&EPA
www.epa.gov/airscience
science in ACTION
CLEAN AIR RESEARCH
PROGRAM
EXPOSURE SCIENCE IMPROVES RISK ASSESSMENTS OF AIR POLLUTANTS
Issue:
Exposure to air pollutants is
known to cause discomfort,
illness, and even death,
particularly among susceptible
individuals. Susceptible groups
include those with pre-existing
cardiovascular or respiratory
problems as well as the very
young and the elderly. Research
funded in part by the U.S.
Environmental Protection Agency
has shown that cleaner air results
in a longer life.
Exposure in the context of air
pollution is typically defined as
the concentration, frequency, and
duration of time that a human
comes into contact with an
airborne pollutant. In the case of
most air pollution, the primary
concern is the concentration of
the contaminant to be inhaled.
Exposures vary depending on an
individual's location relative to
the contaminant source (distance,
indoor/outdoor), the time of day,
lifestyle, and other factors. But
how do we determine the actual
exposure?
Measuring the actual exposure of
an individual requires researchers
to provide a measurement device
to the person and record the
amount of the contaminant he/she
encounters throughout some
defined period. Measuring
exposure over a day is often a
useful measure.
However, performing these
studies is very expensive and
time-consuming; therefore, it
would be helpful to have better
ways to estimate exposure. As a
result, theoretical and
experimental models based on
study data are used to predict
exposures.
Typically, the measured outdoor
concentration of a contaminant is
used as the estimate of exposure,
but for various contaminants it is
not a good measure of the actual
exposure. For this reason, the
Clean Air Research Program in
EPA's Office of Research and
Development is dedicated to
improving measurement
capabilities and is developing and
improving models that will
provide more accurate estimates
of exposure.
Science Objective:
Scientists in the Clean Air
Research Program are
characterizing exposure of
humans through direct
measurements of outdoor
contaminant concentrations and
direct measurements of personal
exposure. As part of this effort,
they are investigating the role
human exposure plays in
observed relationships between
air quality and human health.
The information from exposure
measurements is then being used
continued on back
U.S. Environmental Protection Agency
Office of Research and Development
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&EPA
www.epa.gov/airscience
science in ACTION
CLEAN AIR RESEARCH PROGRAM
continued f-omjront
to develop computer modeling
tools to provide health scientists
and risk assessors with more
accurate exposure estimates.
Key scientific questions include:
• What is the relationship
between (outdoor) ambient air
concentration and actual
human exposures to air
pollutants?
• How does proximity to
sources impact human
exposures?
• How can exposure modeling
approaches be applied to
strengthen studies
investigating relationships
between air quality and
human health?
Application and Impact:
Important information and tools
are being provided to better
understand how we come into
contact with air pollutants and
what effect they may have on the
risk we experience from air
pollution in our day-to-day lives.
With this information, state air
quality managers and federal
regulators like EPA's Office of
Air and Radiation can work to
reduce the public health risk
posed from air pollution.
Exposure science at EPA has
made significant contributions
toward advancing our
understanding of exposure to air
pollution. The document,"200¥
NRC Report on Research
Priorities for Airborne
Particulate Matter" noted that
substantial progress had been
made in understanding
relationships between outdoor
measures of PM and actual
human exposures. In particular,
findings from the PM Exposure
Panel Studies (Williams 2000)
demonstrated that a community
air monitor could be considered a
reasonable surrogate for personal
human exposure to fine particles
of ambient origin, thereby
supporting the epidemiological
findings that were instrumental in
the development of PM standards.
In addition, the value of exposure
assessments has been
demonstrated in specific health
studies. Two examples include
findings that show in-vehicle
exposure measurements,
associated cardiovascular health
outcomes (Riediker 2004), and
differential health impacts
associated with community and
personal monitoring (Brook and
Williams 2008).
References:
National Research Council (2004) Research
Priorities for Airborne Particulate Matter IV -
Continuing Research Progress. Washington DC:
National Academies Press.
Williams, et al The 1998 Baltimore Particulate
Matter Epidemiology-Exposure Study: Part 1.
Comparison of ambient, residential outdoor,
indoor, and apartment particulate matter
monitoring . Journal of Exposure Analysis and
Environmental Epidemiology. 10, 518-532 (2000)
Riediker, M.,et al. Particulate matter exposure in
cars is associated with cardiovascular effects in
healthy, young men. American Journal of
Respiratory and Critical Care Medicine. 169: 934-
940 (2004).
Brook and Willams. Vest monitors show air
pollution is dangerous indoors and out. American
Heart Association Press Release. (Nov 12, 2008)
CONTACT
David Kryak, Ph.D., National Exposure Research
Laboratory, EPA's Office of Research and
Development, 919-541-1457,
krvak. davidd(g!epa. gov
APRIL 2009
U.S. Environmental Protection Agency
Office of Research and Development
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