[Senate Hearing 107-1011]
[From the U.S. Government Publishing Office]
S. Hrg. 107-1011
HEALTH IMPACTS OF PM-2.5 ASSOCIATED WITH POWER PLANT EMISSIONS
=======================================================================
HEARING
before the
COMMITTEE ON ENVIRONMENT AND PUBLIC WORKS
UNITED STATES SENATE
ONE HUNDRED SEVENTH CONGRESS
SECOND SESSION
__________
OCTOBER 2, 2002
__________
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COMMITTEE ON ENVIRONMENT AND PUBLIC WORKS
ONE HUNDRED SEVENTH CONGRESS
SECOND SESSION
JAMES M. JEFFORDS, Vermont, Chairman
MAX BAUCUS, Montana BOB SMITH, New Hampshire
HARRY REID, Nevada JOHN W. WARNER, Virginia
BOB GRAHAM, Florida JAMES M. INHOFE, Oklahoma
JOSEPH I. LIEBERMAN, Connecticut CHRISTOPHER S. BOND, Missouri
BARBARA BOXER, California GEORGE V. VOINOVICH, Ohio
RON WYDEN, Oregon MICHAEL D. CRAPO, Idaho
THOMAS R. CARPER, Delaware LINCOLN CHAFEE, Rhode Island
HILLARY RODHAM CLINTON, New York ARLEN SPECTER, Pennsylvania
JON CORZINE, New Jersey PETE V. DOMENICI, New Mexico
Ken Connolly, Majority Staff Director
Dave Conover, Minority Staff Director
C O N T E N T S
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Page
OCTOBER 2, 2002
OPENING STATEMENTS
Bond, Hon. Christopher S., U.S. Senator from the State of
Missouri....................................................... 4
Jeffords, Hon. James M., U.S. Senator from the State of Vermont.. 1
WITNESSES
Levy, Jonathan, assistant professor, Environmental Health and
Risk Assessment, Department of Environmental Health, Harvard
School of Public Health........................................ 19
Prepared statement........................................... 59
O'Keefe, Robert, vice president, Health Effects Institute........ 13
Prepared statement........................................... 54
Rose, Ben, executive director, The Green Mountain Club, Inc...... 17
Prepared statement........................................... 41
Samet, Jonathan M., M.D., professor and chairman, Department of
Epidemiology, Bloomberg School of Public Health, Johns Hopkins
University..................................................... 11
Prepared statement........................................... 29
Wyzga, Ronald E., technical executive and program manager,
Electric Power Research Institute.............................. 15
Prepared statement........................................... 43
ADDITIONAL MATERIAL
Articles:
Lung Cancer, Cardiopulmonary Mortality, and Long-term
Exposure to Fine Particulate Air Pollution................139-148
The Concentration--Response Relation between PM2.5
and Daily Deaths..........................................149-153
Charts:
American Thoracic Society, 1996.............................. 33
Attributes of Epidemiological Studies of Coal-Fired Power
Plant (CPP) Emissions...................................... 34-39
Human Health Benefits of Reducing Fine Particulate Matter:
Mortality-Related Benefits................................. 9
Human Health Benefits of Reducing Fine Particulate Matter:
Non-Mortality-Related Benefits............................. 10
PM2.5 and 8-hour Ozone Standards Attainment
(current data)............................................. 7
PM2.5 and 8-hour Ozone Standards Attainment (2020) 8
Unnecessary Deaths, Lives Saved.............................. 3
Fact Sheet, Aries: Aerosol Research Inhalation Epidemiology Study 49-53
Reports:
Environmental Health Perspectives, in press, The Importance
of Population Susceptibility for Air Pollution Risk
Assessment: A Case Study of Power Plants Near Washington,
DC.........................................................87-124
Review of Particulate-Related Health Impacts of Eight
Electric Utility Systems, Jonathan Levy, June 2002......... 65-86
Technical Paper, Modeling the Benefits of Power Plant Emission
Controls in Massachusetts, Jonathan I. Levy and John D.
Spengler, Department of Environmental Health, Harvard School of
Public Health, Boston, MA.....................................125-138
HEALTH IMPACTS OF PM-2.5 ASSOCIATED WITH POWER PLANT EMISSIONS
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WEDNESDAY, OCTOBER 2, 2002
U.S. Senate,
Committee on Environment and Public Works,
Washington, DC.
The committee met, pursuant to notice, at 2:02 p.m. in room
406, Senate Dirksen Building, Hon. Jim Jeffords (chairman of
the committee) presiding.
Present: Senators Jeffords and Bond.
OPENING STATEMENT OF HON. JAMES M. JEFFORDS, U.S. SENATOR FROM
THE STATE OF VERMONT
Senator Jeffords. The hearing will come to order.
Good afternoon, everyone. Thank you all for being here
today. I'm glad to have this chance to come together to learn
more about the health impacts of air pollution.
Not long ago, I was shocked to hear that as many as 50,000
people or more may be dying prematurely every year from the
exposure to fine particulate matter, also known as
PM2.5 or sometimes as soot. This chart which we have
up is based on the work done by many researchers, illustrating
this terrible situation. More people are dying from the dirty
air than are killed in auto accidents, from breast cancer and
other causes. Most of this pollution comes from the burning of
fossil fuel. This combustion creates tiny, almost microscopic
particles from solid matter and gases. Then the wind spreads
them afar and wide, sometimes thousands of miles. A few years
ago, researchers documented fine particles coming from China
and being deposited in the Pacific Northwest. More recently,
Asian brown cloud has been in the news because of the
continent-sized nature of this smog, soot and air toxics
phenomenon.
Luckily, our problems are not on the scale of the Asian
brown cloud any more. We can thank the Clean Air Act for that.
The Act has been very effective in reducing pollution to date,
and the Act provides for even greater reduction in the future
if it is fully, faithfully and swiftly implemented. I hope that
it will be, but the signs haven't been too promising as of
late. Since the 1990 amendments, information on the health
effects of fine particulate pollution have increased
dramatically. Unfortunately, most of the news is bad.
In March, the Journal of the American Medical Association
reported on a study which found that for increasing levels of
fine particulate matter, there is a corresponding increased
risk of mortality from all causes. There was an even greater
risk associated with cardiopulmonary and lung cancer mortality.
These findings mean that there are practically 130 million
people who live in areas polluted by fine particles who have
about the same increased risk of dying from heart or lung
disease as people who live with cigar or cigarette smokers and
regularly experience second-hand smoke.
That's just the tip of the iceberg when it comes to the bad
news. There is substantial and mounting evidence that besides
death, heart disease or lung cancer, fine particles also cause
decreased lung function, chronic bronchitis and aggravated
asthma. Exactly how these particles cause such damage and
destruction once they get deep down into the lungs is not
entirely known. But what we do know with some certainty angers
me. A report from the Clean Air Task Force found that fine
particle pollution from power plants is responsible for as many
as 30,000 deaths annually. As you can see from the chart on the
left side, that's more than people who die from homicide or
drunk driving accidents every year. On the right side, the
chart shows how many people we could save by drastically
cutting pollution from power plants. Coincidentally, those are
the lives saved annually by the reductions in the Clean Air
Act.
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Most of that fine particle pollution appears to be coming
from older, grandfathered power plants. Those are the ones
built before 1972 that were largely exempt from applying new
source performance standards. These are the same plants that
are opposing the Government's efforts to make them apply new,
cleaner technology when they make changes to their facilities.
The Administration is now thinking of making their loophole
even larger through changes in the new source review
regulations. That is exactly the wrong direction. We cannot
afford to increase pollution in that way. We certainly cannot
afford to continue wasting the lives of people every year
because of pollution that is controllable and coming from
obvious sources in our own back yard.
We the Congress, the Administration, elected officials,
have a responsibility to act to prevent harm to the American
public when we have evidence that the threat exists. The
terrible attacks of 9/11 took the lives of 2,824 innocent
people in the World Trade Center. There could not be a clearer
or more tangible threat to our national security. Our rapid
response has reached every corner of the world and almost every
facet of American life. Now it may lead us to an expanded war
that could be expensive in dollars and lives.
What troubles me is that we have equal, clear evidence of
the threat of death and damage occurring annually from fine
particulate pollution and yet there is no huge call to action
from most in Congress or the Administration. Every year New
York City power plant pollution causes 2,290 lives, according
to the studies we will be discussing today. Saving these lives
doesn't require war, and it won't cost that much. It just
requires a commitment to swift action.
Perhaps our witnesses will give us good news. Maybe the
threat of the fine particulate pollution is not as bad as the
headlines and the studies suggest. I hope there's a slim chance
that's right, because knowingly throwing away lives when we
know how to save them just doesn't make any sense.
Senator Bond.
OPENING STATEMENT OF HON. CHRISTOPHER S. BOND, U.S. SENATOR
FROM THE STATE OF MISSOURI
Senator Bond. Mr. Chairman, thank you very much for calling
this hearing to examine the health risks associated with fine
particle air emissions. I appreciate the opportunity to come
and join you with the chart presentation, because I'm going to
have some charts myself. I thought we might as well keep it
visual as well as audible.
My real regret is that this committee will end the session
by refusing to pass three pollutant legislation that would save
lives by addressing this very problem. According to EPA and
information you have given, Mr. Chairman, fine particles of
soot and smoke pose the greatest public health risk of any
regulated air pollutant. Fine particulates are associated with
tens of thousands of premature deaths per year in people with
heart and lung diseases. Such emissions also lead to increased
hospitalizations, emergency room and doctor visits, medication
use and delays, numerous days, of missed school and work.
One major source of fine particulates is the coal-fired
electric utility industry. Indeed, reports show that full
implementation by electric utilities of the Federal
Government's acid rain and smog reduction program in 2007 would
annually save 5,900 premature deaths and tens of thousands of
respiratory illnesses associated with just 8 major coal-fired
utilities. The question for us becomes why is this committee
passing up the opportunity to mandate further reductions from
electric utilities of the pollutants that produce particulate
matter?
This year, President Bush proposed his Clear Skies
Initiative to reduce emissions of nitrogen oxides, sulfur
dioxides, and mercury from electric utilities. Reducing
emissions of these three pollutants by over two-thirds, as the
President has called for, would also produce significant fine
particulate emissions reductions.
While we have made great strides in reducing air pollution
since passage of the Clean Air Act in 1970, and the amendments
in 1990, in which I played a role, we still have further to go.
Based on the latest data, 173 counties nationwide are likely to
exceed EPA's PM2.5 fine particle health standard.
The chart here behind me shows where these counties are. As you
can see, 157 counties in the East and in California, well
represented on this committee, and we in Missouri and Illinois
in the center of the Nation have some as well.
Passage and implementation of President Bush's Clear Skies
Initiative would bring 54 additional counties above and beyond
what will be achieved with existing programs into compliance
with the fine particle standard. This chart here shows the
improvement the Clear Skies Initiative would bring to over 21
million people. You can see that only a handful of counties
would remain out of compliance with the PM2.5 health
standard. These are the ozone non-
attainment counties, the orange are the particulate matter 2.5
non-attainment. Red are both non-attainment counties. This is
the base case for 2020. This is what the Clear Skies Initiative
would do, and reduce the number of areas out of compliance with
either or both by a significant number by 2020.
The mortality-related benefits from reducing fine particles
under President Bush's plan are equally striking. This chart
describes the number of lives saved under two different
assumptions analyzing the President's plan. By 2010, Clear
Skies would prevent annually between 3,800 and 6,000 premature
deaths related to fine particles. By 2020, President Bush's
plan would prevent annually between 7,000 and 12,000 premature
deaths. Mr. Chairman, the health of my constituents in Missouri
would clearly benefit under the Clear Skies initiative.
Beginning in 2020, over $2 billion of annual benefits of Clear
Skies would occur. Missourians would face 300 fewer premature
deaths, approximately 200 fewer cases of chronic bronchitis,
approximately 11,000 fewer days with asthma attacks.
Missourians would suffer 300 fewer hospital days and emergency
stays and emergency visits, 46,000 fewer days of work lost,
360,000 fewer total days with respiratory-related symptoms.
This is legislation that should be passed. We're not taking
advantage, we're not seeking an agreement to reduce NOx, SOx
and mercury. The committee is failing to take action on this
legislation that would address the very health risks this
hearing will examine for an unrelated reason. Some people want
to hold up work on reducing the particle pollution in order to
make a political point about climate change, global warming and
carbon dioxide. Count me on the health side of that equation.
Some want to preserve the global warming issue for future
elections, including the election in 2004. I urge my
colleagues, as we listen to today's testimony on the health
risks, to think of ways we can move forward on the three
pollutant legislation. The President has put forward a plan
that will save and benefit thousands. The chairman has his own
plan. The opportunity exists for compromise, and I hope that we
will do so next year, and I thank the chair.
Senator Jeffords. Thank you for your excellent statement.
Our first witness is Dr. Jonathan M. Samet, co-director of
the Risk Sciences and Public Policy Institute, and professor
and chair of the Department of Epidemiology, Johns Hopkins
Bloomberg School of Public Health, Baltimore, MD. Please
proceed. Nice to have you here.
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STATEMENT OF DR. JONATHAN M. SAMET, M.D., PROFESSOR AND
CHAIRMAN, DEPARTMENT OF EPIDEMIOLOGY, BLOOMBERG SCHOOL OF
PUBLIC HEALTH, JOHNS HOPKINS UNIVERSITY
Dr. Samet. Thank you, Chairman Jeffords, Senator Bond,
ladies and gentlemen. Thank you for the opportunity to speak
with you today about the health effects of particulate matter,
and particularly fine particulate matter in the air arising
from power plant emissions.
Just briefly as background, my training includes
specialization in internal medicine and pulmonary diseases,
quite relevant to the topic we're discussing, as well as
epidemiology. I've been involved in the studies of the health
effects of air pollution for more than 20 years, initially
doing work in Steubenville, OH, and then in western
Pennsylvania, where we carried out a series of studies to
assess the effects of large coal-fired power plants on the
respiratory health of women and children in the surrounding
communities.
More recently, I've been involved in a project funded by
the Health Effects Institute known as the National Morbidity,
Mortality and Air Pollution Study. We've been using publicly
available data to try and provide a national picture of the
health effects of air pollution.
I've served as a consultant member of the Clean Air
Scientific Advisory Committee, or CASAC, of the EPA on the
particulate matter issue. Presently, I chair the National
Research Council's Committee on Research Priorities for
Airborne Particulate Matter. I'll be speaking, as does my
testimony, to the question of, is there a hazard from fine
particles? I know that others who will follow will talk about
the actual magnitude of the hazard posed by particulate matter
in the air.
This is a substantial research challenge, but one that the
scientific community has now been addressing for decades. Part
of the challenge is that the particles in air exist in a
complex mixture that includes other pollutants, like ozone, and
they themselves are a mixture coming from different sources.
Particles are described by their size. This is important,
because size is a determinant of how long particles will remain
suspended in the air, whether they will reach the lung, and
where they will deposit once inside the lung.
These characteristics are relevant to health, and
appropriately the Environmental Protection Agency has now
focused in on measuring and setting a standard for the finest
particles, PM2.5, which are in a size range that can
reach into the lung. I would point out that while
PM2.5 measurements, as part of our national
monitoring, are recent, PM10, which has been
monitored nationally since 1987 and which is the basis for much
of our research, includes these smaller particles, so that
studies of PM10 are relevant to PM2.5.
I would also point out that we breathe particles wherever
we are, including this room today, I'm sure. But the particles
we breathe indoors have not only indoor sources, but they
include particles that have outdoor sources. Particles and
other air pollutants are important potentially to our health,
because even though concentrations may sometimes be portrayed
as low, we breathe in large quantities of air, 10,000 liters of
air a day, approximately. We call on our lungs to handle all
those particles. At times, because of the numbers of particles
or because of the toxicity of those particles, injury may
result. We think that key to the action of particles is some
form of inducement or stimulation of inflammation within the
lung.
We know that the deposition of particles within the lung
can cause adverse health effects. We can look back 50 years to
the air pollution disasters in Donora, PA and in London. There
was no need for complicated statistical methods to count those
who died from the air pollution. The excess numbers were
substantial.
Now, as levels have dropped, fortunately, researchers have
faced a challenge to continue to track the health effects of
air pollution and to sort out the effects of the different
pollutants present in air. For this purpose, we use many
different kinds of science. We use epidemiological studies like
those that I carry out. We look to toxicologic evidence that
tells us how particles or other pollutants cause their injury.
We put all of this evidence together, so that our decisions
about the health effects of particles or other pollutants do
not rest on any particular study or any particular line of
evidence, but on the whole body of evidence.
That body of evidence is now large, with literally
thousands of studies published on particles. My written
testimony includes some general references that provide access
to those studies. Of course, they are cataloged by the
Environmental Protection Agency in its now massive Criteria
Document most recently on particles. But just to summarize a
few of the things that we know at present, the numbers of
deaths per day. Here we know that if we look to the numbers of
deaths per day and examine the association or correlation with
air pollution on the same or recent days, something that we've
done in our NMMAPS project, we do find an association. Although
we've recently needed to revise our estimates downward because
of technical issues, we find nationally that an increase in
PM10 is associated with an increment in the number
of total deaths and an even steeper increment in the number of
deaths for cardiovascular and respiratory or lung conditions
each day.
You already mentioned the recent report in March in the
Journal of the American Medical Association. This is one of
several studies showing that in fact, for the longer term, air
pollution, particulate air pollution in particular, is
associated with increased risk of dying. We would take the
daily studies and these longer term studies as evidence that
particulate air pollution is contributing to sufficient life
shortening to be a public health concern.
There are other health indicators. Hospitalization and
emergency care, again, with the numbers of visits to emergency
rooms or the number of people on Medicare coming to hospitals
increased as the levels of particles increased from day to day.
We have further evidence that people with cardiovascular
diseases may be adversely affected. This is one of these areas
of emerging research with a number of studies going on. But the
first indications from this research provide warnings.
Asthma, an all too common condition in our country, rising
in children for reasons unknown, with prevalence rates of 10
percent or more. This is a susceptible group, again with
evidence showing that there are adverse effects on this
important and large population.
In my testimony, I've also summarized a group of
epidemiological studies, some quite old now, that address the
health effects of power plants directly in communities, such as
those we did 20 years ago in the Chestnut Ridge region in
western Pennsylvania. While these studies are quite different
in their methods, my overall interpretation of this evidence is
again a warning of adverse effects of coal-fired power plants
on public health in surrounding communities.
So in summary, the health effects of air pollution have
been a focus of research for nearly a half century. There's no
doubt, there's clear evidence from the past that high levels
can have direct and evident adverse effects on health. While
air pollution constitutes a complex mixture with many toxic
components, the evidence consistently indicates that airborne
particles in our outdoor environments and urban environments
have adverse effects on health associated with premature
morbidity and mortality.
Based on our knowledge of how particles penetrate in the
lung, these effects likely reflect the deposition of smaller
particles in the size range encompassed by PM2.5.
These particles have many man-made sources, vehicles, industry
and electric power generation by coal-fired power plants.
Epidemiological studies of communities located adjacent to such
plants show that the health of community residents can be
harmed, although links to specific products of combustion
cannot be readily made.
I would note that risk assessment approaches that build on
these epidemiological studies have proved quite useful for the
purpose of estimating the burden of disease and ill health
associated with power generation in coal-fired power plants. So
I will say that while research is ongoing, as it should be and
as it always will, the indications at this time provide a clear
warning of a threat to public health.
Thank you.
Senator Jeffords. Thank you.
Our next witness is Robert M. O'Keefe, vice president of
Health Effects Institute, in Boston, MA. Please proceed.
STATEMENT OF ROBERT O'KEEFE, VICE PRESIDENT,
HEALTH EFFECTS INSTITUTE
Mr. O'Keefe. Thank you, Mr. Chairman. It is a pleasure to
appear before you and other members of the committee to share
the perspective of the Health Effects Institute on what we have
learned and what we still need to learn about the health
effects of particulate matter.
For the record, I am Robert O'Keefe, vice president of HEI.
HEI is an independent, not-for-profit research institute funded
jointly and equally by the U.S. Environmental Protection Agency
and industry. We provide impartial, high quality science on the
health effects of air pollution.
In 1997, the U.S. EPA promulgated a new set of National
Ambient Air Quality Standards for fine particulate matter. At
that time, there were nearly 40 short-term studies that found a
link between daily changes in air pollution and daily increases
in death and illness. There were two long-term studies, the
Harvard Six Cities Study and the American Cancer Society study,
which found that those who lived in the most polluted cities
had between a 17 percent and a 26 percent increase in the risk
of premature death relative to those who lived in the least
polluted cities.
At the same time, there were a number of outstanding
questions about these studies, including the individual short-
term studies that were done by diverse investigators using
different methods. Would a more systematic study find the same
results? Could other pollutants, which occur along with PM, be
responsible for the increased mortality? And importantly, could
the Harvard Six Cities study and the American Cancer Society
study stand up to intensive scrutiny and analysis from new
independent investigators?
Since 1997, substantial new research has been undertaken to
advance our understanding. HEI alone has invested in some 40
epidemiology, exposure and toxicology studies to test the
validity of these original assumptions. Key among HEI's work
have been two efforts, the National Morbidity, Mortality and
Air Pollution Study, or NMMAPS, which Dr. Samet alluded to, and
the re-analysis of the landmark Six Cities and the American
Cancer Society studies.
NMMAPS is a systematic study of air pollution, weather and
mortality in the 90 largest cities across the United States
conducted under HEI oversight by John Samet and his colleagues
at Johns Hopkins University. It found a consistent relationship
between PM and mortality in these 90 large cities, and it was
not affected when other pollutants were added to the model. At
the same time, this first nationwide analysis found what may be
differences in levels of effects across regions of the United
States that really remain to be understood.
Recently, NMMAPS investigators identified an issue with the
statistical software package used by air pollution and other
investigators to analyze data. In NMMAPS, this result modified
the study effect estimates. With HEI peer-reviewed alternative
approaches employed, they found that the mean effect estimate
in the studies shifted from a .4 percent increase in mortality
for every 10 micrograms of PM10 to a .2 percent
increase. Importantly, these results remain statistically
significant, and the PM effect still does not appear to be
affected by other pollutants. A further report of these efforts
will be provided in January.
Looking to the long-term side, in response to requests from
Congress, the U.S. EPA and industry, HEI convened a detailed
re-analysis of the Six City Study and the American Cancer
Society studies. Given full access to all data, HEI's expert
panel selected an entirely new team of investigators who
assured the quality of the original data by conducting a
thorough data quality audit, and tested the results against
alternative analytic approaches suggested by scientists and
critics alike, without substantively altering the original
findings of an association between mortality and fine particles
and sulfates (a form of particles created in the atmosphere
primary from coal combustion).
At the same time, the re-analysis found that the effects on
mortality appeared to increase for those with less education
and lower socioeconomic status. Also that there was an
increase, or an association between sulfur dioxide and
mortality that persisted when other variables were included.
As we look ahead over the longer term, it will be important
to understand whether some particles and some sources can
contribute higher toxicity and should be more stringently
controlled. To address questions of particle characteristics,
the HEI review committee in April 2002 issued the second in its
HEI perspectives series titled, ``Understanding the Health
Effects of Components of the Particulate Mix--Progress and Next
Steps.'' This review, which I have provided to your staff,
summarizes recent HEI and other research and lays out
recommended future approaches to understand the differential
effects of particles and sources.
In conclusion, we've made much progress over the last 5
years, especially in testing the validity of the short-term and
the long-term epidemiology studies. We have tested a number of
possible confounding factors and alternative explanations. In
reviewing the latest evidence, the HEI review committee
concluded ``Epidemiologic evidence of PM's effects on mortality
and morbidity persist, even when alternative explanations have
been largely addressed.''
At the same time, some new questions have arisen. In the
near term, it's necessary to complete the re-assessment of
NMMAPS and identify, reassess and provide peer review for other
key studies. Over the longer term, important questions remain
concerning the comparative toxicity of different components and
sources of the PM mixture. Only through a systematic effort to
test and compare the toxicity of these diverse pollutants will
we be able to have the best chance of targeting future
strategies to control emissions that are the most toxic.
Thank you.
Senator Jeffords. Thank you. Very helpful testimony.
Dr. Wyzga is the technical executive and manager of Air
Quality, Health and Risk, Electric Power Research Institute,
Palo Alto, CA. Please proceed.
STATEMENT OF RONALD E. WYZGA, TECHNICAL EXECUTIVE AND PROGRAM
MANAGER, ELECTRIC POWER RESEARCH
INSTITUTE
Mr. Wyzga. Thank you, Mr. Chairman. Thank you very much for
inviting me.
Let me introduce myself a little bit by saying that I work
for EPRI, which is a non-profit, tax-exempt organization that
performs scientific research for the public benefit. I have
worked in environmental health research for over 30 years,
published over 50 peer reviewed papers on the topic of air
pollution and health, and served on numerous EPA and other
scientific panels. The comments that I present today reflect my
personal views and judgments as a scientist.
It was suggested that I highlight some of EPRI's most
important research findings on the health effects of air
pollution. I will summarize these in my oral comments, but my
written comments provide further detail.
There are a large number of scientific studies that report
a link between air pollution and health. From this literature,
I conclude that there is a clear association between air
pollution and health in the United States at current pollution
levels. Among the various pollutants examined, the strongest
associations between air pollution and health are for
particulate matter, or PM. However, as yet there is no accepted
biological explanation for the link between the pollution found
in the United States today and observed health responses.
Particulate matter is made up of thousands of different
components from a wide variety of sources. There are limited
data on the toxicity of the different components of particulate
matter. Few toxicology experiments have been undertaken
examining the different fractions of PM. But those that have
been undertaken have found significant difference in the
toxicity for different components.
The EPRI ARIES, or Aerosol Research Inhalation Epidemiology
Study project was designed specifically to examine the toxicity
of the various components of PM and air pollution. This study,
conducted in metropolitan Atlanta, in conjunction with U.S.
DOE, several universities and others, is unique in terms of the
number of air quality parameters measured and the number of
health effects examined. In the study, we're looking at both
potential death and disease associations with air quality. For
mortality of people over 65 years old, results today show a
statistically significant association for several pollutants.
These include PM2.5, PM10, carbon
monoxide and oxygenated hydrocarbons, which are carbon
containing compounds largely in gaseous form. Indeed, when we
look at several analyses, the latter, the oxygenated
hydrocarbons, appear to be most consistently associated with
death.
The results for disease show that in general, different
components of air pollution are associated with respiratory
effects than with cardiovascular effects. The respiratory
effects appear to be associated with PM10 and the
gaseous pollutants, carbon monoxide, ozone, and nitrogen
dioxide. On the other hand, cardiovascular effects appear to be
associated with fine particles, carbon monoxide and nitrogen
dioxide. However, the only fractions of PM2.5 that
show any statistically significant associations with
cardiovascular effects are particles that contain organic and/
or elemental carbon. There is little evidence of any health
effects tied to acid aerosols, and no significant associations
have been found between any health effect and total soluble
metals, ultra fine particles or sulfates.
Recent concerns have been raised about some of the past
applications of statistical tools to understand the air
pollution-health relationship. In fact, EPA has delayed its
current review of particulate matter effects until the matter
is more fully understood. Our research suggests that
differences and yet other statistical methods can lead to
different results. It is important to understand the influence
of the different statistical methods on the results of the
analyses of this air pollution-health relationship.
We now have a better understanding of the relationship
between average outdoor levels of pollution and personal
exposure. We see, however, that there can be short periods of
time when these exposures to pollution can be extremely high.
We need to identify these time periods and determine whether
these short periods of exposure, a very high exposure, can
impact health.
There is also a great need for additional studies that
focus upon the specific components of particulate matter and
the relationship to human health. I would urge others, such as
the EPA, to consider studies similar to ARIES in other
geographic areas. We also need laboratory studies to examine
the toxic effects of specific components and the sources of PM,
so that we can identify the pollution components and sources
that most impact public health. We need to develop a better
biological understanding of the link between pollution found in
the United States today and health effects.
Finally, statistics is a wonderful tool, and has allowed us
to make considerable progress in understanding the relationship
between pollution and health. But it is important that we fully
understand the implications and potential weaknesses associated
with the tools that we use.
To recap, my main points are as follows. No. 1, air
pollution likely impacts the health of individuals in the
United States today. No. 2, particulate matter is a likely
candidate to explain these impacts. No. 3, in our studies, when
health effects are associated with fine particles, our research
points strongly to particles that contain carbons as the agents
of concern. In most United States cities, carbon containing
particles are the largest component by weight. Gaseous
pollutants may still, however, be of health concern. There is a
great need to apply alternative statistical methods in
analyzing data and to understand the influence of these
methods. There is a strong need to identify with more certainty
those specific components of air pollution that cause health
effects. Finally, decreasing the non-toxic part of particulate
matter will not necessarily reduce health effects.
In summary, our latest results show that when health
effects of fine particles are seen, these effects are most
strongly associated with specific particle constituents. This
may be an important factor in designing control strategies.
Further research is needed to replicate and extend these human
health studies in other geographic areas. Laboratory toxicology
studies are also needed to gain a better biological
understanding of the observed effects.
I would like to thank the committee for the opportunity to
present my views, and would be pleased to respond to questions.
Senator Jeffords. Thank you very much.
Mr. Rose, you're next. executive director of the Green
Mountain Club in guess where--Waterbury Center, VT. Nice to
have you here.
STATEMENT OF BEN ROSE, EXECUTIVE DIRECTOR,
THE GREEN MOUNTAIN CLUB, INC.
Mr. Rose. Chairman Jeffords, thank you for the opportunity
to testify.
My name is Ben Rose, I'm not a scientist. The Green
Mountain Club is a 93-year-old, member-supported, not-for-
profit hiking club in Waterbury Center, VT, headquartered
there. The mission of the club is to make the Vermont Mountains
play a larger part in the life of the people by protecting and
maintaining the Long Trail, which is as you know a hiking trail
which runs the length of Vermont from Massachusetts to Quebec.
The southern 100 miles of the Long Trail are part of the
Appalachian National Scenic Trail from Georgia to Maine, and
the Green Mountain Club is one of 31 local volunteer-based
clubs which maintain specific sections of the AT. The
Appalachian Trail is also the longest linear national park in
the world.
Although most people do not associate scenic mountain
ranges with smog, some of the dirtiest air in the United States
is in our mountains. Mountain air contains fine particulate
matter, largely sulfates derived from burning coal, as well as
nitrates and ozone, by-products of power plant emissions. The
air is often at its worst in the higher elevations. This is of
concern to the Green Mountain Club and our sister hiking clubs
as the Long Trail, the Appalachian Trail and thousands of miles
of other trails beckon hikers up into the air, which we now
know is of poor quality a significant amount of time.
We are also concerned at The Green Mountain Club because we
hire dozens of young people each summer as ridge line
caretakers, to work on the trails and to protect the unique
alpine plants that exist only on some of our highest summits.
These folks spend months at high elevations. They see lots of
haze, and they breathe it, too.
In August 2002, during a stretch of severe haze,
particulate matter and ozone smog in New England, three hikers
were treated with oxygen near the summit of Mount Washington,
New England's highest peak, only tens of miles from Waterbury,
VT. Staff and hikers there reported nausea and shortness of
breath. During the same period, vistas from New England
mountaintops were shrouded in a thick, white haze. These are
the same pollutants that are causing acid rain, forming
sulfuric and nitric acids responsible for the high mortality
rates in our high elevation spruce and fir forests.
While many studies which will be referenced by the medical
researchers on this panel have linked particulate matter to
asthma, heart attacks and premature death, little attention has
been paid to the health effects of fine particulate matter
specifically on healthy people exercising outdoors, such as
hikers. The most important study to date on the subject was
conducted during the summers of 1990 to 1992, when scientists
from the Harvard School of Public Health and the Appalachian
Mountain Club studied the lung responses of hikers climbing
Mount Washington in New Hampshire to fine particulate matter
and ozone pollution.
Hikers' lung functions were measured using spirometers
before and after their hikes. At the same time, ozone and
PM2.5 concentrations were measured in the air at the
top and bottom of the mountain. Data was also collected
regarding past respiratory history and fitness levels, current
smokers were excluded from the study.
In a nutshell, the results show that healthy hikers
experienced measurable declines in short-term lung function
related both to ozone and to PM2.5. Although the
PM2.5 correlation did not meet the 95th percentile
confidence level, the study provided credible evidence that
both ozone and particulate matter independently impact hikers'
lungs. It's important to note that the air quality during the
study was only moderate, with 1-hour and 8-hour ozone levels
and PM2.5 well below the Federal standards. This
suggests that even moderate levels of these pollutants reduced
the lung function of healthy people exercising outdoors.
The study recommended ``Physicians, public health officials
and the general public should be made aware of the potentially
serious health effects of low-level air pollutants, not just in
urban and industrial regions, but specifically on those who
engage in outdoor recreation in various wilderness areas.''
Currently, a similar study is being conducted in the Great
Smoky Mountains National Park, in cooperation with the National
Park Service and Emory University. Air quality in the Great
Smoky Mountains is significantly worse than the air quality
observed during the Mount Washington study. The Great Smokies
have experienced 140 days of unsafe air quality over the past
four summers.
Senator Jeffords. Four summers totaling 140 days?
Mr. Rose. Yes.
Senator Jeffords. Thank you.
Mr. Rose. Old, dirty power plants are the largest source of
fine particulate air pollution in the region, accounting for
half or more of the fine particulate matter and most of the
sulfate deposition in the Appalachians. This means that these
same plants are responsible for most of the haze and the acid
rain as well.
Many coal-burning plants in the region and upwind were
exempted under the Clean Air Act, and have not yet installed
sulfur dioxide scrubbers or NOx catalysts, even though the
technology has been available for many years. Sulfur dioxide
and nitrogen oxide from power plants form sulfates and nitrate
particles that can be suspended in the air for weeks and
transported hundreds of miles downwind into our wilderness
areas, forests and parks.
Grandfathered coal plants are endangering public health,
not only to those living in cities and industrial areas, but
also to those of us who exercise in and enjoy the outdoors. As
a hiking club, we promote the benefits of outdoor exercise and
fresh mountain air. Yet we know that those who recreate in the
mountains are being exposed to unhealthy air. In conclusion,
current air quality and national energy policy allow unsafe
levels of fine particulate matter pollution in the air of
Vermont, of northern New England and of the entire Appalachian
Mountain chain that is harmful to our lungs and those of our
children. People throughout the Eastern United States look to
the mountains for clean, fresh air. If they can't find it in
Vermont, where can they go?
We respectfully ask the Senate of the United States to act
in support of aggressive measures to clean up power plants as
embodied in S. 556, and to reject measures that would weaken
the Clean Air Act. Thank you.
Senator Jeffords. Thank you for your excellent testimony.
Our last witness is Dr. Jonathan Levy, assistant professor
of Environmental Health and Risk Assessment, Department of
Environmental Health, Harvard School of Public Health, Boston,
MA.
STATEMENT OF JONATHAN LEVY, ASSISTANT PROFESSOR,
ENVIRONMENTAL HEALTH AND RISK ASSESSMENT, DEPARTMENT OF
ENVIRONMENTAL HEALTH, HARVARD SCHOOL OF PUBLIC HEALTH
Mr. Levy. Thank you, Mr. Chairman, and thank you for giving
me the opportunity to speak before you today. As you mentioned,
I am an assistant professor of environmental health and risk
assessment, and I am a member of the environmental science and
engineering program, as well as the Harvard Center for Risk
Analysis.
I appear before you today as a risk assessor who has
evaluated the current evidence about the health impacts of
power plant emissions in multiple recent analyses. My comments
will focus on the implications of the health literature for
risk calculations, with more detail provided in my written
materials.
As a risk assessor, I believe that decisions about
alternative policies for controlling power plant pollution
should be based in part on a comparison of the benefits and
costs of those policies, considering the magnitude and
distribution of both benefits and costs. In quantifying
benefits, premature mortality associate with fine particles
invariably contributes a large portion of the benefits, so I
focus on this literature today.
I believe that there are three crucial questions that must
be considered. No. 1, Is there a threshold below which no
health effects of PM2.5 are found, and if so, where
is that threshold? No. 2, Do all types of particulate matter
have similar health impacts, or are some particles more toxic
than others? No. 3, Which is related to one and two, would
alternative control strategies have significant impacts on the
magnitude or distribution of particulate matter health impacts?
On the first point, multiple recent studies have addressed
this question and have found no evidence of a threshold to
date. For example, the American Cancer Society cohort study
found that mortality risks decreased as PM2.5 levels
decreased, down to levels below 10 micrograms per cubic meter.
Similarly, multiple investigations of time series data found no
evidence of thresholds for daily changes in PM levels down to
extremely low concentrations. The observational evidence
therefore supports the assertion that mortality risks will
continue to decrease as PM2.5 levels decreased.
The question of relative toxicity is far more difficult to
answer from a quantitative perspective. When considering power
plant emissions, this is essentially a question about sulfate
toxicity. In the American Cancer Society and Six Cities cohort
mortality studies, the two most comprehensive and
representative studies to date, sulfates show a similar
association with mortality as PM2.5 with an
association also seen with sulfur dioxide.
When considering the time series mortality literature,
sulfate has been associated with premature mortality in the
majority of studies. I would therefore conclude that while it
would be anticipated that different types of particles would
have different effects, there is not sufficient information to
conclude that sulfates differ from average particles in either
direction. It should be noted that this is not the same as
concluding that all particles are identical, but rather that
the best quantitative risk estimate at present is that sulfates
have similar effects as PM2.5 in general.
I address the distribution question in greater detail in my
written materials, but it is worth noting that there are
spatial gradients in particulate matter impacts from power
plants, and that when the health literature regarding
susceptible subpopulations is taken into account, these spatial
variations increased. At the same time, particulate matter from
power plants is transported a long distance. This makes the
exposure question national rather than local in scope.
The general conclusion I would draw is that different
policy structures will lead to different distributions and
exposures in health risks, and that careful consideration of
these distributions should be incorporated into any comparison
of control strategies.
Now, what does the health literature imply for the
magnitude of benefits from alternative controls? That PM
contributes to premature mortality and current concentrations
are above any population threshold, and any reductions in PM
concentrations will provide corresponding benefits. This means
that benefits can be quantified for benefit cost comparisons as
done in research studies by our research team, Abt Associates,
EPA and others. Combining the cohort mortality evidence cited
above with atmospheric models that we have analyzed and found
to be appropriate, Abt Associates estimated that power plant
emissions contribute to 30,000 premature deaths each year.
The EPA has estimated that the Clear Skies Initiative would
reduce this burden by about 12,000 deaths per year, with an
alternative straw proposal yielding benefits of 19,000 fewer
deaths per year. While these estimates are clearly uncertain, I
view the calculations as reasonable central estimates that
provide a crucial foundation for policy comparisons. Thus, it
is reasonable to assume that the Clear Skies Initiative would
provide substantial public health benefits, but that the EPA
straw proposal, which is similar to the Clean Power Act, would
increase those benefits on the order of 7,000 fewer premature
deaths per year.
Despite the quantitative uncertainties, the qualitative
conclusion that greater controls will lead to greater health
benefits appears robust, implying that choices between
alternative control strategies should depend on the incremental
cost and benefits of increased stringencies.
In conclusion, I thank you once again for allowing me to
speak here today, and I would be happy to answer any questions.
Senator Jeffords. Thank you again, for very, very helpful
testimony. I can't thank you all enough for helping us to
really get a better idea as to where we stand and what we must
and should do to help make our country more habitable and
safer.
I will now have some questions for you. Dr. Samet, how do
scientists determine that premature mortality and heart or lung
ailments are associated with air pollution and not other
factors, like diet or lifestyle?
Dr. Samet. Clearly, other factors do influence longevity
and health. But in the epidemiological studies, either the
daily studies, where such factors as lifestyle don't vary day
to day, just implicitly takes such factors into account. In the
Harvard Six Cities and the American Cancer Society studies, the
longer term studies, there was an effort to take account of
such lifestyle factors as smoking, obesity and some other
measures and that is done by collecting information about those
characteristics and then controlling for it in the analytical
approach used by the investigators.
Senator Jeffords. Mr. O'Keefe, I know you have another
engagement. So I will go to you next. What do you think are
some of the remaining gaps in knowledge regarding the health
effects of particulate matter pollution?
Mr. O'Keefe. Thank you. I think one of those has been
raised, and that's the important question of whether or not
there is a threshold below which particle effects exist or not.
As Dr. Levy pointed out, evidence presented in both time series
and studies of long-term effects have not demonstrated that
there is a threshold below which we see effects. That's an
important area of new work to follow up on, No. 1.
No. 2, that I alluded to earlier, as we look ahead to the
next generation of particulate matter research, is there an
ability to tie sources of particles and types of particles with
particular health impacts? This type of analysis, which won't
be done soon, and is not something we need to do before taking
action during the regular course of events, if current
understanding leads us to that, would really allow us over the
longer term, looking forward to best target control measures,
to focus on sources that may be most responsive, to focus on
sensitive subpopulations that might be most toxic, and perhaps
to do so in a very cost-effective manner.
Senator Jeffords. Thank you.
Dr. Levy, in your testimony you cite several studies that
distinguish the health effects of power plant emissions from
natural causes like wind-blown dust. Could you please elaborate
on those findings?
Mr. Levy. There are a number of studies in which it was
tried to determine which species of particulate matter have
greater health effects. Some of those, like the ones that Dr.
Wyzga mentioned, measure a number of different constituents,
sulfates, elemental organic carbon, dust and other elements,
and try to look at the effects of those. Others try to take
elemental data and combine them to try to attribute them to
certain sources.
So one example of the latter study was based on the Harvard
Six Cities data, where they looked at a number of different
elements and then combined them to look at, to attribute them
to coal sources, to residual fuel oil, to automobiles, to dust
and so forth. What they found is particles from motor vehicles
and from coal were significantly associated with premature
death, whereas crustal particles were not. That's consistent
with what a number of different studies have found, really
indicating that the combustion-based fine particles seem to
have greater health implications than crustal particles.
Senator Jeffords. Thank you. Mr. Rose, have you found that
visitors to the Green Mountains express concern over pollution
haze and reduced vistas? Do they feel robbed of their
opportunity to see what they wanted to see?
Mr. Rose. Yes. This is anecdotal, of course, but I do talk
to a lot of hikers and visitors. I hear a lot of people express
disappointment at hazy vistas. I was out quite a bit this
summer and I saw some days that were clear days with a lot of
haze. Other people, especially people who have been coming to
the Green Mountains for a long time, comment on the same thing,
that generally, visibility, even on clear days, is reduced.
There is a general sense that air quality in the mountains is
being impacted.
Senator Jeffords. Thank you.
Mr. Wyzga, your testimony on the ARIES study relies heavily
on draft results but does not reference published peer-reviewed
articles. When will the final results of the ARIES study be
published?
Mr. Wyzga. The results based on 1 year's data have been
published, and they are attachment A that I submitted to my
testimony. Final results on 2 years' worth of data, manuscripts
are in preparation. They will be submitted to peer review
publications, I'm guessing, within the next month. I am asking
the investigators to get them in as soon as possible and I
think it's imminent.
Senator Jeffords. Thank you.
Dr. Samet, you and your colleagues performed a new analysis
of the NMMAPS study. What are the important conclusions of the
study that remain unchanged by re-analysis?
Dr. Samet. Qualitatively, the conclusions are unchanged. I
think Bob O'Keefe already alluded to the quantitative change in
our sort of national average estimate, which dropped by half
when we made some changes in the statistical tools used. The
same patterns were there, seemingly a higher effect of
particles in the northeast region of the United States. The
greater effect for deaths from cardiovascular and respiratory
diseases presumably reflect in the greater susceptibility or
vulnerability of people with heart and lung disease to
particles than for other causes. Again, an association with
particles that was robust to control for other pollutants. I
think those would be the principal findings.
Senator Jeffords. Dr. Levy, the NAS recently issued a
report concluding that EPA's mortality estimates appropriately
referenced long-term cumulative studies. What are the mortality
estimates from the power plant risk assessments based?
Mr. Levy. The ones that I referenced by Abt Associates and
by EPA and by our research team were based on the long-term
cohort mortality studies. There are a few of those studies
available. What is generally used by myself, Abt Associates and
others are estimates from the American Cancer Society study in
part because it's the largest, most scrutinized study to date.
It also has risk estimates that are slightly lower than those
found from the Harvard Six Cities study, so it reflects a
somewhat conservative interpretation of the literature.
Senator Jeffords. Mr. Rose, with environmental effects
aside for the moment, could you tell us a little more about how
severe pollution days affect the ability of volunteers to
maintain trails, and how pollution might affect your business,
tourism and the local economy as well?
Mr. Rose. Well, again I would say, ``yes, that we can
foresee a day when many of our volunteers won't go out.'' In
point of fact, in the last few years we've seen hiker days flat
or declining in many parts of the State. We speculate as to why
that's happening. Part of it is weather related, and it
fluctuates from year to year. Part of it is because it's been
so hot in southern New England that people are probably home in
front of their air conditioners.
We actually saw a big slug of hikers come out over Labor
Day weekend this year, I believe because people had stayed home
all summer and said, ``Wow, the summer got away from us, it was
really hot.'' What's true for hikers is true for volunteers.
I should note that the average age of Green Mountain Club
members and logically, of the volunteers who are a subset of
those members, is 52. It makes sense that at that point in
people's lives they have some time to give back to the trail,
and are able to participate as volunteers. We see a lot of our
best trail maintainers are people in their 60's and 70's. We
have a lot of people who are models of good, healthy aging in
the Green Mountain Club and in other hiking clubs. Those folks
breathe hard when they're going up the trail.
So when we see that air quality is having an impact on
people when they hike, the same is certainly true for
volunteers, and it would have an impact on the long-term health
of the trails that give people access, sure.
Senator Jeffords. Mr. O'Keefe, you mentioned a number of
factors causing particulate matter toxicity. Would you tell us,
in your opinion, which of these is being addressed rigorously
by current regulations and which need further regulatory
attention or research?
Mr. O'Keefe. Well, you really raised the key question that
the scientific community is working very hard to answer. The
current National Ambient Air Quality Standards are mass based
standards. By taking that approach, they act to reduce
particles more broadly across the large spectrum with
PM10, PM2.5 and smaller.
Within that, there are numbers of questions about which
type of particle within that range could be most toxic or not.
There are carbon particles, there are sulfate particles. There
are biogenic particles, there are different metals that travel
with particles. This area is very much an active area of
research. I alluded to an understanding of the active agents in
particulate health effects. They could help protect public
health in the most cost-effective manner.
I will add that a mass-based standard, although it doesn't
necessarily fire the bullet with ultimate precision, does have
measurable effects in reducing health impacts.
Senator Jeffords. Mr. Wyzga, despite the clear linkage
between particulate pollution from utilities and adverse health
effects and death, you are recommending that this committee
consider the culpability of power plant emissions. Would all
the ARIES study researchers agree with your policy?
Mr. Wyzga. I really can't speak for the researchers. I
think that what we're finding in the area that is important is
we're finding that there are health effects at contemporary
levels of pollution in the United States. I think that's
something that's being widely found. We're seeing that the
gases are important, as well as particles. That means we can't
ignore the gases. We're seeing that different particles have
different toxicities. I think it's important to really
basically replicate this study in lots of other areas and see
whether or not we find similar results.
I think when we look at that, we're going to be able to
target specifically those pollutants that are causing our
health problems. I think it's clear, and I would agree with
what others have said, if we look at the data, there doesn't
appear to be any threshold. It looks as if we're seeing health
effects down to background and zero levels of pollution. People
are dying. It's a potentially very serious--looks like a
serious public health problem. To get the results, we've got a
lot more work to do in terms of targeting those specific
sources and pollutants that are going to give us the biggest
bang for the buck. I would urge that everybody work together to
resolve this issue.
Senator Jeffords. Thank you. Dr. Samet, isn't it true that
long-term studies examining the combined effects of chronic and
acute exposure would generally yield estimates on an order of
magnitude higher than the short-term studies, such as NMMAPS?
Dr. Samet. I think one of the difficult areas where we have
a signal from the long-term studies that, in terms of the
effect of particles on mortality, it's about 10 times that we
see in the daily time series. I would again--both estimates are
in the wrong direction, that is, they're signaling an effect of
air pollution on mortality, either short term or long term. We
haven't quite been able to rationalize why we're seeing a
seemingly larger effect on the longer term than on the shorter
term. Actually, I think there will be further research, there's
certainly further research on this. This is an area of research
need, but it's hard to harmonize these two pieces of evidence
at present.
Senator Jeffords. Dr. Levy, you completed new research this
year that for the first time ever shows the disproportionate
health impacts from power plant pollution on poor minority
populations. Would you elaborate on your findings?
Mr. Levy. Sure. This is a study that we did based on the
Washington, DC. area, looking at five power plants in and
around, in about a 50-mile radius around Washington, DC. What
we did is look to the health literature, to the existing
epidemiological studies that focused on susceptible
subpopulations. So as was alluded to earlier, the American
Cancer Society cohort study looked at the effect of educational
attainment on the risk of mortality from air pollution, and
found that those with less than high school education were much
more affected than those with higher education. Similarly, it's
well known that asthma prevalence, for example, and asthma
emergency room visit rates are much higher in African American
populations.
So they took that as a foundation for our analysis to
quantify the magnitude and distribution of health benefits that
would accrue if emission controls were placed on these five
power plants, and found essentially that when you take the
susceptibility into account--what's been documented in the
health literature--that the picture changes somewhat. So if you
look at the example of mortality, the method that is usually
used is to assume that everyone implicitly is equally at risk.
The reason, we looked at 25 percent of people had less than
high school education, so normally you would assume that, well,
25 percent of benefits would accrue in that population. In
fact, when we took account of the information about
susceptibility, more than half of the benefits accrued in that
group. You can tell a similar story for cardiovascular hospital
admissions among diabetics and asthma emergency room visits as
a function of race.
So we were building on the epidemiology, so clearly, more
epidemiology, more studies of this type are needed to be able
to provide a more robust picture. But we think this is an
important direction to consider to better target who are the
susceptible subpopulations, that are their characteristics.
That can potentially help us guide our control strategies.
Senator Jeffords. This is a question for all of you. As you
know, I have been deeply concerned to learn about the health
studies that show tens of thousands of lives are ended
prematurely each year due to air pollution, especially from
power plants. Do any of you know of other peer reviewed studies
that would dispute these findings? We'll start with Dr. Samet.
Dr. Samet. Not really, no. I think there is substantial
literature, that I think have just voiced a consensus on what
it shows now.
Mr. O'Keefe. I would agree.
Mr. Wyzga. I think there are lots of studies out there that
show relationship between air pollution at levels of experience
today and health effects.
Senator Jeffords. Mr. Rose.
Mr. Rose. I guess I would say that there is a large and
growing literature in any literature where there's hundreds or
thousands of studies, there are going to be some studies with
negative findings. But I think the vast majority of studies are
pointing to the direction that power plant air pollution leads
to the premature mortality you described.
Senator Jeffords. Next question for everyone. Will reducing
SOx and NOx by about 75 percent make progress in reducing the
problem of particulate matter? Do you have any ideas for other
ways that Congress can help minimize this public health threat?
Dr. Samet.
Dr. Samet. I guess the first part is the easier one.
Clearly, SOx and NOx contribute to the formation of secondary
particles, and we think in fact these particles that have been
discussed are possibly critically important to health effects.
The second question, you know, what else can be controlled and
how we should control it, I don't think lends itself to a quick
answer. I think in fact you mentioned the gains that we've made
in cleaning up the air with the Clean Air Act, and actually
1970, 1990 and prior attempts to clean the air.
I think the remainder of controls beyond what we've
discussed, we'll have to take a look at what are the other
contributors to particles. I think in line with what some of
the other commenters said, are there particular sources that
are associated with particles having particular toxicity that
we should hone in on? I think the scientific community is
probably not quite ready yet to say what those other sources
might be.
Mr. O'Keefe. I might answer that there are things that have
been done recently in other areas. Being from a health effects
institution, I won't delve too deeply into this area. But I
would observe EPA's heavy duty diesel rule that was put into
place and will significantly reduce particulate emissions from
heavy duty diesel vehicles through the reduction in sulfur
content in fuels and through innovative new technologies, which
include traps and NOx absorbers.
So there do seem to be opportunities here for moving
forward.
Senator Jeffords. Thank you.
Mr. Wyzga.
Mr. Wyzga. First of all, I think that clearly, both SOx and
NOx form particulates, sulfates and nitrates. I think that one
of the things that is--particularly, some of the work we've
seen--NO2 itself is a pollutant that may still have
concerns. But don't forget the gas. That's one message I have.
Second, in our work, we don't see health effects per se of
nitrates and sulfates. We see a stronger signal for some of the
carbon containing particles. We don't really know what the
sources are. One very interesting thing in Atlanta is that we
see a very strong link between carbon containing particles and
cardiovascular effects, emergency room admissions to the
hospital.
These effects are only occurring in the winter. They're not
occurring in the summer. We'd love to see what are the sources
of carbon containing particles in Atlanta in the winter, and to
our surprise, the No. 1 source was actually wood burning. The
No. 2 source were diesel. Diesel contributes in the summer, but
we're not seeing health effects in the summer.
I don't know if we're seeing this because of differences in
pollution sources or differences in behavior, people may spend
more time indoors in the winter in Atlanta. I don't think we
have the answer yet, and I think we have to look a lot further
into it.
But I think we really have to do a lot more work to sort of
hone in on these things. There are a lot of studies out there.
Another important source that sort of surprised me a lot in
that area, in the summer months in Atlanta, whether it's
causing health effects or not, is meat burning. There are a lot
of fast food restaurants out there, and they don't have big
chimneys. They're in our city.
Senator Jeffords. Mr. Rose.
Mr. Rose. I understand the question to be, Is there
anything else we can do? Of course, there's a lot that we can
do in national energy policy and transportation policy. We need
more stringent, in my opinion, vehicle efficiency standards. We
need alternative fuels. We need renewables. People understand
that it's all part of the same policy problem. The Clean Air
Act exempted existing coal plants from requirements to retrofit
with best available technology. Here it is, decades later, and
the status quo is costing lives. I coach soccer on Sunday
mornings, just like a lot of your other constituents. The
parents on the sidelines agree that there's a lot of asthma,
and people understand that the Clean Air Act hasn't realized
its potential and that you're here fighting a much bigger game.
Senator Jeffords. Mr. Levy.
Mr. Levy. I think my comments will echo what a lot of the
other presenters have said. I think it's clear that these
SO2 and NOx controls from power plants, both because
of the fine particle benefits, the ozone benefits, even the
gaseous pollutant benefits, will clearly confer a major public
health benefit. It's an important direction to head in. I think
in terms of another direction, there isn't as obvious of a low
hanging fruit, in my mind, but I think Bob was right to talk
about heavy duty diesel on the transportation side as one of
the other major contributors to combustion-related particles,
to ozone, to a lot of urban air pollution. I think there's a
lot of room for improvement in that direction as well.
Senator Jeffords. Last question. In your opinion, would the
current particulate matter standards be sufficiently able to
meet the Clean Air Act mandate of protecting sensitive
populations with an adequate margin of safety? If not, do you
think EPA should consider a stricter standard?
Mr. O'Keefe. I have to leave now.
[Laughter.]
Dr. Samet. I have to leave before him.
[Laughter.]
Dr. Samet. I'll just comment. This language is very
difficult to interpret. In fact, I have chaired a committee of
the American Thoracic Society, which wrote a statement on what
constitutes an adverse health effect of air pollution, where we
grappled with some of the complexity of the language of the
Clean Air Act, in part around the issue that you raised. I
think in terms of achieving an adequate margin of safety, that
implies that we can identify a level below which effects don't
occur. We can then build in the margin of safety and say, ``set
a standard here.''
What I think you've heard from myself and others along the
table today is that we can't yet identify such a point, that
the evidence, we're finding a signal of an adverse effect, even
as we go down to the lower levels we have today.
So the answer right now is, we haven't identified a
``safe'' level of effect that would allow us to meet that
margin of safety statement in the Clean Air Act.
Senator Jeffords. Mr. O'Keefe.
Mr. O'Keefe. I think the threshold issue is a tough one for
this particular pollutant. I know, and appreciate the nature of
your question. I will say that almost as we speak, EPA, its
Clean Air Act Scientific Advisory Committee and many others are
sifting through the weight of the evidence that's emerged over
the last 5 years to draw exactly, to make exactly this
determination. That process is about two-thirds of the way
through, and I will wait to hear what they say, actually.
Senator Jeffords. Mr. Wyzga.
Mr. Wyzga. I guess first of all, I'm going to get in
trouble if I make a policy statement with my employer. So this
isn't a policy statement. But I think one of the premises of
the Clean Air Act is that there is some threshold below which
there are no health effects. We're having difficulty basically
identifying such a threshold. So I think we might have to sort
of think, are there new ways to set standards.
Senator Jeffords. Interesting.
Mr. Rose.
Mr. Rose. Sorry, but I don't know.
Senator Jeffords. Mr. Levy.
Mr. Levy. Batting cleanup, I have to once again echo some
of the other comments. I agree that what the health literature
is showing, seemingly no threshold, or at least that we have
not yet gotten down to a threshold, the concept of trying to
then set a threshold that adequately protects sensitive
subpopulations seems a bit contradictory. I agree with Ron's
statement that maybe we need to start thinking of alternative
ways of formulating these standards.
Senator Jeffords. Well, thank you all very much. This has
been extremely helpful to the committee. I appreciate all the
work that went into being here today. That concludes our
session. Thank you.
[Whereupon, at 3:16 p.m., the committee was adjourned, to
reconvene at the call of the chair.]
[Additional statements submitted for the record follow:]
Statement of Jonathan M. Samet, M.D., M.S., Professor and Chairman,
Department of Epidemiology, Bloomberg School of Public Health, Johns
Hopkins University
INTRODUCTION
Senator Jeffords and members of the Senate Committee on Environment
and Public Works, thank you for the opportunity to speak with you today
concerning the health effects of particulate matter and particularly
fine particulate matter arising from power plant emissions. This topic
has been a focus of my research for several decades. As background, my
training includes medicine with specialization in internal medicine and
subspecialization in pulmonary diseases. I also have a Masters degree
in epidemiology from the Harvard School of Public Health and my career
has been spent in the settings of academic medicine, largely at the
University of New Mexico School of Medicine, and of academic public
health, now at the Johns Hopkins Bloomberg School of Public Health
where I am professor and chair of the Department of Epidemiology.
Over 20 years ago, I first carried out research directed at the
health effects of particulate matter. These studies were carried out in
Steubenville, Ohio, where we assessed how air pollution affected the
numbers of persons needing care for respiratory and other diseases in
the emergency room of the community hospital, and in western
Pennsylvania, where we carried out a series of studies to assess the
effects of large, coal-fired power plants on the respiratory health of
women and children in the surrounding communities. With colleagues at
Harvard and Marshall University, I participated in an extensive study
of the respiratory health of children in Kanawha County, West Virginia,
following the Bhopal episode. Since 1994, with colleagues at Johns
Hopkins, my research has focused on the effect of airborne particles
and other pollutants on mortality. Our most recent work, the National
Morbidity, Mortality, and Air Pollution Study (NMMAPS) uses publicly
available data from the 90 largest cities in the United States to
provide a national picture of the effect of particles on mortality,
both total and from cardiac and respiratory causes of death. I have
also conducted large studies directed at indoor air pollutants, such as
tobacco smoke and nitrogen dioxide.
Because of my research interest in particulate air pollution, I
have served as a consultant member of the Clean Air Scientific Advisory
Committee (CASAC) of the Environmental Protection Agency's Science
Advisory Board for the mid-1990s review of the Particulate Matter (PM)
National Ambient Air Quality Standard (NAAQS) and again for the review
now in progress. I also chair the National Research Council's Committee
on Research Priorities for Airborne Particulate Matter, which set out a
national plan for research on particulate matter in its first report in
1998. The committee is now evaluating progress since 1998 in reducing
scientific uncertainties concerning particulate matter.
WHAT IS PARTICULATE MATTER AND HOW ARE WE EXPOSED TO IT?
The air that we breathe contains myriad particles that come from
numerous sources that are both natural, e.g., the abrasive action of
wind, and are generated by human activity, e.g., the burning of coal in
a power plant. There are both outdoor and indoor sources, such as
cigarette smoking and cooking. The particles in air are a complex
mixture reflecting the diversity of these sources; they vary in
chemical composition, shape, and size. The particles include sand,
pollen and other biological materials, carbonaceous material from
combustion, and particles formed secondarily from chemical and physical
transformations of gaseous emissions from combustion and other sources.
Particles are often described by their size, which is a key
determinant of how long they remain suspended in the air and also of
whether they will reach the lung when inhaled and where they will
deposit in the lung. The size of particles is described by their
aerodynamic diameter in microns, a measure that is based on equivalence
to a particle having a standard size and mass. Typically, in urban air,
the distribution of particles by size is trimodal. The largest size
mode, generally above about 5 microns in aerodynamic diameter,
primarily contains dust and other particles that have been resuspended
by wind and mechanical action, e.g., motor vehicles, and also some
large biological particles, such as pollens. The intermediate size
mode, centered below one micron contains primarily products formed by
combustion including primary particles emitted directly by the sources,
such as diesel soot, and particles formed secondarily. There may be a
third size mode of very tiny particles that are the immediate
consequence of combustion.
These size characteristics are quite relevant to health
considerations since larger particles tend to be filtered out by
defense mechanisms in the nose and upper airway, and only the smaller
particles, less than approximately 3.5 microns reach the lung. The
sites of deposition within the lung also depend on size; the smaller
particles tend to penetrate more deeply, reaching the smallest airways
and the lung's alveoli or air sacs. Thus, injury to the lungs and other
organ systems from particulate air pollution is thought to result
primarily from the smaller particles. There is also concern, however,
that persons with asthma may be adversely affected by responses to the
larger particles that reach the upper airway.
The Environmental Protection Agency has set NAAQS for progressively
smaller size fractions of particles, reflecting evolving understanding
of how particles affect health and also measurement capability. The
first particle standard was for Total Suspended Particles (TSP), which
encompassed nearly all airborne particles. That standard was replaced
in 1987 by a standard for PM10 and the new standard for
PM2.5 was added with the 1997 NAAQS revisions. The shift
towards measuring and regulating smaller size fractions is well
justified by scientific knowledge of the behavior of particles in the
respiratory system. The size fractions for PM are inclusive: that is
PM2.5 includes all particles below the 2.5 micron diameter
cut-point and PM10 does include the PM2.5 size
fraction. Consequently, studies of PM10 can inform
understanding of the health effects of PM2.5.
We are exposed to particles in all places where we spend time, both
indoors and outdoors. While we spend relatively little time outdoors,
particles in outdoor air, particularly the finer particles, do
penetrate indoors. Consequently, the doses of particles from outdoor
sources like power plants are received not only while we are outdoors,
but also while we are indoors.
HOW DO PARTICLES AFFECT HEALTH?
We inhale about 10,000 liters of air per day containing countless
particles. Fortunately, the lung does have mechanisms for removing
particles and for detoxifying them but these mechanisms may not be
sufficient if the particles are too numerous or have high toxicity. The
general mechanisms of particle toxicity appear to reflect the
inflammatory responses that they evoke in the lung following
deposition. There may be more specific mechanisms at play as well,
reflecting immune responses to antigens or the actions of carcinogens
in particles. While scientific understanding of these mechanisms is
still evolving, we have evidence that particles stimulate the lung's
inflammatory cells, leading to the release of various mediators that
continue the inflammatory process. Particles are thought to possibly
affect the heart by release of mediators into the circulation. The
severity of the response to particles and perhaps the nature of the
response itself are likely to vary with key characteristics of the
particles, such as metal content, acidity, or the various organics that
are adsorbed on the surfaces of particles. Better understanding of the
toxicity--determining characteristics of particles is one of the
research priorities set by the National Research Council's Committee.
WHAT DO WE KNOW ABOUT THE HEALTH EFFECTS OF PARTICULATE MATTER?
The health effects of air pollution have been investigated for
about half-century, following the extraordinary air pollution disasters
in Donora, Pennsylvania in 1948 and in London in 1952. These and other
episodes of evident excess mortality and morbidity showed that high
levels of air pollution could quickly damage the public's health. Over
the 50 years that the health effects of air pollution have been
investigated, we have carried out many studies in communities using
epidemiological approaches to assess the health effects of air
pollution, including particulate matter. One challenge faced by
researchers in investigating the health effects of air pollution is to
attempt to separate the effects of one pollutant from the others that
co-exist in the pollutant mixture that is present in the air that we
breathe. Nonetheless, substantial evidence has now accumulated, much of
it summarized in the references that I have cited in the bibliography
for this testimony.
I will focus on summarizing the more recent literature, as the
earlier studies were generally carried out at levels of air pollution
that are higher than measured today and the characteristics of the air
pollution mixture have changed over time, as sources have changed both
in their numbers and characteristics. Because researchers often use the
monitoring data collected for regulatory purposes, most of the recent
evidence on PM draws on measures of PM10, rather than
PM2.5 as a national monitoring network for PM2.5
has only recently been implemented.
A 1996 review by the American Thoracic Society offered a summary of
literature to that time, synthesizing the information concerning major
pollutants and listing health effects among the populations at greatest
risk (Table 1). The more recent scientific literature includes
thousands of papers on particles, so that I can only offer a general
summary of the findings. The following general conclusions can be
offered based on the now available evidence:
Daily Mortality: Beginning in the early 1990s, many
studies carried out in the United States and other countries have
linked daily mortality counts to levels of air pollutants, and
specifically to particles, on the same or recent days. More recently,
several multi-city studies, including our NMMAPS project, have
confirmed the association of particulate air pollution with mortality
from all causes and from cardiovascular and respiratory causes. As
anticipated, based on the concept that persons with chronic
cardiovascular and respiratory diseases are vulnerable to air
pollution, the effect of particles is stronger for cardiac and
respiratory causes than for total mortality. In the multi-city
approach, we are able to take better control for other pollutants in
assessing effects of particles than with the single city approach. In
NMMAPS, we estimate that the effect of PM10 on mortality is
an increment of about 0.2% for each 10 microgram per cubic meter
increase in concentration. Chicago, for example, has about 100 deaths
daily; with a 20 microgram increment in concentration, about 0.5
additional deaths are projected on average. While we and others have
recently needed to update our findings because of a previously
unidentified statistical issue, the findings are proving robust in
showing increased daily mortality associated with air pollution.
Long-Term Mortality: The daily time-series studies
indicate an effect of particles on mortality rates, but the data do not
provide an indication of longer-term consequences. Longer-term follow-
up or cohort studies provide information relevant to the question of
the extent of life-shortening resulting from particulate air pollution.
The strongest evidence on this question comes from two studies: the
Harvard Six Cities Study and the American Cancer Society's Cancer
Prevention Study II (CPS II). Both studies show that persons living in
more polluted communities tend to have higher mortality rates over the
approximately two decades that the participants in these studies have
been observed. These analyses take into account factors that might
artificially introduce an apparent association with air pollution, such
as smoking and socioeconomic status. The initial findings from the two
studies were replicated with a re-analysis organized by the
Environmental Protection Agency. The general pattern of findings
suggests that the increased mortality observed in these studies is most
strongly associated with particulate air pollution. Several other
studies have now been reported and others are in progress. Gaining a
better understanding of the long-term effects of particulate air
pollution is another of the research priorities of the National
Research Council's committee.
Hospitalization and Emergency Care: Using the time-series
approach, a number of investigators have addressed associations of air
pollution with daily counts of hospitalizations or emergency room
visits. The files of the Medicare system have been used frequently for
this purpose, as they provide nearly complete coverage of persons over
65 years of age in most communities. For example, Drs. Joel Schwartz
and Antonella Zanobetti at the Harvard School of Public Health and
members of the NMMAPS team, analyzed Medicare data from 14 United
States cities. They have found associations of PM10 with
hospitalization for cardiovascular diseases and chronic obstructive
pulmonary diseases. There have been similar findings from other
investigators in the United States, Europe, and other countries.
Cardiovascular Disease: Persons with chronic
cardiovascular diseases, particularly coronary heart disease, have been
considered as susceptible to air pollution exposure, including to
particulate air pollution. A series of recent studies indicate possible
adverse cardiac effects of particulate air pollution, although the
evidence is still somewhat mixed and preliminary. Studies show that air
pollution may adversely affect the heart's rhythm and even trigger
potentially fatal rhythm disturbances in high-risk persons with
implanted defibrillation devices. There are supporting experimental
studies.
Asthma: Persons with asthma are made susceptible to air
pollution by the responsiveness of their lungs to environmental
triggers. Studies that monitor the health status of persons with asthma
on a day-to-day basis indicate that particulate air pollution can have
adverse effects.
In summary, there is now substantial epidemiological evidence
linking particulate air pollution to adverse health effects, ranging
from increased mortality and life-shortening to medical morbidity in
people who are susceptible because they have a chronic heart or lung
disease. While few of these studies have incorporated PM2.5
as the primary exposure indicator, our understanding of particle
dosimetry in the lungs implies that particles in the respirable size
range are responsible for these effects. Emissions associated with
power plants contribute to the PM2.5 mass in many locations
in the U.S.
STUDIES OF THE IMPACT OF POWER PLANTS
Studies have been carried out that directly address the health
effects of coal-fired power plants on surrounding communities. In a
recent review, a graduate student in the Department of Epidemiology of
the Bloomberg School of Public health identified 16 publications (Table
2) describing the findings of such studies. These source-directed
studies considered the effects of multiple pollutants, including
particulate matter. In general, their findings indicate adverse effects
of coal-fired power plants on the public health in surrounding
communities.
SUMMARY AND CONCLUSIONS
The health effects of air pollution have been a focus of research
for nearly a half century, giving clear evidence that the high levels
of the past had obvious adverse effects on health and providing a
warning that air pollution continues to adversely affect public health,
even at the lower levels of outdoor air pollution today. While air
pollution constitutes a complex mixture with many potentially toxic
components, the evidence consistently indicates that airborne particles
in urban environments have adverse effects on health, causing premature
mortality and excess morbidity. Based on our knowledge of how particles
penetrate into the lung, these effects likely reflect the deposition of
smaller particles in the size range encompassed by PM2.5.
These particles have many man-made sources, including vehicles,
industry, and electric power generation by coal-fired power plants.
Epidemiological studies of communities located adjacent to such plants
show that the health of community residents can be harmed, although
links to specific products of combustion cannot be made. Risk
assessment approaches can be used for the purpose of estimating the
burden of disease and ill health associated with power generation in
coal-fired power plants.
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BIBLIOGRAPHY
1. Air Pollution and Health. Holgate ST, Samet JM, Koren HS,
Maynard RL (eds). San Diego: Academic Press, 1999.
2. American Thoracic Society, Committee of the Environmental and
Occupational Health Assembly. Health effects of outdoor air pollution.
Part 1. Am J Resp Crit Care Med 1996; 153: 3-50.
3. American Thoracic Society, Committee of the Environmental and
Occupational Health Assembly, Bascom R, Bromberg PA, Costa DA, Devlin
R, et al. Health effects of outdoor air pollution. Part 2. Am J Resp
Crit Care Med 1996; 153: 477-498.
4. Samet JM, Zeger S, Dominici F, Curriero F, Coursac I, Dockery D,
et al. The National Morbidity, Mortality, and Air Pollution Study
(NMMAPS). Part 2. Morbidity and mortality from air pollution in the
United States. 2000. Cambridge, MA: Health Effects Institute.
5. Samet JM, Zeger S, Dominici F, Dockery D, Schwartz J. The
National Morbidity, Mortality, and Air Pollution Study (NMMAPS). Part
I. Methods and methodological issues. 2000. Cambridge, MA: Health
Effects Institute.
6. Anderson HR, Spix C, Medina S, Schouten J, Castellsague J, Rossi
G, et al. Air pollution and daily admissions for chronic obstructive
pulmonary disease in 6 European cities: results from the APHEA project.
Eur Respir J 1997; 10: 1064-1071.
7. Katsouyanni K, Schwartz J, Spix C, Touloumi G, Zmirou D,
Zanobetti A, et al. Short-term effects of air pollution on health: A
European approach using epidemiologic time series data: The APHEA
protocol. J Epidemiol Community Health 1995; 50 (Suppl 1): S12-S18.
8. Katsouyanni K, Touloumi G, Spix C, Schwartz J, Balducci F,
Medina S, et al. Short-term effects of ambient sulphur dioxide and
particulate matter on mortality in 12 European cities: results from the
APHEA project. Br Med J 1997; 314: 1658-1663.
9. Katsouyanni K, Touloumi G, Samoli E, Gryparis A, Le Tertre A,
Monopolis Y, et al. Confounding and effect modification in the short-
term effects of ambient particles on total mortality: results from 29
European cities within the APHEA2 project. Epidemiol 2001; 12: 521-531.
10. Spix C, Anderson R, Schwartz J, Vigotti M, Le Tertre A, Vonk
JM, et al. Short-term effects of air pollution on hospital admissions
of respiratory diseases in Europe. A quantitative summary of the APHEA
study results. Arch Environ Health 1997; 53: 54-64.
11. Sunyer J, Spix C, Quenel P, Ponce de Leon A, Ponka A,
Barumamdzadeh T, et al. Urban air pollution and emergency admissions
for asthma in four European cities: The APHEA project. Thorax 1997; 52:
760-765.
12. Touloumi G, Samoli E, Katsouyanni K. Daily mortality and
``winter type'' air pollution in Athens, Greece--a time series analysis
within the APHEA project. J Epidemiol Community Health 1996; 50 (Suppl
1): S47-S51.
13. Touloumi G, Katsouyanni K, Zmirou D, Schwartz J, Spix C, Ponce
de Leon A, et al. Short-term effects of ambient oxidant exposure on
mortality: a combined analysis within the APHEA project. Am J Epidemiol
1997; 146: 177-185.
14. Zmirou D, Schwartz J, Saez M, Zanobetti A, Wojtyniak B,
Touloumi G, et al. Time-series analysis of air pollution and cause-
specific mortality. Epidemiol 1998; 9 (5): 495-503.
__________
Statement of Ben Rose, Executive Director, The Green Mountain Club,
Inc.
Senator Jeffords, members of the committee, thank you for the
opportunity to testify. My name is Ben Rose. I am the Executive
Director of the Green Mountain Club, a 93-year-old member-supported
not-for-profit hiking club headquartered in Waterbury Center, Vermont.
The mission of the Green Mountain Club is to make the Vermont mountains
play a larger part in the life of the people, by protecting and
maintaining the Long Trail (a hiking trail which runs the length of
Vermont from Massachusetts to Quebec) and by fostering, through
education, the stewardship of Vermont's hiking trails and mountains.
The southern 100 miles of the Long Trail are part of the Appalachian
National Scenic Trail (AT) from Georgia to Maine, and the Green
Mountain Club is one of 31 local clubs, which maintain specific
sections of the AT. The Appalachian Trail is the longest linear
national park in the world.
Although most people do not associate scenic mountain ranges with
smog, some of the dirtiest air in the United States is in our
mountains.\1\ Mountain air is thick with fine particulate matter--
largely sulfates derived from burning coal--as well as nitrates and
ozone, byproducts of power plant nitrogen oxides emissions.
Unfortunately, we know that the air is often at its worst in the higher
elevations. This is of concern to the Green Mountain Club and sister
organizations, as the Long Trail, Appalachian Trail and thousands of
miles of other trails beckon hikers up into the poor quality air.
---------------------------------------------------------------------------
\1\ ``Out of Sight: Haze in our National Parks: How Power Plants
Cost Billions in Visitor enjoyment Clean Air Task Force for Clear the
Air, September 2000. Available at: http://www.clnatf.org/publications/
reports/out--of--sight.html. See also American Hiker, March/April
2002).
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We also are concerned because we hire dozens of young people each
summer as ridgeline caretakers, to work on the trails and to protect
the unique alpine plants that exist only on our highest summits. These
folks spend months at high elevations. They see lots of sulfate haze,
and breathe it, too.
In August 2002, during a stretch of severe haze, particulate matter
and ozone smog in New England, three hikers were treated with oxygen
near the summit of Mt. Washington, New Hampshire's highest peak, only
tens of miles from the border with Vermont. Staff and hikers there
reported nausea and shortness of breath.\2\ During the same period,
vistas from New England mountaintops were shrouded in a thick white
sulfur laden haze. These are the same pollutants that cause acid rain,
forming sulfuric and nitric acids responsible for the high mortality
rates in our high elevation spruce and fir forests.\3\
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\2\ Georgia Murray, Staff Scientist, Appalachian Mountain Club.
Personal communication. September 2002.
\3\ Dr. L. Bruce Hill, Senior Scientist, Clean Air Task Force.
Personal communication. September 2002.
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While countless studies--many referred to by the medical
researchers on this panel--have linked particulate matter to asthma
attacks, heart attacks and premature death, little attention has been
paid to the health affects of fine particulate matter on healthy people
exercising outdoors, such as hikers.\4\
---------------------------------------------------------------------------
\4\ ``Coal blamed for haze'', Atlanta Journal-Constitution. Friday,
August 30, 2002
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The most important study to date on the subject was conducted
during the summers of 1990 to 1992, when scientists from the Harvard
School of Public Health and the Appalachian Mountain Club (AMC) studied
the lung responses of hikers climbing Mount Washington in New Hampshire
to fine particulate matter and ozone pollution.\5\
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\5\ ``Effects of Ozone and Other Pollutants on the Pulmonary
Function of Adult Hikers'' by Korrick, Neas, Dockery, Gold, Allen,
Hill, Kimball, Rosner, Speizer. Environmental Health Perspectives,
Volume 106 Number 2, Feb. 1998. Conducted 1990-92, Pinkham Notch, New
Hampshire, White Mountain National Forest by Harvard School of Public
Health, Brigham and Women's Hospital and Appalachian Mountain Club.
http://ehpnet1.niehs.nih.gov/docs/1998/106p93-99korrick/korrick-
full.html
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Hikers' lung functions were measured using spirometers before and
after their hikes. At the same time, ozone and PM2.5
concentrations were measured in the air at the top and bottom of the
mountain. Data was also collected regarding past respiratory history
and fitness levels, and current smokers were excluded.\6\
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\6\ Ibid.
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In a nutshell, the results showed that healthy hikers experienced
measurable declines in short-term lung function.\7\ related to ozone
and as well as PM2.5.
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\7\ Ibid.
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Note that, although the PM2.5--correlation did not
technically meet the 95th percentile confidence level, the study
provides credible evidence that both ozone and particulate matter
independently impact hiker's lungs. It is important to note that the
air quality during the study was only moderate, with 1-hour and 8-hour
ozone levels and PM2.5 well below the Federal standards.
This means that even moderate levels of these pollutants reduce the
lung function of healthy people exercising outdoors.
The study recommended:
``Physicians, public health officials and the general public
should be made aware of the potentially serious health affects
of low-level air pollutants, not just in urban and industrial
regions but specifically on those who engage in outdoor
recreation in various wilderness areas.'' \8\
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\8\ Ibid.
Currently a similar study is being conducted in the Great Smoky
Mountains National Park in cooperation with the National Park Service
and Emory University. Air quality in the Great Smoky Mountains is
significantly worse than the air quality observed during the Mount
Washington study. The Great Smokies have experienced 140 days of unsafe
air quality over the past four summers.\9\
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\9\ Source: Jim Renfro, Air Quality Specialist, Great Smoky
Mountains National Park, National Park Service.
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Old dirty power plants are the largest source of fine particulate
air pollution in the region, accounting for half or more of the fine
particulate matter and most of the sulfate deposition in the
Appalachians.\10\ This means that these same plants are responsible for
most of the haze and acid rain as well.\11\
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\10\ According to the National Park Service's ``Air Quality in
National Parks'' 2nd edition, sulfate particles formed from sulfur
dioxide emissions associated with fossil fuel combustion (mostly from
electric generating facilities) accounts for up to 60%-80% of
visibility impairment in eastern parks compared to only 30-40%
visibility impairment in western states.
\11\ Abt Associates (2000). Out of Sight: The Science and Economics
of Visibility Impairment, Bethesda, MD. Available at: http://
www.clnatf.org/publications.
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Many coal burning plants in the region and upwind were exempted
under the Clean Air Act (CAA) and have not yet installed sulfur dioxide
scrubbers or NOx catalysts,\12\ even though the technology has been
available for many years.
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\12\ National Park and Conservation Assoc. (NPCA) Fact Sheet.
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Sulfur dioxide and nitrogen oxides from power plants form sulfates
and nitrate particles that can be suspended in the air for weeks and
can be transported hundreds of miles downwind into our wilderness
areas, forests and parks.
Grandfathered coal plants are endangering public health not only to
those living in cities and industrial areas but also to those of us who
exercise in and enjoy the outdoors.
As a hiking club, we promote the benefits of outdoor exercise and
fresh mountain air and yet we know that those who recreate in the
mountains are being exposed to unhealthy air.
Current air quality and national energy policy allow unsafe levels
of fine particulate matter pollution in the air of Vermont, of Northern
New England, and of the entire Appalachian Mountain chain that is
harmful to our lungs and those of our children. People throughout the
Eastern United States look to the mountains for clean fresh air. If
they can't find it in Vermont, where can they go? We respectfully ask
the Senate of the United States to act in support of aggressive
measures to clean up power plants as embodied in S. 556 and reject
measures that would weaken the Clean Air Act.
Thank you.
__________
Statement Dr. Ronald E. Wyzga, EPRI, Palo Alto, CA
INTRODUCTION
I am Dr. Ronald E. Wyzga. I work for the Electric Power Research
Institute (EPRI), in Palo Alto, California. EPRI, a voluntarily-funded
501(c) (3) non-profit organization operating in the public interest, is
almost 30 years old and has an annual budget of approximately $350
million. EPRI's Environment Sector has an annual budget of
approximately $50 million; this makes EPRI one of the largest
privately-funded health and environmental research organizations in the
world. Within the Environment Sector, I am responsible for air quality
research, including research on the health effects of air pollution.
The results of EPRI's health and environmental research is published
and made publicly available, usually through the peer-reviewed
scientific literature.
I began my research career working on the relationship between
health and air pollution (specifically particulate matter) while a
graduate student at the Harvard School of Public Health, and my
doctoral dissertation in biostatistics in 1971 addressed this topic.
Since then I have been actively engaged in environmental health issues.
I have co-authored a book and published over 50 peer-reviewed papers. I
have served on and chaired subcommittees of the National Research
Council (NRC), National Academy of Sciences. I currently serve on the
NRC Committee on Research Priorities for Airborne Particulate Matter. I
have also served on or chaired several EPA Science Advisory Board
Committees, and I have been appointed a Fellow of the American
Statistical Association. The comments that I present today reflect my
personal views and judgments as a scientist who has worked in this area
for over thirty years. These comments should not be construed to be the
official opinion of my employer or of any associate.
SUMMARY
There are a large number of scientific studies that report a link
between air pollution and human health. I have personally been involved
in some, and EPRI has supported many more. The majority of these
studies link particulate matter with health effects; however, some of
these studies do not show an association with health, and other studies
implicate gaseous pollutants in addition to, or in place of particulate
matter. In any consideration of the health and air pollution issue, it
is important to keep in mind that air pollution is a complex mixture of
many different types of gases and particles. Discerning specific
causative agents is a challenge we in the scientific community are
working to address. Today I want to highlight some of the work that
EPRI has recently been involved in to provide you with some of our
latest results.
There have been several major facets to our research:
1. It is important to understand which specific components of air
pollution are associated with health impacts. In studies undertaken to
date, the strongest associations between air pollution and health are
with particulate matter. In studies which include particulate matter
(PM) and other pollutants, such as ozone and carbon monoxide (CO), in
their analyses, PM is most consistently associated with health
responses; there are, however, some exceptions where other pollutants,
especially carbon monoxide, are most highly associated with health
responses. Very few studies have considered a comprehensive set of the
pollutants, especially the different chemical constituents of
particulate matter, in their analyses. This is because monitoring
programs currently only measure a small number of compounds.
There are limited data on the toxicity of the different components
of particulate matter. Few toxicology experiments have been undertaken
examining the different fractions of PM, but those that have been done
have found differences in toxicity for the different fractions. Other
results show that the total quantity of PM by weight does not explain
biological responses. Certain components in PM appear to explain the
toxicity of PM more readily than total PM.
2. The EPRI ARIES (Aerosol Research Inhalation Epidemiology Study)
project was designed to examine the toxicity of the various components
of PM and air pollution. This study is unique in terms of the number of
air quality parameters measured and the number of health effects
examined. This study, undertaken in Metropolitan Atlanta in conjunction
with several universities, U.S. Department of Energy, and others,
characterized the air quality on a daily or more frequent basis for
over one hundred air quality variables. This characterization,
accompanied by a suite of epidemiological studies, allowed us to
examine the influence of the various components of air pollution on a
variety of health outcomes.
In general, the ARIES study is finding that different components of
air pollution are associated with respiratory effects than are
associated with cardiovascular effects (heart-related effects). More
explanation of the preliminary results is given in the detailed
testimony, but in summary, the respiratory effects appeared to be
related to the gaseous pollutants (carbon monoxide, ozone, and nitrogen
dioxide) and cardiovascular effects appeared to be associated with
PM-2.5 (particles 2.5 microns in size and smaller) and
carbon monoxide. However, the only fraction of PM-2.5 that
showed any association with the cardiovascular effects were particles
containing organic and elemental carbon. It is the PM-2.5
fraction that has been at the center of attention as the potential
cause of negative health impacts. For total mortality, the pollutants
most consistently associated with premature death are oxygenated
hydrocarbons, substances that to date have had limited study.
3. EPRI has initiated smaller ARIES-like studies in Baltimore and
St. Louis to determine whether the results from Atlanta can be
replicated elsewhere. A major effort is also underway to launch a study
very similar to ARIES in Chicago.
4. A major toxicology effort will start soon in which the effects
of coal combustion emissions will be investigated by exposing animals
to diluted, aged emissions from power plants. This effort will provide
important data to help evaluate different combinations of fuel type,
control technologies, and burning configurations. The results of this
work will be particularly useful to help inform and complement the
research underway at the National Environmental Respiratory Center in
Albuquerque, which is also evaluating the toxicity of emissions from
diesel and gasoline engines, as well as wood smoke.
5. EPRI has also been active in trying to understand the
implications of alternative statistical methods used in the analyses of
epidemiological data. Given the recent discovery that the applications
of statistical software have led to erroneous results in some pollution
health studies, the EPA is delaying its review of particulate matter
health effects. Other statistical analyses require judgments that can
impact their outcome. It is important to understand these potential
impacts.
6. EPRI has undertaken studies to understand the nature of exposure
to the various constituents of air pollution, including particulate
matter and its major constituents. We have found that there appears to
be a better association between personal exposure to particulate matter
and outdoor measured levels than there is for many of the gaseous
pollutants.
What is particularly important is that recent results suggest that
there are short periods of time (in specific environments) when
personal exposures to pollutants are much higher (by factors of 5 for
PM and over 50 for carbonaceous particles) than the levels that we
measure at our monitoring stations. We need to establish whether these
short-term peak exposures are related to health responses.
7. Our joint study with Washington University of some 50,000
Veterans was designed to answer the question of whether there are long-
term (chronic) effects associated with air pollution. In this study we
found that after adjusting for many other factors Veterans who lived in
cities with higher levels of nitrogen dioxide and very high ozone
levels died earlier than those living in cleaner cities. We could find
no such effect, however, when we examined particulate matter.
SCIENTIFIC ISSUES
There is a clear association between air pollution and health in
the U.S. at pollution levels we have experienced in the 1990s and
earlier. Several different types of epidemiological studies, undertaken
at a wide variety of locations, have found associations between air
pollution and human health effects in the U.S.. Among the various
pollutants examined, the strongest associations between air pollution
and health are for particulate matter (PM). Many of the earlier studies
(pre-1990s) considered just one or a limited number of pollutants; in
these studies, PM was frequently studied and found to be associated
with health effects. Later studies more frequently examined multiple
pollutants. Most of these studies also found associations between PM
and health effects, although a subset of the studies found greater
associations between health effects and other pollutants, especially
carbon monoxide (CO). In interpreting the results of these studies,
several factors must be taken into account. First, the pollution
measurements used in these studies were made at outdoor monitoring
sites; these are not necessarily representative of personal exposures
to these pollutants. We now have some limited data on the differences
between personal exposures and outdoor measurements. These differences
are not the same for every pollutant measured, leading to possible
statistical impacts on the results of the analyses of the relationships
between air pollution and health.
Second, studies can only consider pollutants for which measurement
data are available, and only a few pollutants/substances are generally
measured. If the pollutant(s) that are truly responsible for health
effects are not measured, then other pollutants that are measured and
present at the same time as the responsible pollutants can be
associated statistically with health effects. In such cases what we
measure and use in our analyses could be a surrogate for something that
is not measured. In all of our study results we need to keep this in
mind. The only way to overcome this issue is to measure as many
components of air pollution as possible, hopefully including the true
culprit (or culprits), which only detailed analyses can reveal.
There is as yet no accepted biological explanation for the link
between the levels of pollution found in the U.S. today and observed
health responses. Past research has focused on epidemiological
studies--observational studies on humans going about their normal
activities. Laboratory research, which has been limited to date, can
focus on establishing the underlying biological mechanisms that can
cause negative health effects. Several possible biological explanations
have been put forth to explain the results from epidemiological
studies, and recent laboratory results support some of these
hypotheses. For example, one study appeared to show that blood clotting
can increase with exposure to higher levels of fine particulates. If
this occurs, it could be an explanation for why some heart disease
effects are related to fine particulate levels in epidemiological
studies. At this time, I believe that the most likely scenario is that
a combination of explanations is responsible for the effects observed,
with different mechanisms acting for different air pollution/PM
components. Different mechanisms may also be acting in susceptible
individuals, such as asthmatics or those with hypertension. Clearly,
much more work is needed to gain insight into the mechanism(s) of PM
action.
Particulate matter is a complex mixture and its composition varies
over time and place. Some of these major components (e.g., organic
matter) contain hundreds of chemical compounds. The most important
fractions of PM are carbon-containing particles and sulfate in the
Eastern U.S., with carbon-containing particles being more important in
urban areas. In the Western U.S., nitrates are more important and
sulfates are generally less important.
There are limited data on the toxicity of the different components
of particulate matter. Several PM components have been hypothesized to
play a role in toxic responses, including acid aerosols, metals,
sulfates, nitrates, ultrafine particles (very tiny particles much
smaller than the PM-2.5 particles), bioaerosols (including
pollen and mold spores), diesel exhaust particles, and organic
compounds. Toxicological and human exposure evidence suggests that acid
aerosols do not contribute much to the adverse respiratory outcomes
observed in epidemiological studies; however, acid components have not
been assessed thoroughly with respect to potential cardiovascular
effects. Metals have been shown in multiple studies to cause cell
injury and other effects. Particle size, specifically the ultrafine
fraction, may also be important in the development of health effects. A
number of studies have investigated the effects of ultrafine particles
and have found lung inflammation and other respiratory effects,
although it appears that chemical composition may play a key role in
the responses observed. Cardiovascular and systemic effects of
ultrafine particles have been investigated to only a limited extent.
Bioaerosols are not considered to account for the reported health
effects of ambient PM as their concentrations are very low and health
effects can occur at times when bioaerosol concentrations are low.
Toxicological evidence is accumulating to suggest that diesel PM can
exacerbate the allergic response to inhaled allergenic material.
Finally, the organic compounds associated with PM have been little-
studied from a toxicological perspective, although they represent a
substantial portion of the mass of ambient PM (10-60% of total dry
mass). Other fractions of PM, including sulfates and nitrates, appear
to be of less concern.
In a recent draft report, the Netherlands Aerosol Programme
concluded: ``Based upon current toxicological and human clinical
knowledge: water, sea salt, ammonium sulfate, ammonium nitrate, and
probably non-crystalline crustal material too, can be considered an
inert part of PM-10 at the ambient concentrations in the
Netherlands.'' This report has not yet been finalized, and the
conclusions are still under discussion.
In order to more fully understand which components of PM are
responsible for the health effects observed, additional toxicological
studies must be conducted. Studies which examine the toxicity of
emissions from various sources of pollution can be informative in
identifying those pollutants (and sources) most highly associated with
health effects.
The EPRI ARIES study was designed to examine the toxicity of the
various components of PM and air pollution. This study is unique in
terms of the number of air quality constituents measured and the number
of health effects examined. The best way to increase our understanding
of the types of PM and air pollution that may be responsible for the
health effects observed in other studies is to undertake a study in
which all of the potentially relevant fractions of PM are measured.
Traditionally we only measure what is required because of local, state
or Federal regulations. On occasion a research study may measure a
larger array of air pollutants, but it is rare to have a large number
of constituents measured systematically over an extended period of
time. ARIES addresses this need through detailed air quality
characterization for a period of over two years and through undertaking
several epidemiological studies to relate air quality characteristics
to health effects. Appendix A provides further details about ARIES.
Extensive daily--and in some cases continuous--measurements were
made for all of the particle size fractions and constituents about
which concerns have been raised. At the same time, several
epidemiological studies were undertaken to examine the potential health
effects of the various constituents. Initial results from the
analytical team focused on the subset of air pollution measures tied to
the major existing hypotheses about the pollution/health relationship.
Results based upon the first year's data have been published in peer-
reviewed journals; two years of data have now been analyzed and
manuscripts based upon analyses of two years worth of data are now
under preparation for peer review. The draft results are very
informative, and I would like to share them with you.
These results are complex and reflect a methodology that examined
pollutants individually. Analyses which consider several pollutants
simultaneously are planned and may help identify the pollution
components that are of greatest concern.
Several pollutants are statistically significantly
associated with mortality of those over 65 years old; they include
PM-2.5, PM-10, CO (carbon monoxide), and
oxygenated hydrocarbons. When alternative statistical models were
applied, the results were most consistent for oxygenated hydrocarbons,
a pollutant that has not previously been considered in air pollution
health studies.
Results are available for several morbidity (disease) measures
including emergency room admissions to Atlanta area hospitals,
unscheduled physician visits to a health maintenance organization
(HMO), and responses of defibrillator devices implanted in patients
with erratic heart rhythms. Preliminary analyses of heart rate
variability considered only PM-2.5 and not its components
nor gases. Based on these limited data, PM-2.5 was found to
be associated with statistically-significant changes in heart rate
variability.
Lung and respiratory problems were related to PM-10
and to pollutant gases including ozone, nitrogen dioxide, and carbon
monoxide.
Heart disease responses were much more likely to be
related to PM-2.5, carbon monoxide, and nitrogen dioxide.
Organic compounds were associated with several
cardiovascular effects.
When the components of PM-2.5 were considered,
the only ones found to be significant were elemental and organic
carbon.
There was little evidence of any health effects tied to
acid aerosols.
No associations were found between any health effect and
total soluble metals; additional analyses are planned to look at
individual metals.
No associations were found with ultrafine particles. Since
the concentrations of these particles appear to change so rapidly over
time and space, it is doubtful that the ARIES study could shed much
light on the effects of these particles. Nevertheless, their
concentrations are unrelated to the concentrations of other particle
fractions; hence it is unlikely that ultrafine particles can explain
the association seen with other particles.
No cardiovascular or respiratory effects were associated
with sulfates.
ARIES did not look at sources of pollution directly. We did,
however, undertake a source-attribution analysis of the organic
compounds in Atlanta. Cardiovascular effects were found in the winter
months only in this study. In the winter months, organic compound
concentrations were tied principally to wood smoke, although diesel
emissions were also a contributor. Diesel emissions were also a major
contributor to organic compounds in the summer months when no
cardiovascular effects were related to these compounds.
There is a great need for additional studies which focus upon the
specific components of particulate matter and examine their
relationship to human health. The ARIES study will provide an important
piece of evidence in understanding which fractions of PM and of air
pollution are the most important in affecting human health. ARIES
results are from one metropolitan area, Atlanta. Atlanta is a logical
place for a study; it has high pollution levels, many sources of
pollution, and no unique sources of pollution that would yield a unique
result. Nevertheless it is important to undertake similar studies in
other metropolitan areas. We are now engaged in similar, although more
limited, studies in St. Louis and Baltimore, where detailed monitoring
is underway. Much of this monitoring is funded by EPA's supersites
monitoring program. Undertaking such studies is expensive because the
air quality monitoring itself is costly; hence, governmental resources
to undertake such studies are critical.
Secondly, more laboratory studies are needed which examine specific
fractions of particulate matter and its toxicity. Since it would be
very costly and time-consuming to test all specific compounds
rigorously in laboratories, special protocols should be considered
which examine the mixture of pollutants associated with specific
sources. For example, studies are now underway at the National
Environmental Respiratory Center to examine the toxicity of emissions
from several sources. EPRI is planning some similar efforts, but
clearly more research is needed. There are a large variety of emissions
from different sources, and we need to learn how these emissions
interact with other pollution elements once they enter the environment
at large.
An ongoing committee of the National Research Council, of which I
am a member, will issue a report next year identifying the highest
priority research needs to inform particulate matter-health policy
issues.
The implications of the statistical methods used to investigate the
relationship between health and air pollution need to be fully
understood. A recent announcement by researchers at Johns Hopkins
University raised some issues about the past use of one particular
statistical approach and its related software. Fortuitously, at a
meeting of EPRI researchers with our advisors, it was decided to use
alternative statistical methods in our research, and we have examined
these methods thoroughly. We have found that, on occasion, ARIES
results, especially in the mortality analyses, can be influenced by
changes in the statistical approach even when the alternative
approaches are judged reasonable by statisticians. For example, carbon
monoxide (CO) was found to be statistically significantly associated
with deaths of those over 65 years old with one approach but not with
the other. Fortunately most results were similar across the various
approaches, but because there are some differences, it is important to
articulate and understand these differences.
CONCLUSIONS
1. Air pollution likely impacts the health of individuals in the
U.S. today.
2. Particulate matter is a likely candidate to explain these
impacts.
3. Not all fractions of particulate matter appear to be equally
toxic.
4. When health effects are associated with fine particles, our
research points strongly to carbon-containing particles as the agents
of concern; in most U.S. cities, carbon-containing particles are also
the largest particle component by weight.
5. Gaseous pollutants are still of concern and cannot be ignored.
6. There is a strong need to identify with more certainty those
specific components of air pollution which cause health effects.
7. We need to understand in more detail the personal exposure of
susceptible individuals to the various air pollution components. In
particular, we need to identify when and where peak exposures occur and
whether these peaks are important to health.
8. There is a great need to apply alternative statistical methods
in analyzing data and to understand the influence of a specific method.
9. Decreasing the non-toxic part of particulate matter will not
reduce health risks.
Appendix A
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Statement of Robert O'Keefe, Vice President, Health Effects Institute
Mr. Chairman, members of the committee, it is a pleasure to have
this chance to appear before you to share the perspective of the Health
Effects Institute on what we have learned and what we still need to
learn about the health effects of particulate matter. For the record, I
am Robert O'Keefe, Vice President of the Health Effects Institute, an
independent research institute funded jointly and equally by the US EPA
and industry to provide impartial and high quality science on the
health effects of air pollution.
THE DATA WE HAD IN 1997--SHORT AND LONG TERM EPIDEMIOLOGY
In 1997, the US EPA promulgated a new set of National Ambient Air
Quality Standards (NAAQS) for fine particulate matter
(PM2.5). In large measure, that action was based on two
types of epidemiology studies:
There were nearly 40 short-term studies that found a
statistical relationship between daily changes in air pollution and
daily small but relatively consistent increases in daily levels of
death, hospitalization, and illness (e.g. 1% to 2% increases in
mortality for every 10 microgram/cubic meter increase in
PM10);
Two long-term ``cohort'' studies--the Harvard Six Cities
Study and the Pope/American Cancer Society Study--that tracked selected
populations of people in a series of more- and less-polluted cities,
and found that those who lived in the most polluted cities had between
a 17% and 26% higher risk of premature death than those who lived in
the least polluted cities.
These studies suggested that a measurable portion of mortality and
respiratory and cardiac illness in the United States might be
attributable to fine particle air pollution, and based on them, EPA set
the new, more stringent NAAQS for PM2.5. At the same time,
there were a number of questions about these studies, key among them:
The individual short-term studies were done by diverse
investigators using somewhat different methods--would a more systematic
study find the same results?
Could other pollutants, which occur along with
PM2.5, be more likely to be responsible for the increased
mortality?
Did the deaths measured in these short-term studies
represent substantial losses of life years, or the advancing of death
for critically ill people by a few days?
Did the exposures measured in these studies--at central
air pollution monitors--accurately represent the exposures of people
who in general spend most of their time indoors?
Could the Harvard Six Cities Study and the American Cancer
Society Study, whose data had only been analyzed by the original
investigators, stand up to intensive scrutiny and analysis from new,
independent investigators? Could there be other differences between the
cities (e.g. differences in socioeconomic status or health care) that
would also explain the differences in mortality?
In addition to these questions about the epidemiology, there were
also questions about the relative toxicity of the many different
components of the complex PM mixture, and about the possible biological
mechanisms that might explain the epidemiology results, questions that
were laid out in a 1998 priority research agenda by the National
Academy of Sciences Committee on Research Priorities for Airborne
Particulate Matter.
WHAT HAVE WE LEARNED SINCE 1997?
Since 1997, substantial new research has been undertaken to advance
our understanding of the health effects of PM. As one part of the
larger effort undertaken, HEI has invested in some 40 epidemiology,
exposure, and toxicology studies to test the validity of the original
studies, and to begin to answer the remaining questions.
Key among HEI's work have been two efforts to determine the
validity of the short- and long-term epidemiology studies--the National
Morbidity, Mortality, and Air Pollution Study (or NMMAPS), and the
Reanalysis of the Harvard Six Cities and American Cancer Society
studies.
The National Morbidity, Mortality, and Air Pollution Study (or NMMAPS)
NMMAPS is a systematic study of air pollution, weather and
mortality in the 90 largest cities in the United States, conducted--
under the oversight, quality assurance procedures, and review of HEI--
by investigators at Johns Hopkins University. NMMAPS also included
similar analyses of air pollution and elderly hospitalization,
conducted in 14 U.S. cities by investigators at Harvard University.
In brief, this systematic and rigorous study found a consistent
relationship between PM10 and mortality in the 90 largest
cities of an approximately 0.4% increase in mortality for every 10
micrograms increase in PM10. This level of effect was about
half the size of that found in the earlier study, but as the graph in
my testimony illustrates, this effect was not substantially affected by
any of the other gaseous air pollutants. (See Figure 1) The NMMAPS
investigators also found that at least a portion of the mortality was
not solely frail people dying a few days early, but deaths advanced 30
days or more, and conducted analyses that suggested that errors from
using centrally-monitored air pollution to estimate exposure were not
likely to change the basic results.
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At the same time, this first nationwide analysis found differences
in levels of effect across the U.S., suggesting that other factors,
perhaps different mixes of pollution, could contribute along with
particles to the effect. (See Figure 2) Overall, the NMMAPS analyses
provided greater confidence in the results of the short-term
epidemiology.
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NMMAPS Update: This past Spring, members of the original team of
investigators from the Johns Hopkins School of Public Health were
conducting additional analysis on their findings of an association
between daily changes in air pollution and mortality. In the course of
testing these analyses against different assumptions and examining the
methods used, they identified a generally unknown aspect of S-Plus, a
statistical software package widely used by air pollution and other
investigators to fit general additive models (GAMs) to data. In NMMAPS
the investigators found that the result of using this approach was to
overstate the effect estimates in this study. Upon notification of
these new findings, HEI mobilized its NMMAPS Review Panel, Chaired by
Dr. Sverre Vedal of the National Jewish Medical and Research Center in
Denver. The panel provided initial peer review of the work of the
investigators to apply alternative analytic techniques to the data to
correct for this effect. In brief the Panel found that:
most of the raw, unadjusted individual city estimates
changed, with an increased number of estimates that were negative or
zero;
the mean effect estimate shifted from .41 increase in
mortality for every 10 micrograms increase in PM10 (in the
original study) to .21 percent (in the revised analysis);
in the revised results, PM10 effect estimates
are unaffected by the addition of co-pollutants such as ozone. (see
Figure 3 below)
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The HEI Panel continues to review the work of the investigator
teams from both Johns Hopkins and Harvard to recalculate key analyses
in the studies and provide comprehensive HEI peer review and
commentary. A final report is expected in January. In addition, a
number of other studies cited in EPA's current draft Criteria Document
for Particulate Matter also use this software and may be affected in
similar or different ways. To assess the nature and extent of this
effect, US EPA and its Clean Air Scientific Advisory Committee (CASAC)
at its July meeting set out a multi-step process to identify studies
central to the NAAQS and recalculate key analyses in these studies.
HEI, at the request of EPA and CASAC will play a central role in the
review of these analyses.
The Reanalysis of the Harvard Six Cities and American Cancer Society
Studies
In addition to NMMAPS, and in response to requests from Congress,
US EPA, industry and others, HEI convened a detailed reanalysis of the
Harvard Six Cities and American Cancer Society studies. Given full
access to the entire medical and air pollution data base from the
original investigators, HEI's Expert Panel selected an entirely new
team of investigators, conducted a detailed quality assurance audit of
the data and replication analyses, and then implemented a large number
of sensitivity analyses to test whether some other difference between
the most and least polluted cities (e.g. differences in the quality of
medical care) could explain the increased mortality risk.
In brief, the reanalysis assured the quality of the data,
replicated the original results, and tested those results against
alternative risk models and analytical approaches without substantively
altering the original findings of an association between sulfates (a
form of particles created in the atmosphere from coal combustion and
other emissions) and fine particles (PM2.5) and mortality
(see Table 1 below).
Table 1.--Relative Risk of Mortality for Those Living in Most Polluted
City in ACS Study for Original Analysis and Reanalyses
[E.G., in original analysis those living in city with the highest PM2.5
had a 17% higher risk of mortality]
------------------------------------------------------------------------
Analysis PM2.5 Sulfates
------------------------------------------------------------------------
Original........................ 1.17 (1.08,1.27) 1.15 (1.08,1.22)
Full............................ 1.18 (1.09,1.26) 1.15 (1.09,1.21)
Extended........................ 1.18 (1.09,1.26) 1.15 (1.09,1.21)
------------------------------------------------------------------------
At the same time, the reanalyses extended and challenged our
understanding of the original results:
the effects on mortality appeared to increase for those
with less education (and likely therefore of lower socioeconomic
status;
when the correlations among cities near one another were
considered, the effects of fine particles remained but were diminished;
and
an association between sulfur dioxide (SO2) and
mortality (but not other pollutants) was observed and persisted when
other variables were included.
In conclusion: the reanalysis identified relatively robust
associations of mortality with fine particles, sulfate, and sulfur
dioxide, and tested those associations in nearly every possible manner
within the limitations of the data sets.
key question for the longer term: are all particles created equal?
To date, most analyses of the effects of particulate matter have
focused on the mass of PM. Particles are, however, a complex mixture of
pollutants, and over the longer term, it will be important to
understand whether all particles have similar levels of toxicity, or
whether some particles, and therefore some sources, contribute higher
toxicity, and should be more stringently controlled. While there are
many actions underway already to reduce overall particle levels--for
example to control diesel vehicle PM emissions and nitrogen oxide
emissions (a precursor of nitrates) from power plants--in the years to
come, it will be especially important to develop the most cost-
effective control strategies aimed at the most toxic sources, or at the
most toxic components of those sources' emissions. This will be a
critical area for new research.
There are a number of components of PM that could cause toxicity.
At a multi-disciplinary NARSTO/EPA workshop in July, 1998, the
following key PM characteristics and components were identified:
PM mass
PM particle size, surface area
Ultra fine PM
Reactive transition metals
Organic compounds (e.g. diesel PM)
Acids
Biogenic particles
Sulfates and nitrates (e.g. from SO2 and NOx)
Peroxides
Soot
Co-pollutants--SO2, CO, Ozone, etc.
Research studies are now underway at EPA, HEI, EPRI, NIEHS, and
other research institutions to begin to identify the relative toxicity
of some of these components. Initial indication of the potency of some
of these elements (e.g. the metals attached to PM) are beginning to
emerge. In some cases, studies have looked at effects of emissions from
power plants. Some studies have not found effects from exposure to
sulfates; however other studies, including the reanalysis and
toxicology studies, have found effects of sulfates and other potential
emissions such as fly ash. Ultimately, identifying whether one or more
of these components is especially toxic will require a systematic,
multidisciplinary effort.
To address these questions, the HEI Review Committee, in April
2002, issued the second in its HEI Perspectives series entitled,
``Understanding the Health Effects of Components of the Particulate
Matter Mix: Progress and Next Steps.'' This review, which I have
provided to your staff and is available on the HEI web site at http://
www.healtheffects.org/Pubs/Perspectives-2.pdf, summarizes recent HEI
and other research on the effects of different components of the mix.
It also lays out a systematic effort necessary to achieve a better
understanding, including:
Parallel epidemiology studies in carefully selected,
representative cities throughout the U.S., with detailed daily
characterization of the particle mixture;
Companion toxicology studies using concentrated ambient
particles, source-
specific particles, and model particles to test the full range of
health endpoints and mechanisms for each particle type.
Many elements of such an effort are currently underway in the EPA
research program and other efforts. A more systematic approach will
require substantial resources dedicated over the next decade. However,
the result of such an effort could be a better-focused and more cost-
effective path to improved public health.
CONCLUSION: PROGRESS AND NEXT STEPS
In conclusion, we have made much progress in the last five years,
especially in testing the validity of the short- and long-term
epidemiology studies which served as the primary basis for the setting
of the 1997 NAAQS for particulate matter. We have tested a number of
possible confounding factors, explored whether errors in measuring
exposure might explain the relationships between PM and health, and
analyzed whether different statistical techniques could change the
results. In reviewing the latest evidence, the HEI Review Committee
concluded ``epidemiologic evidence of PM's effects on mortality and
morbidity persists even when alternative explanations have been largely
addressed''. Based on this evidence, a number of initial control
measures are now moving forward.
At the same time, important new questions have arisen. In the near
term it is necessary to complete the reassessment of NMMAPS and
identify, reassess and provide peer review for other key studies that
use GAM. Over the longer term, other important questions also remain,
especially concerning the comparative toxicity of different components
and sources of the PM mixture. Much research is underway to understand
this important question and to inform and target future strategies for
control of those emissions that may be most responsible. Only through a
systematic effort to test and compare the toxicity of these diverse
particles will we be able to have the best chance of answering these
key questions for the future.
Thank you again for the opportunity to present this testimony. I
would be pleased to answer any questions you might have.
__________
Statement of Jonathan Levy, Assistant Professor, Environmental Health
and Risk Assesment, Department of Environmental Health, Harvard School
of Public Health
The materials included in this written testimony provide support
for my oral presentation regarding the implications of the PM2.5
health literature for power plant risk calculations.
In my oral testimony, I focused on the evidence for mortality risks
from particulate matter, given the important role that mortality has
played in past benefits assessments of air pollution controls (such as
the EPA's benefit-cost analysis of the Clean Air Act). I also asserted
that there are three crucial questions that must be answered to
quantify the public health benefits of power plant pollution controls:
1. Is there a threshold below which no health effects of PM2.5
are found, and if so, where is that threshold?
2. Do all types of particulate matter have similar health impacts,
or are some particles more toxic than others?
3. Would alternative control strategies have significant impacts on
the magnitude or distribution of particulate matter health impacts?
Within this document, I address these three questions in greater
detail, summarizing the key studies that inform my answers to these
questions. Along with this summary document, I have included copies of
selected documents that provide even more information about the core
issues.
IS THERE A THRESHOLD?
An initial point that is important to emphasize is that this is not
the same question as whether PM2.5 concentrations are above
or below National Ambient Air Quality Standards. Quoting directly from
the US EPA in their Final Rule for the PM2.5 NAAQS, ``The
Act does not require the Administrator to establish a primary NAAQS at
a zero-risk level, but rather at a level that reduces risk sufficiently
so as to protect public health with an adequate margin of safety.'' (p.
3). The question is therefore whether the health literature provides
evidence of a threshold above current ambient concentrations.
First considering time-series studies, which evaluate the effects
of changes in daily concentrations of PM on daily mortality risks, two
major studies illustrate the nature of the literature (Daniels et al.,
2000; Schwartz et al., 2002). The first of these studies used
information from the National Morbidity, Mortality, and Air Pollution
Study (NMMAPS) to evaluate whether a threshold existed for short-term
exposure to PM10, either for total mortality or
cardiovascular/respiratory mortality. The authors showed that for daily
changes in PM10, linear models without thresholds were most
appropriate for total or cardiovascular/respiratory mortality. When
considered probabilistically, the threshold for total daily mortality
appeared to be definitely below 30 g/m3 and was most likely
below 15 g/m3. The second study used information from the
Six Cities Study, considering daily mortality risks from changes in
PM2.5 concentrations. As with the NMMAPS study, the authors
concluded that a linear no-threshold model was most appropriate.
Thresholds have also been examined in the cohort mortality
literature, with the most recent evidence provided in the follow-up to
the American Cancer Society cohort study (Pope et al., 2002). Within
the range of concentrations in the study, there was no evidence of a
threshold, and the relationship appeared approximately linear. The
lowest concentrations reported in the study (averaged across the study
period) were less than 10 g/m3.
Thus, the epidemiological literature shows no evidence of a
threshold for mortality risks at current ambient concentrations.
Although this may be counter-intuitive, given the normal assumptions
regarding thresholds for non-carcinogens, this relationship is
biologically plausible. As explained in Schwartz et al. (2002),
individuals will likely have thresholds, but if those thresholds differ
widely across individuals based on numerous factors, then the
distribution of thresholds across the population should be normally
distributed. This would imply that the population concentration-
response curve would approximately a cumulative normal curve, which is
linear at low concentrations. In other words, if current particle
levels were below the mortality threshold for most (but not all)
people, then linearity with no population threshold would be expected.
DO ALL TYPES OF PARTICLES HAVE SIMILAR HEALTH EFFECTS?
Prior to evaluating the literature, it is important to frame this
question appropriately. Because most of the epidemiological evidence
available to date has been based on monitors that measure total
particulate mass in various size ranges, it has been established that
particulate matter concentrations are associated with mortality and
morbidity. However, little information has been available about the
relative toxicity of different types of particles, so the default
assumption has been that all pollutants have equal toxicity.
While that is unlikely to be the case, to deviate from this
assumption, one must be able to quantify relative toxicities and defend
these quantifications. Explicitly, for the case of power plant
emissions, we would need to be able to estimate how toxic a sulfate or
nitrate particle is relative to average particles. Clearly, this is not
a question that can be answered with certainty, nor is it one that will
be definitively solved in the near term.
Focusing on epidemiological evidence, there are two types of
studies available: studies that directly measured at least one of the
constituents of interest (often sulfates) and studies that used
statistical methods to try to determine source-specific differential
toxicity. Each approach has advantages and limitations, and each can
add to the body of evidence.
In cohort mortality investigations, the primary evidence arises
through the analysis of sulfates along with particulate mass in various
size fractions. In the Harvard Six Cities Study (Dockey et al., 1993)
and American Cancer Society study (Pope et al., 2002), long-term
exposure to sulfates displayed a consistent positive association with
premature mortality. In the latter publication, as well as in the
Health Effects Institute reanalysis (Krewski et al., 2000), the authors
concluded that some combination of PM2.5, sulfates, and
possibly SO2 were associated with mortality. In a third
cohort study (McDonnell et al., 2000), sulfates were not statistically
significant, although the central estimate for mortality for male
nonsmokers from sulfates was between the values from the Six Cities and
American Cancer Society studies.
In terms of the relative effect of sulfate versus general
PM2.5, our power plant risk assessment in Massachusetts
(Levy and Spengler, 2002) found that impacts were greater if either the
reported sulfate-mortality or SO2-mortality relationship
were applied rather than the PM2.5-mortality relationship.
Thus, the cohort mortality literature generally shows sulfate effects
that are significant, with a concentration-
response function slightly greater than general PM2.5
effects and no direct information available on other particulate
species.
In the time-series literature, much of the speciation data come
from studies looking at sulfates. These studies have generally found
positive associations, as indicated in the following figure (taken from
the second external review draft of the Particulate Matter Criteria
Document).
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As indicated in the above figure, there has been preliminary
evidence available from the supersite in Atlanta, which measures
numerous chemical species (Klemm and Mason, 2000). This study found no
statistically significant relationship for any particulate measures
using one year of time-series data. Per unit concentration, the central
estimates were higher for elemental carbon and sulfates than for
PM2.5 as a whole, with lower central estimates for organic
carbon and nitrates (although no values were statistically
significant). In interpreting these results, it is important to realize
that lack of statistical significance could be related to either a lack
of an effect or a lack of statistical power to find an effect, given a
relatively small sample size. If we look at the body of sulfate time-
series studies in the above figure, we see that the Klemm and Mason
findings in fact have a central estimate in line with much of the
previous literature, but with substantially wider confidence intervals.
Once this study is completed, it should be combined with other
available studies to determine a best estimate for the time-series
relationship between sulfates and mortality, taking into account
relevant site and population characteristics (e.g., air conditioning
prevalence) to generalize to the U.S. at large.
Looking at studies of source-specific effects, a study by Laden and
colleagues (2000) applied statistical methods to elemental data from
the Six Cities study to determine source-specific particulate matter
factors. Across all six cities, they found that the motor vehicle and
coal factors had statistically significant effects on premature
mortality, with the motor vehicle factor approximately a factor of
three greater than the coal factor (per unit concentration). A crustal
factor was not significant. Although the confidence intervals were
wide, there was some evidence that cardiovascular deaths were more
closely related to motor vehicle particles and respiratory deaths were
more closely related to coal-derived particles.
Additional factor--analytic studies include Ozkaynak and Thurston
(1987) and Mar (2000). In the former study, based on cross--sectional
mortality data across the U.S., particles from industrial sources and
coal combustion had greater coefficients than those from motor vehicles
or crustal sources. In the latter study in Phoenix, combustion-related
pollutants (from motor vehicles and vegetative sources) and secondary
sulfates were associated with cardiovascular mortality. A soil-related
factor had a negative association with mortality. Thus, the findings
from factor analytic studies appear to show lower toxicity of crustal
particles, with significant effects from motor vehicles, power plants,
and other combustion sources. However, the studies do not provide
consistent quantitative evidence for greater toxicity of one combustion
source category over another.
In conclusion, while it is difficult to assign specific
differential toxicities to different particle types, it does appear
likely that combustion particles are more toxic than crustal particles.
In studies looking at both sulfates and PM, the effect per unit
concentration of sulfates is generally slightly higher, but the
relatively small difference and the lack of substantial toxicological
evidence makes a conclusion of equal toxicity reasonable as a central
estimate for risk calculations.
WHAT ARE THE MAGNITUDE AND DISTRIBUTION OF PM HEALTH EFFECTS
FROM POWER PLANTS?
First considering the distributional question, it is clear that the
impacts from a single power plant will vary spatially (since the
concentrations associated with that plant will not be uniform across
the country). The crucial question is whether populations near the
power plants are disproportionately at risk or whether the impacts
occur at longer distances, as this will influence the formulation of
optimal control strategies.
In our initial power plant analysis in Massachusetts (Levy and
Spengler, 2002), we concluded that the answer to this question depended
largely on how the question was framed. We distinguished between
individual risk (the mortality risk to a given individual at a given
location) and aggregate risk (the total public health impact associated
with the facility). When we look at individual risk, the maximum occurs
relatively close to the power plants--approximately 25-40 km away for
the two plants studied in Massachusetts. However, because of the long-
range transport of particulate matter and the number of people who are
impacted at long range, most of the aggregate risk occurs at long
range--more than half beyond 100 km, as illustrated in the figure below
from Levy and Spengler (2002). Thus, we can conclude that individuals
who live closer to a power plant are more impacted by that plant than
individuals living further away, but that local populations contribute
a relatively small fraction of aggregate risk.
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Although this captures broad distributional trends related to
distance from the source, another aspect of the distributional question
is whether selected demographic groups are disproportionately affected
by power plant air pollution. If this is the case, then a greater
amount of the population risk occurs in a smaller set of individuals,
which increases the importance of considering distributional issues.
In a recent power plant risk assessment focused on the Washington,
DC area (Levy et al., in press), we identified high-risk populations
for selected health outcomes and evaluated the implications for the
magnitude and distribution of health benefits. For the case of
premature mortality, we considered the influence of educational
attainment on mortality risk, as documented in Pope et al. (2002). We
concluded that if the observational evidence from the American Cancer
Society cohort study were correct, then more than half of the health
benefits accrued among the 25% of the population with less than high
school education. Furthermore, we showed that small-scale spatial
variations were significantly influenced by the incorporation of
population patterns, as illustrated by Figure 4 from Levy et al. (in
press), a portion of which is reproduced on this page.
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Finally, I turn to the question of estimating the magnitude of
health impacts from power plant emissions. Making this estimate
requires a multi-step process. First, the emissions of SO2
and NOx are quantified (given the structure of multi-pollutant
regulations and the focus on particulate matter impacts). Second,
atmospheric dispersion models are used to evaluate the influence of
these emissions on concentrations of PM2.5 across a large
region. These concentration changes are then combined with
epidemiological evidence to quantify the public health implications.
As an example of this sort of analysis, Abt Associates (2000) used
an economic model to estimate the distribution of SO2 and
NOx emissions from the power sector given proposed emission controls,
applied two atmospheric dispersion models to evaluate the national
PM2.5 implications of these proposals, and linked the
concentration changes with health evidence, including the mortality
risk derived from the American Cancer Society cohort study. They
concluded that current power plant emissions were associated with
approximately 30,000 premature deaths per year, with a 75% reduction
scenario yielding benefits of approximately 19,000 fewer premature
deaths per year.
A critical question is whether these estimates represent reasonable
central estimates or are biased in either direction. In a recent
investigation (Levy, 2002), I reviewed the methodology used by Abt
Associates in a similar analysis, focusing on the question of bias. I
considered separately the atmospheric model and the health evidence. I
concluded that the atmospheric model yielded health impact estimates
that were essentially identical to those using a different model, and
that the concentration-response function chosen for premature mortality
was a reasonable central estimate. Thus, it appeared equally likely
that the Abt Associates methodology yielded an underestimate as an
overestimate, making their findings a reasonable foundation for policy
decisions.
A similar methodology was used by the EPA to estimate the benefits
of alternative power plant control policies. For example, the EPA
estimated that the Clear Skies Act would reduce premature deaths by
about 12,000 per year, by combining the results of atmospheric models
and epidemiological studies (see www.epa.gov/clearskies). Similarly, an
earlier straw proposal from the EPA (which had more stringent caps on
both SO2 and NOx) was associated with a reduction of 19,000
premature deaths per year. Again, this was based on a similar
methodology as used by Abt Associates, implying that the estimate is a
reasonable central estimate.
From the above discussion, it is qualitatively clear that increased
reductions of SO2 and NOx are likely to lead to increased
public health benefits. While the above public health estimates are
clearly uncertain, they appear just as likely to be underestimates as
overestimates. Thus, it is reasonable to assume that the Clear Skies
Act would provide substantial public health benefits, but that the EPA
straw proposal (which is similar to the Clean Power Act) would increase
those benefits by perhaps 7,000 fewer premature deaths per year. This
implies that choices between status quo emissions, the Clear Skies Act,
the Clean Power Act, and other alternative formulations should depend
on a comparison of the incremental costs and benefits of increased
stringency.
Attached Documents
I have attached a subset of the studies cited above, which either
expand on the arguments in this testimony or are not yet publicly
available. Attached documents include:
Levy J. Evaluation of Methodology in ``Particulate-Related
Health Impacts of Eight Electric Utility Systems''. Prepared for
Rockefeller Family Fund, June 2002.
Levy JI, Greco SL, Spengler JD. The importance of
population susceptibility for air pollution risk assessment: A case
study of power plants near Washington, DC. Environ Health Perspect, in
press, December 2002 expected.
Levy JI, Spengler JD. Modeling the benefits of power plant
emission controls in Massachusetts. J Air Waste Manage Assoc 52: 5-18
(2002).
Pope CA III, Burnett RT, Thun MJ, Calle EE, Krewski D, Ito
K, Thurston GD. Lung cancer, cardiopulmonary mortality, and long-term
exposure to fine particulate air pollution. JAMA 287:1132-1141 (2002).
Schwartz J, Laden F, Zanobetti A. The concentration-
response relationship between PM2.5 and daily deaths.
Environ Health Perspect 110: 1025-1029 (2002).
References
Abt Associates, ICF Consulting, E.H. Pechan Associates. The
Particulate-Related Health Benefits of Reducing Power Plant Emissions.
Available: http://www.cleartheair.org/fact/mortality/mortalityabt.pdf,
2000.
Daniels MJ, Dominici F, Samet JM, Zeger SL. Estimating particulate
matter-
mortality dose-response curves and threshold levels: an analysis of
daily time-series for the 20 largest U.S. cities. Am J Epidemiol 52:
397-406 (2000).
Dockery DW, Pope CA III, Xu X, Spengler JD, Ware JH, Fay ME, Ferris
BG. Jr., Speizer FE. An association between air pollution and mortality
in six U.S. cities. N Engl J Med 329: 1753-1759 (1993).
Klemm RJ, Mason RM Jr. Aerosol research and inhalation
epidemiological study (ARIES): air quality and daily mortality
statistical modeling--interim results. J Air Waste Manage Assoc 50:
1433-1439 (2000).
Krewski D, Burnett RT, Goldberg MS, Hoover K, Siemiatycki J,
Jerrett M, Abrahamowicz M, White WH. Reanalysis of the Harvard Six
Cities Study and the American Cancer Society Study of Particulate Air
Pollution and Mortality. Cambridge, MA: Health Effects Institute
(2000).
Laden F, Neas LM, Dockery DW, Schwartz J. Association of fine
particulate matter from different sources with daily mortality in six
U.S. cities. Environ Health Perspect 108: 941-947 (2000).
Levy J. Evaluation of Methodology in ``Particulate-Related Health
Impacts of Eight Electric Utility Systems''. Prepared for Rockefeller
Family Fund, June 2002.
Levy JI, Greco SL, Spengler JD. The importance of population
susceptibility for air pollution risk assessment: A case study of power
plants near Washington, DC. Environ Health Perspect, in press, December
2002 expected.
Levy JI, Spengler JD. Modeling the benefits of power plant emission
controls in Massachusetts. J Air Waste Manage Assoc 52: 5-18 (2002).
Mar TF, Norris GA, Koenig JQ, Larson TV. Associations between air
pollution and mortality in Phoenix, 1995-1997. Environ Health Perspect
108: 347-353 (2000).
McDonnell WF, Nishino-Ishikawa N, Petersen FF, Chen LH, Abbey DE.
Relationships of mortality with the fine and coarse fractions of long-
term ambient PM10 concentrations in nonsmokers. J Exposure
Anal Environ Epidemiol 10: 427-436 (2000).
Ozkaynak H, Thurston GD. Associations between 1980 U.S. mortality
rates and alternative measures of airborne particle concentration. Risk
Anal. 7: 449-461 (1987).
Pope CA III, Burnett RT, Thun MJ, Calle EE, Krewski D, Ito K,
Thurston GD. Lung cancer, cardiopulmonary mortality, and long-term
exposure to fine particulate air pollution. JAMA 287: 1132-1141 (2002).
Schwartz J, Laden F, Zanobetti A. The concentration-response
relationship between PM2.5 and daily deaths. Environ Health
Perspect 110: 1025-1029 (2002).
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