Case 1: Jane is a typical professional woman. She works hard in the company during the day, cooks dinner and cleans up the housework after work. In order to save time, she bought a microwave oven for cooking three years ago, which really saved a lot of time. But recently I often feel headache, fatigue and other symptoms. She suspected that it might be because of the influence of the microwave oven. So every time she turned on the microwave oven, she hid in the next room to "take refuge" and waited until the time was ripe to return to the kitchen. After a while, her symptoms didn't seem to improve. What's going on here? Is the microwave oven safe or not?
Case 2: A Hui worked hard since childhood, worked as an apprentice in a bakery, went to bed late and got up early, and gradually broke out of his own sky; Now he is the owner of a bakery. In order to meet the needs of more and more customers, Hui decided to replace the traditional electric roaster with a microwave roaster and bake his own embryo. The business is getting better and better as scheduled. The only fly in the ointment is that Ah Hui has been married for more than two years, but there has been no sign of pregnancy. Hui is worried about using the microwave oven. Is it true?/You don't say.
Microwave ovens are becoming more and more popular in today's industrial and commercial times, because they save a lot of time than traditional cooking methods, and do not produce oil smoke and steam. It is not only widely used in heating frozen food, baking pasta and drying food in business, but also tends to gradually replace traditional stoves in the family. Due to the recent appreciation of Taiwan dollar, the price of imported microwave ovens has been slightly lowered, and the price of domestic microwave ovens has also been lowered; The number of people using microwave ovens in China has greatly increased. However, few people know that microwave ovens are harmful to health and know how to use them carefully, so this paper will discuss the possible harm and prevention of microwave ovens for readers.
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Structure and microwave characteristics of microwave oven
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As the application of microwave oven is more and more extensive, its functions and types are more and more complicated, but its basic structure and principle are similar. There is a magnetron at the upper right of the microwave oven, which will produce microwave vibration after being impacted by current; Therefore, the magnetron can be said to be a microwave generator. The vibration of the vibration wave is transmitted to the fan-shaped agitator through the metal tube, and the microwave is evenly distributed to the metal inner wall of the microwave oven through the agitator and continuously reflected until the food absorbs the fluctuation and converts it into heat energy.
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Microwave itself is not free radiation, so it has no general radioactivity. Just like other electromagnetic waves, such as sunlight, laser and X-rays, microwaves travel in a straight line at the speed of light, but the difference is their wavelength (frequency). The wavelength of microwave varies from several millimeters to several meters, between shorter visible light and longer radio waves. Its frequency is between 300 million Hz and 300 billion Hz, so it has both short-wave reflection and long-wave heating.
The traditional cooking method is based on the principle of heat conduction and radiation, so it is necessary to heat the container and medium before heating the food. The way of microwave heating is different from the traditional way from the outside to the inside. Microwave is an electromagnetic wave that oscillates several times per second to form an electromagnetic field. Therefore, when polar substances (such as water, fat and protein in food) are placed in a magnetic field, molecules will collide back and forth with the oscillation of the magnetic field and rub against each other to generate heat. Materials lacking polarity, such as air, glass, ceramics and some plastic products, have little influence on microwave. Therefore, every time the food changes from raw to hot and from cold to hot, the temperature of the container (such as glass or porcelain) that packs the food does not change much.
After understanding the heating principle of microwave oven, let's see what harm it will cause.
Potential danger of microwave oven to human body.
We can divide the harm caused by microwave ovens into two categories:
1. Harm of microwave radiation to human body: The human body is mostly composed of water, protein and fat, and the harm of microwave itself to human body is obvious.
Although the exact effect of microwave on human body has not been fully studied, most scientists now believe that there will be the following non-cumulative hazards:
(1) Harm to eyes: The water in eyes is extremely rich, which is easily affected by microwaves; In addition, many parts of the eyeball (such as cornea and lens) have very limited blood flow and poor heat dissipation ability, so once they are attacked by microwaves, they cannot effectively dissipate heat in a short time, resulting in heat residue.
Long-term exposure may lead to the risk of cataract.
(2) Harm of reproductive organs: mainly refers to male testicles. If men's testicles are heated by microwave, it is easy to increase the temperature and destroy the production of sperm. Therefore, when using the microwave oven, it should be placed in a suitable place, and the groin should not be directly exposed to the place where the microwave may leak. If the microwave oven is not maintained for a long time and there is a possibility of leakage, then pregnant women are not suitable for approaching, so as not to affect the fetus.
(3) Skin and subcutaneous tissue: Generally speaking, the harmfulness of microwave is inversely proportional to frequency. The higher the frequency (shorter the wavelength), the weaker the penetration and the less the damage.
Although the microwave oven itself will be harmful to the human body, whether the microwave oven itself is harmful depends on whether it will escape from the microwave oven, that is, whether the structure of the microwave oven itself is tight. Is there a gap that might leak microwave?
In order to ensure the tightness of microwave ovens, most oven doors are designed with double locks or interlocks. When the oven door is not tightly closed or closed, the microwave generator automatically locks and cannot be started. In other words, if you don't close the oven door and start the microwave oven at the same time, there is no microwave oven at all.
Cracks may be caused by improper use or disrepair. When the gap is large, it can be observed with the naked eye; But it may be caused by a small gap or the background in the furnace, which cannot be recognized by the naked eye. In advanced countries in Britain and America, there are special personnel to inspect microwave ovens. The microwave energy measured at any point five centimeters away from the oven door shall not exceed five meters per square centimeter? Watt, this standard is far below the lowest dose known to cause harm to human body; At present, some companies with good reputation have raised the standard of household appliances and microwave ovens to no more than one meter per square centimeter? The degree of watts. Before the relevant domestic laws and regulations and specialized agencies are fully established, consumers must be extra careful when using them; Please visit the maintenance factory regularly to check whether there is any leakage. Generally, domestic microwave ovens are used at least once a year, and commercial users are used at least once every six months.
2. Improper packaging container: If the heated items contain metal films, metal plates and the like, not only the packaging inside cannot be heated, but also sparks may be generated if there are slender metals. Plates painted with gold and silver threads may fall off because of receiving magnetic waves and sparking. Splash metal chips will be scattered in food and may be eaten.
When cooking in a microwave oven, the heat-resistant plastic bags and plastic wrap used should be able to withstand the high temperature above 130℃, so as not to make the ingredients in the package flow out or deteriorate and pollute the food. When the food containing more oil is heated by microwave, the temperature of the food itself will be as high as 160℃, which has exceeded the upper limit of heat resistance of special plastic bags or plastic wrap, and harmful substances in it may flow into the food, leading to health problems of the food itself.
Precautions when using microwave oven:
(1) Usually, the interior is often cleaned with hot water or detergent. Do not leave dregs in the gap of the door, which will affect the sealing of the oven door.
(2) Don't scrape the stove with steel wire or hard and rough objects (such as vegetable cloth with metal particles) to avoid damaging the inner wall of the microwave oven; Resulting in insufficient microwave reflection or increasing the gap of the oven door.
(3) When the oven door is damaged, stop using it immediately and ask professionals to repair it. Never send it to a general pot repair shop for repair or repair it yourself. It's best not to buy your own tester, but to check the microwave oven for leaks.
(4) Operate and maintain the machine according to the user manual.
(5) Don't turn on the power when there is no food in the furnace. Avoid empty furnace operation; Because when the empty furnace is running, the microwave emitted by the magnetron has nowhere to be absorbed; Long-term use may cause damage to the furnace itself.
(6) Do not insert any substance into the oven door inlay.
(7) When the microwave oven is running, do not forcibly open the oven door.
(8) Don't buy second-hand microwave ovens that have not passed the inspection. It is best not to buy second-hand goods before there is a special microwave oven testing institution in China.
(9) Never stand upright in front of the microwave oven and expose your groin to the place where the microwave may escape. Don't look too close to the microwave.
(10) If your microwave oven was manufactured before 1972, or there is no interlock device; When you turn on the stove, be sure to check whether the microwave oven has stopped working.
(1 1) There should be no metal, metal film or metal plate in food and containers; The packaging containers of articles with heat resistance of at least 130℃ should be carefully selected; Foods containing more grease should choose containers such as glass and ceramics.
(12) Ask professionals to carry out regular maintenance. Commercial or industrial microwave ovens should be overhauled at least once every six months, and domestic microwave ovens should be overhauled at least once a year.
(13) You should avoid sitting or standing by the microwave oven for a long time before you fully understand the harm caused by microwave fish.
Conclusions and appeals
Most of the insecurity of microwave ovens does not come from the microwave ovens themselves, but from the users themselves. Unsafe reasons are nothing more than not doing regular maintenance, not knowing the potential harm of microwave ovens, not knowing enough about how to use and maintain microwave ovens correctly, and having a long service life. Generally speaking, due to the progress of industrial technology and precise instrument design, if the key points of correct use can be observed when using microwave ovens, there will usually be no safety problems. We also call on microwave oven suppliers and governments to:
(1) For users who buy microwave ovens for free, the supplier shall provide maintenance service at least once a year; At least check the consumer for microwave leaks.
(2) Commercial microwave oven shops (such as Uni-President Store) should be overhauled at least once every six months; Moreover, every overhaul must be issued or affixed with a certificate to ensure that there is no microwave leakage and to ensure the safety of users and consumers in the store.
(3) The government should formulate complete microwave oven standards as soon as possible, including leak detection standards, and follow the example of some American states (such as Massachusetts). Health bureaus in all counties and cities have professional technicians to check microwave leakage for people at home free of charge, so as to protect people's health.