Controversy
surrounding ozone depletion
There
is little disagreement among atmospheric researchers on major causes
of Ozone depletion, particularly the role of man-made chlorofluorocarbons
in the depletion. For more information on this click on major
and minor sources of stratopheric chlorine. Atmospheric researchers
also agree there are a great many unanswered questions concerning
ozone depletion. The big question which generates disagreement is:
is there sufficient data and sufficient consequences to justify
banning highly valuable CFC's? This question can be separated into
two unressolved issues:
- Is
the amount of ozone depletion proven to be significant enough
to warrent goverment regulations of CFC's?
- Will
the the additional amount of UV exposure be significant to humans,
directly or indirectly?
Two
of the best articles which outline the conlicting science viewpoints
:re:
- P.Zurer
''Ozone Depletion's Recurring Surprises Challenge Atmospheric
Scientists'' Chemical &Engineering News (C&EN) May
24th,1993. Pam Zurer is a staff writer for C&EN
- S.F.Singer
''Ozone, skin cancer and the SST'' Aerospace America
July 1994. S.Fred Singer is director of the Science&Environmental
Policy Project.
An
article which overviews the media and popular conflict of ideas is:
-
G.Taubes ''The Ozone Backlash'' Science vol.260,
June 11th, 1993
Is
ozone depletion of proven significance enough to warrent goverment
regulation of CFC's? S.F.Singer argues No
for the following reasons-
- Insufficient
experimentation or observation to show that the current downward
trend is not due to natural factors, such as the 11year sunspot
cycle. Singer does acknowledge that there is sufficient data to
show that CFC's are the major cause of ozone depletion (Science,
260) but argues even more strongly that scientist have little
certainty about how much ozone is actually being degraded by CFC's.
For more info on natural influences see the ''factors
influencing ozone concentration'' section of the ozone layer
tutorial.
- The
roles of aerosols and nitrogen-oxides in reacting with either
ozone or stratospheric chlorine are not well understood.
- Refitting
and replacing industrial equipment that can not accept CFC alternatives
is estimated at $130 billion in the US alone! Singer strongly
argues that the consequences of the CFC ban are a lot more certain
than the benefits. ''The unfortunate outcome (if the CFC-ozone
link proves false) may be the an unconscionable waste of resources,
a loss of public trust, and a real setback for the environmental
effort.''
P.Zurer
would argue Yes for the following reasons:
- Because
CFC's work catalytically
, a small amount of CFC's can deplete a huge amount of ozone.
CFC's take up to 15 years to reach the stratosphere but can stay
in the atmospere from 50-200 years. This means that the relatively
small depletions in ozone seen now will get much larger as CFC's
that have already been released accumulate in the stratosphere.
- Large
amounts of lab evidence prove a number of pathways by which chlorine
and bromine destroy ozone in carefully simulated stratospheric
conditions.
- There
is more than sufficient evidence
for significant CFC-caused ozone depletion. The simultaneous rise
of CFC's and free chlorine in the stratosphere coupled with a
corresponding decrease in ozone have been repeatedly shown, both
over time and and latitude as one approaches the south pole:
- Al
Globus adds a summary in favor of intervention: There are readily
available examples in both math and science where small changes
made to apparently stable systems radically change the system.
Making poorly understood global changes to vital resources, such
as the air we breath, is unwise.
Will
the the additional amount of UV exposure be significant to humans?
S.F.Singer argues No for the following reasons-
- Very
weak data showing any link at all between ozone-depletion and
UV-increase. Singer cites a recent Canadian study that appeared
to be prematurely alarmed at what turned out to be a short-term
rise in UV radiation in the northern hemisphere. Also since increased
stratospheric UV will form more ozone in the troposphere, especially
in urban areas, most of the human population will experience little
if any increase in UV exposure.
- UV-B
increases naturally by about 5,000% as one moves from the poles
toward the equator, largely due to the angle of the sunlight which
affects the amount of atmosphere that the sunlight must pass through.
To see a 10% increase in UV-B, for a person at the mid-latitudes
such as in the USA, one would merly have to travel 60 miles toward
the equator. This has implications for those who worry about potential
genetic damage to marine life: marine life at low latitudes has
already successfully adapted to high doses of UV exposure.
- The
skin cancers clearly shown to be linked to UV exposure are the
easily cured basal-cell and squamous-cell carcinomas. The far
more dangerous malignant melanomas have not been linked to UV-B
exposure. In fact one experiment published by R.Setlow in 1993
concluded that melonomas may be caused by radiation with wavelengths
above 320 nm, wavelengths not blocked by ozone.
P.Zurer
argues Yes for the following reasons:
- Well
proven link of UV exposure to basal-cell and squamous-cell carcinomas.
The FDA (FDA doc#92-1186) claims there is evidence linking
sun exposure to the least common type of melanoma, latigo melanoma.
R.Parson (UV-B FAQ) claims there is a correlation between melanoma
incidence and latitude; with twice as many melanoma-caused deaths
in Florida and Texas, as in Wisconson and Montana. (But it is
possible that this is due to some other type of solar radiation
that is not blocked by UV).
- United
Nations Environment Protection Agency (UNEP) reports links between
UV exposure and a weakening of the immune system, even in dark
skinned peoples.
- (from
R.Parson FAQ) Ample evidence showing that UV-B causes damage to
DNA, even samples of DNA placed nine feet under seawater. This
has big implications for marine life, especially plankton which
live principally in the top three feet of the oceans waters. There
has been one large study done on antarctic plankton (Smith,Science
,1992) comparing marine phytoplankton
inside and outside the antarctic ozone hole. They found a 6-12%
decrease in phytoplankton productivity, which is compared to worldwide
plankton productivity a small but measurable drop.
- (R.Parson
, UV-B FAQ) It is known that too much UV causes short-term ''snow-blindness''.
The eye lens is known to be a strong absorber of UV light and
there is a higher incidence of cataracts in high UV environments
such as Bolivia and Tibet .
Author: Brien Sparling
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