[REPORT' ON .THE PROGRESS OF

       REGULATIONS  TO  PROTECT

         STRATOSPHERIC OZONE
         REPORT TO  CONGRESS


            February 1982
tf.S. ENVIRONMENT^  'PROTECTION AGENCY
     OFFICE OF TOXIC  SUBSTANCES
        ' 4,01 M Street-,  S.swZ
       Washing ton,. b.C-.

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                        TABLE  OF CONTENTS

     SUMMARY	1
  I. THE OZONE DEPLETION  ISSUE	4
 II. THE AEROSOL RULE			9
III  NONAEROSOL USES	12
 IV. INTERNATIONAL PRODUCTION  AND COOPERATION	14
  V. FURTHER REGULATION OF  CFCS	16
     REFERENCES	17

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                               -1-
                             SUMMARY
     As mandated by Section 155 of the Clean Air Act  Amendments
of 1977, PL 95-95 (CAA), the Environmental Protection Agency
(EPA) submits to Congress this report on the progress of
regulation to protect stratospheric ozone covering  tne  period
from August 1979 to December 1981.  Section 155 requires  that  the
Administrator report to Congress on actions taken by  the
Environmental Protection Agency and other Federal agencies  to
regulate sources of halocarbon emissions/ the results of  such
regulations in protecting the ozone layer, the need for
additional regulatory action, if any, and recommendations for
control of substances, practices, processes, or activities  other
than those involving halocarbons which affect stratospheric ozone
and cause or contribute to harmful effects on public  health or
welfare.
     This report reviews activities related to the  protection  of
stratospheric ozone from potential depletion due to emissions  of
chlorofluorocarbons (CFCs) and other ozone-depleting
substances.  If ozone concentrations are reduced, increased
amounts of solar ultraviolet radiation in the wavelength  region
of 290-320 nanometers (UV-B) would reach the earth's  surface.
This may have a number of consequences, including higher
incidence of nonmelanoma skin cancer among humans,  decreased
plant productivity, and adverse effects on the aquatic  food
chain.
     In March 1978, the Food and Drug Administration  (FDA)  and
EPA promulgated rules that prohibited the manufacturing and
processing of CFCs for nonessential aerosol propellant  uses.
Domestic CFC use as aerosol propellants was about 448 million
pounds in 1973.  In 1980 aerosol uses accounted for about 24.5
million pounds out of a total of 835 million pounds produced
domestically.  However, nonaerosol uses of CFC, including
solvents, blowing and insulating agents in foam manufacturing,
refrigeration, air conditioning, and other specialized  processes,
increased between 1975 and 1979 and then fell slightly  in the

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1979-80 economic slowdown.  Anticipated  recovery  of  the  economy
combined with expected market growtn  in  some  uses  of  CFCs  may
eventually offset the reductions achieved by  the  aerosol rule.
     In October 1980, EPA issued an Advance Notice of Proposed
Rulemaking (ANPR) requesting public comment about  possible
effects on human health and the environment from  the  continuing
use of CFCs, and on the economic aspects of the issue.   The  ANPR
solicited comments on the validity of the ozone depletion  theory,
and the effectiveness of restricting  the use  of CFCs  as  a  means
of dealing with any significant problem.  Also in  1980,  EPA
issued a proposed rule under authority of Part A  of  the  CAA
Amendments of 1977 which would regulate  emissions  of  certain
solvents including CFC-113 and other  substances which may  deplete
ozone from new, modified, or reconstructed organic solvent
cleaners.  EPA is currently studying  whether  to include  these
degreasing solvents in a final rule.
     In addition to CFCs, other potential ozone depleting
substances are being investigated by  EPA and  other agencies.  For
example, EPA recently completed an analysis of production  and
emissions of methyl chloroform.  Other agencies,  including the
National Aeronautics and Space Administration, the National
Oceanic and Atmospheric Administration,  the Federal Aviation
Administration, and the Department of Energy, are  investigating
the effects on stratospheric ozone of compounds other than CFCs,
including other halocarbons, carbon dioxide,  and  nitrogen  oxides.
     Because CFC emissions in any country may be  dispersed
throughout the earth's atmosphere, the protection  of
stratospheric ozone is an international  issue.  A  few countries
have prohibited most aerosol propellant  uses  and many CFC-
producing and using nations have achieved reductions  in  aerosol
propellant uses by regulatory or voluntary actions.   Several
nations are assessing the feasibility of reducing  emissions  from
other uses.  Japan and the European Economic  Community have
limited CFC-11 and CFC-12 production  capacity to present
levels.  The~U~.S. is participating in a  number of  international

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organizations which promote/ coordinate, and assess  research  and
study technical and economic aspects of the CFG/ozone  depletion
issue.
     To fulfill the requirements of the CAA Amendments of  1977
and to improve and expand the scientific basis for evaluating"the
necessity of further reductions in CFG emissions, EPA and  other
Federal agencies are continuing to monitor and support research
related to improving our understanding of atmospheric science,
adverse health and environmental consequences of ozone depletion,
technological capabilities for limiting CFG emissions from major
sources, and the costs of achieving such controls.  Any decision
regarding EPA action would be based on an evaluation of all these
factors.

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                  I.  THE OZONE DEPLETION  ISSUE

     Ozone is found throughout the stratosphere, which  is  10  to
50 kilometers above the earth's surface.   Ozone  is  important
because it limits the amount of solar ultraviolet radiation
reaching the earth, specifically in the wavelength  region  of  290-
320 nanometers (UV-B), which has been correlated to  acute  effects
(e.g., sunburn) and nonmelanoma skin cancer among certain  human
populations.  The concentration of ozone present in  the
stratosphere is determined by a dynamic balance between  natural
processes that produce and destroy ozone.  Based on  theoretical
atmospheric models, it is postulated that  the rate of ozone
destruction and creation can be altered by a buildup in  the
stratosphere of several chemical species including species
containing chlorine (e.g., Cl, CIO), hydrogen (e.g., HO, HO.,,
H2°2^' and nitr°9en (e.g., NO, N0x).
     In view of the screening function of  the ozone  layer, any
significant increase in the rate at which  chlorine species are
injected into the stratosphere is of concern because chlorine
atoms and chlorine oxide act as catalysts  in chemical reactions
that destroy ozone.  Chlorofluorocarbons (CFCs)* are very  stable
in the lower atmosphere.  They migrate very slowly from" the
troposphere across the tropopause and into the stratosphere where
they are decomposed by solar ultraviolet radiation and release
free chlorine.  Consequently, the continued worldwide release of
CFCs has the potential to increase chlorine concentrations in the
stratosphere, resulting in decreased stratospheric ozone.
Increases in chlorine concentrations in the stratosphere have
been measured; however, to date, changes in ozone in the
    Chlorofluorocarbons are a family of chemicals.  Historically,
    CFC-11 and CFC-12 have accounted for about 90 percent of
    worldwide CFC production.  Other commercially important CFCs
    include CFC-113, CFC-114, CFC-115, and a related compound,
    CFC-22, which contains hydrogen.

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                               -5-
stratosphere beyond natural variations have  neither  been measured
nor expected based on model calculations.
     Scientists have developed necessarily simplified  atmospheric
models (computer simulations) of the  complex  chemical,  transport,
and radiative processes in the atmosphere to  describe  and predict
potential stratospheric changes.  These models  are limited by tne
quality and extent of data on actual  atmospheric  levels of the
species of interest.
     A Workshop on the Stratosphere sponsored by  the National
Aeronautics and Space Administration  (NASA)  and the  World
Meteorological Organization (WHO') was held in May 1981.   At the
workshop, scientists reported on computer model results,  using
the most recent chemical reaction rate data  (derived from
laboratory experiments).  Present central estimates  of  their
various computer model calculations are that  continued  emissions
at present levels of CFC-11 and CFC-12 may eventually  result in
"steady-state" ozone depletion of 5-10 percent.   In  other words.
assuming world CFC emissions continued at present levels  into the
future, current models show that the  existing balance  between
ozone-creating and ozone-destroying processes in  the stratosphere
would be changed in such a way that a new equilibrium,  or
"steady-state", would be achieved near the end  of the  2~lst
century and that the total amount of  stratospheric ozone  would be
90-95 percent of what it is today.  If other  halocarbons  at their
present emission rates are included in the models, the  "steady-
state" depletion is calculated to increase by a third  (e.g.,  a
calculated "steady-state" depletion of 6 percent  for CFC-11 and
CFC-12 would increase to 8 percent when other halocarbons are
considered).  Workshop participants noted that  substantial
uncertainty remains with respect to some atmospheric chemical
reactions.   The final report from this workshop  was issued in
February 1982.
     The models have also been used to estimate the  globally-
averaged depletion of stratospheric ozone that  may have  occurred
to date due to CFCs; these estimates  show it  to be less  than 1
percent.  Using these models, the 5 to 10 percent "steady-state"

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depletion calculations imply that continued emissions  of  CFC-11
and CFC-12 at current levels are calculated to  result  in  an  ozone
depletion rate of less than about 0.1 percent per year.   If  this
rate of change is correct, taking the time for  additional and
improved measurements of stratospheric ozone and for the
development of other information may not result in significant
incremental risk.
     Statistical analysis of data from ground monitoring
stations, known as ozone trend analysis, is done to detect trends
in total global ozone.  This analysis indicates the absence  of
any statistically significant trend in total global ozone over
the last decade.  This result is not inconsistent with
atmospheric model calculations.  A recent assessment indicates
that the current network of ground-based monitoring stations may
be sensitive enough to detect as little as a 2-4 percent  change
per decade in total ozone.
     In addition to CFCs, scientists are investigating other
chemical substances including methyl chloroform, nitrogen oxides,
and carbon dioxide (CG>2) for their effects on ozone.
     EPA has completed an analysis of production and emissions  of
methyl chloroform.   Domestic production was 625 million  pounds
in 1978, increasing at an average of 16 percent annually  between
1974 and 1978.  Worldwide production totalled 1.05 billion pounds
in 1978, increasing at about a 30 percent annual"rate  between
1974 and 1978.  Analysis of the relative ozone  depletion
potential of various substances by Lawrence Livermore  National
Laboratory modeling studies indicates that methyl chloroform has,
on a pound per pound basis, about one-seventh (0.14) the
potential of CFC-11 for depleting stratospheric ozone.    Methyl
chloroform is presently included in a proposed  EPA rule that
would limit emissions of certain degreaser substances  from new,
modified, and reconstructed organic solvent cleaners.4
     Nitrogen oxide emissions from aircraft flying at  high
altitudes (either upper troposphere or lower stratosphere) and
carbon dioxide-also may affect stratospheric ozone.  Atmospheric

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raodel calculations indicate that nitrogen oxides  released  by
subsonic aircraft exhausts in the region of  the tropopause may
already have increased ozone concentrations  by between 0.5 and
1.0 percent.  However, as aircraft operate at higher  altitudes
injecting nitrogen oxides directly in the lower stratosphere, • the
effect may be to decrease ozone in that region.   Significant
increases in the number of flights or flight altitudes may be
necessary before significant ozone changes would  occur.
     Increases in carbon dioxide in the atmosphere, due  primarily
to increased burning of fossil fuels, are expected  to  lead to
decreases in stratospheric temperatures.  The consequent slowing
of chemical reactions taking place in the stratosphere could make
the impact of CFCs on stratospheric ozone less than would
otherwise occur without a change in stratospheric temperature.  A
carbon dioxide buildup may also result in global  surface
temperature increases and climatic changes of unknown
variations.
     Although scientists have made great progress in
understanding complex stratospheric processes through  modeling,
laboratory experiments, and atmospheric monitoring, substantial
work remains to decrease scientific uncertainties.
     A decrease in ozone, independent of other factors,  increases
the intensity of UV-B reaching the earth's surface.  Scientists
agree that increased UV-B levels at the earth's surface  would
                           t
increase the incidence of human nonmelanoma  skin,  cancer,
especially among light-skinned people.  Nonmelanoma skin cancer
is a problem primarily because it causes disfigurement and
imposes economic burdens associated with its treatment.    If
detected early, it is usually treatable.
     Although the relationship between malignant  melanoma,  a
dangerous form of skin cancer, and UV-B exposure  has been  studied
for over two decades, a dose-response relationship has not been
established.  For melanoma, total accumulated UV-B dose  does not
appear to be a significant causal factor, although acute or
repeated exposures to sunlight may be important.6  Melanomas are

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increasing at a faster rate than most other  cancers  especially
among younger, more affluent, and better  educated  persons;
however, the relationship between UV-B  exposure  and  melanoma is
not known.
     Information on nonhuman effects of increased  UV-B  is
presently difficult to quantify.  EPA is  funding a three-year
field research study  (through 1983) to  determine the effects of
increased UV-B on selected economically important  crops  grown
under otherwise normal conditions.  Nonagricultural  terrestrial
organisms have been shown to be susceptible  to increases in  UV-B
exposure.  Laboratory studies show that a number of  aquatic
species  (algae, plankton, fish larvae)  which  exist close to  the
surface may be living close to their UV tolerance  levels.  EPA
has funded research over the last three years which  has  provided
excellent data on UV-B penetration many meters below the surface
in a variety of water conditions.
     More detailed information on scientific  issues  related  to
stratospheric ozone will be contained in  EPA's biennial  report to
the appropriate House and Senate committees on the results of
studies and research conducted by EPA and  other agencies.  That
report, required by Section 153(g) of the  CAA Amendments of  1977,
is expected to be issued later this year.
     To provide for an independent review  of "the state of
knowledge of the impact of man's activities on stratospheric
ozone and effects of changes thereto, EPA  has requested  the
National Academy of Sciences (NAS) to consider the most  recent
scientific developments and to reassess the status of the ozone
depletion theory, measurements of ozone and trace  contaminant
concentrations, and health and environmental effects.  A draft
report of the NASA/WHO May 1981 workshop  along with  other
requested reports and materials has been made available  to NAS
for use in their overall assessment of  the issue.  The EPA
contract with NAS requires a report in December 1981, but EPA has
modified the contract to assure that NAS  has adequate additional
time to provide a thorough assessment.  The report is now
expected in March 1982.

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                      II.  THE AEROSOL RULE

     In 1978, EPA and FDA simultaneously published  rules
prohibiting the use of CFC aerosol propellants  in nonessential
             Q
applications.   The final EPA rule prohibited the manufacture-of
fully halogenated chlorofluoroalkanes for nonessential  aerosol
propellant uses after October 15, 1978.  In addition, the  rule
prohibited after December 15, 1978 the processing and
distribution of bulk CFCs in commerce, the processing for  export,
and the importation in bulk for aerosol propellant  uses or as a
propellant in nonessential aerosol articles.
     Under the Federal Food, Drug, and Cosmetic Act, FDA
prohibited the manufacture or packaging of food, drugs, medical
devices, and cosmetic products containing fully halogenated
chlorofluoroalkanes as an aerosol propellant after  December 15,
1978, and the initial introduction into interstate  commerce of
finisned food, drugs, medical devices, and cosmetic products
containing these substances after April 15, 1979.   The  FDA rule
exempted certain drugs and food products.
     In its rule, EPA exempted certain uses determined  to  be
essential on the basis of criteria contained in a support
document for the rule.   These criteria included the availability
of substitutes, the economic significance of the product,  the
environmental and health impacts of the aerosol product and its
substitutes, and the effect on the quality of life  if the  product
or a reasonable substitute were unavailable.  Current exemptions
to the EPA rule include CFC aerosol propellant  applications in
conjunction with mining, aircraft operation, national defense,
pesticide use, manufacture and servicing of electrical  and
electronic equipment, and mold release agents.  The exemption for
mold release-agents included spinnerette release-agents which are
used in the production of manmade fibers.  In January 1981,  EPA
promulgated a rule, effective March 1982, revoking  the
spinnerette exemption.1   Based on new information  submitted to
the Agency indicating that substitutes for all  uses will not be

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available by the effective date, EPA restored  the  exemption.   In
a recent action, EPA granted a temporary  exemption for the  use of
CFCs in automatic pesticide dispensing  units for long-term
storage of flue-cured tobacco, - pending  a  review  of  a request
for a permanent exemption.  EPA has also  exempted  rotary-tablet
press-punch lubricants from the rule.12   Several applications  for
exemptions have been denied, including CFC  use in  fog machines
and spray adhesives. 3  EPA is reviewing  applications to exempt
CFC propellant use in nozzle shield lubricants for inert-gas
welding-guns, graphite solid lubricants,  and crack detectors  for
nuclear power plants*
     Manufacturers and processors are required to  submit annual
reports to EPA if they are manufacturing  or using  CFC propellants
for exempted aerosol products.  In 1981,  EPA's Office of
Enforcement has preliminarily reviewed reports from five
manufacturers and 45 processors for the calendar year 1980.   Data
from the reports indicate that aerosol products accounted for
about 24.5 million pounds of CFCs in 1980.  In comparison,
aerosol use accounted for about 448 million pounds of CFCs  in
1973.14
     A study is being conducted for EPA to  evaluate the  economic
impact of the ban on nonessential CFC aerosol  propellants.
Preliminary results indicate that, in general", the impact on
consumers was small as good substitutes were readily  available,
often at lower cost to the consumer.  There appeared  to  be  a
negative impact on profits, especially on CFC  manufacturers and
on small, aerosol fillers.  There was also  a one-time cost  for
aerosol product manufacturers and fillers to reformulate and
convert to hydrocarbon or carbon dioxide  propelled products.  5
     On December 16, 1980, EPA published  an interpretive rule,
under authority of Section 12(b) of TSCA, requiring individuals
to notify EPA of exports or expected exports rf substances
regulated under Secti n 6 of TSCA. °  Th«  rul<  I requires
individuals to notify EPA of the first shipment of each  year  to a
given country.-  EPA in turn will notify the importing countries

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                               -11-
of the export of CFCs to that country and  the  nature  of  the EPA
regulations.  Since January 1981, EPA has  received  reports  from
37 companies giving notice of export to approximately 94
countries.  These exports include bulk shipments  of CFCs and CFCs
in mixtures such as in exempted aerosol products.

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                      III.  NONAEROSOL  USES

     Domestic CFC production and use has  changed  in  tne  last
decade.  In the U.S., a sharp drop  in CFC  production followed a
peak of about 1.1 billion pounds in 1974.14   1980  production of
about 835 million pounds nearly equalled  the  1979  domestic output
of about 838 million pounds.  Since 1974,  there has  been a
decrease in aerosol propellant uses of  CFCs from over 400 million
pounds to about 24.5 million pounds in  1980.   This decrease in
CFC production for aerosol uses has been  accompanied by  an
increase in nonaerosol uses.  Nonaerosol  uses  grew about
9 percent annually from 1975 to 1979 and  then  fell slightly in
the 1979-80 economic slowdown. 4/17  Anticipated recovery of the
economy combined with expected market growth  in the  use  of CFCs
for solvents, food freezing, and other  applications  may  lead to
                                              18
an increase in production over the  1974 peak.  °
     Concern about expected growth  in nonaerosol uses, combined
with the conclusions of the 1979 NAS report, prompted EPA to
consider the need for further Agency action to control CFC
emissions.  EPA published an Advance Notice of Proposed
Rulemaking (ANPR) in October 1980.19  The  objective  of the ANPR
was to notify the public that EPA was requesting comment about
possible effects on human health and the  environment resulting
from continued use of CFCs and on the economic aspects of the
issue.  The ANPR served as a tool to gather information  from the
public on the validity of the ozone depletion  theory and other
scientific issues, the effectiveness of restricting  the  use of
CFCs as a means of dealing with any significant problem,  and
international aspects of the issue.  The Agency was  particularly
interested in gathering information on  economic impacts  and the
concerns of small businesses.
     EPA received over 2,000 comments on  the ANPR.   From these
comments, it is clear that many segments  of industry consider
regulatory action to be unnecessary at  this time and the
regulatory strategies discussed in  the  ANPR to be

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controversial.  The Agency believes that many  of  the  issues
raised in these comments deserve  further analysis.  The  quality
of the comments indicates that the ANPR has  succeeded in
promoting informed public participation in the evaluation  of  the
issues and an exchange of information among  government,  industry,
and other interested parties.

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          IV.  INTERNATIONAL PRODUCTION AND  COOPERATION

     Worldwide production of CFC-11 and CFC-12 peaked  in  1973-
1974.  As in the U.S., there was a significant drop  in worldwide
aerosol use in recent years but growth continued  in  nonaerosol
uses.  In 1979, the member nations of the European Economic
Community (EEC) accounted for 34.0 percent of total  world sales
of CFC-11 and CFC-12, the U.S. accounted for 25.5 percent, and
the rest of the world totalled 40.5 percent.20
     Many CFC producing and using nations have taken steps to
reduce CFC emissions.  The ten members of tne EEC are  required by
an EEC Council decision to cap production capacity for CFC-11  and
CFC-12 and to reduce aerosol propellant uses of these  CFCs by  at
least 30 percent of 1976 levels by the end of 1981.  Several
member countries have achieved significantly greater reductions
in aerosol uses than the required 30 percent.  Japan has  decided
to cap production capacity informally with end results equivalent
to those of the EEC.  Canada, Sweden, and Norway  have  banned most
aerosol propellant uses of CFC-11 and CFC-12, and many otner
countries have achieved significant reductions without
regulation.
     A number of international organizations are  active in the
CFC issue.  The Organization for Economic Cooperation  and
Development (OECD) through its Environment Committee is reviewing
the CFC issue and preparing a report on the  current  status of  the
atmospheric science, potential UV effects, industry  facts and
figures, and actions by members and international
organizations.  In a related exercise, scientists in several
countries are using an agreed upon set of CFC emission scenarios
in atmospheric modeling studies.  The results of  this  scenario
work will be particularly useful for evaluating the  effects on
eventual ozone depletion of alternative emission  control
strategies.  In the U.S., modelers at Du Pont and Lawrence
Livermore National Laboratory are participating in this effort,
which is being coordinated by EPA.  The results are  intended for
use by OECD and national policy makers.

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     The United Nations Environment Program  (UNEP)  serves  as  the
coordinator and evaluator of international research on  the
scientific issues.  UNEP, through its Coordinating Committee  on
the Ozone Layer (CCOL), conducts an annual scientific assessment
of the ozone depletion issue.  CCOL has agreed with the World
Meteorological Organization  (WMO) suggestion that satellite
measurements be integrated with ground-based observations  to
improve ozone monitoring.  The group also expressed concern at
increases in nonaerosol uses of CFCs and production of  other
potential ozone depleters.   In May 1981, the UNEP Governing
Council agreed to a Swedish  proposal to begin work on a global
convention to protect stratospheric ozone.  The first meeting of
the legal/technical group working on the convention was held  in
Stockholm, Sweden in January 1982.
     Other groups active internationally include the world Health
Organization, which is participating in an epidemiological study
of skin cancer and other potential UV-related health effects; the
International Committee of Scientific Unions, which is  concerned
with biological effects of UV radiation and the overall
scientific issues; and the WMO, which is involved in the
atmospheric science.  The Chemical Manufacturers Association,
through its Fluorocarbon Program Panel  (an international group),
continues to sponsor experimental research related  to improving
the understanding of atmospheric processes, and annually
publishes world production and emissions information for CFC-11
and CFC-12.
     Resolution of the domestic control issues will consider  the
potential for cooperative action with other nations.  It is
anticipated that continuing  cooperation to examine various
scientific and policy issues in international fora will lead  to
better understanding and development of international responses
to the problem.

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                  V.   FURTHER REGULATION OF CFCS

     EPA will conduct a thorough review  (including  the  upcoming
NAS assessment) of the available scientific evidence before
making policy decisions about further control of CFCs.  The
current calculated rate of stratospheric depletion  of  ozone  and
moderation of growth in CFC uses in the U.S. and the world may
allow for scientific research and monitoring activities to
continue in order to decrease uncertainties and increase
knowledge while not incurring potentially  large impacts on
stratosphere ozone.  Any further Agency action will be  based  on
credible scientific evidence and sound economic analyses  subject
to rigorous peer review.
     EPA is working closely with other agencies to  coordinate the
exchange of research and information and to review  potential
responses to the issue by EPA and the other agencies.   Agencies
involved in this effort include FDA, Consumer Product Safety
Commission, Department of Commerce, Small  Business
Administration, Department of State, and Department of  Energy.
     In June 1980, EPA published a proposed rule under  Part A of
the CAA that would limit emissions of volatile organic  compounds
and five halogenated solvents (CFC-113, methyl chloroform,
methylene chloride, perchloroethylene, and trlchloroethylene)
from new, modified, or reconstructed organic solvent cleaners.
EPA is studying whether these halogenated  compounds should be
included in a final rule.

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                            REFERENCES
1.  "International Workshop on the Stratosphere, 1981," May 18-
    22, 1981, Hampton, Virginia.  Draft Report in preparation.

2.  Environmental Protection Agency, Materials Balance for Methyl
    Chloroform, Level II, Washington, D.C.: OTS, January 1980.

3.  D.J. Wuebbles, "The Relative Efficiency of a Number of
    Halocarbons for Destroying Stratospheric Ozone," Livermore,
    CA: Lawrence Livermore' National Laboratory (DOE Contract No.
    W-7405-Eng-48), January 1981.

4.  Environmental Protection Agency, "Standards of Performance
    for New Stationary Sources; Organic Solvent Cleaners,"
    45 FR 39766, June 11, 1980.

5.  National Aeronautics and Space Administration, "Present State
    of Knowledge of the Upper Atmosphere:  An Assessment Report,"
    January 1980.

6.  National Academy of Sciences, Protection Against Depletion of
    Stratospheric Ozone by Chlorofluorocarbons, Washington, D.C.:
    NAS, 1979.

7.  W. Riggan, J. Van Bruggen, J. Acquavella, and J. Beaubier,
    U.S. Cancer Mortality Rates and Trends, 1950-1978, Vol II.,
    EPA publication in preparation.

8.  Environmental Protection Agency, "Fully Halogenated Chloro-
    fluoroalkanes," 43 FR 11318, March 17, 1978 and Food and Drug
    Administration, "Certain Fluorocarbons (Chlorofluorocarbons)
    in Food, Food Additive, Drug, Animal Foodr. Animal Drug,
    Cosmetic, and Medical Device Products as Propellants in Self-
    Pressurized Containers," 43 FR 11301, March 17, 1978.

9.  Environmental Protection Agency, "Essential Use
    Determinations—Revised Support Document to Final Regulation
    on Fully Halogenated Chlorofluoroalkanes," March 17, 1978.

10. Environmental Protection Agency, "Fully Halogenated Cnloro-
    fluoroalkanes," 46 FR 5981, January 21, 1981.

11. Environmental Protection Agency, "Fully Halogenated Chloro-
    fluoroalkanes," 46 FR 27120, May 18, 1981.

12. Environmental Protection Agency, "Fully Halogenated Chloro-
    fluoroalkanes," 47 FR 148, January 5, 1982.

13. Environmental Protection Agency, "Fully Halogenated Chloro-
    fluoroalkanes," 46 FR 6062, January 21, 1981.

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