Is the microwave oven safe after all?

Among all household appliances, microwave oven is probably the one that people are most worried about. Words such as "microwave" and "radiation" always cause many people to panic, and the "terrible" legend about microwave ovens often gets special attention. In this era of "the smell of cancer turns pale", "microwave oven heating produces carcinogens" has become a repeatedly accepted "belief" Starting with why microwave ovens can heat food, this paper introduces the characteristics of microwave ovens and analyzes some rumors about microwave ovens. Why can microwave ovens heat food? Let's talk about water first Water molecules consist of one oxygen atom and two hydrogen atoms. Oxygen atoms are very attractive to electrons, so the electrons in water molecules are concentrated at the end of oxygen atoms, and the corresponding hydrogen atoms are less. On the whole, water molecules are positively charged at one end and negatively charged at the other. Chemically, this molecule is called polar molecule. In normal water, water molecules are disordered, with positive and negative charges in both directions. When water is in an electric field, the positively charged end will turn to the negative pole of the electric field, and the negatively charged end will turn to the positive pole of the electric field, so-called "opposites attract, like attracts". If it is an electrostatic field, the water molecules will line up and be quiet. If the electric field keeps turning, then the water molecules will follow, trying to keep consistent with the electric field. If the electric field rotates rapidly, water molecules will also rotate rapidly to generate heat by friction, and the temperature of water will rise. Electromagnetic waves are equivalent to such a rotating electric field. The electromagnetic waves used in microwave ovens rotate more than 2 billion times per second, and the water molecules rotate with this speed, which naturally makes them "warm all over" and the temperature rises sharply in a short time. Once the microwave stops and the rotating electric field disappears, the water molecules will be quiet and their world will be clean again. In this process, the water molecules themselves are not changed by microwaves. Microwave can not only heat water, but also other polar molecules. Usually food contains water and other polar molecules, so it can be heated quickly under the action of microwave. Non-polar molecules such as air and some containers will not be heated. We usually feel that the container is hot after heating the food, and we are often "scalded" by high-temperature food. Can microwave heating cause cancer? Because microwave is a kind of radiation, many people naturally think it will cause cancer. Microwave is an electromagnetic wave, which is essentially the same as radio waves, infrared rays and visible light used in radios and telegrams. The only difference between them is the frequency. The frequency of microwave is higher than that of electric wave and lower than that of infrared ray and visible light. Radio waves and visible light do not cause cancer, so it is not difficult to understand that microwaves with frequencies between them do not cause cancer. In fact, the "radiation" mentioned here only means that microwave energy can be emitted, which is different from the radiation generated by X-rays and radioisotopes. Although X-ray is also an electromagnetic wave, its frequency is much higher than that of microwave, so its energy is also high, and radioactive isotopes will release particles in the process of decay, so they can make organisms cancerous. Microwave will not cause cancer, nor will it cause food to produce carcinogens. Even, it helps to avoid carcinogens. For fish, meat and other foods, traditional heating methods, especially burning, roasting and frying, can easily lead to meat zooming, thus producing some carcinogens. A scientific review published in 2004 introduced the generation and carcinogenicity of this carcinogen, and finally pointed out that microwave heating can effectively reduce the generation of this carcinogen. Sunlight is an electromagnetic wave with higher energy than microwave. Sunshine, is it safe? The safety of microwave, like sunlight, depends on the strength of energy. Warm sunshine makes people feel comfortable, while exposure to the scorching sun can cause serious skin burns. So is the microwave oven. Since it can heat food, it can naturally heat the human body. The crux of the problem is: how much energy is left in the microwave that reaches the human body? Scientists have done a lot of research for us and found the minimum microwave power that can harm human body. In the intact microwave oven, the leaked microwave power is far from reaching the intensity that harms human body. According to American regulations, the power per square centimeter should not exceed 5 milliwatts at a distance of about 5 centimeters from the microwave oven. China's standard is stricter, which is 1 MW. Moreover, the energy of microwave decreases according to the square of distance. In other words, if it is 1 MW at 5cm, it will be reduced to 1% MW at 50cm, which is more "harmless to people and animals". Therefore, as long as it is a qualified microwave oven product that is not damaged in use, it will not leak microwaves that can harm the human body. Another safety problem when using microwave ovens is the harmful substances released by plastic containers. Indeed, some plastics may release some harmful components when heated. The FDA has determined the amount of harmful substances that may be released into food when heating various plastic containers in ordinary microwave ovens. Only when this amount is lower than 1% or even 1 of the harmful dose determined by animal experiments can it be marked as "microwave heatable". Therefore, those qualified "microwave heatable" plastic containers are quite safe. Of course, if you still don't trust, or don't believe that the label of the manufacturer is worthy of the name, then you can trust to use ceramic or glass containers. Rumors about microwave ovens (II) Where did the microwave oven safety accidents come from? Are these traditional heating methods safe? At least because of cooking, someone got burned and there was a fire. The FDA said that it has received many reports of "injuries" caused by using microwave ovens. However, these "accidents" have nothing to do with the microwave oven itself, but are caused by improper use The following are the two most common types of accidents: liquid overheating. Traditionally, water will flow when it is boiled, and it will "open" when it reaches the boiling point. When microwave heating, water does not flow, but the temperature rises, which may "not open" if it exceeds the boiling point. But at this time, the water temperature is already very high, and it will boil violently if there is a little disturbance. If this disturbance is caused when you go to fetch water, it will be more scalding than boiling water. The cleaner the container, the cleaner the water, and the more prone to such accidents. Therefore, for the sake of safety, it is best not to "try the law". Other liquids, such as milk and soup. It is not easy to overheat due to other components, but it is easy to "boil" out of the container after heating for a long time. It's not that you can't heat these foods in the microwave oven, but that you should calculate the heating time. Eggs explode. It is probably common sense that the microwave oven can't heat eggs. The reason why eggs explode is somewhat similar to the boiling of water. The inside of the egg is overheated and under great pressure. Once disturbed by the outside world, the pressure will be released, so the egg will explode. If the explosion occurs when the egg enters the mouth, it is probably equivalent to setting off firecrackers in the mouth. Generally speaking, it is very safe.