Despite having been debunked time and again, plenty of myths persist over the safety of microwave ovens. That’s not what this article is about, but let’s clear the air, before we get to the question of how to choose a safe microwave and which microwave oven is the safest.
In short, microwaves don’t make food radioactive, don’t destroy the nutrients in food any more than other cooking methods, and don’t cause cancer or other health issues. That is, if they’re in good condition and are used properly. Want to learn more? Check out the easy to understand explainer on microwave radiation from The Health Sciences Academy.
Now that’s out of the way, what about the question of how to use a microwave safely. And how can you choose a safe microwave?
First things first, do you even need a new microwave? The answer is almost certainly yes if:
- You’ve had your microwave for more than 10 years
- Your microwave has faulty doors
- There are spots of rust on the door seal or interior cavity
- Your microwave glass window is cracked
- There are any other obvious faults with the microwave that can’t be repaired and that may allow microwaves to leak during operation
To reduce resource consumption and save money, you might consider getting a broken microwave repaired. If you bought the microwave recently or it’s still within warranty, that’s definitely your best bet. However, if your microwave model has been discontinued, the parts needed for repair may no longer be available. You can check in with a local electronics repair service for guidance, or, ideally, call the company who make/made the microwave.
Why is it important to replace or repair a broken microwave?
It’s important to keep your microwave in good repair not only so it’s better at cooking your food but also for safety. In short, a microwave that isn’t working properly or isn’t properly sealed poses a higher risk of leaking radiation.
One way to test if your microwave is liable to expose you to excessive radiation thanks to a poor seal is to put your phone in there. Yep. Don’t cook it, though. Instead, call your phone from another device while it’s in the microwave with the door shut tight. If it rings, your microwave is clearly letting radio waves through. Also, try making a call over WiFi. Why? Because the electromagnetic frequency needed for these calls is different to that used by a regular cellular phone call.
There’s a reason why spy movies show people putting their phones in the microwave during confidential conversations.
If you run these tests, or use a meter and discover that your microwave is leaky, either fix it or replace it.
Even if your microwave isn’t broken or clearly leaking, keep your distance anyway. That’s because if you’re standing with your nose pressed up against the window as your food turns in circles on the microwave plate, you are at a much higher risk of exposure to microwave radiation compared to if you stand just half a meter away. Microwave energy dissipates over greater distances. So, keep your distance (50 cm ideally) from a microwave during operation and make sure you fully close the microwave door before pressing the ‘start’ button.
Microwave leakage is more common when a microwave is dirty, damaged, or modified improperly, especially if this means that the door doesn’t shut properly. Rust and dirt can affect the seal around a microwave door or other area of the oven. As such, it’s important to remove any food residues after each use and keep the microwave clean and dry. Any areas of damage should be properly assessed and addressed by a qualified service engineer or, if the damage is too extensive, the oven should be replaced.
So, why is it important to avoid microwave leakage? Put simply, it’s because you don’t want to cook yourself in addition to cooking your food. Microwave ovens cook food by transferring energy to the molecules in the food, making them vibrate, which causes friction. It doesn’t change the molecular structure of food, and it won’t change the molecular structure of your body, but it can produce heat in exposed human tissue.
The tissues most at risk of microwave damage are the eye, where a poor blood supply is combined with poor temperature control, and the testes, which are temperature sensitive. So, don’t stand beside a microwave at waist height or stare into the microwave while it’s on.
All this said, thermal damage would only happen if tissues were exposed to very high power levels for a very long time. And such levels just aren’t emitted from microwave ovens, thanks to regulations (and some common sense). Instead, you’re more likely to be injured when removing hot food or drinks from a microwave or by a fire related to a microwave oven (more on this below).
Who regulates microwave oven safety?
The US Food and Drug Administration is, oddly, tasked with regulating the safety and performance of microwave ovens in the US. Through the FDA’s Center for Devices and Radiological Health (CDRH), they set standards to ensure that radiation emissions do not cause a public health hazard.
The current federal standard (21 CFR 1030.10) limits the amount of microwaves that can leak from an oven throughout its lifetime to 5 milliwatts (mW) of microwave radiation per square centimeter at approximately 2 inches from the oven surface. Measuring 20 inches away from the oven (50 cm) would give an emission level around 1/100th of that measured at the 2-inch mark. And, that 2-inch level is set far below the level known to cause harm to human health. In fact, this limit is pretty much there only to establish a baseline for compliance from manufacturers.
So, are there actual exposure limits to help us figure out which microwave ovens are safest? Thankfully, yes. The International Commission on Non-Ionizing Radiation Protection (ICNIRP) has published guidelines on exposure limits for the whole spectrum of the electromagnetic field (EMF). For microwaves, exposure guidelines are set at a level that prevents any known adverse health effect. For workers, and consumers alike, levels are set well below that where any harmful heating might occur. These emission limits are consistent with the FDA’s limits, as set by the CDRH.
The FDA’s CDRH also requires all microwave ovens to have two independent interlock systems that prevent a microwave from producing microwaves if the door is open. The system cuts off microwave production if the door latch is released or if one or both of the interlock systems fail. Microwave manufacturers are also required to install metal mesh in the window of the microwave to minimize emission leakage.
Now, here’s one sneaky tip for figuring out which microwaves are the safest. The FDA requires all microwave ovens to have a label that clearly states that an oven meets the safety standards and that lays out precautions for proper use. But, if the manufacture of the microwave has proven that the oven will not exceed that leakage limit even if used in a way that the operating label warns against, the FDA may drop the requirement for that label.
What does that mean? Well, it may mean that a microwave oven sold without a label clearly explaining precautions may be pretty darned safe even if you use it improperly (not that I’m advocating you to do so; indeed, quite the opposite). Unfortunately, in days of research, I’ve not found a single microwave that doesn’t feature these safety alerts. If you spot one, let me know!
And, for once, the FDA actually runs its own tests on microwave ovens in its own laboratories. The FDA also assesses the quality control programs and radiation testing protocols used by manufacturers. UL also test and certify products for companies to make sure they meet certain standards, with the ASTM International and the American National Standards Institute (ANSI) providing a framework to develop those standards. Saying something is UL-tested is not enough to guarantee safety; it’s a bare minimum.
So, one other thing to consider is where a microwave is made. Manufacturing standards in the US, Canada, and Europe are much higher than in China and many other parts of Asia. While companies claim to be trying to improve standards across their manufacturing facilities, to ensure that US safety standards are met wherever their products are made, there’s no guarantee that this is actually the case. As such, buying a microwave oven made in the US, Canada, or Europe seems a safer bet all round.
All in all, microwave ovens are one of the healthiest ways to cook food, and one of the most energy efficient, assuming you use them properly. Think about it. The size of your microwave is far smaller than the whole of your oven compartment. What’s more, it takes a fraction of the time to cook food in a microwave than it does in your oven. This shorter cooking time can also mean fewer nutrients are lost when cooking in a microwave! And by cooking without extra water or fat, you may further reduce nutrient leaching and dietary fat intake.
Microwaves and WiFi
One thing you may have noticed if you live in a smaller apartment, tend to work in the kitchen, and often use the microwave while also using the internet is that your download/upload speeds may suffer when your microwave is on. Why? Well, because microwaves operate on the same 2.4Ghz frequency as wireless internet.
Because they’re more powerful than your router or computer, most microwave ovens have the potential to interfere with a WiFi signal. And, if they leak, chances are even higher of interference. One slightly crackpot way to test microwave leakage without a meter, then, is to see if it takes longer to transfer a file over WiFi while your microwave heats up a cup of water, compared to when it’s inactive. For a fun experiment, check out this video.
This shared spectrum is why you may see some mention of WiFi interference in microwave oven reviews. In general, if folks are complaining about interference, there’s a strong likelihood that the microwave is leaking emissions. If there’s no interference, this may be a decent indication of a good seal and low emissions. All this said, the only way to actually test microwave emissions is to use a proper meter, especially as other factors (such as your other devices and your neighbors’ devices) can also interfere.
How to use a microwave safely
Never run an empty microwave. Without something in there to absorb the energy, the microwaves reflect back to the sides of the unit and can cause arcing, sparking, damage, and possible fire. And don’t store items in the microwave as these could cause problems if the microwave turns on accidentally.
Safe use of a microwave also means choosing appropriate cookware. Your best options are glass, porcelain, or enamel cookware as microwaves pass through these to heat food instead of cookware. Yes, the cookware still gets hot, but this is from the transfer of energy from heated foods to the cookware.
Avoid using paper products in the microwave, unless they are specifically marked as microwave-safe. Some paper products (particularly recycled paper, including recycled paper towels) can contain impurities that can spark inside a microwave and cause the paper to ignite.
It’s also best to avoid using plastics (especially soft plastics) in microwaves as these can melt as food heats up and leach chemicals into food. They may even burst into flames in some cases. Some plastic containers and plates are marked as microwave-safe, but to be safe, I’d still suggest using enamel, porcelain, or glass cookware if you can.
Also avoid using metal cookware, including aluminum foil, as these reflect microwaves back at the oven, cause food to cook unevenly, and could potentially cause sparks and damage to the microwave and to you or anyone else nearby. I once watched a friend at university put an unopened tin of beans in the microwave and had to quickly intervene. She hadn’t grown up with a microwave and simply didn’t know how unsafe this could be. Melamine cookware is also a no for microwaves as it actually absorbs the energy and gets very, very hot.
Need to know if a container is safe for microwave use? Try the container test (not suitable for plastic containers): Fill a microwave safe cup with cool water and place it in the microwave oven alongside the empty container to be tested. Run the microwave for one minute on high power. If the container is microwave-safe it should stay cool, while the water becomes hot by absorbing the energy instead of the container. If it gets hot, the container has absorbed the energy and is not microwave-safe.
How to cook food and heat drinks safely in the microwave
Other microwave health hazards include super-heated boiling liquids. Water heated by itself beyond its boiling point in the microwave will not look like it’s boiling as steam doesn’t escape in the same way in a microwave as it does when boiling water on a stove.
Disturbing the water slightly, such as by picking up the cup, or dropping in some sugar or instant coffee, can cause a violent eruption of boiling water from the cup. This can cause burns or scalding if you’re not prepared. To lower the risk of this happening, remove water from the microwave using hand protectors and/or let it sit for a moment. Also, add your instant coffee, sugar, or other items before heating the water.
Another thing to watch out for with microwave cooking is the peculiar behavior of foods with non-porous surfaces, such as hot dogs, apples, potatoes, or eggs or chestnuts cooked inside their shells or skin. The different parts of these foods heat unevenly, which can lead to explosions and a risk of burns (and mess!).
Heating baby formula, milk, or food in a microwave is also generally ill-advised. This is because while the outside of a baby’s bottle or other food or drink vessel may feel warm to the touch, the contents may be hot enough to burn an infant.
Other safety considerations for microwaves
Finally, given that some microwaves can get quite hot to the touch on the outside, take care not to store anything on top of or right beside the microwave. The microwave’s ventilation grill(s) should also be free from obstruction.
So, take care when choosing how and what to microwave and, again, make sure your microwave is in good working order and stand at least 50 cm away when it’s in use. Oh, and don’t operate a microwave oven empty. This can cause microwave energy to reflect back into the magnetron which may damage it.
Some researchers have also taken the step of using one of the EMF meters to test microwave emissions. While interesting, I don’t feel this is strictly necessary, given that any microwave on the market in the US has to have been tested by the FDA. If you’re at all concerned, go for a bigger brand and a model that’s been on the market for a few months or more as this makes it more likely that the microwave has been tested and that any problems will have already made themselves known.
Now you’re an expert on using your microwave, which model is best for your needs? Let’s look at which microwave ovens are the safest, and which microwaves to avoid.