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Mobile phone radiation and healthMobile phone radiation and health concerns have been raised following the enormous increase in the use of wireless mobile telephony throughout the world (as of December 2004, there were more than 800 million users worldwide). This is because mobile phones use electromagnetic radiation in the microwave range. These concerns have induced a large body of research (both epidemiological and experimental, in animals as well as in humans). The results, so far, have been controversial: the majority of studies have not found any indication of short and medium term health hazards, while some have described positive results for several biological parameters, such as the growth of certain tumors, the opening of the brain barrier, and others. It has been postulated by some researchers that these could be so-called non-thermal effects of microwave radiation on biological tissue. Most, if not all positive studies, however, could not be replicated in other, similar studies. Moreover, reported effects are usually near statistical non-significance levels. For example, a reported increase in incidence of brain tumors of 2.5 times in cellphone users than non-users might appear a large effect. But, its significance depends on the rarity of the disease. If there were 4 cases in a year, for example, and two other cases appear, this is already a 50% increase, but this doesn't mean that there is a undeniable association with the putative cause. This could have resulted by chance alone, or by other unknown or uncontrolled conditions (such as the increase of longevity of population and the decrease in other causes of death). Possible health hazards of microwave EMF used in cellular telephony could be classified into:
Health hazards of handsetsPart of the radio waves emitted by a mobile telephone are absorbed by the human head; the radio waves emitted by a GSM handset can have a power of up to 2 watts, and an analog phone in the USA (probably very few in use today) can have 3.6 watts, as in the old large mobile phone units installed in cars. Other digital mobile technologies, such as CDMA and TDMA, have today lower rates, under 1 watt. The average radiation rate of cellphones in some countries is regulated and it is mandatory to inform the consumers about it (usually printed in the battery compartment). 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 bodies in many countries. Since the microwave spectrum is non-ionizing electromagnetic fields (EMF), according to the scientific consensus, the only effect on the human body is that the temperature of the head may increase by a harmless fraction of a degree during prolonged calling, actually several orders of magnitude less than that obtained during the exposure of head to direct sunlight for a time. The thick skull bones are a respectable heat shield developed by evolution, and the brain's blood circulation easily disposes of excess heat by instantaneously increasing local blood flow. However, some controversial studies claim that there exist other undesired effects on health as a direct result of the radiation. It has been claimed, for example, 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 continous use of a mobile phone for a decade or longer can lead to a small increase in the probability of getting a certain type of brain tumor (acoustic neuroma). However, according to the study, the overall effect of mobile phone use is not associated with a statistically significant increase in tumour incidence. The increase only occurs in the subgroup who used phones for longer than 10 years. It is not clear whether this subgroup was chosen before or after seeing the data. If the latter, it would be subject to severe bias (data dredging). The study has also been criticised for its reliance on the subject's recall of their own usage over the 10-year period, as such recall bias is a well-established phenomenon. This report is typical of many in this area: a result is reported widely that has potentially major impact on human health, but there are doubts in the scientific community about the experimental design or the data analysis. 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. Because of the study's size the results were replicated many times over leading one researcher to state: "to me there is no doubt that it causes DNA damage under certain conditions." 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.[1] The results of this study run contrary to many similar studies that were conducted before and showed no increase in DNA damage.[2] 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 are thought to 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. These non-thermal effects are summarized in (Hyland, 2000). Health hazards of base stationsAnother area of worry about effects on the population's health have been the radiation emitted by base stations (the antennas located inside geographical areas named cells which are part of the cellular network), because, in contrast to mobile handsets, it is emitted continuously. Many measurements and experiments have shown, however, that radiation levels are low (particularly in modern antennas, in the range of 20 to 100 watts) and decay sharply with distance from the tower (with the square of distance). Thus, if international norms of safety are respected (in relation to minimal distance to human habitations and direction and intensity of field), there is no cause for additional precautions. Governmental authorities usually pass legislation which regulates the application of these norms. The non-thermal effects described in (Hyland, 2000) are due to frequency interactions between the mobile phone communciations protocols and the human body, and not primarily the intensity of radiation. If epidemological evidence is accumulated to show some health risks as a result of these interactions, base stations may be implicated in addition to handsets. The World Health Organization has a special study program on the effects of electromagnetical fields on human health which periodically examines the scientific evidence on these aspects. So far (the next report is scheduled for 2006-2007) it has concluded that there are no demonstrable effects of EMF used in mobile phones and wireless telecommunication systems on human health. Occupational health hazardsIf it is often the case that populated areas are at such a distance from radiating antennas, that the law of inverse square guarantees that radiation levels will be harmless. But this is not true of telecommunication workers who stay sometimes for longer periods at a short distance from the equipment, for the purposes of testing, maintenance, installation, etc. (unfortunately, many times base stations are not turned off during such chores, because that would affect the network, so people work near "live" antennas). In this way, excessive radiation levels may lead to health alterations, 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 passed 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 reduces cancer rates also occurred.[3] Indirect health hazardsMore recently, due to the increase miniaturization and higher power of mobile phone batteries, cases of explosion have been reported, sometimes causing personal injuries and fire. Such incidents are very rare, and have been linked with cheaper, non-manufacturer-approved (and sometimes counterfeit) batteries. Another documented hazard of using mobile phones is electrical interference with some types of digital medical equipment, such as respirators in Intensive Care Units . Such interference could theoretically cause the death of a patient dependent on the equipment. For this reason, using any kind of wireless devices, including mobile phones, inside some areas of hospitals is forbidden. The single greatest indirect health risk (and perhaps the most lethal risk in general from mobile phone use) is using mobile phones while driving. Dialing numbers, receiving calls and holding conversations on mobile phones reduces the concentration required by motorists, and limits the use of one hand while driving. In the United States alone, it has been estimated that more than 2,000 deaths and 30,000 injuries occur every year due to the use of mobile phones by motorists. A study of 699 Canadian drivers with mobile phones found that the risk of a collision when using a mobile phone was four times higher than the risk when a mobile phone was not being used. Some countries, provinces and states are considering or have already banned mobile phone use while driving, or require that a “hands-free” cell phone system be used while driving. Switzerland, Italy, and Hungary already require that “hands-free” devices be used while driving. As of December 2003, Britain has forbidden mobile phone use while driving, by penalty of a fine. But restrictions on mobile phone use while driving remains controversial: Many criticize them as restrictions on personal freedoms, and argue that mobile phones are no more distracting than listening to music while driving, having conversations with passengers, etc. Precautionary PrincipleAlthough 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, the adoption of maximal standards of exposure, RF field intensity and distance of base stations antennas from human habitations, and so forth. Related topicsReferencesExternal linksThe contents of this article are licensed from Wikipedia.org under the GNU Free Documentation License.
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