Microwave Ovens and EMR Exposure Precautions

/ / Environmental Testing, Healthy Building Inspections & Testing
EMR from microwave ovens

Microwave ovens work due to the fact that radio-frequThis technology is in the majority of homes and businesses. Precautions to reduce exposure of EMR from microwave ovens encies/microwaves produce dielectric heating of water molecules when produced with enough wattage.  This effect generally affects outer 1” to 1-1/2” of the foodstuff’s water molecules, hence the reason reheating a thick ribeye may require cutting it into thinner sections to reheat it thoroughly.

This dielectric heating effect was discovered accidentally by and engineer working of Raytheon who was working on radar systems.  While working on an active radar system at his desk, he noticed that the chocolate candy bar in his pocket melted.  So he started testing on other foodstuffs and shortly thereafter Raytheon filed a patent for the microwave cooking process. Now, this technology is in most homes and businesses.  This bog will cover precautions to reduce exposure of EMR from microwave ovens.

Seemed strange to me that he noticed the chocolate bar melted in his pocket but he didn’t feel the front of his body feeling warm. (It turns out that most microwave radiation penetrates below the layer of skin that detects thermal changes.) Anyhow, I digress…

Microwaves (aka RF radiation), due to their specific wavelengths, have difficulty fitting through small apertures.  This is the reason for the mesh or grid that allows you to look into the microwave. Given that when the aperture is one-half (or less) the distance of the wavelength of the microwave radiation, it does not penetrate the grid easily.

This is not to say that it does not penetrate the grid at all however. While the foodstuffs inside the microwave oven are bombarded with 800-1500 Watts of microwave energies, at 5’ away, through the shielding grid, a person will still be exposed to levels of roughly 200 milliWatts per square meter (mW/m2). And, 10’ away, through the shielding grid, a person is still exposed to levels of roughly 50 mW/m2. (The values for this test were performed on a GE brand 1500 Watt model microwave oven. The experimental values follows true to the theoretical inverse square propagation of an electromagnetic point source.)

So, the shielding grid does shield much of the microwaves out!  But, is it enough?  And can something be done?

Based on the more healthful guidelines that Building Biology adherents agree to, levels past 1 mW/m2 is concerned to be a high or extreme concern for long-term exposures.  Working in the kitchen alongside a microwave can easily expose a person to levels of 200+ times this standard when the microwave is active.  Understandably, some people are concerned about even intermittent exposures to levels this high.

(In full disclosure: the US FCC considers levels below 4600 mW/m2 to be safe. However, the FCC’s guidelines are based mainly on the dielectric heating effects of microwaves/RF radiation, they are not based on long-term epidemiological studies.)

Though the shielding grids are very effective, there is so much RF radiation being generated that the shielding cannot block all of it.  Therefore people consider microwave ovens ‘leaky’. EMR from microwave ovens can be minimized by following some precautions.

My personal experience investigating microwave radiation onsite has shown that all microwaves do leak RF radiation.  GE brand microwaves seem to be especially bad, however this may be due to models I have tested of GE’s being higher wattage models than the other brands I have tested.  In the perfect world, it would be possible to go to Best Buy and sample a few dozen at once, but alas they do not leave them plugged in.

In using microwave ovens, it is recommended to realize these things and follow these practices to reduce exposure of EMR from microwave ovens:

  • Microwave ovens only leak RF radiation when they are ‘on’. (I say this because some clients have believed they emit microwave (RF) radiation even when ‘off’.) There is no problem being near it when it is ‘off’.
  • Minimize the use of the microwave.  It is hard to deny that they are handy in some cases though!
  • Once you do activate the microwave, however, step back to at least 10 feet until it is finished.

If you are serious about keeping exposure of EMR from microwave ovens to a minimum: If you happen to buy a countertop version, rather than an overhead version, it is possible to make an RF shield that would fit over the microwave’s front, top and sides, a half-cozy per se.  It could be placed on the microwave when it is activated and easily removed after if it was finished operating.  This would effectively shield the front, top and sides by reflecting the microwave’s leaking radiations down or to the back.

EMR from microwave ovens

EMR Shielding Fabric

There are RF-shielding fabrics with silver or carbon thread woven into it that shield against RF radiation roughly 97% in lab tests. In real world testing I would anticipate a reduction in the range of 70%, though I have not attempted this myself.  This may develop into an in-house test for a subsequent or sequel blog.

There are a few companies that sell these fabrics, however we prefer Safe Living Technologies out of Canada. They seem to have the best prices and best customer service. A direct link to their products page is: http://www.slt.co/Products/, and if you use this promotional code: C10G8-HBI, Safe Living Technologies will offer 10% off to you.

For more information on the possible health effects of microwave/RF radiation: