Electromagnetic field exists not only in vacuum, but also in material space, including biological tissues. In the radio spectrum, the quantum energy of electromagnetic field is very small, so it is impossible to change the molecular structure and break the molecular bond. When the radio frequency is 300× 10 12Hz, the maximum quantum energy caused by electromagnetic field is only 1.2MeV (mega electron volts). It takes 80 MeV to break the weakest hydrogen bond. Therefore, radio electromagnetic waves with a frequency of 300× 10 12Hz and below are called non-ionizing radiation. Ionizing radiation, such as gamma rays of natural nuclides, has a general frequency of10/2hz and a maximum energy of 2.6MeV, that is to say, even the highest intensity of non-ionizing radiation cannot produce ionization in organisms. Nuclear radiation will produce ionization and directly destroy organisms. However, other biological effects produced by non-ionizing radiation, such as heat, chemical reaction and induced current in the body, can also destroy organisms. This is the mechanism of harm caused by electromagnetic radiation.
What is environmental electromagnetic field?
There are two kinds of environmental electromagnetic fields, natural and man-made, which are important components in the natural biosphere.
Natural electromagnetic fields include earth origin, near-earth origin and universe origin, and are divided into fixed earth magnetic field (geomagnetic field), earth electric field and alternating electromagnetic field with frequency from 103Hz to 10 12Hz. Lightning is a kind of atmospheric electricity, or sky electricity. The nuclear radiation of the earth, the sun and galaxies is the source of alternating electromagnetic fields.
Man-made electromagnetic field is caused by human technical engineering. Its electromagnetic field radiation includes power frequency and all radio (high frequency or radio frequency) frequency domain. The intensity of electromagnetic field depends on power, emission parameters and the distance of observation point. There are three kinds of artificial electromagnetic fields: power frequency electromagnetic field, radio frequency electromagnetic radiation field and microwave radiation field, among which radio broadcasting, television, microwave communication and other radio frequency equipment have a large radiation influence area.
People's Republic of China (PRC) national standard
The Regulations on Electromagnetic Radiation Protection clearly stipulates the export limits of occupational exposure and public exposure, and the power density of electromagnetic radiation cannot exceed 20uW/ cm2. In the living environment, the power density of electromagnetic radiation cannot exceed 40uW/ cm2. The value of electromagnetic wave is measured in the unit of magnetic beam density MG (milligauss). Among household appliances, microwave ovens, vacuum cleaners and mobile phones have the strongest electromagnetic radiation, all of which can reach 200MG；; (Note: 20uW/ cm2 is about 2 milligauss)
Harm of electromagnetic radiation to human body
Electromagnetic radiation is harmful to human body in many ways, especially to women and fetuses. The survey shows that:
1 to 3 months is the embryonic stage, and strong electromagnetic radiation may cause limb defects or deformities;
4 ~ 5 months is the period of fetal formation, and exposure to electromagnetic radiation may cause mental retardation and even dementia;
6 to 10 months is the growth period of the fetus. Exposure to electromagnetic radiation will lead to low immune function, weak constitution and poor resistance after birth.
Studies have confirmed that long-term exposure to electromagnetic radiation can make antibodies unable to bind to blood cells as long as the electromagnetic intensity reaches 1 milligauss. If it reaches 10 milligauss, thymocytes will die and immunity will decline. If it reaches 40 milligauss, the embryo will develop abnormally, causing the child to be deformed. For the non-ionizing radiation of high-voltage and low-frequency electromagnetic waves, the recommended value in general environment is 833 milligauss.
Are home appliances safe?
It is difficult to find out the influence of electromagnetic waves on human body scientifically and carefully, because various environmental factors act on human body comprehensively, and it is difficult to do long-term follow-up investigation. Whether electromagnetic waves generated by various household appliances will lead to brain cancer, leukemia, deformed children, abortion and other consequences, although some people have objections, but some experts believe that this is a fact. And a large number of survey reports show that women are particularly sensitive, especially pregnant women. So which household appliances are "dangerous"?
Microwave has a strong thermal effect, and microwave ovens take advantage of this feature. It vibrates and heats water molecules in food in a short time to achieve the purpose of heating cooking. So it will produce strong electromagnetic waves. The research results of Yanqing University show that the magnetic field intensity at the distance of microwave oven 15cm is as low as 100MG and as high as 300MG. Now we know that the microwave oven has the strongest magnetic field among all household appliances. Electromagnetic waves generated by microwave ovens can induce cataracts and cause brain abnormalities. According to research, microwaves can also reduce reproductive capacity.
Electric mattress is a typical product in electrical products that is in close contact with the body for a long time. Medical investigation shows that the electric mattress is in direct contact with the skin, and resting cells are exposed to electromagnetic waves for a long time, thus causing human health obstacles. A few centimeters away from the electric mattress, the magnetic field intensity is as high as 20-50 mg, and its electromagnetic intensity is nearly 2 KVA, while the electromagnetic intensity under 50V high-voltage line is 3 KVA. Strong electric field makes some people feel uncomfortable after sleeping, especially pregnant women. It is best to ban the use of electric mattresses. 1986 report shows that the abortion rate and abnormal delivery rate of pregnant women who use electric mattresses are higher than those who do not use electric mattresses.
The electromagnetic wave generated by TV is similar to that generated by terminal display. Long-term exposure to the electromagnetic wave of terminal display or TV set will cause symptoms such as eyeball pain and fatigue, which will lead to miscarriage, stillbirth and birth of deformed fetus.
With the development of electronic technology and the more and more extensive application of computers, more and more people need to operate and manage computers, and deal with computers all day, especially food terminals, with high contact frequency and long operation time. China Beijing Institute of Labor Protection Science and a systematic institute of medical engineering have measured the computer radiation of relevant departments many times. The results show that the upper and both sides of the computer exceed the standard, usually several times to dozens of times, up to 45 times.
Six Harms of Electromagnetic Radiation
The International Organization for Research on Cancer, which belongs to the World Health Organization, puts forward that electromagnetic waves may cause cancer, and requires governments and power industries of all countries to take corresponding countermeasures. The Indoor Environment Testing Center of China Interior Decoration Association issued a warning; When buying a house, we must pay attention to whether the electromagnetic radiation pollution in the community exceeds the standard. At present, many citizens have reported that the electromagnetic radiation pollution in their newly-built residential areas is very serious, and not only the electrical appliances at home are disturbed and cannot be used normally, but many people have different degrees of discomfort. With the large-scale urban transformation and real estate development, some power transmission and transformation centers and high-voltage lines originally built around the city have also begun to be developed and constructed, and the electromagnetic radiation pollution problems in the living environment and indoor environment have also followed. What harm does electromagnetic radiation do to human body? According to experts, there are six major hazards.
One of the hazards is that
It is probably one of the causes of childhood leukemia. Medical research has proved that long-term exposure to high electromagnetic radiation will change blood, lymph and cell protoplasm. According to the research of Italian experts, more than 400 children in this country suffer from leukemia every year. Mainly because it is too close to the high-voltage line, the electromagnetic radiation pollution is serious.
The second hazard
It can induce cancer and accelerate the proliferation of cancer cells in human body. Electromagnetic radiation pollution will affect the human circulatory system, immunity, reproduction and metabolic functions, and even induce cancer and accelerate the proliferation of cancer cells in severe cases. Swiss research data show that the probability of breast cancer among residents with high-voltage lines passing around is 7.4 times that of ordinary people.
The results of sampling tests conducted by Texas Cancer Medical Foundation on some patients suffering from electromagnetic radiation injury show that the growth rate of cancer cells in workers working near high-voltage lines is 24 times faster than that of ordinary people.
The third hazard
It affects the human reproductive system, mainly manifested in the decline of male sperm quality, spontaneous abortion of pregnant women and fetal malformation.
The fourth danger
Will lead to mental retardation in children. According to the latest survey, among the 20 million children born every year in China, 350,000 are defective children, of whom 250,000 are mentally retarded. Some experts believe that electromagnetic radiation is also one of the influencing factors. The World Health Organization believes that the electromagnetic radiation from computers, televisions and mobile phones has a negative impact on the fetus.
The fifth danger
It affects people's cardiovascular system, manifested as palpitation, insomnia, menstrual disorder in some women, bradycardia, decreased cardiac blood volume, irregular sinus heart rate, leukopenia, decreased immune function and so on. If patients with pacemakers are exposed to high-voltage electromagnetic radiation, it will affect the normal use of pacemakers.
Hazard 6
It has a bad influence on people's visual system. Because eyes belong to the sensitive organs of human body to electromagnetic radiation, too high electromagnetic radiation pollution will cause vision loss, cataracts and so on. High-dose electromagnetic radiation will also affect and destroy the original biological current and biological magnetic field of human body, making the original electromagnetic field of human body abnormal. It is worth noting that different people or the same person have different tolerance to electromagnetic radiation at different ages, and the elderly, children and pregnant women are sensitive to electromagnetic radiation.
Learn to prevent radiation
There are five kinds of people who should pay special attention to electromagnetic radiation pollution: people who live and work near high-voltage lines, substations, radio stations, TV stations, radar stations and electromagnetic wave towers; Personnel who frequently use electronic instruments, medical equipment and office automation equipment; Staff living in a modern environment; Patients wearing pacemakers; Pregnant women, children, the elderly and patients living in the above environment. If the electromagnetic radiation pollution in the living environment is relatively high, the public must take corresponding protective measures.
Don't put household appliances too concentrated to avoid exposure to excessive radiation. Especially some household appliances that are easy to generate electromagnetic waves, such as radios, televisions, computers, refrigerators, etc. , not suitable for centralized display in the bedroom.
All kinds of household appliances, office equipment, mobile phones, etc. Try to avoid long-term operation, and try to avoid multiple office and household appliances being activated at the same time. The electromagnetic radiation released at the moment when the mobile phone is turned on is the largest. When using, the distance between the head and the antenna of the mobile phone should be as far as possible, and it is best to use a separate earphone and microphone to answer the phone.
Pay attention to the distance between human body and office and household appliances, and keep a safe distance when using various appliances. The farther away from the electrical appliance, the less electromagnetic wave will harm. For example, the distance between color TV and people should be 4 to 5 meters, and the distance between color TV and fluorescent tubes should be 2 to 3 meters. After the microwave oven is turned on, it should be at least 1 meter away, and pregnant women and children should stay away from the microwave oven as far as possible.
If the house is close to high-voltage lines, substations, radio stations, televisions, radar stations and electromagnetic wave transmission towers, experts must be invited to carry out electromagnetic radiation detection. If it is found that it exceeds the national standard after testing, measures should be taken in time.
Relevant experts believe that although the influence of electromagnetic radiation on people is universal, it is not terrible, and some preventive work can be done appropriately to reduce the direct effect of electromagnetic radiation.