EPA-6QO/9-75-008
December 1975
REPORT ON THE PROBLEM OF
HALOGENATED AIR POLLUTANTS AND
STRATOSPHERIC OZONE
Environmental Sciences Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
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EPA-600/9-75-008
December 1975
REPORT ON THE PROBLEM OF HALOGENATED
AIR POLLUTANTS AND STRATOSPHERIC OZONE
submitted to
Subcommittee on Public Health and Environment
Committee on Interstate and Foreign Commerce
U. S. House of Representatives
U. S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
ENVIRONMENTAL SCIENCES RESEARCH LABORATORY
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
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DISCLAIMER
This report has been reviewed by the Environmental Sciences
Research Laboratory, U.S. Environmental Protection Agency, and
approved for publication. Mention of trade names or commercial
products does not constitute endorsement or recommendation for
use.
11
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PREFACE
This report was submitted in September, 1975, to the Subcommittee
on Public Health and Environment, Committee on Interstate and Foreign
Commerce, House of Representatives. It discusses the potential problem
of ozone depletion in the stratosphere resulting from the release of
some halogenated hydrocarbons, and presents knowledge gaps existing
in EPA research activities and plans for future research.
This report was prepared by Dr. Aubrey P. Altshuller, Director,
and Dr. Philip L. Hanst, Senior Research Scientist, in the Environmental
Sciences Research Laboratory. Mr. Kenneth H. Lloyd, Office of Air
Quality Planning and Standards, provided the information presented in
Appendix B.
The Chemistry and Physics Advisory Committee and staff members
of the Office of Research and Development and Office of Air and Waste
Management reviewed the report and offered a number of worthy comments.
111
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CONTENTS
Page
Preface
Summary
List of Figures vi
List of Tables vi
I Introduction 1
II Production, Uses, and Emissions of Halogenated Compounds 4
III The Research and Development Program in EPA 6
Program description 6
The results of field measurements 6
The results of laboratory studies 7
IV Atmospheric Chemistry Summary 14
Chlorinated compounds 14
A comment on brominated compounds 14
Natural emissions 14
V Emission Control - Needs and Problems 19
Degree of Threat of Major Halogenated Pollutants 19
VI Regulatory Authorities of EPA 25
VII Research Needs 26
Atmospheric measurements 26
Measurement techniques 27
Laboratory studies 29
VIII References 31
Appendix A: Summary of EPA Research Program on 32
Halogenated Air Pollutants-August 1975
Appendix B: Preliminary Assessment of Economic Impact of 36
Alternatives to Control Fluorocarbon Emissions
to the Atmosphere
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LIST OF FIGURES
Number
World-wide chlorine content of major man-made
chlorinated pollutants - 1973
World-wide amounts of chlorine in halogenated
compounds after photooxidation in troposphere
and lower stratosphere - 1973
Materials flow chart for chlorocarbons
Page
17
17
21
LIST OF TABLES
Number
Estimated Emissions of Halogenated Compounds
into the Atmosphere
Atmospheric Chemistry Summary
Page
5
15
VI
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SUMMARY
The Environmental Protection Agency is actively studying certain
aspects of the problem of the interaction of halogenated chemical species
with stratospheric ozone. The halogenated gaseous pollutants contain
fluorine, chlorine, and/or bromine. About 20 percent of the pollutants
of concern are the fully halogenated compounds such as fluorocarbon-11,
fluorocarbon-12, and carbon tetrachloride. No known ways exist by which
these pollutants are removed from the lower atmosphere by ground surfaces
or oceans. Consideration of chemistry and physical transport models
indicate that fully halogenated substances migrate to the stratosphere
where they are photodissociated, with consequent adverse effects predicted
on the ozone balance. Fully halogenated substances have been measured in
the stratosphere.
The remaining 80 percent of the emissions of halogenated pollutants
involve production and usage losses of various high production industrial
organic chemicals including methyl chloroform, methylene dichloride,
dichloroethane, perchloroethylene, trichloroethylene, vinyl chloride, and
smaller amounts of other chlorinated and brominated industrial chemical.
The chemistry of these compounds is such that they have shorter lifetimes
in the lower atmosphere than the fully halogenated compounds. However,
the lifetimes of these compounds, or the lifetimes of halogenated compounds
formed by chemical reactions, may be long enough for a significant fraction
of the compounds to move into the stratosphere along with the fully halo-
genated compounds. If so, they will likely undergo the same type of
reactions, thus also contributing to potential ozone depletion.
In addition to the urgent need for a continuing program to measure
fluorocarbon-11 and fluorocarbon-12, continuing study of other halogenated
pollutants by EPA is needed. This research will include studies of tro-
pospheric removal processes and their rates as well as stratospheric
photodissociation processes and their rates. These studies should be
directed at both the parent compounds and oxidation products.
Optical and gas chromatographic measurements of atmospheric pollutants
should be carried out as functions of altitude, latitude, and time. Measure-
ments are needed of the potential for removal by rain of a number of these
halogenated substances and their halogenated reaction products. Laboratory
studies must be addressed to unknown factors that limit the accuracy of the
modeling of atmospheric chemical processes. These factors include photo-
oxidation mechanisms, rates of individual oxidation reaction steps, photo-
dissociation rates and products, and hydrolysis rates and products. The
Office of Research and Development of EPA is addressing these needs for
atmospheric measurements and laboratory studies.
If continuing research confirms the danger of stratospheric ozone
depletion by halogenated pollutants, control measures will be necessary.
Use of fluorocarbons as aerosol propellants would have to be curtailed.
VII
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Fluorocarbons used in refrigeration applications would have to be replaced
by other working fluids that are not detrimental to the environment, Halo-
genated pollutants emitted during industrial operations would have to be
controlled by best available control technologies such as vapor recovery,
solvent recycling, or* the substitution of alternate compounds. -Considerations
of atmospheric chemistry and health effects would determine which alternate
compounds were acceptable.
The current research program funded by EPA is described in Appendix A
of this report. Appendix B covers emission sources, current control
technology, and possible chemical substitutes for the fluorocarbons.
The economic impacts of several regulatory options for fluorocarbon are
considered.
V11J.
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SECTION I
INTRODUCTION
This report pertains to a potential problem concerning depletion of
stratospheric ozone by air pollutants containing chlorine, fluorine, and
bromine. Some researchers have predicted that ozone depletion would in-
crease the incidence of skin cancer and might affect climate and crops.
The possible effects have been discussed in the report of the Federal Task
Force, on Inadvertent Modification of the Stratosphere (IMOS) issued in June
1975. UJ
At hearings before the Subcommittee on Public Health and Environment,
Committee on Interstate and Foreign Commerce, House of Representatives on
December 11, 1974, Mr. John R. Quarles, Jr., Deputy Administrator of the
Environmental Protection Agency indicated that EPA would report by August
1975 on progress in its research program on halogenated air pollutants.
This report therefore focuses on EPA activities. It supplements the
IMOS report and is independent of the study of fluorocarbons by the
National Academy of Sciences. The main concern of the EPA program and
this report is to bring out certain aspects of the overall problem that
need consideration if EPA must take future action to regulate production
or usage of fluorocarbons and other halogenated pollutants.
Stratospheric ozone depletion by halogenated pollutants involves
the following chemical sequence. A chlorine atom released in the strato-
sphere attacks ozone, yielding chlorine oxide and diatomic ozygen. The
chlorine oxide reacts with oxygen atoms that exist in photochemical
equilibrium with ozone. This reaction yields diatomic oxygen and re-
generates a chlorine atom that is then free to attack another ozone
molecule.
Cl + 0, -v CIO + 0-
3 2
0_ + hv -* 00 + 0
3 2
CIO + 0 -> 0_ + Cl
This sequence will repeat itself hundreds or thousands of times until
the chlorine atom is removed from the scene in a collision with a hydro
genated molecule such as methane,
Cl + CH. -> HC1 + CH_
4 3
Fluorine atoms released into the ozonosphere will undergo a sim-
ilar sequence of reactions, but with a much shorter chain length. The
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chain is shorter in the fluorine case because the chain-breaking hydro-
gen abstractions are faster. The halogen acids HC1 and HBr can also
return their halogen atoms to the ozone cycle in reactions witli On
radicals: HC1 + OH -» hLO + Cl. Hydrogen fluoride does not under-
go this return reaction.
Bromine atoms will initiate a similar sequence, with chains
longer than those involving chlorine.
The rate of input of halogen atoms to the stratosphere must be
established if the ozone depletion predictions are to be accepted as
reliable. This rate of input depends on two main factors: (1) the
transport of the halogenated pollutants through the troposphere and
stratosphere, and (2) atmospheric chemical reactions during trans-
port.
Most of the scientific effort by other government agencies and
industry is presently associated with transport and reaction pro-
cesses in the stratosphere. This aspect received considerable dis-
cussion in the IMOS report and no doubt will also be discussed in the
NAS report. Therefore, the present EPA program and this report do not
emphasize stratospheric monitoring or models of stratospheric processes,
but address questions concerning the possible role of each of the
major fluorocarbon and halocarbon pollutants and to problems associated
with the control of these emissions.
Concern extends not only to the major fluorocarbons in commercial
production, but also to a substantial number of other chlorine-containing
and bromine-containing pollutants. Fluorocarbons of concern are fluoro-
carbon-11 (CC1_F), fluorocarbon-12 (CC1-F-), fluorocarbon-22 (CHC1F ),
C12F). The other
V-V^J- t-t\SlL 4.JL ^WOJLA^J -1. A IAVS -L W*l
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Recent experimental results indicate the existence of large biogenic
sources of methyl chloride and methyl bromide. The impact of natural
sources of halogen atoms on the stratospheric ozone balance has to
be taken into consideration. Therefore, the worldwide distributions
and residence times of the naturally emitted halocarbons must be
accurately determined.
If research demonstrates that individual halocarbons have significant
potential for stratospheric depletion of ozone, then emission abatement
options may be considered for implementation.
A number of optional strategies are available for control of
fluorocarbons and halocarbons. These strategies are associated
closely with the usage pattern of each individual halocarbon, the
potential for reducing emissions through technology or with use of
alternative means of providing an acceptable end product.
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SECTION II
PRODUCTION, USES, AND EMISSIONS OF HALOGENATED COMPOUNDS
Data on world-wide production, end-use, and estimated emissions of the
principal halogenated air pollutants for the year 1973 are given in Table
1. This tabulation has been extracted from a report prepared by Arthur D.
Little, Inc. under contract to the Environmental Protection Agency, Office
of Air Quality Planning and Standards. That report, entitled Preliminary
Economic Impact Assessment of Possible Regulatory Action to Control At-
mospheric Emissions of Selected Halocarbons, is currently in process of
publication. Emissions of brominated halocarbons have not been pre-
cisely defined and are not tabulated. They appear to be small compared
to the emissions of chlorinated compounds.
Present world-wide production and emission occurs roughly 50 percent
in the United States, 35 percent in Europe, and 15 percent in the rest of the
world. From the table it is seen that the 1973 emissions were proportioned
20 percent fluorocarbons, and 80 percent other chlorinated pollutants.
These figures emphasize the importance of a careful consideration of the
possible impact of these other chlorinated pollutants on the stratospheric
ozone, as discussed in the following sections.
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Table 1. ESTIMATED EMISSIONS OF HALOGENATED
COMPOUNDS INTO THE ATMOSPHERE
Compound World production Principal Estimated emissions into
in 1973, uses (and the atmosphere in 1973
millions of pounds percent of
total World total, U.S. total,
production) millions of percent.
pounds
Fluorocarbon-11
Fluorocarbon-12
Fluorocarbon-22
Fluorocarbon- 113
F luorocarbon- 1 14
Carbon tetra-
chloride
Chloroform
Ethyl chloride
670
980
270
110
100
2090
496
1210
Aerosol propel lant (78%) 600
Aerosol propellant (47%) 740
Refrigerant (34%)
Refrigerant (66%) 120
Solvent (85%) 100
Propellant (91%) 70
Refrigerant (9%)
Production of 88
fluorocarbons (88%)
Production of 12
fluorocarbons (90%)
Produce tetraethyl 29
50
50
50
50
50
50
50
55
Ethylene dichloride 26,400
Methyl chloride 880
Methyl chloroform 900
Methylene chloride 935
Perchloroethylene 1650
Trichloroethylene 1540
Vinyl chloride 15,600
lead (85%)
Produce vinyl 1250
chloride (78%)
Produce silicones (43%) 11
and tetramethyl lead (38%)
Metal cleaning (70%) 835
and degreasing
Paint remover (40%) 760
Dry cleaning (65%) 1370
Metal cleaning (86%) 1390
Produce polyvinyl 774
chloride (89%)
35
60
60
55
45
30
25
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SECTION III
THE RESEARCH AND DEVELOPMENT PROGRAM IN EPA
PROGRAM DESCRIPTION
The Environmental Sciences Research Laboratory of the Office of
Research and Development, EPA, Research Triangle Park, North Carolina,
has been engaged in the study of halogenated air pollutants for three
years. Until recent months the program has been limited to two university
research grants and a small amount of intramural experimental work in-
volving two scientists on a part-time basis. Our interest in the pro-
blem goes back to 1971 when .-the .first measurements of halogenated pol-
lutants became known to us. At that time, the threat of strato-
spheric ozone depletion by chlorine atoms had not been recognized.
Nevertheless, a modest program of study was initiated, with the long
range goals of learning the eventual fate of the halogenated pollutants
and determining if any undesirable effects existed.
The detection of the halogenated pollutants had also led a
number of other research groups into the study of the possible
effects of the pollutants. Rowland and Molina, working under an
Atomic Energy Commission research grant at the University of
California, Irvine, were especially successful in developing an
insight ipto the possible consequences of the chlorinated pol-
lutants. Their publications in 1974, and the publications of
several other groups of researchers, pointed out the potential
dangers of stratospheric chlorine-ozone reactions. As a result,
government agencies with an interest in the problem, including
NASA, NOAA, and EPA, initiated new programs of study. In the
latter part of Fiscal Year 1975, the EPA program was expanded to
four university grants, a three man-year level of research effort
by a contractor at Research Triangle Park, and a three man-year
level of effort by our own research staff. A program summary is
included as an appendix to this report.
The EPA program has had two aspects: (1) field measurements
of the halogenated pollutants, and (2) laboratory studies of the
chemical reactions that the pollutants undergo in the atmosphere.
Following is a discussion of the results obtained in these studies.
THE RESULTS OF FIELD MEASUREMENTS
In the program of field measurements, gas chromatographic
techniques have been applied by Rutgers University personnel and
i-nf-rared absorption techniques have been applied by EPA personnel.
These two measurement programs have made valuable contributions
to the existing state of knowledge of the concentrations and spatial
distributions of the halogenated pollutants. The,detailed results
of this work are in process of being published. In summary,
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the measurements show a spatial distribution of pollutants that can
be accounted for in terms of emissions patterns, atmospheric transport
properties, and atmospheric chemical reactions.
Chemically inert pollutants such as fluorocarbon-11, fluoro-
carbon-12, and carbon tetrachloride, are found to be distributed
throughout the atmosphere. In the clean air of rural areas,
following the passage of a storm front, one sees the true back-
ground concentrations of these pollutants. The observed amounts
of the three compounds are approximately equivalent to an
accumulation of all of man's releases of these compounds up to the
present time. There is no firm evidence that any of the three is
produced by natural processes. In urban areas, the concentrations of
fluorocarbon-11 and fluorocarbon-12 usually are 5 to 10 times greater
than their background concentrations, while the concentration of carbon
tetrachloride in urban air is usually not higher than its background
level. This confirms that fluorocarbon-11 and fluorocarbon-12 are
presently being released by the populace, while carbon tetrachloride
is not. Present releases of CC1. are primarily industrial.
Changes in concentrations of fluorocarbon-11 and fluorocarbon-12
from day to day parallel the changes in auto exhaust pollution. These
changes in general pollution level are directly related to the meteoro-
logical conditions. When the lower atmosphere stagnates, all the pol-
lutants build up, even in rural areas. When a front moves through
vertical mixing seems to dissipate all pollution.
Halogenated pollutants that can be oxidized in the troposphere
are not ubiquitous, but show variations in concentration from near
zero in rural areas to high values in the vicinity of the sources.
Among the oxidizable compounds are the halogenated olefins and the
halogenated paraffins with one ore more hydrogens remaining in the
molecule.
All of the major suspected halogenated pollutants have been
detected either by the gas chromatographic method or by the infrared
absorption method. At present there is a. great need to increase the
sensitivity of these measurements and to carry them out fully as a
function of altitude and latitude. The principal species that are yet
to be detected are the relatively stable intermediate oxidation products
such as phosgene and chloroacetyl chloride. The measurement needs will
be discussed more fully in a following section.
THE RESULTS OF LABORATORY STUDIES
The attack of halogen atoms on stratospheric ozone is triggered
by photodissociation or photooxidation of the halogenated pollutants.
The flux of halogen containing compounds into the stratosphere de-
pends on the chemical stability of the primary halogenated pollutants
as well as on the types of chemical transformations that those pol-
lutants undergo, and finally on the chemistry of the reaction products.
The reaction steps and rate constants obtained from laboratory measure-
ments thus are basic inputs to the mathematical models of the strato-
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spheric chemistry. The ozone loss predictions of these models are
strongly dependent on the input rate constants, pollutant concentra-
tions and pollutant spatial distributions. The chemical processes
have been a major subject of the Environmental Sciences Research
Laboratory program. The work has been carried out in two projects:
the research grant at the Pennsylvania State University and the intra-
mural program at Research Triangle Park. Some of the experimental
results have, been, published and others are in the process of
publication.1 HJ
The experimental results and some of their implications are
discussed below for each principal compound, in alphabetical order.
The atmospheric chemistry in these discussions is based on information
available at the present time. Since there are gaps and uncertainties
in that body of information, some of the interpretations as to life-
times, mechanisms, and product yields are only tentative. As the
research program continues, the details of the atmospheric chemistry
will become more quantitative and more reliable.
Carbon Tetrachloride
The annual release of carbon tetrachloride pollution is small com-
pared to the annual releases of some of the other chlorinated compounds.
Nevertheless, the inertness of carbon tetrachloride has allowed the
compound to accumulate in the air so that it is a major halogenated pol-
lutant. There are no indications of CC1. removal processes at work
in the troposphere. As in the cases of fluorocarbon-11 and fluoro-
carbon-12, the only suspected removal process is the photodissociation
that takes place in the stratosphere. It is likely that this photo-
dissociation occurs in a region where the chlorine atoms are highly
effective in destroying ozone. The following three equations summarize
the degradation mechanism indicated by laboratory studies:
CC14 + hv -> CC13 + Cl
CC1 + 0 -» COC1, + CIO
O 4* ^
COC1 + hv -> CO + 2C1
Since the phosgene (COC1_) is a stronger ultraviolet absorber than
the carbon tetrachloride, the phosgene photolysis will follow the
carbon tetrachloride photolysis rather quickly. Thus all four
chlorine atoms will be released into the stratosphere in the vicinity
of the initial photolytic dissociation.
Carbon tetrachloride has been a major halogenated pollutant longer
than any other. Consequently, it seems possible that the compound is
approaching a steady-state distribution throughout the troposphere and
stratosphere. Carbon tetrachloride may therefore be the halogenafprl
pollutant having the greatest present effect on stratospheric ozone.
The future threat of carbon tetrachloride, however, is not rated as
great as the future threat of fluurocarbon-ii aaJ liuorocaiLon-ii. ,
because the present emission rate of CC1. is relatively small.
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Chloroform
Chloroform is a minor chlorinated pollutant, subject to photo-
oxidation in the troposphere. The abstraction of the hydrogen from
the molecule by OH radicals leaves a CCl^ radical which reacts with
oxygen to yield phosgene, (COCIJ , and chlorine oxide (CIO). The
atmospheric lifetime of chloroform is estimated to be two or three
months. Thus the chlorine oxide will be released in regions of the
atmosphere where there is very little ozone to be destroyed. Before
any ozone is encountered, the CIO will be reduced to Cl, and the Cl
will abstract hydrogen from methane yielding hydrogen chloride. This
HC1 will be removed in precipitation. The phosgene must of course
be considered for its potential interaction with ozone. If this phosgene
were to migrate to the ozone-rich regions of the stratosphere, its
photodissociation would contribute to ozone destruction. Phosgene removal
processes and their rates need to be established for both the troposphere
and the stratosphere.
Ethyl Chloride
The impact of ethyl chloride on stratospheric ozone may be con-
sidered negligible for two reasons: (1) the amount of ethyl chloride
emitted is relatively small, and (2) the compound will largely be
photooxidized in the troposphere, yielding up its chlorine in the
form of hydrogen chloride. The hydrogen chloride will be removed
from the atmosphere either by direct interaction with the earth's
surface or by absorption in precipitation.
Ethylene Dichloride (1,2 Dichloroethane)
Ethylene dichloride is emitted to the atmosphere in large
amounts. The compound may be a threat to stratospheric ozone by
virtue of yielding chloroacetyl chloride during photochemical oxidation.
If this product is formed in the lower troposphere it will probably be
washed out by rain. If it forms in the stratosphere, however, the
chloroacetyl chloride may persist until its chlorine is released in
photodissociation. Available data on the rate of reaction of ethylene
dichloride with hydroxyl radicals indicate an atmospheric lifetime of
three or four months. This might be long enough to allow some ethylene
dichloride to penetrate the stratosphere. Further study of this reaction
rate should be undertaken. Attempts should be made to measure both the
ethylene dichloride and the chloroacetyl chloride in the stratosphere.
FKiorocarbon-11 (Trichlorofluoromethane)
Fluorocarbon-11 has no recognized removal paths within the tro-
posphere. Stratospheric photodissociation is considered to be the
only significant removal process.
+ hv -> CC1F + Cl
The released chlorine atoms react with a large number of ozone mole-
cules before being removed as HC1. The CC12F radicals react with
oxygen to yield CIO and carbonyl chloro fluoride, COC1F. The latter
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compound is then photolyzed to CO, F, and Cl. The result is that the
three chlorine atoms and one fluorine atom are released into the at-
mosphere in the vicinity of the initial photodissociation.
Fluorocarbon-12 (Dichlorodifluoromethane)
Photodissociation in the stratosphere is the only recognized
reaction of dichlorodifluoromethane (fluorocarbon 12) leading to its
removal from the atmosphere. The initial photolytic process is
written:
CC12F2 + hv -» CC1F2 + Cl
The chlorine atoms will then attack ozone. The free radical CC1F_ will
add oxygen and split out CIO, leaving carbonyl fluoride just as in the
case of photooxidation of F-22. In the F-12 case, however, the carbonyl
fluoride will not be washed out, but instead it will be photodissociated
to fluorine atoms and carbon monoxide. The chlorine and fluorine atoms
eventually react with hydrogen-containing molecules to yield the halo-
gen acids, HC1, and HF. These travel down to the troposphere and are
removed in precipitation.
Fluorocarbon-22 (Chlorodifluoromethane)
Chlorodifluoromethane can have its hydrogen atom abstracted by an
OH radical, and therefore will suffer degradation in the troposphere.
CHC1F + OH -> HO + CC1F
^ ^ £*
CC1F2 + 02 -* COF2 + CIO
This OH attack allows an F-22 molecule an atmospheric lifetime of
only three or four months. The carbonyl fluoride may be washed out
in the troposphere, or it may reach the stratosphere and be photo -
dissociated. Since the amount of chlorine available in fluorocarbon
22 is small and since the chlorine is released mainly in the tro-
posphere, the effect of F-22 on stratospheric ozone is considered
minor .
Methyl Chloride
Although methyl chloride is a minor pollutant from the point
of view of direct emissions, measurements have shown it to be the
halogenated pollutant with the highest background atmospheric con-
centration. This indicates a natural source, or at least a large
indirect human source. It is conceivable that the total emissions
of methyl chloride could be carrying into the atmosphere as much
chlorine as is carried by all other chlorinated pollutants com-
bined. It thus becomes of great importance to consider the at-
mospheric chemistry of methyl chloride. The half-life of the com-
pound in the troposphere most likely falls in the range of one to
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six months, similar to the half-lives of chloroform and methylene
chloride. This may permit some of the methyl chloride to cross
into the stratosphere.
The 8^?tr?ction of a hydrogen atom from methyl chloride has
been shown in an EPA study to initiate a series of reactions leading
to formyl chloride. The significant finding in this study is that
the single chlorine is not released from the molecule as CIO, which
can attack ozone, but rather it is released in the carbonyl com-
pound HCOC1. This compound is thermally unstable at room temperature,
decomposing to CO and HC1 with a half-life of about 20 minutes.
Methyl chloride molecules oxidized in the lower troposphere
therefore have little or no potential for destruction of ozone.
For oxidation taking place at higher altitudes, the situation may
be different. In the upper portion of the troposphere and in the
lower stratosphere temperatures can be much lower than room tem-
perature. In these regions the formyl chloride produced in photo-
oxidation may exist long enough to be photodissociated into a
chlorine atom and a formyl radical. The best way to determine
whether or not reactions are occuring would be to measure methyl
chloride in the stratosphere as a function of altitude.
Methyl Chloroform
Methyl chloroform, CH,CC1_, is one of the major chlorine carriers
in the atmosphere. It is a compound that is rather resistant to photo-
oxidation, with a half-life in the troposphere of several years. Thus
it is highly likely that a portion of the methyl chloroform pollution
will find its way into the stratosphere. The slow photooxidation that
takes place both in the troposphere and in the stratosphere yields
trichloro acetaldehyde (chloral). It seems likely that this aldehyde
is then oxidized to trichloro acetic acid, although this has not yet
been demonstrated experimentally. The acid could be washed out of the
troposphere. Both the acid and the aldehyde will be photodissociated
in the stratosphere, yielding chlorine atoms that will be free to
attack ozone. Methyl chloroform must therefore be considered to be
a major threat to stratospheric ozone. The compound should be the
subject of further laboratory study and should be measured with care
in both the troposphere and stratosphere.
Methylene Chloride
Methylene chloride, CH2C12, is a major halogenated pollutant with
a large potential for delivery of chlorine to the stratosphere. The
photooxidation of the compound in the troposphere probably proceeds
with a half life of several months, similar to the cases of methyl
chloride and chloroform. This half-life may be long enough to allow a
substantial part of the methylene chloride to cross the tropopause.
The principal oxidation product of methylene chloride is the phosgene
which Jesuits from the two hydrogens being abstracted from the molecule.
It is conceivable that this phosgene may be photolyzed to yield chlorine
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atoms in the ozone-rich region of the stratosphere. It thus appears
uiat there is some potential for ozone destruction by methylene chloride.
Stratospheric measurements of the parent compound and the phosgene re-
sulting from oxidation are very much needed.
Perchloroethylene
The large release rate of perchloroethylene requires that its
removal processes and secondary products be given the most careful
study. The attack on the double bond by oxygen atoms, hydroxyl
radicals, or ozone molecules produces trichloro acetyl chloride,
CC1_COC1, as a major product and phosgene, COC1?, as a lesser pro-
duct. The four chlorine atoms confer an oxidation resistance on the
molecule, giving it an atmospheric lifetime longer than the life-
times of most other olefin pollutants. A perchloroethylene molecule
may exist in the troposphere for weeks before reacting. A lifetime
of weeks is longer than the tropospheric mixing time under certain
conditions. Thus, it is possible for perchloroethylene to reach
the tropopause and cross into the stratosphere. The important con-
sideration here is not that perchloroethylene may reach the ozone
region in the stratospherethat is unlikely-<-bkt rather that the
trichloroacetyl chloride and phosgene reaction products may reach
the ozone regions. Carbonyl compounds, including phosgene and the
chloro acetyl chlorides, are relatively strong absorbers of ultra-
violet radiation. Since ultraviolet absorption yields chlorine atoms,
it is conceivable that perchloroethylene, through its reaction pro-
ducts, may be influencing the stratospheric ozone balance.
To fully understand the effects of perchloroethylene in the
atmosphere, one must determine the fate of the trichloro acetyl
chloride and phosgene. Are these compounds washed out of the
troposphere by rain? Do they cross the tropopause? Is their
rate of photodissociation in the stratosphere slow enough to
allow them to reach the layer of high ozone content? These
questions must be answered if the role of perchloroethylene in
stratospheric chemistry is to be fully understood. Laboratory
studies of the removal processes can be helpful, but the best way
of determining the role of these reaction products is to directly
measure their concentrations in the atmosphere.
Trichloroethylene
Trichloroethylene will be photooxidized in the troposphere with
a relatively short half lifeless than one day. This, however, does
not mean that the compound should be dismissed as a potential source
of chlorine atoms in the stratosphere. One needs to consider the
reactivity and lifetimes of the chlorinated products of the photo-
oxidation. These products are principally dichloro acetyl chloride
and phosgene. The rate of removal of these gaseous compounds needs
to be known. This removal may occur at the earth's surface or at
the surface of atmospheric particles. Wash-out by rain may be an
important process. If these removal rates are slow, it is conceivable
that the carbonyl compounds could cross the tropopause and diffuse upwards
where they would be photodissociated, yielding chlorine atoms.
-12-
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Vinyl Chloride
Although a large amount of vinyl chloride is lost to the atmosphere
annually, rapid photochemical oxidation removes the compound with a half-
life of a few hours. The chlorine separates from the parent molecule
either in the form of hydrogen chloride, HC1, or in the form of formyl
chloride, HCOC1. The latter compound has been found to decompose
thermally with a half-life at room temperature of about 20 minutes,
yielding CO and HC1. All the chlorine in vinyl chloride will therefore
end up as HC1 within a day or two of release. The HC1 is removed at
surfaces and in precipitation. It is concluded therefore that the
impact of vinyl chloride on stratospheric ozone is negligible.
-15-
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SECTION IV
ATMOSPHERIC CHEMISTRY SUMMARY
CHLORINATED COMPOUNDS
The type of atmospheric degradation of the primary chlorinated pollutants
and the proportions of chlorinated reaction products have been determined
in the EPA research program. The lifetimes of these pollutants are also
fairly well known from EPA studies and from studies in other laboratories.
These data are summarized in Table 2. Figure 1 shows a bar graph presen-
tation of the total chlorine content of the pollutants for the year 1973,
excluding natural emissions. Figure 2 shows a bar graph of the chlorine
content of the primary products that are released by reactions in the
troposphere and lower stratosphere, again excluding natural emissions.
The fluorocarbon-11, fluorocarbon-12, and carbon tetrachloride are con-
sidered to be non-reactive in the troposphere and lower stratosphere.
They thus appear in Figure 2 in the same amount as in Figure 1.
A COMMENT ON BROMINATED COMPOUNDS
A bromine atom in the stratosphere may be more damaging to ozone than
a chlorine atom, because the removal of bromine by methane is much slower.
One must therefore consider whether brominated compounds are finding their
way into the stratosphere.
Ethylene dibromide (C^H.Br^) is by far the largest commercially pro-
duced bromine-containing compound. Its main uses are as a gasoline additive
and as a soil and grain fumigant. In the 1960's world production of ethylene
dibromide was about 240 million pounds per year. Most of this bromine
probably ends up as lead salts that are washed into the ground. If a small
fraction of the total entered the atmosphere as ethylene dibromide, however,
part of the bromine might be able to reach the stratosphere. This matter
should be explored through atmospheric analysis.
Methyl bromide (CH_Br) is the second principal brominated pollutant.
It is mainly used for fumigation of soils and stored commodities to kill
rodent and insect pests. Much of this methyl bromide undoubtedly ends
up in the atmosphere. Methyl bromide is more expensive than ethylene
dibromide, and therefore it is used on a smaller scale. A large amount
of methyl bromide may be released along with methyl chloride by the action
of marine algae. This matter also needs to be investigated by sensitive
atmospheric analysis.
NATURAL EMISSIONS
Natural emissions of methyl chloride are indicated by measurements of
background concentrations as high as one part methyl chloride in 10 parts
air. If this concentration occurs uniformly throughout the atmosphere,
and if the tropospheric lifetime of methyl chloride is six months, the
influx of methyl chloride into the atmosphere might be on the order of
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PERCHLOROETHYLENE
TRICHLOROETHYLENE
ETHYLENE DICHLORIDE
METHYL CHLOROFORM
METHYLENE DICHLORIDE
VINYL CHLORIDE
FLUOROCARBON -11
FLUOROCARBON 12
CARBON TETRACHLORIDE
FLUOROCARBON -22
ETHYL CHLORIDE
CHLOROFORM
METHYL CHLORIDE
0 0.5 1.0
CHLORINE, 109 pounds
Figure 1. World-wide chlorine content of major man-made chlorinated pollutants - 1973.
1.5
TRICHLORO ACETYL CHLORIDE
MONOCHLOROACETYL CHLORIDE
PHOSGENE
DICHLORO ACETYL CHLORIDE
TRICHLORO ACETALDEHYDE
HYDROGEN CHLORIDE
FLUOROCARBON-11
FLUOROCARBON -12
FORMYL CHLORIDE
CARBON TETRACHLORIDE
CHLORINE OXIDE
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CHLORINE, 109 pounds
Figure 2. World-wide amounts of chlorine in halogenated compounds after photo-oxidation in troposphere and lower
stratosphere - 1973.
-17-
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fifty billion pounds per year. That much methyl chloride would carry more
chlorine than all man-made chlorinated pollutants combined. This matter
clearly demands confirmatory atmospheric measurements as well ab laboratory
studies of methyl chloride photooxidation. If methyl chloride is emitted
in such large quantities from natural sources, perhaps methyl bromide is
also emitted.
If a large flux of chlorine into the stratosphere from natural sources
has always existed, then the effect of man-made chlorine on the stratospheric
ozone balance might be smaller than has been predicted. The analogy has been
offered of a bathtub that is being filled with water at the top and drained
from the bottom. The water level at equilibrium will depend on how large
the drain is. Man's enlargement of the stratospheric ozone drain will lower
the ozone level. If the natural size of the ozone drain is shown to be
larger than has been believed up to the present time, then man's lowering of
the ozone level will be smaller than has been anticipated. How large the
natural ozone drain has been and how great man's effect will be are subjects
of current research and current differences of opinion among scientists.
-18-
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SECTION V
EMISSIONS CONTROL - NEEDS AND PROBLEMS
The control of emissions of halogenated pollutants may encounter
technical difficulties and may cause economic disruptions. It is therefore
prudent to consider problems of control now for any compounds that have
a reasonable possibility of needing control in the future. Possible economic
disruptions are discussed in detail in the report, previously cited, to be
issued by the EPA Office of Air Quality Planning and Standards (2). Two
summary figures from that report are presented here as Figures 3 and 4. These
figures, in the form of flow charts, show the close interrelationships
among many of the chlorocarbons, fluorocarbons and other industrial chemicals.
These charts show that disruptions in one sector of the chlorocarbon
industry are likely to have serious effects in other sectors. The charts
also emphasize the important position that chlorocarbons occupy in the
chemical industry. Imposition of fluorocarbon or chlorocarbon controls
would most clearly cause economic disruptions.
DEGREE OF THREAT OF MAJOR HALOGENATED POLLUTANTS
The need for emissions control obviously must be established with
as little uncertainty as possible. It is presumed that if a need is
established, control will be imposed, regardless of the difficulties.
Current research programs in the United States, including the program of
the Environmental Protection Agency, therefore seek to determine the degree
of threat to stratospheric ozone posed by each major halogenated pollutant.
The current state of knowledge of the atmospheric chemistry and transport
processes allows some preliminary conclusions. These are stated below,
along with some comments on problems of emissions control. In most cases,
the current state of knowledge does not allow firm conclusions, but indicates
needs for further study.
Carbon Tetrachloride
Carbon tetrachloride appears to be one of the principal chlorine carriers
presently migrating to the stratosphere and interacting with the ozone.
Current emissions of CC1. are relatively small, so that control of the
compound cannot have a large effect on the projected future flux of chlorine
atoms into the stratosphere. At the same time it is recognized that any
control that can be effected will be of value, especially since CC1. contains
a higher percentage of chlorine, by weight, than any other chlorinated
pollutant.
Home uses of CC1. have been severely curtailed because of health
hazards. Domestic releases thus are not as great as they once were.
Venting of CC1. to the atmosphere presently occurs mainly during industrial
operations, such as the production of fluorocarbons. Control of these
emissions may require xoviaiuu oi manufacturing techniques or installation
of vapor recovery equipment. CC1. is also lost to the atmosphere in its
use as a solvent and a? a grain fnmigant. These losses may be reduced or
eliminated by choosing an alternate compound.
-19-
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Chloroform
Control of chloroform emissions would only have a very small effect on
the flux of chlorine into the stratosphere. Chloroform is not emitted to the
atmosphere in large quantities. The small amount emitted is likely to be
photooxidized in the troposphere. If the phosgene reaction product can
travel from lower troposphere to stratosphere, there might be some effect
on the stratospheric ozone balance, but it would be a small effect.
Ethyl Chloride
There appears to be little need to control ethyl chloride because the
compound is emitted in small amounts and it will largely be photo-oxidized
in the troposphere, yielding up its chlorine as hydrogen chloride. This HC1
will in turn be taken out of the atmosphere by precipitation.
Ethylene Dichloride
Until proven otherwise, ethylene dichloride must be considered a threat
to stratospheric ozone. As shown in Figure 3, ethylene dichloride is the
precursor of vinyl chloride and other large volume chlorinated compounds.
Its production volume is so large that a few percent loss in processing
amounts to a large volume of emission into the atmosphere. The lifetime of
ethylene dichloride in the troposphere is three or four months long enough
to allow a wide distribution of the compound. The chlorinated reaction
product, chloroacetyl chloride, may have sufficient stability to travel
upwards to the ozone layer. These are important matters to be addressed
in the continuing research program. Meanwhile, the problems of control of
ethylene dichloride should be considered. Since the emissions are mainly
industrial, controls might take the form of improvements in handling
methods, vapor recovery systems, or manufacturing process changes.
Fluorocarbon-11
Since no removal processes have been discovered for fluorocarbon-11 in
the troposphere, it must be assumed that stratospheric photo-dissociation
is the outlet for all of the chlorine carried into the atmosphere by the
compound. This chemical behavior and the large tonnage of F-ll releases
have resulted in the compound being ranked as a primary threat to the
stratospheric ozone balance. If further atmospheric measurements and
laboratory studies fail to alter the prevailing concepts of the role of
F-ll in the atmosphere, then control actions should be undertaken.
The major use of F-ll as propellant in personal care products can
probably be discontinued with no great hardship to the general public.
Alternate methods of delivering hair preparations, deodorants, and insect
killers are easy enough to visualize. Non-spray delivery is one
possibility; finger pumping is another. If a propellant must be used,
other gases such as carbon dioxide can be considered.
Fluorocarbon-12
Fluorocarbon-12 is ranked with fluorocarbon-11 as a primary threat
to the stratospheric ozone balance. If this view is maintained through
-22-
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the current program of atmospheric analysis and laboratory study, emissions
control should be undertaken. As in the case of F-ll, it appears that the
use of F-12 as an aerosol propellant could be phased out by the development
cf alternate delivery systems and by the substitution of other propellant
gases. The replacement of F-12 in refrigeration systems will no doubt take
considerably longer than its replacement in propellant applications. A
change to other refrigeration working fluids will require new product develo-
nent by manufacturers a process that takes a number of years. Among the
alternate working fluids is fluorocarbon 22, which is degradable in the
troposphere and is not considered a serious threat to stratospheric ozone.
Fluorocarbon-22
Fluorocarbon-22 is expected to react in the troposphere, yielding chlorine
oxide and carbonyl fluoride. The chlorine oxide will be converted to hydrogen
chloride in the troposphere and then be removed in precipitation. The
carbonyl fluoride might also be removed in precipitation, but even if it
is not, the carbonyl fluoride would not decompose stratospheric ozone to any
great extent. Thus fluorocarbon-22 may become a candidate for increased use
rather than decreased use. The compound is especially useful in refrigeration
applications, whose continuation is highly desired. Fluorocarbon-22 should
be looked at as a possible substitute for fluorocarbon-11 and fluorocarbon-12,
although it will require system redesign. Before a large increase the re-
lease of fluorocarbon-22 is permitted, information should be sought on the
atmosphere lifetime and the health effects of carbonyl fluoride.
Methyl Chloride
If the belief in an extremely large natural source of methyl chloride
persists, it will be difficult to see the need for control of the much
smaller amount of methyl chloride emitted as a result of human activities.
Methyl Chloroform
The large volume of methyl chloroform emissions and the long atmospheric
lifetime require that the compound be ranked tentatively as a threat to
stratospheric ozone. Most emissions of methyl chloroform are a result of
metal cleaning operations. These emissions can be reduced by installation of
vapor confinement systems, condensers, and other control devices. Where these
devices cannot be employed, a shift to alternate solvents would be required.
Methylene Chloride
Methylene chloride (CH2C12) should be rated as a possible threat to
stratospheric ozone, until proven otherwise. This rating is based on the
large volume of methylene chloride released, its moderate rate of photo-
oxidation, and its production of phosgene, which has an unknown atmospheric
behavior. The major releases of methylene chloride occur during its uses
as a solvent and as a paint remover. These will be difficult to control.
If further study confirms that methylene chloride is carrying a substantial
anount of chlorine to the stratosphere, substitute compounds should be sought.
-23-
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Perchloroethylene
Perchloroethylene emissions are very large but the atmospheric lifetime
of the compound is relatively short--probably on the order of a few days.
If the parent compound were the only consideration, there would be no need
to be concerned with control measures. There are, however, photo-oxidation
products to be considered. The main product is trichloroacetyl chloride,
and a lesser product is phosgene. If these compounds are found to persist
in the troposphere long enough for them to cross into the stratosphere,
then perchloreoethylene controls may have to be considered. In dry cleaning
applications perchloroethylene losses may be reduced by the use of carbon
adsorption units or other devices. The feasibility of such control is
shown by the case of fluorocarbon 113, a more expensive dry cleaning agent.
Since the economics of control have been favorable for F-113, installations
using it have been designed for solvent recovery. The result has been a
rate of solvent loss during operation that is only about one-sixth as great
as in installations using perchloroethylene.
Trichloroethylene
Trichloroethylene is emitted on a large scale. The compound is photo-
oxidized rapidly in the air, its lifetime being on the order of one day.
The fate of the oxidation products, dichloroacetyl chloride and phosgene is
not yet established, however, and the compound may therefore be considered
a candidate for control measures. Much of the trichloroethylene losses
occur during metal cleaning operations. These emissions may be controlled
by greater use of vapor confinement systems, condensers and similar devices.
Vinyl Chloride
The chlorine in vinyl chloride is not likely to get out of the
troposphere. The vinyl chloride will be photo-oxidized within a day of
its release, with the formation of hydrogen chloride. This HC1 will
soon be taken out at surfaces or in precipitation. From the point of view
of stratospheric ozone, therefore, there is no need to control vinyl
chloride.
-24-
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SECTION VI
REGULATORY AUTHORITIES OF EPA
As the IMOS study correctly indicated, the nature of the potential
fluorocarbon problem is such that any regulatory decision should be
made with caution and should be based on supportive scientific and
technical data. Yet, by the time the effects become measurable, an
adverse impact may have already resulted. Therefore, decisions on
regulation require that the significant knowledge gaps concerning
the problem be filled within a few years. The fluorocarbon manufacturing
industry is already conducting substantial research in the area; the
results of these studies, coupled with the results of the work by gov-
ernment agencies, the universities and the National Academy of Sciences
should supply the technical information necessary for sound decision-
making. The timetable for the decision-making process is in the
neighborhood of two years.
In terms of current regulatory authority, fluorocarbons used as
propellants in pesticide products can be regulated by EPA under the
Federal Insecticide, Fungicide, and Rodenticide Act. EPA also believes
that it has existing authority under Clean Air Act section 303, the
emergency powers section, to deal to a limited extent with the general
release of fluorocarbons to the upper atmosphere. This section would
permit an action to enjoin the production or use of fluorocarbons if
EPA determines they are presenting an imminent and substantial en-
dangerment to the health of persons. There are difficulties with this
approach, however, as it protects only hazards to public health and
does not extend to broader environmental endangerment. Furthermore
303 makes the courts the initial triers to facts on the health evidence,
and it is possible that a court would be reluctant to ban the production
and use of a product unless presented with extremely strong health case.
A better regulatory approach, should one be needed, is the use
of a comprehensive and general regulatory mechanism such as the pending
Toxic Substances Control Act. Enactment of the Act would address both
the public health risks and environmental threats which may be caused
by chemical substances including fluorocarbons.
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SECTION VII
RESEARCH NEEDS
The mathematical models that predict stratospheric ozone des-
truction are formulations of the chemical facts determined from
experimentation. New data on the atmospheric concentrations of
halogenated pollutants and on their chemical reactions will there-
fore have a direct impact on the predictions. Present and pro-
posed experimental studies within the EPA program will interact
with the model predictions in a major way by indicating the total
flux of chlorine-containing pollutants into the stratosphere. Ob-
taining a value for the flux of bromine containing pollutants into
the stratosphere might also strongly affect the predictions. If
the degree to which the chlorinated carbonyl compounds are penetrating
the stratosphere can be established and the details on their photolysis
rates and products are outlined, then the photodissociation of these
compounds can also be incorporated into the models. The research
needs roughly fall into two groups: needs for measurements in the
atmosphere, and needs for further laboratory studies.
ATMOSPHERIC MEASUREMENTS
The measurement program should have two aspects: (1) improve-
ment of measurement methods, and (2) application of the methods at all
accessible levels of the atmosphere.
While there is a current urgency to the problem of the chlorinated
compounds, the measurement program should not be restricted to them.
The problem of the supersonic transport exhaust and the problem of
the halogenated pollutants both illustrate the need for measurement
of a wide range of physical and chemical properties of both the
stratosphere and troposphere.
The man-made emissions that might perturb the chemistry of the
stratosphere can be classed as direct and indirect. Direct emissions
include halogenated compounds released during industrial and domestic
use, and nitrogen oxides from high flying aircraft. At present the
major uncertainty as to the perturbation of the stratospheric chemistry
lies in the lack of knowledge of the degree in which each of the halo-
genated pollutants is contributing chlorine atoms to the stratosphere.
Indirect emissions include N20 from the soil and sea above the
continental shelves. Farming and other activities may stimulate
these otherwise stable natural emissions. Also included in the in-
direct category may be the emission of methyl chloride by marine
algae and during the smoldering combustion of vegetation. Another
category of indirect emission is the formation of chlorinated com-
pound? during waste treatment with chlorine.
It is not practical or advisable to separate the chemistry of
the halogen atoms from the general chemistry of the stratosphere.
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Measurement needs are therefore defined below from the point of view
of the entire chemical system in the stratosphere.
Within the family of halogenated compounds, we need to measure
both the parent molecules and their decomposition products. Among
the parent compounds we include the chlorofluorocarbons CC1»F , CCl^F,
which are unequivocally man made. Compounds wholly or partially
natural in origin are CH,C1, and CH^Br. The decomposition products
are numerous and important in identifying the significant sources of
stratospheric chlorine. This includes HC1, HF, COC12, COF chlorinated
aldehydes, and chlorinated acid chlorides. Compounds whicn might be
important as sinks for chlorine are HC10_, HC10., and C120_. The free
radicals CIO and Cl are a major importance in the cycle of catalytic
destruction of 0 , and should be measured, if possible.
Nitrogen oxides should be measured. This includes N^O, NO, NO^,
and N^O^. This whole group of compounds is intimately tied into the
stratospheric ozone balance. The ozone itself most certainly needs to
be monitored with greater precision and accuracy than in the past.
Many components of natural origin in the atmosphere such as CH ,
C0? fine particles, and H_0 are important in stratospheric chemistry.
These species also should be the object of further efforts at measurement.
Although the concentrations of free electrons and of negative ions
may be low in the stratosphere, the reactions of these negative charge
carriers with NO and halogens are very rapid. In situ measurements
of these negatively charged particles would be of great value.
The chemistry of the stratosphere is modified by mixing and mass
transfer processes. Especially important are those processes affecting
the transfer of air to and from the troposphere and also to and from
the regions where high energy UV radiation is abundant. Much more
needs to be known about these air motions and their modifications
diurnally, seasonally and long term. The experimental program should
include the calculation of fluxes and eddy diffusion gathered from
the direct measurement of the distribution of tracers of opportunity
such as CC12F2, SF,, and perfluorocarbons.
Concentrations of species should be measured in the three dimensions
of altitude, latitude, and time. For example, altitude and latitude
variations of halogenated compounds can yield their reaction rates in
the atmosphere. Diurnal variations of concentrations give clues to the
chemical kinetic mechanisms and rates for the trace species. Sampling of
rainwater is important to determine whether or not product species are
present as a result of rainout or washout processes.
MEASUREMENT TECHNIQUES
Measurement methods for halogenated pollutants almost all fall into
two classes:
(1) Gas chromatographic methods
C2) Optical methods
The gas chromatographic method has laid the foundation of atmospheric
-------
data that has allowed chemists to perceive the threat of chlorine-ozone
interactions in the stratosphere. This method will continue to be the
primary source of information bearing on the problem. The strength
of the method lies in its capability to detect pollutants at concen-
trations as low as one part pollutant in 10 parts air. Furthermore,
this detection sensitivity is achieved in samples that have not been
concentrated, using a sample volume of approximately five cubic centimeters,
If cold trapping techniques are used, the detection sensitivity is in-
creased further.
Uncertainties in the application of the chromatographic method arise
from the possibility of chemical reactions during the passage of the
pollutant through the column and from a lack of a distinctive signature by
which to identify unknown pollutants. For identification purposes the
chromatograph is often coupled to a mass spectrometer or an infrared
spectrometer.
Development needs of the chromatographic method lie in the direction
of specific identification and absolute calibration. Even without
further development, however, the method can yield much of the needed
data on halocarbon distribution and reactions. A proper balance of
effort on chromatographic work would involve a modest program of dev-
elopment and a heavy program of application of the existing method.
There is a particular need for development of techniques of measuring
ultra trace quantities of halocarbons in rainwater.
Probably the optimum mode of operation in chromatographic studies
is to collect air samples as functions of altitude, latitude, and time,
and return them to the laboratory for analysis. In addition to
measuring the halocarbon pollutants themselves, efforts should be
made to measure the chlorinated aldehydes, acids, and acid chlorides
that are the primary products of photooxidation of the halogenated
pollutants.
Optical methods have their most important role in the measure-
ment of labile and transitory species in the air, especially those
engaged in a sequence of reactions in which the predicted steady
state concentrations are sensitive to the choice of rate constants.
Acids are lost on vessel walls and therefore should be measured
without collection. HC1 is important and probably is feasible to
measure by spectrometers or interferometers looking at sunlight or
moonlight. HF is a key ingredient in the fluorocarbon problem since
the ratio of HF/HC1 can be predicted if these both arise from the
photodissociation. The departure from this ratio could give the
relative importance of the fluorocarbons and the other chlorinated
compounds in the ozone balance.
HC10 and HC10. levels in the stratosphere are key to predicting the
course of reaction and the extent of ozone depletion. Recommended
measurement techniques include the following:
(1) Spectroscopic analysis of pollutant concentrates. A method
of concentrating pollutants from air samples at liquid
nitrogen temperature has been developed in this laboratory
and is currently being used. This method can measure fluoro-
carbons and other halogenated pollutants down to mixing
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ratios of 1 in 10 ". Detection in some important cases, such
as methyl chloride, is limited by spectral overlaps. This
work should be continued.
i^2J Long path absorption spectroscopy through the tropobphere.
A four kilometer controlled path multiple reflection system
is being constructed at Research Triangle Park for this study.
Measurements will be carried out in the coming year at Pasadena,
California, using an infrared Fourier Transform spectrometer sys-
tem.
(3) Non-dispersive analysis for selected pollutants. The non-
dispersive infrared technique has particular promise for
measurement of hydrogen chloride. A system for this purpose
is currently under development at Research Triangle Park,.
(4) Solar and lunar spectroscopy of the upper atmosphere. Grating
spectrometers, interferometers, non-dispersive analyzers or
laser heterodyne spectrometers may be used to measure long
path absorption of the solar or lunar radiation.
(5) Long path absorption measurements in the stratosphere with
folded cavities or between two balloons. This technique could
be specifically applicable to ionic species, unstable free
radicals and in general to strongly reactive gaseous species.
LABORATORY STUDIES
The atmospheric chemistry of the halogenated pollutants is still
not well enough.known to allow reliable predictions of what happens
to the pollutants in the real atmosphere. While atmospheric measure-
ments will give many new clues as to the chemical processes, there are
still unknown factors that can be determined in the laboratory. These
unknown factors can be classed as follows:
(1) Photooxidation mechanisms
(2) Rates of individual oxidation reaction steps
(5) Overall conversion rates for gaseous reactions
(4) Rates of photodissociation of primary pollutants
(5) Rates of photodissociation of secondary pollutants
(Reaction products)
(6) Products of photodissociation
(7) Rates of hydrolysis of acid chlorides and phosgene
(8) Fate of hydrolysis products
(9) Uptake of acids and acid chlorides in precipitation
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The above list indicates the need for a major laboratory effort
on the secondary pollutants. The importance of these reaction pro-
ducts is emphasized by Figures 1 and 2 which illustrate the high pro-
portion of chlorinated pollutants that are not fluorocarbons. It must
be remembered especially that the acids, aldehydes, acid chlorides and
phosgene are all strong absorbers of ultra violet light. Chlorine will
be released from these compounds by photodissociation more readily than
it will be released from fluorocarbons.
In addition to the current major chlorinated pollutants, other
compounds will undoubtedly come to the fore as usage patterns change
and alternates to present compounds are developed. In the program
of laboratory studies, due consideration must be given to the at-
mospheric chemistry of such alternate compounds and their decom-
position products.
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SECTION VIII
REFERENCES
1. Fluorocarbons and the Environment. Report of Federal Task Force on
Inadvertent Modification of the Stratosphere (IMOS). Council on
Environmental Quality and Federal Council for Science and Technology
(co-sponsors). June 1975. 109 p.
2. Preliminary Economic Impact Assessment of Possible Regulatory Action
to Control Atmospheric Emissions of Selected Halocarbons, Draft Report.
U.S. Environmental Protection Agency, Office of Air Quality Planning and
Standards, Research Triangle Park, N.C. EPA Contract No. 68-02-1349,
Task 8. Prepared by Arthur D. Little, Inc., Cambridge, MA. July 1975.
3. Lovelock, J.E. Atmospheric Fluorine Compounds as Indicators of Air
Movements. Nature. 230: 379-380, 1971.
4. Lovelock, J.E., R. J. Maggs, and R. J. Wade. Halogenated Hydrocarbons
in and Over the Atlantic. Nature. 241: 194-196, 1973.
5. Rowland, F.S., and M. J. Molina. Chlorofluoromethanes in the Environment,
Division of Research, U.S. Atomic Energy Commission. AEC Contract No.
AT(04-3)=34, P.A. 126. AEC Report No. 1974-1. Department of Chemistry,
University of California, Irvine, CA. September 1974.
6. Singh, H.B., and D. Lillian. Gas Chromatograhic Methods for Ambient
Halocarbon Measurements. Submitted for publication in the J. Air
Pollu. Contr. Assn.
7. Hanst, P. L., L. Spiller, and D. Watts. Infrared Measurement of Halo-
genated Pollutants and Other Atmospheric Trace Gases. Submitted for
publication in the J. Air. Pollu. Contr. Assn.
8. Relevant reports issued by the Center for Air Environment Studies,
The Pennsylvania State University, University Park, PA. and supported
by EPA grant no. R800949.
9. Gay, B.W., P.L. Hanst, J.J. Bufalini, and R.C. Noonan, Atmospheric
Oxidation of Chlorinated Ethylenes. Submitted for publication on
Environ. Sci. Technol.
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APPENDIX A. SUMMARY OF EPA RESEARCH
PROGRAM ON HALOGENATED AIR POLLUTANTS-AUGUST 1975
1. Title: Determination of Tropospheric Halocarbons by Gas Chromatography
and Mass Spectroscopy
Objective: Measure distributions of halogenated compounds in rural
areas, urban areas, and over water. Samples will be gathered in the
field and returned to the laboratory for analysis by gas chromato-
graphy and mass spectroscopy. Such compounds as CC1., CH,I, CFLC1,
CH Ci , CH_CC1_ will be measured. Insights into the photochemical
reactions will be derived from the detected concentrations and
spatial distributions.
Progress: A research grant proposal was solicited from Washington
State University. The proposal was received and approved by
intramural and extramural reviewers. The grant is presently being
processed for award.
2. Title: Infrared Analysis for Tropospheric Halogenated Compounds
Objective: Condense a large volume of air in a cold trap and boil
off the oxygen and nitrogen. Vaporize the remaining condensate into
a long path infrared cell and run the spectrum, using a Fourier
Transform Spectrometer. Remove carbon dioxide interference by the
ratio technique and measure the infrared bands of the other trace,
constituents. Trace gases with mixing ratios as low as one in 10
are detectable by this method. Samples will be collected at urban,
rural, and maritime locations.
Progress: This task has been carried out on an intramural basis.
The pollutants have been condensed and analyzed using a mobile
laboratory. Tests were carried out at Research Triangle Park, North
Carolina, Atlantic Beach, North Carolina, and New York City. Back-
ground levels of Freon 11, Freon 12, Carbon tetrachloride, acetylene,
carbonyl sulfide and other compounds have been established. Methyl
chloroform and Freon 22 have also been measured, but have been shown
not to be ubiquitous as is the case with the fully halogenated com-
pounds. A paper entitled "Infrared Measurement of Halogenated Pol-
lutants and Other Atmospheric Trace Gases," has been submitted to
Journal of the Air Pollution Control Association.
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3. Title: Atmospheric Measurements to Determine Fates of Halogenated
Compounds
Objective: Study the tropospheric distributions and chemical be-
havior of halocarbons. Direct atmospheric analysis will be carried
out using the gas chromatographic method with electron capture de-
tection and absolute coulometric calibration. Measurements will be
made on urban air, maritime air, and inland air in a rural area.
Progress: A research grant has been awarded to the Stanford Research
Institute. A mobile laboratory is being prepared for measurements
at Los Angeles, Point Reyes, California, and the Coachella Valley.
4. Title: Atmospheric Analysis Over a Four Kilometer Optical Path
Objective: Record the infrared absorption spectrum of the atmosphere
in an urban area, using an optical path long enough to bring out the
weak bands of halocarbons, halogenated acids, phosgene, and related
compounds. This task is directed towards understanding the photo-
chemistry of urban air, including in addition to the halogenated
compounds, the hydrocarbons, oxidants, nitrogenous compounds, and
sulfur compounds.
Progress: This is an intramural task, with contractor support. A
multiple-reflection optical system is being constructed for use with
a Fourier Transform Spectrometer. Eight mirrors will be mounted,
four at each end, in an optical tunnel 25 meters long. The system
will be operated on the roof of the Keck Engineering Building at
the California Institute of Technology, Pasadena. The body of the
absorption cell is under construction. The cell will be installed
at Research Triangle Park for preliminary testing before it is moved
to Pasadena. Mirrors will be delivered this month.
5. Title: Tropospheric Photochemistry of Halogenated Compounds -
Laboratory Studies
Objective: Rates of photooxidation of halogenated compounds will be
determined under simulated tropospheric conditions. Rates of
disappearance of reactants will be determined; products will be
identified, and reaction mechanisms will be derived.
Progress: A research grant was awarded to the Ohio State University
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in July. A long path photochemical reactor of unique design that
has been constructed at the Ohio State University will be used in
these studies. A government owned Fourier Transform Spectrometer
will be used to monitor the progress of the chemical transformations.
6. Title: Chemistry of Degradation of Halogenated Compounds in the
Atmosphere
Objective: The chemical mechanisms of degradation of the halo-
genated pollutants will be determined in laboratory measurements.
Photooxidations will be carried out under simulated atmospheric
conditions in a laboratory reaction chamber that permits observation
of the consumption of reactants and the formation of products. In-
dications of stratospheric effects will be derived from the observed
reaction products and rates.
Progress: This task is being carried out on an intramural basis,
complementary to the Ohio State Research Grant.
Five chlorinated ethylenes, along with chloroform, Freon 22, methyl
chloroform, and methyl chloride have been studied in a long path
infrared cell and photochemical reactor. Identified products in-
clude monochloro, dichloro, and trichloro acetyl chlorides, phosgene,
chlorinated peroxy acetyl nitrates, carbonyl chloro fluoride, tri-
chloro acetaldehyde, formyl chloride, and hydrogen chloride. Many
of these products have ultraviolet absorption characteristics that
could lead to chlorine deposition in the stratosphere. A publication
entitled "Atmospheric Oxidation of Chlorinated Ethylenes," has been
submitted to Environmental Science and Technology.
7. Title: Halocarbon Reactions in the Atmosphere
Objective: Through laboratory experiments determine rates of
degradation of halocarbon pollutants in the troposphere and
stratosphere. Determine the lifetimes and the eventual fate of
the intermediate products of the photooxidation.
Progress: A research grant was awarded to the Illinois Institute
of Technology Research Institute (IITRI) in July. A grant review
was held in Chicago on July 30. The IITRI group will concentrate
on (1) measuring the rate of OH attack on halocarbons, and (2) meas-
uring photolysis rates, quantum yields, and products in the direct
photo-dissociation of the acyl chlorides, phosgene, and other
compounds produced in the photooxidation of the chlorocarbons,
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8. Ti tie: Hydrogen Chloride in the Troposphere
Objective: The abundance and distribution of hydrogen chloride will
be determined in both urban and rural regions. From the measure-
ments, inferences will be drawn as to the sources and sinks of
HC1. Removal rates will be determined. The measurement technique
will be line-reversal infrared correlation spectroscopy which will
be capable of measuring HC1 partial pressures as low as 10 Atm.
Progress: This is an intramural task being carried out with
contractor support. The transmitter for the non-dispersive
analyzer for hydrogen chloride has been constructed, and operated
successfully. Its operation will be tested over a 500 meter
folded path in the laboratory.
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APPENDIX B. PRELIMINARY ASSESSMENT OF ECONOMIC IMPACT OF
ALTERNATIVES TO CONTROL FLUOROCARBON EMISSIONS TO THE ATMOSPHERE
INTRODUCTION
The purpose of this appendix to the report is to provide a preliminary
assessment of the alternatives for emission abatement and the potential
economic impact of possible regulatory controls for selected fluorocarbons.
In particular, this assessment will focus on those compounds which are
produced in large volumes, namely fluorocarbons 11, 12, and 22.
This section will first identify the end use areas of these compounds
where emissions to the atmosphere are the greatest. Then, with these
areas identified, the potential solutions for controlling or eliminating
the emissions will be assessed. One solution that will be considered is
an outright ban of the compounds which will necessitate a switch to
alternative products, processes, or chemicals. These alternatives will
be considered both in terms of product performance and their current
or future availability. Other solutions for controlling emissions other than
a total ban, such as containment and recovery of the emissions, will also be
identified.
Regulatory control strategies for possible emission control alternatives
will be outlined and the possible economic impact associated with each will be
assessed. The intention of this qualitative economic impact analysis is to
identify industry sectors that may be severely impacted by possible
regulatory action. Because of severe time constraints in the original study,
this analysis does not attempt to quantify the impacts.
The information presented in this appendix of the report is taken
from an extensive report entitled "Preliminary Economic Impact Assessment
of Possible Regulatory Action to Control Atmospheric Emissions of Selected
Halocarbons," which was prepared by Arthur D. Little, Inc. for EPA.
EMISSION PROBLEM AREAS
Fluorocarbons
For the fluorocarbons of interest (F-ll, F-12, F-22), the emissions
from production, transport, and storage are small (about one percent), thus
most of the emissions come from the end-use areas (see Table B-l) .
As shown, the largest source of emissions are aerosol sprays,
which contributed 486 million pounds in 1973, or about 66% of the
total U.S. emissions of F-ll, F-12, and F-22. Essentially all of these
emissions were F-ll and F-12 since only an insignificant amount of F-22
is used in aerosol applications. There is little timed release of these
compounds in the propellant applications since they are lost for the
most part within six months of production.
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The next largest source of emissions are refrigeration and air
conditioning systems, where the fluorocarbons are used as refrigerants.
The emissions from these applications amounted to roughly 201 million
pounds in 1973, or 27% of the total f]uorocarbon emissions (Table B-l) .
Of these refrigerant emissions, about two-thirds were F-12 and more
than one-quarter were F-22 while only a small amount were F-ll. The
fluorocarbon emissions from refrigeration systems are not immediate
but are instead phased over the life of the system. Therefore, the
emissions in 1973 were actually fluorocarbons that were produced in
past years, as far back as 15 years or so.
Thus, the propellant and refrigerant applications are the sources of
nearly 94% of the emissions of the three fluorocarbons of interest. Since
the use of these compounds in the other end-use categories is relatively
minor, the emissions are comparatively small. Blowing agent applications
of fluorocarbons contributed nearly 37 million pounds (mostly F-ll) in 1973,
while emissions from solvent and plastic resin usage were negligible.
Table B-2 breaks down the F-ll and F-12 emissions from propellant
applications by aerosol type. Over 80% (by weight) of these compounds
as propellants are used in personal aerosol products, so as expected this
is the prime emission problem area. For the year 1973 nearly 84%
of the emissions of F-ll and F-12 from propellant applications, or
408 million pounds, came from personal products. Of the overall
propellant total, aver 77%, or 375 million pounds of the emissions
came from hair care products and antiperspirants and deodorants.
Use of fluorocarbons as refrigerants is predominantly in air-condi-
tioning applications, which account for over 85% of annual F-ll, F-12,
and F-22 consumption in this end-use category. Thus, it follows that
most of the refrigerant emissions of fluorocarbons come from air condi-
tioning systems, as Table B-3 indicates. By far the largest emission source
is mobile (mainly automobile) air-conditioning, which contributed 71
million pounds or 35% of the total fluorocarbon refrigerant emissions.
The other primary emissions problem areas are: food store refrigeration
of refrigerant emissions), commercial unitary air-conditioning (12.5%),
residential unitary air-conditioning (8.8%), and large centrifugal
chillers (7.7%).
In conclusion, over 74% of the total annual emissions of F-ll, F-12,
and F-22 originate from antiperspirants and deodorants (27%), hair sprays
(22%), and mobile air-conditioners, (10%).
ALTERNATIVES FOR EMISSION ABATEMENT
Aerosol Propellants
The fluorocarbons are one of three major types of propellants used in.
aerosol products today. The other two are compressed gases and hydrocarbons,
the latter of which are liquified gas propellants like the fluorocarbons.
Even though they are significantly more expensive than other propellants,
fluorocarbons have gained widespread use in personal products because they
offer an advantageous combination of properties. These include:
-37-
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-39-
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Table B-3. ESTIMATED U. S. FLUOROCARBON REFRIGERANT EMISSIONS - 1973
(millions of pounds)
Type of
Equipment
Major Appliances
Room A/C
Dehumidifiers
Freezers
Refrigerators
Other
Ice Makers
Water Coolers
Mobile A/C
Unitary Residential A/C
Unitary Commercial A/C
Centrifugal Chillers
Reciprocal Chillers
Unit Coolers
Food Store Refrigeration
Mobile Refrigeration
Beverage Refrigeration
Packaged Terminal A/C
Other
Refrigerant
Commonly Used
22
12
12
12
12
12
12
22
22
11,12,22
11,12,22
12
12,22
12
12
22
" ~
Emissions
7.6
0.2
1.7
2.9
0.1
0.2
70.9
17.6
25.1
15.5
7.2
1.8
26.2
1.2
4.6
0.2
18.0
Percent
3.8
0.1
0.8
1.4
0.1
0.1
35.3
8.8
12.5
7.7
3.6
0.9
13.0
0.6
2.3
0.1
9.0
TOTAL
201.0
100.0
SOURCE: Arthur D. Little, Inc. "Preliminary Economic Impact Assessment of
Possible Regulatory Action to Control Atmospheric Emissions of
Selected Halocarbons."
-40-
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Safety - essentially non-toxic and nonflammable
La.quitled gas form - provide relatively uniform pressure over the
life of the product and aid in producing a fine (true aerosol)
spray
* Versatility - fluorocarbons can be blended to provide a range of
press and solubility characteristics
Chemical Stability/Inertness - little or no deleterious effect on
other components of product formulation or on the container
Odorless - especially important for perfume formulations
In the event of a possible ban on the use of fluorocarbons in
aerosol sprays, which is the only conceivable method to control emissions,
the producers and marketers of aerosols would have to switch to substitute
products which, while not performing as well overall as fluorocarbons,
would nonetheless perform satisfactorily in most cases. These substitutes
would be:
liquid gas propellants,
compressed gas propellants,
mechanical pump systems, or
non-spray products,
However, to make a direct subsitution of one type of propellant for
another or subsitute a mechanical delivery system for an aerosol
system without significantly altering the characteristics of the product
in question is generally conceded to be impossible. Reformulation of
existing products would be necessary since fluorocarbons are an essential
part of the present formulations.
Because of their higher cost, fluorocarbons are used sparingly
in aerosol products other than personal products. Most household and
other products exist satisfactorily with hydrocarbon or compressed gas
propellants because the safety or product performance problems are not
as critical. For example, flammability is not a problem in water-based
products while a true aerosol spray is not important in most applications
other than personal products.
In personal product applications substitutes for fluorocarbons
exist, although these alternatives may not have all the desirable qualities
of fluorocarbons. However, a definitive statement cannot be made as
to whether these products perform effectively enough because consumer
preferences are so varied. These products may perform well enough for
many people, while for others they may be totally inadequate.
Hydrocarbons used as liquified gas propellants include isobutane,
propane, n-butane, and dimethyl ether, with the first two being the most
widely used. Hydrocarbons offer most of the performance features of
fluorocarbons and are appreciably lower in cost. However, they are highly
flammable which has prevented their general use as substitutes for fluoro-
-41-
-------
carbons in personal products. In order to combat this problem, methylene
chloride and methyl chloroform have been used as vapor depressants so
as to suppress the inherent flammability of the hydrocarbons. Indeed,
the combination of hydrocarbons and methylene chloride in both hair sprays
and dry-type antiperspirants have been marketed to a limited extent for
several years. Methylene chloride apparently causes skin irritation,
but some industry representatives contend this problem can be avoided
by correct formulation. However, the status of both methylene chloride
and methyl chloroform with relation to the ozone layer is uncertain at
this time.
Compressed gas propellants, such as nitrogen, carbon dioxide, and
nitrous oxide, are low in cost, nonflammable, and exhibit low toxicity.
In most cases the propellants can readily substitute for fluorocarbons,
especially in non-personal products. However, their drawback is that
they have undesirable pressure characteristics that typically cause a
coarser spray, which is unsatisfactory in most personal products. In
this regard, considerable work has been conducted in developing improved
special valves to accommodate carbon dioxide characteristics that
markedly improve spray quality to the point that they are said to be
entirely satisfactory for hair sprays and other personal products.
At least one carbon dioxide based hair spray is currently undergoing
limited market testing, according to some sources.
Many mechanical devices and other delivery systems provide potential
alternatives to the fluorocarbon propelled aerosols. Finger- or hand-
activated mechanical pumps represent an area of considerable interest
and development effort. A pump-based hair spray was brought on the market
in 1972, and at least seven companies now offer both men's and women's
hair sprays that use pump delivery systems. Because of changing hairstyles,
desire for different hair feel and other considerations, these products
have performed much better than expected and the companies are having
difficulty meeting demand. The current demand level is on the order of
50 to 60 million pumps per year for hair care products. This is approxi-
mately 13% of the number of aerosol hair care units marketed in 1974.
Nearly all antiperspirants and deodorants currently exist in non-
spray form in addition to the aerosol form. These are in the form of
squeeze bottles, roll-on applicators, stick-type applicators, squeeze
tubes, wick-type dispensers, saturated pad applicators, felt tip applica-
tors, and other products which can be applied by hand from a glass or
plastic container. These products have existed for years and still gain
widespread use.
While all these alternatives to fluorocarbons have already undergone
extensive development, none presently exist in sufficient quantities to
satisfy the consumer demand. Of the possible alternatives, the
mechanical pump systems and the non-spray products appear to be most
readily available. It is estimated, however, that incremental capacity
expansions could take place within a relatively short time (one to two
years) that would allow production in sufficient quantities to meet demand.
While the technology for compressed gas aerosols exists, testing
of the acceptance of their different performance characteristics by
consumers is now only beginning. Up to three years are likely before
these products can meet a significant portion of the demand. Provided
-------
the skin irritation and possible environmental problems associated with
methylene chloride in personal products are overcome, hydrocarbon-based
aerosols likely will be available within two years to satisfy a portion
of the consumer demand.
In summation, in the event of a ban on the use of fluorocarbons in
aerosol sprays, aerosol marketers likely would first expand the production
of their non-aerosol products and in parallel refine and further develop
existing liquified gas propellants and compressed gas propellants.
Work would also begin on developing new liquified gas propellants, but
these probably would not be available for several years since no new
propellants have been identified.
Refrigerants
Fluorocarbons have become the basis for our domestic air conditioning
and refrigeration industry. Presently 92% of all refrigerants used in the
dominant vapor compression cycle are either F-ll, F-12, or F-22 with F-12
representing about 56% of the market and F-22 making up about 30%. The
safe properties of these products have permitted their use under conditions
where flammable and more toxic refrigerants would be hazardous to use.
In order to control or eliminate emissions of fluorocarbon refrigerants,
four potential solutions exist, some more viable than others:
Use of alternative refrigeration systems
Use of alternative refrigerants
Leak prevention and recovery of refrigerant during servicing or disposal
Reduction or elimination of refrigeration and air conditioning
Most would agree that the last alternative would have extensive and
drastic ramifications on the U.S. society. Our current food distribution
and storage network is critically dependent on refrigeration. While
air-conditioning may be a luxury item in some cases, it is almost essential
in hotter climates and in modern buildings that were constructed without
opening windows and thus are dependent on air conditioning systems.
Alternative refrigerants in the vapor compression cycle exist, but
their current use is extremely limited because fluorocarbons have proven
to be inherently safer and better refrigerants. Furthermore, these
alternatives cannot be substituted directly in existing systems. Instead,
such substitution would involve total and major redesign of refrigeration
systems.
Ammonia is one of the best refrigerants known today from a
standpoint of system performance because of its attractive physical
properties. However, it is both toxic and flammable; hence its
use has been restricted to industrial food storage and manufacturing
operations where the enforcement of safety practices and precautions is
feasible. For use in commercial buildings and in homes, a major re-
design would be required to contain the ammonia cycle equipment out-of-
doors where ch?nces of hazards would be minimized.
-43-
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Hydrocarbons are good performers as refrigerants and are used in
industrial environments to some degree. But these compounds, though
not toxic, arc highly flammable and would thus require adequate safe-
gards against explosive limits in air mixtures.
In the event F-12 is proven to cause destruction of the ozone
layer while F-22 is not, then possibly the best substitute refrigerant for
F-12 would be F-22. The latter is already well established as a
refrigerant in home air-conditioning units, unitary air-conditioning
systems, and in central air-conditioning and chillers. In all other
refrigerant applications, though, F-22 is not used. Thus, conversion
to F-22 would still constitute a substantial redesign task for the
industry. Yet, this is not believed to be nearly as significant as
with other alternative refrigerants. Nevertheless, the important
consideration is that the technology is well established for use of
F-22 in many refrigeration systems. However, F-22 likely will not be
acceptable for use in auto air-conditioning systems because exposure
to high temperatures under the hood would probably cause stability
problems for the refrigerant. Whether this problem can be satisfactorily
overcome is not known.
Although the vapor compression cycle dominates the refrigeration
and air-conditioning industry, other cycles are used. The absorption
refrigeration cycle is a well established system and is the most commonly
used of these other cycles in home appliances. The ammonia-water
cycle has been used in home refrigerators while the water-lithium bromide
system is limited to refrigeration above 32 F since the refrigerant
freezes at that temperarure. As a result, the latter has been applied
principally to commercial air-conditioning. However, under promotional
support by the gas industry, even home air-conditioning systems using
the absorption cycle have been made and sold in the past. The number
of absorption units peaked at 3,193 sold in 1970 and declined to 2,222
in 1973.
There are several drawbacks to the absorption system that could
possibly place severe constraints on its immediate use. First, because
of the toxicity and flammability of ammonia, this system has not gained
general acceptance. Secondly, these absorption systems have very low
energy efficiency, which is critical in light of the current energy
situation. Furthermore, most unitary absorption equipment and all
domestic absorption refrigerators manufactured in the past have used
natural or liquified petroleum gas as an energy source, both of which are
critically short at this time. Also, because of its extensive heat
transfer and surface area requirements, the absorption cycle does not
appear to be suitable for automobile air-conditioning. Lastly, while
the technology for constructing absorption units is fairly well established,
only a few manufacturers have ever made such equipment. Because of this
limited production capacity, the industry could not switch to absorption
units before three to five years.
Alternative refrigeration systems available for use in automobile
air-conditioning appear to be severely limited. As mentioned previously,
neither the F-22+bksed vapor compression cycle nor the absorption cycle
hold considerable promise. One potential substitute system is the
Brayton cycle which uses a cheap, nontoxic, and safe refrigerant: air.
-44-
-------
This cycle, which is used for air-conditioning in some aircraft, offers
low weight and compactness over vapor compression cycle equipment, but
it has a much higher power requirement that has restricted its use
severely and thus makes it relatively impractical for use in automobiles.
If a relatively low level of fluorocarbon emissions can be tolerated,
an alternative to changing to new refrigerants or systems is the containment
and recovery of a significant portion of the losses to the atmosphere.
Theoretically most systems are constructed so that leakage of the refrigerant
is minimal. However, because no satisfactory incentives exist to
encourage prevention of leaks in the systems, methods have not been
practiced by which leaks can be minimized. In addition, no incentives
presently exist that encourage recovery of the refrigerant during servicing
or disposal. In most cases home refrigeration and air-conditioning
units are discarded without recovering the refrigerant. In rechargeable
units the original charge is vented to the atmosphere during servicing
without being recaptured. This latter practice is believed to be the cause
of the bulk of the losses from large stationary systems.
As Table B-4 indicates, about 85% of the annual emissions of fluoro-
carbon refrigerants are estimated to be potentially preventable through
proper design, servicing, and disposal. Manufacturers admit that
equipment can be designed and manufactured to meet tighter leakage
specifications at an added cost to the consumer, and likewise refrigerant
recovery techniques can be utilized in most cases. But currently it is
not known what engineering practices will be required to achieve a
significant reduction in refrigerant emissions or how much of the emissions
can in actual practice be prevented or recovered. Compared to a total
redesign of existing systems or a switch to new systems, however,
the task of preventing leaks and ensuring proper disposal appears to be
considerably easier and less disruptive to the industry.
Thus, given the very high development costs associated with new
refrigerants or systems, the extended development time requirements,
and large in-service inventory of existing equipment, the containment and
recovery of a significant amount of the fluorocarbon emissions appears
to be the most cost-effective, short-term method of all the potential
solutions discussed, should some level of fluorocarbon emissions still
be acceptable from air conditioning and refrigeration systems.
Blowing Agents
Fluorocarbons 11 and 12 are used in the manufacture of foams
made from polyurethane, polystyrene, and polyolefins. They are used
primarily as the blowing agent which forms the cellular structure. The
use of these compounds in polyolefin foam manufacture is quite small in
comparison to their use in polyurethane and polystyrene foams. F-ll
and F-12 are both safe to use as blowing agents and give the foams
excellent insulating properties.
For rigid polyurethane foams, satisfactory substitutes have not been
found for fluorocarbon blowing agents that will produce a foam of adequate
-45-
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structural and thermal properties. In the manufacture of flexible poly-
urethanes, water/carbon dioxide is the primary blowing agent while there
are several agents that are used as the necessary auxiliary blowing
agent. F-ll is the most common of these auxiliary blowing agents, but
methylene chloride is also used and could replace most of the F-ll use.
Hydrocarbons were traditionally used as the blowing agents for
extruded polystyrene foams, but because of flammability problems they
have been replaced by halocarbons, typically F-12 and methyl chloride.
On the other hand, for expanded polystyrene foams, the major blowing
agents are pentane and isopentane while F-ll and F-12 are used to a
minor extent. For polyolefin foams, other hydrocarbons can readily
take the place of F-12.
Instead of restricting the use of F-ll and F-12 as blowing agents,
opportunities exist for recovery of fluorocarbons from the manufacture
of the foams. For example, the majority (approximately 90%) of the fluoro-
carbon blowing agent emissions come from the foam manufacturing step.
While certain technical problems will have to be overcome, a significant
portion of the emissions can have the potential to be recovered by
the installation of vapor-recovery equipment.
ECONOMIC IMPACT OF POSSIBLE REGULATORY CONTROLS
Introduction
This section of the appendix attempts to qualitatively assess the
economic impact of various alternatives to control the emissions of
fluorocarbons. The economic dislocations that are likely to be experi-
enced are identified along with the relative magnitude of the impacts.
Quantification of the economic impact, such as projected price increases,
job losses or other impacts, is not attempted. Likewise, secondary or
tertiary impacts are not considered. This impact assessment only iden-
tifies those sectors of the affected industries that have the potential
to be impacted so that further study might be directed to them.
There are, however, some general comments which can be made about
the economic effects of restricting the use of the fluorocarbons.
Because the current uses of the chemicals exist in price and performance
competitive environments, one can generally say that for a given product
performance the current use of chemical is the best product for satisfying
the demand. Restrictions on their use would require present consumers to
shift to their next best alternativewhich would either be more expensive
or perform less satisfactorily. If these alternatives did not perform
satisfactorily enough, then consumers would likely discontinue use and
consumption would be reduced. Whether a shift to these alternatives
would result in higher priced products is difficult to say. In many
cases this may be true, but in aerosol applications for example, the
consumer is likely to shift to less expensive products that may perform
somewhat less satisfactorily.
Table B-5 provides a summary characterization of the industry sectors
that are related to fluorocarbon production and use. The directly-
-47-
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Table B-5. ESTIMATED EMPLOYMENT AND PRODUCTION VALUE RELATED
TO FLUOROCARBON PRODUCTION AND CONSUMPTION - 1973
Total
industry
employment
Raw materials:
Chlorinea 10,300
Hydrofluoric acida 800
Directly
related
employment
980
330
Total
industry
production
value (1973)
i ~D
10
490
140
Directly
related
production '
value £1973)
10
45
55
Basic chemical production:
Fluorocarbons 2,700 2,700
Aerosols:
Containers 68,200- 2,500
Valves, caps § related
materials NA° 2,000
Concentrate ingredients NA NA
Aerosol fillers6 14,000 7,000
Aerosol marketers6 (total) 15,000 7,500
Production 6,000 3,000
Support (R$D, marketing,) 9,000 4,500
etc.)
Refrigeration: (1972)
Refrigeration equipment 120,000 120,000
Household refrigerators 32,000 32,000
§ freezers
Blowing agent applications:
Foam products 45,000 30,000
Raw materials 10,000 5,000
240
4,900
NAC
NA
250
2,000
5,600
1,600
1,000
460
240
190
60
NA
130
1,000
5,600
1,600
600
230
a. "Directly-related" values pro-rated on percentage of total chlorine and hydrofluoric
acid demand utilized in the production of the raw materials for fluorocarbons
b. Includes only cans, which represent 95 percent of total aerosol containers
c. NA is not available
d. Related employment refers to production of F-ll, F-12, and F-22
e. Directly related employment and production of aerosol fillers and marketers
was estimated as 50 percent of total industry employment and production
Source: Arthur D. Little, Inc., estimates
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related employment values should not be regarded as an estimate of the
jobs to be lost if the production of the chemicals is ended or reduced.
While the potential for job losses arises, simply counting jobs may not
adequately reflect disruptions resulting from the restrictions because the
additional production of alternative products minimizes the employment
impact. For example, a ban of fluorocarbon production could result in
an increase in the total number of jobs associated with producing the
substitute products and performing the function now performed by the
fluorocarbons. Thus, while the restrictions on the use of these com-
pounds will have an impact on jobs, it cannot be said with any certainty
at this time whether these impacts will be job losses, job gains, or
simply having the workers learn to work with new products or chemicals.
Possible Regulatory Options
In order to have a framework within which to assess the potential
economic impact, nine possible regulatory options have been defined which
are designed to reduce fluorocarbon emissions to the atmosphere by
nine different amounts on three different time schedules. Since Federal
authority does not presently exist to control the wide range of use of
these compounds, these regulatory strategies have no official standing.
They are only intended to identify a range of alternatives and to enable
a more specific discussion of potential disruptions in the U.S. economy
resulting from the options. Other regulatory options are possible and
will certainly be considered if a decision is made to restrict the
emissions of fluorocarbons.
The options discussed here and the resulting scenarios begin at
the point the decision is made. If delays occur before a decision
is made, the affected industry sectors will have more time to prepare
their response and the resulting economic disruptions could be lessened.
The following nine regulatory approaches have been considered:
Immediate (6 months) Restrictions
a. Ban All Uses of Controlled Chemicals After Six Months
All uses (except limited critical uses) of the controlled chemicals
would be banned six months after the issuance of the order.
b. Regulate Non-Propellant Uses and Ban Propellant Uses After Six Months
Design specifications would be promulgated requiring the upgrading of
refrigeration/air conditioning, and solvent and blowing agent equipment
and refrigeration/air conditioning service techniques in order to increase
recovery of emissions now lost to the atmosphere. Use in propellant appli-
cations (except limited critical uses) would be banned at the end of
six months.
c. Do Not Regulate Non-Propellant Uses and Ban Propellant Uses After
Six Months
No new controls would be placed on non-propellant uses of the chemicals,
but their use as propellants (except limited critical uses) would
be banned at the end of six months.
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d. Institute Government Control of Total Chemical Production After
Six Months
The Federal Government would take some action to limit total chemical
production to some tolerable level by the end of six months and let the
market mechanisms allocate its uses. The limited production would go
to those uses that could afford the resulting significant price increase.
Restrictions After Three Years
e. Ban All Uses of Controlled Chemicals After Three Years
This is the same as Option 1 except that the ban goes into effect at
the end of three years.
f. Regulate Non-Propellant Uses and Ban Propellant Uses After Three Years
The regulatory action is the same as Option 2 except that the restric-
tions go into effect at the end of three years.
g. Do Not Regulate Non-Propellant Uses and Ban Propellant Uses After
Three Years
The only restrictions would be a ban of propellant applications three
years after the regulation is issued.
h. Institute Government Control of Total Chemical Production After
Three Years
After three years total chemical production would be limited to some
tolerable level and the market mechanisms would allocate its uses.
i. Do Not Regulate Non-Propellant Applications and Ban Propellant
Uses After Six Years
The only controls under this option would be a ban on propellant
applications six years after promulgation of the order.
Identification of Economic Impacts
The objective of this section is to identify those industry sectors
likely to be impacted by the regulatory options outlined previously and
to assess the relative magnitude of the impact. Table B-6 summarizes the
results of the economic impact assessment. An estimate has been made of
the impact resulting from the 18 regulatory alternatives on 11 primary
impact industry sectors.
As a tool for categorizing the magnitude of economic impact, five
levels of impact were defined:
a. Severe Impact
A Severe Impact implies that most companies in the sector will be
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Table B-6. SUMMARY OF ESTIMATED ECONOMIC IMPACT ASSESSMENT
RESULTING FROM RESTRICTION ON U.S. USE OF F-ll, F-12, AND F-22
Impact Sectors
Propellant applications
Basic Aerosol industry
chemical Independent Can manu- Value manu- Aerosol
producers fillers facture facture marketers
Regulatory
options
a.
b.
c.
d.
e.
f.
g-
h.
i.
REGULATORY
a.
b.
c.
Emission .
reduction
92% 2-3
82% 3
70% 3
80% 3
83% 3
74% 3
63% 3
69% 3
54% 5
OPTIONS
Ban all uses of controlled chemicals
Regulation of non-propellant uses and
No regulation of non-propellant uses
1 3 1
1 3 1
1 3 1
1 3 1
2-3 5 2-3
2-3 5 2-3
2-3 5 2-3
2-3 5 2-3
3-5 S 3-5
after six months
ban of propellant uses after six
and ban of propellant uses after
2
2
2
2
3
3
3
3
S
months
six months
Non-propellant
Air conditioning
refrigeration
manufacturers
F-ll, F-12
and F-22
regulated
1
4
5
5
1
4
5
5
5
applications
and Plastic
foam
producers
Only
F-ll,
F-12
regulated
1
4
5
4
1-2
4
5
5
5
2
3
4
3-4
3
3
4
4
4
IMPACT CODE
1 - severe
2 - substantial
3 - moderate
4 - limited
5 - none
d. Government control of total chemical production after six months
e. Ban all uses of controlled chemicals after three years
f. Regulation of non-propellant uses and ban of propellant uses after three years
g. No regulation of non-propellant uses and a ban of propellant uses after three years
h. Government control of total chemical production after three years
i. No regulation of non-propellant applications and ban of propellant uses after six years
Percent reduction in U.S. F-ll and F-12 emissions to the atmosphere over a 20 year period beginning in 1976. A 5
percent demand growth per year is assumed in the absence of controls, no restriction on critical propellant uses
(5 percent of total), every 5 years one-half of refrigerant in the system at the time escapes, and 50 percent
control of emissions from plastic foams are assumed.
-51-
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affected, at least to a moderate degree (some seriously), and more
than 40 percent of the production in the sector related to the con-
trolled chemicals will be ended or significantly disrupted.
b. Substantial Impact
A Substantial Impact implies that some firms in the sector will experience
at least a moderate and in some cases a serious impact, and a significant
portion (greater than 10 percent but less than 40 percent) of the produc-
tion in the sector related to the controlled chemicals will be ended or
significantly disrupted.
c. Moderate Impact
A Moderate Impact is defined as when a few firms in a sector will
experience a. moderate impact on sales or profits, and no more than
a small portion (less than 10 percent) of the sector production re-
lated to the controlled chemicals will be ended or significantly
disrupted.
d. Limited Impact
The Limited Impact category includes those situations in which the
regulations would impact firms or chemical production in a sector
only through small but nonetheless measurable increases in product
prices. If a reduction in a chemical's production or the imposition of
a tax results in a large increase in the chemical's price, the resulting
product price increase in sectors continuing to use the chemical may
result in some unit sales fall-off. Equipment upgrading to reduce
emissions to the atmosphere would also raise product prices. While the
magnitude of these price and sales changes have not been estimated, the
instances when they may occur have been identified by this impact category.
e. No Impact
The No Impact category covers instances when the proposed regulations
would have essentially no impact on the firms or production of a
particular sector related to the controlled chemicals. Very small
price increases are possible under this category but not enough to
affect sales.
Discussion of Economic Impact
An immediate ban on the use of the controlled chemicals (option a)
would result in a severe and substantial impact on the users of the
compounds. The aerosol industry would not be able to produce adequate
supplies of substitute products within six months and thus the aero-
sol marketers would be affected substantially. While such a ban may
prove to be a boon to producers and marketers of substitute products,
this would be more than offset by the impact on producers, marketers
and others connected with the aerosol industry.
-52-
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The immediate ban would have a very severe impact on the
refrigeration and air conditioning industry, especially if both
F-12 and F-22 are banned. If F-22 could still be used, though,
that portion of the industry using this compound would be unaffected.
However, a conversion to F-22 or some other system by the rest of the
industry, or better containment and servicing methods, could not be
instituted within six months and probably not before a two to three
year period.
While the cessation of production of the controlled chemicals
would represent a substantial blow to the basic chemical producers,
the overall impact on the companies has been categorized as moderate
because the sales of the controlled chemicals do not represent a major
portion of the companies' total business activity.
Options b and c would have the same impact on the aerosol in-
dustry and most other sectors as option a since the ban of the use
of fluorocarbons as aerosol propel1 ants is immediate. However, the
impact of these options on the refrigeration industry is considerably
lessened because the use of fluorocarbons as refrigerants is not
banned. Under option b, though, the regulation would need to take
effect after one year instead of six months in order for the impact to
be lessened since it will take industry a minimum of one year to
manufacture equipment with tighter leakage specifications. Option c
will have no impact on the refrigeration industry.
The impact resulting from option d would tend to have the same
influence on the various industry sectors as the previous two options.
With production curtailed, demand will outstrip the available supply. This
will in turn drive up prices, which could be substantial depending on
on the resulting level of production. The fluorocarbon production
would then be allocated to the highest bidder. Table B-7 indicates
the percentage of the final product price represented by the cost of
the chemical used in the products. As can be seen, the cost of the
propellant (typically fluorocarbons) accounts for 15-25% of the
aerosol product costs, while the cost of the refrigerant is an in-
significant portion of the total product price. As a result, refrig-
eration applications would be more likely to sustain a large price
increase of fluorocarbon prices than would aerosols, where cheaper
substitutes already exist. Furthermore, since refrigeration and air
conditioning are much more critical use areas than aerosols, consumers
would be more likely to pay for a given increase in refrigerator or
air conditioner prices than for the same absolute price rise in
aerosol sprays. Thus, option d would tend to eliminate the use
of fluorocarbons in most aerosol sprays while encouraging containment
and recovery of the more costly refrigerant in refrigeration systems.
Options e through i show that the magnitude of the economic
disruptions resulting from restrictions on the use of the chemicals
is critically dependent on the timing of the restrictions. Under
these options the chemical producers, substitute product producers,
and the consumers of the chemicals have a longer response time avail-
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Table B-7. VALUE OF FLUOROCARBONS
RELATED TO PRICES OF END-USE PRODUCTS (1973)
Chemical
Consuming Product
Cost of Chemical/Price of Product
F-ll, F-12
Propellant Applications'
hair spray
antiperspirant
15-20%
20-25%
Carbon Tetrachloride
Intermediate Applications
F-ll, F-12
35-40%
F-ll, F-12, F-22
F-ll, F-12
Refrigerant Applications
appliances
mobile air conditioner
room and house air conditioner
commercial chiller
<^ 100 tons
> 100 tones
Blowing Agent Applications
0.1% - 0.2%
1-2%
0.2%
0.1-1%
3%
Based on manufacturer's price
Source: Arthur D. Little, Inc., estimates
-54-
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able (three to six years) to bring on new products and thus ease the
economic impact.
In the event of promulgation of any of these latter hypothetical
options, the aerosol industry would have time for a response with
substitute products since fluorocarbons would be banned. The
impact on aerosol marketers would be limited because while
their product line would undergo drastic change, their continuity of
participation in their primary markets would not be interrupted. For
the rest of the aerosol industry (fillers, valve manufacturers, etc.),
the potential impact has a range of uncertainty because the avail-
ability of substitutes after three years is uncertain. If they were
not available, the impact would be substantial while if they were avail-
able the impact would be moderate. The substantial classification indicates
that the potential exists for very serious curtailment of their activities
but the three year lead time would allow for some action to reduce the
effects.
The impact of a ban on the use of fluorocarbons after three years
would have a severe to substantial impact on the refrigeration and
air-conditioning industry. If the use of F-22 was not restricted, the
manufacturer's response to a ban on F-12 would be a conversion to
F-22, which could be substantially completed by the end of three to five
years. In the event F-22 could not be used, then conversion to other
systems or refrigerants could not be completed by the end of three
years; hence, the impact on the industry would be substantial.
The impact of options f through i would be relatively minor. The
aerosol industry would be impacted to the same degree as under option
e, but the other consuming sectors would have only a slight impact.
For the basic chemical manufacturers, the impact of regulations at
the end of three years is only slightly less than that of immediate
action. While three years would allow time for the companies to work
on substitute chemicals for major markets, new chemicals likely can
not be tested and their production facilities brought on line within
this period. Option i would have the slightest impact of any of the
options since six years appears to be ample time for all sectors of
the affected industries to adjust to the regulations and switch to
substitute products or otherwise reduce emissions.
As previously indicated, this economic impact assessment does
not provide a summation of the impacts on the various sectors. A
small impact in many sectors could lead to a substantial impact on
the overall economy or a segment of the economy. In addition, a
large impact on a small number of industry sectors may not be large
enough to create a substantial impact on the overall economy or a
segment of the economy. Only by quantifying these impacts can the
absolute extent of the various impacts on the industry sectors be
determined. With this information available, the component impacts
can be summed and the overall impact on the economy assessed.
-55-
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
REPORT NO.
EPA-600/9-75-008
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
REPORT ON THE PROBLEM OF HALOGENATED AIR POLLUTANTS
AND STRATOSPHERIC OZONE
5. REPORT DATE
December 1975
6. PERFORMING ORGANIZATION CODE
7 AUTHOR(S)
ORD and OAWM Staff
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Environmental Sciences Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
10. PROGRAM ELEMENT NO.
1AA008
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Sciences Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, N.C. 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA-ORD
15. SUPPLEMENTARY NOTES
Prepared for and submitted to the Subcommittee on Public Health and Environment,
Committee on Interstate and Foreign Commerce, House of Representatives
16. ABSTRACT
EPA is conducting a research program on halocarbon air pollutants and
their possible interaction with stratospheric ozone. Principal compounds
under study are fluorocarbon-11, fluorocarbon-12, fluorocarbon-22, carbon
tetrachloride, methyl chloroform, perchloroethylene, trichloroethylene,
dichloroethane, methylene dichloride, and methyl chloride. Laboratory
studies concern the rates of decomposition of these pollutants in the air
and the identity and fate of their decomposition products. Field studies
involve measuring concentrations of halocarbons and their decomposition
products as functions of altitude and distance from sources. Fluorocarbons
are discussed in detail, with regard to emission sources, current control
technology, and possible chemical substitutes. Problems of emissions control
and EPA's regulatory authority are reviewed and the economic impacts of
several regulatory options for fluorocarbons are considered.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
* Halohydrocarbons
* Stratosphere
* Ozone
* Depletion
Air pollution
Problem solving
07C
04A
07B
13. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
64
20 SECURITY CLASS (This page)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
-56-
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