UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON D.C. 20460
OFFICE OF THE ADMINISTRATOR
SCIENCE ADVISORY BOARD
September 29, 2006
EPA-CASAC-LTR-06-003
Honorable Stephen L. Johnson
Administrator
U.S. Environmental Protection Agency
1200 Pennsylvania Avenue, NW
Washington, DC 20460
Subject: Clean Air Scientific Advisory Committee Recommendations Concerning the
Final National Ambient Air Quality Standards for Particulate Matter
Dear Administrator Johnson:
We, the seven members of the Clean Air Scientific Advisory Committee (CASAC or
Committee), are writing to express our serious scientific concerns regarding the public health and
welfare implications of EPA's final primary (health effects) and secondary (welfare effects)
National Ambient Air Quality Standards (NAAQS) for airborne particulate matter (PM). As you
know, the CASAC is mandated by the Clean Air Act to provide scientific advice on the setting of
these standards that are intended to protect both public health and public welfare, and in the case
of the protection of public health, to do so with "an adequate margin of safety." The Committee
has conscientiously fulfilled its duty in providing our best scientific advice and recommendations
to the Agency. Regrettably, however, EPA's final rule on the NAAQS for PM does not reflect
several important aspects of the CAS AC's advice.
In its letter dated June 6, 2005, the CASAC recommended that the 24-hour standard for
PM2.5 be decreased from 65 micrograms per cubic meter (|ig/m3) to 30-35 |ig/m3. We are
pleased with the Agency's decision in the final PM NAAQS rule to decrease the daily primary
PM2 5 standard to a level consistent with the CAS AC's recommendation (35 |ig/m3), as this
decrease will provide additional health protection in some cities. In addition, we recommended a
decrease in the annual primary PM2.5 standard from 15 |ig/m3 to 13-14 |ig/m3. However, the
CASAC is concerned that EPA did not accept our finding that the annual PM2 5 standard was not
protective of human health and did not follow our recommendation for a change in that standard.
The CASAC recommended changes in the annual fine-particle standard because there is
clear and convincing scientific evidence that significant adverse human-health effects occur in
response to short-term and chronic particulate matter exposures at and below 15 jug/m , the
level of the current annual PM2.s standard. The CASAC affirmed this recommended reduction
in the annual fine-particle standard in our letter dated March 21, 2006 concerning the proposed
rule for the PM NAAQS, in which 20 of the 22 members of the CASAC's Particulate Matter
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Review Panel — including all seven members of the chartered (statutory) Committee — were in
complete agreement. While there is uncertainty associated with the risk assessment for the PM2 5
standard, this very uncertainty suggests a need for a prudent approach to providing an adequate
margin of safety. It is the CASAC 's consensus scientific opinion that the decision to retain
without change the annual PM2.5 standard does not provide an "adequate margin of safety ...
requisite to protect the public health" (as required by the Clean Air Act), leaving parts of the
population of this country at significant risk of adverse health effects from exposure to fine PM.
Significantly, we wish to point out that the CASAC's recommendations were consistent
with the mainstream scientific advice that EPA received from virtually every major medical
association and public health organization that provided their input to the Agency, including the
American Medical Association, the American Thoracic Society, the American Lung Association,
the American Academy of Pediatrics, the American College of Cardiology, the American Heart
Association, the American Cancer Society, the American Public Health Association, and the
National Association of Local Boards of Health. Indeed, to our knowledge there is no science,
medical or public health group that disagrees with this very important aspect of the CASAC's
recommendations. EPA's recent "expert elicitation" study {ExpandedExpert Judgment
Assessment of the Concentration-Response Relationship Between PM2.s Exposure and Mortality,
September 21, 2006) only lends additional support to our conclusions concerning the adverse
human health effects of PM2.5.
Furthermore, the CASAC was completely surprised at the decision in the final PM
NAAQS to revert to the use of PMio as the indicator for coarse particles. In our September 15,
2005 letter, the CASAC recommended a new indicator of PMi0-2.5, which EPA put forward in its
proposed rule for the PM NAAQS. The option of retaining the existing daily PMio standard of
150 |ig/m3 was not discussed during the advisory process, and in fact the CASAC views this as
highly-problematic since PMio includes both fine and coarse particulate matter. The Committee
acknowledges the need for the Agency to increase its understanding of the health risks of coarse
particles and is concerned that ongoing dependence on PMio sampling as an imprecise measure
of coarse particulate matter will provide inadequate information on coarse PM concentrations,
compositions and exposures in both urban and rural areas. However, the CASAC agrees that
having a standard for PMio is better than no standard at all for coarse particles, and was pleased
with the Agency's decision against offering exemptions to specific industries (i.e., agricultural,
mining) in its regulation of coarse particles.
With respect to the secondary PM standard, the decision was made "to revise the current
PM secondary standards by making them identical in all respects to the revised suite of primary
PM standards." In our June 6, 2005 letter, the CASAC affirmed the recommendation of Agency
staff regarding a separate secondary fine particle standard to protect visibility. This sub-daily
secondary PM2.5 standard is a better indicator of visibility impairment than the 24-hour primary
standard. The CASAC wishes to emphasize that continuing to rely on primary standards to
protect against all PM-related adverse environmental and welfare effects assures neglect, and
will allow substantial continued degradation, of visual air quality over large areas of the country.
In summary, the Agency has rejected the CASAC's expert scientific advice with regard
to lowering the level of the annual primary fine particle (PM2 5) standard and establishing a new
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coarse particle (PMio-2.s) standard — both of which are consistent with the recommendations of
the nationally-recognized science, medical and public health groups such as those cited above —
and, in addition, EPA has not followed our advice in setting a separate secondary PM2.5 standard.
We note that, since the CASAC's inception in the late 1970s, the Agency has always accepted
the Committee's scientific advice with regard to final NAAQS decisions. In view of this, we
question whether you have appropriately given full consideration to CASAC's expert scientific
advice — obtained through open, public processes — in your final decisions on the PM NAAQS.
The CASAC shares a common goal with EPA to protect the public health and welfare.
We earnestly hope that the Agency's future consideration of the CASAC's scientific advice with
respect to standard-setting for the criteria air pollutants will prove more fruitful in achieving that
very important goal.
Sincerely,
/Signed/
Rogene Henderson, Ph.D.
Chair, Clean Air Scientific Advisory Committee
Scientist Emeritus
Lovelace Respiratory Research Institute
Albuquerque, NM
/Signed/
Mr. Richard L. Poirot
Environmental Analyst
Vermont Agency of Natural Resources
Waterbury, VT
/Signed/
Ellis Cowling, Ph.D.
University Distinguished Professor At-Large
North Carolina State University
Raleigh, NC
/Signed/
Frank Speizer, M.D.
Edward Kass Professor of Medicine
Channing Laboratory
Harvard Medical School
Boston, MA
/Signed/
lames D. Crapo, M.D.
Professor, Department of Medicine
National lewish Medical and Research Center
Denver, CO
/Signed/
Barbara Zielinska, Ph.D.
Research Professor
Desert Research Institute
Reno, NV
/Signed/
Frederick J. Miller, Ph.D.
Gary, NC
Consultant
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