Building
a Scientific
Foundation
for Sound
Environmental
Decisions
December 2003
Volume 6
Issue 2
Office of Research and Development
National Exposure Research Laboratory
Computational Toxicology
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
On September 29-30, the EPA's ORD hosted
a workshop on computational toxicology
at the EPA Campus in Research Triangle Park,
North Carolina. Participants discussed ways to
fully utilize modern computing, chemistry, and
molecular biology to develop predictive models of
toxicity that improve quantitative risk assessments
and reduce uncertainties in the source-to-outcome
continuum. The workshop included presenta-
tions by EPA scientists that described the develop-
ment of a research program within the Agency on
computational toxicology.
Participants heard presentations from other
federal agencies, academia, and outside research
organizations about related goals and examples of
computational approaches. In breakout sessions,
participants envisioned the impact of computa-
tional toxicology on prioritization of chemicals
for testing and improving quantitative risk as-
sessment. Details will be posted at www.epa.gov/
comptox/.
This year an ORD-wide steering committee
has been developing a framework for a future ini-
tiative in computational toxicology. The steering
committee, led by NHEERL's Bob Kavlock, in-
cludes NERL contributors Eric Weber and Tim
Collette (ERD), Jerry Blancato (HEASD), and
Greg Toth (EERD). Toth is the Laboratory's
computational toxicology program manager and
Kate Smith (EERD Director) is NERL's lead.
Contact: Greg Toth
NERL-Cincinnati Ecological Exposure Research Division
(513) 569-7242
ORD's Epidemiological Study of
Beaches Underway
A n important part of EPA's Action Plan for
_t\_Beaches and Recreational Waters is to im-
prove our understanding of the link between
water contaminants, swimming at the beach, and
public health. To help us understand the link,
NHEERL and NERL scientists are conducting
an epidemiological study during the summer
months from 2003 to 2005 at nine fresh and salt
water beaches.
The epidemiological study is going to assist
with development and evaluation of new-genera-
tion water quality tests for microbial contamina-
The EPA is studying water
quality at beaches.
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Office of Research and Development
National Exposure Research Laboratory
tion that would provide same-day results within two hours,
rather than the standard 24 to 48 hours. The study involves
new water sampling protocols, coupled with interviews of
approximately 5,000 families at two beaches in Indiana and
Ohio during the summer of 2003- Families were interviewed
on the beach about a variety of activities, including swim-
ming. Ten to twelve days later, EPA researchers contacted
the families to ask about their health in order to correlate
indicators of poor water quality with reported adverse health
effects.
On August 2, the first day of the study, NERL's Al Du-
four joined Paul Gilman, EPA Science Advisor and Assistant
Administrator for Research and Development, and U.S.
Senator George V. Voinovich of Ohio for a press confer-
ence at Huntington Beach to talk about the importance of
the research. "Swimming in water of poor quality can be a
significant cause of stomach, respiratory, eye and ear illnesses
in the summer time. Our goals are to prevent those illnesses
and improve the quality of the water for recreation. EPA's sci-
ence is providing the critical information that health officials
and beach managers need to make decisions that protect the
public health," said Gilman. "This important field research
could not be done without the support of the community,
and we greatly appreciate the contributions of the Cleveland
Metroparks, Cuyahoga County Health Board and the
citizens who agree to participate in this study. It also requires
the support of Congress. Voinovich is a champion of using
sound science to protect human health and the environment,
and he continues to play a major role in restoring the Great
Lakes to their natural vitality."
Contact: Alfred Dufour
NERL- Cincinnati
Microbiological and Chemical Exposure Assessment Research Division
(513) 569-7330
Community Multiscale Air Quality (CMAQ)
Model — New Version.
CMAQ, the numerical air quality simulation model
developed by NERL and used by OAQPS, states, and
others responsible for air quality planning and management,
simulates tropospheric ozone, fine particles (PM25), visibility,
2 (if
and acid deposition over continental through urban scales.
During the last year, emphasis has been on refining the
capabilities for simulating fine particles because the 2002
version showed considerable overestimates of nitrate and
organic particles. Nitrate was found to be most severely
overestimated during wintertime conditions. Thus, it was
clear that improvements were necessary.
Scientists scrutinized the physical and chemical processes
responsible for the production of nitrate in the CMAQ model
and isolated several for improvement, one of which was the
deposition of ammonia gas to a frozen ground surface dur-
ing winter. (Ammonia is an important precursor gas to the
chemical production of nitrate particles.) Model enhance-
ments included an increase in ammonia deposition, leading
to a decrease in nitrate production.
Scientists also studied the atmospheric chemistry. The
reaction of N2O with water on the surface of existing par-
ticles was found to be an important source of nitric acid,
another precursor of nitrate particles. Recent studies of this
reaction cited in the literature show a much lower probability
of this reaction occurring than was shown in earlier studies.
In response, changes in the CMAQ model were implemented
which reduced nitrate particle concentrations by 25—65%
over the continental U.S. model domain, bringing them
closer to observed ambient levels.
CMAQ Layer 1 Ozone
September 20, 2002 -18:00 EOT
0.060142
0.053
0.045
0.038
0.030
0.023
0.015
0.008
0.000
ppmV 1 166
*?* September 20,2002 22:00:00
tcfic Min- 0.007 at (122.7SX Max- 0.059 at (73,34)
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Office of Research and Development
National Exposure Research Laboratory
Additionally, scientists examined the process of parti-
tioning the organic material between gases and particles.
CMAQ's earlier versions included a gas-to-particle pathway
for organic material, allowing organic particles to grow in the
atmosphere. However, the reverse pathway, from particles
back to gas, is also significant and was added to the CMAQ
model during recent testing. The reverse pathway for organic
partitioning resulted in the lowering of secondary organic
particle concentrations by 60—70% in the CMAQ model
simulations, which compare more favorably with observed
concentration levels.
Last but not least, efforts continue toward making the
CMAQ model run more efficiently on typical user computer
platforms. Recent tests of the CMAQ model on a 12-proces-
sor Linux cluster showed a 24-hour simulation running
in less than two hours of real time. Further efficiency
improvements are anticipated over the coming year. The lat-
est version of the CMAQ model is available from the Com-
munity Modeling and Analysis System (CMAS) web site:
www.cmascenter.org.
Contact: Ken Schere
NERL-RTP Atmospheric Modeling Division
(919) 541-3795
SHEDS Predicts Pesticide Exposure
The Stochastic Human Exposure and Dose Simulation
(SHEDS) model for pesticides
(SHEDS-Pesticides) increases the Agen-
cy's understanding of human exposures
and doses to multimedia, multipathway
pollutants. It is a physically-based,
probabilistic computer model that pre-
dicts exposures and doses incurred by
selected groups of people associated with
contamination from eating, drinking
water, inhaling air, coming in contact
with surface residues, or ingesting
residues from hand- or object-to-mouth
... ~ , , . CTTT,^C „ ... CCA-treated
activities, lo do this, SHEDS-Pesticides
wood is used on
combines information on pesticide usage,
5 playsets & decks.
human activity data (from time/activity diary surveys and
videography studies), environmental residues and concentra-
tions, and exposure and dose factors using one- or two-stage
Monte Carlo probabilistic sampling methods. This research
will help answer the following questions:
• What is the population distribution of exposure for a
given cohort for existing scenarios or for proposed expo-
sure reduction scenarios?
• What is the uncertainty associated with different percen-
tiles of exposure for a population?
• What is the intensity, duration, frequency, and timing of
exposures from different routes?
• What are the most critical media, routes, pathways, and
factors contributing to exposures?
• How can exposures be most effectively reduced?
• What additional human exposure measurements are
needed to reduce uncertainty in population estimates?
• How do modeled estimates compare to real-world data?
Although SHEDS-Pesticides has been developed as a
source-to-dose model, the concentration-to-exposure module
has been the primary focus of development and relatively
simple modules are currently incorporated for source-to-con-
centration and exposure-to-dose estimation.
A scenario-specific model, SHEDS-Wood, was developed
by NERL at the request of the Agency's OPP to focus on
children's exposure and dose to arsenic and chromium from
chromated copper arsenate (CCA)-treated wood on playsets
and decks. The results were presented successfully to OPP's
Federal Insecticide, Fungicide and Rodenticide Act (FIFRA)
Science Advisory Panel (SAP) last summer. Currently, we are
refining the SHEDS-Wood model to incorporate new data
and to address SAP comments. The information will be used
as part of OPP's public health risk assessment to be presented
to the SAP in 2003 as a final technical report. In the in-
terim, scientists at the EPA are completing the modeling runs
and producing the reports needed for the next SAP meeting.
The SHEDS-Wood model will form the basis of the exposure
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Office of Research and Development
National Exposure Research Laboratory
and dose assessments that OPP will use to calculate cancer
and non-cancer risks for children who come in contact with
CCA-treated playsets and decks. The documentation, code,
interface, and a journal article on the SHEDS-Wood assess-
ment of CCA-treated wood will be completed in 2004.
Contact: Valerie Zatarian
NERL-RTP Human Exposure and Atmospheric Sciences Division
(617) 918-1541
Weaver — He's a Smooth Calculator
In most households, a
calculator is used to
balance the checkbook.
However, Jim Weaver,
of NERL's ERD uses
more than 30 calculators
to assess the transport of
subsurface contaminants.
At work Weaver considers
himself not only an engi-
neer, but a public servant
and a teacher as well. He
attributes his perspective on public service to his alma mater,
the University of Texas, Austin, where he received his Ph.D.
in Civil Engineering in 1988. "Where I went to school,
research, consulting, and teaching were a three-pronged
approach for educating people and advancing scientific
knowledge," he says. Weaver exudes a genuine enthusiasm
for helping people, especially environmental professionals in
EPA's regional offices and state agencies.
In 1994, while Weaver was working at EPA's NRMRL in
Ada, Oklahoma, he also taught classes on groundwater model-
ing. At one of his workshops, a State of New York employee
asked him for help with interpretation of a rich data set
depicting MTBE from leaking underground storage tanks
(LUST). Weaver welcomed the opportunity to help and to
this day, continues EPA's nine-year collaboration with them
on subsurface contamination.
In 1996, Weaver joined NERL-Athens where he developed
a new course on modeling subsurface contamination from
US
Jim Weaver
petroleum hydrocarbons to help EPA Region 4. Others were
eager to have access to guidance and tools for the ever-in-
creasing problem of LUST, and Weaver found himself teach-
ing the course to people in more than 20 states nationwide.
As demands for his time grew, Weaver decided to 'prepack-
age' the principles of groundwater flow by developing a suite
of calculators called "OnSite" and to make them available
from the web. OnSite provides methods and data for com-
mon calculations meaningful to a variety of users for as-
sessing impacts from subsurface contamination. Parameter
estimates are also included for the convenience of those with
experience, the education of those with less experience, and
because of their potential to provide consistency among a
diverse user community.
Since their beginning, the OnSite calculators have come
a long way. More than 30 calculators cover parameter esti-
mates, simple transport models, unit conversions, and scien-
tific demonstrations like Darcy flow in a laboratory column.
Some of the concepts contained in the OnSite calculators
have come directly from interactions with the states, includ-
ing plume diving and borehole concentration averaging that
were a result of the interaction with the State of New York on
the aforementioned MTBE sites.
Knowledgeable groundwater experts have said that because
of their high level of confidence in the OnSite calculators
— prepackaged formulas and data — they no longer have
to refer back to written texts. Today, state environmental
agency staff are referring their consultants to the web site
(www.epa.gov/athens/onsite), which receives about 18,000 hits
per month.
"My work helps with their problems. By
offering these calculators, I've learned
the real problems practitioners are
dealing with," says Weaver. "You get
back more than what you give people.
Someone I work with characterized
it as a labor of love. And that's about
right."
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Office of Research and Development
National Exposure Research Laboratory
EPA and NOAA Join. Forces in Atmospheric
Modeling Research and Air Quality Forecasts
In a ceremony in Washington, D.C., then-EPA Administra-
tor Christine T. Whitman and Deputy Secretary of Com-
merce Samuel W. Bod man signed an MOU to reaffirm a
long-standing collaboration on atmospheric sciences research
and an MOA to develop and implement a national air qual-
ity forecasting system. The two agencies are joining forces
to enhance research in air quality modeling and atmospheric
measurements for developing a consistent, national numerical
air quality model for short-term forecasts for ozone, fine par-
ticulate matter, and visibility.
"An improved air quality forecast can mean a higher qual-
ity of life for many Americans, especially those most vulner-
able to the effects of ozone," said Bodman. Air pollution
control agencies across the country will use the new national
prediction model to supplement their forecasts of local air
quality indices.
The partnership between EPA and NOAA dates back to
1955, when a handful of Weather Bureau meteorologists were
assigned to the Public Health Service to work on air pollution
problems. Today, more than 50 atmospheric scientists are on
assignment at EPA where they conduct research in air pollu-
tion meteorology, atmospheric modeling, and air quality data
analysis and management.
Led by S. T. Rao, the NERL's AMD develops air qual-
ity models for use by EPA in its regulatory decision making,
including the Community Multiscale Air Quality (CMAOJ
model (featured on page 2). The MOA brings together the
National Weather Service and AMD in the development of
an integrated meteorological-chemical transport model for
simulating ambient air quality of the continental U.S. Work
continues into the fall of 2004, when EPA and NOAA will
produce a numerical air quality model that provides daily
forecasts for ozone in the northeastern U.S.
The EPA-NOAA partnership will pay benefits well into
the future. Within five years, the system for ozone will be
deployed nationwide; within ten years, the model is expected
to be used in forecasting PM in four-day increments. Citi-
zens at the state and local level will benefit because their local
air quality management agencies will provide them with bet-
ter and more timely air quality forecasts.
Contact: S. T. Rao
NERL-RTP Atmospheric Modeling Division
(919) 541-4542
NERL Scientists Participate in the ISEA
Meeting
arry Cupitt, NERL's Associate Director for Health, led
_l_/a delegation of scientists to the annual International So-
ciety of Exposure Analysis/International Society of Environ-
mental Epidemiology conference in Stresa, Italy (September
21-25, 2003). NERL participants are all members of the
HEASD, including Elaine Hubal (Acting Associate Director
for Human Exposure Modeling), Haluk Ozkaynak (Senior
Science Advisor), Curtis Dary (Acting Chief, HEASD Ex-
posure Dose Research Branch), Thomas McCurdy, Marsha
Morgan, Liu Shi, Jianping Xue, Lance Wallace, and post-
docs Peter Egeghy and Rogelio Tornero-Velez.
The International Society of Exposure Analysis (ISEA), a
multi-disciplinary, international organization, is dedicated to
advancing the science of exposure analysis for human popula-
tions and ecological systems. ISEA is the primary organiza-
tion for EPA's exposure researchers and their counterparts.
This year's agenda included tracks on risk management,
methodological advances, and dietary, indoor, urban, rural,
workday, and population exposures.
Contact: David Kryak
NERL-RTP Human Exposure and Atmospheric Sciences Division
(919) 541-2454
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