Mythconception: microwaves make food radioactive

For this week’s mythconception, Izzie Clarke’s been boiling down the science of microwave ovens...

Izzie - If you’re like me, after a long day you come home starving and the last thing you want to do is spend ages making dinner. Thanks goodness for the trusty microwave oven - the saviour of leftover takeaways. But wait… it’s using microwaves to resurrect my corma and microwaves are radiation. Does this mean, because of my microwave oven, I’m eating a cancer inducing curry?

No, no it doesn’t. So let’s turn up the heat on this mythconception. Let’s start with radiation. It’s all around us in varying amounts and is, essentially, the release of energy. It occurs naturally, but radiation can be given off by everyday items too like from the Sun. Yep, that’s radiation and if you called your mum today radiation was there too. But that doesn’t mean you’re in constant danger. All forms of radiation can be placed within a spectrum - the electromagnetic spectrum. Within this microwaves are fairly low down and, therefore, low in energy.

But how is the food actually heated? When you hit that reheat button, a small wheel-like device, called a magnetron, gets to work. It’s heated core emits electrons that circulate through a constant magnetic field. They seep through small hole-like cavities at a frequency of just under 2.5 billion times a second; this produces a change in field that frazzles our food.

When you nuke your dinner your dinner, it’s actually the water molecules in your food that absorb this thermal energy. It causes them to rotate back and forth and it’s the friction between these molecules that creates heat. Unlike X rays which, in large amounts can be damaging, microwaves are non-ionising radiation and that’s a good thing. This essentially means that whilst the rays have energy, it’s not enough to boot electrons from their atoms and change the chemical structure of your food.

One of the earliest studies into microwave food actually found that no adverse effects were found on the diet cooked by microwaves compared to those cooked conventionally. But be warned, over a ten year period, 21 individuals a day in the US were treated for microwave related injuries, but the majority of cases were for scalding spillages. So, whilst your food won’t be radioactive any time soon, it’s best to pop on some oven gloves before you eagerly took into those leftovers.

Katie - Thank you Izzie, If you have some science you’d like scrutinised, please drop us a line tochris@thenakedscientists.com, you can tweet us @Nakedscientists or find us on facebook and we’ll take a look.