They may seem innocuous now, but microwaves have been mired in controversy since their inception in the 1940s — with many people fearful of radiation, cancer, and Chernobyl-style disasters.
The microwave oven was the child of changing times. Post-World War II, an expansion of government-funded science and technology research in the US brought fervour and enthusiasm for technological developments, including new machines for the modern kitchen. At the same time, the fear of radiation and nuclear fallout loomed greater and greater.
Today, most people would call the microwave oven an innocuous appliance, but controversies have surrounded the microwave oven since its inception. Many early adopters wondered: Will my microwave cause cancer? Will my microwave make food less nutritious — or worse, radioactive?
But what we don’t think about is the radiation we naturally experience every single day. By definition, radiation is the emission of energy in the form of waves or particles through space or through a medium. That’s it. In the broadest sense, radiation includes a slew of things, including radiowaves, microwaves, and even visible light waves.
Types of radiation fall into two broad categories: non-ionising radiation and ionising radiation. For living organisms, this dichotomy can make a big difference. Microwaves are one type of non-ionising radiation; they don’t cause mutations, but the heat they generate can burn. Ionising radiation, on the other hand, carries enough energy to completely remove an electron from an atom or molecule. Ionising radiation is the kind associated with our fear: with a missing electron, molecules or atoms become positively charged and can damage DNA and other cellular components.
Despite the science, many remain fearful of the microwave oven because of the link between ionising radiation and cancer. But how did the microwave become a kitchen appliance? How do events in history give fodder to these fears?
From the 340kg floor model to the countertop
At the 1933 World’s Fair, Westinghouse Corporation demonstrated that a shortwave radio transmitter could cook steak and potatoes between two metal plates in mere minutes. Nothing came from these observations until the end of World War II. The end of the war marked the end of the market for magnetron tubes for use in short-range military radar. Once the war was over, companies such as Raytheon sought new applications for these magnetron tubes.
A Raytheon employee named Percy Spencer is credited with inventing the microwave oven. Legend has it that in the 1940s, Spencer accidentally leaned against an open waveguide, a tube that carries electromagnetic waves in one or two dimensions. Soon, he found that a candy bar in his pocket had begun to melt.
Spencer and his colleagues at Raytheon decided to investigate further through more deliberate observations. Day after day, they brought new foods into the lab to test: popcorn, or an egg in a kettle, for instance. Some engineers were doubtful that the food would cook. One was so unfortunate as to peer over the top of the kettle only to be sprayed in the face with cooked egg. These incidents sparked the development of the microwave oven.
In a microwave oven, water, fat and other substances in food absorb the heat energy from microwaves. The home microwave's heating style takes advantage of the fact that many molecules are slightly positively charged on one end and slightly negative on the other. Microwaves add enough energy to rotate the atoms in these molecules. These newly energised molecules align themselves with the electric field of the microwaves. The microwave is designed so that the electric field is continually oscillating, meaning that the atoms in each molecule are continually rotating and colliding with one another. These collisions over and over again cause the dispersion of energy in the form of heat.
First sold in 1946, by the name “Radarange,” the microwave oven was intended for use in restaurants and for reheating meals on aeroplanes. This model was six feet tall, weighed 340 kilograms and cost about US$5,000. The 1.6 kilo Watt magnetron tubes in the microwave had to be continuously cooled with water (instead of a cooling fan use in today’s microwaves) and the Radarange used about three times as much energy as today’s microwaves.
In the 1950s, microwave oven development took off. The first microwave developed for consumers were wall mounted and cost US$1,295 (the equivalent of almost US$11,000 today). Ten years later, Raytheon finally introduced a more reasonably priced microwave oven in 1967 for US$495, which lit the fuse for a boom in the home microwave market. Throughout the 1970s, the popularity of the microwave increased — just as people were wondering whether these handy machines were safe at all.
Is my microwave going to kill me?
In the 1960s, the US government discovered that Soviet intelligence agencies were bombarding the US embassy in Moscow with microwave radiation. The Soviets' intent of eavesdropping and electronic jamming turned into rumours about mind control via microwave radiation. The US government tried to keep this information secret from the American public, but as soon as word spread, concern grew about the long-term effects of microwave exposure.
Around the same time, the popularisation of colour televisions in the 1960s sparked a scare about x-ray radiation from TV. What followed were highly publicised accounts of unusual amounts of radiation emitted in production lines and stories of the effects of television viewing on children.
In response, the US passed a Radiation Control for Health and Safety Act in 1968. This act mandated the establishment of performance standards for electronics capable of electromagnetic radiation or radiation emission. This law was presumably enacted as a preemptive step to standardise radiation control between states and local governments — not because of any known health or safety problems. The US Bureau of Radiological Health (now part of the US Food and Drug Administration) developed performance standards on the leakage of microwaves and, after two years, they established a very conservative safe “exposure” limit at one milliwatt per centimetre at five centimetres away for new microwaves and at five milliwatts per centimetre at five centimetres thereafter.
With these standards in place, it was found that 10 – 30% of old microwave ovens manufactured before 1970 leaked over 10 milliwatts per centrimetre under test conditions. While manufacturers agreed to repair these ovens, the perception of risk greatly increased because noncompliant microwaves were sitting right there in many home kitchens.
Soon after, warnings about the dangers of microwaves ran rampant in newspapers, TV, and radio outlets. One of the most famous examples is the Consumer’s Union 1973 allegations that microwave ovens were significant radiation hazards which were published in a 1974 New York Times article. Consumer’s Union warns consumers to “beware [of] the microwave oven” reasoning that no microwave could be considered completely safe as there was no solid data on safety levels of radiation emissions.
Though the Consumer’s Union eventually accepted that microwave ovens were safe and dropped its warnings against their use, suspicion still remained and occasional media campaigns lit new fears of microwave ovens. In the craze of microwave conspiracies and cancer links, the real hazards of microwaves have been forgotten: explosions of small objects due to thermal hot-spots, uneven heating that could char food in some areas but fail to destroy harmful microbes, and other fire-related dangers.
Soon after, in 1988, scientists were able to show that low level microwave exposure did not have any effects on tumour development or survival time in mice — debunking the link between microwaves and cancer. This was revisited in 2011 when researchers found that low level microwave exposure did not significantly increase mortality or tumour growth in mice exposed to microwave radiation compared to control groups that were not exposed to radiation.
Radiation has been long ingrained into our consciousness. Godzilla was empowered from nuclear radiation. Spiderman was bitten by a radioactive spider. Personified as monsters and super heroes, radiation has become a force that can both burn and destroy or be harness for good. Like many innovations, the microwave oven has been though its fair share of serendipity, celebration, and doubt. But know that you can rest easy, and enjoy your harmlessly irradiated popcorn in peace.