Difluoromethane
File No: NA/563
March 1998
NATIONAL INDUSTRIAL CHEMICALS NOTIFICATION
AND ASSESSMENT SCHEME
FULL PUBLIC REPORT
Difluoromethane
This Assessment has been compiled in accordance with the provisions of the Industrial Chemicals
(Notification and Assessment) Act 1989 (the Act), and Regulations. This legislation is an Act of
the Commonwealth of Australia. The National Industrial Chemicals Notification and Assessment
S c h e m e (NICNAS) is administered by Worksafe Australia which also conducts the occupational
h e a l t h & safety assessment. The assessment of environmental hazard is conducted by the
Department of the Environment and the assessment of public health is conducted by the
Department of Health and Family Services.
For the purposes of subsection 78(1) of the Act, copies of this full public report may be inspected
b y the public at the Library, Worksafe Australia, 92-94 Parramatta Road, Camperdown NSW
2050, between the following hours:
Monday - Wednesday 8.30 am - 5.00 pm
Thursday 8.30 am - 8.00 pm
Friday 8.30 am - 5.00 pm
Copies of this full public report may also be requested, free of charge, by contacting the
Administration Coordinator on the fax number below.
For enquiries please contact the Administration Coordinator at:
Street Address: 92 Parramatta Rd Camperdown, NSW 2050, AUSTRALIA
Postal Address: GPO Box 58, Sydney 2001, AUSTRALIA
Telephone: (61) (02) 9577-9466 FAX (61) (02) 9577-9465
Director
Chemicals Notification and Assessment
NA/563
ASSESSMENT REPORT
Difluoromethane
1. APPLICANT
Actrol Parts, a division of GSA Industries (Aust.) Pty. Ltd. of 19 King St BLACKBURN
VIC 3130, has submitted a standard notification statement with their application for
an assessment certificate for difluoromethane. The applicant has not claimed
confidentiality for any part of the assessment and the information herein is
available as the full public report in its entirety.
2. IDENTITY OF THE CHEMICAL
Chemical name: difluoromethane
Chemical Abstracts Service
(CAS) Registry No.: 75-10-5
Other name: methylene fluoride
Trade name: HFC-32
R-32
R410A: Genetron AZ-20 (blend)
R407C: Genetron 407C (blend)
Forane 407C
Solkane 407C
HFA32
Molecular formula: CF2H2
Structural formula:
F
HCH
F
Molecular weight: 52
Method of Detection: infrared data (IR) were provided for
and Determination difluoromethane (see below)
Spectral data: IR; absorption peaks occurred at 3 039,
3 010, 2 946, 1 453 and 1 100 cm-1
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3. PHYSICAL AND CHEMICAL PROPERTIES
Appearance at 20癈
and 101.3 kPa: colourless gas with faint ethereal
odour.
Boiling Point: -51.7癈
Vapour Density: 1.8 (air = 1) at 25癈 and 101.3 kPa
1.52 x 103 kPa at 21.1癈
Vapour Pressure:
3.48 x 103 kPa at 54.4癈
Water Solubility: 4.4 g/L at 25癈
Hydrolysis: does not hydrolyse
Partition Co-efficient
(n-octanol/water) log Pow : 0.21 at 25癈
Adsorption/Desorption: not measured, gas
Dissociation Constant: no dissociable groups
Fat Solubility: not provided
Flash Point: not determined
Flammability Limits: L.E.L. = 13.6% by volume in air
U.E.L. = 32.2% by volume in air
Combustion Products hydrofluoric acid, carbonyl fluoride and
carbon oxides
Decomposition Temperature : not provided
Autoignition Temperature 530癈
Reactivity/Stability: pure gas release may result in
explosive air mixtures, violent reactions
occur with alkali or alkaline earth
metals including powdered aluminium,
zinc, beryllium, sodium, potassium,
barium and calcium
Atmospheric Lifetime: 7.7 years
Global Warming Potential: 650 for 100 year time horizon (1)
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Comments on Physico-Chemical Properties
Hydrolysis is not expected to be a significant degradation pathway as the chemical
is a stable gas containing no groups which are generally considered to be
hydrolysable.
Significant sorption to soil of the notified chemical is not expected as it is a gas with
a low octanol/water partition coefficient.
Explanation of particular data:
The "atmospheric lifetime" is defined as the time necessary for 63% degradation; it
is equal to the "half-life" divided by ln2 (= 0.69) (2). These type of gases are slowly
destroyed in the stratosphere by sunlight (photodegradation).
The extent to which a greenhouse gas contributes to global warming depends on
the volume emitted, the length of time which elapses before it is purged from the
atmosphere and the infrared energy absorption properties of the gas. An index
termed the Global Warming Potential (GWP) has been developed which provides a
simplified means of describing the relative ability of each greenhouse gas
emission to affect global climate change. It is the ratio of the warming caused by a
substance to the warming caused by CO2 (on a molecule per molecule basis) to
allow a common basis for comparing impacts (3). Thus, with the GWP of CO2
defined as one, difluoromethane has 650 times the GWP of CO2 over a 100 year
time horizon.
4. PURITY OF THE CHEMICAL
Degree of Purity: >99.8%
Toxic or Hazardous
Impurities:
Chemical name: chlorodifluoromethane
CAS No.: 75-45-6
Weight percentage: < 0.2%
cardiac sensitisation (4)
Toxic properties:
Chemical name: dichlorodifluoromethane
CAS No.: 75-71-8
Weight percentage: < 0.2%
cardiac sensitisation (4)
Toxic properties:
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Chemical name: chloromethane or methyl chloride
CAS No.: 74-87-3
Weight percentage: < 0.2%
kidney, liver damage and central nervous
Toxic properties:
system effects (5)
Chemical name: dichlorofluoromethane
CAS No.: 75-43-4
Weight percentage: < 0.2%
cardiac sensitisation (6)
Toxic properties:
Non-hazardous Impurities nil
(> 1% by weight):
Additives/Adjuvants: (see below).
5. USE, VOLUME AND FORMULATION
Difluoromethane is a refrigerant gas which will be imported for use in low
temperature refrigeration units such as supermarket freezers, air conditioning
units and industrial cooling processes. It has a zero ozone depleting potential and
is being introduced to replace ozone depleting chlorofluorocarbons (CFCs), in
particular R-22, difluorochloromethane. The notified chemical will be imported,
only in blended product forms with other refrigerants, including pentafluoroethane
and tetrafluoroethane. It will be sold to equipment manufacturers and service
contractors as the blends R410A and R407C (see below).
R410A contains:
50 wt.% Difluoromethane
50 wt.% Pentafluoroethane
R407C contains:
23 wt.% Difluoromethane
77 wt.% Pentafluoroethane and Tetrafluoroethane
The import volume of the notified chemical is estimated to be approximately 30
tonnes per year over the next five years.
It is not anticipated that difluoromethane will be manufactured in Australia,
however, reformulation could possibly occur as a result of reblending recovered
blends containing difluoromethane.
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6. OCCUPATIONAL EXPOSURE
Difluoromethane (as a component of the imported gas blends) will be shipped into
Australia in liquefied form in 1 tonne pressurised tanks. These containers will be
taken to warehouses from the dockside for storage. For 2 to 3 hours/day on
approximately 10 days/year 2 to 5 dockside workers and 5 to 15 transport
personnel may be exposed to the notified gas, if it is released accidentally. At the
warehouse, the gas is decanted into smaller cylinders from 12 to 65 kg for
transport to the sites where the gas will be used. The duration of this work would
involve 6 to 10 store workers for up to 12 days/year. The transferral is undertaken
using a closed pipe system. However there is the potential for minor losses of
gas to occur when connections are made and broken when decanting and during
charging and servicing of refrigeration units.
Refrigeration mechanics will drain obsolete refrigerants from existing systems and
recharge with the new refrigerant containing difluoromethane or in the case of new
systems simply charge the systems with R410A or R407C. Charging is performed
using a closed piping system which involves connecting the cylinder to the
refrigeration unit via a flexible hose and allowing the gas to flow into the unit until
the desired pressure is attained. The hose has an automatic shut-off valve which
minimises gas release following charging. The number of service personnel,
including refrigeration mechanics Australia wide using difluoromethane blends
may be as high as fifteen hundred each year.
Service personnel may be exposed to difluoromethane during routine
maintenance of the refrigeration units. Exposure to difluoromethane may occur
through accidents when the cylinder is badly damaged, or through minor leaks
from seals and gaskets in the system. Most accidental exposure will be to the
gaseous form of difluoromethane, but liquid contact will also be possible.
Exposure to difluoromethane may occur during the transfer of gas between
containers and during the charging and maintenance of refrigeration units. It is
estimated that during decanting of bulk cylinders approximately 0.05% (15 kg) of
refrigerant will be lost and that during charging and recharging of refrigeration units
approximately 0.01% (3 kg) will be lost. The notifier expects direct exposure to
difluoromethane will be minimal as refrigeration mechanics and service personnel
follow the refrigeration industry's Code of Good Practice which aims to minimise
gas release (7).
The blending of difluoromethane with tetrafluoroethane and/or pentafluoroethane
suppresses the flammable explosive properties of difluoromethane on its own.
Consequently the use of blended difluoromethane with electrical machinery, for
example, refrigerators and air conditioners, is much safer. There is however, the
potential, through large scale accidental leakage for explosions to occur. This
happened in Germany in 1994 at a Hoechst production facility for HFC-134a (8).
Before this event HFC-134a had been considered safe and completely
inflammable in normal circumstances. Carbon containing gas mixtures should
never be considered completely inflammable; the potential for explosive mixtures
to be spark ignited should not be overlooked.
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7. PUBLIC EXPOSURE
The public will not be exposed to the notified chemical during the handling of the
refrigerant. The refrigerant blends will be used in commercial refrigeration units,
such as supermarket freezers, air conditioning units and industrial cooling units.
Public exposure may occur as a result of slow leaks from refrigerant units;
however, such releases are minimised by good work practices according to the
Australian Refrigeration and Air Conditioning Code of Good Practice (7).
Public exposure may occur from a spill during transport. In the event of a spill the
MSDS advises the affected area be cleared of all personnel who should be aware
of the danger of frost bite and avoid contact. If the spill is major, the liquid should
be contained with sand or soil and allowed to evaporate. Ventilation should be
increased to the area to avoid asphyxiation and the formation of explosive mixtures.
8. ENVIRONMENTAL EXPOSURE
Release
The notified chemical will not enter the environment intentionally when used in
cooling systems, but any releases during filling or use of cooling systems, or
following disposal of obsolete equipment or recovery of refrigerants therefrom, will
rapidly volatilise to the atmosphere. It is not possible to estimate how much of the
refrigerant might be released in this way, but the notifiers indicate that quantities
involved will be small. During decant of bulk cylinders it is estimated that
approximately 0.05% (15 kg) of refrigerant will be lost per annum. Charging and
discharging of refrigeration units is expected to lead to the release of 0.01% (3 kg)
per annum. Fugitive emissions are expected to account for less than 10% of the
working charge per annum. Industry sources in the United States, however, have
argued that leakage from commercial air conditioning units amounts to 22 to 25%
annually despite similar codes of practice (9). The new blends area expensive,
providing a financial incentive to minimise losses and install area monitors around
large installations.
The Australian Refrigeration and Air Conditioning Code of Good Practice (7)
requires that releases of ozone depleting refrigerants to the atmosphere during
manufacturing, installation or servicing operations be reduced to the minimum
level by re-use of refrigerant recovered. Recovery of refrigerant is required from
performance testing during development and production. Refrigerant must be
recovered in dedicated cylinders, identified by valving, labelling and colour coding.
Where contaminated refrigerants are stored, they must be labelled to indicate the
contents. The Code is referred to by legislation in all States.
Recovery, reclamation and recycling of refrigerants is preferred to disposal. For
disposal, the Code requires that unusable or surplus refrigerant not be discharged
to the atmosphere, but be returned to the supplier or stored in a cool shaded place
pending disposal. Reprocessing will not occur in Australia as such activities
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require a production facility. Local disposal will also not occur as acceptable
disposal facilities do not exist currently in Australia.
Fate
Given its high volatility, any difluoromethane released to the environment will
partition almost entirely to the atmosphere. Level 1 Mackay calculations for
difluoromethane indicate that at equilibrium approximately 0.01%, 0%, 0% and
99.9% will be partitioned to soil, sediment, water and air, respectively. Any traces
entering water would not be expected to undergo biodegradation at significant
rates as degradation by activated sludge in a closed bottle test (OECD Test
Guideline 301D) was minimal (28-day biological oxygen demand 5% of
theoretical). The main degradation pathway in the environment is reaction with
tropospheric hydroxyl radicals, which abstract hydrogen (Scheme 1 (2)) which lead
through a series of radical reactions to carbonyl fluoride (C(O)F2).
Scheme 1: CH2F2
+ OH ?H2O
CHF2
+ O2
+ NO2 + OH ?H2O
CHF2O2NO2 CHF2O2 CHF2O2H
?NO2 ( or h) + HO2 ?O2
+ NO ?NO2
CHF2O
?NO3 (h) ?OH (h)
+ O2 ?HO2
C(O)F2
+ H2O (liq.)
CO2 + 2 HF
Analogous experiments (10) with chlorine radicals, more readily generated in the
laboratory than hydroxyl radicals, indicated that both difluoromethane and
chlorodifluoromethane (R-22) degrade to carbonyl fluoride. The estimated
atmospheric lifetime is 7.7 years (11). It is expected that the generated carbonyl
fluoride will be removed from the atmosphere by uptake into clouds, rain and the
oceans where it will rapidly hydrolyse to carbon dioxide (CO2) and hydrofluoric acid
(HF).
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9. EVALUATION OF TOXICOLOGICAL DATA
9.1 Inhalation Toxicity
Summary of the inhalation toxicity of difluoromethane
Test Species Outcome Reference
acute inhalation rat LD 50 > 520 000 ppm (12)
toxicity
28-day repeat dose rat LD 50 > 49 500 ppm (13)
inhalation toxicity
90-day repeat dose rat LD 50 > 49 100 ppm (14)
inhalation toxicity
Note: because of the gaseous nature of difluoromethane at normal temperature
and pressure many standard toxicity tests do not apply
9.1 Inhalation Toxicity
9.1.1 Acute Inhalation Toxicity (12)
Species/strain: rat/Wistar
Number/sex of animals: 5/sex in 4 groups
Dose 0, 5 000, 50 000 and 520 000 ppm for 4
hours
Observation period: 14 days
Method of administration: serially diluted atmosphere with oxygen
supplement for highest dose
Clinical observations: no effect at 5 000 ppm
reduced response to sound at 50 000 ppm
absence of response to sound, increased
breathing depth, reduced breathing rate and
tail erections at 500 000 ppm
Mortality: none
Morphological findings: none related to treatment
Test method: according to OECD Guidelines (15)
LD 50: > 520 000 ppm
Result: the notified chemical exhibited low acute
inhalation toxicity in rats
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9.1.2 28-day repeat dose inhalation toxicity (13)
Species/strain: rat/Wistar
Number/sex of animals: 5/sex in 4 treatment groups
Dose 0, 2 000, 10 000 and 50 000 ppm
Duration 6 hours/day for 5 out of 7 days over 4 weeks
Detailed clinical observation 1, 2, 3, 8, 15, 22, 29 days
Method of administration: gaseous in whole body exposure chambers
Clinical observations: piloerection and nose stains at 10 000 and
50 000 ppm,
Clinical increase in plasma potassium in males at
chemistry/Haematology 50 000 ppm, reduced urine pH at 10 000
ppm in females and 50 000 ppm in males,
reduced red blood cell count in females at 50
000 ppm
Mortality: none
Morphological findings: 3 males at 50 000 ppm exhibited minimal
alveolitis (one female in the control group
and one female in the 2 000 ppm group also
exhibited minimal alveolitis)
Test method: according to OECD Guidelines (15)
Result: the notified chemical exhibited low inhalation
toxicity in rats in this 28-day sub-acute study
9.1.3 90-day repeat dose inhalation toxicity (14)
Species/strain: rat/Wistar
Number/sex of animals: 10/sex in 4 treatment groups
Dose 0, 5 000, 15 000 and 50 000 ppm
Duration 6 hours/day for 5 out of 7 days over 13 weeks
Detailed clinical observation every 7 days
Method of administration: gaseous in whole body exposure chambers
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Clinical observations: no treatment related changes
Mortality: none
Morphological findings: no treatment related changes
Test method: according to OECD Guidelines (15)
Result: the notified chemical exhibited low inhalation
toxicity in rats in this 90-day chronic exposure
study
9.2 Absorption, Metabolism and Toxicokinetics (16)
Species/strain: rat/Wistar and mice Alpk:APfCD-1
Number/sex of animals: 4 males of each species
10 000 ppm of 14C-difluoromethane
Dose
Duration 6 hours
Method of administration: g a s e o u s in glass metabolism chambers
approx 1% 14 C-difluoromethane dose
Metabolism:
recovered in faeces, urine and expired air in
both species; CO2 0.23% rats, 0.27% mice,
urine 0.34% mice, 0.13% rats; uniform tissue
distribution
Result: in rats 2.1% difluoromethane absorbed from
airways, 63% of absorbed compound
metabolised as above,. low absorption and
metabolism exhibited in both species
9.3 Developmental toxicity
9.3.1 Developmental toxicity in the rat (17)
Species/strain: rat/Wistar
Number/sex of animals: 24 females per group
Dose 0, 5 000, 15 000 and 50 000 ppm
Duration 10 days
(7-16 days of gestation, 6 hours/day)
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Necropsy day 22 of gestation
Method of administration: gaseous in whole body exposure chambers
Clinical observations: low incidence of maternal and foetal toxicity at
50 000 ppm, pre and post-implantation loss
of foetuses and minor foetal defects such as
parietal ossification and liver changes
Maternal Mortality: none
Test method: according to OECD Guidelines (15)
Result: the notified chemical exhibited low
developmental toxicity in rats exposed for 10
gestation days
9.3.2 Development toxicity in the rabbit (18)
Species/strain: rabbits/New Zealand White
Number/sex of animals: 24 female for each dose
Dose: 0, 5 000, 15 000 and 50 000 ppm
Duration: 6 hours/day for 13 days
(6-18 days of gestation)
Necropsy: day 29 of gestation
Method of administration: gaseous in whole body exposure chambers
Clinical observations: maternal weight loss at 50 000 ppm for 45%
of animals from days 8 to 10, recovered after
day 10, no treatment related effects on
foetuses evident at any dose, possibility of
pre-implantation loss at all doses but
incidence did not increase with dose
Maternal Mortality: none
Test method: according to OECD Guidelines (15)
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9.3.3 Chernoff-Kavlock Foetotoxicity and Teratogenicity Assay in the Rat
(19)
Species/strain: rats/Wistar (Alpk:APfSD)
Number/sex of animals: 30 female (10 per group)
Dose 0, 10 000 and 50 000 ppm
Duration 10 days for days 7-16 of gestation
(6 hours/day)
Litter observation 5 days post partum
Method of administration: gaseous in whole body exposure chambers
Clinical observations: maternal weight gain unaltered by exposure
at all doses, 3 rats excluded with more than
50% pup mortality (1 control, 2 at 50 000 ppm
difluoromethane), decreased weight gain in
pups of 50 000 ppm treated mothers
Maternal Mortality: none
Test method: not an OECD Guidelines assessed assay
Result: although low maternal and foetal toxicity
apparently reported, this is a preliminary
assay with lack of individual data that
precludes accurate assessment
9.4 Genotoxicity
9.4.1 Salmonella typhimurium and E. coli Reverse Mutation Assay (20)
Strains:
Salmonella typhimurium TA 98, TA 100, TA 1535, TA 1537
E. coli WP2P, WP2P uvrA
Concentration range: 5, 10, 25, 50, 75, 100% v/v atmosphere for 3
days
Test method: according to OECD Guidelines (15)
Result: higher doses (50% and above) frequently
showed toxicity with S. typhimurium
(particularly TA98), and to lesser extent in E.
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coli , causing a significant decline in colony
numbers in many strains; no dose of the
notified chemical consistently induced back
mutation to prototrophy in any of the strains
tested; metabolic activation by rat liver S9
fraction had no effect on observed mutation
frequency; positive controls showed
significant mutation with the expected
increased colony numbers
9.4.2 Micronucleus Assay in the Bone Marrow Cells of the Mouse (21)
Species/strain: mouse/CD-1
Number and sex of animals: 10/sex per dose group
Doses: 0, 150 000 ppm (15% v/v) for 6 hours
2 groups, one sacrificed after 24 hours,
another after 48 hours
Method of administration: whole body gas inhalation
Test method: according to OECD Guidelines (15)
Result: the notified chemical did not induce a
statistically significant increase in
micronucleated polychromatic erythrocytes at
either the 24 hour or 48 hour sampling time
9.4.3 Chromosomal Aberrations in Chinese Hamster Lung Cells (22)
Species: Chinese Hamster lung
Doses: 10, 20, 40, 80% v/v for 6 hours with activation
and 24 and 48 hours without activation
Method of administration: gas exposure
Treatment regime: after 24 and 48 hour treatment with the test
substance, colcemid was added for 2 hours
to arrest mitosis, cells were trypsin harvested
Test method: according to OECD Guidelines (15)
Result: the notified chemical did not induce a
statistically significant increase in
chromosomal aberrations in either the
presence or absence of metabolic activation
provided by rat liver S9 fraction
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9.4.4 Chromosomal Aberrations in Human lymphocytes (23)
Species: human lymphocytes, freshly isolated from
male and female donors
Doses: 5, 10, 25, 50, 75, 100% v/v for 72 hours
and additional female cultures at 96 hours
with and without rat liver S9 mix
Method of administration: gas exposure
Treatment regime: cells stimulated to enter mitosis by
phytohaemaglutin, colcemid was added for 2
hours to arrest mitosis, cells harvested by
centrifugation
Test method: according to OECD Guidelines (15)
Result: the notified chemical did not induce a
statistically significant increase in
chromosomal aberrations in either the
presence or absence of metabolic activation
provided by rat liver S9 fraction in vitro
9.5 Cardiac Sensitisation in Beagle Dogs (24)
Species/strain: dogs/Beagle
Number/sex of animals: 9/male
Doses: 15, 20, 25, 30, 35 % v/v in air for 60 minutes
each day for 6 days
Observation Period: 6 days
Clinical Observations: no changes
Test method: according to the standard protocol of
published cardiac sensitisation literature (4)
Result: the notified chemical did not induce cardiac
sensitisation at any dose level
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9.6 Overall Assessment of Toxicological Data
Difluoromethane was found to have a low acute inhalation toxicity in rats (LD50 >
520 000 ppm). Difluoromethane is essentially non-toxic when administered daily
via inhalation at concentrations up to 50 000 ppm for up to 90 days. In dogs
difluoromethane did not cause cardiac sensitisation to adrenaline at any dose
level. It was poorly absorbed by the rat or mouse and rapidly excreted through the
urine and exhaled CO2 . There was evidence of minor foetal defects in rats treated
with doses of 50 000 ppm but no effect was observed on rabbit foetuses at the
same dose. No effect was observed at lower doses in either animal. Maternal
toxicity was similarly low in both test species.
Difluoromethane was not mutagenic towards Salmonella typhimurium or
Escherichia coli, nor clastogenic towards polychromatic erythrocytes of mouse
bone marrow in vivo, or human peripheral blood lymphocytes, in vitro.
10. ASSESSMENT OF ENVIRONMENTAL EFFECTS
No ecotoxicological data were provided which is required for chemicals with import
volumes more than 1 tonne per year according to the Act. However, effects on
organisms are not expected as hydrofluorocarbons are stable substances that do
not exhibit significant biological activity. Furthermore, significant exposure of
aquatic organisms to this gaseous substance is not expected.
Halocarbon refrigerants can affect the atmosphere. Difluoromethane contains
neither chlorine nor bromine, and thus will not act as a source of ozone depleting
halogen radicals in the stratosphere. Scientists from the US National Oceanic and
Atmospheric Administration concluded recently that hydrofluorocarbons have
negligible potential to destroy ozone (25).
Like other halocarbons, difluoromethane adds to the global warming potential of
the atmosphere. However, its atmospheric lifetime of 7.7 years is considered
short enough that difluoromethane will not contribute significantly to global
warming (11). The atmospheric lifetime is less than that of difluorochloromethane
(R-22), 15.3 years (26), which the notified chemical replaces. The global warming
potentials (GWP) for difluoromethane and difluorochloromethane over a 100 year
time horizon (relative to CO 2 with GWP 1) are 650 and 1 700, respectively (1).
11. ASSESSMENT OF ENVIRONMENTAL HAZARD
Difluoromethane is not expected to exert a direct effect on living organisms as
hydrofluorocarbons are stable substances that do not exhibit significant biological
activity. The high volatility should ensure minimal exposure of aquatic and
terrestrial compartments, and therefore minimal hazard to organisms inhabiting
them.
The hazard to the atmosphere was reduced when the notified chemical replaced
the previously used chlorofluorocarbons, such as R-22, as the replacement
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refrigerant will not carry chlorine or bromine to the stratosphere (hence, it has no
potential for ozone depletion) and has a lower global warming potential.
12. ASSESSMENT OF PUBLIC AND OCCUPATIONAL HEALTH AND SAFETY
EFFECTS
Developmental toxicity effects in laboratory animals were of low frequency
occurring only at the highest exposure levels. These results suggest no likely
hazard from reproductive effects in workers at probable levels of exposure. Very
high acute exposures of difluoromethane (100 000 ppm in rats) may lead to an
anaesthetic effect suggesting that relatively high concentrations of difluoromethane
need to be present before toxic effects become apparent. If a large amount of
difluoromethane accumulates as a result of a leak, oxygen may be displaced,
leading to an asphyxiation hazard. Direct skin or eye contact with the cold liquid or
escaping gas may result in frostbite. Local exhaust ventilation will be used to
capture any emissions during transfer operations and personnel are required to
wear impervious rubber gloves and goggles to prevent skin and eye contact,
respectively.
Difluoromethane is a flammable liquefied gas that may be reactive at high
temperatures. However, it will only be used as a mixture with other HFCs and
these mixtures are not flammable (all are classified dangerous goods class 2.2, ie
non-flammable gases). Its vapour is heavier than air which may result in the gas
collecting in low areas and displacing oxygen. Difluoromethane when used in
confined spaces will not effectively disperse unless positively ventilated.
The greatest risk for those employed as refrigeration and air conditioning
mechanics apart from cold burns would appear to be asphyxiation arising from the
unnoticed accumulation of gas from slow leaks. Standard Australia's HB40-1992
The Australian Refrigeration and Air Conditioning Code of Good Practice (7)
provides guidance for the recommended work practices.
Under normal conditions of use, there will be low potential for public exposure to
difluoromethane since its application will be restricted to industry. If public contact
to difluoromethane does occur during accidental spillages, health hazards arising
from acute exposure are anticipated to be low as difluoromethane has low acute
inhalation toxicity. Accidental exposure to difluoromethane can also arise as a
result of slow leakages of the refrigerant from faulty equipment. Since the overall
toxicity of difluoromethane is low as indicated in the toxicology studies, the
potential for adverse health effects under such circumstances is anticipated to be
low.
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13. RECOMMENDATIONS
To minimise occupational exposure to difluoromethane the following guidelines
and precautions should be observed:
? If engineering controls and work practices are insufficient to significantly
reduce exposure to a safe level, then personal protective devices which
conform to and are used in accordance with Australian Standards (AS) for
eye protection (AS 1336; AS 1337) (27, 28), impermeable gloves (AS 2161)
(29), protective clothing (AS 2919) (30), and respiratory protection
conforming to AS/NZS 1715 (31), and AS/NZS 1716 (32).
? When used in confined spaces positive ventilation is necessary to disperse
escaped gases.
? Good work practices should be implemented to avoid spillages.
? Good personal hygiene should be adopted.
? A copy of the MSDS for products containing the notified chemical should be
easily accessible to employees working with products containing the
chemical.
? Manufacturers, distributors and users must minimise atmospheric
emissions of HFC-32 by leak testing of refrigeration equipment on a regular
basis and adhering to the Australian Refrigeration and Air Conditioning
Code of Good Practice. Storage of cylinders containing difluoromethane
should conform to the maximum recommended temperature of 52oC.
14. MATERIAL SAFETY DATA SHEET
The MSDS for a formulation containing difluoromethane was provided in a format
similar to Worksafe Australia format (33). This MSDS was provided by Actrol Parts,
a division of GSA Industries (Aust.) Pty. Ltd. as part of their notification statement.
The accuracy of this information remains the responsibility of Actrol Parts.
15. REQUIREMENTS FOR SECONDARY NOTIFICATION
Under the Act, secondary notification of difluoromethane shall be required if any of
the circumstances stipulated under subsection 64(2) of the Act arise. No other
specific conditions are prescribed.
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16. REFERENCES
1. Intergovernmental Panel on Climate Change 1995, Climate Change 1994;
Radiative Forcing of Climate Change and an Evaluation of the IPCC IS92
Emission Scenarios, Cambridge University Press, Cambridge, UK.
2. ECETOC, 1995, Difluoromethane (HFC-32) CAS No 75-10-5, Joint
Assessment of Commodity Chemicals, vol. 32, (ECETOC), Brussels,
Belgium.
3. Fischer, S.K. & McFarland, M. 1992, 'Alternatives to CFCs and Global
Warming: A Systems Approach to Evaluating Net Contributions', Materials
Research Society, vol. 17, no. 2, pp. 39-42.
4. Reinhardt 1971, 'Cardiac Arrhythmias and Aerosol Sniffing', Archives of
Environmental Health, vol. 22, pp. 265-279.
5. ACGIH 1991, 'Methyl Chloride', in Documentation of the Threshold Limit
Values and Biological Exposure Indices, American Conference of
Government Industrial Hygienists, pp. 953-957.
6. Mullin, L. 1975, 'Dichlorofluoromethane', in ACGIH - Documentation of the
Threshold Limit Values and Biological Exposure Indices, pp. 434-435.
7. Association of Fluorocarbon Consumers and Manufacturers 1992, The
Australian Refrigeration and Air Conditioning Code of Good Practice,
Revised Edition HB40, Standards Australia, Sydney.
8. Chemical Marketing Reporter 1994, 'Hoechst Suffers Explosion at Frankfurt
134a Facility', Chemical Marketing Reporter, vol. 245, no. 13, pp. 3-40.
9. Maduro, R.A. & Holzknecht, B. 1994, 'The $5 Trillion Mistake', Machine
Design, vol. 66, no. 2, pp. 53-58.
10. Atkinson, R., Tuazon, E.C., Aschmann, S.M., Arey, J. & Corchnoy, S.B. 1993,
Experimental Investigation of the Products Formed from the Tropospheric
Reactions of Alternative Fluorocarbons, Final Report, Project no., D1199,
Statewide Pollution Centre, University of California, Washington D.C.
11. Talukdar, R., Melloiki, A., Gierczak, T., Barkholder, J.B., McKeen, S.A. &
Ravishankara, A.R. 1991, 'Atmospheric fate of CF2H2, CH 3CF3, CHF2CF3,
and CH3CFCl2: Reactions with OH and UV Absorption Cross Sections of
CH3CFCl2', J Phys Chem, vol. 95, pp. 5815-5821.
12. Parr-Dobrzanski, R.J. 1992a, HFC 32: 4-hour Acute Inhalation Toxicity
Study in the Rat, Project no., CTL/P/3456, ICI Central Toxicology Laboratory,
Macclesfield, UK.
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13. Parr-Dobrzanski, R.J. 1992b, HFC 32: 28 Day Sub-Acute Inhalation Toxicity
Study in the Rat, Project no., CTL/P/3746, ICI Central Toxicology Laboratory,
Macclesfield, UK.
14. Parr-Dobrzanski, R.J. 1993, HFC 32: 90 Day Inhalation Toxicity Study in the
Rat, Project no., CTL/P/4064, ICI Central Toxicology Laboratory,
Macclesfield, UK.
15. Organisation for Economic Co-operation and Development 1995-1996,
OECD Guidelines for the Testing of Chemicals on CD-Rom, OECD, Paris.
16. Ellis, M.K., Naylor, J.L. & T., G. 1992, HFC 32: Pharmacokinetics and
Metabolism in Male Rats and Mice Following a Single Exposure by
Inhalation, Project no., CTL/R/1137, ICI Central Toxicology Laboratory,
Macclesfield, UK.
17. Moxon, M.E. 1993, HFC 32: Developmental Toxicity Study in the Rat, Project
no., CTL/P/3835, Zeneca Central Toxicology Laboratory, Macclesfield, UK.
18. Meyers, D.P. 1994, HFC 32: A Study of the Effect on Pregnancy of the
R a b b i t , Project no., MA-RR-94-2087, Huntingdon Research Centre Ltd.,
Huntingdon, UK.
19. Moxon, M.E. 1992, HFC 32: Modified Chernoff-Kavlock Assay in the Rat,
Project no., CTL/P/3695, ICI Central Toxicology Laboratory, Macclesfield, UK.
20. Callendar, R.D. 1992, HFC 32: Evaluation of Mutagenic Potential using
S.typhimurium and E.coli, Project no., CTL/P/3351, ICI Central Toxicology
Laboratory, Macclesfield, UK.
21. Randall, V. & Mackay, J.M. 1993, An evaluation of HFC32 in the Mouse
Micronucleus Test, Project no., CTL/P/3927, Zeneca Central Toxicology
Laboratory, Macclesfield, United Kingdom.
22. Matsushima, T. 1993, Report on a Chromosomal Aberration Test of HFC
32 in Cultured Mammalian Cells, Project no., 5918, Japan Bioassay
Laboratory, Kanagawa-Ken, Japan.
23. Mackay, J.M. & Howard, C.A. 1992, HFC 32: Evaluation in the In Vitro
Cytogenetic Assay in Human Lymphocutes, Project no., CTL/P/3465, ICI
Central Toxicology Laboratory, Macclesfield, UK.
24. Hardy, C.J. & Kieran, P.C. 1992, Hydrofluorocarbon 32: Assessment of
Cardiac Sensitisation Potential in Beagle Dogs., ICI Central Toxicology
Laboratory, Huntingdon United Kingdom.
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25. Ravishankara, A.R., Turnipseed, A.A., Jensen, N.R., Barone, S., Mills, M.,
Howard, C.J. & S Solomon Science 1994, 71-75. 1994, 'Do
Hydrofluorocarbons Destroy Sratospheric Ozone', Science, vol. 263, no.
5143, Jan 7, pp. 71-75.
26. Fisher, D.A., Hales, C.H., Wang, W.-C., Ko, M.K.W. & Sze, N.D. 1990, 'Model
Calculations of the Relative Effects of CFC's and their Replacements on
Global Change', Nature, vol. 344, pp. 513-516.
27. Standards Australia 1994, Australian Standard 1336-1994, Eye protection in
the Industrial Environment, Standards Association of Australia, Sydney.
28. Standards Australia/Standards New Zealand 1992, Australian/New Zealand
Standard 1337-1992, Eye Protectors for Industrial Applications, Standards
Association of Australia/Standards Association of New Zealand,
Sydney/Wellington.
29. Standards Australia 1978, Australian Standard 2161-1978, Industrial Safety
Gloves and Mittens (excluding electrical and medical gloves), Standards
Association of Australia, Sydney.
30. Standards Australia 1987, Australian Standard 2919-1987, Industrial
Clothing, Standards Association of Australia, Sydney.
31. Standards Australia/Standards New Zealand 1994, Australian/New Zealand
Standard 1715-1994, Selection, Use and Maintenance of Respiratory
Protective Devices, Standards Association of Australia/Standards
Association of New Zealand, Sydney/Wellington.
32. Standards Australia/Standards New Zealand 1994, Australian/New Zealand
Standard 1716-1994, Respiratory Protective Devices, Standards
Association of Australia/Standards Association of New Zealand,
Sydney/Wellington.
33. National Occupational Health and Safety Commission 1994, National Code
of Practice for the Preparation of Material Safety Data Sheets
[NOHSC:2011(1994)], Australian Government Publishing Service, Canberra.
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