United Nations
        Environment Programme
           United States
           Environmental Protection
           Agency
                                  October 1986
&EFK
EFFECTS OF CHANGES IN STRATOSPHERIC
OZONE AND GLOBAL CLIMATE
Volume 2:  Stratospheric Ozone

-------
Library of Congress Cataloging - in - Publication Data
Effects of changes in stratospheric ozone and global climate.
Proceedings of a conference convened by the United Nations Environment
Programme and the U.S.  Environmental Protection Agency.
Contents:  v. 1. Overview — v. 2. Stratospheric ozone — v. 3. Climate
change. — v. 4. Sea level rise
1. Atmospheric ozone—Reduction—Congresses.  2. Stratosphere—Con-
gresses.   3. Global  temperature  changes—Congresses;   4.  Climatic
changes—Congresses.  5.  Sea level—Congresses.  6. Greenhouse effect,
Atmospheric—Congresses. 7. Ultraviolet  radiation—Congresses.
I. Titus,  James G.   II. United States Environmental Protection Agency.
III. United Nations  Environment Programme.

-------
EFFECTS OF CHANGES IN STRATOSPHERIC
        OZONE AND GLOBAL CLIMATE
           Volume 2: Stratospheric Ozone
                          Edited by
                       James G. Titus
              U.S. Environmental Protection Agency
        This report represents the proceedings of the INTERNATIONAL CON-
        FERENCE ON HEALTH AND ENVIRONMENTAL EFFECTS OF
        OZONE MODIFICATION AND CLIMATE CHANGE sponsored by the
        United Nations Environment Programme and the U.S. Environmental
        Protection Agency. The purpose of the conference was to make available
        the widest possible set of views. Accordingly, the views expressed herein
        are solely those of the authors and do not represent official positions of
        either agency. Mention of trade names or commercial products does not
        constitute endorsement or recommendation for use.

-------
PREFACE
     This document  is  part  of a  four  volume  report  that  examines the possible
consequences of projected  changes  in  stratospheric  ozone  and global climate
resulting from emissions of chlorofluorocarbons, carbon dioxide, methane, and
other gases released by  human activities.   In June 1986,  the United Nations
Environment Programme  and the U.  S. Environmental Protection Agency sponsored
an International Conference on  the Health and Environmental Effects of Ozone
Modification  and   Climate  Change,  which  was  attended   by   scientists  and
officials, representing  twenty-one countries from all areas of  the world.

     This volume examines the  possible effects of  ozone depletion.   Volume 1
of  the  proceedings  provides  an overview  of  the issues  as  well  as  the
introductory remarks and reactions from  top  officials of  the United Nations
and the United States.   Volumes  3 and  4 focus on the effects of the change in
climate and rise in sea  level that might result from a global warming.

     This  report  does  not  present the  official  views of either  the  U.S.
Environmental  Protection  Agency or the United Nations Environment Programme.

-------
TABLE OF CONTENTS
 INTRODUCTION

 Overview of the Effects of Changing the Atmosphere
      James G. Titus and Stephen  R. Seidel	    3
 HUMAN HEALTH

 UVR Dose-Dependent Life Shortening in Mice
      R.  E. Davies and P. D.  Forbes 	   23

 An Estimation of Sunspot Induced Ozone Changes From a  Sunburn
   Ultraviolet Meter
      Daniel S. Berger 	   27

 Nonmelanoma Skin Cancer - UV-B Effects
      Joseph Scotto 	   33

 Immunomodulation by Ultraviolet Radiation:  Prostaglandins Appear to be
   Involved in the Molecular  Mechanisms Responsible for UVR-Induced
   Changes in Immune Function
      R.  A. Daynes, H. T. Chung,
      B.  Robertson, L. K. Roberts,
      and W. E. Samlowski 	   63

 Stratospheric Ozone Depletion:  Immunologic Effects on Monocyte
   Accessory Function in Humans
      Craig A. Elmets, Jean Krutraann, Elizabeth Rich,
      Hiroshi Fuj iwara, and Jerrold J. Ellner 	   87

 Effects  of UV-B on Infectious Disease
      Suzanne Holmes Giannini	  101

-------
Urocanic Acid:  On  Its  Role  in  the  Regulation of  UVB-Induced
  Systemic  Immune Suppression
     Edward C. De Fabo  and Frances  P. Noonan  	  113

Solar Wavelengths of Ultraviolet Light-Induced Cytoplasmic  Damage
     Glen B. Zamansky and lih-Nan Chou  	  119

Sunscreens  Do Not Abrogate UV-Induced Suppression of  Contact
  Hypersensitivity
     M. S.  Fisher,  J. M. Menter,
     L. Tiller, and I.  Willis 	  131

Sunlight and Malignant  Melanoma in  Western Australia
     Bruce K. Armstrong 	  1 ij 1

Radiometry of Solar UV-B
     A. Baqer and N. Kollias 	  157

The Role of Native Pigment in Providing Protection Against  UV-B
  Damage in Humans
     N. Kollias and A.  Baqer 	  173

Ozone Modification:  Importance for Developing Countries in the
  Tropical/Equatorial Region
     Mohammad Ilyas 	  185

The Tan of Ultraviolet-B Summer
     Petar Jovanovic 	  193
AQUATIC SYSTEMS

Effects of Enhanced UV-B Radiation on the Survival of Micro-Organisms
     Donat-P. Haider 	 197

Is the Impact of UV-B Radiation on Marine Zooplankton of Any
  Significance?
     B. Thomson 	 203

An Estimate of the Role of Current Levels of Solar Ultraviolet
  Radiation in Aquatic Ecosystems
     John Calkins and Mary K. Blakefield	 211

How Might Enhanced Levels of Solar UV-B Radiation Affect Marine
  Ecosystems?
     John R. Kelly	 237
TERRESTRIAL PLANTS

The Potential Consequences of Ozone Depletion Upon Global Agriculture
     Alan H.  Teramura 	 255
                                      vi

-------
Inhibition of Photosynthetic Production in Plants by Ultraviolet
  Radiation
     L. 0. Bjorn, Janet F. Bornman, and Legasse Negash 	 263
MISCELLANEOUS

An Assessment of UV-B Radiation Effects on Polymer Materials:
  A Technical and Economic Study
     Anthony L. Andrady and Robert L. Horst, Jr	 279

The Interaction of Photochemical Processes in the Stratosphere
  and Troposphere
     Gary Z. Whitten and Michael W. Gery 	 295

Tropospheric CHij/CO/NOx:  The Next Fifty Years
     Anne M. Thompson and Michael Kavanaugh 	 305
                                     vii

-------
INTRODUCTION

-------
Overview of the Effects of Changing  the  Atmosphere

James G. Titus and Stephen R. Seidel
Environmental Protection Agency
Washington, DC USA
INTRODUCTION

     Society is  conducting  a global  experiment  on the  earth's  atmosphere.
Human activities are  increasing  the  worldwide  atmospheric  concentrations  of
chlorofluorocarbons,  carbon  dioxide,   methane,  and several  other  gases.    A
growing body of  scientific evidence suggests that  if  these  trends continue,
stratospheric ozone may  decline and global temperature may rise.   Because  the
ozone layer  shields  the earth's  surface  from damaging ultraviolet radiation
(UV) future  depletion could increase  the  incidence of skin  cancer and  other
diseases,  reduce  crop yields, damage materials,  and  place additional stress on
aquatic plants and animals.   A  global warming from  the  "greenhouse  effect"
could also threaten human health, crop yields,  property,  fish,  and wildlife.
Precipitation and storm  patterns  could  change,  and the level of  the  oceans
could eventually  rise.

     To  improve  the  world's  understanding  of  these and  other  potential
implications of  global  atmospheric  changes,  the United  Nations  Environment
Programme (UNEP)  and  the U.S.  Environmental Protection Agency (EPA) sponsored
an  International  Conference  on the Health and Environmental  Effects of  Ozone
Modification and Climate  Change  during  the week of  June  16-20,   1986.    The
conference brought  together  over  three hundred  researchers and  policy makers
from  approximately  twenty nations.   This  four-volume  report  presents  the
seventy-three papers that were  delivered at the  conference by over eighty
speakers,  including two  U.S.  Senators, top officials  from UNEP  and EPA, some
of  the  leading  scientists   investigating  the  implications of  atmospheric
change, and representatives from  industry and environmental groups.  Volume 1
presents a  series  of overview papers  describing  each of the major areas  of
research on  the effects  of atmospheric change,  as well as policy  assessments
of  these   issues  by  well-known  leaders   in  government,  industry,  and  the
environmental community.  Volumes  2,  3,  and 4 present the  more  specialized
papers on  the  impacts  of ozone  modification, climate change, and sea  level
rise, respectively,  and  provide  some  of  the  latest research in these areas.
This paper summarizes the  entire four-volume  report.

-------
OZONE MODIFICATION

Atmospheric Processes

     The ozone  in the  upper part  of the   atmosphere—known as  the strato-
sphere—is  created  by  ultraviolet radiation.    Oxygen  (02)  is  continuously
converted  to  O2one  (0^)  and back  to 02 by numerous  photochemical reactions
that  take  place  in  the  stratosphere,   as  Stordal  and  Isaksen   (Volume  1)
describe.   Chlorofluorocarbons and other gases released  by  human activities
could  alter  the  current  balance of  creative  and  destructive  processes.
Because CFCs  are  very  stable  compounds,  they  do not break  up in the lower
atmosphere  (known as  the troposphere).   Instead, they  slowly migrate to the
stratosphere,   where  ultraviolet  radiation  breaks  them  down,  releasing
chlorine.

     Chlorine acts as a  catalyst  to destroy  ozone;  it promotes reactions that
destroy ozone without being  consumed.  A chlorine (Cl) atom reacts with ozone
(Oo) to  form  CIO  and 02-   The CIO later reacts with another 0?  to form two
molecules  of  02,  which  releases  the  chlorine atom.   Thus,  two molecules  of
ozone are converted  to three molecules of ordinary oxygen, and the chlorine is
once again free  to start the process.   A  single  chlorine  atom  can destroy
thousands  of  ozone  molecules.    Eventually,  it  returns to  the  troposphere,
where it is rained out as hydrochloric acid.

     Stordal and Isaksen point out  that  CFCs are  not the only gas released by
Human  activities   that   might   alter   the  ozone   balance.     Increasing
concentrations of methane  in the  troposphere increase the  water  vapor in the
stratosphere,  which helps  create  ozone.   Carbon dioxide and  other greenhouse
gases  (discussed  below)  warm   the   earth's  surface  but  cool   the  upper
atmosphere; cooler stratospheric  temperatures slow the process of ozone deple-
tion.  Nitrous oxide (N20) reacts  with both chlorine and ozone.

     Stordal  and  Isakson  present  results  of possible  ozone depletion  over
time, using  their  two-dimensional  atmospheric-chemistry model.    Unlike  one-
dimensional models which provide  changes  in  ozone  in  the global  average,  this
model calculates  changes for  specific latitutdes and seasons.    The results
show that if concentrations of the relevant trace gases grow at recent levels,
global average  ozone  depletion  by  2030 would  be  6.5  percent.    However,
countries in the higher latitudes  (60°N)  would  experience 16 percent depletion
during spring.   Even  in  the  case of constant CFC  emissions,  where global
average depletion would be  2  percent by  2030,  average  depletion  would  be  8
percent in the high  northern latitudes.

     Watson (Volume  1) presents evidence  that ozone has been changing recently
more than atmospheric models had  predicted.  As  Plate 1  shows, the ozone over
Antarctica  during  the  month  of  October  appears to  have declined  over  40
percent in  the  last six  to  eight years.  Watson also discusses  observations
from ozone monitors  that suggest a 2 to 3 percent worldwide reduction in ozone
in the upper portion of the stratosphere  (thirty to forty kilometers above the
surface),  which is  consistent with model  predictions.  Finally,  he presents
preliminary data  showing a  small decrease  since  1978  in  the total (column)
ozone worldwide.  However,  he strongly emphasizes that  the data have not yet
been fully reviewed and that it is   not  possible  to conclusively attribute
observed ozone  depletion to  the  gases  released  by  human  activities.   While

-------
there  are  several  hypotheses  to  explain  why  ozone  concentrations  have
declined,  none  have  been  adequately   established;   nor   did  any  of  the
atmospheric models predict the measured loss of ozone over Antarctica.

Ultraviolet Radiation

     Many  of  the  chemical  reactions  investigated  by  atmospheric scientists
take  place only  in the  stratosphere because they  are caused  by  types  of
radiation  only  found  in  the  upper  atmosphere.    As  Frederick  (Volume  1)
explains, the sun emits radiation over a broad range of wavelengths, to which
the human eye responds in the  region from approximately 400 to 700 nanometers
(nm).  Wavelengths from 320  to MOO  ran are known as UV-A; wavelengths from 280
to 320 nm are called UV-B,  and wavelengths  from  200 to 280 nm  are known as
UV-C.

     Frederick explains why  attention has primarily focused on  the UV-B part
of the spectrum.   The  atmosphere absorbs  virtually  all UV-C,  and is expected
to continue to do  so under all foreseeable circumstances.   On the other hand,
UV-A is  not absorbed by  ozone.1.   By  contrast, UV-B is partially absorbed by
ozone, and future depletion would reduce the effectiveness of this shield.

     We  now  examine  the  potential  implications  of  such  changes  on  human
health, plants, aquatic organisms,  materials, and air pollution.

Effects on Human Health

     The  evidence  suggests  that   solar  ultraviolet  radiation   induces  skin
cancer,  cataracts, suppression of the  human  immune  response   system,  and
(indirectly  through immunosuppression)   the  development  of  some  cutaneous
infections, such as herpes.  Emmett (Volume 1) discusses the absorption of UV
radiation by  human tissue and  the  mechanisms by which  damage and repair may
occur.

     Emmett also examines UV radiation as  the  cause of aging of the skin and
both basal and  squamous  skin cancers.   In reviewing  the role  of UV radiation
in melanoma  (the  most frequently  fatal  skin cancer), he  states  that  some
evidence suggests this link, but that  currently there is no acceptable animal
model that can be used  to explore or validate this relationship.  He concludes
that  future  studies must focus on  three major  factors—exposure  to  solar
radiation, individual  susceptibility,  and  personal behavior.   Waxier (Volume
1) presents evidence of a link between UV-B exposure and cataracts.

     Volume 2 presents specific research results and  provides more detail on
many of  the aspects covered  in  this volume.   Scotto presents  epidemiological
evidence linking solar radiation with  skin cancers,  other  than  melanoma.   His
analysis suggests that  Caucasians in the United States have a 12 to 30 percent
chance of developing these cancers  within  their lifetimes,  even without ozone
depletion.   Armstrong  examines the role  of UV-B exposure  to  melanoma  in  a
study  of  511  matched  melanoma patients  and control subjects   in  Western
Australia.   He  shows  that  "intermittent  exposure"  to sunlight  was closely
associated with this type of cancer.
 1 However, 02 and N2 reflect some UV-A back to space,

-------
     In a paper examining nonmelanoma skin cancer  in Kuwait, Kollias and  Baqer
 (Volume  2)  show  that  despite the  presence  of protective  pigmentation,  75
 percent of cancers occur on the 10 percent of  the  skin exposed  to sunlight.   A
 second paper on skin cancer presents experimental  evidence suggesting that the
 mechanism  by  which  skin  cancer  could  occur  involves  disruption  of the
 cytoskeleton  from  exposure  to  UV-A  and  UV-B  light  (Zamansky  and   Chow,
 Volume 2).

     The  pathways  by  which   suppression  of  the  immune  response might  be
 triggered are  explored  in  papers by  DeFabo and  Noonan,  Daynes et  al., and
 Elmets et  al (all  Volume 2).   Davies  and  Forbes (Volume 2)  show that  mice
 exposed to UV-B radiation had a decrease in lifetime that was  proportional  to
 the  quantity  of radiation and  not  directly related to  the  incidence of  skin
 cancer.

     Possible   implications   of  immune   suppression  of  diseases  and  the
 mechanisms by which it occurs are still uncertain.  However,  several papers  in
 Volume 2 suggest that in addition to skin cancer and contact hypersensitivity,
 diseases influenced  by  UV-B  induced  immune  suppression  include leishmaniasis
 and  herpes  infections.   Fisher  et. al  (Volume  2)  show that at  least one
 sunscreen effectively  protects mice  exposed to UV-B  radiation from sunburn;
 but  it does  not stop the immune suppression  from interfering  with a contact
 hypersensitivity (allergic) reaction.

•Effects on Plants

     The effects of  increased exposure  to  UV-B radiation on  plants has been a
 primary area  of research  for nearly a  decade.   Teramura (Volume  1)  reports
 that of the two hundred plants tested for their sensitivity to UV-B radiation,
 over two-thirds  reacted adversely;  peas,  beans, squash, melons,  and cabbage
 appear to  be the  most  sensitive.    Given the  complexities  in this  area of
 research, he warns  that these  results  may be misleading.   For example, most
 experiments have  used growth  chambers.   Studies of plants  in  the  field have
 shown them to be less sensitive to UV-B.  Moreover, different cultivars of the
 same  plant  have  shown  very different   degrees  of  sensitivity  to  UV-B
 radiation.   Finally, Teramura  suggests  that potential  effects from multiple
 stresses (e.g., UV-B  exposure plus  water  stress or  mineral  deficiency)  could
 substantially alter a plant's response to changes in UV-B alone.

     In Volume  2, Teramura  draws extensively from the results of  his five
 years of field  tests on soybeans.  His  data show  that a 25  percent depletion
 in ozone  could  result  in a  20 to 25  percent  reduction in  soybean yield and
 adverse impacts on the  quality of that  yield.   Because soybeans are the fifth
 largest  crop  in  the  world,  a  reduction  in  yields  could  have  serious
 consequences for world  food supplies.   However,  some soybean cultivars appear
 to be less susceptible  to UV-B radiation, which  suggests  that selective crop
 breeding might reduce future  losses,  if  it does not increase vulnerability to
 other environmental stresses.

     BJorn (Volume 2)  examines the mechanisms by which plant  damage  occurs.
 His  research relates  specific wavelengths  with those aspects  of plant growth
 that might be susceptible,  including the destruction of chloroplast,  DMA, or
 enzymes necessary for photosynthesis.

-------
Aquatic Organisms

     Aquatic plants would also be  adversely  affected by increased ultraviolet
radiation.   Worrest (Volume 1) points out that most of these plants, which are
drifters (phytoplankton)f  spend  much  of their  time near the surface  of the
water   (the   euphotic  zone)  and  are  therefore   exposed   to  ultraviolet
radiation.    A reduction  in  their productivities  would be  important because
these plants  directly and indirectly  provide  the  food for almost  all fish.
Furthermore,  the  larvae  of  many  fish found  in the  euphotic  zone  would  be
directly affected, including  crabs, shrimp, and anchovies.  Worrest points out
that fish account for  18  percent  of  the animal protein that people around the
world consume, and 40 percent of the protein consumed in Asia.

     An important  question  is the extent  to which  current UV-B levels are a
constraint on aquatic  organisms.   Calkins and  Blakefield  (Volume 2) conclude
that some species are already exposed to  as much UV-B as  they  can tolerate.
Thomson (Volume  2)  shows that a  10 percent decrease  in  ozone  could increase
the number of abnormal larvae as much as 18 percent.  In a study of anchovies,
a 20 percent  increase in UV-B radiation over  a 15-day period caused the loss
of all the larvae within a 10-meter mixed layer  in April and August.

     Many other factors could affect the magnitude of the impacts on specific
species, ecosystems,  and  the food  chain.    An important mechanism  by which
species could adapt to higher UV-B incidence would be to reduce their exposure
by moving further away from  the  water's surface during  certain times  of the
day or  year when exposure is greatest.  Haeder (Volume 2) suggestst however,
that for certain species such avoidance may be  impaired by UV-B radiation.

     Even for those  organisms  that  could move  to avoid  exposure,  unwanted
consequences may result.  Calkins and  Blakefield present model results  showing
that movement by phytoplankton  away from  sunlight  to reduce exposure to a  10
percent  increase  in  UV-B would  result in  a  2.5   to  5  percent  decrease   in
exposure  to  the  photosynthetically  active  radiation  on which  their  growth
depends.    Increased  movement requires  additional   energy  consumption, while
changes in  location may affect the availability  of food for zooplankton, which
could cause other changes in shifts  in the aquatic food chain.

     To a certain extent, losses within a particular species of plankton may
be compensated by gains in other species.  Although  it  is possible that no net
change  in  productivity will  occur,  questions  arise concerning the ecological
impacts  on  species diversity  and  community  composition  (Kelly,  Volume  1).
Reductions  in diversity may  make  populations more  susceptible  to changes  in
water temperatures, nutrient availability, diseases, or pollution.  Changes  in
community composition  could  alter  the protein content, dry weight, or  overall
food value  of the  initial stages of  the  aquatic  food chain.

Polymer Degradation and Urban Smog

     Current  sunlight  can cause  paints to  fade, transparent window glazing  to
yellow,  and polymer  automobile roofs to  become  chalky.   These changes are
likely  to occur more  in  places  closer to  the equator where UV-B radiation  is
greater.    They  are  all  examples  of degradation  that  could  accelerate  if
depletion of the ozone layer occurs.   Andrady and Horst (Volume 2)  present a
case  study  of  the potential magnitude  of loss due  to increased exposure  to

-------
UV-B radiation on polyvinyl  chloride  (PVC).   This chemical is used in outdoor
applications  where  exposure  to  solar  radiation  occurs over  a  prolonged
period.   It is also  used in the  construction industry in siding  and window
frames and as a roofing membrane.

     To analyze  the potential  economic impact of future ozone  depletion on
PVC, the  authors assumed  that  the future service life of polymers  would be
maintained by increasing  the quantity of light stabilizers (titanuim dioxide)
used in the product.   As  a  result, the costs associated  with increased UV-B
radiation  would  be  roughly equal  to  the   costs  of   increased  stablizers.
Preliminary  results  show that for  a  26  percent  depletion by  2075,  the
undiscounted costs would be $4.7 billion (1984 dollars).

     Increased penetration of UV-B radiation to the earth's surface could play
an  important  role  in  the formation  of ground level  oxidants (smog).   UV-B
affects smog  formation  through the  photolysis  of formaldehyde,  from  which
radicals  are  the  main  source   for deriving  chain  reactions that  generate
photochemical smog.   Whitten and  Gery  (Volume  2)  analyze  the  relationship
between UV-B, smog, and warmer  temperatures.   The results of this preliminary
study of  Nashville,  Philadelphia,  and Los Angeles  show  that  large depletions
in stratospheric ozone and increases  in temperature would increase smog by as
much as 50  percent.   In addition,  because oxidants would form earlier in the
day  and   closer  to  population  centers  (where emissions  occur),  risks  from
exposure  could  increase by an  even higher percentage  increase.   Whitten and
Gery also report a  sensitive relationship  between UV-B and hydrogen peroxide,
an oxidant and precursor to acid rain.

CLIMATE CHANGE

The Greenhouse Effect

     Concern about a possible global warming focuses largely on the same gases
that may  modify the stratospheric  ozone:  carbon dioxide, methane, CFCs,  and
nitrous oxide.  The  report of a recent conference convened by UNEP, the World
Meteorological  Organization,  and   the  International  Council  of  Scientific
Unions  concluded  that  if  current trends  in  the emissions  of  these  gases
continue,   the  earth  could  warm a few  degrees  (C) in  the next  fifty  years
(Villach  1985).   In the next century,  the planet could warm as  much as five
degrees (NAS  1983),  which would leave  the planet warmer  than at any time in
the last  two million years.

     A planet's temperature  is  determined  primarily by  the amount of sunlight
it receives, the  amount of sunlight it  reflects,  and  the extent  to which the
atmosphere  retains  heat.    When  sunlight  strikes  the earth,  it warms  the
surface, which then reradiates the heat as infrared radiation.  However,  water
vapor, COp, and other gases in the atmosphere absorb some of the energy rather
than allowing it  to  pass  undeterred through  the atmosphere to space.   Because
the atmosphere  traps heat and warms the earth in a manner somewhat analogous
to the glass panels  of  a  greenhouse,  this phenomenon is commonly known as the
"greenhouse effect."  Without the  greenhouse effect of  the gases  that  occur
naturally in the atmosphere,  the earth would be approximately 33°C colder than
it is currently (Hansen et al.  1984).
                                       8

-------
     In  recent decades,  the  concentrations  of greenhouse  gases  have  been
increasing.  Since the beginning of  the industrial  revolution, the combustion
of  fossil  fuels,  deforestation,  and  a  few  other  activities have released
enough C02  to  raise  atmospheric concentrations  by  20 percent; concentrations
have risen  8 percent  since  1958 (Keeling,  Bacastow,  and Whorf  1982).   More
recently, Ramanathan  et  al.  (1985)  examined the greenhouse  gases  other  than
C02 (such as methane, CFCs, and nitrous oxide), and concluded that these other
gases  are  likely  to  double the  warming  caused by  C02  alone.   Using these
results, the Villach Conference estimated  that an "effective doubling" of C02
is likely by 2030.2

     Hansen et  al.  (Volume  1) and  Manabe & Wetherald  (Volume 1) present the
results  that their climate models predict for an  effective doubling of C02.
Both models  consider a  number of "climatic feedbacks" that  could  alter the
warming  that would directly  result from C02 and other gases released by human
activities.  Warmer  temperatures  would allow  the  atmosphere  to retain  more
water  vapor, which is also a  greenhouse gas,  thereby resulting  in additional
warming.   Ice  and snow  cover would  retreat, causing  sunlight  that  is now
reflected by these bright surfaces to  be absorbed instead, causing additional
warming.  Finally, a  change  in cloud cover might result, which could increase
or  decrease  the projected warming.    Although the  two models  differ in  many
ways,  both conclude that  an  effective  doubling of greenhouse gases would warm
the earth's surface between two and  four degrees  (C).

     Hansen et  al. project the doubling to occur between 2020 and 2060.  They
also   provide   estimates  of   the  implications   of  temperature  changes  for
Washington,  D.C.,  and  seven  other  U.S.   cities  for the  middle  of  the  next
century.   For   example, Washington  would have  12 and 85 days  per  year above
38°C (100°F) and  32°C  (90°F),  respectively,  compared with 1 and  35 days above
those  levels today.  While evenings  in which the  thermometer fails to go below
27°C  (808F)  occur less  than once  per  year  today in that -city,  they project
that such  evenings would occur  19 times  per  year.   (See Plates 2  and 3 for
worldwide maps  of historical and projected temperature changes.)

Water  Resources

     Manabe  and  Wetherald  (Volume   1)  focus  on  the  potential changes   in
precipitation  patterns  that  might result  from the  greenhouse  warming.   They
project  substantial  increases  in .summer dryness  at  the middle latitudes that
currently support  most  of the  world's agriculture.   Their model  also projects
increased rainfall for late winter.

     Beran  (Volume 1)  reviews the  literature  on the  hydrological  and water
resource impacts  of  climate  change.   He expresses some surprise  that only
twenty-one  papers could be found that  address future water resource impacts.
One of  the  problems,  he  notes,  is  that  there  is  a  better   scientific
understanding  of how  global average temperatures and  rainfall might change,
than  for the changes that specific  regions  may experience.  Nevertheless,  he
   Studies  on the greenhouse effect generally  discuss the impacts of a carbon
   dioxide  doubling.   By  "effective  doubling" we  refer  to any combination of
   increases  in  concentrations of  the  various gases that  causes a warming equal
   to the warming of  a doubling of carbon dioxide alone.

-------
demonstrates  that  useful  Information  can  be  extracted  by  studying  the
implications of particular scenarios.

     Nicholson  (Volume  3)  shows how historical changes  in water availability
have  caused  problems for society  in the past.   The best  lesson  of climatic
history,  she writes,  "is  that agricultural  and  economic  systems must  be
flexible enough to adapt to changing conditions  and, in the face of potential
water  scarcity,  systems  must  be  designed  that  require  minimum  use  of
resources."  Wilhite (Volume 3) examines drought policies in Australia and the
United  States,  concluding  that  the  lack  of  national  drought plans  could
substantially impair the ability of these two nations to successfully adapt to
hydrologic changes resulting from the greenhouse warming.

     Cohen  (Volume  3)  examines  the  potential  implications  of the  global
warming  for  water levels  in   the  Great Lakes that  separate Canada  from the
United States.  Using results  from the models of both Hansen et al. and Manabe
& Wetherald,  he concludes that  lake levels could drop  10 to 30 centimeters.
This drop would significantly  reduce the capacity of ocean-going vessels that
enter the Great Lakes.   On the  other  hand,  such a  drop  might  be viewed as a
benefit by the owners of critically eroding property whose homes are currently
threatened by historically high lake levels.  Street-Perrott et al. (Volume 3)
discuss  the  historic impacts  of changes in climate  on  the levels of lakes in
North America, South America,   Australia, and Africa.

     Gleick  (Volume  3) uses  scenarios  from  the  Hansen  et al. and  Manabe &
Wetherald models  (as well  as a  third developed  by the  National  Center for
Atmospheric  Research) to  drive a water-balance model of the Sacramento Basin
in California.  He finds  that  reductions in runoff could occur even in months
where precipitation  increases  substantially, because of the increased rates of
evaporation  that  take  place at higher  temperatures.   He also points out that
the  models  predict that changes  in  monthly runoff  patterns  will  be far more
dramatic  than changes  in annual averages.   For  seven  of ten scenarios, soil
moisture would  be  reduced  every  month of the  year;  for the other three cases,
slight  increases  in  moisture are projected  for winter months.  Mather (Volume
3)  conducts  a  detailed  analysis  for  southern  Texas  and  northern  Mexico;
examines  in  less  detail twelve regions  around  the world; and projects shifts
in global vegetation zones.

Agriculture  and Forestry

      The  greenhouse  warming  could   affect  agriculture   by  altering  water
availability,  length of  growing  season,  and the  number  of  extremely hot
days.    Increased CO,  concentrations  could  also  have  two  direct  impacts
unrelated to climate change:   At least the laboratory, plants grow faster (the
COp  fertilization effect) and  retain moisture more efficiently.  The extent to
which these  beneficial  effects offset the  impacts of climate  change will
depend  on the extent to  which global warming is  caused  by C02 as opposed to
other greenhouse  gases, which  do not have these positive  impacts.

      Parry  (Volume 1) provides an overview of  the potential impacts of climate
change  on agriculture  and forestry.   He points  out  that commercial farmers
plan according  to the  average year,  while family and subsistence farmers must
ensure  that  even in the  worst years they can  make  ends meet.   Thus,  the
commercial  farmer would be  concerned about  the impact of future  climate  change


                                       10

-------
on average conditions and average yields, while farmers at the margin would be
most  concerned  with  changes  in  the probability  of  (for  example)  a  severe
drought that causes  complete crop failure.  Parry  notes  that the probability
of  two or  more  anomalous  years  in a row  could  create  disproportionately
greater problems  for agriculture.    For example,  a  persistent  drought  in the
U.S. Great Plains from  1932  to 1937  contributed to about two hundred thousand
farm bankruptcies.

     Parry discusses  a  number of historical  changes in  climate.   The Little
Ice  Age  in western  Europe  (1500-1800  A.D.)  resulted  in the  abandonment of
about half the  farms in Norway, an  end to cultivation of cereals in .Iceland,
and some farmland in Scotland being permanently covered with snow.  Concerning
the late medieval cooling (1250-1500) he writes:  "The failure to adapt to the
changing circumstances  is believed to explain  much of the Norse decline.  The
Norse continued to emphasize stock-raising in  the  face of reduced capacity of
the already limited  pastures.  The option  of  exploiting  the rich seas around
them, as the Inuit  (Eskimos) successfully  did, was not taken up ... This is
an  extreme  example  of  how  governments can   fail  to identify  and  implement
appropriate policies  of response."   It  also suggests that effective  responses
can reduce damages from climate change.

     The  paper  reviews  a  number of studies  that  project  impacts  of climate
change on agriculture.   "Warming appears  to be detrimental to cereals in the
core  wheat-growing  areas of North  America  and Europe." If no precipitation
changes take place,  a one-degree warming would decrease yields  1 to  9 percent
while  a  two-degree  (C)  warming would decrease yields 3 to 17 percent.   Parry
also discusses how particular  crop zones might  shift.  A  doubling of  C02  would
substantially expand the wheat-growing area  in Canada due  to  higher winter
temperatures and  increased rainfall.  In Mexico, however, temperature stresses
would  increase, thereby  reducing yields.

      A  number  of studies  have been conducted using the models of Hansen et
al.,  Manabe  &  Wetherald,  and others.   Although  these  projections cannot be
viewed as reliable forecasts,  they do provide  consistent  scenarios  that can be
useful  for  examining vulnerability  to  climate change.   Parry  indicates  that
investigations  of Canada,  Finland,  and the northern USSR  using the model by
Hansen et al. show  reduced yields of spring-sown crops such as  wheat, barley,
and  oats, due  to   increased  moisture   stress early  in  the  growing period.
However,  switching  to  winter wheat or winter rye  might reduce this stress.
Parry goes  on  to outline numerous  measures  by which  farmers  might adapt to
projected climate change.

      Waggoner  (Volume 3) points out that  the  global warming would not affect
plants uniformly.    Some  are more  drought-resistant  than others,  and  some
respond  to higher C02 concentrations more  vigorously than others.  Co plants,
such as wheat, respond to  increased, C02  more than C^ plants  such as maize.
Thus,  the COp  fertilization effect  woulbf not help  the farmer growing Cn  crops
accompanied By  Co weeds.  Waggoner also examines the impact of  future climate
change on average  crop yields  and  pests, and the probability of successive
drought  years.   He  concludes  that although projections of  future  changes are
useful,  historical  evidence suggests that  surprises may  be  in store, and that
"agricultural  scientists will be expected  to  aid  rather than watch  mankind's
adaptation to an  inexorable  increase in C02 and its greenhouse  effect."
                                       11

-------
     The  impact  of  future climate  change  on yields  for  spring  wheat  in
Saskatchewan,  Canada,  is  the  subject  of  the paper  by Stewart  (Volume 3).
Using the output  from the  Hansen et al.  model (Volume 1), which projects that
the  effective  doubling  of  carbon  dioxide  would   increase  average  annual
temperatures  in  that  region  by 4.7°C,  he  estimates  that  the  growing season
would start  two  or  three  weeks  earlier and  end  three  or  four  weeks later.
Although average  precipitation  during  the  growing season  would  increase,  he
also finds  that the area would  become  more prone to  drought.   The impact of
climatic change would be to reduce yields 16 to 26 percent.  Stewart estimates
that the fertilization effect of a CC^  doubling would reduce the losses to 6
to  15 percent.    Cooter  (Volume 3) examines the economic  impact of projected
climate change  on the  economy of  Oklahoma,  concluding that the  Gross State
Product would decline 75 to 300 million  dollars.   (The  state's gross product
in 1985 was approximately 50 billion dollars.)

     Fritts  (Volume  3)  examines  tree  rings  to  assess how past  changes  in
climate have  affected forests,  and  concludes  that tree rings  are useful for
estimating past changes  in climate.  Solomon  and  West (Volume  3)  discuss the
results of their  efforts to model  the future impacts.  Considering the impact
of climate change caused by doubled C02 without the fertilization effect, they
find that  "biomass  (for boreal  forests)  declines  for 50-75 years as warming
kills off large boreal  forest  species,  before  new  northern hardwoods can grow
into the plot."

     "Warming at  the transition site causes  an almost  immediate  response  in
declining biomass from dieback of mature trees, and in decline of tree mass as
large trees  die  and  are  temporarily replaced  by small  young trees,"  they
write.   "The  deciduous forest site  .  .  . results in  permanent  loss of dense
forest.    One  might  expect the  eventual appearance  of subtropical  forests
similar to  those  in  Florida  today, but  the  real  difficulty is  the moisture
balance (which  is)   more  similar to  those  of  treeless  Texas today,  than  to
those  of   southern   Florida."    Solomon and  West  go  on  to  show  how  the
fertilization effect from  increased  concentrations  of COj  could  offset part
but not all of the drop in forest productivity.

Sea Level  Rise

     One of the most  widely recognized consequences  of a global warming would
be a rise  in sea level.   As  Titus (Volume 1) notes,  global temperatures and
sea level  have fluctuated  over periods  of  one hundred thousand  years,  with
temperatures during  ice ages  being three to  five  degrees  (C)  lower  and sea
level over one  hundred  meters  lower  than  today.    By  contrast,  the  last
interglacial period  (one hundred thousand years ago) was one  or  two degrees
warmer than today, and sea level was five to seven meters higher.

     The projected global warming could raise sea level by heating and thereby
expanding  ocean  water,  melting  mountain  glaciers,  and   by  causing  polar
glaciers  in  Greenland  and Antarctica  to melt  and  possibly  slide  into the
oceans.     Thomas  (Volume  4)  presents  new  calculations  of  the  possible
contribution of Antarctica  and combines  them with previous  estimates for the
other sources,  projecting  that  a  worldwide rise  in  sea  level  of 90  to 170
centimeters by  the  year 2100  with  110  centimeters most likely.   However,  he
also estimates that  if the global warming is  substantially  delayed,  the rise
in  sea  level could  be cut in  half.   Such a  delay might result  either from


                                      12

-------
actions to  curtail  emissions or  from  the thermal lag  induced  by the oceans'
ability to absorb heat.

     On the other  hand,  Thomas  also  estimates  that  if a  warming of four
degrees results  from a  C02  doubling  (which the  model  of  Hansen et  al.
projects}  and concentrations continue to grow after 2050, the rise could be as
great as 2.3 meters.   He also notes that an irreversible deglaciation  of the
West Antarctic  Ice  Sheet might begin  in the next century, which would raise
sea level  another six meters in the following centuries.

     Titus  (Volume  1) notes  that  these  projections  imply that sea level could
rise 30 centimeters by 2025,  in addition to  local subsidence trends that have
been important  in Taipei,  Taiwan; Venice,  Italy; the  Nile Delta,  Egypt; and
most of the Atlantic and Gulf Coasts of the United States.  The projected rise
in  sea  level  would  inundate  low-lying  areas,  destroy  coastal marshes  and
swamps,  erode   shorelines,   exacerbate   coastal   flooding,  and   increase  the
salinity of rivers,  bays,  and aquifers.

     Bruun  (Volume  4) argues that with a combination  of coastal engineering
and  sound   planning,  society can  meet  the  challenge  of a  rising  sea.   He
discusses   a number  of  engineering  options,  including  dikes  (levees)  and
seawalls,  and  adding sand  to recreational  beaches  that are eroding,  with a
section on  the battle that  the Dutch  have  fought  with the  sea  for over one
thousand years.   Goemans  (Volume 4}  describes  the  current approach  of the
Dutch for  defending  the  shoreline,  and estimates that the cost of raising
their dikes  for a one meter  rise  in  sea level would be 10  billion  guilders,
which is less  than  0.05 percent of their Gross National Product for a single
year.

     Goemans concludes that there  is no need to anticipate such a rise because
they could  keep up with it.   However,  he is more concerned, by the two-meter
scenario:  "Almost immediately after detection, actions  would  be required.  It
is  not at  all  certain that decision-makers  act that  fast.  .  .  .  The present
flood protection  strategy  came about only after  the  tragic  disaster of  1953.
When nobody can  remember  a specific disaster,  it is  extremely difficult to
obtain consensus  on countermeasures."   For  his own  country,  Goemans sees one
positive  impact:    Referring to  the  unique  experience of Dutch engineering
firms in the battle with the sea,  he suggests that "a rising sea may provide a
new global market for this expertise."  But  he predicts that "the question of
compensation payments may come up," for the poorer countries who did not cause
climate change but must face its consequences.

     Broadus et al.   (Volume 4) examine  two such countries  in  detail:   Egypt
and Bangladesh.  The  inhabited areas of both countries are river deltas, where
low-lying land has been created by the sediment washing down major rivers.  In
the case of Egypt,  the damming of the  Nile  has  interrupted  the sediment, and
as  the delta sinks,  land  is lost to the Mediterranean Sea.   Broadus  et al.
estimate that  a  50-centimeter  rise  in  global  sea level, when combined with
subsidence  and the  loss of  sediment, would  result in the loss  of 0.3  to 0.4
percent of  the  nation's  land  area; a  200-centimeter  rise  would  flood 0.7
percent.  However, because Egypt's population is concentrated in the low-lying
areas, 16  and  21 percent  of the  nation's population currently reside  in the
areas that would be lost in  the two scenarios.
                                       13

-------
     The situation would be even more severe in Bangladesh.  As Plate 4 shows,
this nation, which is  already  overcrowded,  would lose 12 to 28 percent of its
total  area,  which  currently   houses  9  to  27  percent  of its  population.
Moreover, floods could penetrate  farther  inland,  which could leave the nation
more vulnerable  to the type of tropical storm that  killed  300,000 people in
the early 1970s, especially if the frequency of tropical storms doubled due to
warmer water temperatures, which  deSylva  (Volume  4)  projects.   Broadus et al.
conclude  that  the vulnerability  of Bangladesh  to a  rise in sea  level  will
depend in large measure on whether future water projects disrupt land-creating
sediment washing down the Ganges.

     Bird  (Volume  4) examines  the implications  of  sea level rise  for other
African and  Asian  nations,  as  well as Australia.  While holding back the sea
may be viable  in Australia, he shows  areas in New Guinea where people live in
small cottages  on  the  water's  edge on a  barrier island that almost certainly
would be  unable to  justify  construction  of  a dike.   He also  points  to the
Philippines, where many people  have literally  "taken to the water," living in
small boats and maintaining fishing nets  in their own plots of bay instead of
land.  Current wetlands, he suggests,  may convert to these shallow bays,  with
people converting to a more water-based economy.

     Leatherman  (Volume  4)  examines  the  implications  of  sea level  rise for
South  America.   He  notes  that  such popular resorts  as  Copacabana  Beach,
Brazil; Punta  del  Este, Uruguay; and Mar  del Plata,  Argentina,  are already
suffering  serious   erosion.     He concludes   that because  of  the  economic
importance  of  resorts,  governments  will  allocate  the  necessary "funds  to
maintain  their  viability.   However, he  predicts  that  "coastal  wetlands  will
receive benign neglect" and be lost.

     Park et al. (Volume 4)  focus on the expected drowning of coastal wetlands
in the United  States.   Using a computer  model of over 50 sites, they project
that 40-75  percent of existing  U.S.  coastal wetlands could be  lost by 2100.
Although  these  losses  could  be reduced to  20-55  percent if new wetlands  form
inland  as  sea level  rises,   the necessary  wetland  creation  would  require
existing  developed  areas  to  be  vacated  as  sea  level  rises,  even  though
property  owners would  frequently prefer to  construct bulkheads  to protect
their property.  Because coastal  wetlands are  important for many commerically
important seafood  species,  as  well as birds and  furbearing animals,  Park et
al. conclude that  even a one-meter rise  in sea level would have major impacts
on the coastal environment.

     DeSylva  (Volume 4)  also  examines the environmental  implications  of sea
level  rise, noting  that in  addition  to wetlands  being flooded,  estuarine
salinity would increase.   Because 66 to 90 percent of U.S. fisheries depend on
estuaries, he writes that these impacts  could  be important.   He also suggests
that coral  reefs could become  vulnerable  because of  sea level rise, increased
temperatures, and the decrease in the pH  (increased acidity) of the ocean.

     Kuo  (Volume 4)  examines  the implications of  sea level  rise for flooding
in  Taipei,   Taiwan,  and  coastal  drainage  in  general.    Although  Taipei  is
upstream from the sea, Kuo concludes that projected sea level rise would cause
serious problems,  especially  because Taiwan  is also sinking.   He recommends
that engineers around the world take "future sea level rise  into consideration
... to avoid designing a system that may become prematurely obsolete."


                                       14

-------
     Gibbs (Volume 4)  estimates  that sea level rise  could  result in economic
damages in Charleston,  South  Carolina,  equal to as much  as 25  percent of the
annual product of the community.   Anticipatory measures, however, could reduce
these impacts by half.  Gibbs finds that in some areas actions should be taken
today, in spite of the current uncertainty regarding future rates of sea level
rise, while for other  areas it would be more prudent to wait until uncertain-
ties are resolved.

     Ken Smith, a realtor from coastal  New Jersey,  reacts to the other papers
presented in  Volume  4.  He argues that  the  issue of  sea  level  rise should be
taken seriously today,  but  laments the  fact  that many of his fellow realtors
make comments such as  "What do you care?  You won't be around to see it!" and
the  scientific  community  is  "a bunch of eggheads who don't want us (to build
on  the  coast) anyway." Smith  suggests  that part of  the  resistance to taking
the  issue  seriously  is  that  there  are  a number of  "naturalists"  who oppose
building near the shore, and  "most  of  the discussion  seems  to  come from the
'naturalist1  camp."   Nevertheless,  Smith argues that "the solutions—if there
are  any—should be  contemplated now as part  of  a  concerted  global effort.
This is a beautiful world, and we are its stewards."

Human Health  and Ecological Impacts

     Climate  and  weather have  important  impacts on  human health.   A global
warming would increase the stresses due to  heat,  decrease those due to cold,
and  possibly  enable  some  disease that require warm year-round temperatures to
survive  at   higher   latitudes.    Kalkstein  et  al.   (Volume   3)   present  a
preliminary  statistical assessment of  the  relationship of mortality rates to
fluctuations  in temperature in New  York City.   They  find  that  a two to  four
degree  (C)  warming would substantially increase mortality  rates  in New  York
City,  if nothing  else changed.   However, they caution  that  if New  Yorkers are
able to acclimatize  to  temperatures as well as people who currently live in
U.S.  cities  to the  south,  fewer deaths would occur.   Kalkstein et al. write
that knowledgeable  observers  disagree   about  whether  and  how  rapidly people
adapt  to higher temperatures; some people  undoubtedly adjust  more readily  than
others.

      Although people may  be able  to  adapt  to changes  in climate,  other species
on  the planet would also be  affected and may not be as able to  control  their
habitats.   Peters and Darling (Volume 3) examine the  possibility that changes
in  climate would place multiple stresses on  some  species which would become
extinct,  resulting  in  a  significant decline in biodiversity.    (Mass extinc-
tions appear to have accompanied  rapid  changes  in temperatures  in the past.)

      Throughout the world reserves have been set aside where targeted species
can remain relatively free of human intrusion.  Peters and Darling ask:   Will
these reserves continue to  serve the same function  if the climate changes?  In
some cases,  it will depend  on whether the reserve's boundaries  encompass  areas
 to   which  plants and animals could migrate.   Some  species may  be able  to
migrate "up the mountain" to find cooler  temperatures; coastal  wetlands  could
migrate  inland.    A  northerly   migration  of  terrestrial  species  would  be
 possible in  the undeveloped  arctic  regions of Alaska, Canada,  and the Soviet
Union; but human development  would  block migration of larger animals in  many
 areas.
                                       15

-------
POLICY RESPONSES

     Papers by  UNEP  Deputy Director Genady Golubev  and EPA Administrator Lee
Thomas (both in Volume  1)  provide official views on the nature of the effects
from projected changes in the atmosphere and the role of their institutions in
addressing  those  changes.    Golubev notes  that  while  "the  global  issues are
complex, uncertainty  exceeds understanding, and patience  is prudence," there
is an other side  to the story:   "Our legacy to the  future is an environment
less benign than that inherited from our forbearers.  The risks are sufficient
to generate a  collective  concern  that  forebodes  too  much  to  wait  out the
quantifications of scientific  research.   Advocating patience is an invitation
to be a spectator to our own destruction."

     Golubev also points out that UNEP has worked  for  the achievement of the
Vienna Convention for the Protection of the Ozone Layer, in which many nations
have agreed to act in concert  to address an environmental issue whose impacts
have not yet been  detected.   Yet he  notes  that  the agreement is for coopera-
tion in research and does not yet bind nations to observe limits in production
and emissions of gases that could deplete stratospheric ozone.

     Thomas points  out  that both  the  potential depletion  of ozone  and the
global  warming from the  greenhouse  effect  are  examples  of  environmental
problems that involve the "global commons."  Because all nations contribute to
the problem and experience the consequences, only  an international agreement
is likely  to  be effective.  He urges scientists around the world  to discuss
this issue with their colleagues and key officials.

     Richard Benedick,  Deputy   Assistant Secretary  in  the  U.S.  Department of
State (Volume  1), describes  the emerging international  process addressing the
ozone issue.   Although  the process for  addressing  climate change has not yet
proceeded  as  far,  he writes,  "from my  perspective as  a  career  diplomat, it
appears that  the  greenhouse effect has all the  markings of  becoming  a high
visibility foreign policy  issue.  .  .  .  How we  address this issue internation-
ally depends to a  great extent on our success or failure  in dealing with the
ozone depletion issue."

     J.P.   Bruce  (Volume  1)  of  Environment  Canada presents the  issue  of
atmospheric change in the context of air pollution in general.  He writes that
ozone modification and climate  change are  "urgent  issues," especially because
important  long-term  decisions   are  being made today  whose outcomes  could be
strongly affected by changes in climate and the ozone layer.  Bruce recommends
that emissions  of  CFCs  be  reduced, and  concludes that  "a  new approach, a new
ethic towards  discharging  wastes and chemical  materials into the  air we all
breathe must soon be adopted on a international scale."

     Two U.S.  Senators  also  provide their reactions.   John Chafee  from Rhode
Island  (Volume 1)  describes hearings that his Subcommittee  on  Environmental
Pollution  held June  10-11,  1986.   "Why are  policy makers  demanding action
before the  scientists have resolved all of the  questions  and uncertainties?"
he asks.    "We are doing  so because there is a  very  real  possibility that
society—through ignorance or  indifference,  or  both—is irreversibly altering
the ability of our atmosphere  to  perform basic  life support functions for the
planet."  Albert Gore, Jr.  from Tennessee, who has chaired three congressional
hearings on the greenhouse effect, explains why he has introduced  a  bill in


                                      16

-------
the U.S. Senate  to  establish an International Year  of the Greenhouse Effect.
"The  legislations would  coordinate  and  promote  domestic and  international
research efforts  on  both the scientific  and policy aspects  of  this problem,
identify strategies to reduce the  increase  of carbon dioxide  and trace gases,
investigate  ways  to  minimize   the   impact  of  the  greenhouse  effect,  and
establish long-term  research plans." Senator Gore closes  by  quoting Sherwood
Rowland (discussed below): "What's the use  of having developed a science well
enough to make  predictions,  if  in  the end  all  we're  willing to  do is stand
around and  wait for  them to come  true?"   Both Senators call  for immediate
action to reduce global use of CFCs.

     John S. Hoffman  (Volume 1)  emphasizes  the  inertia  of the atmosphere and
oceans.   Because  there  are time  lags  between changes  in   emission  rates,
atmospheric  concentrations,   and   changes   in   ozone  and   global  warming
temperatures, the types of management  strategies must  be different from those
that  are appropriate  for controlling,  for  example,  particulate  pollution,
where  the problem goes away as  soon as  emissions are halted.   CFC emissions
would  have  to  be   cut  80 percent simply  to   keep  concentrations  from
increasing.    Although constant  concentrations would  prevent  ozone depletion
from worsening, Hoffman points out that even if  we hold the concentrations of
greenhouse  gases  constant once  the  earth  has  warmed  one degree,  the  planet
would warm another degree as the oceans come into  equilibrium.  Thus it might
be  impossible  to  prevent a substantial  warming  if  we  wait until a small
warming has taken place.*

     The final section  of this  volume presents  the  papers from  the final day
of the  conference.   Peter Usher of  UNEP  recounts the evolution  of the ozone
issue.   Following Rowland  and  Molina's  hypothesis that  chlorofluorocarbons
could cause a depletion of stratospheric ozone in 1974, UNEP held a conference
in 1977  that  led to a world plan  of action to  assess the issue  and quantify
risks.  Since that time,  UNEP has  held numerous  coordinating  meetings leading
up the the  Vienna Convention.  However, Usher suggests that motivating inter-
national effort on the greenhouse effect will be more difficult:   "Prohibition
of  nonessential  emissions   of   relatively  small  amounts  (to control  ozone
depletion)  is one  thing,  limiting  emissions of  carbon dioxide from coal- and
oil-burning is quite another."

     Dudek  and  Oppenheimer  of the  Environmental Defense  Fund (U.S.)  analyze
some  of the  costs  and  benefits  of  controlling  emissions   of  CFCs.    They
estimate that by holding emissions constant, 1.65 million cases of nonmelanoma
skin cancers could be prevented worldwide, and that the cost of these controls
would be 196 to 455 million dollars,  depending on the availability of alterna-
tive chemicals.

     Two  former  high-ranking  environmental  officials  in  the United  States
argue  that  we should be  doing more  to address  these  problems.   John Topping
recommends that CFCs in aerosol spray cans,  egg cartons,  fast-food containers,
and  other  nonessential uses be phased  out,  and  that  people recognize that
3 Titus  (Volume  1) and  Thomas (Volume 4)  also explore  inertia,  noting that
  even  if temperatures  remained  constant  after  warming somewhat,  sea level
  would rise at an  accelerated rate  as the oceans, mountain glaciers, and ice
  sheets came into equilibrium with the new temperature.
                                      17

-------
along with  energy  conservation,  nuclear power  is  the most likely alternative
to  fossil  fuels over  the next  generation  or  two.   He  also  recommends that
society  take  steps to  minimize  the  impacts  of climate change  and  sea level
rise, for  example, by  requiring environmental impact  statements  to consider
the likely impacts.

     Gus  Speth,  president  of  the  World  Resources  Institute,  recommends
international  efforts  to  stop tropical deforestation;  a production  cap for
chlorofluorocarbons; increased energy conservation;  advanced technologies for
producing  electricity   from  natural  gas;   and tighter  regulations  to limit
carbon monoxide  from automobiles,  which would indirectly limit increases in
atmospheric  methane.     He  agrees  with Topping  that  environmental  impact
statements  for projects  that  could contribute to or be  affected  by climate
change or ozone modification should consider these impacts.

     Doniger  and  Wirth,  from  the  Natural  Resources Defense  Council (U.S.),
argue that the  current  uncertainties  are  no longer  a  reason to  wait  for
additional information: "With  the  stakes so high,  uncertainty  is an even more
powerful argument for taking early action."  These authors conclude that sharp
reductions  in CFCs are  necessary, pointing  out  that even  with a production
cap,  atmospheric  concentrations  of  these  gases  will  continue  to  grow.
Therefore,  Doniger and Wirth propose  an  80  percent cut in production over the
next  five  years  for  CFCs  11  and  12,  the  halons,  and  perhaps some  other
compounds,  with a complete phaseout in the next decade.

     Richard  Barnett  of  the  Alliance  for  a  Responsible  CFC  Policy  (which
represents CFC  using  industries)  agrees that we   should not delay  all action
until the  effects of  ozone depletion  and  climate  change  are  felt;  but  he
"would hardly characterize the activities over the last twelve years as 'wait
and see1 .  .  .  The  science,  as  we currently understand it,  however, tells us
that there  is additional time in  which to  solidify  international  consensus.
This must be  done  through discussion and negotiation,  not through unilateral
regulation."

     Barnett  adds  that  industry  should "take  precautionary  measures  while
research and   negotiations  continue  at the  international  level.    We  will
continue  to  examine  and   adopt   such  prudent   precautionary  measures  as
recapturing,  recycling,   and  recovery  techniques  to  control  CFC  emissions;
transition  to  existing   alternative  CFCs  that  are  considered to  be  more
environmentally  acceptable;   practices   to  replace  existing  systems at  the
expiration of their  useful lives  to  equipment using other  CFC  formulations;
practices in  the field to prevent  emissions  where possible; encouragement of
CFC users to look for processes or substances that are as efficient, safe, and
productive—or better—than what is presently available."

     Barnett  concludes  that  "these environmental concerns  are serious,  but
their successful  resolution  will  require  greater global  cooperation  in con-
ducting  the necessary  research and monitoring, and in developing coordinated,
effective,  and equitable policy decisions for all nations."

     We  hope that this paper has provided the reader with a "road map" through
the papers of this four-volume report on the potential effects  of changing the
atmosphere.   But  we have  barely scratched the surface  of each, Just  as  the
existing  research  has  barely  scratched  the  surface  in  discovering  and


                                      18

-------
demonstrating the possible risks of ozone modification and  climate change.   A
continual evolution of our  understanding will be necessary for  our knowledge
to stay ahead of the global experiment that society is conducting.

REFERENCES

Hansen, J.E., A. Lacis,  D. Rind, and G. Russell. 1984.  Climate sensitivity to
  increasing greenhouse  gases.   In Greenhouse  effect and sea level  rise:   A
  challenge  for  this  generation, eds. M.C.  Earth and J.G. Titus.   New York:
  Van Nostrand Reinhold.

Keeling,  C.D.,  R.B.  Bacastow,  and  T.P.  Whorf.    1982.   Measurements  of the
  concentration of carbon dioxide at Mauna Loa,  Hawaii.   Carbon Dioxide Review
  1982.  377-382,  ed.  by  W. Clark.    New  York:    Oxford University  Press,
  Unpublished data from NOAA after 1981.

NAS.  1983.  Changing Climate.  Washington, D.C.:  National Academy Press.

Nordhaus,  W.D.,  and G.W. Yohe.   1983.  Future  carbon  dioxide emissions from
  fossil  fuels.   In  Changing Climate.   Washington, D.C.:   National Academy
  Press.

Villach.   1985.  International assessment of the role of carbon dioxide and of
  other  greenhouse  gases   in  climate  variations  and  associated  impacts.
  Conference Statement.  Geneva:  United Nations Environment Program.
                                       19

-------
HUMAN HEALTH

-------
UVR  Dose-Dependent Life Shortening in  Mice
RE. Davies and P.O. Forbes
Temple University Health Services Center
Philadelphia, Pennsylvania USA
     The type of ultraviolet  referred to as "UV-B" has properties  and effects
of considerable significance.  It  is absorbed  strongly by  proteins,  nucleic
acids, and other  biological  molecules,  and also  by  ozone and  other  environ-
mental materials.   Absorption by atmospheric ozone largely determines  how much
of the  sun's UV-B emission reaches the earth's  surface.    The  fraction that
does  reach  the surface is strongly absorbed by  exposed tissue and  delivers
sufficient energy  (about  4  eV per  photon)  to  produce  direct or  indirect
chemical reactions,  some of which are deleterious.

     Because of this strong absorption,  most of  the direct effects  of  UV-B  are
limited to superficial tissues a  few tens of microns  thick:  in animals this
usually means the cutis or skin, and  specialized  external tissues  such as  the
eye.  Many animals  have superficial nonliving products such as scales,  hair,
or feathers  that  absorb  most or  all of the UV-B.   In others, such as  our
species, constitutive absorbers, such as stratum corneum and  melanin,  can be
enhanced in  response to damage, reducing the effects of subsequent exposure.
Most biological consequences  of U.V-B, both damage and secondary responses,  are
not  only superficial, but are limited  to   areas not protected  by  natural
absorbers  or  artificial  coverings  such as  clothing.   Characteristic UV-B
induced effects in humans, including acute (sunburn), subacute (pigmentation)
and  chronic  (skin  cancer,  "aging"),  almost  invariably appear  in  the most
exposed areas such as face and hands.

     Not all effects of UV-B are  so highly localized,  and  a few appear to be
beneficial.    Exposure  to UV-B can  prevent  the bone disease rickets:  the
mechanism  involves  production,  in the  exposed  skin, of a  form of vitamin D
from  an  inactive  precursor,  followed   by  redistribution  of  this  essential
vitamin to the rest of the body.   There are also reports, less easily  measured
or  explained,  of  beneficial  physiologic  (work capacity) and  psychologic
effects of sunlight, at least some of which appear to be related to UV-B.
                                     23

-------
     Another category of  systemic  effects was recognized with the observation
that specific immune responses could be inhibited by UV-B.  One such response,
the ability  to  reject  certain transplanted  tumors,  was  reduced or eliminated
on  a  system-wide, apparently  permanent basis by  localized  UV-B irradiation.
In  another response, the  development of contact hypersensitivity, suppression
by  UV-B  is  transient and  the  degree of  systemic  involvement  is less clearly
established.

     We recently  described an  effect apparently attributable  to UV-B that is
unarguably systemic.   Mice  that had  been exposed  chronically  to  "sun-like"
radiation exhibited  an increase in  mortality that  was proportional  to  the
quantity of radiation delivered.  Since the effect was observed in experiments
designed to  study UV-B induced  skin cancer, many of the mice had  cancers at
the time of  their death.   However,  the severity  of the carcinogenic response
was not  sufficient  to account  for  the  difference  in  survival,  especially
considering  that  such   tumors  are   relatively   slow   growing  and  rarely
metastasize.   The amount  of  UV-B delivered was less, in most cases, than that
required to  produce  any obvious acute or chronic  damage, although some skin
thickening undoubtedly occurred.

     Survival curves  in  healthy, genetically  uniform laboratory mice usually
exhibit two  distinct phases.  Initially  deaths are random  and usually infre-
quent,  resulting in  a  slow,  roughly linear  decline   that  is  unrelated  to
specific treatment conditions.   These deaths  usually result  from injuries or
other types of errors.   Subsequently, survival declines rapidly; in a particu-
lar strain,  under uniform conditions, the time of this terminal phase is quite
reproducible.

     In  the  strain  of mice  with   which we  have  the  most  experience,  the
approximate  median  age at death  is about  90 weeks.   Daily exposure  to an
amount  of  radiation  corresponding  to  about two  minutes   at midday  summer
sunshine produces a detectable reduction  in this value, and  doubling the daily
dose reduced median  survival to about  50 weeks.   Higher doses,  some of which
produced chronic  irritation, produced further but  less  dramatic decreases in
life span.   In  all  cases  it is  the  second,  precipitous  stage of the survival
curves that  is  affected.   Comparison  of light sources  delivering different
qualities  of  radiation   indicates   that most   or  all of  the  effect  is
attributable to the UV-B portion of  the spectrum.

     To our  knowledge, no studies  have been  designed specifically  to examine
the effects  of  chronic UV irradiation  on the survival  of mammals.   Available
data  come  from  experiments  designed  to  study photocarcinogenesis,  and most
have been conducted  with mice.   Where mortality  data  are  published, similar
effects on  survival can  be seen  in  other  mice,  both  haired  and hairless.
Specific studies  with  Drosdphila also  show  dose-dependent life shortening in
response to UV-B  irradiation.  Thus  the data, though not extensive, appear to
be  consistent, and suggest that UV-B  can produce  cumulative systemic changes
that reduce the potential life span  in some species.

     It is not  clear whether this phenomenon  has  ecologic  significance.  The
effect in laboratory mice is to accelerate  apparently  spontaneous  death with
no  obvious effect on intermediate  health.  Animal survival  in nature is often
limited by  specific processes such  as  disease or predation, and  this more
closely resembles  the  first phase of the survival  curve.   Clearly, however,


                                      24

-------
accelerated death must result from significant systemic damage.   Whether  such
damage could modify  health  or life span of other species,  including  ours,  is
open to speculation.
                                      25

-------
An Estimation of Sunspot Induced Ozone
Changes  From a Sunburn Ultraviolet Meter
Daniel S. Berger
Temple University
Philadelphia, Pennsylvania USA
     A  sunburn  ultraviolet  meter  recording  continuously  since  1973  has
provided data for determining  ozone  variation over an  11-year sunspot cycle
(Berger and Urback 1982).  This meter is part of a network of similar meters
whose  purpose is  to determine the  normal  levels of  biologically effective
short  ultraviolet radiation  reaching  the biosphere and of long-term trends.
These  purposes have  been  the stated goals of all agencies, both domestic and
international,  charged  with  the  responsibility for studying  the ozone layer
and protecting it  insofar as  anthropogenic activities have an  effect.

     A ground-based  monitor  of short  UV  provides  data  important not only in
itself but from which both ozone variations  and cloud absorption  can be, deter-
mined.  The wavelengths shorter than  330 nm detected  by this meter (Figure 1
and  Berger  1976)  cause sunburn  and  after  protracted  exposure, non-melanoma
skin  cancers.  They have also  been  shown to  have  myriad effects in the bio-
sphere, primarily because they affect DNA, the basic control of all living
organisms.  The  results of the network have therefore been used  in the epide-
miological study  of  non-melanoma skin cancer  (Scotto  et  al.  1976).   Meter
results have also  been  used to  study cloud absorption (Slomka  1976).

     For  the  study presented here,  monthly averages of sunburn dose for the
 11-year period were derived from the semihourly meter printout.   The deviation
of each month from the  mean of  that month was  plotted over the 11-year period;
the  sunspots for that month were plotted  on the  same abscissae.  Smoothing of
the  data  with a  12-month running  average produced the top curve of Figure 2,
which  shows  a clear correlation.   The results are  the  sunburn ultraviolet
variations over  an  11-year  period.   From these  variations, an estimate of
ozone  thickness  variation due  to  sunspot activity is  derived.   The top curve
 in  Figure  2  consists  of  two parts,  the quasi-biennial  fluctuations,  an
approximate  26-month oscillation and the  11-year cyclic variation  due to
sunspot activity.  Separation of the  top curve into its  two component parts is
 shown  on  the lower curves of the figure.
                                    27

-------
                          SUN6URNING  ULTRAVIOLET  METER

                          LOG
                           8
                           6
                           4

                           2


                          QIC
                       OT   6

                       t   4

                       m
                       K
                         0.001
                           8

                           4
Human skin action
spectrum (B«i fit)
                                          xM«ltr normalized
                                           to stun at 300nm
                               273  300  323 »0 375

                                WAVELENGTH,  NM


Figure  1.   Erythema  action spectrum and sunburn  ultraviolet meter
             spectral  response.
                            SUNBURN UV DEVIATIONS FROM AN 11-YEAR MEAN
                                  QUASI/BIENNIAL FLUCTUATIONS
                                  TOTAL SUNBURN UV MINUS QUASI/BIENNIAL FLUCTUATIONS
                                                       1M1
                                                              1M2
                                                                      1983
                                                                             1M4
                                  Figure  2.
                                      28

-------
     The quasi-biennial  fluctuation  is a result  of a variable rate  at which
ozone moves  from the tropics into the  temperate  zone,  in this case  to 40° N
latitude.   No net change  in  stratospheric  ozone occurs.  Consequently,  in a
quasi-biennial period, the time integral should be zero.   Deviations from zero
are attributable to net changes of total ozone due to sunspot activity.

     Comparison of the 11-year cyclic variation of sunburn ultraviolet shows a
close correspondence to sunspot number, as shown in Figure 3.

     There  is also a  relationship  between  the change of sunburn UV  and the
change  in  stratospheric ozone.   If  the meter had  an  exact  erythema action
spectrum, there  would  be about 1.1% change in meter  reading per  ^% change in
ozone at 3 mm of ozone thickness.  (See Figure 4.)  Because the meter spectral
response is  long wave shifted, the meter change  is more  like 1.2J  at 3 mm of
ozone.   Since there was an  8% maximum  change  in sunburn effect due to sun-
spots,  the  ozone  change was  about  6.5%.  This  change  was due  to  160 sun-
spots.  Thus, 25 sunspots caused a '\% ozone change.

     The constancy of extra-terrestrial  radiation  between  295 and 330 nm is
assumed  as   is   the  complete  decoupling of  cloud  variability  from  sunspot
activity.    The  first  assumption  must be  justified   by  extra-terrestrial
spectro-radiometric observations.   The extent to  which  the  second  assumption
is  true  could  be determined  by  a  careful analysis  of  the  meter  record
itself.   Any cloud-sunspot coupling  could  be used  to compensate  the derived
ozone variation.

     It may appear naive to be making a calculation of the effect of a sunspot
on ozone  thickness based on so  thin  a reed as a non-thermostatted monitoring
meter,  but  the  unexpected  and gratifying  11-year record that is  shown here
would have  been  considered naive to  anticipate up until the  time these calcu-
lations were  completed.

     The  information-rich  output, the almost perfect data  captured,  the long
term  stability,  the low cost, and the  ability  of technicians without special
training  to provide  the minimal maintenance  required  argue  that  there is a
place  for  this device for long  term monitoring of the ozone layer or of  the
ultraviolet  levels in  the biosphere required by environmental agencies.
                                       29

-------
  +4-

Ul
O +3-
c
u.
s  °-
1 -1-
Z -2-
ui
« -a
£  a
  -4-
                                                   TOTAL SUNBURN OF UV MINUS
                                                   QUASI-BIENNIAL FLUCTUATIONS
                                 -180

                                 -160

                                 -140

                                 -120

                                 -1OO

                                 - SO

                                 -60

                                 -40

                                 -20

                                 -0
                                                                                        (0
       1974     1975     1978    1977    1978
                                          4 7 10 1
                                          1979
4  7 10
1980
                                                         1981    1982     1983     1984
                                      Figure  3.
                           2.5
                           2.O
                           1.5
                           1.0
                           0.5
                                 .200      .300     .400cm OZONE
                                      OVERHEAD SUN

  Figure 4.   Rate of Change  of Sunburning Capability of  Sunlight with
               Ozone Variation
                                          30

-------
REFERENCES

Berger, D., and  F.  Urback.   1982. A climatology.of  sunburning  UV radiation -
     Photochem. and Photobiol.  35:187-192.

Berger,  D.   1976.   The  sunburning   ultraviolet  meter.    Photochem.   and
     Photobiol.  24:587-593.

Scotto, J. et  al.   1976.   Measurement  of UVR in the US  and  comparisons with
     skin cancer data.  National Cancer Institute  DHEW (NIH)  76-1029.

Slomka, K. 1976. Preliminary Analysis of  the Effect  of Solar  Zenith Distance,
     Total Ozone Content, Atmospheric Turbidity and Cloudiness on the Solar -UiJL
     Radiation Measured  with  a Robertson-Berger Meter.   Publication  of the
     Institute of Geophysics, Polish Academy of Sciences 106:121-131.
                                       31

-------
Nonmelanoma Skin  Cancer—UV-B Effects

Joseph Scotto
National Cancer Institute
National Institutes of Health
Bethesda, Maryland USA
     Since the early  1970s, the National Cancer Institute, in collaboration
with other federal and nonfederal sources, has conducted special epidemiologic
surveys of nomelanoma skin cancer and monitored ground level UV-B measurements
at various geographic locations within the United States.

     These studies  responded  to  the  need  for basic  data  to  be  used  in
measuring  the  extent  of certain  human  health  effects  that  may  result from
stratospheric ozone depletion.

     We  focus  on solar  ultraviolet radiation  in  the  range  of 280  to 320
nanometers,  called  mid-UV  or UV-B  (see  Figure  1).    Under  experimental
conditions, UV-B  has  been shown to produce skin erythema  (sunburn)  in man and
skin  cancer  in animals, and  it  is  effective  in altering DNA.    Cumulative
exposure to UV-B  is  also believed to be partially responsible for the "aging"
process  of the skin  in humans.   Except for  preventing vitamin D  deficiency
rickets, which is now confined to populations with  inadequate nutrition, UV-B
is basically considered  biologically harmful.

     While no solar radiation below 295 nm ever  reaches the earth's  surface, a
small  quantity Of UV-B  does.    Stratospheric ozone  depletion  may  result in
increases of UV-B energy reaching the earth and  its populations.  The  physical
amplification factor has  been  put at  2.    This means  that a 1j6 decrease in
ozone may result  in a 2% increase in solar ultraviolet, UV-B.

     Basal  cell  carcinomas  and squamous cell  carcinomas  of the  skin, the
nonmelanomas, are the most common  malignant  neoplasms occurring in the  white
populations of the world.  Currently, annual  incidence in the  United States is
estimated  at about one-half million patients, and the rates are  increasing at
about 3% per year. Epidemiologic study has  been limited by the  fact that most
patients are customarily seen and treated  in the offices of physicians and not
hospitalized.  Cure rates are  high (about 99%) and only a small percentage of
skin  cancers are  metastatic or result  in death.
                                     33

-------
                          THE ELECTROMAGNETIC SPECTRUM
 X-rays and gamma rays
  Extreme
   xuv
	 Ultraviolet
 Far   i   Middle
 ruv   T^ MUV
                                                                  Infrared and radio
       100
              200
                      300
                    400      500     600

                       Wavelength in Nanometers
                                                     700
                                                             800
                                                                    900
                                                                            1,000
                                    Figure 1

     Because  the primary  source of  data cancer  registries is  the inpatient
hospital  file,  the  statistics routinely  collected on skin  cancer  are usually
very  incomplete  and  not  comparable  with  other  forms of cancer.    Thus,
population-based estimates of skin  cancer incidence require  special surveys to
collect data from offices and outpatient  files.

     Figure  2 shows  the geographic  locations  within  the  continental United
States where  skin cancer surveys were conducted and  ground  level measurements
of  UV-B  were obtained.    In  1971-72,  there were  four areas  in the  Third
National  Cancer  Survey;  in 1977-78,  eight areas of  NCI  Surveillance  Epidemi-
ology and End Results Program (SEER)  were surveyed.

     Two  locations,  Minneapolis-St.   Paul,   Minnesota,   and  San  Francisco-
Oakland, California, were resurveyed  in the  late 1970s.   Skin cancer incidence
data  from  New  Hampshire,  Vermont,  and San  Diego,  California,  were  most
recently  included.  We do not have statistical  details for  other cancers from
these locations, and we  are just now  receiving UV-B readings from Concord, New
Hampshire, and Burlington,  Vermont.  Patient and  general population interview
studies were  conducted  in  nine locations.   These locations span  the United
States from Seattle in the  north (47.5°N) to New  Orleans (30°N).  Most of the
figures  that  follow  display  the  epidemiologic  details for  the  eight-area
survey conducted in 1977-78.  Seven of these are  SEER  locations where NCI has
continuing surveys of all other malignancies.  The results are similar for all
surveys.

     Skin  cancer is  a  disease  that  rarely  occurs  in   black  and  pigmented
races.  The age-adjusted rate of  242 per 100,000  for  whites is more  than 60
times that  for blacks with a rate of under 4 per 100,000.    Among Caucasians
"Anglos" or non-Hispanics, are at greater risk than Hispanics by about 7-10 to
1.

     Figure 3  shows the incidence of  nonmelanoma skin  cancer and all  other
cancers combined among whites for each of eight  locations plotted according to
latitude.    For all other malignancy,  there is  no latitudinal gradient.   In
contrast,  nonmelanoma skin cancer  incidence  rates  were  definitely lower at the
higher latitudes.

-------
                                    OALLAS-FT. WORTH

                                  FT. WORTH
  LEGEND


] TNCS (NONMELANOMA) LOCATIONS


1 TNCS IMELANOMAI LOCATIONS
  SEER LOCATIONS


  TNCS AND SEER
                     Figure  2.  Skin Cancer Measurement
                                 Locations  in the United States
                                        35

-------
D
 •

 I
                               RATE PER 100.000 POPULATION
         8
           8
>
o
   m
   O

   I
   Cfl
   X
   2
5  2

3  5
     o
            New Orleans
Atlanta

Albuquerque (New Mexico)
            San Francisco-Oakland



            Salt Lake City (Utah)




            Detroit   •

            Mfnneapol!a~$t. Paul





            Seattle
      Figure  3.   Age Adjusted Incidence of Cancer (U.S.  1970)
                   Among  Whites by  Latitude
                                      36

-------
     The age-adjusted incidence rates by geographic  location  for each sex are
shown in  Figure 4.   The rates  for males are  always greater than  those for
females.   Overall,  the  male/female ratio is  close  to 2  to  1  (1.83).   Note
there are two sets of bars  for New Mexico.   Because of the high proportion of
highly pigmented Hispanics  in that State, over one-third, the  rates for all
Caucasians are lower than that for Anglos only.

     Figures 5 and  6  show age-specific rates according to region.   The rates
increased with age—the highest rates were seen in the oldest age groups.  The
southern region was clearly at higher risk than the northern region.

     Figures 7 and  8  show age-specific rates by  specific  location, comparing
males and females.   At each location the male rates were lower or equal to the
female rates at early ages.  After age 45,  in the  northern  and middle loca-
tions, male rates consistently exceeded those  of  females,  and the differences
were greatest in the oldest age  groups  (Figure 7).  In the southern locations
(Figure 8), the separation between male and female rates began a decade or two
earlier, presumably because the UV threshold levels  for  skin  cancer detection
were reached sooner.

     Tumors appear on the face, head, and neck in over BQ% of nonmelanoma skin
cancers.   Among  females, the nose  is the most  common site while, among males
tumors  of the nose,  cheek, and  scalp  are equally  high.   Tumors  of the ear
occur more frequently among men,  compared to women, by a factor of 10 or more,
especially  in  the  southern areas.   In  contrast,  tumors of the  legs are more
common  among  females  who have greater  UV exposure  and also  more melanoma of
the  lower leg.   In both sexes tumors  are much more common  in  the lower lip
than in the upper lip.

     Age-specific incidence rates according to anatomical  site are illustrated
in  Figure 9.    Rates  for face,  head and neck,  and upper  extremities progres-
sively  increased,   while those  for  trunk  and  lower  extremities  reached  a
plateau or declined at older ages.

     With respect  to histology,  Figure  10  shows  a  composite of specific
geographic  locations  depicting age-specific  incidence patterns for basal cell
carcinomas  and  squamous cell carcinomas  of  the skin.   Overall the  incidence
rates for BCC was  4 to 5 times higher  than SCC.   Increases have been observed
for  each cell type as  age increases.   The  rate of increase may be slightly
higher  for squamous cell carcinomas.   But the squamous cell carcinomas begin
at  later  ages.  The ratio of BCC  to SCC is greatest  in the northern  region and
lowest  in the southern region, ranging  from  over 12 to 1  in  the north to over
2 to 1  in the southern locations.
                                       37

-------
      I
RATE PER 100,000 POPULATION
       S
       D)
       *
      Seattle
  Minneapolis-
  St. Paul
      Detroit
  Utah (State)
Salt Lake City,
Utah
San Francisco-
Oakland
      Atlanta
  New Orleans
  New Mexico
  < State)

 Albuquergue.
 New Mexico
 Anglo
   All Survey
   Areas
           Figure  4.   Age Adjusted Rates of Nonmelanoma Skin  Cancer
                        in  Various Regions of the United States
                                            38

-------
 10OOCH
Ul
i
u

iu
Q
O

U
O
K
CO
111
  100O
100
    10
                                      jar'
                                                   Legend
                                                   • NORTHERN LOCATIONS

                                                   D SOUTHERN LOCATIONS
           25-34   35-44   45-54   55-04   65-74   75-84    85+

                               AGE
        Figure 5.   Age-Specific Nonmelanoma Skin Cancer
                    Incidence by Region Among White  Males
  100003
giooo
z
111
a
o

o
 a  100
 CO
 iu
     10
                                                    Legend
                                                       • NORTHERN LOCATIONS

                                                       D SOUTHERN LOCATIONS
           	1	1	—r—	1	1	•       —
            25-34    35-44   45-54   55-64   65-74   75-84    85+

                                AGE
        Figure  6.   Age-Specific Nonmelanoma Skin  Cancer
                    Incidence by Region Among White Females
                                 39

-------
                                              NORTHERN REGION (LATITUDES 40-50 DEGREES NORTH)
       1*400
           '- SEATTLE
                                         MALES
                                        FEMALES
             <1S 15-24 25-34 36-44 4M4 S6*4 SS 74 75-t*
                          AGE GROUP
                                                     10.000
                             : MINNEAPOLIS-ST. PAUL
                                                    i
                                                    UJ
                                                                                       MALES
                                                                                      FEMALES
                                  19-24  25-34 35-44 4544 55-64 85-74 7S-B4
                                           AGE GROUP
                                                                                                   10.000!
                                                                                                        .DETROIT
                                                                                                                                     MALES
                                                                                                                                    FEMALES
CIS 15-24 25-34 35-44 4544 554* ES-74 75*4
             AGE GROUP
*•
O
10,000
                           I
                           I
                                                 MID REGION (LATITUDES 35-40 DEGREES NORTH)
                                :SALTLAKECCTY
                                                               MALES
                                                             FEMALES
                                             36-44 46«4 B5<4 (S-74 7S44
                                                AGE GROUP
                                                 10.000
                                                                                  : SAN FRANCISCO-OAKLAND
                                                1
                                                e
                                                                                                                MALES
                                                                                                               FEMALES
                                                       <16  15-J4 1534 35-*4 *S64 S&44 6E 74 TS-M »S»
                                                                   AGE GROUP
                                     Figure  7.   Age-Specific Nonmelanoma  Skin  Cancer Incidence Among
                                                   Whites by  Regions of the  United States,  1977-78

-------
                               SOUTHERN REGION {LATITUDES 30-35 DEGREES NORTH)
: ATLANTA
2
I
8
 <15  1524 25-34 3S-44 4S4S4 H4M
             AGE GROUP
                                      8
                                      |
                                      4
                                          1 NEW ORLEANS
                                                                       MALES
                                                                      FEMALES
                                                                                  10.0
                                                 <15  1S-24 2S-M JB-44 4644 SM4 BS 74 75-«4 H+
                                                             AGE GROUP
I
     :ALBUQUERQUE
     lAngto
                                                                                                                  MALES
                                                                                                                FEMALES
                                                                                       
-------
   5000
    1000
z
o
a
O
a
o
o
5
cc
LU
o
UJ
O
5
100
      10
                                                                       FACE, HEAD
                                                                       OR NECK
       UPPER
       EXTREMITIES
                                                                       TRUNK
                                                                       LOWER
                                                                       EXTREMITIES
                                       I
                                                                  I
              <15     15-24    25-34    35-44    45-S4    55-64

                                          AGE GROUP
                                                        65-74
75-84
85 +
           Figure 9.   Trends in Annual Age-Specific,  Nonmelanoma
                       Skin  Cancer  Rates Among Whites, Both  Sexes

-------
                         NORTHERN REGION (LATITUDES 40-60 DEGREES NORTH)
SEATTLE
                                     MINNEAPOUS-ST. PAUL
                                                  t
                                                                          DETROIT
 <» 1U4 »J4 31-44 4U4 tfrW «M 7M4
          AGE GROUP
<15 1&24 »34 JM4 4E-M »H »74 7M4 «6«
           AGE GROUP
                            MID-REGION (LATITUDES 38-40 DEGREES NORTH)
                                                   10 000 e	-'•••—
                  UTAH
                                          BASAL
                                                        SAN FRANCISCO-OAKLAND
                   <» 1H4 7634 36-44 4»M »«4 16-74
                             AGE GROUP
                   <15 KM 2SM K44 4frM 66-H B)4 7M4
                              AGE GROUP
 ATLANTA
                         SOUTHERN REGION (LATITUDES 30-36 DEGREES NORTH)
                                i-
                                      NEW ORLEANS
       »J4 3*44 4»M JM4 O-74 r»M  »«
           AOf GROUP
                                                                          : NEW MEXICO
          3&44 46-M S644 »74 7»H 16•
            AGE GROUP
1524 7»34 3E-44 4154 55*1 KV14 r»M «»•
        AGE GROUP
          Figure 10.   Age-Specific Nonmelanoma  Skin  Cancer  Incidence  Among
                        Among Whites by Regions of the Unites States, Both Sexes

-------
     In  regard  to our  estimates of  ground  level UV-B  measurements,  we have
been monitoring  and  editing data  in collaboration  with researchers  at the
National Oceanic  and Atmospheric Administration and  their  network of weather
stations  (see Berger in  this  volume for  details  of  the  Robertson-Berger
meter).

     Figure  11   shows,  as   expected,  that  the  annual  amounts   of  sunburn-
producing UV-B correlated with latitude.  To put these numbers in perspective,
it  is  estimated  that a  count  of  440 R-B  units may  produce a perceptible
sunburn.   It  is possible   to  receive such  a dose  within  20  minutes  on  a
midsummer day around noontime.   It is important to  note that  these measure-
ments are affected by altitude, cloud cover or water vapor, and other meteoro-
logical  factors.  At altitudes of  over a mile high  Albuquerque  and Salt Lake
City received greater amounts  of solar UV-B  than  expected;  while Tallahassee
with relatively  high humidity received less  than the  expected dose  for that
latitude.   I should  like  to point  out  that current observations indicate  a
general  downward  trend  in  meter readings at  several  locations.   The relative
positions for Detroit and  Minneapolis have changed,  with current figures now
lower at Detroit.

     The monthly averages  of R-B  counts for Albuquerque,  New   Mexico,  and
Seattle, Washington,  respectively,  are shown  in  Figure  12.  These were  the
highest  and  lowest  exposure areas  included  in NCI's nonmelanoma  skin cancer
surveys.  The ratio of UV-B exposure is about 2 to 1  for these locations.

     Next my discussion focuses on our correlation studies of population-based
skin cancer incidence and estimated UV-B dose.

     The annual  UV-B levels and age-adjusted  incidence  rates for nonmelanoma
skin cancer  in white males and  females  were determined in the  two  special
surveys  conducted in  1971-72 and 1977-78 (see Figures  13 and 14).  The inci-
dence data are plotted on a log  scale so  that a straight line with a positive
slope  represents  a  constant percentage  increase  in  incidence.   Mathematical
models were  used to  describe dose-response  relationships and do  not  reflect
the mechanism  by which  UV  causes  skin  cancer.   Using an  exponential  model
previously applied to the  1971-72 data,  estimates of the biological  amplifi-
cation factor (that is, the relative  change  in skin  cancer incidence due to a
relative change in UV-B radiation) were derived.  Assuming a common slope, the
exponential model may be written as a logarithmic expression as  shown:
                      Ln RJJ = ai + b

                      where u = 1 ,  2 denotes the two survey areas

                      J = 1, 2 ...  10 denotes the locations

                      Rj* = the age-adjusted incidence rate

                      UVj = the annual UV-B count per 10,000

                               = constants
                                      44

-------
3.5
               Mauna Loa
[2  2.5

z
D
00
i


2   2
X
H



8

>  1.5

_i


z
z
                                         • ElPato
                             Tallahastat
                                                  i Albuqutrqut
                                             i Fort Worth
                                                      • Oakland



                                                      DM Moinc*


                                                  Philadelphia •
                                                             Bismarck


                                                         •   •

                                                         Minneapolis
 .5
                           I
                        I
                                                     I
I
   15
20
                             25         30          35         40


                                  DEGREES NORTH LATITUDE
          45
50
                   Figure  11.   Annual UV Count by Latitude

-------
         ESTIMATED MOKTHLY UVB VS. MONTH FDR TWO LOCATIONS
                                                                  Legend
                                                                 • AUUOUBKKJC. M*
                                                                 D SEATTU. WA  ^
JAN   FIB   MAR  APR   MAY  JUN   JUL   AUG  SEP   OCT  NOV  DEC
                             MONTH
   Figure  12.   Estimated Monthly  UV-B vs. Month for Two  Locations

-------
cc
2:
f

K
ui

-------
     800



     700




     600
       Model:  In R:: " «l j +



             (Assumes common slope)
K
     500
     400
     300
          • WHITE FEMALES- 1977-78


          O WHITE FEMALES- 1971-72
3

s

-------
     In the regression analyses,  the  logarithms  of the age-adjusted incidence
rates were weighted by the inverse of their estimated variance.  Assuming that
the annual UV-B  counts  were to increase by  \% at  each location,  the relative
effects on skin  cancer  incidence  were found to vary from a  low of 1.19% to a
high of 2.88^.  The estimates were lowest for females residing in areas of low
UV-B  exposure levels.   Overall,  the biological  amplification  factors were
estimated to be roughly twofold, but steeper for squamous cell carcinomas.

     An update of the incidence and UV-B correlations for males and females is
shown in Figure  15.   There are ten locations plotted,  which include only the
most recent surveys of  1977-80.   We have tentatively estimated the UV-B index
for NH/VT at  96  (x10,000 SU), and we use  average  annual counts for the years
1977 through  1981 for all  other locations.  In  general, the average UV values
are lower than those previously estimated for a one-year period.

     Biological  amplification  factors  (using  exponential  model)  show  no
substantial changes;  however,  the range  is  now between 1.03  and 2.5.   While
these  estimates  are  a  little  lower  than those  previously  calculated,  the
degree of  uncertainty has  been reduced and  the  estimates for the S5% lower
limits have  in fact  increased.   Figures  16 and  17  depict  these correlations
with  respect  to  cell type.  The  slopes  are steeper for SCC  compared to BCC.
Correlations according to anatomical site are shown in Figures  18 and 19.  The
relationship  of  skin incidence and ground level UV-B  exposure is consistent
for each  site group.   However,  there appear to be  stronger associations and
steeper slopes for the face, head, and neck, and upper extremities among white
males and females.  Keep in mind that over 87% of all nonmelanoma skin lesions
occur on these relatively more exposed anatomical sites.

     As many  researchers  have  suggested,  and as  the results  of our studies
show,  there  are  demographic factors  that  may reflect  increased  or decreased
skin  cancer  risk in  certain  population  groups similar  to  the differences we
have  noted  for  Anglos  and  Hispanics.    So,  in addition  to the incidence
surveys,  telephone  interview  sample surveys  of  skin  cancer  patients  and
general population  controls between  the ages of  20 to 75  were  conducted at
nine  locations.    Information was  sought on several  host  and  environmental
factors that  may affect  the risk  of skin cancer.  Examples -follow  showing the
correlation  of  skin  cancer incidence with UV-B  radiation  according  to the
presence or absence of certain constitutional factors.

-------
  1000-1
 .

g

o
o
o

o"

        o
   100-
3
•z.


\
              a
              I

              I
              I
II
            5 U Ld

            WZ Q
s
T
f


I
     ao
               100       t20        UO        180


                   SOLAR ULTRAVIOLET RADIATION (UV8) INDEX
                     180
I
tj
3


I
 Legend


• FEMALES


D MALES
                              200
               Figure  15.  Nonmelanoma Skin Cancer Incidence

                            According  to  UV-B  Index
                                   50

-------
   1000
2
o
o
o
o"
o
   100-
I
10-
     80
             5   i
            as ts
            in x o a
                                    S


                                    I

           100        120        rtO        WO

               SOLAR ULTRAVIOLET RADIATION (UVB) INDEX
I
                                                     180
                                                               Legend


                                                              •  BASAL CELL ONLY


                                                              D  AT LEAST ONE SQUAMOUS
                                                              _«
                                                               200
    Figure 16.  Nonmelanoma Skin Cancer Incidence by UV-B  Index

                 White Males According to Cell Type
                                    51

-------
   WOO-r
'£
 o
 o
 o
 o
 s
 Of.
    too-
 3

 I
    10-
     1-
    0.5
     80
                                 O
                                          D
               tOO        120        MO       1«0

                   SOLAR ULTRAVIOLET RADIATION (UVB) INDEX
                                                                Legend

                                                               •  BASAL CELL OMLY

                                                               D  AT LEAST ONE SQLUMOUS
200
       Figure 17.   Monmelanoma Skin Cancer  Incidence by UV-B
                     Index White Females According  to Cell Type
                                      52

-------
          1000-
       Q
       UJ
       CO
       i
       2
       CJ
       z
       z
       <
       d
Q.
2
o
8
8
UJ 100-
i
CO
            10-
                   IB
                   §E[i
                   MZ Of
                          ft


                          I
il
o
I
              80     100     120    140     160     180

                 SOLAR ULTRAVIOLET RADIATION (UVB) INDEX
3

200
   Figure 18a.
        Nonmelanoraa Skin Cancer Incidence  by  UV-B Index
        According to Anatomical Site Group Among White Males
        Face,  Head, or Neck
             100-

« -
111 O
o ;;
< UJ 10-
_J H ;
if :
i * •
•

•




f
I -
?i f| $
llll I






8 S •
i! I ! i

!i 5 I !
               80      100     120      140     160     180

                     SOLAR ULTRAVIOLET RADIATION (UVB) INDEX
                                                           200
Figure I8b.  Nonmelanoma Skin Cancer Incidence by UV-B  Index
             According  to Anatomical Site Group Among White Males Trunk
                                  53

-------
              10O
            DC.
             » 10-
23
<0 '
>2

ii
0 1


i
S— 1O4
S3
ii
00




s
I
120 140


S
Is

S5
160


w
I
SAN DIEGI
11


NS-tae
S
I
30


T
o
S
2C
  Figure  I8d.
        SOLAR ULTRAVIOLET RADIATION (UVB) INDEX

  Nonmelanoma  Skin Cancer Incidence by UV-B Index According to
  Anatomical Site Group Among White Males  Lower Extremities
                                    54

-------
      gs
      «£
      ^ 2
      a 9.
      ** —
      •? o
      Uj O
         f ioo:
      If
      II
          10
     ?! sf

     Mi
     =1 si
                                s
                                I
            80     100    120     140     160     180     200


               SOLAR ULTRAVIOLET RADIATION (UVB) INDEX
    Figure  19a.
    Nonmelanoma Skin Cancer Incidence by UV-B Index

    According  to Anatomical Site Group White Females

    Face, Head, or Neck
         100 -i
      So-

      fe2
      => o
      38

      *8"
      u o
      o ^
      1!
      a t
      > 2
      < c.
     s


     |  |




    PI
    
-------
       lOO-i
       0.5
         8O
Figure 19c.
   100     120     140     180

  SOLAR ULTRAVIOLET RADIATION (UVB) INDEX
                                                     200
Nonmelanoma Skin Cancer  Incidence by UV-B Index
According to Anatomical  Site Group Among White Females
Upper Extremities
       20-
       10
     o.
    "I
     £
    3
    -j
    Q
    <0
    lil O
    o £.
    < Ul
    si1
    II
       0.1
  I
                 -A
              81 5
              i« J
              ^|I
              §i si
        80      100     120     140      160     180

              SOLAR ULTRAVIOLET RADIATION (UVB) INDEX
                                                     200
Figure 19d.  Nonmelanoma Skin Cancer Incidence by UV-B Index
             According  to Anatomical Site Group Among
             White  Females Lower Extremities
                               56

-------
     In  Figures  20 and  21 we  see  familiar patterns.   Skin cancer  incidence
increases  as  UV-B  radiation  increases   for  white  males  with  and without
freckles.   We also note  that at each location the  risk is greater  for  those
with freckles.  The  estimated relative risk adjusting for age and  location  is
 '•8  and  1.7  for  men  and  women,   respectively,  compared  to  those without
freckles.

     The  correlation for  fair  skinned  complexion  is  illustrated  in Figure
22.  Again,  the UV-B  gradients are observed.  Overall relative  risk  estimates
were 2.6 for men and  1.6 for women,  respectively,  compared to those without
fair skinned complexions.

     Figure  23  shows the  patterns  for Celtics or those of Irish or Scottish
ancestry.   Estimates of  relative  risk  were the  same as  those observed for
individuals with freckles.

     Other high-risk groups  include individuals with blond or red hair color,
blue or green eye color, and  those who sunburn easily; individuals treated for
acne, moles, warts or psoriasis; individuals exposed to  radiation or  radiation
therapy, Coal  tar  or pitch,  and arsenic.   Individuals at  low  relative risk
include  those of Mexican  or  Spanish ancestry and  those who are never outdoors
°n their principal occupation and those who develop deep tans.

     With respect to the  consistent excesses in skin cancer risk observed for
men compared to women, we noted that the average amount of time spent outdoors
was greater for males by a factor of 1.5 to 2.

,    J am  reminded  of a  statement  made in  a  review article by our Chairman
(Emmett, CRC 1973).   It said:

                      ... in  the  USSR where  the  occupations.
                      of women nearly parallel those of men,
                      the incidence rates of skin  cancer are
                      the  same  for males  as  for  females
                      except  in  the elderly females  who may
                      retain more domestic occupations.   On
                      this basis,  it  may  be unlikely that
                      the  male   human  has  a   biological
                      predisposition to solar skin cancer.
     In conclusion,  I  would add  that  this disease represents a  major health
Tu i  economic  problem  in  the  United  States  and  other parts  of the world
dev i6 to  thirty percent  of  the Caucasians  in  this  country  may expect  t
   el°P skin cancer in their lifetime if current rates and trends persist.
to
                                      57

-------
  1000-1
a.

2

o

8
o
o
   100
   30
     80
              si
I    I

I*1

                                                •••    —


                                                I    I
  100       120        140        160       180

      SOLAR ULTRAVIOLET RADIATION (UVB) INDEX
                                                          D
                                                                 Legend
                                                                  WITH FACTOR
I     D WITHOUT FACTOR



 200
     Figure 20.  Nonmelanoma Skin Cancer Incidence by UV-B Index

                 Among  White Males According  to  the Presence or

                 Absence of the Factor "Freckles"
                                    58

-------
  1000
£
o
o
o
r  wo-
   30-
     BO
— r
 100
                                         D
                         170        140        160        180
                   SOLAR ULTRAVIOLET RADIATION (UVB) INDEX
                                                                 D
                                                     u     —    —
                                                     5     I    S
                                                          Legend

                                                         • WITH FACTOR
                                                         D WITHOUT FACTOR
200
         Figure 21.   Nonmelanoraa  Skin Cancer  Incidence by UV-B
                      Index Among  White Females  According to the
                      Presence or  Absence of the Factor "Freckles"
                                      59

-------
            tOOOn
           £
           o
           o
           o
           o
           o
          B
          <
          z
             100-
                       Si
                       LJ —
                      100
                                                    i
                                         i
                              «0       MO      ICO

                         SOLAR ULTRAVIOLET RADIATION (UVB) INDEX
                                                     mo
 Legend


• WITH fA.CTOR


D WITHOUT FACTOR
                                                             200
   Figure 22a.
             30-
   Nonraelanoma Skin  Cancer  Incidence by UV-B Index

   Among White Males According to  the Presence or Absence

   of the Factor Fair Complexion
                                                                  Legend

                                                                 • WITH FACTOR

                                                                 D WITHOUT OkCTOR
                      100       120       WO       1(0      ISO

                         SOLAR ULTRAVIOLET RADIATION (UVB) INDEX
Figure 22b.
Nonmelanoma  Skin Cancer Incidence by  UV-B Index Among

White Females According to  Presence or Absence

of the Factor Fair  Complexion
                                     60

-------
             wo
                   11
                                      li
                                     Ji
                                          legend
                              2   S   S
O WITHOUT FMTOII
                        SOLAR UURAVKX£T RADWnON (UVB) WOEX
Figure 23a.   Nonmelanoma  Skin Cancer  Incidence by UV-B  Index Among
              White Males  According to Presence or Absence
              of the Factor  "Irish/Scot Descent"
                                                         Legend
                                                        • WITH FACTO*
                                                        U WITHOUT RCTOH
                       SOUR UURAVKMn RADIATION (UVB) INDEX
                                              tie     wo
  Figure 23b.
Nonmelanoma Skin Cancer  Incidence by  UV-B Index
Among White Females According to the  Presence or Absence
of the Factor "Irish/Scot Descent."
                                  61

-------
Immunomodulation by Ultraviolet  Radiation:
Prostaglandins Appear to be Involved in the
Molecular  Mechanisms Responsible  for UVR-
Induced Changes in Immune Function
R. A. Daynes, H. T. Chung, B. Robertson,
L- K Roberts, and W. E. Samlowski
University of Utah Medical Center
Salt Lake City, Utah USA
ABSTRACT

    The experimental exposure of animals to sources of ultraviolet .radiation
      that  emit  their energy primarily in the UV-B region  (280-320 nm) is
      to  result  in a number of well-described changes  in  the recipient's
immune  competence.    Two  such   changes  include  a depressed  capacity to
srfectively respond immunologically to transplants of syngeneic UVR tumors and
a markedly reduced  responsiveness to  known inducers of delayed-type (DTH) and
Contact hypersensitivity  (CH) reactions. The results of experiments that  were
^signed   to  elucidate  the   mechanisms   responsible  for   UVR-induced
iwmunomodulation  have  implicated:    (a)  an  altered  pattern   of  lymphocyt
^circulation,  (b) suppressor  T cells  (Ts),  (c)  deviations in  systemic
*ntigen presenting cell  (APC) potential,  (d)  changes  in  the  production of
interleukin-1-like molecules, and (e) the functional inactivation of epidermal
J^ngerhans  cells  (LCs)  in this process.   The  exposure of  skin  to  UVR,
therefore,  causes a number of  both  local and systemic  alterations to the
^normal host and  its immune system.   In spite  of this seeming complexity and
Diversity of responses, our recent studies have established that each of the
"•WR-mediated changes is  probably of  equal importance  to  creating  the  UVR-
 nduced imkmunocompromised state.

    Normal animals were exposed to  low-dose  UVR  on  their  dorsal  surfaces
      conditions  where a 3.0 cm2 area of  skin was physically protected  from
    light energy.  Contact sensitization of these animals with DNFB, to either
the irradiated or  the  protected  back skin,  resulted in markedly  reduced CH
responses.  This was observed in spite of a normal responsiveness following
!;ne skin sensitization  to ventral  surfaces of the UVR-exposed animals Systemic
treatment of  the  low-dose UVR  recipients  with  the drug  indomethacin  (1-3
Aerograms/day) during  the UVR exposures resulted  in a complete reversal of
the depression observed  following DNFB sensitization  to "protected" dorsal
skin while the altered responsiveness found in the group exposed to  the  skin


                                  63

-------
reactive  chemical  through  directly  UVR-exposed  site  was maintained.   These
studies directly implicate the importance of LCs as effective APCs in the skin
and also  suggest  that some of the systemic  influences caused by UUR exposure
involve the productin of prostaglandins.  This  concept  was  further supported
by finding that  indomethacin treatment was also  capable of  totally reversing
the systemic depressions in CH responsiveness caused by high-dose UVR exposure
(30  K  joules/m2)  of mice.    Attempts  to  analyze  the cellular  mechanisms
responsible  established that  the spleens  of  all  animals  that demonstrated
altered CH responses, regardless of whether sensitization was through a normal
or an  irradiated skin  site,  contained  suppressor  cells.   Interestingly,  we
also found normal levels of T  effector cells in the peripheral lymph nodes of
the UVR-exposed  mice that  were  contact sensitized  through  normal  skin.   No
effector  cells  were  found   when   skin  sensitization  took  place  through
irradiated skin sites.

     In  spite  of  such  an  apparent  paradox,  insight  into  the  probable
mechanisms responsible  for  these  observations  was  provided  by establishing
that UVR exposure of skin results in a striking and dose-dependent blockade of
the efferent lymphatic  vessels in all  peripheral lymph nodes.  Therefore, the
afferent phases of immune responses can apparently take place normally in UVR-
exposed animals  when antigen  is applied to normal skin.  The final effector
responses, however,  appear to be inhibited  in the UVR-exposed  animals  by an
apparent block of effector cell mobility.  This contrasts with findings in the
normal  animals.   Following contact sensitization,  normal  animals  were  also
found to  simultaneously contain  both antigen specific suppressor  T cells and
lymph node effector  cells.   However,  these normal  animals were fully capable
of mobilizing  their  effector cells   into  the  systemic  circulation,  thereby
allowing  a  localization  of  these  cells   to  peripheral  sites  of  antigen
challenge.

     Our  results  suggest that  UVR  is probably  not a significant  inducer of
suppressor  T-cell  activity  to   topically   applied  antigens.    Rather,  UVR
exposure  appears  to  modify  the  normal  relationship   that  exists  between
effector  and regulatory immune responses i_n vivo.   It does  so  by  one  of two
mechanisms:  The first causes a  direct reduction in  the skin's APC function
and results  in an  absence of  effector cell  generation to antigens applied to
UVR-exposed  skin  sites,  inhibiting  the capacity of  effector cells to  gain
access  to  skin  sites  of  antigen  challenge;  the  second  sequesters  the
lymphocytes with  effector  cell potential  into the draining  peripheral  lymph
nodes.   Each of these  situations  results  in  a similar effect on  the  UVR-
exposed host—a reduced capacity to elicit a CH response.  We hypothesize that
altered DTH  responses, altered  alloresponses,  and altered  graft-versus-host
responses (all of which have been observed  in  UVR-exposed animals) may result
from similar mechanisms.

INTRODUCTION

     Extensive literature describes  the  biologic  changes that result from the
exposure  of experimental  animals  and man to the  effects of  UVR.   Many  of the
reported  studies focus  on  UVR-induced  alterations of  an exposed host's  immune
system—definable  alterations  that  have  led  to  the  genesis of  the  term
"photoimmunology"  to describe this  area of   investigation.    The field  of
photoimmunology  is  proving to  represent a  correlative  scientific discipline
that   interrelates   many   areas   of  investigation   including  dermatology,


                                       64

-------
 immunology,  photobiology,  and  physiology.    The goal  of  investigators  in
 Pnotoimmunology   is   to  understand  the  immunobiologic  consequences  of  UVR
 exposure  to provide  a  clinically valid  prediction of the potential  benefits
 and/or  detrimental  effects that are associated with the continued  exposure of
 skin  to solar or artificially derived  sources of UVR.   Such information  is
 important  for  a  variety of reasons.   These include both the probability  that
 '"any  biologic life  forms on our planet may  eventually  be faced with increasing
 aoses of UVR due to a reduction in the fidelity  of the protective  ozone  layer
 and  the recent   interest  by  many  individuals  to maintain a  year-round  tan
        the  use  of artificial  sources  of  UVR.
     The major  objectives of  this review will be  to consolidate many of  the
observations  that have been  reported in the  field of photo immunology during
the  past  few years.   Many  of the local  and  systemic changes  that take place
Allowing the UVR exposure of  skin will be described  as they relate to changes
*n  immunologic,  histologic, pathologic,  and  physiologic  processes.   Our goal
is  to  develop the  hypothesis  that many  of  the immunologic consequences that
lollow acute  or  chronic  UVR exposure actually reflect the body's mobilization
°£ a number of normal host  defense mechanisms in response to the inflammatory
effects  of   this   physical   agent.     A  large  body  of  recently  acquired
experimental  evidence will  be presented to  support  this general hypothesis.
While  our  results  do not  support the  concept that  UVR-mediated  effects on
immune function  are  unique,  they do  demonstrate  the fact  that the biologic
changes that manifest following skin exposure  to this physical agent are quite
Diverse.   The immunomodulatory influences of UVR,  therefore,  appear to result
Ir°m its capacity to affect a  large number of  interrelated biologic systems.

IMMUNOBIOLOGY OF EXPERIMENTAL  UVR  CARCIHOGEMESIS
          is a  known  carcinogen  for  the  induction  of  skin  tumors  in  both
experimental animals  and in man  (Blum 1959; Fears,  Scotto,  and Schneiderman
 'y'7; Tanenbaum et al. 1976).  In addition to its carcinogenic properties, UVR
°an  also function  as  a  cocarcinogenic-promoting  agent  and an  immunologic
modulator (Epstein and  Epstein 1962; Elmets and Bergstresser  1982).   It must
°e  appreciated  that  associated   with  the  transformation   event  are  the
immunomodulatory effects of UVR that have a direct  influence  on the emergence
and progression of skin  neoplasia  (Fisher and  Kripke  1982; Roberts and Daynes
 y°°).   Historically,  the  discovery that subcarcinogenic  doses  of UVR induce
a£ irmnunologic state  of UVR tumor  susceptibility in  syngeneic mice suggested
lo?!kUVR was an immunomodulatory agent (Daynes  et al. 1977; Kripke and Fisher
dl  '•   It  is  the tumor-permitting immunomodulatory potential  of UVR  that
 J-stinguishes it from other carcinogenic agents.

     UVR-induced  tumors,  like  most  experimentally  induced  tumors  (e.g.,
°«emically and virally induced), express  tumor-associated antigens (TAA)  that
    elicit specific immune responses in their  syngeneic  host  (Roberts, Lynch,
    Daynes  1982;  Pellis and Kahan  1976;  Leffell and Coggin  1977;  Rogers and
    tto 1985).   For example, a state of tumor-specific  immunity is induced in
mi°e that are immunized with syngeneic UVR-induced tumors (either fragments or
      lines  maintained  in  vitro)  (Daynes  et  al.   1977;  Roberts,  Lynch,  and
   nes 1982;  Kripke 19?T; Spellman  and Daynes  1978;  Roberts, Spellman,  and
 aynes 1980).   This implies  that the  major rejection responses  elicited in
.VInor- immunized hosts are directed toward unique  tumor-specific  transplanta-
 lon  antigens  (TSTA).    In  addition,  experiments  employing  hyper immunized


                                      65

-------
animals have established that common tumor-associated transplantation antigens
(TATA) are  also shared  by different  UVR tumors (Roberts,  Lynch,  and Daynes
1982; Spellman and Daynes  1978; Roberts, Spellman, and Daynes 1980).  Thus, it
appears that any given UVR tumor expresses both unique and common TAA that are
capable of  becoming  involved in the host  immune  response to varying degrees.
The  immune   response  elicited  by  these  TAA  dictates  whether  the  tumor  is
rejected or allowed to grow.

     Aside  from a few  reports,  very  little  is  known about  the biochemical
nature  of  the  TAA  expressed  by  UVR  tumors.    Employing  tumor-reactive
monoclonal antibodies, DeWitt has identified a membrane-bound TAA that appears
to have a molecular  weight of 200-300 KD  (Daynes et  al.  1985).   Although the
exact biochemical nature of these antigens is not understood, preliminary data
suggest that one of these monoclonal antibodies recognizes a glycolipid moiety
(DeWitt,  personal  communication).   Fortner  et al.  (1982) have  reported that
UVR  tumors  express  a virally  encoded gp70 antigen on  their  cell  surface.
Similarly,  DeLuca  et  al.  (1979) have  reported that  cross-reactive antibodies
in the  serum of UVR  tumor-immune  mice  have specificity for  murine  leukemia
viral  products.    Beeson,  Scott,  and Daynes  (1983)   have demonstrated  the
presence of  oncofetal antigens  on UVR and chemically  induced  tumors  that are
also  expressed  on  placental  and  fetal  tissues.    These   particular  viral-
associated or oncofetal  antigens  could very  easily  function as cross-reactive
TAA.    Finally,  Ristau et  al.  (1980)  have reported that  UVR tumors express a
cross-reactive TAA that  appears  to be a  200 KD  glycoprotein.   Although these
studies have  begun to identify some of  the common TAA that are expressed  by
UVR  tumors,  the  exact  biochemical   nature  and  immunogenic  properties  of
individual TAA are currently unknown.

     Unlike   the   tumors  that   are  experimentally   induced   by   chemical
carcinogens,  a  majority   of  the  UVR-induced  tumors  are   rejected  when
transplanted  into  normal  syngeneic hosts (Daynes et  al. 1977;  Kripke 1974;
Roberts,  Bernhard,  and Daynes 1984).  These UVR-induced,  regressor-type tumors
will grow,  however,  when  implanted into  immunologically  compromised  hosts  or
syngeneic animals  that  have been  exposed  to subcarcinogenic  doses  of  UVR
(Daynes et  al.  1977; Kripke  and  Fisher   1976; Kripke  1974).  Thus,  it would
appear that the  predominant immune  response elicited  by  UVR  tumors,  when
implanted into  normal syngeneic  animals,  leads to their  rejection.   A number
of mechanisms have been  investigated  to determine how UVR  tumors are able  to
escape the immune surveillance capability of their host.

     Tumor  rejection  or progression  is a  dynamic  process  involving complex
interactions between the tumor and  its host.  Conditions  that  allow for tumor
progression  are  related  to  the  inability of  the host  to mount  an  effective
immune  response,   as  well as  the  capacity  of  the  tumor to  modulate  its
tumorigenic  potential  in  response to  immunologic  pressures.    A number  of
studies  have been designed  to  investigate  the  ability  of  UVR  tumors  to
modulate their  tumorigenic potential.   Wortzel,  Urban,  and Schreiber  (1984)
have  analyzed  immune  responses  elicited  by  the  TSTA  expressed on  a  UVR
regressor tumor and a number  of epitope  loss variants derived  from that tumor
(Wortzel et al.  1983; Wortzel, Urban,  and Schreiber  1984).  Through the use  of
cloned tumor-specific  cytotoxic T-cell  (Tc-cell)  lines,  these  investigators
have provided compelling evidence that a number of TSTA epitopes are expressed
by a single UVR tumor.   Furthermore,  the loss  of  specific TSTA  epitopes  by
various  tumor  variants  derived  from  the  original  tumor  was  found  to  be


                                      66

-------
associated with  the acquisition  of a progressor phenotype, i.e., the capacity
to grow when implanted into normal syngeneic recipients.  Thus, the loss of ah
immunodominant  epitope(s)  on  a  UVR-induced  regressor  tumor may  represent a
Possible  mechanism  that  allows  for  its  progression.    In  this  regard,
tumorigenic heterogeneity  of UVR  tumors  was  observed by  Schmitt  et al., who
isolated  cloned  lines  from  a   UVR  regressor  tumor   that  was  capable  of
Progressive growth when transplanted into normal syngeneic recipients (Schmitt
and  Daynes  1981;  Schmitt  et al.    1983).   In addition,  these investigators
determined that a UVR regressor clone could be converted from a regressor-type
tumor to one capable of  progressive  growth in normal recipients subsequent to
culture with  normal lymphoid  cells  in vitro, or following  passage through
inununologically  compromised hosts  (Schmitt  et al.  1983).  These investigators
also provided  suggestive  evidence that the regressor-to-progressor conversion
Process correlated with a somatic  cell  hybridization  between cells  of the
tumor and those  of host  origin.   This is not a unique concept, since in other
tumor systems  it has  been shown  that  somatic cell  hybridization correlates
"ith increased metastatic potential of the tumor (Kerbel et al. 1983; Larizza,
  hirrmacher,  and Pfluger 1984).

     Although  these  studies  would  suggest  that  a  UVR tumor  is capable  of
modulating  its  tumorigenic  potential  in  response  to  the host  immunologic
Pressures, it  was  necessary  to confirm that UVR  tumors  were  clonal  in nature
arjd not derived  from  the progressive growth of both progressor and  regressor
clones  arising  from  multiple   transformants  with  the   tumor   mass.     To
investigate this possibility,  Burnham,  Gathering, and Daynes  (1986) employed
the  tool  of  x-chromosome  inactivation  mosaicism with  the  x-linke.d  enzyme
Phosphoglycerate kinase  1  (PGK-1)  to  evaluate  the  clonality  of  UVR-induced
tumors.   Out of thirteen primary  UVR tumors that were induced  in (C3HxC3H.PGK-
1 'pi heterozygote female mice, which phenotype as PGK-1a/b, all were found to
express only  a  single PGK-1  enzyme form.   Based  on   this  finding,  it  was
concluded that the majority of UVR-induced tumors are monoclonal in origin and
result from the  progression  of a single  transformed  cell.  These  experiments
also suggest that the heterogeneity observed within a single tumor  with regard
^° its tumorigenic potential  must arise from events taking place subsequent to
 he original transformation process.

     Although   the  ability  to modulate  TSTA epitopes and  a certain  level  of
     igenic heterogeneity  within  UVR  regressor tumors  indicates  that  these
    rs may  escape  immunologic rejection  through their  ability to  modulate
their growth characteristics  in  an immunologically competent host,  the exact
mechanism of how these  tumors  are capable of emerging and progressing within
their autochthonous  host  is  unclear.   It is  intriguing  that UVR  regressor
tumors are  rejected  when  transplanted  into normal syngeneic recipients,  but
ar®  capable of  progressive  growth  in  the  autochthonous host  as  well  as
ayngeneic  animals  that have  been exposed  to subcarcinogenic  doses of  UVR,
eaPecially  since  UVR-exposed  animals  appear  to  possess  virtually  normal
lnwiunologic competency (Spellman, Woodward, and Daynes  1977; Norbury, Kripke,
a^d Budmen 1977;  Kripke et al.  1977).  This suggests  that UVR  regressor tumors
ffcploy an escape mechanism(s)  to  evade the immunologic  rejection  response  of
their host.  Transplantation  studies  have shown that  the  progressive  growth of
    regressor  tumors is, in  certain  cases, dependent on a  population of UVR-
        suppressor T  cells  (Ts-cells) (Spellman and Daynes  1978).
                                      67

-------
     In contrast to the Ts-cells  that  arise in response to the TSTA expressed
by progressor-type  tumors  (both UVR and  chemically  induced),  the UVR-induced
Ts-cell population possesses functional antigenic specificity for a common TAA
that appears  to  be  expressed by virtually  all  UVR tumors and some chemically
induced tumors  (Roberts,  Lynch,  and Daynes  1982;  Spellman and  Daynes 1978;
Roberts and Daynes 1986).   Because this population of Ts-cells arises prior to
the appearance  of overt tumors,  it appears  that these  Ts-cells  dictate the
emergence and progression of these  neoplasia.   The functional characteristics
of this Ts-cell  population,  as well as the process  for their induction, have
been the subject of recent investigations.

     It has been shown that  the regulation  of immune responses to a number of
complex multideterminant  antigens   is  mediated  through  the  recognition  of
distinct  immunoregulatory  epitopes  (Yowell  et  al.  1979;  Hashim  et  al.
1976).   We  have hypothesized  that  the immune  response to UVR tumors  may be
viewed in a similar context,  since  epitopes associated with the various types
of tumor antigens could function  as  either  strong tumor rejection epitopes or
weak immunoregulatory determinants  (Roberts and  Daynes 1980;  Roberts,  Lynch,
and Daynes 1982; Roberts,  Spellman,  and Daynes 1980).

     Thus,  the  UVR-induced  Ts-cell  population   would  function  through  an
associative recognition mechanism.   Through  its  ability  to  recognize  common
TAA expressed by virtually all UVR tumors, it would inhibit the development of
immune- rejection  responses  elicited by  the  stronger  TSTA  and other  common
TATA.    This  hypothesis  implies  that  the  UVR-induced  Ts-cell population  is
homogeneous,  i.e., consists  of a  single clone or limited number  of clones of
Ts-cells  that are  restricted  in their  ability  to recognize a common  TAA
epitope.    This has  been  confirmed  by  recent studies  employing  a number  of
interleukin-2  dependent  Ts-cell  lines derived  from  animals  that have been
exposed to subcarcinogenic  doses  of UVR (Roberts, Spellman, and  Warner 1983>
Roberts 1986).   In  these  studies,   it  was  shown  that both the  parental  and
cloned  Ts-cell  lines  were  capable  of  rendering  normal  syngeneic  hosts
susceptible to  the  growth of  a  battery of UVR  regressor tumors.   In  vitro,
these cloned  Ts-cell  lines appear to  mediate their effect  by  inhibiting the
differentiation  of   Tc-cells  from  the  draining  lymph   node   (DLN)  cell
populations obtained  from  tumor-immune mice.  Thus,  this Ts-cell population,
through  its  ability  to  recognize these  common   TAA,   would   provide  an
immunologic environment that would allow  for  the  emergence and progression of
virtually any neoplastic cell that expresses  these  antigenic  determinants,
regardless of their expression of other stronger tumor rejection antigens.

     Although the exact mechanism for the induction of the UVR-induced Ts-cell
population  is unknown,  previous  studies  suggest  that  neoantigens, which  are
cross-reactive  with  TAA,  are expressed  in  the skin of  UVR-exposed  mice
(Palaszynski  and Kripke  1983; Spellman  and  Daynes  1984;  Sielstad  et  al.
1985).   Palaszynski and Kripke (1983)  demonstrated that normal syngeneic mice
were rendered  susceptible  to the  growth of UVR regressor tumors  when grafted
with large  pieces  (5 cm  x  2.5  cm)  of  skin  from UVR-treated  donors.   In
contrast,  Spellman and Daynes (1984) found that  animals  grafted  with smaller
pieces (1 cm  diameter) of UVR-exposed  skin  were effectively  immunized against
a  transplantable  UVR tumor.   In  both  studies, normal skin grafts failed  to
produce any detectable immunologic alterations.  We have recently  detected TAA
cross-reactive antigens in  cellular  extracts  from UVR-exposed  epidermal cells
employing TAA-specific monoclonal antibodies in an enzyme-linked immunosorbent


                                      68

-------
assay  (Sielstad  et al.  1985).   Collectively, these  studies  strongly support
the contention that UVR  induces TAA cross-reactive antigens in the skin before
the recognized  emergence of  neoplasia.    It  is conceivable  that  these skin-
associated  TAA  are  responsible for  eliciting  the  Ts-cell  response  that  is
observed in animals that are exposed to subcarcinogenic doses of UVR.

     We have recently  conducted a  series  of experiments to further define the
imnmnogenicity of  the cross-reactive  TAA that are  expressed in  the  skin  of
UVR-exposed mice  (Hong  and  Roberts  1986).   A combined  protocol of  in  vivo
immunization and in  vitro culture of DLN  cells was  employed  for the analysis
°f TAA-specific  Tc-cells.   For these studies, mice were first  immunized  by
injecting their footpads with viable tumor cells or  skin cells.   After eight
to ten days,  the  DLN were  removed  from these animals,  and the  cells  were
suspended in tissue culture.   After four days of tissue culture, the DLN cells
Were  harvested  and  the  Tc-cell   activity was analyzed  in  a  cell-mediated
°ytotoxicity assay.  The results of these studies  are summarized as follows:

     *  It  was  determined  that  Tc-cells  capable  of lysing  cross-reactive
        tumors differentiate  from  the DLN of UVR tumor  and  UVR skin-immune,
        but not normal skin-immune mice.

     *  These Tc-cells  are   capable  of  lysing  a  range of  tumor  targets,
        including  syngeneic   and   allogeneic   UVR   tumors   and   syngeneic
        methylcholanthrene-induced tumors.  However,  these cells  did not  lyse
        Con   A   activated    syngeneic   lymphoblasts,   thioglycolate-induced
        peritoneal  exudate cells,  or YAC 1 lymphoma cells, which are sensitive
        targets  for the lysis by natural killer  cells.

     '  Cold  cell  inhibition experiments  demonstrated  that  these  Tc-cells
        recognize common cross-reactive TAA.

     '  The expression of these cross-reactive TAA in the skin  of UVR-exposed
        mice appears to  be the direct effect of UVR  exposure,  since the  only
        cells that  were  effective  in immunizing  syngeneic  mice against  TAA
        were those that  were  obtained from skin that  was directly  exposed to
        the effects of UVR.

     These  studies were further  expanded  to  characterize  the  immunogenic
Potential of  the cross-reactive  UVR tumor  and UVR  skin-expressed  TAA.    In
these   experiments, cellular  extracts (obtained by  CHAPS detergent) from  UVR
tumors  and  epidermal  cells  of   either   UVR-exposed  or normal  mice  were
incorporated  into  liposomes  for  the   immunization  of normal   syngeneic
animals.    The  lytic  activity of four-day  cultured  DLN cells  from  these
immunized animals was compared with the DLN cells derived from  mice immunized
with either whole cells or nonincorporated soluble cell extracts.   The  results
of these experiments  indicated that the  cross-reactive TAA  expressed by  UVR
^Pidermal or UVR tumor cells  can  elicit a Tc-cell response when  incorporated
into liposomes and  used to immunize normal syngeneic  animals.

     Although the  levels of  lytic activity  were  different,  similar  results
Were obtained when whole cells were  used for  immunization.   In this  study,
n°rmal  epidermal  cells  did  not  display   any  appreciable   level   of   TAA
exPression.    Interestingly,   soluble  cell  extracts  alone were incapable  of
eiiciting a Tc-cell response  in the DLN of immunized  mice. Therefore,  in  vivo


                                      69

-------
experiments  were  conducted  to  identify  the  difference  in  the immunogenic
potential of whole cells, liposome-incorporated TAA, and soluble  cell extracts
for the induction  of TAA-specific  Tc-cells.   The results of these experiments
suggested that presentation of  the antigens  on a membrane surface is required
to elicit an effective  immune response,  while  presentation of soluble antigen
alone may induce  tolerance.   In the first part  of this study, groups of mice
were  immunized repeatedly  with  viable  epidermal cells  obtained  from UVR-
exposed  or   normal syngeneic  donors.    These  immunized  animals   were  then
challenged with a  UVR progressor tumor  that  was capable of progressive growth
in untreated  normal hosts, as  well as  in  those animals  that were immunized
with  normal  epidermal  cells.   However,  mice  immunized  with UVR  skin cells
rejected the UVR tumor implants.   In a second series of experiments, groups of
mice  received  intravenous  injections  of  soluble  epidermal   cell  extract
obtained from UVR-exposed or normal syngeneic donors.  These animals were then
challenged with a  UVR regressor tumor.   This tumor grew progressively in UVR-
treated hosts and was retained for an extended period of time  in  recipients of
soluble UVR  skin  cell  extract.   The  tumor  was rejected at a  similar  rate by
normal mice and  recipients  of soluble normal  skin  cell extracts.  From these
studies, we have concluded that, similar to what was observed  in  vitro, cross-
reactive  UVR  skin  expressed  TAA  that  was  capable of eliciting an  in vivo
immune  response.    When  presented to  their host  in  a  soluble  form,  these
antigens elicit a  UVR tumor rejection  response.   When presented  to  their host
in a soluble form, these antigens elicit a UVR tumor tolerance reaction.  This
supports'  the possibility  that  by  shedding a soluble  cross-reactive  TAA, UVR-
exposed skin  cells may  elicit  the TAA-specific  Ts-cells  that arise  in UVR-
treated mice before the appearance of any overt neoplasia.

     In conclusion,  the  UVR-induced  Ts-cell  population  appears  to arise in
response  to neoantigens  in  the  skin of UVR-exposed animals.   These Ts-cells,
by an unknown  mechanism, suppress  the  ability of  their host  to mount an
effective immune   rejection  response to  emerging  neoplasia.    As  a  result,
highly  immunogenic tumors can  emerge  and progress  to  the death of the host
that  would  have otherwise been eliminated  had  the individual possessed  its
normal  immunologic potential.    We have hypothesized  that  this  particular
immunoregulatory network  may  have arisen as a mechanism  to protect the host
during  repair  of  UVR-damaged  skin, i.e.,  that through an  immunosuppressive
mechanism which  is mediated  by antigen-specific  Ts-cells,  damaged skin  can
undergo  repair  processes without  the   elicitation  of  an   autoimmune  type
response.  Through the  ability  of emerging  neoplasia  to express  a common TAA
that  is also expressed by UVR-damaged  skin  cells, they are able to use this
particular  Ts-cell population  as  an  immune  surveillance escape  mechanism.
Although  not necessarily  the  sole  mechanism for providing the growth  of UVR-
induced   tumors,   this  particular Ts-cell  population does   appear   to  be
responsible  for  the emergence  and progression of  a majority of UVR-induced
neoplasia.

THE EFFECTS OF UVR EXPOSURE ON THE SKIN AND ITS ASSOCIATED LYMPHOID TISSUE

     It is now appreciated that many types of specialized immune responses are
initiated  whose  effector  responses  are primarily  restricted  to  specific
anatomic  compartments within  the   body.   For example,  those  immune  responses
that  are  associated with the  gut-associated  lymphoid  tissue  (GALT)  and  the
bronchial-associated  lymphoid  tissue  (BALT)   represent  two  well-described
examples  of  immunologic  responses  whose  effector  arms  are  anatomically


                                      70

-------
compartmentalized.    This  anatomic  restriction  to  both  the  afferent  and
e*ferent  mechanisms  in  GALT-  and BALT-associated immune  responses provides for
a means  to  achieve  a  marked  enhancement to  the  protective capabilities  of
these systems  (Guy-Grand,  Griscelli, and  Vassalli  197M; Bienstock,  Johnson,
and Perey 1979).

     It has  been  proposed  that  an immunologic circuit  exists that is dedicated
            to the immune  surveillance  and protection of the skin  (Streilein
         This  specialized  circuit has  been given the acronym SALT  for  skin-
associated lymphoid  tissue.  The evidence to support the existence  of such a
specialized   system   is  somewhat   indirect   and  includes:     the   observed
®Pidermotropism for  some   subsets  of  normal and transformed lymphocytes,  a
aem°nstration  of the  antigen presentation capabilities of certain  epidermal
csU subsets,  and a  demonstration that antigen  recognition  and  responsiveness
or iymphocytes can occur exclusively in the  skin.   In  addition,  this concept
18 supported  by  the knowledge  that  the  integrating  and regulatory  elements
 apable of controlling  certain  types  of immune responses can be  found, both in
IQO Skin  itself,  as  well as  in  the draining  peripheral  lymph nodes  {Streilein
 y°5).    it  is  quite  probable  that  UVR- induced skin  damage  can  mediate  a
Pronounced alteration  to the  fidelity of the  SALT system.

,.    The  elegant  experiments  performed by Macher and Chase  (1969) established
  at cells  and/or  soluble factors  derived  from hapten-sensitized  skin  were
 squired  in  the development of  a contact hypersensitivity  (CH) response.   This
"^k was  followed  by  the  finding,   greater  than ten  years  later,   that  the
majority  of  antigen  presenting  cell  (APC) capacity of normal skin resides with
 "e epidermal  Langerhans  cell   (LC)  (Stingl  et al.  1978).   Furthermore,  the
JJPosure  of experimental animals (Toews, Bergstresser, and  Streilein  1980)  or
^n (Cooper  et al.  1985)  to  low doses of  UVR  in the  UV-B  range  (280-320  nm)
  s found to markedly  reduce  the number  and functional properties of LC in the
t*Posed skin,  with a parallel depression in  the capacity  of these individuals
y° elicit a  CH response  to  skin-reactive chemicals applied directly to  the
.•"-exposed    skin   sites    (Toews,   Bergstresser,    and   Streilein   1980).
 nearest ingly,  the exposure of  animals  to high doses of  UVR  (>10 KJ/m^) causes
WhfyStemic dePression  in  their ability  to elicit a  CH  response, a  condition
 "lcn does not correlate  with  a reduction in  LC presence or function at  the
 on-uVR-exposed sites of hapten application  (Noonan,  DeFabo, and  Kripke  1981;
 Wen,  Gurish, and  Daynes 1983).    These two phenomena,  local and  systemic
 oppression  of CH responses, have been the object of  intense  investigative
 Ifort  over the  past  few  years.  In a  later  section of this review  we  will
  scribe  the  results  of recent  experiments  that implicate the formation  of
            acid metabolites  in  the mechanism(s)  responsible  for  these  changes
 n immune  function.

     Greene  et  al.   (1979)  demonstrated  that  the UVR  exposure  of  animals
        in  a  decrease in their  splenic APC potential.   They concluded  that
     UvR-induced  APC reduction  was  ultimately  responsible  for many  of  the
    nornodulatory   influences  of UVR,   including  the  acquisition   of  tumor
    eptibiiity,  the   observed  depressions  in  humoral  and  cellular   immune
 ®sponses,   and  the  reduced  capacity  of  UVR-exposed  animals  to  elicit  CH
6P°nses>    Subsequent  investigations  by  Gurish,  Lynch, and  Daynes  (1982)
             that  the UVR-induced  reduction  in  splenic  APC  function  was
           by a marked  increase in the  APC activity within peripheral  lymph
      that  drain the skin  sites  of  UVR  exposure.   The  results  of  these


                                     71

-------
experiments suggested  that  the  reported changes in APC function  following  UVR
exposure actually  reflect a redistribution of  APC from central  to  peripheral
lymphoid  compartments.    This  was  further  supported  by  the  finding  that
splenectomized  UVR-exposed  animals  did not demonstrate an  increase in  their
peripheral  lymph node  APC  activity.    Investigations  by Lynch,  Gurish,  and
Daynes (1983)  in mice  and Cooper  et al. (1985) in humans established that  la-
positive cells  with  APC  activity  regain access to the epidermis  by  three days
following an acute UVR exposure.   These cells may not be LC since the  results
with humans indicate that the epidermis infiltrating cells are  DR positive  and
T6 negative.  Collectively, the results  of these experiments indicate that  la-
positive cells with APC function are  highly mobile  in  vivo.   Under  normal
conditions, the cell types having  this functional and surface phenotype  are
distributed among a  number  of distinct  anatomic  compartments.   These  include
the  peripheral blood,  spleen,  lymph   nodes,  skin,  as well as  other   tissue
sites.  Exogenous  stimulation of an animal with  an inflammatory agent  (i.e.*
UVH)  results  in:    a  functional   inhibition  of any  directly UVR-exposed
immunocompetent cells  and a marked anatomic redistribution  of the cells with
APC potential, with enhanced numbers going to the tissue sites  of inflammatory
insult.  This is manifested by increased numbers of APC entering  the skin,  and
eventually  localizing   to  draining  peripheral  lymph  nodes  following  their
entrance  via  the  afferent lymphatic  vessels.    This hypothesis  is  fully
consistent with the  recent  findings of Hendricks and Eestermans  (1983)  who
have  analyzed  the  recirculation  patterns of  rat  macrophages  in  vivo  and
concluded  that  their  entry  into  peripheral  lymph  nodes  is  predominantly
through afferent lymphatic drainage.

     Studies performed by Spangrude et al.  (1983) have established that  the
exposure of  normal mice  to UVR  results in a  marked  change  in  the lymphoid
tissue  localization   properties  of  recirculating  lymphocytes.    This  is
reflected  experimentally  by  a   significant  increase  in the percentage  of
intravenously  injected radiolabeled lymphocytes  recovered from  the draining
peripheral lymph nodes of UVR-exposed animals.  This UVR- induced alteration i"
lymphocyte localization  patterns  is  quite  protracted  and  persists for greater
than six weeks  following the cessation of UVR  exposure.   Recent experimental
evidence has now provided us with an appreciation  of  the  mechanisms that are
responsible for  this effect.   Immunohistologic staining of peripheral lymp&
node sections  with the  monoclonal  antibody MECA-325,  which is  specific fof
high endothelial venules (HEV),  revealed that the HEV  content of lymph node*
from UVR-exposed donors is far greater than the HEV content of a similar lympt1
node from  a normal  animal (Samlowski  and Daynes,  unpublished).   Since tb*
quantity of HEV in  a  lymph node dictates the rate of lymphocyte entry into the
tissue, an enhancement  of  HEV  expression  would  result  in  an increase  ifl
lymphocyte localization  potential.   This is due to  the fact that HEV cental11
the lymphocyte  recognition  structures  that are essential for  the entrance of
lymphocytes into various  types of lymphoid  and  nonlymphoid  tissues (Gallatin»
Weissman,  and  Butcher  1983).   Specific  lymphocyte-HEV  interactions  have aW
been proposed  to control the distribution of lymphocytes  between peripheral'
mucosal,  and central  lymphoid organs (Butcher 1983).
     It is  now appreciated  that  the integrity  of peripheral lymph  node
(both the  presence and  the  magnitude)  is  controlled by humoral  or
factors  that  drain  into the  nodes  via  the  afferent  lymphatics.
conclusion was based on  the  results  of studies  that established  that
of  the  afferent  lymphatic   vessels  resulted  in  a  disappearance  of  H6'


                                      72

-------
 structures  in  the draining lymph nodes  (Hendriks and Eestermans  1983).   This
 reduction  in  HEV expression  was followed  by a markedly decreased  rate  of
 lymphocyte  entry  into these manipulated nodes from  the  blood.   Such  experi-
 ments  suggest  that the  skin  actually functions  as a transducer, in some  way
 converting exogenous  inflammatory stimuli  into humoral and/or cellular  signals
 that have an influence on the presence and extent of  vascular endothelium that
 can function as lymphocyte-receptive  HEV.

     There are a  couple  of obvious candidates that can be considered important
 in  the transmission  of HEV  regulating  signals  from the  skin  to  the  lymph
 nodes.  These include the highly mobile macrophages and APC or  their products,
 as  well  as soluble  mediators produced  directly  by  cells within the  skin  in
 response  to  an exogenous  stimulation.    Recent  evidence from  our laboratory
 emphasizes each of these factors in  the  regulation  of the lymphocyte  content
 °f  a  peripheral   lymph  node.    We  now appreciate  that  subsequent   to  the
 treatment  °^  animals with  agents  capable  of  interfering  with macrophage
 "unction  {silica  or  carrageenan)  or  following surgical splenectomy, exogenous
 Simulation with  UVR  does  not result in  an  enhanced  HEV  expression.   Such  an
 activity can be returned to a splenectomized animal  by  the adoptive transfer
 °f  adherent  splenocytes prior  to stimulation  with  UVR  exposure  (Chung and
 jjaynes, unpublished).   Therefore, the extent to which peripheral lymph node
 HEV can be  stimulated via an exogenous  inflammatory  insult appears to depend
 °n the integrity of the animal's macrophage/APC function.

     The lymphocyte content of  a given lymphoid  organ is  a reflection of not
 °nly the  rate  at  which blood-borne cells are  capable of  entering the tissue,
 Dut  is also  dependent  upon  the  length  of  time  that  the  lymphocytes are
 sequestered  within   the  lymphoid  organ   prior to gaining   recirculation
 Potential.  We have recently determined  that the exposure of  animals to UVR
 causes blockade in  the  efferent lymphatic vessels, a situation which  results
 ln the sequestration  of  lymphocytes  within  the lymph nodes draining  the site
 £" UVR exposure (Chung et al., submitted).  A similar condition  can be induced
 ty the  intravenous injection  of murine  and  interferon into normal mice.  Of
 interest was the parallel finding that treatment of mice  with indomethacin (1-
 * vg/day)   totally abrogated  the  development of  the  efferent blockade  by UVR
 and a/0  interferon.   The efferent blockade  caused by the  direct injection of
 P^ostaglandin E2 was not influenced by indomethacin injection, suggesting that
 Prostaglandins were involved in the responsible mechanism.

     In summary,  the  exposure of animals to UVR  is capable of  modifying many
 components of the SALT system.  Both  macrophage/APC and the recirculation and
 tissue localization properties of lymphocytes are equally affected.  The role
Played by such changes in the modulation  of  immune responses  by this physical
a8ent are currently unresolved,  although  the  parallelism  that  exists certainly
3u8gests a cause-effect relationship  to some  of the observed changes.

PROINFLAMMATOHY PROPERTIES OF  ULTRAVIOLET RADIATION

     It is  well  recognized  that  animals exposed  to UVR  (especially  UV-B)
undergo a pronounced  and dosage-dependent inflammatory response.  While the
cellular and molecular  alterations in the skin  that ultimately result  in a
sunburn reaction are both numerous and complex,  it is  now appreciated that the
generation  of  biological  mediators  and  the  elaboration  of   cytokines  by
                                      73

-------
epidermal cells or  infiltrating  cell types may play  an important role in the
immunomodulatory changes that are observed following UVR exposure.

     Keratinocytes  of the  skin  are  capable of  producing  protein  mediators
termed  epidermal-derived  thymocyte  activating   factor  (ETAF),   a  group  of
multifunctional  hormones   that  are   functionally,    physiochemically,   and
structurally  identical  to macrophage-derived  interleukin-1 (IL-1)  (Luger  et
al.  1983).   ETAF/IL-1 is now  appreciated  to function as a major mediator in
both immune and inflammatory responses (Luger and Oppenheim 1983).  Based upon
the  knowledge  that  number  of inflammatory processes  are  initiated by UVR and
that  the  epidermal cells  of  the  skin are  a major  target of  this physical
agent,  we  have  analyzed  whether  modifications  in   the  levels  of  ETAF
production,  plus  a number of  known host  responses  to  this mediator,  were
affected by UVR exposure.  Our results  established  that UVR exposure does not
adversely  affect  ETAF  production  at  subcytotoxic  doses  (Gathering  et  al.
1984).

     Many biologic  effects have  been ascribed to the stimulation and release
of  ETAF/IL-1  in vivo.   ETAF  and  IL-1  can  stimulate numerous  target organs
throughout  the body  including  the brain,  bone   marrow,  liver,   and lymphoid
organs.  Target cell  interactions with  ETAF/IL-1  result in  elevations in core
body  temperature,  the  number  of  circulating  neutrophils,   the  enhanced
production  of  acute  phase  proteins by  the  liver,  as well  as  lymphocyte
activation and chemotaxis (Powanda and Beisel 1982;  Moissec, Chai-Li, and Ziff
1984).   Exposing  mice  to UVR  results  in  an   elevation  in the  number  of
peripheral blood neutrophils as  well as an increase  in plasma  concentrations
of  several  of acute phase proteins  (Gathering  et al.  1984;  Dinarello 1984).
Further, ETAF/IL-1  can be  detected in the  serum of these animals  24 hours
after exposure  to  UVR.   Since UVR  exposure is inflammatory, and mononuclear
cells  have  been  known  to  migrate  into  irradiated  skin   sites,  we  cannot
discriminate whether the observed elevation in acute phase proteins in vivo is
due  to  an  increase in the production of  ETAF  by keratinocytes or  is  due,  in
part,  to  IL-1  produced by  macrophages that  have  infiltrated  the sites  of
inflammation.

     A recent observation in our laboratory has provided  insight into another
possible  source of  ETAF/IL-1.    Normal  murine  and human  stratum  corneum
contains a  substantial amount  of ETAF/IL-1  (Gathering,  Buckley, and Daynes
1985).   The  physiologic role  of  this  stratum   corneum-associated  ETAF/IL-1
remains to  be  determined;  however, one  could speculate  that  it provides  a
preformed pool  of  this mediator  that  is  capable of initiating  inflammatory
responses following wounding or subsequent to protocols  that increase the rate
of  percutaneous absorption.    UVR  is known  to be  capable  of increasing  the
percutaneous  absorption of  small  molecular  weight  substances  through  the
skin.  Therefore, keratinocyte production of ETAF,  percutaneous  absorption of
preformed  mediator,  and/or  mononuclear  cell  production  of  IL-1  may  all
influence the generation of a UVR-induced  systemic inflammatory  response.

     We have demonstrated  that daily  exposure of mice  to  UVR results  in  an
increase in  the production  of  acute phase proteins,  and  have speculated that
this  is due to elevations  in ETAF/IL-1.  It is interesting to note  that this
heightened response is followed by  an eventual return to normal  plasma levels
of  these  acute  phase  proteins  despite  a  continued  UVR exposure  of  the
animal.   The cause of  this  "desensitization"  to the effects mediated by UVR


                                      74

-------
exposure  is   currently   unknown.     We   have,  however,   established  that
Keratinocytes obtained from a  skin  site exposed to daily  UVR  are still fully
capable of producing ETAF  in  vitro.   While some control of ETAF/IL-1 effects
~£ vivo  may reside at  the level of the  keratinocyte,  the possibility  that
 ®8ulation takes place at the site of action  (e.g., liver, brain, etc.) or in
 116 delivery  system  (plasma)  of this important  mediator also  needs to  be
considered.

 ELATIONSHIP BETWEEN  UVR  EXPOSURE-INFLAMMATION AND  MODIFICATIONS TO  NORMAL
            POTENTIAL
.     In the  preceding  sections of  this  review article  a  number  of  known
 romunologic,  physiologic, and  pharmacologic  changes were described  that take
Pface  following  the  exposure  of  experimental  animals   to   UVR.     These
 iterations  include the acquisition of tumor susceptibility,  a  condition that
P^alieig  overt tumor  induction,  suppressor  T-cell induction,  alterations in
"£crophage and  lymphocyte components of the SALT system, plus the  stimulation
   both prostaglandin  and  ETAF/IL-1  mediated effects.   When  experimentally
.  slyzed  individually,  each of  these  known  changes  which  take place  could
 ndividually  be hypothesized to have a modifying influence on the  immunologic
Potential  of  an UVR-exposed  host.

t     It should be  appreciated  that  UVR exposure  of  skin  is  capable  of
  itiating all  of  the reported  changes  simultaneously in  the  exposed  host,
Baking   it   highly   probable   that   significant   overlaps,   cause-effect
 eiationships,  and a  number of biologic generalizations  can be  formulated.
 urthermore,  many  of  the changes  inducible  by  UVR are  not unique to  this
infSlcal agent  as -evidenced by  the  knowledge that a large number  of distinct
/•""lammatory   stimuli  are  capable  of   initiating   a  similar   cascade   of
            and physiologic  changes.    In  an attempt  to  support the  concept
     many  of the apparently distinct immunomodulatory effects of UVR  exposure
gl8nificantlv  overlap with one another mechanistically,  we  will  focus  this
 ectton on two  immunologic  changes  that  take  place subsequent  to UVR exposure.

,     The experimental exposure  of mice to UVR results in a marked reduction in
 ^eir  capacity  to  elicit   contact   hypersensitivity   (CH)  responses   to
UVR Utaneously  applied skin-reactive chemicals.   Mice exposed to low  doses of
  " (4 x 400 J/nr/day) demonstrate a reduced capacity to elicit CH responses
     are  site specific (localized  to  the  skin areas of direct UVR exposure),
 .    as  high-dose  exposure  of mice  to UVR (15-30  KJ/m2)  causes   systemic
 Iterations that leave the animals hyporesponsive  to CH induction regardless
   the skin  site  of hapten  application (Toews, Bergstresser,  and Streilein
   ^J Noonan,  DeFabo,  and Kripke 1981).   Both of these types of UVR-mediated
     ations have been previously reported to be associated with suppressor T-
^  - induction  (Toews,  Bergstresser, and Streilein  1980;  Noonan,  DeFabo,  and
t ipke 1981).   The  capacity of  low-dose  UVR to depress the capacity of animals
   Despond to skin-reactive chemicals has been concluded to be due to  a direct
           inactivation of  LC by this physical agent  (Toews, Bergstresser,  and
          1980). The state of  systemic .suppression requires high doses of UVR
    induction,  and while it  too  is associated with the generation of hapten-
nv!!!!2^0  suppressor T-lymphocytes,   it is  not dependent upon  a functional  or
           modification  of the resident LC at the  site of hapten application
                and  Daynes  1983;   Morison,  Bucana,  and  Kripke 1984).    Due
           to   their  ease  of  manipulation,   these   phenomena now  serve  as


                                     75

-------
prototypes  to  help establish  the  mechanisms responsible  for  the immunologic
changes that follow UVR exposure.

     It  was originally  concluded  that  a  cause-effect  relationship  exists
between the  functional  inactivation  of epidermal LC and the depression in CH
responsiveness that is observed following the exposure of animals to low doses
of UVR.  While attractive,  the validity  of this hypothesis was dependent upon
the generalized  capacity  of low-dose UVR-exposed animals  to respond normally
to skin  sensitization at  non-UVR-exposed  sites.   We  therefore  undertook an
experiment  to  test  this   prediction  formally.   Groups of normal  mice  were
exposed on their dorsal surfaces to UVR  in low doses (400 J/nr/day).  Each of
the  animals had  a  small  3.0 cm2  patch of  UVR  opaque   tape  applied  to a
specified  dorsal  skin  site  just  prior  to  the  irradiation  treatment.    A
phenotypic analysis of epidermal  LC in the exposed, protected,  and unexposed
skin sites  confirmed  that the  tape  treatment  had  protected  the covered area
from UVR exposure.  Subsequent  to  the  UVR  exposures,  the treated animals were
divided into three  groups  and contact sensitized with  DNFB.   The first group
was sensitized through an  unirradiated skin site on the abdomen.  The second
group of animals was contact sensitized through an irradiated dorsal skin site
and  the  third  group  had  hapten applied  to  the  tape-protected dorsal  skin
site.  An additional group of normal animals were contact sensitized through a
normal dorsal  skin site  to serve as  a  positive control.   All  animals  were
challenged with DNFB  five  days later.   The  results of  this experiment (Table
1) established that UVR-exposed animals that had been sensitized through their
abdominal wall  skin responded  normally,  a finding  that is  fully  consistent
with  the original  observation  (Toews,   Bergstresser,   and Streilein  1980).
Likewise, the  animals  that were  contact sensitized  through  the  irradiated
dorsal skin  (LC deficient)  exhibited  a marked  reduction in their capacity to
elicit a CH response.   Interestingly,  the animals that  were contact sensitized
through  the   UVR-protected  dorsal   skin  site  were   also  found   to  be
hyporesponsive, in spite of the fact that  LC density in this area of the skin
was totally normal.  This  finding suggested that LC inactivation by UVR is not
solely responsible for  the  reductions  in  CH  responses  elicited  by  these
animals.

     We  next  questioned   whether  the  known  capacity   of UVR   to  stimulate
prostaglandin  synthesis  was  involved  in  the   immunologic  changes  that  were
taking place  in  low-dose  UVR-exposed  animals.   This was  based  on  the known
capacity of UVR to stimulate an  increase  in  the systemic release of IL-1-like
molecules and to also cause both inflammation and pain  (Gathering et al. 1984;
Eaglstein, Sakai, and Mizuno  1979).  Two large  groups  of skin patch protected
mice were prepared and exposed  to  low  doses  of UVR.  One group of the animals
to be UVR-exposed received  a  subcutaneously  implanted pellet of indomethacin,
designed to deliver a daily dosage of 1.25  ug over a  20-day  period.   After
subjecting all experimental animals to the four daily UVR exposures,  they were
segregated into four  separate  groups.   One group of indomethacin-treated and
one  group  of untreated UVR-exposed mice  were  contact  sensitized  with  DNFB
through  irradiated  dorsal   skin   sites.     Likewise,   a   second   group  of
indomethacin-treated and  a. parallel  group of  untreated UVR-exposed  animals
were  contact sensitized  through  the  protected  area  on  their dorsal  skin
surface.   To establish  the effect of  the  indomethacin  treatment, all experi-
mental and  control  groups were challenged  with hapten  five days later-   The
results  of  this experiment. (Table 2)  clearly demonstrate  that the  in  vivo
inhibition of prostaglandin synthesis had no effect on  the reduced capacity of


                                      76

-------
     Table 1.  The Effect of Low-Dose UVR Exposure on Contact Hypersensitivity
               Responses Elicited to DNFB
            Sensitization                               Percent Depression
 GrouP           Sitea                  Treatment0        of CH Responses3
1
2
3
4
5
6
Abdomen
Back
Abdomen
Back
UVR-Shielded Backb
None
UVR
UVR
UVR
UVR
UVR
None
0
0
7.1
64.1
61.5
-
   Normal C3H mice  were contact sensitized  with a solution of  DNFB  on day 0
   and day  1  by  topical  application to  their  shaved ventral or  dorsal skin
   surfaces.
b
   The  UVR-shielded  site  was   created   by  applying  UVR-opaque  tape  to  a
   specified  area on the dorsal  skin of normal C3H mice.
o
   Animals were  exposed  to UVR  by  irradiating  them with a bank of  six FS-40
   bulbs  which  emit  approximately  2.5  J/m2/sec   of   UV-B   energy.    All
   experimental  animals  received 400 J/m2  of  total  energy per day  for four
   consecutive days.
d
   Percent depression was calculated as a relationship to the  positive normal
   control.
Animals that were hapten  sensitized  directly through an  irradiated  skin site
^° elicit  a CH response.   In contrast,  the reduced capacity  of  UVR-exposed
^imala to  elicit a  CH   response following  sensitization  through a patch-
Protected  dorsal  skin  site  was  not  observed  in  the  indomethacin-treated
group.   These animals responded normally to the DNFB sensitization, suggesting
     the diminished CH  response  to haptens applied  to  normal  (UVR-protected)
      sites  depends  on   the   mobilization  of  arachedonic   acid   and  the
   synthesis of its  metabolites.   Further studies confirmed that the plasma of
~VR-exposed  animals  contained   elevated  levels   of   PGE2  and   that  the
J-hdomethacin  treatment  of  such  animals  inhibited this  elevation in  PGE2
Production.
     We next turned  our  attention to  the phenomenon  of systemic suppression of
Contact hypersensitivity and hypothesized that the induction of this condition
®*-&\t also require the  in vivo stimulation of prostaglandins.   Two  groups of
fJUmals were exposed to  high-dose UVR (30 KJ/m2).  Each  individual  from one of
 "ese groups  was  given  an  indomethacin pellet  to  inhibit their  capacity to
synthesize prostaglandins.  After a three-day rest following the UVR exposure,
    experimental animals plus a group of normal controls were contact
                                      77

-------
      Table 2.  Indomethacin Treatment Abrogates the Immunodepression Observed
                Following  Contact   Sensitization  of   Low-Dose  UVR-Exposed
                Animals Through Protected Skin Sites
             Sensitization                                     Percent Depressio"
Group           Sitea              Treatment0  Indomethacin"    of CH Responses
1
2
3
4
5
6
Back
Back
Back
UVR-Shielded Backb
UVR-Shielded Back
None
None
UVR
UVR +
UVR
UVR +
None
0
61.8
62.3
60.5
3.6
_
a  Normal C3H mice  were contact sensitized with  a solution of DNFB  on day 0
   and day  1  by  topical  application to their  shaved ventral or  dorsal skin
   surfaces.

k  The  UVR-shielded  site was  created  by  applying  UVR-opaque  tape  to  a
   specified area on the dprsal  skin of normal C3H mice.

c  Animals were  exposed  to UVR by  irradiating  them with a bank of  six FS-40
   bulbs  which  emit  approximately  2.5  J/m2/sec   of   UV-B   energy.     All
   experimental animals  received  400 J/m2  of total  energy per day  for four
   consecutive days.

^  Indomethacin treatment  was accomplished  via the  subcutaneous  implantation
   of a  pellet  designed to   release the  drug at  a constant  rate of  1.25
   yg/day  for 20 days.

e  Percent depression was calculated as a relationship to the  positive normal
   control.
sensitized with DNFB on  their  unirradiated ventral skin  surfaces.   Five days
later,  all  animals were  challenged  and  the  extent of  ear  swelling  was
evaluated  after  24  hours.    The  results  of  this representative  experiment
(Table 3)  clearly  demonstrate  that the  ability of high-dose UVR  exposure to
cause a systemic depression in CH responsiveness is inhibited by the treatment
of the  test  animals with indomethacin.   These results strongly  suggest that
the  mechanisms  responsible  for  UVR-induced   systemic  suppression  of  CH
responses involves the stimulation of prostaglandin synthesis.

     Previous investigations have implicated hapten-specific T-suppressor (Ts)
cells in  the mechanisms  responsible for high-dose  UVR-induced  suppression of
CH responses (Noonan, DeFabo, and  Kripke  1981).   These conclusions were drawn
from  the  finding  that  the spleens  of hapten-sensitized UVR-exposed animal3
contained  hapten-specific   Ts   which,  upon   adoptive  transfer   to  naive
recipients, were capable of causing a depression in the recipients' capacity


                                      78

-------
     Table 3.   Indomethacin Treatment Prevents the Development of Systemic
               Suppression of Contact Hypersensitivity Responses by High-Dose
               UVR Exposure
Sensitization
Sitea
Back Skin
Treatment13
Indomethacin0
Percent
of CH
Depression
Responses"
Gr°up
  1              Abdomen          None             -                 0
  2              Abdomen          High-Dose UVR    -                 56.6
  3              Abdomen          High-Dose UVR    +                 6.4
  ^              None             None
   Normal C3H mice  were contact sensiti2ed with  a solution of DNFB  on  day 0
   and day  1  by topical  application to their  shaved ventral or  dorsal skin
   surfaces.

   Animals were  exposed to UVR by irradiating  them with a 100-watt mercury arc
   lamp which emits approximately  500 J/m2 of UV-B energy.   All  experimental
   animals received  15000 J/m2 of UV-B energy.
c
   fhe indomethacin  pellets used in this study delivered 2.5  yg   of drug per
   day.
d
   Percent depression  was calculated as a  relationship  to  the positive normal
   control.
          a CH  response  to the immunizing hapten  (Noonan,  DeFabo,  and Kripke
            therefore  questioned  whether  suppressor cell  activity could  be
Demonstrated in  indomethacin-treated UVR-exposed  animals  subsequent  to  skin
ssnsitization.    The  results  of  our  study  determined  (Table  4A)  that  the
Eduction of splenic suppressor cells represented a normal  consequence of skin
Sensitization with  the hapten DNFB.   Not only  was suppressor  cell  activity
Present  in  the  spleens  of  high-dose  UVR-exposed  donors,   regardless  of
indomethacin treatment,  but  suppressor  cell  activity  could also be found  in
cne spleens of  the DNFB-sensitized normal animals as well.   Normal splenocytes
j °Ptively transferred into  naive recipients were  without  inhibitory  effect.
•n Parallel  to  an analysis  of suppressor cell  activity,   the  draining  lymph
nodes were removed from both normal  DNFB-sensiti2ed donors  and  high-dose  UVR-
~*Posed  DNFB-sensitized  donors for adoptive  transfer  to  naive  recipients.
*his protocol tests for the development  of effector cell  potential.   Recipient
animals  were  immediately  challenged with hapten.   The results (Table  4B)
ae«ionstrate  that  DNFB-sensitized  high-dose  UVR-exposed  animals  and  DNFB-
 ensitized normal  animals generate  an  equivalent  effector cell activity  in
 «eip peripheral  lymph nodes.   Our  results,  therefore,  suggested that  the
 ^pressed capacity of  high-dose  UVR-exposed  animals  to  elicit a CH  response
 as not  due to:   apparent modifications in suppressor  cell generation  or a
^ePression  in  the capacity  of these  animals  to  generate  effector cells  in
 eaponse to  hapten application.   Subsequent  experiments,  where  UVR-exposed
        were contact  sensitized   through irradiated or   UVR-protected  skin


                                      79

-------
   Table 4.  Contact Sensitization of High-Dose UVR-Exposed Animals Results in
             the Simultaneous Induction of  Both Suppressor and Effector Cells
             for CH Responses
A.
Group Donor Treatment3
1
2

3 None

4 High-Dose UVR

5 High-Dose UVR

Plus Indomethacin
B.
Group Donor Sensitization
1
2 +
3 +
Recipient Treatment13
Challenge
Sensitization Plus
Challenge
Sensitization Plus
Challenge
Sensitization Plus
Challenge
Sensitization Plus
Challenge


Donor Treatment6
_
+
High-Dose UVR
Percent
Suppression0
-

0

54.6

64.0

62.1


Percent
Normal Response
0
100
93.1
a  Donor animals were untreated or exposed  to  high-dose  UVR (30 KJ/m2) in the
   presence or absence of indomethacin.

h                                 8
   Recipient  animals  received  10  splenocytes  from DNFB-sensitized  donors.
   The recipient animals were subsequently skin sensitized with DNFB.

c  Percent suppression was calculated as a relationship to normal mice or mice
   that received an adoptive transfer of normal cells.

   Donor  animals  were  footpad  and belly  sensitized with  DNFB.   Peripheral
   lymph  node lymphocytes  (30  x  10  )  were adoptively  transferred to  naive
   recipients that were immediately challenged with DNFB.

e  Certain  donors  were  exposed   to  high-dose  UVR  (30  KJ/m  )  three  days
   previously.
<»
   The capacity to elicit a CH  response  was calculated as a percentage of the
   positive (normal) control.
                                      80

-------
sites, determined that splenic suppressor  cell  activity was induced under all
conditions employed,  while adoptively transferrable effector cell activity was
°nly  found  when  skin sensitization  took  place  through  a skin  site having
normal LC function (data not shown).

     Insight into  the mechanisms  responsible  for  the depressed  capacity of
uvR-exposed animals to elicit CK responses  was  derived from experiments where
normal,  UVR-exposed,  and indomethac in- treated  UVR-exposed animals  served as
recipients of  CH-effector cells  obtained  from normal hapten-primed  donors.
 oth  normal  animals  and  the  indomethacin-treated  UVR-exposed  groups  were
        of eliciting  a  demonstrable  CH response.   However,  the  UVR-exposed
           of  normal  CH-effector  cells exhibited  a tremendous reduction in
      capacity  to manifest a CH response (Table  5).   Therefore the  capacity of
    to inhibit  the elicitation of a CH response  to agents initially applied to
    al skin  sites does  not  appear to  represent the  result of a  diminished
capacity   of  the animal  to  generate  an  immune  response to  the  inducing
   ten.   Rather,  the depressions  in the intensity of CH responses observed in
   -exposed animals appear to reflect  some prostaglandin-induced alteration in
    capacity of  the  effector  arm  of the CH response to  function,  possibly
     gh   a modification   in  lymphocyte  receptiveness  of  the  microvascular
?nd°thelium  associated with the blood vessels at  the specific  site of a given
lmmunologic or  inflammatory  response.

GENERAL CONCLUSIONS AMD FUTURE DIRECTIONS

     The  major  objective of this review was to  present the interrelationships
     exist  between the  seemingly  diverse effects that  UVR  has  on  normal
              and physiological  processes.   Each of these  inducible  changes
     be   similar  mechanistically   to  those  elicited  by  other   types   of
lnflammatory  stimuli.   Ultimately, the changes  caused  by UVR-exposure  produce
  condition in  which immunologic  responsiveness  of animals  is dampened, either
 nrough the dominance  of specific suppression  following antigenic stimulation,
 r due to intrinsic  mechanisms  that  exist to  functionally inhibit  certain
jypes of  effector  cell  responses.     We  have  hypothesized   that  these
r"niunoregulatory   responses   are   reflections   of   normal   host   defense
™echanisms.   Such mechanisms may  exist  to protect  the  individual  against  the
Possible  development  of  autoimmune conditions  during the essential, repair
Processes  taking  place subsequent to  the  UVR-mediated damage to skin.   While
 erying to protect a host from possible autoimmune manifestations represents a
 eneficial aspect of  such processes,   the  creation  of  a  condition where  the
 evelopment of  immune  responses is continually being suppressed would  clearly
^ detrimental.   This represents  the condition  that  would take place  under
 Ituations of  chronic  UVR  exposure.   These could  come   about  from  either
         mores, where  individuals  increase their daily exposure  to solar  or
           UVR  for personal  or  cosmetic reasons, or from  a reduction  in  the
      on  of the  ozone  layer  which  currently  provides  a degree of  protection
     UVR.

.     Photo immunology is providing the  basic  and  clinical scientists  with fresh
 naight  into the types of mechanisms which  can  operate  in  vivo  to  control
            responses.    It  has  long  been appreciated  that  the molecular
           ics  and  the  mode  of  presentation  of  a  given  antigen  to  an
 ^Unocompetent host can play a  significant  role  in the  immunologic outcome  of
    an interaction.  Likewise,  it  is  known  that  an immune response can  take


                                      81

-------
                           Table 5.
00
NJ
                   UVR  Inhibits the Capacity of Animals to Execute a Contact
                   Hypersensitivity Response in the Presence of Normal
                   Immunologic Potential
Experiment
Number Group
I 1
2
3
4
5
II 1
2
3
4
5
Adoptive Transfer
of DNFB-Primed
Treatment of Recipients3 Lymphocytes^
None
None +
Indomethacin +
15 KJ/m2 UVR +
15 KJ/m2 UVR + Indomethacin +
None
None +
Indomethacin +
15 KJ/m2 UVR +
15 KJ/m2 UVR + Indomethacin +
Ear Swelling0
4 ± 1
29 ± .5
27 ± .5
8 ± 2
25 ± .5
3 ± 1
28 ± 2
43 ± 4
9 ± 1
22 ± 1
Percent
Depression
of CH Response
0
0
8
84
16
0
0
0
76
24
              a.
              b.
              c.
UVR was administered 3 days prior to the adoptive  transfer  of DNFB-primed lymph node cells.  Indomethacin


pellets were employed which release 2.5  ug of drug/day.


Normal animals were sensitized with DNFB on their  ventral surface, ears and footpads.  Lymph nodes were


excised after 4 days and 30 x 106 cells  adoptivelly  transferred  to the normal and treated recipients.


Ear swelling was measured 24 hours subsequent to DNFB  challenge.  7« depression of the CH response was

calculated by comparing it to the positive control.

-------
      forms,   with  both  humoral  and  cell-mediated  components  functioning
simultaneously to  either  effectuate  or  regulate the  type or  intensity  of a
given adaptive  immunologic response.   Photoimmunology,  the effect  of light
energy on immunologic  responsiveness,  has served to expand  our understanding
°f  immunologic  control  mechanisms.    The  importance  of anatomic  compart-
mentalization, the  relationship between  inflammation  and adaptive  immunity,
and  the  means   by  which  suppressor   cell   dominated  responses   can  be
preferentially stimulated  are  all apparent from the immunobiologic analysis of
the UVR-exposed host.   Further,  the use of UVR  to  alter a host's immunologic
Potential is now uncovering the  role  played  by interleukin-1,  prostaglandins,
steroids, and other hormones  in  many forms of  immunologic control processes.
Such information should prove  useful,  both in the  elucidation  of the diverse
range of processes that interact to ultimately  control  the immune response, as
well as  in the clinical manipulation of given immunologic situations.
     While  it  is  impossible  to  accurately  predict  the  future  of  this
interesting field of study,  the  tremendous advancements made  during  the past
decade might be used as an indication of the future.  Based upon the number of
diverse  areas   of   investigation   that   are  involved   in  the  field   of
Photo immunology,  one might hypothesize that  the future will bring significant
advances from  both  the basic  and clinical  sciences.   These  advances  should
provide valuable information  concerning  the  means  by  which  environmental
influences can modulate the immunologic potential  of a normal host, as well as
important  insight into  mechanisms that can be used to manipulate certain types
°* immunologic responses for clinical benefit.

ACKNOWLEDGMENTS

     This  work was  supported by grant numbers  CA306S, CA25917,  CA22126,  and
^34302, awarded by  the National  Cancer Institute, NIH.


REFERENCES

Beeson, J.H.  J.R.,  Scott,  and R.A.  Daynes.   1983.   Am.  J. Reprod.  Immunol.
     3:92-96.

Blenstock,  J., H. Johnson,  and D.Y.E Perey.  1979.  Lab. Invest.  28:686-96.

Blum,  H.F.    1959.   Carcinogenesis by  ultraviolet light.    Princeton  Univ.
     Press.

Bupnham, O.K., L.C.  Gathering, and R.A. Daynes.   1986.   J.  Natl.  Cancer Inst.
     76:151-58.

 utcher, E.   1983.   In  Experimental and  clinical  photoimmunology, eds. R.A.
     Daynes and J. Spikes.  Vol.  1:   173-94. Boca Raton, Florida:   CRC  Press.

c°oper, D.,  et al.   1985.   J. Immunol.  134:129-37.

DaVnes, R.A.,  et al.   1977.  Transplantation. 23:343-48.

D&ynes, R.A.,  et al.   1985.  Cancer Surveys.  4:51-99.
                                      83

-------
DeLuca, D., M.L. Kripke, and J.J.  Marchalonis.   1979.   J. Immunol.  123:2696-
     2703.

Dinarello, C.  1984.  Adv.  Inflamm. Res.  8:203-25.

Eaglstein, W.H., M. Sakai, and N.  Mizuno.  1979.   J. Invest. Dermatol.  72:59-
     63.

Elmets, C.A., and P.R. Bergstresser. 1982.   Photochem.  Phobobiol.  36:715-19.

Epstein, J.H., and W.L. Epstein.   1962.  J. Invest Dermatol.  39:455-67.

Fears,  T.R.,  J.  Scotto,  and  M.A.  Schneiderman.  1977.    Am.   J.  Epidemical.,
     105:420-27.

Fisher, M.S., and M.L. Kripke.  1982.  Science. 216:1133-34.

Fortner, et al.   1982.  Cancer  Res.  42:2371-75.

Gathering, et al.  1984.  P.N.A.S.   81:1198-1202.

Gathering, L.C., A. Buckley,  and  R.A Daynes. 1985.  J.  Clin. Invest.  76:1585-
     91.

Gallatin, W., E. Weissman,  and  E. Butcher.  1983.   Nature.  Lond.   304:30-34.

Greene, M., et al.   1979.  P.N.A.S.  76:6591-95.

Gurish, M., D. Lynch,  and R.  Daynes.  1982.  Transplantation.   33:280-84.

Guy-Grand, D., C. Griscelli,  and  P. Vassalli. 1974. Eur.  J. Immunol. 4:435-43.

Hashim, G.A., et al.  1976.  J.  Immunol.  116:126-30.

Hendriks, H., and E. Eestermans.   1983.  Eur. J.  Immunol.   13:663-69.

Hong, S.R., and L.K. Roberts.   1986.  (submitted  for publication).

Kerbel, R.S., et al.  1983.  Mol. Cell. Biol.  3:523-27.

Kripke, M.L.  1974.  J. Natl. Cancer Inst.   53:1333-36.

Kripke, M.L., and M.S. Fisher.   1976.   J. Natl. Cancer  Inst.  57:211-15.

Kripke, M.L., et al.  1977.  J. Matl.  Cancer Inst.  59:1227-30.

Larizza, L., V.  Schirrmacher  and  E. Pfluger.  1984.  J. Exp. Med. 160:1579-84.

Leffell, M.S., and J.H. Coggin  Jr.   1977.  Cancer Res.   37:4112-19.

Luger, T., and J. Oppenheim.   1983.  Adv. Inflamm. Res.  5:1-25.

Luger, T., et al.  1983.  Fed.  Proc.  42:2772-76.
                                      84

-------
LVnch, D., M. Gurish, and R. Daynes.  1983.  J.  Invest. Dermatol.  81:336-341.

Macher, E., and M. Chase.  1969.  J. Exp. Med.  129:103-21.

Moissec, P., K.Y. Chia-Li, and M. Ziff.  1984.   J. Immunol.   133:2007-11.

Morison, W., C. Bucana, and M. Kripke.   1984.   Immunol.  52:299-306.

Noonan, p.,  E.  DeFabo,  and M. Kripke.   1981.   Phobochem.  Photobiol.  34:683-
     89.

Norbury,  K.C.,  M.L. Kripke,  and M.B.  Budmen.   1977.   J.  Nabl.  Cancer Insb.
     59:1231-35.

palaszynski, E.W., and M.L. Kripke.  1983.   Transplantation. 36:465-67.

PelUs, M.R., and B.D.  Kahan.  1976.  Methods Cancer Res.  13:291-330.

powanda, M., and W. Beisel.  1982.  Am.  J.  Clin. Nutr.  35:762-68.

Ristau, E., et al.  1980.  Acta Biologica et Medica Germania.  39:315-25.

Roberts, L.K.  1986.  J. Immunol. 136:1908-16.

Roberts, L.K., and R.A. Daynes.  1980.  J.  Immunol.  125:438-47.

R°berts, L.K., C.W. Spellman, and R.A. Daynes.   1980.  J. Immunol. 125:663-72.

Roberts, L.K., D.H. Lynch, and R.A Daynes.   1982.  Transplantation. 33:352-60.

Roberts, L.K., C.W. Spellman,  and N.L.  Warner.   1983.   J.  Immunol.   131:514-
     19.

Roberts, L.K., E.J. Bernhard,  and R.A.  Daynes.   1984.   Photodermatol.   1:57-
     64.

Roberts,  L.K.,   and R.A.  Daynes.    1986.     In  Experimental  and  clinical
     £hotoimmunology,  eds.   R.A.  Daynes and G.G. Krueger.   111:77-109.   Boca
     Raton, Florida:  CRC Press.

Rogers, M.J., and G. Galetto.  1985.  Cancer Surveys. 4:35-50.

S°hmitt, M.,  and R.A.  Daynes.  1981.  J. Exp.  Med.  153:1344-59.

Sctonitt, M.K., et al.   1983.   Am. J. Path.   113:269-78.

Sielstad,  K.H.,  et al.   1985.  Clin. Res.  33:618 (abst.).

SPangrude, G., et al.   1983.   J.  Immunol.  130:2974-81.

 Peilraan,   C.W.,  J.G.   Woodward,  and  R.A.  Daynes.    1977.    Transplantation.
     24:112-18.

       n,  C.W.,  and R.A. Daynes.   1978.   Cell.  Immunol.   38:25-34.


                                      85

-------
Spellman, C.W., and R.A. Daynes.  1984.  Photodermatol.   1:164-69.



Stingl, G., et al.  1978.  J. Immunol.  121:2005-13.



Streilein, J.  1978.  J. Invest. Dermatol.  71:167-71.



Streilein, J.  1985.  J. Invest. Dermatol.  85:105-45.



Tanenbaum, L., et al.  1976.  J. Invest. Dermatol.  67:513-17.



Toews, G., P. Bergstresser, and J. Streilein.  1980.  J. Immunol.  124:445-53-



Wortzel, R.D., et al.  1983.  J. Immunol.  130:2461-66.



Wortzel, R.D., J.L. Urban,  and H. Schreiber.  1984.  P.N.A.S.  81:2186-90.



Yowell, R.L., et al.  1979.  Nature. 279:70-71.
                                      86

-------
Stratospheric Ozone  Depletion:  Immunologic Effects
°n Monocyte Accessory Function in  Humans
     A. Elmets, Jean Krutmann,
      th Rich, Hiroshi Fujiwara, and Jerrold J. Ellner
     Western University
U|eveland, Ohio USA
    Predicted  increases  in  the  amount  of ultraviolet-B  (UV-B)  radiation
    ing the  earth  due  to stratospheric  ozone  depletion are likely to have
*|l8nificant impact on human health.   One recently recognized target of UV-B
         is the immune  system.  In particular,  UV-B has been shown to  render
           phagocytes deficient in their ability to activate T lymphocytes to
           and to soluble  antigen.  However, nearly all studies dealing with
   deleterious effects  of  UV-B on immunological  function have been conducted
7n sxperimental animals.   The objective of this  study was to characterize the
 nfluence of  UV-B  radiation on  human  monocyte  accessory function, which is
 ssential  for  the  initiation  of  cell-mediated  immune responses.   Human
J"eripheral  blood   monocytes  obtained  by  plastic adherence  were  used  as
r-°essory cells and were exposed  in  vitro  to UV-B radiation from FS20  lamps.
,neir  ability  to  induce a blastogenci response to either  antigen  (tetanus
 °xoid)  or  mitogen (OKT3,  PHA)  when co-cultured with  autologous. peripheral
  °°d T  lymphocytes that had been rigorously rendered accessory  dependent was
    as  an  index of their  accessory  cell  function.  Exposure of monocytes to
    doses as low as 50  J/m2  inhibited the blastogenesis response to antigens
   mitogens  by 90%  (p  = 0.001).  Viability of UVB-irradiated  cells did not
GUI  r slgnificantly  from unirradiated  monocytes over the initial 72 hours of
tht   ' indicating that  inhibition  was not a result of a  lethal  effect on
 ni-s cell population.  The  reduction  in accessory activity was associated with
sti     de°line  in  IL-1  activity  in  supernatants  of  UVB-irradiated, LPS-
 'jimuiated monocytes.    However, addition of exogenous IL-1 to  cultures was
 "8uffiCient  to  completely   restore   the  blastogenesis   response.    UVB-
t.Padiation also  rendered  monocytes deficient  in antigen processing.   When
g 6V were exposed to antigen for 30 minutes before  UV-B rather than after UV-
     loss of> accessory activity was  observed.   Thus, UV-B radiation adversely
     s  the accessory function of human peripheral blood monocytes in antigen-
    mitogen-induced activation of T lymphocytes.   Deficient IL-1  production
    imPaired  antigen processing are  at least  partially  responsible  for this
        These  findings  suggest that modification of the stratospheric ozone

                                   87

-------
layer  with  resultant  increases  in  UV-B  penetration  may  have  deleterious
effects on monocyte accessory activities  in humans.

INTRODUCTION

     Chronic exposure of the skin  to solar ultraviolet radiation  has  a variety
of  deleterious  effects  on human health  (Harber and Bickers  1981).   It causes
premature  aging of  the  skin  and is a  well-recognized  etiologic agent  for
cutaneous  squamous cell  and  basal  cell  cancers.   In addition,  there is  an
increasing  awareness that  sun  exposure  may  play an  important  role in  the
development of malignant melanoma  (Kopf,  Kripke,  and Stern  1984).

     Recent studies  performed  in experimental animal models  have  demonstrated
that  solar ultraviolet radiation  also  profoundly  influences  cell-mediated
immunity  (Elmets  and  Bergstresser  1982; Daynes and Krueger  1983;   Parrish,
Kripke,  and  Morison  1983).    When  animals  are  exposed  to  various  doses  of
ultraviolet radiation,  they develop  impaired  immune  responses to  UVB-induced
skin cancers {Kripke  1974), to  contact sensitizing agents  (Toews  et  al.  1980}
Jessup et  al.  1978),  and to Herpes  simplex  virus {Howie, Norval,  and  Maingay
1986).  A UVB-induced alteration in  the function  of accessory cells appears  to
form the basis  for such disturbances in cell-mediated immunity {Greene et al-
1979; Toews et  al.  1986).   These cells, of  which macrophages and monocytes,
epidermal  Langerhans  cells, and  splenic  dendritic cells have been  the most
thoroughly studied, are essential  for  the activation and expansion  of helper ?
lymphocytes, an obligatory step in the initiation of immune responses.

     Action spectrum  studies  have been performed to  determine the wavelength
bands of  solar  ultraviolet  radiation  that  are  most  efficient  at  producing
these immunologic  alterations  {Elmets, LeVine, and Bickers 1985; Schacter  et
al.  1983;  DeFabo and Noonan  1983).    They have demonstrated that  wavelengths
within  the  UV-B  exert  the  greatest   inhibition  of  cell-mediated   immune
function.    This  is of  imminent  concern  because  the   widespread  use   of
chloroflurocarbons in aerosols and refrigerants has been predicted to  deplete
the atmosphere  of  ozone, which  filters  out solar  UV-B  radiation  (Molina and
Rowland 1974).   It is likely that stratospheric ozone depletion with  resultant
increases  in  the  amount  of UV-B  reaching the earth's  surface  will  have a
significant impact on several  aspects of human health,  including an  increase
in the incidence of diseases that require the immune system for protection.

     The vast majority  of evidence  implicating UV-B  as  a  causative  agent  in
deficient  cell-mediated immune  function, however,  is  derived  from  studies
conducted  in  experimental  animals.    Relatively  little is  known about  the
immunological  effects of UV-B in humans.  We  recently have conducted a number
of   experiments   to  determine   whether  UV-B  inhibits  the   function   of
immunocompetent cells of humans  in a  manner similar  to  its inhibitory effec*
on  the  immunocompetent  cells  of animals.   The cell type we  chose to
was  the  human   peripheral  blood monocyte and  the  immunological  function
elected  to observe  was  its  accessory  activity.   Studies  in  animals
suggested  that  the  accessory  function  of  macrophages  and  monocytes   &.
profoundly altered following  UV-B exposure {Greene  et al.  1979).   Accessory
activity is an  obligatory first step in  the  initiation  of all cell-mediate^
immune responses.  This function is  vitally important  for a broad spectrum of]
sensitivity reactions,  including  immunity  against  tumors,  and  immunity  t°
certain microbial agents including viruses and fungi.


                                      88

-------
METHODS

Blastogenesis Assays

     We assessed  the function  of accessory  cells  in  antigen-  and mitogen-
Induced blastogenesis assays.    Accessory-dependent purified T lymphocytes
served as  the  responding cell  population;  peripheral  blood  monocytes were
employed  as  accessory  cells;  and tetanus toxoid  (for antigen-induced assays)
and PHA or  OKT3 (for mitogen-induced assays) served as the initiating stimuli.

     T lymphocytes  were  purified by  a  three-  or  four-step  procedure from
Peripheral  blood mononuclear cells  (PBMC) obtained from  the heparinized blood
of  healthy  human  volunteers by  Ficoll-Hypaque  (Pharmacia,  Piscataway,  New
Jersey) gradient centrifugation.  PBMC were first  allowed to adhere to  100 mm
tissue culture grade plastic petri dishes (Falcon,  Oxnard, California) for 1-2
hours at 37°C in a 5% C02 incubator.  Then the plastic non-adherent cells were
Pipetted  off  and  incubated  on  acid-washed  nylon  wool  columns  (Fenwall
Laboratories, Deerfield,  Illinois)  for  45  minutes at  37°C.    Finally,  the
faulting T lymphocyte-enriched population was treated with a  1:50 dilution of
a monoclonal antibody to a framework determinant of the  HLA-DR antigen  (OKIA,
Ortho Pharmaceuticals, Raritan,  New Jersey)  and low toxicity rabbit complement
(Cedarlane  Laboratories,  Hornsby,  Ontario).   In some experiments,  cells were
further depleted of accessory cells by treatment with a  5 mm concentration of
L-leucine methyl ester (L-LME,  Sigma Chemical  Co.,  St.  Louis, Missouri) for 40
Minutes at  22°C.  When L-LME was employed, it  was used prior to treatment with
anti-HLA-DR  and  complement.     The  resulting  population  of  T  cells  was
accessory-dependent  and  was  completely  unresponsive   to  antigen  (tetanus
toxoid} and mitogen (OIT3, suboptimal doses  of PHA).

     Accessory  cells  were obtained  by dislodging  those cells that remained
adherent  to  the plastic petri dishes  in the first  step of  the  T  lymphocyte
Purification procedure.   This  population was 85/&-90/S peroxidase  positive and
f°P the purposes of this discussion will  be  called peripheral blood monocytes.

     Tetanus  toxoid  (a  gift  from  Lederle  Laboratories,   Pearl River,  New
Jersey)  was  used   as  the  antigen  in  soluble  antigen-induced   T  cell
olastogenesis assays.   Suboptimal concentrations  of phytohemagglutinin (PHA,
Qibco, Grand  Island,  New York) or  OKT3  (Ortho Pharmaceuticals,  Raritan,  New
Jersey) were used as mitogens in mitogen-induced blastogenesis assays.

     In the blastogenesis assays,  2 x 104 monocytes were  cultured with 1 x 10^
T  lymphocytes  and  with  either  tetanus toxoid,  PHA,  or  OKT3  in 96  well
""i-crotiter   plates   (Corning,  Corning,  New  York).    In   all  the  experiments
Described,   only  autologous  combinations  of  monocytes  and  T  cells  were
en>Ployed.    All variables  were performed  on  triplicate  wells.  Cultures  in
      tetanus toxoid  as used as the stimulus  were incubated for 5 days; those
   which  OKT3 or PHA was  used as  the  stimulus were cultured for 3 days.  Each
      was pulsed with  1  microCurie of  tritia'ted  thymidine  for  the  final  18
hours  of  the  culture  period.    Incorporation  of  tritiated  thymidine  into
Proliferating cells  was  used as  an index of T  lymphocyte  activation.   Data
Were expressed as cmp = (cmp of cultures  containing antigen or mitogen) - (cpm
of unstimulated cultures).
                                      89

-------
UV Irradiation of Cells

     One  x  106  cells  in  1  ml of  colorless HBSS  without  Ca+2 and  Mg+2  (KC
Biological,  Lenexa,  Kansas)  were  irradiated  in  35-rom tissue  culture plates
with  a bank  of  four  FS20  fluorescent UV-B  bulbs  (Westinghouse  Electrical
Corp., Bloomfield, New  Jersey).   These lamps  have  an output primarily in  the
UV-B  range.   Output in  the UV-B at  a tube to target distance of 21  cm  was
approximately 1.7 x  10~* W/cm.   Output was monitored with an IL700 Research
Radiometer and  SEE  240 UV-B  photodetector  (International Light, Newburyport,
Maine).

Interleukin-1  Production and Bioassay

     Peripheral  blood  monocytes  were  prepared  as  described  above  and  were
cultured at a concentration of 5 x  105/ml  in  RPMI-1640 plus 2% PCS.   One ml
was cultured per 16 mm Linbro plate well in the presence or absence of E. coll
lipopolysaccharide (LPS) 10 ug/ml (Difco, Detroit, Michigan).  After 24 hours,
the well  contents were aspirated and the  supernatants filtered  through 0.22
micron filters.

     Interleukin-1 (IL-1) activity was assessed by placing the supernatants in
the thymocyte proliferation bioassay.  Briefly, 100 microliters of supernatant
was added  to  round  bottom microtiter  wells containing  1.5 x  10"  thymocytes
prepared from the thymuses of 8-12 week old female CSH/HeJ mice (Jackson Labs,
Bar Harbor,  Maine).   The plates were  incubated for 72 hours, and the amount of
tritiated thymidine  incorporated  into proliferating cells  during the final 6
hours  of  culture was used  as an index of  IL-1  activity.   IL-1  activity was
calculated  by  modified  probit-type  analysis  and  was  expressed  as  U/ml
according to the method of Luger et al. (1982).

RESULTS

Requirement for an Aocessory-Cell-Dependent System to Demonstrate UV-B Effects
on Monocyte Accessory Function

     In  our  initial  studies we  found  that it  was  essential  to employ  an
accessory-cell-dependent system to demonstrate UVB-induced defects in monocyte
accessory function (Table 1).  Cells  that had been adhered to plastic and then
passed over nylon wool  were not accessory-dependent;  some  proliferation  of T
cells occurred to tetanus  toxoid even without  the addition  of accessory cells
(group  I).   The  addition  of unirradiated  autologous monocytes  to  cultures,
however,  significantly   augmented  the  response  (group   II).   Only  moderate
inhibition  of   blastogenesis  could  be  demonstrated   when   UVB-irradiated
monocytes were  added to nonaccessory-cell-dependent nylon  wool  nonadherent T
cells  (group  III).   On  the other  hand, when  cells  were  additionally treated
with anti-HLA-DR and complement,  there was a reduction in T cell proliferation
T background  levels  (group IV).   The response could  be  reconstituted  by the
readdition of autologous monocytes (group V).
                                      90

-------
         Table 1.   Requirement for an  Accessory Dependent System to Demon-
                   strate UV-B Effects on Monocyte Accessory Function
Group


  I

 II


III
               Cell Cultures'
Responding T
     Cells
NWE'

NWE


NWE
Accessory
   Cells
None

Un1rrad1ated
  Monocytes

UVB Irradiated
  Monocytes
Initiated Thym1d1ne
   Incgrporat1on
 (xlO~JCMP + S.D.)
     5183 ± 2592

   11,523 ± 1591


     9311 ± 1735
 IV

  V


 VI
HLA-DR Treated'

HLA-DR Treated


HLA-DR Treated
     None

Un1rradlated
  Monocytes

UVB-Irrad1ated
  Monocytes
      712 ±  624

   12,185 ± 2103


      965 ±  743
t*   10  T cells were cultured with 2x10  monocytes  with  optimal  amounts of
Jetanus  toxold for 5 days.
    NWE  - nylon wool enriched T lymphocytes; HLA-DR treated  -  T  cells
PuMftec| by plastic adherence, nylon wool columns and  treatment  with HLA-DR
    complement.                     2
    Monocytes were exposed to 50 J/m  UVB.
                                   91

-------
     UVB-irradiated  monocytes  were unable  to  reconstitute  the  response  to
tetanus  toxoid  when T  cells  had been  rendered  accessory-dependent  (group
VI).  This contrasts with what was observed when UVB-irradiated monocytes  were
added   to  cultures   containing  responding   nonaccessory-cell-dependent  T
lymphocytes (group VI vs. group  III).

Inhibition of Human Monocyte Accessory Functionjay UV-B Radiation

     Using  this  accessory-dependent   system,  we  examined  whether  in  vitro
exposure of human peripheral blood monocytes to UV-B radiation inhibited their*
ability  to serve  as accessory  cells  for T  cell  responses to  the soluble
antigen  tentanus toxoid.   As shown  in Table  2,  there was  a dose-dependent
inhibition in T  cell responses  when monocytes  -were irradiated with increasing
doses of  UV-B.   A dose of  50  J/m2 was sufficient  to  inhibit the response  by
greater than BQ%.  This is less  than one half the UV-B dose that would cause a
mild  sunburn  in a  fair-skinned  individual  following outdoor  recreational
activity  and  can be easily achieved  in  the  dermal vasculature  as  monocyte
cells circulate through the skin.

     Inhibition  of accessory  cell function was due to a  nonlethal effect  of
UVB.  At 50 J/m2 there was no significant difference in viability, as assessed
by  trypan  blue  exclusion,  between uhirradiated and  UVB-irradiated monocytes
over the entire duration of the  culture period.

     These experiments indicated that,  similar  to  animal  models in which  UV-B
radiation had been shown to preferentially inhibit  the accessory function  of
macrophages and  epidermal  Langerhans  cells for soluble antigen,  this form  of
radiant energy also  altered the accessory function of  human  peripheral blood
monocytes for tetanus toxoid.

Effects of UV-B Radiation on Accessory Signals Required for Human T Lymphocyte
Activation by Tetanus Toxoid

     Monocytes and other accessory cells contribute at least three essential
signals for T lymphocyte activation (Unanue et al.  1984).   First, they express
large amounts of HLA-DR antigens on their cell surface.  These molecules serve
as  interaction  structures  between the accessory  cell and  the  responding T
lymphocyte.  Second,  they produce the soluble cytokine interleukin-1,  which  is
a  necessary  co-factor required  for T cell activation.   Finally,  accessory
cells take up antigen,  degrade it, and re-express it on the cell surface in  an
antigen  processing   step.    Because UV-B  radiation  inhibited the  accessory
function of monocytes  by a non-lethal insult  to the cell, we next performed
studies  directed  at  examining  which  of  these  signals  essential  for  T
lymphocyte activation was inhibited by UV-B.

     We first  assessed the capacity  of human  peripheral  blood  monocytes  to
produce interleukin-1 following UV-B exposure.   Peripheral blood moncytes  were
exposed  in  vitro to doses  of UV-B ranging  from 0  to  300 Jm2 and were  then
placed in  culture with LPS, which served as a  stimulus  for  IL-1 production.
Twenty-four hours later the supernatants were  removed  from these cultures and
were  examined for IL-1 activity  in the thymocyte proliferation bioassay.   A3
                                      92

-------
     Table 2.  Dose-Dependent Inhibition  of Tetanus Toxoid-
               Induced T Lymphocyte Blastognesis by UV-B1
     UVB  Dose                                  Initiated Thymldlne
          9
      (J/m )                                       Incorporation

                                                 (x 10"3 CPM ± SD)
       0                                             24650 ± 11466

      10                                             16370 +  4182

      25                                             14760 ±  3392

      50                                              2556 ±  2042

     150                                               731 ±   138

     300                                               469 ±   114
Monocytes vere used as  accessory  cells,  were exposed to various doses of
UV-B, and placed  in  culture for 5 days with purified T cells and  tetanus
toxoid in the tetanus  toxoid-induced T lymphocyte blastogenesis assay.
                                  93

-------
shown in  Figure. 1,  unirradiated tnonocytes were  able to produce large amounts
of IL-1 when stimulated  by  PLS.   There was a marked decline in IL-1 activity,
however,  in supernatants derived  from UVB-irradiated monocytes.   A dose of 50
J/ra2 UV-B reduced the  activity  by greater than 95/1, which corresponded to the
UV-B  dose  that  also  caused  marked  inhibition  of  proliferation  in  the
blastogenesis assay.

     To determine  whether  deficient IL-1 production  was the  only accessory
defect  that  was   present   in   UVB-irradiated  monocytes,  experiments  were
performed in which recombinant murine IL-1 was added back to the blastogenesis
cultures  in  an  attempt to reconsititute the response  (Figure  2).   Murine
recombinant IL-1 was not able to substitute for monocytes in the blastogenesis
assay  (group  II).     It  also  failed  to augment  the  response   in  cultures
containing unirradiated  monocytes,  T  lymphocytes,  and  tetanus  toxoid (group
IV).  Only partial  reconstitution of the  tetanus toxoid response was observed
when this  reagent  was added to  cultures  containing UVB-irradiated monocytes,
purified  T  cells,   and tetanus  toxoid  (group VI).    We thus  concluded  that
although UV-B radiation inhibited IL-1 production by monocytes, deficient IL-1
production was  not  the  sole accessory defect  that occurred  following  UV-B
exposure.

     Next, we  tried to examine  the  effect of UVB on  antigen  processing.   In
these experiments,  monocytes  were  preincubated  with  tetanus  toxoid for  30
minutes before UV-B exposure.  Following irradiation, responding T lymphocytes
were added  to the  cultures.   The reasoning  behind this  experiment  was  that
exposure of monocytes to antigen prior to UV-B might allow the accessory cells
to take up and to process antigen before UV-B inhibited the antigen processing
step; and therefore  reconstitution of the response  might  occur.   As shown in
Figure 3,  only slight inhibition of  the response occurred when accessory cells
were treated  in this  manner.    The  fact  that  monocytes became  resistant  to
inhibition  by UV-B  when  exposed to  tetanus  toxoid  for a  period  of  time
sufficient to allow for  antigen  uptake  and processing, suggests that UV-B may
have an effect on antigen processing.

Effects of  UV-B Exposure  on the Ability of Human Monocytes  to  Activate _I
Lymphocytes to Mitogen

     Accessory   cells  are  also   required  for   mitogenic  activation  of  T
lymphocytes.  However, the accessory signals required for T cell activation by
mitogen differ somewhat from those required for antigens.  While both antigens
and  mitogens  are   thought  to  require IL-1  production  for  optimal  T  cell
activation, mitogens,  unlike antigens,  do not require  a processing step.   We
therefore  performed   experiments to  assess  whether  UV-B  irradiation  of
accessory cells inhibited the mitogenic activation of T lymphocytes.  In these
studies,  OKT3 or PHA served as the  mitogenic stimulus.  Mitogens were placed
in  culture  with  UVB-irradiated  monocytes   and  purified  T  cells  and  the
blastogenesis response was  determined three days later.   Similar to what was
observed  for  tetanus  toxoid,  there was a  dose-dependent inhibition of T cell
proliferation  to suboptimal  doses  of  PHA  when increasing  UV-B  doses  were
administered  (Figure  4).   Dose-dependent  inhibition also  occurred when  OKT-3
was used as the mitogenic stimulus (Figure 4).  With both of these mitogens, a
UV-B  dose between 50 J/m2 and  100 J/nr was  sufficient to inhibit the T cell
                                      94

-------
             9
              _
              6
          I  2
       -  g. 2
          8
          £  0
         Monocytes  -
            IL-1

          Column    I
No UVB   No UVB    UVB
                             II
  III
IV
                UVB
VI
     Figure  1.  IL-1 production by UVB-irradiated monocytes.  Peripheral blood
™°nocytes  were  UVB-irradiated  and then placed in culture  with  LPS.   Twenty-
 °ur hours later  the supernatants were removed  and  assayed for IL-1  activity
   the mouse thymocyte bioassay.
                       50
            250
                                300
                                100      150     200

                                 UVB Dose (J/m2)
to   Fi8ure 2.  Incomplete reconstitution  of UVB-induced inhibition of tetanus
^ ^id-induced  T   lymphocyte   blastogenesis   by   recombinant   murine  IL-1.
nuiC?SSOry  cells (unirradiated  or  UVB-irradiated)  and/or  10/Um'  recombinant
to     IL-1  were added  to  cultures  containing purified T  cells  and tetanus
, x°id.   Cultures  were  incubated for  5 days  in  the  tetanus toxoid-induced  T
           blastogenesis assay.
                                    95

-------
       Monocytes

       NoUVB
Pre-exposure to
Tetanus Toxold
       UVB-treated
       UVB-treated
                                            2468
                                      Trltlated Thymidlne Incorporation
                                             (x10'3cpm ± SD)

     Figure 3.   Development of  resistance  by monocytes to  UV-B effects on
accessory function  by preculture with antigen.  Accessory  cells were placed in
culture with tetanus toxoid  (Panel  C).   Thirty minutes later the cells were
UVB-irradiated  with 50 J/ra2.  T lymphocytes were then added and cultured for 5
days in the tetanus toxoid-induced T lymphocyte blastogenesis assay.  Control
panels were included in which accessory cells were unirradiated and received
no  pre-exposure  to  tetanus toxoid  (panel  A)  or  were  UVB-irradiated  and
received no pre-exposure to  tetanus toxoid (panel  B).
                          OKT3
                                                 PHA
                                  100     150     200     250
                                 Ultraviolet-B Radiation, J/m2
                                              300
     Figure  4.    Dose  dependent  inhibition  of T  lymphocyte blastogenesis
responses to mitogens by UV-B.   Accessory  cells  were  exposed  to various doses
of UV-B and  then placed  in culture for 3  days with purified T cells and with
either PHA or OKT3  in a  T lymphocyte blastogenesis assay.
                                     96

-------
 Response by greater than 90?.   This UV-B does was almost  identical to the UVB
 dose that inhibited the  T cell response to tetanus toxoid.

     We then attempted to reconstitute the mitogenic response to OKT3 with IL-
 '•   For these experiments, recombinant human  IL-1-alpha  and  IL-1-beta were
 obtained and  were  added to cultures  containing  OKT3,  purified T  cells,  and
 JVB-irradiated monocytes.   Despite the fact that both IL-1-alpha and IL-1-beta
     significant  bioactivity  in  the  thymocyte  proliferation  assay,  these
          were unable to  augment the T  lymphocyte  response  to  OKT3  (Figure
  '•  These findings indicated that even for mitogens,  IL-1 was insufficient to
 ^constitute the T  cell response.   The fact that mitogens are  not processed
 a^  *^-1  could  not reconstitute  the response  implies  that UV-B  exposure
 affected  an  additional,   as  yet  undefined,  signal   required  for  T  cell
 a°tivation in addition to IL-1 production and antigen processing.
      Additions to Cultures of
   ^Purified T cells A OKT3
   Accessory cells     IL-1

   +  (0 J/m2)

   +  (100 J/m2)

   *  (100 J/m2)   IL-1a(100u)

   +  (100 J/m2)   IL-1|5(10u)
                                     1,000   2,000  "     90,000
                                  Tritiated Thymidine Incorporation
                                           (x 10-3 cpm±SD)
mit-   FiSure  5.    Incomplete  reconstitution  of  UV-B  induced  inhibition of
 itogen-induced  T   lymphocyte   blastogenesis  by   human   recombinant   IL-1.
       ant  human  IL-1-alpha  or   IL-1-beta  was  added  to  OKT3-induced  T
     ocyte blastogenesis assays.
                                    97

-------
 DISCUSSION

      These studies  have  shown  that jin  vitro exposure of human peripheral blood
 monocytes   to  UV-B  radiation   inhibited  the  accessory signals  required  for
 antigen-induced  and mitogen-induced activation  of T lymphocytes.   Inhibition
 occurred  at  UV-B  doses  that  were  sublethal  for monocytes.   Inhibition  of
 accessory  function  was due both  to  deficient IL-1 production and  to  impaired
 antigen processing  by  UVB-irradiated monocytes.

      An  additional, as  yet  unidentified,   monocyte-derived  accessory  signal
 also  appeared to be affected  following UVB  exposure.   This  was based  on  the
 finding  that  although  IL-1   production  by  UVB-irradiated  monocytes   was
 diminished,  the  readdition of exogenous IL-1 was  insufficient to reconstitute
 the T cell response to  the mitogen OKT3.   Because  OKT3  is  not processed  by
 monocytes,  the lack of a response cannot be attributed  to a processing defect.

      One possibility  for  this additional  signal  is an alteration in  HLA-DR
 antigen expression  and/or  function.    HLA-DR antigens are  thought  to function
 by forming  complexes with  processed  antigenic moieties, and thus enabling  the
 recognition of these antigenic moieties by  responding T lymphocytes.  Perhaps
 UV-B  radiation  reduces  the number  of HLA-DR  antigens on the  cell surface,
 produces alterations in the ability  of UVB-irradiated HLA-DR molecules to bind
 processed antigen,  or  impairs  the recognition of HLA-DR antigens by responding
 T  cells.    Alternatively,  UV-B exposure may  disturb membrane-associated IL-1
 activity.    Recent  studies  by  Kurt-Jones  et  al.  (1985)   have   shown that
 paraformaldehyde-fixed  macrophages  are capable  of  presenting  antigen  to T
 lymphocytes despite their  inability  to release  IL-1.   These  cells express an
 IL-1-like  substance  on  their  cell  membrane  and  this  membrane-associated
molecule may play an important  role  in T cell activation.  Thus, an alteration
 in membrane-associated IL-1 could also explain why UVB-irradiated monocytes
 fail  to function as accessory  cells.

      These  studies  have  important implications  with respect  to stratospheric
ozone  depletion.    The immune  system  plays a fundamental role  in  protecting
 individuals  against   noxious   microorganisms  and  provides  a  surveillance
mechanism against neoplastic cells as  they arise.  Because stratospheric ozone
performs the beneficial function of filtering out harmful UV-B, destruction of
this  component of  the  atmosphere would increase UV-B at the  earth's surface.
The observations  of this study,  in  which we  have demonstrated  a UVB-induced
 impairment of immune function  in human monocytes, suggest that deficient cell-
mediated immunity  will  be  a  major  contributing  factor to the  postulated
adverse effects that stratospheric ozone depletion has  on  human  health.   UVB-
induced immune  deficiencies might be  expected  to result  in  rising rates  of
cutaneous and possibly other malignancies,  and  may produce  increases  in the
 incidence of illness caused by viruses, fungi, and other microbes.

ACKNOWLEDGMENTS

     These  studies  were  supported   by  grant  AM32593  from  the National
Institutes of Health.  The excellent  secretarial assistance of Carol Highsmith
is greatly appreciated.
                                      98

-------
REFERENCES

Daynes,  R.A., and  G.  Krueger.  1983.   Experimental and  clinical phoboimmuno-
     IORV.   Vol.  2. Boca Raton, FL:  CRC Press.

De Fabo,  E.G.,  and P.P.  Noonan.  1983.  J. Exp. Med.  157:84-98.

      ,  C.A.,  and P.R.  Bergstresser. 1982.  Photochem.   Photoblol.   36:715-19.

      ,  C.A., M.J.  LeVine.,  and D.R.  Bickers. 1985.   Photochem.   Photobiol.
     42:391-98.

      ,  M.I., M.S.  Sy,  M.L.  Kripke,  and  B.  Benacerraof.   1979.   Proc.  Nabl.
     Acad.  Sci.  U.S.A.  76:6592-95.

Harber,  L.C.,  and D.R.  Bickers. 1981.   Photosensitivity  diseases:   Principles
     of  diagnosis and  treatment.  Philadephia:  W.B. Saunders.

Howie, S.,  J.  Norval, and J.  Maingay.  1986.  J. Invest.  Dermatol.  86:125-28.

Jessup,   J.M.,  N.  Hanna,  E.  Palaszynski,  and   M.L.   Kripke, 1978.    Cell
     Immunol.   38:105-15.
                                                      t
      A.W.,  M.L.  Kripke, and R.S.  Stern.   1984.    J.   Am.  Acad.  Dermatol.
     11:674-84.

KriPke,  M.L.  1974.   J.  Natl.  Cancer Inst.   53:1333-136.

Kurt-Jones,  E.A.,  D.I.  Seller,   S.B.  Mizel,  and  E.R.  Unanue. 1985.   Proc.
     Natl.  Acad.  Sci. U.S.A.   82:1204-08.

Luger, T.A.,  B.M. Stadler, B.M. Luger,  B.J.  Mathieson, M.  Mage, J.A. Schmidt,
     and J.J.  Oppenheim.  1982.   J.  Immunol.  128:2147-52.

M°lina,  M.J.,  and F.S.  Rowland. 1974.   Nature. 249:810-12.

Parrisn,  J. A.,  M.L.  Kripke,  and  W.L.  Morison. 1983.    Photoimmunology.   New
     York:   Plenum.

Schaeter, B.,    M.M.,  Lederman,  M.J.  LeVine,  and J.J.  Ellner.   1983.    «L.
     Immunol.   130:2484-87.

Thiele,  D.L.,  M.  Kurosaba, and P.E. Lipsky.  1983.   J.  Immunol.   131:2282-90.

     , G.B.,   P.R. Bergstresser,  J.W.  Streilein,  and  S. Sullivan.  1980.   J_..
     Immunol.   124:445-453.

     e,  E.R.,   D.I. Seller,   C.Y.  Lu,  and P.M.   Allen.  1984.   J.  Immunol.
     132:1-5.
                                      99

-------
 Effects of UV-B  on  Infectious Disease

 Suzanne Holmes Giannini
 Columbia University College of Physicians and Surgeons
 New York, New York USA
PRODUCTION

     The skin  is our interface with the environment and our bodies'  first line
   defense against  infectious agents.  Other papers in this volume  illustrate
 Qt"y elegantly that UV-B  irradiation has a  selective, suppressive effect  on
immune system  functioning.  They show us, further, that the skin itself is  an
 nanune organ,  in that  certain types of lymphoid cells are found predominantly
 n skin (Daynes et  al.  this volume; De Fabo  and Noonan this volume;  Elmets  et
*J-« this volume).   The function of  this skin-associated lymphoid tissue is  to
 espond to antigens that enter the body by  way of the skin.   This  cutaneous
       surveillance system  is  vital to  our  ability  to resist  invasions  by
lnfectious agents.

     Infectious  diseases remain serious public health  problems  in the  tropics
 nd semitropics.  These are the geographic areas that also receive the  highest
       of solar UV-B  radiation  in the  world  (Schulze 1970).   A critical
         arises:    What  are the  effects  of UV-B  irradiation  on the  body's
 6sPonse  to  infectious agents penetrating  the skin?

     There  are  few  experimental  data to  answer  this  important  question.
         is  further  complicated  because  infection  and  disease outcome are
      ed> not only by the  immun°genetic background of the host, but also by
6f*   environmental factors such as humidity,  temperature,  vector density and
 tficiency,  concomitant  infections,  and host  nutrition,  to  name  but a few.
> though  the issue is very complex,  a growing  body of evidence  suggests that
 »-B  irradiation  can affect  both  pathogenesis and  immunity  in  infectious
         involving skin.

      EFFECTS OF UV-B ON THE CUTANEOUS PHASE OF  INFECTIOUS DISEASES

,     The  effect  of ultraviolet radiation  on the progression of skin disease
 as been the subject of  investigation for almost a century.    In the late


                                    101

-------
1880s, the Danish  physician Niels Finsen began  a  study of the interaction of
skin with sunlight.   By a  series  of  experiments in which various wavelengths
were  filtered  out  from sunlight, he concluded that  it was  the ultraviolet
component, which he  called the "chemical rays," that  caused inflammation and
sunburn.    In  1894,  Finsen  reported that  the "chemical  rays"  of  sunlight
promoted scarring  in smallpox, and that  patients sequestered in rooms thickly
hung with red curtains  healed their pustules without scarring (Finsen 1901a).
This illustrated that  solar radiation could affect  the outcome of infectious
disease,  and launched  him  on  a  study of ultraviolet  radiation in the treat-
ment of tuberculosis (Finsen  1901b).   In 1903, Finsen received the Nobel Prize
in Medicine  for  successful treatment of lupus vulgaris  (tuberculosis  of the
skin) by  local  application  of ultraviolet  irradiation.   Over  the next four
decades,  ultraviolet light applied locally to skin was used to treat a variety
of infectious diseases, including erysipelas,  which had a  10$ fatality rate
until  UV  therapy  appeared  (Licht  1983).    The  advent  of  sulfones  and
antibiotics supplanted  UV  therapy, which  has virtually  disappeared  from the
infectious disease armamentarium.

     As  Finsen  astutely  observed after his  discovery  of  the  promotion  of
sunburn by UV, "What is more natural than  that chemical rays should  exert an
injurious influence upon a diseased skin, when we see such severe inflammation
produced  by  their  influence upon the  healthy skin?"  (Finsen 1901a).   The
infectious'diseases that are likely to be affected by UV are of two types.

TYPES OF INFECTIOUS DISEASES WITH CUTANEOUS INVOLVEMENT

     Infections that have severe cutaneous pathology,  damaging the skin, are
listed in  Table  1.   The  effect  of  ultraviolet light on the  progression  of
disease has been documented for five of these.

     But perhaps of more  concern  to  us  here are  those infectious agents for
which the  skin-associated  lymphoid  tissue  is  the  first encounter with the
host's immune  system  (Table 2).   These  diseases  have a  primary  cutaneous
phase,  often  asymptomatic,   during   which  protective  immunity to  later
infections can  develop.   Such  diseases are of particular  concern,  because
antigens that reach  the immune system via  skin  that has been UV-B irradiated
not only escape the  immune surveillance  system  of  the  skin,  but also  can make
the host tolerant  to later exposure to the  same antigens (Kripke 1984; Elmets
et al.  1983).   For most  of the  diseases with a primary cutaneous phase, the
development of  cell-mediated  immune  responses  is necessary for  protection.
Other  papers  in  this  volume  show  that  cell-mediated  immunity  is  more
critically affected by UV-B.

MODEL FOR UV-B ACTION ON AN INFECTIOUS DISEASE:  LEISHMANIASIS

     As a model for  the effects  of UV-B  on  infectious  disease,  let us turn to
leishmaniasis in the mouse.  Leishmania have an initial cutaneous phase, which
can  be asymptomatic and  precede more serious  sequelae; and they also cause
skin ulcers (Tables 1 and 2).

     The leishmaniases  are a spectrum of  diseases,  caused by  members  of the
genus Leishmania,  which are obligate  intracellular protozoan parasites living
with macrophages and monocytes.   Paradoxically, for Leishmania to survive  in
the body, they must be ingested  by macrophages, whose function normally is to


                                      102

-------
       Table  1.  Infectious Diseases With  Severe Cutaneous  Involvement
      Disease
    Onchocerciasis

    Leishmaniasis

    Lupus vulgaris

    Hansen's disease

    Mycobacterial
      skin ulcers
  Etiologic Agent
Classification
Onchocerca volvulus

Leishmania species

Mycobacterium tuberculosis

Mycobacterium leprae

Mycobacterium ulcerans


Streptococcus pyogenes

Measles virus

Varicella-zoster virus

Herpes Simplex Type II

(Variola virus)
Nematode

Protozoan

Mycobacterium

Mycobacterium

Mycobacterium


Bacterium

Virus

Virus

Virus

(Virus)
    Effects  of the UV  light on progression  of disease have been  documented.
    *n  early studies  before ca.  1935,  broad-spectrum UV  -light sources  were
    shown  to  affect  smallpox,  lupus vulgaris,  and  erysipelas (reviewed  by
    Licht  1983),   Because  such sources emit UV-A and UV-C  as well as  UV-B,
    their  effects cannot be attributed  to  UV-B only.  More  recent  studies  on
    herpes and  leishmaniasis used  lamps  emitting  UV-B only.
       invading microorganisms.   The parasites are  transmitted  from host  to
     by phlebotomine  sandflies,  which  deposit the  Leishmania  in  the  upper
      of the  dermis or  in  the epidermis.   Phlebotomine  proboscides are  too
      to penetrate protective  clothing,  so that sandflies must  feed on exposed
Khi  M°sfc  infecfci°ns witn Leishmania species  lead to self-healing skin ulcers,
^ei    leave tne  patient permanently scarred but immune  to  reinfection with
Son  ed  species of Leishmania.   However, more serious  sequelae are noted  in
SFOH ^ot%ms  °^ leishmaniasis.   In  chiclero's ulcer, the entire ear pinna  can  be
OM  ^  awav? *n  roucocutaneous leishmaniasis, parasites  metastasize from the
le Sinai skin lesion  to the mucocutaneous junctions.   These severe mutilating
i>ec  ns  do not heal  spontaneously,  and they occur on parts  of the body that
  elve  high amounts of UV-B  in  sunlight  (Urbach' 1969).   A primary skin ulcer
                                     103

-------
         Table 2.   Infectious Diseases  With  a  Primary  Cutaneous Phase


    Disease	Etiologic Agent	Classification	.

    Schistosomiasis         Schistosoma species          Trematode

    Leisnmaniasis           Leishmania  species           Protozoan

    African sleeping        Trypanosoma brucei           Protozoan
      sickness                subspecies

    Chagas' disease         Trypanosoma cruzi            Protozoan

    Yaws                    Treponema pertenue           Spirochaete

    Hansen's disease (?)    Mycobacterium leprae         Mycobacterium

    Cutaneous diphtheria    Corynebacterium              Bacterium
                              diphtheriae

    Bubonic plague          Yersinia pestis              Bacterium

    Anthrax                 Bacillus anthracis           Bacterium
 | -    -•--__      	 ._....    	    -II	1--!----".  ......   		   	 	  II- 'I-                  ^^—^^^

does  not  always precede  the onset of  the  most fatal  form of leishmaniasis,
kala-azar,  in  which  the  Leishmania   invade  the  entire  reticuloendothelial
system.    Kala-azar  smoulders   for years   in  endemic  foci,   to  erupt   into
fulminating epidemics in  times of migration, famine, and war.

     Leishmanial  disease  occurs  on  every continent  except Australia  and
Antarctica.  There  are at least four different  species causing human disease
in the Old World,  and at least  three  in the New World.All Leishmania species
can cause  skin ulcers,  but  only some of them can cause more severe disease i"'
immunogenetically  predisposed  individuals.    Yet  because  not  all   infected
persons in groups  at high  risk for serious sequelae  develop  severe disease)
other factors are probably  involved.   In countries endemic for leishmaniasis,
skin is naturally exposed both to the bites of infective sandflies and to  UV-B
in sunlight,  which  is known  to depress the functions of  the  skin-associated
lymphoid  tissue.    So  it   seemed  likely   that  early  immunological  events
occurring  in the skin could critically  determine the outcome of infection  wit11
Leishmania.

     In a  series of experiments designed  to evaluate the  effects  of UV-B on
the development  of  cutaneous leishmaniasis  in mice (Giannini  1986),  I  found
that local irradiation of the injection site with low doses of UV-B around the
time of initial  infection indeed affected  lesion  development (Figure 1).   Th*
doses used were not high enough to cause sunburn,  but were about the amount of
UV-B  in an hour's  exposure  to sunlight in the semitropics  on  a bright day a*.
noon.    Surprisingly,  lesion  severity  was  reduced  in the  irradiated  mice
(Giannini  1986).  .The main  targets of the  UV-B  were host  cells,  and  not
Leishmania, because the parasites were present in the skin and in vitro in the
                                      101

-------
                            Nodule
Small
Ulcer
Expand.
 Ulcer
 Metast.
Tall Loss
Death
           
-------
same  numbers  in both  irradiated and  control  groups  (Tables  3 and  4).   But
despite their  apparently healthy skin,  the irradiated mice had  parasites at
the injection  site  and in their local lymph nodes  (Table  5).   When they were
tested  for   their   ability  to  mount   cell-mediated  immune  responses  to
leishmanial  antigens,   the  UV-B  irradiated  mice   had  almost  no  immunity,
compared with  the  unirradiated  control  mice  (Table 6).   Their  lack of cell-
mediated immunity  reduced the irradiated  mice's  ability to control  a second
challenge  infection  in  a  skin site  different  from  that  of  their  first
exposure, which had been  irradiated  (Figure 2).   Since Leishmania may persist
in the  local  lymph  nodes, long  after  skin lesions  have healed,  and even when
parasites cannot be detected in  the skin (Hill,  North, and Collins 1984; Titus
et al.  1985;  Giannini,  unpublished),  it  is  possible that  depression of the
host  immune  response by  other  factors  such  as stress  or  impaired nutrition
could   put   the  infected,  though  asymptomatic,   individual  at   risk  for
disseminated disease from the parasites lingering in the lymph nodes.

     A similar suppressive effect of UV-B on  cell-mediated immunity to herpes
simplex  Type  II  virus  has  also been  shown  (Hayashi and  Aurelian 1986).
Exposure  to  UV-B   during  the  primary   phase  of   infection  suppresses  the
development of cell-mediated immune responses to the virus (Howie, Norval, and
Maingay  1986),  and  irradiation  of healed skin  lesions  triggers  recurrent
herpes infections (Wheeler 1975;  Blyth et al.  1976).

     From these and other data we can conclude that local perturbations in the
functions of  the  skin-associated lymphoid  tissue during cutaneous  infections
can profoundly  influence the  immunological response to antigens of  invading
microbes and the subsequent development of clinical disease.

PREDICTED ALTERATIONS IN PATTERNS OF INFECTIOUS DISEASES IN HUMANS
FOLLOWING INCREASED SOLAR UV-B RADIATION

     If the immune functions of  the  skin cannot be  protected from the effects
of  UV-B by  the  use  of sunscreens  (Mentef*  this   volume),  then  it may  be
difficult to avoid  exposure  to UV-B, especially in  agricultural  societies in
the tropics and semitropics, where heat  makes protective clothing impractical
to wear.

     Increases  in the  amount of  solar UV-B reaching the earth's surface will
likely  affect  the  severity of infectious disease.   More  precise predictions
are not possible,  because wavelengths and dosages will  critically  affect the
response  curve.    In  addition,   the  global  effects  of  UV-B include  other
environmental  factors  that  impact  on disease  development,  such as  climate,
vector  density,  and food  availability.    It  is probable  that some cutaneous
infectious diseases will be exacerbated by increased UV-B radiation, as is the
case  with  smallpox and  herpes.    In  other  cases,  pathogenesis  of cutaneous
disease  may be suppressed,  such as  in  cutaneous  leishmaniasis  and  lupus
vulgaris.
                                      106

-------
Table  3.  Growth  and  Viability  of  Leishmania
          Macrophage-Like Cells In Vitro
                                       in  UV-B  Irradiated
         mJ/cm2    Leishmaniaa    Host cellsa    Leishmania      Log10 viable
         UV-B     per  host cell   per  0.06 mm2   per 0.06 mm2    parasites3
          15
          5
          1.5
          0.5
          none
3.6 ± 0.4
3.3 ± 1.1
3.3 ± 0.6
3.0 + 0.5
3.5 + 1.0
17
50
45
61
43
10°
21
16
16
16
 61
164
150
183
150
4.5 ±
5.2 +
4.3 ±
5.2 ±
5.0 +
   Means  +  standard  deviation  of  four  J774A.1  host  macrophage-like  cell
   cultures; numbers  of viable parasites were determined by an in  vitro assay
   system   described   in  Giannini  (1985);  no  significant  differences   in
   viability or numbers  of  Leishmania per host cell were  seen.

   Calculated by multiplying  the  mean number of Leishmania per host cell times
   the mean number of host  cells  per 0.06 mm  .
      4.  UV-B  Irradiation In  Vivoa  Does Not Reduce  Viability  of Leishmania
         major"  in Skin at Injection Site
         Experiment

             1

            2
       Time Post
       Infection

         3.5 mo.

         9 mo.
                                           Log viable amastigotes
                                       per 15  ul  of triturated skin
   15 mJ/cm  UV-B

      3.3 ± 3.2

      8.5 + 2.6
                Shielded Controls   g

                  1.3  ±  1.5     n.s.

                   8.0  +  3.1     n.s.
  Groups of 4-8 B10.129  (10M) mice were irradiated with 15 mJ/cm2 1IV-B on the
  tails 24  hours  before and 24  hours after  infection  with 1  x 10^ (Expt.  1)
  Or  1  x 106  (Expt.  2)  L. major  promastigotes,  and subsequently irradiated
  every 48 or 72 hours for 4 weeks.  See Giannini (1986) for further details.

  Determined  by culturing  serial tenfold dilutions  (described  in  Giannini
  1985).
                                     107

-------
Table  5. Effects  of  UV-B  Irradiation  on  Lesion Development  and  Parasite
          Dissemination at 6 Months Post Infection3 With Leishmania Major


Lesion pathology index
Infected injection site
Infected local lymph nodes
Infected spleen
Infected skin distal to
Controls
4.2 + 0.4
100?
100?
89?
33?
Irradiated
2.1 + 1.4
100?
100?
67?
33?
       injection site
a  Only  lesion  pathology  index  was significantly  different between  the two
   groups.

   See Table  4,  footnote  a,  for methods, and  footnote b for  explanation of
   lesion pathology index (from Giannini 1986).
                                      108

-------
Table 6.  Cellular Immune  Responses  of UV-B  Irradiated Micea,  Infected  with
          Leishmania  major, After Challenge with Leishmanial Antigens13
          Time post
          Infection
          hrs
Treatment
Footpad Thickness0
    (mm x 10 ~2)
 4 hrs       24 hrs    48
          2 weeks
          6 weeks
                          Uninfected controls
                          Unirradiated
                          UV-B irradiated
                          Unirradiated
                          UV-B irradiated
                     12C
                                8
                               25C
                               11
         11
                    12C
I8d
 0
   4 to 5 B10.129 (10M) mice per group were  irradiated  with 15 mJ/cm"& on the
   tails 24 hours before  and 24 hours after  infection  with 1  x  10°  L.  major
   promastigotes,  and subsequently  every  48 or 72  hours  for 4 weeks.

   Mice were challenged in the left rear footpad  with 10   yl   containing 2 x
   10& promastigotes, solubilized by  freezing and thawing in  PBS.   The right
   rear footpad was  injected with 10  yl    PBS.

   Thickness of left footpad minus  right  footpad.   Median values  are given
   because  lesion  pathology  (and   therefore  the  mice's  responses) are  not
   normally distributed (see Figure 1).

   Significantly different from the primary response of  uninfected controls (p
   < 0.05).
                                     109

-------
     (0   -***
     UJ   30
o tail infected and irradiated
  challenged in ear
• tail shielded and infected
  challenged In ear
• tail untreated
  challenged in ear
                       4   6   8    10   12  14   16   18   20   22
            Hrs                       Weeks
     Figure  2.   Abrogation  of Protection  to a  Challenge  Infection  by  UV-B
Irradiation  of the Primary Site of  Infection with Leishmania major.  Mice were
irradiated or  shielded and infected in the tail,  as described in the legend to
Figure 1.  At  two weeks after the primary infection in the tail, mice received
a large challenge  infection  in the ear (1  x 10"  parasites).  Expansion of the
secondary  lesions  in the  ear  in  previously  infected mice  was compared  with
that in mice  not  previously exposed to L. major,  for  which the  ear  was the
primary injection  site.    The previously  infected,  shielded controls  had
significantly  smaller lesions in response to  the  challenge infection than the
unexposed  controls,  at  all times between 4 and  18 weeks, while the responses
of  the  previously  infected, irradiated controls  were indistinguishable  froffl
the unexposed  controls at all times.
                                    110

-------
     But we do well to remember that escape from overt skin disease may  have a
     price, namely, forfeiture  of protective immunity to microbes that  escape
     immune  surveillance   network  in  the  skin  while  its  functions   are
 inactivated by UV-B.

 ACKNOWLEDGMENTS

     This work was  supported  by Public Health Service Grant AI 18937 from  the
 National Institutes of  Health.   I thank  Dr.  Edmond A.  Goidl for many helpful
 discussions, and Ms. Susie Mathews for expert technical assistance.

 REFERENCES

 Blyth,  W.A., T.J. Hill,  H.J.  Field,  and D.A.  Harbour.  1976.  Reactivation of
     herpes  simplex  virus   infection  by  ultraviolet  light  and  possible
     involvement of prostaglandins.  J. Gen. Virol.  33:547-50.

 De Fabo, E., and F. Noonan.  1986.  Urocanic acid  and  its role in the  immune
     response.   This symposium.

        C.A.,  P.R. Bergstresser, R.E. Tigelaar,  and J.W. Streilein.  1983.  In
     vivo  low  dose UV-B  irradiation  induces  suppressor  cells  to  contact
     sensitizing agents.   In The effect of ultraviolet radiation on the  immune
     system, ed.  J.A.  Parrish, 317-33.   Skillman,  New  Jersey:   Johnson &
     Johnson Baby Products Company.

 Finsen,  N.R.     1901a.     The  chemical  rays  of   light  and  smallpox.    In
     Phototherapy. 1-36.   London:  Edward Arnold.

 pinsen, N.R.  1901b.  The treatment of lupus vulgaris by concentrated chemical
     rays.   In  Phototherapy.  73-75.   London:   Edward Arnold.

 Giannini,   M.S.H.     1986.     Suppression   of   pathogenesis  in   cutaneous
     leishmaniasis by  UV irradiation.  Infect.  Imroun. 51:838-43.

Giannini, M.S.H.   Cutaneous leishmaniasis:  A lymphatic  infection.   Manuscript
     submitted.

Giannini,  S.H.    1985.    Induction  and  detection  of  leishmanial infections  in
     Rattus norvegicus.   Trans.  Roy.  Soc.  Trop. Med. Hyg.  79:458-61.

         Y., and  L.  Aurelian.   1986.   Immunity  to herpes simplex virus type
     2:    Viral   antigen-presenting   capacity  of  epidermal   cells   and  its
     impairment  by ultraviolet irradiation. J. Immunol.   136:1087-92.

    , J.O., R.J. North, and  F.M.  Collins.   1984.   Advantages of measuring
     changes  in  the  number   of  viable  parasites  in  murine  models   of
     experimental cutaneous leishmaniasis.  Infect.  Immun.  39:1087-94.

Howie,  S.,  M. Norval,  and J.  Maingay.   1986.   Exposure to  low-dose  ultraviolet
     radiation  suppresses   delayed-type   hypersensitivity  to  herpes   simplex
     virus  in mice.  J.  Invest.  Dermatol.  86:125-28.
                                     111

-------
Kripke, M.D.    1984.   Imraunological  unresponsiveness  induced by  ultraviolet
     radiation.  Immunolog.  Rev.  80:87-102.

Licht, S.   1983.  History of ultraviolet  therapy.   In  Therapeutic Electricity
     and  Ultraviolet  Radiation.    3rd  ed.,   ed.  G.K.  Stillwell,    174-93.
     Baltimore:  Williams &  Wilkins.

Schulze, R.  1970.  Global radiation  climate.   Wiss.  Forschungsber.  72:1-220.

Titus, R.G.,  M. Marchand, T. Boon,  and J.A.  Louis.   1985.   A limiting dilution
     assay for quantifying  Leishmania major  in  tissues  of infected  mice.
     Parasite Immunol.   7:545-55.

Urbach, F.    1969.   Geographic  pathology of  skin cancer.   In The  biologic
     effects  of  ultraviolet radiation  (with  emphasis  on  the  skin),  ed.  F.
     Urbach,   635-50.   Oxford:   Pergamon Press.

Wheeler,  C.E.,  Jr.     1975.    Pathogenesis  of  recurrent  herpes   simplex
     infections.  J. Invest. Dermatol.  65:341-46.
                                      112

-------
Urocanic Acid: On  Its Role in the Regulation
of UVB-lnduced Systemic  Immune  Suppression

Edward C. De Fabo and Frances P. Noonan
The George Washington Univeristy Medical Center
Washington, DC USA
ABSTRACT

    We have previously  postulated that UVB-induced  systemic immune suppres-
3ion  is  mediated  by a  specific skin photoreceptor  situated  in  the  stratum
°°rneum  of  mammalian  skin.    This  photoreceptor   is  considered  to  be a
biological signal transducer capable of converting UV-B radiation (290-320 nm)
directly  into  a  biochemical  signal  that then  "switches-on" formation  of
antigen-specific  suppressor cells by  way  of  an   "alteration"  in  antigen
Presentation.

    The  UVB-absorbing  photoreceptor  is  tentatively  identified  as  trans-
        acid (trans-UCA).   The mode of immune regulation associated  with it
 s suggested to be initiated by photoconversion  to  its cis isomer (cis UCA).
R«cent evidence is presented to support this  concept showing that cis UCA in
Contrast to trans-UCA can induce an antigen-presenting "alteration" in splenic
Dendritic cells in the absence  of any UV radiation.

    A model is presented outlining a mechanism in which  UCA-initiated immune
^Ppression  is  involved with  the prevention of  autoimmune  attack  against
 Photoantigens" associated  with sun-damaged skin.  We propose that sunlight-
Educed  skin tumor  outgrowth  may  be an inadvertent  consequence  of  this
n°rmally protective mechanism.

PRODUCTION:  UCA AND IMMUNE SUPPRESSION

    Urocanic  acid  (UCA,   de-aminated  histidine)  is a  major UVB-absorbing
compound located  in  the  stratum corneum.   The naturally occurring form is the
     isomer; it  isoraerizes to  the cis form on absorption  of UV-B radiation.

    Although the existence of UCA has been known  for  more  than  100 years
       1974),  no  physiological function  for it  has ever  been established.
    ermore, even though UCA can attenuate  ultraviolet (UV) radiation striking


                                   113

-------
 the  skin of  mammals,  in  effect acting  as  a photoprotector  of DNA  or as  a
 sunscreen  protecting against erythema,  it  may be  playing  a more  fundamental
 physiological  role  as  an  immune-regulating  skin photoreceptor  (De Fabo  and
 Noonan  1983).  We discuss  the evidence supporting this  idea  in  this paper.

 BACKGROUND

     The ability of  UV  radiation to suppress a variety of immune responses in
 animals  and  humans has  been  well documented and  reviewed  (Kripke and  Fisher
 1976;  Fisher  and Kripke 1977;  Morrison  1984;  Parrish,  Kripke,  and Morrison
 1984;  Daynes  and  Krueger  1983).  It has  been shown that UV-B  (290-320  nm)  is
 responsible for suppressing the  immunologic rejection response  to transplanted
 UV-induced tumor (De Fabo  and Kripke 1979, 1980).

     Another  major  UV-B  effect on  immunity is  its ability to  suppress  the
 delayed-type hypersensitivity (DTH) response  to skin sensitizing antigens such
 as trinitrochlorobenzene (TNCB)  in  mice  (Noonan, De Fabo,  and  Kripke,  198la,
 198lb).   In  this  reaction mice  that  have  been pretreated  with  UV radiation
 show a systemic suppression of the DTH response.  We previously showed that it
 was energy  primarily in the  UV-B band that  can diminish the  DTH response  in
 dose-dependent fashion  (Noonan,  De  Fabo,  and Kripke 198la).   The kinetics  of
 this response  was  similar  to the UVB-induced suppression of  tumor rejection
 (De Fabo and Kripke  1979,  1980).

     In further studies on the systemic suppression of DTH which were designed
 to  elucidate  the   first  light-absorbing   event  a   relative   wavelength
 effectiveness  or  "action"  spectrum  of  this  effect  by  UV  radiation   was
 estimated.    The  significant  finding of this  study was  that radiation   of
 wavelengths between  320 nm and  250  nm  (UV-B  and  UV-C) exhibited differing
 effectiveness in suppressing the DTH response.  This clear-cut differential  in
 wavelength effectiveness suggested  that  a  specific molecule,  i.e.,  a "UVB-
 transducing" photoreceptor was absorbing  this radiation and  using it to "turn
 on" an  immune suppressor response to the skin  sensitizing  chemical antigens.
 We suggested  this  mechanism might  exist  to "down  regulate"  the rejection
 response against new "photoantigens" put on skin cells by exposure to the UV-B
 component of sunlight.   In effect this  suppression  would prevent uncontrolled
 autoimmune attack  against sun-damaged  cells (De Fabo  and  Noonan  1983).   We
 found the shape of the action spectrum closely matched the absorption spectrum
 of UCA  (De Fabo  and Noonan 1983).  Because of the  close  match  between our  in
 vivo derived action  spectrum and  the  in vitro absorption spectrum of urocani°
 acid,   we  suggested  that  trans-UCA  may  be  acting  as  the  UVB-absorbing
 photoreceptor initiating events leading to immune suppression of  DTH (De Fab<>
 and  Noonan   1983).     Furthermore,  because  of  close  photobiological  and
 immunological similarities to the suppression of tumor rejection,  we suggested
 that  perhaps this suppressive response  to transplanted  UV-induced skin tumors
might also involve UCA (De Fabo  and  Noonan 1983).

UCA AND SKIN CANCER:  A POSSIBLE LINK

     One of the major puzzles about skin  cancer  is  that nearly all UV-induced
 skin   tumors   in  mice  are  highly antigenic  and  capable of   evoking  strong
 immunologic rejection responses  by  the  host.  Thus,  it is unclear, given the
 strong immune response against these tumors,  how  they are able  to grow out  *-n
 the host.
                                      114

-------
    E
    p
    I
    D
    E
    R
    M
    I
    S
            *,+
         hv                     systemic
!  t-UCA 	> c-UCA	>	>-	->	>  ANTIGEN
!                                circulation          PRESENTING
!                                                     CELL DEFECT
!
         *,+
!       hv
!  DNA	 MALIGNANT	+
I            TRANSFORMATION
                                      TUMOR —
                                   ASSOCIATED
                                    ANTIGENS
   Anti gen-1
An t i gen~2		•• >

              '•• i
       	  ..• i
                                 Tolerance to
                               tumor-associ ated
                                    antigens
                                                           V V
                                                    Tolerance to
                                                        antigens
       wavelengths are  identical  for activating  both systems
       U.JVB/C:  320-250  nm)
      + IJVB/C -flux is  low for UCA activation;  high for DNA
        transformation.
      t-UCA  = trans isomer;   c-UCA = cis isomer
      T-s  s   Suppressor  T cells specific only  for antigen
        1                                                    1
      T-s  :   Suppressor  T cells specific only  for antigen
        2                                                    2
      T-s  5   Suppressor  T cells specific, only  for tumor—associated
       tumor   antigens
     Figure 1.  Induction of Tolerance to Tumor-Associated Antigens.  In this
tt.  -* a scheme is presented to include  the  production  of a  tumor cell with
w yOr-associated antigens."   This  is  formed when high  doses of radiation of
lean   gtns 250-320  nm  cause a malignant transforming event in  DNA.   This
are   tO  the  formation  of a neoplastic  cell.   Associated with this neoplasm
UCA   ^~*nduced antigens.  We  suggest that these antigens interact with the
^e "induced antigen-presenting  cell alteration  in a  manner  that  eventually
sf    to  the  production of antigen-specific suppressor T cells.   In the case
"tuif *'umor cell, however, the suppressor  cells formed  are  specific  for the
^unior-associated antigens."    Formation of  these suppressor  cells  leads  to
Outeran°e  (acceptance)  of  the tumor  cell  instead  of  rejection.    Tumor
   8»*owth is the final consequence.
                                   115

-------
     One  possible  explanation  may   involve  an   interaction  between  immune
suppression mediated by UCA and  tumor  formation mediated by UV effects on DNA
(De  Fabo  and Noonan  1984).   Figure  1  presents  a  scheme  for  this  type of
interaction.

     As  previously  noted,   the  underlying  immunologic   problem  in  mice
irradiated  with UV-B  appears  to be  an  alteration  or  "defect"  in  antigen
presentation (Greene et al. 1979; Noonan et al.  1981).  It seems that, because
of  this "defect",  antigen-specific  suppressor  cells,  rather than  effector
cells,  are  formed  when antigen  is  given to a   UVB-irradiated  mouse.   The
hypothesis we  put forward  is  that UCA  may interact  with  antigen-presenting
cells, e.g., macrophages,  skin Langerhans cells,  or splenic dendritic cells in
such a way as to make defective  their presentation of antigen to stimulator T
cells.  This process we propose is initiated by  photoisomerization of trans-
UCA  to its  highly  soluble cis  form.    Once  formed,  the cis  isomer  or  a
secondary intermediate would interact  with antigen-presenting  cells in such a
way as  to alter their  capacity to present antigen.   This "defect" in antigen
presentation  (or  processing)  would  become  the  signal for  stimulation  of
suppressor  cells  rather  than  effector  cells.     The  specificity  of  the
suppressor cells would  be  determined  by the type  of  antigen presented to the
"defective" antigen-presenting cell (De Fabo and  Noonan 1983).

     This hypothesis has  received strong  support from  the  observations that
(a) injection of cis UCA into mice induces an antigen-processing alteration in
splenic dendritic cells  without  UV   radiation;   injection  of trans-UCA was
without effect  (Noonan, De Fabo,  and Morrison 1986)  and (b) mice genetically
deficient in histidase and  thus  in epidermal UCA  showed no  suppression of the
CHS response when exposed to known immunosuppressive doses of UV-B (De Fabo et
al. 1983).

     In  conclusion,  it  appears  that a  mechanism exists   in  skin that can
directly bring about interaction between solar UV-B and  the immune system in
a way  previously unknown.   Further  investigations into  such  a mechanism may
open up new directions  for determining the causes of skin cancer and other UV-
B immune-associated diseases.

SUMMARY

     For many years  the physiological role for UCA has remained  obscure, al-
though  a  relatively large amount  of  this substance, in  the  trans  con-
figuration,  accumulates in mammalian epidermis.   UCA has been suggested to act
in  the skin  as  a natural  sunscreen.    Alternatively,  we  have proposed  a
physiological  role  for  trans-UCA  as  a  UVB-absorbing  skin  photoreceptof
necessary to regulate against autoimmune attack on sun-damaged skin.   In this
capacity,  trans-UCA is converted to the  cis isomer that can then initiate the
production of antigen-specific suppressor  cells via an alteration in antigen-
presentation.   Thus, during  prolonged sun exposure, suppressor  cells form,
which  are  specific for "photoantigens"  induced  on  sun-damaged  skin.   These
suppressor cells  can prevent effector cells  from carrying  out an autoimmune
attack against these "photoantigens."

     Because such a mechanism exists,  UCA  may be  involved in the outgrowth of
sun-induced skin  tumors,  inadvertently protecting tumor  cells from attack by
effector cells.    That  is,  due  to  the production  of  these  "photoantigen"-


                                      116

-------
specific suppressor  cells  that also recognize UV-induced  antigens on tumors,
tumor  growth  continues  and the  concentration  of  these  UV-induced antigens
steadily increases, keeping primed the production of specific suppressor cells
(Figure 1).  Without reversing  this  process,  immune surveillance of the tumor
(attack and destruction) will  be  prevented and  tumor outgrowth  will  be the
final outcome.


REFERENCES

°aynes,  R.A.,   and  G.   Krueger,  eds.     1983.    Experimental  and  clinical
     photoimmunology.  Vol  II.   Cleveland, OH:   CRC Press,  Inc.

De  Fabo,  B.C.,  and M.L.  Kripke.    1979.   Dose-response characteristics  of
     immunologic  unresponsiveness   to   UV-induced   tumors  produced   by  UV
     irradiation of mice.  Photochem. Photobiol.   30:385-390.

De Fabo, E.C.,  and M.L. Kripke.   1980.   Wavelength dependence  and dose-rate
     independence   of   UV   radiation-induced   suppression   of   immunologic
     unresponsiveness  of  mice  to   a  UV-induced  fibrosarcoma.    Photochem.
     Photobiol.   32:183-188.

^e Fabo, B.C.,  and P.P. Noonan.   1983.    Mechanism of immune suppression  by
     ultraviolet radiation  in   vivo.   I:   Evidence  for  the  existence of  a
     unique photoreceptor  in skin  and its  role  in photo immunology.   J.  Exp.
     Med.   158:84-98.

De  Fabo,   E.G.,  and  P.P.  Noonan.     1984.     Two-photoreceptor  model  for
     photocarcinogenesis.   In   Photobiology.  1984.   Proceedings  of the  Ninth
     International Congress on  Photobiology. eds. J. Jagger,  J.  Longworth,  and
     W. Shropshire, J.,  144. New  York:   Praeger  Scientific.

De  Fabo,  E.G.,  F.P. Noonan,  M.  Fisher,  J.  Burns,  and  H.  Kacser.    1983.
     Further  evidence  that  the photoreceptor mediating  UV-induced  systemic
     immune suppression is  urocanic  acid.  J.  Invest.  Dermatol.   80:319.

pisher, M.S.,  and M.L.  Kripke.   1977.  Systemic  alteration induced in mice by
     ultraviolet  light  irradiation  and   its   relationship  to   ultraviolet
     carcinogenesis. Proc. Natl.  Acad. Science USA.   74:1688-1692.

Greene, M.I.,  M.S.  Sy,  M.L.  Kripke,  and  B. Benacerraf.  1979.   Impairment  of
     antigen-presenting cell function by ultraviolet radiation.   Proc.  Natl.
     Aoad.  Sci.  USA. 76:6592-6595.

       M.   1974.  Concerning a  new constituent  of dog urine.  Ber. Deut.  Chem.
     Ges.   7:1669-1673.

Kripke, M.L.,  and  M. Fisher.   1976.  Immunologic  parameters of ultraviolet
     carcinogenesis. J. Natl.  Cancer Inst.   57:211-215.

M°rrison,  W.L.  1984. Photoimmunology.  Photochem. Photobiol.  40:781-787.
                                     117

-------
Noonan, P.P., E.G.  De  Fabo,  and M.L. Kripke.   198la.   Suppression of contact
     hypersensitivity  by  UV  radiation  and  its  relationship to  UV-induced
     suppression of tumor immunity.  Photochem. Photobiol.  34:683-690.

Noonan, P.P.,  E.G.  De  Fabo,  and  M.L.  Kripke. 198lb. Suppression  of contact
     hypersensitivity  by  ultraviolet  radiation:    An  experimental  model.
     Springer Seminars in Immunopathology.   4:293-304.

Noonan, P.P., E.G. De Fabo, and  H.  Morrison.   1986.   Cis-urocanic acid, a UVB
     irradiation  product,  initiates  an  antigen  presenting  cell  defect  in
     vivo.  Photochem.  Photobiol. 43 supp:l8s.

Noonan, P.P., M.L. Kripke,  G.M.  Pedersen, and M.I. Greene.  1981.   Suppression
     of  contact  hypersensitivity  in  mice  by  ultraviolet  irradiation  is
     associated with defective antigen-presentation.   Immunology.   43:527-533'

Parrish, J.A., M.L. Kripke, and  W.L.  Morrison, eds.   1984.   Photoimmunologyj.
     New York:  Plenum Medical Book Company.
                                      118

-------
Solar Wavelengths of Ultraviolet Light-
Induced Cytoplasmic Damage

Glen Zamansky andlih-Nan Chow
Boston University School of Medicine
Boston, Massachusetts USA
    Since  solar  ultraviolet  (UV)  light  is  the major cause of  human  skin
°ancer,  it  is important to  determine  the UV-induced  cellular  lesions  that
c°ntribute  to the carcinogenic process.   The  majority  of  investigations  have
examined  DMA  damage  resulting from exposure  to  short  wavelength  UV  light.
This has  led to the suggestion that pyrimidine dimers are  the critical lesion
Responsible for solar  carcinogenesis.   However, people are  not exposed to such
short wavelength UV light, because it  does not penetrate the. atmospheric ozone
laver.   There  is  evidence that cellular lesions  other  than pyrimidine dimers
^e involved  in  the  carcinogenic, mutagenic,  and lethal effects of UV light
cnat reaches the earth's surface.  However, alterations  of non-DNA targets in
*annnalian cells  caused  by  UV  have received  little  attention.   Because  the
cytoskeleton is an important participant in the control  of normal cell growth
and because epigenetic events may play a role in carcinogenesis, we have begun
 0 explore  the  induction of  cytoskeletal alterations induced  by UV light in
   n skin  fibroblasts.   We have been particularly interested in the effects
   irradiation  with  polychromatic  UV  light  composed  of  environmentally
         wavelengths.    Our  data indicate that  exposure  to  germicidal  UV-C
     results  in  no discernible changes  in the  cytoskeletal  organization as
      d  by fluorescence microscopy.  However,  exposure  to polychromatic  UV-B
and UV-A light causes severe injury  to the cytoskeleton.

^RODUCTIOM

    Epidemiological   and  experimental   evidence   has  established   solar
 :;tpaviolet (UV)  light as the major  cause  of human skin cancer.  More than
Q
   non-melanoma cutaneous  tumors  appear to result from exposure to sunlight.
        deal of effort has therefore been expended  trying  to elucidate  the
          by which UV light induces  the  transformation of normal cells  to  a
         phenotype.   The  vast majority of investigations have been performed
     germicidal lamps that emit  primarily  254 nm  light.  Unfortunately,  such


                                   119

-------
short wavelength  UV  light is  environmentally  irrelevant because  it does not
penetrate  the  stratospheric  ozone layer.   The UV  light  spectrum  has been
operationally divided  into three wavebands:  UV-C,  200-290 nm; UV-B, 290-320
nm; and UV-A, 320-400 nm.  The solar spectrum of UV light reaching the earth's
surface is  fairly constant at wavelengths  greater than 320  nm and drops off
precipitously between  320 and 290  nm.   UV-A,  the  least  studied UV waveband,
comprises the  largest  UV component to  which people are exposed.   UV-B light
appears to be responsible for  the  induction of skin cancer.  The contribution
of  interactions  between UV-A  and  UV-B  light  towards  the  development  of
cutaneous tumors remains to be determined.

     Decreases in the concentration of stratospheric ozone,  resulting from the
anthropogenic  release  of  chlorofluorocarbons  and  other  agents  into  the
environment, will significantly increase the levels of carcinogenic UV-B light
reaching the earth's surface.   In a recent report from the National Research
Council, it was  suggested that every '\%  decrease  in ozone  concentration will
result in a 2% to 5% higher incidence of basal  cell carcinomas and a H% to 10^
higher  incidence  of  squamous  cell  carcinomas  (National  Research  Council
1982).  Since it appears that a significant decrease in stratospheric ozone is
likely to occur  during the next century, special  emphasis  needs to be placed
on the adverse  health  effects of increased  exposure  to UV-B light.  Howevert
to attain  an accurate assessment  of  the  potential  health  hazards,  the UV-
induced  .lesions   that  contribute  to  the  carcinogenic   process  must  be
identified.  This paper  explores the possibility that exposure to wavelengths
of UV found in  the environment alters cytoplasmic elements  that are important
in the regulation of cell growth.

     The  cytoplasm  of  eukaryotic  cells  contains  an  intricate network  of
filamentous structures that are  collectively referred to  as the cytoskeletott'
The   three  major   components   of   the   cytoskeleton    are   microtubulesf
microfilaments,   and   intermediate  filaments    (Alberts    et  al.   1983)-
Microtubules are hollow structures consisting primarily of tubulin and have an
outer  diameter  of  22-25 nm.    They  appear   to  originate  at  microtubuie
organizing centers  close to  the nuclear membrane  and extend  throughout the
cytoplasm.    Microfilaments,   composed  primarily  of  F-actin,  are  thinner
filamentous structures having an average  diameter  of 6 nm.   In well flattened
cultured  cells,  microfilaments  are often  found in  bundles,  referred  to  as
stress fibers.   The  diameter  of intermediate filaments, approximately 10 nn»f
falls  between   those  of  microtubules  and  microfilaments.   Inununological  and
biochemical  studies   have  demonstrated   that   the  protein  composition  of
intermediate filaments is very  heterogeneous.   Intermediate  filaments  have
therefore been  grouped into  five subclasses:  keratin (epithelium), vimentio
(mesenchyme), desmin (muscle), glial fibrillary  acidic protein (glial cells)»
and neurofilament proteins (neurons).   Using fluorescence microscopy, we have
investigated alterations of cytoskeletal components induced by exposure to UV'
C light or  polychromatic UV-B and UV-A light  in a human  skin fibroblast cell-
strain .
                                      120

-------
MATERIALS AND METHODS

Cells

     AG  1522,  a human   skin  fibrobast  cell  strain,  was  obtained  from the
Human Genetic Mutant Cell  Repository,  Institute  for Medical Research (Camden,
NJ).  Cells  were  grown in Eagle's minimal  essential medium supplemented with
^Q% fetal  calf  serum,  0.9 g/1  D-glucose,  0.66 mg/1  sodium  pyruvate, 110
u/ml penicillin and  110   yg/ml streptomycin sulfate.  Cultures were incubated
at 37<>c in an atmosphere of 95% air and 5% C02<
     General  Electric  G8T5  germicidal  lamps,  Westinghouse  FS40  lamps,  and
Sylvania FR40T12  lamps were  our  sources  of UV-C,  sunlamp,  and  UV-A light,
respectively.  Polychromatic UV-B and UV-A light sources were selected because
they more closely simulate the type of UV light to which we are exposed at the
earth's surface.   Furthermore,  it has  been demonstrated  that  the biological
sffects of polychromatic  light  frequently do not comprise a  simple composite
°f the  effects  induced by monochromatic  light corrected  for  the appropriate
relative intensities (Suzuki et al. 1981; Wells and Han 1984).  The UV-C lamps
emit greater than 95% of  their  energy  at  254 nm.   The emission spectra of the
Westinghouse FS40 and  Sylvania  FR40T12 lamps, filtered  through plastic petri
dish covers,  are shown  in Figure 1.  The sunlamps transmit approximately equal
Counts of light  in the UV-B and  UV-A  wavebands  with a peak  emission in the
UV-B region between 310  nm and 315 nm.   More than 98% of the  light from the
UV-A lamps  (maximum emission at 350-355  nm) is  in  the UV-A waveband.   UV-C
dose rates were determined with an International Light (Newburyport, MA) IL254
germicidal photometer.    Sunlamp and UV-A  dose rates were determined  with an
international  Light  IL443  photometer  with appropriate  filters  for  the
individual light  sources.   Cultures exposed to UV-C  light were irradiated
without their covers at a dose rate of 0.4 J/nr/sec,  in the presence of Hank's
buffered salt solution  supplemented with 15 mm Hepes (HBSS).  Cultures exposed
to pSunlamp  (approximately 4.5  J/nr/sec)  or UV-A   light (approximately  30
J/nr/sec) were  irradiated, in  the presence  of  HBSS,  through  tfieir  plastic
°overs  in order to  filter out wavelengths shorter than  290 nm.  Sunlamp- and
UV-A treated cultures were maintained  in a  room  temperature water bath during
irradiation.   In order to  protect  cultures  from  ambient UV light, only yellow
iight was used in the laboratory during the course of our experiments.

£y^oskeleton Preparation

     Microtubules and  microfilaments  were  examined using modifications  of
Procedures previously described  (Chou and Shaw 1984;  Wang et al. 1982).  Cells
grown on glass  coverslips  were  washed with a microtubule  stabilizing  buffer,
PH 6.9  (PM2G buffer), that contains 0.1 M  Pipes,  1  mM MgSO^,  2 mM EGTA, and 2
M glycerol.  This buffer condition effectively preserves  microtubules  as well
as microfilaments and  intermediate filaments.    The  cells were fixed  for 30
minutes with 3.7% formaldehyde,  freshly prepared in PM2G  buffer,  followed by
incubation in phosphate  buffer  solution, pH  7.4  (PBS), for 5  minutes.   They
j*sre then treated with 0.1 M Glycine  in  PBS for  5 minutes to quench formalde-
hyde, and extracted with 0.3* Nonidet P-40  (NP40) in PBS for 10 minutes.  All
operations up to this step were  conducted with room temperature reagents.
                                      121

-------

           0
           270    290   310    330   350    370    390   410
     Figure 1.
             WAVELENGTH (nm)

Emission Spectra of Westinghouse FS40 (sunlamp)  and
Sylvania FR40T12 (UV-A)  Lamps.
     The  fixed cytoskeletons  on coverslips  were  incubated  at  37°C for  30
minutes with  a mixture of rabbit anti-tubulin antibodies  and  NBD-phallacidin
to  double   label   microtubules  and  microfilaments,  respectively.     NBD-
phallacidin, a  fluorescent  reagent,  specifically labels F-actin  filaments  of
cultured cells, resulting in a  higher degree  of  resolution than obtained with
indirect  labelling  procedures  using  two  antibodies.    After  the  initial
labelling period,  coverslips were  thoroughly  washed with PBS and  treated for
30 minutes  with goat anti-rabbit antibodies  conjugated  to rhodamine.   After
the 30-minute exposure to rhodamine-conjugated antibodies,  the  coverslips were
again thoroughly washed  with PBS and finally with double-distilled  water  to
remove residual  PBS.   They were then mounted  on glass slides  with a  drop  of
Gelvatol and  allowed  to  harden at  4°C  overnight  before  examination with  a
Nikon fluorescence microscope.   Using coded coverslips,  the percent  of  cells
with intact microtubules and/or microfilaments was determined by examining 200
cells in  randomly  selected microscopic  fields at each UV  dose.   The person
viewing  the  cells was  not  familiar  with the  code used  to  identify  the
coverslips.  Photographs of representative  cells were  taken using  Kodak  Tri-X
film (ASA 400) and  developed by "pushing" to an effective rating of ASA 1600.

RESULTS

     Initial  comparisons  between  cells  irradiated  with  UV-C  and  sunlamps
indicated  that even  at  extremely  toxic  UV-C  doses,  the  microtubules and
raicrofilaments  of  AG1522  cells  remain   intact.    However, we  consistently
observed  disruption   of  microtubular  structures  in  cells irradiated   with
sunlamps.    In  order  to  quantify  this  phenomenon,  we have  performed  dose-
                                     122

-------
response experiments  in which  we estimated  the percent  of cells with  intact
toicrotubules  (Table  1).   Coded coverslips  were used  to  avoid counting  bias.
Because   the  efficiency   of   inducing   erythema,   cellular   inactivation,
toutagenesis, transformation,  and other biological effects usually decreases as
the wavelength  of light  increases,  the  progressively higher  doses at  longer
wavelengths of  light  were selected.   As seen  in Table 1, intact microtubules
were found in cells  irradiated with UV-C doses as high as  100 J/m2.   Exposure
to sunlamps  resulted in  the  disruption  of microtubules,  decreases in  intact
fcicrotubules usually being observed after exposure  to 3000 J/m2.  Experiments
with  UV-A  light  indicated  that it  also  causes  a  dose-dependent  loss  of
organized microtubules.  No perceptible alterations of microfilaments  occurred
*n cells  irradiated  with  UV-C, sunlamps,  or UV-A.   We have previously  found
that the doses required to reduce survival  of AG1522 cells to  "\Q% (as  measured
by colony forming  ability) are approximately 8.2 J/m2 for UV-C,  1180  J/m2 for
sunlamp, and  157  kJ/m2 for  UV-A light  (Zamansky  1986).   The  disruption  of
roicrotubules  therefore  appears  to be induced  by sunlamp  and  UV-A exposures,
which result  in  less cell death than after 100  J/m2  UV-C,  a dose at  which no
effect occurs.
     Table 1.  Disruption of Microtubules by UV-C, Sunlamp, or UV-A Light
j>ose (J/m2)
0
10
20
40
75
100
UV-C
Intact MT (X)*
96.5 ± 0.5
96.0 ± 1.0
96.0 ± 0.5
94.5 ± 0.8
94.8 ± 2.3
91.5 ± 2.5
Sun
Dose {J/m2)
0
750
1500
3000
5000
7500
Lamp
Intact MT (X)*
96.7 ± 0.9
94.3 ± 0.9
89.7 ± 1.3
54.7 t 15.2
37.3 ± 2.8
19.7 ± 9.2
Dose (kJ/m2)
0
50
100
150


UV-A
Intact MT («)
95.8 ± 1.2
83.3 ± 8.3
38.3 ± 3.0
26.5 ± 3.0


    * The percent of cells with intact microtubules is presented as the mean ± 1 standard error of
     2 (UV-C), 3 (sun lamp) or 2 (UV-A) experiments. 200 cells were examined in randomly selected
     microscopic fields of coded coverslips in each experiment.
     The microscopic  appearance of microtubules and  microfilaments in control
    irradiated cells  is shown  in Figures  2A-2F.   As expected, the microtubules
Dr unirradiated  AG1522 cells  (Figure 2A) appear  to emanate  from perinuclear
^icrotubule  organizing  centers and  extend  throughout  the  cytoplasm.   The
intricate network of microtubules  is  also present in cells irradiated with UV-
  (Figure 2C).   However,  distinct microtubules are often completely absent  in
  8  cytoplasm of  cells   irradiated  with sunlamps   (Figure  2E).    Although
reronants  of  the microtubule  organizing center  may  still  be present,  the
^Jority  of  anti-tubulin-stained   cytoplasm   takes   on   a   fine  powdery
?Ppearance.    The extent to  which this occurs  is dependent upon the UV dose.
^Ua»  microtubules  appear  to be  disassembled  or fragmented.  UV-A irradiated
                                      123

-------
     Figure 2.  Microscopic  Appearance  of Microtubules (A,C,E) and MicrofHa'
merits (B,D,F)  in  AG1522  Cells.   No UV light (A and  B),  UV-C,  100 J/m? (C and
D); sunlamp, 5000 J/m2 (E and F).
                                      124

-------
 cells  (not  shown)  have the same  powdery  appearance as sunlamp-treated  cells.
 The microfilaments  of the cells depicted  in  Figures 2A,  2C, and 2E are  shown
 in  Figures  2B, 2D,  and 2F,  respectively.    No  changes were  observed in  the
 microfilaments, which remain quite apparent as distinct actin filament bundles
 stretching across the length of the cells.

 DISCUSSION

     DNA  is  usually  considered  the  critical  site  of UV-induced  cellular
 damage.   Experiments  utilizing  short  wavelength  UV light  have  yielded an
 abundance of  information concerning  the  induction of pyrimidine dimers, and
 the mechanisms by which dimers are removed have become the most understood DNA
 Repair pathways.   However,  the types  and relative  frequencies  of UV-induced
 lesions vary  greatly  for the three wavebands of  the UV spectrum (Cerutti and
 Netrawali 1979; Tyrrell  1982; Han,  Peak,  and  Peak 1984).   Most action spectra
 "or cellular  inactivation correlate well  with the  absorption  spectrum of DNA
 a°d with the  formation  of pyrimidine  dimers out  to 313 nm (Rothman and Setlow
 '979; Kantor,  Sutherland, and Setlow  1980; Jacobson,  Krell,  and Dempsey  1981;
 °oninger et al. 1981; Tyrrell,  Wertelli,  and  Moraes 1984)  supporting the role
 of DMA as the critical target for the lethal effect.   The  action spectra for
 Ration, transformation, cellular  capacity for  viral growth,  reactivation of
 ^-damaged virus, and the induction of virus synthesis in  transformed  cells
 also correspond closely to  the absorption spectrum of DNA  at  wavelengths as
 long as 313 nm (Jacobson, Krell,  and  Dempsey  1981; Doninger 1981; Coohill and
 Jacobson  1981).    These  findings  and the   observation  that  patients  with
 *eroderma pigmentosum (XP) exhibit cutaneous  hypersensitivity to sunlight, the
 Development  of  multiple  malignant  tumors   in  sun-exposed  areas,   and  an
 ^ability to  properly  repair pyrimidine  dimers  (Cleaver  and Bootsma  1975;
 Bobbins  et  al.  1978)  have   led  to  the   suggestion  that  these  lesions  are
 responsible  for  solar  carcinogenesis.     However,  evidence  has  begun  to
 Accumulate that lesions other than pyrimidine dimers may be  involved  in the
 ioo0inogenic»  mutagenic, and  lethal effects of  solar UV light (Zelle  et al.
 ]9oO; Smith and Paterson  1981,  1982;  Suzuki et al.  1981; Zbinden and Cerutti
 19°1; Botcherby et al. 1984;   Wells and Han 1984;   Tyrrell  1984).

 f    We have previously  reported  that  the relative sensitivity of  human skin
 I1broblasts  to  UV-C,  sunlamp  or polychromatic  UV-A  light depends  on  the
 ^position  of  the light to  which they  are  exposed  (Zamansky  et al.  1985;
 ^amansky  1986).   Our  findings suggest   that  the  inability of  XP' cells  to
 Properly remove pyrimidine dimers is of  less importance to cells  exposed to
 Polychromatic, long wavelength  light  and  that no lesion commonly  induced by
 °Ur three UV  light sources  is  likely to  be  solely responsible  for  cellular
 inaotivation.   This agrees well with a recent study by Keyse et al. (1983) in
J»ich monochromatic  UV light was used (1983).    Additional support for  the
 ^toportance of  non-dimer lesions  has  been obtained in studies demonstrating
 wiat  certain   cell   strains   from  patients   with  Bloom's   syndrome,   ataxia
jjeiangiectasia,  and actinic reticuloid  are hypersensitive to  long  wavelength
 v light,  but not  to  254  nm  light  (Smith  and  Paterson  1981;  Zbinden  and
        1981 Botcherby  et al.  1984).   Furthermore, a  lack of  correlation be-
       the  induction  of  pyrimidine  dimers   and   cellular   inactivation,
          i,  and  transformation  has  been noted   in  human   and  rodent  cells
 iQh"""* to uv  Ii8hfc composed of wavelengths greater  than 313 nm (Zelle et al.
 Iyo0;  smith  and Paterson 1981; Suzuki  et al.  1981; Tyrrell  1984).
                                     125

-------
     The  transformation  of normal  cells to a cancerous phenotype is a complex
process that has most often been described as involving two stages:  initiation
and  promotion  (Diamond,  O'Brien,  and  Baird  1980;  Farber and  Cameron  1980).
Current  experimental evidence  suggests that initiation  is  caused  by genetic
damage and that promotion  results  from  epigenetic events.  Because exposure to
promoters  is not  required for  tumor  induction  by  "complete" carcinogens such
as  UV  light, most  investigations  into the  carcinogenic effects of UV light
have  emphasized  its genotoxic capability.     Is  it  likely that  UV-induced
alterations  of  non-DNA targets may contribute  to the  establishment of human
skin cancer?   It has been known  for many years that  solar  wavelengths of UV
light  induce biologically  important  lesions in non-DMA  targets in bacteria.
Several effects due  to  damage of  bacterial membranes have been  studied.  Moss
and  Smith (1981)  have  demonstrated that  membrane  damage contributes  to le-
thality   under   certain   growth   conditions.     Others  have   reported  the
inactivation of membrane  transport systems and  the  inhibition of oxidative
phosphorylation (Kashket and  Brodie 1962;  Robb  and  Peak 1979; Brodie, Suther-
land, and  Lee  1979;  Sharma and Jagger  1981).   Absorption of UV-A light by 4-
thiouridine, an  unusual  base  found  in bacterial  transfer  RNAs,  results  in
growth  inhibition  caused  by  a cessation  of RNA  synthesis  (Ramabhadran  and
Jagger 1976; Favre and  Thomas  1981).   It  has also  been shown that  UV-A light
inhibits  bacterial DMA  repair  enzymes  (Tyrrell 1976).   Very little is known
about  the induction of alterations  in non-DNA targets  in mammalian  cells,
though recent studies have demonstrated that cell membranes  can be  damaged by
broad spectrum UV-A and UV-B light  (Aberer et al.  1981; DeLeo et al. 1985).

     The   results   presented   above   represent the   first   demonstration of
UV-induced  disruption  of  cytoskeletal  elements  in  cultured  cells.    In
addition,  our  data  indicate  that  exposure  to germicidal,  UV-C light  or  to
environmentally relevant  wavelengths  of  UV-B  and  UV-A  light  has  extremely
different effects on the cytoskeleton.  Since the cytoskeleton is an important
participant in the control of normal cell growth and  since  epigenetic events
probably play a role in carcinogenesis, such alterations of the cytoskeleton
may  be an  important  consequence  of  natural  exposure  to  UV  light.    The
individual components  of  the cytoskeleton  are structurally associated  with
each other as well as with the cellular membrane  and nuclear matrix (Brinkley
1981; Schliwa,  van Blerkom, and Pryzwansky 1981; Singer et al. 1981; Ben-Ze'ev
1985).   It has  therefore been  suggested that the cytoskeleton  may  serve as a
critical means of transmitting external signals to the nucleus.   The molecular
mechanisms by which it performs this function are not understood.  The complex
organization of  the  cytoskeleton  participates  in  the  regulation of cellular
shape  and motility,  the  spatial  arrangement of   organelles   and  secretory
processes.   Because  cell  shape  is an important regulator  of  cell  growth,
alterations  of  the   cytoskeleton  disrupt  normal   shape-related  regulatory
signals (Folkman and Moscona  1981;  Penman  et al.  1981).  The structural state
of the cytoskeleton also appears to contribute  to  the control of DNA synthesis
(Friedkin and Rozengurt  1981;  Otto 1982).    Agents  causing the  disassembly of
microtubules enhance the  initiation of  DNA synthesis in  cells exposed  to
peptide growth factors,  though this response may  be dependent  upon the cell
type or culture conditions.   The close  association  between polyribosomal mRNA
and cytoskeletal components has led to the  suggestion that  the cytoskeleton
may also  contribute  to the regulation  of  protein synthesis  (Nielsen,  Goelz,
and  Trachsel   1983).     Because    there   is  extensive  interaction  between
cytoskeletal elements,  agents  that affect  one component may   influence  the
regulatory  capacity   of  others.     It   is   thus  reasonable  to  expect  that


                                      126

-------
Perturbations of the normal assemblage of the cytoskeleton induced by UV light
could result  in  a variety of  functional consequences.   Indeed,  cytoskeletal
Abnormalities  have  now  been  associated  with several  pathologic  phenomena
including  the malignant  transformation  of  cells  (Lockwood,  Trivelte,  and
Pendergast 1981; Penman et  al.  1981; Rungger-Brandle and Gabbiani  1983; Ben-
Ze'ev 1985).   With these considerations in mind,  it is also intriguing to note
that tumor promoters have  recently been found to  cause  structural  changes in
the  three  major  cytoskeletal  components  (Weber,  Wehland,  and Herzog  1976;
Rifkin,  Crowe,  and  Pollack  1979;  Seif  1980; Schliwa  et al.  1984; Fey  and
Penman 1984).


REFERENCES

Aberer,  W.,  G.  Schuler,  G.  Stingl,  H.  Honigsmann,  and K.  Wolff.   1981.  J^_
     Invest.  Dermatol.  76:202-10.

Alberts,  B.,  D. Bray,  J.  Lewis,  M. Raff, K.  Roberts, and J.D.  Watson (eds.).
     1983.  Molecular biology of the cell.   549-609.  New York: Garland Press.

Ben-Ze'ev,  A.  1985.  Biochem.  Biophys.  Acta.  780:197-212.

fiotcherby,  P.K., I.A.  Magnus,  B.  Marino,  and F.  Gianelli.   1984.  Photochem.
     Photobiol.  39:641-49.

Bpinkley,  B.R.  1981.   Cold Spring  Harbor Svmp. Quant. Biol.  46:1029-40.

Br°die,  A.F., T.O. Sutherland, and  S.H.  Lee.   1979.   In  Vitamin  K  metabolism
     and  vitamin K-dependent proteins,  ed.  J.W.  Suttie,  193-202.   Baltimore:
     University Park Press.

Cerutti,  P.A. and M. Metrawali.   1979.  In Proceedings of the  6th International
     Congress of  Radiation Research,  ed.  M.  Imamura,  T. Terashima, and  H.
     Yamaguchi,  423-432.   Tokyo: Toppan.

Chou> I.N., and J.P. Shaw.   1984.   Cell  Biol.  Int.  Rep.  8:441-48.

Cleaver,  J.E., and D. Bootsma.   1975.   Ann.  Rev. Genet.  9:19-38.

Coohin,  T.P., and E.D.  Jacobson.   1981.   Photochem.  Photobiol.  33:941-45.

Deleo,  v.A.,   D.  Hanson,  I.B. Weinstein, and  L.C.  Harber.   1985.   Photochem.
     Photobiol.  41:51-56.

 laJnond,  L.t  T.G. O'Brien,  and  W.M.  Baird.   1980.   Adv.  Cancer Res.  32:1-74.

DoiUnger,  J., E.D. Jacobson, K. Krell,  and J.A.  DiPaolo.  1981.  Proc.  Natl.
     Aoad.  Sci.  USA  78:2378-82.

Papber, £., and R. Cameron.   1980.   Adv.  Cancer Res.  31:125-226.

 avre» A.,  and G. Thomas.   1981.  Ann.  Rev.  Bophys.  Bioeng.  10:175-95.

Pey»  E.G.,  and S.  Penman.   1984.  Proc. Natl.  Acad.  Sci.  USA  81:4409-13.


                                     127

-------
Folkman, J., and A. Moscona.  1978.  Nature 273:345-347.

Friedkin, M., and E. Rozengurt.  1981. Adv. Enz. Reg. 19:39-59.

Han, A., M.J. Peak, and J.G. Peak.  1984.  Photochem. Photobiol. 39:343-48.

Jacobson,  E.D.,  K.  Krell,  and  M.J.  Dempsey.   1981.    Photochem.  Photobiol.
     33:257-60.

Kantor, G.J.,  J.C.  Sutherland,  and R.B. Setlow.   1980.  Photochem.  Photobiol.
     31:459-64.

Kashket, E.R., and A.F. Brodie.  1962.  J. Bacteriol. 83:1094-1100.

Keyse,  S.M.,  S.H.  Moss,  and  D.J.G. Davies.    1983.    Photochem.  Photobiol.
     37:307-12.

Lockwood, A.M., D.D.  Trivelte,  and M. Pendergast.   1981.   Cold Spring Harbor
     Symp. Quant.  Biol. 46:909-19.

Moss, S.H., and K.C. Smith.   1981.  Photochem. Photobiol 34:45-49.

National Research Council Report.   1982.   Causes and Effects of Stratospheric
     Ozone Depletion.  An Update.  Washington, D.C.: National Academy Press.

Nielsen, P., S. Goelz, and H. Trachsel.   1983.  Cell Biol.  Int. Rep. 7:245-54.

Otto, A.M.  1982.   Cell Biol. Int. Rep.  6:1-18.

Penman, S., A. Fulton, D. Capco, A. Ben-Ze'ev, S. Wittelsberger, and C.F. Tse.
     1981.  Cold Spring Harbor Symp. Quant. Biol. 46:1013-1028.

Ramabhadran, T.V., and J. Jagger. 1976.  Prop. Natl. Acad. Sci. USA.  73:59-63-

Rifkin, D.B., R.M. Crowe, and R. Pollack.  1979.  Cell.  18:361-68.

Robb, F.T., and M.J. Peak.  1979.  Photochem. Photobiol. 30:379-83.

Robbins,  J.H., K.H.  Kraemer,  M.A.  Lutzner,  B.W.  Festoff,  and H.G.  Coon.
     1978.  Ann. Intern. Med. 80:221-48.

Rothman, R.H., and, R.B. Setlow.  1979.   Photochem. Photobiol. 29:57-61.

Rungger-Brandle, and G. Gabbiani.   1983.  Amer. J. Pathol.  110:361-92.

Schliwa, M., T. Nakamura, K.R. Porter, and U. Euteneuer.  1984.  J.  Cell Biol.
     99:1045-59.

Schliwa, M.,  J.  van Blerkom,  and  K.B.  Pryzwansky.  1981.  Cold Spring HarbQf.
     Symp.._ Quant.  Biol. 46:51-66.

Seif, R.  1980. J.. Virol. 36:421-28.

Sharma, R.C., and J. Jagger.  1981.  Photochem. Photobiol.  33:173-77.


                                      128

-------
Singer,  S.J.,  E.H. Ball, B. Geiger,  and  W.T.  Chen.   1981.  Cold Spring Harbor
     Symp.  Quant.  Biol.  46:303-16.

Smith,  P.J.,  and M.C.  Paterson.  1981.  Cancer Res.  41:511-18.

Smith,  p.p.,  and M.C.  Paterson.  1982.  Photochem. Photobiol. 36:333-43.

Suzuki,  F., A.  Han,  G.R.  Lankas, H.  Utsumi,  and M.M.  Elkind.   1981.   Cancer
     Res.  41:4916-24.

Tyrell,  R.M.   1976.  Photochem.  Photobiol. 23:13-20.

Tyrrell,  R.M.  1982.   In Trends  in  Photobiology, eds.  C.  Helen,  M.  Charlier,
     T.  Montenay-Garestier,  and  G.  Laustriat,   155-172.    New York:  Plenum
     Press.

Tyrrell,  R.M.  1984.  Mutation Res. 129:103-10.

Tyrrell,  R.M.,  P. Wertelli,  and E.G.  Moraes.    1984.  Photochem.  Photobiol.
     39:183-89.
    ,  K. ,  J.R.  Feramisco,  and J.F.  Ash.   1982.   Methods Enzymol. 85:514-62.

Weber, K., J.  Wehland,  and W. Herzog.   1976.   J. Mol.  Biol. 102:817-29.

wells, R.L., and A.  Han.   1984.   Mutation Res.  129:251-58.

Zamansky,  C- '\   1986.   Mutation  Res.  1 60:55-60.

Zamansky,  G.B.,  D.F.  Minka, C.L.  Deal,  and K.  Hendricks. 1985.  J .  Immunol .
     134:1571-76.

Zbinden,   J.,  and P. Cerutti.    1981.   Biochem.  Biophys.  Res.  Comm.  98:579-
     587.

     , R.B.,  R.J.  Reynolds,  M.T.  Kottenhagen,  A.  Schuik,  and P.M.  Lohman.
     1980,  Mutation Res.  72:491-509.
                                     129

-------
Sunscreens Do Not Abrogate UV-Induced
Suppression of Contact Hypersensitivity

M. S. Fisher, J. M. Menter, L Tiller, and I. Willis
Morehouse School of Medicine
Atlanta, Georgia USA
ABSTRACT

     Contact hypersensitivity (CHS) in mice can be induced by cutaneous sensi-
         followed  by  elicitation via ear-painting with trinitrochlorobenzene
         This CHS reaction  is  systemic and  can  be  suppressed by exposure of
     to suberythemogenic  doses  of 280-315 nra radiation.   In this paper,  we
   estigate whether a commercially available  water-resistant sunscreen (SPF-6)
containing  padimate  0  (UV-B  absorber)  and  oxybenzone  (UV-A  absorber)  was
effective  in  preventing  systemic  suppression of  CHS  induced  by either  FS36
Sunlamp exposure  or  solar simulating radiation.   We observed that this  sun-
screen  preparation  could  not prevent  the  immunologic  suppression of contact
hypersensitivity by UV radiation.  These results indicate that application of
sunscreen  does  not retard the  development  of  suppression  of  CHS following
rePeated  UV  exposure  under conditions  where  erythema  is  not clinically
observed.   Thus,  erythema may not be a good end point  for assessing systemic
lnanune suppression and its consequences.

PRODUCTION

     Exposure of  mice  to ultraviolet  (UV) radiation systemically suppresses
     ability to reject highly antigenic UV-induced skin cancers  (Fisher 1977;
    er  and  Kripke  1977).    This  state  of  unresponsiveness   is  mediated
ln»nuriologically  and  is  due  in  part to  the presence  of  antigen-specific
           T  lymphocytes  (Fisher  1977, 1978;  Fisher and Kripke 1977,  1978,
    J Spellman and Daynes  1977).  A second  UV-induced immunosuppressive defect
j|aa also been described in which a single  exposure of  the dorsal  skin of  mice
!j0 UV radiation was sufficient  to suppress contact  hypersensitivity  (CHS)  to
 ~chloro-1,3,5-trinitroben2ene (TNCB) applied to the abdominal surface (Noonan
j^  al.   1981).     The  cellular  basis   for  the  suppression  of  contact
^Vpersensitivity appears  to  involve a UV-induced  alteration  in the functional
a°Uvity of antigen-presenting cells  (Noonan et al. 1981;  Greene et al. 1979).
                                   131

-------
     The photobiologic  and immunologic  similarities of  these  two UV-induced
systemic immunosuppressive events  suggest  that  they  may share  common steps
(Noonan et  al.  1981;  De Fabo and  Kripke  1979;  Noonan,  De  Fabo,  and Kripke
198la,  b),  which appear to  be:    (a)  an  alteration  in the  presentation of
certain  antigens,   particularly   those  encountered  via  the cutaneous  route
(Noonan  et  al.  1981)  and  (b)   the  induction  of  T  suppressor  cells as  a
consequence of  altered antigen presentation  (Greene et al.  1979).   The main
difference between both  forms  of  systemic immunologic  suppression is that the
antigen that  induces  the suppressor cells  is  applied  exogenously in the case
of contact hypersensitivity, but must be formed endogenously by UV exposure of
the  skin  in  the  induction  of  suppressor  T  cells  that  regulate  tumor
rejection.   Another important difference between the two systems is the actual
dose  of  UV  needed  to  induce   50%  suppression.     For  CHS,  the  dose  is
approximately 13  times  less  than that needed to induce the  tumor suscepti-
bility  in  50%  of  the  UV-irradiated  animals  (Noonan,  De  Fabo,  and  Kripke
198lb).

     Sunscreens, the  majority of which  use para-aminobenzoic acid (PABA) or
one of its derivatives and/or a benzophenone derivative as their active ingre-
dients, protect  against a number of  UV  radiation  effects.   The  ability of
topically applied  sunscreens  to  reduce  erythema and  skin  damage  caused by
chronic UV  exposure,  expressed as  a  "sun  protective  factor"  (SPF),  is well
documented (Pathak  1969; Willis  and Kligman  1970; Kligman,  Akin,  and Kligman
1980, 1982).  In addition,  sunscreens  have  been shown  to protect against both
the cocarcinogenic as well as  the carcinogenic effect  of UV radiation (Snyder
and  May 1975;  Kligman, Akin,  and  Kligman  1980;  Wulf et  al.  1982;  Stern,
Weinstein and Baker 1986).  To date,  however, very few studies have evaluated
the  effect  of  these  sunscreen  agents  on  the  more  subtle  immunoregulatory
effects now  known  to be  produced  by UV-B irradiation.   One such  study by
Gurish  et  al. (1981)  found  that pretreatment of mice with a  PABA sunscreen
completely prevented  the UVB-induced  histologic changes in exposed  skin  and
rendered the  mice  tumors susceptible, although  this susceptibility could not
be  adoptively  transferred  to normal untreated animals  by  lymphoid  cell
injection.    A later  study (Morison 1984)  with a similar sunscreen  but witn
higher  doses of  UV-B  radiation  showed not only  induction  of  the  tumor-
susceptible state, but  also that  this  state could be transferred to syngeneic
animals by lymphoid cells.

     In this  study, we  report  the results of experiments designed to evaluate
the potential protective effect  of a commercial  sunscreen  preparation on the
immunologic  suppression of  contact  hypersensitivity   by  UV  radiation.   We
observed  that this  sunscreen preparation  with  PABA  and  oxybenzone  as
active  ingredients was  incapable  of preventing the immunologic suppression
contact hypersensitivity by UV radiation.

MATERIALS AND METHODS

Animals

     Inbred albino hairless mice which have been bred in our laboratories
the  inbred  HRA/Skh strain  were  obtained from Stanley Mann  of Philadelphia*
The hairless  mice  were from 8 to 16 weeks  old at the  start of an experiment*
but in  any one  experiment,  the age  of the animals did not vary by more than  '
week.   The  animals had free  access to  Purina Lab Chow  and water  and were
                                      132

-------
housed in  rooms  where ambient  lighting  was automatically regulated  on a  12-
hour light/dark cycle.

Contact Sensitization

     Each  experimental  group  utilized  5-10  hairless mice.    Contact hyper-
sensitivity  was  induced  by the  method  of Asherson  and Ptak (1968).   The
abdomen was  painted  with 100 yl (microliters) of  a 5% solution  of trinitro-
chlorobenzene (TNCB) in acetone.  The  mice  were  tested for the development of
contact hypersensitivity  five  days  later by applying  5  jil  of a  1?  TNCB in
acetone to  both  surfaces of each ear.   Ear  thickness  was measured  with an
engineer's micrometer (Model No.  7309,  Mitutoyo,  Japan)  before and  24 hours
after  application  of  the  challenge  dose.   The  ear  swelling obtained  was
compared to  the  ear  swelling  of control mice  that were challenged,  but  not
3ensitized.  The statistical significance of the differences  in  ear  swelling
between groups was  evaluated using the Student's T-test.

          Preparation
     A commercial  sunscreen (SPF-6)  contained padimate  0 and  oxybenzone as
active ingredients.  The sunscreen was applied uniformly to the dorsal skin of
the mice at a final dose of 2  pi/cm2, 20 minutes prior to UV exposure.

       Sources and Measurements
     Two energy sources  were used during  the  experiments.   One  source  was a
    kW  xenon  arc solar-simulating  lamp which has  been previously  described
         Menter,  and Whyte  1981).   Energy output  from this lamp system was
Measured by  a calibrated  Eppley Thermopile  in  conjunction  with a  Keithley
^illlmicroyoltmeter   (Model  149).   The  total  radiation  was  determined  to be
26.2 mW/cm ,  86 cm (11.5 in) from the exit port.   The second  source was a bank
°f three FS36T12-UV-B-VHO lamps  (Light  Sources)  housed  in an Ultralite  bench
top  irradiator  [BT  3-36 VHO(UV-B)].    Energy output  from  this system was
Measured as above 19 cm (7.5 in)  from the source  and the  total output was
determined to  be 1.4 mW/cm2.

HjjUmal Erythema Dose (MED)  Determination

     For each  UV energy  source,  five hairless mice were irradiated at 25% dose
increments.  Erythetnal responses  were  noted 24 hours after  irradiation.  The
MED was taken as  the exposure required to  elicit barely visible  minimal red-
ness.   Each  set  of  experiments was repeated  three times.   SPF  values were
assessed for a sunscreen preparation as  the ratio  of MED with sunscreen to MED
without sunscreen.

S£fect of UV Exposure on the Development of CHS

     To assess  the  depression of  CHS  by  UV  treatment, mice were sensitized
three days after  the last UV treatment and challenged five  days  later.   The
net ear swelling (ear swelling of sensitized and challenged mice minus the ear
Celling of unsensitized, but challenged mice)  was determined for  unirradiated
and UV-treated mice.   The percentage of control response was  determined by the
           formula:   A-B/C-D X  100.   The  letters represent  the  ear  swelling
     (A) mice exposed to UV  and  sensitized with TNCB;  (B) mice  exposed to UV,


                                     133

-------
but not sensitized; (C) unirradiated and sensitized mice; and  (D) unirradiated
and unsensitized.

RESULTS

MED Determination

     The doses required to elicit minimal erythema responses for solar-simula-
ting  radiation  (SSR)   and  FS36  sunlamps  are  given  in  Table  1.   Minimal
erythemal dose determination for three FS36 sunlamps was determined to be  38.5
mJ/cnr while  the total MED dose  for SSR was  8  J/cm .   To test  the  MED of a
commercially available  sunscreen  (SPF-6),  sunscreen  was applied to the dorsal
surface of inbred hairless mice at a final dose of 2  pi/cm2, 20 minutes prior
to  UV exposure.    For both  radiation  sources,  the  commercially available
sunscreen was determined to have a MED of 6.0 ± 0.5.

Topical Application of Sunscreen and
UV-Induced Suppression of Contact Hypersensitivity

     In the first  set  of experiments, two groups  of ten mice were pretreated
with sunscreen;  one group served as  an unirradiated control,  group  2,  while
the other, group, group 4,  was irradiated with a  bank of three FS36 sunlamps-
During the  treatment  regimen, no erythematous response  was observed  in the
group receiving the sunscreen preparation.   Table 2 shows the results obtained
from mice given sunscreen and treated with UV-B radiation.  Sunscreen applica-
tion had  no effect on the contact  hypersensitive  response,  as seen  by the
similarity  in  groups  1 and  2.    The amount  of  suppression  with (44$)  and
without (50%)  topically applied sunscreen was similar.

     In the second part of the experiment (Table 3),  the sunscreen preparation
was topically  applied  to a group  of ten mice receiving  SSR  radiation (group
4), and another  group  of ten mice, group  2,  which served as a  control.   The
results  show   that  topical  application of  sunscreen  had  no  effect on  the
ability of mice to  mount a CHS response, groups  1  and 2.  The presence of the
sunscreen had  no effect on  suppression of  contact  hypersensitivity  by  SSB.
The amount  of  suppression  with  applied sunscreen  was 45/E  (group  4)  while
suppression from SSR  alone  (group 3) was  40$.   As with  the  previous experi-
ment,  no erythematous  response was observed  in  the  group  receiving  the sun-
screen preparation.

     To determine   if  the  previously  observed suppression  was  due  to  heat
alone,  two groups  of  mice were exposed  to SSR radiation through a Schott WG
385 filter, a cut off  filter with 50%  transmission at 385 nm (Table 4,  groups
2 and  3).   Group 3 received  topical  sunscreen application while group  2 was
treated with SSR alone.  The total UV  dose of 36 J/cnr  was unable to  suppress
the contact hypersensitivity  response when filtered  through  a Schott WG 385
filter.  However,  in  the  absence of  the Schott  filter  in both  the SSR  group
alone (group 4) and the group receiving  topical  sunscreen  plus SSR (group 5)»
suppression of contact hypersensitivity was observed.

DISCUSSION

     Treatment of'  hairless mice  with  a commercial  sunscreen (SPF-6)  which
contained padimate  0 and oxybenzone  as the  active ingredients  did not


                                      134

-------
 Table  1.   Minimal  Erythemal  Dose Determination  for UV Sources
              in Presence  and  Absence of Applied Sunscreen
Sunscreen
-
-
4-
4-
UV
Source
SSRC
FS36d
SSR
FS36
Total
UV Dose
(J/cra1)
8
0.0385
44-52*
0.21-0.256
MEDs Rated SPFb
1
1
5.5-6.5e 6
5.5-6.5C 6
  a.    Obtained from a commercial source.  Active Ingredients were Padimate 0 and
       Oxybenzone.

  b.    Manufacturer's rating.

  c.    Solar simulating radiation from a 1.6 kW xenon arc lamp.

  d.    3 FS36T12-UVB-lamps housed in an Ultralite bench top irradiator.


  e.    Range of 3 determinations.
  Table 2.   Effect  of Padimate 0  and  Oxybenzone on Suppression of
              Contact Hypersensitivity  by UV-B  Radiation
Total Ear swelling
UV dose (cm X 10"^
Group Treatment

1
2
3
4

Nil
Sunscreen (SS)
UVB
UVB 4- SS
(mJ/cm1)

0.0
0.0
173. 3e
173. 3e
4-TNCB
44.3 ± 2.3
43.2 ± 2.2
28.3 t 2.3
26.3 i 3.8
Net ear Percent

swelling suppression Pc
-TNCB
8.5 ±
8.2 ±
8.3 i
8.4 ±
1.3
1.2
1.4
1.5
35.8
35.0
20.0 44
17.9 50


<.001
<.001
a  FS36 Sunlamp - see text

b  Mean  (± SD) of 10 mice challenged 24 hours earlier with TNCB on the ears.

c  Probability of no difference from group 1 (no treatment).
d  Commercially available sunscreen. SPF 6.

   Five equal treatments of 34.7 J/cm  were
   after final exposure and challenged  5 days after sensitization.
e  Five equal treatments of 34.7 J/cm  were given on consecutive days.  Mice were sensitized 3 days after
                                        135

-------
  Table  3.   Effect of Padimate 0 and Oxybenzone on  Suppression of  Contact
               Hypersensitivity by  Solar-Simulating Radiation  (SSR)
Group
1
2
3
4
Treatment
Nil
Sunscreen (SS)
SSR
SSR + SS
Total
UV dose0
(31cm1)
0.0
0.0
36.0
36.0
Ear swelling
(cm X 10 )
+TNCB
44.3 ± 2.3
43.2 t 2.2
30.1 ± 2.3
27.7 ± 2.5
-TNCB
8.5
8.2
8.5
8.1
± 1.3
± 1.2
± 1.5
± 1.6
Net ear Percent .
swelling suppression P
35.8
35.0
21.5 40 <.001
19.6 45 <.001
a  Xenon arc. 1.6 kW (see text).

b  Mean (± SD) of 10 mice challenged  24 hours earlier with TNCB on the ears.

c  Five equal treatments of 7.2 J/cm1  given on consecutive days.  Following the last exposure, the mice
   were sensitized 3  days later.  Five days after sensitization,  the mice were challenged.

d  Probability of no difference  from group 1 receiving no treatment.

e  Commercially available sunscreen with an SPF of 6.
               Table 4.  Effect of a Schott WG 385 Filter  on  the
                           Suppression of Contact Hypersensitivity
Group
1
2

3
4
5
Total Ear swelling
UV dose (cm X 10~ ) Net ear Percent
Treatment (mJ/cm2) swelling suppress!
+TNCB -TNCB
Nil 0.0 33.8 ± 3.49 6.2 ± 1.1 27.5
Schott WG385 36 37.2 ± 3.19 6.9 ± 1.3 30.3
+ SSR
Schott WG385 36 35.4 ± 2.6 6.4 ± 1.6 29.0
+ SSR t SSd
SSR 36 23.1 ± 2.6 6.2 ± 1.2 16.9 39
SSR + SS 36 22.9 ± 3.2 6.1 ± 1.3 16.8 40
on PC




<.ooi
<.00l
^--
a  Mean (± SO) of 10 mice challenged 24 hours earlier with TNCB on the ears.

b  Five equal treatments of 7.2 J/cm* given on consecutive days.  Following the last exposure, the mice
   were sensitized 3  days later.  Five days after sensitization, the mice were challenged.

c  Probability of no difference from group 1 receiving no treatment.

d  Commercially available sunscreen with an SPF of 6.
                                              136

-------
prevent systemic immunologic suppression of contact hypersensitivity following
exposure with either SSR or FS36 sunlamps.  These results differ from those of
Morison (1984),  who found that pretreatment  of C3H mice  with PABA sunscreen
(SPF-8) only induced 25%  suppression  of the contact hypersensitivity response
following UV-B exposure,  which he determined not  to  be significant.   We used
different mice,  albino hairless,  and a sunscreen  with an SPF-6  rating.   In
addition,  our total dose  of UV was lower  than  his by a factor  of TO.   These
differences alone could account for the discrepancy between Morison's and our
results.

     In Morison's  study,  the feet and  nose were  neither  covered  nor treated
with sunscreen.   Hence,  the UV-induced suppression  he observed  in  C3H mice
could have  been  due to irradiated areas not  treated with  sunscreen.   In our
experiments, the head and neck were covered with a shield  and the back, feet,
and tail treated with  sunscreen.   Thus, our  results  are difficult to explain
by exposure of non-sunscreen treated sites.

     If mice are irradiated  with  polychromatic  UV  radiation,  which was  insuf-
ficient to  elicit  an erythema "sunburn" response,  then  UV-A  rather than UV-B
might be responsible for  the induction of  immune  suppression  observed  in our
experiments.  However,  because previous  studies have shown  that  wavelengths
shorter than  320  nm  are responsible  for systemic immunologic  suppression
(Noonan et al.  198la;  De  Fabo  and Kripke  1980),  other alternatives  are
considered.  The finding that the sunscreen did not abrogate the effects of UV
radiation   on  contact  hypersensitivity  might  be  explained by  assuming  that
sunscreen agents act as photosensitizers  initiating a  photochemical  reaction
in  the   skin   that   could  then   lead   to   the  suppression   of   contact
hypersensitivity (Gurish et  al.  1981).   In support of  this theory, Hodges et
a^' (1977)  found increased genetic damage  when  E^  coli  were irradiated  in the
Presence of PABA.    Another  explanation  is  that  the  amount  of  energy  not
absorbed by  the  sunscreen agent  is  sufficient  to induce  the  suppression of
contact hypersensitivity.   The location of the sunscreen   in the  skin  may be
very important in  this regard.   Willis and Kligman  (1970) demonstrated that
aignificant photoprotection  from  PABA persisted despite repeated stripping of
the stratum corneum. These results suggest that sunscreens may "pool" beneath
the stratus  corneum.    Recently,  De  Fabo  and Noonan  (1983) suggested  that a
Photoreceptor,  urocanic acid, resides close to  the surface of the  skin  in the
stratum corneum.    This  receptor  mediates  the  initial   event   in  systemic
inanunologic suppression  by  UV  radiation.   Our results are consistent  with
their interpretation:   for  if  sunscreens  pool  beneath the  stratum  corneum,
this would  allow  exposure  of the  photoreceptor, which   is  in  the  stratum
corneum and  above  the  sunscreen,  so that  subsequent  events associated  with
systemic immunologic suppression could take place.

     PABA absorbs radiation  between 270 and 320 nm very efficiently, but not
wavelengths below  270  tun.    The  experiment  using  the FS36  lamps could  be
explained  by radiation  exposure below 270 nm because no  filter was  used  to cut
°ut these  wavelengths.   However,  the experiment  that  used SSR,  which emits
essentially no irradiation  less than 290  nm, cannot  be explained  as due   to
UV-C radiation not  absorbed by the sunscreen.

     Because sunscreens are known to  protect against both  skin  damage and the
carcinogenic effects of UV radiation,  our results seem to suggest a separation
of UV-induced carcinogenic effects from the systemic immunologic effects.   Our


                                      137

-------
results also suggest that  if these results can  be  generalized to humans, the
use  of sunscreens  may  not  provide  the  protection  needed  to  abrogate the
immunologic effects of UV  radiation.   Thus, even sunscreen  users Would be at
increased  risk  for skin  cancer,  because  altered  antigen presentation would
already have been  established  and the  formation of suppressor  T cells would
appear earlier in  these  individuals  than in those  persons who have never had
any sun exposure.


REFERENCES

Asherson,  G.L., and W.  Ptak.  1968.   Contact and delayed hypersensitivity in
     the mouse.    I.  Active  sensitization and  passive  transfer.    Immunol.
     15:405-16.

De  Fabo,   E.G.,  and M.L.  Kripke.  1979.   Dose-response  characteristics  of
     immunologic  unresponsiveness  to   UV-induced  tumors   produced  by  UV-
     irradiation of mice.   Photochem.  Photobiol.  30:385-90.

De  Fabo,  E.G.,  and M.L.  Kripke.  1980.   Wavelength dependence  and dose-rate
     independence of UV radiation-induced immunologic  unresponsiveness of mice
     to a UV-induced fibrosarcoma.  Photochem.  Photobiol.  32:183-88.

De  Fabo,  E:C.,  and F.P.  Moonan.   1983.   Mechanism of immune  suppression by
     ultraviolet irradiation  in  Vivo.   I.  Evidence for  the  existence  of  a
     unique photoreceptor  in  skin and  its  role  in  photoimmunology.   J. Exp^
     Med.  157:84-98.

Fisher, M.S.  1978.   A  systemic  effect  of ultraviolet  irradiation and its
     relationship to tumor immunity.   Natl. Cancer  Inst.  Monogr. 50:185-88.

Fisher, M.S. 1977.   Immunologic  Aspects  of UV Carcinogenesis,  Ph.D.  Thesis,
     University of Utah,  School of Medicine, Salt Lake City,  UT, 124 pp.

Fisher, M.S., and  M.L. Kripke.  1977.   Systemic  alteration induced  in mice by
     ultraviolet  light  irradiation  and   its   relationship  to  ultraviolet
     carcinogenesis.   Proc. Matl.  Acad.  Sci. USA 74:1688-92.

Fisher, M.S., and  M.L.  Kripke. 1978.   Further studies on the tumor-specific
     suppressor cells  induced by ultraviolet radiation.  J.  Immunol. 121:1139-
     44.

Fisher, M.S.,  and  M.L. Kripke.  1982.   Suppressor  T   lymphocytes  control the
     development  of primary  skin  cancers  in  ultraviolet-irradiated  mice.
     Science 216:133-35.

Greene, M.I.,  M.S.,    M.L. Kripke, and  B. Benacerraf.  1979.    Impairment of
     antigen-presenting cell function by ultraviolet  radiation.   Proc. Natl._
     Acad. Sci.  76:6592-95.

Gurish, M.F., L.K. Roberts,  G.G.  Krueger, and R.A. Daynes.  1981.   The effect
     of various  sunscreen agents on  skin damage and  the induction  of tumor
     susceptibility.in mice subjected to  ultraviolet  irradiation.   J. Invest.
     Dermatol.  76:246-251.


                                      138

-------
H°dges,  N.D.M.,  S.H.  Moss,  and D.J.G.  Davies. 1977.   The sensitizing effect of
     a sunscreen agent,  P-aminobenzoic acid, on  near  UV induced damage  in a
     repair  deficient  strain  of  Escherichia  coli.    Photochem.  Photobiol.
     26:493-98.

KUgman,   L.H.,   F.J.  Akin,  and  A.M.  Kligman.  1980.    Sunscreens  prevent
     ultraviolet photocarcinogenesis.   J.  Am. Acad.  Dermatol.  3(a):30-35.

KUgman,  L.H.,  F.J. Akin,  and  A.M.  Kligman.  1982.  Prevention  of ultraviolet
     damage  to   the  dermis  of  hairless  mice  by  sunscreens.    J.  Invest.
     Dermatol. 78:181-89.

Kligman,  L.H.,  F.J. Akin,  and  A.M.  Kligman.  1983.  Sunscreens  promote repair
     of  ultraviolet  radiation-induced  dermal damage.   J.  Invest.  Dermatol
     81:98-102.

^orison,  W.L. 1984.   The effect of a sunscreen  containing para-aminobenzoic
     acid  on  the systemic immunologic alterations induced in mice by exposure
     to UV-B  radiation.   J.  Invest. Dermatol 83:404-8.

N°onan,  P.P., E.G.  De Fabo,  and M.L.  Kripke.  1981.  Suppression  of  contact
     hypersensitivity   by  ultraviolet   radiation;   an  experimental   model.
     Springer Sem.  Immunopatho. 4:293-97.

N°onan,  F.P., E.G.  De  Fabo, and M.L. Kripke.  1981,   Suppression of  contact
     hypersensitivity  by  UV  radiation  and  its  relationship  to   UV-induced
     suppression  of  tumor immunity.  Photochem.  Photobiol. 34:683-89.

M°onan, P.P., M.L.  Kripke,  G.M. Pedersen,  and M.I.  Green.  1981.  Suppression
     of  contact  hypersensitivity  in  mice  by   ultraviolet  irradiation   is
     associated with defective antigen presentation.  Immunology 43:527-33.

p*thak,  M.A., T.B.  Fitzpatrick,  and  E.  Frenk.  1969.   Evaluation of  Topical.
     agents that  prevent sunburn-superiority of  para-aminobenzoic acid  and  its
     esterin  ethyl alcohol.  N. Engl.  J. Med.  280(26):1459-63.

Snyder,  D.S., and M. May.  1975.   Ability  of PABA  to  protect mammalian skin
     from   ultraviolet  light-induced  skin   tumors  and  actinic  damage.    J^
     Invest.  Dermatol. 65:543-49-

 peUman,   C.W.,  and  R.A.  Daynes.   1977.    Modification  of  immunological
     potential by ultraviolet  radiation.  II.  Generation of suppressor cells
     in short-term UV-irradiated mice.   Transplantation 24:120-26.

 ter>n,  R.S.,  M.C.  Weinstein,  and   S.G.   Baker.   1986.  Risk   reduction   for
     nonmelanoma  skin  cancer with childhood sunscreen use.   Arch.   Dermatol.
     122:537-45.

 °8el, H.G.,  H.G.  Alpermann,  and  E.  Futterer.  1981.    Prevention  of  changes
     after  UV-irradiation  by  sunscreen  products  in skin  of hairless mice.
     Arch.  Dermatol. Res. 270:421-28.

  His, I., and   A.M. Kligman.  1970.   Amino-benzoic acid and  its  esters;  the
     quest  for more effective sunscreens.  Arch. Dermatol. 102:405-17.


                                     139

-------
Willis,  I.,  J.M.  Menter,  and  H.J. Whyte.    1981.    The  rapid  induction of
     cancers   in   the   hairless   mouse    utilizing   the   principle   of
     photoaugmentation.   J.  Invest.  Dermatol. 76:404-8.

Wulf, H.C., T.  Poulsen,  H.  Brodthagen,  and I. Hou-Jensen.  1982.   Sunscreens
     for  delay  of ultraviolet  induction  of  skin  tumors.    J.  Am.  AcajU
     Dermatol.  7:194-202.
                                      140

-------
Sunlight and Malignant Melanoma
in Western Australia

Bruce K. Armstrong
University of Western Australia
Western Australia  Australia
PRODUCTION

     The  incidence  (frequency of  occurrence of new  cases per  unit,of  popula-
tion) of  malignant  melanoma  (MM)  of the skin  is  increasing  about  5% per year
in most white populations  (Muir  and Nectoux  1982).   Lancaster (1956)  was  the
first to  suggest that  this cancer  may be substantially  due  to  ultraviolet
radiation  from the  sun.   He observed a threefold variation  in mortality from
Melanoma between the populations  of Queensland in the north of Australia  (high
^rtality)  and  Tasmania in the south (low mortality).  The populations of  the
°ther states  were distributed  between  them approximately  in  relation to  the
latitudes  of  their  main  population centers.   Similarly, Lancaster noted that
European   populations  residing   in  the  comparatively  sunny climates  of
Australia,  South Africa, and  California exhibited  higher  mortality  from MM
than in the European countries  from which they originated.

     A number of observations are apparently inconsistent with a simple causal
relationship  between sun  exposure and  MM.   Other  skin  cancers, which  are
Senerally  believed  to be caused  mainly by sunlight, are  more common in  men
than women (perhaps because men often work outside),  increase exponentially in
incidence  with age  (the  pattern  expected  from lifelong exposure  to an  agent
that can  initiate cancer),  and occur most commonly  on the more exposed  head,
neck, and  hands.  In contrast, MM  occurs  as often in women as in men,  shows a
relative  peak in incidence  in  middle life, and is most common on  the  back in
"fcn and legs  in women (Holman  et al. 1980).   There  are also a number  of geo-
graphical  areas in which the incidence  of MM does not increase with increasing
Proximity   to  the equator.   These  areas include  the  Australian states of
Western Australia and Queensland,  which cover a  wide range  of latitudes,  and
Europe where MM incidence decreases with increasing latitude to about 50°N  and
then increases with  increasing latitude (Armstrong 1984).   These geographical
inconsistencies,  however, may  be caused by a failure  to adequately consider
skin pigmentation and climatic  factors  that modify exposure and sensitivity to
aunlight.   More significant is the  relationship between the  incidence  of MM


                                    141

-------
and occupation and socioeconomic status.   Whereas other skin cancers are more
common in outdoor than indoor workers, as would be expected if they are caused
by exposure to the sun,  the  opposite  is true for MM.  Similarly, incidence of
other  skin cancers  tends to  increase with decreasing  socioeconomic  status
(perhaps because  low status  jobs  tend more often  to  be outside)  while the
opposite is true for MM (Holman et al. 1980).

     These observations led  to  the  "intermittent exposure hypothesis" for the
relationship of sunlight to MM.  Briefly,  this hypothesis states that:

     •  Incidence of MM is determined as  much (or more) by the pattern of sun
        exposure as by the total accumulated "dose" of sun exposure.

     •  Infrequent (intermittent) exposure of untanned skin  to  high doses of
        sunlight  is  particularly  effective  in   increasing  incidence  of MM.
        Thus,  incidence rises initially as frequency of exposure increases but
        may fall as exposure becomes more continuous.

     A simple  rationalization  for  this complex,  postulated exposure-response
pattern  is that developing  and maintaining a  suntan  protects one  from the
carcinogenic effects of  continuing  sun exposure.   With  infrequent  sun expo-
sure, a tan is not maintained  (except  in  those with high natural skin pigmen-
tation or  who  tan  very  easily), and the  melanocytes are substantially unpro-
tected from solar UV on each occasion of exposure.

     The Western  Australian  Lions Melanoma  Research Project, carried  out i°
Western  Australia  in 1980  and  1981,  was designed  to test  the intermittent
exposure hypothesis.

METHODS OF DATA COLLECTION AND ANALYSIS

     The methods  have been  fully  described elsewhere (Holman  and  Armstrong
1984a).    In   brief,  511  patients  with  histologically  confirmed  MM  were
studied.  They were 76$ of a total  of 670 cases less than 80 years of age and
diagnosed  in accessible  regions of  Western  Australia in  a  period  of 675 days
beginning  January  1,  1980.   Clinical  details were  obtained  from  the doctors
who treated the patients and the histopathological  diagnosis  was reviewed and
confirmed by a panel of pathologists.

     Five hundred eleven control subjects, each matched to one of the melanoma
patients by age,  sex,  and area of  residence, were  also studied.    They were
selected at random from the  Australian  Commonwealth Electoral Roll (electoral
registration is compulsory in  Australia)  or, if  the  MM patient  was  less than
18 years of age,  from  the student  roll of the area  public  school.   The final
series of 511  control subjects  was  69% of those approached.

     The patients with MM and the control  subjects  were approached in identi-
cal fashion and  asked  to participate  in  an  interview  on "environment, life-
style, and health," which  lasted from one to  two hours.   The interviews were
conducted  in  the subjects'  homes  (occasionally  workplaces)  by  trained nurse
interviewers who were not told  whether  the person that they interviewed was a
MM patient or a control subject. The interview covered demographic,  constitu-
tional and genetic  factors,  sun exposure, hormone  use,  diet, and  some other*
variables.    Objective measurements  were   made  of skin,  eye  and hair  color*

-------
 weight, height,  amount  of body hair, number of raised moles  (pigmented naevi)
 on the arms and  degree  of sun  damage to  the  skin  on  the  back  of  one  hand.

     It is possible,  by comparing the data obtained from the patients  with MM
 (often  called "cases")  and  the  control  subjects,  to estimate  the extent  to
 which exposure  to specific levels or categories  of particular  exposure  vari-
 ables increases  the  incidence  of MM above  the  incidence in some arbitrarily
 chosen  reference group  (usually  those  not  exposed or those  in  the  lowest
 exposure category).   The statistic  calculated  is the incidence rate ratio  or
 relative risk (as estimated by  the exposure odds  ratio), abbreviated hereafter
 as RR.   Because  it  is  a ratio,  values  of the RR above 1.0  for a particular
 category of  exposure  imply  that  the incidence  of MM  is  increased  in  that
 category in comparison with the incidence  in the  reference category.  RRs  were
 calculated by the  methods recommended  for  matched case-control  studies  by
 Breslow and  Day  (1980).   For each,  a  95% confidence interval  (CI)  was  also
 calculated.  Given that samples of both MM patients  and  controls were studied,
 each of  the   statistics  calculated has  sampling  variability.   The  CI  is  the
 interval in  which it is 95%  likely that the  true value of the RR  for  the
 Population as a whole lies.

     When interpreting an RR  for  a particular exposure category, it is neces-
 sary to consider the  possibility that the observed  association  is influenced
 by some "confounding" variable that  is related to both  the exposure variable
 for which  the RR has been calculated  and to MM.   For example,  people  with
 highly sun-sensitive  skins may  tend  to expose themselves less to the sun  than
 those with not-so-sensitive skins.    If sun  sensitivity  is  associated with  an
 increased incidence of  MM,  this could reduce the strength  of any association
 between sun exposure  and  MM unless  the  confounding effects  of sun sensitivity
 are controlled when examining the effects of sun exposure.   This control was
 achieved by use  of  conditional logistic regression  analysis  (Breslow  and Day
 1980)  and adjusted RRs were calculated,  where relevant, free of  the effects  of
 specific confounding variables.

 RESULTS

pigmentary  Characteristics and Sensitivity of the Skin to the Sun

     The RRs  for categories  of  skin color, hair  color,  and  eye  color  are
 summarized  in Table 1.  The skin  color measurement was a reflectance measure-
ment;  thus low  values represent  dark skin.   It  was made on the  skin  of the
uPper  inner   arm to  avoid,   as  far as  possible,  pigmentation  due  to  sun
exposure.

     Incidence of MM  increased in ordered categories of each of  these vari-
ables  with  increase  in  the  characteristics  that are usually   thought  of as
being  associated with sun sensitivity.   Thus the  highest incidence  of MM was
 in those with light  skin, red  hair,  and blue  eyes.  A "P  value"  of <0.05 means
fchat  the probability  that the pattern observed  in the RRs was  due  solely to
chance  (sampling  variability)  was less  than 5%  (i.e.,  1 in  20).  For skin
color and hair color it  was very much less  than  5%.
                                     143

-------
   Table 1.   Associations Between Pigmentary Characteristics and Incidence
             of Malignant Melanoma in Western Australia, 1980-81
Characteristic
Relative
  Risk
    95%
Confidence
 Interval
Skin color (reflectance)

     <47*
   47-55*
   56-64*
     65*+

Hair color

  Black or dark brown
  Light brown
  Fair or blond
  Red

Eye color

  Brown
  Hazel
  Green
  Grey
  Blue
 1.00
 1.05
 1.59
 3.07*
 1.00
 1.45
 1.89
 2.33*
 1.00
 1.49
 1.57
 1.33
 1.61*
0.69  1.59
0.95  2.66
1.47  6.39
1.08  1.94
1.29  2.77
1.26  4.30
1.01  2.18
0.97  2.53
0.71  2.46
1.16  2.21
* P value for trend in each case <0.05.
  Source:  Holman and Armstrong (1984a)
     Sensitivity  of  the skin  to  the  sun  was  ascertained  by  asking  two
questions:

     If your skin was exposed to  strong  sunlight for the first time in summer
     for one hour, would you...
          (1) Get a severe sunburn with blistering?
          (2) Have a painful sunburn for a few days followed by peeling?
          (3) Get mildly burnt followed by some degree of tanning?
          (4) Go brown without any sunburn?

     After  repeated  and prolonged  exposure  to  sunlight  would  your  skin
     become...
          (1) Very brown and deeply tanned?
          (2) Moderately tanned?
          (3) Only mildly tanned due to a tendency to peel?
          (4) Only freckled or no suntan at all?

     Relative risks of MM for these categories of sun sensitivity are shown in
Table 2.  Both acute and chronic skin response to sunlight were strongly
                                      144

-------
   Table 2.   Associations Between Sensitivity of the Skin to Sunlight and
             Incidence of Malignant Melanoma in Western Australia, 1980-81


                                                            95%
                                            Relative     Confidence
Characteristic                                 Risk        Interval


Acute skin reaction to sunlight

  No sunburn                                 1.00
  Mild sunburn                                2.63        1.63  4.26
  Painful sunburn                             2.63        1-62  4.26
  Blisters                                   3.39*       1-90  6.03
        skin reaction to sunlight

  Deep tan                                    1.00
  Moderate  tan                                1.45        1.08  1.94
  Mild tan                                    2.27        1.58  3.26
  No tan                                     3.53        1.82  6.84
* P value for  trend in each case <0.001.
  Source:  Holman  and Armstrong (1984a)
        to  incidence of MM  with the  highest incidence  being  in  those  with
greatest sensitivity to the sun.

     Of all the  pigmentary characteristics and  measures  of skin  response to
sunlight,  chronic skin response to sunlight was the strongest predictor of the
^isk of MM.  When these variables were  included together in a logistic regres-
sion model, acute skin  response to  sunlight and  hair color,  together  with
°hronic  skin   response  to  sunlight,  were   significantly  correlated  with
incidence of MM.   It is at least  plausible to suggest that skin  response to
Sunlight is  the important predictor of risk of MM and that hair color appeared
to be  independently  predictive only because  skin response was  measured  with
some error.
     MM is  known to  be rare  in pigmented  races (Crombie  1979).    Like  the
Association of MM with  response of the skin to sunlight  in  white races, this
°bservation suggests  that sunlight  may be  a cause  of MM.   In  the Western
Australian study,  subjects  were classified  by  the  ethnic  origin  of  their
Grandparents (if they had two or more  grandparents of the same ethnic origin)
into one  of the  following  categories:  Celtic (Irish,  Scottish,  or Welsh),
^glish,  Australian  (mainly Celtic or English,  there  were no Australian abori-
gines  in   the  study),  Southern  European,  Northern  European,  African,  or
Asian.   RRs for  MM  by ethnic origin are given in Table 3.   The  RRs have been
adJusted  for possible confounding effects of age at arrival in Australia


                                      145

-------
    Table 3.  Associations Between Ethnic Origin and Incidence of Malignant
              Melanoma in Western Australia,  1980-81
                                                             953!
                                            Relative     Confidence
Ethnic Origin                                 Risk        Interval
  Celtic                                     1.18*       0,82   1.70
  English                                    1.03        0.71   1.48
  "Australian"                               0.97        0.66   1.43
  Northern European                          0.57        0.31   1.06
  Southern European                          0.39        0.17   0.89
  African or Asian                           0.42        0.05   3.34
* RRs are adjusted for age at arrival in Australia and each other ethnic
  origin category.

  Source:  Holman and Armstrong (1984a)
(many of  the non-Australian  subjects were migrants  and therefore  had a
incidence  of melanoma  regardless  of  their  ethnic  origin;  see below)
represent the effects of each ethnic group independently of all the others.

     There were few subjects in the study who belonged to ethnic groups (e.g->
born in Africa  or Asia) that might reasonably  have been expected to have had
pigtnented skin.   The  lowest risk, however, was  in those of Southern European
ethnic origin whose skins are generally darker  than  those of people originat-
ing elsewhere in  Europe.   The pattern  is  therefore consistent with a protec-
tive effect of ethnically determined skin pigmentation against MM.

Birthplace. Age at Arrival,  and Duration of Residence in Australia

     Most Australians of European origin who  were born  outside Australia have
migrated to  Australia from  a region  of lower exposure  to the  sun.   Thus, ^
sunlight is  a cause  of MM, they  would be expected  to have  lower  incidence
rates of MM  than native-born Australians.  This has been observed  to be the
case in  descriptive studies  (Armstrong et al.  1982).   In  the 1980-81 case-
control study,  incidence of  melanoma  increased  with increasing  duration of
residence in  Australia  and  fell with increasing  age  at  arrival in Australia.
Since age  at arrival and  duration of  residence  are  correlated  one  with the
other,  both  were  included  in a logistic regression analysis to see  which, if
only one, was independently related to incidence of  MM.   The results of this
analysis are  shown  in Table 4,   After adjustment for duration of residence,
incidence still fell  with  increasing  age at  arrival  while adjustment for age
at arrival removed the observed effect of duration of residence.  Thus, if sun
exposure  is  responsible   for  the   high   incidence  of  MM  in  native-born
Australians relative  to  that  in migrants to  Australia,  it appears that expo*
sure early in life is necessary to have this effect.
                                      146

-------
  Table 4.  Associations Between Incidence of Malignant Melanoma and Age at
            Arrival in Australia and Duration of Residence in Australia, Each
            Adjusted for the Effects of the Other, Western Australia, 1980-81


                                                             9555
                                            Relative     Confidence
Characteristic                                Risk        Interval


Age at arrival

     Birth                                   1.00
     0-9 years                               0.89        0.44  1.80
     10-29 years                             0.34        0.16  0.72
     30+ years                               0.30*       0.08  1.13

Duration of residence

     0-24 years                              1.00
     25-39 years                             0.80        0.41  1.56
     40-59 years                             0.93        0.26  3.25
     60+ years                               1.02        0.20  5.08
* P value for trend <0.001.
  Source:  Holraan and Armstrong (1984b)
J!§an Annual Hours of Bright Sunlight

     To obtain a measure of the potential for exposure to the sun at all their
Places of  residence,  Holman  and Armstrong (1984b) calculated  the  mean annual
hours of  bright sunlight  (as  given  on climatology  maps)  averaged  over  all
Places of  residence  (as  obtained in a residence  history) and  weighted by  the
Duration of  residence.   This measure did  not account for the  time that each
subject  spent  in   the  sun.    The  analysis  was restricted  to  native-born
Australians  to  separate the  effects of  residential sunlight  from  those  of
Place of birth.   The results  are shown in  Table 5.  Incidence of MM nearly
doubled between those with less than 2600 mean annual hours  of bright sunlight
&t places  of residence  and those  with more  than 2800  hours.    Migrants  to
Australia had about  half  the incidence of MM  as  native-born Australians with
less than  2600 annual hours  of bright sunlight on average.  When  mean annual
hours of bright  sunlight were  controlled  in a logistic  regression analysis,
    mean latitude  of residence  showed  no  association with,  risk of melanoma.
     suggests that the effect of latitude  on incidence  of MM can be explained
   the effect of sunlight.
                                      147

-------
    Table 5.  Association Between Mean Annual Hours of Bright Sunlight at
              Places of Residence of Native-Born Australians and Incidence of
              Malignant Melanoma in Western Australia, 1980-81
                                                             95*
Mean Annual Hours of                        Relative     Confidence
Bright Sunlight                               Risk        Interval
Native-born Australians

     <2600 hours                             1.00
     2600-2799 hours                         1.34        0.96  1.86
     2800-1- hours                             1.92*       1.16  3.18

Migrants (all hours)                         0.51        0.35  0.74

* P value for trend 0.003.
  Source:  Holman and Armstrong (1984b)
Other Objective Measures of Total Accumulated Exposure to the Sun

     The degree of  damage caused to skin on  the  back  of the hand by exposure
to the  sun  was measured by means of  cutaneous microtopography (Holman et al«
1984).  A silicone  mold is  made of  the skin markings on the back of the hand,
examined under a  dissecting microscope, and graded on a scale from 1  to 6, 1
indicating  the least  solar  damage and  6 the most.  The  degree of skin damage
was  taken  to be  an indicator  of  total accumulated exposure  to the  sun.   A
history of  past non-melanocytic skin  cancer was  also  obtained.   Because non-
melanocytic  skin  cancers are  believed  to  be predominately  sun-induced they
were considered to  indicate individuals who  had been heavily exposed to the
sun.

     The relationships of MM incidence with cutaneous microtopograph grade and
past history of skin  cancer are shown  in Table  6.   Incidence of MM increased
with increasing severity  of solar damage to  the  skin  such that the incidence
in those with  grade 6  damage was nearly three times that  in  those with only
grades  1-3  damage.  Similarly,  the  incidence  of MM was higher in those with &
past history of non-melanocytic skin cancer than in those without.  Adjustment
of  the latter  association  for possible  confounding  effects  of acute  and
chronic  reactions  of  the  skin  to  sunlight,  hair   color,   and  numbers  of
European, African, and Asian grandparents reduced the RR from 3.71 to 2.87
1.64-5.04).
                                      148

-------
     Table 6.  Associations Between Incidence of Malignant Melanoma and Degree
               of Sun Damage to the Skin of the Back of the Hand and Past
               History of Non-Melanocytic Skin Cancer, Western Australia,
               1980-81
                                                             95%
                                            Relative     Confidence
Characteristic                                Risk        Interval
Sun damage to the skin of the back of the hand
(cutaneous microtopography grade)

     Grades 1-3                              1.00
     Grade  4                                1.64        0.97   2.78
     Grade  5                                1.76        0.97   3.19
     Grade  6                                2.68*       1.44   4.98
Past history of non-melanocytic skin cancer
     No                                      1.00
     Yes                                     3.71*       2.11   6.57
* P value for trend in each case <0.01
  Source:  Holman and Armstrong (1984b)
Pattern of Sun Exposure

     The evidence  on  the  associations between  incidence of  MM and  average
hours of bright sunlight at places  of residence,  sun-induced skin damage, and
Past history of non-melanocytic skin  cancer  strongly  supports  the role of sun
exposure in  the causation of  the disease.   These measures of  sun  exposure,
however, are essentially measures of total accumulated exposure  over  a life-
time and reveal nothing about  the pattern  of exposure.   A detailed history of
sun-exposure habits was taken from subjects in. the Western Australian study to
Provide evidence relevant to the  intermittent exposure  hypothesis.   They were
asked  to  provide estimates  of the  time  spent  outdoors  in  both summer  and
winter on typical working  and  non-working days for all periods  of employment
throughout their working  lifetimes  (Mondays  through  Fridays were treated as
Epical working days for students,  housewives,  and retired  people).   Details
we^e also sought regarding specific outdoor  pursuits  and  clothing habits when
outdoors.   All  the RRs presented are adjusted for the potential confounding
effects of acute  and  chronic  skin reaction  to  sunlight, hair  color,  ethnic
Or*igin, and age at  arrival  in Australia.

     Table 7 summarizes results  for average  estimated  outdoor time per week
°ver  the  lifespan   (since  leaving  school) and  the  proportion  of the  total
outdoor time that  was  recreational  (a measure  of intermittency  of  the expo-
sure) between 10 and 24 years of  age.
                                     149

-------
 Table 7.  Associations Between Incidence of Malignant Melanoma and Average
           Average Estimated Outdoor Time in Summer Over the Lifespan and
           the Proportion of the Total Outdoor Time During the Summer at
           Ages 10-24 Years That Was Recreational, Western Australia, 1980-81


                                                             95*
                                            Relative     Confidence
Characteristic                                Risk        Interval
Average total outdoor time

     0-10 hours/week                         1.00
     11-15 hours/week                        0.85        0.55  1.31
     16-22 hours/week                        0.78        0.52  1.19
     23+ hours/week                          0.70        0.43  1.12

Proportion (%) of outdoor time that was recreational
(Ages 10-24 years)

     0-29                                    1.00         -
     30-39                                   1.14        0.71  1.84
     40-59                                   1.16        0.76  1.77
     60+                                     1.28        0.85  1.94

 Source:  Holman, Armstrong, and Heenan 1986


     The trend in the RRs for  total  outdoor time showed the anomalous pattern
that has been observed  in descriptive  data:   incidence of MM fell rather than
rose with increasing time spent out of doors.  This trend, however, could have
been due  to  chance as  the  P value  was quite  high (0.13).  Both  of the com-
ponents of outdoor time  (outdoor  time  at  work  and time in outdoor recreation)
showed similar downward trends (Holman, Armstrong, and Heenan 1986) but as the
proportion of the outdoor time  that  was recreational  increased,  the incidence
of MM tended to rise (Table 7).  The P value for this trend, however, was also
rather high (0.25).  The recreational exposure proportion was examined for the
period of life from 10 to 24 years of age  because this was the period in which
the negative gradient with total outdoor time was most evident.

     Because  the  intermittent exposure hypothesis  is thought to  relate most
strongly  to  superficial spreading  melanoma  (SSM)  (Holman,  Armstrong,  and
Heenan 1983), the most common of the four  histological types of MM, the analy-
ses of Table  7 were also carried  out for  this particular type of MM.  SSM was
more strongly related negatively to average total outdoor time per week during
the summer (P=0.09) and  positively to  the proportion  of outdoor time that was
recreational  (P=0.15) than was MM as a whole.

     Incidence of SSM was also  strongly related to frequency of participation
in some but not  all outdoor recreations that involve substantial sun exposure
(Table 8).   It  is particularly  interesting that a relationship between fre-
quency of sunbathing  and incidence  of SSM was  evident  when only  SSM  of the
trunk was  analyzed (the trunk is presumably the body site subject to the most


                                      150

-------
 Table 8.  Associations Between Frequency of  Particular Outdoor  Recreations
           in Summer and Incidence of Superficial Spreading Melanoma in
           Western Australia,  1980-81
Activity
                                        Relative
                                          Risk
Confidence
  Interval
Boating

  Never
  Less than once a week
  Once or more a week
                                         1.00
                                         1.06
                                         2.43*
0.54
1.10
2.09
5.39
Fishing

  Never
  Less than once a week
  Once or more a week
                                         1.00
                                         1.03
                                         2.72
0.63
1.15
 1.68
 6.43
Swimming

  Never
  Less than once a week
  Once or more a week
                                         1.00
                                         1.30
                                         1.14
0.76
0.72
2.20
1.82
^bathing
vAges 15-24  years only)

  Never
  Less than  once a week
  Once or  more a week

      15-24  years and SSM of trunk only)

  Never
  Less than  once a week
  Once or  more a week
                                         1.00
                                         1.26
                                         1.32
                                         1.00
                                         1.20
                                        2.55*
0.78
0.80
0.51
1.05
2.05
2.17
2.81
6.19
  P
+ * value  for  trend  in  each case <0.05.
  Detailed questions asked  only for this period of life.
  Source:  Holman, Armstrong,  and Heenan (1986)
se intermittent  exposure with  sunbathing).   MM  other than  SSM did
strong associations with any of these recreational exposures.
                                                                           not
                                     151

-------
     Clothing  may modify the  relationship between sun exposure  and incidence
of  MM,  as Table  9  shows.   Incidence of  both  melanoma and SSM is  examined in
relation  to  the person's clothing  habit  during outdoor work  in  summer at the
primary  site of  the  MM.  The  incidence  of both  was substantially  higher in
those  who sometimes  or usually  exposed  the  primary site  than  in  those who
usually kept it covered.  For  all MM the  RR was highest  in those  who sometimes
exposed  the  site,  an  observation  that  is consistent  with  the  intermittent
exposure  hypothesis.    This  was not  the  case,  however,  for  SSM.  SSM of the
trunk in  women was  very strongly related to the type of bathing  suit that had
been worn in summer between  15  and  24 years of age.   Relative to  an RR of 1.00
in  those  who had  worn a one-piece suit with a  high back-line, the  RR was 4.04
(CI 0.65-25.2) in those  who had worn a  one-piece suit  with  a low back-line,
and 13.0  (CI  1.95-83.9; P value for  trend  0.005)  in  those who had  worn a two-
piece suit or  no  bathing suit at  all.


    Table 9.   Associations Between  Clothing Habit  at  the Primary  Site of
               Malignant Melanoma  During Outdoor Work  in Summer and  Incidence
               of  Malignant Melanoma  in Western  Australia,  1980-81
     —           	     r 	                                              _^^^^^^*

                                                             95%
                                             Relative     Confidence
Clothing Habit                                Risk        Interval
All Melanomas

  Usually covered                             1.00
  Sometimes exposed                           2.49         1.58  3.94
  Usually exposed                             2.08*        1.27  3.40

Superficial Spreading Melanoma Only

  Usually covered                             1.00
  Sometimes exposed                           2.16         1.14  4.10
  Usually exposed                             2.43*        1.18  4.97
* P value for trend in each case <0.01.
  Source:  Holman, Armstrong, and Heenan (1986)
DISCUSSION

     The reduction  of  MM incidence by high natural  skin pigmentation and its
increased  incidence in  skin  that  is  highly  sensitive  to  the sun  are wel1
known.   These  observations have  been  confirmed by  the  Western  Australia0
study.  Indirectly, they implicate sunlight in the etiology of MM.  This study
has also provided  evidence that incidence of  MM  increases with total accumu~
lated exposure to the  sun.   Incidence  was lower in migrants to Australia tha*1
in native-born  Australians,  was positively associated with mean  annual hour3


                                      152

-------
°f bright  sunlight averaged  over  all places  of residence, and  increased in
those with sun-damaged skin and a  past history of non-melanocytic skin cancer
(generally accepted as being due to exposure to the sun).

     Superimposed  on  this  background,  there  was some  evidence  that  inter-
wittency of sun  exposure  may  be particularly  important  in  causing MM.   Inci-
dence rose slightly  with increases  in  the proportion of total  exposure that
was recreational, but certain  outdoor recreations, often involving intense sun
exposure,  appeared  to be particularly  strongly  related  to it,  for  example,
boating, fishing,  and sunbathing for MM  of the trunk.  When  clothing habits
were taken into account,  there was strong association between MM and unclothed
exposure of the  primary  site  of the tumor while  at  work.   Thus  the anomalous
relationship  between MM incidence and outdoor work overall may be due, in part
at least,  to a  tendency of  those who work outdoors to be more  careful in
protecting themselves from the sun  than  those  who  expose themselves  only
recreationally.

     If the  intermittent  exposure hypothesis  for the  relationship of  MM to
sunlight is correct,  it has important implications  for  prevention.   Figure 1
shows a concept  of the  exposure-response relationship  for SSM  and  sunlight
under the  intermittent exposure hypothesis.   While  this  concept  applies to
lesions that have  their  origin in SSM, as they are probably the majority of
MM» it  may be considered to  apply to MM as a whole,   On average  (curve C)
incidence  of  SSM first rises as frequency of exposure increases and then falls
aa some critical exposure frequency  is  passed.   Thus, on average, whether or
not reduction in sun  exposure will be a  "good  thing"  (in  terms  of prevention
of MM)  will  depend  on  where  a  population lies on  this  exposure-response
curve.  The position  will probably depend both on the genetic  composition of
the population and the available sunlight (expected  absorbed dose per unit of
time of exposure to the sun).

     At the individual level, the shape  of the exposure response curve will
Probably be  determined by  the  pigmentary response  of the  skin  to sunlight.
Those with a. poor  pigment  response  (curve B)  may  experience  progressively
increasing incidence  of  SSM,  whatever the  frequency (and dose)  of sun expo-
sure,  because  a protective tan is  never obtained.    Others who  tan readily
(curve A)  may show little rise  in  incidence of SSM at all with increasing sun
exposure before  incidence falls back  to background  levels with  further  sun
exposure.   While the  former may be best advised to protect themselves against
the sun at all  times; the  latter,  if  exposed more  than minimally,  should
perhaps continue sun  exposure to ensure  that  they stay  as  far  as possible to
the right  of the  peak.   Until these  concepts  are  clarified or discarded,
caution should be  exercised in making recommendations about sun  exposure—at
least with reference to prevention of MM.
                                      153

-------
Incidence
rate of SSM
                                                       Low  pigment response
                                                      Average pigment response
                                                   ^ High pigment response



                                                                  ^^-^
                                                                         *^^»
       Figure 1.
              Frequency of UVR exposure

A Concept of  the  Exposure Response Relationship for Super-
ficial Spreading  Melanoma And Sunlight
                                          154

-------
REFERENCES

Armstrong, B.K. 1984. Melanoma of the skin. Brit. Med. Bull. 40:346-50.

Armstrong, B.K.,  C.D.J.  Holman,  J.  M. Ford,  and T.  L. Woodings. 1982. Trends
     in melanoma  incidence and  mortality in  Australia.  In Trends  in cancer
     incidence. Causes  and  practical implications,  ed.  K. Magnus,  399-417.
     Washington:  Hemisphere.

Breslow,  N.E.,  and N.E.  Day 1980.    Statistical Methods  in  Cancer Research.
     Lyon:  International Agency for Research on Cancer.

Crombie, I.K. 1979. Racial differences in melanoma  incidence.  Brit. J. Cancer
     40:185-93.

Holman, C.D.J., and  B.K.  Armstrong.  1984a. Pigmentary traits,  ethnic origin,
     benign nevi, and family  history as  risk  factors  for  cutaneous malignant
     melanoma. J.  Nat.  Cancer Inst.  72:257-66.

Holman, C.D.J., and  B.K. Armstrong.  1984b.  Cutaneous malignant  melanoma and
     indicators  of  total  accumulated  exposure  to  the  sun:  An  analysis
     separating histogenetic types.  J. Nat. Cancer Inst. 73:75-82.

Holman, C.D.J., B.K. Armstrong,  P.R.  Evans,  G.J. Lumsden,  K.J.  Dallimore,  C.
     J. Meehan,  J.  Beagley,  and  I.M.   Gibson.  1984.  Relationship of  solar
     keratosis and history  of skin cancer to  objective, measures  of  actinic
     skin  damage.  Brit.  J. Dermatol. 110:129-38.

Holman, C.D.J.,   B.K.  Armstrong,  and P.J.   Heenan.   1983.  A   theory  of  the
     etiology and pathogenesis of human  cutaneous malignant melanoma.  J.  Mat.
     Cancer Inst.  71:651-6.

Holman, C.D.J.,  B.K.  Armstrong, and P.J.  Heenan.  1986.    Relationship  of
     cutaneous malignant  melanoma to individual sunlight exposure  habits.  J^
     Nat.  Cancer Inst.  76:403-14.

Holman, C.D.J.,  C.D.  Mulroney,  and B.K.  Armstrong.  1980.  Epidemiology  of
     preinvasive and  invasive malignant melanoma in  Western Australia.  Int.  J.
     Cancer 25:317-23.

Lancaster, H.O.  1956. Some geographical aspects  of mortality from melanoma  in
     Europeans.  Med.  J.  Aust.  1:1082-87.

      C.S., and J. Nectoux.  1982.   In Trends  in cancer  incidence.  Causes and
     practical implications,  ed.  K.  Magnus. Washington:  Hemisphere.
                                     155

-------
 Radiometry of Solar UV-B

 A- Baqer and N. Kollias
 Department of Dermatology, Al-Sabah Hospital, and
 Physical Department, Kuwait University, Kuwait
ABSTRACT

     Measurements have  been conducted  using  several detectors:  polysulfone
    , a  Robertson-Berger  (R-B)  meter, an EG&G  Spectroradiometer,  and an  IL
Phototherapy radiometer.   The purpose of the study was to assess the solar UVB
*n  Kuwait  and  to  arrive at  correlations  among  these  detectors,  which are
Widely used internationally.  These relationships have not previously appeared
ln literature.

     Polysulfone-based measurements were carried out over a two-year period  at
solar maximum, as a function of the time of day and the angle of the detector
with the horizontal.   The R-B meter measurements were conducted over one year
w*th a  half-hourly  record.    Spectroradiometric measurements were  conducted
°ver a  two-month period  and  simultaneously with the other  two in order  to
Establish correlations.   The International  Light instrument was operated over
a two-month period simultaneously with the polysulfone measurements.

     We  find that  although  none  of  the  integrating  detectors  adequately
Represents  the  sensitivity  of  human  skin   (erythema  effectiveness)   to
Ultraviolet B radiation (UV-B), they can provide  an  estimate  of the incident
^V-B.  Based on the polysulfone measurements, we have arrived at an empirical
expression that predicts  (within  10£)  the  polysulfone reading for  any half-
hour interval of the year.   We find further that the R-B meter measurements
ape very strongly affected by high temperatures  (>45°C).  The need  therefore
Pemains for a simple recording detector  that is  not  affected  by environmental
conditions.

1»THODUCTION

     In looking through  the  literature for  solar middle  UV-B  measurements,  as
        to  the  effect of UV-B on human skin (Ambach and Rehwald ,1983; Bener
    ; Berger and Urbach  1982; Blumthaler et al.  1985a,  b; Diffey, Larko, and


                                     157

-------
Swanbeck  1982;  Kollias  and Baqer  1984;  Mosely,  Davison,  and  Mackie  1983;
Rosenthal, Safran, and Taylor 1985; Qayyum and Davis 1984; Young et al. 1982),
one  finds that the  following  detectors have been  used predominately:   R-B
meter  (sunburning meter),  Eppley  Labs  UV-B  radiometer,  International  Light
phototherapy radiometer, and polysulfone film.

     Of these, the Eppley Labs radiometer was not available in the market when
our study started in  the fall  of 1983.  There is a  wealth  of data on the R-B
instrument and  a  rapidly  accumulating  set  of data on  the  polysulfone  film
detectors because they are  inexpensive and  easy  to use.   The International
Light instrument  is available  at many  phototherapy  centers,  and therefore it
is tempting to use it  outdoors  to  estimate the dose that the patients receive
after  treatment.   Spectroradiometric  measurements  are  difficult to  find as
they require expensive instruments and competent operators.

     A.E.S.   Green and  his  group  (1976-82)   have   carried  out  a number  of
investigations both theoretically and experimentally to characterize the solar
UV-B flux at the earth's surface.

     The  major aim of this  study  was to determine  the  correlation  among the
various integrating detectors  and  then how they relate  to  the sensitivity of
human skin.   By  setting all measurements  on  a common  denominator we can make
use  of  assessments   made  in   various  parts of  the  world  with  different
detectors'.

MATERIALS AND METHODS

Polysulfone Measurements

     The  films (40 pm in thickness and 12 x  12  inches  in  area) were cut and
mounted  in  35  mm slide mounts and  assessed  before and  after  exposure by
measuring their absorbance at 330 nm (Davis and Gardiner  1982).  The change in
absorbance due to the exposure  to  solar UV-B was converted  to an equivalent
305 nm UV-B  dose  in  J/cm2.  The films showed good  stability with temperature
and humidity;  however, their absorbance post  exposure  changed rather rapidly
with  time,  especially  over the first two days  of post irradiation.   As a
consequence,  all   films  were  assessed  as quickly  as  possible  after  being
exposed to  solar  UV-B.   Measurements  were carried  out  (8/83-10/85)  at solar
maximum,  as a function of the time of  day, and as  a function of the detector
orientation with  the horizontal.

Robertson-Berger Meter (Sunburning Meter) Measurements

     This is  an integrating  detector  that  gives a half-hourly printout of the
measured UV-B radiant  energy in counts, where 440 counts  equal one "sunburning
unit."  Measurements  were conducted from  11/84-11/85 at  a location very near
to  the  polysulfone  detector  holders.   This  detector  had   a  very  large
temperature  coefficient when  the  full range  of  temperatures  attainable in
Kuwait was  realized  (14£ per  10°C).   The dry bulb  temperature in an exposed
thermometer ranges from 10° to  75°C.   This  error becomes  very noticeable in
the summer months when the apparent maximum radiation recorded always occurred
before  solar  maximum.    Because   we   had  no  way  of  knowing  the  internal
temperature of the detector, we decided not to correct the data and not to use
them other than to obtain an estimate of the way the UV-B was varying over the
day and the months of  the year.


                                      158

-------
ii£&CLSpectroradiometer  (Model  550)  Measurements

     This  instrument  was  interfaced  to  a HP-85  microcomputer,  and  thus a
spectral  scan  could  be  conducted  in less  than 30  seconds and  recorded  for
further  analysis.   Measurements  were carried  out  at solar noon  from 3/85 to
5/85.   We could not  continue  beyond May as the  ambient  temperature was above
^°°c  in  the  shade  and  the   instruments  started  overheating   in   the  sun.
Measurements  were  carried out  at the same  location as  the polysulfone and  the
R~B meter and at the  same time.

^International Lipht 442 Radiometer  With  a SEE1240 Detector Measurements

     The  sensitivity  of  this  instrument did not prove to  be  adequate, and we
therefore  installed  an  analogue  output that  could be  read  on a  portable
voltmeter,  Fluke  77.    Measurements were carried out  simultaneously  with
Polysulfone films  in  March and April 1986.

^BLTS  AND DISCUSSION

     Although  it  has a  diffuser at  its input, the spectroradiometer  has a
Deceiving  angle of  ±5°.   This means that our  measurements  record  only  the
Direct  component  of  the solar   radiation.    The  principal  use  of  these
measurements  has  been  to correlate  these with  the  ones  conducted  by   the
Polysulfone  and  by  the  R-B   detectors.    The  correlation  among the  three
instruments can be seen in Figure 1.  The readings  seem to relate well to each
°ther for clear days,  i.e., when  the readings  are at their maximum values,  and
fclley do not  appear  to  relate as well  when the measurements  were attenuated
either due to clouds  or rising dust.  We selected the days that were clear, or
Reasonably clear  to establish  a  relationship  between the  integrated  value of
Radiance over the wavelengths  280-325 nm and over  1/2  hour with the values
°btained  from the  other detectors.   (See Table 1.)

     Table 1.   Spectroradiometric,  Polysulfone, and Robertson-Berger
               Meter  Readings  for Selected "Clear"  Days
Date

12.3.85
26.3.85
30.3.85
01.4.85
03.4.85
07.4.85
09.4.85
13.4.85
15.4.85
29.4.85
Irrad. 1/2 hr.

0.1488
0.2435
0.2320
0.1733
0.1506
0.2424
0.2671
0.2300
0.1893
0,1866
Polysulfone

0.3010
0.3710
0.3280
0.3380
0.3130
0.3940
0.4180
0.4320
0.3940
0.3890
R-B meter
SBU
0.9540
0.3450
0.2600
0.8920
1.0950
1.4000
1.4600
1.3650
1.2700
1.3050
                                      159

-------
d


1.5 -
x-x

*
L
in
O
1
UJ
o
a
CD
i
>
=» .5 -




n
8 Pol.
* SBU.
a SpQC

* * *
o** *
* „ °°* @* ° *
n ** 9 & * o
a Q a n
. • °0 . • t" 8
* « S * ra 9 *
• 8 ' o » %•
*
0 0

*
o
#
o o
0 * *
@
o o
0 i n i
                         MARCH  85
APRIL 85
     Figure  1.   The half-hour  integrated  readings for  the  polysulfone
detectors, the R-B meter,  and  the speetroradiometer,  for the months of March
and April  1985.   The polysulfone readings have  been  multiplied  by 3 and the
speetroradiometer by 50 so  that all  the  points  fall within one range.
                                     160

-------
     The polysulfone  reading is  in  J/cm2 of equivalent  monochromatic 305 nm
 radiation  and  for  this  reason  the  first  two  columns  in  Table   1  are
 different.  The irradiance was  first integrated over the UV-B wavelengths and
 was then  converted to J/cm2  by multiplying the final  result  by 1,800, i.e.,
 the number  of seconds in  1/2 hour.    The R-B meter was  integrating over 1/2
 hour also.

     The  relationship   between  total   irradiance  for   1/2   hour  and  the
 P°lysulfone   detector   readings   was  established  by  assuming   a  linear
 relationship between the  two.  The  equation y  = A + B x was  fitted with the
 v^lue of coefficient  A  = 0.   The value of the  slope  (B) was  calculated from
 the nne  Joining  the  centroid of all the  points to  the  origin  (x  = total
 irradiance per 1/2 hour, y =  polysulfone  reading).  The  centroid was found to
 De (0.206,  0.368).   Thus the value  of  coefficient B was  calculated to be B =
 y/x = 1.78.  Hence the relation between total irradiance per 1/2 hour and the
 Polysulfone readings can be represented by:   Polys,  reading (1/2 hour) = 1.78
  Total irrad.(1/2 hour)  where both  readings are given  in J/cm2.

     The relationship  between  total irradiance and  the  R-B  meter  was  also
 found  in  the  same manner  as  above.   The  centroid was located  at (0.206,
 1-235), yielding a slope  of B = 5.98.  Thus:

           R-B meter (SBU) =  5.98 *  total Irrad.(1/2 hour) (J/cm2).

 p°r the International Light instrument we obtained the following relationship:

             0.145 * polysulfone (J/cra2> = Intern.  Light  (J/cm2).

     Both   detectors  overestimate  the  actual  UV-B;  although   both  the
 Polysulfone and the R-B meter detectors show a  cosine  response with the angle
 °f  incidence  of  the  radiation  on   the  detector   surface,   they  do  not
 discriminate between the  direct and  diffuse  components.   On  the  other hand,
 the spectroradiometer  gives  readings  that  are closely  associated  with  the
 direct component.   Checking our results on the dependence of the solar UV-B on
 the detector   orientation  with  the  horizontal,  we  find  that  the  diffuse
 component  (90°  reading)   is  approximately  50%  of the  total;  therefore  the
 Pplysulfone correlation with  the  spectroradiometer is  approximately correct.
 ^e R-B meter  correlation is high;  however,  there is  no effort made  by  the
 Producers  of  this  instrument   to   correlate   the  readings   to   the  solar
 insolation; their interest is to correlate it to the Minimum Erythema Dose.

     Figure 2  presents the polysulfone measurements at solar  maximum carried
 out over a period of two  and  one-half years.   Given this large  volume of data,
 t seemed natural  to  attempt to model  the  solar UV-B   to predict,  based on  a
toodel, the solar UV-B insolation.   When we considered Figure 2  it became clear
 that the solar UV-B insolations follow a sinusoidal variation with time of the
year.   The  question  then  was whether we fit the average  of each month or  the
 £utline of  the  curve?   We decided to  fit the  outline of the curve from  the
 t°Pi   i.e.,  we selected  the  points  that  represent readings  taken  on  "clear
 dayg/i  Tne judgement  "clear day" was made on our own observations together
with those of the Meteorological Department of  the Civil  Aviation  Directorate
°f the State of Kuwait.   We then  selected the  mathematical expression that  we
 *elt best  represented  the results  and chose,  as  a start,  to fit  the  daily
 totals of solar UV-B.  The following  expression was chosen:


                                      161

-------
     6   -f
     5
OJ
™ .4   --
 E
LJ
uj  .3
CO

a

on
 I    o
>  . 2
ZD
. 1
                    V      +
                                                     *

                                                      4-
                                                    V
                                                     *
                                       V
              ^—i—H*—i—i—i—H—i—H—i—i—h
            1983
                          1984
1985
Figure 2. UV-B  Insolation  Measured From  11:30  to 12:00 Noon  With
          Polysulfone Film Versus  the Time of Year.
                            162

-------
                    Total UV-B (per day) = A + B sin (t),

Where t represents an angle that corresponds to  the day  of the year; A is the
°C level,  i.e., the average over the year, total daily UV-B insolation;  and B
is the AC amplitude, i.e., the amplitude of variation of the solar insolation
above and below the average.   It is interesting to note at  this  point that A
multiplied by 365 gives us the total UV-B  insolation for the year.  The angle
t was chosen so that 0° corresponded to March  21  (the spring equinox), 90° to
June  21,  180°  to  September  21  and  270°  to  December  21.    The angle  was
calculated using the following expression:

                            t  = 30  (M-1) +  D  -  81,

where M is the  month of the year (January  =  1, February = 2,  etc.),  and D is
the day of the month.

     A graph of the total  daily UV-B dose versus sin(t) shows how well the two
variables  are  correlated  (see Figure  3).   A  good straight  line fit to  the
®xPerimental   points  follows.     The regression  analysis  yields   R^  =  0.983
(correlation coefficient R  =  0.991).  The equation  predicting the  amount of
daily UV-B insolation  then becomes:

           Total UV-B (per day) = 3.71 + 2.42 sin[2=30(M-1)+D=8l],

where M is the month of the year and D  the  day  of the month.
                a

                2
              ^

              I'
              v 0
                -z
                -3
                                         SIN ( 8 >
        Figure 3.   Total Daily UV-B Minus the Yearly Average Versus Sin(t),
                   Where t=0 for 3/21,  t=90 for 6/21, etc.
     Because the derived relation worked so well, we proceeded to fit the UV-B
           as a function of the time of day (i.e., the diurnal variation).  To
         we  needed  to describe mathematically  the daylight hours,  i.e., the
     interval  (sunset-sunrise).   This was calculated from  data  obtained from
                                      163

-------
the  Meteorological Department and  was plotted against  sin(t)  where t  is  the
same  angle as in  the previous discussion.   It  was noticed that the midpoint
between sunrise  and sunset  on the average falls  at  11.714 hour
Kuwait local  time  (11  hours, 42 minutes,  50.4 seconds).  The variations  in  the
midpoint  values are  between  11.52  hour  and 11.96 hour  (Kuwait time), with
standard deviation  =  0.191.

     On the other hand,  the maxima of the daily UV-B curves  have an average
value  of   11.81  hour  (11  hours,  48 minutes,  28.8  seconds Kuwait  time),  the
standard  deviation being  0.462.    It  is  interesting to  note  that  both  the
midpoint  of the sunrise-sunset  interval  and the  UV-B  maxima  on the diurnal
measurements are behind  12 noon.   The first  falls 0.286 hour (17 minutes,  9-6
seconds)  before noon  and  the  second  0.192  hour  (11 minutes,  31.2 secondsJ~~
before noon.   For  calculating  the  angle t, we decided to take  11.75 hours  O1
hours, 45  minutes  Kuwait local time) as the  solar noon; that is  to say  that t
=  90°  at   11.75  hours.   This  result is not  surprising:   Kuwait city lies ab
longitude  48°, i.e.,  3°  short  of  the hour meridians that occur every 15°.  We
therefore  should expect  solar noon to occur  0.2  hours before  Kuwait local
time,  that  is  11  hours  48 minutes.   This result  coincides  with  the  one
obtained from  the diurnal measurements.

     •To  fit  the  polysulfone-based  UV-B  measurements  every   1/2  hour,  we
selected the  measurements made on reasonably clear  days.   These are like  the
curves on  Figure 4.   We determined that  the best  mathematical expression to
give a reasonable fit  to the data over  the data collecting period was:

                    UV-B dose  (1/2 hour) = C  + D sin2  (q),

where C and D are arbitrary constants  and q  is an  angle corresponding to  the
time of day expressed as the ratio of the  interval from sunrise to the hour in
question divided by the sunrise sunset  interval times  180°.

     The coefficient of determination R2,  for most of  the readings, was better
than  0.9.   The  average  value of  R =  0.91   for the  days considered  in thi*
sample leads to a correlation coefficient of  0.95 with a standard deviation of
0.094.  The coefficient  C  should be equal to zero and the value calculated i3
-0.006 with  a standard deviation  of 0.0008,  which is very small compared to
the UV-B doses.   The value  of coefficient D  depends on the time of the year
and it should  be equal to  the value of maximum UV-B fialf-hourly dose for  the
day.

     We thus arrived  at  the following  expression for  the  half-hourly dose °*
solar UV-B:

     UV-B  (per 1/2 hour) =  (F * sin2[{l80/G}*{h-nn/60}-{2124/G-90}]) - 0.0063.

where

     F = 0.3346 + 0.1898 *sin[30 *(M-1) + d-81];
     G = 12.17 + 1.81 * sin[30*(M-1) + d-81];
     h = hours (Kuwait local time);
     m = minutes (Kuwait local time);
     M = month of the year  (Jan.=1, Feb.=2 etc.);
     d = day of the month (1,2,3,  etc.).


                                      164

-------
                                            0  08/05/85
                                            +  28/04/85
                                            *  13/03/85
                                            #  22/02/85
                                            3  .23/01/85
                    8        U        14
                        TIME OF DAY  ( Hrs.  )
17
20
Figure 4.  The Diurnal Variation of the Solar UV-B as  Measured by the
          Polysulfone Films
                           165

-------
      Table 2. Comparison Between Calculated and Measured UV-B Insolation
Date
day-mo-yr
26.10.83 	
10.15
12.15
15.15
16.45
05.01.84 	
10.15
12.15
15.15
16.45
16.05.84 	
09.45
11.45
15.15
17.15
21.11.84 	
10.15
11.45
14.15
16.15
13.03.85 	
10.15
12.15
15.15
16.45
Time
hr-min
	 08.45 ...
0.191
0.248
0.045
0.00
...08.15 ...
0.085
0.109
0.023
0.00
...07.15 ...
0.327
0.439
0.173
0.020
...07.45 ...
0.144
0.148
0.092
0.00
	 08.15 ...
0.202
0.292
0.126
0.020
Measured UV-B Calculated UV-B
 
	 0.0963 	 0 OQ3
0.183
0.218
0.064
0.0003
	 0.020 0 030
0.115
0.141
0.030
0.00
	 0.081 .. . 0 120
0.385
0.482
0.228
0.036
	 0.023 . 0 018
0.134
0.165
0.088
0.003
	 0. 120 0 104
0.253
0.292
0.104
0.012
     For any particular month, day, hour, or minute, the variables F and G
first calculated  and their values  are then introduced  in  the UV-B equati°°'
The above  equation is not  as complicated as it seems.   It simply represent*
the product  of  the equations mentioned  in  the  previous discussion, where the
term F gives the  variation  of the UV-B with the time of year, and G describe*
the variation of  the sunrise-sunset time interval  with the time of year.  °
Table 2 we  present a comparison of the  calculated versus the measured v
of solar UV-B at  1/2-hour intervals.  We have tested the validity of the
derived expression by  calculating the  deviation  of   the  observed from
calculated  values for two  years.   From  this  calcuation we obtained  a <^r f
identical to the  one for the  variations  of the ozone  layer with  the  ti»e
year for our latitude.
                                      166

-------
FINDINGS

§£gctral Sensitivities of Detectors

     The relative  spectral  sensitivities of  all  the detectors  considered in
     study are  presented in Figure  5  (Davis, Deane, and Diffey 1976;  Berger
and Urbach 1982).  It can be noticed that  they are all different from that of
human skin — at least as far as erythema  induction  is concerned.   Furthermore,
because of the shape of the curves and the  fact that the spectral composition
°? the solar  UV-B varies with  the time  of year, the relationships we developed
foi> interrelating  the measurements  of  different detectors are fairly precise
°n*y for the months  during  which we measured them and for clear weather.   We
have good reasons  to expect that  the  atmospheric  conditions at  a  given time
will cause unequal attenuation of  the  various UVB spectral  components  (Bener
1969).

       of solar  UV-B  in  Kuwait

     Based on our measurements, an empirical  equation has been developed that
can be used to  predict  fairly  accurately the amount of  solar UV-B  in Kuwait,
"Or any day of the year  and  for any time  during the specified day based  on the
Polysulfone measurements.  Thus,  the  answer  that we obtain  is the reading that
^6 would make if we exposed a polysulfone film for half an hour  to  the  sun on
* clear  day.    Corrections  for  clouds,  humidity,  dust, etc. have not  been
aeveloped as  yet.
^ati
     pnship  of Detector  Readings
,     A  relationship has been established between the polysulfone  readings and
 he R-B readings by correlating  both of them to spectroradiometric  readings.
    relationship is:   3-36  x (polysulfone,  J/cm2/0.5 hr.)  =  1  SBU.
     Furthermore  the  relationship between  each  of the  polysulfone and  R-B
 eter and  the  total  solar  irradiance  for  1/2  hour  has also been established:

     *  Polys,  reading (1/2  hour)  =  1.78  x Total  irrad.  (1/2  hour)

     '  R-B  reading  (SBU)  =  5.98  x Total  Irrad.  (1/2 hour) (J/cm2).

        V-B  Insulation
_  ,  The annual  total  UV-B  insolation  has  been measured  to  be  1/42  x  10^ J/cm2
Or> 1.107 x  103 SBU.

     Using  these, we  can estimate the  conversion  factor between  polysulfone
Rj  SBUs.   By dividing,  we  obtain  a factor of 2.9» which is close to  the above
TVen value.   Scotto,  Rears, and Fraumenti (1982) have  proposed the  following
         for  estimating  the  annual  solar  UV-B  insolation  in  SBUs  as  a function
 1  latitude and altitude:

     UV-B insolation  (SBU) = (1/440)  x  [1,500,000  - 50,000 x

                        (L - 37.9)  +  105  x  (A  -  1,5000)3  x (Cnts)
                                     167

-------
        270
280
290
300
310
320
330
                          WAVELENGTH  ( nm )
Figure 5.  Spectral Sensitivity of Human Skin, Polysulfone Film,
          R-B Meter,  I-L Meter (all curves  are normalized to 1)
                               168

-------
This equation  gives for  Kuwait (29.5°  latitude):  4.01  x  103 SBUs  which  is
Quite close to the measured value.

Jfobertson-Berger Meter Measurement Adjustment

     The R-B meter was found  to have a very large temperature coefficient and
therefore  a very  large  correction  has  been  made  on  the values  obtained.
Berger and Urbach (1982) have  reported R-B meter based data from Tallahassee,
Florida, and  El  Paso,  Texas,  which  have latitudes  very close  to  that  of
Kuwait.  The above equation (Scotto 1982) thus gives the following values:

     •  ELP (calc) = 4.02 x 103 SBU
     •  KWT (calc) = 4.01 x 103 SBU
     '  ELP  = 4.889 x 103 SBU
     •  KWT  = 4.107 x 103 SBU.

     While the calculated values for the two cities are essentially identical,
we find  a  large  difference  in the  measured  values  for  ELP and  KWT.   If we
correct the KWT readings for temperature, normalizing to 43.5°C, we obtain KWT
(temp,  adjusted)  = 5.18  x 103  SBU,  which is  much closer  to the ELP value
considering  the  rough   correction.    It  is   thus   our   contention  that  the
International data reported so far  in climates where the maximum reading of an
exposed dry bulb thermometer reaches  over  50°C  are  in  significant error.  The
R~B meter  when used  in warm  climates needs  to be modified  to  account  for
temperature or  not be  used.    The number  of  counts  is smaller  at  elevated
temperatures than at normal temperatures.

CONCLUSION

     In closing  we summarize  a useful  relation.   We  have found that there
exists a simple relationship  between the total  daily UV-B measures  and  the
arn°unt measured between  11:30 and 12:00 noon.   For polysulfone  readings, if we
multiply the  11:30 to  12:00  reading  by a factor  of  10,  we  obtain  a close
aPproximation to  the daily dose.  The maximum deviation is in the months of
June  and  July when  the  factor  should  be   12.   For the  R-B  meter  the
relationship is similar.   For March  12  to  September 21  the factor is 12  and
for September 21  to March 21  the factor  should be  10.   The answer  is always
within  10#.    It  is  thus possible,  if  one  is  short  handed and   is  only
interested in  rough estimates, to measure  of the solar  UV-B  insolation from
11:30 to 12:00 and then  to calculate the daily total.

ACKNOWLEDGMENT

     This  work was  supported  by  the  Environmental  Protection  Council  of
Kuwait.  We wish  to express our thanks to Dr.  M.M.  Selim for  his  support  and
encouragement and to Mr.  Iqbal Sadik for his careful  calculations.


REFERENCES

        W., and W. Rehwald.   (1983).   Measurements of  the annual  variation of
     the erythema dose of  global radiation. Radiat Environ Biophys.   21:295-
     303.
                                      169

-------
Bener, P.  1969.  Spectral intensity of  natural ultraviolet radiation  and its
     dependence on various parameters.  In The biologic effects of ultraviolet
     radiation, ed. F. Urbach.  Oxford,  U.K.:  Pergamon Press.

Berger, D.S.,  and F.  Urbach.    1982.   Climatology of  sunburning ultraviolet
     radiation.  Photochem Photobiol.   35:187-92.

Blumthaler, M.,  W. Ambach,  and H. Canaval.    1985a.   Seasonal  variation of
     solar  UV-radiation  at  a  high  mountain  station.  Photochem  PhotobioA-
     42:147-52.

Blumthaler, M.,  W. Rehwald,  and W.  Ambach.    1985.   Seasonal  variations of
     erythema dose at two alpine stations  in different altitudes.   Arch Met
     Geoph Biocl (ser B).  35:389-97

Chai, A.T., and  A.E.S.  Green.   1976.   Ratio  measurement of diffuse to direct
     solar irradiances in the middle ultraviolet. App Opt.   15:1182-87.

Davis, A.,  G.H.W. Deane, and  B. L.  Diffey.    1976.   Possible  dosimeter for
     ultraviolet radiation.   Nature.  261.

Davis, A.,  B.L.  Diffey,  and T.  K.  Tate.   1981.    A personal  dosimeter for
     biologically  effective  solar  UV-B  radiation.    Photochem  Photobiol'
     34:283-86.

Davis, A.,  and  D.  Gardiner.   1982.    An ultraviolet  radiation monitor for
     artificial weathering devices.   Pol Degrad Stab.  4:145-57.

Diffey, B.L.,  0.  Larko, and G.  Swanbeck.   1982.  UV-B doses received during
     different outdoor  activities  and UV-B treatment  of  psoriasis.   Brit^Jj.
     Dermatol.  106:33-41.

Doda, D.D.,-and A.E.S.  Green.   1980.  Surface reflectance  measurements in the
     UV from an airborn platform.  Part  1.  App Opt.   19:2140-45.

Doda, D.D., and A.E.S.  Green.   1981.  Surface reflectance  measurements in the
     UV from an airborn platform.  Part  2.  App Opt.  20:636-42.

Fanselow, D.L.,  M.A.  Pathak, M. A. Crone, D.  A. Ersfeld,  P.   B.  Raber,  R. •*•
     Trancik, and M.  V.  Dahl.   1983.  Reusable ultraviolet monitors:  design*
     characteristics, and efficacy.   J Am Acad Dermatol.   9:714-23.

Garrison, L.M.,  L.E.  Murray, D. D. Doda,  and A.E.S. Green.   1978.   Diffuse-
     direct  ultraviolet  ratios  with a  compact double monochromator.    Ag£
     Opt.  17:827-36

Green, A.E.S.   1983.   Ultraviolet ground  reflectivities.   Personal  Communica-
     tion.

Green,  A.E.S.,  K.  R.  Cross,  and  L.  A.  Smith.   1980.   Improved  analytic
     characterization  of ultraviolet  sunlight.  Photochem  Photobiol.   31:59-
     65.
                                      170

-------
     as,  N,.  and  A.  Eager.   1984.   Measurement of  solar middle  ultraviolet
     radiation  in  Kuwait.   Solar Wind Tech.  1:59-62

     y, H., M.  Davison,  and R. M.  Mackie.   1983.  Measurement of daylight  UVA
     in Glasgow.   Phys Med  Biol. 28:589-97.

     ra, M.  M.,  and A.  Davis.   1984.  Ultraviolet radiation for various  angles
     of exposure  at Jeddah and its  relation to the weathering of  polyacetal.
     Pol Degrad Stabil.  6:201-09.

     , p.,  and  A.E.S.  Green.   1978.  Ultraviolet aureole around a  source at  a
     finite distance.  App  Opt.  17:1923-29.

R°senthal,  F.S.,   M.  Safran,  and  H.R.  Taylor.   1985.    The ocular  dose of
     ultraviolet   radiation  from  sunlight  exposure.   Photochem  Photobiol.
     42:163-71.

 chiPpnick,  P.P.,  and A.E.S.  Green.   1982.   Analytical  characterization of
     spectral   actinic   flux  and  spectral   irradiance   in  the    middle
     ultraviolet.  Photochem Photobiol.  35:89-101.

Sc°tto, j.f  T.R.   Rears,  and  J.F.  Fraumenti Jr.   1982.    Solar  radiation.  In
     Cancer  epidemiology   and  prevention,  eds.  D.  Schattenfeld  and J.F.
     Fraumenti  Jr., Chapter 14,  254-76.  Philadelphia:  W. B. Saunders  Co.

*°Un8>  A.R.,  A.V.J.   Challoner,   I.A.  Magnus,  and  A.  Davis.    1982.    UVR
     radiometry   of    solar    simulated     radiation    in    experimental
     Photocarcinogenesis studies.  Brit J. Dermatol.  106:43-52.
                                     171

-------
The Role of Native Pigment in  Providing
Protection Against UV-B Damage in Humans

N- Kollias and A. Baqer
Department of Dermatology, Al-Sabak Hospital
Physical Department, Kuwait University
Kuwait
ABSTRACT

    This  paper  assesses the  average amount of pigment in a  sample  of the
Population of Kuwait and compares  it with the sensitivity of the population to
ai"tificially produced UV-B, as well as monochromatic bands  of UV-B, to arrive
   an estimate of the protection afforded  by the native pigment.  The pigment
     Of  the  population sampled was 2.18  on a scale from 0 to 9,  while the
      in  an equivalent sample of northern  Europeans would be 0.6-0.8.   In
these  measurements  we   estimate  the  pigment level  (melanin  concentration)
a?suming it resides  in  the epidermis.  This  implies that the concentration of
    in in the local population is on the order of 3.5 times larger, while the
      of light that enters the dermis after the above absorption is approxi-
      20 times smaller.  The  correlation  found between the pigment level and
    minimum  dose  for a UVB- induced erythema was very weak, with an average
vaiue  less than  one half  the value of  a  northern European   sample.   The
responses to monochromatic bands of UV-B indicate that the  action spectrum of
°U1:> population is different  from that reported by  WHO  (1982)  for a standard
Population sample, especially  at 295 nm.

    We conclude  that the pigment plays  two  roles in photoprotection.  First,
lt absorbs  light, and  the  suppression of  the erythema effectiveness  of the
^diation is proportional to the absorbance.  Second, it modulates the amount
of UV-B that is delivered to the dermis  and  it appears that carcinogenesis is
Proportional to this intensity.
    Numerous researchers  have  concluded that people who are more pigmented
    less susceptible to UV-B  (Urbach  1982; Pathak and Fitzpatrick 1974; Hawk
    Parrish 1982).   This implies that pigmented people are at a lower risk of
  Veloping  an  erythema reaction  and are  also  at  a lower  risk for  tumor
Production.  Human  skin has been classified in six types according to the way


                                   173

-------
it responds to sunlight  (Pathak,  Fitzpatrick,  and Parrish 1982), i.e.,  always
burn  easily-tan  little  or  none,  usually  burn  easily-tan  minimally,  &urn
moderately and average tan.  Such classification is based on  clinical history
and no  mention  is made  of native pigment.   We are  looking for an  objective
criterion that would allow assessment  of the risk factor.   Native pigment i3
an obvious candidate.

     Amblard et  al.  (1982) show  that  native pigment and eye  color  exhibit a
good  correlation with the erythema threshold  level (minimal erythema dose,
MED).   A recent  study  (Shono  et al.   1985)  suggests that  there  is  a  strong
correlation  between  native  pigment  and  erythema  reaction  with  a  small
statistical sample.

     In Kuwait we find the native pigment to be a weak indicator of a person s
anticipated response  to  UV-B.   That  is  to say,  given   two persons  of e
pigment  level we can only predict their  MED within a  factor of  two  of
measured value — not a precise estimate.  Native pigment is a parameter that  s
perceived by the  eye, i.e., using visible  radiation.   In general, it is not a
good  practice  to  deduce  the absorbance  of any  material in  the ultraviolet
simply by recording its absorbance  in  the  visible,  unless, of course, one
identified the  compound  by its visible spectrum.  The major  absorber  in
skin  is  melanin,  which  resides  mainly in  the  epidermis in  melanocytes an
keratinocy tes .    It absorbs strongly in the  visible and  even more strongly |n
the ultraviolet  (UV).    The absorption by  intact  epidermis  (Kaidbey  et al-
1979) shows a linear relation with  wavelength  down to about 320 nm;  for wave-
lengths shorter  than 320  nm the absorbance  increases rapidly.  Over the  UV-»
range the  absorbance  by  the epidermis shows an  increase by  a  factor  of tw°
(approximately) .

     A method has been  developed for  assessing the melanin concentration *
human skin (Kollias and  Baqer 1985; 1986).   We have used this method  to assess
the pigment  level in a  small  sample  of the population  of Kuwait.   We  fcne_.
tested the sensitivity of  local skin  to polychromatic and monochromatic   -
radiation.  Using the statistics available through the Kuwait Cancer
we  assessed  the  UV-B  risk  and  the  role  that  native pigment  plays  in
erythemogenesis  and carcinogenesis.

MATERIALS AND METHODS

Measurement of the Pigment Level of a Small Sample of the Population  of,

     Over the last two years,  we have carried out measurements of skin pigmerl
on 314 volunteers.  The measurement was non-invasive and only took 1.5 minut6
to complete.  The probe that comes  in contact with  the  skin  was temperatuf
regulated to cause a minimum  of discomfort  to  the  individual  volunteer;  °ve.
250 of  these  were patients.  The  volunteers  came from all walks  of life
were randomly selected.  The measurements on the patients were always taken
uninvolved areas of the skin.   We  did make measurements on involved areas
those  were excluded  from  this study.   We  made  certain that  none  of
volunteers were  under  any medication  which  could possibly have  an effect °
their  pigmentation.    The  healthy  volunteers  were  the  doctors,  nurses*
technicians, and personnel of the Skin Department of Al-Sabah Hospital as v»e*
as some students from  Kuwait University.   All volunteers were informed of ™
nature of the experiment and their consent was obtained.


                                      174

-------
Measurement of the Minimum Erythema Dose to Artificially Produced UV-B
Radiation of Human Skin

     These  measurements  were  conducted  on  26  psoriatic  patients  over the
course of  one  year.   These  patients  were about to begin  treatment with UV-B
radiation,  which  constitutes   a  very  effective  line   of   treatment  for
Psoriasis.  Each  patient was phototested  to determine the minimum UV-B dose
necessary to elicit an erythema reaction.   Before  any radiation was applied,
we made  sure  that  all  the  parameters were recorded  and  pigment  index was
measured.   The pigment level was  evaluated on an  area of normal  skin.   The
information obtained in these measurements was of interest to the physician in
Prescribing the indicated dose of UV-B for the treatment.

     The patients  were given doses of 50,   100,  150,  and 200 mJ/cm2 on four
areas of  the  back, that  were 2,5  cm   in diameter.   Patients with  verv light
complexion  were  initially given  doses of  20, 40,  60, and  80 mJ/cm  .   The
irradiated sites were observed 24 hours after irradiation and the minimum dose
required  to  elicit  an  erythema  reaction  was  recorded.    If  no  reaction
occurred,  the  test was  repeated  with four  higher  doses.   If, on the other
hand, all  areas  showed erythema,  then the  test was repeated with  four lower
doses.    A Waldman  Model   S0001K  upright  UVB-UVA  unit  was  used  for  the
Radiations.    The patient  received   radiation  In a  standing  position  at  a
Power of 0.4 mW/cnr so that  the desired doses could be delivered within a few
ninutes  at minimum  discomfort  to the  patient.    During  the  phototest the
Patients' face and body  were covered   by a  protective  robe which allowed only
the  four  areas on the back  of  the patient  to be  irradiated,   When the dose
1«vel was  reached for the first  areas,  the cubicle door was opened and that
area was covered.   This  procedure was repeated until  all  spots were covered.
The  UV-B   producing   lamps   in  the  apparatus  were  Sylvania  75/85W/UV21
fluorescent lamps.

     All  the  tests  and  measurements  carried  out  in  this  section  were
supervised  by  Dr.  V. Heigy of  the   Department  of  Dermatology of Al-Sabah
H°spital.   All patients  were  informed  of  the  nature of  the  tests and the
Masons  for them; their  consent  was  obtained before the measurements were
made.

            of the Erythema Effectiveness of Three Selected. Wavelengths of
                             -


     In this series of measurements we used  16 healthy volunteers who had skin
      common to the  area of Kuwait.   The wavelengths  used were 295, 305, and
315  ±5  nm.   The irradiation sites  were  on the upper  back  of  each individual
and  we  made sure that we  stayed away from the middle of  the  back since the
Sickness of  tissue  under the  skin as well as the blood  supply  differs from
the  rest  of the back.  The  volunteers were in a sitting  position  during the
test.  At  each wavelength  six spots were  irradiated starting with a  dose that
Was  considered to be  suberythemogenic,   progressing  to higher  doses  at 20%
increments.  Thus, the three wavelength tests generated three  rows of spots 6
"^ in diameter on  the  back of each volunteer„  We further made sure  that none
of the subjects had exposed  their backs  to  the sun in the two to three months
itt>raed.iately before the test.
                                      175

-------
     The instrument used to carry out these irradiations was an Applied Photo-
physics "Clinical Photoirradiator" model UV-90,  which is capable of providing
a monochromatic output in the UV-B wavelengths used in this study.  The output
power of this  instrument was 2.1 mW/cm2 at 295  nm, 2.4  mW/cm2 at 305 nm, and
2.8 mW/cm2 at  315  nm.   The  range  of doses used was  from  12  to 150 mJ/cnr at
295 nm, 33 to 270 mJ/cm2 at 305 nm, and 330 to 2700 mJ/cm2 at 315 nm.  Because
of  the  high doses  necessary to  elicit  an erythema  reaction at  the longest
wavelength the total  time for the test to  be completed  was approximately 1-5
hours.  This narrowed the number of people who were willing to volunteer.

     Each  volunteer  had to return  to  the   Phototherapy Unit  of  Al-Sabah
Hospital eight hours  and 24  hours after  irradiation  to assess  their  skin
reaction.    The   bandpass   of  the  irradiation  was   ±5  nm  for  all  the
wavelengths.  All the tests carried out in this section were supervised by Dr-
Yousef Malallah  of the  Department of Dermatology  of Al-Sabah  Hospital, wn°
worked very closely with the investigators during these measurements.

Skin Cancer Statistics

     The skin  cancer  statistics were provided by the Kuwait  Cancer Registry
and  included  data  collected  from  hospitals where  biopsies were obtained.
Cases  of  patients  who  sought  treatment   overseas  do  not  appear  in   these
statistics.

RESULTS

Measurement of the Pigment Level of a Small Sample of the Population of Kuwait

     The results of these measurements are displayed in Figure 1 .  The mean 1s
2.18 ± 0.08  with a standard deviation of  1.40.   It could  be  argued that this
is  neither a  random  sample  of the  population nor a sufficiently  large one-
These  data are  not presented  as  a true  average but  rather as  an unbiased
indication of the pigment level of the population.

Measurement  of  the  Minimum  Erythema  Dose   to Artificially  Produced  J^§
Radiation of Human Skin

     In the  tests conducted  we  found erythemogenic doses to be from 50 to 35
mJ/cnr, while  the pigmentation  index varied from 0.5  to  5.2.   The correlation
between the  pigmentation index and  the  log of  the minimum erythema dose f°r
all the volunteers  is  displayed in Figure  2.   The correlation is not a strong
one; however,  it is significant.   The  bandpass of the  irradiation was ±5 °w
for all the wavelengths.
     Although we feel that the above results are reliable, we by no means
to  indicate  that  they are truly representative  of what the MED of the K
population would  be.   Such  a conclusion could  only be arrived  at  through
much more thorough study  in  which  we would need to include a well-represente
and large sample of the population of Kuwait.
                                      176

-------
 NO
72

64

56

48

40

32

24

16

8

0
'22.

'20.

'17.

'15.

'12.

 10.

7.6

 5.0

 2.5
  LIM:
                    en
—<     C\J
                               to
                               m
                                            in
•*     m
iri     CD
CM    -i
 •      •
["x    00
       Figure 1.  Pigment Level Histogram for 314 Volunteers
       u
       I
     6

     5

     4

     3

     2

     \
                    •4-	I	
                       3.5
                                          1-
                        4      4.5

                            Ln  < NED )
                          5.5
Figure 2.
    Correlation Between the Pigment Level and the Minimum
    Erythema Dose for 28 Psoriatic Volunteer/Patients.

-------
Measurement of the Erythema Effectiveness of Three Selected Wavelengths^
of UV-B

     The results of these tests are listed below:
                                                                   /j
       1) 295 nm	  7 hr erythema	   56 mJ/cm
                                               In (MED) = 4.0 ± 0.2
                 	24 hr erythema	   56 mJ/cm2
                                               In (MED) = 4.0 ± 0.2

       2) 305 nm	  7 hr erythema	   82 mJ/cm2
                                               In (MED) = 4.4 ± 0.1
                 	24 hr erythema	   100 mJ/cm2
                                               In (MED) = 4.6 ± 0.1

       3) 315 nm	  7 hr erythema	   820 mJ/cm2
                                               In (MED) s 6.7 ± 0.1
                 	24 hr erythema	  1000 mJ/cm2
                                               In (MED) = 6.9 ± 0.1

Skin Cancer Statistics

     These statistics are presented  in Table 1.  They  were  supplied to us Wr
the Kuwait Cancer  Registry  and they include only cases that were biopsied *
the hospitals  of  Kuwait.    The first  numerical column  indicates  the fcota
number of citizens of the  Arabian Gulf countries and  the second column
the grand total.   Of the 125 cases in the first reporting period, 94 were
exposed areas of the  skin;  this constitutes 75% of the total.  Of the 78
in the second  period,  58 were on exposed areas, also  constituting 75%
total.

DISCUSSION

Skin Cancer

     Skin cancer will occur with repeated suberythemogenic doses of UV-B (*
der Leun  1984);  this is a  situation  that  prevails  with  our  population.   ^ /•
data of  the  Kuwait Cancer  Registry  indicate that the most  frequent form3
neoplasm are the basal cell carcinoma, with  H3%  of  all cases reported
1974 and  1980, and  squamous  cell  carcinoma with 42£.    For  Gulf
Council  nationals,  48/t  were  squamous cell  carcinomas  and  37% basal
carcinomas.   The remainder  of the cases were of various  types of skin
nancies (see Table  1).  What we consider very interesting and alarming
skin cancer exists  in this  area even though people do not "burn," and that ' ^
of the  neoplasms are  on exposed  areas  of  the  skin.    As  the  population  e
Kuwait exposes only  the  hands and the face  to the  sun,  a reasonable
of the  exposed area  of the  skin of  the  population  would   be  approxiwa
10J.   Thus 75% of  the neoplasms occur on  10fl  of the skin.   Therefore, ifc
reasonable to  conclude  that solar UV-B does contribute  to  the  occurrence
skin cancer in the  Kuwaiti  population,  as  in other populations.
                                      178

-------
         Table 1.   Data on Skin Cancer Provided to Us by the Kuwait
                   Cancer Registry
W.H.O. Diagnosis Index
Squamous cell carcinoma
"alignant lymphoma
sPindle cell melanoma
Mycosis fungoides
Basal cell carcinoma
pibrous histiocytoma, malignant
^ymphosarcoma
No microsc. confirm., Clinic, malig.
Depniatofibrosarcoma
Raposi's sarcoma
Pithelioma, malignant
^ignant lymphoma
weat gland adenocarcinoma
etastatic signet ring cell carcinoma
^sosquamous carcinoma
Other
74-78
Gulf Tot.
37
0
0
0
19
0
0
0
0
1
0
0
0
0
0
1
37
0
0
0
50
0
0
0
0
1
0
0
0
0
1
2
79-80
Gulf Tot.
11.
0.
1.
2.
18.
1.
1.
2.
1.
0.
0.
1.
1.
1.
1.
0.
15
.1
.1
.3
37
.1
.1
.5
.1
.4
.1
.1
.1
.1
.1
.0
Total                                                  58  125        42.78
                                     179

-------
     Scotto,  Fears,  and Fraumenti  (1982)  report that the annual  age-adjusted
rates of skin cancer in New Mexico are ten times  higher  for "Anglos" than f°r
"Hispanics."   Therefore,  we would  expect  a  reduced rate for  darker  pigmented
persons.    Furthermore, Scotto  and  Fraumenti  (1982)  report that  the  age-
adjusted rate for  skin  cancer  for American whites was 232.6 per  100,000 while
for blacks  it was 3.4  per  100,000.  For all other cancers the rate for whites
was 318.9 and for blacks 347.3 per  100,000; in other words,  the latter was not
as  significantly  different as  the former.   However,  it has been found  that
experimental  animals "...kept  in a heated environment  rapidly developed  more
UV-induced  tumors  than mice  living  in   a  temperate  environment"  and  that
"...wind and  increased  humidity caused increased  acute UV-induced damage and
acceleration  of  tumor  formation."    It  is   therefore  likely   that  these
environmental factors could outweigh the natural protection  that darker peopl6
have for UV-induced neoplasms.   Kagetsu et al. (1985) report that  UV-A-induced
erythema  is  definitely enhanced  by  increased  skin  surface  temperature  i°
humans.    It   is  clear  that  more  work  needs  to be  done  to  evaluate  the
additional risk by  these climatic conditions  (that  is,  heat and  humidity)  a3
well as the genetic protection, if any, associated with skin  type.

Skin Parameters

     The measurements  on the  "pigmentation  index" showed  a  value of 2.1 8 *
0.08  for   a  population of  314  volunteers.     This  is  not  a  large  enough
statistical sample  but  it is large enough to provide us with an estimate  of
where we are.  Similar  measurements do not exist for any other population yet
since the technique  for  carrying  out  these measurements was Just  published  i|J
January 1986  (Kollias and Baqer  1986).  Based on current experience,  we would
guess that  the pigmentation index  for  English people would be approximately
0.8 ± 0.2.

     If we  assume that  the remitted  intensity  from white  Caucasian skin  *s
approximately 20%  of the incident  intensity  (Kollias  and  Baqer  1985),  then
because the  Beer Lambert  law  can  be considered  valid for  intact
(Bruls et al.  1984) we have the following  equation:

               I / Ip = exp(-0.8 x A) = 0.20 for white skin and
                    I /  IQ = exp(-2.2 x A)  for  Kuwaiti skin

where A is an arbitrary parameter representing the product of the  thickness
the absorber  and  the   factor  that relates  the pigmentation index  with
absorption coefficient  times  the concentration.   Solving the first
for A,  we obtain  A =  2.0.   Substituting this value of  A  into the
equation,  we  obtain a  remitted  intensity approximately  1£ of  the
intensity.   This simple calculation implies that the intensity that arrives
the dermis of a white-skinned Caucasian is approximately  20  times larger
that of a typical inhabitant of Kuwait.

     The validity of this calculation hinges  on the validity of the assumpt10!!
that  the   remitted  light   is  attenuated  in  the  epidermis  and that   uV
absorbance by the epidermis  is  linearly related to the visible absorbance.
     If the incident intensity is attenuated so  strongly  by the resident
ment in the  epidermis,  then we  should be able  to  predict the  dose at w
erythema will be induced by artificially  produced UV-B in accordance with fch


                                      180

-------
"Concentration of pigment.  These  measurements on 26 psoriatic patients do not
substantiate this assumption.   In Figure  2 we see a gentle and general corre-
lation between the  pigment  level and the  minimum erythema dose.   [The reason
that it  is  plotted against  the logarithm of  the MED is  because  it has been
determined that the MED  dose for a  population does not  form a normal distri-
bution while  the logarithm  of the  MED does  form a normal  curve  (Mackenzie
      Amblard et al.  1982)].
     It is known that patients  tend  to have a higher sensitivity to UV-B than
"ealthy volunteers.  From  these data we can  conclude that the native pigment
does not  offer  a great deal  of photoprotection against  UV-induced erythema,
al though it obviously absorbs  strongly the incident  UV-B.   The mechanism for
erythema  production  seems  to  be mediated through  a photoproduct  that  is
Produced in the  upper epidermis.   We are  currently  experimenting in order to
establish  a  correlation   between the native  pigment  and  some  measurable-
attenuating factor.

     Because artificial  sources tend  to have a spectral output that is usually
Afferent from  that  of  the sun,  we  tested for the sensitivity  of  human skin
(local) to selected  wavelengths in the UV-B range.   The  wavelengths selected
Were 295,  305,   315  ±  5  nm.    In these  measurements no  effort was  made  to
correlate the MED and the  pigment level; rather phototests were carried out on
1&  volunteers   with  pigment  level   similar  to   the   average  determined
Previously.  The results obtained were compared with those of the photobiology
u*Ut of Dundee,  Scotland (Mackenzie 1983).

     The  log  (MED)  ratio  for  295 nm  was 1.6  times larger  for  the Kuwait
^ubjects.  The ratio for 305  nm was  1.1.   The ratio  for 315 nm  was 0.99.   It
f°Uows that  the difference  in the  MED  is maximum  for  the 295 band and  is
       the same  for  the other  two bands.   The  waveband  for which the  MED's
      is the  largest is the one that is the weakest  in the  solar insolation.
"e can thus  conclude that the  erythemal  effectiveness of monochromatic UV-B
wavelengths is similar at  the  long wavelength  end of the populations of Kuwait
^d Scotland with the difference becoming  maximum for the  295 nm.band.

     Since the erythema effectiveness  maximum factor of five is different  at
the shortest  wavelength [a factor of  1.6  for Log (MED)], it cannot possibly
account for the  factor of  one hundred difference  for the  carcinogenic effect
of> UV-B  on deeply pigmented  versus  white individuals.   These observations
Provide further  evidence that  the erythema effectiveness of UV-B wavelengths
la not necessarily the  same  as the  effectiveness for carcinogenesis or  for
Photokeratosis.

     There is no  doubt  that the  population of Kuwait is  naturally protected
     the  intense rays of the sun more than  Caucasian  people.  The question is,
ai%e they  adequately protected  from their severe UV-B  environment?  The absence
°f severe photodermatoses as well as  the rarity with  which one observes severe
^Unburns  is adequate  testimony to some protection.  The skin  of  our  population
*a more  pigmented than that  of northern  Europe and  the  sensitivity of  the
~°oal skin to artificially  produced solar-simulated radiation is at  least half
that  of   Caucasians  (Y.   Malallah,   private   communication).     The  results
Presented in  the  previous  section relate  to  the log  (dose) and consequently
they  appear small.  The  actual  energy dose  is 12.5 mJ/cnr  for Dundee and  54
                                     181

-------
     p
mJ/cnr for  Kuwait  for 295 nm to produce an  erythema reaction.   At 305 run and
at 315 nm the differences remain small even on a linear scale.

     Skin cancer incidence  according to the statistics  that are available to
us is at  the level of 2.6  per  100,000 for Kuwaiti  males  and 1.3 per  100,000
for Kuwaiti females for the 1979-81 period.  It is interesting that the levels
in the previous  reporting period  were much lower,  i.e.,  1.1 per 100,000 for
Kuwaiti males and  1.0 per 100,000 for  Kuwaiti  females.   This trend indicates
either a  significant increase  in  skin  cancer  incidence  or  a significant
increase  in the reporting  of  skin  cancer  cases  to  the  Registry.   Another
factor that is  completely  beyond the control  of  the  experimenters  and is
difficult to account  for  is the number of  suspected skin  cancer patients who
seek treatment overseas.   These cases are missing  from the local statistics
and could make the numbers smaller than they actually are.   As the majority of
skin neoplasms appear in exposed  areas it  would not be surprising  if a good
number of people seek plastic or reconstructive surgery elsewhere.

     Our conclusion from  these  results  is  that  melanin in  the epidermis plays
two roles:  one in  the case of  carcinogenesis,  and another in the case of UV-
B-induced erythema.   It  appears that  in  the case of carcinogenesis,  melanin
(the primary  pigment  in  human  skin)  acts  as an  absorber, attenuating  the
incident intensity.  Thus,  tumor initiation  appears  to be  proportional to the
amount of UV-B  that arrives to  the  basal cell  layer.   In  the  case  of UV-B-
induced erythema the correlation between the concentration of melanin and the
MED dose  is very  weak, which implies  that there must be  some  other  mediator
for  the  production  of erythema.    The  role of  melanin  in this case  would
possibly be as a scavenger of free radicals generated by the UV-B radiation in
the epidermis.  The radicals that  are  not  compensated would then migrate into
the dermis  through  the basal cell layer  and generate the erythema reaction.
Thus,  the  concentration  of  melanin  will  be  a  determining  factor  in  the
erythema.    In a paper that we are  currently  submitting  .for  publication we
discuss the different forms  that melanin molecules can take up in the skin and
the different functions that these molecules might perform.

CONCLUSIONS

     The estimated average'pigmentation index  of the population  of  Kuwait is
2.2,  while  that of European Caucasians is  estimated to be  less  than  1.0 and
assumed to  be 0.8.   The  pigmentation index is a parameter that varies from 0
to 9  (there are darker  people but  we have not  measured  their  pigmentation
yet), and is directly related  to the  absorbance of the epidermal melanin.

     A weak relationship exists between the minimum  erythema dose of  UV-B and
the pigment level.   Considering  the average values of MED and pigment level we
are  led   to the conclusion that  the  relative  protection  that the  pigment
renders is  related  to the absorbance  or  pigment level; i.e.,  as the pigment
level increases by a  factor of  2+  the  MED  decreases  by a factor of 2+.  It is
unfortunate that for  these preliminary  results we  had  to use  data  obtained
from psoriasis patients  as  the data are  probably slightly biased to  a lower
MED value.   MED values  determined for normal  Kuwaiti subjects  would render
more definite answers.

     Variation in the sensitivity  of  Kuwaiti  skin  and that  of Caucasians is
demonstrated with smaller wavelengths  of  solar UV-B.  At  295 nm, sensitivity


                                     182

-------
varies  by  a  factor  of  four while  at  longer wavelengths  it  is  not very
different.  This is similar  to  results described  in  Nakayama  et al. (1974).
This means  that  to properly evaluate the  UV-B  risk,  we need to establish the
spectral relative sensitivity (action spectrum) of Kuwaiti skin to UV-B.  This
means  that the  Effective  Spectral  Irradiance  is not  the  same as  that  of
Caucasian skin just attenuated by an appropriate factor.  It is essential that
the  action spectrum for  UV-B wavelengths of  Kuwaiti nationals  and typical
expatriates be determined.

     Analysis  of  the cancer statistics  shows that  skin  cancer  in the Kuwaiti
Population relates strongly with UV-B exposure.   It  should  be  noted that 75%
of the skin neoplasms reported between 1974 and 1980 occurred on exposed areas
°f the skin,  i.e.,  on  10£ of the skin.  This  is an unmistakable and alarming
signal.  Statistical evaluation  of the  results  is  not complete  because we are
in the process of obtaining more information from the Kuwait Cancer Registry.

ACKNOWLEDGMENTS

     This  work  was  supported  by  the   Environmental  Protection Council  of
Kuwait.  We wish  to thank  Dr. M.  M.  Selim for his  support and trust.  We also
express our thanks to Dr.  Y. Malallah  and Dr. V.  Heigy for  their valuable
cooperation.


REFERENCES

        P., J. Beani, R. Gautron, J.  Reymond, and  B.  Doyon.  1982. Statistical
     study of  individual  variations  in  sunburn sensitivity in  303 volunteers
     without photodermatosis.  Arch.  Dermatol.  Res. 274:195-206.

Bruls,  w.A.C., and J. C. van  der  Leun.  1984.  Forwarding scattering properties
     of human  epidermal  layers.   Photochem. Photobiol.  10:231-42.

Hawk, J.L.M.,  and J.A. Parrish.  1982.  Responses of normal skin  to ultraviolet
     radiation.    In The  science of photomedicine.  eds.  J.D. Reagan  and J.A.
     Parrish,  219-260.   New York: Plenum Press.

K*getsu N., R.W.  Gange,  and J.A.  Parrish. 1985.   UVA-induced  erythema, pigmen-
     tation,  and  skin  surface temperature  changes are  irradiance  dependent.
     J. Invest.  Dermatol.  85:445-47.

K*idbey,  K.H., P.  Poh  Agin, R.  M. Sayre,  and  A.M. Kligman.   1979.   Photopro-
     tection by  melanin:  A comparison  of  black and Caucasian  skin.  J. Am.
     Acad.  Dermatol.  1:249-60.

       ,  N.,  and  A.  Baqer.  1985.    Spectroscopic characteristics  of  human
     melanin in vivo.  J.  Invest. Dermatol. 85:38-42.

Koilias,  N., and  A. Baqer.  1986.   The assessment of melanin  in human skin  in
     vivo.   Photochem. Photobiol.  43:49-54.
         ,  L.A.  1983.    The  analysis  of the ultraviolet  radiation doses  to
     produce  erythemal  responses  in  normal  skin.   Brit.  J.  Dermatol.  108:1-9.
                                     183

-------
Nakayama, Y., F. Morikawa, M. Fukuda, M. Hamano, K. Toda, and M. Pathak. 1974.
     Monochromatic radiation  and its  application:  Laboratory  studies  on  the
     mechanism of  erythema and pigmentation induced by  psoralen.  In- Sunlight
     and man,   cons.  ed.  T.B. Fitzpatrick, eds.  M.A.  Pathak,  L.C.  Harber, M.
     Seiji, and A. Kukita, 591-611.  Tokyo: University of Tokyo Press.

Pathak, M.A., and T.B. Fitzpatrick.  1974.  The role of natural photoprotective
     agents in human skin.   In Sunlight and man,  cons. ed. T. B. Fitzpatrick,
     eds. M.A.  Pathak,  L.C. Harber, M.  Seiji,  and A. Kukita,  725-50.  Tokyo:
     University of Tokyo Press.

Pathak, M.A., T.B. Fitzpatrick, and J.A.  Parrish.  1982.   Topical and systemic
     approaches to protection  of human skin against harmful  effects of solar
     radiation.   In  The  science of photomedicine,  eds. J.D.  Regan and J.A.
     Parrish, 441-73.   Wew York:  Plenum Press.

Scotto,  J.,  T.R.  Fears,  and  J.F. Fraumenti,  Jr.  1982.   Solar  radiation.  In
     Cancer  epidemiology  and  prevention,  eds.   D.   Schottenfeld  and  J.F.
     Fraumenti Jr., 254-276.  Philadelphia: W.  B.  Saunders Co.

Scotto, J., and J.F. Fraumenti,  Jr.  1982.   Skin cancer (other than melanoma).
     In  Cancer epidemiology  and prevention,  eds. D.  Schottenfeld  and  J.F.
     Fraumenti, Jr.,  996-1011. Philadelphia: W.B.  Saunders Co.

Shono, S., M.  Imura,  M.  Ota,  S.  Ono, and  K. Toda.  1985.   The relationship of
     skin  color,  UVB-induced   erythema,   and  melanogenesis.     J.  Invest.
     Dermatol. 84:265-67.

Urbach, F. 1982.  Photocarcinogenesis.   In The  science of photomedicine. eds.
     J.D. Reagan and J.A.  Parrish, 261-292. New York:  Plenum Press.

van der Leun, J.C. 1984.   UV-carcinogenesis. Photochem. Photobiol.  39:61-68.

World Health Organization. 1982.   Environmental health criteria 23,  lasers  and,
     optical radiation.
                                      184

-------
 Ozone Modification: Importance for
 Developing  Countries in the Tropical/
 Equatorial Region

 Mohammad llyas
 University of Science of Malaysia
 Penang, Malaysia
     The adverse biological and environmental effects  due  to  any  inadvertent
ozone modification  have received  considerable  scientific  attention but have
been largely concerned with  ultraviolet radiation damage to  human  skin  in
specific relation to protection of deficient white  skin.  In this respect, the
ozone problem somehow has  not  appeared to be of serious interest to the people
of developing  countries living in  the  tropical/equatorial  geographical belt.
However,  in  view  of  the manifold  increase in  the  ultraviolet radiation
received at the lower  latitudes  compared to the mid and  high latitudes,  it
seems reasonable that  the ozone layer issue should be  of serious  interest in
the tropics.  In fact,  in  these regions, more serious kinds of  solar UV radia-
tion-induced health effects such as  cataracts,  viral  infections,  and immune
system damage may be connected to the "ozone-UV"  issue.   These  aspects need to
be studied under harsher tropical conditions,  but  the  understanding that has
been achieved so far (for mid-latitude conditions)  can provide  a valuable base
from which the specific situation for tropical countries  can be tackled as an
extension.

INTRODUCTION

     For several decades,  atmospheric  ozone,  especially  the stratospheric
layer,  has been  known  for its important protective role  against the incoming
solar ultraviolet radiation.   In  general,  there  is a natural  balance between
the ozone's production  and its destruction with a net ozone surplus.   Under
the natural equilibrium, there are  small dosages of solar  ultraviolet radia-
tion to which populations,  living organisms, plants, and  aquatic systems have
generally  become adapted.   The harmful  effects  are thus  generally  very small
except  perhaps   in  the  tropical/equatorial  region.   The  surface  dosage  of
natural  ultraviolet radiation'  increases  by many folds in going from high/mid
latitudes  to the equator.   Because  people living  in the  high dosage tropical
belt have  a darker  skin tan  which  provides  greater protection to the  skin
against  ultraviolet radiation,  this high UV  radiation  situation has not been.
                                   185

-------
considered particularly seriously in terms of adverse health and environmental
effects that might occur in these regions.

     The ozone layer  suddenly came into scientific  prominence about 12 years
ago when it was realized that certain human activities may lead to significant
ozone  depletion  from  the naturally  balanced  level,  thereby  increasing the
surface dosage of  ultraviolet radiation leading to  increased  skin cancer and
many other adverse biological, environmental, and climatic effects.  Since any
such ozone destruction would  spread out globally,  the net UV radiation effect
would  be  most serious  in  the equatorial  and  tropical belt when  already the
ozone  column  thickness  is  minimum and ultraviolet radiation  penetration is
maximum.   But perhaps even a more fundamental issue  is  to  ascertain whether
the already  high  UV  radiation  dosages received at the lower  latitudes are
contributing  to tropical diseases  and medical problems.   Whether  the 5 to 10
times  higher  dosages  (in absolute terms) that would  be received  in  the low
latitude region in comparison to the higher latitudes  (if a certain- fraction
of ozone  column  is reduced)  would  bring the radiation level  above a certain
threshold  is  another aspect  relevant  to  the  tropics.   In  other  words,  the
"ozone  modification"  issue   is  of serious  importance  to  the low  latitude
countries.  The whole issue of ozone layer protection is thus indeed of global
dimension.  Yet, there is very little  apparent  involvement of scientists from
the  developing  countries  in  the  "ozone  layer-ultraviolet  radiation"  work.
While financial constraints may account for some of this non-involvement, lack
of  proper  understanding of   the  effects  at  the  public,  scientific,  and
political levels is also a serious factor.  Nevertheless,  in the coming years,
it should  be  appropriate  to examine  the  "ozone  layer-UV-B"  matter  in  the
specific context of tropical countries.

TYPICAL CONDITIONS

     In order to  examine  the  relevance  of  the  ozone  layer  issue for  the
developing countries in the equatorial/tropical region, it would be helpful to
summarize  the  atmospheric  ozone  and  solar  ultraviolet  radiation  influx
globally.   The  seasonal distribution of  vertical  ozone  column  for different
latitudes is  shown  in Figure  1.   It  is clear that at the lower latitudes, not
only the  ozone  column thickness is  significantly  small but it  also does not
vary much  seasonally.    The  solar ultraviolet  radiation  penetration is  thus
maximum at the lower latitudes throughout the year.  The overall effect of the
low ozone content  coupled  with smaller seasonal change  in  the solar declina-
tion  results   in   the  latitudinal  distribution  of annual  erythemal  dosage
(incoming radiation weighted  according to skin erythemal  action spectrum) as
shown  in  Figure 2.   This diagram illustrates the  manifold increase  in  the
damaging UV-B dosage from high latitudes  to  the equator.   Some towns are also
marked on the curve against their  respective latitudes.   Figure 2 is based on
calculated data for clear sky conditions (Mattingly 1976;  Ilyas 1979).

THE EQUATORIAL DATA FROM PENANG

     In the equatorial/tropical  region, there  is  a general lack  of observa-
tional data pertaining to the atmospheric  ozone and solar UV radiation.  Wit"
this consideration  in  mind,  about 10  years  ago we  initiated  a comprehensive
program of measurements involving ozone soundings,  erythemal  UV-B,  UV-A, total
solar radiation, surface ozone,  and a  series of relevant  meteorological para-
meters  at  our equatorial place, Penang (5.5°N).   This is perhaps one  of the


                                      186

-------
               u
                 050
                 045
                 040
                 035
                 030
                 0 25
                 020
                             30'N
                                               J	L.
                                                    eo'N
                                                    7Q'H
                                                    60'N

                                                    50'N
                                                                    40'N
                     Jan Feb  Mar  Apr.  May  Ju^e Ju\v Aug Sept  Oct  Hov Dec
     Figure 1.  Annual Variation of Total  Ozone for  Each 10° of N Latitude
                  200
8

I


W
*-i
S
                  100
                   5.0
                    90
                                  A Oslo
                                  t	I
                             Adelaide
                             Los Angeles

                         Washington
                             70
                       50        30
                         Latitude
                                                         10
     Figure 2.   Variation of  erythemal  dosage  (joules/cm2)  with  latitude  for
clear  days.   Also indicated are the  dosages  for specified places as compared
to an  equatorial location (Malaysia).
                                         187

-------
most rare comprehensive programs in the equatorial/tropical belt.  Some of the
initial results  from this study have  become available  and  more refined data
should follow (Ilyas 1984a, 1984b;  Ilyas and Barton 1983).

     One of our  immediate  interests  from  this  study is to see if the observa-
tional  data  obtained  at  Penang  can  be  used  in  a  general   way  for  the
equatorial/lower tropical  region.   For this, the most  important and directly
usable data  in  the  context  of ozone  layer  effects  study  are  the  directly
involved ultraviolet radiation data.   The input radiation flux does not change
much over  the  entire equatorial/lower  tropical  belt.    It would, however, be
modified differently at  different  places  depending  upon the  sky conditions
(cloud cover).   The long-term  cloud  cover data at Penang  indicate the cloud
cover to be  close  to 85%  (Ilyas et al.  1981)  which reduces  the incoming UV-B
radiation to about half.  This is consistent with the theoretical relationship
of cloud cover  effect on  ultraviolet  radiation  (Johnson et al.  1976).   In a
more comprehensive study  of cloud  cover effect, we used 5-year-long observed
UV-A data (Ilyas et al. 1986), together with the calculated data for clear sky
conditions  (Johnson  et al.   1976).    The  observed  data  were  found to  be in
excellent  agreement  with  the computed data  modified  for  the  average  cloud
cover (Ilyas 1986).  This is shown in Figure 3.

     The excellent  agreement between  observational  data and  calculated data
indicates  that   the  cloud  cover effect  for  other  locations  may be  easily
incorporated into  the  clear  sky calculations  of ultraviolet  radiation.   The
radiation  conditions   for   evaluating   the  adverse  biological/medical  and
environmental effects  can thus be ascertained.   In any  case, because  of the
relatively high  cloud  cover conditions at  Penang (5°N),  the observed UV flux
represents a lower  limit  of UV dosage  that would be  received  anywhere in the
entire equatorial belt.   A  summary of  the erythemal UV-B dosage together with
some  meteorological  conditions  at  Penang is  presented  in Figure  4.    The
information in Figures 3 and 4 thus represents lower tropical model conditions
which  must  be  simulated  for  the  photobiological  effect  studies for  this
region.

UV RADIATION EFFECTS IN THE TROPICAL REGION

     Figures 1-4 provide  a good summary of low  ozone  content  and high ultra-
violet  flux  conditions prevailing  at  the  lower latitudes  against  the high
ozone content and  low ultraviolet flux at mid and high latitudes.   Besides,
the high (air)  temperatures and humidities in the  tropics  prevail throughout
the year  and may  couple  together  with  the  UV radiation  in producing more
severe biological and physiological effects.   Lack  of education and awareness
of UV-induced  damages, skin's  false sense of protection,  increased  outdoor
occupations  including young  school children being exposed to relatively large
amounts  of ultraviolet  radiation  (under  hot and  humid  conditions)  due  t°
inadequate clothing and/or outdoor work (like P.E.  lessons and games) at wrong
times  of  the   day   may  all  add up  to  the  seriousness of  the  situation.
Unfortunately,  there is not  much  basic  data  available let alone  studies of
adverse radiation effects under specific conditions.  Although skin cancer and
other related problems, hitherto the prime  concern in Western populations, way
not be of sufficient importance in the tropics, more serious effects on humans
such  as  viral  infections (herpes,  hepatitis), eye  damage (cataracts),  dainag6
to the  immune  system,  and life expectancy  (perhaps  we don't record many skin
cancer cases in the  tropical  countries because most of such people don't live


                                      188

-------
                N  5  JA p  MA  MY J  JY A   §  0  N  D  JA~F  M
     Figure 3.   Annual  variation of the average  daily  total erythemal dosage
(ED)  (instrument response)  as measured  at  Penang  together  with the  clear
weather dosage  (calculated) and  the  related observational climatic parameters
for the station and the solar position [minimum (noon time) zenith angle].
                                      189

-------
     CVI
     _*:

        30
      o>
      c
      o
      B
      T3
         2-5
         20
         1-5
         1-0
                                    Radiation for Clear Weather (Calculated)
                                     Radiation for Average Weather
                                           (Calculated)
                                     Radiation at Surface (Measured)
J	L
                                    '    '     '	L
             N
          MAM
JL
0   N
     Figure  4.   A  comparison  of  the  calculated  UV-A  dosages outside the
atmosphere and at the surface  (after  accounting for cloud .cover effect) with
the measured data at our station  (Penang).


long  enough  for  the effects  to  show up)  are important  avenues  for future
work.   Also,  what adverse effects the very high dosages  may  have on tropical
plants and aquatic  organisms and  the  exposed materials would also  need to be
studied.  Finally,  whether any further  increase in UV  radiation,  as a result
of ozone reduction due to human activities,  would  affect any threshold limit—
to which  the  tropical systems may have  become adapted—would be important to
examine.  Side by side, populations would  need to  be educated on these effects
and some simple protection methods,  whereas  scientists  in these regions should
be increasingly  involved  in this  program  with the  realization of local rele-
vance and overall importance.   The exercise of protecting  humans globally by
protecting  the ozone  layer would then become a  very  involved matter.   An
organization such as UNEP is well  suited to  make a move  in this direction.

ACKNOWLEDGMENTS

     A  UNEP  Fellowship which  enabled my  participation  in  the  conference is
gratefully acknowledged.   I benefited greatly  from my  discussions  with many
persons at the meeting which has helped  in preparing this paper.
                                      190

-------
REFERENCES



Ilyas, M. 1979. Sains Malaysiana. 8:13.



Ilyas, M. 1984a. In Atmosph. Ozone (D. Reidel: Dordrecht), 274.



Ilyas, M. 1984b. In Atmosph. Ozone (D. Reidel: Dordrecht), 791.



Hyas, M. 1986. Paper under preparation.



Hyas, M., and I.J. Barton. 1983. Atmosph. Env.  17:2069.



Hyas, M., C.Y. Pang, and A.W.  Chan.  1981. Sing.  J.  Trop.  Goeg. 2:27.



Hyas, M., D.A. Aziz, and M.R.  Tajuddin.  1986.  Paper under preparation.



Johnson,  F.S., T.  Mo, and A.E.S.  Green. 1976.  Photochem. Photobiol.  23:179.



Mattingly, S.R. 1976. Atomsph.  Env.  10:935.
                                     191

-------
The Tan of Ultraviolet-6 Summer

Dr. Petar Jovanovic
Omladinskih Brigada
Beograd, Yugoslavia
     During my studies  of  the environmental parameters of ozone depletion, one
idea often  comes  to  mind:  What  is  going  to happen with the surface of our
planet?  As  this  approach was  too prosaic  for  this  solar  and  galactic beauty
of  which  we are  all proud, I  transformed the question  into a more poetic
one:   What  is going  to happen  to its  tan?  I  hope you will agree that the
criteria that  evolve from this approach  are more appropriate because of the
abundant chemical  make-up  of our planet and the ultraviolet tanning  the planet
is starting to acquire  in  the new  "anthropogeochemical" era.

     I beg your pardon  for this novelistic  digression and  let  me approach the
problem as we usually do—more  prosaically.

     I agree  with Watson,  Hansen,  Hoffman,  and others that  we have barely
scratched the surface of  the problem and that  many  unanswered questions have
to be  approached.   I also agree that we possess enough knowledge  to qualify
the risk.   The differences  in  quantifications  all  fall within a  range that
guarantees danger. The nature of  the processes, including  phenomena of momen-
tum and inertia, makes  it possible  to  conclude  that  we  are  in the  incubation
phase of the disease.  The  "infection" is  here, the process  is  irreversible,
the disaster is imminent.  The problem is how to cope with  it.

     I think that we can  cope  with  the disease  of the planet.   The guarantee
is in  the fact  that  there is no disagreement in qualification of the changes
in anthropogeochemistry.   I  could not avoid the implications  of the  facts with
which we are  confronted.  These facts  suggest  one general title that can be
given to all particular parameters of this environmental and  climate complex
discussed in all papers:   "disastrous chemical  summer."  All our estimates of
warming,  ice  melting,  flooding,  rising  sea levels,  inundation,   epidemics,
ultraviolet  aids,  deaths,  droughts and   hunger,  temperature  rising,  etc.
suggest this integrating qualitative  statement:  chemical summer with all its
anthropogeophysical and anthropogeobiological events.  Whether it is going to
be called ultraviolet summer,  chemical  summer,  ozone summer is  a question of


                                     193

-------
convention.   It  seems to me that whether  cool  or  hot,  it still can be called
burning  ultraviolet  summer.    We  all  know  that  ultraviolet radiation  is
burning, although invisible and without heat.

     This  excellent example of a  man-made hazard  that  can  trigger  natural
hazards of incomparable energy and destructive force should remind us that the
disastrous chemical summer  can be  as  disastrous  as  "nuclear winter."   The
nuclear season can  be prevented by avoiding nuclear warfare.   But the summer
produced  by  the  greenhouse effect  and  ozone depletion  surely  has  already
begun.  The  ozone shield has already been transformed  into a less protective
curtain.

     Cosmonauts tell me  that  they often admire this beautiful shield  of life
on earth.   They  look  at  it and  through  it as if  they are looking through a
protective window.   Let us help  them to  always look through  this protective
window and not  through the holes in  it.   Otherwise, instead  of us they will
see only burns and  scratches on the face  of what was once the galactic beauty
Mother Earth.
                                      194

-------
AQUATIC SYSTEMS

-------
Effects of Enhanced UV-B Radiation on the
Survival of Micro-Organisms

Donat-P. Hader
Fachbereich Biologie-Botanik (Lahnberge)
Phillips-Universitat Marburg
Karlsruhe, Federal Republic of Germany
     Microorganisms  play  an important  role in both aquatic and  terrestrial
ecosystems  on our planet since  they represent the  basic level in a complicated
food chain  on  which the  lives  of heterotrophic organisms  such as animals
depend.   In addition,  plants rely heavily  on the activity of  microorganisms
such as  the fixation  of  atmospheric nitrogen,  which  is  also an  important
economical  factor.

     Many microorganisms utilize external signals  for orientation and behavior
in their microenvironment to find  a suitable niche for survival and  growth of
a population.   Not  only  is light  the single most important factor for orien-
tation  in photosynthetic organisms, which naturally depend on the availability
of light for energy fixation,  but  it is  also critical for non-photosynthetic
microorganisms.

     Microorganisms have developed  a number of different strategies  to orient
with respect to  light  including  phototaxis,  which is  a directed  movement
towards  or  away  from  a source of light;  photokinesis, which describes the
dependence  of the speed of movement on the intensity of light; and photophobia
responses,  which are  elicited by  sudden   changes  in  the  light  intensity
(Nultsch 1975).    All  these mechanisms of  orientation  are  utilized  by  a
population  to  find  a suitable environment  and to adapt to  the  continuously
changing conditions (Nelson and Castenholz 1982).

     A  number of  taxonomically  different  microorganisms have  been  found to be
extremely sensitive towards solar UV-B radiation (Damkaer et al. 1980; Ohnishi
et al.  1982; Jagger 1983).   These  organisms, which range from  prokaryotes to
eukaryotes,  from gliding to flaggelated forms, and from photosynthetic to non-
photosynthetic  organisms,  are  under UV-B stress  even  at current levels and
would be seriously endangered by an increase in the UV-B radiation caused by a
partial  reduction of the  ozone layer due to anthropogenic  gaseous pollutants
such as  chlorofluorocarbons (Maugh 1984;  Weiss et  al. 1985).
                                    197

-------
     In  addition  to  immediate  lethal   effects   on  the  organisms,  several
responses  to  UV-B radiation  can be  distinguished,  all  of  which eventually
destroy a  population of microorganisms.   The most obvious effect observed is
an  inhibition  of motility,  which prevents  a  population  from  escaping from
hazardous influences in  its environment.   A  more  indirect effect  is the inhi-
bition of  photoorientation, which  occurs at  even lower  UV-B  doses.    As a
consequence, the organisms are still able to move but are unable to respond to
changes  in their environment  and are  eventually  killed  by  the  unfavorable
conditions  in  their  environment.  A  discussion of these  problems with a few
examples follows.

     Filamentous  cyanobacteria   live   in aquatic  (marine  and  freshwater)
habitats as well as in soil  and other  terrestrial ecosystems  and  produce a
large fraction of the organic material  (Fay  1983).  The organisms glide using
a mechanism not yet  fully understood.    When  exposed to low  doses  of UV-B
irradiation, the populations are killed within a few days after exposure.  The
analysis of the behavior  using  an  artificial UV-B  source showed  that both
motility and photoorientation  are drastically impaired (Hader 1985a).

     Investigations at  an  experimental station near  Lisboa,  Portugal, demon-
strated that the organisms do  not  survive long in solar  radiation.   Neither
the visible component of the radiation nor the temperature increase caused the
organism in the  experiment to  die but rather the  UV-B  component in the solar
radiation killed them  (Hader   et al., in  press).   When exposed to unfiltered
solar  radiation  at noon during  the  summer, the  filamentous  Phormidium was
found  to  stop  moving within 35  minutes.   An action  spectrum  measured in the
Large Spectrograph in Okazaki,  Japan,  indicated that  wavelengths below 300 nm
were extremely  effective (Hader  et al.,  in press).   It  could  be shown that
the UV-B  target is not DMA since  no photorepair  could  be  induced  after UV
damage (Eker 1983; Yamamoto et  al.  1983).   A mechanism involving photodynamic
effects could also be excluded  by studying the  effects  of diagnostic reagents
(Ito 1978;  Spikes and Straight  1981;  Nultsch and  Hader  1984).  The conclusion
of these experiments was that  an intrinsic component of the motor apparatus of
the organisms, probably  a  membrane-bound protein,  is the  molecular  target of
UV-B radiation.

     Cyanobacteria use  a primitive,  but rather effective  mechanism to orient
themselves  with  respect  to their photoenvironment (Hader  1979).   Each time a
filament leaves a bright area by gliding into a shadow, it reverses direction
and  returns to  the  bright  area.     This  so-called  "photophobia  response
guarantees  that  the  population  stays  in  the light, which  is  essential for a
photosynthetic organism.    Light fields  that  are too  bright are  avoided bY
phobic responses upon  entering  the  bright area.   The remarkable precision °*
orientation can be demonstrated by a simple experiment in which a photograph!0
negative is projected  into a  homogeneous suspension  of organisms, which then
accumulate  in   areas  of suitable  light  intensities and  form a sharp  and
detailed positive image (Hader   1984).

     Most  cyanobacteria are  typical  low light  organisms:    When  they  are
exposed  to high light  intensities,  their photosynthetic  pigments are photo-
oxidized and the cells  die within a  few  days  (Walsby 1968).   The consequence
is that populations of cyanobacteria are not only endangered by  increased UV-°
radiation,  which affects motility and directly kills the  organisms,  but also
by  lower  UV-B doses,  which impair  photoorientation  of the organisms.   As a


                                      198

-------
result they either move into the substratum, where they die due to the lack  of
light  or  they  can  no  longer  prevent  themselves  from being  exposed   to
excessively  bright light,  which  bleaches and  eventually kills the  cells  as
well.

     Only a  few organisms have developed mechanisms to  escape UV-B radiation
while most  organisms are  insensitive toward  the  UV-B.    The archaebacterium
Halobacterium uses different sets of photoreceptors  to accumulate in favorable
light fields  and to  escape  from  hazardous radiation  (Wagner  198*0.   Upon  an
increase in the  short wavelength  radiation,  the blue/UV  receptor mediates the
repellent signal and  triggers an instantaneous reversal of movement.

     The cellular  slime mold Dictyostelium  is  also extremely sensitive toward
UV-B radiation  because  its development and motility are  impaired  by very low
doses (Hader 1983a, b).   In its multicellular stage, this organism uses a. lens
effect  to  detect  the direction  of  laterally  incident  light.   Because the
refractive index of  the  cytoplasm is higher than  that of the surrounding air
Parallel, light is  focused to the  rear flank of  the  organisms  (Hader and
Burkart, 1983).   The resulting light gradient  is  used  for  photoorientat'ion
towards  the  light.   In  the  UV-B range,  the  lens  effect  is cancelled  by  a
strongly absorbing substance so that the optical  properties  are  reversed and
the organisms move away from the UV-B source (Hader  1985c).

     Flagellates, such as  the green  uniflagellar Euglena  gracilis,  find their
suitable environment by two antagonistic orientation mechanisms:  At low light
intensities,  the cells move toward the light source  (positive phototaxis) and
at  high  intensities  away  from the  light source  (negative phototaxis).    In
their natural environment, the  cells  swim upward until they reach the optimal
light intensity, where they form a dense population.

     Hader(1985b)  found that  solar  UV-B affects swimming  in  these  organisms.
No motile cell  was found  in samples  exposed to solar radiation  for 2.5 hours
around noontime.   The cells did not  recover from  the damage.  Even  when the
Population  was   transferred  to darkness or  weak light  after  a  short  UV-B
irradiation,  most  of  the  cells  died in  the   subsequent  hours indicating  a
damaging effect even of low UV-B doses.

     Photoorientation was  measured  by an automatic  computer-controlled video
analysis (Hader and Lebert 1985).  The video image  of the cells swimming under
the  microscope  was   digitized  in  real  time   and  stored  in  an  electronic
Memory.   A  microcomputer had access  to the memory and was  programmed to detect
and  follow  individual organisms.   The  deviation  of  the organisms from the
incident light direction was calculated  and stored for subsequent  statistical
treatment  and  histogram   analysis.    Under  appropriate  culture  conditions
Euglena moves with a high  precision  of orientation.  After artificial or solar
UV-B  irradiation,  the  swimming tracks  become increasingly  erratic and  the
organisms move in random directions  independent of  the light direction.

     Both effects  of solar UV-B  radiation  on the  flagellate  Euglena  are
disastrous  for   the   survival   of  the  population.    When  motility,   photo-
orientation,  or both are impaired, the organisms are no longer able to select
a suitable  habitat.   Even  when  we allow  for a  considerable attenuation of the
UV-B radiation  by  the column of water above the cells,  solar UV-B has  to  be
         as a natural stress  factor  even at current levels.   Any  increase  in


                                      199

-------
the  UV-B  doses would  increase  the stress, and  would eventually threaten  the
survival of these and other ecologically important microorganisms.

ACKNOWLEDGMENTS

     This  work  was   supported  by  the  Bundesminister  fur  Forschung   und
Technologie  (KBF  57).    The  author  gratefully acknowledges   the  skillful
technical assistance of U. Neis.

REFERENCES

Damkaer, D.M., D.B. Dey, G.A. Heron, and E.F. Prentice.   1980.  Effects of  UV-
     B  radiation  on   near-surface zooplankton  of  Puget  Sound.   Oecologi§
     (Berl.) 44:149-58.
Eker,  A. P.M.    1983.   Photorepair processes.   In Molecular  Models of
     responsiveness , ed.  G. Montagnoli  and  B.F.  Erlanger.   New York:  Plenum
     Publishing Corporation.

Fay, P.   1983.  The blue-greens.   Studies in Biology  no.  160.   Southampton:
     The Camelot Press Ltd.

Hader,   D.  1979.  Control  of  locomotion.   Photomovement.  In Encyclopedia^*?*!
     Plant Physiology.  New  Series  Vol.  7.   Physiology of Movements,  ed. W.
     Haupt and M.E. Feinleib,  268-309.  New York:  Springer-Verlag.

Hader,   D.  1984.  Wie  orientieren  sich  Cyanobakterien im Licht.  Biologie__iS
     unserer Zeit  14:77-83.

Hader,    D.     1983a.     Inhibition  of   phototaxis   and  motility  by  UV-B
     irradiation  in Dictyostelium discoideum slugs.   Plant Cell Physiol. 24:
     1545-52.

Hader,   D.   1983b.   Effects  of UV-B  irradiation on sorocarp development of
     Dictyostelium discoideum.  Photochem. Photobiol.  38:551-55.

Hader,   D.   1985a.  Effects of  UV-B on  motility and  photoorientation  in the
     cyanobacterium,  Phormidium uncinatum.   Arc.  Microbiol.  140:34-39.

Hader,   D.  1985b.   Effects  of UV-B on motility and photobehavior in the green
     flagellate, Euglena gracilis.  Arch.  Microbiol. 141:159-63.

Hader  D.   1985c.   Negative  phototaxis of  Dictyostelium  discoideum pseudo-
     plasmodia in UV radiation. Photochem.  Photobiol.  41:225-28.

Hader   D.,  and U.  Burkart.  1983.    Optical  properties  of  Dictyosteliug
     discoideum  pseudoplasmodia  responsible  for  phototactic   orientation-
     Experimental Myc.  7:1-8.

Hader  D., and M.  Lebert.   1985.   Real  time computer-controlled  tracking °*
     motile microorganisms.  Photochem.  Photobiol.  42:509-14.
                                     200

-------
Hader, D.,  M.  Watanabe,  and M.  Furuya.    UV inhibition  of mobility  in the
     cyanobacterium,  Phormidium  uncinatum,  by  solar  and  monochromatic  UV
     irradiation.  In press.

I to, T.  1978.    Cellular and  subcellular  mechanisms  of photodynamic action:
     the  Op hypothesis  as  a  driving  force in  recent  research.  Photochem.
     Photobiol. 28:493-508.

Jagger, J.  1983.  Effects of near-UV radiation on bacteria.  In Photochemical
     and  photoblological reviews, ed.  K.C. Smith,   1-75. New  York:   Plenum
     Press.

Maugh, T.H.   1984.   What is the  risk  from chlorofluorocarbons?  Science 223:
     1051-52.

Nelson,  D.C.,  and  R.W.   Castenholz.    1982.   Light  responses  of  Beggiatoa.
     Arch. Microbiol. 131:146-55.

Nultsch,  W.  1975.   Phototaxis and  photokinesis.   In  Primitive sensory and
     communication systems,  ed.  M.J.  Carlile,  29-90.    New York:    Academic
     Press.

Nultsch, W., and  M.   Hader.    1984.   Light-induced  chemotactic responses  of
     the   colorless   flagellate,   Polytomella  magna.   in   the  presence  of
     photodynamic dyes.  Arch. Microbiol. 139:21-27.

Ohnishi, T., M.  Hazama,  K.  Okaichi, and  K. Nozu.   1982.   Formation  of non-
     viable  spores   of  Dictyostelium  discoideum  by   UV-irradiation   and
     caffeine.   Photochem. Photobiol.  36:355-58.

Spikes, J.D. and  R.  Straight.    1981.   The sensitized  photooxidation  of bio-
     molecules,  an  overview.   In  Oxygen   and  oxyradicals  in  chemistry  and
     biology.    ed.   M.A.J.  Rodgers  and  E.L.   Powers,  421-24.    New  York:
     Academic Press.

Wagner, G.  1984.  Blue  light  effects  in halobacteria.  In blue light effects
     in biological  systems,    ed. H.  Senger, 48-54.    New  York:   Springer-
     Verlag.

Walsby,  A.E.    1968.    Mucilage  secretion and  the  movements of  blue-green
     algae.  Protoplasma 65:223-38.

Weiss,  R.F., J.L.  Bullister,  R.H.  Gammon, and M.J. Warner.  1985.  Atmospheric
     chlorofluoromethanes in the deep equatorial  Atlantic. Nature 314:608-10.

Yamamoto,  K., M.  Satake,  H.  Shinagawa, and Y. Fujiwara.   1983.   Amelioration
     of the ultraviolet sensitivity of an  Escherichia  coli  recA mutant in the
     dark by photoreactivating  enzyme.   Mol. Gen.  Genet. 190:511-15.
                                     201

-------
Is the Impact of UV-B Radiation on
Marine Zooplankton of Any Significance?
Bruce E. Thomson
Hatfield Marine Science Center
Oregon State University
Newport, Oregon USA
ABSTRACT

     Over  the  past decade  several  studies  have  examined  the  effects of UV-B
Radiation  on a number of  major marine 2ooplankton groups.    While the adult
organisms  are  commonly found  in  the  upper  meters  of  the  ocean, the eggs and
larval forms may be concentrated in the surface micro-layer.   It has generally
been noted that larval forms of an  organism are more  susceptible to damage by
UV-B than  later life stages.  The species  that have been studied are critical
components of  bioenergetic  pathways  that lead to  larger  animals that are of
•nutritional  and commercial value to man.   The studies indicate that present-
ly  levels  of UV-B  radiation  significantly  affect  the developmental life
stages of these organisms.  For some species a  ]Q%  decrease  in atmospheric
°zone could lead  to  as  much as an  1855  increase  in  the number of abnormal
larvae.

ATMOSPHERIC OZONE EVOLUTION

     It  is generally  accepted  that the  earth's  primeval  atmosphere resulted
from the outgassing of volatiles  from the  interior of the planet.  The atmos-
phere was  devoid of oxygen  and consisted  primarily  of methane,  carbon dioxide,
^onia,  and hydrogen  sulfide.   The absence  of an effective  filter allowed
short wavelength UV from  the sun to penetrate  the surface of the earth.  While
solar ultraviolet radiation can  be  viewed as a major constraint on the evolu-
tion of  life, at the same time it may have been a vital force in the formation
of  biological  macromolecules.    It is thought  that  associations  of  macro-
Molecules  at  some  depth in the could  utilize  the diminished solar  energy
Caching to  that  depth.   These  precursors  to  what we now call phytoplankton
^fe the  principal source  of oxygen  to  the  early atmosphere.   Berkner and
^rshall (1965)  have  implicated  the development of  atmospheric oxygen,  and
therefore, ozone as an important contributing  factor to explosive evolutionary
 dvances in  the  fossil  record.   Two thresholds  of oxygen concentration have
   n postulated.  These correspond to two periods in the fo'ssil record, one in
    Cambrian and another  in the Silurian.

                                    203

-------
 THE IMPACT OF  UV RADIATION OH MARINE  ZOOPLANKTON

     The  first investigations  into  the  effect of  the ultraviolet  radiation
 component  of sunlight  on  aquatic  organisms  were conducted  as early as  1925
 (Huntsman).    By  1930  several  studies  using  a variety of  marine  organisms
 indicated  there was a  detrimental  impact of  the  ultraviolet portion of  sun-
 light  (Klugh 1929,  1930; Harvey  1930).   These early pioneering studies serve
 as  benchmarks and are of historical interest,  but  have  little  relevance  to the
 current ozone  issue because  of the lack of  instrumentation to precisely  and
 absolutely measure  the  quantity  and  quality  of  the  radiation.    It was  not
 until  1970 that instrumentation for precise UV  irradiance measurements  became
 available .

     Worrest (1982) has reviewed  the literature  relating to the impact of  UV-B
 radiation upon  marine  organisms.   This report updates  that information,  adds
 to  its scope, and provides some comparisons between results from a variety of
 experimental methods.  The data presented will clarify  that ultraviolet  radia-
 tion does have an impact on this  portion of the  biosphere.  The extent of  this
 impact is a function of primarily three variables:

     •  The species being exposed to UV

     •  The developmental life stage of the species

     •  The dose of radiation the organism receives.

     The data presented in Table  1 is compiled from a number of investigations
over the  last  decade  by  various authors  using different  experimental  tech-
niques and  criteria  for  assessing  the  impact  of  UV-B  radiation.   Because
standardized  techniques were not used in collecting the data,  some conversions
of  the data  have been made  for the sake of comparison.   Nomographs (Damkaer*
and Dey  1982)  have  been used in  an attempt to account for differences  in ^
exposures among  authors using  different methods  of exposure.   In  spite of
these approximations there are some general statements that can be made and i°
fact some remarkable parallels among the different sets of data:

     •  First,  the  younger the developmental stage of the organism at the time
        of exposure the more  sensitive the organism  is  to  the harmful
        of UV-B.  This  is  demonstrated by looking at the  total dose req
        for  an  early   larval  stage   to  exhibit  a  significant  effect
        comparing it with  the total dose required by a later  larval  stage °f
        that  species.

     •  Next, organisms appear to have differing sensitivities  to  UV-B.   Thi?
        can  be  seen  by  comparing  the  response  of  different  groups   ot
        zooplankton  at  analogous stages of development.
        The third point is  that  the rate at which the total  dose  is
        is a factor in the extent of impact.   In looking  at the copepod data a
        doubling of the dose rate roughly halves the  time for  the end point t°
        be reached.
                                     204

-------
        Finally, the  data in Table  1  show that the  impact  of UV-B on marine
        zooplankton larvae  is significant at present  levels.   For comparison
        purposes the dose rate and total dose for oyster larvae are about what
        we would expect to measure  on a  clear  sunny day at  45N  latitude in
        late June or early July.
        Table 1.  Estimated Biologically Effective UV-B Doses Leading
                  to Significant Effects in Major Marine Zooplankton Groups
                  (Biological weighting referenced to action spectrum
                  normalized to 300 nm.)
Zooplankton Group Dose Rate
DNA(SOO) W/m2
— —
I.

11.


III.

IV.
V.
Shrimp/Euphausiid larvae
Euphausiid adult
Copepod larvae
Copepod postlarvae
Copepod adult
Crab larvae
Crab postlarvae
Anchovy/Mackerel larvae
Oyster /Mussel larvae
6.00 E-2
9.90 E-2
3.39 E-1
1.59 E-1
3.39 E-1
9.90 E-2
2.79 E-1
6.00 E-2
1.20 E-1
Total DMA Dose
kJ/M2/d
2.55 E3
6.115 E3
1.35 E3
2.70 E3
3.00 E3
6.45 E3
6.00 E4
2.50 E4
2.16 E3
Time for
Effect
4 days
6 days
1.0 hr
4.5 hr
2.5 hr
6 days
20 days
12 days
5.0 hr
Source:  Data from:   Damkaer et al.  1980,  1981;  Hunter,  Kaupp, and Taylor
         1982;  Karanas,  Worrest, and Van Dyke 1979,  1981; Thomson et al.
         unpublished.
     The most recent data  in  Table 1 come from studies conducted  in our lab.
Individuals  from  four  species   of  bivalve  molluscs   (Crassostrea  gigas.
saxidomaa gjganteus,  Mytilus edulis, and Clinocardium  nuttallii) were spawned
separately.    Fertilized  eggs were  exposed  to  UV-B  radiation  for  periods
ranging from 1  to  6  hours.   The eggs were  then  held for  24  to 72  hours  at
fhich time they were examined for  abnormal development.   This  examination was
done at  the  end of  the trochophore stage;  the  onset of the  straight-hinged
larvae stage.   The  response of the four  species is shown  in  Figure  1.  A third
Degree polynomial curve was fitted through the means  of  several hundred data
Points.  The shape of the curve  is  typical  of survival  curves in  that there
*r& two inflection points.  Beyond a threshold value  there  is an  increase  in
the rate of abnormal  larvae as the UV dose  increases.   At  the upper end of the
°urve, beyond a second threshold,  the impact  levels off.
                                     205

-------
     Using  these  data  as  a basis,  we calculated  the  increase  in  abnormal
larval  development as a  function of  decreases in  atmospheric ozone  (Figure
2).  The  calculations were referenced to ambient daily doses  that would  occur
during the spawning peak of  these species.  For species such as the  bay mussel
and oyster a 15% decrease  in ozone thickness can lead  to  nearly a 30$  increase
in the  number  of abnormal larvae.  The  impact of  UV-B may be  greater  on some
species while  species  such  as  the  cockle and butter  clam may be less sensi-
tive.   Using the  butter  clam as an  example,  a 15% reduction in atmospheric
ozone could lead to a 15%  decrease in  the harvest.   In comparison, a 1% change
in the harvest from a commercial salmon hatchery can be the difference between
negative cash flow and economic viability.

FUTURE AGENDA

     Phytoplankton serve  as a  major   conduit  through  which the sun's energy
flows into marine  life;  small plants  floating at  or near the  ocean's  surface
or at depths not exceeding the  euphotic zone depth.   A portion of this energy
is  transferred to  the  zooplankton  that  graze in  this   "breadbasket of  the
sea."   As  predator becomes prey, the  sun's  energy is transferred to  the next
strand in a web that can ultimately lead to man.  The  impact of UV-B radiation
on  this  transfer  of  energy  through  a food  web needs  to be  examined.    Two
levels of impact are possible;  direct impact on the predator  organisms or it3
larval stages  and  indirect  effects as a result of  the  availability of  prey-
Organisms surviving increased  levels  of UV-B  may  do so at a biochemical cos
that alters the value of  that  species as a food item.  Preliminary  investiga-
tion of this  question  has  begun.     Initial  results  indicate that, predator*
organisms  grow  at different  rates  when  fed  different  species   of phyt°*
plankton.    In  addition   it  appears  that biological  molecules  in  otherwis6
"healthy" phytoplankton are altered by exposure to UV-B.

     Documentation  of  the  effects   of  UV-B   on  marine  zooplankton shoul
continue with increased attention to  the  need  for  uniformity  in methodologi^
among investigators.   This would  permit  greater accuracy in comparing  result
and predicting effects.   The effort to  investigate  species that are  critica
components of  food webs   needs  to be increased.    Detection  of
alterations  in some  key species would constitute a refinement in our
to assess the  impact  of  UV-B.  Without  this additional  information,        ^
prediction  of  the effect  of  decreased  atmospheric ozone   on  the roar*11
ecosystem is difficult.

ACKNOWLEDGMENT
                                                                            . L|g
     Part of  the  research described  in  this  paper  has  been funded  by  c
United States  Environmental  Protection Agency  through cooperative  agreem®0
CR810288 and CR812688 with Oregon State  University.   However,   it has not jj«Jg
subjected to the Agency's  required  peer and policy  review and therefore do
not necessarily  reflect  the views of the Agency  and  no  official endorse^6
should be inferred.
                                      206

-------
 s:
 o:
 o
 m
 h-
 LLI
 o
 oc
 UJ
 a.
         100-r
          80-•
                    DNA WEIGHTED   (Eff  kJ/m2/d)
     Figure 1.  Bivalve Larvae Following UV-B Exposure.  Fertilized  eggs from
*°ur  species of bivalves molluscs were exposed to various levels of UV-B for 1
to 6  hours.  The eggs were then held  through the larval trochophore stage (24-
72 hr.)  and  were examined for  abnormal  development  at the  onset  of
straight-hinged stage.   Data  points represent the means of  four
         (Unpublished  data, Thomson, Worrest, and Robinson)
       the
replicates
                                   207

-------
          g..  • BAY  MUSSEL
 ui
 W

 o
 a.
 to
 UJ
 DC

 UJ
 G!
 a:
1.4-
1.3-.   * COCKLE
        1.2--
        1.1"
               o OYSTER
       DBUTTER CLAM
                                         10
                            PERCENT OZONE REDUCTION
                                                15
     Figure 2.   Abnormal Bivalve Larval Development.  The response of the f°ur

individual  species  of  bivalve  larvae  to  increased  levels  of  UV-B  waS

calculated using  the  response  of that  species at standard  ozone  thickne$s

(0.32 cm-atm) as  the  reference.   The reference levels  of  UV-B bracketed

spawning season  for these species.
                                    208

-------
 REFERENCES

 Berkner,  L.V-.,  and  L.C.  Marshall.   1965.    On  the origin and  rise of oxgen
     concentration in the earth's  atmosphere.  J. Atmos. Sci.  22:225-261.

 Damkaer, D.M., D.B. Dey, G.A. Heron and E.f.  Prentice.   1980.  Effects of UV-B
     radiation  on   near-surface  zooplankton  of  Puget  Sound.    Oecologia
     (Berl.).  44:149-158.

 Damkaer, D.M.,  D.B.  Dey, and  G.A. Heron.   1981.   Dose/dose-rate response of
     shrip larvae to UV-B radiation.  Pecologia (Berl.) 48:178-182.

 Damkaer,  D.M.,  and  D.B.  Dey.   1982.   Momograms  for  biologically effective
     UV.  In The role of solar ultraviolet radiation in marine ecosystems, ed.
     J. Calkins, 205-211.  New York:  Plenum.

 Harvey, J.M.  1930.  The  action of light on Calanus finmarchicus  (Gunner) as
     determined by its effect on the heart rate.  Contrib Can Biol. 5:85-92.

 Hunter, J.R., S.E Kaupp, and J.H Taylor.   1982.   Assessment of the effects of
     UV radiation  on marine fish  larvae.   In  The  role of  solar ultraviolet
     radiation  in  marine  ecoysystems,  ed.   J.  Calkins,459-497.NewYork:
     Plenum.

 Huntsman,  A.G.   1925.    Limiting  factors  for marine animals  I.   The  lethal
     effect of sunlight.   Contrib.  Can. Biol. 2:83-88.

 Karanas, J.J., R.C.  Worrest, and H.  Van Dyke.   1979.   Mid-ultraviolet  (UV-B)
     sensitivity of  Acartia  clausii  (Copepoda).    Limnol. Oceanogr.  24:1104-
     1116.

 Karanas, J.J.,  R.C. Worrest,  and H. Van Dyke.   Impact  of UV-B radiation (290-
     320 nm)  on the fecundity  of Acartia  clausii (Copepoda).   Mar.  Biol.
     65:125-133.

Klugh,  A.B.   1929.   The  effect of the ultraviolet component of  sunlight  on
     certain marine organisms.   Can. J.  Res.  1:100-109.

         R.C.   1982.   Review  of  literature concerning the  impact of  UV-B
     radiation  upon  marine  organisms.    In  The role  of  solar  ultraviolet
     radiation  in  marine ecosystems,  ed.  J. Calkins,  419-457.   New  York:
     Plenum.
                                     209

-------
An Estimate of the Role of Current Levels of
Solar Ultraviolet Radiation in Aquatic Ecosystems

John Calkins and Mary Blakefield
University of Kentucky
Lexington, Kentucky USA
ABSTRACT

     Organisms  that  use  sunlight  are  exposed  to  solar  UV-B  radiation.
Ultraviolet  radiation  in  the UV-B band,  280-320 nm,  can  produce  lethal  or
toutagenic  lesions  in  DNA  and RNA.   Successful  species  must  be able to cope
^ith the UV-B exposure; the  measures that  render solar UV-B tolerable are not
°ften recognized.   Solar  UV-B exposure may be mitigated by three  pathways:
Avoidance of-exposure, shielding, and repair of DNA  lesions after injury.  It
ls well known that:   (a) many forms  of  biological activity  occur in  the early
Corning or  late  evening,  avoiding the  midday when UV-B is most intense; (b)
animals  heavily  exposed   to  sunlight  tend   to  be   shielded  by  intense
Pigmentation, while cave or  ocean-bottom species are  often  pale or colorless;
*nd (c)  there are  multiple  DNA  repair systems that can  repair  solar UV-B
lnJury, one of which (photoreactivation) has no known function aside from the
Ability  to repair  the  type of  lesions  induced  by  sunlight.    Because the
Actions  that  minimize solar UV-B injury  (avoidance, shielding,  and repair)
exPend  resources  that might  be  used  for  other purposes,   the  best adapted
8Pecies would have  no more  capacity to cope with solar UV than is actually
£equired.    Observations  of a  number  of aquatic   organisms  suggest  their
£°lerance of solar UV-B is remarkably  close to  their present exposure.   When
Tolerance  and  current  exposure  are  essentially  equal, then  a significant
lnerease in  solar UV  would  be  expected  to have an  adverse effect on many
 r8anisms and be especially  damaging to species that are threatened by  other
environmental factors.

^RODUCTIOM

     Almost all  the living  organisms  familiar  to human experience  seem  to
      in the sunlight; so it is  counter to our intuition that the sun's rays
     be a lethal  agent which, if increased, might produce ecological disaster
s   sensitive species.  In spite  of the general impression, studies show that
 °-Ur ultraviolet radiation  is a  potent biological agent-that shapes the form


                                   211

-------
and behavior of most living organisms in such subtle ways that even biological
scientists seldom consider.

     Humans are among  the largest animals, and  the limited penetration of UV
into  tissue  might be  expected to  provide complete and  automatic protection
from solar UV damage.   But this is not the case, and solar UV radiation is as
clear a threat to humans as it is to other species.  Humans protect themselves
from  solar  UV  injury  in  the  same  general  ways  used  by  other  living
organisms:  avoidance,  internal shielding,  and  repair.   People avoid the most
intense  sunlight  (siestas) and reduce  it by clothing  (sombreros,  parasols,
sunbonnets,  etc).   Intense   constitutive  pigmentation  is widespread  among
humans  indigenous  to the  tropics.   Protective  tanning  of skin  is  clearly a
response  to  solar UV  damage  (Giese 1976).   It has been  recently discovered
that  individuals  lacking  DMA  repair  capacity  (suffering  from  the  disease
xeroderma pigmentosum)  may live if  protected  from sunlight but  suffer early
severe cancer if chronically exposed to solar UV (Cleaver 1968).   While these
forms of protection from  solar UV  are  obvious and well-known,  they have often
been subject to misinterpretation.   It was once thought that people with black
skin were protected from  the heating effect of  sunlight when obviously white,
not black,  skin  would   reduce  solar heating.   If  such a large organism as a
human requires  redundant  protection from  solar UV,  then it  is  obvious that
small organisms  may be at extreme risk  from  solar UV  exposure. While  the
interior  of  a human  is  well-protected,  all the  cells of small animals  or
plants are exposed.   Small animals and especially unicellular organisms, which
are more  common  in  aquatic ecosystems, may lack  the sensing capacity and the
rapid and properly directed mobility required to avoid solar UV; they also may
not have sufficient body size to permit an effective internal sunscreen.

     While these arguments suggest  that solar UV may  be a major environmental
hazard,   more  direct   evidence   is required   to   determine  the  particular
relationship  of  solar  UV and aquatic  ecosystems.   The  oceans  and  natural-
waters cover three quarters of the  earth's surface; human life and welfare ^s
intimately bound  to the  earth's  waters and  the organisms  that   live  in  the
seas.   A  significant  part of the  human  food  supply  is harvested  from  the
water, a harvest especially rich  in protein and  generally deficient in plant*
derived foods.  Clean healthy  waters also  provide  an  increasing role in huma0
sports,  pleasure,  and recreation.

     The most likely consequence  of stratospheric ozone depletion would be.,
worldwide increase  of  solar UV,  increasing the  present effects of UV  on  &*
natural waters.   Thus, the possibility that increased UV  from the  sun cou i
have  important  consequences  on  marine  life  and  the  multitude  of
activities depending on it deserves  careful  analysis.   The aquatic biota,
organisms  living in  the  oceans  and  fresh  waters, seem to  be  particular-^
vulnerable to  general  changes  in ozone because all  waters would be affect6"*
Furthermore,  aquatic  organisms  are not  subject  to   direct human
Humans  can  provide  shielding  or  compensation  through  strain  or
selection, which might minimize injury in the case of crops, domestic
and  human  exposure;  but  the  options  would  not  be available  to  aqua?iy
ecosystems.   Even  if  harmful effects were  so  small  as to  be  individual J
undetectable,  such  as  a  5%  decrease  in  the harvest of  a  certain  fish»  5
worldwide  accumulation  of  such  low  level effects  could represent  a sefi°
loss of resources.
                                      212

-------
     The  objective of  the  research reported  here  is  to  assess  currently-
available data and  develop  analytical methods that will permit the  prediction
°f  the potential  effects of  ozone depletion  on aquatic ecosystems  or will
suggest the methods and additional data needed to make such predictions.

PATTERNS OF ORGANIZATION OF AQUATIC ECOSYSTEMS

     Photosynthesis, the conversion of radiant energy from the sun into chemi-
cal  energy  (food)  is  the  basis of  essentially all  life  on earth.   Photo-
synthesis by land plants ordinarily proceeds  in large multicellular  structures
(higher plants)  at a  fixed  location and  with  many specialized  tissues and
structures  that  obtain  and  transport  nutrients and  water, conduct photo-
synthesis, ensure  reproduction,  and protect  the plant from  various kinds of
Physical,  chemical, and biological stresses.

     Aquatic plant  life is  organized along  entirely different  patterns (see
Russell-Hunter 1970).   Photosynthesis is also the source of the energy used by
the aquatic biota;  but  the primary photosynthetic plants are quite different
from land plants in body form,  reproductive patterns, behaviour,  and almost
all  basic  structures.   Photosynthesis  requires light; but  adequate sunlight
seldom  penetrates  to   the  bottom  of  natural  waters.     Thus,  aquatic
Photosynthesis is  largely confined  to  a  relatively  thin layer at  the water
surface termed the  euphotic zone,  the surface layer  where  plants create more
°hemical energy by photosynthesis than they use for their own metabolism.

     The  essential nutrients  required   by  plants   in  aquatic  systems  are
Bailable  only in very low  concentration;  thus,  smaller  plants have an advan-
tage as they  have a large  surface  to volume ratio,  making  them efficient in
capturing  these  essential  but  diluted  nutrients  from the  water.   In fact,
aQuatic photosynthesis is primarily conducted by single-celled organisms, many
species being  very small  (Russell-Hunter  1970).   Microscopic  organisms are
unable to swim or  otherwise move about  in  the water  even against currents of
low velocity, and  thus  are carried  with the bulk movements  of  the  waters in
which  they are suspended.   Those  suspended organisms carried about with the
water  are  termed  plankton  ("drifters").     Planktonic  organisms capable  of
Photosynthesis are  termed phytoplankton, while  those organisms that  live by
eating  (grazing  on)  phytoplankton  or   other floating  organisms are  termed
SSQplankton.   Organisms that swim strongly  (nekton) are  not  included with the
Plankton;  however,  the  embryonic  forms of many aquatic  higher  animals are
Planktonic.     As  feeding  progresses  from  the  phytoplankton   through  the
2°oplankton  to fish and other higher  organisms  (the food web),  the chemical
energy generated by aquatic photosynthesis  becomes more  and  more concentrated
into organisms of larger size, reaching  organisms suitable for harvesting for
human use.

      RADIATION

     Wavelengths   from   200   to   280  nm  are  termed  UV-C > and  are  the  most
Biologically  injurious solar  UV  component when incident on  living organisms.
fortunately,  UV-C is strongly absorbed by  the ozone  (0,)  molecules present in
the stratosphere, the outer  layer  of the atmosphere  beginning ten to fifteen
kilometers (six to nine  miles) above the earth's surface (note Figure 1).  The
strong absorption of UV-C by various  atmospheric  components  (primarily ozone)
      that biologically active  levels  of solar UV-C  do'not  reach  the earth's


                                     213

-------
                 Photosyntheticolly  active radiation

          \<-SoIar outside atmosphere
     UV VISIBLE NEAR INFRARED  FAR INFRARED
               i    i     i
100 300 600 900 1200    1800
               WAVELENGTH (nm)
2400    3000
                 Figure  la.   Solar radiation
                 atmospheric  absorption   and
                 passage   through  the   atmo
                 There  is  a general  absorption
                 much  stronger  absorption by a
                 spheric gases (03, C02,  HgO,
                 particular     wavelength
                 Adapted from Giese 1976.
  L25
                                Solar radiation
                              outside the atmosphere
   0.0
    220  240  280  320  360  400  440
            WAVELENGTH  (nm)
                                                     Figure  1b.   A  comparison
                                                     UV  intensity  (adapted
                                                     and Schippnik  1982) and
                                                     effectiveness  (Setlow
                                                     function of  wavelength.       s
                                                     the biological action, which *
                                                     pendent  on   the  product
                                                     tiveness  and   intensity,   -
                                                     from  the  crossing  tails  ° *
                                                     rapidly  falling  functions a
                                                     most   significant   in   the
                                                     wavelength band.

-------
     Radiation  of wavelengths  from  320  to  400  nm  are  termed  UV-A.    The
atmosphere is  transparent  for UV-A;  and  this band of radiation  from the sun
reaches the earth's surface with high intensity;  UV-A  produces little adverse
biological effect.   Species  easily damaged by UV-A or  visible  light do not
dwell in  the  sunlight.   However,  some animals sensitive to  UV-A  can be  found
as nocturnal  organisms, in  caves,  or deep in the  oceans where  sunlight is
absent.

     Between  the  UV-C and  the  UV-A  lies  the narrow  UV-B band  of  radiation
extending from 280 to  320 nm.   Small  but significant amounts  of  UV-B are
Present  in  sunlight  reaching the  oceans;  and it  has a  high potential for
injury to  most living  organisms  found at  the earth's surface.   Atmospheric
absorption of short  wavelength solar  UV  does not end sharply at 280 nm nor
does UV damage  begin  abruptly at  320 nm.   Figure  1  illustrates that the UV-B
encompasses a transition zone where  solar radiation intensity rapidly  falls
and the  capacity  to injure or  kill living organisms rises  as the wavelength
shortens below 320 nm.

     The strength of the absorption of various spectral components of electro-
""agnetic  radiation  in  both  the  atmosphere and  in natural  waters  is  often
expressed by an absorption coefficient (K).   The  intensity of radiation  inci-
dent on the absorber  (I  )  is  reduced  to  a value  I by passage through a thick-
ness of  absorber  (Z).   It  is usually found that the  relationship between I,
Io» and Z can be expressed by

                               I = I0e-KZ                                Eq. 1

tne  absorption coefficient  (K)  will  depend on  the nature  of  the  material
traversed (air, ozone, clear ocean water, or turbid fresh water) and the  wave-
length of the particular radiation.

     Sunlight is generally absorbed in natural waters,  heating the sunlit zone
      the  lower water remains cold.   Because water becomes  less dense  as it
Marms, sunlight generates  a  stable,  low density  warm layer  overlying  cold,
      water.   The  boundary  between  the  warm and cold  layers is  termed the
            and is of  great  importance in  aquatic  biology.   Wind-generated
          frequently  mix the  waters above  the thermocline producing  a  mixed
     , but the mixing does not ordinarily penetrate into  the dense layer  below
    thermocline.  Because solar energy both generates the thermocline and pro-
    s the photosynthetic light for  the aquatic plants,  it  is often found that
    euphotic  zone essentially coincides with  the  mixed layer.  In small  water
         cooling the  water surface  at night  produces dense water  over the
        less  dense  mixed layer and the entire water body  can be  remixed.  In
       water  bodies, the thermocline  can  remain from spring until cold winter
        cools the mixed layer to the temperature  of the water below; then deep
       will occur and replenish the nutrients, which probably would have been
p6Pleted  by  the photosynthesis  in the  euphotic  zone.   A common  pattern in
      water bodies  is that deep mixing occurs in the  fall or winter as  noted
      and also in the spring when the cold (0°-4°C),  low density surface  water
   warmed  to  the temperature of  underlying water and the density barrier to
       disappears.
                                      215

-------
CONCEPTUAL MODELS

      In  the absence of definitive  knowledge of how a particular human, activity
will  affect the global  environment, it seems  reasonable  to  strive to maintain
the  present  condition.   However,  technologies or  activities  that  become  so
widespread as  to perceptively modify the environment must provide substantial
benefits.   Some method  must  be  developed  to weigh  the  benefits from  the
environmentally  perturbing activity  against the  benefits of the  status  quo-
The  focus of this paper  will  be  on  methods  to evaluate the harm that  might
occur  in aquatic exosystems if UV-B were increased.  The benefits that may &e
derived   from  the  technologies  that  reduce  stratospheric  ozone  and   thus
increase UV-B are not considered.

     There are  several ways to quantify the ecological damage  from a chemical
or  agent.  In  some cases,  historical data  can be  analyzed to  evaluate  the
injury or loss of resources due  to the agent.  Another  widely-used technique
is to construct  a microcosm, a  small scale  model of the ecosystem, that can  &e
subjected  to  the expected  levels  of the agent.    Although  there is a strong
latitudinal dependence  of  UV-B intensity,  it is  not  clear how this or  any
other historical data can be applied to aquatic systems to estimate the impact
of increased UV-B.  Microcosm research holds  some  promise, but  it is difficul
to establish how well the microcosm simulates  the  natural ecosystem especially
for results requiring long  (weeks  or months) exposures or organisms needing
large  range  to  thrive.    A third  approach  is to  measure  selected
parameters,  and,  by  appropriate  modeling,   deduce  some   of  the
consequences of various UV-B exposures.
     The essence  of the analysis  is the capacity  to  quantify the risks
defined changes  in  solar UV-B.  Considering  that aquatic ecosystems are
side human control and the relevant data presently  available are so limited as
to be almost negligible, quantitation would seem  to be an  impossible task.  *
the subsequent sections of this paper, approaches are defined  that may provi a
quantitation for  limited but  important  areas  of the problem.  Quantitation °*
effect is achieved  by developing models that  produce  responses from relevan
and  measurable variables;  in  this  case  the  primary  variable  is  the
intensity and  its  changes.   In  general,  the  models  presented  are
simplifications of  actual  conditions but are necessary  to clarify the
of the problems.

Lethality Models:  Organism Level

     The most  clearly-defined response to UV-B  exposure in aquatic
is  lethality,   and  it  is  particularly  easy   to  quantify   the  predom
components of  the  plankton.    Certain acute  lethality  is the most
effect  that  UV-B  could  exert  on  a  living organism.   Methods  for assay1"*
radiation-induced  lethality  are  well  developed.    Although  dose-respon®
relationships  for  lethality  can   assume  many   forms,   the  combination'
illustrated  in  Figure 2  cover  the various responses observed  in  irradiat fl
organisms.   Figures  2A  and  2B show a  threshold  type  response.   Up  to,he
critical (threshold) dose, little or no lethality would be expected; above *j*
threshold a  small  increment  of dose produces a  large response.  The resp°n e
                                                               .
illustrated in Figures 2C, 2D, and 2E show the "classical single hit"
often  observed  in  irradiated microorganisms.    Single hit  response  can
expressed mathematically as
                                     216

-------
                              S = S0e-D/Do                                Eq. 2

 where  S is the  number  of survivors measured after  exposure to dose D,  S   is
 the  number of survivors measured  with o dose and D  is a  constant  expressing
 the  sensitivity  of the  particular species.  Single  nit response  begins at  the
 lowest  doses and  implies  that some  types  of single  event ("hit") produces
 lethality;  the  larger the dose, the larger the probability  the organisms will
 receive a  lethal "hit."   If a species  shows  the single hit  type response, then
 even small exposures (and current levels of UV-B) produce some lethality;  and
 *t  is  easy to compute the  increased lethality result from  increased incident
 UV-B.
                          dS = j_  e'D/D0                                 Eq.  3
                          dD   D0


 Substituting S/S  =  e"D/Do  ifc is evident that the  incremental survival  per
 unit dose dS/dD  is proportional  to the product of  1/DQ and the survival ratio
   o*

     The threshold model  suggests  that a species may suffer no lethality from
 given  levels  of UV-B because exposures  fall below  the  threshold level.   For
 threshold  responses, it  is  important  to know  the relationship  between  the
 threshold  dose  and  current  UV-B radiation levels.  If  the threshold dose  is
 above the  exposure,  then  the organism  survives current exposure,  and the dif-
 ference represents a reserve of tolerance that permits  a limited increase of
 UV-B exposure without any increased lethality (the  good  news).   However,  the
 bad  news is that if the threshold is  exceeded,  then a small increment  in  the
 dose may produce a large probability of  lethality  (note Figures 2a and  2b).

     It is  possible  to  simulate solar UV-B  or use real  sunlight to determine
 UV-B dose-response curves.   It is  also possible  to estimate the typical  solar
 UV-B exposures   that  individuals will  receive  in  natural  waters;  from such
 estimates  the  incremental  killing of organisms showing  "single hit" response
 and  the  reserve tolerance  of threshold  type  responding species  can  be com-
 Puted.

 Ijgthalitv Models;  Population Level

     If data on  individuals  can  be obtained,  then  the  response of individuals
 should be applied to populations to define the expected ecosystem response.   A
 traditional modeling scheme  (illustrated  in Figure 3)  might use  the  Lotka-
 Voltera approach.  We may assume a three-species  ecosystem having:  a primary
 Producer,  which might be a  bacteria  (or  photosynthetic algae,  etc.); an omni-
 vore or primary  herbivore,  represented by a protozoan (but  could be rotifer,
 arthropod,   etc.);  and a  secondary  carnivore flatworm  (arthropods or fish,
 etc.).   This model  ecosystem can achieve a stable population distribution.  If
 We assume,  for illustration, that only the middle member of the food web would
 be subject  to an  abrupt  increase of solar  UV-B  damage, then  its population
Would be depressed but there would  also be a population-restoring tendency
 because the food supply would increase and the predation would  (after  a time
 *ag) decrease.  Considering the complexities  of even this simplified model and
 the  vast difference  between  it  and  an  actual  aquatic food web, it is very
UlUikely that  this form of modeling will provide useful or believable con-
 tusions for evaluation  of solar UV-B effects.


                                     217

-------
  100
  50
I 20
CO
         246

         UV dose (SU)
8
Figure  2a.   Survival  of the
Chlamydomonas  exposed to
solar   UV-B  and   real
(modified    from    McKnight    e
Nachtwey    1975).      Doses   v r
measured using the Robertson-^6 * t
meter;  the  good response
for   the    two   very
wavelength  distributions
the      Robertson-Berger
weighting   distribution
satisfactory   for   this
Note the sharp threshold;
                                          in
                                          is
                                         °rga"
                                                                         very
                                                                         islB.
                                          survive  without  measurable *••* ^
                                          up  to  5 SU  but  when this l&*
                  to  5 SU but  when this
               exceeded mortality is very

                                          Figure 2b.   The  killing  °r
                                          competent yeast  (N)  and two
                                          defective  strains (A,  B)  l
                                          light  (from Resnick  1970)-  fS
                                          that substan tial killing °c°
                                          a matter of minutes and that
                                          defective strains show "sin&
                                          killing,  while the wild typ«
                                          shows the threshold type
     306090 120
    UVdott (min)
                              218

-------
  10
a:
  -01
 0.01
                                             Figure 2c.   The killing of E. coli
                                             by natural sunlight (Lukeish  1946).
    0     20    40    60

         UV dose (min)
  too


   10


    I
i    .«
to   -01


   .001


  .0001
                                             Figure 2d.   The killing of coliform
                                             bacteria by  sunlight  in  a  waste-
                                             water  lagoon system (Calkins et al.
                                             1976).
           Z   345
           UV dose (SU)
                                            Figure  2e.   The  killing  of  three
                                            marine  diatoms  collected  from  the
                                            waters  off   Iceland  by   simulated
                                            solar  UV-B  (modified  from  Calkins
                                            and Thordardottir  1980).
            254  9
             UV dost  (SU)
                                 219

-------
                    Bacteria   Bacteria feeder
                              Primary carnivore
                                Tetrahymena
                                                    Secondary carnivore
                                                     Flatworm
                                                    Equilibrium condition
                                              WV*
                                                    Assume UV destruction
                                                     of Tetrahymena (tran-
                                                     sient condition]
             o
             r*
            O
10


 8


 6


 4

 2
Tendency to restoration
 of Tetrahymena  popula-
 tion  (transient condi-
 tion
                                                     Equilibrium with
                                                      reduced sensUlvt
                                                      population
Figure 3.   A Schematic Representation of Equilibrium-Type  Modeling of
             Three-Component  Ecosystem With and  Without UVB.
                                        220

-------
     An   even  simpler   model  provides   some  definitive   and  surprising
conclusions.   While the  level of depression of  a  particular population by a
newly  introduced  agent such as UV-B  seems  beyond computation, it is possible
to determine  the  maximum  level of an injurious agent (UV-B)  that a particular
species  can  tolerate.    If  the  daily  UV-B  incident  (given  optimum  growth
conditions  and  with  all  other  sources  of  lethality  such  as  predation
eliminated)  produces  lethality  that exceeds  the  capacity  of  the  subject
Population  to  replace the  killed  component,  then  population  will,  under
prolonged treatment, be depleted  to extinction (Figure  4;  Calkins 1974).  In
actual ecosystems, optimum growth conditions are seldom found and most aquatic
species are  food  for some predators; however,  if a population cannot survive
with the  most favorable  conditions, then it  clearly could not survive in the
feal ecosystem.  In the laboratory, it is possible to determine the parameters
for  the  maximum  tolerable  dose  (the replacement  limiting  dose, RLD):   the
optimum growth rate, the  growth  delaying  effect of radiation,  and  the dose
response  for  lethality.   When the  RLD  is compared  to  the  actual exposure in
nature, one obtains an estimate of the reserve of tolerance a species may have
for increased solar UV-B.

EXPOSURE MODELS

     There are  a  number  of ways  of establishing the UV-B  levels incident at
the water,  which  we consider below.   Because natural waters  are semitrans-
Parent  for  UV-B   wavelengths, Equation  1  can  be  used  to determine  UV-B
intensity at any particular depth and thus,  knowing the UV-B intensity at the
surface and  the  depth of  the organism,  the  instantaneous  exposure can  be
computed  (See  Figure  5).     In  some  cases,  aquatic  organisms  hold  fixed
Positions such as  at the  bottom of a shallow pond or stream.  However,  a fixed
vertical  position  is  rare  and  some  definitive  knowledge  of  position  is
required.

     Planktonic organisms  in many  cases are moved with the water mass in which
they live.  When  there is effective  wind-driven mixing  of the layer above the
thermocline,   a common  condition,  then  the  organism   receives  the  average
exposure (Iav) in  the mixed layer,  i.e.,

                                  -        -KZ)
                                         KZ

Source:  Horowitz 1950 Equation                                          Eq. 4

where z is  the  depth of the mixed  layer  and the other symbols have  the same
significance as in Equation 1  (See Figure 5b).

PRIMARY PRODUCTIVITY MODEL

     Solar  UV  directly reduces  the rate  of photosynthesis  in  plants.   The
sPectral distribution  of  this  inhibitory effect  is quite different  from the
lethal effect.   Because long wavelengths of  UV  and even visible  light inhibit
Photosynthesis,   ozone reduction  producing  a  small  increase in  UV-B  would
aPpear to have  a negligible effect  on the  primary photosynthesis  in aquatic
aystems (Lorenzen 1979; Smith  et al. 1980).


                                     221

-------
                                      Consider only  one species.

                                                Assume;
                                                  1.   Maximum growth rate
                                                      of population
                                                  2.   1 acute exposure
                                                      each 24 hours
                                                  3.   No other loss of
                                                      population
                                                  4.   Population does not
                                                      modify Us behavior
(9
C£
O

u.
o

at
ui
CO
       8-


       6-


       4

       2
      10
       8-
                                      Day  1
                                      Day N
Required  Information:

  1.   Dose-response for
      killing (non-repro-
      duction)
  2.   Maximum growth rate
  3.   Dose-response for
      growth delay
                                   Day N  +1
        Figure 4.   The Replacement-Limiting Model
                               222

-------
                  I—x-
                         X PUERTO RICO

                         DLAKE SUPERIOR

                         ODELAWARE ATLANTIC

                         A LAKE EftlE

                         • LAKE I IRRINGTDN . KT.
                                                          Figure 5a.  The attenuation of
                                                          UV-B   as   measured   by   the
                                                          Robertson-Berger meter in some
                                                          representative natural waters.
                   949

                    DEPTH (METERS)
u
                          Figure  5b.   The  average  UV-B
                          dose  to the  euphotio  zone  at
                          various  locations  off  Iceland
                          as  a  function  of  the   pro-
                          ductivity  of  the waters.   It
                          is assumed that  10 SU  per day
                          are   incident  at  the   water
                          surface.
                      J_
_L
_J
 25
            5          10         l»
                 AVERAGE PRODUCTIVITY MflC/m3/HR
                                           20
                                         223

-------
      There are  indirect ways  by which the  increase of UV-B  might produce a
 larger  effect  than  predicted  from  the  direct photoinhibition  of photosyn-
 pthesis.  Killing  phytoplankton should show the DNA type action spectrum and
 thus reduce photosynthesis in  a way  similar  to other lethality.  However, the
 effect  of lethality  on photosynthesis  would  require much  longer  times  t°
 develop  than  is  required  for  measurement  of  direct  photoinhibition.    ^
 lethality contributes  to  the  loss  of photosynthesis capacity,  it  must  be
 modeled by more  complex models.  There are very few data on UV-B killing alga®
 and also  little  information as  to  the vertical location at  various times of
 day.    Considering the  relatively  large attenuation of  UV-B  in the  tnore
 productive waters  (coastal and upwelling zones),  it would  appear  that  the
 phytoplankton  are well protected from UV-B.

      Another approach has been proposed.   Although photosynthetic productivity
 measurements are usually made  with samples held at  fixed depths for a half or%
 a whole day, mixing is common in natural  waters.  In the well-mixed situation^
 all the photoplankton  receive the same amount  of  light per day  and the  same
 UV-B exposure.   A "ferris wheel" model has been proposed (Calkins et al. 1982)
 where algae enter the circulation (by rising) and  are transported (by Langmui^
 cells,  etc.)  along the  surface where  they  accumulate  a UV-B exposure  that
 produces a sinking  (increased density) stimulus that removes the  algae  fr0in
 the circulation  into the  stable water at or  below the thermocline  (Figure
 6).   The postulated cycle would ensure that the phytoplankton  species received
 the maximum possible photosynthetic  light without exceeding  its  UV-B limits-
 If UV-B exposure  is not random,  but is controlled  by the organism,  then  an
 increased  incident  UV-B will  reduce  the time  the organism remains  in the mixed
 layer.   The loss  of photosynthetic light due  to UV-B increase  will be directly
 related  to the  ratio  of absorption  coefficient  of  UV-B and  photosynthetic
 light  in   the   mixed  layer   (Calkins  1982),  quantities  that   are
 measurable.
BIOLOGICAL DOSIMETRY
     The  solar  UV-B is the principal  parameter of all the analytical  models-
This might seem  to be an  easily determined quantity  but,  referring back ^
Figure  1,  it  should be noted that the biological effectiveness  of UV-B energy
drops by  a factor of  1000  or  more as the wavelength  changes from 290  to   *
nm.   Clearly,  it  is  impossible to  simply measure  UV-B  intensity  w
distinguishing  between  components  that   differ   1000-fold   in   biol
action.   Ideally, UV-B dose should be measured in very small wavelength    0
and  then  each  multiplied  by  an  appropriate  biological weighting factor j; -
obtain  the  instantaneous  intensity (Figure  7).   The product of the  intensity
times the time  of its application for  the entire exposure should  be added c
give the  biologically  weighted dose.   This is a difficult procedure  requir*™;
a  high  resolution  spectroradiometer  and  definitive knowledge  of the  pr°Pe
weighting factor which may  not be  known for  the organism under study.
measure
     The  physical  devices  used  for  measuring  solar  UV  intensity u|u  ^d
     re the  quantity termed irradiance (power  per  unit area in Watts/m ) * „.
the  summation or  time integral  of this  quantity is  termed  the  irradia£i-j2
(energy/unit area, commonly expressed in Joules/nr) .  The biological weighfc~he
unit is simply  an efficiency ratio so  the biologically weighted dose has c
units of irradiation, J/m .
                                      22H

-------
    SURFACE
        t
                                              UV-B  VISIBLE
t
\
1
Ij
[
• u
t
s
     THERMOCLINE
                                    leave —
   2
   o
     Figure  6.   The  "Ferris  Wheel"  model of control of  UV exposure.   It  is
Su8gested that aquatic  organisms  may use the motions of the mixed layer  to
°btain the average light exposure.   At dawn, the  phytoplankton rise into the
^roulation  and ride the currents.   When  the UV-B exposure becomes limiting,
pe algae move  downward  out of the circulation into the  still waters under the
  ermocline.   A small capacity  for movement  plus  the  circulation  in the mixed
      permit the  weak swimming phytoplankton to  control their position for
         photosynthetic  light  while  receiving  a tolerated  UV-B exposure.
   reased UV-B  would  reduce the time spent in the mixed  layer each  day.
                                    225

-------
    100
     10
 CO
 CO
 LU
 z
 UJ
 o
 UJ
 u.
 u.
.UJ
 UJ

 I

 
-------
     Biologically weighted  dose is often  calculated  from a knowledge  of the
spectral distribution of  the irradiation and a weighting  factor  derived from
action spectrum  (the measured  relative  effectiveness  of different wavelengths
to  produce  some  particular  biological  effect)  known  or  assumed  to  be
Appropriate for the organism under study.   The  "DNA"  action spectrum has been
most widely used to derive weighting factors but this action spectrum does not
seem appropriate  in some  cases.   Another widely  used device for  obtaining
biologically weighted doses is the Robertson Berger  meter.   This  instrument
measures irradiation (expressed  in  a  special unit termed  the  SU)  including a
lighting factor.   Approximately  20 SU are incident  on a  sunny midsummer day
in Lexington,  Kentucky;  about 10 SU on a similar day in Reykjavik,  Iceland.

     Organisms that  show shouldered  survival responses  can be analyzed  for
reserve tolerance to UV-B.   Among  the  Icelandic diatoms, the two strains of
Ifealassiosira  have  reserve  tolerance  in excess  of  the typical UV-B  exposure
they would  receive  in  the  mixed  layer.   The other  organisms  are at  present
      to the threshold dose.   Tetrahymena exhibit a threshold dose about twice
the average daily exposure  in a typical  1-m deep pond.  Most other organisms
*je have tested, showing threshold type survival  responses, have  the threshold
dose below the average  daily exposure in a  1-m  deep  pond  (Figure 8).   It is
Possible that they do not live in such shallow ponds or that  they have special
sensing  and  remove   themselves  when  UV-B  irradiance  is  excessive.    The
important point is that making crude  but quantitative estimates of  exposure
    factors  critical to  tolerance  of  UV-B shows  that most  of the  aquatic
          tested are  very near their tolerance limits.
^PLACEMENT LIMITING DOSE

     Figure 8 shows  the  replacement limiting dose  (RLD)  computed for a  wide
        of aquatic organisms compared to the exposure they might  receive  on a
      midsummer  day using the models and data already noted.   Because  the RLD
*8 the upper limit of a species-tolerance, it is evident  that  some additional
Protection against solar UV  must be included  in  species currently  exceeding
•^eir RLD.  Some of these factors have been noted.   Organisms  reduce solar UV
®*Posure by  sinking to the  bottom during high  UV  periods  or collecting  at
flight shielding objects in the  water.   The filamentous algae  Rhizoolonimn
   5  habitat where  exposure exceeds  the  computed  tolerance  remains  at  the
        of the  ponds  where it was  collected, but  all  new growth is downward
      the protection of old moribund filaments.  Coliform bacteria die out in
         waters  in  a  way  suggesting  that  solar  UV   is a  major  cause  of
        r.   However,  their  UV-B  tolerance is great  enough  to suggest  that  they
    survive in natural  waters long  enough to transfer from host to host.

     The models  used in this presentation are great  simplifications  of actual
             It  might be concluded that tolerance and exposure Just  naturally
     out approximately equal.  Figure 9 shows that this is not the case.   The
j^P-'-acement limiting  dose of  ionizing  radiation  (cosmic  rays  and  natural
801  °a°tivity)  can  be  computed in  exactly the same manner  as was  done  for
  Aar uv.  It is  evident  that tolerance to ionizing radiation vastly  exceeds
G*L°?IUre while  these two factors are almost  identical  for solar UV.    One  can
         that current  levels of solar  UV  represent a  positive  evolutionary
        Each species  must  have the  observed  UV-B resistance  to  live  in  its
           ecological  niche,  a value  very close  to the-exposure level.    A
       that might  gain  resources by  losing  a protection factor  (such  as not


                                     227

-------
    MARINE (Iceland)
 20
  10
  5
  2
   I
 Q5
 0.2
 O.t
0.05
                          SUNNY SUMMER
                        DAILY EXPOSURES
                                MAX
                      FRESHWATER  (Kentucky)
                         •MAX
                          »ovg.
                         euphotic
                         .zone
                   ICopepod
JUNE AVERAGE—*
avg- stream
 40cm
avg. pond Im
stream bottom
avg. wastewater
   lagoon
pond bottom
 1.0m
                                                       .20
.2
•I
.05
0*
CM
a*
                                               Bacteria
      Figure  8.    A  comparison  of  solar  UV-B  exposure  and  tolerance of
various organisms.   Dark  shading  indicates exposure exceeds tolerance;
light shading indicates  tolerance greater than  exposure (see  text
methodology and  discussion.)
                                         228

-------
    10
    10
    10'
    o*
5
  lofl°°
   KJOO
   -00
    It
    Oj
                   IONIZING RADIATION
        SOLAR UV
?*5«!S?:
•••I15/'.i tin '
safest!
,tt$ 121
UfeMsh
^:C"«ir]i
/.:%"*ji nil-
™lm*\i - ^
   iy . vii t3t ^_
   ^}..kJt? .• !•«••
 Figure  9.   The  ratio  tolerance  to
 exposure   for   solar  UV   (left
 panel)   and    natural    ionizing
 radiation   (right  panel).    The
 appropriate equality  of tolerance
 and exposure of solar UV  suggests
 resistance  to  solar  UV  to be an
 active  characteristic which would
 be  maintained   in  the  popula-
 tion.     The   large   excess  of
 tolerance   over   exposure   to
 natural     ionizing     radiation
 suggests   that   resistance   to
 ionizing   radiation   may  arise
 indirectly  and  characteristics
 that    increase   resistance   to
 ionizing radiation but  produces
no  other  effect  would  not  be
strongly favored.
              ORGANISMS
                                      229

-------
making  a  repair  enzyme  or  a  protective  pigment  or  not  avoiding  high  UV
exposure)  will be killed by  the UV.   The best adapted strain has  exactly  the
UV-B  tolerance  required but does not waste resources protecting  itself fr°m ^j
levels  not actually encountered.   If  this status (tolerance equals exposure)
is  the  current condition as  indicated  by the available data, then it must &e
concluded   that   an   increase  in  solar   UV-B  levels  will  perturb   aquatic
ecosystems;  they  then will  lose some  of  the  available  photosynthetic  Ught
upon  increased UV-B.   Figure  10 shows the simplest mode,  algae that  occupy
fixed positions.   From Figure  11 one  can see that the loss  of  photosyntheti-0
light  (PSL) will  equal  the  percent increase  in  UV-B  times  the ratio of  fche
attentuation  coefficient  for  photosensitive  light  (K  i)  divided  by  fche
attenuation of UV-B  (photosynthetic) (Kvis)  in  the water.

                      PSL (?) =  UV-B (%)  KpSL                          Eq. 5


                                          KUV-B

For organisms  that circulate in the  mixed  layer  but  remove themselves
the thermocline  upon excessive  UV-B exposure (see Figure  11 for a pot
model of  this  effect), the loss of light approximates the  same ratio but  **
somewhat more  complex  to compute  and depends on the  particular assumpti°
regarding  depth  of the mixed layer, incident  UV-B,  and tolerance limits.   *"
any event, if  the phytoplankton have mechanisms  to  limit  UV-B exposure  W
avoidance  and  if  this mechanism is  utilized with  current levels  of UV-B, fchf™
enhanced UV-B  would  replace  the visible light available  for   photosynthes1
presumably without increasing lethality.

DISCUSSION AND CONCLUSIONS

     It is very  difficult  to evaluate the  potential  effects of solar Uv °J
aquatic ecosystems.   The  systems are so  dynamic  and  human consequences, su ^
as  fish catch,  are  so variable  that  any  attempt  to directly  measure 3W&^
effects  would  be  "lost  in  the noise."    The   laboratory  simulations  &
microcosm  data suggest that enhanced UV-B would modify aquatic ecosystems, "
it  is  difficult  to  judge  how  much  reliance  can be  placed on conclusi°
derived from laboratory'experiments or microcosms where the subject species
exposed to far fewer variables than in natural systems.

     The "replacement limiting dose" model and corresponding data suggest tft
many  species  are  at  present   close   to  their  tolerance   limit  for  s° c&
ultraviolet radiation.   Various species show higher or  lower UV-B resisfcani5
in  close   correlation to  their  exposure  and lifestyle.    If  solar W  ir)
presently  a significant  limitation on  aquatic  organisms,  then changes  ^
incident UV-B will probably produce ecological  changes.   The changes  could ^
fact be favorable, for example,  elimination of coliform pollution of wafcertne
a reduced  time.   However,  in  the  absence of  convincing evidence as to
nature  of  changes that might occur, it seems prudent to try to maintain
status quo.
                                     230

-------
                                          SOLAR UV SCALE
      SURFACE
SU/doy

 10
                                                               20
 PHOTOS YNTHETIC
 LIGHT (PSLi SCALE
 color ies/cmy day
.200  .400600
                                                 NORMAL
                                                   UV
                                     CHANGE IN
                                     AVERAGE
                                       DEPTH

                                     REQUIRED
     Figure  10.    A  model  illustrating  the  loss  of  photosynthetic  light
whenever  organisms  are forced  to move  deeper  in the  water column to  avoid
increased UV-B.
                                       231

-------
   100
                                 Volvox Quretfs


                                V - Control
                                O - 50 tec exposure
                                O - 100 etc «xpoiur«
                                                                                        /»
                                                     Figure  11a.    The  time  courseftgr
                                                     movement  of  Volvox  Aureus   a*
                                                     exposure  to  real   sunlight
                                                     control.  After exposure,  the &i°
                                                     were  layered on the  top  of a  '
                                                     Under.   The data  points
                                                     the  percentage  remaining
                                                     upper half of the cylinder.
                234

                  TIME (min)
  ICO

  90
Seo
  70
o
Q.
O.
= 50

§ 40


I.
o
K
it!  10
                                   V. olobotof
                                   V. our»q»
                                                    Figure  11b.    The  time
                                                    movement of  two  specieis
                                                    in   the   dark  without
                                                    exposure.   Samples  were     f
                                                    the  surface  and the  bottom
                                                    test  chambers.
        20   40  60  80  100 120   140  160  ISO
                   TIME (min)
                                        232

-------
           Total Solar Radiation
                            Total Radiation MimnVHil*
                              (Solar UV Only)
                              A ..  A
    20   40   60   80   100  120   140
             TIME  (min)
                                   228
 Figure  11c.   The  movement of Volvox
 aureus   under    exposure   of   an
 irradiance  of 5.2  W/m2  light  from
 Westinghouse    Agrolamps.       The
 "unirradiated"   control  had   been
 held  in room light,  approximately
 1.6 W/nr prior to testing.   The two
 test  populations  (N  and  A)   were
 exposed  to   June  sunlight  for  5
 minutes.  The squares received  the
 total   solar   irradiance.      The
 triangles  were  exposed  under   UV
 transmissive      Schott      glass
 filters.  They received essentially
 the same total UV irradiance as  the
 "total solar irradiation" group  but
 with    the    visible    component
 removed.   Note  that  although   the
 irradiance was much less  in -UV-only
 group,  the  depression  of  upward
 movement was  extreme.   The UV-only
 group appeared  to  be  killed  upon
 subsequent observation,   while   the
 total  irradiation  group  appeared
 viable.
180-
|I20


3 "00
S

 80

 60

 «0

 20

  0
        j-  0
               1
          Ho	&	"w
           RELATIVE IRRADIANCE
Figure    11d.       A   test    for
reciprocity.   The points  represent
the  mean  of at least 4  tests  using
irradiances ranging  from 1.0 x 10"*
to   .37   W/nr.     The   same  total
irradiation   of   22   J/m2    was
delivered.    The delay  in  minutes
for    50%    of    the   irradiated
population  to move  into the  upper
chamber when  started at the bottom
over  the  time for controls  to make
this  movement was considered  to  be
the   delay   induced  by   the   UV
radiation.    The  source of  the  UV
radiation was 2 to 4 FS-20 sunlamps
filtered  by  a   .3cm  Pyrex  glass
filter  and   a  UG-5  Schott  glass
filter, 1mm thick.
                                    233

-------
      The more direct models  of aquatic photosynthesis suggest  that increased
 solar UV-B would  have little  effect  on primary productivity.   On  the  other
 hand,  some observations  suggest  that solar  UV-B  acts  as a  limit on  light
 exposure for  some  of the  phytoplankton.   If there is  a mechanism whereby  algae
 sense and avoid  excessive UV-B  exposure  by  restricting their time or location,
 then  such  organisms,  although they  would  survive   as  well  as  they  do  at
 present,  would  reduce  their  photosynthesis  (if light limited)  by  an amount
 computed from Equation  5.  Using absorption coefficients from natural  waters,
 the  primary productivity loss  for  a 10% increase in  UV-B  leads to  a loss  of
 visible  light  from 3% to  5%.

      There  is   not  an  adequate  data  base  to reach  firm conclusions  or
 predictions  as  to  how  aquatic  systems  whould  respond   to   changed   solar
 ultraviolet  radiation.    Aquatic species survive large short-term changes  in
 solar  UV  exposure.    But the  near equality  of exposure   and  the  tolerance
 suggests  present average  levels of  solar UV to be  a limiting factor for  many
 species,  and  thus,  if  the average  solar  UV-B level  were  to increase,  there
 would  be shifts in the  composition of aquatic  ecosystems.  Only much  more
 extensive research could  suggest the magnitude of the  shifts and  which species
 might benefit and  which species would lose.


 REFERENCES

 Calkins,  J.  1974.   A preliminary assessment of the effects of UV  irradiation
     on aquatic  microorganisms  and  their ecosystems.   Proc. 3rd conference_on
     CIAP.  DOT  TSC OST 74-15, 505.

 Calkins,  J.   1982.    In  The  Role  of  Solar Ultraviolet  Radiation  in  Marine
     Ecosystems. 539. New York:  Plenum.

 Calkins, J., and M. Blakefield.  Unpublished observations.

 Calkins,  J.,  E.  Colley,  J.  Wallingford, C. Hulsey,  K. Lohr, and  M. Boiling
     1982.    Sunlight-induced  movement   of planktonic  organisms  and  their
     relationships  to water  movements.    Kentucky Water  Resources  Research
     Institute. Report 132.

 Calkins,  J.,  and  T.  Thordardottir.   1980.   The ecological significance of
     solar UV radiation on aquatic organisms.  Nature  283:563.

 Cleaver,  J.E.  1968.   The defective repair  of DNA  in  xeroderma pigmentosum.
     Nature 218:252.

 Cole,  C.A., R.E. Davies,  P.D. Forbes,  and L.C.  D'Aloisio.   1984.  Comparison
     of  action   spectra   for   acute   cutaneous  responses to  ultraviolet
     radiation:  Man and Albino hairless  mouse.  Photochem.  Photobiol. 37:623-
     31.                                         	

Giese, A.C. 1976.  Living  with our  sun's  ultraviolet rays.  New  York:  Plenum.

Green,  A.E.S.,  and  P.P.  Schippnick  1982.    The Role  of  Solar  Ultra-Violg£
     Radiation in Marine Ecosystems.  5.  New York:   Plenum.
                                     234

-------
       ,  P., and J. Calkins 1980.  The inactivation of a natural population of
     coliform bacteria by sunlight.  Photochem. Photobiol.  31:291.

Hunter,  J.R.,   S.A.  Kaupp,  and  J.H.  Taylor  1981.    Effects  of solar  and
     artificial  ultraviolet-B  on  larval northern  anchovy Engraulis  mordak.
     Photochem. Photobiol.  34:477-86.

Lorenzen,  C.J.  1979.     Ultraviolet  radiation  and  phytoplankton  photosyn-
     thesis.  Limnol. Oceanpgr.  24:1117.

Luckiesh,  M.   1946.     Applications   of  germicidal  erythermal  and  infrared
     energy.  Mew York:  van Nostrand.

         and Nachtwey,  D.S.  1975.   Natural resistance of freshwater  algae to
     UV  radiation  -  a  survey.    CIAP Monograph    5:5-75.    NTISPB247724.
     Resnick,  M.A. 1970.  Nature 226:377.

Horowitz,  H.J.   1950.     Absorption  effects   in   volume   irradiation   of
     microorganisms.   Science,  111-229.

Peake,  M.J., J.G. Peak, M.T.  Moekrins, and  R.B. Webb  1984.  Ultraviolet action
     spectra  for  DMA  dimer  induction  lethality,  and  mutagensis   in   E_._
     scheriachia  coli  with emphasis  on UV-B  region.   Photochem.  Photobiol.
     40:613-20.

         M.A.  1970.    Sunlight-induced  killing  of  Saccharomyces  cerevisiae.
     Nature 226:377.

Russell-Hunter, W.D.  Aquatic  Productivity.   New York:  Macmillan.

Setlow, R.B. 1974.   The wavelengths  in  sunlight effective in  producing skin
     cancer: a theoretical analysis.  Proc. Nat.  Acad. Sci. U.S. 71:3363.

Sn>ith,  R.C., K.S. Baker, 0. Holm-Hansen, and  R. Olson. 1980.   Photoinhibition
     of photosynthesis  in  natural waters.   Photochem.  Photobiol.  31:585.

Shettle,  E.P.,  and A.E.S.  Greene  1974.  Multiple  scattering calculation of  the
     middle ultraviolet reaching  the ground.   Applied  Optics.   13:1567-1581.
                                     235

-------
How Might Enhanced  Levels of Solar
UV-B  Radiation Affect  Marine Ecosystems?

John Kelly
Ecosystems Research Center
Cornell University
Khaca, New York USA
ABSTRACT

     One  of  the most challenging tasks facing  environmental scientists  is  to
determine  the  likely consequences of an external change for complex natural
e°osysterns on the basis of observations of the impact  on individual organisms
°r  processes.     Assessing  the  potential  impacts  of  enhanced  solar  UV-B
radiation on the marine environment presents such a  challenge.  The potential
UV-B stress  is  broad-scale; the  response of marine ecosystems  involves many
8Patial  and  temporal  scales,  and also  involves  subtle  changes that may  be
difficult  to detect.    A  particularly  acute  concern  exists,  however,  for
^sting  changes—changes made  possible  because  of  long residence  times  for
^ny oceanic processes, as well as the lack of mitigating measures given the
spatial extent of both stress and effects.   Thus, acknowledging the specula-
te nature of  extrapolations,  the  potential  problems  are  of  a  quality
Inquiring significant  a priori  examination.   In this paper,  I suggest several
types of ecological changes of  concern.   The  examples—including  possible
^ffects  on food  webs,  fisheries,  and biogeochemical  cycles—are chosen  to
lllustrate the scope and urgency of the problem.

^-B INCREASE AND MARINE ECOSYSTEMS:   WHY SHOULD WE BE  CONCERNED?

     Every type of  environmental alteration seems to  carry special  features
that make   assessment  and  resolution  of  potential  ecological  problems
difficult.   In  the  case  of  projected  stratospheric  ozone  depletion  and
increased  UV-B striking  the   earth's  surface,   the  spatial  scale  of  the
etlvironmental modification  is one such confounding feature.   The global nature
    the  problems  brings   associated   challenges:    the  task  of  observing
        i changes,  perhaps subtle,  across the vast expanse of the oceans; and
    problem of considering  effects upon the variety of  ecological systems from
    nearshore to  the deep  sea,  from  polar  to  tropical  regions.   For all  of
these ecosystems, but  particularly for much of  the deep sea surface  waters
     from land  and  ieaat  studied  in  situ,  documenting  changes  distinct from


                                   237

-------
 natural  variation may prove  especially frustrating because .little background
 historical  information  exists.   Yet, ecological changes keyed  to currents and
 movements  of  water masses  have  the  potential  to set  in motion  biologic3-1-
 and/or biogeochemical effects of uncertain magnitude that  endure for the time
 scales of oceanic  circulation—processes  with residence times  of centuries and
 longer.    Unfortunately,  also  associated with  the  spatial  aspect  is  fcne
 probable  lack  of .potential  for  mitigating  observed  effects.    Furthermore,
 mitigation  of the causes of  those effects,  even  if it were achieved quickly»
 would do little to alter the  lengthy recovery times of  any  circulation-related
 ecological  changes that have  been  already induced.
     A  valid concern is  that  significant changes  might occur in many
ecological  systems well before  we  know it; and we might be stuck  with
changes for  a  very long time.   This concern adds urgency to  the  assessment  01
the potential ecological problems.

     A  crucial  part of this  assessment concerns the  effect of  enhanced  U»"
upon marine  ecosystems.   Clear  and convincing evidence from research of fctl
past decade  indicates that UV-B  radiation can  injure the health of some mari'n
organisms.    In this  paper  I  focus  on  the  effects  upon  whole  ecologi0^
systems.    The  level   at  which  I  address  the  problem is  not  limited  c
mechanisms of physiological damage  to tissues  of individual organisms, or, \°
example,  on  possible   reductions  in   certain    sensitive  surface-dwell1^
populations.   Those are  major aspects of  the assessment problem,  but 1t
difficult   to   extrapolate  from   such  directed  effects   to   the  o
consequences  for  natural  ecosystems  which,  in  and  of  themselves,  are
concern to humans.  In the absence  of information on ecological effects at
ecosystem level, I speculate about  those ecological processes, components, a
systems  that  could  be  agents  for,  or  targets  of  UV-B  induced   ec°^°^i^Y\e
change.   The major contribution of this effort  is to  suggest  facets of &
problem  that  do  and  do  not  lend  themselves   to  direct  ecosystem-leV
assessments.

WHAT COMPONENTS AND PROCESSES ARE DIRECTLY AT  RISK?

     The level  of  UV-B  striking the sea varies seasonally and with  lafci   Of
The penetration of UV-B into seawater  varies with  turbidity,  concentration
dissolved organic  matter,  absorption by plants, and other factors.   In SP  n
of  temporal  and  spatial   variance  in  UV-B attenuation,  the global c°n?cai
relates to  ecological  impacts acting directly upon  biological  and cheBILce
activity only  in a relatively  shallow  (perhaps several meters  deep) su  jne
layer of  water.  Though  this represents  a very limited  portion  of the mar.ry
environment, it  includes  an important portion of  the zone  where the pr*® to
food base for  marine  ecosystems originates and where  many processes °cCUL,j.e
influence the  distribution of organisms,  energy,  and  matter  for  the  wn
ocean to its depths.

     There is convincing evidence that direct  effects  on certain near-su**  ^
organisms and processes in marine waters are  caused by  exposures to enha
levels of UV-B  radiation  (Calkins  1982; NRC  1984).  Biological  effects r» ^
from   cellular-level    damage   and   physiological   impairment   to  r~  cted
reproductive potential and  direct mortality.  Organisms that  can be affe ^
include the  two major  biological components of the sea--photoautotrophic  g>
heterotrophic  organisms,   or,   roughly  speaking,   both   plants   and  anil"


                                     238

-------
 Several particular effects  raise significant concerns  for  marine ecosystems.
 I focus on these to suggest potential consequences.

      Photoautotrophic species  of free-floating phyto-  and  bacterio-plankton,
 along with attached  algae and submerged  vascular  plants in the  very shallow
 coastal  areas  of the  sea,   are  the  "primary  producers"  of  the  aquatic
 realm—those   using  the  energy  of  incident  solar photosynthetically  active
 radiation  (PAR)  to  produce their  own organic  tissues.   These  autotrophic
 organisms, active  only  to  water depths  to which  sufficient  PAR  penetrates
 (known as the  "euphotic" surface layers  of the  ocean), are key  to the entire
 marine food web.  Two kinds of noted effects on autotrophic organisms are of
 special  interest.    Experimental  evidence  suggests  that  rates  of  primary
 production of carbon  into  organic matter (both by some species  of floating and
 attached  bottom-dwelling   plants)   are  significantly  reduced  when  natural
 autotrophs are exposed  to slightly increased UV-B doses (see Worrest  1982);
 such a  mechanism  is  responsible  for  "photoinhibition" of  primary  production
 seen  at  high  light  intensities  at  the  very   top  of   a  water  column.
 Furthermore,   evidence   from  laboratory  aquarium   "microcosm"  studies  also
 suggests  that  certain  species  of  phytoplankton  are  more susceptible  than
 others,  so that when a  mix of species  is exposed  to increased UV-B  doses,  a
 different  plankton  community  can develop  in  comparison  to  normal  control
 levels of UV-B (Worrest  1982).

      Heterotrophic species,  ranging  from  microscopic  forms  to  the  great
 whales,  depend for their energy and nutrition upon  organic tissues synthesized
 by autotrophic forms.   Evidence  shows  that  some of the  smaller  heterotrophs
 may be at risk,  especially those  not  afforded UV-B  protection by  pigmentation.
'Although the  animals normally living in  the  upper  layers of  the sea  seem
 generally more resistant  to UV-B damage  than those  living at lower  depths,
 effects  on  surface-dwelling  forms   of  zooplankton   (including   copepods,
 euphausids, and planktonic  larvae of shrimp and  crabs.) have been shown  to
 occur with  increased UV-B.    These  effects  include  increased  mortality  of
 adults,  decreased  survival of early larval stages, and  decreased  fecundity  of
 survivors (reviewed  by MRC  1984).   Additionally,  fish eggs that  float  at the
 sea surface and  larval life  stages of some fish  (e.g.,  anchovy) show cytogenic
 abnormalities  and  reduced  survival caused  by UV-B radiation.

     Value of Direct Effects

      Direct biological  effects from  UV-B  exposures, observed for  individuals
 °r  even  calculated   by  extension  to   conditions  encountered  by   natural
 Populations,  are  considered in  at  least partial  isolation  from  the  other
 ecosystem components  and  processes.   These controlled  experiments,  conducted
 without the many complicating variables  inherent  to the natural situation,  are
 Designed to be simple tests to determine  if UV-B radiation  enhancement  of the
 magnitude presently  envisioned through  past  and  future decades is  sufficient
 to cause biological damage to individuals of certain species.  These  findings
 have created  legitimate  and significant concern regarding possible  changes  to
 "narine ecosystems.  We know for certain that some  individual marine organisms
 and processes which  we  care about are  at risk  from  increasing  UV-B  levels.
 Thus,  the value of the scientific demonstration of  directly  caused UV-B  damage
 is unquestioned.   However, a next step in  the assessment—extension  of results
 to the complex natural environment—is difficult and tenuous.
                                      239

-------
ECOLOGICAL EFFECTS IN NATURAL ECOSYSTEMS

     Ecosystem  modification  of direct  effects  can  arise  from  biological*
physical, and chemical mechanisms that are features of natural ecosystems, but
are not  features contained  in  direct effects  tests.   In  nature, "indirect1
effects can be transmitted  via  ecological  linkages to components or processes
themselves not directly  sensitive  to UV-B.  UV-B  increases itself could also
cause  environmental  modifications   and   indirect  effects.     For  example*
increased photolysis of some dissolved organic or inorganic chemical compounds
in surface seawaters might  occur (e.g.,  Zepp 1982); some modifications of tne
aqueous  chemical   environment   can  indirectly   cause   biological  changes.
Although we  are conscious  of  these  features  of  ecosystems,  we  so  far have
gathered data relating to  effects  only on select  parts  of marine ecosystems;
it is uncertain  that  any of the effects  carry,  unqualified or unmodified, fco
nature (Figure 1).

     The possibilities for  indirect  effects, embedded within a perspective on
the potential ecosystem  responses  to UV-B stress, are  indicated  in  a simple
diagram relating biological effects and ecological changes (Figure 1).  Stress
agents can act  initially upon  individual  organisms directly  or  by modifyin»
the  environment.    Such   individuals   can  then   affect  other  individuals
(populations and communities)  by many biotic mechanisms including predation,
competition for  resources,  and  altered  reproductive  success.   Additionally*
however, an affected  individual (or more usually  a group of individuals) can
create a change in ecosystem processes (e.g., the  rate of primary production*
rates of oxidation  of organic matter, patterns  or timing of the biogeochemica^
cycling  of elements).   These  processes  are  depicted  (Figure  1) as  at
interface between organisms and their environment.   Almost invariably,
in processes modify the chemical broth in which organisms bathe; sometimes &"°
physical environment is also altered.  For example, a change in the balance o
organic  production,   consumption,   and   decomposition processes   changes  tn
concentration  of  plant  biomass,   which  in  turn  changes  solar  radiati°
extinction  coefficients  and  the   light   energies  available  throughout  tn
underlying water column.

     In general,  affected individuals in  ecosystems can spawn indirect effec .
by these paths—biological  interactions and alteration of process rates.
effect upon  individual  organisms  can beget  others,  creating change  in
biological structure (e.g., changes  in  populations,  species interactions,   .
food webs) and processes (e.g., biological rates, biogeochemical interaction
in the  ecosystem.   Sometimes  changes  will be very unexpected  or  far r
from the  original  impact  in  time or  space (e.g., Levin  et al.  1981)•    Q
extrapolations need  to  deal with even  more than the  issue  of  enhancement
direct  effects.   At  the other  horn of our  extrapolation dilemmas  sits
possibility that the same two  general paths for  indirect effects will
compensating  mechanisms,   ameliorating   direct  effects   so  that     rjv
discernible    change   happens  even  where   some  individuals  are  clea
injured.  For compensation, biotic and chemical mechanisms exist, but phY3*  
-------
                                            EnfaiBcnnut of UV-B Ridiiuon
        Enhancement of UV-B Radiation
                                                              •Coamnitr'
                                                         L_ _ _  — — — —I
       Modification of
       physical and
       chemical environment
Individual
Organisms
                                                   Population(s)
                                                   Changes
                                           'Community
                                           'Ecosystem'
     Figure  1.   Potential  ecological effects  of  enhanced  UV-B  in marine
Ecosystems  are shown above.   The  diagram shows direct and indirect  pathways
"or  producing   changes   in   individuals,   populations,   communities,    and
ecosystems.    The shadow  insert  suggests  the  current state  of  information
Existing  for UV-B effects on different pathways and at different  levels in  the
       environment.

-------
     I next illustrate compensatory changes and  indirect  ecosystem  effects  f°r
two cases where extrapolation of effects  is important. These are  effects  that,
if   verified,   should   arouse   human   concerns   for   regional  or  global
repercussions.  The examples involve:

     •  Reduction in rates of photosynthetic production of  the organic  tissues
        forming the primary resource for  marine  food chains

     •  Reduction of  surface-dwelling stages  of fish larvae  and their  adult
        population stocks.

     I  do  not comprehensively  consider all  aspects  of  the   extrapolatio
problem; only certain classes are given.  I simply wish to  illustrate a number
of  existing uncertainties  before  I  suggest  the potential  consequences  f°
marine ecosystems should such reductions  occur.

ECOSYSTEM COMPENSATION AND A KEY PROCESS

     The  first   scenario  considers   the   possible  reduction   in   priwa t
production.   The level of primary production influences many aspects of marin
ecology and biogeochemistry.   These extended effects  form  the major f°cus.°n
my speculated consequences for the oceans.  First, I examine the  extrapolati
problem.   Assume  (following  Smith  and Baker  1982) that with enhanced
productivity reduces  up  to HQ% at  the surface, decreasing to a  0%
within 2 attentuation lengths  (a  value roughly on the order of 1 to 10 m,
dependent upon the optical characteristics of the water (Smith and Baker  19/ "'
1982;  Smith et  al.  1980).    The  question  of concern  is  not,  "Does,, Jut
inhibition  of primary  production  occur in  the  very  surface  waters?"
rather, "Does it change the productivity  of the whole water column?"
     One way to suggest  the  net  quantitative change in an entire water
is  to make  calculations via  mathematical  models.    Smith  and  Baker
examined  the  potential  magnitude  of photosynthesis  reduction for  the wh° ,
euphotic zone  using a simple,  depth- integrated model  without the "nonlinea^r
(including indirect effects) or compensating mechanisms of  Figure  1.   .  ry
calculations predicted that  with a 25% reduction  in  ozone thickness, Prim ,
production would  decline 9%, regardless  of  the absolute  productivity lev
(Note:  the relation  between ozone and  total productivity in the model
quite linear,  as a 5% primary production decrease would occur with a  16$
reduction.)  Smith and Baker (1982)  strongly emphasize limitations  to  n
model, focusing on  some  possible nonlinear relationships relating to s$  ,c&\
quality of the solar radiation and concomitant changes in effective biolPS  ^
doses to marine organisms.  They express concern that several indirect ef fe.&s
not considered by  the model  might  easily  add order of magnitude uncertain
to predictions.   Complicating  features of the natural  ecosystem include
less sensitive  to  enhanced UV-B  (e.g.,  in Figure 1 — reduction  in  numbers
individuals  leading   to  increases  in   individuals   of  another  sped
Additionally,  they  suggest  complications  due  to  the   influence  of  v  Qf
movement  upon  the  depth  of  the  surface mixed  layer.   Vertical  mixin» ^
organisms makes  it  difficult  to estimate biologically  effective doses a"heir
organism's  exposure  regime  for  PAR  or  UV-B  with  precision.  Yet    ,ty
considerations, although perhaps quite comprehensive in relating product!*
                                      242

-------
and solar energies, do not include other facts that may be limiting to primary
production.

     One can  envision yet another wrinkle,  which I believe stands  as a good
example of potential ecosystem compensation.  Plants need nutrients for growth
as well  as light  energy; the  availability of nutrients  in the  photic zone
limits  production,  although  in  some  marine  areas,   particularly  the  high
latitudes, light may be more limiting  through portions of  the  year.   Except
for heavily enriched  coastal areas of the  oceans  and intense upwelling areas,
the level  of  marine  autotrophic  production  is  partially,  if not primarily,
sustained  by   heterotrophic  regeneration   of dissolved  nutrients  (such  as
nitrogen and  phosphorus)  within the ecosystem  (e.g.,  Kelly and Levin 1986).
Thus,   there  exists  an internal  ecosystem  factor  influencing  production  to
complicate the solar radiation/photosynthesis relationship.   But if production
is reduced within an upper portion of the water column, we cannot suggest with
assurance that  internal supplies of nutrients used  to support  a production
level   would  not now  be available below the new  "photoinhibited" zone.   To
accomplish  this  compensation,  mixing   or  simple  diffusion  of  the  unused
nutrients only  several downward  vertical   meters  needs to  occur;  there  are
phytoplankton  species that live  much deeper than this in the water column,  are
adapted  to  lower  light  intensities, and  whose growth  would  be  enhanced  by
greater nutrients.   Thus, within the range of the results  for  enhanced UV-B
and productivity lies the possibility that no net  change in the overall water
column rate of primary production  will occur.

     Note that  this  scenario  easily  has room  for  some  ecological  change
outside  of  an  impact on  the process of  immediate  concern.   The ecological
change from deeper  UV-B photoinhibition  could involve a slight  deepening,  or
expansion, of the "neuston" community of organisms  that  dwells  at the sea-air
interface and  is more  adapted  to  high light  intensities.   Underneath  this
"expanded neuston  layer"   there could  also  be  some  changes  in  the mix  of
species responsible  for the process of  primary  production."  Species  changes
don't  necessarily alter the overall  level of primary production,  which is more
likely set  by  the  supply of available nutrients.   The main  point  of  this
example,  however,  is that the  magnitude of euphotic zone  primary production
fates, even  with  surface  inhibition  and changes  in autotrophic  community
composition,  need not be altered as  a whole.

PHYSICAL FEATURES,  INDIRECT EFFECTS,  AND COMPENSATION:   A POPULATION EXAMPLE

     The first simple extrapolation  problem added a  compensation mechanism to
uncertainties  associated  with modeling  photosynthetic reductions.   My second
example  adds  another  level  of complexity  and  examines an individual  fish
species.    Direct  effects  on   young fish  could  be  a  serious  problem  with
enhanced UV-B because much of the world's  commercially  important fish  species
(e.g.,  tunas,   mackerels,   flatfishes,   pilchards,  anchovies,  cods)  produce
"pelagic" (living  in the  water column   as opposed to  dwelling  on  the  ocean
floor) eggs and larvae; both of  these life  stages  are translucent and allow UV
Penetration deep into tissues.   Consequently,  "most pelagic eggs and larval
stages of  fishes  studied   to  date show   high  sensitivity to UV  radiation  and
often  die if exposed in shallow  containers  to solar UV" (Hunter  et al.  1982).

     Aspects of the extrapolation problem  for larval populations  of northern
anchovy have been discussed rather thoroughly by Hunter et al.  (1982).   In  the


                                     243

-------
 anchovy case, known direct effects  include:   lesions in eyes, brain, or other
 body tissues; increased mortality; and reduced growth in surviving larvae.  To
 illustrate the potential concern for the anchovy larval population as a whole,
 by making simplifying assumptions of a  stable vertical  distribution of larvae
 and no vertical mixing  of eggs and larvae and using short-term exposures (12
 days)   for  mortality  effects,  Hunter  et al.  (1982)  calculated that  annual
 production of larvae  lost to  UV-B  mortality might  rise  by a factor  of 1.38
 with a 25% reduction in ozone thickness.

     Relative to  the  previous primary  production  example, there are  similar
 uncertainties with vertical mixing  for  small animal forms; however, more can
 be made of the  issue  of whether there  is actual damage to individuals in the
 field   because  the  larval  organisms  have  more  ability  to  move  away  fro™
 damaging  exposures than  do most phytoplankton.  Yet in direct  analogy with the
 key process case, a similar  central question  remains—does individual damage
 mean that the numbers  or biomass of  the  adult population will  change?

     Three  relevant aspects of the ecosystem  that  contribute  to  extrapolation
 uncertainties illustrate  different  classes  of  concerns:   physical  oceano-
 graphic features to moderate effects upon individuals, a  biological  mechanism
 to  compensate  for  loss  of  individual  eggs  and   larvae to  maintain  adult
 population   levels,   and   indirect   food   chain   effects that  might   add
 synergistically  to enhance  direct  effects.

     Ocean  surface waters  are  not  static  vertical  strata and  mixing  occurs
 that complicates  projections  of  the  overall  exposure  regime for organisms-
 Implications  of   this  feature,  in  terms  of effects,  have  been   noted by
 Kullenberg  (1982), and by Smith and  Baker (1982)  for photoinhibition, and were
 considered  by Hunter et al.  (1982)  in  their  analysis of  enhanced UV-B  conse-
 quences for the  northern anchovy.   Because mixing  intensities occur across a
 broad range in the ocean and are locally variable,  calculations using exposure
 regimes   and   dose-effect  relationships  from  direct  effects  tests   have
 considerable uncertainty.   Hunter  et al. (1982) also add  the uncertainties of
 the  vertical  distribution  of  the larvae,  seasonality  of larval production,
 seasonality of incident UV-B, and variations  in UV-B  penetration caused  by t°e
 concentration of plants  with which larvae associate for food.  They conclude
 that vertical mixing alone could reduce  estimated UV  (direct) effects to  zero,
 and  that  the  variables of mixing and vertical distribution could account f°r
 the  full range of possible UV effects,  independently  of other variables.

     Even  if  physical  and distributional (habitat)  variables  were well  known
 in some specific case,  there  are  other  problems.   Biological compensation f°r
 early life  stage effects could occur so that effects do not alter year  clas3
 success of the  adult  population.   Density-dependent mechanisms,  including
 changes in  survivorship  at different life  stages or  changes  in reproductive
 capacity,  might ameliorate effects seen  in an individual larva.   For exampie»
 there could be increased survivorship in unexposed individuals.  Additionally*
UV-B mortality might be,  although higher,  still  relatively small  compared *°
other sources of natural mortality.   Over some time, greater  fecundity  (m0^
viable eggs per  adult  female) could  also develop,  compensating  for  a certai"
percentage  of  young lost  to  UV-B.  A   further  compensation could be  that •
lesser number of surviving  individuals might  grow bigger faster  because
 is less competition for a food resource.   These, simple examples of known

-------
density-dependent  mechanisms  could therefore act to maintain adult  numbers  or
biomass within normal bounds of natural variation.

     Compensatory  changes  might  well  negate  egg  or  larval  effects,  yet
interactions  with  primary  production  might act,  synergistically,  to  enhance
the  population  decline.    Besides  direct  UV-B related  mortality  of young
developing   stages  of   fish,   there   could   be   indirect  mortality   from
starvation.    This  could  occur  if  primary   production   decreased   or  the
autotrophic species producing the  preferred  food of  a given  fish  were replaced
by  indirect  ecological changes  (Figure 1).   Perhaps there would even be  an
amplified mortality in that some  larvae die from direct exposure, others  from
lack of  food,  and  still others from  the  combination of reduction in food and
weakening from  exposure  (by being less able to .compete with other organisms
for  limited  food  resources).   One  can  thus  foresee  the  possibility  of a
catastrophic drop  in a fish population, even if  the  direct mortality from  UV-B
alone would not convey that sense  of concern.

     These  simple examples   illustrate   that   the  problem  of   projecting
biological  effects  to marine  ecosystems  is   itself  at a young  stage  of
development; this  task represents  a significant scientific challenge.   What  is
not  yet  known  about ecosystem   changes  adds  up  to  such a  potpourri  of
uncertainty that there are  cases where  we can't confidently  predict whether a
particular component or a process will increase, decrease, or remain the same.

POTENTIAL CONSEQUENCES FOLLOWING EFFECTS

     Having given  due  emphasis  to the tenuous nature  of extrapolations, I am
not the least bit hesitant to suggest that significant ecosystem changes could
ensue.   Ecological repercussions  could arise  especially from  the  following
effects, if they are expressed:

     •  Reduction of certain individual species critical to the maintenance of
        structure or function in the ecological system

     •  Change in the  mixture of species of primary producers

     •  Reduced rates  of primary production of organic matter.

     Some aspects  of  these  have  been  mentioned.   I'll touch  briefly,  with
examples, upon potential  consequences in these three areas.

Mortality or Impairment of Certain Populations

     In general, mortality  or impairment  of certain populations  can lead to
significant changes in  biological structure.   For  such "key"  or "critical"
species,  which can include  phytoplankton, zooplankton, and  fish,  some  chains
of  effects  are  well   documented.    Removal  of a  key  predator  changes  the
distribution and   abundance  of more  than just  prey organisms,  leading  to
species  diversity  changes  and  changes in  community  dynamics  (e.g.,  Paine
1966).    The  structure  of  an entire  pelagic food  web can  be  altered,  for
example,  by  changes  in fish  feeding pressure.   Feeding pressure can  reduce
some zooplankton species,  allowing greater growth in other zooplankton; these
changes in the zooplankton community then contribute, indirectly, to  alter the
type of algal assemblage present.


                                     245

-------
      Cascading from  effects on key  species,  there can  even be alteration of
 the  physical  environment.   Levin et  al.  (1984)  relate an  example  in which
 removal of sea otters along the U.S. Pacific coast increased animal grazing on
 large attached brown algae  (kelp)  and  eventually reduced the kelp beds, whose
 absence  exposed  the  shoreline  to  greater  physical  disruption  from waves.
 Other nearshore  areas,  such as the  Gulf and Atlantic  coasts,  are exposed to
 less wave action than the west  coast.   Yet even in these less severe physical
 environments,  reductions in growth of some attached plants, either directly by
 UV-repressed photosynthesis or indirectly by a sequence of interactions within
 the heterotrophic  community,  would  alter  physical aspects  of  the ecosystem.
 Removal  of  the  physical  habitat  structure   lent   to  shallow  waters  by
 seagrasses,  for example, would  likely  modify wave and  current  energies along
 shorelines,  which  would change  spatial patterns  in  sediment  deposition  and
 water clarity.   Such physical consequences  would be significant;  they would
 involve alteration of  two primary  environmental features that  influence  the
 distribution of marine  organisms and food webs.

      Whether or not those heterotrophic species  of larval fish,  crab or shrimp
 larvae,  or  zooplankton  that are  known to be directly  sensitive and  at  risk
 from UV-B  (e.g.,  Damkaer et  al.   1980;  Damkaer and Dey 1982;   Worrest 1982;
 Hunter  et al.  1982) are critical species remains to be  demonstrated.   But the
 primary producers throughout marine  ecosystems   certainly are key components,
 for they set the  table  for  the  rest of  the  ecosystem.

 Changes  in the  Species Composition  of Primary  Producers

      Changes in  the  species composition  of primary producers   can  influence
 both food webs and ecosystem  processes.   Worrest et  al. (198!a,  198lb)  show
 that shifts in community composition  are possible  with UV-B.   Worrest  (in
 Harwell  and  Hutchinson  1985)  suggests  that  compositional change would alter
 size distribution  of  primary  autochthonous  particles  and  directly  change
 nutritional  quality,  an  effect  already  noted  with   enhanced  UV-B  (i.e.*
 depressed   protein   content,   dry   weight,  and  pigment  concentration  °f
 autotrophs).    Changing  sizes  of  food  particles might alter  the  energy
 allotment  required  for consumption,  perhaps  reducing  feeding efficiencies i°
 consumer  species,  even if wholesale  heterotrophic community  changes were not
 instituted.  Energy efficiency  change in either   individual species or  in f°°d
 webs (by simplification  or  diversification of the species interactions) could
 change   ecosystems;   changes   in  particle  size  distributions  or   in bulK
 nutritional  quality could  translate to  a different level of food  energy being
 available  to top  consumers of a food web.   Such changes might  be of  special
 concern  when considering,  for  example, what nutrition or  size alterations
 might do to  the  pelagic  food  chain  in the  Antarctic   that  seems  to  center
 around the transfer of phytoplankton biomass to only one  next major component!
 the  krill  (e.g.,  Everson  1984).   Effects upon such a  critical  linkage, at a
 latitude where light levels are indeed  important  to production and where ozone
 depletions have been  noted, would have  major   implications  for  the  direct
 consumers  of  kr ill—whales,  seals,  birds,   fish,  squid,   and   even   bottom
 dwelling organisms.

     Particle size alteration and  nutritional  change  with species compositio"
 could   affect   other   ecological    features,    particularly   biogeochemica*
processes.   For example, settling  rates of primary particles vary with s&.
and  shape. Because primary particles  have many chemical elements incorporate
                                     246

-------
within  their    hard parts  and  soft  tissues,  as  well  as adsorbed  to their
surfaces, removal rates of elements and compounds from the surface ocean-mixed
layer by settling, an  important  marine  geochemical  process,  could be altered.
But  biogeochemical  linkages  are  perhaps more likely  to be  affected  in a
significant  manner  if  the  magnitude,   rather  than  quality,  of  primary
Production changed with UV-B enhancement.

Reduced Rates of Primary Production

     I see reduced rates of primary production as potentially driving a number
°f  important  ecosystem  changes,  notable individually  and  collectively  for
their  possible   broadscale  nature.    One  of  these  involves  biogeochemical
Processes,  which, as noted  in Figure 1, are a  major  feature  at the ecosystem
level.  The other relates to potential fish yields from the sea.

     Of interest are those changes associated with  element cycles and organic
"Batter  distribution  throughout  'the  ocean  which  key  to   the  production,
transport,  and  decomposition  of  primary  produced organic matter.    That  the
°ycling of many  elements in  the oceans is very tightly  coupled to biological
Activity, especially primary production, has been recognized for much of this
century.   For example,   oxidation of the primary production of the euphotic
2°ne, although a process most active  closer  to  the  surface,  occurs throughout
^eptn.  This decomposition of organic matter  is,  in part,  responsible for the
Vertical  and horizontal distribution  of some dissolved gases,  including oxygen
and carbon dioxide, and  dissolved inorganic  plant  nutrients of  nitrogen  and
Phosphorus,  as well  as  other  biologically active elements throughout the ocean
Je-g., Riley  1951;  Wyrtki  1962;  Redfield  1934,  1958; Redfield  et  al.  1963).
Additionally,  from  a  summary  by Suess  (1980), we  can  also  see that  the
transport of the organic carbon  to any depth in the  ocean can  be represented
*n a simple  general  relationship, normalized  to  the  level of production.   With
lowering  of  primary production,  Seuss  and  others  suggest  that the  organic
j^Pbon reaching  any depth  in the  ocean will decrease,  leaving less  food  for
the secondary production of the  heterotrophic  organisms dependent upon  that
°a**bon supply.    We don't  know  if   the  magnitude  of  a change  in  primary
  eduction with  UV-B would  cause changes we could easily  observe in  sedimenta-
   n processes,  or whether it would  cause geochemical changes  we would  point
    as  "of  immediate  environmental  concern."   However,  because  the  major
        biogeochemical cycles are tied to  surface  biological  activity,  but
     relate to  the  depths and  circulation  of  the  oceans, important  changes
      be  felt  across many temporal and spatial scales.

     One  should  not  consider marine consequences without  discussing  fisheries,
      is  perhaps the most common  "endpoint" of  human  concern.   I  have already
          some  problems  with fisheries,  but how  would  direct reduction  in
       production translate to  reductions  in fisheries yield?   In  the absence
   information,  we can make the  simple  linear extrapolation, suggesting  that
    percentage reduction in fish  biomass  yield  would  be the same as  that  for
       production;  however,  at  least one summary suggests that  this  relation
   nonlinear.

     Nixon  and Pilson  (1984)  presented a  compilation of. data  for  fisheries
      and primary production of  some  marine  systems.   Although such  data  are
f{?en>selves  subject to great errors and uncertainty (e.g., how do we  account
  p heterogeneities  in production?   How  does  one  choose  the  size of  the


                                     247

-------
system?  How  good  or comparable are yield data?) and  the  scatter  is  such that
predictions   for   yield   at   an  individual  level  of  production   would  be
inadvisable,  a rough  general  correlative relationship  is evident  from  the
summary.   Examination  of the broad  pattern  in the figure by Nixon and  Pilson
reveals  a  nonlinear relationship,  with less  fish yield  per  unit of primary
production (as grams of carbon) seen at lower  primary  production levels.   Fr0in
those data, for example,  it would appear that  about  1000 kg  fish per  ha  per yr
may accompany  primary  production  of about 1000 gC per m   per yr whereas there
may be  only  5-7 kg fish  per  ha per yr associated with  100 gC per m per  yr<
The explanation for such a pattern is  unknown.   Perhaps with lower primary
production,  other  fish,  not  commercially  sought,  are  produced.    Maybe -the
efficiency of energy yield to higher  trophic  levels changes across  different
ocean areas and with different production levels.  In  either event, due  to  the,
scatter observed in  the range of average  ocean and coastal production  lever'
(i.e.,  100  to 500  gC  per  m2 per  yr)  and   fisheries  yields,  I  would &®
uncomfortable  in suggesting a mechanism or in  suggesting how much greater  tn
percent  of  fishery  production  would  be than  the percent of  reduction
primary production.

     If we use  the relationship the ramifications are that with reductions J-
production from UV-B we  should  worry about (a) the fisheries yield decreasing
everywhere, and (b)  a  reduction in  primary production resulting in  a great
than proportional  reduction in fisheries yield.

ASSESSING ECOSYSTEM CHANGES:  PROSPECTS AND LIMITATIONS

     I hope my examples spark some argument, discussion, and research' on  the
and other  issues.    We are uncertain  how the convincing  evidence for  dirtQr
effects  on  important  species  and  processes   (effects  having  potential  *
producing large-scale  ecological  consequences) might actually be expressed
the oceans.   Not  only the magnitude, but  even the very  nature of  ecosys
effects is unclear.  Given this situation,  I  think we are left with  two  b*sce
questions:   What  tools do we have  and what approaches must we use  to  re d
the  uncertainties  as  quickly  as  possible?    Are  there  aspects of.
uncertainty that we are not likely to resolve before the changes occur?
                                                                            *.«!
     To  address ecosystem  changes, the  best  tool  we  have  is experiwen
manipulation  of ecosystems themselves.    Although this  is not  possible
marine  ecosystems  (other than  the global  experiment  itself),  we do JV ^
physical models of some ecosystems, called microcosms or  mesocosms,  in  J!  eve
we can  look  directly  at  some ecosystem-level  effects (e.g.,  Grice  and  B
1982; Kuipers  1984).   For example,  perturbation  studies  on simulated s
coastal  ecosystems  have  been   conducted  at   one   such   facility,   the
mesocosms, at the  University of Rhode  Island along  Narragansett  Bay  in
U.S.  (e.g.,  Nixon et  al.  1984;  Kelly  et al.  1985).  Such  research,   U
complex ecosystems,  is urgently needed  for  assessing UV-B  effects.   Ifc
give us a better sense for the  possibility and extent of  indirect effect3
compensating mechanisms in a most efficient manner.
     We could use  such  ecosystem experiments to identify sensitive
and processes of  natural ecosystems.  This  emphasis could give us indie*
for  monitoring  and  assist  in  mapping  effects  in  nature  related  fccL,C)w'1
penetration  of  UV-B  in  different  marine   waters.   Correlation   of   for
sensitive features  with UV-B penetration changes  is valuable informatio
                                      248

-------
scientific assessment of environmental  risk, although unequivocal data  of  this
nature are difficult to gather.

     Of  equal importance  to identifying  sensitive components  or processes.
however,  is  identifying  critical or sensitive  ecosystems.   I believe  we  need
to  direct some attention to  this  problem; so far we have  only  looked at  the
generic  level assessed.   The last decades, especially  with increased use of
remote   sensing   for   oceans,  have  given  us   an  increased  awareness  of
heterogeneity  in  oceans.   With this comes an  appreciation for the variety of
physical  habitats and  their  interactions  across a variety  of time and space
scales inherent to  the sea.   The UV-B concerns apply across these scales, and
it would be efficient and wise to identify and focus intensively upon at least
three  classes of  marine  ecosystems:   the  sensitive  ones, those  having the
least  capacity for  quick  recovery,  and  those of greatest direct  value to
humans.

     I  must  end   on  a  note  of  pessimism by   returning  to  issues  in  the
introduction.    Although,   for  example,  mesocosm  experiments are  essential
features to the environmental assessment of UV-B, the  principal limitation of
such research centers  on the issue of scale.   Some components  of ecosystems
cannot be included  in  experiments because the  spatial  scale of the enclosure
is not large  enough;  this is particularly  the  case with the larger consumers
that often  cause  us the most concern.   Many  processes,  especially microbial
aspects and primary production processes, can be examined directly in mesocosm
experiments in the proper ecosystem context.   However,  large-scale processes
associated with  physical  features  or  global biogeochemical  cycles obviously
cannot, be  accommodated.    I  remain  concerned  that  we  will be  unable  to
scientifically assess in the near term,  to suitable levels of confidence, some
major aspects  of  potential oceanic effects—especially  large-scale,  sporadic
features, or those happening in the clear waters of the deep sea where we have
the poorest background  information available for comparison to know if effects
are occurring.

ACKNOWLEDGMENTS

     This publication  is  ERC-127  of  the  Ecosystems  Research Center  (ERC),
Cornell  University,  and  was  supported  by  the  U.S. Environmental  Protection
Agency Cooperative Agreement Number CR812685.


REFERENCES

Calkins,  J.,  ed.  1982.   The role  of solar ultraviolet  radiation in  marine
     ecosystems.   New York:  Plenum Press.

Damkaer,  D.M., and  D.B.  Dey. 1982.   Short-term exposures of  some  planktonic
     Crustacea exposed  to  enhanced UV-B  radiation.    In The  role of solar
     ultraviolet  radiation  in marine  ecosystems, ed.  J. Calkins, 417-27.  New
     York:  Plenum Press.

Damkaer,  D.M., D.B.  Dey, G.A.  Heron,  and  E.F.  Prentice.  1980.   Effects  of
     UV-B radiation on  near-surface  zooplankton of Puget  Sound.   Oecologia
     (Berl.)  44:149-58.
                                     249

-------
 Everson,  I.  1984.   Marine interactions.  In Antarctic  Ecology,  ed.  R.M.  Laws,
      783-820.   Academic  Press.
Grice,  G.D.,  and  M.R.  Reeve, eds.  1982.   Marine  mesocosms;
      chemical research  in experimental  ecosystems.   New  York:  Springer.

Harwell, M.A.,  and T.C. Hutchinson, eds. 1985.  Environmental consequenceg_o£
      nuclear war  volume II:  Ecological and  agricultural effects.  SCOPE 28.
      Chichester: John Wiley & Sons  Ltd.

Hunter,  J.R.,  S.E.  Kaupp,  and J.H.  Taylor.  1982.    Assessment  of effects of
      UV  radiation  on marine  fish  larvae.   In The  role  of solar radiation_-JS
      marine ecosystems, ed. J. Calkins, 459-97.  New York:  Plenum Press.

Kelly,  J.R.,  and S.A.  Levin.  1986.  A  comparison  of aquatic and terrestrial
      nutrient  cycling  and  production processes  in  natural  ecosystems, with
      reference  to  ecological  concepts  of relevance to some  waste disposal
      issues.   In The role  of the  oceans  as  a waste disposal option,  ed. G.
      Kullenberg, 165-203.  Dordrecht:  D. Reidel Publishing Co.

Kelly,   J.R.,    V.M.    Berounsky,   S.W.   Nixon,  -and  C.A.   Oviatt.   1985-
      Benethic-pelagic   coupling   across   an   experimental   eutrophication
      gradient.  Marc. Ecol. Prog. Ser. 26:207-219.

Kullenberg, G.  1982.   Note  on  the  role  of  vertical mixing  in  relation
      effects of UV  radiation  on  the marine environment.   In The role of
      ultraviolet radiation  in marine  ecosystems,  ed. J.  Calkins, 283-92.
      York:  Plenum Press.

Kuiper,  J.  1984.    Marine  ecotoxicological  tests:   Multispecies and  model
      ecosystem  experiments.    In   Ecotoxicological  testing   for  the  roariSS
      environment  Volume  1,  eds.  G.  Persoone,  E.  Jaspers,  and  C.  ClauS»
      527-88.  Bredene,  Belgium:   State University  of Ghent  and Institute f°r
      Marine Scientific Research.

Levin, S., S.  Kimball, K. Kimball,  and W. McDowell.  1984.  New perspectives i°
      ecotoxicology.  Environ. Manage. 8(5) :375-442.
National  Research Council  (NRC).  1984.    Causes  and  effects  of
     stratospheric ozone:  Update 1983.  Washington, D.C.:  National Academy-

Nixon,  S.W.,  and  M.E.Q. Pilson.  1984.   Nitrogen  in  estuarine and  coastal
     marine ecosystems.   In  Nitrogen  in  the Marine  Environment,   eds.  E>J*
     Carpenter and D.G. Capone, 656-648.  New York:  Academic Press.

Nixon,  S.W.,   M.E.Q.   Pilson,   C.A.   Oviatt,  P.   Donaghay,  B.  Sullivan,  S'&
     Seitzinger,  D,  Rudniek,  and J.  Frithsen.   1984.    Eutrophication  of
     coastal   marine   ecosystem — an   experimental  study   using   the   "6
     microcosms.   In  Flows  of  energy and  material  in  marine  ecosystems.' e
     M.J.R. Fasham, 105-135. London:  Plenum Press.

Paine,  R.T.  1966.   Food  web  complexity  and species  diversity.
     100:65-76.
                                      250

-------
Redfield,  A.C.  1934.   On  the  proportions  of organic  derivatives  in the
     seawater  and  their relation  to the  composition of plankton.   In  James
     Johnstone   Memorial   Volume,   ed.   R.J.   Daniel,   176-92.    Liverpool:
     University  Press.

Redfield,  A.C.    1958.   The biological  control of  chemical  factors  in the
     environment.  Amer. Sci. 46(3):  205-221.

Redfield,  A.C.,  B.H.  Ketchum,   and  F.A.  Richards.   1963.   The  influence of
     organisms  on   the  composition  of  seawater.    In  The  sea;    Ideas and
     observations  on progress  in  the study  of the  seas,  Vol. 2..  ed.  M.N.
     Hill, 26-27.  New York: Interscience.

Riley,  G.A.   1951.    Oxygen,  phosphate,  and nitrate  in the  Atlantic  Ocean.
     Bull. Bing. Oceanogr.  Coll. 13:1-128.

Smith,  R.C.,  and  K.S.  Baker.    1979.    Penetration  of  UV-B  and biologically
     effective dose rates in natural waters.  Photochem. Photobiol. 29:311-23.

Smith,  R.C.,  and K.S. Baker. 1982.   Assessment of the  influence  of enhanced
     UV-B on  marine primary productivity.   In The role of solar ultraviolet
     radiation in marine ecosystems,  ed. J. Calkins,  509-37.  New York:  Plenum
     Press.

Smith, R.C., K.S. Baker, 0. Holm-Hansen, and R. Olsen.   1980.  Photoinhibition
     of photosynthesis in natural waters.  Photochem.  Photobiol. 31:585-92.

Suess,  E.   1980.    Particulate   organic  carbon  flux   in the  oceans—surface
     productivity and oxygen utilization.  Nature 288:260-63.

Worrest,  R.C.  1982.    Review  of  literature  concerning the  impact  of  UV-B
     radiation upon marine  organisms.     In  The  role  of  'solar  ultraviolet
     radiation in marine ecosystems,  ed. J. Calkins,  429-57. New York:  Plenum
     Press.

Worrest, R.C., B.E. Thomson, and H. Van Dyke. 198la.   Impact of UV-B radiation
     upon estuarine microcosms.   Photochem. Photobiol. 33:861-867.

Worrest, R.C., K.U. Wolniakowski, J.D.  Scott, D.L.  Brooker,   B.E. Thomson, and
     H.  Van  Dyke.  198lb.    Sensitivity  of  marine  phytoplankton  to  UV-B
     radiation:    Impact   upon   a  model  ecosystem.     Photochem.   Photobiol.
     33:223-27.

Wyrtki, K.  1962.   The oxygen minimum in relation to  ocean  circulation.   Deep
     Sea Res.  17(4):751-64.

      R.G.  1982.   Photochemical transformations induced by  solar  ultraviolet
     radiation  in  marine  ecosystems.    In  The role  of  solar  ultraviolet
     radiation in  marine  ecosystems,  ed.  J.  Calkins,   293-307.   New  York:
     Plenum Press.
                                     251

-------
TERRESTRIAL PLANTS

-------
The  Potential Consequences of Ozone Depletion Upon
Global Agriculture
Alan H. Teramura
University of Maryland
College Park, Maryland USA
     Our global agricultural system  depends  on  only a  handful  of key crop
species.  Of  the  350,000  species  of  plants  that  have been described in the
world,  over 80,000  are edible (Table  1).   Of these, only  about 3,000 are
actually harvested for use  as  food  (Vietmeyer  1986).   Of these 3,000, only
about 80 species have been domesticated  and only 15 species supply most of the
food calories  and  three quarters of the protein to the world's people.  Three
""embers of  the grass family—rice,  wheat, and corn—supply two-thirds  of these
°alories and one-half of the protein  (Table 2).

     Over the   course of  the past  decade several  hundred  scientific reports
     been  published documenting the  UV sensitivity of  more  than 200 plant
species and varieties under  a wide variety of growth chamber,  greenhouse, and
fleld experiments  (Teramura  1983; National  Academy of Sciences 198*1).  Of the
°rops examined, approximately  two-thirds are sensitive to  UV  radiation, with
Or>e out  of  every  five identified  as extremely sensitive.   This finding has
Promoted considerable concern over the potential consequences  of  ozone deple-
tion.   However, several critical caveats must be  included with such a "dooms-
day scenario." First,  experiments  conducted in growth chambers or greenhouses
tend to overestimate   and  exaggerate  plant susceptibility  to UV radiation
(Teramura,  Biggs,  and Kossuth 1980; Teramura 1982; Teramura and Murali  1986),
Partly  because natural protective mechanisms  are not fully  developed under
artificial  growing conditions.   Because  over 90? of our knowledge  of UV effec-
tiveness comes from growth chamber  studies, we have a worst case view  of these
effect3.  The second  complication concerns  the  tremendous amount of varia-
^Uity  in UV sensitivity within each  species.  Most of our crops have  numerous
varieties or cultivars  particularly suited to  specific growing regions.  For
lristance, corn grown in Maryland is a  different variety from that  grown  in the
Midwest.   Over 100 crop  varieties or  cultivars  have been  screened for UV
^sponsiveness and approximately two-thirds of these were identified  as being
Sensitive (Biggs,  Kossuth, and Teramura  1981; Dumpert and Boscher  1982; Krizek
        Overall,   nearly  the  same  range  of  sensitivity can be found among
                                    255

-------
                       Table  1.   Plants as a Food Source
          Category
                                             % of Total
350,000 known species of plants

    80,000 edible plants

   3,000 harvested plants

   80 domesticated plants

     15 key crop plants
                                                  100

                                                  23

                                                  0.9

                                                 0.02

                                                0.004
                  Table 2.  Major World Food Crop Production
Crop
    Production
(million metric tons)
Crop
Source:  Food and Agriculture Organization, 1984
                                      256
Production
Cereals
wheat
rice
corn
barley
sorghum



Legumes
soybean
bean
peanut
1984
522
470
449
172
72




90
32
21
Sugar Crops
sugar cane
sugar beet

Root Crops

potato
sweet potato
cassava
Tree Crops
banana
coconut


936
293



312
117
129

41
*•* 4
31
	 	

-------
cultivars  as  among different  species.    Therefore,   a  crop such as soybean
may  be labelled as sensitive  to  UV based on the  response  of the majority of
cultivars  tested despite having some very tolerant cultivars.  In other words,
most crops are not  100? sensitive or 100? resistant  to UV.

     The  third complicating  factor arises  as  a result  of the  endpoint or
criterion  used by various investigators to gauge UV  sensitivity.  Many studies
have  used whole  plant features  such  as plant  height,  number of  leaves, or
total  plant  dry  weight (Biggs and  Kossuth  1978;  Van,  Garrard,  and West  1976;
Tevini  and  Iwanzik 1982).    Others have used  physiological or  biochemical
criteria  such  as  photosynthesis,  respiration, or  protein  content (Brandle et
al.  1977;  Sisson and Caldwell  1976; Vu,  Allen,  and Garrard  1982).  Because of
the  inherent differences in  these diverse  gauges of sensitivity,  it  is not
terribly  surprising that a  plant may be sensitive  to UV  based  on photosyn-
thetic  determinations  while it is  resistant based  on  changes  in dry weight.
Although  crop  yield may  ultimately be the  crucial  feature to study,  only a
handful of investigators have  addressed  this question  because of the enormous
technological difficulties encountered in the field.  Despite these and other
difficulties, our  current uncertainty is not  whether plants are  affected by
UV, but rather  the magnitude of  this  sensitivity.   Because only  a handful of
key  species  supply most of  our agricultural needs, this  potential suscepti-
bility warrants great concern.

     To  illustrate  some of the potential  consequences of  ozone  depletion on
global agriculture, I use soybean as a model.   Table 3 shows that soybean has
become a major plant source of oil and protein for the world, ranking fifth in
the world  in terms of tonnage, behind wheat,  rice,  corn, and barley.   It is
the third  largest crop  in the  United States, which produces nearly 60% of the
world's  total.   Due to its  importance in the United States  and  global agri-
culture, any decrease  in yield  would unquestionably  have  a profound impact on
the world economy.

     Because of the drawbacks inherent in growth chamber experiments, the most
meaningful method to assess  risk  is by examining  the  effects of  UV radiation
on field-grown  crops.   In such a setting one is faced with  a more difficult
task in  performing  the experiment because more UV radiation must  be added to
that normally received by the  plant.   The data  shown in Table 4 spans a five-
year period  between 1981   and  1985 simulating  a 25% ozone  depletion  for one
cultivar of soybean, Essex,  which is one of the most widely grown cultivars in
the United States.   Despite a  large degree  of annual variation, a  25% ozone
depletion  results in up  to  a 20%-25% reduction in-overall  yield.   Years with
little  apparent UV  effectiveness  (1983 and  1984)  were generally hot  and dry
with  plants  experiencing  prolonged  drought.    By  knowing  the  pattern  of
precipitation,   temperature,  and  degree  of  cloud  cover  during  the  growing
season, one  can predict with a high degree  of confidence what  the  effects of
supplemental UV  will  be  on soybean yields  (Figure 1).    The diagonal  line
represents a perfect match  between predicted and  actual yield.  The  bolder,
jagged  line  represents our  model  prediction.   In  addition to reducing the
actual weight of the harvest, UV  radiation also  generally  reduces the overall
quality of the soybean harvest  by  reducing its protein and  oil content (Table
*0;  however, we  currently  know  very little  about  the   mechanism  of  this
phenomenon.
                                     257

-------
              Table 3.  United States and World Crop Production
Crop
wheat
rice
corn
barley
soybeans
World
(million metric tons)
522
470
449
172
90
USA
71
6
195
13
51
% of
World Production
14
1
43
8
57
Source:  Agricultural Statistics - USA,  1984;  FAO Production Yearbook,  1984
        18

        16
   3  14

   1  12
    ^  10
   "O
   S>   8
    •D
    0
    £
6
4

2

0
           0
        Essex
                    6     8    10   12
                     Actual yield (g)
14    16   18
     Figure  1.   Bold, jagged line represents how closely a model regressi°°
equation  predicts  actual  yield.   The  model  inputs  include presentatio°»
temperature,  and cloud cover data.   The diagonal line represents the idea
situation where actual and predicted yields are equivalent.
                                    258

-------
         Table 4.  Summary of UV Effects on Soybean Yield and Quality


Year                   % change in yield            % change in seed quality
                                                   (protein)           (oils)
1981
1982
1983
1984
-25
-23
+6
-7
-5
-4
0
0
-2
+ 1
-2
0
Source:  Teramura (unpublished)


     What does a  20/5-25/5  reduction in yield mean  to  global  agriculture?  For
Perspective,  this  UV-induced  loss  in yield  is compared  with other  current
sources of  crop  loss  in soybean  in Figure 2.    Losses  due to  weeds  reduce
Soybean yields by  17#,  diseases by  12-14?,  mechanical harvesting  by  10j5 and
insects by  3%  (Metcalfe  and Elkins 1980).  Clearly,  if  the  data  presented on
^able 4 are universally  applicable to all soybean  grown  in  the United States
°r the world in general,  the anticipated  loss  due  to  ozone depletion would be
Sweater than  our  current losses to  any  one of  these factors.   Should  these
Experimentally based predictions be  correct,  we could anticipate a one-third
Eduction in our useable  soybean harvest  from  56%  down to 36#.  Additionally,
fchere is some evidence  in the literature  (Esser 1980;  Cams,  Grahm, and Ravity
^78) that  under a  greater  UV  environment, crop losses  from weeds, diseases,
    insects would be even larger due to  the weakened  state  of the crop  host.
   losses in each category  increased  by 25%, then  our useable soybean harvest
      effectively be reduced by one-half  (Figure 3).
     Up until now, we have quite a depressing  picture  of what might happen to
°Ur soybean  harvests;  however,  there is  a brighter  side.    We  know  that  a
tremendous range  of UV  sensitivity  apparently exists  among different  crop
°uUivars.  The U.S. Department of Agriculture currently has  a collection of
fver 12,000 soybean lines and only a  fraction  of  these have  been  screened for
Jv  tolerance.   Of  the 45  cultivars  that  have been  screened (Teramura  and
"Urali 1986;  Biggs, Kossuth,  and  Teramura 198,1),  nearly one-third  were quite
tolerant to even  large UV  doses.   This implies that some degree  of tolerance
*a  already present  in our  modern soybean  germplasm,  and that the potential
e*ists for crop  breeding  as  a  means  of helping  to  lessen  or ameliorate  the
^ticipated loss  in yield  due  to ozone  depletion.   Unfortunately, we  do  not
K^OW enough about the  bases  for these cultivar differences  in sensitivity to
 e able to fully  evaluate  the likelihood of this possibility.  For instance,
Jf  UV  tolerance  were  closely  associated  with  inferior  genes  which  might
ltlcrease drought  susceptibility or lower yields, then  any  breeding  program
w°Uld be of little help.

     In conclusion, the 20%  to 25% yield  reductions reported for  soybean in
      paper are  only  preliminary  estimates  and  may  portray  a  worse-case
           The data represent the response of  only  one out  of the dozens of
                                     259

-------
 cultivars  currently grown  throughout the  United States.   However,  in the
 absence of  similar  detailed  information for other key crops, these data serve
 to  warn us  of the potential  consequences of ozone depletion upon global agri-
 culture.  We can only hope that these data represent an extreme case and not
 the general  status of our global agriculture.
              Disease
             C12-14%3
                       '(10%)
                     Harvesting
                            (3%)
Figure 2.   Current  sources of soybean
crop losses in the  United States in
relation to anticipated  losses due to
a 25% ozone depletion.
Figure 3.  Anticipated  yield
losses due to a 25%  ozone
depletion assuming that UV
produces a significant  (25*' s
interaction with other  source*
of yield reductions.
                                     260

-------
 REFERENCES

 Biggs,  R.H.,  and  S.V.  Kossuth.    1978.   Effects  of ultraviolet-B radiation
     enhancement  under  field  conditions  on  potatoes, tomatoes,  corn, rice,
     southern  peas, peanuts, squash, mustard, and radish.  UV-B Biological and
     Climatic  Effects  Research  (BACER), Final  Report.    Washington, D.C.:
     Environmental Protection  Agency.

 Biggs,  R.H., S.V. Kossuth, and A.H. Teramura.   1981.   Response of  19 cultivars
     of soybeans to ultraviolet-B  irradiance.   Physiol. Plant.  53:19-26.

 Brandle,  J.R., W.F.  Campbell,  W.B.  Sisson,  and  M.M.  Caldwell.   1977.   Net
     photosynthesis,  electron  transport capacity,  and ultrastructure of Pisum
     sativutn L. exposed  to ultraviolet-B radiation.   Plant.  Physiol.   60:165-
     169.

 Cams,  H.R., J.H. Grahm, and S.J.  Ravitz.  1978.  Effects of UV-B radiation on
     selected  leaf pathogenic fungi  and on  disease severity.   EPA-IAG-D6-
     0168.  Washington, D.C.:  BACER Program, EPA,

 Dumpert, K., and J. Boscher.   1982.   Response of different crop and vegetable
     cultivars  to  UV-B  irradiance:    Preliminary  results.   In  Biological
     effects of  UV-B  radiation,  ed.  H. Bauer, M.M.  Caldwell,  M.  Tevini,  and
     R.C.  Worrest,  102-107.    Munchen:   Gesellschaft  fur  Strahlen-und  Umwelt-
     forschung mbH, ISBN 0721-1694.  ISBN 0721-1694.

 Esser,  G.  1980. Einfluss einer nach Schadstoffimission vermehrten Einstrahlung
     von UV-B-light auf Kulturpflanzen,  2. Versuchsjahr,   Frankfurt:  Bericht
     Battelle  Institut e.V.

 Krizek,  D.T.  1978.  Differential  sensitivity  of  two  cultivars  of  cucumber
     (Cucumis  sativus  L.) to  increased UV-B  irradiance:   I.   Dose-response
     studies.  Final Report EPA-IAG-D6-0168,  USDA/EPA BACER Prog.,  Washington,
     D.C.:  Environmental Protection Agency.

Hetcalfe,  D.S. and D.M.  Elkins.   1980.   Crop production.   Principles  and
     practice.   4th ed.  456-460.   New York:   Macmillan Pub.  Co.,  Inc.  ISBN 0-
     02-380710-5.

National Academy of Sciences.  1984.  Causes and effects of changes  in stratos-
     pheric ozone;   Update 1983.   Washington D.C.:   National Academy Press.

Sisson, W.B., and M.M. Caldwell.   1976.  Photosynthesis,  dark respiration,  and
     growth of Rumex  patientia L. exposed  to ultraviolet irradiance  (280  to
     315 nanometers)  simulating  a reduced atmospheric ozone column.    Plant
     Physiol.  581:563-568.

Teramura,  A.H.   1982.   The amelioration of  UV-B  effects'on productivity  by
     visible radiation.  In The role of solar  ultraviolet radiation in marine
     ecosystems,   ed.  J. Calkins,  367-382. New  York:  'Plenum Publ.  Corp.  ISBN
     0-306-40909-7.

Teramura,  A.H.    1983.   Effects  of ultraviolet-B radiation on the  growth  and
     yield of crop  plants.  Physiol.  Plant.  58:415-427.


                                     261

-------
Teramura, A.H.,  R.H.  Biggs,  and S. Kossuth.   1980.   Effects of ultraviolet-B
     irradiances  on  soybean.    II.    Interaction  between  ultraviolet-B  and
     photosynthetically   active   radiation   on   net   photosynthesis,   dark
     respiration, and transpiration.  Plant Physiol.  65:483-488.

Teramura, A.M.,  and N.S.  Murali.   1986.   Intraspecific differences in growth
     and yield of soybean  exposed  to  ultraviolet-B radiation under greenhouse
     and field conditions.  Env. Exp.  Bot. 26:89-95.

Tevini, M., and  W.  Iwanzik.   1982. The effects of UV-B irradiation on higher
     plants.  In The role of solar ultraviolet radiation in marine aQ03y3tg[g§»
     ed. J. Calkins,  581-615.   New York:   Plenum Pub. Corp. ISBN 0-306-40909-
     7.

Tevini, M., and  W.  Iwanzik.   1982.   Untersuchugen uber den Einfluss erhohter
     UV-B Strahlung auf Entwicklung,  Zusammensetzung,  Struktur  und Funktio
     von Pflanzen.  Munchen:   Bereich Projekttrager-schafterm, GSF.

Van, T.K.,  L.A.  Garrard,  and S.H.  West.   1976.   Effects of UV-B radiation °n
     net photosynthesis of some crop plants.   Crop Sci.  16:715-718.

Vietmeyer, N.D.  1986.  Lesser-known plants of potential use in agriculture a
     forestry.  Science 232:1379-1384.

Vu, C.V., L.H. Allen,  and L.A.  Garrard.   1982.   Effects of supplemental W'
     radiation on   primary photosynthetic carboxylating  enzymes  and,. 3°^t
     proteins in leaves of C   and C  crop plants.  Physiol. Plant.  55:11"1
                                      262

-------
Inhibition of Photosynthetic Production in Plants
by Ultraviolet Radiation1

L O. Bjdri\ Janet F. Bornman, and Legasse Negash
University of Lund
Lund, Sweden
     In this lecture we  will  try  to explain some research  findings concerning
the  inhibition  by  ultraviolet   radiation  of  photosynthetic  production  in
plants.  Because of the abundant scientific literature on this topic we will
not attempt to cover all of it, but will concentrate on findings which (a) are
relevant to the ozone depletion  problem and (b)  are  of general significance,
i.e., not relating to  particular  plants only.  Furthermore, we will try to be
nontechnical and not  assume  a background  in plant physiology  or photobiol-
ogy.  These are  our aims,  but the result of our attempt will necessarily be a
compromise, due  to  the short time available.

     It is  necessary  first  to say a  few words about photosynthesis.    The
process can be schematically written:

     Water  + carbon dioxide + light = organic matter + oxygen.  Photosynthesis
takes place in the green parts of plants,  mostly leaves,  where the light for
the process is absorbed, mainly  by the green pigment, chlorophyll.   In land
plants (but not in aqueous plants) the carbon dioxide enters through micro-
scopic adjustable  pores or valves called  stomata  (see  Figure 1).  The stomata
are  adjusted  by  the  plant  for   the best  compromise  between  carbon  dioxide
influx and  water vapor loss.

     The process:   water + carbon dioxide  + light  = organic matter + oxygen,
is not  completed in one  step.   There  are,  in fact,  many  chemical reactions
leading to  chis  net result.   The process can be roughly divided  into  two
Parts:

     •  Photosynthetic electron transport and phosphorylation:
        Water  + light = oxygen +  reducing power + phosphate energy

     •  Assimilation of carbon dioxide:
        Carbon dioxide + reducing  power + phosphate  energy = organic matter.
                                    263

-------
                   1
                                                         50pm
     Figure 1.  Light micrograph of stoma from broad bean (Vicia faba) leaf in
open condition (above, white light only), and stoma closed under the~action of
UV radiation.  The photograph is from an experiment with excised epidermis.
                                      264

-------
     These main parts of  the  photosynthetic  process  take place in microscopic
green particles  in the cells called  chloroplasts  (Figure 2).   Photosynthetic
electron  transport and  phosphorylation  take  place  in  the  chloroplasts  in
membranes called thylakoids, where  carbon  dioxide  is  assimilated in the space
between  these membranes,  which  is filled  with  a solution  (stroma)  of  the
enzymes necessary  to  catalyze the  reactions.   The chloroplasts  also contain
part of the  cell's  genetic  material,  DNA,   and  protein  synthesizing  system
(ribosomes).

     Inhibition of photosynthesis  by ultraviolet radiation has been  estab-
lished  and  measured by  several  types  of experiments.    The  first  type  are
short-term laboratory experiments in which isolated chloroplasts or thylakoids
are first exposed to ultraviolet radiation without simultaneous irradiation by
visible light.  At the end  of the ultraviolet radiation the sample is exposed
to  visible  light,  so  that the  effect on the photosynthetic system  can  be
estimated.  In such experiments it has been found that photosynthetic electron
transport is inhibited by ultraviolet radiation.  The electron transport chain
is damaged at more than one point, and the points of damage have been approxi-
mately determined  (see Bornman  et al. 1984).   In  contrast to moderate photo-
inhibition caused  by intense  visible  light,  photoinhibition by UV-B radiation
is not rapidly reversed during subsequent dark incubation (Bornman 1986).

     Before  we proceed,  we  should be familiar  with  the concept of  action
spectrum.   An action  spectrum  is  a function  describing, or  comparing,  the
effectiveness  (average effect per  incident photon) of  radiation  of different
wavelength to  effect a certain process, such as inactivation of the photosyn-
thetic system.  One  can  think of this as  a  graph  with  a wavelength along the
horizontal axis and effectiveness,  i.e.,  effect in relation  to the intensity
and duration of the irradiation,  along the vertical  axis.  Determining action
spectra  is  one of the  most  important means of characterizing photochemical
processes as  it may  provide  information about  the molecule absorbing  the
effective radiation.   In  connection with  the ozone depletion  problem,  action
spectra  are  important  for computing the so-called  radiation amplification
factor  (see  Figure 3),   and  for  relating  effects   of artificial  radiation
sources to those caused by solar radiation.

     Practically all  action  spectra relating  to deleterious effects  of  UV
radiation show a  decline of  effectiveness from low  to  high wavelengths,  but
the slope varies,  and  there may be "bumps."  Measurements in several labora-
tories using variations on  the first  type  of experiments (Jones and Kok 1966;
Hirosawa and Miyachi 1983; Bornman, BJorn,  and Akerlund 1984) have resulted in
action  spectra with modest slopes  (Figure  4).   This  means  a  low radiation
amplification  factor, in  marked  contrast to  spectra measured for inactivation
of the genetic system (DNA inactivation,  Figure 5), which are very steep.

     On the other  hand, action spectra for inhibition have also been measured
with a  second type of  experiment, which  has yielded different  results.   In
these experiments  (Bogenrieder  1982;  Caldwell et al.  1986)  complete  photo-
synthesis was  measured for intact leaves or  intact  plants' with white light
impinging on  the leaves  simultaneously  with  the UV radiation.  These spectra
(Figure 6) are steeper than the spectra obtained by  the  first method.   These
latter  studies are closer  to a  field situation and  may be regarded  as more
relevant  to  the  ozone depletion problem.    They  indicate  a  higher radiation
amplification  factor  and therefore a greater risk.   However, a scientist can


                                      265

-------
     Figure 2.  Electron  micrograph  of part of a cell from a  sugarbeet  leaf,
showing chloroplast with  stroma (s)  and  thylakoids  (t).   In some  places  the
thylakoids form grana  (g).  From Bornman et al.  (1986).
                Action spectrum A
                 Action spectrum B
Normal daylight
 spectrum (C)
                                                    Daylight spectrum
                                                   after ozone depletion
                                                          CD)
                            WAVELENGTH

     Figure 3.   Diagram to illustrate the dependence of  radiation amplifica-
tion factors on  action  spectra.   The  whole diagram is generated by a computer
program with a  set of equations, and does not  depict real experimental data.
One steep action spectrum  (A)  and one that is less steep (B) are shown (wave-
length  on  horizontal axis,  effectiveness  on vertical  axis),  as  well  as the
short  wavelength tails of  the normal daylight  spectrum (C) and  of daylight
after  ozone depletion  (D)  (wavelength on horizontal axis, spectral irradiance
on  vertical axis).   The radiation amplification  factor  for action spectrum A
is  the  ratio between  the area  below  the  product curves AxD (stippled) and AxC
(black),  in  relation to  the particular ozone  depletion that  has caused the
spectral change  from C to D.  In  the hypothetical example shown, the radiation
ampl: 'ication factor is five times as great for action spectrum B.
                                      266

-------
        Ill
        s

        CO
        (A
        Ul
        z
        Ul
        >

        p
        o
        Uf
        u.
        u.
        IU
        o
        K
            250
275         3QO

 WAVELENGTH, nm
325
     Figure 4.   Action  spectrum  for  inhibition  of  photosynthetic  electron
transport determined  in  isolated spinach chloroplasts (curve 1,  Jones and Kok
1966), isolated spinach  thylakoids (curve 2t  Bornman et al.  1984) and isolated
cyanobacterial thylakoids (curve  3»  Hirosawa and  Miyachi  1983).   Within the
UV-B region (280 to 320  nm) the effectiveness changes about  twofold.
                                     267

-------
                                      a, • Relative dimer yield per quantum
                                       —A Relative lethality  per quantum
                                          Relative mutaqenicity  per quantum
                                      	Average DNA spectrum
                                          (Setlow, 1974)
                                          Xenon lamp
                                      A, o Hg  lines
                                                 (Tyrrell, 1973)
                                          350       400
                                       WAVELENGTH (nm)
     Figure 5.    Absorption  spectrum  for  DNA, as  well  as action spectra  for
various  processes  that depend  on radiation  damage  to  DNA.   Note that  the
vertical scale  is logarithmic.    Within  the  UV-B  region  the  effectiveness
(action  per quantum)  changes about 10,000  fold.  Cited  from various  sources by
Peak et  al. (1984).
                                         268

-------
             UJ
             (0
             0)
             111
             z
             UJ
             o
             UJ
             u.
             u.
             Ul
             o
             I-
                250
   275           300


WAVELENGTH, nm
     Figure  6.    Action  spectrum for  inhibition  of photbsynthetic  carbon
dioxide  fixation  by  intact  plants:   Laotuca  sativa  (triangles,  Bogenrieder
1982), Rumex  alpinus  (circles,  Bogenrieder 1982) and Rumex  patientia  (solid
line, Caldwell et al.  1986).  The slopes  are intermediate between the  slopes

in Figures 3 and 4.
                                     269

-------
hardly be content with such a statement.   We wish neither to underestimate nor
overestimate the consequences of ozone depletion, and,  to  be on solid ground,
we must  understand the  reason  for  the  discrepancy between  the two  sets  of
results.

     A first guess  would be that it is  not  damage  to  photosynthetic electron
transport (measured in the  first method), but damage to the enzymes necessary
for  carbon  dioxide  assimilation  that  is  important  for   inhibiting  overall
photosynthesis (measured by the second method).   Indeed,  inactivation of some
proteins shows steeper action spectra,  and UV-B  has been shown to decrease the
activity  of   the   carbon  dioxide  binding  enzyme,   ribulose  bisphosphate
carboxylase/oxygenase (Vu, Allen, and Garrard 1982,  1984).

     Nevertheless,  there is another possibility  that also explains the differ-
ent action spectra obtained, depending on whether white light is given simul-
taneously with the UV radiation or not.  Although there are facts speaking not
only for, but  also  against  the  following interpretation,  we think it is worth
presenting as an hypothesis;  some background follows to explain it.

     One of the  components  necessary for photosynthetic electron transport is
the  so-called  QB protein.   This protein binds  a quinone that transfers elec-
trons.   It  is a remarkable protein  in many  respects (see  Arntzen and Pakrasi
1986 for a  review).  One feature that is important  in  our context is that it
has  a  very  high turnover rate  in  light,  i.e.,  it is rapidly broken down and
resynthesized.   The rate of breakdown increases  with  light intensity; we may
regard 15 minutes  as a  typical lifetime for a  molecule of QB proteintf  It is
as if  the protein  molecules were  worn  out by working hard.   If resynthesis is
prevented during irradiation with strong light,  the photosynthetic system is
inactivated.   When such  a situation occurs,  trees are exposed to strong light,
but  temperature  is still too low for efficient protein synthesis, e.g., in the
spring in Swedish conifers.

     It  could  be that one  important effect  of  UV radiation is to destroy the
chloroplast DMA, in which  the  blueprint  for resynthesis of the QB  is encoded,
thereby  slowing down  resynthesis  and  photosynthetic electron  transport.   If
this mechanism dominates inhibition  of photosynthesis  by UV, one would expect
action spectra measured  with simultaneous  irradiation  by UV and visible light
to be  steeper  than those determined  with sequential irradiations.  This seems
to  be  supported in  the  results,  although we do  not have strictly comparable
data  yet.    There  is  also  more direct  evidence (Dohler,  Biermann,  and Zink
1986)  that protein  synthesis may be  inhibited by  UV-B radiation.

     If  the above  interpretation  is correct,  we also have,  in principle,  a
recipe for producing more UV-resistant plants:  We should  introduce additional
copies of the  gene  encoding for the  Qn protein  (the correct designation is the
psbA gene)  into  the chloroplasts.  This may be  possible, but  the recipe is, of
course,  a bit naive.   Other genes are inactivated as well.   But all genes are
not  equally critical.   Genes that do their important Job  in, for  example, the
growth zones  (the  meristems)  in root and  shoot tips  can be discounted, for
they are shielded  and  protected from UV.
                                      270

-------
     Plants vary  widely in their  tolerance,  and many  factors  other than the
possibility just  mentioned certainly  contribute to this.   Considerable dif-
ferences  may  exist between closely  related species (Robberecht  and. Caldwell
1986),  or even between cultivars of  the  same  species  (Biggs,  Kossuth,  and
Teramura  1981).   Differences  already  occur at  the  membrane level:   we have
found for example that  spinach thylakoids  are  more resistant than even intact
leaves  of Elodea  (Bjorn, Bornman, and Olsson  1986; Figure 7),   At the organ
level different degrees of protection  are  offered by the outermost cell layer
of  the  leaf,   the  epidermis,   which  often  contains  substances that strongly
absorb  ultraviolet  radiation.   The  content of these shielding substances is
often adjusted to match  the need.  As  an example, we (Bjorn and Bornman 1986)
have  observed  that the  same   Oxalis leaf  is more  sensitive to  UV radiation
coming  from below  (where the  plant "has no reason  to expect"  any UV)  than to
UV  impinging  upon the  upper  side of  the  leaf  (Figure 7).   Caldwell  et al.
(1982)  have  shown a  correlation  between  UV  tolerance and UV  level  in  the
natural habitat, as well as between  UV sensitivity and  epidermal  UV transmit-
tance.  Wellman  (1974)  and Beggs, Schmeider-Ziebert, and Wellman (1986) have
reported  the accumulation  of  UV absorbing flavonoids in  response to UV expo-
sure, and have shown  how  widely  various  plants differ  with  regard  to this
response.

     It has also  been repeatedly  observed (e.g., Klein  1963;  Teramura 1980)
that plant cell cultures and whole plants  tolerate more UV radiation the more
they are  simultaneously exposed to visible light.   The  nature  of this protec-
tive action of visible  light is not  understood.   Even  if inhibition is due to
DMA damage, the  so-called  photoreactivating enzyme  (which is known  to carry
out a  light dependent  DNA  repair in  other  cases) is  probably not involved.
The photoreactivating  enzyme   repairs  a  type  of  damage  (pyrimidine dimeriza-
tion) that is  probably  not the most important type  of  damage  in  the spectral
range of  solar UV  radiation  (Peak et  al.  1984).   Hirosawa and Miyachi (1983)
studied inhibition by  UV-A of photosynthetic  electron  transport  in a cyano-
bacteriura and  concluded that the reactivation achieved with subsequent visible
light is  due to light absorption  in  the  photosynthetic  system.   However, this
may be  a  phenomenon different  from the protection  from UV-B damage; it seems
that no one has studied the spectral  dependence of this protective effect.  It
is possible that  plants become more resistant when they are  grown in strong
white light because of long-term  changes  in  their  properties, especially in
the amounts of protecting  pigments.   Another possibility  is that they  can
repair  damaged systems  faster  in  strong light because they have more energy
available in this case as compared to weak light conditions.

     The  protective effect  of visible light seems to be an argument  against
the hypothesis that an important UV effect  is  the inhibition of resynthesis of
the QD protein, because the need for  resynthesis would  be greater  the stronger
the visible light.  However,  only strong  visible light given  prior to the UV
irradiation has  a  protective effect   (which  thus  can  be  described  as  an
acclimatization to  strong  sunlight),  while  strong  visible  light concomitant
with UV irradiation enhances  UV  inhibition  (Warner and Caldwell  1983),  as
would be expected from the hypothesis.

     When considering  UV effects  on  whole plant photosynthesis,  one  should
take into account not only direct  effects  upon  the photosynthetic system, but
also  indirect effects on photosynthesis.  Inhibition of leaf area growth, for
                                     271

-------
   0.6
 E 0.4
 o
 E
 a
   0.2
     \  ELODEA
      1
                            OXALIS
                                           (ADAXIAL)
                                             ••••••••.
                260
280
300
320
340
                              WAVELENGTH,  nm
     Figure  7.   Action  spectra  for  inhibition  of electron  transport  (as
measured by  the effect  on fluorescence induction) in intact leaves of Elodea
denja and pxalis deppei.  and  isolated spinach thylakoids, all  to  the  same
scale.   Elodea leaves  lack an  epidermis, and the  sensitivity is the same for
both sides.    For  Oxalis  the  sensitivity  is  much greater for  UV radiation
impinging on the lower  (abaxial) side than the  upper  (adaxial)  side.   From
Bjorn,  Bornman, and Olsson (1986).
                                    272

-------
instance, will  lead  to a lowered  input  of light energy, and thus  to  lowered
photosynthetic  production.   Dr.   Hader   (this volume)  has  described how  UV
inhibition of the ability of free-swimming photosynthetic organisms to  swim in
the proper direction can affect photosynthetic production.  Another UV  effect,
which has  been  studied  in our  laboratory  (Negash  and  Bjorn  1986),  is  the
closing  effect  on stomata  (Figure 1).    Closing of  stomata prevents  carbon
dioxide  from  entering  the plant,  and thus inhibits photosynthesis.   Also  in
this case visible light counteracts the  effect of UV  (Figure 8).   Our  conclu-
sion as  regards tef  (Eragrostis tef,  an  important crop  in Ethiopia, where  UV
exposure is high)  is  that UV closure of  stomata is not  important  under  field
conditions as long as  the water  supply  is adequate.   This conclusion is  based
on  our  laboratory experiments  and on  a computer  program  (Bjorn and Murphy
1985)   for   predicting   daylight   spectral  UV   irradiance  under   various
conditions.    Teramura  and Perry (1982)  and Teramura et  al.  (1982,  1984)  have
measured UV  effects on  stomata in  soybeans, radishes,  and cucumbers  under
field conditions and  found  that these  UV  effects  on  stomata  may have  some
importance in certain plants under  water stress conditions.
                   30O
                c
                o
                o
                   200
                o
                c
                m
S
                   100
                o
                flC
                                          WL (450 pmol m $ '
                                 60        120
                                   Time,  min
                                      180
     Figure 8.   Stomatal resistance in  control  plants (tef, Eragrostis  tef)
irradiated  with white  light  (50  ymol  m~^s"')  only  (triangles)  and  plants
simultaneously  exposed  to UV (285 nm,  2.4  y mol nf^s  , circles).  The UV,
exposure commenced at  time  0.   After 90 minutes white  light  fluence  rate was
increased 9  fold.   Stomata start  to close when  exposed to UV  radiation,  but
the closure is  reversed  by  an  increase  in  white  light.   Note that  high  resis-
tance values  correspond  to  small stomatal aperture.  The  roots of the  plants
were immersed in water.  From Negash and Bjorn (1986).
                                      273

-------
REFERENCES

Arntzen, C.J., and H.B. Pakrasi 1986.  Photosystem  II  reaction  center:   Poly-
     peptide subunits and  functional cofactors.  In:   Encyclopedia  of  Plant
     Physiology.  19:459-467.   Springer-Verlag.   ISBN 3-540-16140.

Beggs, C.J., U. Schneider-Ziebert,  and  E.  Wellman.  1986.   UV-B radiation and
     adaptive  mechanisms  in  plants.    In:    NATO   ASI   Series,   Vol.  8:
     Stratospheric  ozone  reduction,  solar  ultraviolet radiation  and  plant
     life, eds. R.C. Worrest, and  M.M. Caldwell, 235-50.  ISBN 3-540-16140.

Biggs, R.H., S.V. Kossuth, and A.H.  Teramura.  1981.  Response of  19  cultivars
     of soybeans to ultraviolet-B  irradiance. Physiol.  Plant. 53:19-26.

Bjorn, L.O., J.F.  Bornman, and E.  Olsson, 1986.  Effects of ultraviolet  radia-
     tion on fluorescence induction kinetics in isolated thylakoids and  intact
     leaves.   In:   NATO  ASI  Series, vol.  8.   Stratospheric ozone reduction,
     solar ultraviolet  radiation  and plant  life, eds.  R.C. Worrest  and M.M.
     Caldwell, 185-98.  ISBN 3-540-16140.

Bjorn, L.O.  and T.M.  Murphy 1985.   Computer calculation of solar ultraviolet
     radiation at ground level.  Physiol Veg. 23:555-561.

Bogenrieder, A. 1982.   Action  spectra for  the  depression of photosynthesis by
     UV irradiation in  Lactuca sativa L. and Rumex  alpinus L.  In:  Biological
     effects of UV-B  radiation, eds.  H.  Bauer,   M.M. Caldwell,  M. Teyini, and
     R.C.  Worrest,  132-39.   Gesellschaft  fur  Strahlen- und  Umweltforschung
     mbH, Munchen: BPT-Bericht.

Bornman,  J.F.  1986.   Inhibition  of  photosystem II  by blue light and  ultra-
     violet radiation: a comparison.  Photobiochem.  Photobiophys.  11:9-17.

Bornman,  J.F., L.O.  Bjorn,  and  H.E. Akerlund.  1984.   Action  spectrum for
      inhibition by ultraviolet radiation of photosystem II  activity in spinach
      thylakoids.  Photobiochem. Photobiophys.  8:305-313.

Bornman,  J.F.,  R.F.   Evert,  R.J.  Mierzwa, and  C.H.   Bornman,  1986.    Fine
      structural effects of UV  radiation  on  leaf tissue of  Beta vulgaris.  In:
     NATO ASI  Series, vol. 8. Stratospheric ozone reduction, solar ultraviolet
      radiation and  plant  life, eds. R.C. Worrest and  M.M.  Caldwell, 199-209.
      Berlin-Heidelberg:  Springer-Verlag ISBN 3-540-16140.

Caldwell, M.M., L.B.  Camp,  C.W. Warner,  and S.D.  Flint. 1986.  Action spectra
      and  their key role  in assessing biological  consequences of  solar UV-B
      radiation change.    In:  NATO  ASI Series,  vol.   8:  Stratospheric  ozone
      reduction, solar ultraviolet  radiation and plant  life, eds.  R.C. Worrest
      and  M.M.  Caldwell, 87-111.   Berlin-Heidelberg: Springer-Verlag,  ISBN 3-
      540-16140.

Caldwell,  M.M.,  R.  Robberecht,      R.S.  Nowak,  and  W.D.  Billings.   1982.
      Differential   photosynthetic   inhibition   by   ultraviolet  radiation  in
      species  from the arctic-alpine  life zone.  Arctic Alpine Res.   14:195-202.
                                      274

-------
Dohler,  G.,  I.  Biermann,  and  J.  Zink, .1986.    Impact  of UV-B  radiation on
     photosynthetic  assimilation   of    C-bicarbonate  and   inorganic   ^It-
     compounds by cyanobacteria.   Z. Naturforsch. 4lc:426-32.

Hirosawa, T.,  and  S.  Miyachi.  1983.   Inactivation of Hill  reaction  by long-
     wavelength  ultraviolet  irradiation (UV-A)  and its photoreactivation by
     visible   light   in   the  cyanobacterium.     Anacystis   nidulans.   Arch.
     Microbiol. 135:98-102.

Jones, L.W., and B.  Kok.  1966.  Photoinhibition  of chloroplast reactions. I.
     Kinetics and action spectra. Plant Phvsiol. 41:1037-1043.

Klein, R.M.  1963.   Interaction  of  ultraviolet and visible  radiations  on the
     growth of cell aggregates of Ginkgo pollen tissue.  Phvsiol. Plant.  16:73-
     81.

Murphy, T.M.,  H.C.  Hurrel, and  T.L.  Sasake.  1985.  Wavelength dependence of
     ultraviolet radiation-induced mortality in K+ efflux in cultured cells of
     Rosa damascena. Photochem. Photobiol.  42:281-86.

Negash,  L.,   and   L.O.   Bjorn.   1986.    Stomatal  closure   by  ultraviolet
     radiation.  Phvsiol.  Plant. 66:360-64.

Peak, M.J.,  J.G. Peak,  M.P. Moehring, and R.B. Webb. 1984.   Ultraviolet action
     spectra   for   DMA  dimer   induction,   lethality,   and   mutagenesis  in
     Escherichia  coli  with   emphasis  on  the  UV-B   region.     Photochem.
     Photobiol.  40:613-20.

Robberecht,  R., and M.M. Caldwell.  1986.  Leaf UV optical  properties of Rumex
     patientia and Rumex obtusifolius  L.  in regard to a protective mechanism
     against solar  UV-B  radiation   injury.    In    NATO  ASI  Series,  Vol.  8:
     Stratospheric   ozone   reduction,  solar  ultraviolet  radiation  and  plant
     life,   eds.  R.  C.  Worrest  and  M.M.   Caldwell,     251-59.     Berlin-
     Heidelberg:  Springer-Verlag ISBN 3-540-16140.

Teramura, A.H.  1980.   Effects of ultraviolet-B  irradiances on soybean.   I.
     Importance  of  photosynthetically   active   radiation   in   evaluating
     ultraviolet-B  irradiance  effects  on soybean and  wheat  growth.  Physiol.
     Plant.  48:333-39.

Teramura, A.H.,  and M.C.   Perry.  1982.  UV-B irradiation  effects  on soybean
     photosynthetic recovery from water stress.   In: NATO  ASI Series, vol. 8.
     Stratospheric   ozone   reduction,  solar  ultraviolet  radiation  and  plant
     life,  eds. R.C. Worrest and M.M.  Caldwell,   192-202.   Berlin-Heidelberg:
     Springer-Verlag,  ISBN 3-540-16140.

Teramura, A.M., R.H. Biggs,  and S.  Kossuth.   1980.  Effects of ultraviolet-B
     irradiances on soybean.   Plant  Physiol.  65:483-88.

Teramura, A.H.,  M.C.  Perry,   J.  Lydon,    M.S.  Mclntosh,  and E.G.  Summers.
     1984.    Effects of ultraviolet-B  radiation  on plants during  mild water
     stress.   III.  Effects  on  photosynthetic recovery and growth  in  soybean.
     Phvsiol. Plant. 60:484-92.
                                     275

-------
Teramura, A.M., S. Salm, and M. Tevini  1982.   The effects of UV-B irradiation
     on  leaf  resistances in two  crop species during  mild water stress.   In
     NATO ASI Series, Vol.  8: Stratospheric ozone reduction,  solar ultraviolet
     radiation and  plant life,  eds.  R.C.  Worrest and  M.M.  Caldwell,   192-
     202.  Berlin-Heidelberg Springer-Verlag:   ISBN 3-540-16140.

Vu, C.V.,  L.H.  Allen,  and L.A. Garrard.  1982.  Effects  of  supplemental UV-B
     radiation on  primary  photosynthetic carboxylating  enzymes and  soluble
     proteins in leaves of C^ and  Cjj crop plants.  Physiol. Plant. 55:11-16.

Vu, C.V., L.H. Allen, and L.A.  Garrard.  1984.   Effects of enhanced UV-B radia-
     tion  (280-320  nm) on ribulose-1,  5-bisphosphate carboxylase in  pea and
     soybean.  Environ. Exp.  Bot.  24:131-43.

Wellmann, E.  1982.   Phenylpropanoid pigment synthesis  and growth reduction as
     adaptive reactions  to  increased  UV-B radiation.   In: Biological  effects
     of  UV-B  radiation,  eds. H. Bauer, M.M.  Caldwell,  M. Tevini,  and R.C.
     Worrest,   BPT-Bericht  5/82.    Gesellschaft  fur Strahlen-  und  Umweltfor-
     schung, mbH, Munchen.

Wellmann, E.  1984.   Regulation der  Flavonoid-biosynthese  durch ultraviolettes
     Licht  und  Phytochrom   in  Zellkulturen   und  Keimlingen  von  Petersilie
     (Petroselinum hortense Hoffm.). Ber.  Dtsch.  Bot. Ges. 87:267-73.
                                      276

-------
MISCELLANEOUS

-------
An Assessment of UV-B Radiation Effects on Polymer
Materials:  A Technical and  Economic Study
Anthony L Andrady
Research Triangle Institute
Research Triangle Park, North Carolina USA

Robert L Horst, Jr.
Mathtech, Inc.
Princeton, New JerseYUSA
INTRODUCTION

     In March  1986,  the  U.S.  Environmental Protection Agency sponsored a
workshop to review the results of several analyses that predicted inpreases  in
future  emissions  of  chlorofluorocarbons  (CFCs)  and  possible depletion  of
stratospheric  ozone.    One  direct result of  ozone  depletion  would  be  an
increase in the  level of UV-B  radiation  reaching the  earth's surface.    In
turn,  the  increase  in  UV-B  radiation would lead to  accelerated damage  in
several effects categories, including polymer materials.  This paper addresses
both technical and economic issues related  to damage to plastics brought about
by hypothesized increases in UV-B radiation.

     Plastics are  increasingly used outdoors where they  are routinely exposed
to sunlight.  Exposure to light of certain  wavelengths  results in a variety  of
chemical reactions  in  most  commonly  used  plastics,   leading to  increased
deterioration  of  useful  physical  and mechanical properties and  therefore
shortening  the useful lifetime of the  plastic.   The most potent region of the
solar  spectrum in  this regard  is  the UV-B region.    The  longer  wavelength
ultraviolet  light  (UV-A) may also  contribute to the degradation  of  plastics
exposed to  light.   The shorter wavelength  (<300 nm) ultraviolet radiation,  if
it were present  in  sunlight  to any  significant extent,  would result in rapid,
extensive degradation of polymeric material.

     On a volume  basis only  a few classes  of plastics  are used outdoors or  in
situations  where   they  are   exposed  to  diffused and reflected  sunlight
(Anonymous  1986).   These are shown in  Table 1 with some examples of typical
products.   Polyvinylchloride  (PVC)  is Jthe most widely used plastic  in the
residential building industry.  It is used  in siding, window frames, rainwater
 1  Protecting the Ozone Layer:   Workshop  on  Demand and Control Technologies,
  Workshop Sponsored by the U.S. Environmental Protection  Agency.


                                   279

-------
goods,  pipes,  and  flexible sheeting.    Polyolefins,  reinforced  polyesters,
acrylics, and polycarbonates are also used outdoors in significant quantities.

     The same polymer is often  compounded  differently  to  yield materials best
suited  for  specific applications.   The  various  additives  (fillers,  plasti-
cizers, heat stabilizers, lubricants) used in the  compound constitute a signi-
ficant fraction of the final plastic product  and  heavily  influence its photo-
susceptibility.  Thus the light-sensitivity and the  nature  of damage suffered
by plastics  exposed  to  light are determined  not  only by the  type of polymer
but also by the compound composition (Weiler 1984; Ho 1984).

                       Table 1.   Plastics Used Outdoors
            Plastic Class
        Typical Use
  1.  Polyvinylchloride rigid
      [PVC]

  2.  Polyvinylchloride
      plasticized [PVC]

  3.  Polyolefins [PE/PP]
      (polyethylene, poly-
      propylene )

  4.  Polyester (thermoset)
      [UPE]

  5.  Polycarbonates [PC]
Siding, window frame, pipes, and
conduits

Roofing membrane, wire/cable
coating, hose

Packaging, agricultural film,
stadium and outdoor furniture
Panels/siding, tanks and pipes,
glazing

Glazing
     A given polymer  product  used outdoors may suffer  damages or undesirable
changes in its properties.  The rate at which such damage occurs is determined
by the kinetics of the reactions responsible for the change.  Consequently, it
is possible to identify a sequence  of progressive damage events where several
desirable  characteristics are in  turn deteriorated below  acceptable levels.
The most rapidly occurring damage determines  the  lifetime of the product, and
is  termed  the "critical  mode of  damage" (CMD).   Table 2 gives the  CMD of
several important classes of polymers used outdoors under current spectral and
climatological conditions.

     Polyvinylchloride  compounded   specifically  for siding or  window  frames
illustrates  the  effects  of  UV-B   radiation  on polymers  used  outdoors.  The
choice of  PVC for  the purpose of  illustration is appropriate  because it is
used in building  applications more  than any other plastic and because of the
                                      280

-------
        Table 2.   Modes of Damage Experienced by Polymers Used Outdoors
   Polymer
      Application
       Damage
   PVC
(a) siding, window frames
   UPE
   PE/PP
   PC
                  (b) roofing materials
outdoor surfaces
paneling
irrigation pipe,
outdoor furniture
synthetic turf, stadium
seats, packaging

glazing material
   [yellowing]
 + chalking
 - impact properties
 - tensile properties
 •+• surface distortion

[+ brittleness]
[+ discoloration]

[+ surface erosion]
 + discoloration
 - strength

[+ brittleness]
 - tensile properties
 - electrical properties
[ + yellowing]
 - transparency
     +  = increase
     -  = decrease
     [] = Brackets indicate critical mode of damage (CMD)
availability of  at least a  limited amount of  relevant research data  on the
polymer.  A typical rigid PVC composition for outdoor use is stabilized solely
by W% to  13* parts by weight  of titanium dioxide pigment (Titow, 1984).  The
pigment particles shield  the plastic matrix below it from light-induced degra-
dation.   On exposure  to light,  the rigid  PVC, originally  white  in  color,
suffers  both  yellowing  and  partial  photobleaching.   The subsequent  uneven
discoloration is the critical  mode damage for rigid  PVC  in applications such
as siding and window frames.

     In the next section we review  technical  issues  that  arise in an analysis
of the effects of increased  UV light on  plastics.  The principal output of the
technical analyses is a damage equation  which relates a measure of the CMD to
the amount of titanium dioxide stabilizer used  in  the PVC resin compound.  We
then integrate this damage equation into a supply and  demand  analysis  of the
PVC market  to  obtain estimates  of the  potential  economic damage that would
result from the hypothesized  depletion in ozone.   We summarize  our conclusions
in the final section.
                                     281

-------
EFFECT OF INCREASED UV LIGHT ON PLASTICS USED OUTDOORS2

CIAP Approach

     The  Climatic  Impact  Assessment  Program  (CIAP)   (Shultz,  Gordon,  and
Hawkins  1975)  study  employed the Beer-Lambert equation  to calculate approxi-
mate increases in  UV-absorbing  stabilizers required to  offset  the  effects of
increased UV light.  While the approach is sound and simple to use,  its appli-
cability is limited to the transparent, homogeneous polymers.  With the excep-
tion of  window glazing,  polymers used  outdoors  are generally  opaque and are
often stabilized using light screeners. Therefore, a parallel  model based on
light-screening stabilization,  applicable to opaque materials,  was developed
in the course of the study.

     Both equations require  the use of an empirical constant that  depends on
polymer and  stabilizer  for  its use.   The equations developed  for  each model
are shown in Table 3.

          Table 3.  Models for Prediction of Stabilizer Requirements
  Transparent  Polymeric  Materials

  CIAP  equation based on Beer
  Lambert  Law
  Opaque Polymeric Materials

  Equation derived in present
  study
  UV-absorption is the main mode
  of stabilization

  Log (fy/I0) = cC-t

  C = concentration of absorber

  e = extinction coefficient

  x = factor increase in light
      intensity
  y = factor increase in stabilizer
      concentration to offset the
      effects of increased light.

  Log x = (y-1)-eC/

  Requires (eCj£) for predictive
  use
UV-screening is the main mode
of stabilization

Log (l£/I0) = //2r3 log(1-3V/2)

V = Volume fract-ion of screener

rj = area-average radius of
     screen particle
Log x - //2r3{(1-3V/2)/(1-3Vy/2»
Requires
use
                 for predictive
   A  more detailed  description of  the  technical  analysis  is available  in
   Andrady, A.L. 1986.   An analysis  of technical issues related to the effect
   of  UV-B on  polymers.   Draft  report  submitted  to the  U.S.  Environmental
   Protection Agency.
                                      282

-------
     Both approaches suffer from  the  same  drawbacks.   First,  they do not take
into account  the spectral sensitivity of  the degradation process  (i.e.,  the
action  spectra).   Second,  they  do  not take  into account the  dose-response
relationship for photo-induced deterioration.  Finally,  they  do  not take into
account  the possible  nonlinearity of  effectiveness  of stabilizers at  dif-
ferent  concentrations.   In spite of these  serious shortcomings,  the  method
yields  approximate  estimates of  the increased  stabilizer requirements at  a
given increased light level.

Comprehensive Approach

     The extent  (and even the nature) of damage  suffered by  a polymer exposed
to sunlight depends  on wavelength.   Since any possible deterioration  of  the
ozone layer  will cause significant  changes  in  the spectral  distribution  of
sunlight, both  the  altered sunlight  spectrum and  the action spectrum  for  a
given mode of damage is required  to estimate the effect of ozone depletion on
material deterioration.   The  terrestrial  solar   spectrum has an   irradiance
H(x) and is altered by a function A(x)      caused by  ozone  depletion.   The
altered  spectrum H(X)A(X)  weighted  by the  appropriate   action   spectrum
F(x) will yield  an estimate of  the damage  at the wavelength X.  Provided that
the damage is additive and is  a linear function of available light energy,  the
following integral gives the total damage (Cutchis 1984).

                    Total  damage D  =   J*  H(X)A(x)F(X) dx
                                        n

     The integral might be  evaluated numerically  with  A(X) = 1  to represent
current baseline conditions.   Using the absorption spectrum of ozone,  A(X) at
various levels of ozone depletion might be   obtained.  However, the  lack of a
suitable  action  spectrum  (i.e.,  one  relating  to  properly  compounded  PVC
containing appropriate quantities of  titanium dioxide)  limits the usefulness
of the  approach.  The  only  action spectra available  in the  literature  relate
to  transparent  PVC  films  and  to  types   of damage other  than  yellowing.
However, a  very  approximate  estimate might  be made using the action spectra
for  polyene  formation  based  on  Reinische,   Gloria,   and   Wilson  (1966).
Yellowing  in   PVC is  a  direct  result  of  the  generation  of  long  polyene
sequences.  The  ratio of integral  D1 calculated  for  a given level  of ozone
depletion to  that at zero ozone  depletion,  D,  is  a measure  of  the expected
increase in damage.   Typical values are shown in Table 4.

     The  question of  how  much  stabilizer  should  be  used   to  counter  the
increased yellowing damage is  more difficult to estimate.  The main difficulty
is that  the data on  stabilizer efficiency with  respect to unaltered sunlight
conditions  cannot be  reliably  extrapolated  to stabilization under high  UV
light conditions.  Stabilizer  effectiveness  of titanium  dioxide  in rigid  PVC
was  reported   by Summers  (1983)  for weathering   under Arizona  conditions.
Assuming  that  the dependence  of stabilization  effectiveness  on  the pigment
concentration as  reported by  Summers  is  applicable under  high UV conditions,
approximate  ranges  for  increased  pigment  levels  required  to  maintain  the
light-resistance of PVC might be  calculated.   The  data on yellowing damage at
the  various  pigment  levels   reported  are  consistent  with the  following
relationship.
                                     283

-------
       Table 4.   Estimated Ranges of Factor Increase in Damage and the
                 Factor Increase in Stabilizer Needed to Counter the
                 Change for Yellowing of Rigid PVC Compositions
Zenith Angle 30° Zenith Angle 60°
Percent Loss
of Ozone
D'/D S'/S D'/D S'/S
0-5 '1.01 1.01-1.02 1.01-1.02 1.01-1
5-10 1.01-1.02 1.01-1.05 1.03-1.04- 1.03-1
10-20 1.02-1.05 1.03-1.11 1.04-1.09 1.05-1
20-30 1.03-1-08 1.03-1.18 1.07-1.18 1.08-1


.05
.09
.20
.38
Note:  D'/D = factor increase in damage
       S'/S = factor increase in titanium dioxide stabilizer

       Zenith angles selected to reflect North American locations.
                       Log  [Damage]  =  -[pigment] k + a

     Since acceptable levels of damage (D*) obtained at the current use levels
of  pigment   (S*)   are  known,   the  factor  increase  in   pigment  (S'/S*)
corresponding to a  given  factor increase in damage  (D'/D*)  can be calculated
using known values of k.   The results are shown in Table 4.

     The  estimates  could be  improved considerably  by using  action spectra,
dose-response  information,  and stabilizer  effectiveness  information  for the
particular polymer/pigment system of interest.   Efforts to obtain some of the
relevant data are currently underway.

     The  use  of increased amounts of titanium dioxide  pigment poses several
difficulties.   These  include  increased melt  viscosity and  therefore higher
power consumption, increased wear and tear on machinery, increased compounding
of  ingredients  to maintain  processibility  and  the  other mechanical properties
of  material,  and  possible  increased  susceptibility  to  oxidation.    Thus,
increasing the levels of titanium dioxide is a limited solution which will not
necessarily be cost-effective beyond a certain level of increased UV light.
                                      284

-------
ECONOMIC DAMAGES TO PVC PRODUCTS3

Methodology

     Economic benefits are  generated whenever a transaction  such  as the sale
of a good or service takes place.  Economists generally agree that any attempt
to measure these benefits should  be  based on an individual's own valuation of
the transaction, demonstrated by their "willingness-to-pay11  to  engage in the
transaction  (Just,  Hueth,  and  Schmitz  1982).    Willingness-to-pay can  be
inferred  from  the market  demand  curve.    In  particular, since  the marginal
purchaser (i.e., the purchaser who would not buy if the price were any higher)
is by  definition  willing to  pay  exactly the price  he pays  and  no more, the
area beneath the demand  curve up to  a  given quantity can be shown  to be the
appropriate  measure   of  total   willingness-to-pay.     This   situation  is
illustrated  in  Figure  1,  where  total  willingness-to-pay  is  given  by  area
abcqQo.

     In  benefit-cost  analysis willingness-to-pay  is frequently  the measured
net of any  charges paid  by consumers for  the  good or service.   When this is
done,   the result is  called net willingness-to-pay,  or more  often, consumers'
surplus.   The  consumers'  surplus measure  represents what consumers  would be
willing to pay over and above what  they do pay.  In Figure 1, if price is po,
consumer surplus is given by the triangular area acp0.

     Any  action or event that leads to a  change  in market  demand  or supply
will change the surplus measure.   In Figure  1,  if market price increases to p1
as a result of a depletion  in stratospheric ozone, consumers,' surplus will be
reduced by the area pibcpp.  This is the measure of welfare change reported in
this  case  study.    To  be  precise,  we  measure  the  willingness-to-pay  by
individuals to  remain  in the  initial situation (with price  p0)  and to avoid
the increased  costs associated  with ozone depletion.   These  costs,  if not
avoided,  represent a real economic loss to society since the costs limit other
productive opportunities in the economy.

     In  the  next  two  subsections we discuss  the data  and  methods  used  to
estimate  demand and  supply  curves  for  PVC products  used  in building  and
construction.  We  then compute economic damages under the assumption that the
producers of the PVC products will  alter  the resin formulation  as UV-B levels
increase  to maintain product  lifetime and  quality.   This change in the resin
compound increases  production costs and is the source of the measured surplus
change.  We note that  the measured  damages do  not include the increased costs
associated with early maintenance or replacement of in-place stock.
   Description of  the economic analysis  is  available in Horst,  R.L.,  et al.
   1986.    The  Economic  Impact  of  Increased  UV-B  Radiation  on  Polymer
   Materials:  A Case Study of rigid  PVC.  Report in preparation for the U.S.
   Environmental Protection Agency.


                                      285

-------
Price
per Unit
                                                      Long-Run Supply
                                                      (with ozone depletion)
                                                      Long-Run Supply
                                                      (without ozone depletion)
                                                            Quantity per
                                                            Unit of Time
     Figure  1.  Aggregate Demand and Supply  in the Market for PVC Products.


 Aggregate Demand

      A demand  equation  for PVC used in construction is estimated using annual
 data for 1970  to  1983.  The demand for PVC  is a derived demand; that  is,  it  is
 derived from a more general demand for construction activity.  The explanatory
 variables included  in  the  equation are the price of PVC, wood, and fabricated
 metal products, and the value  of  construction put in place.

      The results  of a two-stage least squares regression analysis are shown  in
 Table 5.   The explanatory variables are  statistically different from zero  at
 standard levels  of significance.   The signs  of the coefficients agree with a
 priori  expectations.    Since  the  specification  is  double-logarithmic, the
 coefficients are  interpreted  as elasticities.  Thus, the own-price elasticity
 of demand  for  PVC is -1.95.   This is elastic, which  would  be expected  for a
 product with good substitutes.

      The equation shown in Table 5 represents  current preferences.   However,
 the case  study requires that welfare impacts be evaluated  to the year  2075.
 Consequently,  PVC consumption must be forecast over  time.   The approach used
 to obtain future  values of PVC consumption  is based on the assumption that the
                                       286

-------
      Table 5.   Derived Demand for  PVC  Used  in  Building and  Construction*
Variable**
Intercept
LPVCHAT
LPMET
LPVOOD
LCON
Parameter
Estimate
-5.396
-1 .956
2.288
0.740
1.343
Standard
Error
4.
0.
0.
0.
0.
160
316
423
367
635
t-Statistic
-1 .297
-6.190
5.406
2.018
2.115
         Observations:   14

   Dependent Variable:   LQPVC

          Adjusted R2:   0.9573

      Durbin-Watson D:   1.872

          F-Statistic:   73.817
*   The equation  is estimated  using the  REG procedure  in  the SAS  software
    package.

**  Variable names are:  LPVCHAT is the  fitted value of the natural log of PVC
    price; LPMET is the natural  log of the price of fabricated metal products;
    LPWOOD  is  the  natural log of  the price  of soft lumber products;  LCON is
    the natural log  of the index  of construction activity;  and LQPVC  is the
    natural log of the quantity  of PVC used in building and construction.
                                     287

-------
demand   curve   estimated  with   historical  data   also  represents   future
preferences.  Therefore, given forecasts for each of the independent variables
in  the  demand equation,  a forecast  of the dependent  variable (PVC)  can be
made.  Forecasts  of each independent variable in a  future year are 'estimated
using a  combination of time  trend  models and autoregressive  models (Pindyck
and  Rubinfeld  1976).   Table  6  reports the 50%  prediction  interval  for  PVC
demand in selected  future years.  For the mid-range  forecast,  the projections
are consistent with about a 2% annual rate of growth in PVC demand.

Aggregate Supply

     The supply  side of  the  market  for  PVC  products used  in building  and
construction is  determined through  a  model  plant  analysis.   Representative
plants are  constructed  for each of  the three PVC products  considered in  the
case  study:   pipe  and  conduit,  siding,  and window profiles.   Data  for  the
model plant analysis  were  obtained  from the literature and  through conversa-
tions with PVC fabricators, PVC compounders, PVC resin  producers, and extruder
manufacturers  (Perry 1977).

     The data collected for the model plant analysis reflect operating charac-
teristics for a single  level  of  output.  If a supply curve for the PVC market
is  to be estimated econometrically, a significant amount  of other  data is
required.   For  example, resource costs, administrative costs,  and production
methods may be expected to change as output levels vary.  Unfortunately, there
is insufficient data available in published statistics  to develop the detailed
information  that  would  permit a  formal  econometric  analysis  of production
costs.  Furthermore, it is unlikely that an econometric analysis would be able
to  pick  up any  variations in production costs caused  by  variations  in  the
amount of titanium dioxide used in the resin compound.

     As  an  alternative to  the  econometric approach,  we  used a  less formal
method.   For each  of  the model plants  we assumed that  the  market  for  PVC
products used in  building  and construction is perfectly  competitive and that
the output level associated with model  plant operation is consistent with the
economic conditions  for profit maximization.  We also  assumed that each firm
(model plant) is in long-run equilibrium, which implies that equilibrium price
and  quantity are  associated  with the minimum of the  firms'  long-run average
cost curves.  Finally,  we assumed that  the industry  for each of the three PVC
products is characterized by constant costs.  This assumption implies that the
long-run supply curve for each  industry will be horizontal.   In  turn, under
these conditions, price equals long-run average  cost and  also  equals long-run
marginal cost.   Consequently,  the supply curve for the  PVC products market can
be  determined from  knowledge  of total  production costs and output, which is
the  information provided by the model plant analysis.

     The average  costs  ($/lb) of production (inclusive of normal  profit)  are
estimated  to be  $0.52,  $0.75,  and  $1.02  for  pipe,   siding,  and profiles,
respectively.   An  aggregate  price  index  for  these  three products is calcu-
lated as a weighted average of  each  market price.   The weights are based on
the  volume  of output in each market.   The price  index is $0.604 and is nomi-
nally  representative  of  market conditions  in  1984.    As  the  production
processes change to offset the damage caused by increased UV-B  radiation, the
                                      288

-------
          Table 6.  Fifty Percent Prediction Interval for PVC Demand
                    (millions of pounds)

Year
1980
2000
2025
2050
2075
Lower
Estimate

2,440
3,874
6,071
8,910
Point
Estimate
2,198
3,397
6,316
11 ,303
18,563
Upper
Estimate

4,729
10,298
21 ,048
38,671
average  cost of  production will  increase.   This  increase will  lead  to a
corresponding increase  in  the  aggregate price index  for  the PVC products and
is the source of the economic damages estimated for the case study.

Economic Damage Calculations

     A hypothesis of the case study is that producers of the PVC products will
change the  amount of titanium dioxide  in the resin  compound  to maintain the
and lifetime and  quality  of their products.   The change  in compound formula-
tion will affect production costs in several ways.  First, resource costs will
be increased as more titanium dioxide is used per pound  of plastic produced.
In addition,  it  is believed that  the change  in  the  formulation will require
more energy  to  produce and will  lead to more frequent replacement of screws
and barrels.   For  the three model  plants developed  for the  case study,  an
estimated 25% increase  in  titanium dioxide  concentrations in the compound are
expected  to  lead to  price increases of  2.67/1,  1.67?, and  1.73/t  for siding,
profiles, and  pipe,  respectively.    The  aggregate price index  increases  by
1.86?.  Since a 25% increase in titanium dioxide is believed to be  the maximum
increase  that could  be  tolerated without  adversely affecting other attributes
of the PVC products, the 1.86? price increase is the maximum price  effect that
would be observed.

     Table  4,  shown  earlier,  describes  the relationship between  physical
damage to PVC  products and ozone  depletion.   Table 7 shows the scenario for
ozone depletion assumed for this study.   For a given level of ozone depletion,
the  factor   increase  in  titanium  dioxide  stabilizer is  computed by  linear
interpolation.  The cost increase associated with the interpolated  estimate of
titanium  dioxide  concentration  is  proportional to  the cost increase computed
for the model plant analysis.
                                      289

-------
                     Table 7.  Ozone Depletion Estimates

Year
1985
1995
2005
2015
2025
2035
2045
2055
2065
2075
Ozone Depletion
(percent)
0.00
0.15
0.62
1.50
2.84
4.66
7.08
10.41
15-44
26.08
Source:  EPA estimates.
     Forecast values of  the  price index of PVC  products  used in building and
construction are computed for each year s from the equation:

             P1s = r1s(1  * C1s>Pls * r2s<1 + C2s)(p1a(p2o/Pio» +

                         r3s(1 + C3s>  (Pls(P30  /  P10»

   where Pig is an aggregate price index for PVC at time s, with ozone
        depletion

        pig is the price of the ith PVC product at time s

        C*s is the percent increase in costs for product i associated
        with a given level of ozone depletion in year s.

        rig is the ratio of output in year s for the ith good to total
        output for PVC in building and construction.

     The  calculation  of  future  PVC  prices  with  ozone  depletion  requires
several assumptions.   First, we  assumed  that  the mix of  PVC products is not
affected by  ozone  depletion.  Second, we assumed  that the relative prices of
the  three  PVC products  remain  unchanged over  time.   Third,  we assumed that
each firm  produces the same level of output in  each year.  This last assump-
tion implies that  increases  in PVC  consumption over time are met by increases
in the number of firms in the industry.

     The  change  in  economic welfare associated  with   ozone  depletion  is
computed as  the area  under  the  aggregate demand  curve between  prices PQ and
P^.  For the double-logarithmic demand curve, this can be written as:
                                      290

-------
                                        r   0  b1
                              Aw  = A   J      P   dP
                                s    s  J   P
                                            1

where Ag  is a  terra  involving all  arguments of  the  demand curve  except the
price or  PVC and  its  coefficient.   AS varies  over  time,  since each  of the
explanatory variables in the demand equation varies over time.

     Table 8 summarizes  the  discounted value of damage with several discount
rates.   The  discounted  present  value  calculation  is  a  convenient way  to
express values  that occur  over many  time periods.   The  discounted present
value, as of the current year, is defined as follows:
                          DPV  =    z
                                  i =  0
where
           is the welfare change in year i,  and r is the discount rate.
            Table 8.  PVC Damage Associated with Ozone Depletion
                      (Discounted Present Value in Millions of 1984 Dollars)


Low estimate of
Middle estimate
High estimate of


PVC consumption
of PVC consumption
PVC consumption

0
$2,4-40
4,716
9,158
Discount
2
$ 603
1 ,137
2,159
Rate (*)
5
$ 97
174
315

10
$10
17
27
     The  choice of  an  appropriate  discount  rate   is  especially  difficult
because of the extended time horizon for this analysis.   If a real rate of 10*
is assumed, the preferences of future generations  (those actually affected by
the ozone  depletion)  are assigned  little importance.  On the other  hand,  a
discount rate of 0* implies that the preferences of  future generations are to
be given  the  same  weight as the preferences of the current generation.   The
literature provides no clear-cut answer to this dilemma (Lind  1982).   There-
fore,  present values are presented  for several discount  rates.
                                     291

-------
     The results shown in Table 8 apply to the following set of circumstances:

     •  All estimates are reported in millions of 1984 dollars

     •  The factor increase in titanium dioxide concentrations is computed for
        a zenith angle of 60°

     •  Firms do  not respond  to  the hypothesized decreases  in  stratospheric
        ozone until 10 years after the impact is observed.

Additional  research   is  planned  to assess  the  sensitivity  of the  results
reported in Table 7 to alternative assumptions.

CONCLUSIONS

     The conclusions of this case study of PVC damage related to increased UV-
B radiation can be summarized as follows:

     •  An approximate damage  function can be  developed which relates changes
        ozone to changes  in  stabilizer required  to maintain product lifetimes
        at present levels.

     •  The  damage  function can  be improved  by  using action spectra,  dose-
        response information, and stabilizer effectiveness information for the
        polymer/pigment system of interest.

     •  For a given  scenario of ozone depletion, it  is estimated that undis-
        counted, cumulative economic damages are $4.7 billion in 1984 dollars.

     •  A  50%  prediction interval,  which accounts for only  a portion of the
        uncertainty present  in the  analysis,  indicates that the undiscounted,
        accumulated  economic damages could  range from $2.4 billion  to $9.2
        billion.
REFERENCES

Andrady, A.L.  1986.  An Analysis  of Technical  Issues Related to the Effect of
     UV-B  on  Polymers.   Draft  report  submitted  to  the U.S.  Environmental
     Protection Agency.

Anonymous.   1986.  Modern Plastics.  63(1):69.

Ho, B.Y.K. 1984. J. Vinyl Technol. 6(4):162.

Horst, R.L., et al.  1986.   The  Economic Impact of Increased UV-B Radiation on
     Polymer Materials;  A Case Study of Rigid PVC.  Report in preparation for
     the U.S. Environmental Protection Agency.

Just, R.E.,  D.L.  Hueth,  and A.  Schmitz.  1982.   Applied Welfare Economics and
     Public  Policy.  Englewood Cliffs, New Jersey: Prentice Hall, Inc.
                                      292

-------
Lind, R.C.,  et al.  1982.   Discounting  for Time  and  Risk  in  Energy Policy.
     Washington, DC: Resources for the Future.

Perry, N.L.  1977.   General principles of plant  operation:   Operating a plant
     for  profit.    In Encyclopedia  of  PVC.  Volume  3-,  ed.  L.I. Mass.  New
     York:  Marcell Dekker, Inc.

Pindyck,  R.S.,  and  D.L.   Rubinfeld.  1976   Econometric  Models and  Economic
     Forecasts.  New York:  McGraw Hill.

Reinisch  R.F.,   H.R. Gloria, and  D.E.  Wilson.  1966.   ACS  Polymer Preprints.
     7(1):372.

Shultz,  A.R., D.A. Gordon, and  W.L.  Hawkins.   1975.   CIAP Monograph 6, 3-239.
     Cutchis, P.  April 1984.   Science.

Summers J. 1983. J. Vinyl Technol.  5(2):43.

Titow, W.V.  1984.   PVC Technology.  New York:   Elsevier  Applied Science Pub-.
     lishers.

Weiler,  R.G. 1984. J. Vinyl Technol.  6(4):152.
                                     293

-------
The Interaction of Photochemical Processes
in the Stratosphere and Troposphere

Gary Z. Whitten and Michael W. Gery
Systems Applications, Inc.
San Rafael, California USA
     Recent  evidence  of a  dramatic  decrease in stratospheric ozone levels
(Farman,   Gardiner, and Shanklin 1985), which may be related to the  continued
use of halocarbons (Cicerone,  Walters, and Liu 1983; Craig and Chow  1982) and
an increase  in methane  (Craig and Chow 1982) and ^0 (Weiss 1981) emissions,
could forebode  a concurrent increase  in the  transmission of solar ultraviolet
radiation  to the troposphere.   In combination with  a general warming of the
lower atmosphere  through  the  effect  of greenhouse  gases and other  climatic
perturbations  (Wang et al.  1986), a greater transmission of ultraviolet radia-
tion will  augment  the principal energy sources  of photochemical reactions in
the troposphere and  may also lead to  an  increase  in  the  incidence of skin
cancer.    To  date,  the enhancement  of specific chemical reaction  rates has
largely  been  ignored in  tropospheric modeling  studies.   In this  paper,  we
describe an  investigation  of the effect of changes in tropospheric temperature
and the transmission  qualities  of the upper atmosphere on  incident radiant
energy using data obtained from  atmospheric and laboratory  measurements to
estimate  future conditions  and  corresponding changes in  tropospheric photo-
chemistry .

     Because  ozone has  a  strong  ultraviolet  absorption  band  that extends to
approximately 3^0 nm (Inn  and Tanaka 1953), the presence of ozone in  the upper
atmosphere limits  the  transmission  of ultraviolet  radiation to the earth's
surface.   A  reduction  in  stratospheric  ozone  would,  therefore,  allow more
radiation  to  penetrate  into  the troposphere,   primarily  in the wavelength
region between 290 and  320  nm  (Bahe  et al.  1979).   An  increase in  radiation
within this  region will enhance the photolysis rates of important tropospheric
photochemical  reactions,  most  significantly, the  radical-forming photolytic
reactions  of ozone,  formaldehyde, and  other aldehydes  (National Aeronautics
and Space  Administration  1985).   The  free radicals  from these   reactions
initiate and  propogate oxidation  of organic  compounds and result in  continued
radical  production.   Such radical chain reactions  tend  to  promote the forma-
tion of photochemical smog (Whitten  n.d.) and  produce  the  oxidized species
critical to  the formation  of acidic precipitation (Calvert et al.  1985).


                                    295

-------
     The photolysis  of ozone  to oxygen  molecules and  0(^D)  atoms  has  been
shown to be energetically feasible below 310 nm and inversely dependent on the
density of the  atmospheric  ozone column (Bahe et  al.  1983).   This photolytic
process is  very important  in  the troposphere  because the rapid  reaction of
0( D) with water is a primary  source  of tropospheric  hydroxyl  radicals during
daylight hours  (Crutzen and Fishman 1977).   These  radicals react rapidly with
virtually all gaseous  species  in the atmosphere  (Logan  et al. n.d.).   The J
values for photolytic processes  (the  apparent  first-order  rate constants) are
defined as J = / o  I  dX,  where (for  ozone photolysis to 0('D)).
                  A A A
    o  = the ozone absorption cross-section (Bass 1985)
     A
    <|>  = the quantum yield of the 0(1D)  formation process (National
         Aeronautics and Space Administration 1985)

    I  = the surface solar irradiance.
     A
     This integral  is  evaluated over all  wavelength  intervals  for  which the
product o<|>I is  nonzero.   When  plotted  for all  significant wavelengths  of a
given spectral  distribution, the resulting curve is known  as  the photoaction
spectrum,  and the area  under the curve represents the J value for those condi-
tions.  Figure  1 shows  the  photoaction  spectrum  for ozone-to-0(^D) photolysis
derived from the surface solar  data (collected at  300 Dobson1) of Bahe et al.
(1983).  Also shown  is the photoaction curve at 200  Dobson, which was extra-
plated  from  the  measured  300  Dobson   solar  data using  lower  resolution,
computer-generated 200 Dobson  data.   The difference in  area under the photo-
action spectra occurs primarily  on the  shorter wavelength  side because with a
200 Dobson ozone column, additional light  is available in  this photolytically
more efficient  region.   The difference  in rate constants  calculated by inte-
gration of the two curves is nearly a  factor of two greater at 200 Dobson over
the entire range of solar zenith angles.

     Formaldehyde  is  also  an   important  species   in  tropospheric  chemistry
because it  is eventually an  oxidation  product  of almost  all  organic gases.
The most significant chemical  reaction  is  the photolysis  of  formaldehyde to
radical products.   J values similar to those  for  ozone  were calculated using
the  formaldehyde  absorption cross  sections of  the U.S.  National  Bureau of
Standards (Bass 1985)  and  the  quantum yield data  summarized by  Baulch et al.
(1984).  These data indicate that 200  Dobson J values should increase by about
20% over the  300  Dobson values  for the range of possible  zenith angles.   The
current quantum yield  data  for both formaldehyde  and  ozone photolysis appear
to produce  a smooth curve.    However,  these data  do  not  have  the necessary
spectral resolution  or  accuracy to verify  such as assumption.   In addition,
few high-resolution surface solar spectra  exist, and  those that do are poorly
defined with  respect to ozone  column  density and  solar  elevation.  This lack
of resolution limits the  precision of the J value calculations and indicates
an important area for future research.
   The Dobson unit of measure is the height (in 10 cubic centimeters) that all
   ozone  molecules  above the  earth's  surface  would  attain  if  all  those
   molecules existed as pure ozone at standard temperature and pressure.
                                     296

-------
0)

°*J
a

-------
     The changes in ultraviolet radiation that could result from stratospheric
ozone  depletion  are  unique  because  they  involve  specific  increases  in  the
short wavelength region  of the surface solar  spectrum  only.   Therefore, such
changes will cause  significant increases in the  photolysis  rates  of only the
few  species  that absorb in  the  enhanced  region,  e.g.,  the  radical-forming
photolysis reactions  of  formaldehyde and ozone.  Because  these reactions are
major  sources  of new gas-phase  radicals,  the  selective  increases  in those
rates will increase the flux in the free radical reaction cycles, resulting in
more reactive  photochemical  conditions in  both the free  troposphere and the
planetary boundary layer.  Because hydroxyl radicals provide the dominant sink
for  a  variety  of  atmospheric compounds   (including  CO,  CFty,  CoHg,  CHqCl,
C4qCClo,  ChoBr,  I^S,  and  SOg) (Logan et  al.  n.d.),  accurate  estimation  of
hyaroxyl radical concentrations is  essential to  the study of  future chemical
balance and climatic conditions.  Although increased levels of CO and Cfty will
act  to  suppress hydroxyl  radical  formation,  enhanced  photolytic  production
combined with potentially higher levels of ozone, will counteract this effect.

     An  increased  hydroxyl  radical  production  rate  may  also diminish  the
concentrations of some species responsible  for stratospheric ozone depletion,
thereby  providing  a  feedback mechanism   analogous  to chemical  buffering.
However,   the magnitude  of such  a  contribution  from  increased  formaldehyde
photolysis  is  uncertain  because  the  formaldehyde mixing  ratio  is  not  as
clearly  defined  as  that of  ozone.   Figure  2 illustrates the  formaldehyde
absorption cross section and  surface  solar spectrum for  the  region in which
the  photoaction spectrum shows significant  formation  of radical products from
formaldehyde photolysis.   A correspondence exists between the absorption peaks
of  formaldehyde  and  the depressions  in measured  surface  solar  irradiance.
This correspondence  indicates  that  bin sizes on  the order of  0.25  to 0.50 nm
may  be  required  to   accurately  determine  formaldehyde  J  values   near  the
surface.    Formaldehyde in  the free troposphere could add  to this requirement
by additional modification of  the surface  irradiance  within  the corresponding
bands.    This  phenomenon should  be verified with  additional  high-resolution
surface solar data.

     The effects of  projected  spectral changes on near-surface photochemistry
will vary depending on the characteristics of each airshed.  Airsheds affected
by urban emissions have been extensively studied because such emissions signi-
ficantly  increase  their concentrations and types  of  trace  gases  and their
potential  for  photochemical  smog formation.   Since the  pioneering  work  of
Haagen-Smit (1952),  scientists have known that the oxidizing potential of such
air  masses depends  primarily  on  the  concentrations of  nitrogen  oxides (NOX)
and  organic  hydrocarbons,  as  well  as on the  amount  of radiant energy.   The
impact of variations in ozone column densities and surface temperatures on the
chemistry of near-surface air masses can be examined through the use of atmos-
pheric simulation models.   Because  the chemistry of urban smog formation has
   The urban simulation model used  in  this work is the OZIPP trajectory model
   developed for  the U.S.  Environmental  Protection Agency  (Hogo  and Whitten
   1985).   This model uses meteorological data to describe  the motion of an
   air mass  traveling over urban emission sources to the point at which the
   highest  hourly ozone  concentration  was  observed  on  the day simulated.
   Local emission data and a complex gas-phase chemical kinetics mechanism are
   used to describe the chemical processes within the air mass.


                                     298

-------
                                                                            1200
                       Formaldehyde Absorption Cross Section
                       Surface Solar Irradionce (300 Dobson)
                                  310
                            Wavelength (nm)
Figure  2.  Matched High-resolution  for Formaldehyde Absorption
            Spectra and Measured Surfaced Solar  Irradiation.
                                  299

-------
been extensively  studied and  many large  data  collection programs  have been
carried out, simulations  of the photochemistry of  this  condition are thought
to provide a realistic indication of potential impacts.

     These models  can also  be used  to  estimate the  chemical  sensitivity to
alterations in surface temperatures due  to potential changes in concentration
of greenhouse  gases.   Although  it is beyond the scope  of  this discussion to
consider the complex perturbations that may alter future surface temperatures,
the recent work of Ramanathan et  al.  (n.d.)  and  Wang et al. (1986) estimates
that these increases  will be  1°-3°C by  the year  2030.   In  the work described
next,  we bracketed this range by assuming a maximum surface temperature varia-
tion of 4°C.

     We calculated ozone and formaldehyde J values as a function of solar ele-
vation and ozone  column  density for three urban  areas using column densities
of 300, 250 and  200 Dobson and surface  temperatures of  298  K  and 302 K.  The
test data were selected from data sets for Nashville, Tennessee, Philadelphia,
Pennsylvania,  and  Los Angeles,  California.   The  meteorological conditions and
hydrocarbon and NOX emissions  in  these three  cities differ,  as do the maximum
ozone concentrations measured  in  the  late  afternoon on these days.  According
to the  U.S.  National Ambient  Air Quality Standard for  ozone,  air quality on
the Nashville  test  day   was  nearly  in  compliance  with the  standard.   The
Philadelphia test  day was selected to represent  urban conditions that require
moderate  reduction in hydrocarbon emissions to  achieve the  ozone standard.
The Los Angeles test day was selected to examine an extremely reactive region.

     Table 1 presents the results of one-day simulations of these ttiree test
cases for the Dobson number and temperatures selected.  The model consistently
predicted  higher  ozone   concentrations   with increases in  temperature  and
decreases in Dobson number.   For  the  Los Angeles case, the increases in ozone
production were moderate  and quite linear with decreasing  Dobson number.   In
the Nashville simulations, the increases were dramatic and the linearity was a
function  of  temperature:    At 298 K,   the  simulated urban  ozone  tended  to
increase linearly with a decrease  in Dobson number, but at the warmer tempera-
ture,  simulated ozone concentrations  increased more rapidly  for the first 50-
Dobson unit change than for the second.

     The Philadelphia test  was performed differently.   The  hydrocarbon emis-
sion data  for  the  original base-case simulation were lowered  to the values
needed to bring the predicted afternoon ozone maximum into compliance with the
federal law.   In  effect,  this scenario represented the condition  of future
compliance with federal law  for 300 Dobson and  298 K.  The effects of strato-
spheric ozone  and temperature  changes were  then simulated for  these condi-
tions.    The results  showed  a progressive  increase  in ozone  as  the Dobson
number declined.   In addition, the ozone production occurred much more rapidly
at lower Dobson numbers,  reaching levels near the final maximum concentration
earlier in the day.   This finding typifies  the  simulation  results.  Although
the future scenario conditions  resulted  in more  rapid production of ozone and
other oxidants earlier in the simulation period,  the  maximum  predicted ozone
concentrations did not reflect such  extreme  differences,  even  though lower
Dobson numbers and higher temperatures always resulted  in more ozone produc-
tion.    This  is because  ozone  production  later   in  the  day is  often limited
because of  exhausted hydrocarbon  or  NOX concentrations.   Because trajectory
models, such as the one used here, imply an equivalence in time and distance


                                      300

-------
   Table 1.  Ozone concentrations (ppm) predicted for changes in Dobson
             number and temperature for three cities.
      Temperature (K)
      Dobson  Number
300
                                      Ozone Concentrations
        298K
250
200
300
                          302K
250
200
         C1ty_
Los Angeles*
Philadelphia
Nashville
0.288
0.112
0.130
0.301
0.127
0.161
0.315
0.149
0.195
0.306
0.122
0.146
0.318
0.134
0.184
0.331
0.159
0.215
      * For Los  Angeles, values under 298 K used actual hourly temperatures
        and values under 302 K are from simulations using those temperatures
        Increased by 5 K.
from the urban center, a rapid occurrence of high ozone concentrations earlier
in the day, followed by continued moderate increases, implies that more people
will be  exposed to  episodic levels  of ozone.   Population density  is  often
greater nearer to the urban center, therefore, the number of people exposed to
episodic ozone  levels may increase dramatically  if future ozone  peaks  occur
earlier in the day.

     Our  investigation  of  the  key  reactions  involved  in  the  temperature
changes indicated  that peroxyacetyl nitrate  (PAN)  chemistry  explains most of
the effect  in these  cases;  that  is,  less  PAN exists at  higher temperatures
because its  unimolecular decomposition  rate is  temperature-dependent.   This
provides greater amounts of PAN decomposition  products  (NOX and  the organic
peroxyacetyl radical)  for use in oxidant-forming  reactions.   The effects of a
4  K increase  in  temperature  were most pronounced  in  the  Los  Angeles  and
Nashville tests.   The effects of  a combined temperature increase and reduced
Dobson number appear to be always additive,  if not synergistic,  especially for
the Nashville simulations.   When a 4  K temperature increase was combined with
only   a 50-unit  Dobson    reduction,  the    simulated   peak ozone  increased
almost
                                      301

-------
     Enhanced radical  flux in urban  airsheds  should not only  increase their
ozone-forming potential,  but  also  augment  the  production of  other oxidants
such as  hydrogen peroxide.   In  our  preliminary tests,  the  maximum hydrogen
peroxide produced for the Philadelphia and Los Angeles cases increased by over
an order of magnitude.  Additional  simulations designed to directly study the
effects of future  changes on hydrogen peroxide  formation should  be conducted
to verify the magnitude of the processes involved.   For the scenarios tested,
however,   both ozone  and   hydrogen  peroxide concentrations  increased  in  all
cases.
REFERENCES
Bane F.C., H.  Illner,  W.N.  Marx, U. Schurath, and  P.  Roth  1979.   Messung der
     von Veranderungen  der   Ozonschicht   stark  abhangigen	kurzwelligen
     Sonnenstrahlung.     Munich: Gesellschaft fur" Strahlen-und Umweltforschung
     mbH.

Bahe, F.C., W.N.  Marx,  W.  Schurath, and E. P. Roth.   1983.   Determination of
     the Absolute Photolysis Rate of Ozone by Sunlight
     03 + hv * 0(1D) -i- 02 (1Ag),  at Ground Level.  Bonn:  Institute  fur
     Physikalische Chemie der Universitat.

Bass, A.M. 1985. Personal communication Washington,  D.C.: U.S. National Bureau
     of Standards.

Baulch,  D.L.,  R.A.  Cox, R.F.  Hampson,  Jr.,  J.A.  Kerr,  J.  Troe, and  R.T.
     Watson.    1984.  Evaluated kinetic and photochemical data for atmospheric
     chemistry:  Supplement   II,  CODATA  Task  Group  on  Gas  Phase  Chemical
     Kinetics. J. Phys. Chem. Ref. Data. 13(4).

Calvert, J.G., A. Lazrus, G.L.  Kok,  B.C.  Heikes,  J.G.  Walega, J.  Lind, and C.
     A. Cantrell. 1985.  Chemical  mechanisms of acid generation in the tropos-
     phere. Nature.  317:27.

Cicerone, R.J., S. Walters,  and S.C. Liu.  1983. Nonlinear response of stratos-
     pheric ozone  column to chlorine  injections.  J.  Geophys. Res.  88:3647-
     3661.

Craig,  H., and C.C.  Chou. 1982. Geophys. Res.  Lett.  9:1221-1224.

Crutzen, P.J., and J. Fishman. 1977. Geophys.  Res. Lett.  4:321.

Farman, J.C.,  B.C. Gardiner, and J.D. Shanklin. 1985.  Nature. 315:207-210.

Haagen-Smit,  A.J. 1952.  Chemistry and physiology  of Los  Angeles smog.  Indust.
     Engineer. Chem. 44:1342-1346.

Hogo, H., and G.Z. Whitten.  1985.   Guidelines  for using  OZIPM-3 with CBM-X or
     optional mechanisms.  San Rafael, CA: Systems Applications, Inc.

Inn, E.C.Y.,  and Y.J.  Tanaka.  1983. Absorption  coefficient of ozone  in the
     ultraviolet and visible regions. J. Opt.  Soc. Amer.  43:870-873.


                                      302

-------
Logan,  J.A.,   M.J.  Prather,  S.C.  Wofsy,  and  M.B.  McElroy.    Tropospheric
     chemistry:  A global perspective J. Geophys. Res. 86:7210-7254.

National Aeronautics and  Space  Administration.  1985.   Chemical  kinetics and
     photochemical  data   for   use   in   stratospheric  modeling.   National
     Aeronautics and Space Administration: Evaluation Number 7.  Pasadena, CA:
     Jet Propulsion Laboratory,  California Institute of Technology.

Prather, M.J.,  M.B.  McElroy, and S.  C.  Wofsy. 1984.  Reductions  in  ozone at
     high concentrations of stratospheric halogens. Nature.  312:227-231.

Ramanathan, V.,  R.J.  Cicerone,  H.B.  Singh,  and J.T. Kiehl. Trace gas trends
     and their  potential  role  in  climate change.  J. Geophys. Res.  90:5547-
     5566.

Wang, W.C., D.J. Wuebbles, W.M. Washington,  R.G.  Isaacs,  and G.  Molnar. Trace
     gases  and  other  potential  perturbations  to  global   climate.  Rev,  of
     Geophysics.  24:110-140 (1986).

Weiss, R.F. 1981. J. Geophys. Res.  86:7185-7195.

Whitten, G.Z.  The chemistry of smog formation:  A review of  current knowledge.
     Environ.  Int. 9:447-463.
                                     303

-------
Tropospheric CH4/CO/NOX: The Next Fifty Years
Anne M. Thompson
Applied Research Corporation
NASA—Goddard Space Flight Center
Greenbelt, Maryland USA

Michael Kavanaugh
Consulting Economist
Washington, DC USA
ABSTRACT

     Previous  studies  with  photochemical models have emphasized the coupling
of atmospheric CHh-CO-OH-NOX.   Recent  increases in the concentration of atmos-
pheric methane (CHh.), for example,  could be caused by increases  in CHh sources
and/or  a  decrease   in  the  OH  radical  that controls  the  photochemical  CHh
lifetime.                                                                  *

     In this paper  we  use alternate projections of CO and NOX emissions in a
photochemical  model  to predict tropospheric CH^/CO/NO,. concentrations over the
next  fifty  years.    Simple extrapolation  of  current  CHh  and  CO  increases
implies that CH^ will  reach 2.9-3.0 ppmv by  2035 and that background CO will
double or triple.   If we base  calculations on projections for combustion CO
and  NOX that  show a  leveling off  of CO  emissions, there  will be  less
perturbation to  background  OH and smaller increases in CHh and CO over  the
next fifty years.


INTRODUCTION

     Much attention  has  been  given lately to temporal changes in a number of
photochemically  and  radiatively active trace  gases.  The main topic of Volume
2 is  ozone, a gas  whose changes over time  are driven  by  perturbations  in a
large number  of  trace gases  that  interact  photochemically. One such  gas is
methane  (CHjj),  which is  of  interest  for  its  radiative  properties  as  a
greenhouse  gas and  is of  interest  photochemically because  it  helps  control
abundances  of  the principal tropospheric oxidant OH and of stratospheric  H20
vapor and HOX  (HOX  = H + OH + H0*>).   For example,  an  increase in CHh, enhances
temperature  increases  caused  by C02 (generally regarded as undesirable),  but
will offset some of the catalytic destruction  of stratospheric 0?  caused by
reactive odd chlorine and nitrogen  (regarded as a good thing).
                                    305

-------
     An example of the mitigating effect of CHjj on stratospheric 0^ change was
described recently  by Connell and Wuebbles  (1986).   Although  a catastrophic
loss of  stratospheric Oo  is  predicted  in  less  than  100  years for  all CH^
scenarios considered  in  their study,  there  is a  significant  variation in the
evolution of this  loss depending on what  is assumed  for  rates  of CHjj changes
during the period.

     Our purpose here is to discuss changes  in atmospheric methane and related
changes in  tropospheric  chemical composition.   We give  estimates  for future
CHh and offer  insight into the complexity of  predicting  tropospheric change.
Methane changes are  related  to regional and probably global-scale  changes in
CO, Oo,  NOX,  and  the  free  radical  OH,  which,  if anything,  are harder to
predict than changes in CFty.   These  changes  strongly  influence stratosphere
perturbations,   although as   Whitten  and  Gery  (1986)  have  shown,  coupling
between  stratosphere  and  troposphere  goes  both  ways.    Stratospheric  and
climatic  changes  will ultimately  feed  back to  alter  photochemistry  in the
lower atmosphere.

     This paper reviews  atmospheric CHjj  perturbations that  have already taken
place and summarizes  tropospheric  photochemistry related to  CHh.   There is a
basic problem  in discerning  the  cause  and  effect of CH|j trends oecause CH^ is
tightly coupled to  cycles  of other trace  gases  that may  be changing in time,
e.g.,  CO, Oo,  NOX.   We also  describe  results from a photochemical model study
interpreting past  changes in CHn and  predicting trends in CH^ and related
gases,  CO/NO-j/O^ over the next fifty years.  Two types of scenarios for change
in CO/NOX/OH are  considered.   The  first is based on simple  extrapolation of
recent past Cti^ and  CO trends into  the future.  The second scenario assumes a
constant  increase  in  CH^  sources  and  smaller  increases  in  CO based  on
Kavanaugh's  (1986)  predictions  of CO combustion  emissions.  Finally,  since
CH||/CO/OH cycles are coupled  to NOX and tropospheric ozone,  we look at changes
in these  species as  well.  On a global basis tropospheric Oo, for which there
is evidence  for a temporal increase (Logan  1985;  Bojkov  1986), will probably
increase.  Changes in shorter lived constituents (e.g.,  OH,  NOX) are harder to
predict because their sources are variable and their geographical distribution
will probably  change in  time with changing patterns of economic activity.

     In  view  of  large uncertainties   in  global  budgets  of CH^, CO,  and NOX
(Logan et al.  1981;  Logan 1983),  it  is  not possible to specify current and
future emissions  exactly for every geographical  region.  Rather, we simulate
prototypes for various types of environments.  One of the specific  features of
our approach is the  use  of a one-dimensional model run in a  steady-state mode
with inputs appropriate  for  a given year.   That is, long-term  integration has
not been attempted.  Furthermore, there is no attempt to  simulate the dynamics
that allow  various regions  to  communicate with one another,  i.e., we do not
have a truly  global model.    Finally,  climate  changes  and  perturbations to
stratospheric  ozone,  which may  feed  back to  tropospheric  temperature, water
vapor, and photodissociation, are not included in the present study.


METHANE OBSERVATIONS AND PHOTOCHEMISTRY: ANALYSIS OF PAST TRENDS

     A number  of  recent studies (Craig  and Chou 1982;  Khalil and Rasmussen
1985;  Stauffer et  al.   1985)  show  that  atmospheric  CHh has been increasing
steadily  since   approximately  1700,   after  several  millenia  of   constant
                                      306

-------
 concentration.  For example,  detailed  analysis of  CHn  over the past  seven or
 eight years,  as measured by  Rasmussen and Khalil  (1984)  at a  nonpolluted site
 along the  Oregon coast,  reveal seasonal  variations in CH^;  once these  are
 taken out there  is a definite upward trend.  Rowland and  coworkers  (Blake et
 al.  1982; Blake  and  Rowland  1986)  present similar evidence from  sites  around
 the  world,  using gas chromatographic analysis of ambient air  to determine CH^
 levels.   Independent evidence  deduced  from infrared spectra  collected at  a
 European astronomical  observatory  (Rinsland,  Levine,  and  Miles  1985)  shows
 that CH|| has  been increasing  1% per year for at least 30  years.  Over  the past
 century  or so  CFty has roughly  doubled,  going from  0.8  ppbv  to  1.6-1.7  ppbv
 presently in the Northern Hemisphere;  in the Southern  Hemisphere where  CH^
 sources  are fewer background  levels are  slightly  lower.

      Why is atmospheric CHh  increasing?   Will it  continue to do so and at what
 rate?   Basically, causes  for the  increase  fall  into two  categories.   First,
 CHjj  sources,  all of  which  are biological in origin  (outgassing of oceans  and
 marshes, rice  paddies,  enteric  fermentation of  ruminants,  termites),  are
 increasing.   Second,  the photochemical sink  limiting the atmospheric  lifetime
 of CHjj,  the OH  radical, is  decreasing.

      What controls OH and how do we decide  which of  these  processes  is  during
 current  CHjj  changes?   First of all,  the fact that  CHn  is increasing  itself
 suppresses  OH  and  adds CO to the  atmosphere  (Sze 1977;  Chameides,   Liu,  and
 Cicerone 1977).   This  further  suppresses OH,  methane  and  CO being the trace
 gases that  react  most  rapidly  with OH.   Nonmethane hydrocarbons  (NMHC)  also
 react efficiently  with OH   (Greenberg,   Zimmerman, and  Chatfield 1985),  and
 further  study  of their role in OH perturbation  is  needed.   In the present
 study we assume NMHC are  localized and  not significant on a global scale  and
 neglect  NMHC in  our model   except for  C2H6.   There  is  some evidence of  a
 secular  increase  in CO  (Khalil and  Rasmussen 1984;  Rinsland, Levine, and Miles
 1985)  although  this  is harder  to establish than increasing CHh,  owing  to  the
 shorter  lifetime  and  greater  natural  variability of CO.    OH,  a transient
 species  (lifetime approximately 1  s),  is even more  variable,  and so far  has
 been  impossible  to  measure   in the  troposphere.    Additional  evidence  for
 diminishing OH  may be the detection of a temporal  increase  in  atmospheric C2Hg
 over the past 35  years  (Levine,  private  communication 1986).

      It  appears that  recent CHjj  changes  are  caused  by some  combination of both
 increasing  CH/j  sources and  decreasing   OH.    (Thompson  and  Cicerone  1986a;
 Khalil and  Rasmussen  1985;   Levine, Rinsland,  and Tennille  1985).    Figure  1
 shows  results from model calculations simulating CHh, CO, and OH  from I860 to
 1985,  making  several  assumptions about  the  rate  of CO  change  over   the past
 century.  Simulations in Figure  1a  assume no  change in CHji  sources, whereas in
 Figure  1b  we  are  able to   reproduce CHjj observations  oy assuming  that  CO
 increases are accompanied by  an  increase  in  CH^ sources.

 PREDICTING  METHANE, CO, AND OH PERTURBATIONS

 Extrapolation of  Recent Trends

     Predictions  of  future  CHjj have  been  published  (Chameides,  Liu,   and
 Cicerone  1977;  Sze 1977), although  this is not a simple matter.  One reason  is
 the ambiguous nature  of changing Cfy  sources and/or perturbed CO-OH as  causes
of increasing Cfy, as described above. Furthermore, budgets  of Cfty and  CO are



                                     307

-------
                                 1.6  -i
1860
1900       1940
     YEAR
1980
                                0.6  -I
                                                             observed   In
                                                           CH  increase
                                             1860
                                                       1900       1940
                                                            YEAR
                                             1980
        Figure  1.   (a)  Past methane,  CO mixing ratios and  fractional change  in
   tropospheric  OH (relative  to  1985).   No change  assumed in  CHh sources  from
   1860 to  1985.  (b) CO mixing ratios and fractional  OH loss with observed CHjj
   mixing  ratios  (Khalil  and Rasmussen  1985).   Observations are  matched if  an
   increase in CH  sources is  assumed (Thompson and Cicerone 1986a).
                                         308

-------
poorly  known at  present and  predicting  them  in  the  future  is  problematic
because  they  depend  to  a  large  extent  on  human  activity.    Agricultural
practices are  subject  to change; biomass burning  in  developing nations plays
an important role;  economic activity depends heavily on  combustion of fossil
and  nonfossil   fuels;  there  may be switches  away from  the  currently  most
popular fuels.  The  issue is  further complicated  by photochemical coupling of
OH and CHjj changes  to  tropospheric  NO.,,  NMHC,  and ozone,  which also appear to
be changing in time (Volz, Smit, and Kley 1985; Bojkov 1986).

     One  approach to  predicting future  CHn  is   to  extrapolate from recent
trends, making certain assumptions about the  nature of  current City  and CO
perturbations (Thompson and Cicerone 1986b).  For example,  if atmospheric City
over the  next  50  years increases at its current  rate of  1*  per year,  it will
reach 2.9-3.0 ppmv  in  2035  (Figure  2).   Concurrent increases in background CO
and  decreases   in  OH  can  be  calculated  with  a  photochemical  model.    In  a
typical simulation,  total  CO  sources consist  of  35%  surface  flux  in 1985,
mostly  anthropogenic  in  origin,  i.e.,  fossil fuel  combustion and  biomass
burning; the other 65% is mostly natural, i.e.,  photochemical oxidation of CHh
and  C2Hg  and  a  specified  input of CO  to  simulate  the photo-oxidation of
NMHC.   (See  Table 1, Type  1-CO.)   A ground-level  mixing  ratio  of 120 ppbv is
chosen as typical of nonpolluted  northern  midlatitudes.   Inputs for CO in our
calculations simulate  both  natural  and anthropogenic sources with  the former
taken  as  constant  in time and  the latter  assumed to  increase  with world
population  and industrial  growth  continuing  at   their  current rates.    If
combustion CO follows  C02 (increasing in output approximately 2.5%  per year),
background  CO  will  increase  from 120  ppbv in   1985 to  260 ppbv  in  2035
(Figure 2).

                Table  1.  Parameteri2ation of CO Sources—1985
               stotal,CO   _      n          n            ,,
               5           -      QCO    *   fluxCO   *   SNMHC
               Low NOX;  Stofcal = 1.9 x 1011 cm'2 s"1

               Type 1-CO          15*         35*           50*

               Type 2-CO          15*         65*           20*


QC0 is photochemical source of CO (molec cm   s  ) from OH oxidation
    of CHjj and C2Hg as computed by model.

flux/yj is model lower boundary condition, representing CO sources
     introduced at surface (ocean, combustion, plants, etc),

%MHC is co source specified at every altitude, simulating oxidation
     of nonmethane hydrocarbons not included in model.
                                      309

-------
     Perturbations   to  atmospheric   CO  and   CHjj  are  highly  sensitive  to
background NOX (especially in the boundary layer).  The calculations described
above  are  appropriate  for  simulating  background  conditions  in  northern
midlatitudes (low NOX, approximately  25-30 pptv NOX; surface CO, 100-150 ppbv
in  1985).    Increasing  Cfy and  CO suppress  the  concentration of  OH through
their control of the OH lifetime.   In our model CO reacts with 80% of the OH,
while CHjj and C2Hg  react  with  the  remainder.   If higher NOX is assumed at the
surface  (approximately    1  ppbv, a level  characteristic of  many continental
environments,  not   strongly   polluted  but   influenced  by   areas  of  high
combustion),  then   increasing  CHjj  and  CO emissions  contribute  to smog-type
reactions forming ozone and OH through ozone photolysis:

                                 CO + OH -> C02 + H

                                  H + 02 -> H02

                               H02 + N02 -> N02 -i- OH

                                N02 + h /  -> NO + 0(3P)

                           02+ 0(3P)  +  M  -> 03 +  M

                                 03 + h / ->  02 + 0(1D)

                             0(1D)  + H20 -> 20H

In  the  lower  troposphere  these reactions  partially offset  mid-troposphere
losses of  OH to  give a  lower  total column  loss  than  for  low NOX  regimes
(Hameed,  Pinto,  and Stewart 1979; Thompson and Cicerone 1986b).

     Figure 3a shows OH  and 0^  changes corresponding  to  CH^  and CO increases
illustrated in Figure 2.   For  low  NOX,  surface values of 25-30 pptv, as might
be found over unpolluted marine or  even continental regions, present day 0^ is
approximately 30 ppbv.   With CO doubling  and CHjj increasing  from  1.6  to 2.9
ppmv over the next fifity years,  surface Og increases to 36 ppbv, and the loss
in total tropospheric OH  (integrated  from  0-15 km)  is 35%.   For a region with
NOX approximately 1 ppbv,  surface 0^ is 40 ppbv in 1985, increasing to 50 ppbv
by  2035; the  corresponding loss  in OH  is  only 25^  because additional  0,
mitigates OH depletion.

     Assuming constant NO while CO  increases  is not realistic since combustion
is a large source of both gases.   Consider an environment in transition from a
moderately low  background NOX value,  0.1-0.2  ppbv  in the past  two decades,
increasing along  with increasing  NOX emissions  to  0.48 ppbv  by 2035.   The
historical  record   of NOX  is not known,  but  NOX  emissions are  certainly
increasing  (Dignon  and   Hameed  1985),   which  may  be'  a   more   realistic
representation  of   continental   environments   than  assuming  constant  1  ppbv
NOX.  We  refer to  these as "transitional" regions.  With 0, prescribed as in


                                      310

-------
                    CH4and  CO:  1970-2035
                     (Simple  Extrapolation)
                                                          - 300
        O
                                                                 O
                                                                  M


                                                             200 2-
                                                                  (Q
                                                                 cc
                                                                  o>
                                                                  c
O
                                                          -100
    Figure 2.   Ground level CHjj and CO mixing  ratios  from  1970 to 2035
(Thompson and Cicerone 1986b).   Simulations were carried  out with a steady-
state model at 10-year intervals assuming CFty  mixing ratio increases U/year
from 1985 and  CO increases are driven  by fossil fuel combustion and population
growth  continuing at  current  rates  of  increase.    Model conditions  are
appropriate for  the mid-latitude northern hemisphere with  low background NOX
(20-25 pptv).
                                 311

-------
                                                                         60   -iSOO
   1880
                                                                        20   J
                                                                                 E
                                                                                 JC
                                                                                 o
                                                                              300 a
                                                                                 K
                                                                                 w
                                                                                 15
                                                                                 S
                                                                                 ox
     Figure 3.   Surface 03 and percent  changes in column-integrated  OH (0-15
km)  corresponding  to  CHjj  and CO changes  shown  in  Figure 2  (a)  Constant
background NOX.   Solid  lines calculated  with low surface  NOX (25-30  pptv);
dashed lines  calculated with surface NOX  at 1 ppbv.  (b)  0, and change  in OH
calculated with Cfy and CO as in Figure 2 and NO  as  shown.
                                      312

-------
Figure  3b  the corresponding loss  in  OH is  almost  negligible.   If Og is not
prescribed  explicitly  but is calculated self-consistently  with changing CHjj,
CO,  and NOX,  O2one  reaches approximately  60 ppbv  in  2035 and  OH increases
slightly.

CHjj/CO/OH Trends from Kavanaugh's CO and NOX Projections

     Predictions of  CH^,  CO, and  OH  based on simple extrapolation of recent
CHjj  trends  probably  give upper  limits for CHjj  and CO  fifty  years from now.
Recent evaluation of energy-related combustion sources of CO from 1975 to 2025
(Figure  4a;  Kavanaugh  1986) shows  that  this important part of the CO budget
will  level  off  with   increasing   controls   of  mobile  source  emissions  in
developed nations, slowing  population  growth, and a shift  away from rich CO-
producing fuels  for  domestic energy use  (e.g.,  charcoal bricks  in China) in
favor of large-scale utilities that burn carbon more completely.

     We have  performed  a  series of model calculations of CO and CH|| based on
Kavanaugh's emissions projections  for  CO,  making reasonable assumptions about
noncombustion sources of CO.  We find that to the degree that Cfy is currently
responding  to  CO increases  and OH decreases, methane increases over the next
fifty years will slow down  as  CO emissions  rise  more  slowly  than they have
recently.

     Detailed  analysis  of  model  results  shows  that  if  the  CO  changes
illustrated in  Figure  1b  are realistic,  the corresponding  CH^  source change
during the  past  20  to  30 years  is  0.2,  0.4£ or 0.6j& per year when NOX is at
low  levels .(25-30 pptv) as  observed in the  nonpolluted  atmosphere (McFarland
et  al.   1979;  Torres  1985).    These   three cases  form  the  basis  for  our
projections of background  CH^,  CO, and  OH  over  the next  fifty years.   We
assume  that Cfy sources  continue  to  increase  0.2%, 0.45&,  0.656 yr~1  and we
combine  this  with  Kavanaugh's global  estimate  for the rate of combustion CO
increase, assuming that natural CO sources  do  not change  significantly over
the period.  Details of the  scenarios  are  given  in Table 2.  The model is run
at several  specified dates  from 1985  to 2035.   The two types  of CO sources
refer to the fraction of  the  total CO  budget at  1985 that is caused by direct
surface  sources of  CO  (e.g.,   fossil fuel  combustion,  wood- and  biomass-
burning, lightning-induced  forest  fires,  ocean and  plants)  that  are mostly
anthropogenic.   Remaining CO comes from CHjj  and C2Hg oxidation calculated by
the  model  and from  a  specified in situ  source  that represents  oxidation of
NMHC; the  latter  is presumed  mostly natural  in  origin,  but  that  fraction
coming from anthropogenic  sources increases at the rate  predicted by Kavanaugh
(1986),  whose  projections are  also the basis of changes  in the anthropogenic
fraction  of the  flux  (model  lower boundary  condition).   The same rates of
increase are used in both types of CO models, but the one With only 35% of the
CO source being anthropogenic increases more slowly.

     Methane mixing ratios calculated with low NOX from 1985 to 2035 appear in
Figure 5a;  corresponding CO increases and fractional loss in OH appear in
                                     313

-------
                       CO From Combustion
       160
       120
        O
        o
        t-

        6
        u

        80
        40
            (a)
              1960   1975
                             YEAR
              2000
        40
                       NO  From Combustion
                         jn
        30
        z

        en



        O*
        10
            (b)
               JL
J.
                                     J_
              1960   1975         2000
                             YEAR
2025
                           2025
    Figure H.  Total  global emissions from energy combustion  of fossil  and

non-fossil fuels (Kavanaugh 1986). (a) CO, in Tg C per year; (b) tiQK, in Tg N

per year.
                                314

-------
                 Table 2. Scenarios for CHy, CO Perturbations
     Source	Model  1	Model 2	Model 3

       Cfy          City flux**          Cfy flux            CHj, flux
                    inc.  ,2%/yr         inc.  .4jJ/yr         inc.  ,6%/yr

       CO           Type  2-CO*          Type  1-CO*          Type  1-CO
                    increase in combustion CO after Kavanaugh (1986)
   Type  1-CO: 35% surface flux (mostly anthropogenic) CO sources;
   Type  2-CO: 65% surface flux CO sources in 1985. See Table  1 and Thompson
   and Cicerone (1986) for detailed description of CO sources.

   Photochemical model (Thompson and Cicerone 1982; 1986b) run at background
   continental NOX (1 ppbv) and marine (25-30 pptv) conditions,

** 1985  CH4 flux: H.U x 1010 cm'2 s'1 (low NOX); 1.31 x 1011 cm'2 s'1 (high

   NOX).  OH column, 0-15 km (1985): 5.4 x 1011 cm"2 (low NOX); 1.15 x  1012
   cm'2  (high NOX).
Figure 5b.  The  50-year  projection  for Cfy is 2.0-2.6 ppmv, appreciably lower
than  the figure  of 2.9 ppmv  obtained assuming  an  indefinite  \%  per  year
increase  in  mixing  ratio.   We  see that  CO changes  are  much less  than the
doubling  derived  from smooth  extrapolation  of current  trends; with  less CO
there is less perturbation to OH and to CHh.

     Kavanaugh (1986)  shows  that emissions  of  NOX will continue  to  increase
worldwide   (Figure  4b).   We  have considered  several  NO  scenarios  in our
calculations,  but because of the short lifetime and  localized nature of NO ,
it is difficult to  say how NOX increases  will affect background OH.  It seems
likely in  the lower troposphere,  at  least,   that  background NO ,  Q?,  and OH
will increase over  large regions of the earth.  For  example,  greatest growth
in CO and NO   will  be in China  and third  world countries.  At the same time
highly industrialized  nations may  be  controlling  emissions of  these  gases.
This implies  a shift  in global background  photochemistry,  e.g. oxidant and
acid  formation,   away  from   the industrialized  nations  to  the  developing
countries.  OH losses from increasing  CO and CHjj  (also NMHCs)  might be offset
by increasing Oo and NOX, resulting in slower depletion of global OH.

     Model calculations using Kavanaugh's  projected changes in  CO and NOX need
to be  performed  on  a  regional basis,  dividing the continents into  types of
regions according to economic  and population growth patterns,  assuming little
change in NO   over  the  oceans.    In  some regions  there will  be  substantial
changes  in  CO and  NOX  simultaneously,  in  others  there will  be  little  NOX
change.   In  still others  there will be nearly constant combustion CO but large
increases in NOX.
                                     315

-------
                                       3.0
                                              165
                  0.6% per Year Increeae
                  0.4% per Year Increase
               -— 0.2% per Year Increaee
                                              135
          1.6
120
                                                                       (b)
                                                  1990
              2010

               Year
                                                                             -5
                                                                            -10
                                  £>
                                  o
                                                                                 o
                                                                                 o.
                                                                                 c

                                                                                 _i_
                                                                                 5'
                                                                                 f-»
                                                                                 (D
                                                                                 CL
                                                                       2030
     Figure 5.   (a)  Ground  level  CFty  and  (b)  CO  mixing  ratios  and percent
changes   in column-integrated   tropospheric  OH   from  1985  to  2035  assuming
various  rates  of  increase  in   CHjj  surface fluxes.    Results  from  Models  1-3
(Table 2).
                                       316

-------
     Global  change  in  OH  is a  composite  of regional  changes.    We compute
global OH and ozone  in  a greatly  oversimplified way, given the limitations of
a one-dimensional model.   First,  we divide  the  earth into six broad latitude
bands; then,  we use  a  model to  calculate  OH from  typical  CHjj/CO/NOx/Oo for
continental and marine  areas within  each  band.   We add marine and continental
OH  within  each  band and  take a weighted  mean throughout  the  troposphere.
Total mean  OH (4.8 x IQr  molecules per cubic centimeter)  compares well with
global OH computed  from a  similar set of model  calculations by Chameides and
Tan (1981).  To make  a  very  crude estimate  of future changes in global OH, we
(a)  assume   that  OH  changes over  the  oceans  follow  the  course  of  OH  in
constant,  low  NOX   environments  as   calculated  from  the  Kavanaugh-based
scenario, decreasing  \}% from  1985 to 2035  (Figure  5b);  and (b)  that OH over
continental  areas  follows  the  course  of   "transitional"  NOX  environments,
virtually unchanged from 1985 to 2035 (Figure 3b.) :
   [OH(land)]1985 x (1 + frac. change OH2035ttransitional NQ ) +
                                                            A
      [OH(marine)]1985 x (1 + frac. change OH2035jlow m)  = [OH]2035
                                                        A
The result  is  5% to  10£  less OH in  2035  than at  present.   If we  apply the
formula assuming  that marine areas lose OH  at the rates shown  in Figure 3a,
the loss  is 18£  to  25%  after 50  years.    These  values  are different from
assuming that Northern  Hemisphere midlatitude trends in CH^, CO,  and OH will
continue at current rates and are representative  of the earth as a whole.  It
looks as if the recent  OH decline deduced  from CO/Cfy perturbations will slow
down because CO combustion is leveling off and NOX combustion will continue to
increase.   However, increasing NOX may  contribute to substantial increases in
tropospheric ozone.

SUMMARY AND CONCLUSIONS

     This  paper  describes   photochemical   aspects  of  atmospheric  methane
perturbations  and presents  model  predictions of  CHjj  over the  next  fifty
years.  Simple extrapolation  of  recent CO/OH  trends  implies a doubling of CO
from  1985 to 2035 and Cfy increasing from 1.6-1.7  to 2.9 ppmv.   Depending on
background NOX  levels,  these CO/CHjj  increases will suppress tropospheric OH
15? to  30%.   However,  reduced emissions  of combustion CO and increasing NOX
(Kavanaugh  1986)  maintain higher  OH and,  given a constant increase ,in CH^
sources, lower  Cti^ levels are predicted in 2035, i.e., 2-2.5 ppmv.

     Strictly speaking, CO  and NOX changes  must  be considered  on a regional
basis to calculate perturbations in OH  and CHjj, with an appropriate averaging
to estimate global changes in OH.   The best way to predict future CHn, CO, and
OH  is with a  multidimensional  model that  includes NOX, CO,  and CHjj  source
changes on a well-resolved  spatial  grid along with transport of longer lived
trace gases.   A  further  uncertainty in  our  calculations  is the neglect of
explicit nonmethane hydrocarbon (NMHC) chemistry.   NMHC emissions are probably
changing in  time, and  because NMHC produce  CO and 0^  photochemically their
effects may be complex, working either  to destroy or enhance OH.  Finally, we
note  that our  study does not  include explicit perturbations to CO emissions
from  photochemical  oxidation of vegetative  hydrocarbon emissions or biomass
burning, both  of which may  be altered by  changing  patterns  of  land  use in
developing nations.
                                     317

-------
REFERENCES

Blake,  D.R.,  E.W.  Mayer,  S.C.  Tyler,  Y.  Makide,  D.C.  Montague,  and F.S.
     Rowland.   1982.  Global  increase  in  atmospheric  methane concentrations
     between 1978 and  1980. Geophys. Res. Lett. 9:477-480.

Blake,  D.R.,  and F.S.  Rowland.    1986.  World-wide increases  in tropospheric
     methane,  1978-1983.  J. Atmos. Chem. 4:43-62.

Bojkov,  R.   1986.  Surface  ozone  during  the  second  half  of  the  nineteenth
     century. J. Clim. Appl. Meteor. 25:343-352.

Chameides, W.L.,  S.C.  Liu, and  R.J.  Cicerone.   1977.  Possible variations in
     atmospheric methane. J. Geophys. Res.  82:1795-1798.

Chameides, W.L.,  and  A. Tan.  1981.  The two-dimensional  diagnostic model for
     tropospheric OH: An uncertainty analysis. J. Geophys. Res. 86:5209-5223.

Connell, P.S.,  and  D.J. Wuebbles  1986.  Ozone perturbations  in the LNLL one-
     dimensional model - calculated effects of projected trends in CFC's, CHjj,
     CQ2» M2^'  an(* Halons over 90 years. EPA Report.

Craig,  H.,  and  C.C.   Chou.  1982.   Methane:  The  record  in  polar  ice  cores.
     Geophys. Res. Lett. 9:1221-1224.

Dignon,  J.,  and  S.  Hameed.   1985. A  model  investigation  of the  impact  of
     increases  in  anthropogenic  NOX   emissions   between  1967 and  1980  on
     tropospheric ozone. J. Atmos.  Chem. 3:491-506.

Greenberg, J.P.,  P.R.  Zimmerman,  and  R.B.  Chatfield.   1985.  Hydrocarbons and
     carbon monoxide in African savannah air. Geophys.  Res. Lett. 12:113-116.

Hameed, S.,  J.P.  Pinto,  and R.W. Stewart.  1979.  Sensitivity of the predicted
     CO-OH-CHh   perturbation  to  tropospheric  NOX concentrations. J.  Geophys.
     Res. 84:763-768.

Kavanaugh, M, 1986.  Estimates of future CO,  N20, and  NOX emissions from energy
     combustion. Atmos. Environ.  In press.

Khalil,  M.A.K.,  and R.A.  Rasmussen.  1984.    Carbon monoxide  in the earth's
     atmosphere: Increasing trend.  Science  224:54-56.

Khalil, M.A.K., and  R.A. Rasmussen.   1985.  Causes of  increasing  atmospheric
     methane:  Depletion of  hydroxyl  radicals  and  the  rise of  emissions.
     Atmos.   Environ.  19:397-407.

Levine, J.S.,  C.P.  Rinsland,  and  G.M.  Tennille.  1985.   The  photochemistry  of
     methane and  carbon  monoxide in the troposphere in  1950 and 1985.  Nature
     318:254-257.

Logan,  J.A.  1983. Nitrogen  oxides  in  the  troposphere:  Global and  regional
     budgets, J. Geophys. Res.  88:10785-10808.
                                     318

-------
 Logan,   J.A.   1985.  Tropospheric   ozone:  Seasonal   behavior,   trends  and
     anthropogenic  influence. J. Geophys.  Res. 90:10463-10482.

 Logan,  J.A.,  M.J.  Prather, S.C. Wofsy,  and  M.B.  McElroy.  1981. Tropospheric
     chemistry: A global perspective. J. Geophys. Res. 86:7210-7254.

 McFarland,  M.,  D.  Kley, J.W.  Drummond,  A.C. Schmeltekopf, and R.H. Winkler.
     1979.  Nitric  oxide  measurements  in  the  equatorial  Pacific  region.
     Geophys. Res. Lett. 6:605-608.

 Rasmussen,  R.A., and  M.A.K.  Khalil.   1984.  Atmospheric  methane in the recent
     and ancient atmospheres: Concerns,  trends, and interhemispheric gradient.
     J. Geophys. Res. 89:11599-11605.

 Rinsland, C.P., J.S.  Levine,  and T. Miles.  1985. Concentration of methane in
     the  troposphere  deduced  from  1951  infrared  solar  spectra.  Nature
     318:245-249.

 Rinsland, C.P.,  and  J.S.  Levine.    1985. Free  tropospheric carbon monoxide
     concentrations in  1950 and 1951 deduced from infrared total column amount
     measurements.  Nature.   318:250-254.

 Stauffer, B.,  G. Fischer,  A.  Neftel,  and  H.  Oeschger.   1985.  Increase of
     atmospheric methane  recorded   in  Antarctic  ice  core.  Science.  229:1386-
     1388.

 Sze, N. D.  1977. Anthropogenic  CO  emissions: Implications for the atmospheric
     CO-OH-CH4 cycle.  Science 195:673-675.

 Thompson, A.M., and R.J.  Cicerone  1982.  Clouds  and wet  removal  as  causes of
     variability in  the trace-gas  composition of the marine  troposphere. J^
     Geophys.  Res.  87:8811-8826.

 Thompson, A.M.,  and  R.J.  Cicerone. 1986a.  Atmospheric  CH|i,  CO, and  OH from
     1860 to 1985.  Nature 321:148-150.

Thompson, A.M., and R.J. Cicerone 1986b. Possible perturbations to atmospheric
     CO, CHjj,  and OH.   J.  Geophys.  Res. 91.  In press.

Torres,  A.L.  1985.  Nitric  oxide measurements  at a  nonurban  Eastern  United
     States  site: Wallops  instrument results from July  1983 GTE/CITE mission.
     J. Geophys.  Res.  90:12875-12880.

Volz,  A., H.G.J.  Smit,  and  D.  Kley.    1985. Ozone  measurements in  the 19th
     century:  The Montsouris Series.  Eos 66:815.
                                     319

-------