Re: Melanoma cancer/UV info

[Neon John <johngd@bellsouth.net>]

"Neil, David M" wrote:
> 
> Fluorescent lights produce UV initially, this is converted to visible
> frequency peaks by the phosphors coating the tube; hence the name
> _fluorescent_.   I'm less than totally sure that the plastic is intended
> primarily as a filter - it's mostly for esthetics, but that it does absorb
> some UV is obvious from the yellowing and embrittlement of the plastic
> diffusers.

There isn't any plastic on a fluorescent bulb with the exception of
the PopGuard (R) lamps designated for food prep areas.  There is
enough turmoil in the fluorescent lamp industry due to irrational
fears of the tiny bit of mercury used in the lamp and the lead in
the glass (the theological parallels with our biz is apparent.) that
generalizations are not possible. Nonetheless, in general :-), for
lamps made using the traditional techniques and glass formula, the
glass stops essentially all the shortwave UV that makes its way
through the phosphor.  The phosphor is stimulated primarily by
mercury's short wavelength lines.  The longwave UV is attenuated by
the phosphor.  Most of what gets through the phosphor passes through
the glass.  By my rather imprecise measurements using a photometer
to look at the visible response of longwave phosphor, the typical
plastic fixture shade attenuates this UV no more than 1 or 2 db. 
This UV is very desirable because it stimulates natural fluorescence
and the fluorescent dye that almost all laundry detergent makers add
to their product to make clothes "bright".  It also stimulates this
same dye that is added to almost all high quality paper to make it
"brighter". (A sheet of super bright white inkjet paper is almost
blindly bright under blacklight!) Because of the rather narrow band
nature of the phosphor emissions, the room would seem duller without
the longwave UV.

-- 
John De Armond
johngdSPAMNOT@bellsouth.net
http://personal.bellsouth.net/~johngd/
Neon John's Custom Neon
Cleveland, TN
"Bendin' Glass 'n Passin' Gas"
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