HFC-134a in Cars - Can it make you Crash?
Ian Maclaine-cross, 1st October 1997
In a preliminary report of the 19th August 1997, Vinegar and others
describe the effects of inhaling refrigerants 1301, 134a and 227ea at
the USAF Medical Center, Wright-Patterson AFB, Ohio. The seven human
subjects were healthy male volunteers with ages from 21 to 49. All
subjects showed no adverse affects when breathing through the
apparatus pure air or 0.5% by volume R-1301 in air for 30 minutes and
none were expected for R-134a.
After 4.5 minutes of breathing R-134a at 0.4% by volume in air,
subject three lost consciousness and both pulse and blood pressure
dropped to zero. Medical personnel restored pulse and blood pressure
and administered 100% oxygen. Vital signs returned to pre-exposure
values after approximately one hour. After 10.5 minutes breathing 0.4%
R-134a, subject fives blood pressure and pulse rose rapidly and the
exposure was terminated. After one hour breathing room air and then
only 2.5 minutes breathing 0.2% R-134a, subject fives blood pressure
and pulse again rose rapidly and exposure was terminated. These were
the only two subjects exposed to R-134a. Both subjects were still
reporting problems with dizziness and balance six weeks after the
exposure.
In The Lancet of the 23rd August 1997, Hoet and others describe an
epidemic of liver disease in nine Belgian crane drivers. In March
1996, R-114 had been replaced in the air conditioning system of the
crane cabin by a mixture of R-123 and R-124. At the end of April one
of the drivers became progressively ill and was admitted to hospital
with acute hepatitis. At the end of June he returned to work but
within a week returned ill to hospital. Another driver developed acute
hepatitis in May and a third was admitted to hospital in July. Six
additional drivers developed symptoms of hepatitis. An inspection in
July revealed a refrigerant leak into the cabin and after repairs in
August no recurrences or new cases of liver diseases were recorded.
Clinical tests on blood and a biopsy also indicated refrigerant as the
cause. Similar disease has been observed in humans exposed to
halothane and in animals exposed to R-123. The concentration the crane
drivers were exposed to must have been of the order of 0.002% by
volume since the leak occurred over four months.
In 1995, a technician in Brisbane Australia accidently exposed for
about a minute to an R-134a concentration of about 2% had to recover
in hospital. In 1996, a taxi-driver with a slowly leaking
air-conditioner in the same city complained of feeling ill, recovered
when he took a week off, got sick again when he returned to work and
had no further symptoms when the evaporator was repaired.
Hoet and others (1997) suggest that metabolism to trifluoroacetic acid
which modifies proteins causes the R-123 disease. Trifluoroacetic acid
is also a decomposition product of R-134a but not of R-12 or R-1301 so
the suggestion of Hoet and others may explain all the observations
above.
The average exposure of refrigeration technicians to R-123 is much
less than 0.002%, about 0.0001% and the peak during some procedures
about 0.001% (NICNAS 1996). The exposure of car air-conditioner
technicians to R-134a may be higher. These refrigerants are odorless
so technicians rarely connect refrigerant exposure with any illness
which occurs.
Sudden failure of air-conditioner components in car passenger
compartments may occur as frequently as once in a million operating
years for some designs. Failures in cars retrofitted to R-134a could
cause compartment concentration to exceed 0.4% by volume for over five
minutes (Maclaine-cross 1997). The frequency of small pinhole and
fatigue fracture leaks into the passenger compartment is of the order
of once in a thousand years. R-134a is original equipment on most cars
manufactured after 1994. The toxicology data above suggests that leaks
may cause driver errors resulting in personal injury and property
damage.
The following precautions reduce R-134a risk to drivers, their
passengers and the general public:-
* While the car is occupied, keep the compartment fan running
or, in weather above freezing, wind down one window or the
equivalent.
* If a fresh air vent control exists, keep it open at all
times.
* If a refrigerant leak is noticed and the car is in motion,
wind down the driver's window immediately and leave it open for
at least an hour after the leak appears to cease.
* If a refrigerant leak is noticed and the car is stationary,
immediately get out of the car or wind all windows down and
keep them down for at least an hour after the leak appears to
cease. If you must drive off, keep the driver's window open as
above.
The ultimate solution is a non-toxic replacement refrigerant.
Environmental legislation make CFC-12 expensive in many countries.
Many new blends contain components whose toxicology is now uncertain.
The only replacement refrigerants known to be non-toxic are blends
consisting of pure saturated hydrocarbons only, for example HC-12a
(tm).
References
To obtain these references electronicly point your browser at URL:
http://ilm.mech.unsw.edu.au/pub/archive/HC/news/toxicity.html
Hoet, P., Graf, M.L.M., Bourdi, M., Pohl, L.R., Duray, P.H.,
Chen, W., Peter, R.M., Nelson, S.D., Verlinden, N. and Lison,
D., Epidemic of liver disease caused by
hydrochlorofluorocarbons used as ozone-sparing substitutes of
chlorofluorocarbons, The Lancet, Vol. 350, No. 9077, 23rd
August, 1997.
Maclaine-cross, I. L., Refrigerant Concentrations in Car
Passenger Compartments, Paper accepted for International
Conference on Ozone Protection Technologies, Baltimore MD,
November 12-13th, 1997.
NICNAS, 2,2-dichloro-1,1,1,-trifluoroethane (HFC-123), Priority
Existing Chemical No.4, Full Public Report, National Industrial
Chemicals Notification and Assessment Scheme, Australian
Government Publishing Service, ISBN 0 644 45140 8, 119 p.,
March 1996.
Vinegar, A., Cook, R., McCafferty, J., Caracci, M. and Jepson,
G., Human Inhalation of Halon 1301, HFC-134a and HFC-227ea for
Collection of Pharmacokinetic Data, Report, Air Force Contract
No. F41624-96-C-9010, Wright-Patterson AFB OH, 17 p., August
19th, 1997
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Regards,
Ian Maclaine-cross (ian at ilm.mech.unsw.edu.au)
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