移动电话辐射和健康

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移动电话辐射和健康问题随着世界上移动电话用户的急剧增长(到2005年8月,全世界有20多亿用户)收到越来越多的关注，因为移动电话使用微波范围的电磁波。These concerns have induced a large body of research (both epidemiological and experimental, in non-human animals as well as in humans). Concerns about effects on health have also been raised regarding other 数字无线系统, such as data communication networks.

The results, so far, have been controversial: the majority of epidemiological studies have not found any clear indication of short and medium term health hazards. On the other hand there is extensive literature (参看 "斯图尔特报告") on so-called non-thermal effects of weak microwave radiation on 生物组织 in animal models or in-vitro, including affecting the growth of certain 肿瘤, 细胞死亡, increased permeability of the blood-brain barrier, DNA损伤 and others, which suggest the possibility of adverse health effects in humans.

目录 1 听筒的健康危害 1.1 热效应 1.2 非热效应 1.3 电磁超敏感度综合症 2 基站的健康危害 3 职业病 4 安全标准和许可 5 诉讼 6 预防法则 7 参看 8 参考 9 外部链接

[编辑] 听筒的健康危害

一部分从移动电话听筒部分发射的无线电波就被人类头部吸收了; 例如:由GSM手持設備發射的電波可能有超过2 瓦特的功率、模拟电话(可能很少见了)可达到3.6瓦特, 如同车载的旧式大型移动电话。今天其它如CDMA和TDMA这样的数字移动电话, 功率都要小于1瓦特。 在某些國家，針對行動電話的平均發射功率制定了標準並有提醒消費者相關資訊的義務(通常印在电池組件)。在一些系统中，移动电话和基站检测收訊品質和信号强度，在前述的限制之下发射功率水平自动的提升或者降低（例如在建築物或車輛中）。

The rate at which radiation is absorbed by the human body is measured by the Specific Absorption Rate (SAR), and its maximum levels for modern handsets have been set by governmental regulating agencies in many countries. In the USA, the FCC has set a SAR limit of 1.6 W/kg, averaged over a volume of 1 gram of tissue, for most parts of the body. (SAR values are heavily dependent on the size of the averaging volume. Without information about the averaging volume used comparisons between different measurements can not be made.)

[编辑] 热效应

One well-understood effect of microwave radiation is dielectric heating, in which any dielectric material (such as living tissue) is heated by rotations of polar molecules induced by the electromagnetic field. In the case of a person using a cell phone, most of the heating effect may occur in the head surface, causing its temperature to increase by a fraction of a degree. The level of temperature increase is an order of magnitude less than that obtained during the exposure of head to direct 阳光. The brain's 血液循环 easily disposes of excess heat by instantaneously increasing local blood flow. However, the cornea of the eye does not have this 温度调节机制. Premature cataracts is known as an occupational disease of engineers who work on high power radio transmitters at similar frequencies. Due to the low power of mobile phones, cataracts have not been reported to occur in users of these.

It has been claimed that some parts of the human head are more sensitive to damage due to increases in temperature, particularly in anatomical structures with poor vasculature, such as nerve fibers. More recent results from a Swedish scientific team at the Karolinska Institute (Lonn, Ahlbom, Hall and Feychting) have suggested that continuous use of a mobile phone for a decade or longer can lead to a small increase in the probability of getting acoustic neuroma, a type of brain tumor. The increase was not noted in those who used phones for less than 10 years. The study has been criticized for possible problems in data analysis such as recall bias. However, another study conducted by the Swedish National Institute for Working Life supported an increased risk of "malignant tumors on the side of the head the phone is used." [1] It should be noted such long term heavy use involved phones of older higher power analog designs; that were first introduced to Sweden in 1984, earlier than many other countries.

[编辑] 非热效应

In December 2004 a pan-European study showed compelling evidence of DNA damage of cells when exposed between 0.3 to 2 watts/kg. This overlaps with the level of radiation typically emitted by digital cell phones of around 0.2 to 1 watt/kg. There were indications, but not rigorous evidence of other cell changes, including damage to chromosomes, alterations in the activity of certain genes and a boosted rate of cell division. [2] The results of this study run contrary to many similar studies that were conducted before and showed no increase in DNA damage. [3]

The communications protocols used by mobile phones often result in low-frequency pulsing of the carrier signal. These low frequencies are similar to those that exist in the electrical oscillations of the human body, specifically the alpha and delta brain waves. Non-linear interactions could theoretically result when resonances are created when the brain is subjected to mobile phone radiation, in a manner similar to that observed when light strobing induces photosensitive epilepsy in susceptible individuals. No experimental results have indicated this theoretical possibility, however. These and other non-thermal effects are summarized in (Hyland, 2000).

[编辑] 电磁超敏感度综合症

Many users of mobile handsets have reported feeling several unspecific symptoms during and after its use, such as burning and tingling sensations in the skin of the head and extremities, fatigue, sleep disturbances, dizziness, loss of mental attention, reaction times and memory retentiveness, headaches, malaise, tachycardia (heart palpitations) and disturbances of the digestive system. Some researchers, implying a causal relationship, have named this syndrome as a new diagnostic entity, EHS or ES (electrosensitivity). The World Health Organization prefers to name it "idiopathic environmental intolerance", in order to avoid the implication of causation. This entity is quite controversial, because albeit identified in unmistaken terms by the patients who affirm to suffer from it, in some cases in such a radical way that they avoid using cellphones, it has not been recognized as a separate clinical entity by most medical researchers.

Two recent literature reviews, however, one reviewing 13 published papers in 2003 and 2004, and another reviewing 31 papers published before 2004, have concluded that there is no scientific evidence for a causal relationship between the reported clusters of symptoms and exposure to microwave radiation used in cellphones, well below the safety standards. A workshop conducted by the WHO in Prague in 2004 also reached the same conclusions, viz., that 1) reported symptoms are very unspecific and could have other causes; 2) there is no causal association demonstrated between exposure and symptoms, 3) that patients who display those symptoms should be medically examined for alternative explanations and causes, including psychiatric/psychological ones (since they are typical manifestations of stress and other somatization/psychosomatic causes), and that the environment where they work or live should be assessed in order to discover other factors at work that could explain the symptoms; and 4) lowering the safety limits for handset radiation (SAR levels) will not affect the situation.

[编辑] 基站的健康危害

Another area of worry about effects on the population's health have been the radiation emitted by base stations (the antennas on the surface which communicate with the phones), because, in contrast to mobile handsets, it is emitted continuously. Due to the attenuation of power with the square of distance, field intensities drop rapidly with distance away from the base of the antenna. A 2002 survey study by Santini et al. found a variety of health effects for people living within 300 m of base stations. Fatigue, headache, sleep disruption and loss of memory were among the effects found. [4]

As technology progresses and data demands have increased on the mobile network, the number of towers has increased sharply in many cities, and competing companies usually do not make an effort towards sharing towers. The latest trend is 3G towers, which work with higher bandwidths. The buildup of networks has sparked many health concerns and much community outrage. Examples of such can be seen from headlines around the world; locals pulling down base station masts, or even, in some countries, physically attacking installation crews, communities lobbying against the rollout of cell networks, protest banners, demonstrations near hospitals, houses and local schools.

Many measurements and experiments have shown, however, that transmitter power levels are relatively low - in modern 2G antennas, in the range of 20 to 100 watts. The ACA (Australian Communications Authority) and ARPANSA (Australian Radiation Protection and Nuclear Safety Agency) recently announced that the 3G towers actually cause less radiation than the already present 2G network. An average radiation power output of 3 watt is used. 'Micro-cell geometries' inside cities have decreased the amount of irradiated power even further. ^{[來源請求]}

A common misconception is that the propagation of more towers inevitably adds to a more strongly irradiated area. In fact, it can result in lower radiated powers since the distance between transmitter and receiver is lower. This was noted by Prof Stephen Barton in his report for Manchester City Council in June 2001 (not available online, referenced in section 2.21 of [5], [6]). Base stations create interference patterns or regions where their signals add (in phase) or cancel (out of phase). Base stations which are too closely located can also interfere with each other's operation, leading to competition between cell phone companies for sites.

In May 2006, the top two floors of the RMIT University in Melbourne, Australia were closed pending further investigation after seven staff members who worked there were found to have developed brain tumours over a seven year period. Newspaper reports speculated that a mobile phone transmission tower located on the roof of the RMIT building may have been a factor. While experts were quick to point out that there is no accepted proof of causal relationship between brain tumours and close proximity to mobile phone towers, the incident is now being investigated. [7][8][9]

[编辑] 职业病

Telecommunication workers who spend time at a short distance from the active equipment, for the purposes of testing, maintenance, installation, etc. may be at risk of much greater exposure than the general population. Unfortunately, many times base stations are not turned off during maintenance, because that would affect the network, so people work near "live" antennas.

In this way, excessive radiation levels may lead to adverse health effects, including severe acute burns or milder chronic alterations of the skin, and perhaps other non-thermal effects which have not yet been fully documented. Adequate individual protection equipment, short stays and turning off the equipment while nearer to them should suffice to prevent health hazards for the workers.

A variety of studies over the past 50 years have been done on workers exposed to high RF radiation levels: Studies including radar laboratory workers, military radar workers, electrical workers, amateur radio operators. Most of these studies found no increase in cancer rates over the general population or a control group. Many positive results could have been attributed to other work environment conditions, and many negative results of reduced cancer rates also occurred. [10]

[编辑] 安全标准和许可

In order to protect the population living around base stations and users of mobile handsets, governments and regulatory bodies adopt safety standards, which translate to limits on exposure levels below a certain value. There are many proposed national and international standards, but that of the International Committee for Non-Ionizing Radiation Protection (ICNIRP) is the most respected one, and has been adopted so far by more than 80 countries. For radio stations, ICNIRP proposes two safety levels: one for occupational exposure, another one for the general population. Currently there are efforts underway to harmonise the different standards in existence.

Radio base licensing procedures have been established in the majority of urban spaces regulated either at municipal/county, provincial/state or national level. Telcos are required to obtain construction licenses, provide certification of antenna emission levels and assure compliance to ICNIRP standards and/or to other environmental legislation. Posterior alterations in the level of emission, number of active antennas or technology standards used in an installed antenna array might require new licensing procedures.

Many governmental bodies also require that competing telcos try to achieve sharing of towers so as to decrease environmental and cosmetic impact. Regarding this issue, it is an influential factor of rejection of installation of new antennas and towers in communities. In some cases, camouflaging the towers like tree trunks and other more visually acceptable structures has been tried.

[编辑] 诉讼

In the USA, a small number of personal injury lawsuits have been filed by individuals against cellphone manufacturers, such as 摩托罗拉, NEC, 西门子 and 诺基亚, on the basis of allegations of causation of brain cancer and death [11]. So far, most of these lawsuits have been dismissed by the courts, on lack of scientific evidence of such a causal relationship, and this has been reducing the motivation of tort lawyers eager to mine a new vein of health injury lawsuits.

[编辑] 预防法则

Although scientific evidence for health hazards of low level cellphone radiation is weak, the World Health Organization has recommended that the precautionary principle could be voluntarily adopted in this case (see WHO Electromagnetic Fields and Public Health Cautionary Policies). It follows the recommendations of the European Community for environmental risks. According to the WHO, the Precautionary Principle is "a risk management policy applied in circumstances with a high degree of scientific uncertainty, reflecting the need to take action for a potentially serious risk without awaiting the results of scientific research." Other less stringent recommended approaches are prudent avoidance principle and ALARA (As Low as Reasonably Achievable). Although all of these are problematic in application, due to the widespread use and economical importance of wireless telecommunication systems in modern civilization, there is an increased popularity of such measures in the general public. They involve recommendations such as the minimization of cellphone usage, the limitation of use by at-risk population (such as children), the adoption of cellphones and microcells with ALARA levels of radiation, the wider use of hands-off and earphone technologies such as Bluetooth headsets, the adoption of maximal standards of exposure, RF field intensity and distance of base stations antennas from human habitations, and so forth.

[编辑] 参看

• 电磁辐射危害
• 无线电设备和健康
• Specific absorption rate
• 辐射生物学
• Electrical sensitivity

[编辑] 参考

• Repacholi, M.H. Health risks from the use of mobile phones. Toxicology Letters, 2000. available at [12] (PDF Format)
• G J Hyland (2000). "Physics and biology of mobile telephony". The Lancet 356: 1833-1836.

• Shaw CI, Kacmarek RM, Hampton RL, Riggi V, Masry AE, Cooper JB, Hurford WE. (2004). "Cellular phone interference with the operation of mechanical ventilators.". Crit Care Med. 32: 928-31.

• Lawrentschuk N, Bolton DM. (2004). "Mobile phone interference with medical equipment and its clinical relevance: a systematic review.". Med J Aust. 181: 145-9.

• Seitz, H, Stinner, D, Eikmann, Th, Herr, C, Roosli, M. Electromagnetic hypersensitivity (EHS) and subjective health complaints associated with electromagnetic fields of mobile phone communication -- a literature review published between 2000 and 2004. Science of the Total Environment, June 20 [e-publication ahead of print], 2005, available at http://www.sciencedirect.com.
• Rubin, GJ, Das Munchi, J, Wessely, S. Electromagnetic hypersensitivity: a systematic review of provocation studies. Psychosom Med. Mar-Apr; 67(2): 224-32. 2005, available at [13].
• WHO Workshop on Electromagnetic Hypersensitivy, Prague 2004.

[编辑] 外部链接

• WHO International EMF Program
  • Electromagnetic fields and public health: Mobile telephones and their base stations. WHO Fact Sheet 193. June 2000.
• MMF Mobile Manufacturers Forum
• International Commission on Non-Ionizing Radiation Protection (ICNIRP)
• Independent Expert Group on Mobile Phones (IEGMP), UK
  • Mobile Phones and Health ("Stewart Report", 2000)
• A Biomedical Science and Engineering Clearinghouse on Electric and Magnetic Fields. EMF-Link.
  • Cellular phones/towers and public health
• The Karolinska study
• Review of studies of Cell phone radiation and cancer (PDF)
• Reported Biological Effects From Radiofrequency Non-Ionizing Radiation. WaveGuide.Org
• Cell phones - do they cause cancer? (NIH)
• FDA Cell Phone Facts
• FCC Radio Frequency Safety
• Happiness Is a Low-SAR Cell Phone (Evaluation Engineering, February 2003)
• Cell Phone Base Antennas and Human Health FAQ (John Moulder, Medical College of Wisconsin)
• Health Risks of Cellular Telephones: The Myth and the Reality (Ontario Public Health Association position paper, 2003)
• Guide to Wireless Industry Health Questions
• FDA/CTIA Research Agreement
• GAO Report: Research and Regulatory Efforts on Mobile Phone Health Issues - PDF
• How cell phone radiation can cause visual damage - an online article
• Sins Of Transmission? Vatican Radio's high-power antennas stand accused of causing cancer. Article by Alexander Hellemans, IEEE Spectrum On-Line, Oct. 2005.
• Microwave News Reporting on electromagnetic fields and radiation since 1981.