Wednesday, 29 August 2007

Bad Medicine and Microwaves

I have just finished reading Christopher Wanjek's Bad Medicine, a book that in my opinion everyone on the planet should read. It is thoroughly well written and well set out with easy to understand debunking of most health fallacies.

However a review of the book is not my main reason for this post. One of the topics covered was radiation and the worry people have of microwaves. Chris covers the topic well but I realised something rather ironic when I read this section and that is: Infra-red (IR) radiation has a higher frequency than microwaves so standing in front of the stove while cooking is more likely to cause cancer than the the microwave.

For the physics of it all, electromagnetic radiation (light, UV, IR, microwaves, gamma rays, x rays and radio waves) interacts with matter as a photon. The energy of a photon is determined by the frequency of the radiation.

There is a cutoff in energy level for a photon to remove an electron from an atom (called the photoelectric effect), and this is required for their to be any harm (esp. to DNA) other wise the only effect is heating (which is short term and goes away as soon as you remove the source of radiation i.e. cell phone).

Now the cutoff frequencies for this is in the spectrum of visible light, so anything with a lower frequency (IR, microwaves, radio waves)than this is not going to do any lasting damage (like cause cancer).

So to reiterate, although neither is going to cause cancer, IR radiation from your stove top is more dangerous than your microwave.


Margaret said...

"...IR radiation from your stove top is more dangerous than your microwave."

Thanks, I'm going to use this next time some idiot talks about the imaginary evils of cooking in a microwave oven.

mc2 said...

Unfortunately there are too many people out there like that, but if we can educate some of them then maybe the world can be a better place

Anonymous said...

I don't think you are correct in stating that the IR radiation form a stove is more dangerous than microwave radiation. There are three reasons for this:
1) The cuttoff where radiation becomes ionizing is fairly sharp. Any radiation below that fequency will not cause any ionization damage so IR and microwaves both cause exactly the same amount of damage (i.e. zero).
Thank you for taking the time to write this blog.
2) As you point out, the only damage that can be caused is heating. This damage only becomes a problem if it causes temperatures to raise to dangerous levels within the body. Since the microwave oven uses only radiation to transfer heat to foods, and your stove uses primarily conduction, the total heat energy that the microwaves can deliver using radiation is much higher than what the stove can deliver.
3) Because your skin is opaque to IR radiation, but transparent to microwaves the microwave oven can deliver the heat direcly to ones internal organs which is much more dangerous.
This is why microwaves are sheilded and stoves are not.
Don't get the wrong idea, I am a huge advocate of microwave ovens. I believe that on the hole they improve nutrition since they make cooking healthy foods, such as vegetables, much easier.