INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY
ENVIRONMENTAL HEALTH CRITERIA 126
PARTIALLY HALOGENATED CHLOROFLUROCARBONS
(METHANE DERIVATIVES)
This report contains the collective views of an international group of
experts and does not necessarily represent the decisions or the stated
policy of the United Nations Environment Programme, the International
Labour Organisation, or the World Health Organization.
Published under the joint sponsorship of
the United Nations Environment Programme,
the International Labour Organisation,
and the World Health Organization
Draft prepared by Professor D. Beritic-Stahuljak and
Professor F. Valic, University of Zagreb, Yugoslavia,
using texts made available by Dr. D.S. Mayer, Hoechst AG,
Frankfurt am Main, Germany and by Dr. I.C. Peterson
and Dr. G.D. Wade, ICI Central Toxicological Laboratory,
Macclesfield, United Kingdom
World Health Organization
Geneva, 1991
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venture of the United Nations Environment Programme, the International
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carried out by the IPCS include the development of know-how for coping
with chemical accidents, coordination of laboratory testing and
epidemiological studies, and promotion of research on the mechanisms
of the biological action of chemicals.
WHO Library Cataloguing in Publication Data
Partially halogenated chlorofluorocarbons (methane derivatives).
Environmental health criteria: 126)
1. Freons - adverse effects 2. Freons - toxicity
3. Environmental exposure I. Series
ISBN 92 4 157126 8 (NLM Classification QV 633)
ISSN 0250-863X
(c) World Health Organization 1991
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CONTENTS
ENVIRONMENTAL HEALTH CRITERIA FOR PARTIALLY
HALOGENATED CHLOROFLUOROCARBONS (METHANE DERIVATIVES)
INTRODUCTION
1. SUMMARY
1.1. Identity, physical and chemical properties, and
analytical methods
1.2. Sources of human and environmental exposure
1.3. Environmental transport, distribution, and
transformation
1.4. Environmental levels and human exposure
1.5. Kinetics and metabolism in laboratory animals
and humans
1.6. Effects on laboratory mammals and in vitro test
systems
1.7. Effects on humans
1.8. Effects on other organisms in the laboratory
and field
1.9. Evaluation and conclusions
2. IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, AND ANALYTICAL
METHODS
2.1. Identity
2.2. Physical and chemical properties
2.3. Conversion factors
2.4. Analytical methods
3. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE
3.1. Natural occurrence
3.2. Anthropogenic sources
3.2.1. Production levels
3.2.2. Manufacturing processes
3.2.3. Loss during disposal, transport, storage,
and accidents
3.3. Use patterns
3.3.1. Major uses
3.3.2. Releases during use: controlled or
uncontrolled
4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION
4.1. Biodegradation and bioaccumulation
4.2. Environmental transformation and interaction with
other environmental factors
5. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE
5.1. Environmental levels
5.1.1. Air
5.1.2. Water
5.1.3. Food and other edible products
5.2. General population exposure
5.3. Occupational exposure
6. KINETICS AND METABOLISM IN LABORATORY ANIMALS AND HUMANS
6.1. Animal studies
6.1.1. Absorption
6.1.2. Distribution
6.1.3. Metabolic transformation
6.1.4. Elimination
6.2. Human studies
6.2.1. Absorption and elimination
6.2.2. Distribution
7. EFFECTS ON LABORATORY MAMMALS AND IN VITRO TEST SYSTEMS
7.1. Single exposure
7.1.1. Acute oral toxicity
7.1.2. Acute inhalation toxicity
7.2. Short-term inhalation exposure
7.2.1. HCFC 21
7.2.2. HCFC 22
7.2.3. Mixed exposure
7.3. Skin and eye irritation; sensitization
7.3.1. Skin irritation
7.3.2. Eye irritation
7.3.3. Skin sensitization
7.4. Long-term inhalation exposure
7.5. Reproduction, embryotoxicity, and teratogenicity
7.5.1. Reproduction
7.5.2. Embryotoxicity and teratogenicity
7.5.2.1 HCFC 21
7.5.2.2 HCFC 22
7.6. Mutagenicity
7.6.1. HCFC 21
7.6.2. HCFC 22
7.7. Carcinogenicity
7.8. Special studies - cardiovascular and respiratory
effects
7.8.1. HCFC 21
7.8.2. HCFC 22
8. EFFECTS ON HUMANS
8.1. General population exposure
8.1.1. Accidents
8.1.2. Controlled human studies
8.2. Occupational exposure
9. EFFECTS ON OTHER ORGANISMS IN THE LABORATORY AND FIELD
10. EVALUATION OF HUMAN HEALTH RISKS AND EFFECTS ON THE ENVIRONMENT
10.1. Evaluation of human health risks
10.1.1. Direct health effects resulting from
exposure to partially halogenated
chlorofluorocarbons
10.1.2. Health effects expected from a depletion of
stratospheric ozone by partially halogenated
chlorofluorocarbons
10.2. Effects on the environment
11. CONCLUSIONS AND RECOMMENDATIONS FOR PROTECTION OF HUMAN HEALTH
AND THE ENVIRONMENT
11.1. Conclusions
11.2. Recommendations for protection of human health
and the environment
12. FURTHER RESEARCH
13. PREVIOUS EVALUATIONS BY INTERNATIONAL BODIES
REFERENCES
RESUME
RESUMEN
WHO TASK GROUP ON ENVIRONMENTAL HEALTH CRITERIA FOR PARTIALLY
HALOGENATED CHLOROFLUOROCARBONS (METHANE DERIVATIVES)
Members
Professor D. Beritic-Stahuljak, Andrija Stampar School of Public
Health, University of Zagreb, Zagreb, Yugoslavia
Dr B. Gilbert, Technology Development Company (CODETEC), Cidade
Universitaria, Campinas, Brazil (Joint Rapporteur)
Professor H.A. Greim, Institute of Toxicology, Association for
Radiation and Environmental Research, Neuherberg, Germany
(Chairman)
Dr H. Illing, Health and Safety Executive, Merseyside, United
Kingdom
Dr W. Jameson, Office of the Senior Scientific Advisor to the
Director, National Institute of Environmental Health Sciences,
Research Triangle Park, North Carolina, USA
Dr H. Kraus, Chemicals Hazardous to the Environment, Federal
Ministry for the Environment, Nature Conservation and Nuclear
Safety, Bonn, Germany
Dr J. Sokal, Department of Toxicity Evaluation, Institute of
Occupational Medicine, Lodz, Poland
Dr V. Vu, Oncology Branch, Office of Toxic Substances, US
Environmental Protection Agency, Washington, DC, USA
Observers
Dr D.S. Mayer, Department of Toxicology, Hoechst AG, Frankfurt am
Main, Germany
Dr H. Trochimowicz, E.I. Du Pont de Nemours & Co., Haskell
Laboratory for Toxicology and Industrial Medicine, Newark,
Delaware, USA
Secretariat
Professor F. Valic, Consultant, IPCS, World Health Organization,
Geneva, Switzerland, also Vice-Rector, University of Zagreb,
Zagreb, Yugoslavia (Responsible Officer and Secretary)
Dr S. Swierenga, Health and Welfare Canada, Ottawa, Canada, also
Representative of the International Agency for Research on
Cancer, Lyon, France (Joint Rapporteur)
NOTE TO READERS OF THE CRITERIA MONOGRAPHS
Every effort has been made to present information in the
criteria monographs as accurately as possible without unduly
delaying their publication. In the interest of all users of the
environmental health criteria monographs, readers are kindly
requested to communicate any errors that may have occurred to the
Manager of the International Programme on Chemical Safety, World
Health Organization, Geneva, Switzerland, in order that they may be
included in corrigenda, which will appear in subsequent volumes.
* * *
A detailed data profile and a legal file can be obtained from
the International Register of Potentially Toxic Chemicals, Palais
des Nations, 1211 Geneva 10, Switzerland (Telephone No. 7988400 or
7985850).
ENVIRONMENTAL HEALTH CRITERIA FOR PARTIALLY HALOGENATED
CHLOROFLUOROCARBONS (METHANE DERIVATIVES)
A Task Group on Environmental Health Criteria for Partially
Halogenated Chlorofluorocarbons (Methane Derivatives) met at the
Institute of Toxicology, Neuherberg, Germany, from 17 to 21 December
1990. Professor H.A. Greim opened the meeting on behalf of the host
institute. Dr H. Kraus spoke on behalf of the Federal Government,
which sponsored the meeting. Professor F. Valic welcomed the members
on behalf of the three cooperating organizations of the IPCS
(UNEP/ILO/WHO). The Task Group reviewed and revised the draft
criteria document, made an evaluation of the direct and indirect
risks for human health from exposure to the partially halogenated
chlorofluorocarbons reviewed, and made recommendations for health
protection and further research.
The first draft on HCFC 21 was prepared by Dr D.S. Mayer
(Department of Toxicology, Hoechst AG, Frankfurt am Main, Germany)
and on HCFC 22 by Dr I.C. Peterson and Dr J.D. Wade (ICI Central
Toxicology Laboratory, Macclesfield, United Kingdom). The second
draft of the monograph was prepared by Professors D. Beritic-
Stahuljak and F. Valic.
Professor F. Valic was responsible for the overall scientific
content, and Dr P.G. Jenkins, IPCS, for the technical editing of the
monograph.
* * *
Financial support for the Task Group meeting was provided by
the Ministry for the Environment, Nature Conservation and Nuclear
Safety, Germany, which also generously supported the cost of
printing this monograph.
ABBREVIATIONS
ALAT alanine aminotransferase
ASAT aspartate aminotransferase
CNS central nervous system
ECG electrocardiogram
EEC European Economic Community
FSH follicle stimulating hormone
GWP global-warming potential
HCFC hydrochlorofluorocarbon
ip intraperitoneal
LH luteinizing hormone
ODP ozone-depletion potential
TLV threshold limit value
UNEP United Nations Environment Programme
INTRODUCTION
Chlorofluorocarbons were developed as refrigerants some 60
years ago. However, their application soon significantly
diversified, owing to their properties of non-flammability, chemical
and thermal stability, and generally low toxicity. They are now used
as blowing agents in foam insulation production, as propellants in
aerosols, as cleaning agents of metals and electronic components,
and to a lesser extent as chemical intermediates. Their current
production is more than 1 000 000 tonnes per year with a market
value estimated to be close to US$ l.5 billion.
Chlorofluorocarbons are very stable compounds, which remain
intact in the air, releasing chlorine only when they reach the
stratosphere. The active chlorine destroys ozone molecules, thus
depleting the ozone layer, which is a natural barrier to ultraviolet
radiation potentially harmful to human health and the environment.
The growing global concern over this effect resulted in the
development of the Vienna Convention for the Protection of the Ozone
Layer, adopted in March 1985, and its "Montreal Protocol on
Substances that Deplete the Ozone Layer", signed by 24 countries in
September 1987. The agreement required a freeze in the production
and use of the fully halogenated chlorofluorocarbons 11, 12, 113,
114, and 115 at 1986 levels by mid-1989, a 20% reduction in their
use from 1 July 1993, and a further 30% reduction from 1 July 1998.
The Protocol has been in effect since January 1989; 67 countries and
the European Economic Community had signed the Protocol by July
1989. As a further development, the Helsinki Declaration, a non-
binding agreement of April 1989, called for a total phase-out of the
fully halogenated chlorofluorocarbons. The European Economic
Community, the Nordic countries, Canada, the USA, and certain other
countries have called for this complete phase-out, rather than a
mere reduction in use of the fully halogenated chlorofluorocarbons.
Adjustments of the Protocol were agreed by the Parties to the
Protocol in June 1990. A total phase-out of 15 fully halogenated
chlorofluorocarbons, halons 1211, 1301, and 2402, and carbon
tetrachloride is to be effected by the year 2000. In addition,
methyl chloroform must be phased out by the year 2005.
These developments have created an urgent need for acceptable
substitute chemicals. These should have similar physical and
chemical properties and safety characteristics to the
chlorofluorocarbons included in the Montreal Protocol. There should
be a realistic anticipation that their commercial-scale production
will be technologically and economically feasible, and their ozone-
depleting potential and possible global-warming potential should be
considerably lower.
The phase-out of chlorofluorocarbons can also be accomplished
by employing alternative technologies.
The chemical industry worldwide is already engaged in efforts
to develop substitutes for the chlorofluorocarbons included in the
Montreal Protocol. In order to avoid the risk of introducing
chemicals that could prove to be either health or environmental
hazards, the toxicological and environmental evaluation of the
potential substitutes is of utmost importance and urgence. There are
already two international industry-supported efforts underway: the
Programme for Alternative Fluorocarbon Toxicity Testing (PAFT), and
the Alternative Fluorocarbon Environmental Acceptability Studies
(AFEAS).
There is a need to help prevent the use of harmful
chlorofluorocarbons and of any substitutes for the harmful
chlorofluorocarbons that would pose an unreasonable risk to human
health or the environment. There is also a need for producers to
make decisions about the manufacture of acceptable substitutes in
time. Environmental Health Criteria 113: Fully Halogenated
Chloroflurocarbons (WHO, 1990) evaluated ten fully halogenated
chlorofluorocarbons. Among these are the five compounds included in
the Montreal Protocol mainly on the basis of their high ozone-
depleting potential and long residence times in the atmosphere. The
ozone-depleting and global-warming potentials of the partially
halogenated chlorofluorocarbons are considerably lower and their
atmospheric residence times are shorter. Thus certain of these
partially halogenated chlorofluorocarbons, i.e. those for which the
toxicity evaluation suggests no unreasonable health or environmental
risk and which are likely to be technologically and economically
feasible, could be possible substitutes for the fully halogenated
derivatives. In this monograph, the evaluation of two partially
halogenated chlorofluorocarbons (methane derivatives) is presented.
The evaluation of six other partially halogenated
chlorofluorocarbons (ethane derivatives) has already started and
will shortly be published in the Environmental Health Criteria
series. The mere selection of a chemical for the evaluation
programme of the IPCS does not mean its endorsement as a substitute
chemical. Only a full toxicological and environmental evaluation can
be a basis for such a conclusion.
1. SUMMARY
1.1 Identity, physical and chemical properties, and analytical
methods
The two chlorofluorocarbons reviewed in this monograph
(dichlorofluoromethane, HCFC 21, and chlorodifluoromethane, HCFC 22)
are hydrochlorofluorocarbons (HCFCs), i.e. compounds derived by the
partial substitution of the hydrogen atoms in methane with both
fluorine and chlorine atoms. Only HCFC 22 has commercial
significance. Both HCFC 21 and HCFC 22 are non-flammable gases (at
normal temperatures and pressures), colourless, and practically
odourless. HCFC 21 is slightly soluble and HCFC 22 moderately
soluble in water, and both are miscible with organic solvents. HCFC
22 is available as a liquified gas.
There are several analytical methods for determining these two
HCFCs. These include gas chromatography with electron capture and
flame ionization detection, gas chromatography/mass spectrometry,
and photothermal deflection spectrophotometry.
1.2 Sources of human and environmental exposure
The two HCFCs reviewed in this monograph are not known to occur
as natural products. HCFC 21 is only produced in small quantities
for non-occupational purposes. The total annual worldwide production
of HCFC 22 was estimated in 1987 to be 246 000 tonnes.
The main loss of HCFC 22 is due to its release during the
repair, use, and disposal of refrigerators and air-conditioning
units. The estimated maximum current world-wide loss is around 120
000 tonnes per year. There have been reports of accidental release
of HCFC 22 on fishing vessels.
HCFC 22 is used as a refrigerant, as an intermediate in the
production of tetrafluoroethylene, and as a blowing agent for
polystyrene. A small quantity is used as an aerosol propellant.
1.3 Environmental transport, distribution, and transformation
The log octanol/water partition coefficient for HCFC 22 is
l.08, which makes bioaccumulation unlikely. The estimated
tropospheric lifetime of HCFC 21 is about 2 years and that of HCFC
22 about 17 years. Reaction with hydroxy radicals in the troposphere
is likely to be the primary route of degradation. Only a small
fraction of HCFCs 21 and 22 reach the stratosphere, where, mainly by
reaction with oxygen radicals, they release ozone-depleting
chlorine. However, it is estimated that HCFC 22 is responsible for
less than 1% of the ozone-depleting chlorine in the stratosphere.
The ozone-depleting potential (ODP) of HCFC 22 has been estimated to
be 0.05, while that of HCFC 21 is assumed to be lower.
The global-warming potential (GWP), relative to CFC 11 (taken
as 1.0), has been estimated to be lower by a factor of about 3-4 for
HCFC 22 and lower still for HCFC 21.
1.4 Environmental levels and human exposure
There are no data available on concentrations in water or on
the presence of these compounds in food, although HCFC 22 is used in
the manufacture of expanded polystyrene food containers. There are
no data on human exposure to HCFC 21, but two studies on the use of
experimental sprays containing 17-65% HCFC 22 have shown that short
(l0-20 secs) exposures might result in peak concentrations ranging
from 5000 to 8000 mg/m3. Workers in beauty parlours could be
exposed to 8-h time-weighted average levels of 90-125 mg/m3, but
these are well below the currently regulatory MAK or LTV levels of
1800-3540 mg/m3 for Germany, USA, and the Netherlands.
HCFC 22 mixes rapidly in the atmosphere. Concentrations of
about 326 mg/m3ere reported in 1986 and the level is believed to
be increasing by about 11% annually.
1.5 Kinetics and metabolism in laboratory animals and humans
There are limited data on the absorption, distribution,
metabolism, and excretion of HCFC 21. That HCFC 21 is absorbed
following inhalation can be inferred from systemic effects and the
elevated urinary fluoride levels seen in toxicity studies in rats.
HCFC 21 is exhaled by rats following intraperitoneal injection, and
both kinetic data and evidence from fluoride excretion suggest that
HCFC 21 is metabolized. However, the extent of metabolism is unknown
and, apart from fluoride, the products have not been identified.
HCFC 22 is rapidly and well absorbed following inhalation in
rat, rabbit, and humans and is distributed widely. High levels of
HCFC 22 have been found in the blood, brain, heart, lung, liver,
kidney, and visceral fat of rabbits dying during exposure and in
postmortem samples of brain, lung, liver, and kidney from accidental
victims of HCFC 22 exposure. Elimination is rapid, most of the HCFC
being eliminated with a half-life of 1 min in the rabbit and 3 min
in the rat. In humans, a limited amount of material is eliminated in
three phases (half-lives of 3 min, l2 min, and 2.7 h).
Inhaled or intraperitoneally administered HCFC 22 is almost
entirely exhaled unchanged in both rats and humans. There is good
evidence that no significant metabolism occurs in vivo in rats or
in rat liver preparations.
1.6 Effects on laboratory mammals and in vitro test systems
There are no satisfactory data on the acute oral toxicity of
HCFC 21 or HCFC 22.
The principal effects of a single inhalation exposure to HCFC
21 or HCFC 22 are essentially similar in a variety of animal
species. Both substances have low toxicity by this route. Effects
seen are typical of those of chlorofluorocarbons, i.e. loss of
coordination and narcosis. Cardiac arrhythmias and pulmonary effects
may occur at high concentrations (106.7 g/m3 or more).
It has been claimed that both HCFC 21 and HCFC 22 cause skin
and eye irritation, although these effects may have been related to
the consequences of heat loss due to evaporation rather than to the
chemical properties of the HCFCs. Neither substance caused skin
sensitization.
The only studies conducted on the short-term toxicity of HCFC
21 have investigated the inhalation route. Liver damage was the
principal effect noted in the rat, guinea-pig, dog, and cat; a no-
observed-effect level was not determined. Histopathological lesions
of the liver were seen in rats at levels as low as 0.213 g/m3
given 6 h/day, 5 days/week, for 90 days. Pancreatic interstitial
oedema and seminiferous tubule epithelial degeneration also occurred
at this level. Lesions were essentially absent in studies with HCFC
22 at exposure levels between 17.5 g/m3 (for 13 weeks) and l75
g/m3 (for 4 or 8 weeks).
There have been no long-term studies on HCFC 21 in animals. The
only consistent non-tumorigenic finding in long-term studies with
HCFC 22 was hyperactivity seen in male mice given 175 g/m3, 5
h/day, 5 days/week in a lifetime inhalation study.
No conventional studies have investigated the effects of HCFC
21 on fertility. In an embryotoxicity study on rats (42.7 g/m3, 6
h/day on days 6-15 of gestation) no teratogenic effect was observed,
but a high rate of implantation loss was found. HCFC 22 (l75 g/m3
per day, 5 h/day, 5 days/week for 8 weeks) had no effect on the
reproductive capacity of male rats. As a consequence of a small,
non-significant excess of eye defects seen in three teratology
studies in rats, an extensive study was conducted on the potential
ability of HCFC 22 to cause eye defects. In this study a small, but
statistically significant, increase in the number of litters
containing fetuses with microphthalmia or anophthalmia was found
following maternal exposure to 175 g/m3, 6 h/day on days 6-15 of
gestation. This exposure level gave slight maternal toxicity (lower
body weight compared to controls). No other effects were seen, and
3.5 g/m3 was the no-observed-effect level in this study. HCFC 22
was not teratogenic in a conventional study on rabbits at similar
exposure regimens.
HCFC 21 was found to be non-mutagenic in two bacterial and one
yeast assay (no further data was available). HCFC 22 was mutagenic
in bacterial assays using S. typhimurium, but did not show
activity in tests on other micro-organisms or in mammalian systems,
either in vitro or in vivo. These tests covered gene mutation
and unscheduled DNA synthesis in vitro, in vivo bone marrow
cytogenetic assays, and dominant lethal assays in both rat and
mouse.
Carcinogenicity assays in vivo have only been conducted with
HCFC 22. Two groups of investigators have conducted lifetime
inhalation studies on both rats and mice. The only evidence of
excess tumours occurred in the one study in which male rats were
given 175 g/m3, 5 days per week, for up to 131 weeks. Small
excesses of fibrosarcomas of the salivary gland region and of
Zymbal's gland were noted. These effects were not seen at lower
doses (up to 35 g/m3), and this high dose was not used in the
second study. Although it was not an adequate demonstration of the
absence of tumorigenic effects, no excess of tumours was seen in an
oral gavage study on rats. These animals were given HCFC 22 at a
level of 300 mg/kg per day, 5 days/week, for 52 weeks, and the study
terminated at l25 weeks.
1.7 Effects on humans
Only very limited data are available on the effects of HCFC 21
and HCFC 22 in humans.
Death has occurred following accidental or intentional exposure
to high levels of HCFC 22. Histopathological examination of the
tissues of some of these victims revealed oedematous lungs and
cytoplasmic fatty droplets mainly in the peripheral liver
hepatocytes.
Although an increase in the incidence of palpitations has been
claimed in a questionnaire study on people occupationally exposed to
HCFC 22, there is no good evidence that volunteer or occupational
exposure to HCFC 21 or HCFC 22 leads to ill health effects. No
conclusions can be drawn from a very small mortality study on people
occupationally exposed to several chlorofluorocarbons including HCFC
22.
1.8 Effects on other organisms in the laboratory and field
There are no data available on the effects of HCFCs 21 and 22
on organisms in the environment.
1.9 Evaluation and conclusions
Environmental exposure levels of both HCFC 21 and HCFC 22 are
extremely low and are not considered likely to cause direct effects
on human health. Controlled occupational exposures are also unlikely
to represent a significant risk to humans.
Both HCFC 21 and HCFC 22 have a lower ozone-depleting potential
and a shorter atmospheric residence time than the fully halogenated
chlorofluorocarbons and should therefore pose a lower indirect
health risk. Their global-warming potentials are considerably lower
than those of the fully halogenated chlorofluorocarbons suggesting a
lower environmental effect.
Since the toxicity of HCFC 22 is low, the ozone-depleting and
global-warming potentials lower, and the atmospheric residence time
shorter than those of the fully halogenated chlorofluorocarbons, it
can be considered as a transient substitute for the CFCs included in
the Montreal Protocol. Although HCFC 21 poses a low environmental
and indirect health risk, it is not recommended as a substitute for
the chlorofluorocarbons included in the Montreal Protocol because of
possible direct health risk due to its liver toxicity.
2. IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, AND ANALYTICAL
METHODS
2.1 Identity
The chlorofluorocarbons reviewed in this monograph are
dichlorofluoromethane (HCFC 21) and chlorodifluoromethane (HCFC 22).
These are hydrochlorofluorocarbons (HCFCs), i.e. compounds derived
by the partial substitution of the hydrogen atoms in methane with
both fluorine and chlorine atoms. The chemical formulae, chemical
structures, common names, common synonyms, trade names and CAS
registry numbers are presented in Table 1.
2.2 Physical and chemical properties
The physical and chemical properties of HCFCs 21 and 22 are
summarized in Table 2. They are non-flammable gases at normal
temperatures and pressures, colourless, and practically odourless.
They are slightly or moderately soluble in water and miscible with
organic solvents (Horrath, 1982; Weast, 1985).
Generally, hydrochlorofluorocarbons of low relative molecular
mass are characterized by high vapour pressure, density, and
refractive index, and low viscosity and surface tension (Bower,
1973).
HCFC 22 is available as a liquified gas with a minimum purity
of 99.9% or in a variety of blends and azeotropic mixtures.
2.3 Conversion factors
Conversion factors for HCFCs 21 and 22 are given in Table 1.
2.4 Analytical methods
Analytical procedures for the determination of HCFCs 21 and 22
are summarized in Table 3. By far the most frequently applied
methods use gas chromatography with various detection techniques.
A number of methods have been described for the determination
of HCFC 21. These include gas chromatography with dual flame
detection (Lindberg, 1979) and with electron capture detection
(Vidal-Madjar et al., 1981; Rasmussen et al., 1983 and Höfler et
al., 1986). Similarly, a number of methods have been described for
the determination of HCFC 22. These include gas chromatography/mass
spectrometry (Brunner et al., 1981), gas chromatography with
electron capture detection (Shimohara et al., 1979), and
photothermal deflection spectrophotometry (Long & Bialkowski, 1985).
Table 1. Identity of HCFC 21 and HCFC 22a
HCFC 21 HCFC 22
Chemical structure
Cl Cl
' '
H - C - F H - C - F
' '
Cl F
Chemical formula CHCl2F CHClF2
Common name dichlorofluoromethane chlorodifluoromethane
Common synonyms methane, dichlorofluoro-; Algeon 22; Arcton 22;
and trade names fluorodichloromethane; Chlorofluorocarbon 22;
F-21; R-21; Freon 21; difluorochloromethane;
Genetron 21; difluoromonochloromethane;
dichloromonofluoromethane; Electro-CF 22; Eskimon 22;
monofluorodichloromethane F-22; FC-22; Flugene 22;
Fluorocarbon 22; Forane 22;
Freon 22; Frigen 22;
Genetron 22; HFA 22;
Hydrochlorofluorocarbon 22;
Hydrofluoroalkane 22; Isceon 22;
Osotron 22; Khladon 22; methane,
chlorodifluoro-;
monochlorodifluoromethane;
Propellant 22; R-22;
Refrigerant 22; UCON 22
CAS registry number 75-43-4 75-45-6
Conversion factors (20 °C)
ppm --> mg/m3 4.276 3.54
mg/m3 --> ppm 0.234 0.282
a Chlorofluorocarbons are numbered as follows:
the first digit = number of C atoms minus 1
for methane derivatives it is therefore zero);
second digit = number of H atoms plus 1;
third digit = number of F atoms.
Table 2. Physical and chemical properties of HCFC 21 and HCFC 22a
HCFC 21 HCFC 22
Physical state gas gas
Colour colourless colourless
Relative molecular mass 102.92 86.47
Boiling point (°C) at 103 kPa 8.9 - 40.8
Freezing point (°C) -135.0 -146.0
Liquid density (g/ml) 1.405 1.49
(at 9 °C) (at -68 °C)
Vapour density (g/litre) 4.57 4.82
at boiling point
Vapour pressure (atm) at 21 °C 1.57 9.33
Surface tension (dynes/cm) at -41 °C - 15
Refractive index at 9 °C 1.3724 -
a From: Grasselli & Richey (1975); Hawley (1981);
Horrath (1982); Sax (1984); Weast (1985).
Table 3. Analytical methods for the determination of partially
halogenated methane derivatives
Medium Analytical method Detection limit Reference
HCFC 21
Air gas chromatography with Lindberg (1979)
dual flame ionization
detection
gas chromatography with NIOSH (1985)
flame ionization detection
gas chromatography with Höfler et al. (1986)
electron capture detection
gas chromatography with 0.009µg/m3 Rasmussen et al. (1983)
electron capture detection
gas chromatography with 0.08µg/m3 Vidal-Madjar et al. (1981)
electron capture detection
HCFC 22
Air gas chromatography with 0.14-0.46µg/m3 Shimohara et al. (1979)
electron capture detection
gas chromatography/ 0.4µg/m3 Brunner et al. (1981)
mass spectrometry
photothermal deflection 0.6µg/m3 Long & Bialkowski (1985)
spectrophotometry
Blood and head space method, gas 0.1µl/g Sakata et al. (1981)
tissues chromatography with flame
ionization detection
head space method, gas Morita et al. (1977)
chromatography with flame
ionization detection
3. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE
3.1 Natural occurrence
HCFC 21 and HCFC 22 are not known to occur as natural products.
Stoibe et al. (1971) reported the presence of HCFC 22 in
volcanic emissions, but Rasmussen et al. (1980) did not observe any
excess of this compound, compared with normal atmospheric levels, in
their studies of volcanic emissions. In their analyses of air
samples collected over the State of Washington, USA, Leifer et al.
(1981) found that the concentrations of HCFC 22 (110-195 ng/m3)
after the eruption of the Mount St. Helens volcano were no higher
than normal.
3.2 Anthropogenic sources
3.2.1 Production levels
HCFC 21 has been manufactured by one company in the USA, but
only in very small quantities, and is no longer produced (personal
communication by H. Trochimowicz to IPCS, 1990).
HCFC 22 is produced by companies in the USA, Western Europe,
Japan, Latin America, and elsewhere, the total annual world-wide
production in 1987 being estimated to be 246 000 tonnes (personal
communication by E.I. Du Pont de Nemours & Co. Inc., 1989).
3.2.2 Manufacturing processes
Both HCFC 21 and HCFC 22 are manufactured by the liquid phase
reaction of chloroform with anhydrous hydrofluoric acid in the
presence of an antimony halide catalyst (Hawley, 1981) at various
reaction temperatures and pressures (SRI, 1985). This process is
being replaced by a continuous vapour-phase process employing
gaseous hydrogen fluoride in the presence of chromium oxide or
halide, ferric chloride, or thorium tetrafluoride catalysts
(Grayson, 1978).
3.2.3 Loss during disposal, transport, storage, and accidents
The source of the main loss of HCFC 22 during disposal is
discarded refrigerators and air conditioners. Trace quantities of
HCFCs 21 and 22 have been detected in landfill gas (Höfler et al.,
1986).
Equipment for the transport and storage of HCFC 22 is designed
to withstand high pressure and is fitted with safety valves,
bursting discs, and fusible plugs. Losses of product during normal
transport and storage should, therefore, be relatively small because
of the completely closed systems used.
The main release of HCFC 22 occurs in the form of leakages from
refrigeration and air-conditioning units (see section 3.3.2). Two
accidental releases with fatal consequences on fishing vessels have
been described by Morita et al. (1977) and Haba & Yamamoto (1985).
In general, some fugitive losses during manufacturing are likely.
3.3 Use patterns
3.3.1 Major uses
HCFC 21 has been reported to be used as a refrigerant for
centrifugal machines, as a solvent (where its high Kauri-butanol
number is desirable), in combinations with Freon 12 in aerosol
products (National Library of Medicine, 1990), in fire extinguishers
(Hawley, 1981), as a propellant gas (Sittig, 1985), and as a heat
exchange fluid in geothermal energy applications (Grayson, 1978).
However, it is no longer manufactured for any commercial purpose
(personal communication by H. Trochimowicz, 1990).
HCFC 22 is used as a refrigerant in residential, commercial,
and mobile air-conditioning units. An azeotropic mixture (HCFC 502)
of HCFC 22 and CFC 115 (48.8:51.2 wt.%) is used as a refrigerant in
food display cases, ice makers, home freezers, and heat pumps
(American Chemical Society, 1985). It is also used as an
intermediate in the production of tetrafluoroethylene by pyrolysis
at 650-700 °C (Smart, 1980). It is estimated that approximately 34%
of the total amount is currently used for this latter purpose. HCFC
22 is used as a blowing agent, especially for polystyrene (see
section 5.1.3) and as a propellant in aerosols (Hanhoff-Stemping,
1989). It is not used to any significant extent as an industrial
solvent but has been in the past (US EPA, 1981).
3.3.2 Releases during use: controlled or uncontrolled
Data are only available for HCFC 22. The major loss to the
environment results from equipment and system leaks during use,
repair, servicing, and after scrapping (Salzburger et al., 1989).
Assuming no significant loss from its use as a polymer intermediate,
it has been estimated that the maximum current worldwide release of
HCFC 22 is around 120 000 tonnes per year (personal communication by
E.I. Du Pont de Nemours & Co. Inc., 1988).
4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION
Environmental Health Criteria 113: Fully Halogenated
Chlorofluorocarbons considered the transport between media,
environmental transformation processes, interaction with other
physical, chemical or biological factors, and bioconcentration and
bioaccumulation of fully halogenated chlorofluorocarbons (WHO,
1990). Much more information has been published on fully halogenated
than on partially halogenated chlorofluorocarbons.
4.1 Biodegradation and bioaccumulation
There is practically no information on the biodegradation in
the environment of HCFC 21 and HCFC 22. The log octanol/water
partition coefficient of HCFC 22 is 1.08, which makes
bioaccumulation of this hydrochlorofluorocarbon unlikely (Hansch &
Leo, 1979).
4.2 Environmental transformation and interaction with other
environmental factors
The physical and chemical properties of the partially
halogenated chlorofluorocarbons suggest that they would mix rapidly
within the lower region of the troposphere. Mixing would be expected
to be complete in the hemisphere of the emission (northern or
southern) within months and in the entire troposphere possibly
within about three years. The tropospheric concentration of HCFC 22
is rapidly increasing (Hanhoff-Stemping, 1989). Reaction with
naturally occurring hydroxy radicals in the troposphere is thought
to be the primary degradation route. The estimated tropospheric rate
of this reaction is such that the average lifetime is about 2 years
for HCFC 21 (UNEP/WMO, 1989) and 13-25 years for HCFC 22 (Makide &
Rowland, 1981; WMO, 1986; UNEP/WMO, 1989; Zurer, 1989). It should be
noted that the lifetimes of fully halogenated chlorofluorocarbons
are much longer (75 years for CFC 11 and 111 years for CFC 12). The
mechanism of decomposition of HCFC 22 following the initial reaction
with hydroxy radicals has been studied but not fully elucidated. The
most likely product of the gas-phase reaction in the atmosphere is
carbonyl fluoride (COF2) (Atkinson, 1985), which would be
hydrolysed rapidly by atmospheric water to carbon dioxide and
hydrogen fluoride, the latter being removed by precipitation.
The small fraction of HCFC 22 not destroyed in the troposphere
slowly enters and mixes with the upper layer of the atmosphere, the
stratosphere. Seigneur et al. (1977), in their discussion of the
photochemical and chemical processes of HCFCs 21 and 22 in the
atmosphere, used a one-dimensional model at steady state to estimate
the upward diffusion of these HCFCs in the atmosphere from ground
level to 60 km. Their models of diffusion and reaction predict that,
at steady state, the amounts of these chemicals reaching the
stratosphere would be, relative to the amount released at ground
level, between 1 and 3% for HCFC 21 and between 4 and 12% for HCFC
22. The major destruction mechanisms are reactions with hydroxy
radicals and excited oxygen atoms (Seigneur et al., 1977). Photo-
decomposition by solar ultraviolet radiation, which is a major
process for the fully halogenated chlorofluorocarbons, does not play
a significant role in the destruction of HCFC 22 in the stratosphere
(Molina et al., 1976).
The major part of the ozone-depleting chlorine in the
stratosphere comes from fully halogenated chlorofluorocarbons. The
above model indicates that the partially halogenated
chlorofluorocarbons are not expected to have high ozone-depleting
potential (ODP). The ODP is defined as the calculated ozone
depletion due to the emission of a unit mass of the
chlorofluorocarbon divided by the ozone depletion calculated to be
due to the emission of CFC 11; calculations are based on steady-
state conditions (UNEP/WMO, 1989).
No ODP value has been determined for HCFC 21 although Seigneur
et al. (1977) stated that the compound is "50-100 times less
hazardous than CFC 11" to the stratospheric ozone level, based on
calculations by Molina et al. (1976). The ODP for HCFC 22 has been
estimated to be 0.05 (Hammitt et al., 1987; UNEP, 1988). Solomon &
Tuck (1990) believe that reaction on ice particles in the Antarctic
stratosphere may raise this figure by a factor of two or more, but
Fisher et al. (1990b) do not completely agree with this supposition.
A value of 0.05 means that continuous emissions of HCFC 22 would
have to be 20 times as large as continuous emissions of CFC 11 to
have the same effect on ozone. A 5% annual increase in HCFC 22
emissions has been estimated by Ramanathan et al. (1985), but the
11-12% figure calculated by Khalil & Rasmussen (1981, 1983) agrees
better with the published data. The 16% yearly increase assumed by
Krüger & Fabian (1986) is probably too high. The transitional use of
HCFC 22 as a substitute for the highly ozone-depleting fully
halogenated CFC 12 has been agreed, but the phase-out of HCFC 22 is
also foreseen (Zurer, 1990; UNEP, 1990; FRG, 1990).
Current assessment of the global-warming potential (GWP)
("greenhouse effect") of HCFC 22, based on the comparison with CFC
11 (the reference compound with a GWP of 1.0), indicates that it is
lower by a factor of about 3-4 (Garber, 1989; Fisher et al., 1990a).
The GWP of HCFC 21 is lower still (Garber, 1989).
5. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE
5.1 Environmental levels
5.1.1 Air
Penkett et al. (1980) reported that extremely low background
concentrations of HCFC 21, ranging from 4.3 to 8.6 ng/m3 (1-2
ppt), have been found in the atmosphere. However, other
investigators have determined much higher concentrations ranging
from 43 to 86 ng/m3 (10-20 ppt) (Crescentini & Bruner, 1979).
Rasmussen et al. (1983) concluded that this difference in the
reported concentrations of HCFC 21 in the troposphere cannot be
reconciled on the basis of difficulties in identification or
differences in absolute accuracy.
Rasmussen et al. (1980) determined an average global HCFC 22
concentration of 159 ng/m3 (45 ppt) in mid-1979. The average
concentrations were 177 ng/m3 (50 ppt) and 149 ng/m3 (42 ppt) in
the northern and southern hemispheres, respectively. These values
are considerably higher than the value of 89-106 ng/m3 (25-30 ppt)
calculated from estimates of emissions. Leifer et al. (1981) found
values (110-190 ng/m3) over the State of Washington, USA, in 1980.
Khalil & Rasmussen (1981) determined concentrations of HCFC 22
in 100 atmospheric samples collected between April 1978 and January
1981 at a latitude of 45 °N in the north-west Pacific. The
concentration of HCFC 22 increased at an average rate of 11.7% per
year over the two and a half years of the study, and in January 1981
was about 230 ng/m3 (65 ppt). The same authors calculated the
concentrations expected from the estimated industrial release of
HCFC 22 since 1950. The observed concentrations were, on average, 60
ng/m3 (17 ppt) higher than the estimated concentrations. The
authors considered the difference to be the consequence of an
underestimation of past industrial release.
Rasmussen & Khalil (1983) measured an average HCFC 22
concentration of 259 ng/m3 (73 ppt) in the lower Arctic atmosphere
(0-4 km) at 70 °N in May 1982. This concentration was 1.3 times
greater than that found at 30-40 °S in November 1981 (Rasmussen et
al., 1982), a difference which the authors considered significant.
In the Arctic (72 °N in Alaska), the winter concentrations of
HCFC 22, as well as those of other halocarbons, carbon monoxide, and
soot from combustion, are higher than at other times of the year.
This is attributable to faster transport of anthropogenic emissions
in winter. The average winter concentration of HCFC 22 in the years
1980 and 1981 was 217 ng/m3 (61 ppt), whereas the average during
the summer was 198 ng/m3 (56 ppt). The rate of increase from
August 1980 to February 1982 was 11.9% per year (Khalil & Rasmussen,
1983). The most recent studies reported a concentration of 326
ng/m3 (92 ppt) in 1986 (NASA, 1988), which corresponds
approximately to the expected value based on an average annual
increase of 11% since 1979. The rate of increase is somewhat
uncertain due to the limited number of measurements, and lower
values have been assumed by other authors (Ramanathan et al., 1985).
These authors pointed out that, at an estimated increase of 5% per
year, the average concentration in the global atmosphere would reach
3200 ng/m3 by the year 2030.
5.1.2 Water
No data are available on the concentrations in water of the
HCFCs 21 and 22.
5.1.3 Food and other edible products
No information is available on the possible content of
partially halogenated chlorofluorocarbons in food or other edible
products.
HCFC 22 is used in the USA, the United Kingdom, and several
other countries as a blowing agent for polystyrene foam, an
authorized food contact plastic.
5.2 General population exposure
There are no data on human exposure to HCFC 21. The maximum
workplace concentration (MAK) is limited to 45 mg/m3 in Germany
(DFG, 1990) and to 42 mg/m3 in the USA (ACGIH, 1990).
Simulated-use studies have been carried out to assess the
potential human exposure to HCFC 22 arising from its assumed use as
an aerosol propellant. After a single spray (5 or 10 seconds
duration) of an aerosol containing 17% HCFC in a closed room of 22
m3, the air concentration was determined at various positions
relative to the spray cone. When the spray was directed towards the
sampling tube, peak concentrations were 5075 and 8050 mg/m3 after
5 and 10 seconds spraying, respectively. The concentrations declined
after about 10 or 20 seconds, respectively, stabilizing at levels of
25 or 45 mg/m3. In all other spray positions the concentration did
not exceed the level calculated for homogeneous distribution in the
air of the room (Bouraly & Lemoine, 1988).
Hartop & Adams (1989) reported a series of similar studies in
which the concentrations of HCFC 22 were measured during simulated
human use using experimental manikins representing adult and child.
They examined hair sprays containing 20-40% HCFC 22, whole body
deodorants containing 20-65%, and antiperspirants containing 20-40%.
The peak concentrations found in a closed room of 21 m3 ranged
from 53 mg/m3 (for a 4-second spray of an anti-perspirant
containing 18.8% HCFC 22) to 5000 mg/m3 (for a 20-second spray of
a deodorant containing 65%). This corresponds to 10-min weighted
average concentrations of about 50 mg/m3 and 1440 mg/m3,
respectively. In the same study, simulated use of a hair spray in a
beauty parlour gave 10-min weighted average values of 160-225
mg/m3 for the "customer" and 8-h weighted average values of 90-125
mg/m3 for the "beautician", based on the assumption that the
latter would use one 10-second spray every 15 min with the door of
the beauty parlour open. This latter value is well below the MAK
(Maximale Arbeitsplatzkonzentration, maximum working place
concentration) of 1800 mg/m3 in Germany (DFG, 1990) and the TLV of
3540 mg/m3 in the USA (ACGIH, 1990).
5.3 Occupational exposure
Bales (1978) reported HCFC 22 exposure levels of 17-48 mg/m3
for workers in a fluorocarbon packaging and shipping plant.
6. KINETICS AND METABOLISM IN LABORATORY ANIMALS AND HUMANS
6.1 Animal studies
6.1.1 Absorption
There are no quantitative data on the absorption of HCFC 21,
but the increase in fluoride levels observed in 90-day inhalation
toxicity studies (section 7.2) and the data on metabolic
transformation (section 6.1.3) suggest that inhaled HCFC 21 is
absorbed.
Carney (1977) studied the relationship between exposure to HCFC
22 and blood levels in anaesthetized rats. The gas in air was
applied through a canula inserted into the trachea. After 15 min of
exposure, a blood sample was withdrawn from the carotid artery, and
further blood samples were taken at intervals up to 30 min. Male and
female rats were exposed to nominal air concentrations of 35 or 175
g/m3. At 35 g/m3 the mean blood concentration was 31 mg/litre,
while at 175 g/m3 it was 155 mg/litre, showing a relationship
between the inhaled air and blood concentrations of HCFC 22. The
clearance was rapid with a half-life of 3 min.
Similar results have been reported by Sakata et al. (1981) in
experiments with rabbits. Animals, anaesthetized with phenobarbitone
(25 mg/kg ip), received HCFC 22/air mixtures via a plastic mask, and
blood samples were taken through a catheter in a femoral artery. The
concentration of HCFC 22 inhaled ranged from 175 g/m3 (5%) to 1400
g/m3 (40%). At every air concentration, blood concentrations
increased rapidly from the beginning of inhalation, and saturation
was reached in about 5 min. The blood concentration was related to
the concentration in inhaled air: at 175 g/m3 it was 148 mg/litre
(similar to the blood level found by Carney (1977) in rats under the
same conditions), and at 700 g/m3 it was 583 mg/litre. Clearance
was rapid with a half-life of 1 min; no HCFC 22 could be detected
one hour following cessation of exposure.
Woollen (1988) exposed pregnant rats to atmospheric HCFC 22
concentrations of between 1239 and 609 g/m3 (350 and 175 000 ppm).
Blood samples taken at various intervals showed that the compound
rapidly reached equilibrium with the blood. At the highest exposure
level, the blood level reached 118.5 mg/litre after 30 min and there
was no significant increase after a further 5.5 h of exposure (121
mg/litre).
6.1.2 Distribution
No information is available on the distribution of HCFC 21.
Sakata et al. (1981) determined the amount of HCFC 22 in the
tissues of rabbits exposed by inhalation to concentrations of up to
1400 g/m3 (see section 6.1.1). The results are presented in Table
4. No major differences were found in the tissues examined except
for fat tissue, where there was a difference after long and short
inhalation times at high concentrations. The authors postulated that
the effect was related to the poor vascular blood supply of adipose
tissue and that the distribution depended on partial pressures.
Those tissues with a good blood supply would reach equilibrium
quickly, whereas fat would equilibrate only slowly. Komoriya et al.
(1980) found HCFC 22 to be widely distributed in rats after a
variety of lethal exposures.
6.1.3 Metabolic transformation
A saturable dose-related increase in urinary fluoride was
observed in both sexes of Charles River albino rats in a 90-day
inhalation study with HCFC 21 (Lindberg, 1979). Details are given in
section 7.2.
The pharmacokinetics of HCFC 21 has been investigated in male
Wistar rats. Animals were injected intraperitoneally with a dose of
3.25 ml gas/kg body weight and placed in a closed chamber. Exhaled
HCFC 21 was monitored for 7 h by gas chromatography. Only part of
the injected compound was exhaled and it was assumed that the
remainder was metabolized (Peter et al., 1986).
Peter et al. (1986) found that HCFC 22 was not metabolized by
Wistar rats after intraperitoneal exposure (3.08 ml gas/kg body
weight). In their first experiment, rats received a single ip
injection of HCFC 22, after which they were placed in a closed
desiccator with a gas sample loop connected to a gas chromatograph.
The injected HCFC 22 was almost completely exhaled. Pretreatment of
the animals with phenobarbital (80 mg/kg ip followed by 3 days with
0.1% phenobarbital in the drinking-water) or DDT (200 mg/kg, one
week prior to the experiment) did not alter the observation. The
authors concluded that there was no detectable metabolism of HCFC
22. From these studies, it seems that HCFC 22, unlike HCFC 21, is
not metabolized.
The findings of Peter et al. (1986) support the earlier, more
comprehensive, studies of Salmon et al. (1979) who carried out
in vivo studies using 14C- and 36Cl-labelled HCFC 22. Alderley
Park Wistar-derived rats were exposed to 14C-labelled HCFC 22 at
levels of 1.75 g/m3 in three experiments and 35 g/m3 in three
others. The exposure durations were 15-24 h. Exhaled carbon dioxide
was collected by absorption on barium hydroxide and radioactivity
was subsequently measured. Separate collection of urine and faeces
Table 4. Tissue levels of HCFC 22 in rabbits following lethal inhalation exposurea
Rabbit no.
1 2 3 4 5 6 7 8
HCFC 22 concentration
(%, v/v)c 0-32 0-29 0-33 0-42 30 30 40 40
O2concentration
(%, v/v) 20-14 20-14 20-13 20-14 20 20 20 20
Time of death
after start of
inhalation (min) 67 31 25 19 15 92 7 10
Amount of HCFC 22b
Brain 145 138 76 156 137 148 140 159
Heart 145 150 100 158 135 140 125 129
Lung 167 128 187 231 139 136 121 186
Liver 143 95 72 78 101 153 44 60
Kidney 160 90 81 89 102 142 82 56
Visceral fat 327 93 48 33 38 196 23 27
Blood 219 193 140 161 131 219 147 199
a From: Sakata et al. (1981).
b Values are µl/g at 20-25 °C, 1 atmosphere
c Animals 1-4 were exposed to increasing concentrations of HCFC 22.
Values are inhaled concentrations; highest concentrations in rabbits
1-4 indicate those at the time of death.
into containers cooled to 0 °C was followed by measuring
radioactivity, directly in the case of urine and after appropriate
oxidation in the case of faeces. Similar exposure and collection
conditions were used for the experiments with 36Cl-labelled HCFC
22, in which the exposure applied was 35 g/m3 for 17.5 h. The
study showed that metabolism of HCFC 22 in the rat was minimal. The
amount of 14CO2 released was equivalent to approximately 0.1% of
the inhaled HCFC 22 at the exposure level of 1.75 g/m3 and 0.06%
at 35 g/m3. The amounts of 14C in the urine were also small,
equivalent to approximately 0.03 and 0.01% of the inhaled dose at
1.750 and 35 g/m3, respectively. Insignificant quantities were
found in the faeces. The results of the experiment with 36Cl
supported those obtained with 14C; only 0.01% of the inhaled dose
was detected in urine. It is not quite clear whether the minimal
metabolism observed was of HCFC 22 or of an impurity present in the
test compound (Salmon et al., 1979).
Salmon et al. (1979) also conducted in vitro studies, using a
microsomal preparation derived from liver homogenates of the same
rat strain induced with Aroclor 1254. Microsomes, NADPH, and 36Cl-
labelled HCFC 22 were incubated in a repeat-dosing syringe, and
samples were taken for analysis at 2-min intervals. Released
36Cl- was isolated as silver chloride and estimated by
scintillation counting. Under the test conditions, there was no
release of chloride ion from HCFC 22 (studied over the concentration
range 0.2-1.3 mmol/litre). This was a further indication of the
resistance of HCFC 22 to breakdown in biological systems and
suggested that any potential biological activity of the compound was
unlikely to be due to the formation of reactive intermediates.
6.1.4 Elimination
Peter et al. (1986), in their pharmacokinetic studies of HCFC
21 and HCFC 22 (details in section 6.1.3), calculated the total
clearance values of these compounds to be 4400 and 120 ml/h per kg,
respectively.
Carney (1977) showed that the clearance of HCFC 22 from the
blood of rats was rapid, the half-life being approximately 3 min
(details given in section 6.1.1). In studies by Sakata et al. (1981)
on rabbits, using exposure concentrations of 175 and 1400 g/m3, it
was found that the blood concentration decreased rapidly after
cessation of exposure, the maximum half-life being 1 min. After
15-30 min, blood concentrations were 27-31 mg/litre irrespective of
the concentration inhaled. Once the exposure ceased, HCFC 22 was
rapidly cleared from the blood and alveolar air, this being followed
by slower elimination from poorly perfused tissues.
Studies of Salmon et al. (1979) demonstrated that only minimal
amounts of the dose were excreted in the urine of rats following
exposure to a HCFC 22 concentration of 35 g/m3. Peter et al.
(1986) demonstrated that after ip injection the compound was exhaled
unchanged almost completely (see section 6.1.3).
6.2 Human studies
Data are available on the absorption and elimination of HCFC 22
only.
6.2.1 Absorption and elimination
In studies by Woollen et al. (1989), two groups of three male
subjects were exposed to average air HCFC 22 concentrations of 0.32
or 1.81 g/m3 for 4 h. Blood and expired air samples were collected
during the exposure period and for up to 26 h after exposure, and
were analysed for HCFC 22. Urine samples were collected for up to 22
h after exposure and analysed for HCFC 22 and fluorides. During the
exposure period blood concentrations approached a plateau, the
maximum blood concentrations of 0.25 and 1.36 µg/ml being related to
the exposure level. The concentrations of HCFC 22 in the expired air
were similar to the air concentrations during the exposure period.
The ratio between blood and expired air concentrations towards the
end of the exposure period was, on average, 0.77. This is consistent
with in vitro measurements of the solubility of HCFC 22 in human
blood (blood/air partition coefficient: 0.79). In the post-exposure
period, three phases of elimination were apparent with half-lifes of
3 min, 12 min, and 2.7 h. The first phase, identified only from
expired air analyses, probably represented elimination from alveolar
air and/or lung tissues. The second and third phases may correspond
to elimination from better and more poorly perfused tissues,
respectively. HCFC 22 was detected in urine samples collected in the
post-exposure period at both exposure levels, and the rate of
decline was consistent with the terminal rate of elimination
determined by blood and breath analyses. Fluoride concentrations in
urine did not increase significantly following exposure, indicating
that no detectable HCFC 22 metabolism occurs at these exposure
levels.
6.2.2 Distribution
Three days after a fatal accident on board a fishing vessel
(for details see section 8.2), samples of major tissues taken from
two of the deceased people were analysed for HCFC 22 by gas
chromatography (Morita et al., 1977). The findings are presented in
Table 5. The concentrations were similar to those found in two
rabbits examined three days after death by asphyxiation with HCFC 22
(Sakata et al., 1981; see section 6.1.2, Table 4).
Table 5. Concentration (µg/g) of HCFC 22 in major human tissues
after fatal poisoninga
Brain Lung Liver Kidney Blood
Subject A 68 18 71 18 69
Subject B 100 20 92 8 130
a From: Morita et al. (1977).
In a survey of organic compounds in human milk, HCFC 22 was
detected in one of twelve samples as one of 184 compounds
(Pellizzari et al., 1982). No information on exposure or
quantification of the amount found was given in the report.
7. EFFECTS ON LABORATORY MAMMALS AND IN VITRO TEST SYSTEMS
7.1 Single exposure
7.1.1 Acute oral toxicity
No published data on the oral toxicity of HCFC 21 or HCFC 22
are available except for a study by Anatova et al. (1983), in which
no signs of toxicity were noted in rats administered 4 ml of an
aqueous HCFC 22 solution at a concentration of 2700 mg/litre.
7.1.2 Acute inhalation toxicity
Detailed information on the acute effects of HCFC 21 in various
animal species is given in Table 6.
The signs of acute intoxication indicate that the CNS is the
major target organ when animals are exposed to high concentrations
of HCFC 21. Levels higher than 400 g per m3 were lethal to the rat
and guinea-pig within a few minutes to two hours. The 4-h LC50 in
rats was 213.07 g per m3 (Tappan & Waritz, 1964). Animals exposed
to concentrations above 42.7 g/m3 for 5 min or more exhibited
signs typical of various stages of anaesthesia. Dyspnoea was
observed at exposure levels above 50 g/m3.
In addition to central nervous system depression, increased
lacrimation, piloerection, and mydriasis were observed.
The concentrations and durations of exposure at which HCFC 22
proved lethal to a variety of animal species are given in Table 7.
These data show that HCFC 22 has a low order of acute toxicity to
several laboratory animal species. Deaths have been reported in
rats, mice, and guinea-pigs exposed to HCFC 22 concentrations of
775-1295 g/m3 (220 000 to 365 000 ppm) of HCFC 22 for periods of
15-240 min (Table 7). The signs of toxicity in rats were tremor of
the limbs and head, convulsions, narcosis, shallow respiration, and
death from respiratory depression. Death always occurred during
exposure, never after. Recovery from non-lethal exposure was rapid.
Rats appeared normal within 10 min and showed no delayed after-
effects.
The 10-min EC50 for the CNS effects described was 490 g/m3
for rats (Clark & Tinston, 1982). Signs in rabbits were similar to
those in rats, namely incoordination and other signs of CNS
depression, followed by respiratory depression and asphyxiation
(Sakata et al., 1981). The primary toxic effect of the single
inhalation exposure was central nervous system depression, which
occurred at very high exposure levels.
Cardiac and pulmonary effects are described in section 7.8.
Table 6. Acute effects of HCFC 21 in various animal species
Species Concentration Time of Symptoms Reference
(g/m3) exposure
Mouse 42.7 30-100 min hyperactivity Booth & Bixby (1932)
Rat 213.07 4 h (LC50); central Tappan & Waritz (1964)
nervous system
depression, lacrimation,
piloerection, mydriasis
Rat and 427 15-50 min deep narcosis, Weigand (1971)
guinea-pig death
213.5 2 h loss of balance, Weigand (1971)
narcosis
106.75 2 h loss of balance, Weigand (1971)
tremors, excitation
10 2 h no changes Weigand (1971)
Guinea-pig 1708 6 min tremors, death Booth & Bixby (1932)
854 11 min tremors, death Booth & Bixby (1932)
435.54 35-65 min death Nuckolls (1935)
256 5 min deep narcosis Booth & Bixby (1932)
213.5 2 h loss of coordination, Nuckolls (1935)
unconsciousness
213.5 2 h death within 2 h Caujolle (1964)
106.75 2 h seizures, Nuckolls (1935)
98.21 loss of balance
51.24 2 h dyspnoea, stupor Nuckolls (1935)
Table 7. Acute inhalation toxicity of HCFC 22
Species Concentration Exposure Effects observed Reference
(g/m3) period
(min)
Mouse 1295 120 death (MLC) Karpov (1963)
970 30 incoordination, deep Sakata et al. (1981)
narcosis, death (LC50)
Rabbit 1050 30 incoordination, cyanosis, Sakata et al. (1981)
death (MLC)
Rat 2100 2 depressed heart rate Pantaleoni & Luzi (1975a,b)
and blood pressure,
ECG changes
1225 15 deep narcosis, death Clark & Tinston (1982)
(LC50)
1050 120 incoordination, Weigand (1971)
accelerated respiration,
deep narcosis, death (MLC)
875 240 death (MLC) NIOSH (1976)
775 240 death (LC50) Litchfield & Longstaff (1984)
700 120 incoordination, accelerated Weigand (1971)
respiration, narcosis
Rat and 1400 120 incoordination, narcosis Weigand (1971)
guinea-pig
Guinea-pig 1050 120 narcosis Weigand (1971)
700 2 lacrimation, stupor, Nuckolls (1940)
tremor
Dog 2450 90 partial narcosis, Poznak & Artusio (1960)
depressed respiration,
death
Table 7 (contd)
Species Concentration Exposure Effects observed Reference
(g/m3) period
(min)
Dog (contd) 1400 90 incoordination, partial Poznak & Artusio (1960)
narcosis
Monkey 700 5 depressed respiration, Aviado & Smith (1975)
heart rate, and blood
pressure
MLC = Minimum lethal concentration.
7.2 Short-term inhalation exposure
In this monograph, short-term exposures are defined as those
involving repeated daily exposures for up to 90 days and long-term
exposures as those lasting more than 90 days.
Cardiac and pulmonary effects are described in section 7.8.
7.2.1 HCFC 21
Weigand (1971) exposed five rats, five guinea-pigs, two beagle
dogs, and two cats to HCFC 21 (42.7 g/m3) for 3.5 h/day, 5
days/week, for 4 weeks. The behaviour of all animals remained normal
throughout the experiment. The increase in body weight of rats was
somewhat retarded and the guinea-pigs lost weight. The blood and
urine analyses were normal. Gross pathological examination revealed
alterations in the livers of all the guinea-pigs and cats, and one
of the dogs, but not of the rats. Histopathological examination
showed hepatic single cell necrosis and fatty degeneration in all
exposed animals.
Kelly (1976, 1977) and Trochimowicz et al. (1977) exposed a
group of 10 male rats to HCFC 21 (42.7 g/m3) 6 h per day, 5
days/week, for 2 weeks. There were no deaths but the rats lost
weight and exhibited marked anaemia and increased serum transaminase
levels, indicating liver damage. Pathological examination
immediately after the last exposure showed liver necrosis; this
necrosis was still present in a recovery group examined 14 days
later.
In a further study (Kelly, 1977) groups of 27 male and 27
female Charles River albino rats and 4 male beagle dogs were exposed
to HCFC 21 levels of 4.27 or 21.35 g/m3 6 h per day, 5 days/week,
for 90 days. Rats were severely affected; between days 59 and 90,
37% of the rats exposed to the low and 29% exposed to the high
concentration died. Standard clinical chemistry investigations
showed alterations in liver function. Histopathological examination
revealed extensive liver cirrhosis. Neither the mortality nor the
histopathological damage was related to the dosage. None of the dogs
died; the only significant effects occurred at 21.35 g/m3 and
consisted of slight weight loss during exposure and minimal
unspecified morphological changes in the liver.
Lindberg (1979) exposed four groups of Charles River albino
rats (35 males and 35 females in each group) to HCFC 21
concentrations of 0, 0.213, 0.64, and 2.13 g/m3 for 6 h/day, 5
days/week, for 90 days. At a level of 2.13 g/m3 the average body
weight gain was lower than in controls during the early phase of the
experiment. Leucocyte counts were elevated in animals exposed to the
highest concentration, as were serum alkaline phosphatase and
alanine aminotransferase activities. Urine volumes showed a tendency
to increase. At this exposure level an increase in urine fluoride
concentration was observed in both sexes after 45 days of treatment.
There was a similar increase in urinary fluoride concentration at 90
days, with essentially no difference between rats exposed to 0.64
and 2.13 g/m3. This suggests that saturation of the metabolic
transformations occurs at exposure levels at or below 0.64 g/m3.
Histopathological evaluation revealed portal cirrhosis of the liver,
interstitial oedema of the pancreas, and degeneration of the
seminiferous epithelium at all dose levels. The liver toxicity and
indications for metabolism suggest a similar mechanism of toxicity
to that demonstrated for trichloromethane (DFG, 1986). Thus, a
reactive metabolite may be responsible for the induction of liver
effects.
7.2.2 HCFC 22
No effects were seen on body weight, haematological parameters,
urine analysis, organ weights or macroscopic and microscopic
appearance of the tissues in rats, guinea-pigs, dogs or cats exposed
to HCFC 22 (175 g/m3) 3.5 h per day, 5 days/week, for 4 weeks
(Weigand, 1971).
Lee & Suzuki (1981) exposed two groups of 16 male Sprague-
Dawley rats to HCFC 22 (0 or 175 g/m3), 5 h/day for 8 weeks, after
which 6 rats in each group were killed and blood and tissue samples
taken for haematological and biochemical assays and for
histopathological examination. The remaining animals were retained
for a fertility study, the results of which are presented in section
7.5. No signs of toxicity were apparent in the exposed animals, and
body weight was not affected. Prostate weight was decreased slightly
but not the weights of other organs. No histopathological lesion was
related to exposure in any of the organs examined. Plasma glucose
and triglyceride levels were reduced and plasma cholesterol slightly
raised, but no haematological parameter was affected.
Leuschner et al. (1983) exposed Sprague-Dawley rats (35 and
17.5 g/m3) and beagle dogs (17.5 g/m3 only) to HCFC 22 6 h/day
for 13 weeks. The treatment and control groups consisted of 20 male
and 20 female rats and 3 male and 3 female dogs. Investigations of
behaviour, body weight, haematology, clinical biochemistry, and
organ weights were carried out in both species, and dogs were also
subjected to ECG measurements and to an examination of circulatory
function. The clinical biochemistry examinations included assays for
serum alanine transaminase, aspartate transaminase, and alkaline
phosphatase activities, as well as liver function tests.
Histopathological examinations were undertaken on a wide variety of
tissues. No changes were found in any of these examinations. It was
therefore concluded that the no-observed-effect level for HCFC 22
was in excess of 35 g/m3 in the rat and in excess of 17.5 g/m3
in the dog.
In a limited experiment on rabbits that also received sodium
barbital in the drinking-water, Van Stee & McConnell (1977) found
that exposure to HCFC 22 (210 g per m3, 5 h/day, 5 days/week for
8-12 weeks) induced cardiac arrhythmia in one of 14 rabbits. In
addition, some rabbits (number unknown) showed slight
histopathological liver damage and a modest elevation in the level
of unspecified serum enzymes. The lack of detail and the fact that
no controls were used make meaningful conclusions impossible.
7.2.3 Mixed exposure
Two unweaned beagle puppies (one male, one female) weighing
1.5-3 kg inhaled a mixture of HCFC 22 and HCFC 21 (60% : 40%) for 5
min, twice daily, 5 days a week for 2 weeks, at a concentration of
1714 mg/kg body weight. After 1-2 min the puppies became sedated and
ataxic, but they recovered a few minutes after removal from
exposure. No other effects were noted during investigations that
included blood chemistry and urine analyses, and gross and
microscopic examinations of the lungs (Knox-Smith & Case, 1973).
7.3 Skin and eye irritation; sensitization
7.3.1 Skin irritation
HCFC 21 produced mild irritation when applied at concentrations
higher than 25% in propylene glycol to the shaved, intact skin of
guinea-pigs. No irritation was observed at a concentration of 2.5%
(Goodman, 1975).
Quevauvillier et al. (1964) reported that a 10-second spray of
HCFC 22 on the shaved belly of the rat twice a day, 5 days/week, for
6 weeks caused reddening of the skin and slight swelling of the
surface. There was also a delay in hair regrowth. A more recent
report (Atochem, 1986) classified the compound as a skin irritant
but this effect was only observed following the application of 0.5
ml in liquified form under occlusion to the intact and abraded skin
of rabbits.
The irritation induced by a chemical with a boiling point at or
near room temperature appears to be related to rapid evaporation,
resulting in a drying effect on the skin or mucous membrane.
7.3.2 Eye irritation
Undiluted liquid HCFC 21, chilled to the temperature of dry
ice, was placed into the right conjunctival sacs of two rabbits.
After 20 seconds, the treated eye of one rabbit was washed with 0.9%
saline for 1 min. Slight corneal opacity, transient congestion of
the iris and moderate conjunctival irritation in the unwashed eye
was seen. There was slight corneal opacity and moderate conjunctival
irritation but no iris involvement in the washed eye. Both eyes were
normal within 5 days (Brittelli, 1975). This report did not
distinguish between the effects of cold, including that caused by
evaporation, and the intrinsic properties of HCFC 21. In another
study, HCFC 21 was sprayed directly into the eyes of each of six
rabbits from a distance of 5 cms. No corneal or iris injury was seen
but lacrimation was observed in four of the rabbits examined 1 and 4
h after exposure (Hood, 1964a). Two additional studies on rabbits
evaluated the eye irritation potential of diluted HCFC 21 in various
solvents (Hood, 1964b; Eddy, 1970). In both studies, 0.1 ml of the
test solution was instilled in one eye of each of six albino
rabbits. The other eye, which was treated with vehicle, served as a
control. The eyes were not washed after treatment. HCFC 21, as
either a 50% solution in mineral oil or a 40% solution in propylene
glycol or dimethyl phthalate, produced varying degrees of injuries
to the cornea, iris, and conjunctivae. Milder irritant effects were
seen with a 15% solution. All these effects disappeared within 7 to
10 days.
HCFC 22 was reported to be a slight irritant when the corneas
of albino rabbits were exposed to the gas for 5 or 30 seconds
(Atochem, 1986).
7.3.3 Skin sensitization
No evidence of skin sensitization with HCFC 21 was found in
guinea-pigs by Hood (1964b) or Goodman (1975).
The skin-sensitizing potential of HCFC 22 was tested in 10 male
and 10 female Hartley albino guinea-pigs using a modification of the
Magnusson-Kligman maximization text. On day 0, Freund Complete
Adjuvant was injected intradermally and 0.25 ml of liquified
compound was applied topically to the skin under a capsule for 28 h.
On days 2, 4, 7, 9, 11, and 14, 0.5 ml of liquified HCFC 22 was
applied topically at the same place for 48 h under occlusion. After
a period of 2 weeks, the challenge exposure was performed on day 28
at the opposite side of the body: 0.25 ml of liquified HCFC 22
(maximum non-irritating dose as determined in the previous
experiment) was applied under a capsule for 48 h. No cutaneous
sensitizing reaction was observed during a macroscopic or
histological evaluation of the skin 1, 6, 24, and 48 h after removal
of the occlusive patch (Atochem, 1986).
7.4 Long-term inhalation exposure
No data are available on the chronic toxicity of HCFC 21 based
on exposures longer than 90 days.
Karpov (1963) exposed rats, mice, and rabbits to HCFC 22 (50
g/m3), as well as rats and mice to 7 g per m3, for 6 h/day, 6
days/week, over a 10-month period. Body weights, oxygen consumption,
CNS function, and biochemical and haematological parameters were
recorded, and histopathological examinations of some tissues were
undertaken at the end of the test. Depressed body weight gain in
mice after 4-6 months, depressed oxygen consumption in rats, CNS
function changes in rats and mice, decreased haemoglobin
concentration in rabbits, and histopathological (dystrophic) changes
in the liver, lungs, and nervous tissue were observed at 50 g/m3.
No effect was seen at the lower exposure level (7 g/m3).
In a life-time study, Tinston et al. (1981a) exposed Alderley
Park Swiss-derived mice (80 male and 80 female per group) to HCFC 22
(0, 3.5, 35, and 175 g/m3) 5 h per day, 5 days/week, for up to 83
weeks (females) and 94 weeks (males), at which time there was 80%
mortality. At week 38, 10 mice per group were killed in order to
perform blood assays, including red and white blood cell counts,
platelet counts, prothrombin and kaolin-cephalin times, and bone
marrow examination. Measurements of plasma ASAT (EC 2.6.1.1) and
ALAT (2.6.1.2) activities and urine analyses were also undertaken.
The only consistent finding was hyperactivity observed in the male
mice exposed to 175 g/m3. There were no treatment-related effects
on mortality or body weight gain. No abnormalities were observed
during haematological, biochemical or histopathological
investigations, with the exception of the neoplasia described in
section 7.7.
Tinston et al. (1981b) performed a similar lifetime study on
Alderley Park Wistar-derived rats using the same group sizes and
exposure levels. The study lasted 118 weeks in females and 131 weeks
in males (80% mortality). Some animals were killed at week 52. The
same investigations were carried out as in the case of the mouse
study. No clinical abnormalities, increased mortality, or
haematological or biochemical changes could be attributed to HCFC 22
at any exposure level. At the highest level (175 g/m3), there was
a decrease in body weight gain in males and increased liver, kidney,
and adrenal and pituitary gland weights in the females. A number of
non-neoplastic lesions were observed histologically in all the
groups but there was no evidence of exposure-relatedness.
7.5 Reproduction, embryotoxicity, and teratogenicity
7.5.1 Reproduction
No data are available on the effects of HCFC 21 on
reproduction, except for a limited study by Aranjina (1972) who
claimed a decrease in the levels of DNA and total nucleic acids in
the liver, brain, ovaries, and placenta of female rats exposed to
0.153 or 0.303 g/m3 for the whole gestation period. The biological
significance of this finding cannot be evaluated due to the lack of
adequate reporting.
Lee & Suzuki (1981) tested HCFC 22 for effects on male
reproduction in Sprague-Dawley rats. A group of 16 male rats was
exposed to a concentration of 175 g/m3, 5 h per day, for 8 weeks,
and a control group of the same size was exposed to filtered air.
The animals were examined and weighed weekly. At the end of the 8-
week period, six rats from each group were killed, organ weights
determined, and histopathological, clinical, chemical, and
haematological examinations were carried out. The prostate glands
were assayed for fructose and acid phosphatase (EC 3.1.3.2)
activity. Immediately after the final exposure, blood was collected
from the remaining 10 rats in each group, and the plasma was assayed
for follicle stimulating hormone (FSH) and luteinizing hormone (LH).
These animals were then used for serial mating, each male being
housed with a virgin female for 7 days, after which time the female
was replaced with another virgin female; this regime was followed
for 10 weeks. Nine days after removal, each female was killed, and
the numbers of corpora lutea, total implants, live implants,
resorption sites, and dead implants were determined. There was no
sign of any overt toxicity. The major organs of treated animals,
including testes and epididymes, did not differ in weight from those
of the controls. There was a slight decrease in weight of the
prostate and coagulating gland in the treated rats but there were no
accompanying histological changes. Prostatic fructose and acid
phosphatase (EC 3.1.3.2) levels, as well as FSH and LH levels, were
not different from those in controls. Serum cholesterol levels were
slightly higher, and glucose and triglyceride levels were slightly
lower in treated rats than in controls. Overall, there was no
significant effect upon the fertility of male rats.
7.5.2 Embryotoxicity and teratogenicity
7.5.2.1 HCFC 21
When Kelly et al. (1978) exposed pregnant rats to 42.7 g/m3
(6 h/day on days 6-15 of gestation), no clinical signs of toxicity
were observed but the rats gained substantially less weight than the
control animals. HCFC 21 interfered with the process of
implantation: 15 of 25 mated rats had no implants or viable fetuses.
The outcome of pregnancy and the fetal development in the other 10
rats were not affected. No teratogenic activity was observed.
7.5.2.2 HCFC 22
Three inhalation teratology studies with HCFC 22 were carried
out in 1977 and 1978 (Culik et al., 1976; Culik & Crowe, 1978).
Groups of 20-40 pregnant Charles River CD rats were exposed to
several concentrations ranging from 0.35 to 70 g/m3 for 6 h/day on
days 4-13 or 6-15 of gestation. There was no evidence of maternal or
overt fetal toxicity. The only teratogenic abnormalities observed
were small statistically insignificant increases in microphthalmia
or anophthalmia. The incidence of microphthalmia/anophthalmia in the
three studies is presented in Table 8.
Table 8. Incidence (fetuses/litters) of microphthalmia or anophthalmia in
three preliminary studies of HCFC 22 in Charles River CD ratsa
Exposure levels (g/m3)
Study 0 0.350 1.05 1.75 3.5 35 70
1 0/21 1A/22 2A/21
2 0/34 1M/33 (2M+/33) 1A/35
3 0/38 1M/40 0/35 2M/34
a From: Culik et al. (1976) and Culik & Crowe (1978)
A = anophthalmia; M = microphthalmia
(no quantitative procedures were applied to the assessment of microphthalmia);
+ = two fetuses were affected in the same litter.
The comparatively low incidence of microphthalmia or
anophthalmia in the above study led Palmer et al. (1978a) to conduct
a large study designed to improve the sensitivity of the
investigation of these infrequent malformations. Female CD rats were
exposed to concentrations of 0, 0.35, 3.5 or 175 g/m3 for 6 h/day
on days 6-15 of gestation. Nineteen batches of time-mated females
were used, each batch consisting of 34 control rats and 22 rats in
each of the three test groups; more than 6000 control fetuses and
4000 fetuses from exposed animals were examined. The animals were
killed on day 20 of pregnancy and examined macroscopically. The
ovaries were examined for numbers of corpora lutea and the uteri for
live young and embryonic fetal death; litter and mean pup weights
were recorded. The heads of all fetuses were sectioned and examined
with particular reference to microphthalmia, anophthalmia, and
associated anomalies. Maternal body weights in the group exposed to
175 g/m3 were slightly lower than in controls in most batches; the
body weight gain was consistently lower in this group than in the
controls during the first day of exposure. No other change in the
dams was observed. Overall, there was no effect on litter size,
post-implantation loss or litter weight. Mean fetal weight was
slightly but consistently lower in the group exposed to 175 g/m3
than in controls, but not at the two lower levels of exposure. The
number of fetuses and the incidence of litters with anophthalmia or
microphthalmia are shown in Table 9. There was no significant
difference from controls with respect to the incidence of
anophthalmia/microphthalmia at low or intermediate exposure levels.
At the highest exposure level, there was a small but significant
(P < 0.05) increase in the incidence of litters containing fetuses
with total eye malformations and anophthalmia. No other gross fetal
abnormality was found.
Palmer et al. (1978b) also carried out a teratology study in
rabbits. New Zealand white rabbits were exposed to 0, 0.35, 3.5, or
175 g/m3 for 6 h/day on days 6-18 of pregnancy. There were 14-16
pregnant females per group. The animals were killed on day 29 of
pregnancy for an assessment of litter data and an examination of
fetuses for major malformations, minor anomalies, and variants.
There were no significant treatment-related effects in females, and
pregnancies were normal. Maternal body weight gain was slightly but
consistently lower in the animals exposed to 175 g/m3 during the
first 4 days of exposure but, thereafter, weight gain was comparable
to that in the controls. Litter size, post-implantation loss, and
litter and mean fetal weights were unaffected. There was no
significant increase in the incidence of major or minor fetal
abnormalities.
7.6 Mutagenicity
7.6.1 HCFC 21
HCFC 21 was not mutagenic when incubated for 72 h with
Salmonella typhimurium (TA98, TA100, TA1535, TA1537, TA1538) with
or without metabolic activation. The compound was not mutagenic to
Saccharomyces cerevisiae D4 (Brusick, 1976).
7.6.2 HCFC 22
The data from in vitro and in vivo studies are summarized
in Table 10. HCFC 22 induced mutations in Salmonella typhimurium
base-pair substitution strains TA1535 and TA100 but not strains
TA98, TA1537 or TA1538 after gaseous exposure.
The response was independent of the presence or absence of a
metabolizing system, as would be expected from the lack of
metabolism in animals. Negative responses were reported in mutation
assays using Schizosaccharomyces pombe and Saccharomyces
cerevisiae (Loprieno & Abbondandolo, 1980), plant cells (Van't
Hoft & Schairer, 1982), Chinese hamster cells (McCooey, 1980;
Loprieno & Abbondandolo, 1980), and in a cell transformation assay
(BHK21; Loprieno & Abbondandolo, 1980).
Table 9. The number and incidence of fetuses with eye malformations (anophthalmia and microphthalmia)
in rats exposed to HCFC 22a
Eye malformations Anophthalmia Microphthalmia
HCFC 22 No. of Incidence No. of Incidence No. of Incidence
concentration fetuses per 1000 fetuses per 1000 fetuses per 1000
(g/m3) affected litters affected litters affected litters
0 3 4.94 1 1.65 2 3.29
0.35 5 12.66 1 2.53 4 10.13
3.5 3 7.69 1 2.56 2 5.13
175 10 26.11b 6 15.67a 4 10.44
a From: Palmer et al. (1978a).
b Statistically significant (P < 0.05) by a one-sided stratified contingency chi-square test
Table 10. The genetic toxicity of HCFC 22
Assay Organism Species/strain/cell type Metabolic Testing conditions Results Reference
activationa
Reverse bacteria Salmonella typhimurium ± 20 & 40% gas for 6 h negative Barsky (1976)
mutation TA1535; TA1537; TA1538;
TA98; TA100
Reverse bacteria Salmonella typhimurium ± up to 40% gas for 48 h positive for Koops (1977)
mutation TA1535; TA1537; TA98; TA100 TA1535 only,
activation
independent
Reverse bacteria Salmonella typhimurium ± incubated with 50% gas positive for Longstaff & McGregor
mutation TA1535; TA1538; TA98; TA100 for 24 h TA1535, (TA100 (1978)
positive in 1 of
3 experiments),
activation
independent
Reverse bacteria Salmonella typhimurium ± 50% gas for 24 h positive Bartsch et al. (1980)
mutation TA100
Reverse bacteria Salmonella typhimurium ± 50% for 24 h positive for Longstaff et al. (1984)
mutation TA1535; TA1538; TA98; TA100 TA1535 and
TA100,
activation
independent
Forward yeast Schizosaccharomyces pombe ± 20 mM solution generated negative Loprieno & Abbondandolo
mutation at 500 ml/min of (1980)
50% gas
Table 10 (contd)
Assay Organism Species/strain/cell type Metabolic Testing conditions Results Reference
activationa
Cell mutation plant Tradescantia N/A closed chamber, highest negative Van't Hoft & Schairer
ineffective dose (1982)
1.16 g/m3
Cell mutation hamster Chinese hamster ovary cells ± tested at 20-92% gas negative McCooey (1980)
Cell mutation hamster Chinese hamster lung ± 20 mM solution generated negative Loprieno & Abbondandolo
V 79 cells at 500 ml/min of (1980)
50% gas
Cell mutation yeast Schizosaccharomyces pombe N/A 816 mg/kg body weight negative Loprieno & Abbondandolo
(host or Saccharomyces cerevisiae in corn oil by gavage (1980)
mediated) in CD-1 mice
Gene yeast Saccharomyces cerevisiae ± 20 mM solution generated negative Loprieno & Abbondandolo
conversion at 500 ml/min of (1980)
50% gas
Unscheduled human heteroploid EUE cell line ± 20 mM solution generated negative Loprieno & Abbondandolo
DNA at 500 ml/min of (1980)
synthesis 50% gas
Cell hamster BHK-21 cells - 20 mM solution generated negative Loprieno & Abbondandolo
transformation at 500 ml/min of (1980)
50% gas
Chromosome mouse CD-1, bone marrow cells N/A 816 mg/kg body weight negative Loprieno & Abbondandolo
aberrations in corn oil by gavage (1980)
in vivo
Table 10 (contd)
Assay Organism Species/strain/cell type Metabolic Testing conditions Results Reference
activationa
Chromosome rats bone marrow cells N/A inhalation for 2 h at dose/related Anderson et al. (1977a)
aberrations 8/group 3.5, 35, or 525 g/m3 increase of
in vivo chromosome
damage,
significant only
at high dose
Chromosome rats bone marrow cells N/A inhalation at 3.5, 35, significant Anderson et al. (1977)
aberrations 8/group or 525 g/m3, 6 h/day increase of
in vivo for 5 days chromosome
aberrations at
low and mid-dose
but not at high
dose
Chromosome mouse CD-1, bone marrow cells N/A 816 mg/kg body weight negative Loprieno & Abbondandolo
aberrations in corn oil by gavage (1980)
in vivo
Dominant mouse CD-1 N/A inhalation for 6 h/day, positive in some Hodge et al. (1979)
lethal 20/group 5 days, at 3.5, 35, or parameters, not
350 g/m3 time or dose
related
Dominant mouse CD-1 N/A inhalation for 6 h/day, positive in some Hodge et al. (1979)
lethal 20/group 5 days, at 0.035, 0.35, parameters, not
1.75, 3.5, 35, 175 g/m3 time or dose
dependent
Dominant rat Sprague-Dawley N/A 175 g/m3, 5 h/day, for negative Lee & Suzuki (1981)
lethal 8 weeks
Table 10 (contd)
Assay Organism Species/strain/cell type Metabolic Testing conditions Results Reference
activationa
Micronucleus mouse bone marrow cells N/A 175 and 525 g/m3 negative Howard et al. (1989)
in vivo for 6 h
a ± indicates that separate experiments were carried out with and without metabolic activation; NA = not applicable
Anderson et al. (1977a) found an increase in chromosomal damage
in rats exposed to 3.5 g/m3, 6 h/day, for 5 days. However, there
was less evidence of chromosomal damage at exposures of 35 and 525
g/m3. Similar results were observed following a single 2-h
exposure using the same concentrations. Anderson & Richardson (1979)
repeated the experiment using lower exposure levels (0.035, 0.35,
1.75, and 3.5 g/m3). There was an increase in chromosomal damage,
but again it was not dose related. Both of these studies were
reviewed by Litchfield & Longstaff (1984) and Longstaff (1988).
Loprieno & Abbondandolo (1980) did not find chromosomal changes in
the bone marrow of mice in a study in which HCFC 22 was administered
by gavage.
There was no evidence for dominant lethality in a study on male
Sprague-Dawley rats exposed to 177 g/m3, 5 h/day, for 8 weeks (Lee
& Suzuki, 1981). In two dominant lethal assays on mice at exposure
levels of 0.035-350 g/m3, there were statistically significant
differences from control values in certain parameters (e.g., early
fetal death, reduction of fertility) at various points (Anderson et
al., 1977b; Hodge et al., 1979). However, there was no time or
exposure-relatedness. In addition, results were not reproducible.
In an inhalation study in mice, Howard et al. (1989) found no
evidence of micronucleus induction at exposure levels at 175 and 525
g/m3.
Most of these studies have been reviewed by Litchfield &
Longstaff (1984) and Longstaff (1988). With the exception of
positive findings in mutation assays using specific strains of
Salmonella (TA1535 and TA100), HCFC 22 did not show activity in
microorganisms or in mammalian in vitro and in vivo systems.
These included mutation, unscheduled DNA synthesis assays in vitro,
and cytogenetic and dominant lethal assays in two species of
rodents. Overall, the available information does not indicate a
genotoxic effect of HCFC 22 in mammalian systems.
7.7 Carcinogenicity
No data are available on the carcinogenicity of HCFC 21.
In a life-time study, Tinston et al. (1981b) exposed groups of
80 male and 80 female Alderley Park Wistar-derived rats to HCFC 22
(0, 3.5, 35, or 175 g/m3, 5 h per day, 5 days/week) for 118 weeks
in females and 131 weeks in males (the period by which mortality had
reached approximately 80%). No treatment-related clinical
abnormalities, increased mortality, or haematological or biochemical
changes were observed. The only effects were a body weight reduction
in males exposed to 175 g/m3 and increased weight of liver,
kidney, and adrenal and pituitary glands in females. In males there
was no increase in the number of benign tumours, but there was a
slight increase in the number of rats with malignant tumours at the
highest exposure level (Table 11). This increase was primarily due
to the increased incidence of rats with fibbrosarcoma. The only
organ that was consistently associated with this increase was the
salivary gland, but, according to Litchfield & Longstaff (1984),
this may have been the consequence of generalized subcutaneous
fibrosarcomas developing in a submandibular site and involving the
salivary gland only by chance. The increase in fibrosarcomas was
observed only in the late stages of the study (between 105 and 130
weeks). No significant increase was found at lower exposure levels.
Four male rats in the group exposed to 175 g/m3 were found to have
Zymbal gland tumours at the highest exposure level. Female rats did
not exhibit such changes at any of the exposure levels.
Table 11. Tumour incidence in male rats exposed to HCFC 22
in a lifetime inhalation studya
HCFC concentrations (g/m3)
0b 3.5 35 175
Total malignant 16/80 27/80 22/80 33/80
tumours 18/80
Selected sites
Fibrosarcomas 5/80 8/80 5/80 18/80c
7/80
Salivary gland 1/80 1/80 0/80 7/80c
fibrosarcomas 0/80
Zymbal's gland 0/80 0/80 0/80 4/80c
tumours 0/80
a From: Tinston et al. (1981b).
b Two control groups were used.
c Statistically significant difference in relation to the control group
(P < 0.05)
In a further study, Tinston et al. (1981a) exposed groups of 80
male and 80 female Alderley Park Swiss-derived mice to HCFC 22 (0,
3.5, 35, or 175 g/m3, 5 h per day, 5 days/week) for up to 83 weeks
in males and 94 weeks in females (approximately 80% mortality). The
only finding was hyperactivity. There was no significant increase in
the incidences of benign or malignant tumours in treated male or
female mice compared to the controls, with the exception of a small
increase in the incidence of hepatocellular carcinomas in the males
at the highest exposure level. However, the incidences of both
benign and malignant nodules were within the range of historical
control values for this strain of mouse.
There have been two well-documented and well-conducted lifetime
inhalation studies by Tinston et al. (1981a,b) in rats and mice.
These did not indicate any increased tumour incidence except for
fibrosarcomas in male rats at the highest exposure level of 175
g/m3. The lack of tumour response was also seen in another
inhalation study using a different mouse strain and a maximum
exposure level of 17.5 g/m3, and in a limited gavage study in
rats.
The overall results of these studies indicate no tumorigenic
effect up to exposure levels of 35 g/m3. It has been suggested
that the increased tumorigenic response in male rats at the high
exposure level may be due to the presence of HCFC 31, a known
mutagen and animal carcinogen, as an impurity (DFG, 1986), but more
evidence is needed to confirm this suggestion.
Maltoni et al. (1982, 1988) exposed groups of 60 male and 60
female Sprague-Dawley rats and Swiss mice by inhalation to HCFC 22
(concentrations of 0, 3.5, and 17.5 g/m3, for 6 h/day, 5
days/week) for 104 weeks (rats) or 78 weeks (mice). There were no
differences in body weights or survival between treated and control
animals (details not given). No increases in tumour incidence were
observed.
Longstaff et al. (1984) administered to a group of 36 male and
a group of 36 female Alderley Park Wistar-derived rats HCFC 22 (300
mg/kg body weight) in corn oil by gavage daily (on 5 days/week) for
52 weeks. One similarly sized control group received no treatment
and two control groups were dosed with corn oil. The study was
terminated at week 125. The treatment had no effect on body weight
gain or mortality. No increased incidence of tumours was observed in
any of the organs in the treated groups compared either with
untreated controls or those given corn oil.
7.8 Special studies - cardiovascular and respiratory effects
Chlorofluorocarbons have long been known to sensitize the heart
to adrenaline-induced arrhythmias (Reinhardt et al., 1971; Zakhari &
Aviado, 1982). Respiratory effects have also been noted.
7.8.1 HCFC 21
A summary of data on the effects of HCFC 21 on cardiovascular
and respiratory function is given in Table 12.
Table 12. Cardiovascular and respiratory function studies on HCFC 21
in different animal species
Species Concentration Effect Reference
(g/m3)
Mouse 427 arrhythmia (with and without exogenous Aviado & Belej
adrenaline) (1974)
Rat 811.3 apnoea, cardiac arrest Friedman et al.
(1973)
Cat 1700 sensitization to exogenous adrenaline, Branch et al.
cardiac arrhythmia (1990)
Dog 42.7 lowest concentration causing cardiac Mullin (1975)
sensitization (with exogenous adrenaline)
106.75 EC50 for cardiac sensitization (with Clark & Tinston
exogenous adrenaline) (1973)
106.75 tachycardia, bronchoconstriction Aviado (1975a,b)
106.75 rise in pulmonary resistance, decrease in Belej & Aviado
pulmonary compliance (1975)
427 hypotension
Monkey 106.75 minimal concentration for induction of Aviado (1975);
cardiac arrhythmia, tachycardia, myocardial Belej et al.
depression, and hypotension (1974)
106.75 reduction in respiratory minute volume Aviado & Smith
(1975)
213.5 bronchodilation with depression of Aviado (1973,
respiration 1975)
In non-anaesthetized dogs, the concentration of HCFC 21 leading
to cardiac arrhythmias in 50% of catecholamine-treated dogs (EC50
value) was calculated to be 107 g/m3 for a 5-min exposure period
(Clark & Tinston, 1973). In a separate study, the lowest dose
causing this effect was 43 g/m3 (Mullin, 1975). Tachycardia,
broncho-constriction, and loss of pulmonary compliance were also
found at exposure levels of 107 g/m3 when anaesthetized dogs were
given a 7-min exposure (Aviado, 1975a,b; Belej & Aviado, 1975).
In anaesthetized monkeys (species not further defined),
spontaneous cardiac arrhythmias, tachycardia, and hypertension, as
well as reduced respiratory minute volume, were found following
exposure to 107 g/m3 for 7 min (Belej et al., 1974; Aviado &
Smith, 1975). In contrast to dogs, bronchodilation and early
respiratory depression were found in monkeys exposed to 214 g/m3
(Aviado, 1975a,b).
Spontaneous arrhythmias occurred in mice exposed to 425 g/m3
for 7 min (Aviado & Belej, 1974). Brachycardia, apnoea, and cardiac
arrest, accompanied by lowered respiratory rates and raised lung
tidal volumes, were apparent in rats exposed to 811 g/m3 (Friedman
et al., 1973).
These effects of HCFC 21 are also characteristic of the fully
halogenated chlorofluorocarbons (see WHO, 1990).
7.8.2 HCFC 22
A summary of data on the cardiovascular and respiratory effects
of HCFC 22 in experimental animals is presented in Table 13.
Belej et al. (1974) evaluated the cardiotoxic potential of HCFC
22 in three Rhesus monkeys anaesthetized with sodium pentobarbitone.
The trachea of each animal was canulated and the chest was open for
direct measurement of cardiac function. Following exposure to 350 or
700 g/m3 for 5 min, various indices of cardiac function were
measured, i.e. heart rate, myocardial force, aortic blood pressure,
and left atrial pressure. The only changes found were a slight but
significant depression of myocardial contractility and a drop in
aortic blood pressure in monkeys exposed to either concentration.
The effect of HCFC 22 on respiratory function was studied by
Aviado & Smith (1975) in three Rhesus monkeys anaesthetized by
intravenous application of sodium phenobarbital (30 mg/kg) and
exposed for 5 min to 350 g/m3 through a canulated trachea.
Electrocardiograms and femoral arterial blood pressures were
recorded, and pulmonary airway resistance and compliance were
estimated from measurements of tracheal airflow and transpulmonary
pressure. No significant change was recorded at 350 g/m3, but a
slight, yet significant, elevation in pulmonary resistance was
observed at 700 g/m3.
Arrhythmias were also noted in cats given 1700 g per m3 of
40% HCFC 22 for 10 minutes (Branch et al., 1990).
Table 13. Cardiovascular and respiratory function studies of HCFC 22 in different animal species
Species Concentration Duration Effects Reference
(g/m3) of
exposure
Rat 525-2100 2 min decreased heart rate and changes Pantaleoni &
in ECG Luzi (1975a)
1050-2100 2 min decreased myocardiac contractility, Pantaleoni &
ECG changes, arterial hypotension Luzi (1975b)
Mouse 700 6 min no arrhythmias with or without Aviado & Belej
exogenous adrenaline; (1974)
1400 6 min arrhythmias seen only with exogenous
exogenous adrenaline
Rabbit 210 5 h/day one of 14 rabbits developed Van Stee &
for 8-12 arrhythmias; also received phenobarbital McConnell (1977)
weeks (no controls were used)
Dog 1750 5 min lowest concentration causing cardiac Mullin (1975)
sensitization (with exogenous adrenaline)
87.5 5 min no effects (with exogenous adrenaline) Reinhart et al.
175 5 min cardiac sensitization (with exogenous (1971)
adrenaline)
490 5 min EC50 for cardiac sensitization (with Clark & Tinston
exogenous adrenaline) (1982)
Table 13 (contd)
Species Concentration Duration Effects Reference
(g/m3) of
exposure
Dog 17.5 6 h/day no effect on ECG and circulatory Leuschner et al.
(contd) for functions (1983)
90 days
Monkey 350 5 min depression of myocardial contractility; Belej et al.
700 5 min decreased aortic blood pressure (1974)
350 5 min no effect on pulmonary measurement Aviado & Smith
700 5 min slightly increased pulmonary resistance (1975)
Reinhardt et al. (1971) assessed the ability of HCFC 22 to
induce cardiac sensitization to adrenaline in male beagle dogs
exposed to 87.5 or 175 g/m3 via a face mask, using 12 dogs at each
exposure level. After 5 min of exposure, a challenge injection of
adrenaline (0.008 mg/kg) was given. At 87.5 g/m3 no effect was
noted, but at 175 g/m3 two animals displayed cardiac sensitization
as demonstrated by serious arrhythmias. The authors classified HCFC
22 as a weak cardiac sensitizing agent. This is consistent with the
finding of Mullin (1975) that the minimum concentration of HCFC 22
at which cardiac sensitization occurs in dogs injected with
adrenaline is 175 g/m3.
Leuschner et al. (1983) did not observe any effect on ECG and
circulatory functions in dogs exposed to 17.5 g per m3 (6 h/day, 7
days/week) for 90 days.
Clark & Tinston (1982) determined the exposure levels of HCFC
22 causing acute cardiac sensitization after adrenaline treatment in
dogs and mice. The concentration affecting 50% of the animals
(EC50) was 490 g/m3 for both species.
Aviado & Belej (1974) exposed anaesthetized Swiss mice to 700
or 1400 g/m3 for 6 min via a face mask. In the first experiment no
adrenaline was given, whereas in the second 6 µg/kg was administered
intravenously. Only at the higher exposure level with adrenaline
were arrhythmias recorded.
Pantaleoni & Luzi (1975a,b) found a decreasing heart rate and
ECG changes in rats exposed to 525-2100 g/m3 for 2 min. In a
second study, rats exposed to 1050-2100 g/m3 for 2 min showed a
decrease in cardiac contractile strength, followed by a decrease in
carotid pressure, ECG changes, and arterial hypotension. Vagotomy
partially inhibited the appearance of the ECG changes. In both
experiments the modified parameters returned to normal within 2 min
of breathing normal air.
When Van Stee & McConnell (1977) exposed 7 male and 7 female
rabbits to 210 g/m3 for 5 h/day (5 days/week, for 8-12 weeks), 1
female rabbit, which was also receiving phenobarbital, developed
arrhythmia, probably of supraventricular origin. No controls were
used in this limited study.
8. EFFECTS ON HUMANS
8.1 General population exposure
8.1.1 Accidents
One case of acute poisoning has been reported. A young boy was
found dead in a small room with his mouth around the nozzle of a
tank containing HCFC 22. No details were provided (Garriot & Petty,
1980).
8.1.2 Controlled human studies
Ten healthy volunteers and ten patients suffering from a
pronounced arterial hypoxaemia due to broncho-pulmonary disease were
exposed by inhalation to an aerosol mixture containing 60% HCFC 21
and 40% CFC 11. They inhaled 202 ml of the aerosol within 2.5 h or
126 ml during 10 successive breaths. No ECG changes were observed in
either group (Fabel et al., 1972).
A group of eleven subjects, of whom seven were maintenance
technicians of large cooling and refrigerating systems, were exposed
to chlorofluorocarbons at weighted exposure levels similar to their
usual occupational exposures. They were also exposed experimentally
for 130 min to HCFC 22 concentrations of 0.71 or 1.89 g/m3, to a
mixture of HCFC 115 (4 g/m3) and HCFC 22 (1.4 g/m3), or to HCFC
115 (23.4 g/m3) and HCFC 22 (10.5 g/m3). No significant changes
in ventilatory lung function or cardiac function were observed
(Valic et al., 1982).
8.2 Occupational exposure
A fisherman working in the hold of a fishing boat, and another
man who attempted to rescue him, died when the hold was filled with
HCFC 22 from a broken refrigerant pipe. A judicial autopsy,
performed 5 days after the accident, revealed that the blood of both
cadavers was dark red. The lungs showed remarkable congestion,
oedema, haemorrhage, emphysema and pigment-laden macrophages in the
alveoli, which were detected histologically. Fine fatty droplets
were observed in the cytoplasm of liver cells. No other signs that
might have caused injury or sudden death were noted. HCFC 22 was
detected by gas chromatography in samples of various tissues, blood,
urine, and pericardial fluid. From these results, the cause of death
was concluded to be oxygen deficiency resulting from the filling of
the ship's hold with HCFC 22 from the broken refrigerant pipe (Haba
& Yamamoto, 1985).
Speizer et al. (1975) carried out a questionnaire survey on the
incidence of palpitations in a group of hospital pathology
laboratory workers (118 people, 94% of total staff in the pathology
department) who used HCFC 22 in the preparation of frozen sections.
This study was triggered by the death of one of the workers from
myocardial infarction. A 3.5-fold excess of palpitations was
reported amongst exposed workers compared to an unexposed control
group from the radiology department (85 people, 93% of total staff
in the department). Using the number of slides produced as an
indicator of HCFC 22 exposure, the authors reported a dose-response
relationship. The only exposure data provided were breathing-zone
samples collected from two subjects during a 2-min period of HCFC 22
use; these revealed concentrations of 1062 mg per m3. The possible
role of exposure to other substances was not taken into
consideration, the control group was not adequate, and the validity
of making estimates of exposure on the basis of the number of frozen
sections prepared is questionable.
Antti-Poika et al. (1990) did not find a clear connection
between cardiac arrhythmia and exposure to a mixture of HCFC 22 and
CFC 12 (average concentrations were 170-815 ppm HCFC 22 and 202 ppm
CFC 12). One subject, however, had several ventricular ectopic
beats; his average level of exposure was 170 ppm but the peak
concentration was as high as 3200 ppm.
A case of peripheral neuropathy in a commercial refrigeration
repair worker prompted a survey of a group of 27 refrigeration
workers (Gunter et al., 1982; Campbell et al., 1986). No case of
peripheral neuropathy was identified, and chest radiograms,
pulmonary function tests, electrocardiograms, and blood and urine
analysis results were all within normal limits. A questionnaire
completed by all subjects indicated that light-headedness and
palpitations were more common in the refrigeration workers than in
the control group of 14 unexposed workers. Personal air samples
collected over a "typical" shift showed levels of HCFC 22 of 5.1
mg/m3, and co-exposure to CFC 115 and CFC 12 was assumed.
In a survey by Edling & Ohlson (1988), 89 workers with
intermittent exposure to chlorofluorocarbons were examined during
their work with refrigerant equipment. The refrigerants used were
mainly CFC 12 (in 56% of the cases) and HCFC 22 (in 32% of cases),
the rest being CFC 11, CFC 500, and CFC 502 (a mixture of CFC 115
and HCFC 22). There was no statistically significant difference in
ECG results between periods with and without exposure nor was there
any exposure-related trend when workers were grouped in exposure
groups. No effect on the central nervous system was found. Edling et
al. (1990) confirmed that the data did not indicate that these
fluorocarbons induced cardiac arrhythmia among occupationally
exposed refrigerator repair workers.
In a preliminary report, death rates were investigated in 539
workers occupationally exposed to chlorofluorocarbons CFC 12, HCFC
22, and CFC 502. No increase in total deaths (18 cases) was found
among those employed for more than 6 months when compared with the
expected number (26) derived from national statistics. There were
five deaths due to heart disorders (compared to 9.6 expected), six
deaths due to cancer (versus 5.7 expected), and two deaths from lung
cancer (versus 1.0 expected). No significant increase was found even
in those exposed for more than 3 or 10 years (Szmidt et al., 1981).
In view of the limited data, no conclusions could be drawn from this
study.
9. EFFECTS ON OTHER ORGANISMS IN THE LABORATORY AND FIELD
No information is available on the effects of HCFCs 21 or 22 on
organisms in the environment.
10. EVALUATION OF HUMAN HEALTH RISKS AND EFFECTS ON THE ENVIRONMENT
10.1 Evaluation of human health risks
10.1.1 Direct health effects resulting from exposure to partially
halogenated chlorofluorocarbons
No information on exposure levels for the general population
has been reported. Tropospheric concentration measurements range
from 4.3 to 86 ng/m3 (1-20 ppt) for HCFC 21 and from 110 to 326
ng/m3 (31-92 ppt) for HCFC 22.
Information on simulated aerosol propellant use indicates peak
HCFC 22 exposures ranging from 5 to 8 g/m3. These levels rapidly
(in 10-20 seconds) decline to back-ground values of 0.025 to 0.045
g/m3. No information is available regarding exposure
concentrations at the work-place, but in a simulated beauty-salon
model an 8-h time-weighted average HCFC 22 exposure level of
0.09-0.125 g per m3 was measured.
The recommended occupational exposure limits in different
countries range from 1800 to 3540 mg/m3 (500-1000 ppm) for HCFC 22
and from 40 to 45 mg/m3 (approximately 10 ppm) for HCFC 21.
On the basis of available information, the kinetics and
metabolism of HCFC 21 and HCFC 22 are characterized by rapid
pulmonary absorption and distribution throughout the body. After
cessation of exposure these chemicals are cleared from the blood
within minutes. Metabolic transformation of HCFC 22 is minimal, if
it occurs at all. Therefore, toxic effects of metabolites are
extremely unlikely. However, there is evidence for some metabolism
of HCFC 21, based on increased urinary excretion of fluoride after
exposure of animals.
The acute toxicity of both chemicals is very low. As with the
fully halogenated chlorofluorocarbons, it is characterized in
animals by effects on the central nervous and cardiopulmonary
systems at inhalation concentrations of 175 g/m3 or more.
In animal studies with repeated inhalation exposure, HCFC 21 is
more toxic than HCFC 22. The latter causes little or no toxicity at
exposure levels likely to be of any practical significance to
humans. In various animal species HCFC 21 induces liver damage,
which might be due to the formation of one or more reactive
metabolites.
The carcinogenicity of HCFC 21 has not been studied. However,
the substance is not genotoxic in bacterial and yeast systems. In
one lifetime study, exposure to HCFC 22 led to small, but
statistically significant, increases in the incidence of
fibrosarcomas in the salivary gland region and Zymbal's gland, but
only in male rats at high exposure levels (175 g/m3). Other
lifetime studies in rat and mouse did not produce any indication of
carcinogenicity, and HCFC 22 was not genotoxic in mammalian systems.
Thus, HCFC 22 is unlikely to constitute a carcinogenic risk to
humans at environmental or controlled occupational exposure levels.
An embryotoxicity study with HCFC 21 in rats revealed
implantation losses at maternally toxic doses (42.7 g per m3), but
there were no teratogenic effects. No further information is
available on the potential effects of HCFC 21 on reproduction. At
the maternally toxic high HCFC 22 exposure concentration of 175
g/m3, a small increase in the incidence of eye malformations was
reported in rats. In view of these findings and the absence of any
effects in rabbits at similar exposure levels, HCFC 22 is considered
unlikely to pose a risk to developmental processes in humans at
environmental or controlled occupational exposure levels. No effects
were observed in a one-generation reproduction study on rats exposed
to HCFC 22 at a concentration of 175 g/m3 (5 h/day for 8 weeks).
In summary, the toxic potency of HCFC 21 is greater than that
of HCFC 22. This is reflected in the 50- to 100-fold lower
occupational exposure limits for HCFC 21 than for HCFC 22.
Controlled occupational exposures are unlikely to represent a
significant risk to humans. Although high peak exposure levels may
occur during consumer use of products containing HCFC 22 as a
propellant, the exposure period is short and so adverse health
effects are unlikely. Environmental exposure levels are extremely
low and are not considered likely to cause direct effects to human
health.
10.1.2 Health effects expected from a depletion of stratospheric
ozone by partially halogenated chlorofluorocarbons
The possible indirect health effects (e.g., an increase in the
incidence of skin cancer and immunotoxic and ocular effects) of
fully halogenated chlorofluorocarbons, resulting from an increase in
UV-B radiation due to a depletion of the ozone layer, have been
discussed in Environmental Health Criteria 113. The ozone-depleting
potential (ODP) of HCFC 22 is about 20 times lower than for CFC 11
and that of HCFC 21 is estimated to be lower still. Based on this
information, the indirect health effects of these chemicals are
expected to be considerably lower than those of the fully
halogenated chlorofluorocarbons.
10.2 Effects on the environment
No information is available to evaluate the direct ecological
effects posed by HCFC 21 and HCFC 22. With respect to the indirect
"greenhouse" effect, HCFC 22 is calculated to have a third to a
quarter of the "global-warming potential" of the fully halogenated
CFC 11, while that of HCFC 21 is lower still.
11. CONCLUSIONS AND RECOMMENDATIONS FOR PROTECTION OF HUMAN HEALTH
AND THE ENVIRONMENT
11.1 Conclusions
The available toxicological data on HCFC 21 and HCFC 22
reviewed in this monograph show differences in their toxicological
potential. HCFC 22 exhibits a low acute and chronic toxicity and the
data indicate no mutagenic and only a low carcinogenic potential in
animals. Developmental effects only occur at high and maternally
toxic exposure concentrations. Although HCFC 21 also has a low acute
toxicity potential, it appears to be more toxic than HCFC 22,
causing damage mainly to the liver following repeated exposure.
Owing to the observed differences in the toxicity profiles,
different occupational exposure limits have been recommended for
these two chemicals. Based on available exposure information, it is
concluded that these chemicals are unlikely to elicit adverse health
effects in humans associated with consumer and environmental
exposures and workplace exposures at or below current occupational
limits. The human health risks are mainly confined to those
following accidental exposures and might also result from
occupational exposure if this is not properly controlled.
HCFC 21 and HCFC 22 have a lower ozone-depleting potential than
the fully halogenated chlorofluorocarbons and should therefore pose
a lower indirect health risk.
The global-warming potentials of HCFC 21 and HCFC 22 are
considerably lower than those of the fully halogenated
chlorofluorocarbons.
11.2 Recommendations for protection of human health and the
environment
1. Since the toxicity of HCFC 22 is low and the ozone-depleting
and global-warming potentials are lower than those of the fully
halogenated chlorofluorocarbons, it can be considered as a
transient substitute for the chlorofluorocarbons included in
the Montreal Protocol. However, in line with the conclusions of
the 1990 London Meeting of the Montreal Protocol Parties,
efforts should be maintained to develop substitutes that would
pose negligible or no risk to the environment and to develop
alternative technologies.
2. Although HCFC 21 poses a low risk to the environment, it is
not recommended as a substitute for the chlorofluorocarbons
included in the Montreal Protocol because of its liver
toxicity.
12. FURTHER RESEARCH
1. In order to fill in gaps in the available information on
general population exposure and global environmental effects,
it is recommended that:
* the concentrations of HCFCs in food packaging materials
and in packaged food should be measured;
* monitoring of atmospheric levels of HCFCs in different
parts of the world should be maintained;
* more studies of heterogeneous atmospheric phenomena over
polar regions should be conducted in order to substantiate
the values for the ozone-depleting potential of HCFCs.
2. HCFC 21 is used on a very limited scale and it is not likely to
become a substitute for the chlorofluorocarbons included in the
Montreal Protocol. If its use is expected to increase
substantially in the future, more information on potential
health effects are needed, such as:
* chronic toxicity in animals, with special reference to
hepatotoxicity;
* the mechanism of action in relation to liver toxicity;
* genotoxic and carcinogenic potential;
* results of targeted health surveillance in populations
under exposure.
3. In view of the interim use of HCFC 22, the existing gaps in
knowledge concerning its effects on human health and the
environment should be filled. The following areas of research
are recommended:
* a study of the mechanism of action in order to clarify the
genotoxic and carcinogenic effects;
* targeted health surveillance in populations subject to
elevated levels of exposure to this substance.
13. PREVIOUS EVALUATIONS BY INTERNATIONAL BODIES
An evaluation of the carcinogenicity of HCFC 22 by the
International Agency for Research on Cancer (IARC, 1987) was
reported as follows:
"There is inadequate evidence of carcinogenicity in humans;
there is limited evidence of carcinogenicity in experimental
animals. The agent cannot be classified as to its carcinogenicity to
humans (group 3)."
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RESUME
1. Identité, propriétés physiques et méthodes d'analysew
Les deux chlorofluorocarbures étudiés dans la présente
monographie (le dichlorofluorométhane, HCFC 21, et le
chlorodifluorométhane, HCFC 22) sont des hydrofluorocarbures (HCFC),
c'est-à-dire des composés obtenus par substitution partielle des
atomes d'hydrogène du méthane par des atomes de fluor et de chlore.
Seul le HCFC 22 a une importance commerciale. Le HCFC 21 et le HCFC
22 sont des gaz ininflammables (dans des conditions normales de
température et de pression). Ils sont incolores et pratiquement
inodores. Le HCFC 21 est légèrement et le HCFC 22 moyennement
soluble dans l'eau. Tous deux sont miscibles aux solvants
organiques. Le HCFC existe sous forme de gaz liquéfié.
Il existe plusieurs méthodes pour doser ces deux composés,
notamment la chromatographie en phase gazeuse avec détection par
capture d'électrons ou ionisation de flamme, la chromatographie en
phase gazeuse couplée à la spectrométrie de masse ou encore la
spectrométrie par déflection photothermique.
2. Sources d'exposition humaine et environnementale
Ces deux HCFC n'existent pas dans la nature. Le HCFC 21 n'est
produit qu'en petites quantités sans application professionnelle. On
estime qu'en 1987, la production mondiale de HCFC 22 était de 246
000 tonnes.
Le HCFC 22 est essentiellement dissipé dans l'environnement
lors de la réparation, de l'utilisation et de la mise au rebut de
réfrigérateurs ou de climatiseurs. On estime qu'à l'heure actuelle,
il se perd chaque année dans le monde environ 120 000 tonnes de HCFC
22. On a également fait état d'émissions accidentelles par des
bateaux de pêche.
Le HCFC est utilisé comme réfrigérant, comme intermédiaire dans
la production de tétrafluoréthylène et comme agent de soufflage dans
la fabrication du polystyrène. On l'utilise également en petites
quantités comme gaz propulseur dans les bombes aérosols.
3. Transport, répartition et transformation dans l'environnement
Le logarithme du coefficient de partage octanol/eau du HCFC 22
est de 1,08, ce qui rend la bioaccumulation improbable. On estime
que la durée de séjour du HCFC 21 dans la troposphère est d'environ
2 ans et celle du HCFC 22 d'environ 17 ans. Dans la troposphère, la
principale voie de dégradation consiste sans doute dans la réaction
avec les radicaux OH. Seule une petite fraction de ces deux composés
pénètre dans la stratosphère, où, par suite de leur réaction avec
des radicaux oxygénés, ils libèrent du chlore qui attaque la couche
d'ozone. Toutefois, on pense que le HCFC 22 produit moins de 1% du
chlore qui s'attaque à la couche d'ozone. On estime que le potentiel
de destruction de l'ozone du HCFC 22 est de 0,05, celui du HCFC 21
étant sans doute plus faible. Quant au potentiel de réchauffement de
la planète, calculé par rapport à celui du CFC 11 pris comme unité,
on estime qu'il est de 1/3 à 1/4, celui du HCFC 21 étant encore plus
faible.
4. Concentrations dans l'environnement et exposition humaine
On ne dispose d'aucune donnée sur les concentrations dans l'eau
ni sur la présence de ces composés dans des denrées alimentaires,
encore que le HCFC 22 soit utilisé pour la fabrication de récipients
en polystyrène expansé destinés au conditionnement de produits
alimentaires. Il n'existe pas non plus de données sur l'exposition
humaine au HCFC 21, mais deux études relatives à l'utilisation
d'aérosols contenant 17-65% de HCFC 22 ont montré que lors
d'expositions de courte durée (10-20 s), des concentrations
maximales de l'ordre de 5000 à 8000 mg/m3 pouvaient être
atteintes. Les employés d'instituts de beauté pourraient être
exposés à des concentrations de 90-125 mg/m3 (moyenne pondérée par
rapport au temps sur 8 h). Cependant, il s'agit là de valeurs qui
sont bien inférieures aux limites fixées par la réglementation en
vigueur en Allemagne, aux Etats-Unis et aux Pays-Bas.
Le HCFC 22 se dissipe rapidement dans l'atmosphère. On a fait
état de concentrations de l'ordre de 326 mg/m3 en 1986 et il
semble que cette valeur augmente de 11% par an.
5. Cinétique et métabolisme chez l'animal de laboratoire et chez
l'homme
Il existe quelques données concernant l'absorption, la
distribution, le métabolisme et l'excrétion du HCFC 21. Ce composé
est très probablement absorbé après inhalation, à en juger d'après
les effets généraux et les taux élevés de fluorures dans l'urine que
l'on a observés lors d'études toxicologiques sur le rat. Après
injection intrapéritonéale à des rats, le HCFC 21 est exhalé et les
données cinétiques, de même que l'excrétion des fluorures indiquent
que le composé est effectivement métabolisé. Toutefois, on ignore
dans quelle proportion le HCFC 21 est transformé et aucun autre
métabolite que le fluorure n'a été identifié.
Après inhalation, le HCFC 22 est rapidement et bien absorbé
chez le rat, le lapin, et l'homme et il se répartit largement dans
l'organisme. De fortes concentrations de HCFC 22 ont été retrouvées
dans le sang, le cerveau, le coeur, le foie, les reins et la graisse
des viscères chez des lapins morts des suites d'une exposition à ce
composé ainsi que dans des échantillons nécropsiques prélevés sur le
cerveau, les poumons, le foie et les reins de victimes d'une
intoxication par le HCFC 22. L'élimination est rapide, la majeure
partie du composé étant excrétée avec une demi-vie de 1 min chez le
lapin et de 3 min chez le rat. Chez l'homme, le produit est éliminé
en quantité limitée selon un processus triphasique (demi-vie de 3
min, 12 min et 2,7 h respectivement).
Le HCFC 22 réapparaît presque entièrement et sans modification
dans l'air exhalé, après avoir été inhalé ou injecté par voie
intrapéritonéale à des rats ou à des sujets humains. Il y a de
bonnes raisons de penser qu'il ne subit pas de transformation
métabolique notable chez le rat in vivo ni en présence de
préparations de foie de rat.
6. Effets sur les mammifères de laboratoire et les systèmes
in vitro
On ne possède pas de données satisfaisantes sur les effets
toxiques aigus par voie orale de ces deux composés.
Les principaux effets d'une seule inhalation de HCFC 21 ou de
HCFC 22 sont en gros les mêmes chez nombre d'espèces animales. Par
cette voie, leur toxicité est faible. Les manifestations toxiques
observées sont caractéristiques des chlorofluorocarbures, c'est-à-
dire qu'elles consistent en une perte de coordination et une
narcose. A forte concentration, on voit quelquefois des arythmies
cardiaques et des effets pulmonaires (concentrations supérieures ou
égales à 106,7 g/m3).
On a rapporté des cas d'irritation cutanée ou oculaire dus à
ces deux composés. On peut toutefois penser que ces effets étaient
dus davantage à des pertes thermiques par évaporation qu'aux
propriétés chimiques des produits en cause. D'ailleurs, aucun d'eux
n'a provoqué de sensibilisation cutanée.
Les seules études consacrées à ces deux composés ne portaient
que sur une seule voie d'administration, la voie respiratoire. Les
principaux effets observés chez le rat, le cobaye, le chien et le
chat consistaient en lésions au niveau du foie. On n'en a pas tiré
de valeur pour la dose sans effet observable. Des lésions
histopathologiques du foie ont été notées à des doses ne dépassant
pas 0,213 g/m3 administrées 6 h par jour, 5 jours par semaine
pendant 90 jours. A ces doses on a également observé un oedème
interstitiel du pancréas et une dégénérescence des cellules
épithéliales au niveau des tubes séminifères. Ces lésions
n'apparaissaient pas lors des études où le HCFC 22 était administré
à des doses comprises entre 17,5 g/m3 (13 semaines) et 175 g/m3
(4 ou 8 semaines).
Aucune étude de longue durée n'a été consacrée au HCFC 21 chez
l'animal. Le seul effet non cancérogène qui ait été systématiquement
relevé dans le cas du HCFC 22, consistait dans l'hyperactivité
manifestée par des souris mâles exposées à des doses de 175 g/m3
de ce produit 5 h par jour, 5 jours par semaine pendant toute leur
existence.
Il n'y a pas eu d'étude toxicologique classique consacrée aux
effets du HCFC 21 sur la fécondité. Lors d'une étude
d'embryotoxicité effectuée sur des rats, on n'a pas observé d'effets
tératogènes, mais dans un grand nombre de cas, la nidation n'a pas
pu s'effectuer. Le HCFC 22 (175 g/m3, 5 h par jour, 5 jours par
semaine pendant 8 semaines) n'a eu aucun effet sur la capacité de
reproduction des rats mâles. Un léger surnombre de malformations
oculaires sans signification véritable ayant été observé lors de
trois études tératologiques chez le rat, on a entrepris une étude de
grande envergure afin de voir si le HCFC 22 avait effectivement
tendance à provoquer des lésions oculaires. On a ainsi constaté une
augmentation faible, mais néanmoins statistiquement significative,
du nombre de portées dans lesquelles des foetus présentaient une
microphtalmie ou une anophtalmie lorsque les mères étaient exposées
à une dose de 175 g/m3, 6 h par jour, du 6ème au 15ème jour de la
gestation. Cette dose était légèrement toxique pour les mères
(réduction du poids corporel par rapport aux témoins).
Le HCFC 21 s'est révélé non mutagène dans trois tests de
mutagénicité, l'un sur levure et les deux autres sur bactéries.
Aucune autre donnée sur ce point n'a pu être obtenue. Le HCFC 22 a
présenté une activité mutagène sur modèle bactérien (S.
typhimurium) mais cette activité ne s'est pas confirmée sur
d'autres systèmes bactériens ni sur cellules mammaliennes, que ce
soit in vivo ou in vitro. Ces épreuves portaient sur les
mutations géniques, la synthèse non programmée de l'ADN, la
cytogénétique des cellules de moelle osseuse et les mutations
léthales dominantes (rat et souris).
Seul le HCFC 22 a fait l'objet d'épreuves de cancérogénicité
in vivo. Deux groupes de chercheurs ont fait inhaler du HCFC 22 à
des rats et à des souris pendant toute la durée de leur existence.
On n'a observé une surfréquence des tumeurs cancéreuses que dans une
seule étude au cours de laquelle des rats mâles avaient été soumis à
175 g/m3, 5 jours par semaine, pendant des périodes allant jusqu'à
131 semaines. Un léger excès de fibrosarcomes a été noté dans la
région des glandes salivaires et de la glande de Zymbal. Ces effets
n'apparaissaient pas à dose plus faible (jusqu'à 35 g/m3) et la
dose la plus élevée n'a pas été utilisée lors de la seconde étude.
Même si cela ne constitue pas une véritable démonstration de
l'absence d'effets oncogènes, il n'y a pas eu d'augmentation de la
fréquence des tumeurs après administration du composé par gavage à
des rats. Ces animaux ont reçu le HCFC 22 à raison de 300 mg/kg par
jour, 5 jours par semaine, pendant 52 semaines et l'étude s'est
achevée au bout de 125 semaines.
7. Effets sur l'homme
On ne dispose que de données très limitées à propos des effets
du HCFC 21 et du HCFC 22 sur l'homme.
Dans certains cas d'exposition accidentelle ou délibérée à de
fortes concentrations de HCFC 22, les intéressés sont décédés.
L'examen histopathologique d'échantillons de tissus prélevés sur
quelques-unes de ces victimes a révélé la présence d'un oedème du
poumon et d'inclusions lipidiques dans le cytoplasme, surtout dans
les hépatocytes périphériques.
Un questionnaire que l'on a fait remplir par des personnes
professionnellement exposées à du HCFC 22, a révélé une augmentation
de l'incidence des palpitations, mais rien ne prouve avec certitude
que l'exposition à l'un ou à l'autre des deux produits ait des
effets nocifs. Une étude de mortalité a été effectuée sur des
chlorofluorocarbures, dont le HCFC 22, mais elle portait sur un
effectif trop faible pour qu'on puisse en tirer des conclusions.
8. Effets sur d'autres organismes au laboratoire et dans leur
milieu naturel
On ne possède aucune donnée concernant les effets que le HCFC
21 ou le HCFC 22 pourraient exercer sur les êtres vivants dans leur
milieu naturel.
RESUMEN
1. Identidad, propiedades físicas y químicas y métodos analíticos
Los dos clorofluorocarburos examinados en la presente
monografía (diclorofluorometano, HCFC 21 y clorodifluorometano, HCFC
22) son hidroclorofluorocarburos (HCFC), es decir, compuestos
obtenidos por la sustitución parcial de los átomos de hidrógeno del
metano por átomos de flúor y cloro. Sólo el HCFC 22 tiene
importancia comercial. El HCFC 21 y el HCFC 22 son gases no
inflamables (a temperaturas y presiones normales), incoloros y
prácticamente inodoros. El HCFC 21 es ligeramente soluble y el HCFC
22 moderadamente soluble en agua, y ambos son miscibles con
disolventes orgánicos. El HCFC 22 puede encontrarse en forma de gas
licuado.
Existen varios métodos analíticos para determinar esos dos
compuestos. Entre ellos figuran la cromatografía de gases con
captura electrónica y detección por ionización de llama, la
cromatografía de gases/espectrometría de masas, y la
espectrofotometría de deflección fototérmica.
2. Fuentes de exposición humana y ambiental
No se tiene noticia de que los dos HCFC estudiados en esta
monografía existan como tales en la naturaleza. El HCFC 21 sólo se
produce en pequeñas cantidades con fines no ocupacionales. Se
calcula que la producción mundial total de HCFC 22 en 1987 ascendió
a 246 000 toneladas.
La principal pérdida de HCFC 22 se produce durante la
reparación, el uso y el desecho de frigoríficos y aparatos
acondicionadores de aire. Actualmente se calcula que la pérdida
mundial máxima está en torno a las 120 000 toneladas. Se han
comunicado casos de liberación accidental de HCFC 22 en
embarcaciones de pesca.
El HCFC 22 se utiliza como refrigerante como intermedio en la
producción de tetrafluoroetileno, y como agente expansor del
poliestireno. Una pequeña cantidad se utiliza como propulsor de
aerosoles.
3. Transporte, distribución y transformación en el medio ambiente
El coeficiente de partición log octanol/agua del HCFC 22 es
1,08, lo que hace poco probable que se bioacumule. Se ha calculado
que la persistencia del HCFC 21 en la troposfera es de unos 2 años y
la del HCFC 22 de unos 17 años. Es probable que la reacción con
radicales hidroxilo en la troposfera sea la principal vía de
degradación. Sólo una pequeña fracción de los HCFC 21 y 22 alcanza
la estratosfera donde, principalmente por reacción con radicales de
oxígeno, liberan cloro que ataca al ozono. No obstante, se calcula
que el HCFC 22 produce menos del 1% del cloro que ataca al ozono en
la estratosfera. El potencial de destrucción de ozono (PDO) del HCFC
22 se ha calculado en 0,05 y se supone que el del HCFC 21 es aún
menor.
Se estima que el potencial de calentamiento de la tierra (PCT),
en relación con el del CFC 11, al que se asigna el valor 1,0, es
inferior por un factor de 3 ó 4 el el caso del HCFC 22 y aún menor
en el HCFC 21.
4. Niveles en el medio ambiente y exposición humana
No se dispone de datos sobre las concentraciones en el agua ni
sobre la presencia de estos compuestos en los alimentos, aunque el
HCFC 22 se utiliza en la fabricación de recipientes alimentarios de
poliestireno expandido. No se tienen datos sobre la exposición
humana al HCFC 21, pero en dos estudios sobre el uso de
vaporizadores experimentales con un 17-65% de HCFC 22 se ha
demostrado que las exposiciones breves (10-20 segundos) pueden
originar concentraciones máximas que van desde 5000 hasta 8000
mg/m3. Los trabajadores de peluquerías pueden estar expuestos a
niveles medios ponderados en un tiempo de 8 horas de 90-125 mg/m3,
pero esos niveles se encuentran muy por debajo de los niveles
reglamentarios MAK o LTV de 1800-3540 mg/m3 en Alemania, EE.UU. y
los Países Bajos.
El HCFC 22 se mezcla rápidamente en la atmósfera. En 1986 se
comunicaron concentraciones de unos 326 mg/m3 y se cree que el
nivel aumenta en un 11% al año, aproximadamente.
5. Cinética y metabolismo en animales de laboratorio y en el ser
humano
Se cuenta con datos limitados sobre la absorción, la
distribución, el metabolismo y la excreción de HCFC 21. Puede
inferirse que este compuesto se absorbe tras la inhalación a partir
de los efectos sistémicos y de los elevados niveles de fluoruros en
la orina observados en estudios de toxicidad en ratas. Las ratas
exhalan HCFC 21 tras la inyección intraperitoneal y tanto los datos
cinéticos como las pruebas de excreción de fluoruro sugieren que el
HCFC 21 es metabolizado. No obstante, no se sabe hasta qué punto se
metaboliza y, aparte del fluoruro, los productos no se han
identificado.
En la rata, el conejo y el ser humano el HCFC 22 se absorbe
rápidamente y sin dificultad tras la inhalación y se distribuye por
todo el organismo. Se han encontrado niveles elevados de HCFC 22 en
la sangre, el cerebro, el corazón, el pulmón, el hígado, el riñón y
la grasa visceral de conejos moribundos durante la exposición y en
muestras postmortem de cerebro, pulmón, hígado y riñón de víctimas
accidentales de la exposición a HCFC 22. La eliminación es rápida;
la mayor parte del HCFC se elimina con una semivida de 1 minuto en
el conejo y 3 minutos en la rata. En el ser humano, una cantidad
limitada de material se elimina en tres fases (semividas de 3
minutos, 12 minutos y 2,7 h).
El HCFC 22 inhalado o administrado por vía intraperitoneal se
exhala casi por completo sin alteraciones tanto en la rata como en
el hombre. Existen pruebas convincentes de que en la rata no se
metaboliza en grado significativo ni in vivo ni en preparaciones
de hígado.
6. Efectos en mamíferos de laboratorio y en sistemas de ensayo
in vitro
No se dispone de datos satisfactorios sobre la toxicidad aguda
por vía oral del HCFC 21 ni del HCFC 22.
Los efectos principales de una sola exposición por inhalación
de HCFC 21 o HCFC 22 son esencialmente similares en diversas
especies animales. Ambas sustancias tienen baja toxicidad por esta
vía. Los efectos observados son característicos de los
clorofluorocarburos, a saber, pérdida de coordinación y narcosis.
Con elevadas concentraciones (106,7 g/m3 o más) pueden producirse
arritmias cardiacas y efectos pulmonares.
Aunque se ha indicado que tanto el HCFC 21 como el HCFC 22
causan irritación cutánea y ocular, esos efectos pueden haber
guardado relación con las consecuencias de la pérdida de calor por
evaporación antes que con las propiedades químicas de los HCFC.
Ninguna de las dos sustancias provocó sensibilización cutánea.
Los únicos estudios realizados sobre la toxicidad a corto plazo
del HCFC 21 han investigado la vía de inhalación. El principal
efecto observado en la rata, el cobayo, el perro y el gato fueron
las lesiones hepáticas; no se determinó el nivel sin efectos
observados. Con niveles tan bajos como 0,213 g/m3 administrados 6
h/día, 5 días por semana, durante 90 días, se observaron lesiones
histopatológicas en el hígado. Con esa concentración también se
observó edema pancreático intersticial y degeneración del epitelio
de los túbulos seminíferos. En estudios realizados con el HCFC 22 a
niveles de exposición entre 17,5 g por m3 (durante 13 semanas) y
175 g/m3 (durante 4 u 8 semanas) no se observaron lesiones.
No se han hecho estudios a largo plazo sobre el HCFC 21 en
animales. La única conclusión coherente no tumorigénica observada en
estudios a largo plazo con HCFC 22 fue la hiperactividad observada
en ratones machos a los que se administraron 175 g/m3, 5 h/día, 5
días por semana en un estudio de inhalación durante un lapso de vida
entera.
No se han hecho estudios convencionales sobre los efectos del
HCFC 21 en la fecundidad. En un estudio de la embriotoxicidad en
ratas (42,7 g/m3, 6 h/día los días 6-15 de la gestación) no se
observaron efectos teratogénicos, pero se encontró una tasa elevada
de pérdida de la implantación. El HCFC 22 (175 g/m3 al día, 5
h/día, 5 días/semana durante 8 semanas) no tuvo efecto alguno en la
capacidad de reproducción de las ratas macho. Al observarse un
exceso pequeño, no significativo, de defectos oculares en tres
estudios de teratología en ratas, se realizó un amplio estudio sobre
la posible capacidad del HCFC 22 de provocar defectos oculares. En
ese estudio, se observó un aumento pequeño, aunque estadísticamente
significativo, del número de camadas con fetos afectados de
microftalmía o anoftalmía tras la exposición de la madre a 175
g/m3, 6 h/día durante los días 6-15 de la gestación. Ese nivel de
exposición produjo ligera toxicidad materna (peso corporal inferior
en comparación con los testigos). No se observaron otros efectos; el
nivel sin efectos observados en ese estudio fue de 3,5 g/m3. El
HCFC 22 no resultó teratogénico en un estudio convencional realizado
en ratones con regímenes de exposición similares.
Se encontró que el HCFC 21 no era mutagénico en dos ensayos en
bacterias y uno en levaduras (no se obtuvieron otros datos). El HCFC
22 fue mutagénico en ensayos bacterianos con S. typhimurium, pero
no mostró actividad en ensayos con otros microorganismos ni en
sistemas de mamíferos, ni in vitro ni in vivo. En esos ensayos
se hicieron pruebas de mutación génica y de síntesis no programada
del ADN in vitro, pruebas citogenéticas en médula ósea in vivo,
y pruebas de letalidad dominante en la rata y en el ratón.
Sólo se han realizado ensayos de carcinogenicidad in vivo con
el HCFC 22. Dos grupos de investigadores han realizado estudios de
inhalación durante un lapso de vida entera tanto en ratas como en
ratones. Tan sólo se observó excedente de tumores en el único
estudio en el que se administraron a ratas macho 175 g/m3, 5 días
a la semana, durante hasta 131 semanas. Se observaron pequeños
excedentes de fibrosarcomas en la región de las glándulas salivares
y de la glándula de Zymbal. Esos efectos no se observaron con dosis
inferiores (hasta 35 g/m3), y esa dosis elevada no se utilizó en
el segundo estudio. Aunque no sirva como demostración adecuada de la
ausencia de efectos tumorigénicos, no se observó excedente de
tumores en un estudio de alimentación forzada por vía oral en ratas.
Se administró a esos animales HCFC 22 en dosis de 300 mg/kg al día,
5 días/semana, durante 52 semanas, y el estudio terminó a las 125
semanas.
7. Efectos en el ser humano
Se dispone de datos muy limitados sobre los efectos del HCFC 21
y el HCFC 22 en el ser humano.
Se han producido casos de muerte por exposición accidental o
intencionada a niveles elevados de HCFC 22. El examen
histopatológico de los tejidos de algunas de esas víctimas reveló la
existencia de edema pulmonar y gotitas grasas citoplásmicas
principalmente en los hepatocitos periféricos.
Aunque se ha indicado un aumento de la incidencia de
palpitaciones en un estudio realizado con cuestionarios entre
individuos expuestos al HCFC 22 en el trabajo, no existen pruebas
sólidas de que la exposición de volunarios o de trabajadores al HCFC
21 o al HCFC 22 produzca efectos nocivos en la salud. Nada puede
concluirse a partir de un estudio de mortalidad sumamente reducido
en personas expuestas por su profesión a varios clorofluorocarburos,
entre ellos el HCFC 22.
8. Efectos en otros organismos en el laboratorio y sobre el terreno
No se dispone de datos sobre los efectos de los HCFC 21 y 22 en
los organismos del medio ambiente.