EPA model applied to investigate human and ecosystem impact of alternative
motor vehicle refrigerant
ŁEPA
www.epa.gov/ord
a
science in ACTION
BUILDING A SCIENTIFIC FOUNDATION FOR SOUND ENVIRONMENTAL DECISIONS
Issue
The refrigerant chlorofluorocarbon-12 (known
by many as CFC-12 or Freon™) has been
widely used in motor vehicle air conditioning
systems. Beginning in the 1990s, it was largely
replaced by hydrofluorocarbon (HFC)-134a as
the dominant refrigerant worldwide.
Both CFC-12 and HFC-134a have significant
global warming potential. As a result, air quality
professionals at EPA and industry reinvigorated
their search for alternative refrigerants that do
not (1) deplete ozone in the stratosphere, (2)
promote unsafe levels of ground-level ozone
production, or (3) contribute to global warming.
The European Union has begun using a new
alternative refrigerant, FIFC-1234yf, which
appears to be the choice among global car
manufactures for future vehicle air conditioning
systems. It does not contribute to stratospheric
ozone depletion and has a negligible direct
impact on global warming.
However, the new alternative produces ground-
level ozone and an aquatic toxin (trifluoroacetic
acid). The vehicle air conditioning refrigerant
currently in wide use, HFC-134a, also has these
characteristics.
The issue scientists needed to determine was
whether use of the alternative refrigerant would
cause problems for human and ecosystem health
that did not exist before.
Science Objective
EPA scientists and regulators, together with
researchers in industry sought to determine
whether the potential adverse effects from the
European Union's alternative refrigerant —
HFC-1234yf—presented a greater overall risk
compared to other alternative refrigerants used
in motor vehicles.
To accomplish this, EPA scientists used EPA's
Community Multiscale Air Quality (CMAQ)
model to simulate the atmospheric reactions
from this alternative refrigerant to determine its
impact on ozone and trifluoroacetic acid
formation. This was the first time that a new
alternative refrigerant was studied in a
comprehensive regional air quality model.
The first step was to develop a spatial and
temporal inventory of refrigerant emissions
across the United States, since this emissions
inventory did not exist. The inventory identified
potential future HFC refrigerant emissions
based on air conditioner efficiency, system
leakages, servicing and vehicle end-of-life
leakages(l;.
Next, EPA scientists modified the CMAQ
model to account for the photochemical
reactions of HFC-1234yf and its degradation
products, and to determine the impact on
production of trifluoroacetic acid, including
concentrations that may be re-deposited on
Earth's surface and potentially impact open
waters. They then layered on a real-world
perspective by examining three summertime
scenarios across the United States'"'.
Results and Impact
The analysis by EPA concluded that:
o Concentrations of ozone from HFC-
1234yf emissions from car air
1
U.S. Environmental Protection Agency
Office of Research and Development

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conditioners were not significant enough
to increase ground-level ozone
concentrations,
o HFC-1234yf has a significantly lower
global warming potential (4) than the
widely used HFC-134a refrigerant
(1430), and
o Trifluoroacetic acid concentrations in
rainwater were only l/800th to l/80th the
level at which adverse effects would be
observed in sensitive aquatic plants.
This research enabled EPA to make better
estimates of potentially harmful impacts of
emissions from the more than 300 million U.S.
vehicles expected to be in use by 2013.
Based on these and other findings, EPA
Administrator Lisa P. Jackson signed a new rule
on Feb. 24 listing HFC-1234vf as acceptable in
new cars and light-duty vehicles under EPA's
Significant New Alternatives Policy (SNAP)
Program. The SNAP Program is the only
government program worldwide that reviews
health and environmental impacts of substitutes
for ozone-depleting substances.
This research enabled EPA to provide an
additional refrigerant choice to the automotive
industry and help lower overall risk to human
health and the environment.
2. Papasavva, S., Taddonio, K.N.,
Hutzell, W.T., Rugh, J.P., Andersen,
S.O., 2010, Ozone and TFA Impacts
in North America from degradation
of 2.3.3.3-tetrafluoropropene (HFO-
1234vf). a potential greenhouse gas
replacement. Environmental Science
and Technology 44: 343-348.
Technical Contact
Deborah Luecken
(luecken.deborah@epa.gov, 919-541 -0244)
EPA's National Exposure Research Laboratory
Related News
Reisch, Marc S. (July 26, 2010). Chemical &
Engineering News. Automakers Go HFO:
http: // pub s. acs. or g/i sub scrib e/i ournal s/cen/88/i3
0/html/8830bus3.html.
Hogue, Cheryl. (March 7, 2011). Chemical &
Engineering News. Greenlight for New
Automotive Refrigerant:
http ://pubs. acs. org/cen/news/89/i 10/8910news2.
html
July 2011
References
1. Papasavva, S., Luecken, D.J.,
Waterland, R.L. Taddonio, K.N.,
Andersen, S.O., 2009, Estimated
2017 Refrigerant Emissions of
2.3.3.3-tetrafluoropropene (HFC-
1234vf) in the United States
Resulting from Automobile Air
Conditioning. Environmental
Science and Technology 43: 9252-
9259.
2
U.S. Environmental Protection Agency
Office of Research and Development

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