Re: FW: - Climate Change Hearings and the roll(?) of nuclear power

[RuthWeiner@AOL.COM]

In a message dated 8/1/02 10:52:29 PM Mountain Daylight Time, hflong@postoffice.pacbell.net writes:



> to the similar "Freon causes ozone hole and
>
> melanoma" myth. 


Please do not call this a "myth".  The influence of chlorofluorocarbons ("freons"), expecially chlorofluoromethane, on the ozone layer was first elucidated by McElroy and co-workers around 1980 -- the peer-reviewed paper is published in SCIENCE.  There have been a considerable number of studies of ozone layer depletion by chlorine free radicals (essentially free atoms).  F. Sherwood Rowland was awarded the Nobel Prize in Chemistry for his work in this area, and has written several first-rate review articles on the subject.


In stark contrast to the speculations about the "greenhouse effect" and "greenhouse gas" influence on climate, the effect of chlorofluorocarbons on the atmospheric ozone layer, and the mechanism of that effect are well understood.  Chlorofluormethane (CF2Cl2) was commonly used as an aerosol propellant as well as a refrigerant in the 1960s and 1970s.  CF2CL2 undegoes photochemical decomposition, liberating a Cl free radical.  The equilibrium that forms the ozone layer is O3 (ozone) in equilibrium with O2 (molecular oxygen) and O (atomic oxygen).  The Cl free radical can combine with the atomic oxygen, driving the equilibrium toward dissociation of ozone and essentially depleting the ozone in the ozone layer.  The establishment of holes in the ozone layer, and the correlation of those holes and of ozone layer thinning with the use of chlorofluorocarbon aerosol propellants has been confirmed by measurement.  Such propellants have not been used si!

nce the mid-1980s.  The extent to which the leaking of Freon refrigerants into the air contributes to this is more uncertain, but the mechanism of Freon action is the same.


The ozone layer acts as a filter for the UV in sunlight because the UV energy is absorbed in the dissociation reaction of the ozone.  It is therefore believed that the ozone layer affords some protection against UV-caused skin cancers, and this belief is justified.  Most skin cancers are basal cell cancers (I have had four of these removed from my face -- not fun -- that's how I came to read up on them).  However, squamous cell cancers, like the cancer that killed our 

 Congressman Steve Schiff, is also understood to be caused by the UV in sunlight.  UV is at least a contributor to melanoma, if not the sole cause.


I have used this contrast between the science supporting ozone layer depletion and the uncertainty in the science of climate change as an example in my environmental engineering textbook.


Please understand that my purpose here is to show that some environmental effects that are popularized are in fact based on sound science.  Not all of the popular discussion of environmental threats is hogwash, nor can one even assume that most of it is.  The distortion of the adverse effects of ionizing radiation, and the lack of good science in public discussion does a disservice to environmental science.


So use that sunscreen and avoid leaking Freons into the air.  



Ruth Weiner, Ph. D.

ruthweiner@aol.com