November 30, 1995

EPA-SAB-CASAC-LTR-96-002

Honorable Carol M. Browner
Administrator
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, DC 20460

                  RE:   CASAC Closure on the Primary Standard Portion of the Staff
                       Paper for Ozone

Dear Ms. Browner:

      A Panel of the Clean Air Scientific Advisory Committee (CASAC) of EPA's
Science Advisory Board (SAB) met on March 22, 1995, to review a draft of the primary
standard part of the document entitled Review of National Ambient Air Quality
Standards for Ozone Assessment of Scientific and Technical Information OAQPS Staff
Paper.  At that time, a draft of the secondary standard portion of the document was not
completed. At the March meeting, the Panel made extensive recommendations for
strengthening the document. In August 1995, a revised Staff Paper, which included a
first draft of the secondary standard portion was sent to CASAC panel members for
review.  On September 19 and 20,  1995, the Panel met to compete this review. The
Panel members' comments reflect their satisfaction with the improvements made in the
scientific quality and completeness of the primary standard portion of the Staff Paper.
The changes made in that portion of the document are consistent with CASAC's
recommendations.   However, the Panel Members provided additional comments to your
staff at the meeting and subsequently in writing.  Although the Panel would like to have
these comments considered for incorporation in the Staff Paper, the  Panel did not feel
that it was necessary to review another revised version and came to closure on the
primary standard portion.  It was the consensus of the Panel that although our
understanding of the health effects of ozone is far from complete, the document
provides an adequate scientific basis for making regulatory decisions concerning a
primary ozone standard.

      The Panel could not come to closure, however, on the secondary standard

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portion of the Staff Paper which was a first draft. To facilitate further development of
this part of the Staff Paper, the Panel members have provided detailed comments to
your staff.  The Panel felt that the suggested revisions were extensive enough to
warrant a review of the next draft.

      I would like to summarize for you the Panel's recommendations concerning the
primary standard. It was the consensus of the Panel that EPA's selection of ozone as
the surrogate for controlling photochemical oxidants is correct. It was also the
consensus of the Panel that an 8-hour standard was more appropriate for a human
health-based standard than a 1-hour standard.  The Panel was in unanimous
agreement that the present 1-hour standard be eliminated and replaced with an 8-hour
standard.

      The Panel felt that the weight of the health effects evidence indicates that there
is no threshold concentration for the onset of biological responses due to exposure to
ozone above background concentrations. Based on information now available, it
appears that ozone may elicit a continuum of biological responses down to background
concentrations. This means that the paradigm  of selecting a standard at the lowest-
observable-effects-level and then providing an "adequate margin of safety" is no longer
possible.  It further means that EPA's risk assessments must play a central role in
identifying an appropriate level.

      To conduct the risk assessments, the Agency had to identify the population at
risk and the physiological responses of concern, develop a model to estimate the
exposure of this population to ozone, and develop a model to estimate the probability of
an adverse physiological response to the exposure. The Panel agrees with EPA that
the selection of "outdoor children" and "outdoor workers," particularly those with
preexisting respiratory disease are the appropriate populations with the highest risks.
After considerable debate,  it was the consensus of the Panel that the Agency's criteria
for the determination of an  adverse physiological response was reasonable.
Nevertheless, there was considerable concern  that the criteria for grading physiological
and clinical responses to ozone was confusing  if not misleading.  The Panel concurs,
with the Agency that the models selected to estimate exposure and risk are appropriate
models. However, because of the myriad of assumptions that are made to estimate
population exposure and risk, large uncertainties exist in these estimates.

      The results of two of the risk analyses are presented in Tables VI-1 and VI-2 in
the Staff Paper and are reproduced in the attached tables. The ranges of the risk
estimates  across nine cities for outdoor children are presented in Table VI-1. Because
of the large number of stochastic variables used in the exposure models, the exposure

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estimates vary from run to run. However, the ranges are not reflective of all of the

uncertainties associated with the numerous assumptions that were made to develop the
estimates.

      The single estimates presented in Table VI-2 do not reflect any of the
uncertainties associated with these estimates. (Table VI-2 contains only the estimated
hospital admissions due to asthma which account for over 85% of the estimated total
hospital admissions due to ozone exposure). These uncertainties need to be explicitly
articulated in order to put the estimates in  proper perspective. Nevertheless, based on
the results presented in these and other similar tables presented in the Staff Paper, the
Panel concluded that there is no "bright line" which distinguishes any of the proposed
standards (either the level or the number of allowable exceedences) as being
significantly more protective of public health. For example, the differences in the
percent of outdoor children (Table VI-1) responding between the present standard and
the most stringent proposal (8H1 EX at 0.07 ppm) are small and their ranges overlap for
all health endpoints.  In Table VI-2, the estimates in row 1, which appeared in the draft
Staff Paper, suggest considerable differences between the several options.  However,
when ozone-aggravated asthma  admissions are compared to total asthma admissions
(rows 5 and 6), the differences between the various options are small. Consequently,
the selection of a specific level and number of allowable exceedences is a policy
judgment. Although  it was the consensus  of the Panel that the ranges of
concentrations and allowable exceedences proposed by the Agency were appropriate,
a number of Panel members expressed "personal"  preferences for the level and
number of allowable  exceedences. Of the ten panel members who expressed their
opinions, all ten favored multiple allowable exceedences, three favored a level of 0.08
ppm, one favored the mid to upper range (0.08 - 0.09 ppm), three favored the upper
range (0.09 ppm),  one favored a 0.009 - 0.10 ppm range with health advisories issued
when the 8-hour ozone concentration was forecasted to exceed 0.007 ppm, and two
just endorsed the range presented by the Agency as appropriate and stated that the
selection should be a policy decision. The members who favored the lower numbers
expressed concern over the evidence for chronic deep lung inflammation from the
controlled human and animal exposure studies and the observations of pain on deep
inspiration in some subjects.

      Because  there is no apparent threshold for responses and no "bright line" in the
risk assessment, a number of panel members recommended that an expanded air
pollution warning system be initiated so that sensitive individuals can take appropriate
"exposure avoidance" behavior.  Since many areas of the country already have an
infrastructure in  place to designate "ozone action days" when voluntary emission

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reduction measures are put in place, this idea may be fairly easy to implement.

      It was also the consensus of the Panel that the form of the 8-hr standard be
more robust than the  present 1-hour standard.  The present standard is based on an
extreme value statistic which  is significantly dependent on stochastic processes such
as extreme meteorological conditions. The result is that areas which are near
attainment will randomly flip in and out of compliance. A more robust,  concentration-
based form will minimize the "flip-flops," and provide some insulation from the impacts
of extreme meteorological events. The Panel also endorses the staff recommendation
for creating a "too close to call" category.

      Since the last ozone NAAQS review, the scientific community has made great
strides in their understanding of the health effects of ozone exposure because of
ongoing research programs.  Panel members were very  impressed with how much
more we understand now  as compared to the prior round.  Nevertheless, there are still
many gaps in our knowledge  and large uncertainties in many of the assessments.  For
example, there is little information available on the frequency of human activity patterns
involving outdoor physical exercise.  Little is also known about the possible chronic
health impacts of ozone exposure over a period of many years.  In addition, there is no
clear understanding of the significance of the inflammatory response inferred from the
broncholavage data.  Panel members stated, however, that the scientific community is
now in a position to frame the questions that  need to be  better resolved so the
uncertainties can be reduced before the next ozone review in 5 years.  For this reason,
it is important that research efforts on the  health and ecological effects of ozone not be
reduced because we  have come to closure on this review.

      CASAC would  appreciate being kept informed of progress on establishing a
revised or new ozone standard, and plans for research on ozone effects.  Please do
not hesitate to contact me if CASAC can be of further assistance in this matter. We
look forward to receiving the revisions of the  secondary standard portion of the Staff
Paper.

                                          Sincerely,
                                            /signed/
                                    Dr. George T. Wolff, Chair
                              Clean Air Scientific Advisory Committee

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Page left blank to accomodate insert table - see meeting file or report file for a copy of
this page.

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                                              Table VI-2 (revised)
      ESTIMATED HOSPITAL ADMISSIONS FOR ASTHMATICS IN THE NEW YORK CITY AREA

Excess Admissions3
% A from present std
Excess + background"
% A from present std
All asthma admissions0
% A from present std
1H1EX
0.12
210
0%
890
0%
28,295
0%
1H1EX
0.10
130
-38%
810
-9%
28,215
-0.3%
8H1EX
0.10
240
+14%
920
+3%
28,325
+0.1%
8H1EX
0.09
180
-14%
860
-3%
28,265
-0.1%
8H1EX
0.08
110
-48%
790
-11%
28,195
-0.4%
8H1EX
0.07
60
-71%
740
-17%
28,145
-0.5%
8H5EX
0.09
180
-14%
860
-3%
28,265
-0.1%
8H5EX
0.08
120
-42%
800
-10%
28,205
-0.3%
AS IS
=385d
+83%
1065e
+20%
28,470f
+0.6%
a - excess asthma admissions attributed to ozone levels exceeding a background concentration of 0.04 ppm; from Table VI-2, page 155 in the
      August 1995 OAQPS Draft Staff Paper
b - asthma admissions included in (a) plus those due to background ozone concentrations; admissions due to background = 1065e - 385d = 680
c - asthma admissions due to all causes = 28,470f - 385d - Excess Admissions from row 1
d - estimated from Figure V-15, page 125 in the August 1995 OAQPS Draft Staff Paper
e - from page 127, line 13 in the August 1995 OAQPS Draft Staff Paper
f - total admissions from asthma = total asthmatics (365,000 - from page 126, line 24) x hospitalization rate (78/1000 asthmatics - from page 126,
      line 29)

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                            SCIENCE ADVISORY BOARD
                CLEAN AIR SCIENTIFIC ADVISORY COMMITTEE
                              OZONE PANEL ROSTER

Chair
Dr. George T. Wolff, General Motors Environmental & Energy Staff, Detroit, Ml

Members
Dr. Stephen M. Ayres, Office of International Health Programs, Virginia Commonwealth University, Medical
       College of Virginia, Richmond, VA

Dr. Jay S. Jacobson, Boyce Thompson Institute, Cornell University, Ithaca, NY

Dr. Joe L. Mauderly, Inhalation Toxicology Research Institute, Lovelace Biomedical & Environmental Research
       Institute,  Albuquerque,  NM

Dr. Paulette Middleton, Science & Policy Associates, Inc.,Boulder, CO (did not participate)

Dr. James H. Price, Jr., Texas  Natural Resource Conservation Commission, Austin, TX

Consultants to CASAC
Dr. Stephen D. Colome, Integrated Environmental Services, University Tower, Irvine, CA

Dr. A. Myrick Freeman, Department of Economics, Bowdoin College,, Brunswick, ME

Dr. Allan Legge,  Biosphere Solutions,Calgary, Alberta, CANADA

Dr. Morton Lippmann, Institute of Environmental Medicine, New York University Medical Center, Tuxedo, NY

Dr. William Manning, Department of Plant Pathology, University of Massachusetts, Amherst, MA

Dr. Roger O. McClellan, Chemical Industry Institute of Toxicology, Research Triangle Park, NC

Dr. D. Warner North, Decision Focus, Inc., Mountain View, CA

Dr. Frank E. Speizer, Harvard Medical School, Channing Lab, Boston, MA

Dr. George Taylor, Biological Services Center, Desert Research Institute, University of Nevada, Reno, NV

Dr. Mark J. Utell, Pulmonary Disease Unit, University of Rochester Medical Center, Rochester, NY

Science Advisory Board Staff
Mr. A. Robert Flaak, Designated Federal Official, U. S. Environmental Protection Agency, Science Advisory
       Board (1400F), 401 M Street, SW, Washington, DC 20460

Ms. Connie Valentine, Staff Secretary, U. S. Environmental Protection Agency, Science Advisory Board
       (1400F), 401 M Street, SW, Washington, DC 20460

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                                            NOTICE

       This report has been written as part of the activities of the Science Advisory Board, a public advisory
group providing extramural scientific information and advice to the Administrator and other officials of the
Environmental Protection Agency. The Board is structured to provide balanced, expert assessment of scientific
matters related to problems facing the Agency. This report has not been reviewed for approval by the Agency
and, hence, the contents of this report do not necessarily represent the views and policies of the Environmental
Protection Agency, nor of other agencies in the Executive Branch of the Federal government, nor does mention
of trade names or commercial  products constitute a recommendation for use.

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