckles, H.A. (Ed.) 1994. "Indicator Development: Seagrass
Monitoring and Research in the Gulf of Mexico." EPA/620/R-
94/029.
Neilson, Ronald P. 1993. "Transient ecotone response to climatic
change: Some conceptual and modeling approaches." Ecological
Applications. 3(3):385-395.
Neilson, Ronald P. 1995. "A Model for predicting continental-scale
vegetation distribution and water balance." Ecological
Applications. 5(2):362-385.
Neldon, D.L, R.W. Lange, G.J. Rosenthal, C.E. Comment, and G.R.
Burleson. 1995. "Macrophage Non-specific Phagocytosis Assay."
Methods in Immunotoxicology. Ed. G.R. Burleson, j.H. Dean,
and A.E. Munson. John C. Wiley & Sons, 2(4):39-57.
Nelson, G., and S. George. 1995. "Comparison of media for selection
and enumeration of mouse fecal flora populations." Journal of
Microbiological Methods. 22:293-300.
Nelson, W.G., B.J. Bergen, and D.J. Cobb. 1995. "Comparison of
PCB and Trace Metal Bioaccumulation in the Blue Mussel, Mytilus
edulis, and the Ribbed Mussel, Modiotus demissus, in New Bedford
Harbor, Massachusetts." Environmental Toxicology and
Chemistry. I4(3):5I3-52I.
Nesnow, S., et al. 1995. "Mechanistic linkage between DMA adducts,
mutations in oncogenes and tumorigenesis of carcinogenic
environmental polycyclic aromatic hydrocarbons in strain A/J
mice." Toxicology. 105:403-414.
Nesnow, S., et al. 1995. "Morphological Transformation and DNA
Adduct Formation by Dibenz[a,h]anthracene and its Metabolites
in C3HIOTI/2CL8 Cells." Carcinogenesis. 15( 10):2225-2231.
Nesnow, S., et al. 1995. "Synthesis and Characterization of Adducts
of Alachlor 2-Chloro-N-(2,6-Diethylphenyl)Acetamide with 2'-
Deoxyguanosine, Thymidine and their 3'-Monophosphates."
Chemical Research in Toxicology. 8:209-217.
Neue, H.-U., LH. Ziska, R.B. Matthews, and Q. Dai. 1995.
"Reducing global warming: the role of rice." Geo-Journal.
35(3):35l-362.
Neue, H.U., R.S. Lantin, R. Wassman, J.B. Aduna, Ma. C.R. Alberto,
and M.J.F. Andales. 1994. "Methane emission from rice soils of the
Philippines." CH4 and N2O: Global Emissions and Controls
from Rice Fields and Other Agricultural Industrial Sources,
NIAES. 55-73.
Newsted, J.L, J.P. Giesy, G.T. Ankley, D.E. Tillitt, R.A. Crawford,
J.W. Gooch, P.D.Jones, and M.S. Dension. 1995. "Development
of toxic equivalency factors for PCB congeners and the assessment
of TCDD and PCB mixtures in rainbow trout." Environmental
Toxicology and Chemistry. 14(5):861 -871.
Nichols, J.W., C.P. Larsen, M.E. McDonald, G.J. Niemi, and G.T.
Ankley. 1995. "A bioenergetics-based model for accumulation of
polychlorinated biphenyls by nestling tree swallows, Tocnyc/neto
bicolor." Environmental Science and Technology. 29(3):604-
612.
Nichols, J.W., P. Rheingans, D.B. Lothenbach, R. McGeachie, L.
Skow, and J. McKim. 1994. "Three-dimensional visualization of
physiologically based kinetic model outputs." Environmental
Health Perspectives. 102:952-956.
Noah, T.L, F. W. Henderson, M.M. Henry, D.B. Peden, and R.B.
Devlin. 1995. "Nasal lavage cytokines in normal, allergic, and
asthmatic school age children." American Journal of
Respiratory Critical Care Medicine. 152:1290-1296.
Noah, T.L, F.W. Henderson, I. Wortman, R.B. Devlin, J.H. Handy,
H.S. Koren, and S. Becker. 1995. "Nasal cytokine production in
viral acute upper respiratory infection of childhood." Journal of
Infectious Disease. 171:584-592.
Noah, T.L, J.R. Yankaskas, J.L Carson, T.M. Gambling, LH. Cazares,
K.P. McKinnon, and R.B. Devlin. 1995. "Tight junctions and mucin
mRNA in BEAS-2B cells." In Vitro Cellular and Developmental
Biology.
Norwood, J., K. Crissman, and G.E. Hatch. November, 1994. "Nasal
Lavage Antioxidants in Guinea Pigs, Rats, and Mice." Inhalation
Toxicology. 6:376-383. 600/J-95/086.
Oliver, L.M., and W.S. Fisher. 1995. "Comparative Form and
Function of Oyster Crassostrea virginica Hemocytes from
Chesapeake Bay (Virginia) and Apalachicola Bay (Florida)."
Diseases of Aquatic Organisms. 22(3):217-225.
152
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Olson, R.J., and E.R. Zettler. 1995. "Potential of Flow Cytometry for
>Pump an Probe = Fluorescence Measurements of Phytoplankton
Photosynthetic Characteristics." Limnology and Oceanography.
40(4):8I6-820.
Olszyk, David M. 1993. "UV-B Effects on Terrestrial Ecosystems."
Proceedings of Impact of Increased UV-B Exposure on
Human Health and Ecosystem. Kitakyushu, Japan. October
1993.
Olszyk, David, Quille Dai, Paul Teng, Hei Leung, Yong Luo, and
Shaobing Peng. 1996. "UV-B effects on crops: Response of the
irrigated rice ecosystem." Journal of Plant Physiology. 148:26-
34
Oremland, R.S., LG. Miller, P. Dowdle, T. Connell, and T. Barkay.
1995. "Methylmercury Oxidative Degradation Potentials in
Contaminated and Pristine Sediments of the Carson River,
Nevada." Applied Environmental Microbiology. 6I(7):2745-
2753.
Overton, J.H., and R.C. Graham. July, 1995. "Simulation of the
uptake of a Reactive Gas in a Rat Respiratory Tract Model With an
Asymmetric Tracheobronchial Region Patterned on Complete
Conducting Airway Cast Data." Computers and Biomedical
Research. 28:171-190.
Overton, J.H., and R.C. Graham. November, 1994. "Modeling the
Uptake of Gases by the Dog Nasal-Pharyngeal Region: Effects of
Morphometric and Physicochemical Factors." Inhalation
Toxicology. 6:113-124.
Oviatt, C, P. Doering, B. Nowicki, L Reed.J. Cole, andj. Frithsen.
1995. "An Ecosystem Level Experiment on Nutrient Limitation in
Temperate Coastal Marine Environments." Marine Ecology
Progress Series. I 16:1 71 -179.
Oviatt, C.A. 1994. "Biological Considerations in Marine Enclosure
Experiments: Challenges and Revelations." Oceanography.
7(2):45-5l.
Oviatt, C.A., P. Doering, B. Norwicki, L. Reed, J. Cole, and J.
Frithsen. 1995. "An Ecosystem Level Experiment on Nutrient
Limitation in Temperate Coastal Marine Environments." Marine
Ecology Progress Series. I 16:171 -179.
Ozretich, R.J., LM. Smith, and F.R. Roberts. 1995. "Reverse-Phase
Separation of Estuarine Interstitial Water Fractions and the
Consequences of C]e Retention of Organic Matter."
Environmental Contamination and Toxicology. 14(8): 1261 -
1272.
Padilla, S.J., V.Z. Wilson, and A.C. Nostrandt. 1995. "A Novel
Method That Markedly Increases the Sensitivity of the Erythrocyte
Acetylcholinesterase Assay, Suitable for Use in Pesticide-treated
Rats." Toxicology Methods. 5( I ):41 -49.
Paterson, Sally, Donald Mackay, and Craig McFarlane. 1994. "A
Model of Chemical Uptake by Plants from Soil and the
Atmosphere." Environmental Science & Technology.
28(l3):2259-2266.
Paul, J.S., H.R. Walker, and W.R. Munns, Jr. "Reevaluation of
assessment conducted prior to disposal of New York/New Jersey
sludge at the 106-Mile Deposition." Journal of Marine
Environmental Engineering. In press in Great Britain.
Peden, D.B., WA Setzer, and R.B. Devlin. 1995. "Ozone exposure
has both a priming effect on allergen-induced responses as well as
an intrinsic inflammatory action in the nasal airways of perennially
allergic asthmatics." Respiratory Critical Care Medicine.
151:1336-1345..
Pegram, RA.J.J. Diliberto, T.C. Moore, P. Gao, and LS. Birnbaum.
March, 1995. "2,3,7,8-Tetra- chlorodibenzo-p-dioxin (TCDD)
Distribution and Cytochrome P450IA Induction in Young Adult
and Senescent Male Mice." Toxicology Letters. 76:119-126.
Perez, K. 1995. "Role and Significance of Scale to Ecotoxicology."
Ecological Toxicity Testing: Scale, Complexity, and
Relevance. Ed. J. Cairns, Jr. and B.R. Niederleher. Lewis
Publishers, Boca Raton, FL. Chapter 4, 49-72.
Perry, D.A., J.G. Borchers, D.P. Turner, S.V. Gregory, R.K. Dixon,
S.C. Hart, B. Kauffman, R.P. Neilson, and P. Sollins. 1991.
"Biological feedbacks to climate change: terrestrial ecosystems as
sinks and sources of carbon and nitrogen." Northwest
Environmental Journal. 7:203-231.
Pesch, C.E., D.J. Hansen, W.S. Boothman, W.J. Berry, and J.D.
Mahony. 1995. "The Role of Acid-Volatile Sulfide."
Environmental Toxicology and Chemistry. 14( I): 129- Ml.
Peters, E.C., P.P. Yevich, J.C. Harshbarger, and G.E. Zaroogian.
1994. "Comparative Histolopathology of Gonadal Neoplasms in
Marine Bivalve Molluscs." Diseases of Aquatic Animals. 20:59-
76.
Peterson, Jeffrey A., and Alan V. Nebeker. 1992. "Estimating
waterborne selenium concentrations that are toxicity thresholds
for wildlife." Archives of Environmental Contamination and
Toxicology. 23:154-162.
Peterson, Spencer A., John J. Barich, III, Jos C. Greene. 1992. "How
chemically stable is stabilized hazardous waste? Remediation:"
Journal of Environmental Costs, Technologies, and Technics.
447-458.
Peterson, Spencer A., Robert M. Hughes, David P. Larsen, Steven G.
Paulsen, and James M. Omernik. 1995. "The significance of
regional lake quality patterns to management/restoration of
specific lakes." Proceedings of 6th International Conference
on the Conservation and Management of Lakes. October
23-23-27. Kasumigaura, Japan. 2:653-656.
ADVANCING KNOWLEDGE FOR A PURPOSE
153
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Phillips, Donald L, and Danny G. Marks. 1996. "Spatial uncertainty
analysis: propagation of interpolation errors in spatially distributed
models." Ecological Modeling. In press.
Phipps, G.L, V.R. Mattson, and G.T. Ankley. 1995. "Relative
sensitivity of three freshwater benthic invertebrates to ten
contaminants." Archives of Environmental Contamination and
Toxicology. 28:281-286.
Pietarinen, P., K. Raivio, R.B. Devlin, J.D. Crapo, L.Y. Chang, and V.L.
Kinnula. 1995. "Catalase and glutathione reductase protection of
human alveolar macrophages during oxidant exposure in vitro."
American Journal of Respiratory Cell, and Molecular
Biology. "131:434-441.
Poiani, Karen A., W. Carter Johnson, and Timothy G.F. Kittel. 1995.
"Sensitivity of a prairie wetland to increased temperature and
seasonal precipitation changes." Water Resources Bulletin.
3l(2):283-294.
Porteous, L.A., J.L. Armstrong, R.J. Seidler, and LS. Watrud. 1994.
"An Effective Method to Extract DMAs from Environmental
Samples for Polymerase Chain Reaction Amplification and DNA
Fingerprint Analysis." Current Microbiology. 29:301-307.
Prah, J.D., G.M. Goldstein, R.B. Devlin, D.A. Otto, D. Ashley, D.
House, K.L. Cohen, and T. Gerrity. 1994. "Sensory symptomatic,
inflammatory, and ocular responses to and the metabolism of
methyl tertiary butyl ether (MTBE) in a controlled exposure
experiment." Inhalation Toxicology. 6:521-538.
Pritchard, R.J., A.J. Ghio, J.R. Lehmann, D.W. Winsett, J.S. Tepper,
P. Park, M.I. Gilmour, K.L. Dreher, and D.L Costa. "Oxidant
generation and lung injury after paniculate air pollutant exposure
increase with the concentrations of associated metals." Inhalation
Toxicology.
Pritchard, R.J., A.J. Ghio, J.R. Lehmann, D.W. Winsett, J.S. Tepper,
P. Park, M.I. Gilmour, K.L. Dreher, and D.L Costa. 1996.
"Oxidant Generation and Lung Injury after Paniculate Air Pollutant
Exposure increase with the Concentrations of Associated Metals."
Inhalation Toxicology. 8:457-477.
Qian, Z., M.E. Gilbert, and E.R. Kandel. 1994. "Temporal and Spatial
Regulation of the Expression of BAD2, a MAP Kinase Phosphatase,
during Seizure, Kindling and Long-term Potentiation." Learning
& Memory. (I):180-188.
Rahman, I., M. Shahamat, P.A. Kirchman, E. Russek-Cohen, and R.R.
Colwell. 1994. "Methionine Uptake and Cytopathogenicity of
Viable but Nonculturable Shigella dysenteriae Type I." Applied
Environmental Microbiology. 60(IO):3573-3578.
Raynor, S., F. Bretherton, S. Buol, M. Fosberg, W. Grossman, R.
Houghton, R. Lai, Jeffrey Lee, S. Lonergan, J. Olson, R. Rockwell,
C. Sage, and E. van Imhoff. 1994. "A wiring diagram for the study
of land-use/cover change: Report of Working Group A." Changes
in Land Use and Land Cover: A Global Perspective. Ed.
William B. Meyer and B. L. Turner, II. Chapter 2, 13-53.
Cambridge University Press, Cambridge.
Reams, Gregory A., and Charles E. Peterson. 1992. "Evaluating
changes in forest condition potentially related to acid deposition:
an example using red spruce." Forest Ecology and
Management. 51:5-16.
Redmond, M.S., K.J. Scott, R.C. Swartz, and J.K.P. Jones. 1994.
"Preliminary Culture and Life-Cycle Experiments with the Benthic
Amphipod Ampe/isco abdita." Environmental Toxicology and
Chemistry. 13(8): 1355-1365.
Richard, A. 1995. "Role of Computational Chemistry in Support of
Hazard ID: Mechanism-based SARs." Toxicology Letters.
79:115-122.
Richmond, R., et al. 1995. "Immunohistochemical Analysis of
Dichloroacetic Acid (DCA)- induced Hepatocarcinogenesis in Male
Fischer (F344) Rats." Cancer Letters. 92:67-76.
Riddle, M.M., W.C. Williams, and R.J. Smialowicz. 1996. "Repeated
Oral Dosing of Continuous Subcutaneous Infusion of
2-Methoxyacetic Acid Are Not Immunosuppressive in the Mouse."
Toxicology. 109:67-74.
Riley, R.H., D.L Phillips, M.J. Schuft, and M.C. Garcia. 1996.
"Resolution and error in measuring land-cover change: Effects on
estimating net carbon release from Mexican terrestrial
ecosystems." International Journal of Remote Sensing.
Accepted.
Robinson, B.L, D.E. Guinnup, J.E. Andrews, J.W. Allis, A. McDonald,
J.C. Seely, T.J. Mohin, and J.E. Simmons. March, 1995. "Hepatic
and Renal Assessment of Acute Exposure to Inhaled
Epichlorohydrin: Toxicological Evaluation and Exposure
Modeling." Inhalation Toxicology. 7:289-301.
Robinson, B.L, J.W. Allis, J.E. Simmons, and D.E. House. November,
1995. "Fasting for Less Than 24 Hours Induces Cytochrome P450
2EI and 2B1/2 Activities in Rats." Toxicology Letters. 81:39-44.
Ross, J., et al. 1995. "Adenomas Induced by Polycyclic Aromatic
Hydrocarbons in Strain A/J Mouse Lung Correlate with Time-
Integrated DNA Adduct Levels." Cancer Research. 55:1039-
1044.
Russom, C.L., S.P. Bradbury, and A.R. Carlson. 1995. "Use of
knowledge bases and QSARs to estimate the relative ecological
risk of agrichemicals: A problem formulation exercises." SAR and
QSAR Environmental Research. 4:83-95.
154
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Rygiewicz, P.T., K.J. Martin, A.R. Tuininga, and E.R. Ingham. 1995.
"Global Climate Change and Diversity of Mycorrhizae."
International Symposium on Microbial Ecology. August-
September. Santos, Brazil.
Rygiewicz, P.T., K.J. Martin, and A.R. Tuininga. 1996. "Global climate
change and mycorrhizal fungi." Seventh International
Symposium of Microbial Ecology.
Rygiewicz, Paul T., and Christian P. Andersen. 1994. "Mycorrhizae
alter quality and quantity of carbon allocated below ground."
Nature. 369:58-60.
Rygiewicz, Paul T., and Elaine R. Ingham. 1993. "Soil Biology and
Ecology." Encyclopedia of Environmental Science. The Van
Nostrand Reinhold. publ. Ed. R. W. Fairbridge and D. E.
Alexander.
Sailstad, D.M., J.S. Tepper, D.L. Doerfler, M. Qasim, and M.J.K.
Selgrade. November, 1994. "Evaluation of an Azo and Two
Anthraquinone Dyes for Allergic Potential." Fundamental and
Applied Toxicology. 23(4):569-577.
Sailstad, D.M., S.D. Krishnan, J.S. Tepper, D.L. Doerfler, and M.J.K.
Selgrade. February, 1995. "Dietary Vitamin A Enhances Sensitivity
of the Local Lymph Node Assay." Toxicology. 96:157-163.
Sanders, B.M., L.S. Martin, S.R. Howe, W.G. Nelson, C.S. Hegre, and
D.K. Phelps. 1994. "Tissue Specific Differences in Accumulation of
Stress Proteins in Myt//us edulis Exposed to a Range of Copper
Concentrations." Toxicology and Applied Pharmacology.
125:206-213.
Sandhu, S., et al. 1995. "A Summary of Results and
Recommendations of the IPCS Collaborative Study on Plant Test
Systems." Mutation Research. 3 IO(2):257-263.
Sandhu, S., et al. I 995. "IPCS Collaborative Study on the Utility of
Plant Test Systems in Genetic Toxicology: An Introduction and
Study Design." Mutation Research. 310(2): 169-1 73.
Santostefano, M.J., K.L.Johnson, M.J. DeVito.J.J. Diliberto, and LS.
Birnbaum. 1995. "Subcellular Localization of
[3H]2,3,7,8-Tetrachlorodibenzo- p-dioxin (TCDD) Differs
Between the Liver and Kidneys After Acute and Subchronic
Exposure." Toxicology and Applied Pharmacology.
MS-95-258.
Sanzgiri, U.Y., H.J., Kim, S. Muralidhara, C.E. Dallas, and J.V.
Bruckner. September, 1995. "Effect of Route and Pattern of
Exposure on the Pharmacokinetics and Acute Hepatotoxicity of
Carbon Tetrachloride." Toxicology and Applied
Pharmacology. 134:148-154.
Saouter, E., M. Qllman, and T. Barkay. 1995. "Evaluation of mer-
Specified Reduction of Ionic Mercury as a Remedial Tool of a
Mercury-Contaminated Freshwater Pond." journal of Industrial
Microbiology. !4(3/4):343-348.
Saouter, E., M. Gillman, R. Turner, and T. Barkay. 1995.
"Development and Field Validation of a Microcosm to Simulate the
Mercury Cycle in a Contaminated Pond." Environmental
Toxicology and Chemistry. !4(l):69-77.
Savela, K., L King.J. Gallagher and J. Lewtas. 1995. "32P-postlabeling
and HPLC Analysis of DNA Adducts Formed by Diesel Exhaust
Extracts In vitro and in Mouse Skin and Lung after Topical
Treatment." Carcinogenesis. I6(9):2083-2089.
Schein, O.D., C. Vicencio, K. Gelatt, B. Munoz, S. West, J.
Honeyman, D.D. Duncan, H.S. Koren, andj. Nethercoitt. 1995.
"Ocular and dermatologic health effects of ultraviolet light
exposure in the ozone hole in southern Chile." American Journal
of Public Health. 85:546-550.
Schmieder, P., D. Lothenbach, J. Tietge, R. Erickson, and R. Johnson.
1995. "[3H]-2,3,7,8-TCDD uptake and elimination kinetics of
medaka Oryzias latipes." Environmental Toxicology and
Chemistry. 14(10): 1735-1743.
Schroeder, Paul E. 1993. "Agroforestry systems: Integrated land use
to store and conserve carbon." Climate Research. 3:53-60.
Schroeder, Paul, and Jack K. Winjum. 1995. "Brazil's land-based CO2
exchange for 1990 and links to the global carbon cycle."
Proceedings, International Symposium on Environmental
and Biometeorology. July 20-22. Beijing, China.
Schroeder, Paul, Jack K. Winjum. 1995. "Brazil's carbon budget for
1990." Interciencia. (20)2:68-75.
Schubauer-Berigan, M.K., P.O. Monson, C.W. West, and G.T.
Ankley. 1995. "Influence of pH on the toxicity of ammonia to
Chironomus tentans and Lubriculus variegatus." Environmental
Toxicology and Chemistry. 14:713-718.
Schuytema, Gerald S., Alan V. Nebeker, and William L. Griffis. 1995.
"Comparative toxicity of guthion and futhion 2S to Xenopus laevis
and Pseudacris regilla tadpoles." Bulletin of Environmental
Contamination and Toxicology. 54:382-388.
Seal, E., W.F. McDonnell, and D.E. House. "The effect of age,
socioeconomic status, and menstrual cycle on the pulmonary
response to ozone." 1996. Archives of Environmental Health.
51 (2): 132-137.
Selgrade, M.J.K. 1996. "Approaches to inter-species extrapolation:
use of human clinical and laboratory mouse data from ozone and
ultraviolet radiation immunotoxicity studies to generate prototype
parallelogram and ladder models" in Evolutionary Trail. (J.S.
Stolen, T.C. Fletcher, C.J. Zelikoff, L.E. Twerdok, and D.P.
Anderson, eds). pp 365-373.
ADVANCING KNOWLEDGE FOR A PURPOSE
155
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Belgrade, M.J.K.July, 1995. "Immunotoxicity and Risk Assessment:
Effect of Temporal Factors." Inhalation Toxicology. 7:891-901.
Belgrade, M.J.K., and M.I. Gilmour. 1994. "Effects of Gaseous Air
Pollutants on Immune Responses and Susceptibility to Infectious
and Allergic Disease." Immunotoxicology and
Immunopharmacology. Ed. J.H. Dean, M.I. Luster, A.E. Munson,
and I. Kimber. Raven Press, Ltd., New York. 22(2):395-4l I.
Belgrade, M.J.K., and M.J. Daniels. 1995. "Murine Cytomegalovirus
Host Resistance Models." Ed. Gary Burleson, Jack H. Dean, and
Albert E. Munson. John Wiley & Sons, Inc. 15:203-219.
Selgrade, M.J.K., K.D. Cooper, R.B. Devlin, H. van Loveren, R.E.
Biagini, and M.I. Luster. January, 1995. "Immunotoxicity - Bridging
the Gap Between Animal Research and Human Health Effects."
Fundamental and Applied Toxicology. 24(1): 13-21.
Selgrade, M.J.K., K.D. Cooper, R.B. Devlin, H. van Loveren, R.E.
Biagini, and M.I. Luster. 1995. "Immunotoxicity — Bridging the Gap
Between Animal Research and Human Health Effects."
Fundamental and Applied Toxicology. 24( I): 13-21.
Selgrade, M.K., M.I. Gilmour, Y.G. Yang, G. Burleson, and G. Hatch.
1995. "Pulmonary host defenses and resistance to infection
following subchronic exposure to phosgene." Inhalation
Toxicology. 7:1257-1268.
Selifonov, S.A., J.E. Gurst, and L.P. Wackett. 1995. "Regioselective
Dioxygenation as a Mechanism in ortho-Halobenzoate
Dehalogenation." Biochemical and Biophysical Research
Communications. 2l3(3):759-767.
Selifonova, O.V., and T. Barkay. 1994. "Role of Na+ in Transport of
HG2+ and Induction of the Tn2l mer-Operon." Applied
Environmental Microbiology. 60(IO):3503-3507.
Sengstock, G.J., A.J. Dunn, C.W. Olanow, S. Barone, and G.W.
Arendash. 1994. "Progressive Changes in Striatal Dopaminergic
Markers, Nigral Volume, and Rotational Behavior Following Iron
Infusion into the Rat Substantia Nigra." Experimental
Neurology. I 30(l):82-94.
Shafer, R.J., and W.R. Mundy. 1995. "Effects of Aluminum on Signal
Transduction: Mechanisms Underlying Disruption of
Phosphoinositide Hydrolysis." General Pharmacology.
26(5):889-895.
Shelton, M., and D. DeMarini. 1995. "Mutagenicity and Mutation
Spectra of 2-Acetylaminofluorene at Frameshift and Base-
Substitution Alleles in Four DNA Repair Backgrounds of
Salmonella." Mutation Research. 327:75-86.
Shiba, T., R.T. Hill, W.L. Straube, and R. Colwell. 1995. "Decrease
in Culturability of Vibrio cholerae Caused by Glucose." Applied
Environmental Microbiology. 561 (7):2583-2588.
Shields, M.S., M.J. Reagin, R.R. Gerger, R. Campbell, and C.
Somervill. 1995. "TOM, a New Aromatic Degradative Plasmid
from Burkholderia (Pseudomonas) cepacia G4." Applied
Environmental Microbiology. 61 (4): 1352-1356.
Shirazi, MA, M.L. Robideaux, L.A. Kapustka, J.J. Wagner, and M.C.
Reporter. 1994. "Cell Growth in Plant Cultures: An Interpretation
of the Influence of Initial Weight in Cadmium and Copper Toxicity
Tests." Archives of Environmental Contamination. 27:331-
337.
Shuey, D.L, A.R. Buckalew, T.S. Wilke, J.M. Rogers, and B.A.
Abbott. 1994. "Early events following maternal exposure to
5-fluorouracil lead to dysmorphology in cultured embryonic
tissues." Teratology. 50:379-386.
Shy, C.M., D. Degnan, D.L. Fox, S. Mukerjee, M.J. Hazucha, B.A.
Boehlecke, D. Rothenbacher, P.M. Briggs, R.B. Devlin, D.D.
Wallace, R.K. Stevens, and P.A. Bromberg. 1995. "Do waste
incinerators induce adverse respiratory effects? An air quality and
epidemiological study of six communities." Environmental
Health Perspectives. !03(7-8):7l4-724.
Sigleo, A.C., and P.J. Neale. 1995. "Phytoplankton Pigment Profile at
the Wedell-Scotia Confluence During the 1993 Austral Spring."
Antarctic Journal of the United States. 29(5): 147-148.
Sikorski, R.J., A.C. Sigleo, and P.J. Neale. 1995. "Spectral
Measurements of Ultraviolet and Visible Solar Irradiance at the
Wed dell-Scotia Confluence During 1993 Austral Spring."
Antarctic Journal of the United States. 29(5):270-272.
Silver, W.L. Sandra Brown, A.E. Lugo. 1996. "A framework for
understanding the function of biodiversity in tropical forests and its
application to ecosystem rehabilitation." Conservation Biology.
10(1): 17-24.
Simmons, J.E. (Ed.). "Chemical Mixtures and Quantitative Risk
Assessment." Toxicology. Volume 105. MS-95-192.
Simmons, J.E., A. McDonald, J.C. Seely, and Y. Sey. 1995.
"Potentiation of Carbon Tetrachloride Hepatotoxicity by Inhaled
Methanoi: Time-Course of Injury and Recovery." Journal of
Toxicology and Environmental Health. 46:101 -1 14.
Simmons, J.E., E.W. Van Stee, R.A. Sloane, M.P. Moorman, and K.D.
Brunnemann. January, 1995. "Endogenous Formation of N-
Nitrosomorpholine in Mice from I5NO2 by Inhalation and
Morpholine by Gavage." Carcinogenesis. !6(l):89-92.
Simmons,J.E., R.S.H.Yang, and E. Berman. May, 1995. "Evaluation
of the Nephrotoxicity of Complex Mixtures Containing Organics
and Metals: Advantages and Disadvantages of the Use of
Real-World Complex Mixtures." Environmental Health
Perspectives. I03(I):67-7I.
156
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Simmons, J.E., R.S.H. Yang, D.J. Svendsgaard, M.B. Thompson, J.C.
Seely, and A. McDonald. November, 1994. "Toxicology Studies of
a Chemical Mixtures of 25 Groundwater Contaminants: Hepatic
and Renal Assessment, Response to Carbon Tetrachloride
Challenge and Influence of Treatment- induced Water
Restriction." Journal of Toxicology and Environmental Health.
43:305-325.
Sinokrot, B.A., H.G. Stefan, J.H. McCormick, andJ.G. Eaton. 1995.
"Modeling of climate change effects on stream temperature and
fish habitats betow dams and near groundwater imputs." Climatic
Change. 30:181-200.
Slott, V.L, S.C. Jeffay, J.D. Suarez, R.R. Barbee, and S.D. Perreault.
November-December, 1995. "Synchronous assessment of sperm
motility and fertilizing ability in the hamster following treatment
with alpha-chlorhydrin." Journal of Andrology. !6(6):523-535.
Smialowicz, R.J., W.C. Williams, and M.M. Riddle. 1996.
"Comparison of the T Cell-Independent Antibody Response of
Mice and Rats Exposed to 2,3,7,8-Tetrachloroibenzo-p- Dioxin."
Fundamental and Applied Toxicology. MS-95-274. In press.
Smith, J.C., P.V. Allen, M.D. Turner, B.M. Most, H.L Fisher, and LL
Hall. October, 1994. "The Kinetics of Intravenously Administered
Methyl Mercury in Man." Toxicology and Applied
Pharmacology. !28(2):25l-256.
Snyder, R., et al. 1995. "In Vivo Administration of Dichloroacetic Acid
Suppresses Spontaneous Apoptosis in Munne Hepatocytes."
Cancer Research. 55:3702-3705.
Solomon, A.M., N.H. Ravindranath, R.B. Stewart, M. Weber, and S.
Nilsson. 1995. "Wood production under changing climate and land
use." Intergovernmental Panel on Climate Change (IPCC)
Working Group II Assessment. Cambridge University Press.
Chapter 15.
Solomon, Allen M. 1995. "Potential responses of global forest
growing stocks to interrelated effects of future climate, land use
and wood harvesting." Commonwealth Forestry Review.
Oxford UK.
Solomon, Allen M. 1996. "Maximum natural migration rates of tree
species: Global terrestrial carbon cycle implications." Biotic
Response to Rapid Environmental Change of the Past,
Present and Future. Ed. Bryan Huntley et al. Sprmger-Verlag.
Solomon, Allen M., Andrew P. Kirilenko. 1996. "Implications for
terrestrial carbon stocks of delayed tree species immigration under
changed climate." Climate Change. Accepted.
Stay, F.S., and A.W. Jarvinen. 1995. "Use of microcosm and fish
toxicity data to select mesocosm treatment concentrations."
Archives of Environmental Contamination and Toxicology.
28:451-458.
Stefan, H.G., M. Hondzo. J.G. Eaton, and J.H. McCormick. 1995.
"Predicted effects of global climate change on fishes in Minnesota
lakes." Canadian Special Publication of Fish and Aquatic
Science. 121:57-72.
Stefan, H.G., M. Hondzo, J.G. Eaton, and J.H. McCormick. 1995.
"Validation of a fish habitat model for lakes." Ecological
Modeling. 82:211-224.
Stefan, H.G., X. Fang, J.G. Eaton, and J.H. McCormick. 1995.
"Simulation of dissolved oxygen profiles in a transparent, dimictic
lake." Limnology and Oceanography. 40( I): 105-1 18.
Stehman, S. V. 1995. "Thematic map accuracy assessment from the
perspective of finite population sampling." International Journal
of Remote Sensing. 16(3):589-593.
Stemberger, Richard S., Alan T. Herlihy, Dan L Kugler, Steven G.
Paulsen. 1996. "Climatic forcing on zooplankton richness in lakes
of the Northeastern United States." Special Issue of Limnology
and Oceanography.
Stevens, D. L., Jr. 1994. "Implementation of a National
Environmental Monitoring Program." Journal of Environmental
Management. 42:1 -29.
Stotzky, G., M.W. Broder, J.D. Doyle, and R.A. James. 1993.
"Selected methods for the detection and assessment of ecological
effects resulting from the release of genetically engineered
microorganisms to the terrestrial environment." Advances in
Applied Microbiology. 38:1-99.
Strobel, C.J., and R.M. Valente. September, 1995. Quality
Assurance Report EMAP-Virginian Province 1990-1993. U.S.
Environmental Protection Agency, National Health and
Environmental Effects Research Laboratory-Atlantic Ecology
Division, 27Tarzwell Drive, Narragansett, Rl. EPA/620/R-95/007.
Strobel, C.J., D.J. Klemm, L.B. Lobring, j.W. Eichelberger, A. Alford-
Stevens, B.B. Potter, R.F. Thomas, J.M. Lazorchak, G.B. Collins,
and R.L. Graves (Ed). August, 1995. Environmental Monitoring
and Assessment Program (EMAP) Laboratory Methods
Manual-estuaries-volume I-biological and Physical Analyses.
Office of Research and Development, U.S. Environmental
Protection Agency, Narragansett, Rl 02882. EPA/620/R-95/008.
Strobel, C.J., H.W. Buffum, S.J. Benyi, E.A. Petrocelli, D.R. Reifsteck,
and D.J. Keith. June 1995. Statistical Summary, EMAP-
Estuaries Virginian Province-1990 to 1993. U.S.
Environmental Protection Agency, National Health and
Environmental Effect Research Laboratory-Atlantic Ecology
Division, 27 Tarzwell Drive, Narragansett, Rl 02882. EPA/620/R-
94/026.
Styblo, M., and D.J. Thomas. February, 1995. "In Vitro Inhibition of
Glutathione Reductase By Arsenotriglutathione." Biochemical
Pharmacology. 49(7):97l-977.
ADVANCING KNOWLEDGE FOR A PURPOSE
157
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Styblo, M, H. Yamauchi, and D.j. Thomas. November, 1995.
"Comparative In Vitro Methylation of Trivalent and Pentavalent
Arsenicals." Toxicology and Applied Pharmacology.
135:172-178.
Styblo, M., M. Delnomdedieu, and D.J. Thomas. 1995. "Biological
Mechanisms and Toxicological Consequences of the Methylation
of Arsenic."Handbook of Experimental Pharmacology. Ed.
R.A. Goyer and M.G. Cherian. Springer-Verlag, New York, NY.
18:407-433.
Styblo, M., M. Delnomdedieu, and D.J. Thomas. January, 1996.
"Mono- and Dimethylation of Arsenic in Rat Liver Cytosol In
Vitro." Chemico-Biological Interactions. 99:147-164.
Styblo, M., M. Delnomdedieu, M.F. Hughes, and D.J. Thomas. 1995.
"Identification of methylated metabolites of inorganic arsenic by
thin-layer chromatography." Journal of Chromatography.
6.668:21-29.
Styblo, M., M.F. Hughes, and D.J. Thomas. 1996. "Liberation and
Analysis of Protein-Bound Arsenicals." Journal of
Chromatography. B.677:161-166.
Summers, J.K., J.F. Paul, and A. Robertson. 1995. "Monitoring the
Estuaries of the United States." Toxicology and Environmental
Chemistry. 49:93-108.
Sun, K., G.F. Krause, F.L Mayer, M.R. Ellersieck, and A.P. Basu.
1995. "Estimation of Acute Toxicity by Fitting a Dose-Time-
Response Surface." Risk Analysis. 15(2):247-252.
Sun, K., G.F. Krause, F.L. Mayer, M.R. Ellersieck, and A.P. Basu.
1995. "Predicting Chronic Lethality of Chemicals to Fishes from
Acute Toxicity Test Data: Theory of Accelerated Life Testing."
Environmental Toxicology and Chemistry. 14:1745-1752.
Swartz, R.C., D.W. Schults, R.J. Ozretich, j.O. Lamberson, F.A. Cole,
T.H. DeWitt, M.S. Redmond, and S.P. Ferraro. 1995. "EPAH: A
model to predict the toxicity of polynuclear aromatic hydrocarbon
mixtures in field-collected sediments." Environmental
Toxicology and Chemistry. 14( I I): 1977-1987.
Tanner, D.K., and M.F. Moffet. 1995. "Effects of diflubenzuron on
the reproductive success of the bluegill sunfish, Lepom/s
marcmchirus." Environmental Toxicology and Chemistry.
14(8): 1345-1 355.
Tanner, D.K., and M.L Knuth. 1995. "Effects of azinphos-methyl on
the reproductive success of bluegill sunfish Lepomis macrochirus."
Ecotoxicology and Environmental Safety. 32:184-193.
Taylor, D.S., W.P. Davis, and B.J. Turner. 1995. "Rivulus
marmoratus: Ecology of Distributional Patterns in Florida and the
Central Indian River Lagoon." Bulletin of Marine Science.
57(l):202-207.
Taylor, George E. Jr., Dale W. Johnson, and Chris P. Andersen. 1994.
"Air pollution and forest ecosystems: A regional to global
perspective." Ecological Applications. 4(4):662-689.
Taylor, M., R. Setzer, and D. DeMarini. 1995. "Examination of the
Additivity Assumption using the Spiral and Standard Salmonella
Assays to Evaluate Binary Combinations of Mutagens." Mutation
Research. 335.1-14.
Tepper.J.S., M.C.Jackson, J.K. McGee, D.L Costa, andJ.A. Graham.
April, 1995. "Estimation of Respiratory Irritancy From Inhaled
Methyl Tertiary Butyl Ether in Mice." Inhalation Toxicology.
61:563-569.
Tepper, J.S., V.C. Moser, D.L. Costa, M.A. Mason, N. Roache, Z.
Guo, and R.S. Dyer. February, 1995. "Toxicological and Chemical
Evaluation of Emissions from Carpet Samples." American
Industrial Hygiene Association Journal. 56:158-170.
Thomas, D.J., and R.A. Goyer. 1995. "Effects of arsenic, lead and
cadmium on the cardiovascular System."in Metal Toxicology, (R.A.
Goyer, C.D. Klaassen and M.A. Waalkes, eds.), Academic Press.
pp 265-285.
Thursby, G.B., and R.L. Steele. 1995. "Sexual Reproduction Tests
WitrMarine Seaweeds (Macroalgae)." Fundamentals of Aquatic
Toxicology, Second Edition, Effects, Environmental Fate,
and Risk Assessment. Ed. G.M. Rand. Taylor and Francis
Publishers, USA. Chapter 5, 171 -188.
Tilson, H.A. 1995. "The Concern for Developmental
Neurotoxicology: Is It Justified and What Is Being Done About It?"
Environmental Health Perspectives. 103:147-151.
Tilson, H.A., R.C. MacPhail, and K.M. Crofton. 1995. "Defining
Neurotoxicity in a Decision-Making Context." Neurotoxicology.
16:363-376.
Tingey, D.T., W.E. Hogsett, K.D. Rodecap, E.H. Lee, and T.J. Moser.
1994. "The Impact of O3 on Leaf Construction Cost and Carbon
Isotope Discrimination." ESSENER OKOLGISCHEN
SCHRIFTEN Ed. W. Kuttler and M. Jochinsen. Verlag Wolf Grav
von Westart, Magdeburg. 195-206.
Tingey, David T., Bruce McVeety, Ron Waschmann, Mark Johnson,
Donald L. Phillips, Paul T. Rygiewicz, and Dave Olszyk. 1995. "A
versatile sun-lit controlled-environment facility for studying plant
and soil processes." Journal of Environmental Quality. 25:614-
625.
Turk, J.T., D.H. Campbell, and N.E. Spahr. 1993. "Use of Chemistry
and Stable Sulfur Isotopes to Determine Sources of Trends in
Sulfate of Colorado Lakes." Water, Air, and Soil Pollution.
67:415-431.
Turner, David P., Greg Koerper, Mark Harmon, and Jeffrey J. Lee.
1995. "A carbon budget for the conterminous United States."
Ecological Applications. 5(2):42l-436.
158
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Turner, David P., Greg Koerper, Mark Harmon, and Jeffrey]. Lee.
1995. "Carbon sequestration by forests of the United States:
Current status and projections to the year 2040." Tellus.
476:232-239.
Turner, R.E., E.M. Swenson, and J.K. Summers. 1995. "Coastal
Wetlands Indicator Study: EMAP-Estuaries Louisianian Province -
I99I."EPA/620/R-9S/005.
Ubeda, A., et al. 1995. "Melatonin Enchances Junctional Transfer in
Normal C3H/IOTI/2 Cells." Cancer Letters. 91:241-245.
Vaishnav, D.D., and R.L. Anderson. 1995. "Uptake and loss of Bacillus
thunngiensis var.israelensis by Daphnia magna in laboratory
exposure." Environmental Toxicology and Chemistry.
!4(5):763-766.
van Birgelen, APJM, M.J. DeVito, J.M. Akins, J.J. Diliberto, and LS.
Birnbaum. 1996. "Relative Potencies Derived from Hepatic
Pophyrin Accumulation Following Subchronic Exposure to
Polychlorinated Dibenzo-p-dioxins, Dibenzofurans, or Biphenyls
in Female B6C3FI Mice." Toxicology and Applied
Pharmacology. 138:98-109.
van der Valk, A.G., L Squires, and C.H. Welling. 1994. "Assessing the
impacts of an increase in water level on wetland vegetation."
Ecological Applications. 4(3):525-354.
Vassiliev, I.R., O. Prasil, K.D. Wyman, Z. Kolber, A.K. Hanson, J.E.
Prentice, and P.G. Falkowski. 1994. "Inhibition of PS II
Photochemistry by PAR and UV Radiation in Natural
Phytoplankton Communities." Photosynthesis Research. 42:51 -
64.
Veith, G.D., O.G. Mekenyan, G.T. Ankley, and D.J. Call. 1995. "A
QSAR analysis of substituent effects on the photoinduced acute
toxicity of PAHs." Chemosphere. 30:2129-2142.
Veith, G.D., O.G. Mekenyan, G.T. Ankley, and D.J. Call. 1995. "A
QSAR evaluation of alph-terthienyl phototoxicity."
Environmental Science and Technology. 29:1267-1272.
Velleux, M., D. Endicott, J. Steuer, S.Jaeger, and D. Patterson. 1995.
"Long-term simulation of PCB export from the Fox River to Green
Bay." Journal of Great Lakes Research. 2l(3):359-372.
Vender, R.L., D.H. Horstman, and S. Mangione. 1994. "Red blood
cell antioxidants in human volunteers exposed to ozone." Journal
of Toxicology and Industrial Health. 1-10:53-58.
Verbrugge, D.A., J.P. Geisy, M.A. Mora, L.L. Williams, R. Rossmann,
R.A. Moll, and M. Tuchman. 1995. "Concentrations of dissolved
and particulate polychlorinated biphenyls in water from the
Saginaw River, Michigan." Journal of Great Lakes Research.
2l(2):2l9-233.
Vermeulen, H.L, R. Sangaiah, LM. Ball, and A. Gold. 1995.
"Synthesis of Mixed Halogenated Trihalomethanes Labeled With
Stable Isotopes." Journal of Labeled Compounds. XX-95-003.
Veronesi, B., D.M. Sailstad, D.L Doerfler, and M.J. Selgrade. 1995.
"A Role for Neuropeptides in the Early Symptoms of
Chemically-Induced Skin Irritation." Toxicology and Applied
Pharmacology. 135:258-267.
Veronesi, B., D.M. Sailstad, D.L. Doerfler, and M.J. Selgrade.
November 1995. Neuropeptide I Modulation of Chemically
Induced Skin Irritation." Toxicology and Applied
Pharmacology. 135:258-267.
Vose, James M., Katherine J. Elliott, Dale W. Johnson, Roger F.
Walker, Mark G. Johnson, and David T. Tingey. 1995. "Effects of
elevated CO2 and N fertilization on soil respiration from
ponderosa pine (Pinus ponderosa) in open-top chambers."
Canadian Journal of Forest Research. 25:1243-1251.
Walker, MX., P.M. Cook, A.R. Batterman, and B.C. Butterworth.
1994. "Translocation of 2,3,7,8-TCDD from adult female lake
trout to oocytes: Effects on early lifestage development and sac fry
survival." Canadian Journal of Fisheries and Aquatic Science.
51:1410-1419.
Waller, C.L, and J.D. McKinney. 1995. "3D-QSAR of Dioxin-like
Compounds. II. Model Validation and Ah Receptor
Characterization." Chemical Research in Toxicology. 8:847-
858.
Waller, C.L., B.W. Juma, LE. Gray, and W.R. Kelce. 1996. "Three
Dimensional Quantitative Structure Activity Relationships for
Androgen Receptor Ligans." Toxicology and Applied
Pharmacology. 137:219-227.
Waller, C.L, D.L. Minor, and J.D. McKinney. 1995. "Using Three-
Dimensional Quantitative Structure-Activity Relationships to
Examine Estrogen Receptor Binding Affinities of Polychlorinated
Hydroxybiphenyls." Environmental Health Perspectives.
103:702-707.
Wassmann, R., H.U. Neue, R.S. Lantin, J.B. Aduna, M.C.R. Alberto,
M.J. Andals, M.J. Tan, H.A.C. Denier van der Gon, H. Hoffmann,
H. Papen, H. Rennenberg, and W. Seller. 1994. "Temporal
Patterns of Methane Emissions from Wetland Rice Fields Treated
by Different Modes of N Application." Journal of Geophysical
Research. 99(D8) 16:457-462.
Watanabe, T., et al. 1995. "Mutagenicity of nitrodibenzopyranones
in the Salmonella plate-incorporation and microsuspension assays."
Mutation Research.
Watanabe, T., M.J. Kohan, D. Walsh, LM. Ball, D.M. Marini, and J.
Lewtas. 1995. "Mutagenicity of nitrodibenzopyranones in the
Salmonella plate-incorporation and microsuspension assays."
Mutation Research. 345:1 -9.
ADVANCING KNOWLEDGE FOR A PURPOSE
159
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Watkinson, W.P., J.W. Highfill, R. Slade, and G.E. Hatch. 1995.
"Acute Effects of Ozone on Body Temperature and Biochemical
Indices of Toxicity in the Unanesthetized Mouse: Potential
Explanation for Observed Strain Differences." Journal of Applied
Physiology. MS-95-145.
Watkinson, W.P., M.J. Wiester, and J.W. Highfill. March, 1995.
"Ozone Toxicity in the Rat. I. Effect of Changes in Ambient
Temperature on Extrapulmonary Physiological Parameters."
Journal of Applied Physiology. 78(3): 1108-1120.
Watts, R., J. Lewtas, R. Stevens, T. Hartlage, and J. Pinto. 1994.
"Czech-U.S. EPA Health Study: Assessment of personal and
ambient air exposures to PAH and organic mutagens in the Teplice
district of Northern Bohemia." International Journal of
Environmental and Analytical Chemistry. 56:271-287.
Webster, K.E., P.L. Brezonik, and B.J. Holdhusen. 1993. "Temporal
Trends in Low Alkalinity Lakes in Minnesota, Wisconsin, and
Michigan (1983-1989): The Influence of Climate and Deposition
Factors." Water, Air, and Soil Pollution. 67:397-414.
Weis, J.S., and P. Weis. 1995. "Effects of Chromated Copper
Arsenate (CCA) Pressure-treated Wood in the Aquatic
Environment." Ambiology. 24(5):269-274.
Weis, P., J.S. Weis, J. Couch, C. Daniels, and T. Chen. 1995.
"Pathological and Genotoxicological Observations in Oysters
(Crassostrea virginica) Living on Chromated Copper Arsenate
(CCA-)Treated Wood." Marine Environmental Research.
39(l/4):275-278.
Wells, J.D., J.R. Fuxa, and G. Henderson. 1995. "Virulence of Four
Fungal Pathogens to Coptotermes formosanus (Isoptera:
Rhinotermitidae)." Journal of Entomological Science.
30(2):208-2I5.
Whiteman, F.W., G.T. Ankley, D.J. Call, and P.M. Cook. 1996.
"Evaluation of interstitial water as a route of exposure for
ammonia in sediment tests with benthic macroinvertebrates."
Environmental Toxicology and Chemistry. 15(5):794-80l.
Wiester, M.J., J.S. Tepper, D.L. Doerfler, and D.L. Costa. January,
1995. "Ozone Adaptation in Rats after Chronic Exposure to a
Simulated Urban Profile of Ozone." Fundamental and Applied
Toxicology. 24:42-51.
Wiester, M.J., J.S. Tepper, D.W. Winsett, K.M. Crissman, J.H.
Richards, and D.L. Costa. 1995. "Adaptation to Ozone in Rats and
its Association With Ascorbic Acid in the Lung." Fundamental
and Applied Toxicology. MS-95-098.
Wiester, M.J., M.A. Stevens, M.G. Menache, J.L McKee, and T.R.
Gerrity. January, 1996. "Ozone Uptake in Healthy Adult Males
During Quiet Breathing." Fundamental and Applied
Toxicology. 29:102-109.
Wigington, P.J., Jr., J.P. Baker, D.H. Landers, S.G. Leibowitz, S.G.
Paulsen, SA Peterson, and N.E. Detenbeck. 1995. "An overview
of selected U.S. Environmental Protection Agency ecological
research in the Prairie Pothole and Pacific Northwest regions."
Symposium proceedings, Watersheds '94: Respect, Rethink
and Restore. November 16-18, 1994. Ashland, OR.
Williams, W.C., M.M. Riddle, C.B. Copeland, D.L Andrews, and R.J.
Smialowicz. June, 1995. "Immunological Effects of
2-Methyoxyethanol Administered Dermally or Orally to Fischer
344 Rats." Toxicology. 98:215-223..
Williams, W.C., M.M. Riddle, C.B. Copeland, D.L. Andrews, and R.J.
Smialowicz. April, 1995. "Immunological Effects of
2-Methoxyethanol Administered Dermally or Orally to Fischer 344
Rats." Toxicology. 98:215-223.
Wilson, R., A. Cataldo, and C. Andersen. 1995. "Determination of
total nonstructural carbohydrates in tree species by high-
performance anion-exchange chromatography with pulsed
amperometric detection." Canadian Journal of Forest
Research. 25:2022-2028.
Winjum.Jack K., and David K. Lewis. 1993. "Forest management and
the economics of carbon storage: The nonfinancial component."
Climate Research. 3:111-119.
Winjum, Jack K., Robert K. Dixon, and Paul E. Schroeder. 1992.
"Estimating the global potential of forest and agroforest
management practices to sequester Carbon." Journal of World
Forest Resource Management. 64:213-237.
Winjum, Jack K., Robert K. Dixon, and Paul E. Schroeder. 1993.
"Forest management and carbon storage: an analysis of 12 key
forest nations." Water, Air, and Soil Pollution. 70:239-257.
Winkler, J., K.N. Timmis, and R.A. Snyder. 1995. "Tracking the
Response of Burkholderia cepacia G4 5223-PRI in Aquifer
Microcosms." Applied Environmental Microbiology. 61 (2):448-
455.
Winstead, J.T. 1995. "Digestive Tubule Atrophy in Eastern Oysters,
Crassostrea virginica (Gmelin 1791), Exposed to Salinity and
Starvation Stress." Journal of Shellfish Research. 14( I): 105-11 I.
Wolff, Jerry O., W. Daniel Edge, and Ray Bentley. 1995.
"Reproductive and behavioral biology of the gray-tailed vole."
Journal of Mammalogy. 75:873-879.
Wong C., W.R. Kelce, M. Sar, and E.M. Wilson. 1995. "Androgen
receptor antagonist versus agonist activities of the fungicide
vinclozolin relative to hydroxyflutamide." The Journal of
Biological Chemistry. 270(34): 19998-20003.
Woodall, G.J., W. Dauterman, and D. DeMarini. 1995. "Effect of
dietary casein levels on the ability of rat liver S9s to activate
promutagens in the spiral Salmonella mutagenicity assay."
Mutation Research.
160
ADVANCING KNOWLEDGE FOR A PURPOSE
-------
NHEERL FY95 ANNUAL REPORT
REFERENCES
Yan, Keying, Dickman, Martin B., jin-Rong Xu, and John F. Leslie.
1993. "Sensitivity of field strains of Gibberella fujikuroi (Fusarium
section L/seo/o) to benomyl and hygromycin B1." Mycologia.
85(3):206-2I3.
Yang, Y.G., M.I. Gilmour, R. Lange, G.R. Burleson, and M.J.K.
Selgrade. February, 1995. "Effect of Acute Exposure to Phosgene
on Pulmonary Host Defenses and Resistance to Infection."
Inhalation Toxicology. 7:393-404.
Yevich, P.P., and C.A. Yevich. 1994. "Use of Histopathology in
Biomonitoring Marine Invertebrates." Biomonitoring of Coastal
Waters and Estuaries. Ed. K.J.M. Kramer. CRC Press, Boca
Raton, FL Chapter 8, 179-204.
You, L, et al. 1995. "Tumor Multiplicity, DNA Adducts and K-ras
Mutation Pattern of 5-Methylchrysene in Strain A/J Mouse Lung."
Carcinogenesis. 15(1 I):26I3-26I8.
Yousten, A.A., E.F. Benfield, and F.J. Genthner. 1995. "Bacillus
sphaericus Mosquito Pathogens in the Aquatic Environment."
Memorial Institute Oswaldo Cruz Rio. 90(1): 125-129.
Zabel, E.W., M.W. Hornung, P.M. Cook, and R.E. Peterson. 1994.
"Toxic equivalency factors of polychlorinated dibenzo-p-dioxin,
dibenzofuran and biphenyl congeners based on early lifestage
mortality in rainbow trout Oncorhynchus mykiss." Aquatic
Toxicology. 31:315-328.
Zabowski, D., M.F. Skinner, P.T. Rygiewicz. 1994. "Timber
Harvesting and Long-term Productivity: Weathering Processes and
Soil Disturbance." Forest Ecology and Management. 66:55-68.
Zaroogian, G., and R.A. Voyer. 1995. "Interactive cytotoxicities of
selected organic and inorganic substances to brown cells of
Mercenaria mercenaria." Cell Biology and Toxicology. 11:26I-
271.
Zaroogian, G., and S. Anderson. 1995. "Comparison of Cadmium,
Nickel and Benzo(a)pyrene Uptake Into Cultured Brown Cells of
the Hard Clam, Mercenaria mercenaria." Comparative
Biochemistry and Physiology. I I I C( I): 109-1 16.
Zelikoff, J.T., and R.J. Smialowicz. "Metal-induced Alterations in
Natural Killer Cell Activity." Toxicology of Metals. Ed. L. Chang.
CRC Press. Second Edition, pp 807-821.
Zhan, D., D. Herreno-Saenz, L. Chie, LS. Von tuungeln, Y. Wu, J.
Lewtas, and P. Fu. 1995. "Separation of "P-labeled 3',5'-
bisphosphate nucleotides of polycyclic aromatic hydrocarbon anti-
diol-epoxides and derivatives." Journal of Chromatography.
710:149-157.
Zhang, Z., T.B. Martonen, and R. Lessman. November, 1994.
"Numerical Simulation of Laryngea! Flow." journal of Mechanical
Engineering. 22:451 -454.
Zucker, R.M., K.H. Elstein, D.L. Shuey, andJ.M. Rogers. 1995. "Flow
cytometric detection of abnormal fetal erythropoiesis: application
to 5-fluorouracil-induced anemia." Teratology. 51:37-44.
Zuelke, K.A., and S.D. Perreault. 1995. "Carbendazim (MBC)
disrupts oocyte spindle function and induces aneuploidy in
hamsters exposed during fertilization (Meiosis II)." Molecular
Reproductive Development. 42:200-209.
ADVANCING KNOWLEDGE FOR A PURPOSE
'U.S. Government Printing Office: 1996—750-001/41043
161
-------
U.S. Environmental Protection Agency
Region 5, Library (PL-12J)
77 West Jackson Boulevard, 12th Floor
Chicago, IL 60604-3590
-------
m
Tl
>
S>
o
o
cb
O
O
w "°9
o M ^5-
~ ».
-j, CD
O c
"• 03
-05'
5- CD
< en
S- w
CD"
C
o
o »
~ CD
03 O
z m c
Q) U 3
cr. < ^f
o =r CD
3 O Q.
=r*l£8
- 2 CD »
O M £ S CD
&§ » 7
go g o
05 J (5 CD
00 - CD a
O 3 6'
ro
to
CD
o
1
CD ^J
e> ^
y- m
s°
W I
=1 rn
„ 3)
3- m
1 detach or
left-hand
°8
3 T3
5
d
CD
3
r—
5
CD
0)
w
5
g:
CD
-5
•g
Please m
1"
a
m
O
OD
W
»<
t
D
CQ
|
3"
CD
CD"
s
CT
- —
Tl
O
s §
i ^g
=! ™ rn r—
9
CO
en
m
------- |