RE: Melanoma cancer/UV info

["Wright, Will (DHS-PSB)" <WWright2@dhs.ca.gov>]

Visible light from fluorescent lamps produce UV in addition to the total
spectrum of visible light waves as well which combined appear as
white(heterochromatic) and very dispersed.  Fluorescent lights are filtered
with the plastic cover to reduce the UV levels.  Lasers produce
monochromatic light either red or green and can concentrate the beam, I am
not sure these beams are pure since the rubies etc used act as filters only?
These concentrated beams produce heat much the same way radiowaves and
microwaves do and indirectly form reactive products that might effect DNA.
Some of the products of heat will be products of the cell "heat shock
response" and other injury induced chemical and messenger systems. just
sheer replacement of cells due to heat killing etc might also contribute to
initiation events. I have not read the papers referenced on the visible
light effects but I find it difficult to adhere to the direct effect
mechanism.  All cells that use oxygen must be protected from reactive oxygen
and some of its products but may be unable to handle excess due to heat
shock or other processes, where as white blood cells have a huge arsenal for
this molecular battle, which includes making use of reactive Oxygen in the
phagocytic process.

There is other interesting work developing with UV induced positive ion
transfer along a DNA chain which causes the chain to break when two adjacent
guanines exist that capture the charge and cause the chain to break. This
might ultimately lead to misrepair as deletion, frameshift or substitution
mutation.

		-----Original Message-----
		From:	Rick Mannix [mailto:rcmannix@uci.edu]
		Sent:	Monday, August 07, 2000 3:57 PM
		To:	Multiple recipients of list
		Subject:	Re: Melanoma cancer/UV info

		At 04:15 PM 08/07/2000 -0500, you wrote:
		>I received the following message from an astronomer I am
acquainted with.  I
		>am unaware of any reports of links between visible light
and melanoma and/or
		>genetic damage, but then I'm not a biologist or physician.
I'd appreciate
		>any information anyone might have. 
		------------------------------------------------

		I did a quick search of the Medline data base. It sounds
like visible
		radiation can cause melanoma. There were several other
studies that
		implicated visible radiation in melanoma, as well.

		======
		Setlow, RB.  Spectral regions contributing to melanoma: a
personal view.
		Journal of Investigative Dermatology. Symposium Proceedings,
1999 Sep,
		4(1):46-9. (UI:
		20005399)
		                      
		 Language: English;  Pub type: JOURNAL ARTICLE; REVIEW;
REVIEW, TUTORIAL

		Abstract: Although human cutaneous melanoma is a complicated
disease, the
		principal etiologic
		agent for its incidence in fair skin individuals is exposure
to sunlight.
		In order to understand the
		epidemiology of melanoma - temporal effects, latitude
effects, sunscreen
		effects, albino
		susceptibility, and differences from nonmelanoma skin cancer
-one must
		approach the problem
		by obtaining clues indicating which wavelengths in sunlight
are effective
		in inducing melanomas.

		One way is to use an animal model. At present, the only
suitable model is a
		backcross hybrid of
		small tropical fish of the genus Xiphophorus, bred to have
only one tumor
		suppressor gene.
		Single UV exposures to 7-d-old fish induce melanomas readily
observable by
		4 mo. The initial
		slopes of dose-response curves for exposures at 302, 313,
365, 405, 436,
		and 547 nm yield
		sensitivity as a function of wavelength. This action
spectrum does not look
		like the spectrum for
		light absorption by DNA (mostly in the UVB), but has
appreciable
		sensitivities in the UVA and
		visible regions, and looks like a direct effect of light on
DNA plus a
		large indirect effect on DNA
		by absorption of light by the intracellular melanin. Because
the UVB is
		only a fraction of solar
		irradiance, one may calculate that 90% of melanoma induction
in humans
		arises from UVA and
		visible, assuming the human spectrum is similar to the fish
spectrum. 

		The implications of this calculation are that (i) depletion
of
		stratospheric ozone will not affect melanoma incidence, (ii)
an increase in
		sun exposure time as a result of using UVB sunscreens could
increase the
		risk of melanoma, and (iii) the use of high UVA sun tanning
devices could
		increase the risk 


		Rick Mannix
		Health Physicist
		Laser Safety Officer
		University of California
		Irvine, CA 92697-2725

		949-824-6098
		949-824-8539   fax
		rcmannix@uci.edu
	
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