For an appliance that exists in 97% of American kitchens, the microwave is a black box to most of us. Functionally, an oven is straightforward enough to understand (air gets hot; put food in), as is a dishwasher (put plate in; water rinses). But we stand before our microwaves equal parts wary and credulous, with the internet always ready to assist in the perpetual cycle of spreading and debunking every urban myth about them.
You might have been warned as a kid about all the Very Important Microwave Rules: Don’t microwave foil, don’t microwave utensils, don’t microwave plastic, don’t microwave anything for too long, don’t stand near the microwave, don’t open the door before pressing the stop button, cover everything you microwave to prevent splatter, but don’t cover anything too tightly, and for God’s sake, if you’re going to microwave bacon, put 8,000 paper towels underneath it to catch the grease. But none of these warnings really tell you what you need to know: Are microwaves dangerous, actually?
Glad you asked. The answer will cost you a strip of that bacon.
We’ve already covered how microwaves work in this handy explainer about why we can’t put metal in the microwave. Quick recap: Microwave ovens produce a type of light that vibrates water molecules in your food, and the energy of those vibrating, colliding molecules is absorbed into food in the form of heat. This also means that both beverages and foods with a higher water content heat up much faster. And according to the FDA, that’s what actually causes the vast majority of microwave-related injuries: We’re getting scalded by reaching for our overheated foods too fast. Can we really blame the microwave for that? It’s easily avoided. Just let the food sit for a moment after you hear the ding, and go conservative on your cooking times. You can always add a quick 30 seconds if needed. (Another note here: If a plastic container is “not microwave safe,” that doesn’t mean the microwaves themselves turn the plastic into something radioactive and dangerous. It just means that the hot food within the container can melt the plastic, the way it could if it were heated any other way.)
The microwaves that cook your food are being generated by a device in the back of the oven called a magnetron, which contains a small amount of radioactive metal to function. So, is that dangerous? Not really. As the World Health Organization notes, the part of the process that involves radioactive metal is separated from you and your food the entire time. The electromagnetic radiation happening inside the magnetron produces microwaves, which are shuttled through a tube into the food chamber while any potential toxins are safely contained behind the scenes. Indeed, the magnetron rests in a part of your microwave that you can’t even access with normal household tools—the screws and bolts separating you from the guts of your microwave are tamper-proof.
Because microwaves excite water molecules in your food, it stands to reason that humans, who are 70% water, could be badly burned by the same microwaves. True! But the FDA and the microwave manufacturers of the world are pretty good at making sure those waves don’t reach you in the first place. Modern microwave ovens are protected by two separate security mechanisms that shut down wave production the moment that any break in the door seal or latch is detected. That means you’re technically safe when you yank the microwave door open instead of pressing the “stop” button first—but it’s worth noting that, because the whole system had to enact an emergency override when you pulled open the door, you’re more liable to break your microwave by doing that repeatedly. (The “stop” button is there for a reason! Just use it!)
So, you won’t get burned if you sneak up on your active microwave and throw the door open. But what if you’re so excited about reheating your leftovers that you gaze upon them from close range while they warm up? Does standing in front of microwaves pose a risk? If the microwave is functioning properly, then no. The FDA’s Center for Devices and Radiological Health sets limits on the amount of microwave radiation that can leak out beyond the chamber of the oven. The federal limit is 5 milliwatts per square centimeter, and even that’s only permitted at a distance of 2 inches from the microwave. Even if you’re nose-to-nose with the thing, 5 mW is far, far less than any amount of microwave radiation capable of harming a human being. (For context, the food inside the microwave is being heated with somewhere between 500-1,100 watts of energy.) If you’re a skeptic who thinks that your microwave might be the one rogue appliance that decided not to abide FDA limitations, consider two things: First, the FDA tests the ovens in a controlled laboratory once the appliance manufacturer has already done so. Second, any leakage beyond 5 mW would probably point to a break in the door seal, and the door seal, remember, includes those dual safety systems that shut off microwaves when the seal is broken. So, never operate a microwave capable of functioning while its door is open, and you should be fine.
Do you have a pacemaker? No reason to worry about that, either. Pacemakers, like microwave ovens themselves, still suffer from the initial rumors that swirled around their debut. But modern pacemakers have hermetically sealed cases covered in enough insulated coating that these devices are pretty unequivocally safe around microwaves.
So, excluding typical injuries like burning your mouth on reheated pizza, here’s what we’ve learned you’d have to do to be harmed by your microwave:
- Bust into your microwave’s back end with a tamper-proof wrench and snort magnetron filament
- Become a contortionist, crawl into the microwave, then have someone close the door and select the “baked potato” setting
- Same as above, plus a fistful of forks
- Pouring water all over the wall socket it’s plugged into
- Any number of bad ideas that this user manual might accidentally inspire (see page 4 for the prudent advice, “Do not store combustible items... in the oven, because if lightning strikes the power lines it may cause the oven to turn on.”)
But we hope it doesn’t come to this. If your microwave is functioning normally, and you use it for cooking or reheating food in microwave-safe containers (never for YouTube pranks and viral experimentation), then no electromagnetic boogeyman will come for you. It’s an appliance just like any other: keep it clean and well-maintained, and it should treat you pretty well. As long as you remember to push the damn “stop” button.