United States
Environmental Protection
Agency
Office of
Research and Development
Washington, DC 20460
I
February 1998
Volume 2 Number 1
EPA/600/IM-98/001
vvEPA ORD Science Highlights
Replicating Reality: The Growing
Application of Environmental Models
When environmental managers must devise the most
effective way to reduce the levels of an air pollutant, they
need to understand what happens to it in the atmosphere.
When cleanup specialists discover chemical contamination
of groundwater beneath a Superfund site, they need to know
the direction in which chemicals are likely to flow and how
quickly. What do these problems have in common? They
can be solved, in part, through the use of models. The Office
of Research and Development is at the forefront of creating
such models to understand and solve scientific questions
about human health and the environment.
A model is a simplified numerical representation of
some aspect of the world around us. In its most basic form, a
model may describe a single kind of event, such as the ac-
celeration of an object due to gravity. By using principles
from meteorology, physics, chemistry, and other fields, a
model can be expanded to simulate more complicated phe-
nomena. The escalating power and sophistication of com-
puters are allowing an increasingly realistic depiction of the
environment.
A successful model offers advantages that may not be
achievable by any other approach to a problem. It can reveal
insights about the functioning of a complicated system, such
as the atmosphere or the human circulatory system, that
would not have been recognized by studying the individual
components. It allows the user to make predictions — in
effect, to conduct experiments — that may not be feasible or
acceptable to do in the real world.
Over the past decade the Office of Research and De-
velopment has developed and provided training for more than
a dozen environmental models. Many are in use by govern-
ment agencies and other organizations. ORD is also helping
to develop consistent practices for validating and peer-re-
viewing models across the Agency.
A few of the models that ORD has helped to design
include the following:
• AgDRIFT, one of ORD's newest models, is being
evaluated for use by regulators from both the United
States and Canada. Developed in cooperation with the
U.S. Department of Agriculture and a consortium of
agricultural chemical companies, the model can be used
to assess pesticide drift from spray operations.
Three-dimensional depiction of plumes of ozone (blue), sulfur
dioxide (green), and sulfate (yellow) using EPA's Models-3.
• Models-3, under development for EPA's Office of Air
and Radiation and scheduled for public release later this
year, simulates the long-range transport and interactions
of air pollutants like ozone, nitrogen oxides, and
particulate matter.
• SWMM (the Storm Water Management Model) is used
by EPA's Office of Water to simulate the runoff of
pollutants from urban areas.
• EPANET simulates the flow of drinking water within
networks of distribution pipes, allowing water managers
to improve the effectiveness of their facilities.
• HSSM (the Hydrocarbon Spill Screening Model) is
designed to assess how certain insoluble fluids migrate
through soil and the groundwater zone. This model is
used in assessing Superfund sites.
Many models are publicly available from EPA, some of
which can be accessed at ORD's Center for Exposure
Assessment Modeling website, www.epa.gov/CEAM.
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One of the most exciting developments underway is
the integration of models so that they can simultaneously
consider multiple stressors and media (such as air and
water). Some day, ORD may be able to create comprehen-
sive risk models that combine information about emis-
sions, environmental fate and transport, exposure, and
effects to present a total risk picture for humans and
ecological resources.
CONTACTS: Robert Carsel, (706) 355-8300 and Francis
Sehiermeier, (919) 541-4542
Sharing America's Technologies for
Preventing Waterborne Disease
Many communities in developing countries suffer
from high rates of illness and death from waterborne
disease because they lack basic drinking water treatment
facilities. Scientists and engineers at ORD's National Risk
Management Research Laboratory are now helping to
remedy this problem in Ecuador, China, and Mexico,
under the U.S. Technology for International Environmental
Solutions (U.S. TIES) program.
The federal government initiated U.S. TIES in 1994
to match pressing environmental needs in other countries
with U.S. suppliers of proven, cost-effective technologies.
In Ecuador, for example, ORD experts have entered into a
partnership with the U.S. Agency for International Devel-
opment, Ecuadorian health officials, and local utility
operators to demonstrate low-cost drinking water tech-
nologies. ORD's "drinking-water ambassadors" have
helped install small disinfection units and small-scale
treatment plants in the communities of Monteoscuro, La
America, and Manta.
To analyze the cost-effectiveness of the treatment,
before-and-after waterborne disease data are being col-
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package plant is easily portable for delivery to rural sites.
lected by EPA from health clinic records at each site.
Health statistics will be monitored for another year of
operation. This program has great potential to benefit both
the local communities in developing countries and U.S.
manufacturers of low-cost treatment technologies.
CONTACT: BenLykins, (513) 569-7460
EPA Releases Mercury
Report to Congress
In December of 1997, EPA released an eight-
volume report to Congress, mandated by the Clean Air
Act, that evaluates the impacts of air emissions of mercury
on human health and the environment. The report esti-
mates that about 159 tons of this heavy metal were emitted
into the air in 1995 from all U.S. industrial sources. Major
emission sources are electric utilities, municipal waste
combustors, commercial and industrial boilers, medical
waste incinerators, and chlor-alkali plants.
Mercury is of particular concern because it persists
and accumulates in the environment and can damage the
nervous system of humans and wildlife, especially during
development. Atmospheric emissions can end up in
waterways as a result of rainfall or runoff and then build
up as methylmercury in the tissues of predatory fish that
feed on contaminated smaller fish. The greatest exposure
of humans to methylmercury is through consumption of
contaminated fish. The report noted that, given the mer-
cury levels generally found in commercial fish, it is safe to
eat fish and other seafood in moderation from grocery
stores and restaurants. The individuals who are expected
to be among the most highly exposed to methylmercury
are those who regularly eat large amounts of fish from
mercury-polluted waters or fish from the top of the marine
food web. Birds and mammals are also exposed to methyl-
mercury through the consumption of fish.
The Mercury Report was a multi-year effort involv-
ing scientists across the Agency, particularly in ORD and
the Office of Air and Radiation. ORD contributed to a
series of innovative models used in the report that examine
atmospheric and water transport, bioaccumulation, expo-
sure, and adverse health effects of mercury. The report
was developed with substantial input from, the public and
other government agencies, peer-reviewed by panels of
outside EPA scientific experts, and reviewed and approved
by EPA's Science Advisory Board. The complete Mercury
Report to Congress is accessible on the Internet at
http://www. epa. gov/airlinks.
CONTACT: Kathryn Mahaffey, (513) 569-7957
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Vitamin Deficiencies May Worsen
Effects of Air Pollution
Strong oxidizing chemicals can react with living
tissues, causing damage. Because antioxidant vitamins C,
E, and beta-carotene appear to reduce these effects and
protect against a variety of aging-related diseases, they are
receiving increased attention from researchers. New
studies by ORD investigators have revealed that even
modest deficiencies of vitamin C make guinea pigs more
sensitive to oxidant air pollutants such as ozone and
nitrogen dioxide. The lung appears to utilize antioxidant
vitamins as a coating for the sensitive cells that exchange
oxygen with the blood and protect against respiratory
infections. ORD has recently broadened this research by
studying healthy men who consumed varying levels of
vitamins C, E and other antioxidants for two weeks and
then were exposed to ozone. Preliminary results suggest
that the men who consumed high levels of antioxidant
vitamins were less sensitive to ozone-induced effects.
These studies are among the first to demonstrate the
importance of diet in protecting against the effects of air
pollutants. Of course, many other factors such as health
status and degree of exposure can affect the severity of
health effects from pollutants. But given research indicat-
ing that up to 90 percent of Americans do not eat sufficient
quantities of fruits and vegetables, and therefore do not get
enough antioxidant vitamins, diet may turn out to have an
important role in mitigating the impacts of air pollution.
CONTACTS: Gary Hatch, (919) 541-2658; Jim Samet,
(919) 966-0665; and Bob Devlin, (919) 966-6255
Potential Cancer Mechanism of
Drinking Water Contaminants is Found
If a chemical causes cancer in animals, what risks do
people face? This is one of the most challenging questions
for EPA risk assessors. Understanding the mechanisms of
carcinogenesis in animals — that is, the steps by which a
chemical causes changes in the body that lead to cancer —
can be essential in answering this question. As a result,
ORD scientists are studying carcinogenic mechanisms as a
way of improving assessments of risks to human health.
Recently, scientists at ORD's National Health and
Environmental Effects Research Laboratory (NHEERL)
have discovered a new pathway by which certain
trihalomethanes (THMs) may cause cancer in laboratory
animals. THMs are one of the most prevalent classes of
byproducts of drinking water disinfection. They can form
when chlorine used in disinfection reacts with natural
organic matter in the water. Although disinfectants have
successfully protected people from dangerous microbes in
drinking water for more than a century, scientists have
grown concerned about health risks from unwanted
byproducts such as THMs. As a result, understanding these
risks has become an EPA research priority.
Scientists have long known that THMs are exten-
sively metabolized, or converted to other chemical
compounds (metabolites), once inside the body. ORD's
new findings reveal that the metabolism of THMs contain-
ing bromine can produce highly reactive metabolites that
damage DNA and cause gene mutations. This direct DNA
damage, or genotoxicity, can occur at low doses and may
initiate the cancer process. The new genotoxic pathway
does not appear to occur with chloroform, a common
THM that lacks bromine. These findings demonstrate that
different THMs can induce carcinogenic effects through
different mechanisms — an important indication that, in
the assessment of health risks, it should not be assumed
that all THMs act in the same way. The research teams
will now focus on the implications of the new metabolic
pathway for human health.
CONTACT: Rex Pegram, (919) 541-0410
Rocket Fuel Contamination
Prompts New Research Effort
Perchlorate, an ingredient in solid rocket propellant
and munitions, has been detected at levels of concern in
water supplies in California, Arizona and Nevada, and
environmental managers in these states have turned to
ORD for help in analyzing the risks and understanding the
available cleanup technologies. Perchlorate has long been
known to interfere with iodide uptake in the thyroid gland,
a useful property in the treatment of hyperthyroidism
(Graves' Disease). Produced in limited areas as a rocket
fuel component, it has attracted little environmental
concern and no federal drinking water standards have been
established. However, perchlorate concentrations from 600
to 3,700 parts per billion (ppb) have been found in some
drinking and groundwater supplies which greatly exceed
the state of California's 18 ppb action level.
In response to requests from EPA's Region 9 office
based in California, the National Exposure Research
Laboratory (NERL) in Las Vegas has been reviewing the
California protocols established for measuring perchlorate
contamination in water. The goal is to determine the
reliability of the ion chromatographic method in measur-
ing perchlorate in the 4-to-10 ppb range. NERL is also
implementing studies on other issues pertaining to per-
chlorate analysis.
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The National Risk Management Research Labora-
tory (NRMRL) in Cincinnati is also contributing by
examining options for treating drinking water. In a Decem-
ber symposium hosted by NRMRL, ORD scientists met
with academic, military, and commercial researchers to
assess perchlorate effects and remediation. Current treat-
ment options for perchlorate include reverse osmosis and
ion exchange, which are expensive; thermal reduction,
which is untested; and bioremediation (bacterial degrada-
tion), as well as possible chemical technologies.
Bioremediation appears to be the most effective treatment
for large quantities of contaminated water and is currently
being evaluated at several sites. A steering committee
composed of representatives from ORD, the U.S. Air
Force, and other federal agencies was recently formed to
exchange perchlorate information. The committee includes
researchers from ORD's National Center for Environmen-
tal Assessment (NCEA), which will develop a perchlorate
reference dose (the concentration below which health
problems would not be expected).
CONTACTS: Steve Pia, (702) 798-2102; Edward
Urbansky, (513) 569-7655; and Kenneth W. Brown,
(702) 798-2270
STAR Grants and Fellowships
Awarded to Top Scientists
ORD has announced the award of competitive grants
to preeminent researchers across the country and fellow-
ships to some of the nation's most promising environmen-
tal science and technology students. Scientists from 111
institutions in more than 40 states received a total of 169
grants from ORD and 30 grants from other agencies
participating hi the Science to Achieve Results (STAR)
program. The award winners were chosen from more than
1,700 applications. ORD has also awarded 116 fellowships
(out of over 1,300 applications) to graduate students from
59 institutions in more than 30 states. ORD relied on
extensive peer review by hundreds of scientists from
outside EPA in making the selections.
Under the STAR program, EPA awards grants
annually to universities and other institutions. STAR, now
in its third year, is administered by ORD's National Center
for Environmental Research and Quality Assurance
(NCERQA). Grants are typically funded for three years at
about $250,000 per year. ORD selects high priority grant
topics that complement ORD's internal research capabili-
ties based on recommendations from across EPA. The
grants program also allows ORD to coordinate research
with other federal agencies that play an important role in
environmental science, such as the National Science
Foundation, the National Oceanic and Atmospheric
Administration (NOAA), NASA, and the Department of
Energy. More information about STAR, including this
year's awards and next year's grant topics, is available on
the Internet at www.epa.gov/ncerqa.
CONTACT: Ron Slotkin, (202) 564-6854
ORD Science Highlights is edited and published by
ORD's Center for Environmental Research Information
in Cincinnati, Ohio. It is available on the ORD web
site, http://www.epa.gov/ORD/, or by calling (513) 569-
7562.
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
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EPA/600/N-98/001
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