United States Office of the Administrator SAB-EC-87-025
Environmental Protection Science Advisory Board • March 1987
Agency Washington, DB 20460
?/EPA Review of EPA's
Assessment of the Risks
of Stratospheric Modification
Review of the
Stratospheric Ozone
Subcommittee of the
Science Advisory Board
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600R87055
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON. D.C. 20460
March 23, 1987 SAB-EC-87-025
OFFICE Of
THE AD
Honorable Lee M. Thomas
Administrator
U. S. Environmental Protection Agency
401 M Street, S. W.
Washington, D. C. 20460
Dear Mr. Thomas:
The Science Advisory Board's Stratospheric Ozone Subcommittee has
completed its review of EPA's risk assessment document entitled An Assess-
ment of the Risks of Stratospheric Modification and is pleased to transmit its
final report to you.
The Subcommittee carried out an independent evaluation of the assumptions,
conclusions and interpretations used by EPA in assessing the existing scientific
information related to stratospheric ozone modification. The Subcommittee
also advised EPA on the thoroughness and balance of its treatment of particular
scientific issues, noting areas of emission as well as areas emphasized in
the assessment document, and reviewing EPA's characterization of scientific
uncertainties.
EPA's draft assessment document represents an extensive effort to develop
an integrated risk assessment, based upon currently available scientific
information, to ascertain the potential threat to the stratosphere posed by a
continued growth world-wide of emissions of chlorofluorocarbon compounds
(CFCs). The Subcommittee generally finds that EPA had done a commendable job
in the body of the report of assembling the relevant scientific information,
although the Subcommittee has many recommendations for improving the document.
The uncertainty in future CFC emissions has been characterized in the EPA
draft as encompassing a cange of 0 to 5% for annual emissions growth, with
1-4% as the most likely portion of the range. The Subcommittee recommends that
EPA present the 2.5% growth rate as one of a series of illustrative "what-if"
scenarios, rather than as a most likely case. The revised Executive Summary
adopts this advice.
Depletion of the ozone column can increase ultraviolet radiation (UVB),
resulting in an increase in nonmelanona skin cancer. Available scientific
evidence suggests that melanoma nay also increase as a result of increased
ultraviolet radiation. The- re nay hx3 other significant health effects, in
addition to adverse impacts on plants and aquatic organisms. Information
on the impacts of increased ultraviolet radiation on plants and aquatic
organisms is extremely limited. The Subcommittee believes that the potential
for adverse impacts on plants and aquatic organisms is sufficiently large to
warrant high priority for further investigation.
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The Subcommittee believes that the information summarized in the draft
risk assessment supports the conclusion*that the possible impact of CFCs on
the stratosphere should be considered a high priority issue for further
investigation and analysis by EPA and other Federal agencies, and provides a
scientific basis for the recently initiated international efforts to address
this problem.
The Subcommittee reviewed the first draft of the entire assessment
document during its initial meeting. Following that session, using continents
received from members of the Subcommittee and the public, EPA staff rewrote
the Executive Summary. This revision was resubmitted in time for the
Subcommittee's second meeting. The Subcommittee's report, therefore, provides
scientific advice on the revised Executive Summary and the first draft of the
individual chapters of the assessment document. The Subcommittee members
have not seen revisions to the individual chapters and request that EPA staff
transmit the revised chapters and any further revision of the Executive
Summary for their individual review once this task is completed. Following
this individual member cycle of review, the Chair and Vice Chair will transmit
a letter to EPA noting the extent to which the Agency has responded to its
scientific advice.
We appreciate the opportunity to participate in the evaluation of this
important public health and environmental issue. We request that the Agency
formally respond to the scientific advice provided in the attached report.
Sincerely,
£.3^"
'' 7
Margaret Kripke
Chair
Stratospheric Ozone Subcommittee
Science Advisory Board
Norton Nelson
Chair
Executive Committee
Science Advisory Board
cc: A. James Barnes
Jack Campbell
Vaun"Newill
Craig Potter
Terry F. Yosie
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SAB-EC-87-025
REVIEW OF EPA'S
AN ASSESSMENT OF THE RISKS OF STRATOSPHERIC MODIFICATION
BY THE
STRATOSPHERIC OZONE SUBCOMMITTEE
SCIENCE ADVISORY BOARD
U. S. ENVIRONMENTAL PROTECTION AGENCY
March, 1987
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U. S. ENVIRONMENTAL PROTECTION AGENCY
NOTICE
This report has been written as a 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 a 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 endorsement of recommendation for use.
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U. S. ENVIRONMENTAL PROTECTION AGENCY
SCIENCE ADVISORY BOARD
STRATOSPHERIC OZONE SUBCOMMITTEE
Dr. Margaret Kripke, Chair
Anderson Hospital and
Tumor Institute
Box 178
6723 Bertner Street
Houston, Texas 77030
Dr. Martyn Caldwell
Department of Range Science
Utah State University
Logan, Utah 84322-5230
Dr. Robert Dean
3218 Northwest 31st Street
Gainesville, Florida 32605
Dr. James Friend
Department of Chemistry
Drexel University
Philadelphia, Pa. 19104
Dr. Terry F. Yosie, Director
Science Advisory Board
U. S. Environmental Protection Agency
401 M Street, S. W. Roan 1145
Washington, D. C. 20460
Dr. Leo T. Chylack, Jr.
Center for Clinical Cataract Research
1 Charles Circle
Boston, Mass. 02114
Dr. Thomas Fitzpatrick
Department of Dermatology
Warren-5
Massachusetts General Hospital
Boston, Massachusetts 02114
Dr. Donald Hunten
Lunar and Planetary Laboratory
University of Arizona
Tucson, Arizona 85721
Dr. Warren Johnson
Manager, Research Aviation
Facility
National Center for Atmospheric
Research
Jefferson County Airport
10800 West 120th Street
Broomfield, CO. 80020
Dr. Irving Mintzer
Director, Energy and Climate
World Resources Institute
1735 New York Avenue, N. W.
Washington, D. C. 20006
Dr. Nien Dak Sze
A.E.R., Inc.
840 Memorial Drive
Cambridge, Mass. 02139
Dr. Charles Yentsch
Bigelow Laboratory
McKown Point
West Boothbay Harbor, Maine 04575
Dr. Lester Lave
Graduate School of
Industrial Administration
Carnegie Mellon University
5000 Forbes Avenue
Pittsburgh, Pa. 15213
Dr. Warner North, Vice Chair
Principal, Decision Focus, Inc.
Los Altos Office Center
Suite 200
4984 El Camino Real
Los Altos, California 94022
Dr. Robert Watson
National Aeronautics and
Space Administration
600 Independence Avenue
Mail Code EE4
Washington, D. C. 20546
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TABLE OF CONTENTS
Page
••»., •.;.
I. Introduction 1
A. Scope and Charge of the Subconmittee's 1
Review
B. Subcommittee Review Procedures 2
II. General Connents and Conclusions 3
III. Specific Garments: Executive Summary 6
IV. Specific Garments on Individual Chapters 9
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I. Introduction
A. Scope and Charge of the Subcomnittee's Review
On January 9, 1986 EPA's Assistant Administrator for Air requested
the Science Advisory Board to evaluate the Agency's assessment of the
risks of stratospheric modification. Specific questions posed to the
Board included reviewing and assessing EPA's treatment of the scientific
issues of concern (e.g., long term trends in trace gases, atmospheric
science, and health and ecological effects from ozone depletion).
On January 31, 1986 the Science Advisory Board Executive Committee
accepted this request and authorized the formation of a Stratospheric
Ozone Subcommittee to conduct the review. The Subcommittee's role was to
carry out an independent evaluation of the assumptions, conclusions and
interpretations developed or used by EPA in assessing the existing scientific
information related to stratospheric ozone modification. The Subcommittee
also advised EPA on the thoroughness and balance of its treatment of
particular scientific issues, noting areas of omission as well as areas
emphasized in the assessment document, and reviewing EPA's characterization
of scientific uncertainties.
The Subccnmittee's primary effort was directed at examining the
scientific logic used by EPA in its efforts to synthesize the available
scientific literature. While it conducted a chapter-by-chapter review of
the assessment document, the Subcommittee recognizes that not all of the
issues discussed in each chapter are of equal public health or environmental
importance.
At no time did the Sijrxxonittee believe that its role was to assist
EPA in writing the asso.s.-rv-nt document. Instead, it has offered specific
technical advice for i^.-r-'Viny the scientific quality of the document. EPA
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must then decide whether to accept or not accept this advice. The Sub-
committee also construed its role as an advisor rather than as a final
•••>».. '.;-
approval body that would supervise detailed editorial and factual changes
to all sections of the document. The latter role was beyond the Subcom-
mittee's resource capability and was also inconsistent with the role of
an advisor performing a timely review.
B. Subcommittee Review Procedures
The Subcommittee met twice in public session in Washington, D. C.,
on November 24-25, 1986 and January 26-27, 1987. Notice of each meeting
was published in the Federal Register. IXiring its meetings the Subcommittee
heard presentations from EPA staff and had the opportunity to provide
both verbal and written criticisms of the material submitted for review.
In addition, the Subcommittee made time available for members of the
public to present verbal and written comments on the scientific adequacy
of EPA's assessment document. Participating organizations included the
Alliance for a Responsible CFC Policy, Chemical Manufacturers Association,
Dupont Corporation, Environmental Defense Fund and Natural Resources
Defense Council, as well as individual numbers of the scientific community.
These presentations, and the interactions between the Subcommittee and
EPA staff, resulted in a wide ranging scientific dialogue whose aim was
to solicit information and facilitate the Subcommittee's effort to achieve
consensus on the major issues for which it was advising EPA.
The Subcommittee reviewed the first draft of the entire assessment
document during its initial meeting. Following that session, using
comments received from nemtxirs of the Subcommittee and the public,
EPA staff rewrote the Executive Summary. This revision was resubmitted
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in time for the Subcommittee's second meeting. The Subcommittee's report,
therefore, provides scientific advice on the revised Executive Summary
and the first draft of the individual chapters of the assessment document.
Following its first meeting, the Subcommittee drafted an interim
report that summarized its major thoughts at that stage of the review.
This was expanded and updated at the second meeting. Final editing of
the report was carried out by mail and telephone conversations. The Science
Advisory Board's Executive Committee approved the report by mail on
February 25, 1987.
The Subcommittee members have not seen revisions to the individual
chapters and request that EPA staff transmit the revised chapters and any
further revision of the Executive Summary for their individual review
once this task is completed. Following this individual member cycle of
review, the Subcommittee Chair and Vice-Chair will transmit a letter to
EPA noting the extent to which the Agency has responded to its scientific
advice.
II. General Comments and Conclusions
EPA's draft document represents an extensive effort to develop an
integrated risk assessment based upon currently available scientific
information to ascertain the potential threat to the stratosphere posed
6
by a continued growth world-wide of emissions of chlorofluorocarbon (CFCs)
compounds. The Subcommittee generally finds that EPA has done a commendable
job of assembling the relevant scientific information in the body of the
document, although the Subcommittee has many specific reccmmendations' for
improving the treatment of particular scientific issues and characterizing
scientific uncertainties.
EPA states the uncertainty in future CFC emissions as encompassing a
range of 0 to 5% for annual emissions growth, with 1-4% as the most
likely scenario within the range. The Subcommittee recommended that EPA
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present the 2.5% growth rate as one of a series of illustrative "what-if"
scenarios, rather than as a most likely case. The revised Executive
Summary adepts this advice. ••»•-,
Calculations with one and two dimensional atmospheric models indicate
that continued CFC annual emissions growth of 2.5% or above could lead to
depletion of global column ozone by several percent within the next forty
years and much higher reductions in subsequent decades if this rate of
CFC emissions growth continues. Ozone reduction will continue, albeit at
*
a slower rate even if the rate of emissions becomes constant. The retention
time of CFC gases in the atmospheric is decades to centuries, so that the
CFC buildup cannot be quickly reversed once it has occurred. The impacts
of ozone depletion will be largest at high latitudes and at high elevations
of the stratosphere, although changes in ultraviolet radiation will be
determined by column ozone (total ozone in a column through all levels of
the atmosphere).
Changes in CFC gases interact with changes in jreenhouse gases (CC>2,
N20, CH4) in determining changes in ozone concentrations. The impact of
CFC emissions on ozone concentrations may be even larger if growth in
these greenhouse gases is reduced from current trends. In addition, CFC
gases have a potential impact on global climate, although this impact
appears to be only about 20 percent of that anticipated from changes in
CC>2, N20, and Gfy. The impact on climate of changes in ozone concentration
appears to be small by comparison.
Depletion of the ozone column can increase ultraviolet radiation
(UVB), resulting in an increase in non-melanoma skin cancer. Available
scientific evidence suj.-jt.-st-.s that melanoma may also increase as a result
of increased ultraviolet radiation. There may be other significant health
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effects, in addition to adverse impacts on plants and aquatic organisms.
Information on the impacts of increased ultraviolet radiation on plants
and aquatic organisms is extremely limited. The Subcommittee believes
that the potential for adverse impacts on plants and aquatic organisms is
sufficiently large so that further research of these areas should receive
high priority.
The Subcommittee believes that the information summarized in the
draft risk assessment supports a conclusion that the possible impact of CFCs
on the stratosphere should be considered a high priority issue for further
investigation and analysis by EPA and other Federal agencies, and provides
a scientific basis for the recently initiated international efforts to
address this problem.
The draft document represents a useful step toward communicating the
applicable scientific information to decision makers, but decisions on
CFC regulations will require further analysis of the regulatory options
beyond the analyses presented in the draft risk assessment.
The Subcommittee has reviewed, but has not evaluated in detail, the
quantitative projections of health and other impacts associated with growth
in CFC emissions that are contained in the draft risk assessment. The
integrating model appears to be a useful vehicle for summarizing the
implications of alternative assumptions regarding emissions, atmospheric
response to CFCs and other trace gases, implications for changes in
ultraviolet radiation, and consequent changes in the incidence of skin
cancer in the U. S. population during the lifetimes of the current
population and those individuals born during the next century. Some
other impacts (e.g., econanic costs of damage to polymeric materials,
soybeans as an example ot crop loss, and anchovy loss as an example of
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population impact for a sensitive aquatic species) are included in the
quantitative analysis using the integrating model. Many potentially
..v.,
important iapacts are not included since the information to support
quantitative projections of these impacts is not yet available.
The draft document makes a reasonable attempt to characterize
uncertainties in scientific knowledge and in the assumptions for growth
of CFC emissions. The Subcommittee•recommends further efforts to state
assumptions more explicitly and to more clearly characterize the limits
of currently available information.
The draft document is long and repetitive and, yet, some critical
information is not readily available. As an example, much of the discussion
of CFC emissions' projections in Chapter 3 -presents results with little
information on underlying assumptions and data. EPA has taken these
results from contractor reports that are not available in the peer reviewed
literature. It is highly desirable that the final document, with its
appendices, be self-contained and reasonably complete. Additional appendices
summarizing contractor work and documenting more fully the integrating
model of Chapter 17 may, therefore, be needed.
In summary, the entire draft document represents a good first effort
to summarize an exceedingly complex set of issues, and the Subcommittee
commends EPA for the progress achieved to date.
III. Specific Comments on the Revised Executive Summary
The Subcommittee believes the Executive Summary is extremely important
because it is likely t-> roc^iv* the most attention and will be used for a
variety of purposes, inclntiing domestic regulatory decision making and
international negotiation. ror this reason, the Executive Summary needs
to be accurate and exphi-i?., dn>i provide a balanced overview of the
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content and conclusions of the entire assessment document. The Subcommittee
spent most of the time at its second meeting reviewing and discussing
• * ^-.^ '•;.
this portion- of the document. It reached the following conclusions and
recommendations:
1. The revised Executive Summary represents a marked improvement
over the original version. Our major criticism of the original Executive
Summary was its failure to reflect accurately and objectively the content
of the individual chapters in the report. EPA staff have made significant
progress in correcting this problem.
2. Additional revisions are still needed to reach the necessary level
of accuracy, balance and clarity. The Subcommittee recommends that both
the findings summary and the chapter summaries be organized into subsections
to facilitate their presentation. All long headings in the chapter
summaries should be shortened to a brief sentence. The document should
also present an outline or diagram illustrating the atmospheric processes
involved in the creation and destruction of ozone. Many specific suggestions
for improvement of the Executive Summary were discussed with or submitted
in writing to.Mr. John Hoffman for incorporation into a second revision
of the Executive Summary.
3. Although the Executive Summary is now more accurate and objective
in describing the information and conclusions of the entire document,
statements interpreting the results for non-scientists, and indications
of the relative, importance of the issues considered, need to be provided.
For example, each point made in the Executive Summary appears to be given
equal weight, when clearly, the issues differ widely in terms of their
potential significance. Specific recommendations for'addressing this
problem include:
a) EPA should clearly and forcefully state that, by the time it is
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possible to detect decreases in ozone concentration with a high degree of
confidence, it may be too late to institute corrective measures that
••».-, •.:-
would reverse this trend.
b) Predictions of ozone depletion derived fron atmospheric models
are consistent, in most instances., with actual measurements of ozone
concentration, even though these measurements are subject to considerable
uncertainty.
c) Both the relative state of knowledge, and our ability to obtain
new information in the immediate future are different for each area
summarized in the document. For some issues, it will take decades to
obtain missing information whereas, on others, rapid progress can be
predicted. However, this variation in the information base should not
preclude recognition of the potential problem of ozone depletion or
making decisions that address the problem. Decisions can and should be
made, even in the face of current uncertainties.
d) The Executive Summary should provide a sense of proportion and
balance among the scientific issues evaluated, particularly in presenting
the findings of the document. Clearly, the consequences of ozone depletion
could be major for some effects, even though the amount of information
available is small. A large amount of information does not necessarily
imply greater importance compared to the effects on which little information
is available. EPA should attempt to prioritize the effects that night
result frcrn ozone depletion and to distinguish between effects that are
of greater or lesser consequence on a global scale. The following table
is provided to illustrate the Subcommittee's view of the relative significance
and state of knowledge eor each of the effects summarized in the report:
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Ef.fect
Skin Cancer
Immune System
Cataracts
Plant Life
Aquatic Life
Climate Impacts*
Tropospheric 03
and H^
Polymers
State of Knowledge^
Moderate to high
Low
Moderate
Low
Low
Moderate
Moderate
Moderate
Potent ial.Global Impact
Moderate
High
Low
High
High
Moderate
Low
Low
* Contribution of 03 to climate changes, including sea level rise
A principal use of this table could be as a guide to research planning,
especially in conducting research for effects where current knowledge is
low and potential global impacts are high. Such a table is, however, an
imperfect guide for allocating research dollars, and is subject to change
as new information becomes .available.
The Subcommittee does not know, based on current knowledge, whether
effects with a potential global impact designated as "high" with a state of
knowledge designated as low will occur but, if such effects are experienced,
they could be significant.
e) The Executive Summary should devote less emphasis to climate change
and its effects, such as sea level rise. It should focus, instead, on
the contribution of changes in ozone concentration to climate modification,
rather than reviewing all the radiatively-active gases that affect climate.
We recognize that the ozone depletion and global warming (greenhouse)
issues are linked; nonetheless, the emphasis in this document should be
placed on stratospheric, rather than tropospheric processes.
IV. Specific Comments on Individual Chapters
Chapter Ij Goal_s__and Approach
This short introductory chapter was not formally reviewed. The
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Subcommittee endorses the statement of purpose for the risk assessment.
Chapter 2; Stratospheric Perturbants: Past Changes in Concentrations
This chapter on past changes iiv.2 and other
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greenhouse gases may project a misleading impression of current ability
to predict the future evolution of atmospheric conditions. The EPA
responded to the Subcommittee's suggestion to explore a set of scenarios
and a range of plausible future conditions. However, insights on the
potential role of fossil fuel uses, changes in deforestation, and other
factors underlying changes in greenhouse gas levels should be described.
Uncertainty on non-anthropogenic emissions and resulting uncertainties in
the trends for Cffy and N20 should be discussed further. This chapter could
benefit from extensive rewriting and reorganization.
Chapter 5: Assessment of the Risk of Stratospheric Ozone Modification
The discussion of one dimensional (1-D) models should be condensed, while
more discussion of two dimensional (2-D) models and perhaps three dimensional
(3-D) modeling approaches would be useful in explaining the current under-
standing of the complex set of relationships determining ozone levels and
climate changes. It is crucial to communicate the extent of predictive
power of current models. We recognize the need for improved models that
can describe seasonal and regional changes in ozone abundance and the
resulting climatic changes.
The Monte Carlo analysis of Stolarski and Douglas indicates that
screening sets of variables to combinations that are reasonably consistent
with available atmospheric measurement data changes the character of the
results as stated in the r"xec-jtive Summary and the findings of Chapter 5.
The discussion on pages 5-JJH and 5-93 with Figures 5-57 and 5-58 should
become the basis for revising the statement of these results. The choice
of material for the cha^t-.-'r sur^rary should be improved. The chapter
could benefit by extens i.--^ "Tilting and rewriting.
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Chapter 6; Climate Change
The Subcommittee judged this to be one of the better written chapters,
providing a balanced summary of the'Available scientific information on
climate change. However, the focus of the chapter should be the contribution
of changes in ozone concentration from climate modification, rather than
a review of all the radiatively-active gases that affect climate. The
chapter should place more emphasis on stratospheric, rather than tropospheric
processes. Linkages between ozone concentration changes and climate change
should be highlighted, and more attention paid to the effect of changes
in the vertical distribution of ozone to climate impacts. A separation
of direct and indirect effects would be useful. The chapter should focus
on the direct effects of ozone on climate, and briefly summarize the
indirect effects of trace gases whose concentrations affect both ozone
concentration and climate.
The document should define the eddy diffusion .roefficient. The
discussion of the importance of cloud cover in determining heat balance
should be expanded to at least half a page. More discussion of sensitivity
analysis and comparison of 1-D and 2-D model results would be appropriate,
and some discussion of further research using 2-D models to explore
sensitivity issues would be a useful addition to the chapter. Ocean
thermal lag is another important issue for determining climate response
and could use more discussion. Absolute concentration information should
be added to exhibit 6-3.
Chapter 7; Nonmelanoma Skin Cancer
The Subcommittee 'jen^rally agrees that this chapter is concise,
comprehensive, and well written. No deficiencies were noted in the
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breadth of the material reviewed in this chapter. The Subcommittee concurs
that considerable evidence supports the conclusion that increased UVB
would increase the incidence and mortality of nonmelanoma skin cancer.
Specific errors in the text were noted and discussed with appropriate
staff members.
Points requiring revision or remaining to be addressed in the body
of the text are the following:
1. There needs to be a clear statement of the potential impact of
increased UVB radiation on mortality from basal cell carcinoma and squamous
cell carcinoma.
2. The document should present a discussion of the validity of
existing mortality data for nonmelonma skin cancer and justification for
not basing predictions on these data.
3. The action spectra discussed in the chapter should be presented
diagrammatically. These include the action spectra for DMA, the modified
DMA action spectrum corrected for skin transmission, the RB meter action
spectrum, the cutaneous edema action spectrum, and the ereythema action
spectrum.
4. The chapter should justifiy the selection of the action spectra
used in the calculations.
5. The major problem with this chapter concerns the translation of
information within the chapter into statements concerning the expected
numbers of additional cancer cases and additional cancer deaths. The Sub-
committee requested an addendum that contains a list of the assumptions
underlying the calculated increases in cancer incidence and mortality and
some indication of the uncertainties contained within these predictions.
This addendum was received, and information from it needs to be incorporated
into the chapter. The addendum itself should be included in the appendix.
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6. The Subcommittee earlier suggested that a range of values for
incidence and mortality be utilized that would reflect predicted upper
and lower limits of increased UVB exposure, rather than using the central
case values. The staff have adopted this suggestion in the revised
Executive Summary; it needs to be incorporated in Chapter 7.
Chapter 8; Melanoma
In general, the Subcommittee agrees that this chapter provides a
conprehensive analysis of the evidence for and against the role of sunlight
and UVB radiation as a contributing factor in the development of cutaneous
melanoma in humans. Although there are still many uncertainties concerning
the relationship between UVB and melanoma, the weight of current evidence,
especially that provided by recent epidemiologic studies, favors the
conclusion that increased UVB radiation is likely to increase the incidence
and mortality of cutaneous melanoma in humans.
The points remaining to be addressed in this chapter are the following:
1. The staff has provided a statement of the assumptions underlying
the calculated increases in the incidence and mortality of melanoma to
the Subcommittee, along with justifications for the choice of critical
assumptions. This information needs to be incorporated into the chapter.
2. Two concepts need to be addressed in a revised chapter. The
first is that UVB radiation could contribute to the incidence and mortality
of melanoma without being a direct, causative agent responsible for the
transformation of normal melanocytes into cancer cells. The chapter
presently considers only the likelihood that UVB is a direct, causative
agent that induces cutaneous melanoma (See Figure 1). Second, the
chapter should emphasize that the term "melanoma" may actually encompass
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FIGURE 1:
Solar Ultraviolet and Malignant Melanoma of the Skin*
Solar UVR
\
Initiator
Inability to tan
(Skin types I & II)
Normal melanocyte
Promoter
?Systemic alteration
conducive to MM growth
(Rosdahl Effect)
Transformed cell
Melanoma cell
Clark's (dysplastic)
melanocytic nevus
Common acquired
melanocytic nevus
Altered
melanocyte
Defective DNA repair
(e.g. Xeroderma
pigmentosum)
Defective immunologic
surveillance
(e.g. following
renal transplant)
'in the white population
© T. B. Fitzpatrick
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a heterogeneous group of disease entities. The possibility that there
may be subsets of cutaneous melanoma that are caused, exacerbated or
completely unrelated to UVB should be raised in seeking explanations
••»•, •.:-
for the obscure relationship between sunlight exposure and melanoma
incidence.
3. Material included in this chapter as background information (pp.
8-7 to 8-13) also applies to chapter 7 and should be moved to the beginning
of chapter 7 and integrated with the information on action spectra.
4. The statements on the evidence supporting the conclusion that
solar radiation is one cause of melanoma (p. 8-4) need to be revised to
reflect more accurately the available scientific information.
Chapter 9; Immune System
The Subcommittee concurs with the general summary and conclusions
reached in this chapter. Specifically, there is reason to believe that
UVB radiation has the potential to modify immune responses in humans and
that such modifications could conceivably increase the incidence or
severity of some infectious diseases.
In general, the chapter is not well written or well organized, and
the Subcommittee made many detailed suggestions concerning appropriate
revision of the material to increase both its accuracy and its clarity.
However, the suggested revisions would not alter the general conclusions.
The Subcommittee notes several deficiencies in the presentation of
the work that require revision. They include:
1. The chapter does not clarify the fact that several different
immunologic consequencps of UVB irradiation occur, each of which nay havp
a different action spectrun. The available action spectra should be
illustrated in a figure.
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2. The document should state that UVB exposure produces systemic
..•»., •.;.
immunologic changes, as well as local changes within irradiated skin.
Restricting consideration to cutaneous infections may represent too narrow
a view of the potential consequences of increased UVB irradiation.
3. This chapter should state that, although UVB induced effects
on the imnune system might contribute to the induction and pathogenesis
of skin cancers, this fact is not likely to increase the predicted
estimates of increases in skin cancer incidence and mortality.
4. A point needing further emphasis is that most immunologic studies
to date have not assessed the effects of long-term, chronic UVB irradiation,
but have concentrated on acute effects.
Chapter 10; Cataracts
The chapter on cataracts and other eye disorders is ccnprehensive and
extremely well written. The Subcommittee does not believe that any major
study has been omitted in the bibliography, and EPA's assessment of each
paper appears to be accurate and balanced.
The findings are accurately stated and succinctly express the
legitimate concern that an increase in the flux of the UVB radiation may
lead to an increase in cataract incidence around the world. The Subcommittee
agrees with these findings and with the Agency's method of presenting them.
Near the end of the chapter, the document emphasizes the effect of
UVB radiation on the DN'A content of lens cells. This represents an
important point that is well treated in the chapter. Researchers have
emphasized the effect of irradiation on lens protein, and there has been
relatively little discussion of the impact of (JVB radiation on lens DMA.
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The selection of epidemiologic studies relevant to this issue is
• • V.,
correct and well presented. A major limitation which EPA staff may wish to
address is that all of the studies are handicapped by the lack of an
individual dose meter to measure the ultraviolet exposure on a case by
case basis. To date, we have not had such an instrument for use in prospective
studies and, therefore, have relied on general radiation levels at different
latitudes to estimate the exposures of individuals living at those latitudes.
The discussion of the multifactorial nature of senile cataract formation
is accurate. Within one to three years, three major studies of the risk factors
in senile cataract formation will be completed in Boston, Parma, Italy
and Delhi, India. These studies will also indirectly address the question of
ultraviolet exposure and cataract type and severity.
Chapter 11; Terrestrial Effects
The Subcommittee agrees that this chapter presents a balanced overview
of available material. The only concern is that the summary statements
for this chapter are not balanced and tend to emphasize the negative
aspects of the material.
This chapter reviews the available information concerning UVB
radiation effects on plants as this relates to the question of potential
effects of ozone reduction. Ultraviolet screening tests with agricultural
species and cultivars, as well as actual field trials using UV lanps, are
described.
Complicating factors such as the appropriate action spectra to use
in evaluating ozone change and effects of UV lamp supplementation on the
resulting ozone reduction simulations, plant acclimation to enhanced UV
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radiation, and interactions with other environmental factors such as
••V.,
drought and carton dioxide enhancement are discussed. Interpretation of
the data and caveats concerning limitations in drawing conclusions from
these data are offered.
Overall, the text, considering the length allotted, is reasonably
complete and balanced. On the other hand, the summary tends to accentuate
results supporting the detrimental effects of ozone reduction. This
results in a statement of findings and a summary which are much less
balanced than the text itself.
Chapter 12; Aquatic Effects
This is a very thorough, well written chapter. It accurately conveys
the extant information on the effects of solar ultraviolet radiation on
aquatic systems and explains the difficulties in extending these data to
an assessment of the effects of stratospheric ozone reduction. There are
a few passages describing laboratory experiments where it is not clear
whether the ultraviolet radiation simulating a certain ozone reduction
is calculated as that striking the water surface or at some depth in the
water. Occasionally, experimental results are not always clearly
distinguished from calculated impacts. We believe the issue of large
migrations of aquatic populations, e.g. 30° latitude, while illustrative,
are unrealistic and could he misleading. These could be eliminated
without detracting from the content of the chapter.
As with Chapter 11, assessing the impacts of stratospheric ozone
reduction on communities and ecosystems has received less attention and
research than issues such as skin cancer. The Subcommittee believes the
potential impacts on aquatic and terrestrial food chains, and the potential
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effects on the equilibrium of plant and animal assemblages, are just as
••»., -.*.
important as the more intensively studied human effects. This importance
needs to be conveyed not only in Chapters 11 and 12 but also in the summaries
of these chapters and in the Executive Summary.
Chapter 13; Polymers
The economic analysis on polymer damages is based on the assumption
of a small increase in the destruction rate of the polymer material
multiplied by a large value for the inventory of material in place. The
assumptions of the analysis should be stated more clearly, and the
uncertainties in this economic analysis should be highlighted. Discounting
future damages should be discussed.
The rate of polymer degradation depends on the actual action spectrum,
which is undoubtedly different for each kind of polymer. These spectra
should be measured experimentally before any confidence can be placed in
the predictions. In many cases, it would be expected that UVB contributes
only a small fraction of the total rate and, therefore, -the rate would
be very insensitive to changes in stratospheric ozone.
The estimates presented by EPA are reasonable in the absence of real
data, but the required measurements are not difficult and should be made.
Chapter 14; Potential Effects on Tropospheric Ozone
The document should present a more extensive introduction to the
discussion of health and welfare effects of tropospheric ozone. The
modeling discussion now found on page 14-11 should be expanded and placed
near the front of the chapter. The material on page; 9 should be shown as
a graph. All three citif-s should be shown in the figure, page 14-12.
The word "snog" is colloquial and should be avoided. The discussion of
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the spectral resolution of UV needed for photochemistry should be strengthened.
The question of what happens to global tropospheric ozone as UVB increases
.••»••«
needs expanding (sane discussion of this issue is found in Chapter 5).
The limitations of the analysis in this chapter should be stressed more.
The effect of CFC emissions reductions on tropospheric ozone .should be
discussed. Discussion of mass flux and other interactions between the
troposphere and stratosphere should be added.
Chapter 15; Sea Level Rise
The Subcommittee reached a consensus that this chapter adequately covers
the subject material. However, additional qualifying statements need to be
added to the summary statements.
This chapter requires more careful caveats in the summary and findings
and references to major reports on sea level rise. Assumptions should be
clearly stated. The range of 50-200 cm. of sea level rise seems narrow in
view of the many uncertainties on climate change, and the basis for
calculating this range should be made explicit. The implications for loss
of land of a 1 meter rise might be stated.
More discussion of the economic aspects of sea level rise would be
desirable.
Chapter 16 and Appendix B: Impacts of Climate Change
The discussion focuses mainly on North America and Europe. The Subcom-
mittee encourages the staff to present more information on the rice crop
and other aspects of agriculture in the developing world. The document
should emphasize that uncertainty in the regional effects is substantial.
Catastrophic episodes such as floods, droughts, and severe storms may
cause much of the damage, 2nd these episodes cannot be reliably predicted.
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This chapter represents a compilation of potential consequences of global
warming. These synoposes address potential changes in forest and other
vegetation distributions, agricultural implications, hydrological cycles
and weather effects on morbidity and mortality. This collection of
vignettes is, of course, one of only many possible compilatio"hs since
global wanning can have many ramifications.
Chapters 17 and 18; Integrating Model and Results
The objective of the integrating model is to provide a framework
within which the implications of alternative assumptions and policies can
be identified. The Subcommittee finds this objective commendable and
supports EPA's effort to make the assumptions and the logic used in the
risk assessment explicit and readily available to interested members of
the public. The integrating model appears to be a good vehicle for
summarizing the assumptions and calculations described in previous chapters
of the risk assessment. An integrating model such as this represents an.
excellent tool for examining the implications of alternative assumptions—
"what if" scenarios—and for investigating the importance of uncertainties
in different areas of science for policy and research conclusions.
The logic and implementation of the integrating model as a computer
code were the subject of a factfinding meeting of four members of the Sub-
committee on January 14, that also included John Hoffman of EPA, and
representatives from EPA's contractor, ICF. Prior to the meeting, these
Subcommittee members received a listing of input files and the FORTRAN
computer code for the model. Other technical documentation for the model
does not exist at this time. Based on the written material in Chapter 17
and the discussion at this meeting, the Subcommittee believes that the model,
and the results of the nodel calculations presented in Chapter 18, appear
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reasonable. However, the model has not undergone detailed review outside
of the EPA/ICF team that developed--it, and it has not been documented and
placed in a form accessible to outside parties.
The material in Chapters 17 and 18 will need substantial revision as
the analysis with the integrating model is revised to meet recommendations
from the Subcanmittee regarding the Executive Summary and the other
chapters. The revised versions of Chapter 17 and 18 should stress the
structure of the model and the insights obtained from the analysis that
has been carried out using the model, including: what issues were addressed
and not addressed in the model, and how issues not included in the
integrating model could affect overall conclusions. The sensitivity analysis
and the interpretation of the sensitivity analysis should be expanded, and
conclusions on the importance of uncertainty in various areas of science
made more explicit. Wiat areas of science are most significant for policy
conclusions and as targets for future research? As one example, the Sub-
canmittee judged that impacts on plants and aquatic organisms are among
the most important potential effects of ozone depletion, yet these impacts
are included in the model only by considering changes in one crop, soybeans,
and one species of aquatic organisms, anchovies. More comprehensive quanti-
tative assessment of potential impacts on plants and aquatic organisms should
be identified as a target for further research and analysis as the risk
assessment methodology is further refined. As another example, the
integrating model does not include mechanisms relating to the recent
observations of ozone depletion over Antarctica. As a result, it would
be inappropriate to cite the results of the model as indicating that
changes exceeding a few percent in stratospheric ozone concentration will
not take place until well into the next century.
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Hie integrating model should h"ave extensive''"additional technical
documentation. A listing of the FORTRAN code is inadequate as a basis for
communicating the details of the model. Many parties interested in
stratospheric ozone risk assessment may find it valuable to have access
to the integrating model in order to carry out analyses of the impacts of
CPC emissions on ozone and climate change. The Subcommittee recommends
that EPA provide adequate technical documentation of the integrating
model in the form of appendices to the risk assessment, and that EPA
include in its future plans the development of a "user-friendly" version
of the integrating model that can be placed in the public domain for use
by others.
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