|
Air
Conditioning Definitions
Benefits
of the CFC Phase-out
Case
Studies of Successful CFC Elimination
Decibel Comparisons
Faq Ozone
Depletions
How
Air Conditioning Works
Ozone
Science Phase Outs
Understanding
Air Conditioning
|
Questions and Answers on Ozone Depletion
- What is the ozone layer and why is
it important?
The ozone layer is a concentration of ozone molecules in the
stratosphere. About 90% of the planet's ozone is in the ozone
layer. The layer of the Earth's atmosphere that surrounds us
is called the troposphere. The stratosphere, the next higher
layer, extends about 10-50 kilometers above the Earth's surface.
Stratospheric ozone is a naturally-occurring gas that filters
the sun's ultraviolet (UV) radiation. A diminished ozone layer
allows more radiation to reach the Earth's surface. For people,
overexposure to UV rays can lead to skin cancer, cataracts,
and weakened immune systems. Increased UV can also lead to reduced
crop yield and disruptions in the marine food chain. UV also
has other harmful effects.
- How does ozone depletion occur?
It is caused by the release of chlorofluorocarbons (CFC's) and
other ozone-depleting substances (ODS), which were used widely
as refrigerants, insulating foams, and solvents. The discussion
below focuses on CFCs, but is relevant to all ODS. Although
CFCs are heavier than air, they are eventually carried into
the stratosphere in a process that can take as long as 2 to
5 years. Measurements of CFCs in the stratosphere are made from
balloons, aircraft, and satellites.
When CFCs reach the stratosphere, the ultraviolet radiation
from the sun causes them to break apart and release chlorine
atoms which react with ozone, starting chemical cycles of ozone
destruction that deplete the ozone layer. One chlorine atom
can break apart more than 100,000 ozone molecules.
Other chemicals that damage the ozone layer include methyl bromide
(used as a pesticide), halons (used in fire extinguishers),
and methyl chloroform (used as a solvent in industrial processes).
As methyl bromide and halons are broken apart, they release
bromine atoms, which are 40 times more destructive to ozone
molecules than chlorine atoms.
- How do we know that natural sources
are not responsible for ozone depletion?
While it is true that volcanoes and oceans release large
amounts of chlorine, the chlorine from these sources is easily
dissolved in water and washes out of the atmosphere in rain.
In contrast, CFCs are not broken down in the lower atmosphere
and do not dissolve in water. The chlorine in these human-made
molecules does reach the stratosphere. Measurements show that
the increase in stratospheric chlorine since 1985 matches the
amount released from CFCs and other ozone-depleting substances
produced and released by human activities.
- What is being done about ozone depletion?
In 1978, the use of CFC propellants in spray cans was banned
in the U.S. In the 1980s, the Antarctic "ozone hole"
appeared and an international science assessment more strongly
linked the release of CFCs and ozone depletion. It became evident
that a stronger world wide response was needed. In 1987,
the Montreal Protocol was signed and the signatory nations committed
themselves to a reduction in the use of CFCs and other ozone-depleting
substances.
Since that time, the treaty has been amended to ban CFC production
after 1995 in the developed countries, and later in developing.
Today, over 160 countries have signed the treaty. Beginning
January 1, 1996, only recycled and stockpiled CFCs will be available
for use in developed countries like the US. This production
phaseout is possible because of efforts to ensure that there
will be substitute chemicals and technologies for all CFC uses.
EPA coordinates numerous regulatory programs designed to help
the ozone layer and continues to be active in developing international
ozone protection policies. Individuals can also help, primarily
by ensuring that technicians working on air conditioning and
refrigeration equipment are certified by EPA, that refrigerants
are recaptured and not released, and by educating themselves
about the issue of ozone depletion.
- Is there general agreement among scientists
on the science of ozone depletion?
Yes. Under the sponsorship of the UN Environment Programme (UNEP)
and the World Meteorological Organization (WMO), the scientific
community issues periodic reports. Almost 300 scientists worldwide
drafted and reviewed the WMO/UNEP Scientific Assessment of Ozone
Depletion: 1994 ( can be obtained from EPA's Stratospheric Ozone
Protection hotline at 800-296-1996). An international consensus
about the causes and effects of ozone depletion has emerged.
- Will the ozone layer recover? Can
we make more ozone to fill in the hole?
The answers, in order, are: yes and no. We can't make enough
ozone to replace what's been destroyed, but provided that we
stop producing ozone-depleting substances, natural ozone production
reactions should return the ozone layer to normal levels by
about 2050. It is very important that the world comply with
the Montreal Protocol; delays in ending production could result
in additional damage and prolong the ozone layer's recovery.
Written by EPA's Statospheric protection Division
Last updated on April 22, 1999
http://www.epa.gov/ozone/science/q_a.html
|
