From: ornitz@kodak.kodak.com (Barry Ornitz)
Subject: Re: ******** MICROWAVE HAZARDS ******* [Pacemakers]
Followup-To: sci.med
Summary: Modern ovens are safe.  Your uncle may not be...
Keywords: microwaves, radiation, leakage, interlocks
Organization: Eastman Kodak Company, Eastman Chemical Company Research Labs
Distribution: net
Date: Fri, 21 Aug 92 21:45:07 GMT

In article <1992Aug21.164835.14121@gateway.novell.com> 
terry@thisbe.Eng.Sandy.Novell.COM (Terry Lambert) writes:
>In article <8k_nd4_@dixie.com> jgd@dixie.com (John De Armond) writes:
>>terry@ithaca.Eng.Sandy.Novell.COM (Terry Lambert) writes:
>[ .. Uncle Stan who invented microwave ovens refuses to have one in house ... ]
>>Senility, perhaps?
>
>	A pacemaker would be a better reason, since apparently there are
>enough emissions from a microwave oven to fry them, but he doesn't have a
>pacemaker.  Also, he didn't say "Stops your pacemaker!", he said "Cooks your
>gonies!".  Amazing that pacemakers can be fried even with the hand dandy Tandy
>device says they're not leaking.
>
>	Given an absence of personal investigation by myself (I'll probably
>haul some real equipment down the hall or confiscate the microwave for a bit
>now that there is a "controversy" 8-)), I have to take the word of the
>inventor of the things that they are "bad", and do what I usually do:  rely
>on the inverse square law to keep me out of harms way by making sure I'm
>not in the immediate area when a microwave oven is running.  Besides, the
>high frequency sound drives me nuts.  I can barely stand < 70 Hz computer
>monitors from the noise.

There is a considerable amount of confusing information and outright 
misinformation here.  Perhaps I can shed some more light...

Home microwave ovens do NOT have enough leakage to affect pacemakers.  Stuffing
your uncle into the oven and turning it on might, however.  ;-)  It would take
a fairly high power level to provide enough microwave energy to penetrate the
chest cavity deep enough to affect a pacemaker.  I would worry far more about
using a cellular telephone if I had a pacemaker that was affected by radio
energy.  The real problem with pacemakers and microwave ovens is the magnetic
field used by the magnetron in the oven.  Many pacemakers are "tuned" by
using external magnetic fields.  Since virtually all microwave ovens use
permanent magnets in their magnetrons, this problem may occur if the oven is
on, off, or even unplugged!  We have nice warning signs on the doors where
our analytical laboratories have NMR machines with their big superconducting
magnets but the signs clearly state the danger to pacemaker wearers is a
magnetic one, not radio frequency energy.

I have tested a number of home and laboratory-grade ovens with professional
Polarad field strength leakage monitors.  I have never found any new oven to
be even close to the acceptable leakage limits - most were two orders of
magnitude below.  After considerable use, leakage increased slightly but it
was well below the published limits.

By Federal law, microwave ovens must have interlock systems and door seals
that can withstand considerable abuse.  It can almost be said that if the door
can be shut and the oven operated, it must pass the leakage test.  Most home
microwave oven doors use what is called a choke-flange seal to prevent leakage
without having to have a mechanical seal.

The very early (1950's) ovens did not have the safety features found in the
modern ovens.  I doubt if you will find many of these still operating today;
where would you ever find the replacement magnetrons?

I do not understand your comments about sounds from the microwave.  Most home
ovens use a simple voltage doubler circuit with the magnetron tube as one of
the diodes.  The waveform is full of harmonics and I guess you might hear the
transformer buzz.  But the infernal microprocessor beeping is what annoys me!
Also how do you avoid flicker on your 70 Hz computer monitors?    :-)

Microwave ovens produce non-ionizing radiation.  Food heated by microwave
ovens is chemically quite different than raw food.  {Aha, you say!}  But
the differences are due to the heating, not the microwave radiation.  You
can virtually always find the same differences in food heated by other 
conventional means.  There are likely to be far less carcinogens in microwave
heated food than in food cooked over an open fire like our ancestors ate.

Quit worrying about your microwave oven and look at something to be really
worried about - the upcoming presidential election.  It is like the new fall
television shows.  Every year you ask yourself how the networks can come up
with something more stupid and inane than last year - but they always do!  Do
you watch the new shows or do you watch the re-runs of the old stupid shows?

For those of you who still wish to fry their pacemaker or "cook your gonies"
yet conserve energy, I suggest the Fry Daddio (r) personal grease cooker! ;-)

			Barry (who is getting quite cynical as he ages)

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|  ___  ________  |       Dr. Barry L. Ornitz          WA4VZQ
| |  / /        | |       Eastman Kodak Company
| | / /         | |       Eastman Chemical Company Research Laboratories
| |< < K O D A K| |       Process Instrumentation Research Laboratory
| | \ \         | |       P. O. Box 1972, Building 167B
| |__\ \________| |       Kingsport, TN  37662       615/229-4904
|                 |       INTERNET:   ornitz@kodak.com
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