Is Microwave Cooking Hazardous to Health?

The history of the microwave oven is a fascinating tale that, like many inventions, began serendipitously. At the end of World War II, Percy Spencer, an American engineer, was working on a device known as a magnetron, used in radars for detecting aircraft. One day, he noticed that a chocolate bar in his pocket had melted. Intrigued, he placed popcorn kernels in front of the magnetron, resulting in popcorn. Thus, the concept of the microwave oven was born.

The first model, dubbed the Radarange, was far from practical. Standing at 1.8 meters and weighing over 300 kilograms, it cost between $2,000 and $3,000—equivalent to $30,000 today. Initially, it found use primarily in military canteens and hospitals. It wasn't until the mid-1950s that microwaves began to penetrate American households. In Europe, widespread adoption had to wait until the 1970s. At that time, it was a luxury item, costing up to ten times the minimum monthly wage. However, with the rise of convenience foods and technological advancements, microwaves became increasingly affordable and ubiquitous, with 90% of French households now owning one.

But how does a microwave function? The underlying principle relies on the magnetron, which emits electromagnetic waves at a frequency of 2450 MHz. These waves penetrate food and oscillate its water molecules. This molecular agitation generates heat, thereby warming or cooking the food.

These electromagnetic waves are of the same nature as visible light, infrared, and ultraviolet rays, albeit invisible. They also belong to the same family as radio waves or those used by Wi-Fi. Their high frequency and short wavelength enable efficient heating of food.

So, is microwave cooking safe for health? Can one place anything inside it? The electromagnetic waves in microwaves are designed to agitate water molecules in food, generating heat. They neither render food radioactive nor destroy its nutrients more than traditional cooking methods. However, it is crucial to adhere to safety guidelines, such as avoiding the placement of metal objects in the microwave, to mitigate risks.

Popcorn serves as a fascinating example of how microwaves operate. Corn kernels contain water, lipids, and starch. When exposed to microwaves, the water molecules oscillate, the temperature rises, and the water turns into steam. This steam occupies more volume, increasing internal pressure. The starch is pushed towards the periphery and becomes viscous until the pressure becomes too great, causing the kernel to burst. This process occurs in less than two minutes.

The same principle explains why certain containers may explode in the microwave. If a container holding water-rich food is hermetically sealed, the steam pressure can blow off the lid. Hence, it is advisable to slightly open the lid or pierce the plastic film to allow steam to escape.

Regarding safety, microwave radiation can be harmful upon direct skin contact, but it remains confined within the appliance when the door is closed. A tightly woven grid on the door and the metallic enclosure of the oven, known as a Faraday cage, trap the microwaves inside.

It is true that metal and microwaves are incompatible. Metallic objects with protruding edges, such as tin cans or utensils, can generate dangerous electrical arcs. To mitigate risks, it is preferable to use containers made of plastic, glass, or ceramic. However, not all plastics are safe; some may release toxic substances like bisphenol A. Therefore, it is important to check the symbols on plastic containers to ensure microwave compatibility.

Finally, contrary to popular misconceptions, microwaves do not make food radioactive. Moreover, they help preserve the nutrients in food, much like steam cooking. When used correctly, the microwave is a safe and efficient means of cooking or reheating food.