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From: dhinds@portia.Stanford.EDU (David Hinds)
Newsgroups: comp.sys.ibm.pc
Subject: Re: GAS PLASMA SCREENS!!
Message-ID: <11133@portia.Stanford.EDU>
Date: 13 Apr 90 00:16:28 GMT
References: <1990Apr10.002440.9812@ux1.cso.uiuc.edu> <3366@jato.Jpl.Nasa.Gov>
Sender: David Hinds <dhinds@portia.stanford.edu>
Organization: Stanford University
Lines: 52

In article <3366@jato.Jpl.Nasa.Gov>, kaleb@mars.jpl.nasa.gov (Kaleb Keithley) writes:
> In article <26226d66.1467@petunia.CalPoly.EDU>,
> >jdudeck@polyslo.CalPoly.EDU (John R. Dudeck) writes:
> 
> >CRT's DO NOT emit any radiation other than visible light!
> 
> Bzzzzzzt! Wrong!  If CRTs don't emit any radiation, then please explain:
> 
> 1.  Why pregnant women who work in front of CRTs have a statistically higher
>     chance of miscarriage than pregnant women who don't work in front of
>     CRTs.

    A statistical correlation does not imply cause and effect relationships.
CRT's DO emit very low levels of soft X-rays, in addition to low amounts of
non-ionizing electromagnetic radiation.  The effect of long-term exposure
to this sort of radiation has been notoriously difficult to pin down.  It
is extremely difficult to make sound statistical judgements about human
populations when the signal to noise is already expected to be weak - how
do you control for the effects of sitting in a particular position for
extended amounts of time?  Perhaps eye strain, or stress in general, is
the relevant causal factor in this case.  Maybe people who work for long
periods in front of CRT's tend to be more irritable than others.  Or maybe
they tend to drink too much coffee to combat their sore eyes.  If it
were shown that when women work with better-shielded CRT's their risk of
miscarriage declines to baseline, then this would be convincing.

> 2.  Why the Scandinavian countries *require* CRTs with additional shielding
>     to reduce the emission of electro-magnetic radiation.

    Government regulatory policy is seldom a reliable guide in risk
assessment.

> 3.  Not really germain to the subject, but why do families who live near
>     high tension (voltage) power lines have a statistically higher rate of
>     cancer, miscarriage, learning disabilities, and other maladies.  In fact
>     so much higher, that in many countries, housing may not be built anywhere
>     near such power lines.

    I don't know if this is true or false, but I thought the issue had not
been resolved.  The levels of low-frequency radiation emitted by an unshielded
115000 volt power line are considerably higher than those from a CRT, however.

> This sounds like the age old delusion; If you can't see it, it must not exist.
    As opposed to the growing delusion that if you can't see it, or spell
it, or know your grandfather lived to a ripe old age eating it, it must
be bad for you.  Neither is much of a substitute for careful analysis of 
risks.  You might say, err on the side of caution, but if these "invisible
enemies" come to dominate popular conceptions of risk, many ordinary yet
far more serious risks may be neglected.

 -David Hinds
  dhinds@popserver.stanford.edu