U.S. EPA Office of Research
and Development's Science
To Achieve Results (STAR)
Research in Progress
Vol. 2 Issue 1 Jan. 1998 A product of the National Center for Environmental Research and Quality Assurance
THE ENDOCRINE DISRUPTOR PROBLEM
is not yet known, although conditions in some
locations indicate cause for concern. While
some studies find declines in
the quantity
In recent years there have been reports of
wildlife with reproductive disorders, deformities
and other developmental disorders caused by
environmental chemicals that affected the ani-
mals' endocrine systems. The endocrine system
is a complex of organs, tissues and hormones in
humans and other living things. The system is
responsible for maintaining normal reproduc-
tion, development and other aspects of "ho-
meostasis" (maintaining equilibrium of the
body's chemistry and other condition factors).
Substances that interfere with these processes
are called "endocrine disrupters".
Endocrine disruption problems have been
identified primarily in wildlife and laboratory ani- and quality of
mals exposed to relatively high concentrations sperm production in humans
of some chemicals, most of which are man-made
environmental contaminants, but some of which
occur naturally. These include organochlorine
pesticides and breakdown products, industrial
chemicals such as polychlorinated biphenyls
(PCBs) and organometals, waste chemicals such
over the last four decades, other studies show
no decrease. Reported increased incidences of
human cancers in organs of the reproductive and
hormonal systems (breast, testes, prostate) have
led to speculation that this could be related to
environmental endocrine disruption. And corre-
as dioxins, a few plastics-related chemicals such lational evidence from many areas indicates that
as bisphenol, nonaphenols and phthalates, syn- some populations of birds, fish, reptiles and mam-
thetic hormones and natural plant-derived hor- mals have been harmed by environmental con-
mones. Whether effects are occuring in humans, taminants affecting their endocrine systems.
or whether wildlife frequently incur harm from Some endocrine disrupter research fo-
environmental concentrations of these substances cuses on the ways these chemicals interfere
Because the endocrine system plays a critical role in growth, development and
reproduction, even small disturbances in endocrine function can have profound
and lasting effects.
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Many of the chemicals associ-
ated with endocrine disruption,
such as the pesticide DDT and
the industrial compounds PCBs,
have been banned for U.S.
manufacture and new use for
a number of years. However,
they remain in the U.S. environ-
ment because of residual con-
tamination, or possibly because
of illegal use or disposal, or air,
water or human transport
across international bound-
aries. Another important ques-
tion is the extent to which
chemicals currently in produc-
tion and use may be acting as
endocrine disrupters of wildlife
or humans in the United States.
continued from page 7
with reproduction, including the production of normal germ
cells (eggs and sperm). In addition, it is known that impacts of
endocrine disturbances in humans or animals can be particularly
damaging if exposure occurs during the highly sensitive prena-
tal and early postnatal periods. Small changes in endocrine
status during gestation can have delayed consequences that are
evident much later in adult life or in a subsequent generation.
Consequently, other studies are targeted towards understanding
effects of exposures during pregnancy.
THE NATIONAL ENDOCRINE
DISRUPTORS RESEARCH INITIATIVE
Because of the potential for serious consequences to
humans or wildlife, the United States has joined with other
nations to conduct laboratory and field research of many types
to investigate whether human health is being threatened by
endocrine disrupters in the environment, and whether environ-
mental harm to wildlife is more widespread than had previously
been understood. A coordinated research effort is being led in
the U.S. by the National Science and Technology Council
(NSTC) Committee on Environment and Natural Resources.
The NSTC is a cabinet-level council chaired by the President
that serves as the principal means for coordinating science and
technology issues across the Federal government.
This report summarizes academic research into endocrine
disrupters supported by the U.S. Environmental Protection
Agency (EPA). This work is supported through EPA's principal
external scientific research program, the Science to Achieve
Results (STAR) program. Other federal agencies also support
academic research on endocrine disrupters. In addition, EPA,
General Information: The Environmental Protection Agency's STAR Research Program
Grants described in this report are part of EPA's Science to Achieve Results (STAR) program, a major research
initiative designed to improve the quality of scientific information available to support environmental decision
making. The STAR program is managed by EPA's National Center for Environmental Research and Quality Assur-
ance in the Office of Research and Development (ORD). The program funds approximately 200 new grants every
year, with the typical grant lasting three years. Funding levels vary from $50,000 to over $500,000 per year, with
FY1997 funding level at about $80 million for grants to individual principal investigators or groups of investigators.
Additional STAR funds are provided for a number of Research Centers specializing in scientific areas of particular
concern to EPA, and for a fellowship program supporting graduate students conducting environmental research.
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the National Institute of Environmental Health Sciences (NIEHS),
the Department of the Interior and other agencies are conduct-
ing research addressing the national agenda in their own labora-
tories. Information on the overall body of research coordinated
through the NSTC Endocrine Disrupters Research Intiative
(EDRI) can be found at EDRI and EPA sites on the World Wide
Web, or by mail, at websites and addresses listed at the end of
this report.
Research Areas Particularly Supported by EPA
••••••••••••••••••••••••••••••
EPA supports endocrine disruptor research primarily in the following areas:
0 Methods to monitor and characterize exposure of humans or wildlife to
endocrine disruptors;
0 Models to estimate exposure to endocrine disruptors from different
sources and multiple pathways;
0 Development of biomarkers of endocrine disruptor exposure and effects;
0 Development and validation of test systems to screen for chemicals with
specific mechanisms of action that affect different endocrine pathways;
particularly methods that are applicable to many types of living organ-
isms;
0 Development of toxicological models describing how particular chemi-
cals act to interfere with endocrine systems, based on species-specific
characteristics, with particular emphasis on models that can extrapolate
effects from one animal species to another, or to humans; and
0 Methods and models that relate effects at subcellular levels to effects in
individual humans or animals, or in human or animal populations.
ENDOCRINE DISRUPTOR RESEARCH
SUPPORTED BY EPA'S "STAR" PROGRAM
Research Concerning Impacts on Humans
One of the few well-documented cases of widespread
human exposure to chemicals that may mimic the female
hormone estrogen, and thus may cause endocrine disruption,
was a 1973 incident in Michigan, in which cattle feed was
contaminated by polybrominated biphenyls (PBBs). After it was
determined that many people had been exposed to meat and
dairy products from contaminated cattle, the Michigan Depart-
ment of Community Health began to gather public health data
on the exposed human population. This included data on
people's blood levels of PBBs
three years after the exposure.
PBBs are of concern because
chemically similar compounds,
such as PCBs, are known to
impair female reproductive
development. A grant from
the EPA STAR program has
been awarded to Emory
University to assess whether
there have been any health
effects in Michigan in exposed
women or their daughters.
Data reviewed will include
reproductive defects or dis-
eases, thyroid dysfunctions,
infertility or other endocrine-
related effects. The findings
concerning any effects in
humans, together with data
on known exposure to a
contaminant, will be invalu-
able in assessing potential
health risks from exposures in
other circumstances.
In an important federal/
academic research partner-
ship, EPA is providing addi-
tional support to investigators
at the University of Missouri
who participate in the Food
and Drug Administration's
program to develop an Estro-
gen Knowledge Base (EKB).
The EKB program incorporates
a wealth of data on observed
health impacts in humans and
animals with information on
theoretical impacts. Theoreti-
cal information is developed
through a statistical modeling
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an
technique called the "Quanti-
tative Structure Activity Rela-
tionships" approach. The
new EPA grant will allow
investigators to expand the
database to better establish
quantitative relationships
among effects in various
animals and in humans. This
will expand the number of
chemicals for which we can
obtain sound estimates of the
likelihood of adverse health
effects. This will help EPA and
the Food and Drug Adminis-
tration more effectively target
their own screening and
testing programs, and those
they require chemical manu-
facturers to conduct.
Research into
Effects on Wildlife
The alligators of Florida's
Lake Apopka have serious
reproductive failures that have
been attributed to endocrine
disrupters. Many of the
alligators are sterile, and
abnormalities such as
underedeveloped penises,
are common. Known endo-
crine disrupters found in the
lake at levels of concern
include the banned pesticides
dieldrin, toxaphene and DDT,
and DDT's breakdown prod-
uct DDE. The University of
Florida has received a STAR
grant to study the condition
of Lake Apopka alligators and
their eggs. Researchers will
investigate mechanisms by
which the chemicals may take
effect, including direct disrup-
tion of sex hormones, devel-
opmental effects before and
after hatching, and the addi-
tional possibility that harm to
immune systems increases
susceptibility to disease. In a
abnormal testes and abnor-
mally high levels of estrogen
related study, Texas Tech
University will compare Lake
Apopka data to the conditions
of crocodiles in lagoons in
Belize, Central America,
some of which are contami-
nated with DDE. A full
analysis will be done of
chemicals present in each
lagoon, and of whether
endocrine disruption is
occuring in the crocodiles.
This study is important in
supporting risk assessment for
the Belize ecosystem, as well
as helping to establish the
relative severity of Lake
Apopka impacts.
Florida's Mote Marine
Laboratory is leading a team
of investigators from Florida
and Oregon in a study of the
causes of infertility in
Bonnethead sharks in the
Tampa Bay area. Female
sharks are frequently retaining
unfertilized rather than fertil-
ized eggs following mating,
either due to abnormal sperm
production in males, or dam-
age to sperm stored in fe-
males. There may be other
impairments as well. Hypoth-
eses include the possibility that
organochlorine pesticides are
the cause. A full range of
mechanisms will be assessed
by evaluating tissues, cells,
immune systems and hormone
levels.
A particularly severe case
of ecosystem contamination
was the manufacturer's release
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of DDT in the 1960s and '70s
to the Southern California
sewer system, which dis-
charges to the sea. The near
extinction of brown pelicans in
the area was widely reported,
and fish and other animals also
experienced reproductive
disorders. Since the release
ended and DDT was banned,
the pelican population has
I I
recovered, but contamination
remains in marine sediments
and fish. The University of
Texas is conducting a labora-
tory study to try to elucidate
possible endocrine disruption
mechanisms in fish exposed to
endocrine disrupters that
mimic combinations of DDTs
and DDEs found in California
fish tissues.The study will
determine mechanisms of
impairment to gonads, other
organs and embryos. Fish
used will be a well-established
laboratory test species, a
croaker, not native to Califor-
nia. However, investigators feel
any findings will be sufficiently
generalizable that they would
be relevant to risk assessments
for the California fishes, as well
as to species in other loca-
tions.
Many birds, including all
songbirds, are "altricial"
species whose chicks are
incompletely developed at
hatching, requiring weeks for
full development of brains,
reproductive systems and
other organs. We know that
endocrine disrupters such as
DDT and DDE cause reproduc-
tive damage in some species
such as bald eagles, osprey
and pelicans. These chemi-
cals are "xenoestrogens",
estrogen-like chemicals
found in the environment.
They are also anti andro-
genic, interfering with
hormones involved in male
development and reproduc-
tion. The University of
California at Davis has re-
ceived a STAR grant to study
effects of xenoestrogen expo-
sure on hormonal processes
and development of altricial
chicks.
Research Using
Laboratory Animals
as Models of
Potential Risk to
Humans or Wildlife
The University of Mis-
souri is studying effects of the
pesticide methoxychlor, an
environmental estrogen, on
mice whose characteristics
make them a good model to
assess how endocrine
disrupters act in other animals
and humans. Such mechanis-
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tic animal studies can help in
developing treatments or
interventions to protect
human health. The university
received a grant from NIEHS
for research with a mouse
strain lacking a functional
estrogen receptor gene.
Comparing effects of exposure
in these and normal mice will
reveal whether certain non-
estrogen receptor proteins are
involved in responses to
methoxychlor. The University
has also received an EPA STAR
grant to clone the gene
believed to serve as the meth-
oxychlor receptor. This cloned
gene is needed to fully investi-
gate whether the methoxy-
chlor receptor mechanism
operates in the way hypoth-
esized by these investigators.
ronment. The dioxin TCDD, a
potent endocrine disrupter,
and other dioxins and
dibenzofurans, are waste
products of a number of
industrial processes, including
chlorine-using processes and
waste combustion. The
University of Kansas is study-
ing ovarian disorders and
other effects caused by expos-
ing rats to TCDD, other
dioxins, furans and PCBs.
Preliminary data indicate that
direct ovarian damage, rather
than indirect effects from
influences on organs such as
the pituitary, is one reason
endocrine disrupters impair
female reproduction. In a
study of another aspect of
female reproduction, the
enzymes responsible for
CCL
o,p - DDT
gestation are longer than in
rodents, and thus more like
humans, Colorado State
University is investigating
effects of DDT and the pesti-
cide vinclozolin in male rab-
bits. Sub-cellular changes and
abnormalities in levels of
pituitary and sex hormones
will be among the mecha-
nisms investigated. Another
It is known that impacts of endocrine disturbances
in humans or animals can be particularly damaging if
exposure occurs during the highly sensitive prenatal
A STAR grant to study
PCB effects in rats has been
awarded to Mississippi State
University. Questions to be
asked include: 1) whether
organ dysfunctions are caused
by mechanisms involving
reduced blood or liver levels of
sex steroids; and 2) whether
such effects occur at exposures
that might occur in the envi-
maintaining healthy endome-
trial condition, Vanderbilt
University is using cell cul-
tures, corroborated by mouse
experiments, to evaluate the
hypothesis that TCDD may
interfere with normal regula-
tion of these hormones.
To study impacts in a
mammal whose life span and
study of male reproductive
system impacts uses dogfish
sharks. This species is of
ecological importance in its
own right, and is a model of
possible effects in other
animals or humans. Investiga-
tors at Boston University will
expose male sharks to a
number of xenoestrogens.
Objectives are to understand
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genetic or cellular mechanisms
by which the chemicals act; to
seek molecular markers that
indicate that an animal has
been exposed; and to docu-
ment health impacts such as
sterility or testicular cancer.
Duke University is using
zebrafish embryos for a related
study. Advanced gene scan-
ning techniques will character-
ize the structure and location
of estrogen receptor RNA, to
increase understanding of how
genes act in response to
environmental estrogens.
The University of Cali-
fornia at Davis is assessing
effects of two chemicals, one a
xenoestrogen, and one an
anti-androgen, on males and
females of a fish called
medaka. Potential impacts
include gonad and liver
damage, disturbed mating
behavior, abnormal sperm or
eggs, and low survival of the
young.
One animal study uses a
bird as the model species. The
University of Maryland will
work with Japanese quail to
assess when in their life cycle
susceptibility to endocrine
disruption is the greatest.
Impacts on gonads and other
glands, including the hypo-
thalamus and pituitary, will be
assessed. This species is used
because it is a good laboratory
subject with an exceptionally
well documented reproductive
cycle and physiology. Results
will be relevant to a range of
bird species.
Some endocrine
disrupters are natural sub-
stances. Duke University has
received a grant for work
using laboratory rats to assess
whether some phytoestrogens,
compounds that occur natu-
rally in plants, could poten-
tially have endocrine disrupt-
ing effects at concentrations
that could occur in human
diets. This study will look for
any impacts from soy
phytoestrogens on the rats'
brain or reproductive system
development, mating or
related behaviors such as
adolescent behavior patterns.
Developing Screening
Procedures for Endo-
crine Disruptors
In an effort to develop a
practical screening procedure
for endocrine disrupting
effects in aquatic vertebrates,
the University of Alabama is
leading a project to refine a
mosquitofish test system. A
range of chemicals will be
tested and readily observed
effects on developmental
abnormalities and blood
chemistry will be defined as
screening procedures. North
Carolina State University is
working under a STAR grant to
develop routine testing proce-
dures for potential endocrine
disrupters, using water fleas as
a model for other aquatic
invertebrates.
Find Out More About the STAR Research Program
For further information about the National Endocrine Disruptors
Research Initiative is available at the following Internet websites:
The Endocrine Disrupter Research Initiative website of the NSTC Committee
on the Environment and Natural Resources: www.epa.gov/endocrine/
edrifact.html
EPA's Endocrine Disruptor Screening and Testing Advisory Committee website:
www.epa.gov/opptintr/opptendo/index.htm
General information on EPA's STAR research program is available from
the following sources:
ORD's National Center for Environmental Research and Quality Assurance
(NCERQA): Internet website: http://www.epa.gov/ncerqa
Mailing Address:
Office of Research and Development
National Center for Environmental Research and Quality Assurance
Office of the Director (8701 R)
401 M Street, SW
Washington, DC 20460
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STAR Research Projects Described in this Report
Duke Medical Center, Examina-
tion of the Estrogen Response
Pathways in a New Vertebrate
Model
U. California-Davis, Critical
Stages in Avian Development:
Estrogenic Hazards to Altricial
and Precocial Birds
Mississippi State University,
Biochemical and Reproductive
Effects of Gestational/Lactational
Exposure to PCB's with Respect
to Endogenous Sex Steroids and
the Proestrogen, Methoxychlor
U. California-Davis, An in Vivo
Model for Detection of Repro-
ductive Effects of Endocrine
Disruptors
Duke University, Developmental
Effects of Dietary Soy
Phytoestrogens
Emory University, The Michigan
PBB Cohort 20 Years Later:
Endocrine Disruption?
Boston University, Xenoestrogen
Effects During Premeiotic Stages
of Spermatogenesis: Develop-
ment of an in Vitro Test System
and Molecular Markers of Action
U. Missouri-Columbia,
Methoxychlor and Environmen-
tal Estrogen Receptors in ER-
Minus Mice
1997 STAR Awards
Colorado State University,
Anti-androgenic Pesticides:
Impact on Male Reproduction
Duke University, Developmen-
tal Effects of Dietary Soy
Phytoestrogens
Mote Marine Laboratory, The
Mechanisms and Effects of
Endocrine Disruption on
Infertility in the Bonnethead
Shark on Florida's Gulf Coast
North Carolina State University,
Metabolic Androgenization of
Invertebrates by Endocrine-
Disrupting Chemicals
Texas Tech University,
Exposure and Response of
Morelet's Crocodile (Crocodylus
moreletii) Populations to
Endocrine Disrupting Com-
pounds in Belize, Central
America
U. Alabama - Birmingham, A
Short-Term in Vivo Screening
System for Endocrine Disruptors
Utilizing Mosquito-Fishes
(Gambusia affinis or G.
holbrooki)
U. California - Davis, Environ-
mental Endocrine Disruption in
Avian Wildlife
University of Florida, Endocrine
Disruptors and Host Resistance
in Lake Apopka Alligators
U. Kansas Medical Center,
Endocrine Disruptors: Effects on
the Thyroid
U. Kansas Medical Center,
Models Assessing Direct Effects
of Dioxins and Related Com-
pounds on the Ovary
U.Maryland - College Park,
Critical Stages in Sublethal
Exposure to EDCs in a Quail
Model System
U. Missouri - St. Louis,
Computational Tools for the
Prediction and Classification of
Estrogenic Compounds
U. Texas - Austin, Reproductive
and Endocrine Effects of o,p'-
DDT, an Environmental
Estrogen, and p,p'-DDE, an
Antiandrogen, in Male and
Female Atlantic Croaker during
Critical Periods of their Repro-
ductive Life History Cycles
Vanderbilt University, Dioxin
and Steroid Regulation in an
Endometriosis Model
xvEPA
United States
Environmental Protection Agency
Mail Code 8701R
Washington, D.C. 20460
Offical Business
Penalty for Private Use
$300
EPA/600/F-98/003
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