From: terry@thisbe.npd.Novell.COM (Terry Lambert)
Subject: Re: ******** MICROWAVE HAZARDS ******* [Pacemakers]
Keywords: microwaves, radiation, leakage, interlocks
Organization: Novell NPD -- Sandy, UT
Date: Thu, 27 Aug 1992 20:23:07 GMT

In article <1992Aug26.003419.22166@kodak.kodak.com>, ornitz@kodak.kodak.com (Barry Ornitz) writes:
|> I wish I had time to take this apart, piece by piece, and correct all of the
|> erroneous information.  Unfortunately, emergency family business will keep
|> me away from the network for at least a week.  If anyone wants to be kind and
|> mail me any ensuing discussion, I would be grateful.
|> 
|> In article <1992Aug24.235158.7965@gateway.novell.com> 
|> terry@thisbe.npd.Novell.COM (Terry Lambert) writes:
|> >	[ ... Barry goes on to point out that the primary danger is from the
|> >	      magnetron, and says that the danger is always present due to the
|> >	      permanent magnets therein ... ]
|> >
|> >Testing the "Magic Chef" with real equipment reveals that it, indeed, does not
|> >have enough leakage to pose a serious threat, and that there is a permanent
|> >magnet in it.  However, the amount of induced current in a probe perpendicular
|> >to the magnetic field is (as expected) much higher when the oven is on. I posit
|> >that induced current is the real danger to a pacemaker wearer, since the amount
|> >of current induced is significant compared to the amount of current a pacemaker
|> >from it's documentation, delivers to stimulate the bundle of Hiss.
|> 
|> Just what is being measured here?  The magnetic field at low frequencies or the
|> electromagnetic field at 2450 GHz?  Microwave leakage from a home oven would
|> generally not be polarized due to the effects of the multimode cavity and the
|> "stirrer".  If you are talking transformer leakage, pacemaker wearers should
|> certainly avoid home audio systems too!

If you are referring to the measurement of "leakage", I am referring to the EM
field.

If you are referring to the measured induced current, I am referring to induced
current in a 3 meter section of 12 gauge copper wire.  There are 135 degree bends
1/2 meter from each end to accomodate probe connection.  Induced current was ~.3
volts AC.

All tests were performed with the oven operating on a "high" setting with test
loads of 0, .1, .5, and 1 liters of water in a 2 mil polyethylene container.
No measurable difference within the accuracy of the test equipment (.01 volts)
was noted in induced current.  No change in leakage was detected.

[ re: high frequencies heard from TV's, computer monitors, and microwaves ]

|> The whine is generally much higher pitched that 60 Hz.  You are hearing
|> transformer buzz and harmonics caused by the non-sinusoidal waveform.

I realize the "dog whistle noise" from these appliances is coming from the
flyback transformer in the TV and computer monitor, and from the magnetron
in the microwave.  My, perhaps ill-worded, remarks on the frequency were in
reference to higher freqyency monitors being "less noisy" than microwaves
and TV's, and lower frequency (60Hz) monitors.  I was not attempting to state
the frequency of the sound being eminated by these devices was *actually* 60Hz.
Any dolt with a frequency counter cold tell that.

[ ... heating is based on excitation resonance of water molecules ... ]

|> Unfortuantely this is the point where Terry really shows his misunderstanding
|> of how microwave ovens work.  MICROWAVE OVENS ARE NOT BASED ON EXCITING
|> RESONANCE OF WATER MOLECULES.
|> 
|> Microwave ovens generate heat in many materials based on the dissipation
|> factor of the material.  The technical term is the imaginary component of the
|> complex permittivity.  Any material that has a significant loss or dissipation
|> factor at the microwave frequency will heat.  Water has a broadband high
|> dissipation factor which is nice because water heats easily in a microwave.
|> Ice has a much lower dissipation factor, and it barely heats in a microwave,
|> hence the special defrost cycles.

So, in my misunderstanding, I have misconstrued black-body absorbsion spectra,
as a determination of a materials emissivity (which, I believe, is the *correct*
term) for "dissipation factor"?

In terms of adding energy to a system with energetic photons (such as those
produced by Mr. Microwave), one is generally encouraged to think of photon
absorbtion in terms of input to a damped, driven harmonic oscillator.  This
certainly *sounds* like "resonance" to me.  "Modern Physics" by Halliday and
Resnik, on about page 485, the section on emissivity, absorbtion, and black-body
radiators, tend to agree with me.  Photons are generally *absorbed* in such a
system, *not* "disipated" (what a ridiculous violation of conservation law!).
In what precise physical model do you ascribe the term "disipation" to the
process of converting potential energy stored in an excited valence electron
into kinetic energy (the energy of motion of the water molecule as a whole)?

|> It really gets bad here...
|> The original police radars operated at S-band, the same frequency range as
|> home microwave ovens, 2.45 GHz.  Later units operate at X-band, or 10.525 GHz.
|> Even newer police radars operate on the Ku-band or 24 GHz.  Water absorption
|> of microwaves is FAR higher at X-band than at S-band.  It is far higher still
|> at the Ku-band which is close to the lowest resonant frequency of water for
|> rotational (microwave) spectra [as opposed to vibrational (infrared) spectra].

	Then it would seem to me that you are saying the heating properties of an
X or Ku band radar gun (there are very few, if any, S band guns in use in most
states today), would be "FAR higher"/10000.  What is the magnitude of "FAR higher"
...enough to notice in ones lap?  Yes, I discounted the S band, which *are* in
"the range of" 2.45 GHz, since there aren't many left.

|> 
|> >
|> >Many radar setups are also mounted permanently in the direction of travel and
|> >180 degrees from the direction of travel.  In order to "shoot" cars ahead of
|> >the officer, they shoot through the officers head.  This has caused the expected
|> >results in several officers, one of them here in Utah.  They certainly would be
|> >well aware of heating effects and left the things off if they were the same
|> >frequency.
|> 
|> See above.  Police radar units operate at power levels usually greater than
|> 10,000 times lower than home microwave ovens.

Same calculation for "FAR higer"/10000.  I would think one would be well aware
of heating, even if "FAR higher" were only 2 orders of magnitude.

|> 
|> >As Barry pointed out (omitted for space) in his posting, leakage is real low on
|> >most modern microwave ovens, both the several he tested, and the one I did
|> >after everyone started geting excited.
|> >
|> >All of this leads us to believe that operation of microwave ovens won't cause
|> >cancer as we have been led to believe that radar guns will... in other words,
|> >"the names "radar gun" and "radar range" are coincidental.
|> 
|> I have not been convinced that police radar guns really cause cancer.  As
|> others have pointed out, conclusive evidence in not yet in.  Statistics can
|> show relationships but they cannot show cause and effect.   As of now, I
|> consider the statistics showing a relationship between police and cancer
|> too poor to draw any conclusions from.

Which is why I said "as we have been led to believe that radar guns will" rather
than "as we now know radar guns do".  For someone who picks on the slightest
semantic distinction as a point of contention, you haven't read very closely.

|> 
|> >Radar guns also have to have an unshielded "horn" to work, whereas microwave
|> >ovens are shielded boxes.
|> >
|> >If you are still concerned, stay in the other room after you have started your
|> >microwave, since distance should be an adequate countermeasure to any danger
|> >you believe is present.  Of course, you could just not buy ovens from the
|> >freight damage store, or avoid runing them while they are on your lap.  8-).
|> 
|> As I have pointed out before, the interlocks on home ovens are quite well
|> designed.  Damage severe enough to cause excessive seal leakage will be
|> quite obvious to the naked eye.  Part of the normal testing protocols involves
|> heavy blows to the door and seal assembly, and the oven must still be safe
|> to be certified.

First of all, there isn't purchase-time certification, so the faceiously offered
"freight damaged" ovens, even when not taken for the humorous value with which
they were intended, do not necessarily get recertified after damage.  Second,
this whole argument here falls into the "As Barry pointed out (omitted for space)
in his posting", and really doesn't require reiteration as if restating a point
which I disagreed with or did not understand, both of which are not the case.

|> >Now... anyone have any idea about the helth effects of the RF emissions from
|> >thos motion detectors that set your radar detectors off?
|> 
|> These Part 15 Field Distrurbance Sensors generally use even lower power levels
|> than police radars.  I once calculated you need to be within centimeters of
|> even high-powered sensors to come close to meeting the maximum allowable 
|> field strength limits.

This was offered as yet another topic of paranoid discussion after I felt the
microwave issue to be resolved.  It wasn't supposed to have been taken seriously.

|> The above was not meant as a personal attack on Terry.  However, it is obvious
|> he has no understanding of how microwave ovens work and how materials
|> interact with electromagnetic fields.  It is regrettable that the public 
|> often bases their fear of electromagnetic radiation on such misinformation.

	I feel that I have sufficient understanding of such things to have
designed a 200 watt thermal pumped CO2 laser using the a microwave heated
material as the thermal source.

	The point here is not comparison of credentials (and therefore
credibility), but one of stating that I *agree* and *have agreed* since the
start that microwave ovens are probably not a risk, and are certainly not a
risk in comparison to police radar, whose efficacy in causing testicular cancer
is still in question.

	The episode of "cooks your gonies", quoting my Uncle Stan, a physicist
and one of the inventors of microwave oven technology in the first place, was
offered as a humerous diatribe, of equal anecdotal value to the anecdotal
evidence offered, up until that point, to support the position that microwaves
and/or police radar do not cause cancer.  The point, which was apparently too
subtle for the grasp of most, was that in the absence of verifiable evidence
for one position or the other, anecdotal evidence was equally useless on either
side of the equation.  Perhaps you missed the "8-)" character sequences, which
are customarily indicative of "The preceeding was of humerous content".

	The assumption seems to be that, by virtue of relation to this person,
I am claiming expertise to which I do not otherwise hold title, or that I share
his views on the subject.  Certainly I do not, and I do not claim status as
physicist by relation to a physicist.  I so claim this status by education, as
I claim my status as a mathemetician and computer scientist.

	That you believe the readers of sci.med incapable of drawing a distinction
between anecdotal information and evidence, even were they so dense as to not
recognize the intended humor (which, for the most part, was so flagged), speaks
not of culpability on my part, but of your estimation of them.


					Terry Lambert
					terry_lambert@gateway.novell.com
					terry@icarus.weber.edu

---
Disclaimer:  Any opinions in this posting are my own and not those of
my present or previous employers.