United State:*
Environmental Protection
"Agency
Office of Air and Radiation
Washington O.C. 20460
EPA 400/1-87/001A
December 1987
Assessing the Risks of
Trace Gases That Can
Modify the Stratosphere
Volume I:
Executive Summary

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Assessing The Risks of Trace Gases
 That Can Modify The Stratosphere

    Volume I: Executive Summary
 Senior Editor and Author John S. Hoffman
         Office of Air and Radiation
    U.S. Environmental Protection Agency
         Washington, D.C. 20460
            December 1987
                            U.S. Environmental Protection Aser
                            •: '-'.•,i -% L'brary (".PL-16)
                            ': •.  •.'. D.^.'born SWeet, Room -i670j
                            CLioago,  IL  60604

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    Many people made this document possible.

    A Science Advisory Board (SAB) panel chaired by Dr. Margaret Kripke and co-
chaired by Dr. Warner Horth conducted an extensive and constructive review of
diis document.  Members of die panel provided important insights and assistance
in die assessments development.  Members of the panel are:

    Dr. Martyn Caldvell (Utah State University)
    Dr. Leo T. Chylack, Jr. (Center for Clinical Cataract Research)
    Dr. lien Dak Sxe (A.E.&.. Inc.)
    Dr. Robert Dean
    Dr. Thomas Fitzpfttriek (Massachusetts General Hospital)
    Dr. James Friend (Drexel University)
    Dr. Donald Bunten (University of Arizona)
    Dr. Warren Johnson (national Center for Atmospheric Research)
    Dr. Margaret Kripke (Anderson Hospital and Tumor Institute)
    Dr. Lester Lave (Carnegie-Melon University)
    Dr. Irving Miatzer (World Resources Institute)
    Dr. Warner Hordi (Decision Focus, Inc.)
    Dr. Robert Watson (Rational Aeronautics «nd Space Administration)
    Dr. Charles Yentsch (Bigelev Laboratory)
    Dr. Terry F. Yosie (U.S. turiiiuimmmtil Protection Agency)

The panel's contribution to die process of protecting stratospheric ozone has
been critical.  We also want to diank Terry Yoaie, Director of die Science
Advisory Board, for setting up and helping to run die panels, and Joanna
Foellaer for helping to organize meetings.
    Other scientists and analysts, too numerous to name, provided reviews of
early drafts of die chapters.

    Production assistance, including editing, typing, and graphics, was
provided by die staff of ICF Incorporated, including;

    Bonita Bailey
    Susan MacMillaa
    Mary O'Connor

Maria Tikmff of die U.S. Environmental Protection Agency, coordinated
logisticmf parts of diis
    The cover photograph was supplied by die National Aeronautics and Space
Administration.

    Technical support documents (Volumes VI. VII, and VIII) have been published
along with die first five volumes of die Risk Assessment.  These documents are
not part of die official Risk Assessment, and have not been reviewed by die
SAB.  Their publication is simply to assist readers who wish more background
dian available in die Risk Assessment.

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Alan F. Teraaura
Department of Botany,
University of Maryland,
College Park. MD  20742

Dennis Tirpak
U.S. Environmental Protaction Agancy.
401 M Street, S.V..
Washington, DC  20460

Jia Titus
U.S. Environmental Protaction Agancy,
401 M Street* S.W.,
Waahington. DC  20460

John B. Walla
Tha Bruca Coopany,
Suita 410. 3701 Hanachuaatta Ava.( B.V..
Vaahington, DC  20016

G. Z. ihittan
Syataaa Applications, Inc.,
101 Lucua Vallay Road,
San Rafaal, CA 94903

Robert Vorrast
Corvallia Environaantal Raaaareh Laboratory,
200 Southwaat 35th Straat,
Corvallia, OR  97333

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                       List of Conerlbators
Craig Ebarr
ICF Incorporated,
9300 Laa Highway.
Fairfax, VA  22031

Sarah Foatar
ICF-Claaant,
9300 Laa Highway,
Fairfax, VA  22031

Miehaal J. Ctbba
ICF Ineorporatad,
9300 Laa Highway,
Fairfax. VA  22031

Ravin Haarla
ICF Ineorporatad,
9300 Laa Highway.
Fairfax, VA  22031

Brian Hicks
ICF Ineorporatad,
9300 Laa Highway,
Fairfax, VA  22031

Patsy H. Lill
Dapartaant of Pathology,
Univarsity of South Carolina School of Madicina,
VA Bldg No. 1, Carnat Farry Rd,
Coluabia, SC  29208

Janica Longstrath
ICF-Clamant,
9300 Laa Highway,
Fairfax, VA  22031

Hail Fatal
U.S. Environswntal Protaetion Agancy,
401 H Straat, S.W.,
            DC  20460
••ft M. Pitchar
V.T; ttnrirooMntal Protaetion Agancy,
401 M Scraat, S.tf.,
Vashington, DC  20460

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                                  ORGAHXZalXOH*

    This document summarizes a multi-volume assessment of tha risks of
stratospheric modification.  Since the early 1970s, scientists have been
concerned that huaan activities could altar the composition of the stratosphere,
leading to raductions in the quantity of ozone protecting earth from the sun's
ultraviolet-B (UVB) radiation.  If such raductions in ozona levels occurred,
public health and welfare would' be harmed.

    Substantial scientific progress has baan made since concern about ozona
depletion was first raised.  Ibis document represents a synopsis of currant
undarstanding of how ataospheric composition may changa, tha affects this changa
is likely to hava on ozona abundance and its vertical distribution, and tha
impacts of these changes in ozone en skin cancer, cataracts, suppression of the
iamune system, polymers, plants, sad aquatic systems.  It-also examines related
changas in climate and tha potential impacts of climate changa on sea level
rise, agriculture, human health, water resources, and forests.

    Despite significant improvement in our undarstanding of these issues,
substantial uncartaintias remain.  Ibis risk assessment identifies and discusses
these uncertainties and, where possible, eetiaatea quantitatively their
potential significance.

    Following a brief introduction, this summary volume is organized into five
sections:

        o   Summary findings (page ES-5)',

        o   Changes in atpnospharie composition covers chapters 2, 3, and
            4 (page ES-15);

        o   Potential eh^ttgas iti ozone and climate covers chapters S 'and
            6 (page ES-23);

        o   Hunan health, welfare, and environmental effects  covers
            chapters 7 through 16 (page ES-32); and
                                 nt of rifles vith  tacagracad •odel  covers
            chapters 17 and 18  (page ES-54).

Readers desiring greater detail are encouraged to  refer to the five-volume risk
assessment and tha three volumes of die rr^Mt'**'1  support reports.
    This_wssaary concludes with a briaf listing of aajor prior assassaents of
this

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                               TABLE OF UJHfUIS

                                                                      PAGE
VOLDME I

ACKNOWLEDGMENTS	,	   i

ORGANIZATION	  ES-l

INTRODUCTION 	  ES-2

SUMMARY FINDINGS 	.'....  ES-5

CHARGES IN ATMOSPHERIC COMPOSITION  	;	  ES-15

POTENTIAL CHANGES IN OZONE AND CLIMATE	  ES-23

HUMAN HEALTH, WELFARE. AND ENVIRONMENTAL  EFFECTS  	  ES-32

QUANTITAnVE ASSESSMENT OF RISKS WITH INTEGRATED MODEL	  ES-54

TABLE OF CONTENTS FOR FULL RISK ASSESSMENT	  ES-65

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     Current scientific theory and evidence indicate that continued increases in
 the concentrations of a variety of trace gases in the atmosphere .are likely to
 aodify the vertical distribution and coluan abundance of stratospheric and
 tropospherie ozone.  Changes in the total abundance of column ozone would alter the
 flux of ultraviolet radiation reaching the surface of the earth, and consequently
 affect public health and welfare.  Scientific evidence indicates that increases in
 ultraviolet>B radiation (DV-B) would alter skin cancer morbidity and Mortality,
 increase cataracts, and probably suppress the human insuine system.  Evidence also
 supports the conclusion that such increases could reduce crop yields and alter
 terrestrial and aquatic ecosystems.  Scientific theory and studies also support the
 conclusion that polymers would be degraded sore quickly and that urban tropospherie
 oxidants would increase as a result of UV-» increases, although additional
 scientific study is needed to validate the possible effects on tropospherie air
 quality.  The dimensions of many of these risks are at this time unquantifiable.
 Exhibit ES-1 susnarizes these relationships.

     Changes in trace gases that can modify the stratosphere can be expected to
 contribute to climate change in three ways:  they are all greenhouse gases that
 would increase global warming; by modifying vertical distribution of ozone, they
 could change the Earth's radiative-balance and climate dynamics; by adding.water
 vapor to the stratosphere, one of these gases (methane) directly adds to the
 stratosphere's greenhouse or warming capacity,  the effects of global warming
 include changes in weather and climate patterns; rises in sea level; changes in
 forests, hydrologic processes, and agriculture; and a variety of associated
 impacts.

     Current science projects that changes in ozone and climate will occur slowly
 enough in the next decade that it is unclear that monitoring systems will  be
 capable of clearly detecting change, or of attributing changes to particular trace
 gas increases.  Because of the large lags expected between the emission of gases
 and their ultimate effect on ozone and climate, the stabilization of atmospheric
 concentrations and the prevention of further change would require large decreases
 in trace gas emissions.  Consequently, while monitoring can provide a valuable
 system to test model projections, as well as to better understand atmospheric
 systems, except in the ease of a larger than expected aaospheric change,
 monitoring cannot be expected to provide definitive information about the  nature of
 future risks.  With the exception of Antarctic ozone depletion, an unexpected and,
 at this time, unexplained phenomenon, past monitoring supports current models.
 which project that ozone depletion and climate change are likely to occur  in the
 face of grafJCa. in the concentrations of trace gases.2- It is important to recognize
     1 This Risk Assessment was written before the results of the two Antarctic
campaigns were available and has not 'been revised to consider them.  It now appears
that the Antarctic ozone hole is at least partly  caused by man-made  chemicals.   The
implications for ozone in the rest of the world are unclear,  depending  on whether
the loss mechanisms operating in Antarctica are likely to operate elsewhere and on
whether Antarctic losses themselves might have global  implications.  Consequently,
until those issues are resolved, we cannot conclude that the  'hole'  is  a portent of
things to come elsewhere on the Earth.  In the rest of this summary  the original
Risk Assessment findings on Antarctica and trends are  kept intact.

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                            EXHIBIT E8-1
           Tho Baala for Conoorn About CFCa and Oxono Ooplotlon
 CD Production of CFCa
 (2) Emlaalona thon ooour

 O) Conoontratlona buNd up
 (4) Slow tranaport to atratoaphoro

 (0) Pbotodlaaoolatlon of CFCa
  roloaaoa chlorbio
 ft) CMorlno oatalytleaNy
  roduooa oxono
 (7) Oiono doplotlon oauaoa
  ohangoa In UV-B
 (B) CFCa and ftolumn reorganization
  ohanga tha attmata
Cauaal Chain:
                        (f) Incroaaoa In UV-B produeo affoeta
                          For oxamplo:
                                  On okln oanoor

                            l"*
                                                  On Larval Northorn Anchovy
                                    INCKASCO WV-i MWtfMM (»l
 Production
EmJtilont
Conoon-
tratlona
                                            Atntoaphorlo
                                            Rotponao
                                          **  UV-B -
                                          and oHmato
                                                                                    C?
 Sourc«: HAS (|tf«), Icosto (I9M), mn* Hunt.t. R.upp .nd Uylor (INt).

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                                      ES-4
chat "by ch« tine ie is possible to detect decreases ir. jzone concentrations
with a high degree of confidence,  it n»y ba too l*ta to instituta corrective
measures that would reverse this trend*  (EPA Science Advisory Board, March
1987).


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                                     ES-5
last and Poaaible Future

1.  Considerable research has taken place since 1974 when die theory linking
    chlorine from chlorofluorocarbons (CFCs) and depletion of ozone waa first
    developed.  While uncertainties remain, die evidence to date continues to
    support the original theory diat CFCa have the potential to decrease
    stratospheric ozone.

2.  Atmospheric measurements show that the chemical composition of the
    atmosphere -- including gases that affect ozone •• has been et
    Recently measured annual rates of growth in global
    concentrations of trace gases that influence ozone include:  CFC-11:
    5 percent; CFC-12: 5 percent; CFC-113: 10 percent; carbon tetrachloride: 1
    percent; methyl chloroform: 7 percent; nitrous oxide: 0.2 percent; carbon
    monoxide: 1 to 2 percent; carbon dioxide: O.S percent; and prtfraw 1
    percent.  More limited measurements of Halon 1211 show recent annual
    increases of 23 percent in atmospheric concentrations.

3.  CFCs,  Halons, methyl chloroform, and carbon tetrachloride release chlorine
    or bromine into the stratosphere where they act as catalysts to reduce the
    net amount of ozone.  In contrast, carbon dioxide and median* either add to
    die total column of ozone or alow die rate of depletion.  The effect of
    increases in nitrous oxide varies depending on die relative level of
    chlorine.

4.  CFCs,  methyl chloroform, carbon tetrachloride, and Halons are industrially
    produced.  Emissions of mediane, carbon dioxide, and nitrous oxide occur
    from bodx human activity and die natural biosphere.  Because all these gases
    (with die exception of mediane and mediyl chloroform) remain in die
    atmosphere for many decades to over a century, emissions today will
    influence ozone levels for more than a century.  Also, aa a result of diese
    long lifetimes, concentrations of diaae gasea will rise for more than a
    century, even if emissions remain at constant levels.  For example, to
    stabilize concentrations of CFC-11 or -12 would require a reduction in
    .current global emissions of about 85 percent.  (Exhibit ES-2 demonstrates
    effects of varioua reduction levels on CFC-12 concentrations).
5.  In order to assess risks, scenarios of atmospheric change ware evaluated
    usingledels.  For CFCs, methyl chloroform, carbon tatrachloride, and
    Halons, demand for goods that contain or are manufactured with these
    chemicals (e.g., refrigerators, computers, automobile air conditioners) and
    the historic relationship between economic activity and the uae of these
    chemicals were analyzed.  Theae analysea indicate that in the abaence of
    regulation, the uae and emissions of these compounds are expected to
    increase in the future.  However, for purposes of analyzing risks, six
    •what-if* scenarios were adopted that cover a greater range of future
    production of ozone-depleting substance than is likely to occur.

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                                ES-6
                            EXHIBIT KS-2

                  CFC-12:  AtBocpfaaric Cnnranrraciona
                 from Diffaranc Eadaaion Trajactoriaa
I
1
S
                                                           Constant
                                                           emissions
                                                           15%  Cut
                                                         50% Cut -
                                                         85% Cut
      1930
                       1985
2100
                ration* of CFC-12 will c<
                                            ua to riaa unlaaa aaiaaiona ara
Ataoapnaric • i-^ii  —w—^-»^ »— —— —  — _— 	
cut.  Holding aadsaiona constant at today's l*v»l or avan 15 parcant or 50
parcant lowar would »till allow ataoapharie concantrationa to grow.  Only a cut
of 85 parcant or aora could atabiliza ataoapharic coneantrationa.

Sourca:  Hoffman, 1986.

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                                      ES-7


Modal Projection for Ozone Changes

6.  Ataospheric chemistry models were used to assess the potential effects of
    possible; future changes in atmospheric concentrations of trace gases.   Thes
    node Is attempt to simulate processes that influence the creation and
    destruction of ozone.  While the Models replicate many of the
    characteristics of the atmosphere accurately, they are inconsistent with
    measured values of other constituents, thus lowering our confidence in thei
    ability to predict future ozone changes accurately.

7.  Based on the'results fro* these Models, the cause of future changes in ozon
    will be highly dependent on future eaissions of trace gases.
    One-dimensional models project that if the use of chlorine and bronine
    containing substances remains constant globally, and other trace gas
    concentrations continue to grow, total column ozone levels would at first
    decrease slightly, and then would subsequently increase.  If the use of CFC
    continues to grow at past rates and other gases also increase at recent
    rates, substantial total coluon ozone depletion would occur by the middle o
    the next century.  If the use of CFCs stays at current levels and the growt
    in the concentrations of other trace gases slows over tine, model results
    indicate total eoluan ozone depletion will also occur.  (Exhibit
    ES-3 shows various aodel projections for "what-if" scenarios.)

8.  In all scenarios examined, substantial changes are expected in the vertical
    distribution of ozone.  Ozone decreases are generally expected at higher
    altitudes in all scenarios in which CFC concentrations increase.  Ozone
    increases are expected at lower altitudes in soae scenarios exaained due to
    increases in asthane concentrations.  Such changes aay have important
    cliaatic effects.

9.  Two-dimensional (2-D) aodels provide information on possible changes in
    ozone by season and by latitude.  Results from 2-D aodels suggest that
    global average depletion could be higher than estimates froa a
    one-dimensional (1-D) model for the same scenario.  Moreover, the 2-D model
    results suggest that average annual ozon* depletion above the global averag
    would occur at higher latitudes (above 40 degrees), while depletion over
    tropics is predicted to be lower than tfam global average; and depletion
    would be greater in the spring than tae manual average.  Uncertainties in
    the representation of the transport of chemical species used in 2-D models
    intremmeee uncertainty in die magnitude of the latitudinal  gradient of ozon
    depletion, but all 2-D models project a gradient.
10. Measurements of ozone concentrations are another valuable tool  for assassin
    the risks of ozone modification.  Based on analysis of data for over  a
    decade from a global network of ground-based monitoring stations, ozone
    concentrations have decreased at mid-latitudes in the upper and lower
    stratosphere and increased in the troposphere.  According to  studies  using
    ground-based instruments, there appears to have been no statistically
    significant change in column ozone between 1970 sad 1983.  High altitude,
    lower stratospheric, and total column trends are roughly consistent with
    current two-dimensional aodel predictions.

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                                     ES-8



                                 EXHIBIT ES-3
              Global Awaraga
      10.0
     •50.0
         1985     2009     2020    2046     2065     2089
*This acanario assunas no growth in global production of ozona daplatars, and
concantrationa of othar traca gasaa ara prawntad £roai rising to an aaount
graatar than that eoapatibla with an incraaaa  in •quillbriiai global tavparatura
of 3.0°C ± 1.5«C«y 2075.
—  Currant 1-D awdals accurataly raflact global  daplation; Antarctic ozona hola
    has no iapact on global ozona lavals.

..  Graanhouaa gaaas that countar daplation grow  at biatorically-axtrapolatad
    rataa.

--  Growth rataa for ozona daplatars ara  for global amisslona; it is asauawd
    that anisaiona do not incraaaa aftar  2050.

--  Ozona daplation limicad to 50 parcant.

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                                     ES-9
11. Recent evidence indicates that since the late 1970s substantial decreases
    ozone (up to 50 percent) have occurred over and near Antarctica during its
    springtime.  These losses have been verified by different measurement
    techniques, and different theories have been suggested to explain the caus
    of the seasonal loss in ozone.  Insufficient data exist to state whether
    chlorine and bromine are responsible for die observed depletion, or whethe
    some other factor is the cause (e.g., dynamics or changes in solar flux th
    •leers HOx).  Furthermore, even if Ban-Bade chemicals are the cause of the
    phenomenon, stratospheric conditions surrounding Antarctica are different
    from the stratospheric conditions for the rest of the world, so that it
    cannot be assumed that similar depletion would occur elsewhere.  Models di
    not predict the Antarctic ozone depletion, however.  Consequently, the
    change in Antarctica suggests that ozone, abundance is sensitive to yet
    unknown natural or anthropogenic factors not yet incorporated in current
    models.                                 .

12. Preliminary data from Nimbus-7 suggest a decrease in global ozone
    concentrations (4-6 percent) may have occurred during the past several
    years.  These data have not yet been published and require additional revi<
    and verification.  If verified, further analysis would be required to
    determine if chlorine is responsible for the reported decrease in ozone
    levels, or whether the decrease is due to other factors or reflects
    short-term natural variations.
Potential Health Effects from Osoos Depletion

13. Decreases in total column ozone would increase the penetration of
    ultraviolet-B (UV-B) radiation (i.e., 290-320 nanometers) reaching the
    earth's surface.  (Exhibit ES-4 shows relative increases in UV-B at 295,
    305, and 315 nanometers.)

14. Exposure to UV-B radiation has been implicated by laboratory and
    epidemiologic studies as a cause of two common types of skin cancers
    (squamous cell and basal cell).  It is estimated that there are more than
    400,000 new cases of these skin cancers each year.  while uncertainty exist
    concerning the appropriate action spectrum (i.e., the relative biological
    effectiveness of different wavelengths of ultraviolet radiation), a range <
    relationships was developed that allows increased incidence of these skins
    cancers Co bo estimated for future ozone depletion (these cancers are also
    refer*** to as nonmelanoma skin cancers).
          *
IS. Studied predict that for every 1 percene increase in UV-B radiation (which
    corresponds to less than a 1 percent decrease in ozone because the amount  <
    increase in UV-B radiation, depending on die action spectrum, is greater
    Chan rather than proportional to ozone depletion), nonmelanoma skin cancer
    cases would increase by about 1 to 3 percent.  The mortality for these  fon
    of cancer has been estimated at approximately 1 percent of total cases  bas<
    on limited available information.

16. Malignant melanoma is a less common form of skin cancer.  There are
    currently approximately 25,000 cases per year and 5,000 deaths.  The
    relationship-.between cutaneous malignant melanoma and UV-B radiation  is a
    complex one.  Laboratory experiments have not succeeded  in transforming^.  _

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                                    ES-10
                                 EXHIBIT ES-4

                      Incraaaas in Ultraviolat Radiadon
                      Dua to a 1 parcant Ozooa Daplation
     4-
     2-
     1 -
             295
3OS
313
                                        (nm)
Ozona daplation would laad to increaaaa in tha aaount of ultrcviolat radiation,
particularly at tha hara£ul lovar wavalangAa, Chat raaehaa tha aart±'» aurfaea.
Sourea: Estioates baaad on tha ozona-UV nodal davalopad by Sarafino and
        Fradarick (1986).

-------
                                     ES-11
    aalanocytaa with UV-8 radiation.  However, raeant epidemiological studies.
    including large case control studies, suggest that DV-B radiation plays an
    important-role in causing melanoma.  Uncertainties in action spectrum,  dos
    measurement, and other factor* nacasaitataa the uaa of a range of
    dose-response estimates.  Taking into account such uncertainties, recent
    studies predict that for each 1 pareant change in 0V-E intensity, the
    incidence of melanoma could increaaa from 0.5 to 1 percent.
17. Studies have demonstrated that UV-B radiation can auppresa the
    response system in «rfMl • and possibly h"~T*ir.  While UV-B-induced iamune
    suppression baa been linkad Co chronic reinfection with herpes simplex vin
    and laiahmaniaaia in animals, its poaaible impact on other diseases and it;
    impact on humans haa not bean studied.

18. Increases in exposure to UV-B radiation are likely to increaae the incident
    of cataracta and could adversely affect die retina.

Potential Iffacts on Plants and Aquatic Organisms

19. While studies generally shov adverse impacts on planta from increased UV-B
    exposure, difficulties in experimental daaign, the Hyf*** number of speci<
    and cultivars tasted, and the complex interactions batwaen planta and thai:
    environments prevent firm conclusions from being made for the purpose of
    quantifying risks.  Field studies on soybeans suggest that yield reduction:
    could occur in some cultivars of soybeans, while erridanca from laboratory
    studies suggest that two out of three cultivars are sensitive to UV-B.

20. Laboratory studies with numerous other crop spaciaa also show many to be
    adversely affected by UV-B.  Increased UV-B has baan shown to alter the
    balance of competition between plants,  while the magnitude of this change
    cannot be presently estimated, the implications of UV-eltared, competitive
    balance for crops and waads and for nonagricultural areas such aa forests,
    grasslands, and desert may be far reaching.

21. Aquatic organisms, particularly phytoplankton, zooplankton, and the larvae
    of many fishes, appear to be susceptible to harm from increased exposure t<
    UV-B radiation because they spend at least part of their time- at or near
    surface waters.  However, additional raaaarch is needed to bettor wnderstai
    the ability of these organisms to mitigate advetsa affects and any possiblt
    impliavtiona of changes in I'l'iamnnf ry composition as more susceptible
    organ**** decrease in numbers,  Tha Implications of possible affects  on thi
    aquatic food chain requires additional study.
Effaces of Depletion on Tropoapfaarle OBona and Polymers

22. Research has only recently baan initiated  into tha affects of UV-B on the
    formation of tropospheric ozona (an air pollutant with negative health  and
    plant effects).  An initial chambar and modal study shows that tropoapheri<
    ozona levels could increaaa, resulting in  additional urban areas being  in
    non-compliance with national Ambient Air Quality Standards.  Tha increaae  i
    UV-B would also produce ozona peaks closer to urban canters, expoaing larg<
    populations to unhealthy concentrations of tropospheric  ozona.  The  same
    study also predicts substantial increaaa in hydrogen peroxide, an acid.rail
    precursor.  However, because only one study has been done, the results, ausi

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                                     ES-12


    be treated with eaucion.   Additional  theoretical and empirical work will be
    needed to verify these projections.

23.  Research indicates that increased exposure Co UV-B would likely  cause
    accelerated weathering of polymers, necessitating polymer refemulation or
    the use of stabilizers in SOM products,  and possibly curtailing use of
    certain polymer* in SOM areas.
24. The Rational Academy of Science* (HAS)  has recommended diat 1.5°C to 4.5°C
    represents a reasonable range of uncertainty about die temperature
    sensitivity of die Earth to a doubling of C02 or an increase in odier trace
    gases of die equivalent radiative forcing.  While some of die trace gasea
    discussed above deplete ozone and others result in higher ozone levels, all,
    on net, would increase die radiative forcing of die Bardt and would
    contribute to global warming.

25. Using die middle of die HAS range for die Eardi's temperature sensitivity
    and a wide range of future trace gas growdi (e.g., from a phase-down of CFCs
    by 80 percent from current levels by 2010 to a 5 percent annual increase
    through 2050; C02 doubling by 2060; R20 increasing at 0.2 percent; CH4
    increasing by 0.017 ppm/year through 2100), equilibrium temperatures can be
    expected to rise from 4°C to 11.6°C by 2075.  Of dlis amount, depending on
    die scenario, CFCs and changes in ozone would be responsible for
    approximately 15-25% of die projected climate change.  (See Exhibit ES-5)

26. In most situations, inadequate information exists to quantify die risks
    related to climate change.  Studies predict that sea level could rise by
    10-20 centimeters by 2025, and by 55-190 centimeters by 2075.  Such
    increases could damage wetlands, erode coastlines, and increase damage from
    storms.  Changes in hydrology, along widi warmer temperatures, could affect
    forests and agriculture.  However, lack of information about die regional
    nature of climatic change makes quantification of risks difficult.  A study
    suggests diet rising temperatures could adversely affect human health if
    acclimatization lags.                        *
                                                4


27. To perfotsJHfca computations necessary to evaluate die risks associated with
    stratosphesK modification, an integrating model was developed to evaluate
    die Joint implications of scenarios or estimates for: (1) potential  future
    use of CFCs and change in other trace-gases; (2) ozone change as a
    consequence of trace gas emissions; (3) changes la UV-B radiation associated
    widi ozone change; and (4) changes in akin cancer eases and cataracts
    associated widi changes in UV-B radiation.  Potential impacts of
    stratospheric modification that could not be quantified were not addreaaed
    by die integrating model.  On a global basis, die risks of ozone depletion
    may be greatest for plants, aquatic systems and ^he  immune system,  even
    though knowledge to asaess dteaa efforts is much less certain dian for skin
    cancers.

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                                          ES-13
                                       EXHIBIT ES-5
              Equilibria T<
         trature
         jig 3.0*C
                              for the Six teission Scanaric
                                 for Doubled C02*
     12.0
o
y
•

o
1
                                                                           5.0% Growt
                                                                         ;: 3.8% Growt
                                                            2.5% Growt

                                                            1.2% Growt
I                                                               Growth
                                                              % Raduct
        1985
1995
2005
2015
                                    2025
                            2035
                             2045
                             2055
2065
2075
         * Cooputad assuming that cha cliaata sensitivity to a doubling of carbon
     dioxida  is 3*C.   This assuoption is in tha viddla of tha HAS rang* of l.S*C to
     4.5*C (saa Chaptar 6).  Nota that Cha actual waning that Bay ba raalized will
     lag by savaral daeadas or aora.  To eoaputa tha aquilibrium warming associated
     with high or low HAS aatiaatas aultiply tha y  axis  'taaparacura change'  by 1.5
     or  0.5.

         Growth levels refer to global estimates of production of all ozone
     dapleters.             .                          -

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                                     ES-14


28.  Uncertainty about future risks is partly driven by the rata at which CFC and
    Halon lisa and other trace gases grow or decline.  For this reason,  a vide
    range of "what-if" scenarios of potential CFC and Halon use and growth in
    trace gas concentration was evaluated.  To reflect the large uncertainties,
    the scenarios range froa an 80 percent global phase-down in the use of CFC*
    by 2010 to an average annual growth in use of S percent par year fro* 1985
    to 2050.  For ozone-Modifying gasas other than CFCa, scenarios were based en
    recently Measured trends, with uncertaintiea being evaluated by considering
    a range of future emissions and concentrations.

29.  Across the wide range of "what•if" scenarios considered, ozone change by
    2075 could vary froa aa high as over SO percent ozone depletion to increased
    abundance of ozone of approxiaatsly 3 percent.  This rang* of ozone changa
    iaplias a change in the nuaber of akin cancer eases aaong people alive today
    and born through 2075 ranging froa an increaae of over 200 aillion- to a
    decrease on the order of 6.5 aillion.  The overwhelming Majority (over 95
    percent) of the increases and decreases in akin cancer caaes estiaated for
    this wide range of scenarios is associated with basal and squaaous cell
    cancers (i.e., nonaelanoaa skin cancer).  Mortality iapacts are estiaated-to
    be on the order of 1.5 to 2.0 percent of the changes in total cases, and a
    large percentage of the estiaated iapacts are associated with people born in
    the future.  The statistical uncertainty of these astiaatas is on the order
    of plus and ainus 50 percent.  Additional uncertainties exist, soae of which
    cannot be quantified.  The greataat single uncertainty about future risks is
    driven by the rata at which CFC and Halon use grows or declines.  This
    uncertainty is reflected in the assessaent by «*«^fMTTg a wide range of
    •what if" scenarios of future use.

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                                     ES-15
                                          2C
    Tho sbuDdsaeo of stratospheric ozone depends upon chemical sad physical
processes that create and destroy ozono.  For over a decade scientists have
hypothesized that changes in the concentrations of trace gases in the ataosph*
could possibly perturb the processes that control ozone abundance and its
distribution at different altitudes.  The findings of this section suanariza t
currently available evidence on how esdssions and concentrations of various
gases aay change over tiae.  The findings in this section can be found in
chapters 2 through 4 of the body of the risk assessasnt.

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                                     ES-16
1.  HUMAN ACTIVITIES ARE THE ONLY SOURCE OF EMISSIONS TOR THREE CLASSES OF
    POTENTIAL OZONE -P1?T.irK; CHEMICATJg •
    CHLQROCARBOHS (CARBON TET[frftpfl^jftlDE ***& METHYL EHTflPf}fQRM^ ;  Afifl
    (chapters)*.

    la.   Sine* their development In the 1930s, CFCs have become useful
          chemicals in « wide rang* of consumer and industrial  goods,  including;
          aerosol spray cans; air conditioning; refrigeration;  foam products
          (e.g., in cushions and insulating foaas); solvents {e.g.,
          electronics') ; and a variety of miscellaneous uses.

    Ib.   CFC-11 (CC13F) and CFG -12 (CC12F2) have dominated the use and
          emissions of CFCs, accounting for over 80 percent of current CFG
          production worldwide.  Because of increased *^w* for its use as a
          solvent, CFC-113 (CC12FCC1F2) has become increasingly important as a
          potential ozone-depleting chemical.
2.  MEASTME^FyTfi Qf TROPOSPHB^Te CONCENTRATIONS OP IMPPSTgTALty	
    POTENTIAL OZONE-DEPLETING GASES SHOP SUBSTANTIAL INCREASES (chapter 2).

    2a.   Measurements of current global average concentrations of CFC-11 are
          200 parts per trillion volume (pptv), CFC-12 are 320 pptv. CFC-113 are
          32 pptv, carbon tetrachloride (CC14) are 140 pptv, and methyl
          chloroform (CH3CCL3) are 120 pptv.

    2b.   Based on measurements from a global monitoring network, worldwide
          concentrations of chlorine-bear ing perturbants (i.e., potential ozone
          depleters) have been growing annually in recent years at the following
          rates:  CFC-11 and CFC-12 at 5 percent; CFC-22 (CHC1F2) at 11 percent;
          CFC-113 at 10 percent; carbon tetrachloride (CC14) at 1 percent; and
          methyl chloroform at 7 percent.

    2e.   Limited measurements show that global tropospheric concentrations of
          Halon 1211, a bromochlorofluorocarbon containing both chlorine and
          bromine (which is potentially more effective at depleting ozone), have
          been growing recently at 23 percent annually.  Concentrations have
          been measured as one pptv.
    2d.   KeaeVmeents of tropospheric concentrations of Halon 1301, another
          bromVmted compound that is a potential ozone depleter, estimate that
          concentrations are approximately one pptv.  86 trend estimates have
          been published.
     2 The chapter references refer to die main body of the  risk assessment.

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                                     ES-17
3.   ALMOST ftf^, EMISSIONS OF CTC-ll. -12.  -11?,  HAVQN 1211. AND HALON \301
     PERSIST IN THE; TROPOSPHERE WITHOUT CHEMICAL TRANSFORMATION OR PHYSICAL
     DEPOSITION.  AS A RESULT. MOST OF THESE EMISSIONS UT1T. EVENTUALLY BE
     TRANSPORTED TQ THE STRATOSPHERE (chapter 2).

     3a.   Gases which are photochemically inert accumulate in the lower
           atmosphere.  Their emissions migrate to the stratosphere slowly.
           Estimates of their atmospheric lifetimes (generally calculated base
           on the time when 37 percent of the compound still remains in the
           atmosphere) are the following:   CFC-11 is 75 years (107/58 years);
           CFC-12 is 111 years (400/55 years); C7C-113 is 90 years; CC14 is SO
           years; Halon 1211 is 25 years;  R20 is 150 years; and Halon 1301 is
           110 years.  (Where provided, the range in parentheses shows one
           standard deviation).

     3b.   Because of their long atmospheric lifetimes, the concentrations of
           these gases are currently far from steady state and will increase
           over time unless there is a large reduction in future emissions.

     3c.   Because of their long atmospheric lifetimes, these gases would
           continue to contribute to possible future ozone depletion and climai
           change (CFCs and other gases affecting ozone are also greenhouse
           gases) long after they are emitted.  Full recovery from any depletii
           or climate change would take decades to centuries.

4.   WHILE CFCa TTSED IN AEROSOLS PBCLYNED FROM 1974 PHTTL 1984. NONAEROSOL USE!
     OF CFCa HAVE CROWN CONTnTOOPSLY AND APPEAR CLOSELY cntpT.Eft TO ECONOMIC
            (chapter 3).
     4a.   From 1960 to 1974, the combined production of CFC-11 and CFC-12 froi
           both aerosol and nonaerosol applications grew at an average annual
           rate of approximately 8.7 percent.  Total global CFC-11 and -12
           production peaked in 1974 at over 700 million kilograms.

     4b.   From 1976 to 1984, sales of CFC-11 and CFC-12 for aerosol
           applications declined from 432 million kilograms to 219 million
           kilograms, an average annual rate of decline of over 8 percent.
           During'the same period, sales for nonaerosol applications grew from
           318 million kilograms to 476 million kilograms, an average annual
           compounded growth rate of 5 percent.  By 1986, total CFC-11 and -12
        .** global production was nearly that in 1974.
                     g PRQPPCTTQH OF CTC«-11 AMD .12
                     >f
           (chapter 3).
•ATE OF APPBOyTMATRtY l.Q TO 4.0 FERCEHT OVER THE HETJ  IS TO 65
     5a.    A large number of studies of future global demand for CFCs were
           conducted by experts from six countries under the auspices of  the
           United Rations Environment Programme.  These studies used a variety
           of methods for estimating both near- and long-term periods.  In
           general, these studies assumed that:  (1) demand for CFCs was  drive:
           by economic factors; (2) no additional regulations on CFC use  were
           imposed; and (3)  consumers or producers do not voluntarily shift awj
           from CFCs because of concern about ozone depletion.  These studies

-------
                                ES-18
      provide a rang* of growth rates for developing alternative baseline
      scenarios of future CFC use and emissions.

5b.   In general, these'studies projected that CFC aerosol propellant
      applications would remain constant or decrease further in many
      regions of the world.          .    «, —    •:-*•. .-.=
5c.   In die U.S. over the past four decades new uses of CFCs have
      developed first in refrigeration, then ia aerosols, then in -foam
      blowing, and then in solvents.
                *                                   •
5d.   Studies have projected that growth ia developed countries for
      aonaerosol applications is expected to bo driven by increased use in
      foam blowing (primarily for insulation) and aa solvents, and by the
      continued introduction of new uses.  The wide raage of estimates of
      future growth reflects the large uncertainties related to population
      and economic growth, and technological change.

5e.   Studies suggest that future CFC use in developing countries will grow
      faster (i.e., at a higher rate) than future CFC use in the developed
      world.  Nevertheless, the .projected rates for the developing
      countries are lower than the historical rates that have been
      experienced in wealthier countries.  Vhila these studies were done
      using aggregate relationships of GRP and CFC use, they made different
      assumptions about how closely the pattern of CFC use in developing
      nations would replicate the pattern ia developed nations, generally
      assuming lower use rates.  However, evidence from one recently .
      completed study (not completed at the time of the UHEP workshop)
      indicates that in developing countries the penetration of CFC-using
      goods may be occurring faster than expected on the basis of the
      historical relationship in developed nations.  If that study is
      correct, growth in developing nations would be larger than projected
      in the above-mentioned studies, which generally assumed less
      penetration in developing nations than had occurred in developed
      nations.                          . i3 %.
                                         -  4. •"
5f.   Three long-term studies of CFC demaad^peport annual average rates of
      growth for CFC-11 and CFC-12 over cj^mext 65 years ranging from 0.2
      percent to 4.7 percent, with a median, eetimate of about 2.5 percent.
              it-if* scenarios used for ouaatitati.vc risk assessment
              18 spaa a wider range of growth, including one scenario with
                  decline.                            -\ :• ~

5g.   Limited studies on CFC-113 and CFC-22 project that ia the absence of
      regulation or-voluntary shifts away from these ehemirilt. their
      growth will increase at a faster rate than CFC«11 and -12 as new
      markets develop and existing ones expand («.g., use of CFC-113 as a
      solvent in metal cleaning).

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                                     ES-19
6.   THE Q^iQRflCARBQMS (METHYL. CHTflBOTOBM ASP CJSRMff TETRACHLDRIPE^  ARE USED
     ppTMA»TT,Y AS SOLVENTS ACT CHEMICAL imTBMP^TA'rgs -._- ASALYSIS  SUGGESTS
             nn*UR£ CRQtTTH FOR THESE CHEMICALS (ehaptar 3) .
     6a.   Ma thy 1 chloroform IM primarily uaad aa a general purpose solvent.
           Global use in 1980 was estimated at naarly 460 million kilograms.
           Limited analysis of future demand indicates that it is expected to
           grov at the rate of growth of economic activity (as measured by GNI
           Factors affecting future demand include possible control on it or
           other solvents due to their health effects.  Thus,  use' of methyl
           chloroform could increase if other solvents are found more dangerot
           Similarly, its use could be increased if..CFC-113 use is restricted.
           Because methyl chloroform has a substantially shorter atmospheric
           lifetime than CFC-113, it has relatively less potential for depUti
           ozone.

     6b.   Carbon tetrachloride is primarily used to make CFCs in the U.S. Ir
           developing countries it is also sometimes used as a general purpose
           solvent.  In general, future production and emission of carbon
           tetrachloride is expected to follow the pattern of production of
           CFCs.
7.   RALPHS. °tf A PP* MOHP RASTS. POSE A 
-------
                                     ES-20
      7f.
Diaeuaaiona with Halon uaara indieaca that Halon 1301 emission* may
be uadaraatimatad in tha study uaad for this riak aaaaeament.  A
racanc survey showed that axisting systems ara undergoing vidaapraad
taating and accidancal discharge occurs more fraquantly than assumed
in prior studies.4

Additional analyaia of Halon emiasion eatlmataa an nacaaaary to
aaaaaa more adequately the riaka aaaociatad with tfaia traca gaa.
     BTOGEffTC  SOURCES  CAftBON DTOTTTJB  MCTHANP.  Aim IHTIMMIV flflrTTW  APT nTPPTrTTTT
                 (chaptar 4).
The size of axisting source terms (wetland
                                                  Cor
                                                                      le)  is not
           known with eartainty today for all thaaa traea apaeiaa.  Graataat
           uncartainty axists for methane, laaat for C02.  To eatimata  futura
           emissions raliably roquiraa estimating the growth of aourca  tans
           (a.g., acraaga of riea paddiaa, wetlands area), which will ba
           datarminad by oany tachnical, political. anvironBantal, and  social
           factors.
Currant amission factors for aach aourca tars sjuat ba aatiaatad; a
ara not known today or hava not baan raliably astiMtad (aaissiona
from soils, for axaapla).
      8b.
     8c.   Possible changes  in amission factors due to changes  in
           environment must  be projected.  Projection of changes  is difficult
           because tha underlying physical or biological processes  that
           determine emissions ara not well understood and because  changaa in
           the environment that could altar amiaaiona are  not easy  to project.

     8d.   Biogeoehemical cycles that control tha  fate of  ealaaions once
           released into tha atmosphere must be understood to determine futura
           concentrations of these traca species;  severe limitations to our
           current understanding of theae cyclea limits our  capacity to
           determine the consequences of «*•**§*«•§  emissions  in  the  future.

     8e.   Possible changes  in theae biogeocbeaiJcal cycles due  to changaa in the
                        •ast  be projected; again^wjofleianciai in existing
                     makes this task difficult.  '
     USED    TV THTS VT«P A
                          '»« OTTT  RV
                                                    rr  AQ
                                                              (AT
     SCENARIOS TO gXAMTNE THE  SCTS
     SCEHARIQS (chaptar 4).
                       ITIVITY
                               OF A
                                           1C KVOIDTTOH TO THE
     4 Since this risk assessment was  originally completed, Halon users in the
U.S. hava taken a variety  of steps  to  reduce amiaaiona.  this atep is
considered in this Risk Assessment.

-------
                                £5-21
9a.   Tbm scenario* used in this risk assesisjeut are  consistent with that
      cosswnly used by the ataocpheric i ne»mili]i and  assune  the following
      changes in trace gas concentrations:

      o   for C02, a scenario developed by the National Acadesy of
          Sciences (its 50th pereentile, i.e., pre- industrial C02
                  ations doubling by about 2065) ;

          for CH4, a linaar increase la concantzationa of 0.017 ppa
          par
      o   jfor H20, concentration increase* of 0»2 percent per year.

9b.   Additional scenarios used to analyze risks will include:

      • for C02

      o   HAS 25th pereentile (pre- industrial concentrations
          doubling by 2100)

      o   HAS 75th pereentile (pre •industrial concentrations
          doubling by 2050)

      • for CH4

      o   0.01275 pp» per year growth in concentrations (75
          percent of the historically observed 0.017 ppa per
          year increase)

      o   0.02125 ppm per year growth in concentrations (125
          percent of the historically observed 0.017 ppa per
          year increase)

      o   1 percent compound growth per year in concentrations

      o   1 percent compound growth per year in concentrations
          fro* 1985 to 2010, followed by constant concentrations
          at 2.23 pp»

    _ o   1 percent compound growth per year in concentrations
          from 1985 to 2020, growing to 1.5 percent
          annual growth by 2050 and thereafter

      • for 820

      o   0.15 percent per year compound growth  in
          concentrations

      o   0.25 percent per year compound growth  in
          concentrations

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                                     ES-22
10.  DECISION MAKERS SHOPLD BE MADE A«*gP JftAT THE MOST COMMONLY USED SCENARIOS
     TK STttATOSTOCTTC *nPET.THC TMMJCTTLY ASSUME THAT TOTlBtg PECISION MAKERS
     NEVER TACT AflTTQH TQ 1.TMTT THE RISE IH CONCENTRATIONS OF CARBON PIQ3CIDE.

     METHANE. ACT) HTTROPS QYTpg, THff8^ CASES COHTRIMTTMC TO THE CgEENHOTISE

     WARMING (Ch*pt«t 4).
     10».  Th« standard aasuvptlon in aosc ataoapharie Modeling baa b«an, by
           dafaulc, thac graanhouaa gaaaa will b« allowed co ineraaaa vithoat
           liait ragardlaaa of tha laval of global waning chat occur* or ia
           projactad.
     lOb.  In ordar to provida daciaion makara with adaquata information to
           aaaaaa tha riaka of ozona modification due to riaing CFCa and Halona..
           altarnativa aaaumptiona about tha futura of graanhouaa  gaaaa  naad to
           ba axaminad.  Two acanarioa ara

           —  limiting global warming to 2°C.
           --  limiting global warming to 3°C.

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                                     ES-23
           pg THE ATMPSPffggg tHAT TMCOgPQttATK
        ATTOHS GROW STCSTyTCAirrT^r   TMCBTAlIg  ABODT MACiTLIPES REXAIM lARCg.

    Hodals chat laeorporata eorr«nt scientific undarataaOiag ar« us«d as th«
primary tool to project th« potential consaqumcas of futura changes in
abundances of trace cases.  These models can be partly tea tad by coopering their
results vith measurements of the ataospherie, historically observed changes in
ozone, and in the case of climate, with paleoclimatic and extraterrestrial
environments.  While current models accurately represent some aspects of the
atmosphere, they fall to replicate other characteristics .  This section
summarizes the currently available evidence on how changing atmospheric
abundance could modify total column ozone, altar column distribution, and change
global climate.

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                                    ES-2&
11.   STRATOSPHERIC MODELING PROJECTS THAT THE  COMBINED gSTgCTS OF A VARIETY OF
     TRACE CASES f CTfl^gflpFUTOROCARBONS. SITROUS tMCIPg. CARBON PTQTTMj,
     AMP METHANE)  ARE LIKELY Tt) BTOnCE THE COLUMN PBtSITV OF Q2OWE
     EMISSIOMS OF Q2QEE PgPLETEES AM PgETPTTEP fMM CMgT»e (chapter 5).

     11*.  Photochemical theory continues to support tfao conclusion that
           chlorine,  nitrogen,  and hydrogen can catalytieally destroy ozone in
           the stratosphere, thus depleting coluan levels.

     lib.  One-dimensional  (1-D) Models currently predict a 5-9 percent
           depletion  for the equilibrium  concentrations of chlorine that would
           result froa constant emission  of CFCa at 1977 levels.  while useful
           for intercemparing Bodels, these values cannot be used to assess die
           risks of depletion in an atmosphere in which other gases are also
           changing.

     lie.  One-dimensional  (1-D) models predict average column ozone will
           decrease if global emissions of CFCs and other ozone depleters
           continue to rise from current  levels, even if concentrations of
           methane, carbon  dioxide, and nitrous oxide continue to grow at past
           rates.   For a 3  percent growth of CFCs, models predict over a 25
           percent depletion by 2075 if the other gases continue to grow.

     lid.   Two-dimensional  models (2-D) used in steady state multi-perturbant
           studies that include chlorine, methane, and nitrous oxide project
           depletion  higher dun global averages at latitudes greater dun 40°H,
           especially in die spring.

     lie.   Time-dependent simulations of  stratospheric change in which 2-0
           models  are used  predict dkat depletion over 4 percent will occur at
           some latitudes for all eases of positive growth in CFC emissions.
           Such models even predict ozone depletion of up to 3 percent at
           inhabited  latitudes  for a scenario  in which emissions of chlorine-
           bearing substances are reduced from current to 1980 levels and in
           which halon emissions are eliminated, but in which die greenhouse
           gases dtat counter depletion are •lleweil to grow at historical ratea.
    llf -  Timm»4ependent simulation widt one 2-D model, widi CFCs growing at 3
          pexisjmt, medians rising at 1 percent, nitrous oxide at 0.25 percent
          anensmrbon dioxide growing at 0.6 percent, projects annual average
          depletion at 40°H of approximately 1.1 percent by 2000 and 5.2
          percent by 2030.  At 50°H. depletion is projected to be 1.5 percent
          by 2000 and 6.5 percent by 2030.  At 60°H, depletion is projected to
          be 2.1 percent by 2000 and 8.1 percent by 2030.   Springtime depletion
          would be higher.

    llg.  Time-dependent simulation widi one 2-D model, widi CFC-11 and -12
          emissions rolled back to 1980 levels, CFC-113. capped, odiar
          chlorinated emissions and bromine emissions  eliminated, methane
          rising at 1. percent, nitrous oxide at 0.25 percent, and carbon
          dioxide at 0.6 percent, projects depletion by 2030 of about 0.5
          percent at 40°N, 0.7 .percent at 50°N, and 1.1 percent at 60°N (dtese

-------
                                     ES-25
           depletion values ara from 1985 levels) .   If carbon dioxide
           concentration* ara prevented from growing from currant levels,
           depletion would, ba anticipated to ba higher.

     llh.  Time-dependent simulations with two otfaar evo-dimensional models  sho
           roomily comparable raaults to choc* raportad hate, with a slightly
           laaa latitudinal gradient.  However, thaaa models also project
           latitudinal gradianta from equatorial to polar aad ragiona.

     Hi.  Bacauaa of poaaible increases in the emiaaiona of bromine molecules
           (see Chapter 4} , Halona praaant a more important riak for
           stratospheric daplation than baa generally boon appreciated.
12.  enagfur THEORY Aflft ffipy^* TATT. fn
     OF TME ATMQSPHEBE AMP PROCESSES THAT gTLl. TMtUBfOt STBATQSPBgRIC CHANCE 1
     A COMPLETE AMP ACCTOATE HAMMER (chapter 5).

     12a.  while accurately reproducing many meaaurements in die currant
           atmosphere, currant modala fail to reproduce aoma measurements; the
           amount of ozone at 40 kilometers is undareatlmatad, for example.

     12b.  while including representations of moat atmospheric proeeaaea,
                it modala fail to include all the proeeaaea that influence
           stratospheric compoaition and-structure in a realistic manner.
           Transport processes, for example, ara rapraaantad in a simplified
           manner that does not oncompaaa all the complications of movement in
           the real afiaaaphara.
     12c.  The inability of modala to wholly reproduce measurements of the
           current atmosphere lowers our confidence in them to predict the
           future; it is possible that models ara over- or under-predicting
           future depletion.
13.  UNCERTAINTY ANALYSES THAT COWS T DP A BeltCT QF fO^^TIItJ! VATTTBg POP (THEMTCAL
     AMD PffyffTflATi TW^Ffffs GftlTICAla PQft wiflftyj^ MSTTmyroM Of OKyT^ETTOH rHPTCA"f£


     13a.  Uncertainty analyses conductmdjro&i ooa-dimenaional models predict
           daplation for a variety of CFC levels.

     13b.  fccartainty analyses uaing different aets of kinotiea and cross
           fractions have not bean tested in two-dimensional modala.  However,
           different 2-D models have used different approachea for transporting
           species.  This providaa a useful teat of the aenaitivity of modal
           predictions to the uncertainty of how transport actually works.
           while differing somewhat in the latitudinal gradianta of depletion,
           the models with different transport both predict daplation that
           increases with distance from the equator.

     13c.  Not all uncertainties can be tested in .the modeling process.  The
           possibility that missing factors may laad to a greater or lesser
           depletion than indicated in formal uncertainty analysaa cannot be
           excluded.     *                                                    ...

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                                ES-26
PREPTCTTOHS. giTH TBO EXCEPTIONS (chapter 5).

14*.  Measurements by balloons and Uakehr ahov 3 percent depletion at
      aid-latitudes in the upper ataoaphara,  1.3 percent depletion in the
      lover stratoaphara, and 12 percent increaaee ia die lower
      troposphere.  Uncertainty exists about the accuracy of all these
      observations.  These results, huwevat.  ara roughly consistent with
      the expectations generated by one-dlaensional and two-diaanaional
      aodela.  The ground based measurement ayataa covers only a small part
      of the Earth and ia liaitad at high latitudes.

14b.  Niabus 7 measurements appear to show a decreaaa ia global ozone,
      especially at both poles.  However, the decrease ia Arctic ozona froa
      1978 to 1984 aay have occurred only ia tha last aavaral years.
      Concern exists about calibration probleas, which make an exact
      determination of the absolute magnitude of daplation difficult.
      However, the latitudinal variations in depletion seea to indicate
      that a raal phenomenon ia being observed, not just instrumental  -
      drift.

14c.  The cause of these apparent ozone decreases measured by Hiabua 7 has
      not been sufficiently analyzed to determine whether the changes (if
      they are real) can be attributed to manmsrte rhaalrala.  Othar
      possible explanations include natural variations caused by solar
      cycles or other processes.  The latitudinal gradients of the changes,
      are, however, roughly consistent with those projected by 2-D model
      results, although the mffgrl***"1* is substantially larger than models
      predict.  Until further analysis is performed to determine whether
      depletion is actually occurring and whether it can be attributed to
      man-made chemicals, models to asseaa risks to tha  stratoaphere should
      not be revised.
14d.  Measurements in the Antarctic spring show that tha gradual depletion
      that occurrad ia the mid-1970s over and near Antarctica haa given way
      to  a steep non-linear depletion £roaT.f79 to 1985.  The ozone maximum
      outside Antarctica (between 50°S and 70°S)  appears to ba  shoving a
      decline.  Tha daplation of all szaas^wooth  of 80°S appears to ba 16
      percent.

14e.  Moeflb with conventional  chemistry do  not pradict "the  Antarctic
      osoas  hale.*  Care should be exercised ia interpreting  the meaning  of
      tike phanoaanon. Several  hypotheses have boon put forward, InrluiHng
      * rtiaalral  explanation that attributes tha  loss  of ozona  to maT»aria
      sources  (bromine and chlorine), a chemical  explanation that
      attributes  the  loas to natural sources (10x,  solar cycle), or an
      explanation that claims tha phanoaanon is entirely duo to the change
      in cliaate  dynamics.   Until more is understood about the  true cauaea
      of the hole,  it ia iapossible to determine  whathar  tha hola  ia a
      precursor of  atmospheric  behavior that win occur la othar regions of
      tha world.  Until  a better understanding of the aorhanlsas creating
      tike depletion is obtained, the existence of the Antarctic ozona hole
      should not  be used as  a basis for asking regulatory decisions.

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                                     ES-27
     14f.  This risk assessment will assuma that Antarctic oxon* and global
           tread* have no implications for global projection*.  Future ravi*vs
           should update this conclusion as naeassary.
15.  TWgggAOTg Tfl Ttnt ABCTlPAHCg OF CFG* AHP OffflKR TRACTS CASK CAM HfCRE*3E
     ffT/TBAT. TBOpOSpHKBJC SHItPACB 'l'jmi*EAA3TlR2S.  TJffiSK (SASZS CAM AUHEa^THE
     VEBTTCAT. nTffTgTItnTTCTT OF QZQtTE AND THCRgASK STBATPfiPHEgTC gATffP VAPOR.



     15a.  Trace gasas that act as stratospheric parturbaats also ara graenhouai
           gases-res their concentrations increase in' the troposphere they will
           retard tha escape of infrarad radiation from earth, causing global
     15b.  Incraaaaa la s*thana (CB4) will also add vaear vapor to tha
           stratoaphara, tharaby ^W~»-*«n; global wsraiTig.  Bathana iacraasas
           will also add ozona to tiia tropoapbara, vhar* it acts as a strong
           graaahousa gas that will furthar iacraaia global warming.
     13c.  In all modal-generated scenario* of oxona daplation, oxona dacraasaa
           in tha stratosphara shove 28 km.  This allows more ultraviolet
           radiation to penetrate to lowar altitudes whara da •self-healing
           effect' increases oxona to partially compensate for the oxone loss
           abova.  In some scenarios sufficient depletion occurs so that oxone
           eventually decreases at all altitudes.

     ISd.  Decreases in oxona at approximately 28 km or abova will have a
           warming affact on the Barth.  There is a small nat gain in energy
           because the increase in ultraviolet radiation (TJV-B) allowad to  reach
           die earth'* surf sea more than compensates for tha infrared radiation
           that is allowad to aseape due to daplatioa of oxona above that
           altituda.
     15a.  Balow approxiaataly 28 ka, incraasas  in oxona ara mor« affactivs as
           absorbars of infrarad radiation.  Consaquantly,  ineraasas in ozona
           balow 28 km also will produca * nat warming.   la this caaa,  th*
           additional TJV blockad by mora oxoaa ia lasa taaa taa additional
           infrarad that is blockad from ascsplng tha aarth.  Coararsaly,  a
                    ia ocona balow  28 km will  tand to cool tha Earth'*  surfaea.
     ISf.  £tt dixact affact of column daplation of oxona on global tamparaturcs
           1U1 dapand on tha aagnituda of tha daplatioa.  Until tha daplation
           is of sttffieiant •rcrl^"1* that it occurs at tha lowar part of' th*
           column, oxoa*  daplatioa will ba a aat contributor to global warming.
           If tha stratosphara  coatiauas to daplata so that oxon* is daplatad
           balow 28 km, this daplatioa will causa a cooling.  Oaa-dimansional
           modal* diffar  from two-dimanaional modals ia tha Wrtical
           distribution of oxona  changa, with daplation occurring at all
           altitudas in tha highar latitadas in two-dimaasionsl modals, rathar
           than Just at high altitudas.  Thus, according to 2-D modals, sha
           chsngas ia radiativa balanca will ba latitada dapandant.  At tha
           currant tima,  no studias hava baan undartakan to dstsrmiaa ch« nat
           radiativo forcing of chaagas projactad* by 2-0 modals.

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                                ES-28
15g.  Radiative forcing way vary atrongly with changes  in ozone at
      diffarant altitudes and latltudaa.   Consequently, until comparisons
      ara made between tha models in terms of thair global  impact,
      eatimatea of* tha affaeta of changes in tha vortical colian of ozone
      on global warning mada. with 1-D model* must ba viewed cautiously.  In
      addition, changed vertical *** ycrtbuttop of ozom  cviild influence
      stratospheric dynamiea.

                                 ^QEES ASSQCTAJ8P
                                                     LY (chapter
16a.  Two National Academy of Sciences panels have concluded  that the
      equilibrium warming for doubling atmospheric concentrations of 002,
      or for an equivalent incraaaa in tha radiative forcing  of other  trace
      gasea, will moat likely be between 1.5° and 4.5°C.

16b.  Tha magnitude of warming that would ba directly associated with
      radiative forcing from increases in trace gasas without feedback
      enhancement would increase temperature by approximately 1.2°C for a
      doubling of 002, and approximately am additional 0.45°C for a
      simultaneous doubling of H20 and- CB4.  Direct  radiative forcing
      a uniform 1 ppb increase in both CFC-11 and CFC-12  would increase
      temperature by about 0.15°C.
16c.  The initial warming from direct radiative forcing would change
      of tha geophysical factors that determine the earth's radiative
      balance (i.e.. feedbacks will occur) and these changes would amplify
      tha initial warming.  Increased water vapor and altered albedo
      affects (snow and ice malting, reducing tha reflection of radiation
      back to apace) have bean projected by aeveral modeling groups to
      increase die warming by aa much aa 2.5°C for doubled 002 or its
      radiative equivalent.  Large uneartaintiaa exist about the
      feedbacks between global warming and clouds, which could further
      amplify, or possibly reduce, tha r^g******1^ of warming.
16d.  Tha three major general circulation modeling groups in tine D.S.
      aatimata an average global ••^•ftvg of. aopound 4°C for doubled 002 or
      its radiative equivalent.   Itowavarf. because of uncertainties in the
                     of the cloud contributes**, greater or lesser
      amplifications, including a negative gaedback that would reduce the
             .to 2°C or an even lower value, nsniwir ba ruled out.
""IP1
GMlE*
16*.  ClaMpfcavaraga temperature has been earl mat-ad as having risen about
      O.il1 •••! the last century. 'This incraaaa is consistent with
      ganaral predictions of climate models.  Attempt• to use these data to
      derive empirically the temperature sensitivity of tha earth to a
      greenhouse forcing are not likely to aueeeed.  uncertainty about die
      past concentrations of trace gaaaa in the atmosphere, other exogenous
      factors that affect the climate (such as aerosols or solar input),
      jyd oscillation *r*** InTtihiliTl^f 5** the internal dynamics of the
      climate system (such as ocean circulation). currently prevent die
      derivation of the earth's temperature sensitivity from examination of
      tha historic.rise of temperature.  This limitation is likely to
      remain for more titan another decade.

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                                     ES-29
     16f.   The global warming associated with increases ia ozone-oodifying  gases
           varies with scenarios of future growth in these gases.   If the use  o:
           CFCs grows at 2;5 percent per year through 2050. C02 concentrations
           grow at the 50th pereentile rate defined by the HAS (approximately
           0.6 percent per year from 1985 to 2050). 120 concentrations grow at
           0.20 percent per year, and CB4 concentrations grow at 0.017 ppm  per
           year1 (spprtrnimafs ty 1«0 parcant of currant concentrations), then
           equilibrium temperatures would riaa by about 5.6°C by 2075 (relative
        '  to observed temperature in 1985), based on a temperature eenaitivity
           of 3°C for doubled G02.  Valuaa would be about 50 percent higher for
           a 4.5°C-baaed tamperatura sensitivity and about 50 percent lower for
           1.5°C.  If CFC use remains constant through 2050, tha projected
           warming would be about 4.3°C by 2075 (± 50%). and if use were phased
           out by 2010, projected warming would be about 4.0°C (± 50%).

     16g.   Efforts to gather worldwide time series data for clouds have  begun.
           If adequate, these data may narrow estimates of the cloud
           contribution to temperature sensitivity within the next decade.
           However, because of the complexity of t&is issue, this  effort aay
           fail to resolve the large uncertainties affecting thia aspect of
           climate.
17.  THE TIMING Of CrLOKAL yAJPfTP*? OTi^f^^ °^ **** MATIS AT VHTCH CggglHOPSt
               THE RATES AT WHTOf CmtfS. FORCINGS fflCfl Ag YOMftlWKi? *^P SOIAR
               (THAMfiT  AKT» TVR 9ATV AT BHTffll OCKA1K TACK tTP 0JCAT AMB VABTTAtiY
     PHA?
iY TEKPERATURZ
              THT*8 PART
     ASP SOIAR FACTORS PO MOT snBST^p^i^y pgAja^K (chapter 6).

     17a.  The delay in tamperatura riaa introduced by abaorption of heat by tho
           ocaana can only be roughly eatimatad.  Tba aimple one-dimensional
           modela of oceana that have been uaad for thia purpoaa do not
           realistically portray the aartianltmt for beat transport into tha
           ocaana.  Instead, these models uaa eddy diffusion to treat heat in a
           parameterized manner so that beat absorption ia consistent with data
           from the paths of tranaieat tracers.  These modela indicate that the
           earth will experience anbstantial delays (on tha order of several
           decades) ia experiencing the ^jMadaf tram jxeeubuuse gaaea.
     17b. .lha earth'a currant average rmmjsi-sfuri ia mvt-in equilibrium with
           the radiative forcing from current concentrations of greenhouse
                        quently, global average tamperatura would increase in
               future even if conceatrationa of gases did net rise any further.
           for example, if 2°C ia the actual sensitivity of the earth's climate
           system to a C02 doubling, simple modela eatimate tba currant
           •unrealized warming" to be approximately 0.34°C; for a 4°C
           temperature sensitivity, the currant unrealized warming would ba
           approximately 1.0°C.

     17c.  Only one three-dimensional general circulation model baa been used tc
           simulate changes in temperature aa concentrationa of greenhouse gssea
           increase over time.  This simulation shows a faster warming than
           predicted by'-simpler one-dimensional modela that use ocean box modal4
           to simulate time-dependent warming.                    '*'            ~

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                                    ES-30
     17d.   Future uptake  of heat by the oeaana «ay ehaaga aa global wanting
           altars ocean circulation, poaaibly altariag tfaa dalaying affaet of
           tfaa oeaana  aa  vail aa radueiag their uptaka of C02.
     17a.
      Inadequate information exiata to predict how volcanic or solar
      forcings may change over time.  Analyses done of transient warming
      assume that peat levela  of volcanic aeroaola «ill continue into the
      future and diet aolar forcing changea will average out over
      relatively abort period* of
18.
                                           CUTMATTC OtA
                                                      ASSOCIATED OTTH
                    AA'
                           Ml WTTAft.TV'
                                   IKBTi
(chapter 6).

18a.  In general, as the earth
      with increasing distance from the equator.
                                                                     be greater
     18b.  Global warming alao can be expected to increase precipitation and
           evaporation,  intensifying the hydrologieal cycle,   while models  lack
           sufficient reliability to make projections for any single  region- all
           perturbation atudies-with •three-dimensional models (general
           circulation models) show  significant regional ahifta in dryneaa  and
           wetness,  which suggests that ahifta in hydrologie  conditions will
           occur throughout the world., •

     18c.  Current general circulation sjodela represent oceanic, bioapherie, and
           cloud proceesea with insufficient realism to defenrtne bow extreme
           weather events and climatic  norms are likely to change on a regional
           basis.  For example, one  analysis of general circulation model
           outputs suggests that the frequency of extreme climatic conditions
           will change in many regions  of the world.  Another model projects
           increased summer drying in mid-latitudes for perturbation studies,
           utilizing either of two different repreaentatioaa  of clouds.  Still
           another analyaia suggests changea in latitudinal gradients of aea
           surface temperature will  play a critical role in determining regional
           climatic effecta.                   .* ' .
                                            -. - is. -
     19a
     19b.
                  •that is, chloroflt
                                          and aitrous oxides—would
      decreaae the rate and magnitude of global warming.  .

      Oecreaaea in methane amisaiona, which have the potential to
      stratospheric and tropoapharic ozone and thereby buffer ozone
      depletion, would decreaae warming in three ways:  by reducing direct
      radiative effecta from its presence In the troposphere; by lowering
           water vapor in the stratosphere; and by reducing
           28 km.
                                                             build-up below

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                                     ES-31
     19c.  Decreases in C02 emissions vould decrease global warming.  but would
           also have the effect of increasing the stratoaphere's vulnerability
           to ozone depletion.

     19d.  Decreases in carbon monoxide concantrationa ,  which may occur as
           energy production practices change, could result in decreases in
           •ethane concantrationa by increasing OH* radical abundance which , in
           turn, would shorten the lifetime of methane and could shorten the
           lifetiae of methyl chloroform and C7C-22.
20.  APPTTTOHAZ* RBSRARCH TS ffEJEDED Off CTJDCA.TR TO ftlfflCJGy PMC8SJA-Llff.LBS A&QUT
     ctjOBAj. VABMTMC ASSOCTATFP WITH TSACT CAS 
-------
                                     ES-32
                     HKAItXH, BKUttlS* JUID
    CHANCES TH COIXMH    SE ABDHPAMCT AMP PTSTBTMTnOH AMP A »TSg TH G
                         CTKP TO HAM BBiAff HEAUHi WtfAEBi AHD THE
                         CAW M" CPAJfl I f I Uli TTSTHC BASCKS   UTHU RTSTtS
CARROT BE QQAfTIKIED OR DATA WBCKi'T^AKT ^^ onAifliyiCATTQff Agg
(MfLY FOB 'LTMTTED CASE STHPTRS.

    Ozoiw «hi«ld« th« ««rth froa UV-B radiation.  A dacraaa* in total
coition ozone will increase this radiation, •specially *« ic* »o»t haraful
wavelengths.  For the DKA action speconsm, a 1 percent depletion would
increase the weighted UV flux by about 2 percent.  Changes in coluom ozone
and increases in global temperatures could altar aany environBental
conditions.  The findings of this section cover the effects of these
changes on human health, ecosystems, crops, materials, air pollution, sea
level and other areas that influence human welfare.

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                                     ES-33
ruu)j
21.  BASED ft* SURVEYS (PARTICULARLY in THE uHjTBtf STATES AMD IN
               5W EXPOSURE IS CONSIDERED TO BK THE POMimilT RISK FACTOR FOR
                 SKIN TUMORS (chapter 7).
     21*.  Nonas lanoaa «kin tueors tend t» develop la sun-exposed sits* (e.g.,
           the head, face, aad neck).
     21b.  Higher incidence rats* occur eaong groups. subject to greater exposui
           to tha sun'* rays because of occupations -that necessitate Chair
           working outdoors.

     21c.  A latitudinal gradioat exists for UV-B radiation, and higher
           incidence cat** of nnns»linnM skin tnaors generally occur in
           gsographie aroas of roladwlj high UV radiation «xposura.

     21d.  Skin pignontation providaa a protsctiv* barrior that rtduca* the rij
           of dowloping nonMlanoaa skin oasors.
     21o.  Tho riak of nnnsxltnosii skin tuaors is nighast sjwng gonotically
           prodisposod individuals (o.g., thoa« wiA xarodars* pigBMntosua).
     21f.  A prodisposition to dowlop nonaolinnai skin tuaors axists aaong
           light'Skinnad individuals (skin phonotrpos I and II) who ar«
           suscaptibla to sunburn and vho bar* rod/blood hair, bluo/graan «y«s,
           and a Celtic haritago.
22.  f^f^U£lJ^ ^f'nfXIOLDBTC^L ffVTPEHCg qmTCArgg tTIAT T^B{ JBD HAJOR TYPES Of
     HOMMELAHQMA SXTtt Ty^Ogg ,  SOOAMOpff CBTJi CAlCIHOMA (SCC1 AMP
     CARCIKOMA. < >cc^ .                        SOLAH.
          mJ) THAT COMniATIVE 0V ftADIATTOU HAS A. CggATtB. gPPgCT OH
     PEVgLQgMEMT OF SCC THAN QM BCC (ehaptar 7).

     22a.  Tha BCC/SCC incidanca ratio dacrsasoa vith docroastng latituda and
           Charafora, incraaslng UV lavala.

     22b.  BCC is s»ra likaly to davalop on normally unaxposod sitas («.g., tha
           trunk) cosyarad to SCC.

     22e.  SCC is sora likaly than BCC to darelop on sitaa racaiving tha highest
           oavolativo UV radiation dosaa <«.g. , tha noaa) .

     22d.  for a givan eusulativ* laval of sunlight axposura, tha risk of
           developing SCC may be greater than tha risk of developing BCC.
23.  fur B;»^T1LTS VftOM SgTgffAJ, EaTSyff**^^- ^™P^*S SUGGEST THAT PV-S MAY fK THE
     MOST IMPORTANT COMPQMgMT f\V ^flTAB BAnTATTOS! THAT CAHSKS VARTATTOWS  Tff THE
     acnmcg OF noimgLMiOMA ej^i T^nf g (ehaptar 7).
     23a.  UV radiation producaa m-jnaelinnais skin tuaors  in  sniaals.  DV-B
              tlangths have been shown to be s»st affective  in producing these

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                                     ES-34
     23b.  UV-B has been shown to cause a variety of DHA lesions,  to indues
           nsoplastie transforaation in colls,  and to bo a autagen in both
                  and baetsrial calls.
24.  SEVERAL RESEARCHERS HAVE INVESTIGATED TH1 OUHCES Til TUB INCIDENCE OF
                             THAT MAV BV^ITTT verm TWCBKACM TW
     fly RADIATION.  GIVEN UMCERTA.TWTTES,  BAHCES OF BTiJIATES OF IHC8EASEP
     TNCTPENCE THAT COULD OCCDR gTTH DgKJTTQII AM KSTTMATm (chapter 7).

     24a.  The action spoetra for initiation and proaotion of basal cell  and
           squaaous- esll skin cancer have not been precisely doterained.
           Fhotocare'inogenie studies indicate that the erytheaa and DHA action
           spectra span a range likely to eneoapass that of squaaous cell and
           basal cell skin cancer.  The Bobertson-Berger (s>B) aster, while
           providing useful data for describing aabieat UV radiation, does not
           relate as closely to those wavelengths thought to proaote sunburn and
           skin cancer.

     24b.  Several studies have provided estiaates of a biological amplification
           factor (BAF), which is defined as the percent change in tumor
           incidence that results froa a 1 percent change in UV-B radiation.
           The results froa six studies produced an overall BAF range that is
           1.8-2.85 for all nonaelanoaa skin tuaors.

     24c.  BAF estiaates are generally higher for aales than for feaales and
           generally increase with decreasing latitude.  In addition, the BAF
           estiaates for SCC are higher than the BAF estiaatas for BCC.  This
           finding is consistent with observations that the BCC/SCC ratio
           decreases with decreasing latitude and that BCC is aore likely to
           develop on unexposed sites.

     24d.  Optical amplification  (the change la UV-B radiation related to ozone
           depletion) increases the response of these cancers to ozone
           depletion, because the relevant action spectra increase aore  than 1
           percent for a 1 percent depletion.  For exaaple, a 1 percent
           depletion has an optical amplification of over 2 for die DKA  action
           speet
     24e.  Uncertainty exists in the actual doses of solar UV radiation received
           by aaaulitions and in the statistical estiaates of the dose-response
           coapRcients.  Therefore, a range of estiaates Bust bo developed for
                   la .incidence associated with changes  in dose.
     24f.  Currently available nonaelanoaa aortality data are of uncertain
           accuracy because of the discrepancy of reporting between death
           certificates and hospital diagnoses sad the lev proportion of deaths
           reported on both hospital diagnoses sad death certificates.  Based on
           published studies, the rates of aetastasis among SCCs and BCCs have
           been estiaated to be 2-20%  and 0.0028-0.55%, respectively.  The
           overall case fatality rate  for nonaelanoaa skin tuaors is
           approximately  1-2% with three-fourths to four-fifths of the deaths
           attributable to SCC.

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                                     ES-35


     24g.  Changes in behavior have tended to increase skin cancer incidence &i
           mortality.  While soae evidence exists that this is reaching a li»i
           tMn cancer rates, even in the absence of ozone depletion, would be
           likely to rise.  Future rates of skin cancer could be reduced if
           people changed their behavior.  Care should be taken, however, in
           interpreting such a change- aa a 'coat- free' response.
                                                       c •
23.  CDTAMgQPS MAt-TCWAMT mrLUJOHA (Qflf) JlSf \ gfRTQPS LTyr«THP1tATENIt«i DISEASE
     THAT APVEL.TS A LARGE MMBER OF fTOFLIS T* ™ "JTTP f**™8 -  THKRg ARE
                  T       FORMS Qg MgLAIiOMA THAT ABB Limy TO HAVE SOMEWHAT
               ETTOt/iCTES AMP RgtATTQMSHIPS tQ SOLAR ABB OV-8 ttAPlATTOH (chaptC
     8).
     25a.  CMM incidence and mortality is Increasing rmnng fair-skinned
           populations.  These increases appear not to be Merely the result of
           improved diagnosis and reporting.

     2Sb.  In 1987, it is estimated that there will be an estimated 25,800 cas«
           of CMM and 5,800 fatalities related to melanoma la the United State »
           In die absence of ozone, depletion, the lifetime risk of QfM in the
           United States is expected to be about 1 in 150.
26.  E.TMTTATIQNS IH THE n*Tfc1U.je» V9VMV3fT AASOTjDTl CpCTACTTY ABOUT TOE
                           BAPTAT      V-R. ASP CPTAOTOPS
           (chapter 8).

     26a.  There currently is no aniaal sjodal in which exposure  to UV-B
           radiation experimentally induces •elsncem.
     26b.  There is also no experimental ia ^H.trn model for malignant
           transformation of melanocytas.

     26c.  Ho epidemiologic studies of QOC have been conducted in which
           individual human UV-B exposures (and biologically  effective doses of
           solar radiation) have been adequately assessed.

27   KVAT.TTATIQN OF THlt RPTPPMTOLQCTCAL AND KLfRltTMPlTAL. PAIABASRS FOR  MELANOMA.
                                                                  IP PQSg AHP T(
                                                                   (chapter 8) .
         —                                .           -.      .
     27a.  Osone differentially removes wavelengths of BV-B between 295 end 320
          -»»; OV-a, (320-400 nm) in wavelengtha  above 350 •«• ia not removed, no
           ia visible light (400-900 OB).  Ozone removes all OV-C (i.e. ,
           wavelengths leaa than 295 oa).

     27b.  Bavelengths between 295 oe and 300 at are generally more biological!
           effective (i.e., damage target molecules in the akin, including DHA)
           than other wavelengths in QV-B and even more so than TJV-A, radiation.

     27e.  Latitudinal variations exist  in solar radiation; model predictions
           indicate that the greatest variability ia seen la camulative UV-B
           (e.g., monthly doses) followed by peak UV-B (highest one-day doses)
           and then cumulative UV-A.  Peak UV-A does aoc vary significantly

-------
                                     ES-36
           acroaa latitudaa up to 60*H.   Craatar ambiant variation alao axiata
           in UV-B than in UV-A by tima  of day.

     27d.  Tha biologically affactiva doaa of radiation that actually raaehaa
           cargat molaculaa dapanda on tha duration of axpoaura at particular
           locations, tima of day, dma  of yaar, bahavior (i.a., in tarma of
           elothaa and sunscreens), pigmantation, and otbar charaetariaties of
           tha akin including tamporal varlationa (a.g., fhangaa in pigmantation
           dua co canning).              .-*r'~:~~f"~?   , \ • "
     27a.  Cloudinaaa •••*** albado,  although cauaing larga ^"^T^icm? 1^ tha
           amount of -axpoaura to UV-B and UV-A,  do not graatly *»V"f» tha ratio
           of UV-B to UV-A.
                                                        - ,
-------
                                     ES-37


           develop rates approaching those of prior (but native born)  imaigran
           to the adopted country; this is particularly accentuated in
           individuals arriving before the age of puberty (10-14 years).

     28h.  It has been suggested that QfiC risk may be associated with childhoo<
           sunburn; other evidence suggests that childhood sunburn may reflect
           an Individual's pigmentary characteristics or may be related to nevi
           development, rather than being * separate risk factor.
                                                                 t
     281.  Most studies that have used latitude as a surrogate for sunlight or
           UV-B exposure have found an increase la the incidence or mortality <
           Qttt correlated to proximity to the equator.  A recent -study of
           incidence using measured UV-B and Qtf survey data found a strong
           relationship between UV-B and incidence of QM.  Another study that
           used modeled UV-B data and an expanded database on mortality found i
           strong UV-B/mortallty relationship.

     28J.  One form of QQC, Hutchinson's melanotle freckle, appears almost
           invariably on tike chronically sun-damaged skin of older people.
29.  SOME EVTPEHCg ^RfjftTBS VHffRTftTTrTT ABCPT TUB fflffnfiTTff^Hiy Bgrvgai SOLAR
     RADIATTOW AMP COTAHttQPS IJALTflWfT MgLAMQtfA. (chapter 8).

     29a.  Some ecologic epidemiology studies, primarily in Europe or close to
           the equator, have failed to find a latitudinal gradient for QM.
     29b.  Outdoor workers generally have lower incidence and mortality rates
           for QOf than indoor workers, which appears incompatible with a
           hypothesis that cumulative dose from solar exposure causes CMK.

     29c.  Unlike basal cell and squamous cell carcinomas, most QM occurs on
           sites that are not habitually exposed to sunlight; this contrast
           suggests that cumulative exposure to solar radiation or UV-B is not
           solely responsible for variations in GMM.

30.  UV-B RAPIATTOK IS * T.TgTTV COM KM Ml' O* SOLAS BAPTATIQS THAT CAPSBS
                                              R TOBODffl T
                                              (chapter 8)
CnTAMFOlTS MAtTCMAJn* tOJAVrttli SCMn . 'S1TTHKU TH8OPCH TWTTTATTON fff TUMORS OR
     30s.  Xaroderma pigmentoeum patients M» fall to repair UV-B-induced
          •vyrlmidine dimers in daeir MA-feave a 2,000-fold excess rate of CMM
           by the time they arm 20.

     30b.  UV-B Is the most active part of the solar spectrum in the induction
           of wflffsgynfrsi* *r>*^ transformation £a. ylcro.

     30c.  UV-B is die most active part of die solar spectrum in die induction
           of csrcinogenesis in experimental ••*<••*• and is considered by most
           to be a causative agent of nonmelanoma skin cancer'in humans.

     30d.  UV-B is die most active portion of die solar spectrum in Inducing
           immunosuppression, which may have a role in melanoma development.

-------
                                     ES-38
     30e.  The limitations in the epideaiologie and experimental database leave
                doubt as to the effectiveness of UV-B wavelengths in causing
31.  UHTT.E TmCEBTAIMTY EXISTS.  PK^fi^SfjS, ™ *™ IHCIPiHCg AMD HQETAT.TTY OF
               MAT TOVAIIT MELANOMA ABC TJgKLv AS A RSSITLT OF OZONE BEFLETTOH.
                              dST fE.C.. MtBMMBC ACTilsH SFECT8A. PEAK VERSUS
     CDMPLATTVE DOSE.  KTC.i ABOUT THE «ATPBK OF THE KgtAtiOBMlMlP
     AMP MFLAMOMA. THE FACT THAT Off-B lADTATIQB VA1TES AgQSS TffE EMVTBONMEST III
     THE RAMCT OF VABTATTnH tTP»"fgf> »MH MFLgTTOM MOVtMS
              TMFEgFgCT.  PTPe«OLfflfTg THFTB?'*'"011 «""« ^P «TTHATg A BA
     CHAHCES TIT TMCTPEMCK AMD MORTALITY IF THK omit LATKM. TS DEPUTED (chaptoe
     31a.  Uncertainty exists about the appropriata action spectrum to be used
           in estimating dose, the best functional fora for dose-response, and
           the best way to characterize dose (peak value, cumulative summer
           exposure, etc.).  Histologically different QMs (or possibly QJK  _
           located at different anatomical sites) are likely to have different
           dose-response relationships.  Most estimates of Qtt dose-response
           relationships fail to consider these histologies! or site
           differences.  Nonetheless, by encompassing a range of possibilities,
           it is possible to estimate doee-response because of die systematic
           variations in UV-B.

     31b.  A recent study by die NIB presents a well-designed ecological study
           of melanoma and UV-B using survey data and aeasured UV-B at ground
           level.  Vhile uncertainties exist, dxis dose-response relationship,
           when used with different action spectra aad assuaptions about die
           importance of peak versus cumulative exposure, can be utilized to
           estimate a range of values for cases.  The relationship estimates
           Chat a 1 percent change in ozone is likely to increase incidence by
           between slightly less than 1 to 2 percent, depending on die choice of
           action spectrum.  The appropriate action spectrum is likely to be
                       in die range of erydMaa and DBA.
                                            '!•: .*-.'.
     31c.  Melanoma mortality is estimated at about 25 percent of all eases.
           This result is consistent widi the jcojeetions of a dose-response
                 of mortality developed by EPA/BCI.  It  is eatimeted diet a 1
                   change in ozone would result  la between a 0.3 aad a 2.0
                   change in CMM aortality depending en  die  assuaptions about
           the appropriata dose and UV weighting functions aaed in the model.

     3Id.  Additional uncertainties for projecting future incidence and
           aortality of OM in the U.S. include  the lack of  aa adequate database
           describing variations in skin pigmentation and human sun-exposure
           behavior among different populations  and estimates  of how these
           relationships may change in die future.

^9   TI9 • gl!DDI*F*!Cge 1>UV TMMTINF gVgTBM TV AVTWAT **1MB I MKI^B /t&trnnfmf Q\
JA.  uv»B_ayjrj'|UodiLa_^ui£_^UQUlQfi_jUM««M^M&JBB^flAMBHM^RSMflUil^Ati \*•**•!•••* */ •
     32a.  UV radiation administered at  relatively low doses causes a depression
           in local contact hypersensitivity (a fora of cell-mediated immunity)

-------
                                     ES-39


           resulting froa an inability to reapond to an ancigen presented
        ,  through UV- irradiated skin.

     32b.   High doaaa of UV radiation cause a depression in systsaic contact  son
           delayed type hypersensitivity reactions,  tbat reault in an inability
           of tha aniaal to reapond to an antigen which is presented to  the
           tnirisl through "ffiTTi*Ha^*t akin.

     32c.-  Both the local and systeaic effecta on contact hypersensitivity are
           aediated by a T suppressor cell which prevents tha developaent of
           active laamilr/ to the ancigen.

     32d.   The iaaunosupprasaive effecta of ultraviolet radiation (UVR)  have
           been found to reaide alaoat entirely in the UV-B portion of the
           ground level solar radiation.

33.  SUPPRESSION Of THE TMMPHE SYSTEM MAY WAY AM TXPQgTAflT flffljj flf
                    (chapter 9).
     33*.  Aniaals which are* UV- irradiated develop T suppressor cells which
           interfere with the iaaune reaponaa to UV- induced tuaors in such a waj
           that the aniaala are aora susceptible to the growth of autochthonous
           UV- induced tumors.  The contribution of the suppression of the faenni
           systea to cancer incidence that would reault froei ozone depletion is
           reflected in the dose-response estimates of photocarcinogenesis
           assuming that the action spectra for the two phenomena are the saae.
           If these two iapacta have different action spectra, die estimates
           could be either high or low.

34.  LIMITED EigERIMESTAL DATA CTDICATE UV-B StTPPagSSES THg HDMAH IMMOSE SYSTEM
     (chapter 9).

     34a.  Although tiiere is limited Information about the effects of UV
           radiation on huaans, several studies indicate that the iaaune
           response of huaans is depreaaed by UV radiation and is depressed in
           UV-irradiated skin.
                        PITH ggcxpp TO MMiY HP1AH PISEASBS (chapter 9) .
     3Sa.  Freliadnary studies indicate that UV radiation aay prevent an
           'effective iaaune response to aicro-organiaaa that infect via the
           akin, thua predisposing to reexpreaaion or chronic infection.
     35b.  Two buaan diseaaea that aay be Inflnanrad by UV-B-induced iaaune
           suppreasion are herpea virus infections and laiahaaniaais.

     35c.  Alaoat no research has bean conducted on tha influence of UV-B  on
           other infectious diseaaea; additional investigation ia clearly
           warranted.

     35d.  For at leaat one theory of the aechanisaa of UV-B-induced suppression
           of the-.iaaune systea  (that involving urpcanic acid),  a possibility
           exists that non-whites, aa well aa whites, would be vulnerable  to.
           increased ianune suppression caused by ozone depletion.           . _.

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                                    ES-40
     35e.   Because UV-B can produce  systemic  immunologic change, the possibility
           exists that changes  in UV-B could  have  resulted in effects on
           diseases whose control requires  systemic  rather than local immunity.

     35f.   Immunologic studies  to date have not assessed the effects of long-
           term,  low-dose UV-B  irradiation.  Consequently, the  magnitude of this
           risk cannot be assessed.
36.  EVIDENCE EXISTS SUGGESTING THAT CATARACT INCIDENCE PTTJ. CHAMCE PITH
     ALTERATIONS IN THE FLUX OF UV-8 CAUSED KY OZONE DEPLETION (chapter 10).

     36a.  Many possible mechanisms exist for formation of cataracts.   UV-B may
           play an important role in
     36b.  Although the cornea and aqueous humor of the hmsn eye screen out
           significant amounts of UV-A aad UV-B radiation,  nearly 50 percent of
           radiation at 320 am is transmitted to the lens.   Transmittance
           declines substantially below 320 am. so that less than 1 percent is
           transmitted below approximately 290 to 300 nm.  However, the results
           of laboratory experiments on ««•«•»• indicate that short wavelength
           UV-B (i.e., below 290 nm) is perhaps 250 times more effective than
           long wavelength UV-B (i.e., 320 nm) in inducing cataracts.

     36c.  Human cataract prevalence varies with latitude and UV radiation;
           brunescent nuclear cataracts show the strongest relationship.
37.  INCREASES IH THE AMOUNT OF UV-> THAT fi^ BttAffH TffB fl^TTT^ APPEAR CAfAjm 9F
     CAUSING STAftlJj MTINAL DISORDERS AMP RgTTNAL PKfmUKHATION. TBO CAUSES OF
     BLINDNESS (chapter 10).

38.  t-TMTTEQ STUDIES ANALYZING THE EFFECT Of TffCRBAStiP W"^ RADIATION OH CROPS
          l            VERSE IMPACTS .  HQgEV     OCLPSIONS ABOUT THE AMOUNT OF
     YIELD LOSSES ATTBIBOTA»TJj] JO, PV-B CANNOT BE PttABN (chapter 11).

     38a.  Difficulties in experimental design, the large number of species and
           eultivars, and complex interactions between plants and their
           environment have prevented TffiB*l*lM*f'"* °* total crop loss from
                     in UV-B.
     38b.  Act^d spectra for UV damage to higher plants are limited, but
                    a strong weighting toward shorter UV-B wavelengths which are
                      affected by ozone reduction.
39.  QF P^mT CPMTVARS TBSTKft Tff ^^ TABORATBBY. AypBonrrwLTKLy 70
     PETESlCNEn TO BE SENSITIVE TO UV-Br CARg MIIST Kg TAIBT IH PffgBPBETIHC THIS
     FINDING (chapter 11).

     39a.  Different eultivars within a species have exhibited different degrees
           of UV-B sensitivity.  While this suggests selective breeding could
           limit damage, neither the basis for selectivity nor die potential
           effect on other aspects of growth has been studied.

-------
                                     ZS-41
      39b.  Laboratory experiments haw b««n shown to inadequately replicate
           effects in to* field, thus the implications of eultivar sensitivity
           ara not .certain.

      39e.  In some species, mitigation rosponsos sora raadily apparent in tha
           field  (a.g., increased production of DV absorbing flavonoids) have
           reduced adverse impacts.
40.  *n*g gypicrs OF ov-g BAPIATTQW HAVE im> gTAnrmirn «QP QML
     MAJOR TlBMyF^jAj, ^QSYSTBUS AMP TOft OHLY A THTgP OF THE PTJLMT CRQBTH FOR]
     (chapter
     40a.  Little or no data exist on enhanced 0V- B effects on trees, woody
           shrubs, vines, or lower vascular plants.
41.  LAgCg-PMCgRTAHrrTaS BCTST AS A ggSTTLT OF AH tMCTgCTCT BPgttMgHTAT. DESIGN
     fflt_DQSIMET8y.  RXJ.ST1JIC KXPKftJMPlTAL FIKLD PAUL SOOCKST A POTPfflAL
     PtttfCTICH TH CSOF TTFT^ TOg s°*ff ff^ffff8 PP^ ^Q PIHAIICB> PV-B RADIATION
     (chapter 11).

     41a.  Field experiments in which UV-B radiation has been supplemented are
           limited.  Several of the earlier field experiments are of limited
           value since UV-B doses or other factors such as soil temperature vei
           not sufficiently controlled or representative of field conditions.
           Dose-response studies in the field are particularly different.

     41b.  The only long-term field studies of a crop involved soybeans.  Th«s<
           studies have found that enhanced levels of UV-B, simulating between
           16 and 25 percent ozone depletion, caused crop yield reductions of v
           to 25 percent in a particular eultivar.  Smaller reductions in yielc
           were experienced in years where drought conditions existed.

     41c.  Soybean (CV Essex) yield could be accurately predicted when total
           UV-fi dose, daily i"*'"*?""* temperature, and number of.jtays of
           precipitation were included in a regression model.

     41d.  The lipid and protein content «•£ soybean vas reduced up to 10
           percent; however, higher UV-1 doses alone did not consistently resul
           la the largest reductions.
     41m.  mie only several cultivars have been tested la die field,  two out
           •f three soybean cultivars tested under  laboratory conditions were
           sensitive to UV-B.  If this relationship holds true in the field,  it
           suggests (when considered la light of yield reduction experiments)
           that JJV-B increases could baza die potential of the world
           agricultural system to produce soybeans.
42.  THE gygKLTS OF flV-B OH PTOSAL Oft VHtAL PATBOCHIIS fA^Y wTTH ?ATHOCZH.  PLANT
     SMCTBS . AMD cnt3T7A^ (chapter 11) .

     42a.  Current evidence ee> possible interactions with pathogens is very
           limited.

-------
                                     ES-42
     42b.  Reduced vigor in UV- sensitive planes could render the planes more or
           laaa susceptible to post or disaasa damage and thus result in changes
           in crop yield.
43.  CHAM2£S^^LJZ!LJLi.i^£££2£_Ii^C_iUiI2U£E_iiUuQ2^
     (chapter 11).

     43a.  If enhanced UV-B favors weeds over crops, agricultural costs (e.g.,
           for increased tilling and herbicide application) could increase.
           However, .insufficient evidence exiats to form a basis for evaluating
           this effect.

     43b.  Increases in UV-B could altar the results of the competition in
           natural ecosystems and thus shift community composition.  Since UV-B
           changes would be both global and long term, possible UV- induced
           alterations of plant species balances could result in large-scale
           changes in the character and equilibrium of vegetation in
           nonagricultural areas such as forests and grasslands.

44.  DV-B RADIATION INHIBITS AM) STIMULATE* FLOW]{im4C . PEPEMPCTC OH THE SPBCIRfi
     AMP GROWTH COHDTTIOSS (chapter 11).

     44a.  The timing of flowering may also be influenced by UV-B radiation,  and
           there is limited evidence that pollen may be susceptible to UV damage
           upon germination.

     44b.  Reproductive structures enclosed within the ovary appear to be.
           well-protected from UV-B radiation.
45.  TMTERACnOHS BETUKEM PV-B RAPIAXIfff Miff ffiiH^*^ PiyTSiOMMBJfl!AL. FACTORS ARE
     IMPORTANT IN DETERMINING PQTEHTIAL PV-B EFFECTS COS  PLAHTS  (chapter 11) .

     45a.  UV-B effects may be worsened under low light  regimes or less apparent
           under conditions of limited nutrients  or water.

     4Sb.  Interactions with other environmental  affects make extrapolation of
           data from growth chambers or grsenheuees to field conditions
           difficult ***** often unreliable.
     45c.  Thafflimtilnsil affect of higher UV-B and other environmental changes
           eamfvt be adequately assessed by currant data,   Extensive, long-term
           stalls* would be required.
46.  TMTTTAL ICTKgTMgHTS SHOP THAT
                     mTBAVTATJPr BABTATTOt  RAW TJR POTSHTTAL TO HARM AQUATIC
                                          PKSTffltS AMP Tflg UMITRD SCOPE OF THE
     STUDIES PREVENT THE OPAMTTflCATIQH Of glSIEg (chaptar 12)-

     46*.  Increases in energy in the 290-320 nm wavelengths that would occur if
           the ozone layer were depleted could harm aquatic life.

     46b.  Various experiments have shown that UV-B radiation damages fish
           larvae and juveniles, shrimp larvae, crab larvae, copepods, and
           plants essential  to the marine food web.

-------
                                     ES-43
     46e.  Op to some threshold level of exposure, most zooplankton show no
           effect due to increased exposure to uV-B radiation.  However,
           exposure above tha dose threshold elicits significant and
           irreversible physiological and behavioral effect*.
     46d.  While the exact limits of col<
           been precisely determined, -as
           variety of aquatic organisms
     46«.
     46 j
47.
48.
                                             im and current exposure have not
                                                of these two properties for a
                                                  to bo aaaantially equal.
           Tha equality of tolerance and
           radiation is currently an Important
                                           * suggests that solar UV-B
                                                   ecological factor, and
      tha sunlight-exposed organisms sacrifice potential resources to avoid
      increased- UV-B exposure.  Thus, even small increases of UV-B exposure
      would be likely to further injure species currently under UV-B
      stress.

46f.  A decrease in column ozone is reasonably likely to diminish the time
      that zooplankton can survive or broad at or near the surface of
      waters they inhabit.  For some zooplankton. the time they spend at or
      near the surface is critical far breading,  whether the population
      could endure a significant shortening of surface time is unknown.

46g.  Sublethal exposure of copepods produces a reduction in fecundity.

46h.  Of the animals tested, no zooplankton possess « sensory mechanism for
      directly detecting UV-B radiation; therefore, it would be unlikely
      that they would actively avoid enhanced levels of exposure resulting
      from a reduction in colt

461.
           Exposure of a community to UV-B streaa in controlled experiments has
           resulted in * decrease in species diversity, and therefore  a possible
           reduction in ecosystem resilience and flaxibility.

           One experiment predicted an t percent annual loaa of the  larval
           anchovy population from a 9 percent reduction in column ozone  in a
           marina system with a 10-meter mixed layer.
                   ny py.g
                                                             BECAUSE
     VARIABLE Al'l'lHUATTOM OF TTV.ft BADTATTflH TTt
     48a.
                                                                         XBE
                                                         saaaaa. (chapter 12) .
             :ausa aquatic organisms are- mmall and do not ^ssually have fixed
           locations, it is vary difficult to obtain accurate data needed to
           modal the systems and verify results. ^Current maderstsnding of the
           life cycle of organisms la vary
49.  ABOPT OWE
                    OF THE gQRlP'S PRflTETl TS
MANY THTTIO WOBTJ5 eonNTRTBS  THTS
                                 PggrgHT
                                              fi»  TS
                                                             MSEARCH TS
     TO IMPROVE OUR nWDERSTANnTHC OP HOB OTfiH* arVfxTTOH COOTJ)
     SYSTEMS (chapter 12).
                                                                          THESE

-------
                                     ES-44


     49a.  A comprehensive analysis of sublethal and lethal effects of solar UV
           on littoral, benthos, and planktonic ecosystems is needed.

     49b.  A model of energy flow analysis leading to protein production where
           solar input ia augmented by increased ultraviolet radiation would be
           required to better evaluate potential affects.  Marine organisms
           responses to projected increaaaa is UV must be considered in the
           context of the «*ff?«n> as a dynamic moving fluid.
     49c.  Battar documentation of tha off acts of praaant levels of ultraviolet
           light on marine organisms is
     49d.  Intensive research is needed to identify biochemical indict that
           reflect UV stress in marine
     (chapter 13).

     SOa.  Several commercial polymers (e.g., polyethylene, polypropyli
           poly(vinylehloride)). although theoretically UV transparent, contain
           chromophore impurities diet absorb light in the UV-B region of the
           spectrum.  Other polymers (e.g.. polycarbonate) have structural
           features in their molecules that result in strong UV-B light
           absorption.

     50b.  Several polymers have important outdoor applications (e.g., used in
           siding and window glazing in the building industry, in film and
           containers in packaging, in housewares and toys, and in paints and
           protective coatings).  Such polymers are likely to be exposed to
           significant amounts of UV-B radiation.  Other polymers are stored
           outside before use and could deteriorate ****rHg these periods.

     50c.  Absorption of UV-B radiation in polymers causes photo-induced
           reactions and altars important machsnicsl. physical, or optical
           properties of the polymers (e.g., yellowing, brittleneas) and thus
           degrade* (i.e.. reduce* the useful life of) the polymers.

51.
     Sla.  XsmVMaod amounts of stabilizers might adversely affect the
           prooais!ii» «* «*• properties of some polymers 
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                                     ES-45
52.  TMCREASZP Py-B BAPIATIQN DOE TO Q2ONF pfyy^XIOH COPID HAVE ADVERSE ECONOMIC
             (chapter 13).
     S2a.  Changes in polymer processing properties can result in more equipment
           shutdowns, higher maintenance coses, and increased utility casts.

     52b.  Increased operating costs and material coats (e.g., for stabilizers,
           lubricants, and other additivea) vould have an adverse economic
           impact on the polymer/plastic and related industries. -

     52c.  In a. case study using preliminary data and methods, and a given
           scenario of ozone depletion (26% depletion by 2075), undiscountad
           cumulative (1984-2075) economic damage for poly(vinylchloride)  is
           estimated at $4.7 billion (USA only).  Due to the lack of data,
           possible damage to other polymers hast not been aaaessed.
53.  PqTEN'^IAL DAMAGES TO PQLVinrPg ymjrtirp TQ QZOHB PPLKTIOif *|fp
     f^v. i)fyyrctnj TO gsriMATg (chapter 13).

     S3a.  Due to lack of relevant; experimental 4ata, only approxiaate
           estimation •ethods are available to determine the potential extant of
           light-induced damage to polymera and other materials.

     53b.  Depending upon the chemical nature of a polymer, the components of
           «?h* compound, innj **«^ watfaerlog factors, frofb temperature
           humidity tend to increase t±a rate of
     53c.  Research on dose-response relationahlps for polymers could increase
           our ability to project the effecta of ozone depletion.

     53d.  Actual action spectra need to be developed for different polymers.

     53e.  The feasibility of different mitigation measures needs to be
           experimentally determined.

     53f.  The synergistic effects of increaaed humidity and temperature need to
           be considered.               •. ».•• •
                                         •***•
     54a.  According to these studies, increaaea in OV-B associated with ozone
           depletion vould increase the quantity of ground-baaed ozone
           associated with various hydrocarbon and nitrogen oxides emission
           levels.  Results for individual cities vary, denenrtl-ng on the city's
           location and on the exact nature of the pollution.
     54b.  According to these studies, global warming would enhance  the effects
           of increased UV-B radiation on the formation of ground-baaed ozone.

     54c.  According to these studies, ground-based ozone would form closer to
           urban centers;.  This would cause  larger populations in some cities to
           be exposed to peak values.                              •>         • — - -

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                                     ES-46
     54d.  Mora raaaareh is needed to verify and axpaad the results of these
           initial studies.
55.
TO DV.» BAPTATTMI
                                                                  (chapter 14)
     HYPRQGEH PgRffldPE BODLD MSPLT MOM TBCMAfi

     55a.  If hydrogen peroxide iaereaaes aa predicted la *Mf study,
           oxidizing capability potantial of the atmosphere, including the
           formation of acid rain, would be influenced.

     55b.  Mora research, especially a chamber study, is needed to -verify this
           affect.
56.
               TM CROnSP-flASgB QZOK1 O
                                                                   ttYAT Iff At
             (chapter 14).

           If UV-B increases enhanced ozone production, more U.S. cities would
           be unable to meet health-baaed ground-level ozone standards,  and
           background ozone would increase.

           Crops, ecosystems, and materials would be adversely affected by
           increased ground-level
     56a.
     56b.
57.
     EVKNTUAT-^Y TffCRFASTTf6 'fm 3ATB AT HHTm priTJhP rr» «ugBT«i mnT r»
     ICE THTO THE OCTAHS (chapter 15).
58.
            AYBRA^ SEA UVEL APPEARS TO HAVE RISES 10 TO is oc vtun *t^ ~~-^*.
     CEMTURY (chapter 15).

     58a.   Studies of the possible contribution of thermal expansion and alpine
           meltwatar to sea level rise, baaed on the 0.6°C warming of the past
           century, indicate that these two sources are insufficient to explain
           the eatimated sea level rise Oat has occurred during this period.  •
           Consequently, some other source, such aa melting of the polar ice
           caps, must be considered a poasibility.
59.
     59a.  According to published studies, tbarmal expansion of the oceans alone
           would increase sea level rise between about 30 cm and 100 cm by 2100.
           depending on the realized temperature change.  This is the most
           certain contribution.

     59b.  Melting of alpine glaciers sad possibly of ice on Greenland could
           each contribute 10 to 30 cm through 2100, depending on the scenario.
           This contribution also has a high degree of likelihood.
     59e.   The contribution of Antarctic deglaciation is
           project.  It has been estimated at between 0
           possibilities cannot be ruled out that (1) i
                                                         •ore difficult to
                                                            100 cm; however, the
                                                           aaed snowfall could

-------
                                     BS-47
               lase the size of tho Antarctic lc» sheet and thereby partially
           offset pare of the sea level riaa froa othar soureaa;  or (2)
           saltwater and .enhanced calving of tha lea shaet could incraaae  che
           contribution of Antarctic daglaciation to aa such aa 2 a.  Tha
           Antarctic contribution to aaa larval riaa aay be aore sensitive  eo
           tiaa delays after certain threshold conditions are reached than to
           die aagnituda of total waraing.
60.  OVER THE MUCH T/WCTP TKKM ^TffB inocT TKP cMTumm^ PTSTHTBSBATTON OF THE
     BEST ANTARCTIC ICT MHiLgT MldBP RAISE SEA LKVC. _BY 6 JiKtEHS (chapter 15).

     60a.  If a disintegration tafcea place, glaciologists generally believe th
           such a complete disintegration of the weat.Aatarctic ice sheet woul
           take at leaat 300 years, sad probably at least 500 years.

     60b.  A global waraing might result ia sufficient thinning of the Ross an
           Flleher-Ronae Ice Shelvea ia die next century to sake the process o
           disintegration irreversible.

61   T/VMT. TRENDS IN SPBSTPdCB AMP BttKCCTCK iBIST BK APOED 08. SUBTRACTED^TO
     cr/?BAL RISK ESTTMATKS Tlf QBPEft TO KTUJAT8 BBLATTVE SKA LZVEL RISE_AI
     PARTICULAR LOCATIONS (chapter 15).

     61a.  Host of die Atlantic aad Gulf Coasts of die United States--as well
           die Southern Pacific coast—are subsiding 10-20 ca per century.

     61b.  Louisiana is subsiding 1 a per century, while parts of Alaska are
           emerging 10-150 cm per century.

     61c.  Due to subsidence already occurring ia areas such as Bangladesh,
           Bangkok, and die Bile delta, dieae areas are extremely vulnerable t
           aea level rise.
62.  A SUBSTANTIAL RTSB Tit *)f^ Hnf^T- POPTJ PBMAingiTLY THIMPATE WETLANDS AND
                  ^n TPA
              TH8 SAT.TMtTY nv 'ESTUARIISS ejTO /^QPTy^ft^  (chapter 15).

     62a.  Louisiana is die scats aoatjwalaerable to  a rise ia aaa  level.
           Important impacts would also fggor ia Florida, jfarylaad, Delaware,
           •aw Jersey, and' ia dsa coastal regions of  acher statea.

     62b.  A. rise ia sea level of 1 to 2 a by die year 2100 could destroy 50
           percent to 80 percent of U.S. coastal wetlands.

     62c.  Limited studies predict daat increased salinity froa sea level rise
           would convert cypress swaaps to open water aad dureatan  drinking
           water supplies ia areas such as Louisiana, Philadelphia, and New
           Jersey.  Other areas, such as Southern Florida, may also be
           vulnerable but have not bean investigated.

     62d.  Studies of Bangladesh and  die Rile Kiver Delta indicate  th*c dxese
           river deltas, which are already subsiding, would be greatly affects
           by rising sea level, experiencing significant economic and
           environmental losses.                                 -        ' "*'•-

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           ' -                        ES-48


63.  EROSION PROJECTED IM VARIOUS STUDIES TO RESULT FROM ACCELERATE SEA
     RISS CfflTLP THPEATES U.S.  RECREATIOMAL BEACHES (ehaptar 15).

     63a.  Caaa atudias of baacfaas in Haw Jaraay, Maryland, California, South
           Carolina, and Florida hava concluded that a 30-em riaa in saa laval
           would result in beaches aroding 20-60 • or Jwara. .Major beach
           preservation efforts would ba raquirad if racraational baachaa ara to
           be maintained.

£A   AfifiyT_lftt a\Tffft SCA. T-W^FBT^ ftYSC flOOZJD ^MGBSASZ TOT? ttaVmmCKS tltflM wff-flQpTjIlC TW
     COASTAL AREAS (chapter 15).

     64a.  Flood damages would increase bacauaa highar water levels would
           provide a highar base for stora aurgaa.

     64b.  Erosion would incraaaa die vulnerability to atorm waves, and
           dacraaaed natural and artificial drainage would Increase flooding
           during rainstorms.
65.  ESTIMATES OF DAMAGE EKOH SEA TJtVg. ttTSK JgtST COMSlftiK TOSSI^^* MTTIGA.TIOH
     BY HDMAN RZSPQHSgS (chap tar 15).

     65a.  Tha advarsa iapaeta of aaa larval riaa could ba awalioratad through
           anticipatory land uaa planning and atructural daaign changaa.

     65b.  In a caaa study of two eitiaa, Charlaaton, South Carolina, and
           Galvaston, Taxaa, acealaratad anticipatory planning waa aat'imatad to
           raduca nat daaagas by 20 to 60 pareant*
66.  ttglATBP TMPACTS OF A ClJPBAV gABMTWC BPPLP AI.SQ AVVRt.'!' IMPACTS OF SEA LEVEL
     RISE (ehaptar 15).

     66a.  Ineraasad droughts might aoplify dia salinity ijapacts of  aaa laval
           riaa.

     66b.  Ineraasad hurricanaa and ineraaaad ratnf al 1 in coaatal araaa could
           amplify flooding froai aaa laval riaa.  ~
     66c.  Waraar tavparaturaa light iapair paat Jofiaation of salt warahaa and
           weul^anabla •angrova awaapa to taka awar araaa that ara  praaantly
           aaltyprah.

     66d.  Dacraaaad nerdiaaatara wight raduca
67.   RESEARCH OPPQRnnTTTIBS ECTST TO DtP80V15 SKA LKTEL tt.IS8 BSTIMAIliS AHD
     IMPACTS (ehaptar 15).

     67a.  Tha wost critical araaa of raaaarch for Ta4nr1ng tha -variation in
           aatimatas of fueara aaa laval riaa  axa  ica Malting and runoff in
           Antarctica and Graanland and ica diacharga.

     67b.  Raaaareh in glacial diseharga in Antarctica ahould focus not just on
           Vaat Antarctica, but on Piaa Island and East  Antarctica.

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                                     ES-49
      67e.  An improved program of tidal gauge station*, •specially in tha
           southern hemisphere, and satellite altimatry should be used to
                 re  saa level rise and the Bass balance of ice sheets.
 68.   CT-TMATE  CHABCE HAS 'HAD A SICHIFICAHT IMPACT OH FORESTS HT THE PAST.  IF
      CURRENT  PREDICTIONS WQWij ACgnttATg. Bggg IS A POTENTIAL FOR DRAMATIC
            IH  POBKSTS AND VKCKTA.TTOH OVUB ^ffi ^PtT TOO Y8ARS (chaster 16)•
      68a.  Climate models predict that a global •"^^ng of approximately 1.5°C
           Co 4.5°C will be induced by a doubling of atmospheric 002 and other
           trace gaaaa during tha next 50 Co 100 Tears.  The period 18,000 to 0
           year* B.P. is the only general analog for a global climate change of
           this magnitude.  The geological record from this glacial to
           inter-glacial interval provide* a baaia far ^qualitatively
           understanding how vegetation may ebanga in raaponaa to large climatic
           ebanga.

      68b.  The paleovegetational rocord abova that climatic change as large aa
           that expected to occur in raaponaa to C02 doubling is likely to
           induce significant changes in cha eoaposition and patterns o£ the
           world's bioaaa.  Changes of 2°C to 4°C hare bean significant enough
           to altar the composition of blames, and to eauae new biomes to appear
           and others to disappear.  At 18,000 B.P., the vegetation in eastern
           North America was quite distinct from that of the present day.  The
           cold, dry climate of that time teems to have precluded the widespread
           growth of birch. hemlorV, beech, alder, hornbeam, aah, elm, and
           chestnut, all of which are fairly abundant in present-day deciduous
           forest.  Southern pinea were limited to grow with oak and hickory in
           Florida.

      68c.  Available paleoecologieal and paleoclimatological records do not
           provide an analog for the high rate of climate change and
           unprecedented global warming predicted to occur over the next
           century.  Previous changes in vegetation have been associated with
           climates that ware nearly 5°C £o 7°C cooler and took thousands of
           years to evolve rather than rtejeiles, the time during which such
           changes are now predicted to eoovr.  Insufficient tempera! resolution
           (e.g.. via radiocarbon dates) limits our ability to analyze the
           deeadal-acale rates of change tfeat occurred vrior to the present
     6S4.~ T.tmired experiments conducted with dynamic vegetation models for
           •orth America suggest that deereaaea in net blomaaa may occur and
           that significant changes- in species composition are likely.
           Experiments with one model auggeat that eastern Berth American
           biomass may be reduced by 11 megagrams per hectare (10% of live
           biomaaa) given the equivalent of a doubled C02 environment.  Plant
           taza will respond individualiatically rather than aa whole
           communities to regional changes in climate variables.  At this time
           such analyses must be treated aa only suggestive of the kinds of
     4 Findings 68 to 71 are summarized from Appendix B, which provides a
comprehensive review of potential impacts of global climate change.

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                                     ES-50
           chang* that could occur.  Many critical processes arc  simplified or
           oaittad and the actual situation could be versa or better.

      68*. Future forest management decisions in major timber* growing ragions
           ara likaly to ba affected by 'pfr^rfi'* in natural growing conditions.
           For axample, ona study suggests that loblolly pin* populations ara
           likaly to aova north and northaast into Pennsylvania and Bev Jersey,
           while its rang* shrinks in tha wast.  Tha total gaographic rang* of
           tha spacias asy ineraaaa, but a net loss in produetiTity may result
           baeausa of ahifts to lass aceaasibla sad lass -productive sitas.
           Vhila tha axtant of such changes is unclear, adjustaents will ba
           naadad in forest technology, resource allirestiop, planning,  tree
           breading programs, and decision-Baking to aaintain and increase
           productivity.

     68f.  Dynsaic vegetation Bodela based on theoretical descriptions  of all
           factors that could influence plant growth must ba improved and/or
           developed for all major kinds of vagatation.  In order to make more
           accurate future predictions, these models must ba validated  using the
           geological record and empirical ecological rasponse surfaces.  In
           particular, tha geological record can ba used to teat  the ability of
           vegetation Models to simulate vegetation that grew under climate
           conditions unlike any of tha modern day conditions.
     68g,  Dynamic vagatation models should incorporate direct effects of
           atmospheric C02 increases on plant growth and other air pollution
           effects.  Improved estimates of future regional climataa are also
           required in order to make accurate predictions of future vegetation
           changes.
69.  T-TKT-nm Assasst^ffg gycCTsr THAT mpoBTMrr emmeies n> AcaTCPLTDRE AND FARM
     PB.OPUCTTVITY. ARE LIKELY THBOOtSfflTf TSB ffOKTJ? Ty CTJUAJK OUMCS OCCURS AS
                 gsTTM*T^s (py IMPACTS OH spgg]7IC MSIQHS mfiK f>| fFlflf^T TO MAKE
     AlTEBMATIVK SCUTARTQS (chapter 16) .    -" --ev'*
     69a.  Climate has had a significant impaet'«n faxm productivity and
                        distribution of crops,  fetamplaa include tttm 1983
                       «f^ gome fluted to a nearly 30 percent reduction in corn
                  la the U.S. ; tha persistent Great Plains drought between
           1932-1937, which contributed to nearly 200,000 farm bankruptciaa; and
           tie climate shift of tha Little-lea Age (1300-1800), which led to the
           •handonmant of agricultural settlements in fr?i>tlmy| and Borway.

     69b.  World agriculture is likaly to undergo significant shifts if
           traca-gaa-inducad climate warming in tha range of l.~3°C to 4.5°C
           occurs over the next SO to 100 years.  Climatic effects on
           agriculture will extend from local to regional aad international
           levels.  However, modern agriculture is vary dynamic aad is
           constantly responding to changea in production, marketing, and
           government- programs.

     69c.  The main effects likaly to occur at tha field level will be physical

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                                    ES-51
           impacts of changes  in thermal regimes, water eonditiona, and past
           infestations.   High tenperaturea have caused direct damage  to crops
           auch aa wheat  and corn; moisture atraaa, often associated with
           elevated temperatures,, is harmful  to corn,  soybean, and wheat during
           flowering and  grain fill; and increased pests  are associated with
           higher, •ore favorable temperatures.

     69d.   Ivan relatively snail increases in the mean temperature can inci
           the probability of harmful effects  in acme regions.  Analysis of
           hiatorical data has ahown that an incraaaa of 1.7°C  (3°F)  in mean
           temperature changes by about a factor of  three  the likelihood of a
           five-consecutive-day maartmnm temperature  event  of at laaat 35°C  .
           (9S°P)  occurring  in a city like Dee Moines.   Xa regions where crops
           are grown eloae to their maTlmna  tolerance limits, extreme
           temperature events may nave  aignif icant barmful ef fecta on crop
           growth  and yield.

     69e.   Limited axperimenta using climate scenarios  and agricultural
           productivity models have demonstrated the sensitivity  of agricultural
           systems to climate change.   Future  farm yields  are likely  to be
           affected by climate because  of changes  in the length of the growing
           season, heating units, extreme winter temperatures,  precipitation,
           and evaporative «I*M«MI-.   In  addition, field  evaluations show that
           total productivity is a  function  of the drought tolerance  of the land
           and the moisture  reserve, the  availability of land,  the ability of
           farmers to shift  to different  crops,  and  other  factors.

     69f .   The transition costs associated with  adjusting  to global climatic
           change  are not easily calculated, but are likely  to  be very, large .
           Accommodating to  climate change may require  ahifting to new lands and
           crops,  creating support  aarvieaa  and  induatriea,  improving and
           relocating irrigation systems, developing naw soil management  and
           peat control programs, and breeding and introducing  new heat*  or
           drought •tolerant  species. The consequences  of  these decisions  on the
           total quantity, quality, and coat of  food are difficult to predict.

     69g.   Current projections of the effects  of climate change on agriculture
           are limited because of uncertainties  in predicting local temperature
           and precipitation pattar&a talma; -global climate models, and because
           of the  need for improved reaearch atudies uaing controlled
           atmoapherec, statiatieal regreaaion modela,  dynamic  crop models and
           integrated modeling approachea.
70.  H&TZB^ RESOURCE SYSTEMS HAVE PitPRBQQHP IMPORTANT CHARGES AS THE EARTH'S
     CLIMATE HAS SHIFTED TH Tfflt PAST.   CPMBMT AHAI.YSKS BfflPSST AH 1NTENST"PTTT>
                       jf CT.TMATR  eHAnen oeenftfi AS gftKPTCTED (chapter 16).
     70a.  There is evidence that climate change aince the laat ice age (18,000
           years B.P.)  has significantly altered the location of lakes --
           although tiie extant of preaent day lakes is broadly comparable with
           18,000 years B.P.  For example, there is evidence indicating the
           existence of many tropical lakes and swamps in the Sahara, Arabian,
           and Thor Deserts around 9,000 to 8,000 yeara B.P.

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                                     ES-52
     70b.  Tho  inextricable  linkages between tha water cycle and climate ensure
          that potential future climate change will significantly alter
          hydrologic processes  throughout  tha world.  All natural hydrologic
          processes --precipitation, infiltration, storage and movement of soil
          moisture, surface and subsurface runoff, recharge of groundwater, and
          evapotranspiration— will be affeetad if climate changes,

     70c.  As a result of changes in key hydrologic variables such as
          precipitation, evaporation, soil •oisture, and runoff, cliaata change
          ia expected to have significant  affects on water availability.  Early
          hydrologie Impact studies provide evidence that relatively small
          changes in precipitation and evaporation patterns might result in
          significant, perhaps  critical, changes in water availability.  For
          many aspects of water resources, including human consumption,
          agricultural water  supply,  flooding and drought management,
          groundwater use and recharge, and reservoir design and operation,
          these hydrologic  changes will have serious Implications.

     70d.  Despite significant differences  among climate change scenarios, a
          consistent finding  among hydrologic Impact studies is the prediction
          of a reduction in summer soil moisture and changes in the timing and
          magnitude of runoff.   Vintar runoff is expected to Increase and
          summer runoff to  decrease.  These results appear  to be robust across
          a range of climate  change  scenarios.

     70e.  Future directions for research  and analyses suggest that  Improved
          estimates of climate  variables  are needed from large-scale climate
          models; innovative  techniques are needed for  regional assessments;
           increased numbers of  assessments are necessary to broaden our
          knowledge of effects  on different users; and  increased analyses  of
           the  impacts of changes in water resources on  the  economy  and society
          are  necessary.
71.  MORBIDITY AKP MQRTAt^TTY RATES ARE ASSQCTATKP fflTP PEA.THBB ETTMjflgg m OUR
     SOCIETY (chapter 16).

     71*.  Weather has a profound affect on hmman health and wall being.  It has
           been demonstrated that weather is assort arid with changes ia birth
           races, outbreaks of pneumonia, iaflmawca, and bronchitis, and related
           to other morbidity effects, and is linked to pollen concentrations
           and high pollution levels.

     Tib.  Large increases la mortality have occurred, during previous heat and
           cold waves.  It is estimated that 1,327 fsrsllrlas occurred la the
           United States as a result of tha 1980 heat wave, and Missouri alone
           accounted for over 25 percent of that total.

     71c.  Hot weather extremes appear to have a more substantial Impact on
           mortality than cold.wave episodes.
     Tld.  Threshold temperaturea, which represent marl mum and minimum
           temperatures associated with Increases in total mortality, have beexv.
           determined for varioua cities.  These threshold temperatures vary
           regionally; for example, the threshold temperature for winter

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                                ES-S3


      mortality IB mild southern cities such a* Atlanta is 0°C and for more
      northerly cities such as Philadelphia, threshold temperature is -5°C.

71*.  If future global warning induced by increased concentrations of trace
      gases does occur, it has the potential to affect human Mortality
      significantly.  In one study, total summertime mortality in New York
      City was estimated to increase by over 3,200 deaths per year for a
      7°F trsce-gas-induced warming without acclimatization.  Zf Bew
      Yorkers fully acclimatize, the number of adrtiffmial deaths is
      estimated to be no different than today.  It is hypothesized that if
      climate warming occurs, some additional deaths are likely .to occur
      because' economic conditions and the basic infrastructure of the city
      will prohibit full acclimatization even if behavior change*,

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                                     ES-S4
            QOAHriTATTVE ASSESSOR! OF KXSXS HTH XHIB3AZID MODEL

    AS INTEGRATED ASSESSMENT Ot5 TOR VARIOUS SCENARIOS OF
SUBSTANCES SHOWS THAT HARM DEPENDS OW THE ^fl**^ Of THE gROPDCTIOK OF
AND BRQMINE . B^tlNC SOTSTANCEg.

    Risks ara avalxsatad by using Cha intagratad aodal to aiaulata tha impact of
"what -if" scenarios of production of ozona-daplating substancas and scenarios of
othar trace gas concentrations on tha ataosphara and on huaan health and tha
environaent.   Sensitivity analyses of alternative assuaptions are also
conducted.

    Analysis of tha results of all tha scenarios indicates that adverse iapacts
on health and welfare are lowered with reductions in tha production of ozone*
depleting substances.

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                                     ES-55


72. ttopiyrcATTos OF THE TRACE CAS  coaposinQK OF THE ATMOSPHERE CAN BE
    TO ALTBt COMIC? Q2QHE ABUHDAHCfi (chapter 18).

    72a.    The range of global average total coluan ozone change projected for
            the year 2075 baaed on a paraaeterized representation of a
            one-diaensional aodel  could vary froa  as high as over 50 percent
            depletion, for a case  where global use of chlorine aad  broalne
            bearing aubataacea grows at aa average *wvfl rate of 2.8 percent
            froa 1985 to 2100 (5.0 pereeat pax year froa 1985 to 2030, followed
            by no growth through 2100), to increased abundance of ozone of
            approxiaataly 3 percent, for a ease where global use of chlorine aad
            broaine hearing substances declines  to 20 pereeat of its 1985 value
            by 2010.  Exhibit ES-6 displays  the  global ozone change estiaates
            for these two scenarios, aa well aa estiaates for four  aeenarioe in
            between; the aix "what if* scenarios eraainad include:
                   RffaCtlPTT  Vaa  of chlorina aad bromina baaring aubataaeaa
               daeliaaa to 20 pareaat of  ita 1985 valua by 2010, aad ramaiaa
                        thereafter, yialdiag approxiaataly 3.0 percent increased
                     abundance by 2075;
               Bo Crovefa;  no  growth  in uae of chlorina aad broadna •bearing
               aubataneea  froa 1985 to  2100, yielding approxiaately 0.3 percent
               iaereaaed ozone abundance >y .2075;

               l.gt firowch;  1.2 percent growth froa 1985  to 2050, followed by
               no growth,  yielding approziaataly 4.5 percent depletion by 2075;

               2.S» Croveh;  2.5 percent growth froa 1985  to 2050, followed by
               no growth,  yielding approxiaataly 25  percent depletion by  2075;

               3.8% Crovgh:  3.8 percent growth froa 1985  to 2050, followed by
               no growth,  yielding over 50 percent depletion by 2075;

               3.0* Growth:  5.0 percent growth froa 1985  to 2050, followed by
               no growth,  yielding over 50 percent depletion by 2075.
           The trace  gaa concentration aaaoaptions uaed in theae aix eases are:
           C02 — HAS 50th percentile; CB4 -.-.0.017 ppa per yaar (approxiaataly
           1 percent  of current CH4 concentration); aad H20 — 0.20  percent par
     72b.   Current data are not sufficient for distinguishing whether CB4
           concentrations are likely to increase in a linear manner  (e.g. at
           0.017 ppa per year, or approxiaataly 1 pareaat of currant
           concentrations) or in a coapound aaaner (e.g., at 1 pareeat par year.
           coapouaded annually).  The sensitivity of the ozone change esdaatas
           in 2075 was  evaluated for the following aix aaauaptiona regarding
           future  CH4 concentrations:

           o   Seansrio A!  coapound annual growth of 1 percent froa 1985 to
              2010, followed by constant concentrations at 2.23 ppa;

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                                     ES-56
                            OF GLOBAL OZOB 9BUZXOB XI 2075
                            FOR. SIX CASES OP CIC QSB
               10
               •10
    OzanaCtMnaa
               •20
               •SO
               •40
               •40
                             •raw*   12S   U»
                                              •raatamMftMftaaatatton
     Uaing a paraaMtarizad rapraaantation of a ona-diaanaional Bodal, tha
potantial changa in ozona waa avaluatad for aiz acanarioa:  80% Raduction:
global CFC uaa daclinaa to 20 parcant of currant larval* by 2010, and raaains
constant tharaaftar; No Growth:  no growth in CFC uaa froa currant lavals; 1.2%
Growth:  1.2 parcant growth fro* 1985 to 2050, followad by no growth; 2.5%
Growth:  2.5 parcant growth froai 1985 to 7050, followad by no growth; 3.8%
Growth 3.8 parcant growth froai 1985 to 2050, followad by no growth; 5.0% Growth:
5.0 parcant growth froai 1985 to 2050. *«*§jfe by no growth through 2100).  Tha
                 p**imi ***i«>eiona uaadlS^Baaa aiac caaaa ara: C02: HAS 50th
par cant ila; CB4: 0.017 ppa par yaar (approxliiataly 1 parcant of currant CH4
concantratioa); and H20: 0.20 parcant par yaar.
     Currant 1-D aodala aecurataly raflact global daplation; Antarctic oxona
     hola haa no lapaet on global oxona laval*.
                                                                         latad
Graanhouaa gasaa that countar daplation grow at hiatorically-axtr
rataa.

Growth rataa for ozona daplation ara for global aaiaaiona;  it ia aaauoad
that aaisaiona do not incraaaa aftar 2050.
     Ozona daplation lioitad to 50 parcant.

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                                     ES-57
           o   Seanario B:  linaar growth at 0.01275 ppa par yaar (75 pareant of
               tfaa 0.017 ppa growth);
           o   geanmrlo C:  linear growth of 0.017 ppa par yaar (approxiaataly 1
               parcant of currant concentrations);
           o   pe«M*-La P;  linear growth at 0.02125 ppa par year (125 parcant
               of tha 0.017 ppa growth);

           0   geanario E:  coapouad «mn«l growth of 1 pareant;
           «   $fifBICi&_£:  eoapouad aimnsT growth of 1 percent froa 1985 to
               2020, growing to 1.5 parcant i"*ar*iimf •«"""1 growth by 2050 and
           For tha 2.5% Growth aeenario, the astlaeta of ocone daplation by 2075
           rangaa from about 14 parcant (Scenario F) to 30 pareant (Scanario A)
           acroaa tha*a six CB4 assuaptiona evaluated.  Exhibit ES-7 displays •
           tha results for these six CB4 asauBpcions.  Aa ahown in tha axhibit,
           dia diffaranea batwaaa tha 1 pareant linaar (0.017 ppa par yaar) and
           1 parcant coapoundad aaauaptioaa (Scanarioa C and E) i* approxiaataly
           6 parcant daplation.  Thia aancitivlQr of tiia ozoaa daplation
           aatiaata* to tha aacuaption about linaar Taraua coapound growth of
           CHA eoncantrations ia auch largar than tha aansitivity to tha ranga
           of aaauaptiona rxaninad ragarding futura 002 concantrationc (froa tha
           25th to tha 75th pareaatila HAS aatiaataa) and ragarding futura N20
           eoncantrations (froa 0.15 parcant simusl coapound growth to 0.25
           pareant annual coapound growth).
73.  TOP.PTKRttSTOHAL (g.p) MOPgTS fmTOTgT Cyg***'*g AYfflA'jfP GLOBAL PCTTBTIOS THAU
     OffE-PTMEHSTQKAL fl»g> MffgE^S-  2-P *ataa&_L1SR WlgPTgy THAT Q70KK DEPLETIC»I
     cm. Bteggp THE GLOBAL AVERAGE AT HTCH IATITPPES A»» *« TJ!!g5 TB/tfT THfi
     GLOBAL AVgRACE AT THE EQUATOR (chaptar 18).
     73a.  For a eaaa of 3 pareant *^"**1 growtii in aaiaaions of CFCs, no
           oaiaaions of Halons, and incraaaas in traea gaaaa of: C02 --
           approxiaataly 0.6 pareant par yaar; CB4 •• 1 pareaat par yaar; and
           K20 •• 0.25 pareant par yaar, a 2-D aodal aatiaataa approxiaataly 5.A
           pareaat global avaraga 4aplatioa*ftgr 2030.  For tha aaaa aeanario of
                               tmm fwitfwyfff^tfi . t**^ paraaatarizad
           Representation of a 1-D aodal aatiaataa only 3.0 pareant daplation by
           •1030.

     73b.  For thia aaaa eaaa of aaia'sions aad trace gaa eoncantrations, tha 2-D
           aodal eatiaataa of ocoaa daplation in 2030 at high latitudes are
           approxiaataly; 60°H — 8.7 pareaat; and 50°I — 7.0 pareant.

74.  KSTTMATKfi nv MMPSPHEPTe MOPTTTCATIOW. ffltTK CAHCTB CASKS AHT) PEATHS.
     fiATAPAfT ftWVC  MATVPTATC 1\AltA  CTfMLAT
     an TOT; BATE AT WHICH OZONE-DEPICTING CAS*S CRffffi A*n
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                                     ES-58
                                 EXHIBIT ES-7
                                                      01 2075
  no
           •10
           •20
           •so
     Using a paraaotorizod representation of a one-dimensional model, the
potential change in ozone vas evaluated for aix aasuBptions about future aethane
concentration:  Seenaiflp ^: compound annual growth of 1 percent from 1985 to
2010, followed by constant concentrations at 2.23 pper, gfitTTflTlf* ft* linear growth
at 0.01275 ppm per year (75 percent of the 0.017 ppm growth); Scenario C: linear
growth of 0.017 ppm per year (approximately 1 percent of current
concentrations); fr^jnario Pi linear growth at 0.02125 ppm per year (125 percent
of the 0.017 ppa growth); s«t«Mrta E: compound annual growth of 1 percent; and
          : compound annual growth of 1 percent fro» 1985 to 2020. growing to
1.5 percent compound annual growth by 2050 and thereafter.
     All estimates based on the 2.5% Growth
growth from 1985 to 2050, followed by no
gas assumptions used in these cases arm: 002:
percent growth per year.
                                                •rio 1985 to 2100 (2.5 percent
                                                thereafter).  The other trace
                                              •AS 50th percentile; and H20: 0.20
     Current 1-0 models accurately reflect global depletion; Antarctic ozone
     hole has no impact on global ozone levels.

 ..   Greenhouse gases that counter depletion grow at historically-extrapolated
     *»tes.

 -   Growth rates for ozone depletion are for global emissions;  it is as
     that emissions do not increase after 2050.
     Ozone depletion limited to 50 percent.

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                                     ES-59
     74*.   The models used in this risk assessment assume  that Antarctic ozone
           depletion haa no global implications and  that global  trends do not
           invalidate estimates of current models.

     74b.   Except as noted, projected effects assume that:  greenhouse gases grow
           at historical rates indefinitely;  current one-dimensional models
           accurately project depletion; production  of ozone deplaters does not
           grow after 2050; ozone depletion is Hsrffad «o  50 percent; the action
           spectrum causing skin cancers is OKI; sad the temperature sensitivity
           of the earth to doubled C02 is 3°C.

     74c.   In 2100, projections of ozone depletion range from over SO percent
           for the 5% Growth scenario (ozone  depletion is  constrained at 50
           percent in this analysis) to 47 percent for the 2.5%  Growth scenario
           to an increase in column ozone abundance  of marly 5  percent for the
           80% Reduction scenario.

     74d.   For cohorts born before 2075, the  number  of additional nonmelanoma
           skin cancers projected ranges from a 261.5 million increase for the*
           5% Growth scenario to a 115 million increase  for the  2.5% Growth
           scenario to a reduction of 6.5 million skin cancers for the scenario
           of 80% Reduction in all ozone depletars,

     74e.   For cohorts born before 2075, the  increase in total melanoma eases
           ranges from a 1.3 million case increase for the 5% Growth scenario to
           a 609,000 increase for the 2.5% Growth scenario to 54,000 fewer cases
           for the scenario of an 80% Reduction in all ezoae depleters.

     74f.   For cohorts born before 2075, total mortality from melanoma and
           nonmelanoma ranges from a 5.6 million  increase  for the 5% Growth
           scenario to a 2.4 million increase for the 2.5% Growth scenario to
           115,000 fewer cases for the scenario of 80% Reduction in all ozone
           depleters.

     74g.   For cohorts born before 2075, the  increase in total cataract cases
           ranges from 26 million for the 5%  Growth  scenario to  15.1 million for
           the 2.5% Growth acenario to 9,500  for  the scenario of 80% Reduction
           in ozone depleters.
     74h.  The rise in global temperature W-.J075 rangea from U.6°C in the 5%
           Growth acenario to 5.6°C in the^5* Growth scenario:co 4°C in thai
           scenario of 80% Reduction in all ozone depletars.

     74i.  Impacts are also projected for ot&er areaa such aa aaa .level rise.
           ground-baaed ozone. Materials, aquatics, sad aoybean yield.

75.  ODAMT1TATIVE ESTIMATES OP BISKS VMEY wTTH ASSIBgTTOWS ABOOT FPTDRE
     gMISSTOMS QP CttgEHUOPSE CASES THAT PTTJ. COSffBTinTg TO GLOBAL gARMTBC
     
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                                     BS-60
     75b.   If future deeiaionmakars limit the concentrations of C02, H20, and
           CB4 to prevent global warming from exceeding 2°C (±50%)  in 2075, thay
           would by -necessity have to li»it growth of ozona daplatars to tha No
           Growth case;  for'other eaaas increases in ozona daplatara would ba
           too largo to achieve that objective.

     75c.   Ozona daplation aaaoelatad with tha Bo Growth or 1.2% Growth
           scenarios iaoraaaaa naarly 3 to 5 pareant if global  warming ia
           limited to 3°C (±50%); akin eanear deaths would increase 43 pareant
          ' for.paopla alive today.               v                •
     7Sd.  Estimates of T*****"* •^••f»«^ ara inherently uncertain even without
           consideration of futura policy daciaiona and could affact
           quantitative riak eatimataa.
76.  QPANT1TATTVE ESTIMATES Of RTSK VMBT BTTB"t!WJC*JTATMTT ABflOyPOSE-pJESPOlTSE
     coEFFTcimrrs.  Adirion SPECTRUM-  IJKTTS of QZONK PEPUTTQH.  AHP
     BE5POJf5IVP^^^ OF MOPET^ TO ATitos^tBS^c PRPLBTTOR (chanter 18)

     76a.  For people aliva today and born bafora 2075, additional skin cancer
           eases would be reduced 45 pareant if one assumes the lower dose*
           response coefficients that are one standard arror below the best
           estimate and 66 percent higher if ona assumes the higher coefficients
           that are one standard arror above the beat estimate.

     76b.  For people alive today sad born bafora 2075, additional skin cancer
           cases would ba raducad 11 percent if the Erythema action spectrum,
           rather than tha DHA, action spectrum, ware used to measure health
           effects.

     76c.  Limiting projected daplation to 50 pareant from what the
           parameterized 1-D model would project reduces projected deaths for
           later cohorts.  For people born from 2030 to 2074, limiting depletion
           to 50 percent reduces deaths by 13 percent for tha 2.5% Growth
           scenario and 66 pareant for tha 5% Growth scenario.

     76d.  For people alive today and born'Before 2075, akin cancer cases would
           be reduced 62 percent in the 2.5% Growth scenario if the atmosphere
           wars lass sensitive to potential jeVtioa daplatars (using the 10th
           pereantila)» and increased 54 paromut If tha. atmosphere wore
           sensitive (using the 90th parcenrflbe). -
                                      **- MAPK AT TWTS TTMK. CASK SRSHPI MSOLTS
                    .      PAMACg. MiP LOSS OF C80F TULfl /MKB PMSCTK (chapte
     18).

-------
                                     ES-61
                        OF ms ISSUE

     A number of prior assessments of atratoapharie modification and climate
change have bean dona.  A partial liat with daaeriptiona is ineludad balow:
1.   National Academy of Sciences (HAS). 1975. 1976. 1979. 1982.  1983

     Several assessments of anthropogenic influaneea on the stratospheric ozone
layer were coordinated by the National Academy of Sciences.  The  first report,
in 1975, focused-on the effects of propoaed floats of supersonic  transports on
the stratosphere.-  Subsequent reports focused OB ehlorofluorocarbons.

2.   National Aeronautics and Spaee Administration (NASA), 1977.  1986

     NASA has convened several technical panela to review models  and chemistry.
In addition, it completed a scientific assessment in 1986.

3.   Vorld Meteorological Organization.
     National Aeronautics and Spaea Administration,
     Federal Aviation Administration,
     National Oceanic and Atmospheric Administration,
     United Nations Environment Programme,
     Commiaaion of the European Communities, and
     Bundeministerium fur Forschung und Technologic

     International assessments of the stratosphere have been conducted by the
European Community, the United Kingdom's Department of the Environment (1979),
and by the United Nations Environment Coordinating Committee on the Ozone Layer
(1981, 1984, 1986).

     The most recent and most ambitious assessment of the scientific issues
regarding the stratosphere was coordinated by the Vorld Meteorological
Organization with the assistance of several other organizations.   Approximately
150 of the world'a leading scientists participated in this assessment.
1.  Climatic Impact Aaaeasment Program. 1974

    Initial concern over anthropogenic influences on the climate and the
stratospheric ozone layer lad in 1971 to the establishment of the Climatic
Impact Assessment Program (CIAP).  Coordinated by the Department of
Transportation, CIAP's objective waa to aaaeaa, by a report in 1974. the Impacts
of climatic changes duo to projected fleeta of supersonic transports.

2.  National Academy of Sciences:  1979, 1982, 1983

    Three panels were convened by the National Academy of Sciences to aaaeas the
scientific basis and certainty of the effecta of carbon dioxide concentrations
on global climate.  Reports ware raleaaad in 1979., 1982. and 1983.

-------
                                     KS-62
3.  tforld Matarological Organization,
    International Council of Scientific Unions, .sad
    Unitad Rations Emrironaant
    Efforts to aehisva an iatarnational  scientific eoasonsus oa carbon dioxide,
trac* gasea, and cliaata war* eoordiaatad by the World Hatarological
Organization (WO), TTH*^n^y1
-------
                                      ES-63
 Commission of th« European Communities,  (1981),  Evalnatier^ of the Effaces of
     ChlaraflAiefaearpotia on Ataoapheri.e Ozene !   Pf eaeat S**a
    Brussels , Belgium.

Department of the Environment,  (1979),
              '
                                                                    if f •t on
                   Ozone.  Pollution Paper No.  15,  Central Directorate of
     Environmental Pollution,  Department of the Environment,  London, 'U.K.

 EPA Science Advisory Board,  (March 1987),  Review of EPA 'a An Aaaeaa»eng of the
     Rlaka of Stratospheric Madtfteatloy. prepared by EPA'S Science Advisory
     Board, Washington,  D.C..  SAB-EC- 87-025.

 Crobecker, A.J.,  S.C. Coroniti,  and R.H. Cannon. Jr., (1974), Keoort of
     Findings.  The Effects o^ Strataapherie  Pollution bv Aircraft.
     DOT-TST-75-50, prepared by the Department of Transportation Climatic Impact
     Assessment Program, Washington, DC.  •

 Hoffman,  J.S.  (1986), "The Importance of Knowing Sooner," in J.C.  Titus (ed.),

     Overview.  U.S. Environmental Protection Agency,  Washington, DC.

 Hunter, J.R. ,  S.E. Kaupp, and J.H.  Taylor. (1982), •Assessment of Effects of
     Radiation on  Marine Fish  Larvae," in J.  Collins (ed.), The ttola  of Solar
     Ultraviolet Radiation in  Marine Keosvsteaa. pp 459*497,  Plenum,  Hev York.
National Academy of Sciences  (HAS),  (1979),  Carbon Pieride mA Q|p^fy;   A.
    Scientific As«e«siMflt. National  Academy  of Sciences,  Washington, DC.

NAS (1982), Carbon Dioxide and Cliaatei   A Second Asse««»en1^.  National Academy
    of Sciences, Washington,  DC.
NAS (1983), Changing
                                      nf
IMnvfil* &*•*«•
    fifiejBi££ee., National Academy of Sciences, Washington, DC.



NAS (1976), H*T«^»»^»ona;  Effeeta on Stratnaphgrte Qgone. HAS, Washington, DC.

HAS (1979), PrefcaeCion Ayainat Depletion of StraCoaaharte Qgena bv
    Chlorofltiaraftarfao|ia. NAS, Washington, DC.

NAS (1979), Stragaapherie Ozone Dealetiatt by Tial ftearbona;
               NAS, Washington, DC.

                       Effects of Stratoanhairle Oeone ftaduerdi
NAS (1982) ,
    NAS, Washington, DC.
NAS (1984), Cauaes and Effect^ of Changea  in Stratosphgrie  Qzt
    NAS, Washington, DC.

-------
                                     ES-64
National Aeronautics and Space Administration (RASA) (1977),
    ChlorofluoroiMthanea and, the Stratosphere. RASA Reference Publication 1010
    RASA. Washington, DC.

RASA (1986), Freaanc State of Knowladfa of th» Pppag Aea
         . NASA Reference Publication 1162, HASA, Washington, DC.

Seotto, J. (1986), •Hon*slanoaa Skin Cancar - TJV-B Iff acts," in J.G. Titus
    (ad.)  Z{f&ct.3 of Changes in Stratoan^**TJ.c Qgat>* *ftd Clohal. CllMattti  Voli
    2: Stratospheric Ozone. U.S. Environmental Protection Agency, Washington.
    DC.

Sarafino. G. and J. Frederick (1986), •Global Modeling of the Ultraviolet Solar
    Flux Incident on the Biosphere,* prepared for the U.S. Environmental
    Protection Agency.

United Nations Environment Programme, UHEP (1984), gnviTa**M«e*l Aaaaasagne  of
    Ozone Laver Depletion and its Impact as of October 198A. Coordinating
    Committee on the Ozone Layer (CCOL), UHEP.

UHEP (1986), draft report of the CCOL meeting, 1986.
World Meteorological Organization (1979), gfpftyt of  the Pir«g  Seagion of the  CAS
    WorVei.Tig Group or> ^P>oyph*ri-c Carbon Ptori^*  WHO Project on Rssaarch
    Monitoring of Atmospheric C02, Aep. No. 2, Coewission for  Atmospheric
    Sciences, WHO, Geneva, Switzerland.
                                                              ling Staff,  WHO,
WHO (1981), Joint VMQAK
    of C02 on Gliaao Variations and their laoaet. Joint
    Geneva, Switzerland.

WHO (198S), Report of the InternagJOBal Ca^rfaranea on the Asaegaaent of  the  Role
    of Carbon Ptmcld* and of ofchor Cr*anhati«a ^"SlI in CH«ag« TJ»fl*tlem*  and
    Aaaoeiaired lapaeta. WMO-Ro. 661, WMO/ICSU/UflEP, WHO, Geneva, Switzerland.
WHO  (1986).
                                                        fikmnf*  TOD Global Ozone
    Research
Mont
                      oring Project — ftaporc Bfa. 16, WO, Geneva,  Switzerland.

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                                     ES-65
                                  TABLE OF

                                                                       PAGE
       I

ACKNOWLEDGMENTS	   i

ORGANIZATION	  ES-1

INTRODUCTION ...*.	*	  ES-2

SUMMARY FINDINGS \	  ES-5

CHANGES IN ATMOSPHERIC COMPOSITION	  ES-I5

POTENTIAL CHANGES IN 02OHE AND CLIMATE	  ES-23

HUMAN HEALTH, WELFARE, AND ENVBtONHENTAL EFFECTS 	  ES-32

QUANTITATIVE ASSESSMENT OF RISKS WITH INTEGRATED MODEL	  ES-5*

VOUME II

fifyyfrsftfntxvMVMTK [[[   i

INTRODUCTION	.	   I

    The Rise of Concern About Stratospheric Change 	   1
    Concern About Public Health and Welfare Effects of Global
        Atmospheric Change 	   1
    Need for Assessaents 	   2

1.  GOALS AND APPROACH OF THIS RISK ASSESSMENT	   1-1

    Analytic Framework	   1-1
    Supporting Docuaents and Analysis for this Review	   1-2
    Chapter Outlines	   1-2

2.  STRATOSPHERIC PERTORBARTS:  PAST CHABdS HI CONCENTRATIONS
        J0D FACTORS THAT DETERMINE COBCimiSZQKS	   2-1
             			.'.	   2-1
    Findings	   2-3
    Measured Increases la Tropospberic Concentrations of
        Potential Ozone Depleters	   2-4
    Measured Increases in Tropospheric Concentrations of
        Potential Ozone Increasers	  2-13
    Factors that Influence Trace Gas Lifetimes	   2-21
    Long-Lived Trace Gases 	   2-22
    Trace Gases with Shorter Lifetimes 	.	   2-26
    Carbon Dioxide and the Carbon Cycle 	   2-26

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                                     SS-66


                                  TABLE OF COBUBTS
                                                                         PAGE

    Appendix A: -CFC Emissions-Concentrations Model  	   2-28
    Reference*  ...;	.......	]"!!!!!!!   2-30

3.  EMISSIONS OF INDUSTRIAIIX PRODUCED POTENTIAL OZONE MODIFIERS	   3-1

             	   3-1
                                                            .
    Introduction  .... ............ . ..... . ..... . ....... ~. ........ m .......   3..$
    Chlorofluorocarbon* ............. . ............... !!!!!!!!!!"!!-!!!   3-6
    Chlorocarbon*  ..... , ..... ...... ......... ... ..... . ...... !!!!!!!!!!!   3-58
    Haion*  — '. .................................. I!!!IIII'II!!!I!!!!!!   3-59
    Reference* .................... ....                                   .
    Appendix A:  Ch«aic*l T3»m E*ti»»tc Had* Av*il»bl«
            Sine* Publication of ta* &i«k A«M«aMnt .................   A-l

    Appendix At  Reference* ......... .................................   A- 10
                    «•»

4.  FUTURE EMISSIONS AND CONCENTRATIONS OF TRACE GASES HITH
        PARTLY BIOCENIC SOURCES ......................................   4-1
    Suanery	;   4.^
    Findings 	f	   4.2
    The Influence of Trace G«se< on the Stratosphere and
        Troposphere	   4.4
    Trace Gas Scenarios	   4.4
    Effects of Possible Future Lisdts on Global Warming	   4-23
    Conclusion	   4-23
    References	   4-25

5.  ASSESSMENT OF THE RISK OF OZONE MODIFICATION	   5-1

    S«*»*ry	   5-1
    Findings	.".	.»..	   5O
    Introduction	   5.5
    Equilibriua Prediction* for Tiro-Di»en*ion*l Model* 	   5-18
    Time Dependent Prediction* for Ooe-DlMnslonal
        Model* for Different Scenario* of Trace Ca*e*	   5-32
         Dependent Prediction* for Tvo-Dlaoa«io«al Model*
        with Different Scenario* of Trace Ca*e*	   5-40
    Model* Fail to Represent All Processes That Govern
        Stratospheric Change la * Coaaloto end Accurate Manner	   5-61
    The Implication* of Ozone Monitoring for /H««+tttlng Risk*
        of Ozone Modification	   5-80
    Reference*	   5.104

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                                    ES-67
                                                                         FACE
       zzz

6.   CLIMATE ........... ; ...... '. ............... . .......................   6-1

                                                                           -1
Findings	
The Greenhouse Theory	
Radiative Forcing by Increases in Greenhouse Casea
Ultisiate Temperature Sensitivity	
The Timing of Global Baning	
  igional Changes in Climate Due to Global Wanting
                                                                1 • •

                                                                           •15
                                                                           r!8
                                                                           -22
     Effects on the Stratosphere of Possible Control of
          Gases ...................... .... ..... ............... ...........
6-26
     Attachment A:  Description of Model to be Used in Integrating
                       Chapter .................... . ..... . .................
6-28
     Attachment B:  Trace Gas Scenarios ................................  6-32
     References .................... . . . . .............. ... ..... .........   6-33

7.   RONMELANOMA SKIN TUMORS . . . ............... . .......................   7-1

     Suanary .................... . ................................. ....   7-1
     Findings [[[   7-2
     Background on Solar Radiation and the Concept of Dose ............   7-5
     Introduction .................................. ..... . .............   7-5
     Biology of Nonmelanoma Skin Tumors : Links to UV-B ................   7-11
     Epideaiological Evidence . ........................ . ...............   7-27
     Dose-Response Relationships ......................................   7-40
     Attachment A ....................... ...............................   7-49
     References [[[   7-58

8.   CUTANEOUS MAUGHANT MELAKMA ---- . ................................   8-1

     Summary [[[ •. .....   8-1
     Findings ........................... ; .............................   8-3
     Introduction ... ......... . ........ . . . ...................... ~ ......   8-7
     Epiolsjiologic Evidence .............. . ............................   8-U
     Experimental Evidence .............. ;.'... ......... .. ...............   8-28
     Dose-Response Relationships .................... ,..»... ...........   8-29
     References ..... .......... .. ....... . ................ . .............   8-41

9.   DVR-IHDUCED DOfDHOSDPFRESSIOR: "CHARACTERISTICS AID
          IMPACTS ................................... ..

     Suamary [[[   9-1
     Findings ................................. . .......................   9-3
     Introduction ............... ......................................   9-5

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                                     ES-68
                                                                         PAGE

    Human Studie*	.-	*.	   9-14
    Effects of Ultraviolet Radiation oa Infectious Diseases	   9-15
    References	   9-18

10. CATARACTS AND OTHER EYE DXSOtB0S	   10-1
            ,	   10-1
    Findings	'.	'.	   10-2
    Cataract*  .:	   10-3
    Potential  Change* in S«nil« Cataract Prevalence for
        Changes in DV-B	   10-29
    Other Eye  Disorder* 	   10-33
    References	   10-37

11. RISKS TO CROPS AND TERRESTRIAL ECOSYSTEMS FROM ENHANCED
        UV-B RADIATIOH	   11-1

    Suanary	   11-1
    Findings 	,	   11-2
    Introduction	   11-5
    Issues and Uncertainties in Assessing the Effects
        of UV-B Radiation on Plants 	   11-5
    Issues Concerning UV Dose sad Current Action Spectra
        for UV-B Impact Assessment	   11-5
    Issues Concerning Natural Plant Adaptations to UV Radiation	   11-7
    Issues Associated with the Extrapolation of Data fro*
        Controlled Environments to the Field	   11-10
    Uncertainties in Our Current Knowledge of UV-B Effects on
        Terrestrial Ecosystems and Plant Growth Forms 	   11-11
    Uncertainties with the Ability to Extrapolate Knowledge to Higher
        Aabient C02 Environment sad Other Atmospheric Pollutants	   11-13
    Risks to Crop Yield Resulting from an Increase in
        Solar UV-B Radiation	   11-15
    Risks to Yield Due to a Decrease in Ojuality	   U-20
    Risks to Yield Due to Possible Increases In
        Disease or Pest Attack	Jtrr;	   11-20
    Risks to Yield Doe to Competition with Otter Plants 	   11-22
    Risks .to Y$»ld Due to Change* la Pollination and Flowering	   11-23
    References	   11-25

12. AH ASSESSMENT OF THE lHHa» OF ULTRAVTOLZT-B
        RADIATION OH AQUATIC ORCAIfTSHS	   12-1

    Summary	'.	   12-1
    Findings 	   12-2
    Introduction	   12-4
    Background on Marina Organisms and Solar Ultraviolet
        Radiation	-	   12-*
    Effects of UV-B Radiation in Fltytwlsnliftn  ............«••••••••••   12-9

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                                     ES-69


                                  TABLE OF UJB1U1&
                                                                         PACE

    Effaces on Invertebrate Zooplankton	   12-11
    Effects on Ichthyoplankton (Fisheries) 	.„.«.....   12-23
    Conclusion*	   12-28
    References ... „	   12-29
                                                                   •

13. EFFECTS OP UV-B ON POLYMERS	„	'...   13-1

    Su*Bary	.".	   13-1
    findings	....	   13-2
    Pbotodegradation of Poly»ers	   13-4
    Polymers in Outdoor Uses and the Potential for Degradation	   13-7
    Dsaage Functions and Response to Daaage 	   13-16
    Effect of Temperature and Humidity on Photodegradation	   13-29
    Future Research	*	   13-31
    References 	«...,...   13-32

14. POTENTIAL EFFECTS OF STRATOSPHERIC OZONE DEPLETION OH
        TROPOSPHERIC OZONE 	   14-1

    Summary	   14-1
    Findings 	   14-2
    Introduction	   14-3
    Potential Effects of Ultraviolet Radiation and Increased
        Temperatures on Ground-based Ozone	   14-5
    Conclusions and Future Research Directions	   14-9
    References 	•	   14-14

15. CAUSES AND EFFECTS OF SEA LEVEL RISE	   15-1

    Susnary	   15-1
    Findings	   15-2
    Causes .of Sea Level Rise	   15-5
    Effects of Sea Level Rise 	„	   15-15
    Conclusion	,.	   15-32
    Hots*	!.'.'.'.'.'.'.'.'.'.'/.'.'.'.'.'.'.'.'.'.!!!!!I!!!I™*!*""*! ..15-33
    References	   15-34

16. POTENTIAL EFFECTS OF FUTURE CLIMATE CHARGES OH FORESTS
        AND VEGETATION, AGRICULTURE, HATER. RESOURCES
        AHD HUMAN HEALTH	;.	   16-1

        ary	   1$-1
    Findings	   16-5
    References 	^	   16-10

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                                     ES-70


                                        OF
                                           sued)

                                                                          PACE
17. MODELS FOR. IHTEG&AXXBG THE AHALTSES OF ««ATTU
                    . £ISKS ASSOCIATE) WITH OZOBE MODITICATIOH	   17-1
            	    17-1
    Introduction ...,	,	..	    17-2
    The Modal as a-Framework	,	<.!.I!II1!!!!I!!    17-2
    Analysis Proeadura 	..	    17-4
    Modal Limitations 	    17-9
    Rafaranca*	    17-11
    Appendix A:  Model Design and Modal Flow ..	    A-l
    Appendix B:  Scanarios of fihaairsl Production, Population,
        and CMP	    B-l
    Appandix C:  Evaluation of Policy Alternatives	    C-l
    Appendix 0:  Emissions of Potential Oxone-Depleting Compound*	    D-l
    Appandix E:  Ataospharic Scianca Modula	    B-l
    Appandix F:  Haalth and EnvlronBantal Lapaets of Ccona
        Daplation	    F-l

18. HUMAN HE1ATH AND ENVIRONMENTAL EFFECTS 	    18-1

    Suaaary	,...	    18-1
    Findings 	    18-2
    Introduction	    18-6
    Methods for Estimating Haalth and Exnriroaasntal Kisks 	    18-11
    Daacription of Ranga of Production, Emissions, and Concantrations
        Scanarioa for Evaluating Risks 	    18-12
    Sansitivity of Haalth and Environaantal Effacts to Oiffarancaa
        in Emissions of Ozona Daplatars 	    18-18
    Sansitivity of Raaults to Altarnativa Atmospharlc Assumptions	    18-23
    Sansitivity of Effacts to Oncartainty in Doaa Rasponsa	    18-54
    Ralativa Importanca of Kay Uncartaintias	    18-61
    Summary	    18-62
    Rafarancas	    18-65

       X*

    Appandix A

    Ultrsviolat Radiation and
    Appandix B

    Potantial Effacts of Future Climata Changas on Forests and
        Vegetation, Agriculture, Water Resources, and Tftaisn Haalth

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                                     IS-71
VQUME VI

    Technical Support Documents

          LSC C
    Projecting Production of Ozone Depleting
    Technical Support Doeu»«nts

    Appondix D

    Scientific Pcpor»

fDUDHE 7ZZZ

    Technical Support Docuaents

    Appendix E

    Current Risks end Uncertainties of Stratospheric Ozone Depletion
        Upon Plants

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                                     ES-72
                               LIST OP EXHIBITS
 1-L    Relationships Among the Chapters	  1-3

 2-1    Measured Increases in Tropospheric Concentrations
        of CFC-11 (CTC-13)	,  2-5

 2-2    Measured Increases in Tropoapbarie Coneentrationa
        of CFC-12 (CF2CL2) 	'.	  2-6

 2-3    Measured Inereaaea in Tropoapheric Coneentrationa
        of HCFC-22 (CHC1F2)	  2-7

 2-4    Measured Inereaaea in Tropospheric Coneentrationa
        of CFC-113 (C2CL3F3) 	  2-7

 2-5    Measured Increased in Tropospheric Coneentrationa
        of Carbon Tetriehloride  (CC14)  	  2-9

 2-6    Measured Increases in Tropospheric Coneentrationa
        of Methyl Chloroform (CH3CC13)	  2-10

 2-7    Measured Increases in Tropospheric Coneentrationa
        of Halon-1211 (CF2ClBr)  	  2-11

 2-8    Measured Increases in Tropospheric Concentrations
        of Nitrous Oxide (S20)	  2-12

 2-9    Measured Increases in Tropospheric Coneentrationa
        of Nitrous Oxide (N20)  	  2-14

 2-10   lee Core Measurements of Historical  Nitrous Oxide
        (N20) Concentrations 	   2-15

 2-11   Measured Inereaaea in Tropospheric Concentrations
        of Carbon Dioxide (C02)  	   2-16
               *
 2-12   lee Can Measurements of Historical  Carbon Dioxide
        (C02) Concentrations	   2-17

 2-13   Measured Increases in Tropoapbarie Concentrations
        of Methane (CH4) 	2-19

 2-14   Ice Core Measurements of Historical  Methane (CH4)
        Coneentrationa	  2-20

2-15a   CFC-12:  Constant Emissions 	  2-23

2-L5b   CFC-12:  Atmospheric Concentrations 	.'	  2-23

2-16a   CFC-12:  Emissions	.;....	  2-24

-------
                                     ES-73


                                LIST OF HUHIMfct
2-16b   CFC-12:  Ataoapharlc Coneancratioaa	i  2-24

2-17    CFC-12:  Ataoapharic Concentration* from Different
        Eaiaaion Trajactoriaa 	„	'.,  2-25

A-l     Concentration* of Fluoroeatbeaa	..«	'.....	  2-29

A-2     Location* of Station*	  2-29

3-1     Salaetad Propartlaa of CFCS	  3-8

3-2     CFC Charaetariatiea and Subatitutaa	  3-10

3-3     Coapanie* Reporting Data to CMA	  3-11

3-4     Production of CFC-11 and CFC-12 Baportad to CMA ...........  3-13

3-5     Historical Production of CFC-11 and CFC-12 	  3-15

3-6     CFC-11 aad CFC-12 Uaad in Aaroaol and Honaeroaol
        Application* in tba EEC	,	  3-16

3-7     Coapariaon of Eatiaated CFC-11 DM: 1985 	  3-18

3-8     Coaparicon of Eatiaated CFC-12 Baa: 1985 	  3-19

3-9     Ectiaate* of Production and Eaiaaiona of CFC-11
        and CFC-12 	  3-21

3-10    Published Eatiaataa of U.S.S.R. Production of CFC-11
        and CFC-12 	  3-22

3-11    Historical Production of CFC-11 and CFC-12 in the U.S	  3-24
                                         •' .'ji.
3-12    EIC Production arkl Salaa Data	  3-25

3-13    Tha Bottoa Up Approach	  3-27

3-14    Rang* of Population and GBP Pax Capita Projection*	  3-30

3-15    Suaaary of Oaaaad Projection Ictiaata*	  3-32

3-16    Suaoary of Oaaaad ProJaction Sattaata*
        (Average annual rate of growtii in parcant) .-	  3-34

 3-17   Long Tata Projection* CFC-11 and CFC-12  -
        World Production (2000-2050)	  3-35

-------
                                     5-74
3-18   Bavlngton'* Projections for Use of CFC* In the DC ........  3-38

3-19   Cemm Projections of World U*e	'..  3.40

3-20   Summary.of KFCTC Projections	  3-42

3-21   Global Population and 60 Scenario* Used in
       Gibbs' Analysis	  3-43

3-22   Gibbs Scenarios of World CFC Use	  3-45

3-23   Bammitt Projections of World CFC Use	  3-47

3-24   Susmary of Bedenstrom Projections for Sweden	;...  3-49

3-25   Knolly* Projection*	'.	»	  3-51

3-26   Summary of Kurocawa Projection* for Japan	  3-53

3-27   Hordhau* Scenario* of world Honaarosol CFC Consumption .-...  3-55

3-28   Summary of Sheffield Projections for-Canada	.-ic.:.  3-57
       (1984-2005)

3-29   Global Balon Projections for Quinn	TJ.'.  3-62

3-30   Bemmitt and Came Global Balon Projection* 	  3-64

A-la   Global Annual Production in Millions of Kilograms	  A-4

A-lb   U.S. Annual Production In Million* of Kilogram* 	  A-4

A-2    Assiapffmis for He Balon PrejectJsos	  A-5

A-3    Me Projection* of Sale* and Emissions for Halon-1301
       and Balon-1211	.........	  A-6

A-4    Global Halon-1301 and Balon-1211 Growth Bates	  A-7

A-5    Dupont Ectimates of CFC par Capita Us*	*..  A-8

4-L    Effects of Change* in Composition of Atmosphere	  4-5

4-2    Bi*torical Carbon Dioxide Emissions from Fossil Fuels
       and Cement	...	;.  4-7

4-3    A Schematic of the. Carbon Cycle  	  4-8

-------
                                    ES-75


                              LIST OF
4-4    Projected Carbon Dioxide Emissions and Doubling
       Time of Concentrations	  4-10

4-5    Estimated CB4 Emission Soureaa (10   grams mar year)	•  4-12

4-6    Two Says 'That CB4 Concentrations Could Batvm Changed .......  4-14

4-7    Poaaible Changes in CB4 Soureaa and la
       Emission Factors	*	  4-15

4-8    Currant Soureaa and Sinks of Carbon Monoxida
       (1984 concentration of CO:  30-200 ppb) 	  4-17

4-9    Scenarios of Carbon Monoxide (CO) Emissions from
       Combustion	  4-18

4-10   Preliminary Scenario of Future Growth in B20
       Emissions by Source	  4-21

4-11   Projected Nitrous Oxide (K2O) Concentrations 	  4-22

4-12   Summary of Standard Scenarios Proposed for Assessment .....  4-24

5-1    Temperature Profile and Ozone Distribution in the
       Atmosphere	  5-7

5-2    Steady-State Scenarios Used in International Assesamant  ...  5-10

5-3    Change in Total Ozone from Representative One-Dimensional
       Models for Steady-State Scenarios *V*r*-1"f«*t Clx
       Perturbations	  5-12

5-4    Change in Total Ozone at 40 Kilometers for Steady-Stata
       Scenarios Containing Clx Perturbations	  5-13

5-5    Change in Total Ozone for Steady-State Scenarios	  5-14

5-6    Effect of Stratospheric Nitrogen (BOy) on Chlorine-Induced
       Ozone Depletion	  5-15

5-7    Effect of Doubled C02 Concentrations on Ozone
       Temperature	,.	  5-16

5-8    Calculated Changes in Ozone Versus Altitude	  5-17

5-9    Two-Dimensional Modal Scenarios Used in International
       Assessment	  5-19

-------
                                    ES-76


                               LIST OF EXHIBITS
                                 CContlnttad)
                                 ^ ^^^^^•^•^I^^^^^^^P^

                                                                    Paga
5-10   2-Dinenaional Model Raaulta: Globally and Saaaonally-
       Averaged Ozone Depletion	„.'	  5-20
5-11   Ozone Depletion by Latitude, Altitude, and Seaaon for Clx
       lacraasa of 6.8 ppbv (MPIC 2-0 Model)	' 5-21

5-12   Oxone Depletion by Latitude, Altitude, and Month for Clx
       Increase of 6.8 ppbv (AKR 2-0 Modal) 	  5-22

5-13   Ozone Depletion by Latitude, Altitude, and Month for Clx
       Incraaaa of 14.2 ppbv (AKR 2-D Modal) 	  5-23

5-14   Ozone Depletion of Latitude, Altitude, and Month for Clx
       Increase of 6.8 ppbv (GS 2-0 Modal) 	  5-24

5-15   Ozone Depletion by Latitude and Season for Clx Increase
       of 6.0 ppbv (IS 2-D Modal) (AIR 2-0 Modal)	  5-25

5-16   Change in Ozone by Latitude and Season for Clx
       Perturbations (MPIC 2-0 Modal) 	  5-26

5-17   Change in Ozone by Latitude and Season for Clx
       Perturbations (AZR 2-0 Model)	  5-27

5-18   Latitudinal Dependence of AER and MPIC 2-0 Models	5-28

5-19   Change in Ozone by Latitude, Altitude, and Month for
       Coupled Perturbations (GS 2-0 Model) 	  5-29

5-20   Changes in Ozone by Latitude, Altitude, and Season for
       Coupled Perturbations (MPIC 2-D Modal)	  5-30
5-21   Changes in Ozone by Latitude *r*** Altitude in Winter for
       Coupled Perturbations (MPIC 2-D Modal)' „	  5-31

5-22   Models With Reported Tim* Dependent tuna	  5-33

5-23   LLHL 1-D Modal Versus Parameterization Fit	  5-34

5-24   Trace Gaa Assumptions for Raaults in Exhibit 5-2S
       (Brassaur and DaRuddar 1-D Modal. 1986) 	  5-35

5-25   Tine-Dependent Change in Ozone for CFC Growth and Coupled
       Perturbations (Brassaur and DaRuddar 1-D Model)	  5-36

5-26   Tine-Dependent Change in Ozone for Constant CFC  Emissions
       and Growth in Other Trace Gaaas (Braaaaur and Oeindrtar
       1-DModal)	.*....	  5-37

-------
                                    ES-77


                              LIST OF
5-27   Sensitivity of 1-D Models to Representation of Radiative
       Processes (Brasseur and DeRudder 1-D Model) 	  5-38

5-28   Model Comparison: Time-Dependent Change in Ozone for CFC •
       Growth and Coupled Perturbations	  5-39
                                                                  t
5-29   Trace Gas Assumptions for Results in Exhibit 5-30
       (AER 1-D'Model. 1986) 	'.	  5-41

5-30   Time-Dependent Change in Ozone for Various Scenarios of
       Coupled Perturbations (AER 1-D Model) 	  5-42

5-31   Trace Gas Scenarios Tested in LLHL 1-D Model	  5-43

5-32   Time-Dependent, Globally Averaged Change in Ozone for
       Coupled Perturbations (IZJO. 1-D Model) "Reference Case9 ...  5-45

5-33   Tim* Dependent, Globally Averaged Change in Ozone for
       Coupled Perturbations (UAL 1-D Model)	  5-46

5-34   Effect of Potential Greenhouse Gas Controls on Ozone
       Depletion (Results from 1-D Parameterization) 	  5-47

5-35   Calculated Ozone Depletion for 1970 to 1980 Versus
       Umkahr Measurements	  5-49

5-36   Tim*-Dependent Globally and Seasonally Averaged Changes
       in Ozone for Coupled Perturbations (IS 2-D Model)  	  5-50

5-37   Time-Dependent Globally and Seasonally Averaged Changes
       in Ozone for Coupled Perturbations (IS 2-D Model)  	  5-51

5-38   Time-Dependent Seasonally Averaged Change in Ozone for
       1980 CFC Emissions and Coupled Perturbations (IS 2-D
       Model) 	  5-52

5-39   Time-Dependent Seasonally Averaged Change in Ozone for
       1.2% Growth i*> eye Emissions *r**f Coupled PrrTTfratslopT
       (IS 2-D Model) 	  5-53

5-40   Time-Dependent Seasonally Averaged Change in Ozone for
       3% Growth in CFC Emissions sad Coupled Perturbations
       (IS 2-D Model)	  5-54

5-41 -  Tim*-Dependent Seasonally Averaged Change in Ozone for
       3.8% Growth in CFC Emissions and Coupled Perturbations
       (IS 2-D Model)			  5-55

-------
                                    ES-78
                              LIST Of HHXBZ7S
5-42   Temperature Feedback Experiment: Time-Dependeat,  Globally
       and Seasonally Averaged Change ia Ozone for 3% Growth ia
       CFC Emissions aad Coupled Perturbations (IS 2-0 Model) ....  5-57

5-43a  Two-Dimensional* Time-Dependent Simulation for Constant
       CTC Emissions (AIR. 2-D Model) 	.'.	  5-58

5-43b  Two-Dimensional, Time-Dependent Simulation for CTC Growth
       of 62 Percent Per Tear (AIR 2-0 Model)	  5-59

5-44   Model Comparison for Coupled Perturbations Scenario	  5-60

5-45   Calcualted Ozone — Column Change to Steady-State for Two
       Standard Assumed Perturbations	  5-63

5-46   Latitudinal Gradients ia Odd Mitrogen: Models TS
       Measurements	  5-65

5-47   Logical Flow Diagram for Monte Carlo Calculations	  5-67

5-48   Histogram of Measurements for a Rate Constant	  5-68

5-49   Recommended Rate Constants and Uncertainties Used in
       Monte Carlo Analyses	  5-70

5-50   Monte Carlo Results: Change in Ozone Versus Fluorocarbon
       Flux	  5-71

5-51   Monte Carlo Results: Change ia Ozone Versus Fluorocarbon
       Flux			  5-72

5-52   Monte Carlo Results: Ozone Depletion for Coupled
       Pertubations	  5-73

5-53   A Monte Carlo Distribution of Column Ozone Changes
       for Changes in CTC Production	  5-74

5-54   Monte Carlo Results: Changes ia Ozone- by Altitude	  5-76
5-55   Monte Carlo Results: Changes ia Ozone by Colon
       Altitude. Onscreen Data	  5-77

5-56   Monte Carlo Analysis With the LLHL l-D Model	  5-78

5-57   Monte Carlo Results:  Changes ia Ozone by Altitude	  5-79

5-58   Ozone Trend Estimates by Latitude	  5-83

-------
       25-79
LEST OF
   ^^^^mm^fcaiaimmmmw*^
5-59

5-60*
5-61
5-62
5-63
5-64

5-65
5-66
5-67
5-68
5-69

6-1
6-2
6-3
6-4
6-5
6-6
6-7
6-8
Ch*ng«* i« OZMMI tTom 197*0 to 1980: Qakahr Ma««itrMMnnt
**w4 ttnAml C« 1 mil »fi eimm ......................... 	
SBOV Zonal Trand* Batimataa Varaua •Omkahr Station
Ozona Trand Batimataa and 95% Conf idonca Intarrala ........


Ozona Trand Bmiaaiona (t par yoar) Aa Datarminod from
Balloon Ozonaaondaa Varaua Thoaa Datarminad from Dodaon
MaaauramantB (Tlao, at al . t parvonal communication) 	
Monthly Maana of Total Oceo* *t B*ll«y l*y ,,.,, T »,,,-,, T ,,
Himbua 7 Antarctic Ozona Maaauramanta: 12 -Day Saquanca . . .
Rimbua 7 Antarctic Ozona Maaauramanta: Maan Total
Global (60*R-60*S) Monthly Ozona Datarminad from
Preliminary Ozona Trond Data (Haaltii varau* 2-D Modal
Raaulta) (laakaan) 	 	 	
Stratoapharic Parturbanta and Th*ir Bffacta 	 	 	
Abaorption Charactariatiea of Traca Gaaaa 	
Radiativ* Forcing for a Uniform Incraaaa in Traca Gaaaa . . .
Iff acta of Vortical Ozona Distribution on
fuifnrt Tomparatura 	 	 	 	 	
Vatar Vapor, Altituda, and Radiativa Forcing 	
Tamparatura Sanaitivity to Climatic Faadback Machaniama . . .
Empirical Batimataa of Climata Sonaitivity era Sanaitlva
to Batimataa of Historical Tamparatura Incraaaaa aad
Ralationahip of Radiativa Forcing, Ocaan Baat Uptaka,
and Raalizad and Unraalizad Varminc 	

5*85
5-86
5-88
5-90
5-91

5-93
5-96
5-97
5-98
5-100

5-102
6-9
6-10
6-11
6-13
6-14
6-16
6-17
6-20

-------
                                    gg.80


                              LIST OP EXHIBITS
6-9    Transient Estimates of Global Warming	   6-21

6-10   Expected Temperature Inereasea	   6-23

6-11   Results of Transient Analysis Using a General
       Circulation Model	   6-24

6-12   Regions of U.S.:  Change in Runoff	.".	   6-25

7-1    Variation in UV Radiation by Latitude aa Fercent of Levels
       at the Equator on March 21 at Boon	*....   7-6

7-2    UV Radiation by Month in Washington, D.C	   7-8

7-3    Ratio of Instantaneous Flux Throughout the Day to
       Flux at 5:15 a.m. in Washington on June 21 (Assumes
       a Clear Day) 	   7-9

7-4    Average DRA-Dsmage Action Spectrum	   7-10

7-5    Organization of the Adult Skin	   7-12

7-6    Ultraviolet Absorption Spectra of Major Epidermal
       Chromophores	,-.....	   7-14

7*7    Skin Types and Skin Tanning Responses	   7-16

7-8    Ultraviolet Action Spectra for DHA Dimer Induction,
       Lethality and Mutagenicity	...,	   7-19

7-9    Effectiveness of UVR at Inducing Pyrlmidine Diaers
       and Transformation	   7-21

7-10   Action Spectrum for the Induction of Single-Strand Breaks
       in OKA	   7-24
7-11   Action Sfactrua of Mouse Edeaa (MBE48) aa Compared
       to that of DMA. Damage and the Robartson-Bargar
       Meter	^	  7-26

7-12   Comparison of Age-Adjusted Incidence Rates Far 100,000
       Persons for Squamous Cell Carcinoma (SCC) and Basal Call
       Carcinoma (BCC) Among White Males and Females in the
       United States 	  7-29
7-13   Percentage of Tumors by Anatomic Site for
       Skin Cancer Among White Males and Females in the United
       States (1977-1978 SCI Survey Data)  	  7-31

-------
                                    ZS-81


                              LIST OF BZHXBZTS
7-14   Distribution by Sex and Aaatoaie Sito of
       Skin Tuaors: Canton of V«ud, Switzerland (1974-1978)  	   7-32
7-15   Annual Age Adjusted Incidence Bates for Basal •
       Cell Carciaoaa (1977-1978 BCI Survey Data) aad
       (1973-1976 SBBB, Data) Aaong White Males	   7-35

7-16   Annual Age Adjusted Incidence Bates for Basal sad "
       Squaaous Cell Cirrinoass (1977-1978 9d Survey Data)  and
       Melanoaa (1973-1976 SBBB Data) Aaong White Foailss 	   7-36
7-17   Estiaated of  Belative Bisks of Basal and Squaaous Coll
       Carcinoaas for 32 Coabinations of Bisk Factors	   7-38

7-18   Belative Mutagenieity of QV-B as a Function of Wavelength .   7-46

 A-l   Correlation of Alternative Measureaents of CV-B Badiation
       for Ten Locations in the Halted States 	   7-51

 A-2   Population Weights for Ton Locations in tho United
       States 	   7-52

 A-3   Estimated Dose-Response Coeffieeints (and t-Statistics) for
       Basal and Squaaous Cell Skin Cancers (TJV-B Dose-Skin
       Cancer Incidence) .........................................   7-53

 A-4   Estiaatod Percentage Changes in UV-B Badiation in San
       Francisco for a Two and Ton Percent Depletion in Ozone ....   7-55

 A-5   Percentage Change in Incidence of Basal and Squaaous Cell
       Skin Cancers for a Two Percent Doplotion in Ozone for
       San Francisco	   7-56

 A-6   Percentage Change in Incidence of Basal and Squaaous Cell
       Skin Cancers for a Ten Percent Depletion in Ozone for
       San Francisco	  '7-57

8-1    Location of Melanocyto in the Bpiderais	»...   8-8

8-2    Cooperative Transaittance of U7 Badiation	   8-9

8-3    Increases in Incidence and Mortality Bates froa
       Malignant Melanoaa in Different Countries	   8-17

8-4    Aaatoaie Site Distribution of Cutaneous Malignant
       Molanoaa	   8-19

-------
                                     BS-82
                               USX OF BHXBXIS
 8-5    Anatoaic Sit* Diatrlbucion of «^*-T^HII Malignant
        Malanoaa by Gaodar	 8-20

 «-«    Kalignant Ma.lanoaa liak Factor* by Maaaur** of Skin
        Plgaantation Within tfaa Caucaaian Population ."	  8-26
 8-7    Hultipla Bay* in vhich OVt can nay a tola in
        Davalopaant	  g.30

 8*8    Suaaary Statiatie* for tograaaiona of Skin Caacar
        Iscidanca *pv4- Mortality on Lat'lfytr .......................  8-32
 8-9    Eatiaatad ftalativ* Ineraaaaa in Malaaoaa Skin Cancar
        Incidanca and Mortality Aaaociatad with Chang** in
        Erythaaa Do**	  g-33

 8-10   Suaaary of Faara. Scotto,  and SchaaidarBaa (1977)
        tograaaion Aaalysaa of Malanoaa Incidanca Doaa-Baapon** ...  8-35
 8-11   Biological Amplification Factor* for Skin Malanoaa by
        Sax and Anatoaical Sit* Group*,  Adjusting for A«a and
        Salactad Coaatitutional and tzpoaura Variablaa 	  8-35
 8-12   Biological Amplification Factor* for Malanoaa laeidaaca
        by Sax and Anatomical Sita Croup*,  Adjuating for Aga
        and Coabinationa of Salactad Constitutional and
        Expoaura Variablaa	  8-36

 8-13   Pareantag* Zncraaa* in Malanoaa Oaatib lataa for a On*
        Parcant Oaclina in Oxoua 	  8-39

 9-1    Action Spactra for Local Suppraaaioa of Contact
        ByparaaaaitiTity Aa«aaia§ tlthar Ona-Mt or Multi-ait
                    	.Vi	  9-11
 9-2    Action fpactrua For Syataadc Suppraaaioo of Contact
                        . ........... ... .......... ^ ..................  9-12
10-1    Cataract Pravmlane* by WT Zona ..... . ...................... 10-7

10-2    Coapariaoa of Cataract Fravalaae* for Aboriginaa and
        Mon-Aborigina* .......... . .......... ... ..... . ............... 10-7

10-3    Coapocita Traaaaittanca Curw* for tiba Babbie ............ . 10-9

10-4    Calculated Total Tranaaittanc* of th* Huaan Eya ........... 10-10

10-5    Parcant Tr«n*ai**ivtcy Through th« Entir* Rha*us Ey* ...... 10
-------
                                     ZS-83
                               UST OP EXHIBITS
10-6    Tranaaittanea of tha Total tabbit Goroaa.  tha Total
        Buaan CotnM, and tha Rabbit Cotnaal Epithaliua	.  10-12
10-7    Tranaaittanca of tha Antarior-Ocular Structiuoa of
        tba Btavm and Babbit Eyaa	10-13
10-8    0V Radiant Expoaura Thraahold Data for tha
        Hr, Lana HL Cataracta,  and Batina H_
        for tha tabbit and Priaata	7	10-14

10-9    Tba Action Spoetra for Photokaratitia and Cataracta
        for tha Priaata and tabbit	10-15
10-10   Fraa P«dt?fllt tr4 Oxidation:  taduction tjacaai ... ......... 10-17
                                       .      »
10-11   Enryaa Syataam Involved in Oxidation: tadaetion ........... 10-18

10-12   Standardized tagraaaion Coaflieianta for Cataract ......... 10-31

10-13   Eatiaatad talationahip Batvoan tiak of Cataract
        and UV-B Flux ............................................. 10-32
11-1    A Suanary of Studiaa Itr*"*"**! **»* Sansitivity of Cultivarc
        to UV-B Radiation ......................................... 11-8

11-2    Survay of UV Studiaa by Major Tarraatrial Plant
        Ecosyataaa (aftar Vhittakar 1975) ......................... 11-12

11-3    Suaaary of UV-B and C02 Effacta on Planta ................. 11-14

11-4    Suaaaxy of Fiald Studiaa BraainJTH tba Kffacta of
        UV-B Radiation on Crop Yialda ....* ................... *.... 11-16

11-5    Dataila of Fiald Study by Taraaura, <1981-1985) ............ 11-17
11-6    Itiam i j of Changaa in Tiald Quality in Soyboan
        Batvaon tha 1982 and 1985 Growing Saaaona
        (Taraaura 1982-1985)	11-21

12-1    Solar Irradianca Outaida tb* larth'a AtBoapharo and at
        ch« Surfaca of tb« Earth for * Solar Zanith Angla of 60*... 12-5

12-2    talationahip Batwaan Oxona Daplation and Biological
        Effactivanaaa of Incraaaad UV-B Radiation	12-6

12-3    Solar Spactral Irradianca at tha Surfaea of tha Ocaan
        and at Four Daptha 	12-7

-------
                                     ES-84
                               LIST OP UK! BTTS
                                  ^•a^sewABHaiaaavspvav^

                                                                     Pjgt

12-4    Lethal Effects on Shrlap Larvae for Various Coabinations
        of DV-R, Dose-Rate, and Total Dose	  12-13

12-5    Estiaatad Effective UV-B Solar Daily Dose at Various
        Atteospherlc Ozone Concentrations Baaed on a 4-Year
        Mean of Medians, Manchester, Washington, 1977-1980	12-14

12-6    Estiaatad Biologically Effective UV-B Doses Leading to
       • Significant Effects in Major Marina Zooplaakton Groups .... 12-17

12-7    Percentage of Total Dose Halt to be Reached on Any
        Particular Day:  Lethal Doses Accuaulatad Only After
        Dose-Bate Threshold is Exceeded 	 12-20

12-8    Effect of Increased Levels of Solar OV-B Radiation on
        tha Predicted Loss of Larval northern Anchovy froa Annual
        Populations, Considering the Dose/Doee-Rate Threshold
        and Three Vertical Miacing Models	12-27
13-1    Vcvalangths of DV Radiation and Polyaars with
        Sensitivity and Corrasponding Photon Bnargias  	 13-4

13-2    Plastics Usad in Applications Vhara Exposura of tha
        Matarial to Sunlight Might Ba Expactad	 13-8

13-3    Modas of Daaaga Exparianead by Poljaara Usad in
        Outdoor Application	.'	   3-11

13-4    PVC Siding Compound Coapoaition	 13-13

13-5    UV Seraaning Effactivanass of Salactad Pigpants	 13-14

13-6    DosMStie Conauajption of Light Stabiltmars, 1984-85	13-15

13-7    IncraaMd Stabilization Markat (1970-2020) 	13-18

13-8    Oxooa aeplation Estiaatas	13-19

13-9    Qawlatlm Addad Cost	13-20

13-10   Diagraamatic Bapraaantation of tha Iff act of
        Pigaant/Fillara as Light Shialdars
        (Monodisparsa Spharical FUlar) 		13-22

13-11   Ralativ* Daaaga Zndieas for Yallovlng of PVC Ttadar Miaai
        (March 22nd) Conditions, at Diffarant Extanta  of
        Ozona Layar Datarioration	 13-25

13-12   Estiaatad Rangas of Factor Incraasa  in  Daaaga  and  tha
        Factor Incraasa in Stabilizer Naadad to Counter tha
        Change of Yellowing of Rigid PVC  Compositions  	  13-28

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                                     ES-85
                               LIST Of OH I FITS
                                  (I
13-13   PVC Damage with Ozone Depletion	13-29
13-14   Projections of Future Demand for Selected Y«
        (Thmitsndt of Metric TOM)	13-30
14-1    Ozone Concentrations for Short-Term Exposure That
        Produce 5% to 20% Injury to Vegetation Growth Under
        Sensitive Conditions	  14-6

14-2    Ozone Concentrations at Which Significant Yield •
        Losses Have Been Noted for a Variety of Plant
        Species Exposed Under Various Experimental Conditions	14-7

14-3    Ozone Concentrations Predicted for Changes in
        Dobson Number and Temperature for Three Cities (ppm) 	14-10
   t
14-4    Global Warming Would Exacerbate Effects of Depletion
        on Ground-Based Ozone in Nashville	  14-11

15-1    Snow and Ice Components 	  15-6

15-2    Worldwide Sea Level in the Last Century	15-8

15-3    Temperature Increase At Various Depths and Latitudes 	  15-10

15-4    Estimates of Future Sea Level Rise 	  15-13

15-5    Local Sea Level Rise	15-14

15-6    Evolution of Marsh as Sea Level Riaas 	  15-17

15-7    Composite Transect — Charleston, S.C	15-18

15-8    Louisiana Shoreline IB the Year 2030	15-20

15-9    Distribution of Population in »—»*-«—*	15-21

15-10   Ae Bruun Rule	  15-23

15-11   Percent of Tidal Cycle* in Which Specified
        Concentration is Exceeded at Torrasdale During a
        Recurrence of the 1960's Drought for Throe Sea Level
        Scenarios 	15-28
15-12   Estimates of Flood Damages for Charleston and Call
        Resulting From Sea Level Rise	15-30

16-1    Summary of Findings from the OMO/OHEP/TCSU Conference
        on Global Climate Held in Villach, Austria, October 1985 .. 16-1

17-1    Modular Structure 	 17-3

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                                    ES-86
                              vat or
                                 C
17-2   Major Modal Input Choieaa	  17-5

17-3   Bffecta »ot Quantified	  17-10

 A-l   Flow of. Aaalyaia Program	  A-4

 A-2   Pilea Required to Specify a Run .	  A-6

 B-l   Ftttura Global Production Scaaarioa:  Middla Scaaario	  B-3

 B-2   Ragioaal Uaa Sharaa for CFC-11 .....'	  B-4

 B-3   U.S. End Uaa Sharaa far CFC-11	  B-6

 B-4   Middla U.S. Population Seanario	  B-7

 B-5   Middla U.S. GNP Scaaario	  B-7

 B-6   Uaar-Modifiad Seaaario Specifying a Growth Rata of 2
       Parcant Annually for CFC-11 la the U.S	  B-9

 B-7   A Uaar-Modifiad Seaaario: Production aa a Function of
       Population	  B-9

 0-1   Raleaae Tablaa for C7C-11 	_	   D-2

 0-2   Eaiaaiona from a Hypothetical 100 Million Kilogram* of
       Production in 1985 	   0-4

 0-3   Emiaaiona from Production Over a Seriaa of Tears
       (Milliona of Ulograma)  	   0-5

 0-4   Sample Tabla of Exoganoualy Specified Emiaaiona	   0-6

 E-l   Trace Gaa Aaaumptiona Uaad to Develop the Ozone Depletion
       Relationship .»	..i?t^	  1-2
 E-2   Compaxtaoa of Total Column Ozoaa Daplation Baaulta from
       tha 1-0 Modal and tha Paramatarixad Bumvrical Fit .........  E-3

 E-3   Hypothatieal Tabla of Qaar-Spaeiflad Ocoaa Oaplatioa ......  E-6

 S-4   Exampla Osona Oaplatioa Scaling Factors  ...................  E-7

 F-l   Citiaa Uaad to Evaluata Chaagaa in U7 Flux for tha .Taraa
       Ragiona of tha U.S ...................... ." .................  '-3
 F-2   Stataa Ineludad in tha Thraa Kagiona of tha U.S.  ... .......  F-5

 F-3   Parcant Changa in  UV aa a Function of Changa  in Ocoaa
       Abundance for Thraa U.S. Ragiona  ........ ..... .............  F-6.

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                                    BS-87


                              LIST OP EXHIBITS
 F-4   Age Distribution of the U.S. Population Over Time in the
       North Region	  F-8

 P-S   Baseline Incidence for Henmelanome Skin Cancers	   P-10

 F-6   Basal Incidence for Melanoma Skin Cancers	..,„*  F-12

 F-7   Mortality Rates for Melanoma Skin Cancers 	  F-14

 F-8   Standardized Regression Coefficients for Cataract	  F-16

 F-9   Estimated Relationship Between Risk of Cataract and UV-B
                                                                    P-17
 P-10  Sample Table for Specifying Relative Weights for Exposure
       During a Person's Lifetime 	  F-19

 F-ll  Coefficients Relating Percent Change in UV to Percent
       Change in Skin Cancer Incidence 	  F-22

 F-12  Coefficients Relating Percent Change in UV to Percent
       Change in Melanoma Mortality	  F-23

 F-13  Dose-Response Coefficients 	  F-25

 F-14  Damage Index and Increase in Stabilizer for Ranges of
       Ozone Depletion	  F-29

18-1   Types of Human Health and Environmental Effects
       Estimated	 18-8

18-2A  Real World Equivalent to the No-Growth Scenario In Risk
       Assessment	 18-15

18-2B  Real Vorld Equivalent to the 1.2% Growth Scenario in Risk
       Risk Asaessment	,	18*16
        m
18-3   Global Average Ozone Depletion:  Central Case	18-.20
18-4   Additional Cases of Hnnsulinomt Skin Cancer by Type of
       Bonmelanoma	,	 18-21
18-5   Additional Mortality From Hnnm>1 snnsM Skin Cancer by Type
       of Nonrnel •uriiM	,	 18-22

18-6   Additional Cases of Melanoma Skin Cancer by Cohort	18-23

18-7   Additional Mortality From Melanoma Skin Cancer by Cohort .. 18-24

18-8   Additional Senile Cataract Cases by Cohort 	 18-25

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                                    ES-38






18-9   EznrironMatal Effaces Eatiaatad Quantitatively for tfa* U.S.  18-26

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                                     ES-89


                               LEST OF EXHIBITS
18-10   Environmental Effects Baaed on Case Studies and Research
        in Early Stage* 	 18-27

18-11   Equilibrium Temperature Change for the Emissions Scenarioa
        Assuming 3°C Waning for Doubled CO2	18-28
                                                                 t
18-12   Global Average Ozone Depletion:  Comparison to Results  .
        with a *-D Dimensional Atmospheric Model	18-30

18-13   Climate, and Other Effects:  Sensitivity to Relationship
        Between Climate Change sad C02 Emissions	18-31

18-14   Summary of Effects of Greenhouse Gases on Ozone Depletion
        and Global Equilibrium Temperature	 18-33
18-15   Global Awrag* Oxon* D*pl*tion:  Scenario of liait*
        to Futur* Global Waning	•	18-34

18-16   Human Health Effect*:  Scenario* of Liait* to Future
        Global Waning.  Additional Cumulative Caaea and Dead*
        Over UfatiBe* of People Alive Today	18-36

18-17   Human Health Effect*:  Scenario* of Limit* to Futur*
        Global Warming.  Additional emulative Cue* and Death*
        Ov*r Lifetime* of People Born 1986-2029 	 18-37

18-18   Human Health Effect*:  Scenario* of limit* to Future
        Global Warming.  Additional Cvoulative Caae* and Death*
        Over Lifetime* of People Born 2030-2074	 18-38

18-19   Material*, Climate, and Other Effect*:  Scenario*
        of Limit* to Future Global Warming	 18-39

18-20   Global Average Ozone Depletion:  Methane Scenario*	18-41
18-21   Bu«*n Health Effect*:  Methane Scenario* Additional
        domulative Caae* and Death* Over lifetime*
        *€ People Alive Today	 18-42
18-22   Human Health Effect*:  Methane Scenarioa
        Artdtrtonal Cumulative Ca*e* and Death* Over Lifetime*
        of People Born 1986-2029	 18-43

18-23   Human Health Effect*:  methane Emi*«ion* Caaea
        Additional Cumulative Caae* and Death* Over Lifetime*
        of People Born 2030-2074 	 18-44

18-24   Material*, Climate and Other Effects:  Methane Scenarioa .. 18-45

18-25   Global Average Ozone Depletion:  Sensitivity to

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                             KS-90





Relationship B*ttr*ari Ozon* D*pl«cioa and £*l««iena	 18-46

-------
                                     ES-9J.
                               LIST 09P 8IHLUXS
18-26   Human Health Effects:  Sanaitivity to Ralationahip
        Batwaan Ozona Daplation mad Eadaaiona.  Additional
        Cumulative Caaaa and Daatha Ovar Lifatimaa of Paopla
        Aliva Today .......................................... ..... 18-48

18-27   Human Haalth Effaeta:  Sanaitivity to Ralationahip
        Batvaan Ozone Daplation and Imlaalona.  artrtiHonal
        Cumulative Caaea and Daatha Ovar Lifatimea of People
        Bon 1985-2029 .................................. ... .......... 18-49

18-28   Human Haalth Effoeta:  Satuilti-rlty to lalationabip
        BatwMa Oxom Doplotion and toiaainna.  4iMiti«mal
        Cuaulativa Caaaa and Daatha Ovar Llfatiaaa of taopla
        Bom 2030-2074 ............................................. 18-50

18-29   Human Haalth Effaeta:  Maximal Daplation of 95 P«rcant.
        Additional Cuaulativa Caaaa and Daatiaa Ovar Ltf atiaaa
        of Paopla Aliva Today ......... .. .............. . .............. 18-51

18-30   Human Haalth Effaeta:  Maximum Daplation of 95 Pareant.
        Additional Cuaulativa Caaaa and Oaatha Ovar Lif atiaaa of
        Paopla Born 1986-2029 ....................................... 18-52

18-31   Human Haalth Effaeta:  Mariana Daplation of 95 Pareant.
        Additional Cuaulativa Caaaa and Oaatha Ovar Ufatiaaa of
        Paopla Born 2030-2074 ....................................... 18-53

18-32   Human Haalth Effaeta:  Sanaitivit? to Doaa-Raaponaa
        Ralationahip.  Additional Cuaulativa Caaaa and
        Daatha Ovar Ufatiaaa of Paopla Aliva Today ................. 18-55

18-33   Human Haalth Effaeta:  Sanaitivity to Doaa-Raaponaa
        Ralationahip Additional Cuaulativa Caaaa and
        Daatha Ovar Lif atiaaa of Paopla Born 1986-2029 .............. 18-56

18-34   Human Haalth Effaeta:  Sanaitivity to Doaa-Raaponaa
        Btla't1yp«*tip Additional Cnmiilaf !»•
        Daatha Ovar Ufatimaa of Paopla Born 2030-2074  .............. 18-57
18-35   H«ai«n Haalth Effaeta:  Sanaitivity to Ralationahip Baewaan
        Ozona Daplation and Action Spaetrum.  Additional Cumulative
        Caaaa and Daatha Ovar Ufatimaa of Paopla Aliva Today	18-58

18-36   Human Haalth Effaeta:  Sanaitivity to Ralationahip Batvaan
        Ozona Daplation and Action Spaetrum.  Additional Cuaulativa
        Caaaa and Daatha Ovar Lifatimaa of Paopla Born 1986-2029  	 18-59

18-37   Human Haalth Effaeta:  Sanaitivity to Ralationahip Batvaan
        Ozona Daplation and Aetion Spaetrum.  Additional Caaaa and
        Daaths Ovar Liftimas of  Paopla Born 2030-2074 	 18-60
                                                       Protection A^cno

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                                      ES-52


                                 13SI Of BHXXXXS
18-38   Coaparaeir* Saaaitivity of Mortality Fnaa Skin Caaear to
        Various Factors	
                      M.S. fmnmrn* FrtMiac Offto* : UM • «MH«M/tMU

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