In recent years, the development of mobile communications business is rapidly changing, the rapid expansion of the user base, only in Guangdong Province, cell phone users have exceeded 60 million. In order to ensure smooth mobile communications and achieve seamless coverage, telecom operators sometimes need to build additional mobile communication base stations in office buildings and residential areas with high call demand.
However, out of misunderstanding and concern about electromagnetic radiation, residents in many areas have shown resistance and rejection, and in some areas have even obstructed the construction of base stations.
On the one hand, many cell phone users require good signal coverage, calls do not drop; on the other hand, no one is willing to communications base stations built in front of their homes. This has become a dilemma for mobile communication services. And, for the base station radiation "panic complex", now there is also a big trend of spreading.
Will mobile base stations bring radiation pollution? Will it cause harm to human health? In order to help the majority of readers a deeper understanding of the radiation of mobile base stations, we visited the relevant departments and electromagnetic radiation research experts, hoping to clarify the truth through science and facts, to solve the mystery of people's depression in the heart.
As one of the products of high-tech, mobile communication technology is unfamiliar to the general public. The lack of knowledge about mobile communications is the root cause of the fear of radiation from base stations. This, coupled with the inevitable academic controversies and sensationalized reports in the media at home and abroad, has led to some inexplicable fear and resistance among the public.
We live in electromagnetic radiation every moment, but only electromagnetic radiation exceeds a certain frequency and power caused by "electromagnetic pollution", will be harmful to the human body.
The interaction of electric and magnetic fields produce electromagnetic waves, electromagnetic waves into the air or the phenomenon of convergence, called electromagnetic radiation.
In fact, human beings live in an electromagnetic radiation environment every moment. Because the earth itself is a large magnetic field, it is the surface of the thermal radiation and lightning can produce electromagnetic radiation, the sun and other planets from outer space is also a constant source of electromagnetic radiation. Although electromagnetic radiation is widespread, in the vast majority of cases it is not frightening. When electromagnetic radiation energy (its size expressed in field strength) is controlled within certain limits, it is beneficial to the human body, organisms and other living organisms, it can accelerate the microcirculation of living organisms, to prevent the occurrence of inflammation, but also to promote the growth and development of plants.
Whether electromagnetic radiation is harmful to the human body depends mainly on two factors: one is to look at the frequency of electromagnetic radiation, and the other is to look at the size of the electromagnetic radiation power. Only when these two factors exceed a certain permissible value and cause radiation pollution, it is possible to have a negative impact on the human body.
Therefore, electromagnetic radiation is not yet directly equivalent to electromagnetic pollution, not to mention directly linked directly to human health.
The radiation frequency of the base station is about 900 megahertz, which is basically comparable to that of a television. The power it emits and receives is only ten or twenty milliwatts, not enough to constitute radiation pollution.
So, what are the places in our living and working environment where electromagnetic radiation is greater? This is mainly 1) computer 0.6-1.5 meters away; (2) living room in the television, stereo and other home appliances are more concentrated; (3) industrial, scientific, medical electrical equipment and VDT around; (4) high-voltage transmission lines and equipment around.
Although mobile communication base station is also through the electromagnetic wave transmission of information, but compared with computers, home appliances and professional electrical equipment, etc., the base station does not belong to one of the stronger radiation sources. Especially based on the use of digital technology, modern mobile communications radiation intensity has been further controlled.
Currently, China's mobile communication base station standards mainly refer to the State Environmental Protection Administration and the Ministry of Health issued by the "electromagnetic radiation protection regulations" and "environmental electromagnetic wave health standards". Specifically, the national standard requires that the electric field strength is less than 12 volts / m or that the power density per square centimeter is less than 40 microwatts. Compared with developed countries in Europe and the United States, this standard is much stricter.
And the radiation frequency of mobile communication base stations is about 900 megahertz, which is basically comparable to that of television. Mobile communications are now taking the micro-cellular technology, both issued and received power is very low, only a dozen milliwatts, 20 milliwatts of energy level, completely insufficient to cause radiation pollution.
At the same time, the general GSM base station antenna height are in 35 to 55 meters, the transmit power of 20 watts of high-power base station, the antenna of the first 10 meters of the power density is 0.6 microwatts per square centimeter. Therefore, the GSM base station if the antenna height is above the safety value, a certain distance from the residential building, electromagnetic waves in the air will be further attenuation, people receive electromagnetic radiation is even smaller.
The more base stations are built, the greater the radiation - such a view is a misunderstanding. On the contrary, the higher the density of base stations, the lower the power, electromagnetic radiation may be lower.
GSM mobile communications using micro-cellular technology, cell phones and base stations through the electromagnetic wave two-way contact, each base station has a certain range of action. In order to ensure good call quality, it is necessary to establish multiple mobile base stations in multiple locations to increase the coverage of information. Many people are concerned that the more base stations built in residential areas, the greater the radiation.
The opposite is true. The higher the density of base stations, the less electromagnetic radiation they emit. At the same time, the closer you are to a base station, the lower the power of electromagnetic radiation emitted by your cell phone. In order to ensure smooth and sensitive mobile communications, mobile communications base stations must be deployed according to geographic location and benefit area.
There is also a question of whether the electromagnetic radiation in the overlap area of two base stations is double? Experts take a negative view on this, the radiation value at the edge of the radiation range of the base station is very low, even if people are in the overlap zone of the radiation range of the two base stations, they will not be subjected to a lot of radiation.
Sayings
Professor Wang Liangyuan, dean of the Nanjing Institute of Posts and Telecommunications:
No need to be nervous about the radiation from base stations
So far, there is no sufficient evidence to prove that the radiation from base stations can be harmful to adults. In fact, any radiation is not good for the human body, but there are big and small radiation, we usually live in the environment itself is an environment full of radiation, base station radiation is only a very small piece of it, so there is no need for people to be overly nervous.
Guangdong Mobile:
Base station construction strictly enforce the national standards
Guangdong Mobile in the process of base station construction, the strict implementation of the national base station radiation standards, strict control of its radiation value. In addition, the opened and to be built base station will be entrusted to the relevant units to carry out environmental impact assessment of electromagnetic radiation, each phase of the base station expansion project will also be carried out environmental impact assessment, to master the identification parameters of this indicator, in order to ensure that the base station will not be caused by radiation radiation pollution, will not bring harm to the people.
Guangdong Provincial Communications Bureau:
Misunderstanding jeopardizes national communications security
Some local people do not quite understand the fear of electromagnetic radiation harmful to health, some are in the name of feudal superstition, feng shui to obstruct the construction of base stations, and now there are indeed a number of completed base stations are forced to dismantle the loss of national property, the necessary communications facilities can not be guaranteed.
This has been a relatively prominent contradiction, and I hope that enterprises and relevant government departments will strengthen publicity to break down superstitions and protect legitimate communication facilities.
Base station monitoring results in line with national standards
Now assuming that the base station antenna is in the state of transmitting the maximum power, while assuming that the antenna is directly in front of the antenna, no obstruction, in the indoor and outdoor in line with the GB9175-88 environmental electromagnetic wave permissible radiation field strength of the first level of intensity of the minimum distance (i.e., the safety protection distance), the resulting value of the safety distance as shown in the table.
The safety distance calculated here is obtained in an ideal state, and the actual situation is that residents or residential and other buildings are generally not directly opposite the antenna, not to mention close proximity to the antenna. At the same time, buildings, vegetation blocking, and the atmosphere of water, condensation and suspended matter on the electromagnetic wave absorption and scattering, will also cause propagation of attenuation. Moreover, in general, it is extremely rare for an antenna to be in a state of maximum transmitting power, and even if it occurs, it will not be maintained for a very long time. Therefore, the actual safety distance should be smaller than the above theoretical projection.
Based on the monitoring results of the Guangdong Environmental Radiation Research and Monitoring Center from January 2000 to June 2003 on some of the province's mobile communication base stations (Zhuhai Guihua Yuan, Foshan Distillery, Guangzhou Sports Center and other places of the mobile communication base station), it can be concluded in three aspects: First, any base station test point, the integrated electric field strength in the 900 megahertz passband of the mobile communication are lower than 12 V/m public exposure export limit; Second, the electromagnetic radiation around the base station in the range of 0.2-3.7 V/m, in line with the GB9175-88 environmental electromagnetic wave permissible radiation field strength of the first level of intensity of the safety standard requirements; Third, the public reflects the stronger "hot spot areas "Electromagnetic radiation problems, field strength test values are in line with engineering requirements and electromagnetic radiation design safety values.
Related links
No conclusive evidence of electromagnetic radiation causes cancer
As early as the 19th century, French scientists began to pay attention to the impact of radio waves on human health issues. However, until now, there has been no conclusive evidence that the usual electromagnetic radiation is harmful to the human body.
The Dutch Health Council published "Electromagnetic Fields: 2003 Update" in 2004. In the report, it was stated that since the strength of the electromagnetic fields generated by cell phones is below the radiation limits, these magnetic field emissions do not directly cause health problems. In addition, the committee said there was no need to restrict children's use of cell phones for health reasons.
Britain's National Council on Radiological Protection's Independent Advisory Group on Non-Ionizing Radiation (AGNIR) issued a comprehensive report, "Health Effects of Radiofrequency Electromagnetic Fields," in January 2004, which made the following conclusions:The Independent Advisory Group reviewed the evidence on the health effects of radiofrequency transmissions, in particular since the publication of the 2000 Stewart Report on cell phones and health, and the biological and epidemiological experimental evidence suggests that radiofrequency radiation below the levels specified in the guidelines, and in particular the use of cell phones, does not cause cancer or any other adverse health effects.
The Swedish Society for Radiation Protection (SSI) issued its first annual report on its Independent Expert Group (IEG) study on electromagnetic fields in December 2003, concluding:SSI's first annual report of the Independent Expert Group on the possible biological effects of radiofrequency electromagnetic fields focused mainly on epidemiological diseases, experimental cancer studies, damage to the blood-brain barrier, and heat shock proteins. There were no breakthrough results in any of these areas that could lead to definitive conclusions one way or the other.
In fact, much new research has been published in these areas in recent years, and the overall scientific assessment has not yet changed substantially since the release of the Stewart Report. As renowned physicist and member of the Chinese Academy of Sciences He Joao said, up to now, the world has not found a single confirmed case of harm to the human body due to electromagnetic radiation. Evidently, it is completely unnecessary to talk about base stations.