Reporter: electricity and magnetism is one of the greatest discoveries of mankind, today we have been living in the electrification of the era of high development, surrounded by all kinds of equipment that uses electricity, so, electromagnetic waves, electromagnetic radiation and electricity what is the relationship? Electrically charged things have electromagnetic radiation?
Zhang Hui: In 1831, the British scientist Faraday discovered the phenomenon of electromagnetic induction, and in 1880, the German physicist Hertz was the first to realize the electromagnetic wave propagation. Any AC circuit may release electromagnetic energy into the space around it, forming an AC electromagnetic field. When the frequency of alternating current reaches more than 100,000 times per second, it will be formed around the high-frequency electric field and magnetic field, magnetic field and electric field mutual excitation, mutual formation, correlation, change, from near and far to a certain speed in space the process of propagation is electromagnetic radiation.
Reporter: people often say that electromagnetic radiation has an impact on the human body, so is it as long as there is electromagnetic radiation will have a negative impact on human health, if so, that all kinds of electrical appliances are not becoming very scary?
Zhang Hui: electromagnetic radiation is an objective existence, as a kind of energy flow, human beings can not be felt directly, but it is always and everywhere. Talking about the impact, we must introduce another concept - electromagnetic radiation pollution, also known as electromagnetic smog pollution. Any electrically charged body may have electromagnetic radiation, when the intensity of electromagnetic radiation exceeds the standards set by the environmental protection, it will produce negative effects and cause different lesions and harm to the human body, this part of the radiation that exceeds the standard electromagnetic field intensity is called electromagnetic radiation pollution. Electromagnetic wave distribution in space is extremely similar to the characteristics of smoke, although electromagnetic waves are tasteless, invisible and non-tactile, but penetrating, can pass through a variety of substances, including the human body. It should be said that electromagnetic waves have made a great contribution to mankind at the same time, but also produced a variety of negative effects, the most important of which is the electromagnetic smog pollution, affecting the application of legitimate emission function facilities, directly or indirectly jeopardize human health, some people refer to them as "invisible public health".
Reporter: which charged body is most likely to produce electromagnetic radiation pollution?
Zhang Hui: the electromagnetic spectrum is quite large, from long-wave, medium-wave, short-wave, ultra-short-wave radio waves, to thermal radiation-based far infrared and infrared, and then visible light, ultraviolet light, up to X-rays, Y-rays, and other radioactive radiation, are all part of the scope of electromagnetic waves. Today, I will only talk about the narrow sense of the environment electromagnetic radiation pollution, that is, by the radio wave range of radiation caused by the environmental pollution and the existence of electromagnetic pollution in the form of seemingly steady state electromagnetic field. The most common of the natural sources of electromagnetic pollution is lightning, and intense lightning will radiate electromagnetic waves of extremely wide frequency from a few kilohertz to several hundred megahertz over a considerable area, but usually, the intensity of natural radiation generally does not pose a serious hazard to human beings. It is worthwhile to pay attention to the artificial type of electromagnetic pollution sources. Artificial electromagnetic pollution sources generated from man-made electronic equipment and electrical devices, according to different frequencies can be divided into industrial frequency field sources, radio frequency field sources and pulse discharge three categories. Industrial frequency electromagnetic field refers to low-frequency power equipment and transmission lines excited by the electromagnetic field. In China, the frequency of industrial frequency is 50 Hz, Europe and the United States also have 60 Hz. High-power motors, substations and transmission lines near the distribution of industrial frequency electromagnetic field, it is a kind of seemingly stable field, not in the form of electromagnetic waves radiated outward, but in the near-field area will produce serious electromagnetic interference. Radio frequency electromagnetic radiation from radio communication and radio and television transmission systems has become a major factor in electromagnetic pollution of the environment with the development of communication and radio and television business, which is characterized by a wide range of frequencies and a large area of influence, endangering the staff in the near-field area. Pulse discharge, such as cutting off the high-current circuit when the spark discharge, due to the instantaneous change in current strength is very large, resulting in a very strong electromagnetic interference, it is in essence the same as lightning, only the impact area is smaller. In the electromagnetic radiation pollution, to radio frequency equipment in the work of electromagnetic radiation to the environment brought about by the most prominent pollution.
Reporter: Because the electromagnetic wave is invisible, so we would like to know how it spreads, that is, what are the transmission channels of electromagnetic radiation pollution?
Zhang Hui: you may have seen the schematic diagram of the propagation of electric waves, radiation in the form of waves spread through space and wires. When electronic equipment or electrical devices work, the equipment itself is a multi-type transmitting antenna, will constantly radiate electromagnetic energy into space. With the field source as the center, the electromagnetic energy propagation within a radius of 1/6 wavelength is dominated by electromagnetic induction, which applies energy to nearby instruments, electronic devices and the human body. In the radius of 1 / 6 wavelength range outside the electromagnetic energy propagation, is to space radiation will be applied to the energy. And when RF equipment and other equipment*** are powered by a single power source, or when there is an electrical connection between them, then electromagnetic signals are also propagated through wires. Simultaneous existence of space radiation and wire propagation when the electromagnetic radiation pollution is called compound pollution.
More than a certain limit of electromagnetic radiation affects the application of other normal electronic facilities, directly or indirectly harmful to human health
Reporter: you just mentioned, electromagnetic radiation pollution on devices, substances and equipment will have an impact and harm, we have encountered such a situation, in the vicinity of the TV set of cell phones receive "incoming calls! "
Reporter: You just mentioned that electromagnetic radiation pollution can affect and harm devices, substances and equipment.
Zhang Hui: Yes, electromagnetic radiation on other electronic equipment, the brunt of the interference. Radio frequency equipment and broadcast transmitter oscillation circuit of electromagnetic leakage and power lines, feeder lines and antennas and other electromagnetic energy radiated to the outside can interfere with the normal work of a variety of electronic equipment located within the scope of this region, such as radio communications, radio measurement, radar navigation, television, electronic computers and electrical medical equipment and other electronic systems. Under the interference of space radio waves, can make the signal error, graphic distortion, control failure, so that can not work properly. You just said that cell phone interference with television is this phenomenon, cell phone at this time is a radio frequency equipment. 1997 August 13, Shenzhen Airport due to the dozens of wireless paging stations on the nearby hills of electromagnetic radiation emitted by the airport command tower of the radio communication system caused by serious interference, so that the ground-to-air command failure, the airport was forced to close for two hours. Before that, a similar incident had occurred at the capital airport. Therefore, it is necessary to pay close attention to and limit this.
Explosives, detonators and volatile liquids and gases, such as alcohol, kerosene, liquefied petroleum gas, gas and other flammable substances have low ignition points and can explode or burn unexpectedly under the action of radiant energy. On the other hand, many conventional weapons using electrical detonation device, such as the electromagnetic induction and radiation in the case of high battery, may cause the control mechanism of the misuse of the control failure or accidental explosion, such as high-frequency radiation strong field can make the missile guidance system control failure, the effect of electric detonation tube in advance or lag. Therefore, electromagnetic radiation on explosive substances and devices and volatile gases can not be ignored.
Reporter: We are most concerned about the impact of electromagnetic radiation pollution on human health and harm, in recent years, domestic and international reports on the harm of electromagnetic radiation are numerous, can you summarize what will be the specific impact and harm?
Zhang Hui: Domestic and foreign experts and scholars on electromagnetic radiation research and comments have been up to half a century, but due to the purpose of the study, methodology, conditions (exposure to electromagnetic radiation sources of distance, time, biological models, etc.) and other factors are not consistent, the current global experts and scholars on the biological effects of electromagnetic radiation research results and views are not consistent. However, the harm caused by electromagnetic pollution does exist and cannot be underestimated. Some herdsmen in pastoral areas have reflected that when grazing through high-voltage power lines, sheep and cattle often do not need to whip and drive will be since the hoof, fast through. Europe and the United States, some botanists have observed, and around a vigorous scene is very different, in the environment of ultra-high voltage electromagnetic fields, plant growth is often a stumble. 1998 World Health Organization survey shows that long-term in a high electromagnetic radiation environment will have a negative impact on human health: the impact on the cardiovascular system, manifested in palpitations, headaches, insomnia, some women menstrual disorders, bradycardia, reduced cardiac blood flow, sinusoidal blood flow. Reduced heart blood volume, sinus heart rate irregularities, leukocyte reduction, decreased immune function, etc.; the impact on the visual system, manifested in decreased visual acuity, resulting in cataracts, etc.; the impact on the reproductive system, manifested in reduced sexual function, lower sperm quality in men, so that pregnant women have spontaneous abortions and fetal malformations, etc.; long term exposure to high electromagnetic radiation in the environment will cause changes in the blood, lymphatic fluids and cellular protoplasm; the effects of the The human body's circulatory system, immunity, reproduction and metabolic functions, serious cancer will also be induced, and will accelerate the proliferation of cancer cells in the human body; equipped with a pacemaker patients in the environment of high electromagnetic radiation will affect the normal use of pacemakers.
Reporter: So, why electromagnetic radiation pollution will have a harmful effect on human health, that is, what is its mechanism of action?
Zhang Hui: electromagnetic radiation harms the human body mechanism is mainly thermal effect, non-thermal effect and cumulative effect. First of all, the thermal effect. The human body absorbs too much radiation energy, relying on the regulation of body temperature can not be distributed heat, will cause an increase in body temperature, and then cause protein denaturation, heart rate changes, triggering a variety of symptoms. As electromagnetic waves are penetrating the biological surface layer directly on the internal tissue "heating", often the body surface can not see anything, but the internal tissue has been seriously "burned". As for the non-thermal effect of electromagnetic waves, is under further study, generally believed to be the impact of low-frequency waves, that is, the human body was electromagnetic wave radiation, body temperature did not rise significantly, but has interfered with the body's intrinsic weak electromagnetic field, resulting in intracellular genetic aberrations and mutations, which in turn induced leukemia and tumors, will also cause chromosomal changes in the embryo, resulting in deformity of infants or pregnant women's spontaneous abortions. Thermal and non-thermal effects on the human body, the damage to the human body has not yet had time to repair itself before (usually referred to as the human body's tolerance), and then again subjected to electromagnetic radiation, the extent of the damage will occur cumulatively, and in the long term, will become permanent lesions, life-threatening. For long-term exposure to electromagnetic radiation group, even if the power is very small, low frequency, may also induce unexpected lesions, should be alert, which is the cumulative effect of the two.
Reporter: is not the power of the device the more electromagnetic radiation, the stronger, "pollution" is also greater? In addition to the power level, what other factors can affect the degree of "pollution" strength?
Zhang Hui: domestic and foreign research has found that electromagnetic radiation on human health hazards associated with the following factors: power density, the higher the power density, the stronger the effect of radiation; electromagnetic wave length, the shorter the wavelength, the greater the impact on the human body; waveforms, pulsed waves than the impact of continuous waves; the distance from the source of radiation, the distance and the field strength of the inverse proportionality of the relationship between the distance from the source of radiation, the radiation intensity will be greatly weakened; exposure time, the exposure time, the distance and the field strength of the radiation will be greatly weakened. greatly weakened; exposure time, the longer the exposure to radiation, the greater the impact; the surrounding environment, the higher the temperature of the surrounding environment, the stronger the human body's response to radiation; in addition, the physiological state of the human body, gender, age, the degree of sensitivity to radiation is also different, the impact on women and children is generally larger than that of adult males. Finally, different individuals on the electromagnetic radiation response is also very different, some people "adaptive" ability is stronger, while some people in the same environment can not endure.
Strengthening radiation protection knowledge of publicity and popularization, so that people correctly understand the source of radiation and harm, to take a variety of protective measures to curb the pollution of electromagnetic radiation
Reporter: What measures should we take to prevent the infringement of electromagnetic radiation?
Zhang Hui: understand the mechanism and factors of electromagnetic radiation pollution, then prevent the infringement of electromagnetic radiation by the most basic principles and ideas is to control and protection. For us personally, it is no more than two points - away from and blocking. Although electromagnetic radiation has a strong ability to penetrate, but also can be blocked with special methods and materials, which need to start from the perspective of product design, shielding and absorption, to take the root causes and symptoms of the combination of methods.
Reporter: Can you talk about it specifically.
Zhang Hui: electromagnetic radiation pollution on the one hand, there is a radiation source radiation, on the other hand, people or equipment in the acceptance of radiation, "pollution", so pollution control is basically divided into two categories. The first category, belonging to the leakage and radiation sources in the protective measures taken, mainly focusing on reducing the electromagnetic leakage of equipment and electromagnetic leakage, so that the leakage of electromagnetic field strength and power density into space to minimize the extent of its protective technology has electromagnetic shielding, grounding technology, filtering, absorption protection and so on. In terms of anti-interference, shielding is the best measure. In layman's terms, electromagnetic shielding is the use of some kind of material made of a closed object - the interior of its object and the external area of the closed body is not affected by the electromagnetic field inside it. RF grounding is the field source shielding body or shielding body components due to the generation of induced currents and take rapid diversion, resulting in equal potential distribution measures. Line filtering is one of the most effective means of suppressing electromagnetic interference, its role is to ensure that useful signals through, and block useless signals. Absorption protection is a kind of radiation energy has a strong absorption effect of the material laid on the periphery of the field source, in order to prevent a wide range of pollution. In recent years, science and technology workers have developed a low-frequency electromagnetic radiation of general-purpose materials, the key components of the material is made of zinc, cobalt, lithium, cadmium, magnesium, copper and other iron compound, the formation of low-frequency electromagnetic radiation can effectively absorb 500-5600 MHz ferrite magnetic materials. This "compound" material ratio is the use of computer simulation and experimental technology combined with the means to prove and optimize, has a high degree of scientific and advanced, greatly improving the absorption rate, such as the material added to the ordinary paint, can be prepared to be widely used in the interior and exterior walls of buildings, furniture, electronic equipment, military stealth technology and many other fields. Home appliance manufacturers can reduce the electromagnetic leakage and radiation of home appliances through these methods. In addition, large-scale afforestation and greening is also an effective way to reduce electromagnetic radiation, because trees and other green plants have an absorption effect on electromagnetic radiation.
The second category, belonging to the operator, including the working environment of the operator to take protective measures, personal protective measures are mainly wearing protective clothing, protective helmets and protective glasses, etc.; in the daily work life, a variety of household appliances, office equipment, cell phones, etc., should try to avoid prolonged operation, the person should be kept at arm's length, while trying to avoid a variety of office and Home appliances at the same time, etc..
Reporter: now buy a house and choose a place to consider the surrounding there is no large transformer station, transmission lines, it seems that these ideas are not superfluous, but the complete absence of electromagnetic radiation is almost impossible, then, people are more concerned about the human body's health, electromagnetic radiation to what extent is safe? What are the current national control standards on electromagnetic radiation?
Zhang Hui: everything has a degree, as long as the control within the scope of this degree, things will be good. Electromagnetic radiation protection standards is the degree of environmental protection. Electromagnetic radiation protection standards have experienced a long time of discussion, and so far there is still no unified standards around the world. However, China has formulated a national standard: "Regulations on Protection against Electromagnetic Radiation", which stipulates that the protection limit of electromagnetic radiation ranges from 100KHz to 300GHz, and "Health Standards for Microwave Radiation in Workplaces" stipulates that the standard of electromagnetic protection is 40 microwatts/square centimeter. This is four times stricter than Western and international standards. The Environmental Electromagnetic Wave Health Standards, with the electromagnetic wave radiation intensity and its frequency band characteristics of the human body may cause potentially adverse effects of the sub-threshold value as the boundary of the permissible radiation intensity of the environmental electromagnetic wave standards are divided into two levels: the first level of standards for the safety zone, refers to the environmental electromagnetic wave intensity of the long-term residence, work, life of all the people (including infants, pregnant women and the old, weak, sick and disabled) will not be subjected to any harmful effects of the Area. Newly built, reconstructed or expanded radio, television and radar stations and other transmitting antennas must meet the requirements of the "Level 1 standard" in their residential coverage areas. The secondary standard is the intermediate zone, which refers to the area where all people (including infants, pregnant women, the elderly, the infirm, the sick, and the disabled) who live, work, or work for a long time under the intensity of electromagnetic waves in the environment may cause potentially adverse reactions. In this area, factories and organizations can be built, but not residential houses, schools, hospitals and nursing homes, etc., and appropriate protective measures must be taken for those that have been built. Areas exceeding the secondary standards can have harmful effects on human beings. In this area, greening or planting of crops is allowed, but the construction of residential houses and all public **** facilities where people often move around, such as institutions, factories, stores and theaters, etc. is prohibited. In addition, the State Environmental Protection Administration has issued the "National Management Measures for Electromagnetic Radiation Environmental Protection", so that there is a legal basis for governance.
Reporter: What problems do you think still exist in electromagnetic radiation pollution? The development of protection technology can solve this problem?
Zhang Hui: Today, more and more electronic and electrical equipment put into use, so that a variety of frequencies, different energies of electromagnetic waves flooding every corner of the earth, and even the broader cosmic space. Among them, electromagnetic radiation equipment design is unreasonable, the lack of necessary suppression of technical measures, operation is not standardized, etc. is the cause of electromagnetic radiation pollution obvious reasons. It should be said that electromagnetic radiation pollution is becoming more and more serious, and some of the problems brought about by it in many aspects are still far from being recognized. Therefore, should strengthen the radiation protection knowledge of extensive publicity and popularization, so that people correctly understand the source of radiation and harm, improve self-protection and health awareness; electromagnetic radiation pollution for special studies, and to be a comprehensive treatment, the relevant departments should be formulated as soon as possible to prevent electromagnetic radiation pollution laws and regulations, improve and supplement the original standards, the development of the corresponding regulation and treatment, and clear authority and responsibility of the Department of the law, the management of the non-compliance of the Frequency management, electromagnetic pollution caused by the behavior of investigation and punishment, electromagnetic radiation pollution management into the daily environmental protection work track. With the rapid development of science and technology, I believe that in the near future electromagnetic radiation protection technology will be further improved, many research institutions and manufacturers will develop more, more effective anti-electromagnetic radiation civilian products, electromagnetic radiation on human health hazards will gradually reduce the people will be safe and secure to enjoy the convenience and comfort of electrical equipment.