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CLEAN AIR RESEARCH
PROGRAM
AIR POLLUTION RESEARCH IMPROVES UNDERSTANDING OF
MULTIPOLLUTANT IMPACTS ON HUMAN HEALTH
Issue:
People are exposed to mixtures of
air pollutants throughout life.
Clear advances have been made
in understanding and minimizing
the risks associated with some air
pollutants with known singular
toxicity risk, but the impacts of
mixtures of low levels of air
pollutants are still uncertain.
Historically, outdoor air research
has largely focused on individual
air pollutants like particulate
matter (PM), ozone, or priority
hazardous air pollutants (HAPs).
This research has been critical for
the development and
implementation of clean air
standards by the U.S.
Environmental Protection
Agency. As a result, air quality in
the United States has improved.
To further advance air quality
management, EPA is adding a
multipollutant component. This
"one atmosphere" approach takes
into account that humans and
ecosystems are exposed to many
air pollutants at the same time,
and that there exist many
atmospheric processes and
conditions that underlie this mix
of pollutants.
Currently, each pollutant is
assessed separately and controlled
by independent measures. A
multipollutant approach offers an
opportunity to more effectively
target air pollutants at their
sources and reduce more than a
single pollutant with control
measures. The desired outcome is
to have a broader impact on
outdoor air pollutant levels and
reduce the cost of pollution
control.
Multipollutant approaches to
environmental decision making
require new science to understand
and appreciate the complexities of
co-pollutant interactions
(chemical and biological). More
advanced scientific methods,
models and tools are needed.
In response, the Clean Air
Research Program in EPA's
Office of Research and
Development is shifting toward a
multipollutant approach to air
research. This research emphasis
is based on recommendations by
science advisory groups,
including the
National Research Council,
Science Advisory Board, and
Board of Scientific Counselors,
which have encouraged EPA to
transition from individual
pollutant control and regulation to
an air quality management theme
that includes multipollutants.
Scientific Objective:
The Clean Air Research Program
has developed a three-pronged
strategy to address multipollutant
issues that builds on earlier
scientific contributions in this
area. The strategy integrates the
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Office of Research and Development
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CLEAN AIR RESEARCH PROGRAM
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many scientific disciplines that
advance knowledge about air
pollution. These disciplines
include the study of sources and
atmospheric processes, the study
of how people are exposed, and
subsequent health implications.
The strategy includes:
• Conducting laboratory studies
to evaluate controlled source
emissions and health effects.
Conducting laboratory studies
of artificial mixtures that test
hypothetical interactions that
may be driving more
generalized atmospheric
exposure mixtures.
• Conducting real-world studies
in cities where emission,
exposure, and health data can
be collected or integrated on
multipollutant exposures that
may impact human health.
Areas of scientific focus include:
• Understanding the relationships
between sources of air
pollutants and atmospheric
transformation (secondary) air
pollutant products.
• Understanding the health risks
posed by mixtures of air
pollutants.
• Advancing atmospheric and
exposure modeling of
multipollutants.
• Developing methods and
controls for sources or air
pollutants that impact health
relevant emissions or products.
• Determining a hierarchy of
sources and related emission
components regarding relative
health risks.
As part of this effort, there is an
initial emphasis directed to near-
road exposures since mobile
sources emit a complex mix of
gases, vapors, and particles.
Application and Impact
The Clean Air Research Program
has already made significant
contributions to our
understanding of multipollutants.
Work has revealed how
multipollutants are generated as
primary emissions as well as
secondary transformation
byproducts. Scientists have also
expanded the capabilities to
measure multipollutants.
There also have been advances in
our understanding of how people
are exposed and impacted by
mixtures of pollutants.
The research program has led the
way in multipollutant
assessments. The atmospheric
model called the Community
Model for Air Quality (CMAQ)
has recently been expanded
beyond just predicting ozone
pollution to include PM and a
host of air toxics or hazardous air
pollutants as well. This model is
used by states and local air
quality managers to develop
implementation plans to meet
EPA's air quality standards and is
used by other researchers
conducting epidemiology studies.
REFERENCES
Office of Air Quality Planning and Standards: The
Multi-pollutant Report: Technical Concepts &
Examples
http://www.epa.gov/air/airtrends/studies.html
CONTACT
Dan Costa, National Program Director, Clean Air
Research Program, EPA's Office of Research and
Development, 919-541-2532, costa.dan@epa.gov.
JANUARY 2009
U.S. Environmental Protection Agency
Office of Research and Development
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