About 70 years ago, when microwave oven first appeared in the market, it remained a gadget of industrial use because of its bulk, and the prohibitively high price tag of $5,000, which would be the equivalent of over $50,000 US dollars today. The smaller countertop model that came out 20 years later was still a luxury item at $495 then.
Microwave ovens became truly affordable in the 1970s, but in less than 50 years, it has become a permanent fixture in almost every household. Today it has become as essential as the refrigerator. After all, if you have a refrigerator stuffed with frozen foods, how will you manage without a microwave oven to thaw all those items?
There’s no doubt that these time-saving gadgets make life easy, but at what cost? Are microwave ovens as harmless as they are made out to be? Or, are they potential health hazards? Ever since the gadget was invented, there have been apprehensions about its safety, but they were either brushed aside or ignored.
How microwave oven was invented
When a Mr. Goodbar melted in the pocket of his coat, American engineer Percy Spencer, who was experimenting with radar at Raytheon, first became aware of the heating power of these electromagnetic waves. Intrigued, he tried making popcorn with it, which turned out to be a success. Knowing that microwaves cannot pass through metal, he designed a metal box in which he placed a magnetron which produced low frequency electromagnetic radiation. He was delighted that it heated up foods very rapidly, compared to conventional cooking methods.
What are “microwaves” in the scientific use of the word? They are low frequency electromagnetic radiation with wavelengths of about 1mm to 1meter. X-rays are high frequency electromagnetic radiations with a low wavelength of 1 nanometer. High frequency radiations can pass through different materials and cause molecular changes called ionization, which make them extremely dangerous. Ultraviolet radiation, visible light, and the infrared radiation given off light bulbs, all come in between. They belong in the non-ionizing spectrum, and are thought to cause changes to matter only through their thermal effect.
How do microwaves cook food?
Some molecules like water have differences in the charge at their opposite poles. When the radiation produced by the magnetron in the microwave passes through food, it changes the polarity of water molecules, causing them to rotate. Repeated rotations produce heat by a process called dielectric heating, rapidly raising the temperature of the food without heating the food containers.
Is non-ionizing radiation harmless?
Ultraviolet rays are considered non-ionizing radiation, but excessive exposure to them do produce adverse effects like premature aging and skin cancer. These changes cannot be attributed to the thermal effect alone.
By the same yardstick, even though the frequency of microwaves is much lower than that of ultraviolet rays, the foods cooked in the microwave might be undergoing subtle changes in their biochemistry.
Possible denaturing of food
As we have seen, microwave radiation causes water molecules to change their polarity and the direction of their spin. Amino acids, which are the building blocks of proteins, have left-spinning levo forms and right-spinning dextro forms. The toxic dextro forms rarely occur in food items. But if microwaves can change the spin direction, dextro form of amino acids could build up in the microwaved food. We can only imagine the health hazards of consuming such potentially toxic food on a regular basis.
Direct exposure to radiation
Repeated exposure to microwaves as we use the ovens in our kitchens is another major concern. The metal casing of the microwave oven is supposed to hold in all the radiation within the cavity. But, the door has only a thin metal mesh through which we can view the contents inside.
The changes in the biochemistry of foods subjected to microwaving have not been sufficiently investigated. Hans Hertel, a Swiss scientist, conducted a small study in collaboration with Bernard H. Blanc to compare the effects of foods cooked conventionally and foods microwaved. After two months they concluded that microwaved food reduced hemoglobin count and worsened cholesterol values. A decrease in white blood cell count, indicating lowered immunity, was also reported.
The study was not taken seriously because it was too small, involving only eight participants. A complaint was filed by FEA, a Swiss association of electrical appliance dealers, that Hertel’s fear-mongering can adversely affect the industry. Hertel soon received a gag order. This incident raises ethical issues, and doubts about transparency in microwave related research.
Ban of microwave ovens in Russia
From 1976 onwards there was a ban on microwave ovens in Russia which was lifted only when Russia opened up to international trade post-Perestroika. It is not clear whether this change was due to new insights into the safety of microwaves or they were just buckling under industry pressure.
There are many pitfalls of microwave cooking:
1. Uneven heating. As we all know, microwaves heat food unevenly, especially if the food has a heterogeneous composition. The case of Norma Levitt dying of blood transfusion with microwave-warmed blood could have been due to uneven heating causing coagulation of blood cells. John A. Kerner, a pediatrician, and his colleagues at Stanford University reported that frozen breast milk, when warmed in a microwave, loses lysozymes which protect it from harmful bacterial growth. That could be because even at low settings some parts of the milk get heated beyond normal body temperature. Warming baby bottles in a microwave can cause severe burns in infants, too.
2. Hot spots and burning. High fat and high sugar foods typically develop hot spots. Some areas get burned while most other parts of the food remain uncooked. It can result in carcinogens developing in the burned area.
3. Improper sterilization. The microwaves only penetrate into the outermost 2- 4 cm of the food. The insides of thick items of food can get cooked by the conduction of heat only. Some areas in the food can remain uncooked in the short period it is microwaved. This can leave pockets of raw or non-sterile food that can harbor harmful microbes. They may later multiply and cause food poisoning.
Better be safe than sorry
With all the uncertainties about the safety of microwave usage many people have returned to conventional ways of cooking. If you cannot do away with the microwave, at least follow these precautions while using it:
- Keep a minimum distance of two feet between you and the microwave when it is working. Better still, leave the kitchen during the period.
- After the cooking time is over, wait for a few minutes before opening the door.
- Teach children to stay away from it. Do not allow naturally inquisitive children to peek into the oven when it is running, or experiment with it.
- Do not heat high fat/high sugar foods in it.
- Never warm baby bottles in a microwave, whether it contains breast milk or formula.
- Do not store or refrigerate food that has been thawed or heated in the microwave.
- Discard faulty microwave ovens.