U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON : 

For sale by the Superintendent of Documents, U.S. Government Printing Office

Internet: bookstore.gpo.gov Phone: toll free (866) 512–1800; DC area (202) 512–1800

Fax: (202) 512–2104 Mail: Stop IDCC, Washington, DC 20402–0001

47–635 PDF 2009

S. HRG. 109–1048 

THE SCIENCE AND RISK ASSESSMENT BEHIND 

EPA’S PROPOSED REVISIONS TO THE PARTICULATE MATTER AIR QUALITY STANDARDS 

HEARING 

BEFORE THE

COMMITTEE ON 

ENVIRONMENT AND PUBLIC WORKS 

UNITED STATES SENATE 

ONE HUNDRED NINTH CONGRESS 

SECOND SESSION 

July 19, 2006 

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

( 

Available via the World Wide Web: http://access.gpo.gov/congress.senate 
COMMITTEE ON ENVIRONMENT AND PUBLIC WORKS 

ONE HUNDRED NINTH CONGRESS 

SECOND SESSION 

JAMES M. INHOFE, Oklahoma, Chairman 

JOHN W. WARNER, Virginia 

CHRISTOPHER S. BOND, Missouri 

GEORGE V. VOINOVICH, Ohio 

LINCOLN CHAFEE, Rhode Island 

LISA MURKOWSKI, Alaska 

JOHN THUNE, South Dakota 

JIM DEMINT, South Carolina 

JOHNNY ISAKSON, Georgia 

DAVID VITTER, Louisiana 

JAMES M. JEFFORDS, Vermont 

MAX BAUCUS, Montana 

JOSEPH I. LIEBERMAN, Connecticut 

BARBARA BOXER, California 

THOMAS R. CARPER, Delaware 

HILLARY RODHAM CLINTON, New York 

FRANK R. LAUTENBERG, New Jersey 

BARACK OBAMA, Illinois 

ANDREW WHEELER, Majority Staff Director 

KEN CONNOLLY, Minority Staff Director 

(II) 
(III) 

C O N T E N T S 

Page 

July 19, 2006 

OPENING STATEMENTS 

Boxer, Hon. Barbara, U.S. Senator from the State of California ....................... 6 

Carper, Hon. Thomas R., U.S. Senator from the State of Delaware .................. 10 

Clinton, Hon. Hillary Rodham, U.S. Senator from the State of New York ........ 9 

DeMint, Hon. Jim, U.S. Senator from the State of South Carolina ................... 7 

Inhofe, Hon. James M., U.S. Senator from the State of Oklahoma .................... 1 

Jeffords, Hon. James M., U.S. Senator from the State of Vermont .................... 3 

Lautenberg, Hon. Frank R., U.S. Senator from the State of New Jersey .......... 8 

Voinovich, Hon. George V., U.S. Senator from the State of Ohio ....................... 4 

WITNESSES 

Lieberman, Hon. Joseph, U.S. Senator from the State of Connecticut, prepared statement ................................................................................................... 47 

Gray, George, Assistant Administrator for Research and Development, U.S. 

Environmental Protection Agency ...................................................................... 11 

Prepared statement .......................................................................................... 47 

Responses to additional questions from: 

Senator Inhofe ........................................................................................... 50 

Senator Voinovich ..................................................................................... 51 

Greenbaum, Daniel, President, Health Effects Institute ..................................... 33 

Prepared statement .......................................................................................... 54 

Responses to additional questions from Senator Voinovich .......................... 58 

McClellan, Roger, Advisor, Toxicology and Human Health Risk Analysis ......... 28 

Prepared statement .......................................................................................... 60 

Responses to additional questions from Senator Voinovich .......................... 66 

Smith, Anne, Vice President, CRA International ................................................. 32 

Prepared statement .......................................................................................... 68 

Responses to additional questions from Senator Voinovich .......................... 81 

Stephenson, John, Director, Natural Resources and Environment, U.S. General Accountability Office .................................................................................... 13 

Prepared statement .......................................................................................... 86 

Responses to additional questions from Senator Voinovich .......................... 90 

Thurston, George, Associate Professor, New York University, School of Medicine, Department of Environmental Medicine ................................................... 30 

Prepared statement .......................................................................................... 92 

Responses to additional questions from Senator Voinovich .......................... 95 

ADDITIONAL MATERIAL 

Letters: 

Children’s Health Protection Advisory Committee ........................................ 163 

Undersigned by Bart Ostro and Michael Lipsett (regarding support for 

revising particulate matter standards) ....................................................... 188 

Undersigned by National, Regional, State, and Local Organizations 

(regarding supprt for revising particulate matter standards) ................... 193 

Undersigned by Senators (regarding funding for the State and Local 

Air Quality Management Program) ............................................................. 202 

Statements: 

CRA International ............................................................................................96-162 

Fran Pavley, Assembly California Legislature .............................................. 191-192 
Page

IV 

—Continued 

Jonathan Borak & Company Inc ..................................................................... 171-187 
(1) 

THE SCIENCE AND RISK ASSESSMENT BEHIND EPA’S PROPOSED REVISIONS TO THE 

PARTICULATE MATTER AIR QUALITY 

STANDARDS 

Wednesday, July 19, 2006 

U.S. SENATE, 

COMMITTEE ON ENVIRONMENT AND PUBLIC WORKS, 

Washington, DC. 

The committee met, pursuant to notice, at 9 o’clock a.m. in room 

628, Dirksen Senate Office Building, Hon. James Inhofe (chairman 

of the committee) presiding. 

Present: Senators Inhofe, Voinovich, Chafee, DeMint, Isakson, 

Jeffords, Boxer, Carper, Clinton, and Lautenberg. 

Senator INHOFE. Consistent with our policy of starting on time, 

we will call this meeting to order. 

OPENING STATEMENT OF HON. JAMES M. INHOFE, 

U.S. SENATOR FROM THE STATE OF OKLAHOMA 

I would like to tell our members, since we have quite a number 

of people here and of course we have the WRDA bill on the floor, 

which I have to manage so I am not going to be able to stay very 

long, we are going to try to keep everyone to about 3 minutes. I 

think we put a notice out if we could encourage both sides to do 

that, and then anyone who arrives after the conclusion of our opening statements would have to just submit the statements for the 

record, if that is acceptable. 

I am managing the WRDA bill, along with my colleague Senator 

Jeffords, on the floor so I am going to have to go down and prepare 

for that and won’t be able to stay here very long. I am going to ask 

that Senator Voinovich, who is kind of the master of all air issues 

anyway, would handle chairing this committee. 

Last week, the Air Subcommittee examined the impacts of tightening particulate matter standards on our Nation. Although EPA 

failed to analyze the regulatory impact on the Nation, these impacts will be enormous. I was particularly struck by the testimony 

of Harry Alford, president of the National Black Chamber of Commerce, who testified that the greatest health threat to minorities 

is access to health care and a tightened standard which would 

threaten the paychecks that cure that threat. 

Today, we are examining the science underlying the particulate 

matter review. The estimated risk today is less than it was estimated in 1997 under Carol Browner when the current standard 

was set. So while I feel EPA’s proposal to tighten the daily stand-
2 

ard to 35 micrograms is overly stringent, I am pleased EPA proposed to retain the existing annual standard. 

The rationale to tighten this standard is weak. The EPA cherrypicked what studies it was relying on, downplaying many key studies that shed light on the health effect of particulate matter, some 

of which are listed on this chart which is difficult even for me to 

read this close. But anyway, these are the studies. 

It also cherry-picked what information it provided to the Clean 

Air Science Advisory Committee, an important document that seriously skewed the review. A lot of times, CASAC is not given their 

assigned task. CASAC, the Clean Air Scientific Advisory Committee, is one of a set of some 21 scientists that are supposed to 

be giving advice and we are supposed to be listening to that advice. 

They were never told by the EPA that the estimated risk from PM 

exposure is now considered lower than the risk level estimated during the last review. 

EPA’s process for this review is also radically different from 

every previous scientific assessment, calling into question the credibility of the entire review. CASAC is supposed to review relevant 

science and the public is supposed to provide input. This time, EPA 

had a cutoff date of April, 2002 which meant that CASAC’s assessment does not include almost 4 1/2 years of new studies. Only after 

I asked EPA to collect the newer studies did it do so. Now, it plans 

to issue a final rule without an opportunity for public review of 

how it is assessing those studies. 

Worse, the General Accounting Office report being released today 

shows EPA has failed to follow the National Academy of Sciences 

recommendations to examine the health effect associated with different kinds of particulates and to incorporate the range of particulate toxicity assumptions into its uncertainty analysis. If we don’t 

know the types of particles causing the health effects, we can’t really accurately assess those. 

The system that is in place today only considers the size of the 

particulate matter. I think we all know that the health effects of 

a molecule of asbestos is much more dangerous than would be a 

molecule of dust. These things should be considered. 

Senator JEFFORDS. 

[The prepared statement of Senator Inhofe follows:] 

STATEMENT OF HON. JAMES M. INHOFE, U.S. SENATOR FROM

THE STATE OF OKLAHOMA

Last week, the Air Subcommittee examined the impacts of tightening particulate 

matter standards on our nation. Although EPA failed to analyze the regulatory impact on the Nation, these impacts will be enormous. I was particularly struck by 

the testimony of Harry Alford, President of the National Black Chamber of Commerce, who testified that the greatest health threat to minorities is access to health 

care and a tightened standard would threaten the paychecks that cure that threat. 

Today, we are examining the science underlying the particulate matter review. 

The estimated risk today is less than what was estimated in 1997 under Carol 

Browner when the current standard was set. So while I feel EPA’s proposal to tighten the daily standard to 35 micrograms is overly stringent, I am pleased EPA proposed to retain the existing annual standard. 

The rationale to tighten the standard is weak. EPA cherry-picked what studies 

it relied on, downplaying many key studies that shed light on the health effect of 

PM, some of which are listed on this chart. 

It also cherry-picked what information it provided to the Clean Air Science Advisory Committee in important documents, seriously skewing the review. For instance, 
3 

CASAC was never told by EPA that the estimated risks from PM exposure is now 

considered lower than the risk level estimated during the last review. 

EPA’s process for this review is also radically different from every previous scientific assessment, calling into question the credibility of the entire review. CASAC 

is supposed to review relevant science and the public is supposed to provide input. 

This time, EPA had a cut-off date of April 2002, which meant CASAC’s assessment 

doesn’t include almost 4 1/2 years of new studies. Only after I asked EPA to collect 

the newer studies did it do so, and now it plans to issue the final rule without an 

opportunity for public review of how it is assessing those studies. 

Worse, as the General Accountability Office report being released today shows, 

EPA has failed to follow the National Academy of Science’s recommendations to examine the health effect associated with different kinds of particles and to incorporate a range of particle toxicity assumptions into its uncertainty analyses. If we 

don’t know what types of particle cause health effects, we may well spend billions 

of dollars on pollution controls while doing little to improve health. 

Thank you. 

Senator JEFFORDS. Mr. Chairman, thank you. 

Senator INHOFE. Let me just repeat what we said earlier to our 

new arrivals here. We are going to try to adhere to 3 minutes in 

opening statements, and then cutoff statements after those who are 

present have concluded. 

Senator JEFFORDS. 

OPENING STATEMENT OF HON. JAMES M. JEFFORDS, 

U.S. SENATOR FROM THE STATE OF VERMONT 

Senator JEFFORDS. Mr. Chairman, thank you for having this 

hearing on the EPA’s proposed standards for particulate matter. 

There is perhaps no more important environmental standard than 

the national ambient air quality standard for particulate matter. 

Tens of thousands of Americans die prematurely each year from 

particulate matter. 

The NAAQS are the cornerstone of the entire Clean Air Act. 

Their fundamental purpose is to tell us when the air is safe to 

breathe. For more than 30 years, these standards have been set 

solely on health considerations, using the latest scientific evidence. 

Congress specifically chose not to allow consideration of cost when 

setting these standards. 

Those who call for a cost-benefit analysis would have us set a 

standard that fails to protect the health of all Americans. We cannot afford the human costs of such an approach. 

Consider this, if the cost-benefit analysis was used to set the 

NAAQS and the compliance costs of the standards are estimated at 

$1 billion, the EPA would be required to set a standard that would 

allow up to $1 billion worth of people to die from air pollution. So 

just how do we measure $1 billion in human life. Setting the 

NAAQS in that way was unconscionable. Telling people their air is 

safe to breathe when it is actually not safe is unacceptable public 

policy. 

We need to revise the existing standards set in 1997. Although 

the EPA itself has recognized this fact, EPA’s proposal falls short 

of what the scientific evidence requires. The Clean Air Scientific 

Advisory Committee recommended the EPA revise both the annual 

standard and the daily standard, but the EPA disregarded this advice, forcing the Scientific Advisory Committee to reconvene and reiterate its advice to the EPA. 

The committee has made it clear that the EPA’s proposal for the 

coarse particle standard was outside the bounds of scientific evi-
4 

dence. If the EPA were to listen to the advice of its science advisors, tens of thousands of lives could be saved. The standard proposed by the EPA would result in a 22 percent reduction in deaths. 

Standards set within the range recommended by the Scientific Advisory Committee would save up to 48 percent more lives. 

Particulate matter kills more people than HIV/AIDS and more 

people than drunk driving. It is a big killer and we need to reduce 

it as soon as possible. That is what the science shows. 

Thank you. I look forward to hearing from the witnesses. 

[The prepared statement of Senator Jeffords follows:] 

STATEMENT OF HON. JAMES M. JEFFORDS, U.S. SENATOR FROM

THE STATE OF VERMONT

Mr. Chairman, thank you for having this hearing on the EPA’s proposed standards for Particulate Matter. 

There is perhaps no more important environmental standard than the National 

Ambient Air Quality Standard for Particulate Matter. Tens of thousands of Americans die prematurely each year from particulate matter. 

The NAAAQS are the cornerstone of the entire Clean Air Act. Their fundamental 

purpose is to tell us when the air is safe to breathe. For more than 30 years, these 

standards have been set based solely on health considerations, using the latest scientific evidence. Congress specifically chose to not allow consideration of costs when 

setting these standards. 

Those who call for a cost-benefit analysis would have us set a standard that fails 

to protect the health of all Americans. We cannot afford the human cost of such an 

approach. 

Consider this: If cost benefit analysis is used to set the NAAAQS and the compliance costs of a standard are estimated at $1 billion, the EPA would be required to 

set a standard that would allow up to $1 billion worth of people to die from air pollution. So just how do we measure $1 billion in human life? Setting the NAAAQS 

in that way is unconscionable. Telling people their air is safe to breathe, when it 

is actually not safe, is unacceptable public policy. 

We need to revise the existing standard set in 1997. Although the EPA itself has 

recognized that fact, the EPA’s proposal falls far short of what the scientific evidence requires. The Clean Air Scientific Advisory Committee recommended that the 

EPA revise both the annual standard and the daily standard. But the EPA disregarded that advice, forcing the scientific advisory committee to reconvene and reiterate its advice to the EPA. 

The Committee also made it clear that the EPA’s proposal for the coarse particle 

standard was outside the bounds of the scientific evidence. If the EPA were to listen 

to the advice of its science advisors, tens of thousands of lives could be saved. 

The standard proposed by EPA would result in a 22 percent reduction in deaths, 

but a standard set within the range recommended by the scientific advisory committee could save up to 48 percent more lives. Particulate matter kills more people 

than HIV/AIDS and more people than drunk driving. It is a big killer and we need 

to reduce it as soon as possible. That is what the science shows. 

Thank you, and I look forward to hearing from our witnesses. 

Senator INHOFE. Thank you, Senator Jeffords. 

Senator VOINOVICH. 

OPENING STATEMENT OF HON. GEORGE V. VOINOVICH, 

U.S. SENATOR FROM THE STATE OF OHIO 

Senator VOINOVICH. Thank you, Mr. Chairman. I appreciate the 

fact that you bumped this hearing from my subcommittee to the 

full committee. It shows how important this matter is. To sum up 

last week’s hearing, we do not know the impact of revising the particulate matter standards, and let’s review what we do know. 

We know that the air is significantly cleaner; that the EPA has 

proposed to move the goal posts in the States as they implement 

the current standards. We believe that the Agency is under-
5 

estimating the number of non-attainment counties. We know that 

the current non-attainment designations threaten highway funding 

and jobs and increase energy prices and that revised standards 

would exacerbate the situation. 

We also know this decision has a profound impact on the health 

and well being of many, as the National Black Chamber of Commerce President Harry Alford stated, ‘‘The biggest health risk to 

African Americans anywhere is poverty.’’ I will never forget when 

Tom Mullen from the Catholic Charities came here several years 

ago and testified that in setting ambient air standards and environmental policy, that we should take into consideration its impact 

on the poor and the elderly, and the Clean Air Trust named him 

villain of the month because he had the audacity to raise the issue. 

Today’s hearing focuses on the science and risk assessment behind the standards. I make three points. First, according to the recent proposal and risk assessment, we will hear today the EPA’s 

estimates, the risk from exposure to fine particulate matter has declined from the level of risk estimated in setting the last standards. 

Second, the health benefits of EPA’s proposal are not fully understood. A 2002 National Academy of Sciences report made 34 recommendations to improve our understanding of the estimation of 

the public health benefits. According to GAO that we asked for, 

EPA has fully implemented less than 25 percent of recommendations made back in 2002 by the National Academy of Sciences. For 

example, the NAS, along with the Office of Management and Budget and EPA’s Inspector General, has urged the Agency not to assume that all fine particulate constituents have the same potency. 

As stated in the IG’s report, otherwise some facilities may install 

unneeded controls, while some needed controls may go uninstalled. 

Ultimately, compliance may be further delayed and more costly. 

Unfortunately, the EPA has largely not implemented the recommendations. The standards should not be revised until we have 

adequate information that tells us with greater certainty the 

health benefits and whether we are targeting the most harmful 

constituents of particulate matter, especially considering the negative impacts on this country’s economy. Air quality will continue to 

improve through implementation of the current standards and the 

Federal clean air rules. 

I know you want me to cut this short. I will just basically say, 

Mr. Chairman, it is important that everyone understand that 

science can only take us so far, but ultimately it is a policy decision 

whether or not to change a standard. That is why the Clean Air 

Act states the air quality standards are to be set in the judgment 

of the Administrator. Given this judgment discretion, how can EPA 

revise the particulate matter standards when the public health 

benefit is not fully understood? 

Thank you, Mr. Chairman. 

[The prepared statement of Senator Voinovich follows:] 

STATEMENT OF HON. GEORGE V. VOINOVICH, U.S. SENATOR FROM

THE STATE OF OHIO

Mr. Chairman, after our hearing in the subcommittee, I appreciate this important 

issue being elevated to the full committee. 

To sum up last week’s hearing, we do not know the impact of revising the particulate matter standards. Let’s review what we do know: 
6 

• We know that the air is significantly cleaner and that EPA has proposed to 

move the goal posts on States as they implement the current standards. 

We believe that the Agency is underestimating the number of nonattainment 

counties and that Federal clean air rules will only mitigate this problem. • We know that the current nonattainment designations threaten highway funding and jobs and increase energy prices and that revised standards would exacerbate the situation. • We also know that this decision has a profound impact on the health and wellbeing of many, as National Black Chamber of Commerce President Harry Alford 

stated: ‘‘the biggest health risk to African Americans anywhere is poverty.’’ 

Today’s hearing focuses on the science and risk assessment behind the proposed 

standards. I will make three points. 

First, according to the recent proposal and risk assessment, we will hear today 

that EPA’s estimate of the risk from exposure to fine particulate matter has declined from the level of risk estimated in setting the 1997 standards. 

Second, the health benefits of EPA’s proposal are not fully understood. A 2002 National Academy of Sciences (NAS) report made 34 recommendations to improve our 

understanding of the estimation of the public health benefits. According to the Government Accountability Office report that Chairman Inhofe and I requested, EPA 

has fully implemented less than 25 percent of them. 

For example, the NAS along with the Office of Management and Budget and 

EPA’s Inspector General has urged the Agency not to assume that all fine particle 

constituents have the same potency. As stated by the IG: ‘‘Otherwise, some facilities 

may install unneeded controls, while some needed controls may go uninstalled; ultimately, compliance may be further delayed and more costly.’’ 

Unfortunately, EPA has largely not implemented the recommendations. The 

standards should not be revised until we have adequate information that tells us 

with greater certainty the health benefits and whether we are targeting the most 

harmful constituents of particulate matter—especially considering the negative impacts on our economy. Air quality will continue to improve through implementation 

of the current standards and the Federal clean air rules. 

EPA claims that they will address more of the NAS recommendations when the 

final rule is issued. At this time, we are told that there will also be a more complete 

Regulatory Impact Analysis and new science will be considered. It is unacceptable 

for the public and this committee to get critical information only after the final decision has already been made. 

Third, testimony that we will hear today indicates that EPA selectively used 

study results in developing the proposal. 

In conclusion, it is important that everyone understand that science can only take 

us so far, but ultimately, it is a policy decision whether or not to change a standard. 

That is why the Clean Air Act states that air quality standards are to be set ‘‘in 

the judgment of the Administrator.’’ Given this judgment discretion, how can EPA 

revise the particulate matter standards when the public health benefit is not fully 

understood? 

Mr. Chairman, I again thank you for holding this hearing and look forward to 

hearing from the witnesses. Thank you.–— 

Senator INHOFE. Thank you, Senator Voinovich. 

Senator BOXER. 

OPENING STATEMENT OF HON. BARBARA BOXER, 

U.S. SENATOR FROM THE STATE OF CALIFORNIA 

Senator BOXER. Thank you, Mr. Chairman, for holding this hearing. I ask that my full statement be placed in the record. 

Senator INHOFE. Without objection, so ordered. 

Senator BOXER. I will read part of it. 

This hearing is important because protecting the air that Americans breathe is important. It is a critical responsibility of this committee. We have made great strides in this country, but unfortunately EPA’s proposed standards for controlling toxic soot and dust 

drastically depart from this path. 

Now, I won’t get into politicizing science, but what I want to say 

here is EPA has rejected advice from its own Clean Air Science Advisory Committee on health-based standards for toxic soot and 
7 

dust. This, despite the fact that the American Lung Association 

and other public health groups say the children, the elderly and 

people with heart disease, diabetes or respiratory diseases are especially vulnerable to the adverse impacts of such pollution. 

Let me be more specific. Particulate pollution causes premature 

death, whether you are in Oklahoma, New York, New Jersey, 

Vermont, California or Ohio. Particulate pollution causes premature death. It exacerbates asthma, cardiovascular disease, including heart attacks and strokes, and it increases hospital admissions. 

I have to say, sometimes in this committee we talk about things 

as if they were very interesting scientific issues. But the bottom 

line is what we are talking about here is the longevity or lack of 

such of the American people and the quality of their lives, be they 

children or adults. More than 160 national, State, local, environmental, religious groups, and I want to point out religious groups 

are getting involved in this, and public interest groups have urged 

EPA to increase these clean air protections. EPA’s Children’s 

Health Advisory Committee also urged EPA to revise these standards to protect children. 

I would ask unanimous consent that these letters be placed in 

the record at this time. Mr. Chairman, I would like to place these 

letters from the religious groups and others into the record at this 

time. 

Senator INHOFE. Without objection. 

[The referenced letters can be found on pages 193-201.] 

Senator BOXER. EPA has also proposed a protective standard for 

coarse particulate matter. The Agency proposal ignores pollution by 

exempting some industries, exempting them, industries such as 

mining. In addition, EPA proposes such a limited amount of monitoring that pollution will go undetected in many of our medium size 

and small cities. 

So EPA must stop this politicizing. They are politicizing scientific 

decisions, and I resent it as a U.S. Senator from the largest State 

in the union, where we are deeply affected by this. A particularly 

egregious example was identified by Mr. Bart Ostro, chief of California’s Office of Environmental Health, regarding the particulate 

pollution rule. On February 3, 2006, Mr. Ostro testified before 

EPA’s Science Committee that ‘‘last minute additions of edits and 

opinions by OMB and others circumvented the entire peer review 

process.’’ That is a condemning statement. 

The Clean Air Act has it right. Sound science and the protection 

of public health should guide the establishment of Clean Air Act 

standards and sadly, Mr. Chairman, I am very worried about the 

fact that we seem to be veering away from science and making politics the key ingredient in these decisions. 

Thank you. 

Senator INHOFE. Thank you, Senator Boxer. 

Senator DEMINT. 

OPENING STATEMENT OF HON. JIM DEMINT, U.S. SENATOR 

FROM THE STATE OF SOUTH CAROLINA 

Senator DEMINT. Thank you, Mr. Chairman. I am very interested in the results today. I appreciate our witnesses. 
8 

Last week, we looked at the possibility of a rule change. As we 

all know, the Clean Air Science Advisory Committee has recommended that EPA lower its annual standard for particulate matter. What I find interesting is that the air today is significantly 

cleaner than it was years ago, and even more intriguing is the risk 

assessment of health complications due to long-term exposure, 

PM2.5 ambient air, have been reduced. 

Studies have shown that the risk assessment for PM2.5 have either stayed the same or been reduced. Then why is the EPA receiving a recommendation from the committee to tighten the standard? 

Obviously, I am very interested in clean air. I just want to make 

sure that we find the source and really do something that cleans 

the air, not just do something to do something. 

The mechanisms that were used to direct the committee to recommend more stringent annual standards are actually disturbing. 

The EPA staff memo directed the committee to study three specific 

scientific studies. One of the studies gave mixed results of the 

human risk of high levels of PM2.5; another was nullified by the scientists who performed the study because the data constantly 

changed based on their assumptions; and the third one was based 

on cities outside the United States over a 6-year process that 

showed a drop in ambient air quality. 

So I am very interested in the testimony today. We want to know 

about good science. We want to know how to clean the air. I am 

just afraid we are looking at doing something just to look like we 

are doing something. We will end up costing this country a lot of 

jobs and prosperity, and not leave the air any cleaner. 

So I am here to learn, and I thank you, Mr. Chairman. 

Senator INHOFE. Thank you, Senator DeMint. 

Senator LAUTENBERG. 

OPENING STATEMENT OF HON. FRANK R. LAUTENBERG, 

U.S. SENATOR FROM THE STATE OF NEW JERSEY 

Senator LAUTENBERG. Thanks, Mr. Chairman, for giving us another opportunity to examine the need to protect our air. 

This week gives us an urgent reminder about what we have to 

do. The red air days are oppressive. I felt it myself, not enough to 

make me ill, but enough to make me realize that that air wasn’t 

particularly clean. 

Parents are warned not to let children play outdoors if they have 

respiratory problems because of increased danger of asthma attack 

or other complications. We know that particulate matter pollution 

triggers asthma attacks and affects the health of people with other 

respiratory and lung conditions. 

Today, we are going to hear how it also poses threats to people 

with heart conditions. But we will hear a lot of talk about uncertainty. We are not sure. It is like saying, well, the fire is only in 

the basement; let’s not get excited upstairs. 

I heard the same thing 20 years ago when I wrote the law to ban 

smoking on airplanes. The tobacco industry said there was too 

much uncertainty about the effects of secondhand smoke. There is 

no doubt anymore about it. Today, we know that there is real danger from secondhand smoke and we are so grateful that we did 

something when we did it. 
9 

We have heard the same excuse about uncertainty for years in 

the discussion of global warming. Look outside; feel it. The claim 

of uncertainty is the smokescreen that diverts attention from real 

problems. It is merely an excuse to avoid taking any action that 

might cost an extra few bucks to accommodate our need. 

We are here to represent the 25 million American adults with 

heart disease and 6 million children with asthma, one of whom is 

my grandson, Alexander. There is no uncertainty about whether 

they deserve clean, healthy air. This week, we learned of a report 

on particulate matter which had been requested by OMB. That report suggests that particulate matter is actually a worse problem 

than we previously thought. So much for uncertainty. 

So we ought not to let a handful of particular interests pressure 

us into doing anything that will permit more harm to millions of 

Americans. I think that this is a matter of urgency and I think we 

have to get on to making sure that the standards that we have are 

the highest and are the toughest than we get to meet. 

And not without consideration for either jobs or investment. But 

I will tell you, when we talk about jobs and I read the reports 

about what is happening, where things are being made today, they 

are not being made in India and other places, or Bangladesh because of environmental issues. They are being taken away because 

of cost issues. So we shouldn’t confuse the facts. 

I thank you, Mr. Chairman, once again, for the opportunity to air 

this problem. 

Senator INHOFE. OK. Senator Clinton. 

OPENING STATEMENT OF HON. HILLARY RODHAM CLINTON, 

U.S. SENATOR FROM THE STATE OF NEW YORK 

Senator CLINTON. Thank you, Mr. Chairman. 

Although we are making opening remarks, I want to begin by 

welcoming someone whom I have a great deal of regard for, Dr. 

George Thurston, to the committee. Dr. Thurston is on the faculty 

at New York University School of Medicine, where he conducts investigations into the human health effects of air pollution. He is 

truly one of the leading scientists in this field. I am pleased that 

he will be testifying on the second panel. 

I have particular regard for Dr. Thurston because when I was 

raising questions about the quality of air after 9/11 and the Administration was assuring everyone that there were no problems in the 

air, and in fact everything was fine, Dr. Thurston was one of those 

who said this is just not squaring with the scientific work I have 

done. 

Well, now nearly 5 years later, we have hundreds and hundreds 

of firefighters, police officers, construction workers, residents and 

others who are suffering from respiratory distress. Now, that was 

an intense experience because the air was so contaminated with everything that came from the World Trade Center. We can look at 

that and we can draw some conclusions about the impact of such 

a horrible event. 

But it is also true that after 9/11 when all the planes were 

grounded, there are a lot of pictures showing how clean the air 

was. We are facing a very serious question here. This is an important issue, not just in New York, but across our country. Since the 
10 

1997 revisions to the particulate matter standards, numerous scientific studies have been published. These have not been partisan 

studies. These have not been ideological studies. They have ranged 

from scholarly academic studies like Dr. Thurston, to the American 

Lung Association. 

These studies have overwhelmingly strengthened the links between particulate pollution and a range of adverse health outcomes, including asthma, heart attacks, hospital admissions, adverse birth outcomes, and premature death. Some recent studies 

have even linked long-term particulate matter exposure to increased risk of lung cancer. 

In addition, our understanding of the biological mechanisms at 

work helps explain these links better than we understood back in 

1997. So I was dismayed when the EPA disregarded the advice of 

its Clean Air Science Advisory Committee. 

You know, when CASAC recommended what it thought needed 

to be done, the EPA decided not to lower the annual PM standard 

in its proposed revisions. This action prompted a letter back to the 

EPA from CASAC, which I think is unprecedented. That letter reiterated the CASAC’s finding. All of these scientists who have no 

particular ax to grind, ‘‘the epidemiological evidence supported by 

emerging mechanistic understanding indicates adverse PM2.5

health effects below 15 micrograms per cubic meter.’’ 

Now, I think the science is clear. One of the reasons the air is 

cleaner today is that for more than 30 years we have been cleaning 

it up. So we have a little bit in the bank, but that is not going to 

stand. 

So Mr. Chairman, I hope that we will go with the lower standard, and I ask unanimous consent to submit the full statement to 

the record. 

Senator INHOFE. Without objection, so ordered. 

Senator INHOFE. Senator Carper. 

OPENING STATEMENT OF HON. THOMAS R. CARPER, 

U.S. SENATOR FROM THE STATE OF DELAWARE 

Senator CARPER. Thanks, Mr. Chairman. 

I want to follow up on what Senator Clinton has said, if I may, 

and also just kind of respond to what Senator DeMint has said. 

EPA doesn’t come up with these recommendations out of thin air. 

They have this CASAC committee that Senator Clinton just referred to. They made their recommendations for advising the annual and the daily limits on this particulate matter. 

Good people, they are all scientists. They have no ax to grind. 

What they try to do is to use good science and to give us their best 

recommendations, and also to give those recommendations to EPA. 

EPA has reviewed, I am told, over 2,000 scientific studies I believe 

since 1997, and they found an association between particulates in 

ambient air and all kinds of health problems. We have heard a couple of them, a recitation of them from Senator Clinton. I want to 

mention them again: aggravated asthma, chronic bronchitis, reduced lung function, irregular heartbeat, heart attacks, and premature death in people with heart or lung diseases. 

In just nine cities that EPA looked at, particulates would cause 

an estimated almost 5,000 premature deaths unless current stand-
11 

ards are strengthened. EPA could have come in and frankly followed the advice of CASAC. They didn’t. They erred the other way. 

For some of us on this committee, we were disappointed with that 

result. 

I do want to commend Administrator Johnson for acknowledging 

that the science does support strengthening the current particulate 

matter standards. I am concerned that the proposed standard is 

higher than the range recommended by EPA’s CASAC. I look forward to hearing today EPA’s justification for that decision. 

Finally, I would like to follow on a point made during last week’s 

hearing by a number of Senators, as well as Bill Wehrum of EPA. 

To do so, let me just quote Mr. Wehrum’s testimony from last 

week. Here is what he said: ‘‘between 1970 and 2005, gross domestic product increased by 195 percent. Vehicle miles traveled increased 178 percent. Energy consumption increased 48 percent. 

The U.S. population grew by 42 percent. During the same time period, total emissions of the six principle air pollutants dropped by 

53 percent.’’ 

In other words, since the inception of the Clean Air Act, our 

country has made significant increases in our energy usage, mobility and an ever-growing economy, and at the same time we have 

seen our air pollution decrease. Our Nation’s air has not become 

cleaner on its own. The improvements are a direct result of specific 

air regulations and the implementation of the National Ambient 

Air Quality Standards. The arguments we are hearing today that 

claim that tighter air regs will hurt our economy and cost people 

jobs are not new. We have heard these claims every time EPA has 

proposed a new regulation over the past 30 years. 

However, as Mr. Wehrum and others on the committee correctly 

pointed out last week, those claims have not proven to be true. We 

can have cleaner air. We can grow our economy and we can do 

those things today, as we have in the last 30 years. 

Thank you, Mr. Chairman. 

Senator INHOFE. Thank you, Senator Carper. 

That will conclude our opening statements. We have on our first 

panel Dr. George Gray, Assistant Administrator for Research and 

Development for the EPA; and John Stephenson, Director, Natural 

Resources and Environment for the United States GAO. 

We will start with you, and try to confine your remarks to 5 minutes, if you could. Dr. Gray, you are recognized. 

STATEMENT OF GEORGE GRAY, ASSISTANT ADMINISTRATOR 

FOR RESEARCH AND DEVELOPMENT, U.S. ENVIRONMENTAL 

PROTECTION AGENCY 

Mr. GRAY. Thank you, Mr. Chairman, members of the committee. 

I am George Gray, the Assistant Administrator for the Office of Research and Development at the Environmental Protection Agency. 

I want to thank you for the opportunity to discuss EPA’s evaluation of the scientific evidence for potential health effects of airborne 

particulate matter known as PM. Last week, the subcommittee 

heard from my colleague Bill Wehrum, the Acting Assistant Administrator for Air and Radiation and the EPA’s review of the National Ambient Air Quality Standards, we call them the NAAQS. 
12 

During the testimony, he explained to you the crucial role that 

science plays in helping to inform our decisions about the NAAQS. 

Today, what I would like to talk to you about in more detail is the 

science, how it is prioritized, how it is developed, and how it is synthesized and integrated. 

As the Assistant Administrator for the Office of Research and 

Development, I am responsible for both the development of new scientific information targeted at specific Agency needs, and for the 

evaluation, synthesis and integration of the world’s peer reviewed 

literature and to a document that informs EPA decisionmakers. 

As we characterize the current state of our collective scientific 

knowledge, we are careful to point out the strengths and weaknesses of this large body of information so that informed decisions 

can be made. It is clear that scientists and staff of EPA play a crucial role in the development and evaluation of the world’s scientific 

information to inform their review of the NAAQS. 

A very important function of EPA is the synthesis and integration of these thousands of individual acts of science to provide a 

clear characterization of our knowledge and the degree to which we 

are still uncertain about some aspects of PM health and environmental effects. 

We have a scientifically rigorous process by which we evaluate 

and interpret this important body of knowledge and we ensure that 

our interpretation of them is complete, transparent, unbiased, and 

consistent with an array of views in the scientific community. 

A fundamental step in the review of the NAAQS is the evaluation of scientific evidence in the preparation of scientific assessments known as criteria documents by the National Center for Environmental Assessment, which is part of the Office of Research 

and Development. The development of criteria documents involves 

a review of thousands of peer-reviewed research publications, evaluation of those studies that are most relevant to the review of air 

quality standards and the integration of scientific information 

across disciplines. 

The body of evidence must be reviewed, evaluated, weighed and 

then accurately and objectively described to help inform our decisions about National Ambient Air Quality Standards. For the current PM review, EPA evaluated research studies that addressed a 

wide range of issues, including PM toxicology, epidemiology, atmospheric chemistry, human exposure and other areas of environmental effects. Thousands of studies were reviewed and over 2,000 

were referenced in the final criteria document, many of which were 

conducted or funded by EPA’s Office of Research and Development. 

Considered together, these new studies significantly advanced 

our understanding of PM’s potential effects on public health and 

welfare and reduced the uncertainties associated with some important aspects of the science. Drawing on the evaluation of studies 

reviewed in the PM criteria document about health effects and dose 

response, as well as information about exposures to PM, EPA also 

completed a risk assessment to estimate the degree to which various approaches for revising the standards would potentially affect 

the public health risks that are posed by PM. 

Further, the Agency prepared a document known as a staff paper 

that utilized the evaluation and characterization of scientific evi-
13 

dence in the criteria document, together with the results of the risk 

assessment, to help inform policy judgments that are required in 

making decisions about the NAAQS. 

In summary, the Bush administration is committed to the development and use of the highest quality scientific information to inform decisionmaking. The mission of the Office of Research and Development is to develop, evaluate and communicate relevant scientific information to the Administrator and to assure that the Administrator is well informed of the nature, the strengths, and the 

limitations of this information. EPA has sponsored a targeted and 

effective research program on particulate matter, and I am pleased 

to convey to you and others the value of this investment. 

We have made a great effort to evaluate and characterize the existing and new scientific results available on particulate matter 

and I am personally pleased to share with you my views on this 

work. I look forward to addressing any questions that you may 

have, and I respectfully request that my full written testimony, as 

submitted, be inserted into the record. 

Senator VOINOVICH. [Presiding] Thank you, Mr. Gray. 

Mr. Stephenson, before you give your testimony to the committee, I am going to ask that this report by the GAO be made a 

part of the record. I look forward to your testimony. 

[The referenced document can be found on pages 86-90.] 

STATEMENT OF JOHN STEPHENSON, DIRECTOR, NATURAL RESOURCES AND ENVIRONMENT, U.S. GENERAL ACCOUNTABILITY OFFICE 

Mr. STEPHENSON. Thank you, Mr. Chairman and other members 

of the committee. I am pleased to be here today as the committee 

considers the science and risk assessment supporting EPA’s proposed revisions to the national air quality standards for particulate 

matter. 

A large body of scientific evidence over the past several years 

links exposure to particulate matter to serious health problems, including asthma, chronic bronchitis, heart attack and premature 

death. EPA, as part of its authority under the Clean Air Act to periodically review and revise as appropriate the air quality level at 

which to set national standards, proposed revisions to the particulate standards. It issued a draft regulatory impact analysis in January, 2006 of the revisions’ expected costs and benefits. 

As you know, EPA’s estimates of the expected benefits from its 

air pollution regulations have in the past often been controversial 

and the methods the Agency used to prepare these estimates have 

been questioned. As a result, at the direction of the Senate Appropriations Committee, the National Academy of Sciences evaluated 

EPA’s overall methodology and approach for estimating the health 

benefits of all proposed air regulations, and in 2002 issued a report 

that made recommendations to EPA to, among other things, conduct more rigorous assessments of uncertainty, increase the transparency of how it estimates benefits, conduct more detailed analysis of exposure, and estimate the benefits of each regulatory option under consideration. 

Mr. Chairman, you asked GAO to determine the extent to which 

EPA has implemented the academy’s recommendations and our re-
14 

port that you just mentioned being released today provides a detailed discussion of each recommendation and EPA’s efforts to respond to them. 

In summary, we found that while the National Academy generally supported EPA’s overall approach to estimating benefits, it 

made 34 specific recommendations for improvements. EPA is making progress in responding to the National Academy’s recommendations, but in the case of its January, 2006 analysis, EPA had applied 8 of the recommendations, partially applied 14, and did not 

apply 12. 

For example, in response to the Academy’s recommendations, 

EPA evaluated how benefits might change, given alternative assumptions, and discussed sources of uncertainty not included in the 

benefit estimates. Although EPA applied an alternative technique 

for evaluating one key uncertainty that concerning the causal link 

between exposure to particulate matter and premature death, the 

health benefits analysis did not assess how the benefit estimates 

would vary in light of other key uncertainties, as the Academy had 

recommended. 

Consequently, EPA’s response represents a partial application of 

some of the recommendations. EPA told us that insufficient resources impeded its progress in applying some of the Academy’s 

recommendations, citing in particular the limited availability of 

skilled staff, time and other resources to conduct the recommended 

analyses. EPA also stated that in some cases, it did not believe the 

state of the scientific knowledge was sufficient to implement other 

academy recommendations. One such area has been mentioned 

today, is for EPA to determine the relative toxicity of particulate 

matter components. EPA intends to pursue research and development so that additional academy recommendations such as that 

can be incorporated in future air regulations. 

We believe that continued commitment and dedication of resources will be needed if EPA is to fully implement the improvements recommended by the National Academy. In particular, EPA 

will need to ensure that it allocates resources to needed research 

on emerging issues such as the relative toxicity of particulate matter, and to assessing which sources of uncertainty have the greatest influence on the benefit estimates. EPA officials said that they 

expect the final rule, due September 27, will better address other 

academy recommendations pertaining to uncertainties associated 

with the health benefits estimates. 

We should all be closely examining EPA’s final rule because a 

more robust analysis of the remaining uncertainties, not addressing the proposal, will be critical if decisionmakers and the public 

are to better understand the likelihood of actually attaining the 

health benefit estimates. 

Mr. Chairman, that concludes my summary. I will be happy to 

answer questions. 

Senator VOINOVICH. [Presiding.] Thank you very much. 

In our last hearing, we talked particularly about asthma. I would 

like to read a statement to both of you and have you comment on 

it in terms of what impact do you believe that increasing the particulate role would have on the issue of asthma. 
15 

According to the Centers for Disease Control and Prevention, 

from 1980 to 2001, the number of Americans with asthma tripled 

to 20.3 million. From 1975 to 2000, the number of asthma attacks 

also tripled. At the same time, EPA data indicates the emissions 

of the six principal air pollutants dropped by 53 percent since 1970. 

Thus, while the number of people with asthma and the incidence 

of attacks have increased, air pollution has decreased substantially 

over the same time. 

Senator Lautenberg stated at the hearing, ‘‘But during the summertime when most people are enjoying their vacation playing outside, children with asthma often have to stay indoors, and the reason that they have to stay indoors is the air is just too dangerous 

for them to breathe.’’ 

However, staying indoors is exactly the opposite of what children 

should be doing, according to a report on the indoor air pollution. 

EPA ‘‘studies of human exposure to air pollutants indicate the indoor levels of many pollutants may be 25 times and occasionally 

more than 100 times higher than outdoor levels. These levels of indoor air pollutants are of particular concern because it is estimated 

that most people spend as much as 90 percent of their time indoors. The poor quality of indoor air and the amount of time spent 

indoors seems to explain the increased incidence of asthma better 

than outdoor air which is greatly improved.’’ 

Furthermore, according to NIH, air pollution is one of the many 

things that can bring on asthma symptoms. They talk about animal dander, dust mites, cockroaches, pollen and mold, cigarette 

smoke, air pollution, cold air, strong odor, scented products, strong 

emotional expression and stress, medicines, sulfites in food, or beverages. 

Will you comment on how you think, if we improve this particulate matter, it is going to make a difference in terms of something 

like asthma, that is always the subject matter here before this committee? 

Mr. GRAY. Senator, as many of you have stated, it is very clear 

that the issue of particulate matter and the ambient air quality 

standard is one of the most important decisions that EPA makes. 

Particulate matter is linked with a variety of adverse health outcomes, exacerbation of asthma being one of them. That is, no one 

is suggesting that in fact particulate matter causes asthma, but 

that it may be something that helps to trigger an attack or make 

them worse. 

That is part of the evidence, along with the other health effects 

that we can consider. They were part of the rationale behind our 

proposed rule that you can read about, where we suggested a particulate matter ambient air standard. We also asked for people’s 

views. We asked for input from the scientific community and from 

the public about that. The information we are going to get is going 

to be an important part of the ultimate decision we make. We are 

trying to understand the range of scientific information on all of 

the health effects of particulate matter, and the role that that 

might play in the ultimate judgment of an appropriate standard. 

Senator VOINOVICH. Mr. Stephenson, the fact that your report 

says that the recommendations of the National Academy of 

Sciences in terms of the things that you need to do to measure 
16 

whether or not particulate matter has an impact on health have 

not been carried out by the Environmental Protection Agency. Do 

you believe that they have enough information now that they can 

intelligently, objectively make a decision in terms of what this 

rule’s impact will have on public health? 

Mr. STEPHENSON. Well, one of the problems is the rulemaking 

process doesn’t lend itself to a broad picture of air quality in general. We are looking at particulate matter in this case. Our concern 

was that many of the uncertainty analyses were done, but they 

were never rolled up into a more robust analysis of all the uncertainties such that you could determine the ranges of exposure and 

project the health benefits in that way. 

So we think they have data. It is a question of how you analyze 

that data. 

Senator VOINOVICH. Do they have enough data to intelligently, 

objectively decide whether or not for public health, and I am not 

talking about weighing all the other sides of this. In other words, 

they are not supposed to weigh the impact on the economy and jobs 

and poor people’s energy costs and all the rest of that. They close 

their eyes to that. But do they have enough information to intelligently, objectively make a decision in terms of what impact a new 

rulemaking it more stringent would have on public health? 

Mr. STEPHENSON. In some cases yes and in some cases no. They 

need more exposure data. They need more data to determine how 

particulate matter affects various populations, how people inhale 

the particulate matter, etc. There is another category, which you 

mentioned, on the components of particulate matter, what makes 

up particulate matter. As Chairman Inhofe mentioned, asbestos is 

certainly more dangerous than dust. There is more research that 

is needed in that area in order to determine if there is in fact a 

difference between different types of particulate matter. 

Senator VOINOVICH. Thank you. 

At the request of the Ranking Member of the subcommittee, he 

asked that Senator Boxer be next. 

Senator BOXER. Thank you very much. I appreciate that. 

I really have one question that I want to ask to both of you. Assistant Administrator Gray, EPA’s proposal to reduce dangerous 

levels of coarse particulate matter or toxic dust relies on air pollution monitoring to detect potential violations. However, the President’s proposed budget for fiscal year 2007 cuts these monitoring 

funds by $17 million. State and local Clean Air Act administrators 

believe this will severely weaken monitoring programs and likely 

result in significant staff cuts across the country, so we will not 

have the people necessary to tell us what this monitoring is showing us. And what the monitoring is showing us is very important 

because at certain levels, we know our most vulnerable populations, our children, our elderly, our sick, our weakest, are impacted. 

So I don’t quite get why we see that kind of a cut, $17 million 

is not a lot in the scheme of things, when you think of what we 

are spending in Iraq every week. It is in the billions. We need the 

$17 million to be restored. It just boggles the mind that would be 

gone. 
17 

Let me tell you the impact of it that we are being told. We are 

being told that as a result of this, dangerous pollution will go undetected in rural areas and cities, such as California’s San Joaquin 

Valley where we have our farms and workers, farm workers; Missoula, MT; Carson City, NV; the Raleigh-Durham metro area in 

North Carolina; the Fort Worth-Arlington area in Texas. 

I am just giving you examples of cities and regions that don’t 

meet the population set out here. So I am wondering if you think 

that people in these areas deserve less protection than people in 

larger areas. To Mr. Stephenson, given the same set of facts, you 

have testified before that EPA fully or partially implemented only 

two thirds of the National Academy of Sciences’ recommendations, 

but that Agency officials complained of a lack of funds hampered 

their ability to do so. Your testimony states that continued commitment and dedication of resources will be needed if EPA is to fully 

implement the improvements recommended by the National Academy. 

This is an Administration, and my colleagues on the other side 

and we join them in this. We want to do everything that is based 

on science, and the National Academy of Sciences puts forward the 

plans, and then we don’t have the funding. So this $17 million cut 

that I am coming back to, and then there is $1 million in cuts to 

EPA’s budget for science and research for developing and implementing clean air standards. 

So I would like both of you to react to these budget cuts, and how 

do you, first of all defend them, if you do, Mr. Gray and Mr. Stephenson. Can you just give us some straight talk about what it 

really means to our people? 

Mr. STEPHENSON. Well, let me just say that we have in the past 

recommended in other reports on other air issues that more monitoring is needed. We are a data-based organization. We support the 

need for real monitoring data. That is the cornerstone of scientific 

research. So if there is a cutback in the amount of data you actually collect, we would see that as a problem. 

Senator BOXER. And Mr. Gray, I assume you don’t think it is a 

problem? 

Mr. GRAY. I want you to know that the EPA is committed to having the information that they need to make good science-based decisions. In fact, it is our network of thousands of monitors that we 

operate, together with our partners in the States, that helps give 

the public information Senator Lautenberg referred to, when there 

is a Code Red day. That information comes from monitors that are 

like those or even perhaps from those that are maintained by the 

Agency. But it also helps to support the research that we are talking about. 

Senator BOXER. Wait a minute. Excuse me for interrupting you. 

Mr. GRAY. Yes. 

Senator BOXER. We agree that monitoring is important. I am 

asking you to tell me why, then, would you be cutting that budget? 

Mr. GRAY. First of all, we have invested over $100 million since 

1998 in monitoring and specifically in monitoring speciation, questions that we are being asked to address by the National Academy, 

by this committee and by others. In addition, we believe that we 

can find efficiencies. We can do our monitoring in better ways. We 
18 

are all being asked to do things more efficiently and we are looking 

for efficiencies. 

Senator BOXER. So you don’t believe that the local people who 

are telling us that as a result of these cuts there will be pollution 

undetected in rural areas and cities, including for example, San 

Joaquin Valley in California; Missoula, MT; Carson City, NV; Raleigh-Durham metro. We have a whole list of them. You think that 

is an overreaction and that these people will in fact have their air 

monitored? Is that what you are telling us? 

Mr. GRAY. I am telling you that I am sure that they may be concerned, but that we are committed to making sure that we have 

the information that we need to monitor the air, to make sure that 

everyone has an adequate level of protection. 

Senator BOXER. So they may be concerned, but they shouldn’t be 

concerned because you are going to monitor their air. Is that what 

you are saying? 

Mr. GRAY. I am saying that. 

Senator BOXER. Yes or no? Are you going to monitor the air in 

those areas and those regions? 

Mr. GRAY. Most of the monitoring that is done is not done by the 

Agency. 

Senator BOXER. Yes or no? Are you going to monitor the air in 

those regions? 

Mr. GRAY. We are going to do what we need to do to make sure 

that we have the information. 

Senator BOXER. Mr. Chairman, they are not going to monitor the 

air in these areas. You can’t get a yes or no answer. It is very disturbing. Yes or no, can’t get it. 

Thank you. 

Senator VOINOVICH. Thank you, Senator Boxer. 

For the record, I would like insert a letter signed by 33 members 

of the U.S. Senate to the Appropriations Committee asking that 

they restore this $33 million to your budget, $17 million of which 

is to be used for monitoring. I think it is outrageous that some of 

the domestic budgets of this Government have not been given the 

dollars they need to get the job done that they are being asked to 

do. The non-defense discretionary budget is being clobbered, and 

we just stick our heads in the sand and ignore it. 

If we ask you to do a job, you ought to have the money to get 

the job done and we are not giving you the money and the Administration should wake up to the fact that we have a problem not 

only in the EPA, but across the board. I am sorry. 

Senator ISAKSON. 

Senator ISAKSON. Thank you, Mr. Chairman. 

On that subject, just to help educate me, this is a prospective cut 

that is being discussed based on last year’s funding and this year’s 

appropriation. Do you feel like you have sufficient funding at this 

year’s level to do the monitoring necessary to make a reasonably 

informed determination on your standards? 

Mr. GRAY. The information that we use to make judgments about 

our standards is based on a range of scientific information. It includes not only this monitoring. 

Senator ISAKSON. No, no, no. Excuse me for interrupting. But in 

terms of funding for monitors, which was the question, I am just 
19 

wondering if you think you have enough funding at current levels, 

not contemplating the future proposed cut, to make reasonable determinations? 

Mr. GRAY. We believe that we have the information that we need 

to make the determinations that we need to make. 

Senator ISAKSON. OK. Second, the GAO report, and excuse me, 

but I will read this so I will get it correct, in referring to the 

unexecuted 12 recommendations where you all cited insufficient resources, the GAO report says, the Agency will need to ensure that 

it allocates resources to needed research on emerging issues such 

as the relative toxicity of particulate matter components and to assessing which sources of uncertainty have the greatest influence on 

benefits. 

This portends that you have some discretion in allocation that 

you could use to move moneys to complete all the 34 recommendations that GAO recommended. Is that correct? 

Mr. GRAY. We take the recommendations from the National 

Academy of Sciences very seriously. Characterizing the science well 

in a balanced way and characterizing uncertainty are very important to the Agency. I, in fact, take some comfort in the fact that 

we have achieved, at least partially two thirds of those, and when 

our final RIA comes out in September, I think you will find we 

have made even more progress. 

Some of the recommendations will require additional work. They 

will require us to do methods development. They will require us to 

do research. At this point, for example, we have committed over 

$150 million for research to help address the question of speciation, 

one of the very highest priorities that we have in addressing National Ambient Air Quality Standards. So we are setting our priorities to help to meet many of those recommendations that came 

from the National Academy. 

Senator ISAKSON. Should you implement a rule before you have 

reached all the conclusions you need to reach based on the studies 

of the science? 

Mr. GRAY. I think that the recommendations from the National 

Academy are important for us in the way we do our Regulatory Impact Analyses. Those are very important documents that help the 

Nation, that help you understand the costs and benefits of the actions that we take. We cannot consider those in setting our National Ambient Air Quality Standard. 

Senator ISAKSON. You cannot consider them? 

Mr. GRAY. We cannot consider the costs in setting our National 

Ambient Air Quality Standard. For that reason, we evaluate the 

scientific evidence. We consult with the scientific community. We 

have our panel of experts that we use, and that is the information 

that goes into the setting of the National Ambient Air Quality 

Standard. 

Senator ISAKSON. One final question, and I want to thank the 

Chairman for holding this hearing and the hearing we held I guess 

last week, wasn’t it? 

At the hearing last week, we had a county commissioner from 

Georgia, Walker County, GA, that is in non-attainment; entered 

into a compact with EPA; has from what I can understand from 

EPA and them, done everything that was asked of them within 
20 

their control. But they find themselves the recipient of pollution 

from other continents, as well as larger cities near them, and also 

Mother Nature with the Bermuda High which over the southeast 

traps so much of this stuff for about 5 months out of the year. 

I know everybody has heard this before, but just one more time. 

It seems to me like the restrictions and the punishment, if you will, 

that somebody who has done everything admittedly within their 

control to do, that we are punishing the wrong person. There ought 

to be some attention to the unintended consequences of them receiving this pollution without any ability to stop or divert it after 

they have taken care of all of the things at the local level they need 

to do. 

So I know there was some testimony by one of the gentlemen testifying that there is a way out through appeal to EPA? I want to 

just perfect the record from last week. Walker County, at their own 

expense, did extensive studies to do that, and demonstrate the 

point source of this pollution, but still was unable to get any 

breathing room from the EPA restrictions. 

So I think we do, I am very much for clean and cleaner air, and 

I am very much for doing everything we can in terms of standards 

to implement that. But I also am for reasonable common sense on 

the application, particularly of these non-attainment standards 

when there is no control by the people who are being restricted, 

and in my case it is 63 percent of my State. 

Thank you, Mr. Chairman. 

Senator VOINOVICH. Thank you, Senator. 

Senator LAUTENBERG. Senator LAUTENBERG. Yes, thanks, Mr. Chairman. 

Mr. Gray, the EPA is proposing to attain an annual health 

standard of particulates that is much less protective than that 

which California has adopted. Can you explain why? 

Mr. GRAY. In the case of our proposed rule, first, it is important 

to note that we are committed to making sure that our National 

Ambient Air Quality Standards fulfill the Clean Air Act goal of protecting human health. Setting a standard, as we have already discussed, is a judgment of the Administrator. The job of my office, 

and a job that I think we have done very well, is to present the 

Administrator with a picture, a complete picture of the science, its 

strengths and its limitations, and the uncertainties of what we 

know and don’t know, and to help inform that judgment. 

In our proposed rule, we did describe the basis for the level of 

15 that we proposed, but we did ask for comments on other levels. 

I want you to know that those comments are going to be taken seriously and they will be an important factor in the Administrator’s 

decision. We are in the middle of an open-ended, deliberative process that is going to result in a final standard in September. It will 

fulfill that goal of protecting human health, taking into account the 

science that is available, the advice of our advisory committees like 

CASAC, and public comment. 

Senator LAUTENBERG. Do you think that we are at a point in 

time where we think that there ought to be any making the standards more rigid, to raise the standards for particulate matter that 

we ought to move on with? Have we done enough research, in your 

judgment, Mr. Gray, to say that there are significant problems with 
21 

the ambient air quality as we know it? We ought to, particularly 

as it affects particulate matter, should we strengthen those standards, make them more rigid than they are? Or should we reduce 

them? 

Mr. GRAY. Again, this is an important judgment that has to be 

made. National Ambient Air Quality Standards for particulate matter are some of the most important decisions that are made by the 

Environmental Protection Agency and the decisions are not made 

lightly. They are made with as much scientific information, as 

much scientific advice, as much scientific input as we can muster. 

That information is put before the Administrator in a balanced 

way, in a careful way, describing the strengths and limitations to 

help inform the judgment about whether the standard needs to be 

retained, needs to be raised, or needs to be lowered. 

Senator LAUTENBERG. Do you make recommendations when you 

submit it to the Administrator as to the direction that EPA ought 

to take? Or is this simply, I’ve done my job and here it is? Or do 

you do all the decisionmaking as to the Administrator? 

Mr. GRAY. My office does not do that. We prepare what we call 

the criteria document, thousands of pages of scientific information 

summarizing what we know and don’t know. There are recommendations that come from the staff in the Office of Air and Radiation in EPA that make suggestions to the Administrator. 

CASAC makes suggestions to the Administrator. All of that informs their judgment. 

Senator LAUTENBERG. You are aware of those recommendations? 

Mr. GRAY. I am very aware of them, yes. 

Senator LAUTENBERG. What is the conclusion that you would 

come to, hearing their recommendations? Do you think that the 

standards ought to be reduced, lowered? 

Mr. GRAY. I think that when we put out our proposed rule and 

our proposed standards, we very clearly articulated the thinking 

behind them, the science behind them. We asked for public comment, scientific information that might be out there that we might 

find useful. All of that will inform our judgments. 

Senator LAUTENBERG. I understand the mechanics, but there 

must be some conclusions out of this that say we could do better. 

We certainly ought not to do worse. The Chairman talked about a 

statement I made about keeping kids indoors. So I think I can 

come up with a conclusion that you have to choose your poison. In 

other words, if a mother unwittingly says, well, I am going to bring 

my child inside, or keep my child indoors because I think that the 

air quality is better. Here we come up with a conclusion that no, 

that there is more danger indoors than there is outside. 

So that is quite a dilemma. I think that what we ought to do is 

understand people’s emotion, and understand what people’s thinking is. In the house, air conditioned, etc., and you think that the 

air quality is better. I know it’s easier to breathe when you are in 

a house that has some air quality action going on. 

So maybe we ought to meet outside in the interest of safety for 

the Senators and the visitors. 

[Laughter.] 

Senator VOINOVICH. Thank you, Senator. 

Senator CHAFEE. 
22 

Senator CHAFEE. Thank you, Mr. Chairman. 

Senator Isakson was talking about his county in Georgia, Walker 

County, and he mentioned particulate matter coming from other 

continents. In your studies, are there any other countries that are 

similar to us in our research? I don’t want to put you on the spot, 

but that we can work with as we try and wrestle with reconciling 

the health benefits toward some of the regulations on particulate 

matter? 

Mr. GRAY. There are two parts here. One is that we, as EPA, review the scientific information that is available to us to help us understand the appropriate levels that inform the judgments about 

the appropriate levels of air quality standards, we use information 

from around the globe. We use research that is done in the United 

States, Europe, and North America. We tend to focus on certain 

areas, partly for technical reasons. There is better monitoring data 

in the United States than in Canada, or monitoring is done differently than it is in other parts of the world and interpretation 

can become a little tricky. 

We work with international experts. We work with international 

data to try to inform our decisions, to bring the best information 

to bear. In implementation, we do have to think about the fact that 

some of these pollutants can travel a very long way, when we think 

about how we control them. 

Senator CHAFEE. Any countries in particular really leading the 

way, that we work more closely with? Or are we more on the forefront? 

Mr. GRAY. Well, I don’t know that I can speak to that very authoritatively, though I will say that in many cases we do think 

about international transport of pollutants, and we have efforts 

under way in EPA to help reduce the pollution that comes out of 

power plants in China because we know that that can affect air 

quality in the United States. So we are thinking about the global 

environment and trying to transfer some of the practices that we 

have to other countries not only to benefit them but to benefit us. 

Senator CHAFEE. Again, I don’t want to put you on the spot, but 

I am just curious. Are there any other countries that have stricter 

standards than we do? 

Mr. GRAY. There are countries that have mixes of standards 

some parts of which are stricter than ours, and some they are not. 

In some parts of the world, even in some parts of this country, they 

may have standards that are very strict, but the rules for implementation are not as strict. When we set a rule, we mean it and 

it is going to mean something. That is not always the case; for example, the World Health Organization has set a standard that is 

stricter than ours, but it is completely aspirational and has no 

teeth to it. 

Senator CHAFEE. Can we learn from some of the economic impacts from those stricter standards? 

Mr. GRAY. Again, because many of them are not being implemented, because they are aspirational, it is hard to learn. If there 

are opportunities to learn, we will use them. As I said, we take our 

requirement for doing a Regulatory Impact Analysis very seriously. 

We want to make sure that we inform the Nation and you and any-
23 

one else who is interested in it, of the costs and the benefits of 

these actions that we take. 

Senator CHAFEE. OK, thank you. 

On another subject, does the science dictate that the Administrator, I think this is following up on Senator Lautenberg’s question, dictate that the Administrator choose a specific number in setting the particulate matter standards? Does the Administrator 

have some leeway? 

Mr. GRAY. It is my understanding—and again I am a toxicologist, 

not a lawyer—that in the Clean Air Act recognizes that in fact, setting a National Ambient Air Quality Standard is a judgment on the 

part of the Administrator that considers the science, scientific advice, and a variety of other factors. So in fact setting a national ambient air quality standard is a judgment. In the Office of Research 

and Development, we do our very best to make sure that he has 

an accurate, unbiased characterization of the science to inform that 

judgment. 

Senator CHAFEE. Thank you, gentlemen. 

Thank you, Mr. Chairman. 

Senator VOINOVICH. Senator Clinton. 

Senator CLINTON. Thank you, Mr. Chairman. Mr. Gray, in your testimony you said that EPA has spent $500 

million since 1997 to improve our scientific understanding of the 

health impacts of particulate matter. Now, it is my understanding, 

based on all of this research that has been conducted since 1997 

and the extensive review that the research has received from outside experts, as well as the public, that there is a consensus. 

Let me ask you, does EPA have significantly more confidence 

now that current levels of PM are responsible for very serious 

health effects, including premature death? 

Mr. GRAY. When we look at the science that is available to us, 

especially that which has been developed since the last evaluation 

of the standard in the late 1990’s, I can say that there is better 

causal evidence linking particulate matter to a range of adverse 

health effects. The understanding of the levels at which that happens is much less clear. 

Senator CLINTON. Right, but we actually know more today about 

the causal effects than we did in 1997. Is that correct? 

Mr. GRAY. Based on what we have learned from epidemiology, 

from studies in people, from toxicology, it is believed we have a better understanding of the causal relationship, yes. 

Senator CLINTON. What I am confused about is that given our 

understanding of the causal effects, which is greater than it was 

in 1997, given the recommendations from CASAC and others, in 

your proposed rule, EPA itself said that risk assessment was too 

uncertain for standard-setting purposes. What is the basis for that 

assertion? 

I know that we are searching for the best way to implement a 

rule that does take into account the scientific evidence, particularly 

the causal connections, so how did EPA reach a different conclusion 

than all of the other experts who have reviewed this matter? 

Mr. GRAY. I think an important point is that EPA doesn’t come 

to a different conclusion on this issue of causality, is there a relationship between particulate matter and adverse health effects. 
24 

Where there is uncertainty and where the Agency felt there was 

too much uncertainty to rely upon the risk assessment for setting 

a standard is in the ultimate understanding of the strength of 

those relationships and the levels at which the effects occur. 

Senator CLINTON. Well, then may I ask you, because we are limited, this is a very frustrating experience asking difficult question 

in 5 minutes, but may I ask you then, why wouldn’t our Government err on the side of health? If there is an uncertainty of the 

mechanism, why wouldn’t we go with the stricter standard as recommended by the weight of scientific evidence? 

Mr. GRAY. I think I would echo your final sentence, that is the 

importance of the weight of scientific evidence. What we have done 

in our proposed rule is lay out what we think the scientific evidence is for the standards that we proposed. We asked for further 

comments, recognizing that others, reasonable minds can differ on 

this very large and very complex body of information. We have 

asked for comments. We have asked for further information, and 

that is all going to play a role in the final judgment of the Administrator for the final standard that will be coming out in September. 

Senator CLINTON. Mr. Gray, may I also ask you, have you or anyone on your staff had contact with or from anyone in the White 

House concerning this proposed rule? 

Mr. GRAY. In the preparation of the science here, the work that 

we do in the Office of Research and Development has been done in 

a completely public and open way through the CASAC process. All 

of our CASAC meetings are open to the public. All of their deliberations are public. 

Senator CLINTON. I know, but have you or anyone on your staff 

had any contact with or from anyone in the White House with respect to this proposed rule? 

Mr. GRAY. I can speak for myself and say that I have not. In 

terms of the science here, I cannot speak for my staff. I don’t know. 

Senator CLINTON. OK. But when you say in terms of the science 

that is a blanket denial of any contact whatsoever from or through 

the White House? 

Mr. GRAY. It is important to recognize, and I have said this—— 

Senator CLINTON. Can you answer that yes or no? 

Mr. GRAY. These are very important standards and that there 

are interagency reviews. 

Senator CLINTON. Mr. Gray, I just want a yes or no answer. 

Mr. GRAY. Our scientific information is in our hands. 

Senator CLINTON. I know, but you haven’t answered my question. 

Have you or anyone on your staff had any kind of contact with 

from or through the White House with respect to this proposed 

rule? 

Mr. GRAY. In respect to the proposed rule, yes, of course we have. 

Senator CLINTON. OK. 

Mr. Chairman, could we get further information about this? I 

asked because, again, I go back to the very difficult experience I 

had after 9/11 when it became clear that the White House was directly interfering with the EPA scientific assessments and the public information provided to my constituents. I think that this committee deserves to know what, if any, kind of contact, pressure or 
25 

other relationship exists between the White House and the EPA 

with respect to this proposed rule. 

Senator VOINOVICH. I would like to comment that I was just concerned about that as you are. I would really like to discuss that because I was not aware of the fact that the White House had had 

anything to do with whatever they came out with after that. I 

know one thing, that when Joe Albaugh came before this committee, no one seemed to know what was going on, and that was 

one of the things that disturbed me. That is why our legislation is 

so important. The President can move in and immediately determine what folks are exposed to. 

I do not see that there is any problem with it, that we look into 

that. I would be surprised if there wasn’t. I suspect once you are 

done with this, don’t you have to submit it to OIRA to look at the 

cost-benefit analysis at OMB? 

Mr. GRAY. As I said, with our proposed rule, there is clearly contact with the other parts of the executive branch. 

Senator VOINOVICH. I think if you talk about the official contact, 

I think it is reasonable that we get an answer to that question. 

Mr. GRAY. There is an interagency process that we use with all 

of our rulemakings. 

Senator VOINOVICH. Why don’t you share it with us, OK? Then 

I think we will feel a lot better about it. 

Mr. GRAY. Certainly. 

Senator VOINOVICH. Respond to Senator Clinton’s concerns. 

Senator CARPER. Senator CARPER. Thanks, Mr. Chairman. Mr. Chairman, let me 

ask a first question of you. Do you recall several years ago when, 

maybe 3 or 4 years ago when Governor Whitman was EPA Administrator that you and I collaborated on a proposal calling for the establishment of a position within EPA? 

Senator VOINOVICH. Here it is. 

Senator CARPER. The Deputy Administrator for Science and 

Technology. There you go. You may have been talking about this 

when I was out of the room. 

Senator VOINOVICH. No, we didn’t talk about it. Why don’t you 

talk about it? 

[Laughter.] 

Senator CARPER. We had this notion, silly notion that maybe we 

ought to have somebody who was pretty senior within EPA who 

would be part of the top dog for science and technology. It is an 

idea that was not warmly embraced by EPA and maybe by the Administration. We introduced it as legislation and not a whole lot 

has come of it, but I am still interested. I know Senator Voinovich 

is still interested in making sure that we are making decisions that 

are based on good science. 

Let me just follow it up by asking you to talk a little bit more 

with us about CASAC, this Clean Air Scientific Advisory Committee. Just start out by saying, who are these people? 

Mr. GRAY. CASAC is actually called for in the Clean Air Act, and 

its base is a seven member panel of experts with the requirement 

for one member to be a physician, one member to be from the National Academy of Sciences, and one member to be from a State 

pollution control Agency. Then it is filled in with nationally recog-
26 

nized experts to help to provide advice to the Agency on ambient 

air quality standards. 

On any specific standard, whether it is particulate matter, ozone, 

lead or something else, the base group of CASAC is augmented by 

topic-specific experts, again to help us in our evaluation, characterization, and presentation of the science. 

Senator CARPER. Who selects or appoints these folks? 

Mr. GRAY. They are selected by the Administrator. 

Senator CARPER. What is the criteria used, just roughly? 

Mr. GRAY. Roughly, it is relevant expertise and knowledge. 

Senator CARPER. They serve a period of several years? 

Mr. GRAY. I don’t know the exact period. Yes, they serve for several years. 

Senator CARPER. OK, thank you. 

Why should EPA, why should the Congress, frankly why should 

anybody else heed the recommendations of the CASAC? 

Mr. GRAY. Well, the EPA certainly values the advice of the 

CASAC. It is very, very important to us. The current proposal on 

National Ambient Air Quality Standards for particulate matter, for 

example, our proposal for a daily standard is something that reflects very clearly the advice of CASAC. Advice from CASAC, 

again, is one of the important factors that are weighed by the Administrator in making the sort judgments that are made. 

Senator CARPER. What are the other factors? 

Mr. GRAY. There are a range of other factors, comments from 

outside scientists, comments from others, the range of science that 

is presented to the Administrator. All of these are going to be before the Administrator. When we proposed our standards in every 

case, whether we were matching the recommendation of CASAC or 

not, we asked for comment. We asked people to advise us on levels 

that included everything that CASAC had recommended across a 

wide range of different potential standards. All of those comments 

and all of that information will be an important part of the factors 

that are weighed by the Administrator in making a final judgment. 

Senator CARPER. Just to understand this, the current standards 

that exist are for annual, and there is a standard for daily exposures. If my life depended on it, I don’t know that I could well explain what a microgram is, but I understand that the current PM 

standard on an annual basis is 15 micrograms per cubic meter. On 

a daily basis, it is 65. 

Just explain that. As a toxicologist, I am glad that you aren’t a 

lawyer for this question, but as a toxicologist and someone who 

studied some science himself, explain that so that the lay person 

can understand it. 

Mr. GRAY. The numbers you are citing are the concentration of 

particles that are in the air. These are particles that are all around 

us right now. We can’t see them. In our monitoring system, we 

suck air into a collector, put it on a filter, and measure it, and that 

is how we learn about how much is there. That information plays 

a role in our doing epidemiology, comparing the health effects in 

populations with higher levels of exposure to those with lower levels of exposure. It helps us to understand what happens when we 

give animals exposure to this, to help us understand the mechanisms by which adverse effects might occur. 
27 

So these standards, these numbers are simply ways of identifying 

a certain amount of this particulate matter that is in the air. 

Senator CARPER. Again, drawing on your own expertise and 

training as a toxicologist, could you describe for us how these 

small, tiny pieces of matter, how they actually contribute to asthma, how they contribute to chronic bronchitis, how they contribute 

to heart disease or irregular heartbeat? How does it actually happen? 

Mr. GRAY. That is one of the areas that we have learned much 

more about in the last 10 years, partially through research that 

has been funded by the Environmental Protection Agency. We 

know that at certain levels of exposure, for example, levels that are 

frankly higher than what we have in the air today, it can increase 

the thickness of atherosclerotic plaques. 

Senator CARPER. Say that again? 

Mr. GRAY. Atherosclerotic plaques, atherosclerosis, the stuff you 

worry about with cholesterol building up and making your arteries 

get small. That can happen in mice. They are sensitive mice. They 

are bred to be sensitive, but that can happen to them if they are 

exposed to high levels of particulate air pollution. It is one example 

of a study that has been done to help us understand how these particles may have their adverse effects. 

Senator CARPER. My last question, Mr. Chairman, would be this, 

we have our current standard, and I think you said the annual 

standard is 15 micrograms. The CASAC had recommended I think 

going down to anywhere from 12 to 14. EPA chose to stay at 15. 

With respect to the daily standard, the current standard is 65. The 

CASAC had suggested going anywhere from 25 to 40, and you have 

come in at EPA at 35 micrograms. 

You chose not to adopt or move toward the annual standard, and 

you chose, or adjusted the daily standard. You went to the high end 

of the CASAC recommendation. Could I ask why? 

Mr. GRAY. Again, these are judgments on behalf of the Administrator and they are laid out very nicely in our proposed rule with 

the scientific reasoning behind each of the choices that were made. 

But the important thing, and I want to emphasize this again, I 

have said it a lot of times, we asked for comments about a range 

of other potential standards to get information from the outside 

community, from scientists, from the interested public about other 

potential levels, and that is all going to play a role in setting the 

final standard, and it will happen in September. 

Senator CARPER. All right. Thanks very much. 

Mr. Stephenson, sorry I didn’t get to you, but another day. 

Thank you. 

Senator VOINOVICH. I would like to thank both of you for your 

testimony before the committee. Mr. Gray, I want to thank you for 

your fine testimony here today, not an enviable position if you are 

getting shot at from both sides on this one. So maybe that is good. 

Thank you very much. 

Our next panel will come forward: Dr. Roger McClellan who is 

the Advisor for Toxicology and Human Health Risk Analysis, and 

also is a CASAC, Clean Air Science Advisory Committee member; 

Dr. George Thurston from New York University; Dr. Anne Smith 
28 

from CRA International; and Mr. Dan Greenbaum from the Health 

Effects Institute, which is jointly funded by EPA and the industry. 

I would like to urge the witnesses to limit their testimony to no 

more than 5 minutes. Your entire testimony has been inserted into 

the record. We really appreciate your being here today. We look 

forward to hearing what you have to say. 

Dr. McClellan, we are going to start with you. 

STATEMENT OF ROGER McCLELLAN, ADVISOR, TOXICOLOGY 

AND HUMAN HEALTH RISK ANALYSIS 

Dr. MCCLELLAN. Thank you very much. Good morning, Mr. 

Chairman and members of the committee. I appreciate this invitation to present my views on EPA’s current review of the national 

ambient air quality standard for particulate matter. 

Since 1999, I have served as an advisor on issues related to air 

quality, drawing on my more than 45 years of experience in comparative medicine, toxicology, and aerosol science and risk analysis. 

In particular, my testimony draws on my experience serving on the 

Clean Air Scientific Advisory Committee, which I chaired from 

1988 to 1992, and service on all of the CASAC PM panels from the 

late 1970’s to the most recent PM panel, as we moved from consideration of total suspended particulates to PM10 to PM2.5, and now 

consideration of a PM10–2.5 standard. 

I would like to make several points. First, I want to emphasize 

there is no scientific methodology which can determine a specific 

indicator, precise averaging time, numerical level, or statistical 

form that will be adequate to protect public health. The available 

scientific information can inform those decisions, however the Administrator must ultimately use policy judgments in making decisions on each of those four elements of the standard, drawing on 

an array of scientifically acceptable options. 

Two, I personally find acceptable the Administrator’s policy 

choices for the PM standard as were published in the Federal Register. Specifically, I find acceptable a proposal to reduce the 24- 

hour standard from 65 to 35 micrograms per cubic meter, with a 

98th percentile form. I found it acceptable in terms of science for 

him to propose retention of the PM2.5 annual standard at 15 

micrograms per cubic meter. With reluctance, I concurred scientifically with the setting of a PM10–2.5 indicator for the 24 hour averaging time concentration set at 70 micrograms per cubic meter, 

within a 98th percentile form. 

I say with reluctance because the science base for that is extremely weak and uncertain. I would have preferred retention of 

the PM10 standard. 

Third, it is important to recognize that although the criteria document is hundreds of pages in length and compiling the results of 

what we know in terms of the world of science about PM, at the 

end of the day the key information for setting the standards are 

the results of the epidemiological studies. That has been the basis 

for changes in standards from a total suspended particulates set in 

1971, to the PM10 standard set in 1987, PM2.5 in 1997, and now 

consideration of this new PM10–2.5 standard. 

So the current review focused on the PM2.5 indicator. Now, some 

might have said, well, why didn’t we look at sulfates or elemental 
29 

carbon or some particular chemical species? The fact of the matter 

is we are chained to the ‘‘regulatory compliance lamppost’’ in terms 

of monitoring data. You cannot conduct epidemiological studies unless you have the monitoring data. Our past obsession with monitoring that which is regulated has precluded the development of 

the richer science base that really need to consider these options 

in terms of speciation. 

I am not optimistic that that is going to change. I can envision 

us sitting here 5 years, 7 years from now and discussing, well, why 

not for specific standards; why didn’t we perhaps preclude or set 

outside of the standards on material, because it is very innocuous; 

or why didn’t we focus on something in particular? In fact, we 

won’t have the epidemiological data because I don’t think we are 

developing adequate monitoring data. 

Fourth, we can then turn to the question of toxicology. I am a 

toxicologist. I am intellectually married to the subject, if you will. 

We have exciting new methods at hand, but at the end of the day, 

I have to say that our toxicology methods are simply too blunt and 

yield results that can only be qualitatively extrapolated to the 

human population. I know of no scientific method for using the results of the toxicology studies with PM, including those conducted 

with specific chemical constituents, to develop quantitative numerical standards that are the core of the PM NAAQS. 

Fifth, we have heard some discussion about the issue of uncertainty. I certainly, as a scientific colleague of Dr. Gray, am an enthusiast for trying to determine how we can bring our scientific information together and relate all of the uncertainties, so we can 

have better informed policy decisions. 

I want to comment on one aspect of that, and that is the use of 

expert elicitation. That was covered in the GAO report. I served as 

one of those five experts on the pilot expert elicitation. I hesitate 

to say whether it is expert advice or expert opinion. It is a challenge when you are asked to present information. The answers that 

are given can be heavily influenced not only by your knowledge of 

the science, but your personal choices. All of us want quality life. 

Well, how do we separate that from our judgment on the science? 

I am concerned about the use of that expert elicitation advice, 

and I certainly would urge the Administrator to use a high degree 

of caution in using that in the regulatory impact analysis and in 

making decisions on the standard. 

Senator VOINOVICH. Dr. McClellan, could you finish up? 

Dr. MCCLELLAN. I am going to just wrap up with that and emphasize that one of the challenges we have today is separating out 

people’s views on the science versus their views on the science 

wrapped up with the policy and some desired outcome—the level 

of the standard. I think in some cases, as individuals and professional groups have weighed in, they are weighing in not just on the 

science, but the policy outcome they want. 

I do think it is important to have a distinction between the 

science and policy choices. In my comments on the acceptability of 

the Administrator’s choices, I viewed the science options laid out in 

the staff paper as acceptable, and he used his judgment in selecting 

from among those options. I think that was appropriate. 

Thank you. 
30 

Senator VOINOVICH. Thank you very much for being here. 

Dr. THURSTON. 

STATEMENT OF GEORGE THURSTON, ASSOCIATE PROFESSOR, 

NEW YORK UNIVERSITY, SCHOOL OF MEDICINE, DEPARTMENT OF ENVIRONMENTAL MEDICINE 

Dr. THURSTON. Good morning. I am George Thurston, a tenured 

Associate Professor of Environmental Medicine at the New York 

University School of Medicine, where my research involves the investigation of human health effects of air pollution. 

I first wish to present for inclusion in the record letters from 

many major medical societies and public health groups, including 

the American Medical Association, the American Thoracic Society, 

and the American College of Chest Physicians, the American Public 

Health Association, the American Lung Association, the American 

Heart Association, the American Cancer Society, and more. These 

letters show the unprecedented support that exists for PM standards that are much tighter than EPA has proposed. 

Especially note that they all agree that the science supports 

tightening annual standards to no more than 12 micrograms per 

meter cubed. If this were to be done, many thousands of premature 

deaths could be avoided each year. 

I also present a copy of Dr. Rogene Henderson’s letter from the 

EPA’s Clean Air Science Committee, CASAC, urging that the Administrator comply with their recommendations, with CASAC’s recommendations, to implement more stringent PM standards than 

now proposed by the EPA. 

Now, in my written testimony, I have addressed three factors 

that need to be considered in the EPA’s proposed revisions to the 

particulate matter air quality standards. First, I address the fact 

that we are now far more certain, as discussed earlier, of the adverse impacts and biological mechanisms of PM health effects. The 

uncertainties raised at the time of the initial setting of the PM2.5

standard are now greatly reduced. 

As outlined in figure one, if someone could put that up, from my 

testimony, the PM research funded since the setting of the last 

PM2.5 standard has collectively shown the existence of numerous 

biological pathways capable of causing damage to the human heart, 

the lung, the nervous system and the circulatory system. This is 

consistent with the health impacts found by the PM epidemiology 

studies upon which the PM2.5 standard was set. 

This has greatly reduced scientific uncertainty associated with 

the mechanisms by which PM has such severe effects on human 

health. 

Second, I documented reducing ambient PM levels can and do result in significant reductions in the mortality risk associated with 

this pollutant. Since the setting of the original PM2.5 standard, 

more recent follow-up analyses of the landmark Harvard Six Cities 

and ACS studies have now considered longer records of time and 

have confirmed and expanded the conclusions from these two major 

studies. 

As shown in figure two, an extended analysis of the Harvard Six 

City study through 1990 has now shown that reductions in longterm ambient PM pollution results in concomitant reductions in 
31 

health risks associated with PM. Large reductions in PM at four 

of the Harvard cities have resulted in likewise large reductions in 

the relative risk of mortality in those cities. We see S, Steubenville, 

where the pollution levels have come down, and so has the risk of 

mortality from that pollution. In Harriman, TN, the pollution levels 

have come down and the risk of mortality in that city has diminished as a result of the lower pollution. St. Louis, the L, has come 

down similarly, and Watertown, right, Boston, has similarly come 

down. 

So the places where they have had improvements, we see that 

lower PM2.5 lowers mortality. But I think it is important to say we 

still have a long way to go, and a lot of improvement yet to be 

made and benefits to be reaped from lowering the PM standard. 

Finally, I show that the adverse health effects of PM air pollution extend below the PM2.5 standard of 15. A recent NIOSH-funded extension of the ACS study, of which I was a principal investigator, strengthens the original conclusions of the ACS study, and 

it importantly now links increased risk of lung cancer to long-term 

exposure to PM, as shown here. As the pollution level goes up, the 

risks of lung cancer rise, as do all cause and cardiopulmonary. 

As seen in this figure, the risks from PM2.5 extend well below 15 

micrograms per meter-cubed. 

In conclusion, since it was the level of uncertainty about PM biological mechanisms and effects at concentrations lower than 15 

micrograms per meter-cubed that limited the standard to that level 

in 1997, and, I point out, not some specific acceptable level of 

health risk from PM, and since new sound scientific studies have 

greatly reduced or resolved those uncertainties, then concern about 

the health of the public clearly indicates that the long-term PM2.5

standard should now be reduced below 15, consistent with CASAC’s 

advice. 

And finally, I just want to point out that I was involved with the 

actual expert elicitation that has just been finished. It is finishing 

up under EPA. It is clear from the expert elicitation; I was shown 

the results of all the experts at the final meeting in New Orleans 

a few weeks ago. It is clear that the experts are, there is a consensus that, the risk from fine particle is much higher than previously thought, and that expert elicitation gives us an estimate of 

somewhere on the order of 1 percent decline in mortality per 

microgram per meter-cubed of fine particles. 

So we are talking about a very large reduction in health risk, if 

you consider the fact that over two million people die every year 

in the United States, a reduction of 1 percent in that would be 

20,000 deaths per year. So we are talking about many thousands 

of premature deaths that can be avoided by lowering this pollution. 

I did want to respond to the question that you raised about asthma, if I have a second. Do I have time to respond to that? 

Senator VOINOVICH. Why don’t you bring it up in the question 

period. 

Dr. THURSTON. OK, we will talk about it then. 

Well, thank you for this opportunity to testify. 

Senator VOINOVICH. Thank you. 

Dr. SMITH. 
32 

STATEMENT OF ANNE SMITH, VICE PRESIDENT, CRA 

INTERNATIONAL 

Dr. SMITH. Mr. Chairman, thank you for inviting me to participate in today’s hearing. I am Dr. Anne Smith. I am a Vice President, CRA International. 

I have been analyzing the risks and policy options associated 

with fine particle standards for over 10 years. The opinions I will 

present today are my own and not those of my company, CRA 

International. 

When EPA set the first ever national ambient air quality standards for PM2.5 back in 1997, in the face of substantial knowledge 

gaps at that time, it presumed that fine particles do have a causal 

relationship with public health. The law then required that standards be set for that PM2.5 at a level that would protect the public 

health with an adequate margin of safety. 

The courts ruled that the current standards they set did indeed 

provide that adequate margin of safety. EPA and the courts have 

also made it clear that that margin of safety does not eliminate estimated risk. Today, EPA is deciding whether new evidence accumulated since 1997 justifies tightening these standards. In both 

1997 and now, EPA prepared a quantitative risk analysis using the 

available health studies. EPA says this is to help decide whether 

to tighten the standard. As I will show, it can help with this. 

However, if you take the position that the PM2.5 standard has to 

be tightened just because the risk analysis produces a body count 

at the prevailing standard, you will find yourself having pre-decided to tighten the standard in every future review cycle, even if 

the evidence never changes in the interim. This cannot be what 

Congress intended. 

In thinking about whether to tighten the standard, the more appropriate question to ask is: Has anything changed in our knowledge that would undermine the Administrator’s 1997 judgment regarding the adequacy of the margin of safety? Having a large number of new studies today, having successfully reanalyzed the studies we had originally, and even having some evidence of a still elusive biological mechanism, all fail to provide a justification to tighten the standard. They merely confirm that a standard is needed in 

the first place, which was the judgment made in 1997. 

However, one could justify tightening the standard if the new 

evidence that I have just spoken of indicated that risks at the attainment level of the current standard have increased since 1997. 

To test this, I went back to my 1997 files to construct a comparison 

of EPA’s estimates of mortality risks on a then and now sort of 

basis. I found that the estimates of mortality risk at the attainment level have actually fallen since they were first estimated in 

1997. 

Risks due to long-term mortality have fallen in every location. 

The risks due to daily exposure, which vary by city, have fallen in 

six of the eight cities that are in EPA’s risk analysis. This new information suggests that the margin of safety provided by the current standards is actually greater than we originally thought. 

What I have told you so far is based entirely on EPA’s own point 

estimates of risk. However, it is worth looking more closely at those 

estimates and the basis for them. Every one of the new epidemio-
33 

logical studies actually contains multiple alternative risk estimates. 

Sometimes there are dozens of them within a single paper. Which 

one is best? Which one should be used in the risk analysis? The 

Health Effects Institute has pointed out in the face of this issue 

that there is no gold standard for deciding this. 

When I reviewed the full body of evidence in each paper that 

EPA used for its risk analysis, I went back to the original papers, 

I noticed that EPA had consistently selected the highest risk estimate or nearly the highest one from each of the papers. Therefore, 

EPA’s risk estimates overstate what the full body of evidence supports today. 

The evidence on fine particle risks has weakened in a number of 

other ways. Several of EPA’s own point estimates today of the risk 

are not statistically significant. What this means is that behind the 

purported body count that comes out the risk analysis there is also 

actually a rather large probability of no health impact at all associated with that very same estimate. I found that none of the risk 

estimates for any of the eight cities in EPA’s risk analysis remains 

statistically significant across all of the reasonable estimates in 

those papers. 

This body of new evidence has also substantiated some of the 

concerns that were raised in 1997 that fine particles may be a 

scapegoat, while the real villain hides behind a veil of statistical 

uncertainty. The only clear trend in the new evidence has been 

that the estimated levels of risk that are being attributed to fine 

particles are lower than originally thought. 

I would like to conclude by saying that we still have no idea of 

which constituent of PM2.5, if any, is the culprit underlying this 

complex body of evidence. Even if the risk estimates are good, correct risk estimates, by regulating this generic mass of many compounds that is PM2.5, we may gain little if any public health benefit. 

Thank you for this opportunity to share my views on this important topic. 

Senator VOINOVICH. Thank you, Dr. Smith. 

Dr. GREENBAUM. 

STATEMENT OF DANIEL GREENBAUM, PRESIDENT, HEALTH 

EFFECTS INSTITUTE 

Mr. GREENBAUM. Thank you, Mr. Chairman. It is a pleasure to 

be back in front of the committee. I thank you for the opportunity 

to testify. 

I am the President of the Health Effects Institute, which as you 

know is an independent research institute funded jointly by the 

EPA and industry to provide high quality, impartial science on the 

health effects of air pollution. 

I am going to focus today on the science progress we have made 

since 1997, the most recent findings on the relationships between 

different ambient concentrations of PM and health, and key science 

needs going forward. 

Since Congress identified the need for substantial enhanced research in 1997, much progress has been made. We know much 

more about the sources of fine particles and about personal exposure. We have conducted the first multi-city epidemiology studies 
34 

and analyzed and reanalyzed many of these studies, finding that 

in general the earlier studies were well done. 

At the same time, there has been some evidence that the health 

effects we have seen in those earlier studies may in some cases be 

smaller. Unlike in 1997, we now have a number of toxicology studies that have begun to indicate potential biological mechanisms by 

which PM may cause health effects, although as always there is 

still much more to learn. 

Among the most important questions addressed in recent years 

is whether exposure to PM has health effects at all levels, or 

whether there is a threshold below which no effects are expected. 

This question is central to setting the level of the NAAQS. This has 

been looked at in both short-term and long-term studies. Perhaps 

the most rigorous short-term study conducted since 1997 is the National Morbidity, Mortality and Air Pollution Study, which was 

funded by HEI and led by Johns Hopkins. That study examined 

daily changes in air pollution and health in the 90 largest U.S. cities. 

As shown in figure one in my testimony, the study found that 

there appeared to be a linear relationship between mortality and 

air pollution for all causes of mortality and for deaths from heart 

and lung disease without an apparent threshold. Our review committee, which intensively peer-reviews all HEI research, advised 

caution in drawing conclusions from the apparent absence of a 

threshold, but noted that the reported associations in the study are 

at ambient concentrations well below the current U.S. daily standard. 

There were two principal long-term studies in 1997, the Harvard 

Six Cities and the American Cancer Society study, and there have 

been some additional studies since, but attention has primarily focused on HEI’s reanalysis of these two and on extended analysis 

in the ACS population. 

For the reanalysis, we gained access to all underlying data in the 

studies and chose independent investigators who tested the original 

studies against a wide variety of alternative explanations. The investigators also conducted an analysis of the concentration response and figure two in my testimony presents the results, summarizing for each community the annual air pollution level and the 

risk of death due to heart and lung disease. As you can see, there 

is some scatter of effects. It is not all in a straight line, especially 

at the highest and lowest PM levels studied, but also an overall 

trend of increasing mortality risk with increases in pollution levels, 

starting at relatively low levels. 

Following the reanalysis, the original investigators for the ACS 

study conducted an extended analysis of the data, which Dr. Thurston has mentioned and participated in, and found similar results. 

While we have made much progress, there continue to be, as 

there always are in science, important questions. Two key areas 

are: First, we need continuous improvement in the statistics used 

in epidemiology to better test the sensitivity of the results, to quantify the uncertainty, and to communicate both the results and the 

uncertainties clearly. 

Second, no other question will have as much impact on future 

regulations than determining whether some components of the 
35 

complex mixture of PM are more toxic than other components. Ultimately, this data will be essential to ensuring that regulations are 

targeted at reducing those emissions which will have the most public health benefit at the least cost. 

This has also become important in light of the current proposal 

for a PM NAAQS for coarse particles, which is proposed to exclude 

certain particles from regulation. There have been some individual 

city studies of this question, but no systematic national effort to 

compare results from both epidemiology and toxicology. To fill that 

gap in time to inform a next round of PM NAAQS review, HEI has 

launched, with support from both EPA and multiple industries, a 

set of systematic multidisciplinary national studies. 

As indicated in both the NRC review of PM research priorities 

and in today’s GAO report, these PM component studies will be 

central to ensuring that future PM actions are the most effective 

possible. 

I might add that while I obviously have the utmost respect for 

Dr. McClellan and take his skepticism that we can answer this 

question as a true challenge, as a long-time Boston Red Sox fan 

and a hopeless optimist, I enter this challenge with the hope that 

we can, if we all put our minds to it, answer this question of which 

components much better 5 or 6 years from now than we can today. 

Thank you for this opportunity to testify. I would be pleased to 

answer any questions you might have. 

Senator VOINOVICH. I want to thank all the witnesses for your 

testimony this morning. 

Before I start the questioning, Chairman Inhofe asked that I insert testimony for the record from Dr. Borack on the issue of coarse 

particulate matter. Without objection, we will do that. 

[The referenced Testimony can be found on pages 171-187.] 

Senator VOINOVICH. Mr. Greenbaum, as you know, there is an 

ongoing debate about whether EPA must lower the annual standard. We talked about it last week, and this week we are trying to 

get some of you that are smarter than we are in the scientific area 

to give us your best thoughts. 

Your opinion is invaluable in this debate as an entity that sits 

squarely in the middle. You are funded by both industry and the 

EPA. Clearly, the statute says the standard shall be set, ‘‘in the 

judgment of the Administrator.’’ In your opinion, is it reasonable 

from a scientific and health perspective for the Administrator to retain the annual standard at 15 and not lower it? 

Mr. GREENBAUM. Well, Mr. Chairman, I appreciate that that is 

the $64 million question at this hearing. I tried to present the best 

view of the science that we at HEI can give you on that question. 

While the dose response or the relationships going down to the lowest levels are very clear for why we are tightening the daily standard, they are strong, but not as clear, for the long-term studies, as 

shown in the data I presented. 

There is evidence with cities showing reduced effects as you go 

down below 15 micrograms per cubic meter. I think it is exactly in 

that area where there is some certainty about these results, but 

where the Administrator has to make a policy judgment about 

whether that is certain enough to require additional actions. As Dr. 
36 

McClellan said, there is really no scientific method even that HEI 

has that could set that. 

I should add that we at HEI, since our inception, have never 

taken a position on a specific standard because of the clear concern 

that such a position would be viewed as therefore biasing any of 

our future science. So we don’t take positions on this. We don’t advocate. The science is definitely stronger on the concentration. 

Senator VOINOVICH. The question is, is it reasonable? 

Mr. GREENBAUM. I think I am going to have to leave that to the 

Administrator to make that judgment. I think that there is evidence that we didn’t have in 1997 of effects still continuing below 

15. But whether that is enough evidence to make a call for a reduction in the standard is a public health policy judgment, not a scientific judgment. 

Senator VOINOVICH. Dr. Smith, what is your opinion? 

Dr. SMITH. The way to think about setting the annual standard 

is to look at the chronic health studies. The chronic health studies 

have been the ones that have been found to have FE. 

Senator VOINOVICH. What studies again? 

Dr. SMITH. I am sorry. Chronic health studies, which are studies 

of long-term exposure to PM2.5 so they are more relevant to measures like the annual standard and annual average, rather than to 

a day to day peak, which is the daily standard. So the studies that 

look at the long-term exposure of PM2.5 with mortality are the ones 

that are in question for whether we need to tighten the annual 

standard. Those studies are some of the most difficult ones to properly control for in statistical methods. 

What we found in the reanalysis that Dr. Greenbaum’s organization performed is that in fact when reanalyzed with alternative 

methods of control, the estimate gets more and more insignificant 

as additional factors are brought into play such as SO2. SO2 when 

added into the analysis causes the PM2.5 health effect to become insignificant, issues that are complex statistical issues, and I will use 

a technical term, spatial autocorrelation, are problems if you have 

those in the analysis. They were found in the health effects studies 

for long-term standards and when controlled for, the effect becomes 

statistically insignificant, again meaning a very large probability 

that there may be no effect at all. 

So the evidence has weakened since the standard was set at 15 

micrograms per cubic meter based on that data set. I will also say, 

when that standard was set, there was evidence of effects below 15 

in that data set. That hasn’t changed. That is not new information. 

So while the analyses have held up to reanalysis and been confirmed that you can find this sort of correlation in the long-term 

studies, they are much weaker in terms of how well you can make 

a causal interpretation of them. 

Another very important finding that came out of the Health Effects Institute’s reanalysis is that in fact if you break the population that the data, if you break the cohort that is being studied 

into three groups, different educational levels, and you look at the 

group that has even 1 year of education beyond high school, which 

is what good deal of our population has, there is no effect at all. 

It is gone. It is not in that analysis. 
37 

So the effects are very dependent, the effects that are being purported and attributed to PM2.5 out of that study are now known to 

be very dependent on whether a person has had any education beyond high school or not. That relationship is found in all the studies. 

Senator VOINOVICH. What does that mean? 

Dr. SMITH. It suggests that there is a missing variable in the 

equation, basically. We know that education does not in itself make 

somebody more or less susceptible to exposures to fine particles, 

but there may be something. 

Senator VOINOVICH. Does this mean that the people that are 1 

year in high school live out in the suburbs and others live in the 

urban area and are more impacted by this? 

Dr. SMITH. It may have something to do with the poor evidence 

on what they are being exposed to. It may be something about lifestyle that actually creates risk for them that the PM2.5 is picking 

up on, but isn’t really exacerbating. It is just serving as another 

thing, a scapegoat. 

Senator VOINOVICH. Let me ask you something. If I am a smoker, 

and please forgive me if these are elementary question, but if I am 

a smoker, am I more subject to fine particle PM than if I am a nonsmoker? 

Dr. SMITH. I actually am not quite sure how that relationship 

works out in the study, but they have controlled for smoking in the 

relationship. Certainly, smoking is related to educational level, but 

smoking was controlled for when they did this analysis of whether 

there was an effect at different educational levels. So the correlation between smoking and educational level is not the education for 

what is going on there. It means there is something totally different at play. 

Until you find out what that problem is, through more study, 

more research, and it can be done, until you find out what that 

problem is that explains this unexpected and bizarre result, you 

don’t have an unbiased estimate of what the risk is. It could be 

larger or it could vanish, the PM2.5 risk, that is. 

Senator VOINOVICH. OK. In terms of the particulate matter, 

again, we are trying to reduce NOX and SOX, mercury. When they 

do the analysis of the particulate matter, they just segregate that 

out and you don’t take into consideration the impact that NOX or 

SOX. Or does particulate matter have something to do with NOX

and SOX? 

Dr. SMITH. The results that are being used in the risk analysis 

do not account for SOX or NOX or any of the other pollutants and 

whether they may have an explanatory role, too. As I said a minute 

ago. 

Senator VOINOVICH. In other words, when you are doing the, I 

always have a tough time with that word, epidemiologist do the 

studies, OK, the fact is that they are just looking, they are trying 

to figure out just what the particulate matter is. They don’t take 

into consideration that I am exposed as a person to both NOX, SOX, 

particulate matter, mercury and the rest of it, and somehow they 

are able to pull out and say these particulate matters are the 

things that are really contributing to morbidity. 
38 

Dr. SMITH. As I was saying, the mortality, as I was saying, the 

estimates that are being used right now to estimate risk from 

PM2.5 only consider PM2.5. However, the studies in the many, many 

other results that are in these papers look at other formulations, 

other methods of doing the estimate that put the other pollutants 

in to the model as well and try to understand which pollutant is 

it. Does one of them explain the effect that we are seeing for PM2.5

when that is the only one in the model? Is there another pollutant 

that could explain it better, when we put them both in the model? 

What is found in study after study after study when this is done 

is that the PM2.5 effect goes away, becomes statistically insignificant is what I mean. The other pollutant that is in the model that 

is being explained by the analysis at the same time retains its statistical significance. I looked at all the PM2.5 short-term studies 

that I could find that did this analysis, this type of two pollutant 

analysis. I found that the vast majority of them had the PM2.5 effect that was statistically significant if it was the only one in the 

model, become statistically insignificant when one of the gaseous 

pollutants, and these included ozone, SO2, NOX, and carbon monoxide. The same thing is going on in the chronic studies for SO2. 

Senator VOINOVICH. To get back to the original question. If the 

Administrator, is it reasonable from a scientific and health perspective for him to retain the annual standard at 15 and not lower it? 

Is it reasonable? 

Dr. SMITH. Given the basis for the standard of 15, which was the 

same chronic studies that I have just described to you, but before 

we studied them and discovered some of the underlying uncertainties in them, and given that the risks are lower now based on the 

new evidence using their point estimates, it seems quite reasonable 

to say that we haven’t learned anything that says that that standard has a smaller margin of safety than it had when the standard 

was set. 

Senator VOINOVICH. So you would say that if he did it, it would 

be reasonable. 

Dr. SMITH. That could be reasonable. 

Senator VOINOVICH. May I ask another question? In terms of sulfur and NOX, in terms of public health, and particulate matter, 

which is the worst? 

Dr. SMITH. Between sulfur and NOX SO2 and NOX

Senator VOINOVICH. Sulfur dioxide or NOX, if you were able to 

reduce those substantially, in terms of public health, which one of 

those is the worst? 

Dr. SMITH. I really cannot say. 

Senator VOINOVICH. I would be interested in all of you. 

Dr. SMITH. I just don’t know. I have not actually done a relative 

analysis of SO2 and NOX. 

Senator VOINOVICH. Well, has anybody done an analysis at the 

table? Dr. Thurston, you have been around a long time. You have 

testified a lot of times before this committee. Do you have an opinion? 

Dr. THURSTON. Well, yes, I would like to respond to a few things 

that were just said, including that. 

Mr. GREENBAUM. Senator, I realize you are going to go through 

everybody, but I would like, since it was HEI who conducted the 
39 

reanalysis I would like to have the opportunity to clarify for the 

record what we did conclude. 

Senator VOINOVICH. Get your mike there, please. Go ahead. 

Mr. GREENBAUM. I’m sorry. 

Senator VOINOVICH. OK, go ahead. 

Mr. GREENBAUM. I just want to, and I don’t mean to take away 

from Dr. Thurston, but I did want to clarify what the HEI reanalysis of the long-term studies in effect did and didn’t find, because 

there has been some degree of confusion just thrown into it unfortunately by Dr. Smith’s comments. 

First of all, I think everybody can in this process pick their favorite study and their favorite result from the study and try to emphasize that, so they can emphasize the one that has multiple pollutants in it and say there is no effect, or they might emphasize the 

one that has no other pollutants but PM in it and say there is a 

big effect of PM. 

Our Review Committee, in our review of the reanalysis—this 

very intensive look these studies—had to look across all of the 

analyses to figure out which ones were the right ones, which ones 

were the wrong ones, which ones were statistically stronger or 

weaker. While, of course, that group of scientists identified continuing questions for those studies, we did find as strength of the 

evidence that the effects of PM were robust to a number of analyses that were done. 

We also found for the first time a strong effect of sulfur dioxide 

in that, although our committee, and this is in partial answer to 

your question, did not think that sulfur dioxide itself could be attributed to doing that, based on toxicology information, but that it 

might be a marker for something else in the air that would travel 

with it, but we are just not measuring that, and therefore we don’t 

have information about that other substance. 

The reanalysis definitely found, after test after test after test, 

stronger results from those studies, with some continuing questions. We certainly had that. 

Second, on the question of education, and how education modifies 

the results, certainly there was a stronger result shown for those 

with the least education in terms of increased mortality. We do 

largely view educational levels as one marker for poverty or socioeconomic status. We know that poverty and socioeconomic status 

themselves can have effects on health. People can have less good 

medical care, less good nutrition, and a number of other things 

that shorten their lives. We know that and our reviewers certainly 

understood that as well. 

In that analysis, in the reanalysis, however, when you looked at 

heart and lung disease deaths, which is not what Dr. Smith put in 

her testimony, you still see some effect in everybody else in the 

population. That effect was marginally statistically significant, but 

still there. Our investigators, our reviewers felt two things, that: 

One, that there was a continued effect at these different levels, 

with the strongest effect being that those with the least education 

and probably least socioeconomic status, and that might be because 

of higher exposures, less access to air conditioning, and a number 

of other things that would increase the effect. 
40 

Two, they also did note that no study is perfect, so there probably is still, somewhere in there, some continued confounding 

where the results are showing an effect of being poor, but they 

didn’t suggest that that explained the whole effect. I just wanted 

to clarify that. 

And then they did test all of the pollutants in the reanalysis, including nitrogen oxides and sulfur dioxide and ozone. Sulfur dioxide was the only one that showed effects and had any effect on the 

PM results. As I said earlier, they thought that was important to 

understand. They understood that we need to do more work on 

that. They weren’t sure that it was the sulfur dioxide. In fact, the 

sulfur dioxide might have been a marker for other types of particles that are coming along with the sulfur dioxide, not the gases 

themselves. There could, for example, be metals that come out of 

the same sources. 

So I thank you for the opportunity. I just wanted to clarify what 

our reanalysis did say, and obviously the full report was actually 

presented to you at an earlier hearing. 

Thanks. 

Senator VOINOVICH. Dr. Thurston. 

Dr. THURSTON. Yes, thank you. 

Before we start out, you were noting that Dr. Greenbaum is between Government and industry. I just want to point out that I 

represent, I think, a disinterested party. I am a tenured professor 

at NYU. My salary is paid by NYU. I don’t do consulting for the 

vested interests involved here. So I feel that my testimony should 

be viewed as a disinterested party, not an uninterested party, but 

a disinterested party. 

I have to agree with Dr. Greenbaum’s discussion of the SO2 and 

the HEI reanalysis. SO2, it is clearly stated. You know, I think that 

unfortunately what Dr. Smith has done here is exactly what she 

accuses EPA of having done. She has cherry-picked certain results 

that support her position and unfortunately hasn’t looked in a balanced unbiased way at this question. 

Senator VOINOVICH. Can I ask you something? 

Dr. THURSTON. Yes. 

Senator VOINOVICH. What is it that contributes to the particles? 

You have coarse particles, you have fine particles. We are becoming 

more concerned about fine particles. I know I have been at the University of Cincinnati, the Children’s Hospital down there. They are 

doing a study of diesel fumes on urban kids—— 

Dr. THURSTON. Yes, I have done that myself. 

Senator VOINOVICH [continuing]. The development and so forth. 

But we are talking about the things that cause the particles. Is it 

basically emissions from automobiles? What is it? What is the 

cause of this? 

Dr. THURSTON. On that question, you made a good point, you 

know, that these are oftentimes markers. I think the SO2 being a 

marker of largely power plant pollution in the United States; NOX

being largely a marker of traffic. It is very likely, actually, that 

that SO2 in the ACS study, because I have done some of this analysis, of course, as being PI of the NIH-funded portion of that, that 

the SO2 is a marker for power plant pollution, and that contribution to mortality. 
41 

It depends on the health outcome you are looking at and where 

you are. 

Senator VOINOVICH. The particulate matter we are talking about, 

you know, what is the biggest source of particulate matter? 

Dr. THURSTON. Well, there are different types, and I think what 

we are wrestling with is: Which effects are caused by which types? 

But I think it is safe to say if you lower the fine particle levels, 

you are going to better protect health. So the standard is necessary. It is appropriate. As we learn more, we may be able to refine that further. 

Senator VOINOVICH. Just for example, we are trying to make 

things better, and we are going to set a standard. Well, somebody 

is going to have to meet a standard, but if you were going to meet 

the standard, do you do that by reducing diesel emissions? Or what 

is it that is going to have the biggest impact on, if you assume 

what you are saying, that fine particle matters are bad and if you 

set it at 12, everybody’s going to live longer than if you have it at 

15, what is it that you have to do in order to make sure that you 

don’t expose people to these things? 

Dr. THURSTON. Well, I think that is going to vary depending on 

where you are. If you are in Los Angeles, I think traffic would be 

a good thing to try, the pollution from traffic. If you are in the 

Northeastern United States, power plants are a big problem there, 

but not so much in Los Angeles. 

So I think that the States will implement controls on the pollution problems that are the largest. I think as we go on, I mean, this 

is going to take us 20 years before we are finished with this process, in reality, of meeting the standard that is set. So as we go 

through it in that time, we should be able to provide the kind of 

research that HEI is funding, that EPA is funding. In 5 years, I 

think we will be able to give you a better answer. As the States 

move to the implementation phase, they will have that information 

about the sources. 

Senator VOINOVICH. But the answer that they come up with is 

that at 12 it would have a major impact on the economy of this 

country and the environment in various places. There is just no 

question about it. 

Dr. THURSTON. But it would have major benefits, health benefits 

of lowering it to 12. I agree with that. The past has shown that environmental controls are not a big problem economically. We have 

been able to. We have other problems with economics, as you are 

well aware. 

Senator VOINOVICH. Dr. Thurston, let me tell you something. I 

am a former Governor of Ohio, OK. The first thing I did was try 

to get my counties into compliance with the current ambient air 

standards because my businesses told me they weren’t going to expand, and we knew from an economic development point of view 

that those counties that weren’t in attainment wouldn’t even get 

smelled by businesses that we were trying to bring to our State. 

Today, with the new rule, we have a number of counties throughout the United States that are not compliant with particulate matter. They have this stamp on them: don’t expand, cost you more, 

don’t go there, cost you more. If we reduce the standard from 15 

to 12, and there are going to be a whole lot more of those through-
42 

out the country, it will have an impact on the economy of those respective communities. 

Now, that is not supposed to even be paid attention to, so they 

can’t do it, but it seems to me that we have a lot of speculation 

going on whether it should be 15 or 12 or 14, that we ought to be 

pretty sure, pretty certain about some of the conclusions that we 

come to. 

I have a problem, that I am just wondering about, you know, the 

budget, the monitoring budget, the $17 million. Senator Carper and 

I have been trying to get them to have an Assistant Administrator 

for Science in the EPA. Does the EPA have the brains and the people to get the job done? 

Dr. THURSTON. I can’t answer that one. But you know, I think 

the last time we spoke, we both agreed that we as a country need 

to set a standard for the rest of the world, and we need to develop 

the technology to meet these standards and then sell it to the rest 

of the world. 

Look at China. The pollution problems there are huge. That is 

a huge market for the United States. If we develop the control 

technology here first, if we confront this problem first, we can then 

turn lemons into lemonade, if you want to view it that way. We can 

be first to clean the air, and sell that to the rest of the world. We 

agreed on that, as I recall, the last time. I think it is time we got 

on with that process. 

Now, to get back to the issues, this education question. Being one 

of the authors of this, we have looked into this. I agree with Mr. 

Greenbaum on this. I just would like to point out, one of the things 

we have looked at is the migration question, and that is that people 

of lower income tend to not move out of their MSA. They are not 

highly mobile. We looked at the data and they tend to stay exactly 

where they are year after year after year. 

Whereas higher educated people are much more mobile, and that 

makes it so that the exposure estimates that we are using in our 

studies are less reliable and therefore, some of them move to higher exposure areas, some move to lower, so that we are going to 

have greater difficulty finding an association in those places. 

That leads us to believe that the estimates of the lower income 

people are probably more accurate and yes, the higher income people, the higher educated people are having the effects, but they 

don’t show up in a study because the studies’ estimates of their exposures are not as good as for the less educated people. 

So I think what that says is that what we have reported is the 

average of all three. Probably the lower income people are giving 

us the most accurate estimates, which means they are much higher 

than we thought, and that is part of the equation why, in the expert elicitation, the various experts, a dozen experts, have come up 

with estimates much higher than the ACS study because they have 

adjusted for this factor and others that have come. 

So when you resolve uncertainties, we are not going to lower estimates of the pollution. We are resolving uncertainties and figuring 

out what is going on, and actually, the impacts are going up in 

terms of the long-term exposure which is, you know, that is what 

most of the deaths are associated with, the long-term exposure to 
43 

this pollutant, which is pervasive year after year, day after day, for 

every American. 

Senator VOINOVICH. Thank you. 

Senator Carper, I didn’t think you were coming back. I was taking everybody’s questioning time. 

I think in fairness to Dr. McClellan, we have less than a minute, 

because Senator Carper is here. 

Dr. MCCLELLAN. I would like to respond to your question in 

terms of lowering the annual standard. 

Senator VOINOVICH. The question was reasonable, would it be 

reasonable? 

Dr. MCCLELLAN. Yes. I am on record as stating that I think that 

the staff paper laid out the science. It had a range of 12 to 15 mg/ 

m3. I felt that was the appropriate expression of the science, and, 

thus, the Administrator’s policy judgment to go with 15 mg/m3 I 

thought was appropriate. 

I did not think, as a member of CASAC, that it was appropriate 

to narrow the range of 12 to 15 down to 13 to 14. In fact, I thought 

that was just one step away from saying, this is the standard that 

should be set. I thought that overstepped the bounds. 

I would like to use one of Dr. Thurston’s graphs, if I could, to 

point out some of the difficulties here. This is the Harvard Six Cities study, started back in 1979 which I view as a platnium study. 

The late Dr. Ben Ferris was the guiding light that pulled together 

people in teams of six different communities. One of those happens 

to be in your State, Steubenville. OH. It started as an extensive 

study I think of about 8,000 people over time. 

Now, here are the results from this. I think it is important to 

look at the graph. Across the bottom we have PM2.5 micrograms 

per cubic meter, zero to 30. Now, we have a single number there 

on that. Now, you will note that each of the cities has changed over 

time. Steubenville was originally up close to 30 and now it is down 

just above 20. You can’t express in this graph what it was in 1950? 

What was it in 1940? Most of the deaths that are expressed in here 

are of the elderly. We know that. In the United States, people live 

long lives. So in any expression of death, they are going to be the 

individuals being counted. 

What we are not able to show on this graph is what these people 

were exposed to in those earlier years before we had the monitoring? We know that that was substantially higher, so we haven’t 

captured that value in this data. What I am willing to say, looking 

at long-term data, is those values must have been substantially 

higher. 

Now, we look over here at the mortality relative risk of mortality 

related to PM exposive. I want to emphasize, we sometimes talk 

about excess deaths. It is important to recognize that when we conduct epidemiological studies we do not create extra deaths. What 

we do is try to take the deaths that have occurred and tease out 

what they may have been associated with. 

In terms of cardiopulmonary deaths, we know the biggest risk 

factor is cigarette smoking. If you go to the data of Engstrom, out 

of LA, his relative risk factors for the all cause mortality for smokers, about a pack a day, was 2.0. That would be way the heck up 
44 

there on this graph. A value of 1.0 means there are no deaths assignable to PM. 

So one of the things we do know if we look in terms of the baseline for this relative risk, death rates for cardiopulmonary deaths 

have been going down. For lung cancer, we have seen for the first 

time a decrease in lung cancer mortality. Why, because people quit 

smoking? 

So the data that Dr. Smith related to, I suspect, if I were able 

to examine her calculations, we would find that in all of the eight 

cities, there were improvements, and so the base for that relative 

risk factor is going down resulting in fewer calculated deaths related to PM in the air. 

What I am saying is when you look at all of this data, I think 

the Administrator was fully appropriate in his policy judgment to 

continue at 15 micrograms per cubic meter, and I think when that 

is ultimately met across the country, we will have I think some 

small improvement in total health. 

Senator VOINOVICH. I thank you very much for that. I will turn 

it over to Senator Carper. I just couldn’t help, and I think you will 

understand this, I will never forget campaigning for Governor in 

1990 in Steubenville, OH. I ran into a woman who was an immigrant, and we were talking about the air, and she said, ‘‘Mr. Voinovich, I put the sheets out in the old days and there would be black 

stuff on it. Now I put it out, no black stuff. The sheets are clean, 

but nobody is working.’’ 

And that was it. We didn’t get into the health or anything else, 

but the fact of the matter was that things were better for her environment, but the thing that she was concerned about is that nobody was working and wanted me to do something about bringing 

jobs to Steubenville, OH. 

Senator CARPER. That was actually a pretty good segue, because 

I have just come from a hearing in the Banking Committee which 

is going on downstairs. Every 6 months, the Chairman of the Federal Reserve comes and testifies to brief the House and the Senate 

on monetary policy. He was just sharing with us how strong our 

GDP growth is, 5.6 percent I guess for the last quarter, how many 

new jobs are created thus far this year, and large growth in Federal revenues and that sort of thing. 

But the progress, the economic growth is uneven across the country. Frankly, the growth in incomes is uneven across our citizenry, 

as we know. 

I apologize for missing your testimony. Whenever the Chairman 

of the Federal Reserve comes and testifies, he doesn’t do it often, 

I try to be there. I like to kid and say he won’t go forward until 

I am there, but that is not really the case. But I wanted to be there 

to be able to offer a statement or two and maybe ask a question 

of him. 

I appreciate the fact that you are here. We appreciate your testimony, your input, and your willingness to respond to our questions. 

I have a couple of specific questions of Dr. Thurston. Before I do, 

I have sort of an unwritten rule that whenever one witness uses 

the charts of another witness to make a point, we always give the 

owner of the charts the opportunity to have the last word. Do you 
45 

have any comment or any response you want to make to Dr. 

McClellan’s comments? 

Dr. THURSTON. Yes, I do. I thank you for that opportunity. 

Well, you know, I think that his reference to, well, first of all, 

his references to cigarette smoking, these studies have been controlled for cigarette smoking. 

Senator CARPER. Say that again? 

Dr. THURSTON. Have been controlled for, this study that is represented here has been controlled for cigarette smoking. 

Senator CARPER. OK. 

Dr. THURSTON. OK. So these reductions in relative risk have 

nothing at all to do with cigarette smoking and the fact that people 

are smoking less. This has to do with the reductions in air pollution after controlling for all these other factors that they studied. 

This is a cohort study where they had individual information about 

each of the people in the study. 

The other thing he is talking about, well, exposures long ago that 

could be responsible for these effects. There is recent research that 

indicates that it is really the exposure in the last 5, at most 10 

years of your life, or up until the time of death that are the most 

important. Even if you look at cigarette smoking, when someone 

quits cigarette smoking, the Surgeon General’s report points out, 

within 10 years their mortality risk is the same as the general public. It is similar with air pollution. The benefits are yielded very 

quickly, actually, after the exposure is reduced. We see that in this 

study and we see it in others. 

We are looking at the ACS study, looking at these windows of exposures, and we will be publishing on that as well. But I know 

there are papers out there, like Kunsley’s recent paper pointing 

this out. So that is really my response to his comments. 

Senator CARPER. Good. Well, thank for sharing that. 

Perhaps a couple of specific questions of Dr. Thurston. Dr. Smith 

and Mr. Greenbaum, I missed your testimony, as you know. What 

I am going to ask you to do is, take no more than a minute, but 

just give me my takeaways. It is impossible for us to remember everything you said or say, but just, if we remember nothing else, of 

a couple of key points that you made, what should we take away 

from here? 

Dr. SMITH. Just a minute. 

I think the key takeaway is that if you want to understand 

whether to tighten the standard, rather than whether we need the 

standard that we have, then you need to look to the question of 

what is happening to the margin of safety that was deemed acceptable when that standard was set, and using the new evidence that 

we have today is that the margin of safety that is associated with 

the current standard has, if anything, grown, not narrowed. 

So while there is better information across the board, there does 

seem to be confirmation that there is some subtle effect going on 

with air pollution, that was assumed at the time the standard was 

set, and the standard at that time was set so that it provided a 

margin of safety, and that margin of safety remains today even in 

the face of all of this new evidence. 

Senator CARPER. Thank you. 

Mr. GREENBAUM. 
46 

Mr. GREENBAUM. Sure. Just three things. First, we have made 

tremendous progress since 1997 in understanding a whole series of 

questions we had then. In fact, they are not even on the table now 

in the same way because of research that was chartered by Congress and then put into place over the last 6 to 7 years to answer 

those questions. 

Second, one part of that research has been to look at the socalled concentration response, what happens at higher and lower 

levels of pollution? Do we see more effects, less effects? Is there a 

point below which we don’t see any effects? And there, we have 

seen, 0 with some uncertainty at both ends of the range, generally 

increasing effects with increasing levels of pollution, a generally 

linear relationship between those two. 

At the same time, and the third point, looking forward, there are 

still, as science always has, important continuing questions, probably most importantly, the one around understanding whether 

there is a different toxicity of different components of PM, really 

different sources of PM, to guide future regulatory decisions. 

Senator CARPER. Good, thanks. My thanks to both of you. 

Dr. Thurston, a couple of questions, if I could. Do you believe 

that there is certain, I would underline the word certain, scientific 

evidence to justify lowering the annual standard? 

Dr. THURSTON. Yes, I certainly do. The bulk of the evidence, as 

EPA has presented it, shows that we need to tighten these standards, that there are health effects below the present standards and 

that they need to be tightened. 

Senator CARPER. OK. I think, and I didn’t hear this issue, but 

Dr. Smith I believe you may have suggested that the risk of fine 

particles has actually decreased in your testimony. I would ask of 

Dr. Thurston if you want to comment on that. I don’t want to 

mischaracterize what she said, but if I have that right, would you 

just comment on it? 

Dr. THURSTON. Well, as I said in my testimony, I believe that, 

and I think the evidence supports, that the uncertainties associated 

with our estimates have actually decreased. We are more certain 

of the effects, the biological mechanism, and the size of the effects. 

So uncertainty has been diminished. 

I want to clarify the distinction between, I guess, uncertainty 

and doubt. There is no doubt that air pollution is causing these effects, and there is no doubt that lowering these pollution levels will 

reap huge health benefits. There is uncertainty exactly how much 

benefit for how much pollution. So that is uncertainty of the estimate. It could be higher. It could be lower. In the case of the long 

term, the scientific consensus is moving that the health effects of 

PM2.5 long-term exposures are actually higher than we previously 

thought. 

So there is uncertainty around the estimates, but there is really 

no doubt here. 

Senator CARPER. All right. My thanks to each of you. I am glad 

you were still here when I got back. Again, I appreciate very much 

your testimony and responding to our questions. Thank you. 

Senator VOINOVICH. Thank you much. I really believe that I have 

gotten some more clarity here, at least in terms of people’s dif-
47 

ferences in terms of this standard. Hopefully, this will help the Administrator make the right decision. 

Thank you very, very much. The hearing is adjourned. 

[Whereupon, at 11:30 a.m. the committee was adjourned, to reconvene at the call of the Chair.] 

[Additional statements submitted for the record follows.] 

STATEMENT OF HON. JOSEPH LIEBERMAN, U.S. SENATOR FROM

THE STATE OF CONNECTICUT

Thank you, Mr. Chairman. 

In my view, EPA’s most fundamental responsibility under the Clean Air Act is 

to tell Americans truthfully whether the concentrations of pollution in the air they 

breathe are at levels that endanger their health. If EPA knows that particulate matter hurts people at lower concentrations than those reflected in the agency’s existing 

air-quality standards, then I believe the agency has a legal and a moral responsibility to tighten the standards. 

Following an exhaustive review of peer-reviewed studies on the subject, the scientists, doctors, and public servants on the congressionally chartered Clean Air 

Science Advisory Committee have told EPA that air-borne particulate matter is triggering large numbers of asthma attacks, heart attacks, and premature deaths in 

many areas of the country that meet EPA’s existing air quality standards for particulate matter. That leads me directly to the conclusion that EPA must make those 

standards more stringent. An alternative risk analysis requested by the White 

House Office of Information and Regulatory Affairs has just come to the same conclusion. 

Unfortunately, EPA has proposed to not lower the annual particulate standard at 

all, and to lower the daily standard to a level that remains above the limit that the 

Science Advisory Committee has identified as necessary to protect public health. 

I do not believe that EPA can justify this disregard for the Science Advisory Committee’s recommendations. Skeptics enjoyed representation on the Committee and 

ample opportunity to press their views. To me, it makes no sense to disregard the 

Committee’s conclusions based on complaints that were not sufficiently compelling 

to convince that expert body. Here I note that only two of the twenty-two members 

of the Committee’s panel on particulate matter dissented from the panel’s conclusions, and that all seven members of the committee agreed with the panel’s majority. 

Having reviewed the statements and testimony delivered at last week’s hearing, 

it appears to me that the impetus behind the calls for EPA to disregard the Science 

Advisory Committee’s recommendations is not dissatisfaction with the scientific 

work of the Committee, but rather concern over the cost of bringing air quality into 

line with more stringent standards. 

Clearly, achieving further reductions in particulate-forming emissions will cost 

money. That is why the Clean Air Act’s system for implementing the health-based 

air-quality standards includes, at nearly every turn, generous regard for what is 

practicable and what is not. There is no need, then, to flout the Act by infecting 

the standard-setting process with considerations of implementation costs. I would 

point out, moreover, that by any reasonable measure, the economic benefit of the 

lives saved and illnesses averted by bringing particulate levels down to the levels 

recommended by the Science Advisory Committee would vastly outweigh the economic costs of the added pollution controls. 

The concentrations of particulate matter persisting in many parts of the country 

cause more than 45,000 premature deaths every year. The problem is too grave and 

too large to be concealed. We can solve this problem, and the first step is to level 

with the American people. That is why I urge EPA to set the revised particulate 

matter standards at the levels that the Science Advisory Committee has determined 

necessary to protect public health. Thank you, Mr. Chairman. 

STATEMENT OF GEORGE GRAY, ASSISTANT ADMINISTRATOR FOR RESEARCH AND

DEVELOPMENT, U.S. ENVIRONMENTAL PROTECTION AGENCY

Good morning, my name is George Gray, and I am the Assistant Administrator 

for the Office of Research and Development in EPA. I wish to thank you for the 

opportunity to discuss the EPA’s evaluation of the scientific evidence for potential 

health effects of airborne particulate matter (PM). Last week the Subcommittee on 

Clean Air, Climate Change and Nuclear Safety heard from my colleague, William 
48 

L. Wehrum, the Acting Assistant Administrator for Air and Radiation, on the EPA’s 

review of the national ambient air quality standards (NAAQS) for PM. During that 

testimony he explained the crucial role of science in helping to inform decisions 

about the National Ambient Air Quality Standards. 

Today, I would like to talk with you in more detail about this science: how it is 

prioritized and developed, and how it is synthesized and integrated. As Assistant 

Administrator for EPA’s Office of Research and Development (ORD), I am responsible both for the development of new scientific information targeted to address critical Agency research needs and for the evaluation, synthesis, and integration of the 

world’s peer-reviewed science literature into a document that informs EPA decisionmakers. As we characterize the current state of our collective scientific knowledge, 

we are careful to point out the strengths and weaknesses of this large body of information, so that informed decisions can be made. It is clear that the scientists and 

staff of ORD play a crucial role in the development and evaluation of the world’s 

scientific information to inform the review of National Ambient Air Quality Standards. 

We all agree that environmental protection efforts must be based on high quality 

science. High quality science includes both the conduct of research—in the laboratory and in the field—and the careful evaluation of that body of research to inform 

policy making. High quality research is focused appropriately on generating new 

knowledge that addresses complex scientific issues and helps reduce important scientific uncertainties. It is carefully planned, well conducted, and thoroughly peer reviewed by independent scientific experts. The careful and balanced characterization 

of the body of knowledge created by high quality science requires an open process, 

interaction with appropriate subject matter experts, and serious consideration of the 

ways in which the results are communicated to decision makers. To me, an important component of high quality science is the characterization of the uncertainties 

related to individual studies and, more generally, the characterization of the weight 

of the scientific evidence. 

First, let me discuss EPA’s efforts to develop new and relevant science on particulate matter. The Agency has a longstanding and strong program to develop and use 

new scientific knowledge on the health effects of airborne PM. After the last review 

of the PM NAAQS in 1997, EPA embarked on a very ambitious research effort to 

advance our knowledge and address important uncertainties in the science related 

to PM. Congress requested that we sponsor the National Academies of Science 

(NAS) to provide us advice. The NAS Committee on Research Priorities for Airborne 

Particulate Matter in the National Research Council completed four reports, published between 1998 and 2004, which provided the scientific basis EPA used to target its resources to address the highest priority PM research needs. These needs are 

being addressed by the Agency’s particulate matter research program, with more 

than $500 million during the past 10 years committed by EPA in support of the 

highest priority research topics identified by the NAS. These funds have supported 

numerous research efforts by EPA’s intramural laboratories, as well as extramural 

researchers funded through our competitively awarded Science to Achieve Results 

(STAR) program, our PM Research Centers, and interagency agreements with other 

federal agencies. EPA also coordinates closely with other federal agencies on PM research through the Committee on Environment and Natural Resources (CENR) Air 

Quality Research Subcommittee and its Interagency Working Group on Particulate 

Matter. 

We learn about the potential health effects of PM through several different types 

of research, especially epidemiology and toxicology. Guided by the NAS and other 

advisors, the Agency has funded research in all of these areas. Epidemiologic studies 

supported by EPA and others provide key information in our evaluation of PM. This 

research includes population-based studies that evaluate potential associations between human exposure to PM and health outcomes, including death, hospitalization, 

illness, and potential precursors to illness. We have sponsored research on populations of tens to hundreds of thousands of individuals in the United States that 

evaluates the effects of long-term exposure to PM on illness and death. These include both cohort studies and panel studies. Other research uses a different design—called time-series studies—in which air pollution levels are tracked on a dayto-day basis and compared with daily variations in health statistics to evaluate the 

effects of short-term exposures to PM on health. These time-series studies included 

hundreds of communities and databases that describe millions of residents. Other 

epidemiologic studies attempt to identify factors affecting people’s susceptibility and 

the role of co-pollutant exposures. 

Toxicology studies, sponsored by EPA and others, provide both information to 

evaluate the strength and plausibility of the associations identified through epidemiology and hypotheses that form the basis of new epidemiological studies. Important 
49 

studies include those that evaluate the components of PM that may be producing 

toxicity, and the mechanisms by which such toxicity might occur. 

These research efforts have resulted in literally thousands of published studies in 

the peer-reviewed literature over the past several years. In 2005, EPA prepared a 

report, Particulate Matter Research Program: Five Years of Progress, which highlighted the early results of EPA’s substantial investment in PM. When it came time 

to prepare the science basis for the next evaluation of the PM standards (the 2004 

Air Quality Criteria Document), more than 4000 articles from the peer-reviewed literature were reviewed—many of which came from research EPA had done in our 

laboratories or had funded through our STAR grants. 

A second, and equally important, function of EPA efforts is the synthesis and integration of these thousands of individual ‘‘acts of science’’ to provide a clear characterization of our knowledge and the degree to which we still are uncertain about 

aspects of PM health and environmental effects. We have a scientifically rigorous 

process by which we evaluate and interpret this important body of knowledge and 

ensure that our interpretation of them is complete, transparent, unbiased, and consistent with the array of views in the scientific community. A fundamental step in 

the review of the National Ambient Air Quality Standards is the evaluation of scientific evidence and the preparation of scientific assessments, by the National Center for Environmental Assessment of the Office of Research and Development, 

known as ‘‘criteria documents.’’ The development of criteria documents involves the 

review of thousands of peer-reviewed research publications, evaluation of those 

studies most relevant to the review of the air quality standards, and integration of 

the scientific evidence across disciplines. The body of evidence must be reviewed, 

evaluated, weighed and then accurately and objectively described to inform our decisions about National Ambient Air Quality Standards. 

For the current PM review, EPA evaluated research studies that addressed a wide 

range of issues including PM toxicology, epidemiology, atmospheric chemistry, 

human exposure, and other areas such as environmental effects. Thousands of studies were reviewed and over 2000 studies were referenced in the criteria document, 

many of which were conducted or funded by EPA’s Office of Research and Development. Considered together, these new studies significantly advanced our understanding of PM’s potential effects on public health and welfare and reduced the uncertainty associated with some important aspects of the science. Drawing on the 

evaluation of studies reviewed in the PM criteria document about health effects and 

dose-response, as well as information about exposures to PM, EPA also completed 

a risk assessment to estimate the degree to which various approaches for revising 

the standards would potentially affect the public health risks posed by PM. Further, 

the Agency prepared a document known as a ‘‘staff paper’’ that utilized the evaluation and characterization of scientific evidence in the criteria document together 

with the results of the risk assessment to help inform the policy judgments required 

in making decisions on the NAAQS. 

Extensive independent external peer review was conducted on the criteria document, risk assessment, and staff paper by the Clean Air Scientific Advisory Committee (CASAC). CASAC, statutorily-mandated under the Clean Air Act, is a group 

of independent scientific and technical experts appointed by the Administrator to review EPA’s evaluation and use of scientific and technical information related to air 

quality and make recommendations as appropriate. CASAC is made up of nationally-recognized scientists from a variety of relevant disciplines. For PM, CASAC was 

extensively involved in reviewing and commenting on several drafts of the PM criteria document, staff paper, and risk assessment. Their efforts, and those by EPA 

staff to address CASAC’s comments, resulted in a PM science assessment that provides comprehensive, relevant information suitable to serve as the scientific basis 

for Administrator Johnson’s decisions on the PM NAAQS. 

Let me briefly highlight some scientific information available on particulate matter. First, as a scientist, I know that all scientific research includes aspects of uncertainty. For example, we often do not understand the mechanisms by which pollutants such as particulate matter produce health effects in the population. We know 

our measurements of environmental conditions and biological response contain some 

uncertainty due both to our understanding and technological limits. To have uncertainty is normal. Uncertainty is a factor to be characterized and considered in the 

evaluation of studies and other data. We always consider the strengths and limitations of the available evidence when drawing conclusions about what that evidence 

means for decision making. 

For example, we highlighted the uncertainty in the evidence linking chronic exposure to PM2.5 with premature mortality in the 1997 review of the PM NAAQS. In 

the next few years, EPA responded by funding a major reanalysis by independent 

investigators of two important long-term studies that used data from a Harvard Six 
50 

Cities cohort and an American Cancer Society cohort. The quality of the data was 

evaluated, and an extensive series of sensitivity analyses were performed using various statistical models to test for the influence of many potential co-variables. The 

results duplicated the association between levels of chronic exposure to PM2.5 and 

premature mortality. These analyses were important in reducing our uncertainty 

about the consideration of these data in the standard-setting process. In addition, 

the analyses identified other avenues of research. For example, one study indicated 

that the estimated effects of fine particles appeared to vary with education level. 

In another example of our efforts to tackle uncertainty, EPA sponsored a number 

of multi-city epidemiologic studies designed to address the limitations inherent in 

single-city studies. Multi-city studies allow the assessment of risks of mortality or 

hospitalization across cities, thus reducing uncertainty regarding the effects of local 

features, such as differing mixes of pollutants and climates, on the interpretation 

of study findings. The results of these multi-city studies provide additional evidence 

that levels of exposure to PM2.5 are likely to be linked with serious health effects. 

Another major area of uncertainty remaining from the previous review was the 

lack of demonstrated biological mechanisms or pathways by which PM exposure 

could result in the effects observed in population-based studies. An important factor 

in evaluating the associations uncovered in epidemiologic investigations is biological 

plausibility, i.e., whether there is a coherent way in which the reported association 

could be expected to occur in the body. As noted in our 2005 report, EPA-funded 

research has provided crucial insights into numerous hypothesized mechanisms; including evidence that exposure to particles may contribute to atherosclerosis development and affect cardiac rhythm, thus linking the findings of mortality in the epidemiologic studies to plausible biological mechanisms of toxicity. 

Looking across the large landscape of study findings, our assessment of the research results for particulate matter finds evidence of a coherence of health effects 

associated with PM2.5 across many types of study designs, biological endpoints and 

time frames. The body of evidence—the thousands of studies from a wide variety 

of disciplines we have evaluated with the help of CASAC—demonstrates that PM2.5

exposure is likely causally associated with outcomes such as cardiovascular and respiratory morbidity and premature mortality from both epidemiologic and toxicology 

studies. Toxicology studies help us understand the mechanisms that provide some 

evidence of biological plausibility in the observations from epidemiological studies. 

We recognize that uncertainty exists, but uncertainty is not a barrier to decisionmaking; rather it is critical information to be factored into informed decisions. 

We also recognize that science is not static. New studies on PM are being published in the peer-reviewed literature all the time. As a continuation of the scientific 

review process, EPA recently conducted a survey of the evidence reported in the scientific literature since completion of the literature review reflected in the 2004 criteria document. This new survey includes some 700 additional studies and has emphasized the studies most relevant to the PM NAAQS decision. The provisional assessment of these new studies has only just been completed. To provide the public 

with an opportunity to review the survey results, we will provide notice of the completion of this survey and post the results on our Web sites. In brief, the provisional 

assessment concluded that taken in context, the new information and findings provide additional support regarding the health effects of PM exposure made in the 

2004 PM Air Quality Criteria Document but do not materially change any of the 

broad scientific conclusions. 

In summary, the Bush Administration is committed to the development and use 

of the highest quality science to inform environmental decision making. The mission 

of the Office of Research and Development is to develop, evaluate, and communicate 

relevant scientific information to the Administrator, and to assure that the Administrator is well informed of the nature, strengths, and limitations of this information. 

EPA has sponsored a targeted and effective research program on particulate matter 

and I am pleased to convey to you and others the value of this investment. We have 

made a great effort to evaluate and characterize the existing and new scientific results available on particulate matter, and I am personally pleased to share with you 

my views on this work. I look forward to addressing any questions you may have. 

Thank you. 

RESPONSES BY GEORGE GRAY TO AN ADDITIONAL QUESTION FROM

SENATOR INHOFE

Question 1. The General Accountability Office found that EPA has fully implemented only 8 of the National Academy of Sciences’ 34 recommendations in conducting its PM air quality review. One of its recommendations was to include a cal 
51 

culation of the total costs and benefits, including indirect benefits, in its regulatory 

impact analysis. It is well established that economic growth is associated with 

health, and conversely, economic costs and associated job losses is associated with 

increased mortality. In light of this, it is only possible to determine the net health 

benefit if these indirect costs are calculated. Does EPA intend to in the final RIA 

calculate the net benefits, including indirect disbenefits? 

Response. EPA believes there are indirect effects that should be considered when 

the measured costs and benefits are sufficiently large. However, quantifying these 

issues is very difficult. Until better methods are developed to assess these secondorder effects, EPA has focused on assessing the primary benefits and costs that result from a partial equilibrium analysis. 

EPA uses a partial equilibrium analysis when assessing the benefits and costs of 

regulatory options. Partial equilibrium analysis, by definition, only looks at the direct effects of the regulation. It ignores the general equilibrium effects that may 

occur throughout the economy. Note that the partial equilibrium models ignore both 

the secondary benefits and the secondary costs that may occur. Partial equilibrium 

models are generally used when the costs and benefit impacts are small so that secondary impacts may be safely ignored. 

However, if the regulation has sufficient impacts on benefits and costs, these secondary costs may be significant. There are at least two effects that must be measured to do this correctly: 

The health-wealth tradeoff with costs: This literature suggests that costs of environmental regulation may be higher than the direct expenditures of a regulation. 

Specifically, raising costs also raises prices and reduces real wage income. This 

lower real wage reduces net income and may, therefore, reduce the overall health 

of workers. (The lower our income, the less health we can afford.) This is the effect 

mentioned in the question. 

The health-wealth tradeoff with benefits: When our environment improves, we reduce the sick loss days of workers, and improve the overall health of the population. 

These changes increase labor productivity, raising the real wage. As the real wage 

increases, the populations’ health increases. (As our income increases, we can afford 

to buy better health care, etc.) 

In general, EPA assumes that these two effects roughly cancel. We have taken 

some exploratory looks at this issue and found this to be the case, though generalized conclusions cannot be made. These issues are also discussed in the context of 

EPA’s analysis done under section 812 of the Clean Air Act amendments. 

In addition to the above issues, it is our understanding that the NAS recommendation concerning indirect benefits focuses on whether any particular EPA 

analysis can and should try to capture potential indirect effects pertaining to 

changes in exposures. For example, the NAS gave as its first illustrative example 

of the indirect effects concept the possibility that air pollution regulations may 

change how fuels are made or how combustion devices are operated, which could 

in turn affect human health through other pathways. 

RESPONSES BY GEORGE GRAY TO ADDITIONAL QUESTIONS FROM

SENATOR VOINOVICH

Question 1. Dr. Gray, please put yourself in our position as the oversight Committee or the publics position whether a regulated industry, environmental group, 

or just a concerned citizen. Last week, we discussed at length the fact that EPA has 

put together an incomplete Regulatory Impact Analysis. Basically, we do not know 

the impact of revising the standards. Let me remind EPA that this information is 

required by Section 108 of the Clean Air Act: Administrator shall. . . issue to the 

States. . . information on air pollution control techniques, which information shall 

include data relating to the cost of installation and operation, energy requirements, 

emission reduction benefits, and environmental impact of the emission control technology. 

We are told that a more complete analysis will be addressed in the final rule. 

Today, we learn from GAO that EPA has implemented less than 25 percent of the 

National Academies recommendations. We are told more of these recommendations 

will be addressed in the final rule. 

Chairman Inhofe has pushed EPA to consider the numerous new studies that 

have been completed since the criteria document was finished. We are told that this 

new science will be addressed in the final rule. 

Don’t we have an oversight responsibility and doesn’t the public have a right to 

know what EPA is doing behind closed doors on this rule? 
52 

Response. EPA is committed to working with Members and committee staff to ensure the public is well-informed with regard to Agency rulemakings. EPA has been, 

and will continue to be, in regular contact with the committee regarding the PM2.5

NAAQS and the associated RIA, and we believe our final analysis will be comprehensive, useful, and robust. 

The Clean Air Act (Act) requires EPA to set a primary standard for each criteria 

pollutant that protects public health with an adequate margin of safety. As interpreted by the Agency and the courts, the Act requires EPA to base this decision on 

health considerations and forbids consideration of economic factors. Thus, while the 

final RIA can provide important insights into the costs and human health benefits 

associated with attaining a revised PM2.5 NAAQS, EPA cannot use estimates of attainment cost to inform the NAAQS decision. 

This prohibition against the consideration of cost in the setting of the primary air 

quality standard, however, does not mean that costs or other economic considerations are unimportant or should be ignored. The Agency believes that consideration 

of cost is an essential decision-making tool for the cost-effective implementation of 

these standards. Under the Clean Air Act, the impact of cost and efficiency are considered by the States during this process, when States are making decisions regarding what timelines, strategies, and policies make the most sense. The PM NAAQS 

final RIA is intended to inform the public about the potential costs and benefits that 

may result when any revised PM standards are implemented. 

With regard to the new studies cited in your question, EPA’s Office of Research 

and Development has conducted a survey and provisional assessment of relevant 

scientific information that became available since the completion of the 2004 Criteria Document, as discussed in EPA’s notice of proposed rulemaking on the PM 

NAAQS. In summary, our provisional assessment concluded that the new studies 

do not materially change the broad conclusions of the 2004 document. 

Question 2. Dr. Gray, Congress established the Clean Air Act to protect human 

health. Last week: 

Georgia Commissioner Heiskell stated: As an elected official, I fear the lost tax 

revenues and increased stresses on local health services that lay-offs associated with 

our non-attainment status bring. 

National Black Chamber of Commerce President Harry Alford stated: . . . the 

biggest health risk to African Americans anywhere. . . is poverty. 

Now, I understand that EPA cannot consider costs. However, according to the 

GAO report: 

Another recommendation (from NAS) that EPA. . . did not apply to the draft 

regulatory impact analysis concerns whether the proposed revisions to the particulate matter standards would have important indirect impacts on human health and 

the environment. 

This is a health based standard and there are indirect, negative impacts on health 

from nonattainment designations that reduce jobs and increase energy prices. Why 

isn’t EPA following the NAS recommendations and considering these impacts? 

Response. Please see our answer to Question 1. 

Question 3. Dr. Gray, does science dictate a particular number for the air quality 

standards? 

Response. Uncertainty is inherent in science. As new data become available, our 

understanding of the health protectiveness of a given air quality standard grows, 

as does our understanding of the extent of uncertainties. That is why rarely, if ever, 

it is the case that a body of scientific evidence has the potential to dictate a particular number for an air quality standard. Science does provide the basic information used in setting air quality standards, and our analysis of the science includes 

consideration of the strengths and uncertainties in the available evidence. We know 

that our measurements of environmental conditions and biological responses contain 

some uncertainty due both to the limits of our understanding of the underlying process and available technology. EPA recognizes the importance of characterizing the 

implications of this scientific uncertainty. 

In the review of the PM air quality standards, the scientific evidence has provided 

strong support that PM exposures can have adverse effects on public health and the 

environment. The science summarized in EPA’s Criteria Document and used in 

EPA’s risk assessment provided the scientific basis for the range of options recommended in EPA’s staff paper. There is uncertainty even within this range of options. The strength of the scientific evidence as well as the uncertainties are necessarily considered by the EPA Administrator in proposing and promulgating final 

PM NAAQS. 

Question 4. Dr. Gray, as I stated in my opening statement, I do not understand 

how EPA can revise the particulate matter standards when the public health benefit 
53 

is not fully understood. For example, there are areas of the country, namely Southern California, that will never be able to meet the Agency’s proposal, not to mention 

even tighter standards. When EPA estimates health benefits, how do you take into 

account that this area will never attain the standards? Basically, does the Agency 

estimate real benefits? 

Response. This Nation has an excellent record of rising to the challenge of reducing air pollution in a cost effective fashion. All areas have made significant progress 

in reducing air pollution even if some areas are still not yet in attainment of the 

current standards. The regulatory impact analysis that will accompany EPA’s decision reflects the need to develop new ways and ideas for some areas to attain the 

proposed standard. To the extent that known controls are not sufficient to bring an 

area like Southern California into attainment by 2020, EPA has relied on information from a variety of sources on the effectiveness of new control strategies under 

development to project what the costs and benefits of attainment might be. While 

these estimates have additional uncertainty associated with them, they give the 

public an idea of the likely magnitude of the potential costs and benefits of attainment. 

Because of its severe air pollution problems, Southern California has been one of 

the leaders in the development of creative ways to reduce air pollution by harnessing the free market. For example, the RECLAIM (Regional Clean Air Incentives 

Market) program has been in place since 1994 to harness market forces to reduce 

air pollution. See http://www.aqmd.gov/reclaim/reclaim.html for more information. 

Also, the California Air Resource Board (CARB) is now aggressively pursuing options for continuing to reduce air pollution. On April 20, 2006, CARB announced a 

new program for reducing air pollution from its ports which includes economic incentive elements. See http://www.arb.ca.gov/gmp/gmp.htm for more information. 

Question 5. Dr. Gray, the GAO report states that the Agency has implemented 

less than 25 percent of the National Academies’ recommendations for estimating 

health benefits. Does the Agency have a plan to implement all of the recommendations? 

Response. EPA is committed to showing further progress in the final RIA, which 

will be published when the NAAQS is finalized this September. As noted in the 

GAO report ‘‘Particulate Matter: EPA Has Started to Address the National Academies’ Recommendations on Estimating Health Benefits, But More Progress is 

Needed,’’ EPA expressed to GAO that the Agency is committed ‘‘to further enhancing the transparency of the analysis by presenting clear and accurate references to 

the supporting technical documents, which detail the analytical assumptions and describe the data supporting the estimates [of our Regulatory Impact Analyses.]’’ GAO 

found that of the 34 detailed recommendations in the NAS report, the draft RIA implemented (in full or in part) 22 of them. Some of the remaining 12 recommendations will be addressed in the final RIA to accompany the final rule in September; 

others require further research or development. For example, over the past few 

years, EPA ran an expert elicitation designed to characterize uncertainty in the estimation of PM-related mortality resulting from both short-term and long-term exposure. This work has recently been completed and peer reviewed. The results from 

this expert elicitation are being applied to the benefits analysis in the RIA. However, it has not been possible to address all the NAS recommendations since the 

September 2002 publication of the report. In its report and its recommendations, the 

NAS recognized that additional research and resources were going to be needed to 

address some of its recommendations. And, in some cases, the recommendations 

were in fact conditioned on the availability of improved scientific data. EPA is committed to addressing these recommendations, including those on PM speciation, and 

improving its analyses as new research becomes available. 

In its July 19, 2006, report, GAO acknowledged the progress EPA has made on 

implementing the recommendations while also noting that EPA needs to make more 

progress in addressing the National Academies’ recommendations on estimating 

health benefits. 

Question 6. Dr. Gray, how does EPA decide which studies to rely on and which 

ones to ignore? Do CASAC or EPA have any written criteria for determining which 

studies are more important than others? Any intention of developing this so that 

the NAAQS review process is more objective and transparent? 

Response. We believe that the consideration of scientific evidence in the NAAQS 

review process is comprehensive, objective, and transparent. EPA conducts an extensive literature search to identify potential studies for inclusion in its science assessments. For example, EPA uses standard searches of systems such as MEDLINE in 

the National Library of Medicine, independent table of content searches by EPA 

staff, and input from the public and independent scientists outside EPA. These 
54 

search methods are summarized in the Criteria Document. The selection of studies 

for consideration in a NAAQS review, the strengths and uncertainties of individual 

studies, and the subsequent determination of studies to be given greatest weight are 

outlined and discussed in the science assessment. These selections and determinations are evaluated by the public and by CASAC at public meetings. The inputs 

from the public and CASAC are documented, considered, and incorporated as needed. 

Question 7. What role did the White House and other Federal Agencies play in 

setting the NAAQS proposal? 

Response. Under Executive Order No. 12866, ‘‘Regulatory Planning and Review,’’ 

signed by President Clinton in September 1993, the Administrator of the Office of 

Information and Regulatory Affairs (OIRA) carries out a regulatory review process 

on behalf of the President. The objectives of this Executive order are to enhance 

planning and coordination with respect to both new and existing regulations; to reaffirm the primacy of Federal agencies in the regulatory decision-making process; 

to restore the integrity and legitimacy of regulatory review and oversight; and to 

make the process more accessible and open to the public. In general, involvement 

by other Federal agencies or the White House offices occurs during the routine 

interagency review process, when the Agency is developing its proposal and before 

making a final regulatory decision. Following this procedure, the proposal package 

for the PM NAAQS went through the interagency review process, which was managed by the OIRA and included input from various agencies and offices throughout 

the executive branch. 

Once EPA has issued a proposal to the NAAQS, the Agency evaluates public comments received on the proposal and develops a draft final rule. The draft will then 

be subject to the interagency review process, per Executive Order 12866, which includes input from across the executive branch. 

STATEMENT OF DANIEL GREENBAUM, PRESIDENT, HEALTH EFFECTS INSTITUTE

Mr. Chairman and members of the committee, thank you for the opportunity to 

testify before you today on the health effects of particulate matter (PM). I come before you as the President of the Health Effects Institute, a non-profit, independent 

research institute funded jointly and equally by the U.S. EPA and industry to provide high-quality, impartial science on the health effects of air pollution. For over 

25 years we have conducted targeted research on a variety of pollutants and health 

effects, and I am pleased to summarize our understanding concerning PM and 

health for you today. 

I also had the privilege to serve from 1998 until 2004, as a member of the National-Research Council Committee on Research Priorities for Airborne Particulate 

Matter, a congressionally chartered panel that both set priorities for national PM 

research, and monitored the progress in implementing those priorities by U.S. EPA 

and other public and private agencies. 

I would like today to briefly highlight three topics of direct relevance to the current discussion of U.S. EPA’s proposal for revisions to the National Ambient Air 

Quality Standards for PM (the ‘‘PMNAAQS’’): 

• Science progress we have made since 1997, 

• The most recent findings on the relationships between different levels of ambient PM and health effects (so-called ‘‘concentration-response’’), and 

• Keyscience needs going forward. 

PROGRESS SINCE 1997

Since Congress identified the need for substantial enhanced research on PM in 

the wake of the 1997 PM2.5 NAAQS decision, established the NRC Committee, and 

appropriated substantial new funds for PM research, much progress has been made 

in answering key questions for the current NAAQS review process, and for future 

ones. 

Specifically: 

• We know much more about the sources and transport of fine particles, and 

about personal exposure to those particles, especially for sensitive groups like the 

elderly and children. 

• We have conducted the first multi-city epidemiology studies of effects, and analyzed and reanalyzed many of the major studies of human effects, finding that in 

general the earlier studies were well done and could be confirmed. At the same time 

there has been some evidence that the population health effects we had seen in 

those earlier studies may in some cases be smaller than previously thought. 
55 

• Unlike in 1997, we now have numerous laboratory, animal, and human toxicology studies that have begun to indicate potential biological mechanisms by which 

PM may cause health effects, especially new findings of effects on the heart and circulatory system. Although we have made progress, most science observers would 

agree that there is still much to learn about the mechanisms by which PM may 

cause these effects. 

Although there continue to be, as there always are, important questions about PM 

that need further research, I think Congress, the Federal Government, and the scientific community can take tremendous pride in the substantial progress that has 

been made. 

The ‘‘Concentration-Response’’ Relationship: Ambient PM Levels and Health Effects 

Among the most important questions addressed over the past few years is the 

question of whether exposure to PM has been shown to have health effects at.all 

levels of pollution—ie. down to zero—or whether there is a ‘‘threshold’’ below which 

no effects are expected. This question is, of course, central to deciding at what level 

to set a NAAQS. There are two major types of epidemiologic studies that have been 

done—of short term effects and long term effects—and I would like to briefly review 

what these studies have shown us. 

Short Term Effects 

In 1997, there were studies of daily changes in air pollution and health effects 

in a number of individual cities (so-called ‘‘daily time series studies’’). Since then, 

scientists have conducted much more rigorous multi-city studies of daily air pollution and health, most notably the National Morbidity Mortality and Air Pollution 

Study (NMMAPS) funded by HEI and led by investigators at the Johns Hopkins 

Bloomberg School of Public Health. That study examined daily changes in air pollution and health in the 90 largest U.S. cities. To answer the question of whether 

there is a threshold for effects, the investigators analyzed mortality and pollution 

levels across the 20 largest cities and the 90 largest. 

In brief, as shown in Figure 1, they found that there appeared to be a linear relationship between mortality and air pollution down to the lowest measured levels for 

all causes of mortality, and for deaths from heart and lung disease, without an apparent threshold. There did appear, however, to be a threshold for the effect of PM 

on ‘‘other’’ causes of mortality (e.g. non-respiratory cancer, liver disease). The HEI 

Review Committee, which intensively peer reviews all HEI research, advised ‘‘caution in drawing conclusions from the apparent absence of a threshold’’ for all-cause 

and cardiopulmonary mortality, for a number of statistical and analytic reasons. 

They noted however that ‘‘the reported associations are at ambient concentrations 

well below the current U.S. daily standard . . . thus the ambient concentration 

level at which any threshold might exist is likely to be correspondingly low.’’ 

Long-Term Effects 

In 1997, there were two principle studies of the effects of longer term exposure 

on mortality, the Harvard Six Cities Study and the American Cancer Society Study 

(ACS), which examined death rates among thousands of individuals living in cities 

with varying levels of pollution. Since that time, although there have been other 

long-term studies published there are still very few, and much attention has focused 

on HEI’s Reanalysis of these two studies and on extended analyses in the American 

Cancer Society Study population (which still covers the broadest national popu-
56 

lation). In both of these efforts, initial analyses have examined the ‘‘concentrationresponse’’ relationship between levels of pollution in each community and levels of 

health effects. 

HEIReanalysis—At the request of Congress (in the FY 1998 Appropriations Bill), 

U.S. EPA, and others, HEI gained access to all underlying data in the two studies 

and selected an independent investigator—Dr. Daniel Krewski—and his team to 

conduct a detailed audit and reanalysis. Their work, which was also intensively peer 

reviewed by the HEI Review Committee, tested the original studies against a wide 

variety of alternative explanations about why people in the most polluted cities 

would have higher rates of premature mortality. In the end, the investigators and 

HEI’s Review Committee agreed that these alternative analyses did not change the 

original findings of associations between PM and premature mortality, although 

there were new findings as well about an association of mortality with sulfur dioxide. 

Dr. Krewski and his team also conducted an initial analysis of the 

‘‘concentrationresponse’’ relationship between PM levels in each of the cities and relative risks of mortality. Figure 2 presents the results, summarizing for each community (signified by a point on the graph) the annual air pollution level and the risk 

of death due to heart and, lung disease. They then attempted to estimate the ‘‘average’’ relationship across all of the communities (the solid line) and the range of uncertainty around that average (the ‘‘95 percent confidence intervals’’ indicated by the 

dashed lines). As you can see there is some ‘‘scatter’’ in the data, especially at the 

highest and lowest PM levels studied, but also an overall trend of increasing mortality risk with increases in pollution levels starting at relatively low levels. In reviewing this initial analysis, the HEI Review Committee found that ‘‘for all-cause 

and cardiopulmonary mortality, the results show an increasing effect across the entire range of fine particles or sulfate but no clear evidence either for or against overall linearity.’’ 

Extended Analyses in the American Cancer society Cohort Following the reanalysis, the original investigators for the ACS study led a broad team of experts in an 

extended analysis of the data, including additional follow-up of more recent deaths 

among the study population, and using new PM2.5 data from monitors installed 

since 1997. That study found results similar to those found in the Reanalysis and 

also conducted analyses of the ‘‘concentration-response’’ relationship (shown in Figure 3). This also shows a general, though less steep, upward trend in mortality with 

increasing pollution levels, with the largest uncertainty being found at the very lowest and very highest levels where there are fewer cities. The Investigators concluded 

that: ‘‘Within the range of pollution observed in this analysis, the concentration re-
57 

sponse function appears to be monotonic and nearly linear. This does not preclude 

a leveling off (or even steepening) at much higher levels of air pollution.’’ 

Summary: PM-Mortality Concentration-Response 

In sum, recent analyses of the relationship between ambient levels of pollution 

and mortality have found a generally increasing trend of mortality with increases 

in pollution across a wide range of locations. The strongest evidence that there is 

not a threshold for these effects comes from studies of short-term effects, where any 

threshold is likely to be well below the current ambient standards. The initial analyses of these relationships in long term studies also shows this general pattern, albeit with somewhat greater uncertainty at the lowest and highest levels. 

KEY RESEARCH NEEDS LOOKING FORWARD

While we have made much progress in understanding PM exposure and health 

effects over the past decade, there continue to be, as there always are in science, 

important questions to be answered to help inform future decisions about ambient 

air quality standards and protecting public health. Two key areas needing continued 

attention are: 

Continuous Improvement in the Statistics Used in Epidemiology 

The analysis and reanalysis of studies on population health, air pollution and 

weather over the last decade have enhanced our ability to determine whether health 

effects can be tied to certain air pollutants. However, those same analyses have 

shown that the results can be significantly affected by the choices of statistical techniques and the assumptions made in each analysis. Looking forward, we need to pay 

continued attention to understanding the sensitivity of the results to different assumptions, quantifying the uncertainty of the results, and communicating clearly for 

each analysis both the results and the continuing uncertainties around those results. 
58 

Systematic Analyses of which PM Components and Sources May Contribute 

the Most to Toxicity 

Perhaps no other question will need as much attention, and will have as much 

implication for future regulations, than determining whether some components of 

the complex mixture of PM are more toxic than other components. Ultimately, this 

data will be essential to ensuring that regulations and control strategies are targeted at reducing those emissions which will have the most public health benefit 

at the least cost. This has also become important in light of the current proposal 

for a PMNAAQS for ‘‘coarse particles’’ which has proposed to exclude certain particles from consideration even before the needed studies are complete. 

To date, there have been some individual city analyses of toxicity of different components supported by U.S. EPA and others; but no systematic national effort to compare results from across the country and from epidemiology and toxicology studies. 

To fill that gap in time to inform a next round of PMNAAQS review, HEI has 

launched, with support from EPA and multiple industries, a sysatematic, multi-disciplinary effort which will: 

• Conduct comprehensive, multi-city analyses of PM components and health 

• Combine and compare epidemiology and toxicology across the country, and 

• Provide the first-ever analyses of long-term effects of different PM components 

(all studies to date have looked only at daily changes in air pollution and health) 

As indicated in both the NRC review of priorities for future PM and health research (NRC 2004), and in today’s report of the Government Accountability Office 

concerning data needed for future PM benefits analysis, these studies will be central 

to ensuring that future PM actions are the most effective possible. 

SUMMARY: PROGRESS MADE AND MORE TO BE DONE

In sum, we have made much progress since 1997 in answering key questions 

about whether and how PM can affect public health. Initial analyses have also 

helped us better understand the ‘‘concentration-response’’ relationship between levels of ambient air pollution and health effects and the generally increasing effects 

with increasing levels of pollution. At the same, looking forward there continue to 

be important issues to be addressed to inform future NAAQS and regulatory decisions, especially around the toxicity of different component and sources of PM. 

Thank you for this opportunity to testify; I would be pleased to answer any questions you might have. 

RESPONSES BY DANIEL GREENBAUM TO ADDITIONAL QUESTIONS FROM

SENATOR VOINOVICH

Question 1. Mr. Greenbaum, as you know, there is an ongoing debate about 

whether EPA must lower the annual standard. Your opinion is invaluable in this 

debate as an entity that sits squarely in the middle -funded by both industry and 

EPA. Clearly, the statute says that standards shall be set ′′ in the judgment of the 

Administrator.′′ In your opinion, is it reasonable from a scientific and health perspective for the Administrator to retain the annual standard at 15 and not lower 

it, does science dictate a particular number for the air quality standards? 

Response. This is of course one of the major questions facing the Administrator 

as he makes final decisions on the NAAQS. As I noted in my testimony, the Health 

Effects Institute has not, since its inception over 25 years ago, taken a position advocating either changing or retaining a specific level of a standard. We do this so 

that no one can ever question our science as having been created solely for the purpose of supporting an advocacy position. We do, however, attempt to provide the 

best possible impartial interpretation of the science to help inform such decisions. 

In that spirit, I would like to re-iterate and strengthen several points I made on 

this question in the hearing: 

(a) First, the science on the relation between different levels of air pollution—and 

whether there are health effects at all levels or a ′′threshold′′ level below which 

there are no effects—has improved since 1997. 

(b) Second, as I noted in my testimony, these so-called ′′concentration-response′′ 

relationships have shown for short-term studies (that inform the 24-hour standard) 

a fairly consistent relationship between levels of air pollution and increases in premature mortality at levels below the current standard. 

(c) Third, for longer-term studies such as the American Cancer Society Study (that 

inform decisions on the annual standard), there is also evidence of a relationship 

between air pollution and premature mortality that extends below 15, but the level 
59 

of uncertainty on that relationship is somewhat greater than for the short term 

studies. 

(d) Finally, there is no widely accepted scientific method for setting the level of 

a standard. Rather, as the Clean Air Act envisions, decisions on levels of the standard are a public health policy judgment by the Administrator, in which he has to 

weigh evidence that suggests that there are effects below the current standard 

against the level of certainty or uncertainty surrounding that evidence (i.e. the degree to which he can be certain from the science that a lower standard would result 

in greater public health benefits than the current standard.) 

Question 2. Mr. Greenbaum, please explain what you mean by this statement in 

your testimony: ‘‘there has been some evidence that the population health effects we 

had seen in those earlier studies may in some cases be smaller than previously 

thought.′′ Since 1997 there have been extended reanalyses of a number of daily and 

long term studies of relationships between air pollution and health. 

In the case of short term (daily) studies, after HEI investigators at Johns Hopkins 

discovered an issue with the software to conduct these studies in 2002, those investigators and many others revised their analyses using better techniques, and HEI 

was asked to intensively peer review those results and draw conclusions on the new 

findings. In that report HEl’s Review Committee found, among other things, that 

for the major multi-city daily time series studies done in the United States and Europe—some of the most systematic and rigorous of these studies—the estimates of 

risk went down between 30 percent and 50 percent (although they were still statistically significant). For example, for the National Morbidity, Mortality, and Air Pollution Study (NMMAPS) conducted by HEI investigators, the estimates of effects 

went from 0.4 percent increase in premature mortality per 10 u/m3 of paniculate 

matter to 0.2 percent per 10 u/m3. (Health Effects Institute. 2003. Revised Analyses 

of Time-Series Studies of Air Pollution and Health. Special Report. Health Effects 

Institute, Boston MA.) In the case of long-term studies (of people living for many 

years in more-and less-polluted cities), the effects have been smaller in some analyses and larger in others. HEI’s reanalysis of the American Cancer Society (ACS), 

which audited and in general validated the results of the original study, found lower 

estimates of health risk when one includes other pollutants in the analysis. However, some recent analyses of the ACS data by HEI investigators using improved 

estimates of personal exposure have actually found higher estimates of effect (see: 

Jerrett, M; Burnett, R. T.; Ma, R.; Pope, C. A., Ill; Krewski, D.; Newbold, K. B.; 

Thurston, G.; Shi, Y.; Finkelstein, N.; Calle, E. E.; Thun, M. J. (2005) Spatial analysis of air pollution and mortality in Los Angeles. Epidemiology 16: 727-736. ) 

Question 3. Mr. Greenbaum, please comment on the peculiarity that no effect is 

found for people with higher education? 

Response. As I mentioned in response to a similar question in the hearing, a careful reading of the full results of recent studies does not necessarily suggest that the 

studies have found ‘‘no effect’’ for people with a higher education. The HEI Reanalysis of the Harvard Six Cities and American Cancer Society studies was the first 

analysis to attempt to look at whether there were differential effects in people with 

different levels of education (which is generally an indicator of different levels of socioeconomic status). That analysis, and a subsequent extended analysis in the ACS 

study, found a distinctly higher effect on mortality for those with lower education 

(and likely lower socioeconomic status). The HEI Reanalysis also found, for those 

with more than a high school education, a positive but not statistically significant 

association with all- cause mortality (a relatively crude measure of mortality since 

it includes causes of death which we expect could not be related to air pollution). 

When one looks at more specific causes of death, one finds that even for those with 

higher education, there is an association of mortality for cardiopulmonary deaths, 

and especially cardiovascular deaths. (See Table 52 in Health Effects Institute. 

2000. Reanalysis of the Harvard Six Cities Study and the American Cancer Society 

Study of Paniculate Air Pollution and Mortality: A Special Report of the Institute’s 

Particle Epidemiology Reanalysis Project.) There are several reasons why these differences in effects among people of different levels of socioeconomic status might be 

seen. First, it is plausible that people of lower socioeconomic status have higher exposures to air pollution due to: living in more heavily polluted areas; the likelihood 

that they have less access to air conditioning; and the jobs they have which may 

involve more outdoor exposure. Second, it is also well known that poorer people 

have worse levels of nutrition and poorer access to quality medical care, which could 

reduce their underlying health and make them more susceptible to the effects of air 

pollution. Third, it is also possible that, although these studies have made extensive 

efforts to separate the effects of ‘‘being poor’’ from the effects of ‘‘being exposed to 
60 

air pollution’’, there are some results in these studies that continue to reflect the 

impacts of poverty on health. 

STATEMENT OF ROGER MCCLELLAN, ADVISOR, TOXICOLOGY AND HUMAN HEALTH RISK

ANALYSIS

EXECUTIVE SUMMARY

• The scientific basis for policy decisions on setting the PM2.5 National Ambient 

Air Quality Standard remain highly uncertain. 

• The continued use of the PM2.5 indicator is a default decision driven by EPA’s 

past emphasis on regulatory compliance monitoring—‘‘monitor that which is regulated.’’ As a result, there is no database for considering alternative PM indicators 

that might target specific PM constituents or exclude certain constituents. 

• The scientific database provides a basis for the Administrator making policy 

choices for a PM2.5 NAAQS with 24-hour averaging time concentration in the range 

of 25 to 35 m3, with a 98th percentile form, and an annual standard in the range 

of 12 to 15 m3. 

• The scientific database for policy decisions on setting a PM10-2.5 NAAQS is very 

weak and highly uncertain. A science-based decision, as contrasted with a judicial 

decision, would be to continue with a PM10 NAAQS. 

• There are major uncertainties in risks associated with exposure to ambient 

PM2.5 at current levels and the benefits of reducing PM2.5. These uncertainties need 

to be clearly documented and conveyed in numerical calculations used for policy decisions and in the Agency’s final Regulatory Impact Analysis. 

• Expert elicitations of opinions on PM2.5 risks are very likely flawed with a blurring of the distinction between scientific evaluation and policy choices. Scientists, as 

do all citizens, have values that influence choices of standard setting options. However, scientific evaluations should be as free as possible of concern for the ultimate 

policy decisions. 

Good Morning, Mr. Chairman and members of the subcommittee. Thank you for 

the invitation to present my views on the U.S. Environmental Protection Agency’s 

current review on the National Ambient Air Quality Standards (NAAQS) for Particulate Matter (PM). 

MY BACKGROUND

My biography is attached to this statement. Since 1999, I have served as an Advisor to public and private organizations on issues related to air quality in the ambient environment and workplace drawing on more than 45 years of experience in 

comparative medicine, toxicology, aerosol science, and risk analysis. I served as 

President of the Chemical Industry Institute of Toxicology in Research Triangle 

Park, NC from 1988 to 1999, providing leadership for a research program directed 

to understanding the mechanisms of action of chemicals in producing either beneficial or harmful effects on humans. I was with the Lovelace organization in Albuquerque, NM from 1966 to 1988, providing leadership for one of the World’s major 

research programs directed toward understanding the potential human health effects of inhaled materials. 

The testimony I offer today draws on my experience serving on numerous scientific advisory committees. This has included service on many EPA advisory committees from the origin of the Agency to date, including the Clean Air Scientific Advisory Committee (CASAC), which I chaired from 1988 to 1992, all of the CASAC 

PM Panels as well as CASAC Panels that considered other criteria pollutants. My 

involvement in advising EPA on the setting of NAAQS for criteria pollutants began 

with my chairing in 1977 and 1978 an ad hoc committee to review the first lead 

criteria document, a committee that was required since the Congress had not yet 

authorized creation of CASAC. I also served on the National Academy of Sciences/ 

National Research Council (NAS/NRC) on Research Priorities for Airborne Particulate Matter and the earlier NAS/NRC Committee that produced the report ‘‘Science 

and Judgment in Risk Assessment.’’ It is important to note that the testimony I 

offer today reflects my own views and is not being offered on behalf of any of the 

Committees I have served on for the EPA, the NAS/NRC nor for any other agencies 

or firms. 

SETTING NATIONAL AMBIENT QUALITY STANDARDS

Each NAAQS consists of four elements: (a) an indicator (such as PM2.5), (b) an 

averaging time (such as 24 hours or annual), (c) a numerical level (such as 65 m3
61 

for PM2.5 averaged over 24 hours), and (d) a statistical form (such as a 98th percentile). The indicators for five of the criteria pollutants are for measurement of the 

mass concentration of specific chemicals such as O3, SO2, NO2, CO and Lead. Only 

in the case of particulate matter is the indicator based on the mass concentration 

of airborne particulate matter in a specific size range, irrespective of the chemical 

composition of the PM. 

Under the Clean Air Act, the EPA Administrator is required to review the 

NAAQS for the criteria pollutants at 5-year intervals to evaluate whether or not the 

four elements of the NAAQS are still deemed to be acceptable based on current scientific knowledge as it applies to the assessment of public health risks. In practice 

the interval between reviews has been longer. The process for review and promulgation of a NAAQS, either continuation of the existing standard or establishing a new 

NAAQS, consists of multiple phases. The initial phase, which is obviously on-going, 

consists of conduct of research on the various criteria pollutants. This includes a 

broad spectrum of activities; understanding emissions of pollutants, transport and 

transformation of pollutants in the atmosphere, ambient measurements of pollutants, estimation of personal exposures to pollutants, assessment of toxic effects and 

mechanisms of action in cells, tissues and animals, conduct of controlled exposure 

studies to pollutants in human volunteers and epidemiological investigations of 

human populations. Most of the research is funded by the EPA, some in the Agency’s own laboratories and some in academic and other laboratories, the National Institutes of Health and, to a modest extent, private industry. The dominance of Federal Government support of research on criteria pollutants relates to their effects 

being of broad societal concerns with the pollutants, by and large, having no unique 

industrial emission source. 

The findings of this research are used by the EPA’s Office of Research and Development to prepare a criteria document (CD). Each CD traditionally has been essentially an encyclopedia of everything known about a given criteria pollutant and is 

used as a basis of information for the preparation of a Staff Paper (SP) by the EPA’s 

Office of Air Quality Planning and Standards. This is a Policy Assessment of Scientific and Technical Information; in short, an integration and synthesis of the information in the CD that is most relevant to setting the four elements of a NAAQS. 

In recent years, the Staff Papers have made substantial use of risk assessments for 

the criteria pollutant being considered. These risk assessments have been conducted 

by a single EPA Contractor organization. The various versions of the CD and SP 

are released to the public with an invitation to provide comments as a basis for improving the documents. 

Throughout this process, a Clean Air Scientific Advisory Committee Panel, operating as an element of the EPA’s Science Advisory Board, is involved in reviewing 

and advising on the scientific content of both the CD and the SP, including the related risk assessment. This has typically involved several revisions. Prior to the current cycle of PM review, the CASAC Panel sent a closure letter to the EPA Administrator when the CASAC was of the opinion that the revised documents were suitable for use by the Administrator in promulgating a NAAQS. In the current review, 

the ‘‘closure letter’’ process was abandoned. 

At the next step, the Administrator proposes, via a Federal Register Notice, a 

NAAQS including specific proposals for each of the four elements of the NAAQS; 

the indicator, averaging times, numerical levels and statistical forms. Comments are 

solicited from the Public with the opportunity to submit written comments to a specific Docket. In the current PM review, the CASAC PM Panel offered written comments on the Administrator’s proposal. 

The next step is for the Administrator to promulgate a NAAQS consisting of the 

four elements discussed previously. I purposefully do not use the phrase ‘‘final step,’’ 

because the Courts may have a role in deciding whether the Administrator’s proposed NAAQS will stand. The NAAQS are to be based on the available scientific 

information reviewed in the CD and SP and summarized in the notice of proposed 

standards. The primary, health-based NAAQS are to be set at a level that will protect public health, including sensitive populations, with an adequate margin of safety. The Administrator is precluded from considering cost in the setting of the 

NAAQS. 

At this point, I would like to emphasize that there exists no absolute and unambiguous scientific methodology that can determine which specific indicator, the precise averaging time, numerical level or statistical form that will be adequate to protect public health. The available scientific information can inform the NAAQS decisions, however, the Administrator must ultimately use policy judgment in making 

decisions on each of the four elements from among an array of scientifically acceptable options including consideration of their attendant scientific uncertainties. 
62 

Once the NAAQS are finalized, individual states have responsibility for planning 

and taking actions to meet the NAAQS. This includes the formal step of preparing 

‘‘State Implementation Plans (SIPs). In developing strategies for meeting the 

NAAQS, the States can give consideration to costs in setting the pace for achieving 

the NAAQS. However, attainment of the NAAQS cannot be postponed indefinitely. 

EPA ADMINISTRATOR MADE POLICY CHOICES CONSISTENT WITH THE SCIENCE

At this juncture, I note that I personally find acceptable the Administrator’s policy 

choices for the PM NAAQS, as published in the Federal Register (January 17, 2006) 

from among an array of science-based options, to be acceptable. Specifically, I find 

scientifically acceptable his proposal to use (a) a PM2.5 indicator with a 24-hour 

averaging time and a reduction in the concentration level from 65 m3 to 35 m3 with 

a 98th percentile form, (b) retention of the PM2.5 annual standard at 15 m3 with 

additional constraints on the use of spatial averaging, and (c) use of a PM10-2.5 indicator with a 24-hour averaging time concentration level set at 70 m3 with a 98th 

percentile form. I support the exclusion of any ambient mix of PM10-2.5 where the 

majority of coarse particles are rural windblown dust and soils and PM generated 

by agricultural and mining sources. 

Of these several policy choices, I have the greatest reservation concerning the proposal for a PM10-2.5 indicator with a 24-hour averaging time concentration level set 

a 70 m3 with a 98th percentile form. The scientific basis for the proposed PM10-2.5

standard is very weak and uncertain. I would have personally preferred to see the 

PM10 standard continued to provide public health protection from particulate matter 

mass in the PM10-2.5 range. However, EPA personnel have related that this option 

has been precluded by Court decisions. 

SELECTION OF A PM INDICATOR—CHAINED TO THE REGULATORY COMPLIANCE

MONITORING LAMP POST

The primary scientific data used to select indicators for PM NAAQS has been derived from epidemiological investigations. Prior to 1970, there was limited regulation of particulate matter in air pollution. Limited monitoring, relative to that being 

carried out today, was conducted using relative crude metrics of Black Smoke and 

Total Suspended Particulates (TSP). TSP was the mass of particulate matter, not 

identified as to chemical form, collected on a filter in a high volume air sampler. 

This included material up to about 40 m in size. Scientists studied the relationship 

between the air concentration of these TSP measurements and increases in health 

effects. This epidemiological data provided the basis for setting the 1971 PM 

NAAQS with TSP as an indicator. The 24-hour averaging time standard set at 260 

m3, not to be exceeded more than once a year, and an annual standard set at 75 

m3, annual geometric mean. The TSP indicator then became the ‘‘law of the land’’ 

and TSP began to be routinely monitored to determine regulatory compliance. 

During the 1970s and early 1980s, an increased awareness emerged on the role 

of particle size in determining the fraction of inhaled particles that would be deposited and where they would be deposited in the respiratory tract. This led to some 

groups making measurements of ambient air particulate matter mass in different 

size fractions; less than 15 m, less than 10 m, less than 2.5 m and less than 1 m. 

However, the primary epidemiological data in the 1980s that could be used for 

standard setting was TSP—remember TSP was required to be measured for regulatory compliance. 

In 1987, the PM NAAQS indicator was changed from TSP to PM10. The choice 

of PM10 was heavily influenced by a decision in the international community to use 

a PM10 metric rather than a PM15 metric. The United States followed suit. Much 

of the epidemiological evidence for setting a PM10 NAAQS was based on extrapolations from epidemiological studies using the TSP monitoring data. The PM10 primary standards were set at 50 m3, expected annual arithmetic mean over 3 years, 

and 150 m3, 24-hour average, with no more than one expected exceedance per year. 

With the promulgation of the PM10 indicator the regulatory compliance monitoring 

shifted from TSP to PM10. Unfortunately, ambient air monitoring of PM15, PM2.5

and PM10 was essentially discontinued. Obviously, it would have been expensive to 

continue, and, after all, it was not required for regulatory compliance. 

In the early 1990s, epidemiological data began to be published on the association 

between elevated PM2.5 levels and their association with increased health effects. 

The data came principally from the Harvard Six Cities study that fortunately had 

included in its early years measurements of PM10 and PM2.5. Other analyses were 

published based on an American Cancer Society cohort taking advantage of fragmentary PM2.5 ambient monitoring data. Other investigations conducted using the 

PM10 ambient monitoring data were extrapolated to a PM2.5 indicator. These data 
63 

provided the basis for promulgating a PM2.5 NAAQS in 1997. The PM2.5 NAAQS 

were set at 15 m3, annual arithmetic mean, and 65 m3, 24-hour averaging time with 

a 98th percentile of concentration at each population-oriented monitor. Associated 

with this was a change in the regulatory compliance monitoring network to emphasize PM2.5 mass measurements without regard to chemical composition. Because a 

PM10 mass NAAQS was still in place measurements of PM10 mass, not characterized 

as to chemical composition, continued. Using the difference between the PM10 mass 

measurements and PM2.5 mass measurements, it was possible to estimate PM10-2.5

mass concentrations. 

At various times there has been an interest in measuring PM sulfate mass concentration, a secondary pollutant arising in the atmosphere from conversion of SO2

gas. There have also been some short-term monitoring campaigns in which extensive chemical characterization of a number of particulate matter constituents have 

been measured. However, the extent of this monitoring data is limited in comparison with that developed for regulatory compliance purposes on PM10 mass and PM2.5

mass, not characterized as to chemical composition. Indeed, to date the database on 

specific PM constituents has been insufficient to set a NAAQS for a specific PM 

component. Obviously, Lead is an exception. Likewise, the data on specific PM constituents were not viewed as to exclude any constituent from regulation. 

The most recent CD and SP focuses on the PM2.5 indicator. The focus on PM2.5

was not based on any careful scientific analysis that led to the conclusion that PM2.5

mass, not identified as to chemical composition, as the most appropriate metric to 

relate to an increase in health effects. The simple fact is that because of the EPA’s 

emphasis on regulatory compliance monitoring, the only PM air quality metrics that 

could be evaluated epidemiologically were PM10 mass, PM2.5 mass and to a lesser 

extent PM sulfate and to an even lesser extent, PM10-2.5. I will be so bold as to say 

the focus on PM2.5 mass, irrespective of chemical composition, was a default decision, not a science-based decision. 

My discussion so far has focused on epidemiological evidence without considering 

the results of toxicological studies using cells, tissues or laboratory animals. As a 

toxicologist, I wish I could give more emphasis to the conduct and interpretation of 

toxicological studies. However, such studies have a very limited role in the PM 

NAAQS setting process. Although such studies can use new tools of modern molecular and cellular biology and genomics, the results are not necessarily relevant to 

setting the NAAQS. The challenges of extrapolating from laboratory animals to humans, from high to low levels of exposure, from studies of a few days or even a few 

months to human lifetimes and from studies of a few normal healthy young animals 

to large human populations including individuals with cardiopulmonary disease, 

principally from smoking, are substantial. At best, the toxicological investigations 

can help provide some guidance to the design and conduct of epidemiological investigations. The toxicological methods are simply to blunt and yield results that at 

best can be extrapolated qualitatively to human populations. I know of no scientific 

methods for using the results of toxicological studies with PM, not characterized as 

to chemical composition, or those conducted with specific PM constituents to develop 

quantitative numerical standards that are at the core of PM NAAQS. 

A SHIFT IN MONITORING STRATEGY TO FACILITATE EPIDEMIOLOGICAL EVALUATIONS

What are the prospects for the next PM NAAQS review in 5 years including a 

rigorous evaluation of specific PM constituents? Without a major revolutionary 

change in the EPA’s approach to ambient air monitoring, I think it will be more 

of the same. In short, because of the past focus on measuring PM2.5 and PM10-2.5, 

these metrics will continue to be evaluated in future epidemiological studies. Because of the substantial and continuing improvements in air quality, including 

PM2.5, PM10 and PM10-2.5, it will be even more difficult to detect associations between these PM mass metrics and health effects. Future epidemiological studies will 

also be challenged due to continuing reductions in cardiopulmonary disease related 

to reductions in the primary risk factor for these diseases—Cigarette Smoking. 

How can the prospects for improved epidemiological investigations be changed? If 

the EPA, in cooperation with States and Municipalities, radically modifies its ambient air monitoring network over the next 2 years, it may be possible to have the 

results of improved epidemiological studies in 8 to 10 years. The development of an 

improved ambient air monitoring network will require some tough decisions. It is 

obvious that the expense of an altered monitoring network will require that only 

a modest number of PM constituents be measured in multiple cities in different regions across the United States. Some clear candidates would be sulfates, nitrates, 

organic carbon, elemental carbon, silica and some specific metals for which concern 

may exist as to their potential hazard. It is essential that all of the criteria pollut-
64 

ant gases, ozone, SO2, NO2 and CO, continue to be measured. With a richer array 

of monitoring data available it may be possible to test hypotheses as to the relative 

potency of the various PM constituents as well as the gaseous pollutants. In any 

long-term studies, it will be crucial to have accurate smoking history data if the 

very small potential effects of air pollution are to be separated from the large 

cardiopulmonary impacts of cigarette smoking. In addition, because of the relationship between PM-associated hydrocarbons and volatile and semi-volatile hydrocarbons these should be measured. In my opinion, it will be futile to measure dozens 

of individual chemical species with the view that these measurements could be useful in future epidemiological studies. The current highly uncertain signal of air pollution associated health effects is so small that ‘‘teasing out’’ effects related to any 

single PM chemical constituent will be extraordinarily challenging. 

SELECTION OF AVERAGING TIMES, NUMERICAL LEVELS AND STATISTICAL FORMS

Having selected an indicator, it is necessary to proceed to decisions on the averaging times, numerical levels and statistical forms for the NAAQS. These three elements are inter-related and are set based on the epidemiological database. The averaging times are driven by the temporal characteristics of the monitoring data, 24- 

hour measurements that can be aggregated to yield annual values which, in turn, 

are used in the epidemiological investigations. Hence, it is reasonable to use 24-hour 

and annual averaging times. 

The selection of specific numerical levels for the 24-hour standard has been guided primarily by considering the results of epidemiological studies of the association 

between daily changes in the PM indicator and changes in mortality (all cause, cardiovascular and respiratory mortality). The power of these studies is directly related 

to the size of the population being studied and the number of days being monitored. 

Thus, results can only be developed for quite large cities. This approach would not 

be feasible for small communities and rural areas. 

The primary input for establishing the PM2.5 annual standard comes from longterm follow-up of cohort populations, the Harvard Six City Study of about 8,000 individuals initiated in 1979 and the American Cancer Society cohort assembled starting in 1979. In these studies, sophisticated statistical techniques have been used to 

attempt to tease out an association between differences in PM2.5 ambient concentrations in different communities and the risk of death from various diseases. The 

analyses are very complicated because of the numerous factors that can influence 

the death rate including age, cigarette smoking, work history, education, socio-economic status, exposure to other pollutants as well as other factors. 

The results of the cohort epidemiological studies are typically reported as a linear 

coefficient of increase in relative risk per 10 m3 of PM2.5 using whatever PM2.5 monitoring data are available for the specific cohort. Thus, for the studies initiated in 

1979, this may be PM2.5 measurements made in 1979-1983. Recall that in the 1980s, 

there was a move to regulate PM10 measurements of PM2.5 were discontinued and 

not re-instituted until after the PM2.5 NAAQS was promulgated in 1997. The PM2.5

exposure of individuals in the cohort prior to 1979 is unknown although it is well 

recognized that in most areas air quality has substantially improved since 1970. 

A major challenge in analyzing and interpreting the results of the cohort studies 

relates to the uncertain role of pollution exposures for the individual populations 

prior to initiation of the studies and the uncertainty in the statistical models used 

to attribute relative risk to the various risk factors including PM2.5. The small size 

of the PM2.5 relative risk poses a special challenge. This includes the difficulty of 

determining the shape of the exposure-health response relationship extending from 

past high levels down to current levels. Especially vexing is the issue of whether 

a threshold does or does not exist in the exposure-health response relationship. In 

my view, the exposure-response relationships are highly uncertain in the range of 

typical ambient PM2.5 concentrations in the United States. The substantial uncertainty in the applicability of the PM2.5 exposure-health response coefficients at current ambient concentrations requires caution in calculating either PM2.5 associated 

risks or the benefits of any reductions in PM2.5 concentrations. 

EXPERT ADVICE ELICITATION

In an attempt to better characterize the uncertainties in PM2.5-associated health 

risks and, conversely, the benefits in reductions in PM2.5, some individuals have 

suggested the use of an ‘‘expert advice elicitation’’ approach. I am familiar with this 

approach having served as one of the five experts in EPA’s pilot project to elicit 

opinions on the relationship between PM2.5 exposure and death. I have also participated in such approaches in the initial stages of planning and interpreting safety 

assessment studies. I think the expert opinion elicitation process may have merit 
65 

in obtaining a qualitative assessment of the impact of exposure to hazardous materials. However, I have serious reservations as to its use in eliciting quantitative 

characterizations of risk for various levels of PM2.5 exposure for different populations in different parts of the United States. 

The interviewers eliciting the expert opinions play a major role in determining the 

outcome of the process. In the session I participated in, I found the interviewer focusing on eliciting quantitative linear exposure-response coefficients. Since it is my 

professional opinion that it is very unlikely that a linear relationship exists between 

PM2.5 exposure and health responses down to and including current ambient levels, 

the interview and the follow-up discussions proved frustrating for both me and the 

interviewer. In short, the sponsor (in this case, the EPA) can influence the interviewer to frame a series of questions that will yield a pre-determined answer. In 

my case, I felt the desired answer was what linear risk coefficient (exposure healthresponse) would I prefer. 

I am also concerned about the process used to select experts for participation. In 

my opinion, the process should be very transparent with regard to the criteria used 

to include or exclude individual experts from a Panel. My concerns extend to the 

inclusion of individuals who may have conducted and reported on the key studies 

being used in the expert opinion elicitation process. It is human nature to want to 

have one’s own data and analyses used in the same manner as originally reported. 

Any additional concern with the process is the approach of using secondary interviews in an attempt to gain consensus from the experts as to the outcome. I understand that was done with the full-scale expert elicitation panel whose input is to 

be used in the final regulatory impact analysis. A major challenge in any elicitation 

of expert advice is separating the individuals science-based input from their personal sources with regard to a policy outcome. In my opinion, the results of that 

expert elicitation are likely to be seriously flawed. I would urge the Administrator 

to not use the results of the expert opinion elicitation as input for quantitative estimates of risks/benefits associated with PM2.5 exposure. Such an approach is not a 

substitute for more rigorous uncertainty analysis that attempts to characterize all 

the factors that impact on estimating risks of PM2.5 exposure and the benefits of 

reductions in PM2.5 exposure. 

As an alternative to expert opinion elicitation, I urge CASAC to document the scientific views of each of the CASAC PM Panel members with regard to quantitative 

aspects of the PM NAAQS. This approach was used in the previous PM review that 

concluded with promulgation of the 1997 PM2.5 NAAQS. A copy of the table included 

in the CASAC PM Panel’s ‘‘closure letter’’ is attached. As may be noted, individual 

Panel members had a wide range of views with regard to setting the PM2.5 NAAQS. 

I would personally prefer to see each of my scientific colleagues express their individual science-based opinions rather than have CASAC Panel participants cajoled 

to reach a consensus. 

SCIENTIFIC EVALUATIONS VERSUS POLICY DECISIONS

A major challenge I see for all scientists, and especially for CASAC PM Panel 

members participating in the NAAQS review process, is to recognize the distinction 

between scientific evaluations and policy judgments. In my comments to Mr. Bill 

Wehrum and Dr. George Gray on improving the NAAQS review process, I noted— 

‘‘It would be helpful if, at each step in the NAAQS process including each meeting 

of the scientists preparing the Criteria Documents and the Staff Paper and their 

review by CASAC, if each participant were reminded. ‘‘Every individual should recognize the distinction between scientific evaluation and policy decisions and recognize that the matters being dealt with are at the interface of science and policy. 

Each individual participant is asked to leave their individual ideologies and 

thoughts on policy decision outcomes at the door before deliberating on the science.’’ 

This is not a matter of an individual’s employment, i.e., academic, government, industry, etc. or political affiliation. It applies to all participants. This is an especially 

vexing issue for scientists involved in evaluating their own research results or that 

of close colleagues. In today’s resource constrained world everyone wants to have 

their work used in the public arena, moreover, they would like to see the door left 

open or opened wider for them to do more work on the topic under consideration. 

Indeed, some individuals, including CASAC Panel Members, desire a ‘‘sense of accomplishment’’—some individuals interpret that as—did we participate in lowering 

the NAAQSs’ Some have suggested that there would be a ‘‘limited sense of accomplishment’’ if only the 24-hour PM2.5 standard were lowered and the Annual PM2.5

standard was left unchanged. Yes, scientific evaluations and policy decisions do get 

intertwined by individual scientists in expressing their own personal preferences on 

life science issues.’’ 
66 

RESPONSE BY ROGER MCCLELLAN TO ADDITIONAL QUESTION FROM

SENATOR VOINOVICH

Question 1. Dr. McClellan, as you heard Dr. Gray testify, he said characterization 

of uncertainties is extremely important. EPA is using a process called expert 

elicitation to respond to the NAS recommendation on this important issue. We will 

see the elicitation’s results when the rule is finalized. Please elaborate on your concerns with this process. 

Response. I am very familiar with the ’’expert elicitation’’ being used by the EPA 

to obtain expert opinions on the quantitative relationship between changes in PM.5

concentrations in ambient air and changes in indices of adverse health effects. As 

I noted in my written testimony, I participated in a pilot expert elicitation study 

conducted by an EPA contractor as a prelude to the larger study recently conducted 

for the EPA. 

In my professional opinion, the expert opinion elicitation process being used by 

the EPA is not a scientifically adequate approach to characterizing either the central estimate nor associated range of potential values for changes in adverse health 

outcomes associated with changes in ambient PM2.5 concentrations for contemporary 

PM2.5 levels found across the United States. The process is at best an elicitation of 

the opinions of a selected group of experts. It is not a substitute for rigorous scientific characterization of uncertainty of the kind I understand was recommended 

by the National Academy of Science/National Research Council in its 2002 report, 

‘‘Estimating the Public Health Benefits of Proposed Air Regulations.’’ 

The outcome of the expert opinion elicitation process is influenced by five factors: 

(1) the nature of the request from the sponsor, in this case the EPA, to the 

organization or individual(s) eliciting the opinions; 

(2) the nature of the questions posed by the opinion elicitators; 

(3) the manner in which the experts are identified and selected; 

(4) the scientific background and personal biases of the experts; and 

(5) how the individual opinions are compiled and reported. 

It is apparent that a requested organization can influence the results by how they 

frame the question(s) presented for use in the elicitation process. In similar fashion 

the manner in which the questions are posed to the experts is critical. I understand 

that the central question asked, which was similar to that posed to me in the pilot 

study, was ‘‘What is the percent reduction in excess health risks associated with a 

1 m3 decrease in the ambient PM2.5 concentration’’ This question assumes that there 

is a linear relationship between changes in PM2.5 concentrations and excess health 

risks. This is an assumption, not a scientific fact. Indeed, I would argue that the 

results of the recent papers by Enstrom (2005) and Laden et al. (2006) clearly indicate a lack of a statistically 

significant excess in mortality associated with contemporary ambient PM2.5 levels 

and, thus, an absence of a linear exposure-response relationship at low levels of 

PM2.5. Interestingly, this includes results from SouthernCalifornia and Stuebenville, 

OH, areas in which PM2.5 levels were quite high in the past and have been substantially reduced. 

The scientific background of the experts, their personal biases and how they are 

selected can influence the outcome of the elicitation process. Individuals whose research findings are under consideration in the expert opinion elicitation process are 

placed in an awkward position. Are they willing to set aside their own vested interest in seeing their results used in favor of giving a broader opinion? In giving an 

opinion, can they avoid being concerned with how the results will be used? Will a 

tighter standard result in a generally more favorable view of their research? 

The manner in which results are ultimately compiled and presented is of critical 

importance. In the most recent process, the experts were polled individually and 

then brought together as a group to re-affirm the outcome. I argue that this consensus building approach suppresses uncertainty rather than contributing to a full 

expression of uncertainty. I would urge the EPA Administrator to not give significant weight to the results of the expert opinion elicitation process in setting the annual standard for PM2.5. Moreover, I definitely feel it would be inappropriate to use 

the results of the expert elicitation process as input to the calculation of benefits 

in the Regulatory Impact Analysis. 

Let me again emphasize that it is my professional opinion that it is imperative 

that the uncertainties associated with estimation of the excess adverse health effects 

of exposure to PM2.5 at contemporary levels be rigorously characterized. In my opinion, the EPA at each step in the PM review process, failed to adequately characterize uncertainties. This was true of the Criteria Document, the Staff Paper and 

the Risk Assessment that under-girded the Staff Paper. 
67 

A rigorous uncertainty analyses would have started with critically examining the 

base data from critical studies and the very sophisticated statistical methods used. 

When the original published reports did not contain sufficient detail, the EPA 

should have obtained more detailed data and, if necessary, conduct additional analyses. This was done in a laudatory manner for some studies under the auspices of 

the Health Effects Institute, however, even more critical analysis would have been 

useful in better characterizing uncertainty in estimating PM2.5 risks. 

For example, very little was done to examine the validity of the Cox proportional 

hazard model for characterizing the very small estimated excess risks for PM2.5 ex- posure and other confounders. Moolgavkar (2005 and 2006) has noted the limitations in this widely used model for estimating small excess risks. In none of the key 

studies being used to set the annual PM2.5 standard were results presented for cigarette smoking, the major risk factor for cardiorespiratory disease. These results 

would have given an indication of how well the Cox model was working for the 

major risk factor, cigarette smoking, and, thus, gave some greater confidence in the 

use of the model for characterizing much lower levels of risk for PM2.5. If historical 

information were not available on cigarette smoking this should have been identified 

as an uncertainty and, indeed, quantified. 

The impact of cigarette smoking is apparent from the analysis of Enstrom (2005) 

using data for Southern California. Beyond presenting the analysis of PM2.5 risks, 

the Enstrom paper also included the results of an analysis of the relative risk of 

death from all causes by cigarette smoking status. These results are of special value 

because they illustrate the substantial magnitude of the cigarette smoking effects 

relative to other risk factors such as air pollution. The baseline was never smokers 

(as of 1959 and 1972) for deaths 1973 to 2002 set at 1.000. Former smokers (as of 

1959 and 1972) were Relative Risk (RR)-1.054 and increased to 1.253 for former 

smokers (as of 1972 only). Current smokers (as of 1972) had relative risks that increased with smoking intensity 1-9 cigarettes per day (cpd)RR-1.239; 10-19 cpdRR1.97 cpdRR-1.871, 21-39 cpdRR-2.068 and 40+ cpdRR-2.543. The large relative risks 

related to cigarette smoking level provide perspective for the small relative risks reported for long-term PM2.5 exposure. Indeed, in part because he had smoking histories available on the subjects in the Southern California cohort he was able to conclude These epidemiologic results do not support a current relationship between fine 

particulate pollution and total mortality in elderly Californians, but they do not rule 

out a small effect, particularly before 1988. For 1983-2002, the RR was 1.00. This 

included a substantial number of individuals exposed to PM2.5 at concentrations 

above the current Annual Standard of 15 m3. Moreover, the substantial effects of 

cigarette smoking emphasize the importance of accurate inclusion of cigarette smoking history in any long-term cohort study of the effects of PM and dictate that consideration of smoking be included in any quantitative characterization of uncertainty in estimating PM2.5 risks. 

Question 2. Dr. McClellan, you have been on these panels for a long time. Does 

the science ever point specifically to a number or are these standards really set in 

the judgment of the Administrator? 

Response. I have served on each of EPA Clean Air Scientific Advisory Committees 

that have provided advice to the Administrator of the setting on revision of National 

Ambient Air Quality Standards for Particulate Matter. There has been a general acknowledgement by the Advisory Panel members that the science should inform the 

decisions on the four elements of the standard; (a) indicator, such as PM2.5, (b) averaging time, such as annual, (c) numerical level, such as 15 m3, and (d) the statistical 

form. There has also been general recognition that the Administrator has the ultimate responsibility for setting the standard using his/her judgment. The Advisory 

Panels have regularly reviewed and commented on the range of numerical levels 

presented in the Staff Paper, thereby acknowledging that the science can inform a 

broad range for setting the standard rather than the science yielding a specific numerical level. Each successive review of the Particulate Matter standard has become 

more contentious. In my opinion, some of the contentious nature has been driven 

by early concern by special interest groups and some members of the Panel as to 

the outcome of the process. In short, a premature view has developed that the PM2.5

standard should be tightened, a view advanced long before the scientific evaluation 

had been completed. One way for CASAC to enhance the potential for the standard 

being tightened is to endorse a range of numerical values below that of the current 

standard. If this is done the judgment of the Administrator is constrained. This is 

exactly what was done when the CASAC PM Panel truncated the proposed range 

for setting an Annual PM2.5 standard from 12 to 15 m3 to 13-14 m3. The CASAC 

PM Panel advanced an argument for changing the lower limit of the range from 12 

to 13 m3, i.e. uncertainty increased below 13 m3. In none of the letters from the 

CASAC Chair to the Administrator was a rigorous rationale provided for reducing 
68 

the upper bound of the range from 15 to 14 m3. In my view, by endorsing an exceptionally narrow range of 13 to 14 m3 the CASAC PM Panel ignored the uncertainty 

in the science and attempted, inappropriately in my view, to exercise some of the 

judgment that is reserved for the Administrator by the Clean Air Act. The CAA 

wisely calls for CASAC to advise the Administrator and for the Administrator to use 

judgment in setting the standard. The CASAC PM Panel, in narrowing the range 

to 13 to 14 m3, stopped one small step short of attempting to set the PM2.5 Annual 

standard. 

Question 3. As a member of the CASAC panel was there complete agreement on 

the recommendations. 

Response. There was not complete agreement among CASAC PM Panel Members 

on the narrowing of the range for the Annual PM2.5 standard from 12 to 15 G53 

to 13 to 14 m3. George Wolff and I, who had both previously served as Chair of the 

Clean Air Scientific Advisory Committee, disagreed with the proposal. It is of interest that the decision to narrow the range was reached during short conference calls 

of the Panel and by electronic exchanges among small groups of members. The decision was not one reached on the basis of a typical face-to-face public meeting of the 

Panel. There was also intense pressure to obtain and present a consensus view and 

to provide a letter from CASAC to the Administrator that was devoid of attached 

individual views as customary for CASAC letters to the Administrator, especially on 

important matters. I exercised my rights as a private citizen to prepare a letter to 

the docket expressing my views on the setting of the PM standard. In my professional opinion, the available scientific information is consistent with setting an Annual PM.5 Standard in the range of 12 to 15 m3 as articulated in the EPA Staff 

Paper with the specific numerical level to be selected by the Administrator based 

on judgment as specified in the Clean Air Act. 

PREPARED STATEMENT OF ANNE SMITH, VICE PRESIDENT, CRA INTERNATIONAL

Mr. Chairman and members of the committee, thank you for your invitation to 

participate in today’s hearing. I am Anne Smith, and I am a Vice President of CRA 

International. I am a specialist in environmental risk assessment and integrated assessment to support environmental policy decisions, which was a core element of my 

Ph.D. thesis at Stanford University in economics and decision sciences. I have performed work in the area of risk assessment over the past 30 years, including as an 

economist in the USEPA’s Office of Policy, Planning, and Evaluation, as a consultant to the USEPA Air Office, and in many consulting engagements since then for 

Government and private sector clients globally while employed first at Decision 

Focus Incorporated and then CRA International. I have also served as a member 

of several committees of the National Academy of Sciences focusing on risk assessment and risk-based decision making. 

I have been deeply involved in assessment of the evidence on risks from ambient 

fine particulate matter (PM2.5) since EPA first turned to the task of identifying an 

appropriate National Ambient Air Quality Standard (NAAQS) for PM2.5 over 10 

years ago. I testified to this same committee in 1997 on the nature of the scientific 

evidence underlying the PM2.5 NAAQS proposed at that time. I thank you for the 

opportunity to share my perspective today on the current scientific evidence and associated risk assessment for PM2.5 and how it has evolved since 1997. My written 

and oral testimony today provide a statement of my own research and opinions, and 

does not represent a position of my company, CRA International. 

I would like to start by summarizing what I think are the most important and 

overarching considerations that should be accounted for when considering whether 

to alter the current PM2.5 NAAQS, which include an annual average limit of 15 m3

and a 24-hour average limit where the 98th percentile of observations over all days 

must be below 65 m3. I will then summarize results of analyses I have done to synthesize the recent PM2.5 health studies into an assessment of risks. Complete details 

and documentation of my analyses are in my written comments on the current Proposed Rule for a revised PM2.5 NAAQS, which were submitted into the PM2.5 docket 

in April, 2006. I am attaching a copy of my written comments to EPA to further 

substantiate the points that I make in my testimony today. 

The key points that I wish to make about the scientific evidence on risks of PM2.5

that are relevant for making a decision on the standard are: 

• EPA and the courts recognize that the PM2.5 NAAQS must be set at a level that 

still has some positive level of risk, because the science has yet to advance far 

enough to identify any threshold exposure level for effects, below which risk would 

be indistinguishable from zero. This was true in 1997 and it remains true today. 
69 

1See, for example, the Proposed Rule, p. 2622 (i.e., 71 FR 2622). 

2 71 FR 2648. 

3 71 FR 2640. 

4 71 FR 2640. 

• EPA’s own quantitative estimates of mortality risk at attainment of the current 

NAAQS are lower today than they were when EPA set that standard in 1997 ‘‘with 

an adequate margin of safety,’’ after accounting for the many uncertainties. This is 

true for both long-term (‘‘chronic’’) exposures to PM2.5 (which are addressed by the 

annual average limit) and short-term (‘‘acute’’) exposures (which are addressed by 

the 24-hour average limit). 

• The reduction in the quantitative estimates of risk is apparent even in EPA’s 

own risk analysis, but most of the reasonable alternative results reported in the 

same studies that EPA has relied on imply even lower quantitative risk estimates 

for PM2.5. 

• Looking more broadly beyond quantitative risk estimates, the many additional 

studies of PM2.5 mortality risks since 1997 have demonstrated that many of the risk 

estimates become ‘‘statistically insignificant’’ when re-estimated in reasonable alternative ways. A ‘‘statistically insignificant’’ result directly implies a positive probability that there is no effect at all. Thus, when we look at all of the data in the 

new studies as a group, we find more statistical evidence now than was available 

in 1997 that PM2.5 may not be the culprit pollutant, and that there may be no causal relationship at all between PM2.5 and mortality. 

In thinking about whether to tighten either the annual or daily standard, one 

might ask, what has changed in our knowledge since 1997 that would undermine 

the Administrator’s 1997 judgment that the current PM2.5 NAAQS are neither more 

nor less stringent than necessary to protect the public health with an adequate margin of safety? A thorough review of the new evidence suggests that the margin of 

safety that the Administrator selected in 1997 is likely to be larger than was 

thought at the time. 

QUANTITATIVE ESTIMATES OF RISK REMAINING AT THE CURRENT STANDARD HAVE

FALLEN

EPA has acknowledged that the PM2.5 NAAQS cannot be set at a level that corresponds to zero risk.1 However, EPA has also argued that its quantitative risk estimates cannot be used to identify a specific point where it should set a standard: 

‘‘[I]n the Administrator’s view, a risk assessment based on studies that do not resolve the issue of a threshold is inherently limited as a basis for standard setting, 

since it will necessarily predict that ever lower standards result in ever lower risks, 

which has the effect of masking the increasing uncertainty inherent as lower levels 

are considered. As a result, while the Administrator views the risk assessment as providing supporting evidence for the conclusion that there is a need to revise the current suite of PM2.5 standards, he judges that it does not provide a reliable basis to 

determine what specific quantitative revisions are appropriate.’’ 2

I concur that a risk assessment that makes no attempt to incorporate the uncertainty on where a threshold may exist will indeed only serve to promote ever lower 

standards without a sound basis. Since EPA has not incorporated such uncertainty 

into its risk assessment, that risk assessment is indeed incapable of helping to identify where to set the standard. However, since EPA views the risk assessment as 

supporting a conclusion on whether there is a need to revise the standard, it is appropriate and relevant to compare EPA’s current quantitative risk estimates and 

the associated statistical measures of a PM2.5 effect to those estimates that were 

available in 1997. In the Proposed Rule, EPA partially acknowledges that risk estimates are lower today than in 1997 for the two cities that were included in both 

its 1997 and current risk analyses. With respect to short-term exposure risk estimates, EPA states that ‘‘the magnitude of the estimates associated with just meeting the current annual standard. . . is similar in one of the locations. . . and the 

current estimate is lower in the other location.’’ 3 With respect to the long-term exposure risks, EPA states that the risk estimates ‘‘are very similar for the two specific locations included in both the prior and current assessments.’’ 4

EPA does not provide the actual numerical estimates for these two cities. They 

are: 

• For acute risks in Los Angeles, in 1997 EPA estimated that 1.7 percent of mortality would continue to be attributable to PM2.5 once Los Angeles would be in attainment with the current NAAQS. Today EPA’s risk estimate has fallen to 0.5 percent and this current estimate is statistically insignificant (which means that there 
70 

5This was the paper by Schwartz, Dockery, and Neas (1996) on acute risks in six U.S. cities. 

6That is, EPA’s risk estimate for San Jose is based on a 1-pollutant regression that associated 

mortality with PM2.5 on the same day as death. The study also reported results of a comparable 

1-pollutant regression that was identical in all ways except that it associated mortality with 

PM2.5 from the day before death. The latter regression produced a negative risk estimate, which 

I interpret to be evidence of no effect at all (rather than evidence of a beneficial effect of PM2.5). 

is a fairly large chance that this particular estimate suggests that there is really 

no PM2.5 effect at all). 

• For acute risks in Philadelphia, in 1997 EPA estimated that 1.5 percent of mortality would continue to be attributable to PM2.5 at attainment of the current 

NAAQS. The risk estimate that EPA now uses for Philadelphia is 2.2 percent. Although this is higher than in 1997, EPA has selected a single estimate out of a very 

large number of estimates reported in the epidemiological study it is relying on for 

Philadelphia. In fact, that study actually concluded that PM2.5 did not appear to explain the mortality risk as well as ozone, and the residual risk for PM2.5 after simultaneously accounting for the role of ozone would have produced a lower estimate— 

about 0.8 percent—which is lower than in 1997. This more thoroughly-controlled estimate also is not statistically significant. 

• Chronic risk estimates do not vary from city to city, because the statistical 

method to estimate relative chronic risks produces a single value that applies to all 

cities. I will therefore only relate the results for Los Angeles here. For chronic risks, 

in 1997 EPA estimated that 2.0 percent of mortality would continue to be attributable to PM2.5 at attainment of the current NAAQS. Today, EPA’s risk estimate 

for the same attainment status is 1.8 percent—in other words, the chronic risk estimate also is lower now, even though the quote from the Proposed Rule above suggests that the estimate has not changed. 

The Proposed Rule only referred to a comparison of risks for these two cities. 

However, it is actually possible to make the same comparison for the other six cities 

that EPA has included in its current risk analysis. This is because there was only 

one PM2.5 acute mortality study it could have used for each of those cities back in 

1997 the same one that it used for Los Angeles and Philadelphia.5 For five of the 

other six cities in the current risk analysis, EPA’s acute risk estimates today are 

lower than they would have been estimated to be in 1997, and all the cities have 

lower chronic risk estimates. Table 1 summarizes the cities and the results of my 

comparison of their risk estimates. 

When I reviewed the original papers that EPA is relying on, I also found that 

EPA’s risk analysis has selectively used the highest or near-highest risk estimates 

supported by each paper. This means that risks estimates that more fully reflect 

the body of evidence are likely lower still than EPA’s risk analysis suggests. Additionally, as for Philadelphia, I found that San Jose would have had a much lower 

risk estimate than in 1997—literally zero now—if EPA had chosen to use the one 

reasonable alternative result for PM2.5 reported in the San Jose study.6 Thus, the 

full body of evidence can support risk estimates that would be lower now than in 

1997 for every one of the eight cities in EPA’s current risk analysis. 
71 

7 71 FR 2648. 

Table 1 also reports that the PM2.5 findings are not statistically significant across 

all of the alternative reasonable risk estimates in each underlying study. This was 

not the case in 1997. At that time, there was a much more limited set of studies 

and estimates within each study—but for some cities, all the estimates available at 

the time were statistically significant. Today, the opposite it true. Every single 

study that EPA has relied on for its current risk analysis contains alternative estimates that indicate that PM2.5 does not have a statistically significant association 

with mortality, yet EPA chose not to use this part of the new information. 

In conclusion, EPA has stated that the risk assessment’s role is to provide ‘‘supporting evidence’’ on whether there is a need to revise the PM2.5 standard. In this 

role, EPA’s own risk analysis provides no evidence supporting a decision to tighten 

the standard now. The risks are lower now than they were when the standard was 

set in 1997. The higher estimates of risks were determined to be ‘‘requisite to protect the public health with an adequate margin of safety’’ in 1997, and the quantitative risk analysis suggests that that margin of safety has grown, not narrowed, 

as a result of the many more recent PM2.5 health effects studies. 

The question then remains whether other aspects of the new evidence provide an 

overriding reason for tightening the standard. The other part of EPA’s reasoning for 

how to set the standard relies on what EPA calls an ‘‘evidence-based approach.’’ 

Simply put, EPA looks at all of the studies that estimate the statistical relationship 

of PM2.5 with health effects, and seeks to identify a level of PM2.5 above which statistically significant effects are found, and below which statistically significant effects are not found. 

In applying the evidence-based approach, EPA states that the large quantity of 

new studies of acute effects justifies the use of acute studies to set the 24-hour 

standard, and that chronic studies should be used to determine where to set the annual standard: 

‘‘Given the extensive body of new evidence based specifically on PM2.5 that is now 

available, and the resulting broader approach presented in the Staff Paper, the Administrator considers it appropriate to use a different approach from that used in 

the last review to select appropriate standard levels. More specifically, the Administrator’s proposal relies on an evidence-based approach that considers the much expanded body of evidence from short-term exposure PM2.5 studies as the principal 

basis for selecting the level of the 24-hour standard and the stronger and more robust 

body of evidence from the long-term exposure PM2.5 studies as the principal basis for 

selecting the level of the annual standard.’’ 7

I will next discuss how the evidence in the long-term exposure studies of PM2.5

has weakened since 1997, thus removing any necessity to tighten the annual stand-
72 

8The report on findings of these reanalyses is Krewski et al. (2000). 

9 71 FR 2652. 

ard under EPA’s evidence-based approach. I will then discuss how the evidence in 

the short-term exposure studies of PM2.5 that are the basis for the 24-hour standard 

also has weakened. 

THE EVIDENCE IN LONG-TERM EXPOSURE STUDIES HAS WEAKENED SINCE 1997

In 1997, the two prominent long-term exposure studies (one based on a sample 

population, or ‘‘cohort’’ in 154 U.S. cities that was tracked by the American Cancer 

Society, and one based on a sample population in just six US cities that was tracked 

by Harvard School of Public Health) both had published findings of a statistically 

significant relationship between long-term exposure to PM2.5 and life expectancy. 

These studies were subjected to an extensive process of reanalysis under the auspices of the Health Effects Institute (HEI) that was released in 2000.8 This reanalysis is widely reputed to have confirmed the original studies’ results; however, a complete reading of the actual report shows that some major statistical concerns underlying those results were unearthed. Although a positive PM2.5 effect was still found 

in those data sets, the ability to interpret those results as clearly causal in nature 

was weakened. 

EPA acknowledges that the concerns identified in the HEI reanalyses of the longterm exposure studies for PM2.5 remain unresolved to the present time: 

The Administrator also recognizes a contrasting view as to the interpretation of 

and weight to be accorded to the results from the ACS-based studies (Pope et al., 

1995; Krewski et al., 2000; Pope et al., 2002). In this view, the ACS-based studies 

are not sufficiently robust to support a policy response that would tighten the annual PM2.5 standard based on the evidence. This view emphasizes the sensitivity of 

the results of these studies to plausible changes in model specification with regard 

to accounting for the geographical proximity of cities and the correlation of air pollutant concentrations within a region, effect modification by education level, and inclusion of SO2 in the model. In this view, these sensitivities suggest potential confounding or effect modification that has not been taken into account. For example, 

concern has been raised about the sensitivity of results in the reanalysis of data 

from the ACS cohort study (Krewski et al., 2000) to inclusion of SO2 in the models. 

[T]he reanalysis found that PM2.5, sulfates, and SO2 were each associated with mortality in single-pollutant models. However, in two-pollutant models with SO2 and 

PM2.5, the relative risk for PM2.5 was substantially smaller and no longer statistically significant, whereas the effect estimates for SO2 were not sensitive to inclusion of PM2.5 or sulfates in two-pollutant models. In this view, the ACS-based risk 

estimates are more robust for SO2 than for PM2.5 or sulfates. In further extended 

analyses, Pope et al. (2002) reported that effect estimates were not highly sensitive 

to spatial smoothing approaches intended to address spatial autocorrelation, while 

findings of effect modification by education level were reaffirmed. Results of multipollutant models were not reported by Pope et al. (2002). Because the correlation 

coefficient between PM2.5 and SO2 was 0.50 in the ACS data, in this view it is plausible to believe that the independent effects of the two pollutants could be disentangled with additional study.’’ 9

The quote above is lengthy, which highlights that the concerns identified in the 

long-term exposure studies are many. The quote above also indicates that the new 

set of results using the American 

Cancer Society cohort that was published after the HEI reanalyses (i.e., Pope et 

al., 2002) did not help resolve these issues. Specifically, the 2002 paper ignores concerns that the purported PM2.5 effect instead might be attributable to the gaseous 

pollutant SO2, and re-affirms a troubling finding that PM2.5 only seems to create 

mortality risk only for individuals who have not continued their education beyond 

the high school level. (The latter finding is discussed further below.) Additionally, 

the 2002 paper still finds that the PM2.5 effect is diminished and rendered insignificant when applying statistical methods to correct a clear statistical error that the 

HEI report found in the original results. Nevertheless, the Pope et al. (2002) paper 

continues to use the estimation method that is subject to error except in a sensitivity analysis; and EPA continues to rely on the uncorrected estimates in its risk 

analysis. Even with these dubious selections from the full body of literature, EPA’s 

estimates of long-term exposure risk are lower than in 1997. 

Figure 1 illustrates the degree to which the evidence on long-term exposure risk 

has fallen, both in the overall magnitude of the risk estimate, and also in terms of 

a greater degree of uncertainty in the estimate. Figure 1 uses the case of Los Angeles at attainment of the current standard, yet the relative patterns evident in this 
73 

figure are the same for all cities in the U.S. All of the risk estimates in Figure 1 

labeled ‘‘1’’ through ‘‘7’’ are based on the American Cancer Society cohort, which has 

received the majority of attention. The estimate on the far left of the figure, labeled 

‘‘1’’ is the estimate from 1997 (note that the estimate is 1.5 percent, as reported for 

Los Angeles in the preceding section), and the estimates to the right are other key 

results from the HEI reanalyses and from the more recent Pope et al. (2002) paper. 

The estimate labeled ‘‘2’’ is the single result from the many new estimates that is 

used for the current EPA estimates of long-term risk (which is 1.3 percent, as I stated in the previous section). 

It is quite apparent from the figure that the current risk estimate is among the 

highest that could be found among the more recent results. If any of the others (labeled ‘‘3’’ through ‘‘7’’) had been used for EPA’s risk analysis, the current risk estimate of 1.3 percent for Los Angeles would instead be in the range of 0.3 percent 

to 1.0 percent—much lower than the original 1997 risk estimate that was available 

when the current standard was first set. 

The set of results on the far right of the figure (labeled ‘‘8’’ through ‘‘12’’) reflect 

the findings based on a new study of a third sample population that had not been 

identified or studied as of 1997. It is known as the ‘‘Veterans’ Cohort.’’ I believe this 

study to be of some policy relevance regarding whether or not the annual standard 

needs to be tightened, given that this study finds no effect at all of PM2.5 on life 

expectancy in this particular cohort. EPA has chosen to give ‘‘greatest weight’’ to 

results from the American Cancer Society and the Six Cities cohorts because they 

have been reanalyzed and scrutinized so thoroughly. While this may be a reasonable 

judgment, EPA has actually gone further than that, and accorded the Veterans’ Cohort results zero weight. Its findings should be acknowledged with somewhat more 

than zero weight. When one does so, the overall evidence regarding long-term PM2.5

risks is further weakened. 
74 

10 CASAC’s reasoning is stated in a letter to the Administrator on March, 21 2006, pp. 3-4. 

EPA also refers to the perplexing finding that level of education determines 

whether or not there is a PM2.5 association. Figure 2 illustrates this finding, which 

was first identified in the HEI reanalyses, and which remains in the more recent 

Pope et al. (2002) study. Clearly education per se is not believed to be the cause 

of sensitivity to exposure to PM2.5, yet the important (and still unanswered) question is: what is educational level indicating about risks that these sample populations face? What could possibly explain the complete lack of a PM2.5 effect among 

those with higher educations? When such a pattern appears in epidemiological 

study results, it indicates that there is still an important explanatory factor that 

is missing from the statistical estimation method something correlated with education. Until that factor is identified and included in the estimation of PM2.5 risks, 

estimates of the effect of PM2.5 are biased. The PM2.5 estimate could be higher, or 

it could vanish altogether. Thus, the unexplained pattern related to education in all 

of these studies remains a very important warning about the pitfalls of making a 

causal interpretation regarding long-term exposure risks of PM2.5. In summary, the evidence against a need to tighten the annual standard is not 

just founded on the fact that the numerical long-term risk estimates are now lower 

than when the current standard was set. The more important point is that the basis 

for interpreting the long-term studies as unbiased evidence of a causal relationship 

between PM2.5 and chronic mortality risk has weakened. This was a concern in 

1997, and the reanalyses and new studies since then have done more to amplify 

these concerns than to allay them. In the face of this evidence of greater uncertainty, combined with the reduced quantitative risk estimates, there is no justification for tightening the annual standard on the basis of the long-term exposure studies. 

A Summary CASAC’s Case for Tightening the Annual Standard 

EPA’s Clean Air Scientific Advisory Committee (CASAC) has made the case to 

tighten the annual standard with two lines of reasoning, neither of which is founded 

on the long-term risk studies.10

CASAC’s first line of reasoning is that EPA reports substantial risk would remain 

at the current standard. As EPA and the courts have long established, the PM2.5

NAAQS cannot be a zero-risk standard. CASAC was concerned by the estimates of 

remaining risk, but never deliberated the question of whether this risk estimate had 

risen or fallen since the standard was deemed ‘‘requisite to protect the public health 

with an adequate margin of safety.’’ As I have shown above, the risk estimates fell, 

both for chronic and acute risks, but EPA never reported this fact to CASAC during 
75 

11 CASAC actually cites a paper by Lipsett et al. (1997) in its letter, but that paper has nothing to do with PM2.5 mortality. I interpret CASAC to have wanted to cite Fairley (2003). 12See the quote on p. 5 above, taken from 71 FR 2648. 13The other multi-city PM2.5 mortality studies (based on the Six Cities data set) report effects 

by individual city as well as for the combined set. This was the data on which EPA set the current standards, and in doing so, EPA used annual averages for only the individual cities that 

did have significant effects within the set of six. The lowest such city was Boston, with an annual average of 15.6 m3, which was the basis for the current annual average standard of 15 

m3. 

CASAC’s review of the Staff Paper and associated risk assessment. In the face of 

this fact, the only other argument to tighten the annual standard might be if there 

were stronger reason to believe that the effects found in these studies are causal 

in nature. However, EPA set the current standards with a presumption (precautionary in nature) that the estimated PM2.5 risks were causal. This cannot therefore be the rationale to tighten the standards. 

Hence, to argue that the standard should be tightened because there is evidence 

that risk remains at the current standard is a logic that would force a tightening 

of the standard in every future review cycle, even if no new evidence were to have 

become available at all since the previous review. There is nothing in the law or 

in precedent that dictates that the standard has to be tightened as the result of a 

NAAQS review. 

CASAC’s second line of reasoning comes closer to the heart of how EPA first set 

the standard. CASAC notes that there are three new acute studies that find PM2.5

associations with mortality at annual averages below the current annual standard 

(all with reported annual averages in the range of 13 to 14 m3). These studies are: 

Burnett and Goldberg (2003) for 8 Canadian cities combined; Mar et al. (2003) for 

Phoenix, and Fairley (2003) for Santa Clara County, CA (referred to in the risk 

analysis as San Jose).11

The first thing to realize about this part of CASAC’s case for a tightened annual 

standard is that it is using studies that consider only how day-to-day changes in 

PM2.5 levels affect day-to-day numbers of deaths relative to the number of deaths 

that might otherwise be expected on each day (e.g., relative to numbers of deaths 

that are expected to occur on each day based on established patterns related to the 

time of year, time of week, weather, etc.). Such acute effects of a pollutant are generally believed to be associated with spikes in PM2.5, although studies to date rarely 

report evidence of any threshold level below which the association disappears. Nevertheless, there is no clear linkage between the annual average in a city, and the 

extent to which day-to-day spikes in PM2.5 might be occurring. If an acute effect is 

found in a city that happens to have a low annual average, there is no reason to 

believe that the estimated association is not still due to sudden upward changes in 

PM2.5 from one day to the next. The city may simply have a large number of very 

clean days that pull the annual average PM2.5 down, while not eliminating the presence of many days of sudden increases in pollution that are logically likely to be 

the cause of any acute risk that the study is finding. 

Thus, it is not necessarily correct to assume that if acute risks are found in a city 

with a low annual average pollution, then such risks exist in all cities with low annual average pollution. In fact, if one believes that there must be a threshold where 

the acute risk from exposure to pollution drops off somewhere above zero, then the 

linkage between the annual average of pollution and existence of acute risk is not 

only unclear, but illogical. For reasons such as these, EPA has decided to use the 

plethora of acute risk studies now available to set the 24-hour standard that that 

type of study more meaningfully informs. EPA has decided not to use acute studies 

to set an annual standard.12

Nevertheless, even if one were to use acute effects studies to determine an ‘‘adequate margin of safety’’ for lower levels of long-term exposure to pollution, there are 

good reasons to believe that the annual average PM2.5 reported for each of the three 

studies cited by CASAC may not be a good indicator of the long-term exposure levels 

that account for the risk findings in these studies. I explain why for each of the 

three: 

Goldberg and Burnett (2003). This study reports a PM2.5 association for eight Canadian cities combined. The annual average of 13.3 m3 is an average over all of the 

eight cities, while the annual averages in the individual cities vary from 9.5 m3 to 

17.7 m3. There are no city-specific results reported to help indicate whether the estimate of an acute effect is due to effects in each of the eight cities, or only in a few.13

Evidence in the paper suggests that there may in fact be different effects in each 

city. 
76 

14The original paper was Burnett et al. (2000) 15 To know this, one must go back and read the original study that this is a reanalysis of, 

Fairley (1999). 16 Clyde et al. (2000). 17Smith et al., (2000) 

Another concern with this study is that it is a reanalysis of a more comprehensive 

study that included consideration of the role of gaseous pollutants as well.14 The 

original study concluded that the gaseous pollutants had a much greater ability to 

explain mortality risks 

than both PM2.5 and PM10-2.5 combined. However, when the paper had to be reanalyzed, the authors did not reanalyze the portions that considered gaseous pollutants in conjunction with particulate pollution, and so this finding is no longer discussed. 

Fairley (2003). This study used data from Santa Clara County, CA, over a seven 

year period, and during that time pollution levels were falling dramatically. Although the annual average PM2.5 that is attributed to this study is 13.6 m3, the annual average was as high as 18.4 m3 at the start, and fell progressively to 9.5 m3

by the end of the 7 years studied.15 Peak levels of PM2.5 were also falling, starting 

at a 98th percentile of 88 m3 for the first year and ending at 25 m3. Such a wide 

range within this one city’s data set begs the question: are the reported acute effects 

relationship driven largely by the high levels in the early years, or are they also 

evident in the later years? This highly relevant question is never mentioned, let 

alone analyzed, by the authors. Lacking any exploration of such an obviously relevant issue, it would seem a dubious proposition to use the annual average over the 

entire time period in this one study as the basis for a national ambient standard. 

Another concern with this study is that it reports PM2.5 risk estimates for two alternative methods of estimation, both of which are reasonable. One method considers whether deaths tend to fluctuate with the same day’s PM2.5 levels and the 

other method considers whether deaths tend to fluctuate with the previous day’s 

PM2.5 levels. The same-day estimate finds the positive association that this study 

is known for, but the estimate based on PM2.5 on just the previous day is actually 

in the negative direction. Complete reversal of evidence of a PM2.5 mortality effect 

by considering PM2.5 levels only 24 hours apart in time presents a concern for interpreting the study’s same-day estimate as a causal one. However, there is no discussion of what these conflicting results might mean. 

Mar et al. (2003). This study considered acute risks in Phoenix, AZ, with annual 

average PM2.5 levels of 13.5 m3. There are 10 estimates of PM2.5 risk in the paper, 

and only 3 of them are significant. More importantly, this is not the only paper that 

studied the ability of this same set of PM2.5 data to explain acute mortality risks 

in Phoenix. One of the other studies found that PM2.5 did not have any explanatory 

power, and found instead that the coarse fraction of PM had explanatory power.16

The third study found evidence that there is a threshold below which PM2.5’s apparent ability to explain changes in daily mortality disappeared.17 That threshold appeared to be above 20 m3. If there is a threshold, then the rationale for a linkage 

between annual average PM2.5 and acute risks simply falls apart. 

A final concern with all three of the Phoenix studies is that none of them considered whether the PM2.5 effect would remain if pollutants such as CO, SO2, ozone, 

or NO2 were also included in the analysis. This is a critical gap in many of the current studies because the new body of papers on PM2.5 health effects reveals that 

PM2.5 effects usually disappear when one of the gaseous pollutants is explored. This 

is addressed in the next part of my testimony. 

In summary, CASAC makes its case to tighten the annual standard on the basis 

of acute, not chronic effects studies. There are logical problems with this approach 

to setting an annual standard; these logical problems become apparent when looking 

at each of the three acute studies that CASAC cites as its basis for recommending 

an annual standard that is tighter than the current one. 

THE STATISTICAL EVIDENCE ON ACUTE EFFECTS OF PM2.5 HAS ALSO WEAKENED SINCE

1997. 

In 1997, there existed only one study that had used actual measurements of PM2.5

and estimated whether daily numbers of deaths might be associated with day-today variations in the PM2.5. This was a study using the data from the Harvard 

study of six U.S. cities reported in Schwartz et al. (1996), and it was used as the 

basis for the current standards. In that study, statistically significant associations 

of PM2.5 and acute mortality were found in three of the four cities with the highest 

98th percentile PM2.5 levels, which ranged from 42 m3 to 44 m3. The city with the 

highest PM2.5 98th percentile (which was 82 mG53) did not produce a statistically 
77 

significant association, nor did the two cities with the lowest 98th percentile levels 

of 32 and 34 m3. This was the best available information at the time,. Other than 

the anomaly for the city with the highest PM2.5 exposures, it did at least suggest 

that there might be a range above which effects were more likely and below which 

they were more unlikely. 

While this study was used as the primary basis for the current standards (including the annual standard), there were many concerns expressed with uncertainties 

in the estimation methods. In particular, there was concern that this study had not 

considered the explanatory role of any of the other common pollutants like CO, SO2, 

ozone, and NO2. (These are often called the ‘‘gaseous pollutants’’ because that distinguishes them from various forms of particulate pollutants that are regulated under 

the PM NAAQS.) It was argued that PM2.5 might be simply playing a proxy role 

for a gaseous pollutant also present in the air in these cities. 

As new acute PM2.5 studies were performed after 1997, a number of these studies 

did strive to explore the respective roles of PM2.5 and gaseous pollutants in the observed statistical associations. This was done by using ‘‘2-pollutant’’ or ‘‘multi-pollutant’’ methods, as contrasted to the ‘‘1-pollutant’’ method that only allows a single 

pollutant (e.g., PM2.5 in this case) to have any opportunity to explain mortality risk. 

One of the little recognized but important insights of this body of studies is that 

when gaseous pollutants also have been considered in a study, the gaseous pollutant 

has taken over the explanatory role from PM2.5 in a majority of the cases. 

I determined this in my review of the studies since 1997. Specifically, I attempted 

to identify all of the PM2.5 health effects studies cited in the Criteria Document (including both mortality and morbidity effects studies) that had reported results of 

any estimates for PM2.5 using a 2-pollutant method of estimation for at least one 

gaseous pollutant. I found 10 such papers among all the new studies that did report 

a statistically significant association for PM2.5. Of these 10, 8 saw PM2.5 lose its ability to explain mortality risk when studied using a 2-pollutant method. (In the other 

two studies, both the PM2.5 and gaseous pollutant retained statistical explanatory 

power.) 

Often it is suggested that 2-pollutant methods are not useful because it is impossible to unravel the effects of two pollutants that both move up and down together 

in near synchrony (i.e., they are highly ‘‘correlated’’). However, my review of these 

papers did not find evidence that this was a problem. If it were a problem, then 

both the PM2.5 and gaseous pollutant would lose their explanatory power. What I 

found instead was that in seven of the eight studies where PM2.5 lost its erstwhile 

explanatory power when it was the only pollutant considered, the gaseous pollutant 

retained its explanatory power. Otherwise stated, of the ten studies that I started 

with, only one seemed to be affected by intractable statistical problems making it 

impossible to unravel the separate effects of the two pollutants. 

These papers are summarized in Table 2, which is more fully explained in my 

written comments to EPA of April 2006, which I am submitting with this testimony. 
78 

18See 71 FR 2649. 19My written comments to EPA that are being submitted into the record with this testimony 

provide complete documentation of my review of the literature and application of an evidencebased approach for the 24-hour standard. Although the full discussion includes both mortality 

and morbidity studies, I only summarize the mortality findings here. However, the patterns I 

describe are similar in studies of hospitalizations, emergency room visits, and frequency of 

‘‘symptoms’’ that are not severe enough to entail a hospital visit.20 Further, although a majority 

of estimates are statistically significant because the paper focused on the lag period that was 

found to be significant in the simplest, 1-pollutant starting point of the analysis, the single other 

alternative 1-pollutant result found a negative risk estimate, implying no risk at all. 

The above findings represent just one of many ways that the new body of acute 

effects evidence has been found to vary depending on the particular method of estimation. Other sources of variation in the evidence include the methods for accounting for time and weather considerations. The new studies have demonstrated that 

concerns with variability of epidemiological estimates of risk, which were expressed 

but not well explored in 1997, are real. Table 1 at the beginning of my testimony 

shows that even the ‘‘best’’ PM2.5 health effects studies that EPA could select for 

its risk analysis present a highly uncertain picture of whether PM2.5 is playing a 

causal role for acute effects. Even if there is a causal relationship, which is what 

the current standard assumed when EPA set it in 1997, there appears to be great 

difficulty in determining what the size of the effect is. The one trend that is clear 

is that the size of the PM2.5 acute mortality estimates found in the many new studies since 1997 are generally lower than the estimates that were available when the 

current standards were set. 

As I have already noted, EPA has chosen to use an evidence-based approach to 

set the 24-hour standard. EPA has proposed to tighten the 24-hour standard from 

the current level of 65 m3 to 35 m3. This decision was made even though the quantitative risk estimates based on these studies are lower and statistically weaker 

than they were when the standard was set. Nevertheless, it is true that there are 

many more studies available now than at the time of the standard, and it is relevant to ask if this new body of evidence might provide a better indication of a 98th 

percentile PM2.5 level where observed effects start to drop off. EPA has attempted 

to make such a case for a cut-off point of 35 m3 in the Proposed Rule.18 I have gone 

through that case very carefully, and I have found it incomplete. I will state what 

I found in general terms here.19

EPA’s verbal summary of its evidence-based approach used a selected subset of 

ten PM2.5 mortality studies. I found another eight such acute studies of United 

States or Canadian mortality cited in the Criteria Document, that used actual meas-
79 

20Furthery, although a majority of estimates are statistically significant because the paper 

focused on the lag period that was found to be significant in the simplest, 1-pollutant starting 

point of the analysis, the single other alternative 1-pollutant result found a negative risk estimate, implying no risk at all. 

urements of PM2.5, and that did not appear to have any unreanalyzed statistical 

problems associated with the GAM software. (If a single paper reports results for 

more than one city, I treat each city as a separate ‘‘study’’.) Six of the eighteen studies that I considered are the original ‘‘Six Cities’’ used to set the current standard. 

All of the others are studies published between 1997 and the cut-off time for consideration in this review cycle. 

I read each study, and determined whether all the PM2.5 estimates reported in 

a study were ‘‘more often insignificant than significant’’, ‘‘a near 50-50 mix’’, or 

‘‘more often significant than insignificant.’’ After categorizing them in this way, I 

found that there is no clear pattern where statistically significant results tend to 

be found for studies with higher PM2.5 levels, and that increasingly mixed evidence 

is found in studies with progressively lower PM2.5 levels. Figure 3 graphically summarizes my findings for the mortality studies. It shows that many of the data sets 

with the highest 24-hour average PM2.5 levels demonstrate the least likelihood of 

a statistically-significant association with mortality. This is contrary to what EPA 

states in its discussion of the evidence-based approach in the Proposed Rule. I attribute the difference to the fact EPA considered only a selected set of the new studies, and not the more complete set that I identified. (The ten studies EPA considered 

are shown as blue diamonds in Figure 3, while the additional eight studies that I 

also considered are shown as red diamonds in Figure 3.) 

Figure 3 also shows that I determined that only 3 of the 18 studies found statistically significant PM2.5 effects for a majority of the methods of estimation that they 

reported. Of these: 

• One is for eight Canadian cities combined by Goldberg and Burnett (2003), 

which I described earlier in this testimony. Its 98th percentile value is about 39 m3, 

but this value has the same flaw that I described for its annual average—the actual 

peak exposures faced by people in the eight separate cities ranged from 27 to 48 

m3, and there is no information to indicate which of the various city-specific 98th 

percentiles might be accounting for the effects estimated when all cities are combined. 

• Another of these was Fairley (2003) for Santa Clara County, CA, with a 98th 

percentile value of 59 m3, which I also discussed above. This study had very high 

exposures at first, and we have no idea whether the statistical significance is related 

to the earlier high levels, or equally attributable to later, lower PM2.5 peaks.20

• The third is the Boston data from the Harvard Six Cities study that served as 

the basis for the current PM2.5 NAAQS in 1997. The magnitude and statistical significance of the association observed in this data set has been reduced in reanalyses 

since 1997, and none of these estimates include consideration of the potential role 

of any gaseous pollutants in explaining these associations. 
80 

In conclusion, the evidence regarding a causal relationship between short-term exposures to PM2.5 and health has not strengthened since 1997. To draw this conclusion, one must consider more than just the number of new studies that have reported at least one statistically significant association; one must also explore the extent to which the effects reported in these studies remain statistically significant 

under a range of different plausible methods for making such estimates. In particular, the new evidence strongly suggests that many or most of these associations 

may actually be attributable to a gaseous pollutant, not PM2.5. 

But even setting aside the weaknesses in the statistical evidence, EPA’s evidencebased approach for where to set a 24-hour standard for PM2.5 leads us right back 

to the very data set on which the current PM2.5 NAAQS were based in the Boston 

‘‘Six Cities’’ data set. Thus, the evidence-based approach that EPA is trying to apply 

provides little additional insight beyond the simple point that I started my testimony with: the quantitative estimates of risks remaining at the current standards 

are lower now than when they were determined to offer an ‘‘adequate margin of 

safety.’’ They therefore do not support a tightening of the current NAAQS. 

INTEGRATED ANALYSES OF ALTERNATIVE RESULTS MAY HELP INFORM

NAAQS DECISIONS BETTER

It is easy to feel lost regarding how to effectively interpret a plethora of alternative studies, and of alternative risk estimates within each study. EPA’s method 

in performing risk analyses has been to rely on a single estimate that it selects from 

the large pool of alternatives, and to base its summaries of quantitative risk esti-
81 

21For documentation of these calculations, see Smith (2003). 

mates on that single estimate. In many of these summaries, even the statistical errors associated with that one estimate are often not reported. Some, but not all, of 

the remaining alternative estimates are studied through ‘‘sensitivity analyses.’’ 

However, these are usually relegated to the back pages of a technical support document. The result of this approach is that the degree of certainty about the risk estimates becomes greatly overstated by the time summary results reach the eyes of 

decision makers, advisors, and the public. Further, the method of selecting the single risk estimate to rely on for the primary analysis can lead to a substantial bias 

in the quantitative risk estimates reported. 

There are alternative methods for performing risk assessments that integrate 

multiple alternative risk estimates, and even key uncertainties that remain purely 

judgmental. These methods are sometimes called probabilistic analysis, or integrated uncertainty analysis. EPA has not used such methods in the documents supporting the Administrator’s decision on the PM2.5 NAAQS, such as the Staff Paper. 

I believe that such methods could be very useful, and would reveal better the true 

extent of uncertainty that I have tried to characterize qualitatively in my testimony 

above. 

In 2003, at an early stage of the drafting of the current risk assessment, I prepared some illustrative examples of an integrated uncertainty analysis to show how 

the reams and reams of sensitivity results in the risk assessment document could 

be condensed to more decision-relevant information. The results of that illustrative 

analysis remain of some interest: 

• Using just the alternative long-term exposure studies in the Criteria Document, 

I found that there could be about a 40 percent probability that there would be no 

long-term mortality benefit from tightening the current NAAQS. I also estimated 

that the probability that actual longterm mortality would be less than the primary 

risk estimate that EPA reports in its risk analysis is about 75 percent. 

• I did a less thorough example for the short-term mortality risk, based only on 

Los Angeles. (Short-term risk estimates and their uncertainty vary by city). For Los 

Angeles, I estimated a 42 percent probability there would be no benefits from tightening the standard from the current level when using only the risk estimates that 

EPA had itself cited in its risk analysis, and a 64 percent probability that acute risk 

reductions would be lower than EPA’s primary risk estimate.21

These probability estimates were based solely on actual estimates in the new body 

of literature on PM2.5 mortality, and do not include any external judgments such 

as whether any of these estimates can be interpreted as causal, whether some particles are more toxic than others, or the hypothetical presence of a threshold. (Consideration of these issues would raise the probabilities that I calculated.) They are 

strictly based in the published evidence reviewed in the Criteria Document. They 

are thus indicative of the degree of uncertainty that the published studies themselves reveal. 

I believe that the process of decision making leading up to the point where a new 

rule is proposed would benefit greatly if such a synthesis of statistical and modeling 

uncertainties were to be developed as a part of that process. Controversies would 

remain regarding the judgments that are necessary for such estimates, but if they 

are conducted in an open manner, with ample opportunity for public review and 

comment, more insight about the overall implications of the body of scientific evidence would be created before a decision must be made than we have at the present 

moment. I emphasize that this should be done during the NAAQS review cycle, with 

opportunities for public review and comment, before a rule is proposed. 

RESPONSES BY ANNE SMITH TO ADDITIONAL QUESTIONS FROM

SENATOR VOINOVICH

Question 1. As you stated in your statement, EPA, Dr. Thurston, and others seem 

to be ignoring your argument that the acceptable level of risk identified in 1997 has 

gone down. This is a very intuitive and convincing argument. If risk has gone down, 

then the standard should not be revised. I would like to give you more time to explain this argument and respond to the other side. 

Response. The current standards for PM2.5 were set by EPA in 1997 with full 

knowledge that these standards would not reduce health risks to zero. The risk 

analysis produced by EPA at that time reported positive estimates of risk remaining 

at the current standard. EPA’s risk analysis also explicitly estimated lower levels 

of risk for alternative, tighter standards than the standard that EPA ultimately se-
82 

1 United States Court of Appeals for the District Of Columbia Circuit in American Trucking 

Associations, Inc., et al., v. Environmental Protection Agency, No. 97-1440, March 26, 2001. 2 Ibid, p. 10. 

3 Although my risk comparisons are based on material that EPA placed into the record during 

both the 1997 and current rulemakings, CASAC could not be expected to have easily made such 

comparisons on their own. For one, the relevant measures of risk are not readily observed given 

the formats in which EPA has presented its risk findings. Further, they require one to consult 

risk analysis documents from 10 years ago. 4PR, p. 2640. 

5 EPW Committee Hearing transcript, July 19, 2006. 

lected. EPA had to defend the risk level that it adopted in court. The DC Circuit 

Court of Appeals ruled that the risks associated with the current PM2.5 standards 

were ‘‘requisite’’ to protect the public health with an adequate margin of safety, as 

required by the Clean Air Act.1 ( ‘‘Requisite′′ means that the standards are ‘‘not 

lower or higher than is necessary’’ to protect public health with an adequate margin 

of safety.2) Thus, the level of risk estimated in 1997 for the current standards was 

associated with an adequate margin of safety. 

As I wrote in my statement: ‘‘In thinking about whether to tighten either the annual or daily standard, one might ask, what has changed in our knowledge since 

1997 that would undermine the Administrator’s 1997 judgment that the current 

PM2.5 NAAQS are neither more nor less stringent than necessary to protect the public health with an adequate margin of safety? A thorough review of the new evidence suggests that the margin of safety that the Administrator selected in 1997 

is likely to be larger than was thought at the time.′′ 

As I documented in my written testimony to the Committee, EPA’s own estimates 

of health risks remaining at the current standards are lower now than the earlier 

1997 estimates. They are lower in all cities for long-term exposure risks, and they 

are lower for short-term exposure risks in 6 of the 8 cities that are in the current 

risk analysis. 

I presented my comparison of risk estimates from 1997 to those estimated today 

in person to EPA air office staff on several occasions, and never heard any disagreement regarding its factual accuracy. I have never heard secondhand of EPA staff 

disagreeing with these facts in any subsequent meetings or conversations where I 

was not present. I also submitted detailed documentation of the risk comparisons 

in my written comments to EPA on the draft risk analysis documents and staff 

paper for PM2.5. However, EPA did not provide any such comparative analysis to 

its Clean Air Scientific Advisory Committee (CASAC) during the course of CASAC’s 

deliberations leading up to CASAC’s recommendation to EPA for tightening the 

PM2.5 standards. Thus, CASAC members were probably unaware of these facts 

when they made their recommendation.3

EPA is clearly aware of these facts, however, and even partially acknowledged 

them at the time that it published the Federal Register notice for the proposed new 

PM2.5 standards: 

With respect to short-term exposure mortality and morbidity . . . [c]omparing the 

risk estimates for the only two specific locations that were included in both the prior 

and current assessments, the magnitude of the estimates associated with just meeting the current annual standard, in terms of percentage of total incidence, is similar 

in one of the locations (Philadelphia) and the current estimate is lower in the other 

location (Los Angeles). . . . With respect to long-term exposure mortality risk estimates, the estimates in terms of percentage of total incidence are very similar for 

the two specific locations included in both the prior and current assessments.4

This quote is only a partial acknowledgment of the risk comparison, however, because it only mentions two cities’ risk estimates, and for those two cities, one risk 

estimate rose and the other fell. However, there were actually 8 cities in the current 

risk analysis, and the risk estimate has fallen in 6 of those 8. Further, the statement that risk estimates are ‘‘similar’’ for long-term exposure does not reveal that 

the current risk estimate is actually lower. Notably, this statement was made only 

after EPA had finalized the Staff Paper, and after CASAC had made its recommendations. 

Dr. Thurston, in his testimony before the committee, attempted to rebut my argument in the following way: 

You know, I think that unfortunately what Dr. Smith has done here is exactly 

what she accuses EPA of having done. She has cherry- picked certain results that 

support her position and unfortunately hasn’t looked in a balanced unbiased way 

at this question.5

This is a completely false statement, as anyone should be able to tell from the 

record of the hearing: my comparison is based only on EPA’s own numbers. All that 
83 

6 Ibid, emphasis added. 

7Statement of Dr. George D. Thurston, Sc. D. to the Committee on Environment and Public 

Works of the United States Senate RE: the Science and Risk Assessment of Particulate Matter 

(PM) Air Pollution Health Effects, July 19, 2006. 

I have done is assemble the information from EPA documents and repeat it in a 

format that allows a direct comparison. I made this clear in my own oral statement: 

Risks due to long-term mortality have fallen in every location. The risks due to 

daily exposure, which vary by city, have fallen in six of the eight cities that are in 

EPA’s risk analysis. This new information suggests that the margin of safety provided by the current standards is actually greater than we originally thought. What 

I have told you so far is based entirely on EPA’s own point estimates of risk.6

Dr. Thurston’s comment is an attempt to sidestep the inconvenient truth that 

even EPA’s analyses support the conclusion that the estimates of mortality risk associated with the current ambient PM2.5 standard have fallen since the time that 

they were deemed acceptable by EPA and the Court. His sidestepping tactic may 

be useful in a purely oral exchange, but the transcript makes it clear that his comment has no substance or merit in refuting my argument. 

I did go on to describe how the evidence on lower risk estimates is even stronger 

when one looks at the full body of evidence in the studies that have been released 

since 1997, rather than just using EPA’s own numbers. However, it is illogical to 

claim that I have ‘‘cherry-picked’’ the evidence when I show that the downward risk 

trends would be more pronounced if I use almost any other risk estimate than those 

used by EPA. This is the opposite of cherry-picking. 

I would also like to directly address Dr. Thurston’s own argument that there is 

new evidence to support tightening the annual standard. The essence of his argument is that further analyses of the American Cancer Society study find that there 

is no evidence of a threshold in the long-term exposure risk data below the level 

of the current annual standard. He presents a figure (Figure 3 in his written testimony), that indicates that the risks from PM2.5 exposure extend below 15 m3, supporting a reduction in the annual PM2.5 standard at this time.7 While it is true that 

this specific figure had not been produced at the time that the current annual 

standard was established, it does not provide a case for tightening the standard to 

a level below 15 m3. Dr. Thurston’s implicit premise is that the PM2.5 standard 

should be a zero-risk standard, which was not and still is not the premise of EPA 

(and upheld by the Court). Moreover, EPA assumed that a causal relationship between PM2.5 and long-term mortality risk did exist down to 9 m3

in its risk analyses when it chose to set the annual standard at 15 m3. Thus, the 

‘‘new’’ information that Dr. Thurston says supports reducing the standard to a lower 

level was already assumed to exist in the 1997 risk analyses. 

Question 2. Your testimony indicates that EPA has selectively used study results 

in developing the proposal. EPA emphasized studies that show associations between 

particulates and negative health effects and ignored those that do not. You also 

point out that in many of the studies relied upon, the associations become statistically insignificant when another pollutant is included in the analysis. Please elaborate. 

Response. Each of the epidemiological studies of PM2.5 risk contains many different alternative estimates of risk. Different estimates of risk are possible because 

the researchers have to specify what set of risk factors in addition to PM2.5 will be 

simultaneously accounted for when estimating the quantitative amount of risk that 

is associated with PM2.5. For example, one can estimate a PM2.5 risk level with or 

without also including the humidity level. PM2.5 concentrations may tend to be higher on days of higher humidity, yet humidity is known to be a physiological stressor 

and there is an established increased risk of a sick individual dying on the relatively 

more humid days of a year. If humidity is left out of the analysis, then PM2.5 could 

serve as a ‘‘proxy’’ for the missing humidity information, and this could bias the 

level of risk estimated for PM2.5 upwards. All of the current studies take care to 

address humidity, because its role as a stressor is so well established. However, 

there is no objective method for determining exactly how to specify humidity. Further, there are many alternative ways to specify a wide range of other factors that 

also need to be accounted for to avoid bias in the PM2.5 effect, and not all of the 

relevant health stressors are known. Thus, researchers tend to try different methods 

for incorporating non-PM2.5 determinants of health, and each different method results in a different PM2.5 risk estimate. 

Sometimes two seemingly comparable methods produce dramatically different results. For example, the study of PM2.5 risk in Santa Clara County, CA by Fairley 

(2003) reports results of two estimates that differ in one single way: in one case, 
84 

8Fairley, D. (2003) Mortality and Air Pollution for Santa Clara County, CA, 1989-1996 Revised Analyses of Time-series Studies of Air Pollution and Health, Special Report. Boston, MA: 

Health Effects Institute; pp. 97-106. 9Moolgavkar, S. H. (2003) ′′Air Pollution and Daily Deaths and Hospital Admissions in Los 

Angeles and Cook Counties′′ Revised Analyses of Time-series Studies of Air Pollution and 

Health, Special Report Boston, MA: Health Effects Institute; pp. 183-198. 10Lipfert, F. W.; Morris, S. C.; Wyzga, R. E. (2000a) Daily Mortality in the Philadelphia Metropolitan Area and Size-classified Particulate Matter Journal of the Air & Waste Management 

Association 15011513. 11 Chock, D. P.; Winkler, S.; Chen, C. (2000) A Study of the Association Between Daily Mortality and Ambient Air Pollutant Concentrations in Pittsburgh, Pennsylvania Journal of the Air 

& Waste Management Association 50: 1481-1500. 12 Ito, K. (2003) Associations of Particulate Matter Components with Daily Mortality and Morbidity in Detroit, Michigan. Revised Analyses of Time-series Studies of Air Pollution and Health. 

Special report. Boston, MA: Health Effects Institute; pp. 143-156. 13The paper EPA relies on is: Mar, T. F.; Norris, G. A.; Larson, T. V.; Wilson, W. E.; Koenig, 

J. Q. (2003) ’’Air Pollution and Cardiovascular Mortality in Phoenix, 1995-1997’’ Revised Analyses of Time-series Studies of Air Pollution and Health, Special Report Boston, MA: Health Effects Institute; pp. 177-182. 

mortality risk one a particular day was compared to PM2.5 levels on the same day, 

and in the second, mortality risk on each day was compared to PM2.5 levels that 

occurred the day before.8 The first of these finds a positive and statistically significant association between rises in PM2.5 and mortality risk. The second finds the opposite: a negative association (i.e., mortality risk tended to be lower if PM2.5 on the 

day before had been relatively high). There is no objective statistical means for determining whether one of these statistical findings is closer to the truth than the 

other, but they produce extremely different estimates of health risk from ambient 

PM2.5. In this case, EPA has selected the positive and statistically significant result 

for use in its risk analysis, and EPA makes no mention of the opposite alternative 

result that it could have selected from the same paper. 

One important class of researcher judgments where very different risk estimates 

can result is that related to ‘‘single-pollutant’’ versus ‘‘multi-pollutant’’ estimation 

methods. Most commonly, the only pollutant that is included in the statistical estimation procedure is PM2.5 (at least, in studies that report PM2.5 risk estimates). If 

any other pollutant has an association with mortality risks, then PM2.5 will be the 

only pollutant that could adopt its explanatory power and it will do so if PM2.5 is 

statistically correlated with the missing pollutant. As a result, the PM2.5 risk estimate will be biased, and may appear falsely to be statistically significant. In a 

multi-pollutant statistical estimation procedure, PM2.5 and one or more other pollutants are all included in the analysis at the same time. Then, each can account for 

its own role as a health stressor, and the resulting estimates for each pollutant, including PM2.5, are less likely to be biased. 

I attempted to identify all of the PM2.5 health effects studies cited in the Criteria 

Document (including both mortality and morbidity effects studies) that had reported 

results of any estimates for PM2.5 using a multi-pollutant method of estimation for 

at least one gaseous pollutant. I found ten such papers among all the new studies 

that did report a statistically significant association for PM2.5. Of these 10, 8 found 

that PM2.5 lost its ability to explain mortality risk when studied using a 2-pollutant 

method. (In the other two studies, both the PM2.5 and gaseous pollutant retained 

statistical explanatory power.) This suggests a reasonable concern that PM2.5 may 

not be the pollutant that is actually causing the reported health risks. However, 

EPA’s risk analysis is relying solely on the one-pollutant results from each of these 

papers, and thus is overstating the degree of confidence in these results. Notably, 

2 of the 8 cities in EPA’s risk analysis are being estimated using single-pollutant 

estimates from papers that also reported that PM2.5 risk estimates are not statistically significant if estimated in a two-pollutant model: Los Angeles and Philadelphia.9, 10 In both cases, the authors concluded that a different pollutant had more 

explanatory power than PM2.5, yet EPA has used only the obviously biased estimate 

of PM2.5 risk that came from the single-pollutant methods that the original researchers have repudiated. (Even with use of the one-pollutant estimate, EPA’s mortality risk estimate for Los Angeles is not statistically significant.) 

In my response so far, I have explained how EPA has been selective in the way 

it has made risk estimates for 3 of the 8 cities in its mortality risk assessment (i.e., 

for Santa Clara County/San Jose, Philadelphia, and Los Angeles). Problems with the 

remaining 5 cities risk estimates also deserve mention: 

• For both Pittsburgh and Detroit, the risk estimate that EPA uses is not statistically significant.11, 12

• For Phoenix, there are 2 other papers by other authors that use the same PM2.5

data set.13 One of the other papers finds no PM2.5 association at all (but does find 
85 

14 Clyde, M. A.; Guttorp, P.; Sullivan, E. (2000) ’’Effects of Ambient Fine and Coarse Particles 

on Mortality in Phoenix, Arizona’’ Seattle, WA: University of Washington, National Research 

Center for Statistics and the Environment; NRCSE technical report series, NRCSE-TRS no. 040. 15Smith, R. L.; Spitzner, D.; Kim, Y.; Fuentes, M. (2000) ’’Threshold Dependence of Mortality 

Effects for Fine and Coarse Particles in Phoenix, Arizona’’ Journal of the Air & Waste Management Association 50: 1367-1379. 16Klemm, R. J.; Mason, R. (2003) ‘‘Replication of Reanalysis of Harvard Six-City Mortality 

Study.’’ Revised Analyses of Time-series Studies of Air Pollution and Health. Special report. Boston, MA: Health Effects Institute; pp. 165-172. 17Schwartz, J. (2003) ‘‘Daily Deaths Associated with Air Pollution in Six US Cities and Shortterm Mortality Displacement in Boston’’ Revised Analyses of Time-series Studies of Air Pollution 

and Health. Special report. Boston, MA: Health Effects Institute; pp. 219-226. 18 Burnett, R. T.; Goldberg, M. S. (2003) ‘‘Size-fractionated Particulate Mass and Daily Mortality in Eight Canadian Cities.’’ Revised Analyses of Time-series Studies of Air Pollution and 

Health. Special report. Boston, MA: Health Effects Institute; pp. 85-90. 19The other multi-city PM.5 mortality studies (based on the Six Cities data set) report effects 

by individual city as well as for the combined set. This was the data on which EPA set the current standards, and in doing so, EPA used annual averages for only the individual cities that 

did have significant effects within the set of six. The lowest such city was Boston, with an annual average of 15.6 um3, which was the basis for the current annual average standard of 15 

m3. 

20 Burnett, R. T.; Brook, J.; Dann, T.; Delocla, C.; Philips, O.; Cakmak, S.; Vincent, R.; Goldberg, M. S.; Krewski, D. (2000) ’’Association Between Particulate- and Gas-phase Components 

of Urban Air Pollution and Daily Mortality in Eight Canadian Cities’’ In: Grant, L. D., ed. 

PM2000: Particulate Matter and Health. Inhalation Toxicology 12(suppl. 4): 15-39. 

a coarse fraction association).14 The third paper reports a PM2.5 association only 

above a threshold. EPA’s risk assessment does not include such a threshold.15

• Risk estimates for both St. Louis and Boston are based on single-pollutant 

methods because the researchers do not report any multi-pollutant methods at 

all.16, 17 However, for both cities, the authors do report a number of different PM2.5

risk estimates using different ways of accounting for non-pollutant variables that 

also account for changes in mortality risk and EPA has adopted the estimate for 

each city that produces the highest level of PM2.5 risk. Several of the alternative 

estimates are also not statistically significant (particularly for St. Louis). There is 

no reason to expect those higher risk estimates to be more valid than the alternative 

estimates reported by the researchers. In summary, there is a substantial amount 

of uncertainty associated with risk estimates for all eight of the cities in EPA’s current risk assessment. The way EPA has selected a single risk estimate out of the 

many estimates provided in the original epidemiological studies for each city has a 

clear tendency to overstate the level of PM2.5 mortality risk and to understate the 

uncertainties. 

Question 3. Please summarize the concerns that you have with the three studies 

that CASAC relied on in recommending a tightened annual standard. 

Response. CASAC notes that there are three new acute studies that find PM2.5

associations with mortality at annual averages below the current annual standard 

(all with reported annual averages in the range of 13 to 14 g/m3). Most importantly, 

there are logical flaws in setting an annual standard based on studies of daily mortality risk. Acute risks are associated with increases in PM2.5 on certain days and 

there is no logical link between the the annual average conditions at a given location and the riskiness of spikes in PM2.5 at that location. 

However, even if one were to want to set an annual standard based on short-term 

exposure risk studies, each of these papers presents reasons to be concerned about 

the prospect of using them as the basis for a national standard: 

Goldberg and Burnett (2003).18 This study reports a PM2.5 association for eight 

Canadian cities combined. The annual average of 13.3 m3 is an average over all of 

the eight cities, while the annual averages in the individual cities vary from 9.5 m3

to 17.7 m3. There are no city-specific results reported to help indicate whether the 

estimate of an acute effect is due to effects in each of the eight cities, or only in 

a few.19 Evidence in the paper suggests that there may in fact be different effects 

in each city. 

Another concern with this study is that it is a reanalysis of a more comprehensive 

study that included consideration of the role of gaseous pollutants as well.20 The 

original study concluded that the gaseous pollutants had a much greater ability to 

explain mortality risks than both PM2.5 and PM10-2.5 combined. However, when the 

paper had to be reanalyzed, the authors did not reanalyze the portions that considered gaseous pollutants in conjunction with particulate pollution, and so this finding 

is no longer discussed. 
86 

21Fairley, op. cit. 22To know this, one must go back and read the original study that Fairley (2003) reanalyzes: 

Fairley, D. (1999) Daily Mortality and Air Pollution in Santa Clara County, CA: 1989-1996? Environmental Health Perspectives 107: 637-641. 23Mar et al., op. cit. 24 Clyde et al., op. cit. 25Smith et al., op. cit. 

• Fairley (2003).21This study used data from Santa Clara County, CA, over a 

seven year period, and during that time pollution levels were falling dramatically. 

Although the annual average PM2.5 that is attributed to this study is 13.6 m3, the 

annual average was as high as 18.4 m3 at the start, and fell progressively to 9.5 m3 by the end of the 7 years studied.22 Peak levels of PM2.5 were also falling, starting at a 98th percentile of 88 m3 for the first year and ending at 25 m3. Such a 

wide range of PM2.5 levels within this one city’s data set begs the question: Are the 

reported acute effects relationship driven largely by the high levels in the early 

years, or are they also evident in the later years? This highly relevant question is 

never mentioned, let alone analyzed, by the authors. Lacking any exploration of 

such an obviously relevant issue, it would seem a dubious proposition to use the annual average over the entire time period in this one study as the basis for a national 

ambient standard. 

Another concern with this study is that it reports PM2.5 risk estimates for two alternative methods of estimation, both of which are reasonable. One method considers whether deaths tend to fluctuate with the same day’s PM2.5 levels and the 

other method considers whether deaths tend to fluctuate with the previous day’s 

PM2.5 levels. The same-day estimate finds the positive association that this study 

is known for, but the estimate based on PM2.5 on just the previous day is actually 

in the negative direction. Complete reversal of evidence of a PM2.5 mortality effect 

by considering PM2.5 levels only 24 hours apart in time presents a concern for interpreting the study’s same-day estimate as a causal one. However, there is no discussion of what these conflicting results might mean. • Mar et al. (2003).23 This study considered acute risks in Phoenix, AZ, with annual average PM2.5 levels of 13.5 m3. There are ten estimates of PM2.5 risk in the 

paper, and only three of them are significant. More importantly, this is not the only 

paper that studied the ability of this same set of PM.5 data to explain acute mortality risks in Phoenix. One of the other studies found that PM2.5 did not have any 

explanatory power, and found instead that the coarse fraction of PM had explanatory power.24 The third study found evidence that there is a threshold below which 

PM2.5’s apparent ability to explain changes in daily mortality disappeared.25 That 

threshold appeared to be above 20 m3. If there is a threshold, then the rationale 

for a linkage between annual average PM2.5 and acute risks simply falls apart. 

A final concern with all three of the Phoenix studies is that none of them considered whether the PM2.5 effect would remain if pollutants such as CO, SO2, ozone, 

or NO2 were also included in the analysis. This is a critical gap in many of the current studies because the new body of papers on PM2.5 health effects reveals that 

PM2.5 effects usually disappear when one of the gaseous pollutants is explored. (My 

response to Question 2 above addresses this point in more detail.) 

STATEMENT OF JOHN STEPHENSON, DIRECTOR, NATURAL RESOURCES AND

ENVIRONMENT, U.S. GENERAL ACCOUNTABILITY OFFICE

Mr. Chairman and members of the committee, I am pleased to be here today as 

the committee considers the science and risk assessment supporting the Environmental Protection Agency’s (EPA) proposed revisions to the national air quality 

standards for particulate matter. A large body of scientific evidence links exposure 

to particulate matter a ubiquitous form of air pollution commonly referred to as soot 

to serious health problems, including asthma, chronic bronchitis, heart attack, and 

premature death. Under the Clean Air Act, EPA periodically reviews the appropriate air quality level at which to set national standards to protect the public 

against the health effects of particulate matter. As you are aware, EPA proposed 

revisions to the particulate matter standards in January 2006 and issued a draft 

regulatory impact analysis of the revisions expected costs and benefits. 

EPA’s estimates of the expected benefits from its air pollution regulations have 

often been controversial, and the methods the agency has used to prepare these estimates have been questioned. In 2000, at the direction of the Senate Appropriations 

Committee, EPA asked the National Academies (Academies) to evaluate EPA’s overall methodology for estimating the health benefits of proposed air regulations. In 

2002, the Academies issued a report that made recommendations focusing on con 
87 

1See GAO, Particulate Matter: EPA Has Started to Address the National Academies Recommendations on EstimatingHealth Benefits, but MoreProgress Is Needed, GAO-06-780 (Washington, DC: July 14, 2006). 

ducting more rigorous assessments of uncertainty, increasing the transparency of 

how EPA estimates benefits, conducting more detailed analyses of exposure, and estimating the benefits of each regulatory option under consideration. My testimony 

summarizes the highlights of our report being released today on the extent to which 

EPA applied the recommendations made by the Academies to its January 2006 proposed revisions to the particulate matter standards.1 Our report provides a more detailed discussion of each recommendation, including whether and how EPA applied 

it to the regulatory impact analysis on particulate matter. 

SUMMARY

While the National Academies report generally supported EPA’s overall approach 

to estimating benefits, it included 34 recommendations for improvements. EPA has 

begun to change the way it conducts and presents its analyses of health benefits 

in response to the National Academies? recommendations. In the case of the January 2006 proposed rule on particulate matter standards, EPA applied, at least in 

part, about two-thirds of the recommendations to its particulate matter health benefit analysis; it applied 8 and partially applied 14 more. For example, in applying 

the recommendations, EPA evaluated how benefits might change given alternative 

assumptions and discussed sources of uncertainty not included in the benefit estimates. In addition, EPA applied an alternative technique for evaluating one important source of uncertainty in its analysis the uncertainty underlying the causal link 

between exposure to particulate matter and premature death. Consistent with the 

National Academies recommendation to assess uncertainty by developing ranges of 

estimates of benefits and specifying the likelihood of attaining those levels of benefits, EPA systematically gathered expert opinions about this link and developed 

ranges reflecting the experts confidence in attaining reductions in premature death 

expected from the proposed revisions. However, the health benefit analysis did not 

assess how the benefit estimates would vary in light of other key uncertainties as 

the Academies recommended. Consequently, EPA’s response represents a partial application of the recommendation. Agency officials told us that ongoing research and 

development efforts will allow EPA to gradually make more progress in applying 

this and other recommendations to future analyses. 

EPA did not apply the remaining 12 recommendations to the analysis, such as 

the recommendation to evaluate the impact of using the assumption that the components of particulate matter are equally toxic. EPA officials viewed most of these 12 

recommendations as relevant to its health benefit analyses but noted that the agency was not ready to apply specific recommendations because of, among other things, 

the need to overcome technical challenges stemming from limitations in the state 

of available science. For example, EPA did not believe that the state of scientific 

knowledge on the relative toxicity of particulate matter components was sufficiently 

developed to include it in the January 2006 regulatory impact analysis, but the 

agency is sponsoring research on this issue. 

BACKGROUND

EPA is required by the Clean Air Act to conduct reviews of the National Ambient 

Air Quality Standards (NAAQS) for the six criteria pollutants, including particulate 

matter, every 5 years to determine whether the current standards are sufficient to 

protect public health, with an adequate margin of safety. If EPA decides to revise 

the NAAQS, the agency proposes changes to the standards and estimates the costs 

and benefits expected from the revisions in an assessment called a regulatory impact analysis. In January 2006, EPA prepared a regulatory impact analysis for one 

such rule?particulate matter that presented limited estimates of the costs and benefits expected to result from the proposed particulate matter rule. EPA developed the 

estimates by, for example, quantifying the changes in the number of deaths and illnesses in five urban areas that are likely to result from the proposed rule. 

The National Academies’ 2002 report examined how EPA estimates the health 

benefits of its proposed air regulations and emphasized the need for EPA to account 

for uncertainties and maintain transparency in the course of conducting benefit 

analyses. Identifying and accounting for uncertainties in these analyses can help decision makers evaluate the likelihood that certain regulatory decisions will achieve 

the estimated benefits. Transparency is important because it enables the public and 

relevant decision makers to see clearly how EPA arrived at its estimates and conclusions. Many of the recommendations include qualifying language indicating that it 
88 

2Monte Carlo simulation refers to a computer-based analysis that uses probability distributions for key variables, selects random values from each of the distributions simultaneously, and 

repeats the random selection over and over. Rather than presenting a single outcome such as 

the mostly likely or average scenario Monte Carlo simulations produce a distribution of outcomes that reflect the probability distributions of modeled uncertain variables. 3 Recent EPA analyses used the natural background concentrations of particulate matter, 

rather than zero, for its assumption of no threshold level. The National Academies supported 

the assumption of no threshold level, but it recommended that EPA conduct a consistent and 

transparent sensitivity analysis to consider various threshold levels. 

is reasonable to expect that they can be applied in stages, over time; moreover, a 

number of the recommendations are interrelated and, in some cases, overlapping. 

Soon after the National Academies issued its report, EPA roughly approximated the 

time and resource requirements to respond to the recommendations, identifying 

those the agency could address within 2 or 3 years and those that would take 

longer. According to EPA officials, the agency focused primarily on the numerous 

recommendations related to analyzing uncertainty. As is discussed below, EPA applied some of these recommendations to the particulate matter analysis. 

EPA Applied Some, but Not All, of the National Academies Recommendations to 

the Particulate Matter Regulatory Impact Analysis 

EPA applied either wholly or in part approximately two-thirds of the Academies 

recommendations in preparing its January 2006 particulate matter regulatory impact analysis and continues to address the recommendations through ongoing research and development. According to EPA, the agency intends to address some of 

the remaining recommendations in the final rule and has undertaken research and 

development to address others. 

Recommendations EPA Applied or Partially Applied to Its Particulate Matter Health 

Benefit Analysis 

The January 2006 regulatory impact analysis on particulate matter represents a 

snapshot of an ongoing EPA effort to respond to the National Academies recommendations on developing estimates of health benefits for air pollution regulations. Specifically, the agency applied, at least in part, approximately two-thirds of 

the recommendations 8 were applied and 14 were partially applied by taking steps 

toward conducting a more rigorous assessment of uncertainty by, for example, evaluating the different assumptions about the link between human exposure to particulate matter and health effects and discussing sources of uncertainty not included in 

the benefit estimates. According to EPA officials, the agency focused much of its 

time and resources on the recommendations related to uncertainty. In particular, 

one overarching recommendation suggests that EPA take steps toward conducting 

a formal, comprehensive uncertainty analysis the systematic application of mathematical techniques, such as Monte Carlo simulation and include the uncertainty 

analysis in the regulatory impact analysis to provide a more realistic depiction of 

the overall uncertainty in EPA’s estimates of the benefits.2

Overall, the uncertainty recommendations call for EPA to determine (1) which 

sources of uncertainties have the greatest effect on benefit estimates and (2) the degree to which the uncertainties affect the estimates by specifying a range of estimates and the likelihood of attaining them. In response, EPA examined a key source 

of uncertainty its assumption about the causal link between exposure to particulate 

matter and premature death and presented a range of expected reductions in death 

rates. EPA based these ranges on expert opinion systematically gathered in a multiphased pilot project. The agency did not, however, incorporate these ranges into its 

benefit estimates as the National Academies had recommended. 

Moreover, the Academies recommended that EPA’s benefit analysis reflect how 

the benefit estimates would vary in light of multiple uncertainties. In addition to 

the uncertainty underlying the causal link between exposure and premature death, 

other key uncertainties can influence the estimates. For example, there is uncertainty about the effects of the age and health status of people exposed to particulate 

matter, the varying composition of particulate matter, and the measurements of actual exposure to particulate matter. EPA’s health benefit analysis, however, does 

not account for these key uncertainties by specifying a range of estimates and the 

likelihood of attaining them. For these reasons, EPA’s responses reflect a partial application of the Academies recommendation. 

In addition, the Academies recommended that EPA both continue to conduct sensitivity analyses on sources of uncertainty and expand these analyses. In the particulate matter regulatory impact analysis, EPA included a new sensitivity analysis regarding assumptions about thresholds, or levels below which those exposed to particulate matter are not at risk of experiencing harmful effects. EPA has assumed 

no threshold level exists that is, any exposure poses potential health risks.3 Some 
89 

4Particulate matter is a highly complex mixture comprising particles emitted directly from 

sources and particles formed through atmospheric chemical reactions. Particles span many sizes 

and shapes and consist of hundreds of different chemicals. EPA identifies the major components 

of fine particulate matter as carbon, sulfate and nitrate compounds, and crustal/metallic materials such as soil and ash. 5 Relative toxicity refers to the premise that different components of particulate matter have 

different levels of potency affecting premature mortality and illness. In the draft particulate 

matter regulatory impact analysis, EPA assumed equivalent toxicity, stating that while it is reasonable to expect that the potency of components may vary across the numerous effect categories associated with particulate matter, EPA’s interpretation of scientific information considered to date is that such information does not yet provide a basis for quantification beyond using 

fine particle mass. EPA, Draft Regulatory Impact Analysis for the PMPM-2.5 National Ambient 

Air Quality Standards (Washington, DC, 2006), 3-21. 6 In the context of the National Academies recommendations, a sensitivity analysis would assess how changes in one or more variables affect the outcome, whereas a comprehensive or formal uncertainty analysis evaluates the probability distributions of multiple variables. 

experts have suggested that different thresholds may exist, and the National Academies recommended that EPA determine how changing its assumption that no 

threshold exists would influence the estimates. The sensitivity analysis EPA provided in the regulatory impact analysis examined how its estimates of expected 

health benefits would change assuming varying thresholds. 

In response to another recommendation by the National Academies, EPA identified some of the sources of uncertainty that are not reflected in its benefit estimates. 

For example, EPA’s regulatory impact analysis disclosed that its benefit estimates 

do not reflect the uncertainty associated with future year projections of particulate 

matter emissions. EPA presented a qualitative description about emissions uncertainty, elaborating on technical reasons such as the limited information about the 

effectiveness of particulate matter control programs why the analysis likely underestimates future emissions levels. 

Recommendations EPA Did Not Apply to the Particulate Matter Analysis 

EPA did not apply the remaining 12 recommendations to the analysis for various 

reasons. Agency officials viewed most of these recommendations as relevant to its 

health benefit analyses and, citing the need for additional research and development, emphasized the Agency’s commitment to continue to respond to the recommendations. EPA has undertaken research and development to respond to some 

of these recommendations but, according to agency officials, did not apply them to 

the analysis because the agency had not made sufficient progress. 

For example, EPA is in the process of responding to a recommendation involving 

the relative toxicity4 of components of particulate matter, an emerging area of research that has the potential to influence EPA’s regulatory decisions in the future.5

Hypothetically, the agency could refine national air quality standards to address the 

potentially varying health consequences associated with different components of 

particulate matter. The National Academies recommended that EPA strengthen its 

benefit analyses by evaluating a range of alternative assumptions regarding relative 

toxicity and incorporate these assumptions into sensitivity or uncertainty analyses 

as more data become available.6 EPA did not believe the state of scientific knowledge on relative toxicity was sufficiently developed at the time it prepared the draft 

regulatory impact analysis to include this kind of analysis. In a separate report 

issued in 2004, the National Academies noted that technical challenges have impeded research progress on relative toxicity but nonetheless identified this issue as 

a priority research topic. The Clean Air Scientific Advisory Committee also noted 

the need for more research and concluded in 2005 that not enough data are available to base the particulate matter standards on composition. The Office of Management and Budget, however, encouraged EPA in 2006 to conduct a sensitivity analysis on relative toxicity and referred the agency to a sensitivity analysis on relative 

toxicity funded by the European Commission. 

We found that EPA is sponsoring research on the relative toxicity of particulate 

matter components. For example, EPA is supporting long-term research on this 

issue through its intramural research program and is also funding research through 

its five Particulate Matter Research Centers and the Health Effects Institute. In addition, an EPA contractor has begun to investigate methods for conducting a formal 

analysis that would consider sources of uncertainty, including relative toxicity. To 

date, the contractor has created a model to assess whether and how much these 

sources of uncertainty may affect benefit estimates in one urban area. Agency officials told us, however, that this work was not sufficiently developed to include in 

the final particulate matter analysis, which it says will present benefits on a national scale. 
90 

7 Because the precise levels of total emissions are not knowable but rather are approximations 

based on a sample of measurements, there is uncertainty about the true quantity of emissions. 8 EPA compiles the National Emissions Inventory, a national database of air emissions data 

that includes estimates of annual emissions, by source, of air pollutants in each area of the 

country on an annual basis. 

Another recommendation that EPA did not apply to the particulate matter analysis focused on assessing the uncertainty of particulate matter emissions. The National Academies recommended that EPA conduct a formal analysis to characterize 

the uncertainty of its emissions estimates, which serve as the basis for its benefit 

estimates.7 While the agency is investigating ways to assess or characterize this uncertainty, EPA did not conduct a formal uncertainty analysis for particulate matter 

emissions for the draft regulatory impact analysis because of data limitations. These 

limitations stem largely from the source of emissions data, the National Emissions 

Inventory,8 an amalgamation of data from a variety of entities, including state and 

local air agencies, tribes, and industry. According to EPA, these entities use different methods to collect data, which have different implications for how to characterize the uncertainty. EPA officials stated that the agency needs much more time 

to address this data limitation and to resolve other technical challenges of such an 

analysis. While the final particulate matter analysis will not include a formal assessment of uncertainty about emissions levels, EPA officials noted that the final 

analysis will demonstrate steps toward this recommendation by presenting emissions data according to the level emitted by the different kinds of sources, such as 

utilities, cars, and trucks. 

Finally, EPA did not apply a recommendation concerning the transparency of its 

benefit estimation process to the particulate matter analysis. Specifically, the National Academies recommended that EPA clearly summarize the key elements of the 

benefit analysis in an executive summary that includes a table that lists and briefly 

describes the regulatory options for which EPA estimated the benefits, the assumptions that had a substantial impact on the benefit estimates, and the health benefits 

evaluated. EPA did not, however, present a summary table as called for by the recommendation or summarize the benefits in the executive summary. EPA stated in 

the regulatory impact analysis that the agency decided not to present the benefit 

estimates in the executive summary because they were too uncertain. Agency officials told us that the agency could not resolve some significant data limitations before issuing the draft regulatory impact analysis in January 2006 but that EPA has 

resolved some of these data challenges. For example, EPA officials said they have 

obtained more robust data on anticipated strategies for reducing emissions, which 

will affect the estimates of benefits. The officials also said that EPA intends to include in the executive summary of the regulatory impact analysis supporting the 

final rule a summary table that describes key analytical information. 

CONCLUDING OBSERVATIONS

While EPA officials said that the final regulatory impact analysis on particulate 

matter will reflect further responsiveness to the Academies recommendations, continued commitment and dedication of resources will be needed if EPA is to fully implement the improvements recommended by the National Academies. In particular, 

the agency will need to ensure that it allocates resources to needed research on 

emerging issues, such as the relative toxicity of particulate matter components, and 

to assessing which sources of uncertainty have the greatest influence on benefit estimates. The uncertainty of the agency’s estimates of health benefits in the draft regulatory impact analysis for particulate matter underscores the importance of uncertainty analysis that can enable decision makers and the public to better evaluate 

the basis for EPA’s air regulations. While EPA officials said they expect to reduce 

the uncertainties associated with the health benefit estimates in the final particulate matter analysis, a robust uncertainty analysis of the remaining uncertainties 

will nonetheless be important for decision makers and the public to understand the 

likelihood of attaining the estimated health benefits. 

Mr. Chairman, this concludes my prepared statement. I would be happy to respond to any questions that you or members of the committee may have. 

RESPONSES BY JOHN STEPHENSON TO ADDITIONAL QUESTIONS

FROM SENATOR VOINOVICH. 

Question 1. Mr. Stephenson, your testimony states ‘‘The National Academies’’ 

2002 report examined how EPA estimates the health benefits of its proposed air regulations and emphasized the need for EPA to account for uncertainties and main-
91 

tain transparency in the course of conducting benefit analyses. I agree that transparency is very important. However, right now, EPA is simply telling us that we 

need to wait until the final rule to see a more complete RIA, how they addressed 

more of these recommendations, and the inclusion of new science. In your opinion, 

has EPA ‘‘maintained transparency’’ through this process with the PM standards? 

Response. EPA has maintained transparency to the extent feasible under federal 

rulemaking procedures, which include collecting and reviewing public comments on 

the proposed rule and submitting the final rule package to the White House Office 

of Management and Budget for review at least 45 days before the EPA Administrator signs the rule. Proposed and final rules can differ substantially for a number 

of reasons, including changes made in response to public comments on the proposed 

rule and the availability of new or more complete data. Therefore, in developing and 

supporting both proposed and final rules, it is important for agencies to be transparent that is, to provide decision makers and the public with clear and relevant 

information about the data, assumptions, methodologies, uncertainties, etc., underlying its regulatory impact analyses. As you are aware, the Congressional Review 

Act of 1996 established an expedited process under which Congress may disapprove 

a broad range of regulatory rules issued by Federal agencies by enacting a joint resolution of disapproval within 60 days after receiving the rule. The rule would not 

go into effect without subsequent statutory authorization. 

To date we have not identified major shortcomings concerning the transparency 

of EPA’s current rulemaking process for particulate matter standards. For example, 

in the January 2006 regulatory impact analysis for proposed rule, EPA highlighted 

the fact that the benefits estimates were based only on five cities and were highly 

uncertain. According to EPA officials, the agency could not resolve data limitations 

in time to meet the court-issued deadline for the proposed changes. As you know, 

EPA plans to provide national estimates of the health benefits in the final rule 

using more robust data that it has subsequently been able to obtain. Thus, the regulatory impact analyses supporting the proposed and final rules are expected to be 

significantly different. EPA can maintain transparency in this rulemaking process 

by clearly discussing in the final regulatory impact analysis due in September 2006 

the changes in its approach to estimating the benefits and the Agency’s rationale 

for doing so and by clearly identifying key data, assumptions, methodologies, and 

uncertainties. 

In terms of transparency and the science supporting the rulemaking efforts, EPA 

made a commitment in the proposed rule to conduct a review and assessment of 

studies published after the completion of the scientific review of health effects 

linked to particulate matter emissions. EPA has recently made information about 

its review of new science available to the public; see EPA, Provisional Assessment 

of Recent Studies on Health Effects of Particulate Matter Exposure (Research Triangle Park, N.C., 2006). The July 2006 provisional assessment presents EPA’s approach to reviewing new studies and summarizes the findings of these studies, including those that evaluated the links between particulate matter components and 

adverse health effects. 

Question 2. Mr. Stephenson, please elaborate on this very important statement 

that you make at the end of your testimony (quote): ′′While EPA officials said they 

expect to reduce the uncertainties associated with the health benefit estimates in 

the final particulate matter analysis, a robust uncertainty analysis of the remaining 

uncertainties will nonetheless be important for decision makers and the public to 

understand the likelihood of attaining the estimated health benefits.’’ 

Response. In estimating potential health benefits stemming from regulatory actions, some level of uncertainty is unavoidable, in part because the scientific information used to develop estimates, such as the inventory of particulate matter emissions, will never be perfect or complete. According to the Academies, high uncertainty does not imply that action to promote or protect public health should be delayed, but rather that a comprehensive and rigorous assessment of uncertainty 

would improve policy decisions. Many of the recommendations of the National Academies to EPA are aimed at the agency developing a more robust uncertainty analysis by providing comprehensive, quantitative information about the uncertainties 

underlying the estimates of health benefits. A quantitative uncertainty analysis can, 

among other things, identify which sources of uncertainties have the greatest effect 

on the benefit estimates and assess the degree to which the uncertainties affect the 

estimates by specifying a range of estimates and the likelihood of attaining them. 

While EPA has taken steps toward a more robust uncertainty analysis, the agency 

has not assessed uncertainty in the quantitative manner 

recommended by the National Academies. GAO believes it is important for EPA 

to continue to strengthen its uncertainty analysis. In evaluating estimates of health 

benefits, decision makers and the public can better assess the likelihood of achieving 
92 

such benefits if they are provided with qualitative and quantitative information 

about the underlying uncertainties. 

Question 3. Mr. Stephenson, in your testimony (quote): ‘‘We note that continued 

commitment and dedication of resources will be needed if EPA is to fully implement 

the improvements recommended by the National Academies.’’ However, EPA’s 2006 

budget proposes to reduce funding for the State and Local Air Quality Management 

Program which is used by states and localities to conduct monitoring among other 

things. How would this budget cut impact EPA’s ability to address more of these 

recommendations? 

Response. The proposed budget cuts could adversely impact EPA’s ability to address more of the Academies recommendations, such as those concerning particulate 

matter emissions data. Emissions estimates are a key element in the analysis of potential health benefits, and EPA relies largely on state and local entities emissions 

monitoring data to develop estimates of emissions on a national scale. Thus, any reductions in emissions monitoring could affect EPA’s ability to develop meaningful 

nationwide emissions estimates, increasing, for example, the uncertainty of such estimates. Moreover, as noted in our report, EPA has initiated long-term research and 

development to understand the relative toxicity of particulate matter components 

and to better evaluate the uncertainty of estimates of emissions. A reduction in 

monitoring data would likely limit EPA’s progress to address these areas of research. 

STATEMENT OF GEORGE THURSTON, ASSOCIATE PROFESSOR, NEW YORK UNIVERSITY, SCHOOL OF MEDICINE, DEPARTMENT OF ENVIRONMENTAL MEDICINE

I am George D. Thurston, a tenured Associate Professor of environmental Medicine at the New York University (NYU) School of medicine. In addition, I served 

as the Deputy Director of the NYU-EPA Particulate Matter (PM) Health Research 

Center for the past 4 years. My scientific research involves the investigation of the 

human health effects of air pollution. In this testimony, I will primarily address 

three factors that need to be considered in the EPA’s proposed revisions to the particulate matter air quality standards. First, I will address the fact that we are now 

far more certain of the adverse impacts and biological mechanisms of PM health effects: most of the uncertainties raised at the time of the initial setting of the PM2.5

standard are far better understood. Second, I will document that reducing ambient 

PM levels can and do result in significant reductions in the mortality risk associated 

with this pollutant. Finally, I will show that the adverse health impacts of PM air 

pollution extend below the current PM2.5 standard, and that there is, therefore, a 

public health imperative to reduce the fine particle (PM2.5) annual standard below 

15 wg/m3, consistent with the advice of the U.S. EPA’s Clean Air Science Advisory 

Committee (CASAC). 

Despite progress over the last few decades, Americans are still suffering from the 

adverse health effects of air pollution. The adverse health consequences of breathing 

air pollution are severe and well documented in the published medical and scientific 

literature. Over the past few decades, medical researchers examining air pollution 

and public health, including myself, have shown that air pollution is associated with 

a host of serious adverse human health effects, including: asthma attacks, heart attacks, hospital admissions, adverse birth outcomes, and premature death. 

PM is one of the air pollutants most carefully studied in the last decade. Small 

particles can bypass the defensive mechanisms of the lung, and become lodged deep 

in the lung where they can cause a variety of health problems. Indeed, the latest 

evidence indicates that exposures cannot only cause respiratory damage, but also 

cardiac effects, including heart attacks. Moreover, long-term exposure to fine particles increases the risk of death, and has been estimated to take years from the 

life expectancy of people living in the most polluted cities, relative to those living 

in cleaner cities (Brunekreef, 1997). 

The State of the science on particulate matter and health was thoroughly reviewed in the recently released U.S. EPA Criteria Document for Particulate Matter 

(U.S. EPA, 2004). Since the PM2.5 standard was last set in 1997, more than 100 new 

published studies, taken together, collectively confirm the relationship between 

PM2.5 pollution and severe adverse human health effects. In the process, this new 

research has eliminated many of the doubts that were raised in the past regarding 

the causality and size of the PM-health effects relationships, and has now provided 

plausible biological mechanisms for the serious impacts associated with PM exposure. As outlined in Figure 1, the PM research funded since the setting of the last 

PM2.5 standard has collectively shown the existence of numerous biological pathways capable of causing damage in the human heart, lung, nervous system, and cir-
93 

culatory system consistent with the health impacts found by the PM epidemiology 

studies upon which the PM2.5 standard was set. 

At the time of the last PM standard revisions, the largest landmark studies on 

particulate matter and death were the Harvard Six Cities Study (Dockery et al, 

1993) and the American Cancer Society Study (Pope et al, 1995). The American 

Cancer Society study examined half a million people in over 150 metropolitan areas 

throughout the United States, finding a 17 percent greater risk of mortality between 

the city with the least PM and the city wit the highest levels of this particulate pollution. The results of these studies were challenged by industry, resulting in an 

independent reanalysis by the Health Effects Institute (HEI)—an organization funded by both industry and Government. The results of the HEI re-analyses have now 

confirmed the associations found by the original investigators, increasing our confidence in the results of these two already highly regarded studies of PM mortality. 

Since the setting of the original PM2.5 standard, more recent follow-up analyses 

of the Harvard and ACS studies have now considered longer records of time, and 

have confirmed and extended the conclusions from these two major studies. An extended analysis of the Harvard Six Cities Study (to include follow-up through 1990) 

has now shown that reductions in long-term ambient PM pollution results in concomitant reductions in the health risks associated with PM. As shown in Figure 2, 

large reductions in PM at four of the Harvard cities have resulted in likewise large 

reductions in the relative risk (RR) of mortality in those cities: Steubenville, OH(S), 

Harriman, TN(H), St. Louis, MO(L), and Watertown, MA(W). Other published studies have similarly found indications that reductions in ambient PM are associated 

with reduced mortality risk (e.g., Clancy et al., 2002). Thus, although we still carry 

very large health risks in the United States from our present levels of PM air pollution, amounting to tens of thousands of premature deaths per year, and although 

we still have a long way to go to have what can be called ‘‘clean air’’, recent research 

shows that the lowering of PM levels in the air is an effective way to improve public 

health. 
94 

In addition, a recent National Institute of environmental Health Sciences 

(NIEHS)-funded extension of the ACS study, of which I was Principal Investigator, 

strengthens the original conclusions of the ACM study and, importantly, now links 

increased risk of lung cancer to long-term exposure to particulate matter (Pope et 

al, 2002). As seen in Figure 3, this recent JAMA study also clearly indicates that 

the risks from PM2.5 exposure extend below 15 ug/m3, supporting a reduction in the 

annual PM2.5 standard at this time, consistent with the advice of the EPA’s Clean 

Air Scientific Advisory Committee (Henderson, 2006). 

In conclusion, since it was the level of uncertainty about PM biological mechanisms and effects at lower concentrations than 15 wg/m3 that limited the standard 

to that level in 1997 (and not some specific acceptable level of health risk from PM), 
95 

and since new sound scientific studies have greatly reduced or resolved those uncertainties, then concern about the health of the public clearly indicates that the longterm PMPM2.5 standard should now be reduced below 15 ug/m3, consistent with the 

advice of CASAC. 

Thank you for the opportunity to testify on this important issue. 

RESPONSE BY GEORGE THURSTON TO AN ADDITIONAL QUESTION FROM

SENATOR VOINOVICH

Question. Dr. Thurston, at the end of your testimony, you state the annual standard was limited to 15 not because of (quote): ‘‘some specific acceptable level of health 

risk from PM.’’ 

Am I correct that you are saying that you agree with Dr. Smith that the risk level 

identified in 1997 has gone down? I know that you do not think this should be the 

basis of setting the standard, but I am just looking for a yes or no answer on the 

level of risk. 

Response. No, I do not agree with Dr. Smith. As I noted in my verbal testimony, 

the consensus ‘‘best-estimates’’ for the mortality effects of long-term exposure to PM 

have actually increased in recent years, relative to what the U.S. EPA has been assuming in their risk analyses. Indeed, the Pope et al. (2002) overall mortality effect 

estimate, as derived from the American Cancer Society Cancer Prevention II study 

cohort, is now thought to be an underestimate of the actual risk for the general U.S. 

population. In fact, preliminary results from the EPA’s recent PM Expert Elicitation 

evaluation of PM risk indicate that the central effect estimate, as derived from a 

distillation of all available studies by experts, yield a PM2.5 mortality effect (some 

1 percent per ug/m3 PM2.5) that is roughly two thirds higher than given by the Pope 

et al. (2002) study. This further indicates that 

lowering the long-term PM2.5 standard below 15 ug/m3 would yield significant 

public health benefits when implemented across the United States. 
96 
97 
98 
99 
100 
101 
102 
103 
104 
105 
106 
107 
108 
109 
110 
111 
112 
113 
114 
115 
116 
117 
118 
119 
120 
121 
122 
123 
124 
125 
126 
127 
128 
129 
130 
131 
132 
133 
134 
135 
136 
137 
138 
139 
140 
141 
142 
143 
144 
145 
146 
147 
148 
149 
150 
151 
152 
153 
154 
155 
156 
157 
158 
159 
160 
161 
162 
163 
164 
165 
166 
167 
168 
169 
170 
171 
172 
173 
174 
175 
176 
177 
178 
179 
180 
181 
182 
183 
184 
185 
186 
187 
188 
189 
190 
191 
192 
193 
194 
195 
196 
197 
198 
199 
200 
201 
202 
203 
204 
205 
206 

Æ