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83–723 PDF 2004

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

Printed for the use of the Committee on Environment and Public Works

(
(II)

COMMITTEE ON ENVIRONMENT AND PUBLIC WORKS

ONE HUNDRED SEVENTH CONGRESS

SECOND SESSION

JAMES M. JEFFORDS, Vermont, Chairman

MAX BAUCUS, Montana

HARRY REID, Nevada

BOB GRAHAM, Florida

JOSEPH I. LIEBERMAN, Connecticut

BARBARA BOXER, California

RON WYDEN, Oregon

THOMAS R. CARPER, Delaware

HILLARY RODHAM CLINTON, New York

JON CORZINE, New Jersey

BOB SMITH, New Hampshire

JOHN W. WARNER, Virginia

JAMES M. INHOFE, Oklahoma

CHRISTOPHER S. BOND, Missouri

GEORGE V. VOINOVICH, Ohio

MICHAEL D. CRAPO, Idaho

LINCOLN CHAFEE, Rhode Island

ARLEN SPECTER, Pennsylvania

PETE V. DOMENICI, New Mexico

KEN CONNOLLY, Majority Staff Director

DAVE CONOVER, Minority Staff Director
(III)

CONTENTS

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: MortalityRelated 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

(1)

HEALTH IMPACTS OF PM–2.5 ASSOCIATED

WITH POWER PLANT EMISSIONS

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 continentsized 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
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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
5

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 nonattainment counties, the orange are the particulate matter 2.5 nonattainment. 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
6

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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8
9
10
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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
12

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.
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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 manmade 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
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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.
15

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 longterm 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 pollu-
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tion 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
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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 nontoxic 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.
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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 in-
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dustrial 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.
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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.
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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?
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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 combustionbased 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.
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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.
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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,
25

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 longterm 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,
26

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.
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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
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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.
29

[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
30

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 coexist 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.
31

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 lifeshortening 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
32

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 sourcedirected 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.
42

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). 2Georgia Murray, Staff Scientist, Appalachian Mountain Club. Personal communication. September 2002. 3Dr. L. Bruce Hill, Senior Scientist, Clean Air Task Force. Personal communication. September 2002. 4 ‘‘Coal blamed for haze’’, Atlanta Journal-Constitution. Friday, August 30, 2002

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 6 Ibid.

7 Ibid.

8 Ibid.

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.

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

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

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

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

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.

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

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
43

9Source: Jim Renfro, Air Quality Specialist, Great Smoky Mountains National Park, National

Park Service. 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. 12 National Park and Conservation Assoc. (NPCA) Fact Sheet.

observed during the Mount Washington study. The Great Smokies have experienced

140 days of unsafe air quality over the past four summers.9

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

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.

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 privatelyfunded 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 peerreviewed 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.
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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.
45

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
46

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.
47

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
48

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.
49

APPENDIX A
50
51
52
53
54

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
55

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.

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.
56

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 SPlus, 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)
57

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)
58

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 multidisciplinary 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, sourcespecific 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
59

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 μg/m3 and was most likely below 15 μg/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 co-
60

hort 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 μg/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 concentrationresponse 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 concentrationresponse 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).
61

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.
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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.

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
63

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.

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
64

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 mattermortality 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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