Tonight, a friend of a friend came over to my apartment so we could all make chili together. During this process, we came to a point when we needed to defrost a bunch of ground beef. When I moved to the microwave to get that going, Friend-of-a-Friend says to me, “You know, you can also defrost meat in a bowl of warm water. That’s healthier for you.”

Usually the method I choose by which to defrost meat is governed by how long I feel like waiting for dinner, and how much I am thinking ahead. But I was curious about this new rationale, so I asked Friend-of-a-Friend to explain how the warm-water method is healthier than punching the “defrost” button on my microwave. “Well,” this person says, “one is cooking with radiation, and one isn’t.” Then they shrug and make a waffling gesture with their hands. “Ehhhh…” The implication was clear.

Something about this situation bugs me. Here is a person who has enough scientific knowledge to see that there is a connection between microwaves, radiation, and certain health concerns – but not enough knowledge about these things to realize that they have constructed a problem or fear that has no justification.

Microwave ovens work by bouncing radiation with a wavelength of a few centimeters or so around in a cavity. This wavelength lines up nicely with some of the vibration modes of water molecules, and the vibrations thus excited get passed along to food as heat.

Ionizing radiation can cause health risks in a number of ways, including killing things outright at high enough doses. However, the more relevant concern at the low levels of radiation found in a household appliance would be that the radiation could damage the structure of some cells’ DNA, and those cells would run amok – becoming cancer.

However, microwave radiation is non-ionizing: it is not energetic enough to do much more than excite molecular modes or maybe kick a few electrons into a valence band. It can’t cause any more direct damage to you than a walkie-talkie does by blasting you with radio waves, or a household radiator does by bathing you in infrared radiation. Furthermore, it can’t cause any damage to the DNA or cell membranes in the steak or pork chop or broccoli cut or baked potato or whatever else you put in your microwave oven. Even with ionizing radiation, irradiating the steak doesn’t make it radioactive. The result you get is a hot steak, not a carcinogen.

So, here is a person who knows that microwaves work by radiation, and that radiation causes cancer. But this person doesn’t realize that the physical mechanisms in each case are different, that the food cannot transfer the effects of radiation to you by being eaten, and that there is no syllogism here. But I wonder just how pervasive this kind of thing is: would this person be surprised if I shined a flashlight on them, and then announced – accurately and truthfully – that I was irradiating them? And how many other people are out there with similar misconceptions?

It strikes me that this sort of incomplete knowledge is a little dangerous, because it creates fear where none should exist. And there are many forces out there that would love for us to receive only partial knowledge, because then we can be driven by those constructed fears. If only more people could be motivated to pursue a fuller understanding of science…

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