Pregnant women radiation suit: safe? effective?

China Textile Newspaper, General Logistics Department, Quartermaster Equipment Research Institute, Beijing University of Technology Joint Sampling Test

————Pregnant women’s radiation protection test data released

Recently, the "radiation-proof door" incident that has been stirred up by the media has caused many domestic well-known radiation protection clothing brands to linger in the whirlpool. Is it a "dark war" between industries or commercial speculation? The focus of the debate is all about the core issue of whether wearing radiation protection suits is effective. "Seeking truth" and "requiring data" have become the most urgent demands of the public and the media. In response to these problems, the newspaper interviewed Dr. Shi Wei, the drafter of GB/T 23463-2009 protective clothing microwave radiation protective clothing. With his many years of research and accurate testing of radiation, the public also has a clear truth. .

â–  It is unrealistic to expect radiation protection clothing to be protected.

In order to confirm whether the radiation protection suits are effective or not, what is the shielding effect of the radiation protection suits of various brands? On December 31, 2011, Shi Wei and his team were selling the best selling moms and cherries in the market at Beijing University of Technology. 19 sets of anti-radiation samples from 8 brands, such as Youjia, were tested. The conclusion is that the radiation protection suit has a certain anti-radiation effect, but it is impossible to completely wrap people because of the radiation protection suit. In an environment with strong electromagnetic radiation, it is unrealistic to expect radiation protection suits to be protected.

According to Shi Wei, the test uses the flange coaxial transmission line method specified in QJ2809-1996 "Shielding Effectiveness Measurement of Planar Shielding Materials", which tests three kinds of materials such as nylon silver plating, metal fiber and metal plating. , vest, apron, tops, trousers and other styles of radiation protection suits, the test refers to the "GB/T 23463-2009 protective clothing microwave radiation protective clothing" standard, the test frequency is divided into low frequency band 30 ~ 1000MHz (MHz) and high frequency band 1 ~18GHz (gih), the protection effect of the radiation protection suit in these two frequency bands is measured by two sets of transmitting and receiving systems, and the test power is 20.00dBm (decibel millivolt).

In the shielding effectiveness test of the radiation-proof sample, the inspector placed sensors for receiving electromagnetic waves of two frequency bands of high frequency and low frequency in the head, chest and abdomen of the two dummy. Firstly, the intensity of the back-end electromagnetic field in the low-frequency band and the high-frequency band is measured, and then the electromagnetic field strength of the dummy after wearing the radiation-proof suit is measured, and the shielding effectiveness of the garment is calculated according to the calculation formula specified in GB/T 23463.

Through rigorous testing, the test data that the public and the media are most concerned about are freshly released: electromagnetic shielding materials made of metal fiber, chemical fiber metallization or fabric metallization can shield the electromagnetic field and attenuate the electromagnetic field strength. The more tightly the radiation protection suit is shielded from the human body, the better the protective effect; for electromagnetic waves from frontal irradiation, such as vests and halter tops, the electromagnetic field of the exposed structure is still fixed. Degree of attenuation. The measurement results also show that the electromagnetic shielding effectiveness of the unprocessed shielding material is much higher than that of the radiation shielding suit made of the same shielding material, especially the radiation shielding suit with a small coverage area. For example, the material shielding effectiveness of the No. 8 sample is about 30 dB (decibel), and the shielding effectiveness of the garment is about 10-20 dB (equivalent to the energy of electromagnetic radiation is attenuated by 90% to 99%); No. 18 and No. 19 The shielding effectiveness of the clothing is about 60dB, the shielding effectiveness of the clothing is about 6~20dB (equivalent to 75%~99% of the energy of electromagnetic radiation), and the basic sealing performance is 20~40dB (equivalent to electromagnetic The energy of the radiation is attenuated by 99% to 99.99%). Since the electromagnetic shielding material generally has a higher shielding ability against high frequency than the low frequency, the high-frequency shielding performance is higher than the low-frequency shielding performance, whether the electromagnetic shielding material or the radiation protection device thus made, and the shielding effectiveness value is higher, the electromagnetic shielding The better the effect.

Shi Wei said that because the shielding layer has different results for multiple reflection of electromagnetic waves at different frequencies, the shielding effectiveness of the radiation protection suit at different frequencies has a certain degree of fluctuation. When the peak is high, it indicates that the shielding effectiveness is high at this frequency. The protection effect is good, and vice versa. In addition, if the position of the sensor is changed, the shielding effectiveness will also change.

Regarding the question of whether there is a difference between the dummy and the real person in the shielding test, Shi Wei explained that when the dummy is tested, the material of the dummy is electromagnetic wave transparent material, and basically does not absorb electromagnetic waves. For the real person, the electromagnetic wave When entering the human body, most of it is consumed on the epidermal tissue. Since the epidermal tissue is a tissue that is relatively insensitive to electromagnetic waves, it is not as susceptible to disease as organs such as the heart and brain that are sensitive to electromagnetic waves.

Compared with the state in which a real person wears a radiation suit, the use of a dummy to measure the radiation protection suit, since the skin's absorption of electromagnetic waves is neglected, the measured result should be more conservative.

â–  Popularizing scientific knowledge is the best gift for mothers

Shi Wei talked about his personal opinion when summarizing the test results: electromagnetic radiation protective clothing was developed for professional personnel (such as missiles, radar debuggers, communication base station maintenance personnel, etc.) working in a strong electromagnetic field environment, It should be worn by the public. Shi Wei said: "At present, the electromagnetic environment we are in has not deteriorated to the extent that individuals need to protect themselves. According to the data of the electromagnetic environment measurement conducted by the German Federal Radiation Safety Office, the color TV is taken as an example and measured at 30cm (cm). The resulting magnetic field strength is only 60v/m (volts per meter), far below the international standard of 5000v/m2 (volts per square meter)."

In fact, even the nuclear accident at the Chernobyl nuclear power plant, the world's most serious, has only 28 people who died of nuclear radiation, and 30 others died. According to Pan Ziqiang, a member of the International Committee of Radiological Protection and a member of the Chinese Academy of Engineering, "A follow-up study 14 years after the accident showed that no cancers attributable to ionizing radiation were observed except for the increase in thyroid cancer after exposure to childhood. Incidence or mortality has risen. One of the major concerns of the disease, the risk of leukemia, has not shown an increased trend, nor has it found evidence of other non-malignant diseases associated with ionizing radiation. But the psychological impact of accidents on people is widespread. Existence, this is mainly due to fear of radiation, not due to the actual radiation dose."

Based on this, Shi Wei believes that popularizing scientific knowledge is the best gift for mothers.

Related Links:

Electromagnetic radiation protection standard system and exposure limits

Since 1988, China has drafted and formulated six national standards on electromagnetic radiation by the Ministry of Health, the State Environmental Protection Administration and the Ministry of Electronics. The electromagnetic standards promulgated by the Ministry of Health include: GB 18555-2001 Occupational exposure limits for high-frequency electromagnetic fields in workplaces, GB 16203-1996 workplace frequency electric field sanitary standards, GB 10437-1989 UHF radiation hygiene standards for workplaces, GB 10436-1989 Hygienic standard for microwave radiation in workplaces, GB 9175-1988 Environmental electromagnetic wave sanitation standards.
The electromagnetic radiation protection standards promulgated and promulgated by the State Environmental Protection Administration have GB 8702-1988 electric field radiation protection regulations. In addition, for the environmental protection, HJ/T 10.3-1996 electromagnetic radiation environmental impact assessment methods and standards, HJ/T 24-1998 500kV ultra-high voltage transmission and transformation engineering electromagnetic radiation environmental impact assessment technical specifications two standards.

The electromagnetic protection standards formulated by the Ministry of Electronics have the radiation safety requirements for microwave and ultrashort wave communication equipment of GB 12638-1990.

However, due to the fact that the ministries have drawn their final business standards from their respective business and academic perspectives, they are still at the stage of “draft for comment”.

In addition, the national standards for electromagnetic protection are: GJB 7-1984 microwave radiation safety limit, GJB 475-1988 microwave radiation living area safety limit, GJB 476 living area microwave radiation measurement method, GJB 1001-1990 operation area ultrashort wave radiation measurement method , GJB 1002-1990 ultrashort wave operation area safety limit, GJB 2420-1995 ultrashort wave radiation living area safety limit and measurement method, GJB 3861-1999 short wave radiation exposure limit and measurement method.

In response to the above-mentioned standard ageing and content confusion, the General Armament Department took the lead and consolidated and unified the seven national military standards related to electromagnetic protection formulated since 1984, and also considered the concept of “exposure” and “limit”. GJB 5313 "Electromagnetic Radiation Exposure Limits and Measurement Methods" standard, which redefines the "exposure limit", was officially released in 2004.

The newly-developed GB/T 23463-2009 protective clothing microwave radiation protective clothing standard specifies that the shielding effectiveness of at least the electromagnetic radiation protective clothing should be calculated according to the exposure limit of GJB5313 and the electromagnetic radiation field strength of the workplace. Similarly, whether the public needs to wear electromagnetic shielding protective clothing, as long as the exposure limit corresponding to the standard and the actual electromagnetic field strength of the environment in which it is proposed can be concluded.

The chart below shows the comparison of exposure limits for typical domestic electromagnetic standards. For the sake of comparison, the electric field strength was used as an evaluation index of the exposure limit.
It can be seen from the figure that the exposure limits of various typical electromagnetic standards are shown as the "two heads high and the middle low" curve on the frequency axis, that is, electromagnetic waves for frequencies below about 30 MHz, and electromagnetic wave pairs above about 10 GHz. The human body has less damage, and the human body can withstand even when exposed to a high electric field strength; it becomes the most sensitive frequency band in the range of about 30 MHz to 10 GHz, and each typical electromagnetic standard specifies a relatively low exposure limit. That is, in this frequency range, the human body can only be tolerated under a lower field strength.

Pregnant women radiation suit test results (8 brands, a total of 19 samples)

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