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From: dsi@unccvax.UUCP (Dataspan Inc)
Newsgroups: net.med,net.cse,net.periphs
Subject: Re: HELP! Need to show VDTs not dangerous to pregnant women
Message-ID: <375@unccvax.unccvax.UUCP>
Date: Sun, 1-Dec-85 09:04:33 EST
Article-I.D.: unccvax.375
Posted: Sun Dec  1 09:04:33 1985
Date-Received: Tue, 3-Dec-85 07:41:55 EST
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Keywords: Silly, preposterous
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     I would casually approach the recalcitrant subject(s) about how much
regular television they watch.  Strictly from the point of view of a 
video engineer, I'd much rather sit in front of a VDT than my Conrac
5111/19 master monitor; although both devices meet the applicable Federal
DHHS/Canadian DOC requirements for X-radiation.

     The accelerating voltage in your typical terminal is between 8 and 12
kv.  Most CRT specification sheets have a "clause" in their warning that
states "shielding of this tube and its enclosure may be required when this
cathode ray tube is operated above 12 kV."

     On the other hand, entertainment televisions typically have accelerating
voltages from 26 to 38 kV and occasionally more.  At 38 kv, CRT's are usually
equipped with a bonded or T-band faceplate which has been treated to 
attenuate the X-radiation generated at the aluminized "rear" of the CRT face.

     The amount of harmful radiation produced is a direct (though not 
proportional) function of the accelerating voltage and certain design
parameters within the CRT.  Real medical X-rays start at (I think) an accel
potential of 80 kV.

     Unless and until someone does a study which compares the number of 
birth anomalies/pregnancy complications among (or even throughout the spectrum
of) TV viewers and non-TV viewers, I might suggest that a sedentary lifestyle
in front of the terminal, while pregnant, could be equally the cause as
minimal amounts of radiation from the VDT.  Even if it were shown that 
"heavy viewers" had the most problems, this still would not conclusively
prove that the CRT faceplate is the problem.

     BUT, should you desire, there is a product made by Victoreen/Nuclear
Associates (I think, ask any medical X-ray supply house) called "Clear-PB"
which your local glass shop can cut up and put in front of the CRT faceplate.
A very thin sheet of this (1/4 inch) is probably all that is required.

David Anthony
DataSpan, Incorporated

P.S.  I am NOT giving engineering advice here. The statements are simply
      a matter of opinion.