Radiation and Microwaves

Health!  Wealth!  Happiness!  I’m Dr. Michael Greger and you’re listening to the Nutrition Facts podcast.  And while I can’t promise you all of those things – if you take a listen to the evidence-based nutrition found in this podcast, chances are you’ll learn something that you can use to make a positive change in your diet and in your health.  My job here is to bring you the information you need to make that reality possible.

In our episode today, we’ll take a look at something you may have always had a sneaking suspicion could be bad for you–the radiation from microwave ovens.  As it turns out, the hazards of microwaves may not be what you might expect.

When people have asked me if microwave ovens are hazardous, my typical snide response is, “Yes… if, you drop them on your foot”. But, it turns out that’s actually a real thing. Hundreds of Americans end up in the emergency room every year because a microwave dropped on them. Or, they hurt their back trying to lift one, or falling onto a microwave oven—I’m not sure how that works; maybe they like tripped on it? But, the majority of microwave injuries involve scalding oneself on hot foods or liquids.

But, when people go to PubMed and search the medical literature, and see all these scary-sounding titles about the “hazards of microwave ovens,” they may not realize that these are like articles about jelly doughnuts: “Hazards of a microwave oven. …An adolescent patient…, ravenously hungry, rushed home from school for his afternoon snack,” found a jelly doughnut, popped it in the microwave. The outside was just “comfortably warm,” and so, he “gulped [it] down”—before the “searing pain” started from the burning jelly inside, and he had to go to the hospital.

And, that’s the tricky thing about microwave cooking. You know, with conventional cooking, the outside is hotter than the inside. But with microwaving, the inside can get burning hot, even while the outside remains relatively cool.

Now, there’s still a lot more kids getting burned from regular stoves. The “injuries related to stove use vastly exceed those associated with [microwave ovens]”—over a five-year period, about 40,000, compared to 5,000 with microwaves. And, the stove burns tend to be more severe as well.

In fact, you know how you’re never supposed to heat infant formula in a microwave, since you may not be able to judge the heat of the contents just by feeling the outside of the bottle? Well, if you heed that warning, and use a pot or bowl of hot water to warm it instead, you may actually end up with higher burn risk, from accidentally knocking over scalding water. So, what’s their solution? They suggest not warming it up at all, and that it’s basically just a cultural thing that we feel the need to warm it. Or, even better, how about not bottle-feeding at all, and go for scald-proof milk at perfect body temperature?

And, when it comes to food, whether it’s a jelly doughnut, or jelly roll, or “microwaved treacle tart,” or a “cheese-pie”—basically, anything that’s kinda soft in the middle can present a problem. But look, anytime there’s anything liquid inside, can’t you just open it up and let it cool before you eat it? What’s the big deal? That brings us to: “The case of the exploding egg.”

“Although there are many mishaps…regarding the microwave, the most pertinent for pediatric patients seems to be the exploding egg. When heated in the microwave, the…yolk absorbs the energy,…getting overheated and pressurized.” Both “the yolk membrane and shell acts as a [pressure] barrier,” and “[a]ny disturbance…can [make it go boom]. There have even been cases [in which the shells] have been cracked” open, but then it still explodes when “the yolk membrane [was] pierced with a fork.” And, “[t]he explosion [can be] so powerful and sudden that it exceeds the blinking reflex [leaving] the eyes unprotected,” which can lead to vision-threatening injuries. “Ophthalmologists should be aware of this serious risk and caution the public against the dangers of cooking eggs in microwave ovens.”

But, come on. How common is this? There’s all sorts of quirky case reports in the medical literature, like people getting eye injuries from eggs thrown around on Halloween or something. But if you do a search, there do seem to be a bunch of papers on exploding eggs. But, I figured the best way to tell if this was a real phenomenon would be to search on YouTube, and holy moly: 25,000 videos, including one with more than a million views. Do not try this at home.

There’s even an article, in a journal on teaching physics, about how to use microwave ovens to perform “exciting demonstrations,” like “spectacular [egg] explosions” denting the metal wall, blowing the door open, and making the whole oven jump up. Now, if the eggs just exploded inside, that’s one thing, but the problem is that it can happen at the table. You sit down to eat them and then—boom. The majority of egg injuries are to the face, eyes, and nose, but it can also explode straight into your mouth, then put you in the hospital.

“Microwave oven manufacturers evidently “specifically warn against microwaving eggs…intact…and advise [not only] removing the…shell [but] piercing the yolk…prior to cooking.” Even reheating can be a problem, causing a serious-enough injury that this group of ophthalmologists were like, look, forget just putting it in the instruction manual; maybe there should be a warning about eggs “on the microwave…itself.”

Simple kitchen experiments confirm that microwaves do leak from microwave ovens during operation, but do they pose a health risk?

About 20 people a day end up in American emergency rooms from “microwave oven-related injuries”, a few from microwave popcorn steam, overheated “hair removal wax,” nearly one-a-day from exploding eggs; but most are from overheated water. See, when you boil water on the stove, “bubbles rise from the bottom, and as they burst…, the excess heat is dissipated. Water heated [in] a microwave oven [though may] not bubble,” and so, can get even hotter than normal boiling temperature. Then if you sprinkle in some powder, “tiny air bubbles are carried into the [liquid],” and can expand into steam bubbles, and erupt onto your hand. The FDA warns to be careful when trying to boil water in a microwave—particularly in a “shiny container [or] more than once,” or for too long, or when not letting it cool down a bit first, or when dumping something into it.

Most “microwave-related burns in young children occur” when the child reaches in to grab something hot. Toddlers “as young as 18 months can open a microwave.” So, some public health advocates have recommended that instead of just warning people to let stuff cool first for a few minutes, there should be some kind of door lock that doesn’t even let you open the thing for two minutes after it stops—which kind of undermines the whole point of quick microwave convenience. A better idea may be to just kind of childproof the door, so you have to like turn a knob while pressing a button to pop the door open.

When people express concerns over microwave oven safety, though, they are probably not thinking about exploding eggs or hair wax injuries; they’re concerned about the microwave radiation itself. Microwave oven manufacturers caution people not “to operate [the] oven with the door open.” But, there are interlocking safety switches that should turn it off automatically when you open the door, unless, you’re stuck inside one. God, I couldn’t even read that article.

There is some leakage of microwave radiation, though, during operation. There’s this famous radio telescope scanning the cosmos for extraterrestrial civilizations. “Fast radio bursts” were detected. A sign of “extragalactic” intelligence? Nope, turns out ET was a microwave in the staff cafeteria that the telescope caught when it was just at the right angle, right when someone yanked the door open.

You don’t need a radio telescope to see it, though. A “cheap way of detecting microwave oven leakage is to [just] place a computer monitor next to the oven,” you can see “disturbances on the screen.” Or, just use the microwave detector you have in your pocket or purse right now–cell phones. Look, if microwaves can leak out, then they should also be able to leak in. The microwaves are actually quite similar in size, the wavelengths, though obviously different intensity between microwave ovens and cell phones. So, stick your phone in the microwave—DO NOT TURN THE MICROWAVE ON, but close the door, and see if you can call it. When you hear it ringing, that’s confirmation that microwave-type radiation can leak in and out.

And indeed, you can just directly measure the leakage during operation—though nearly all within prescribed safety limits. And, once you move the detectors like a foot away from the door, the levels fall nearly to zero, even if there’s like some food particle or something caught in the door seal. Now, the industry will tell you that “there has never been any verified case of [human] injury due to exposure from [radiation] leakage from microwave ovens.” This is from a guy at Raytheon, though, where the microwave oven was invented, after an engineer in a radar lab noticed the chocolate bar in his pocket had melted.

There has been the rare case report of a malfunctioning machine that didn’t turn off when the door was open, and someone burned themselves, but this was after her hand was in there for like a full minute. Raytheon engineers talk about how they “inadvertently” exposed themselves lots of times to open, active microwaves. They get a warm tummy; they feel a little “transient warmth” when they pass their arm in and out of the oven. But, no big deal, they say.

In fact, the same microwaves used in microwave ovens are “the same…used [for] medical microwave diathermy,” which physical therapists use like a hot pack to treat like rotator cuff injuries. Now, making the claim that, “Well, if the medical profession uses it, it must be safe” isn’t exactly the strongest argument, but does help to put things in perspective. “When the heating of people is not deliberate,…it [may be] desirable to limit exposure.”

Is that “minor leakage” during operation anything to worry about, though? In other words, are there non-thermal effects of microwaves? If it doesn’t burn you, can it still hurt you? The Soviets thought so, irradiating everyone in the U.S. Embassy in Moscow for decades.

In terms of microwave ovens, though, the only report I could find was from over 40 years ago: a case report of a woman who developed cataracts after using a leaky microwave oven. But, that’s all there was, just this kind of circumstantial evidence correlation. Lots of people get cataracts; lots of people use microwaves; there has to be more that.

The only follow-up study I could find was the Turkish study published a few decades later—but, it was on rats.  Now, they did end up finding some superficial eye abnormalities on the rats placed next to the microwave, but they were like right up against the door, and people don’t tend to stick their faces right up to the glass while things are cooking. So, even if the same thing happened to human eyes, this study might be of limited relevance. But, it can’t hurt to stand back from the microwave while it’s on. Otherwise, microwaves should be safe, unless…you drop it on your foot.

To see any graphs, charts, graphics, images or studies mentioned here, please go to the Nutrition Facts podcast landing page.  There you’ll find all the detailed information you need – plus links to all the sources we cite for each of these topics.

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Thanks for listening to Nutrition Facts. I’m Dr. Michael Greger.

This is just an approximation of the audio content, contributed by Allyson Burnett.