EJWIRQNMBNTAL
 INBIC&TOES
                            Protection of the  Ozone Layer
     Over 60 years ago, chlorofluorocarbons (CFCs) were invented in
     the United States, and they soon found many uses throughout
the world in refrigeration, air conditioning, and other industrial
processes. Due to scientific  evidence that CFCs and other chemicals
destroy ozone in the upper atmosphere, the United States, the
country which has traditionally been the largest emitter of CFCs
worldwide, is rapidly scaling back the use of these chemicals and
phasing out their production.
                              The ozone (Os) layer in the stratosphere protects life on earth from
                            exposure to dangerous levels of ultraviolet light. It does so by filtering
                            out harmful ultraviolet radiation from the sun. When CFCs and other
"Indicator,*  ,
 U.S. Impact
*on "the* Ozone
 Layer
                    1958    1962
                      m  cFc-11
       1966    1970

      H CFC-12
1974    1978    1982

HCFC-22  D  CFC-113
 1986    1990

B  GH3CCI3
United States iiwfranmental
 Office of Policy, Planning
 -°  and Evaluation
 Office of Air and ftsdiiftifn
      World Resources"
      Institute
       199S
ozone-degrading chemicals are emitted, they mix with the atmosphere
and eventually rise to the stratosphere. There, the chlorine and the
bromine they contain catalyze the destruction of ozone. This
destruction is occurring at a more rapid rate than ozone can be created
through natural processes.
  The degradation of the ozone layer leads to higher levels of
ultraviolet radiation reaching Earth's surface. This in turn can lead to a
greater incidence of skin cancer, cataracts, and impaired immune
systems, and is expected also to reduce crop yields, diminish the

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productivity of the oceans, and possibly to contribute to
the decline of amphibious populations that is occurring
around the world.
   The chemicals most responsible for the destruction of
the ozone layer are chlorofluorocarbons, carbon
tetrachloride, methyl bromide, methyl chloroform, and
halons. Chlorofluorocarbons have long been widely used as
coolants in refrigerators and air conditioners and as
foaming agents, solvents, and aerosol propellants. Carbon
tetrachloride and methyl chloroform are important
industrial solvents. In the United States, carbon
tetrachloride is now used almost entirely as a feedstock for
the production of chlorofluorocarbons. Halogenated CFCs
(HCFCs) have many of the same uses as CFCs and are
increasingly employed as interim substitutes for CFCs.
Halons have been used in fire extinguishers.
   Long predicted, the degradation of the ozone layer was
dramatically confirmed when a large hole in the layer over
Antarctica was reported in 1985. Smaller but significant
stratospheric decreases have been seen over more
populated regions of the Earth. Subsequent research
established that industrial chemicals are responsible for the
observed depletions of ozone over Antarctica and play'a
major role in global ozone losses.

HUMAN
ACTIVITIES
Chlorine and bromine are emitted to the atmosphere from
both natural and human sources. These very stable
human-made chemicals are not soluble in water and are
not broken down chemically in the lower atmosphere.
Thus they survive long enough to reach the stratosphere.
The CFCs and carbon tetrachloride are relatively
                                      unreactive in the lower atmosphere (the troposphere) and
                                      move unscathed into the stratosphere where they are
                                      decomposed by intense sunlight, releasing chlorine to
                                      catalyze the destruction of ozone molecules. Certain
                                      ozone-depleting chemicals (HCFC-22 and methyl
                                      chloroform) are more reactive in the troposphere and
                                      deliver less of their initial chlorine load to the
                                      stratosphere. Halons also are generally reactive in the
                                      troposphere and'deliver only a fraction of their initial load
                                      of bromine to the stratosphere, but bromine is 40 times
                                      more efficient at destroying ozone than chlorine.
                                      Increasing attention is being focused on the
                                      ozone-depleting role of methyl bromide, which has three
                                      potentially major human sources (soil fumigation, biomass
                                      burning, and the exhaust of automobiles using leaded
                                      gasoline), in addition to a natural oceanic source.

                                         U.S. production of ozone-depleting gases has declined
                                      significantly since 1988, and has now reached levels
                                      (measured by their ozone depleting potential) comparable
                                      to those of 30 years-ago. Because of international
                                      agreements to decrease production and ultimately to phase
                                      out production of CFCs and halons, scientists expect that
                                      total chlorine and bromine concentrations in the
                                      troposphere will peak by 1996 and begin a slow decline
                                      soon thereafter. Concentrations are expected to peak in
                                      the stratosphere 3-5 years  later. Increasing ozone losses are
                                      predicted for the remainder of the decade, with gradual
                                      recovery by the mid-21st century.
                                       STATE OF
                                      Worldwide monitoring has shown that stratospheric ozone
                                      has been decreasing for the past two decades or more.
Indicator
Cumulative
U.S. Impact
on the Ozone
Layer
Production (thousand metricians of GFC-11 equivalent}
    24000
                                  1960
                                            1965
                                                       1970
                                                                 1975
                                                                            1980
                                                                                       1985.
                                                                                                ;:1990

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           1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992'1993 1994
                             CFC-11
                             CHgCC'g
CFC-12
CCIk  '
                                                                                             Indicator
                                                                                             Atmospheric
                                                                                             Concentration
                                                                                             of Selected
                                                                                             Ozone-
                                                                                             Depleting
                                                                                             Chemicals
Source: Atmospheric Lifetime Experiment/Global Atmospheric Gases Experiment (ALE/GAGE)

The average loss across the globe totaled about 5 percent
since the mid-1960s, with cumulative losses of about 10
percent in the winter and spring and a 5 percent loss in the
summer and autumn over North America, Europe, and
Australia. Since the late 1970s, an ozone hole has formed
over Antarctica each austral spring (September/October),
in which up to 60 percent of the total ozone is depleted.
Record low global ozone levels were recorded in 1992 and
1993. These lows were due, in part, to large amounts of
stratospheric sulfate particles from the volcanic eruption of
Mount Pinatubo in the Philippines in 1991; the sulfate
particles temporarily accelerated the ozone depletion
caused by human-made chlorine and bromine compounds.
   As expected from the increasing use of CFC substitutes,
observations from several sites have revealed rising
 concentrations of these compounds in the atmosphere.
 These substitutes have short tropospheric lifetimes, which
 tends to reduce their impact on stratospheric ozone as
 compared to CFCs and halons. However, some are potent
 greenhouse gases.
    The link between a decrease in stratospheric ozone and
 an increase in surface ultraviolet (UV) radiation at the
 Earth's surface has been strengthened during the last
 several years by simultaneous measurements of total ozone
 and UV radiation in Antarctica and the southern part of
 South America during the period of the seasonal ozone
 "hole." The measurements show that when total ozone
 decreases, UV increases. Furthermore, elevated surface UV
 levels in mid-to-high latitudes were observed in the
 Northern Hemisphere in 1992 and 1993, corresponding to
                                      Indicator
                                                                                               Ozone
                                                                                               Depletion
                                                                                               Over
                                                                                               Antarctica
Source: National Aeronautics and Space Administration (NASA)

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Indicator
impact of
Montreal
Protocol on
Chlorine
Content of
the
Atmosphere
I	fcttxfoe Cbneenteafew (parts per fetoj
     12
                          1985     1990    1995     2000    2005    2010     2015    2020     2025    2030

                                        ——   Without Controls      -<""—'•   1996 Phaseout
the low ozone levels of those years. However, the lack of
long-term monitoring of surface UV levels and
uncertainties introduced by clouds and ground-level
pollutants have precluded the unequivocal identification
of a long-term trend in surface UV radiation.

RESPONSE
Reacting to the environmental threat of ozone depletion,
the nations of the world came together to create a global
treaty, the Vienna Convention for the Protection of the
Ozone Layer. The agreement entered into force in 1988
and the subsequent Montreal Protocol on Substances that
Deplete the Ozone Layer entered into force in 1989.
Currently HO countries are parties to the Montreal
Protocol. The parties to the Protocol decided on a
timetable for countries to reduce and to end their
production and consumption of eight major halocarbons.
The Protocol also provides a ten-year delay in this
timetable for those developing countries consuming less
than 0.3 kilograms per capita.
  The Montreal Protocol timetable was accelerated in
1990 and 1992. Amendments were adopted in response to
scientific evidence that stratospheric ozone is depleting
faster than predicted. As part of an effort to speed  the
phase-out of production and consumption of
                                        ozone-depleting chemicals, the parties to the Protocol
                                        decided to provide technology transfer and funds from
                                        industrial to developing countries. Under the accelerated
                                        schedule, the production of most controlled gases is to
                                        cease by January 1, 1996. The developing countries,
                                        however, may receive residual production from
                                        industrialized countries not to exceed 15 percent of 1986
                                        levels. Some individual governments have committed to
                                        even earlier phaseout deadlines.
                                          The U.S. Environmental Protection Agency (EPA),
                                        under authority of the U.S. Clean Air Act Amendments
                                        of 1990, issued regulations for the phaseout of production
                                        and importation of ozone-depleting chemicals controlled
                                        under the Protocol through a marketable permit program.
                                        In addition, EPA established controls on refrigerant
                                        recycling to prevent emissions, a ban on nonessential
                                        products, labeling requirements, a program to review safe
                                        alternative substances, and requirements to revise federal
                                        procurement specifications. Under the regulations, surplus
                                        or recycled substances can in general be stored to service
                                        existing machinery.
                                          Because of the importance of the ozone layer and the
                                        complexity of the chemical reactions affecting it, the
                                        condition of the ozone layer must continue to be
                                        monitored.
" Acknowledgements! This bulletin is first in a series of environment indicator bulletins covering major topics of environmental protection. It is a •
 produce of a collaboration between die World Resources Institute and the Environmental Indicators Team of BPA's Office of Policy, Planning, and
^Evaluation, Division of Environmental Statistics and Information. This report was prepared in collaboration with the EPA Office of Air and'
 Radiation's Stratospheric Protection Division.
 For Further Information: Contact Ms. Bonita Crockett, Office of Strategic Planning and Environmental Data, Mail Code 2161, USEPA, 401 M St., SW,,
 Washington, D.C 20460 (phone:202-260-4030)

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