c/EPA
United States
Environmental Protection
Agency
-
Five Years of Progress
-------
Particul
Background
The U.S. Environmental Protection Agency
(EPA) strives for every American community to
have safe and healthy air. Research has shown
that exposure to particulate matter (PM) air
pollution is linked to increases in respiratory
health problems, hospitalization for heart or lung
disease and even premature death. The National
Ambient Air Quality Standards (NAAQS)
for PM, set by EPA in 1997, were designed
to respond to this PM research and move the
nation closer to achieving the Clean Air Goal. In
1998, Congress mandated that EPA accelerate its
investigation of PM health effects and find ways
to reduce the risks associated with exposure to
PM. In response, EPA's research office developed
a program to coordinate the work of its own
scientists with that conducted by academics,
partners such as the Health Effects Institute,
and other Federal agencies such as the National
Institutes of Health and the Department of
Energy. The results of this effort have improved
our understanding of the potential impacts of
PM on human health, helped us develop tools
to reduce harmful exposures, and advanced the
science for future reviews of the PM NAAQS.
EPA research on PM has been conducted within
a framework developed by the National Research
Council (NRC) of the National Academy of
Sciences, an independent committee of experts
that was assembled at the request of EPA in 1998.
The NRC Committee on Research Priorities for
Airborne Particulate Matter identified the agenda
that guided EPA in developing its PM research
program. Eleven areas were specified to encourage
researchers to:
Evaluate actual PM exposures
Determine the exposures of susceptible
subpopulations to PM
I Determine the characteristics of PM from
various emission sources
I Develop models to test air quality management
strategies
Assess the hazardous components of PM
I Determine what happens to PM after it is
deposited in the lung
I Separate the effects of PM from other, gaseous
pollutants and assess the effects of long-term
exposure to PM
Ascertain which subpopulations are most
susceptible to PM effects
I Discover the specific biologic mechanisms by
which PM causes adverse health effects
I Examine various statistical methods for
estimating exposure to PM
I Develop technical support for modeling and
measurement techniques
Five Years
-------
Results
PM Is Linked to Disease: Numerous studies
conducted throughout the U.S. and the world
have shown that short-term exposure to PM
can adversely affect human health. Generally,
exposure to PM is associated with illness and
premature death independent of the effects of
other, gaseous pollutants in the atmosphere.
The very young, the genetically predisposed, the
elderly, and those with pre-existing heart or lung
disease are most susceptible to the adverse health
effects of PM. Striking findings also suggest that
extended PM exposure can lead to chronic disease
and/or a shortened life span.
Fine Particles Move Indoors: Scientists have
found that PM2 , the component of PM smaller
than 2.5 micrometers in diameter, penetrates easily
into most indoor environments—where people
spend much of their time. While the strength of
the correlation can vary by season and location,
it appears that outdoor PM25 levels reasonably
represent personal exposure to PM2 . Exposure
studies have also shown that background levels
of other, gaseous pollutants, such as ozone and
nitrogen dioxide, can be surrogate indicators for
personal PM2 exposure.
People with Lung Disease Collect More
Particles in their Lungs: New findings
demonstrate that PM2 deposits in critical regions
of the lung after it enters the respiratory tract.
Some parts of a diseased lung collect 8 to 10 times
more particles than a healthy lung, a fact that has
major implications for people with lung disease.
This work suggests that people with lung disease
may be more affected by increasing levels of PM
because they receive greater doses.
Possible Mechanisms for Disease: We now have
multiple hypotheses to explain how the chemical
and physical properties of PM could produce
disease. Further, we can now experimentally
investigate the mechanisms that enable very small
concentrations of inhaled PM to cause changes in
the heart and lung that lead to increased illness
and death. The laboratory and field evidence
does not implicate one specific toxic quality of
PM to the exclusion of others. Qualities such
as the size of the PM and presence of certain
chemical components, such as metals, all appear
to contribute to its toxicity.
Models and Tools to Implement the PM
NAAQS: Researchers have developed more
advanced tools to measure and model fine
particles. The models enable researchers to
estimate how much PM will travel from a source
of potentially toxic particles to populations that
can be affected and to predict how reductions
in PM emissions can impact exposure miles
away. New, specialized measurement techniques
should help us measure the particle size and
composition of diverse kinds of PM and PM
from unconventional sources.
Progress
-------
What's Next?
Expanded research during the past five years
has answered many pressing questions about
the health effects of PM and related exposures,
but much remains to be learned. We do not
yet understand the role of long-term PM
exposure in the development of chronic disease.
Further research is also needed to determine
how long-term exposure combines with short-
term fluctuations in PM levels to trigger acute
problems such as heart attacks. In response to
these needs, EPA recently issued a Request for
Applications to examine the health effects of
exposure to PM over a 10-year period.
EPA's research office will be investigating the
significance of new hypotheses to explain
the mechanisms by which PM causes disease
and death. New research is needed to explain
the effects of different physical and chemical
properties of PM on human health, particularly
on the most susceptible populations. With this
understanding and an ability to link sources of
PM to observed health effects, researchers will
be able to produce information to help develop
targeted control strategies to reduce human
exposure.
EPA is completing the Air Quality Criteria
Document for Particulate Matter, a comprehensive
assessment of PM health and exposure science.
results of
This document will review the results of the
approximately 2,000 studies that have be^B
published since the last review in 1996. EPA will
use this information to issue a proposal outlining
whether the NAAQS should be revised.
Now that the National Monitoring Network
has compiled several years of detailed PM25
monitoring data, there is a critical need to
accelerate research to help implement the
NAAQS. EPA will use modeling and monitoring
data to determine which states and regions are
out of compliance with the NAAQS. EPA's
research office is developing new analytical tools
that will help these states and regions achieve
NAAQS compliance.
Conclusions
EPA estimates that its current regulations to
reduce air pollution can save tens of thousands
of lives per year. It is estimated that hundreds
of thousands of annual hospitalizations for
cardiovascular and respiratory illnesses can be
prevented by implementing these regulations.
The monetary benefits alone from reduced
deaths are estimated to be in the range of $100
billion per year. Future research will help to
ensure that the populations most vulnerable to
the effects of PM will be protected, and that
the regulations will be implemented in the most
effective ways possible.
For more information contact;:
James Vickery
Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
EPA-600-F-04-025
April 2004
www.epa.gov/ord
Recycled/Recyclable, Printed with vegetable-based ink on paper that contains
a minimum of 50% post-consumer fiber and is processed chlorine free.
------- |