A Review Of The Health Effects And Benefits As Result Of Living Close To A Cell-phone Base Station

Transcription

1 A Review Of The Health Effects And Benefits As Result Of Living Close To A Cell-phone Base Station Prepared By Dr Derek Nitch CTO & CIO Antennas

2 1. In Summary Cell-phone radiation differs from X-ray (and nuclear) radiation in that it is non-ionising and hence cannot cause molecular changes in living tissue. The main effect of radio waves on living tissue is thermal heating (like in a microwave oven). Cell-phone handsets used in areas of poor signal strength expose users to 1000 times or more radio frequency power (RF power) than a cell-phone base station 20 m away. This is due to the fact that the cell-phone is much closer to the body than the base station and the power of radio waves dissipates very quickly with distance. Scientific studies have not shown that cell-phone radiation causes any cancer given that 100's of millions of people have been using cell-phones for around 30+ years and hundreds of studies have been performed around the world this risk must be low. The World Health Organisation (WHO) has recently (June 2011) classified prolonged cell-phone usage as possibly carcinogenic to humans. Cell-phones are now classified in the same category as coffee and pickled vegetables; they used to be classified in the group of agents below this group ( Not classifiable as to its carcinogenicity to humans ). The next classification used by the WHO is probably carcinogenic to humans in which we find the agents creosote and formaldehyde. The group thereafter contains agents that are carcinogenic to humans. In this group we find the agents alcohol, tobacco and radon amongst others. NOTE that the revised classification reported by the WHO refers to the effect of the use of the cell-phone and NOT the effect of the base station (which radiates humans to a much lesser extent than cell-phones). The GSM standard forces the cell-phone to reduce its radio power when it is in a region of strong base station signal. There is hence a benefit in having a base station close to you when making a call, since your cell-phone radio power will be reduced by a factor of 10 or more thereby reducing your total exposure to RF radiation and hence protecting you against the possibly carcinogenic effect referred to by the WHO. Of course, the major benefit is clear voice calls, fast data and long battery life for your phone! Sometimes being able to call the ambulance/police or not having the stress of a slow internet connection is of more health and wealth benefit. The scaremongering on TV, populist magazines and some internet articles is often based on hysteria and sensation rather than fact. 2. Discussion Does exposure to radio waves cause cancer or other adverse health effects? It is a question thousands of people are asking. It is easy to find articles on the internet and the public media lambasting cell-phone towers due to the 'dangerous radiation' they are emitting. In such articles, 'proof' is sometimes offered by showing how trees have died as a result of being too close to cell phone towers. Other articles claim that people have suffered from headaches and other ailments since the erection of a cell-phone mast. The evidence in these articles seems to corroborate the theory that living near a cell-phone mast is bad for your health. But is this really the case? There are two aspects of a cell phone network that need to be considered when contemplating the question of exposure to radio waves. First, there is the handset which is a relatively low power device but is used in close proximity to the body. Secondly, there are network base stations which have a higher power output and better antennas, but are generally situated many meters from users. Both aspects of the network have to be considered when discussing the possible health hazard of a base station in close proximity to one's home. The reason being that when one is close to a base station, (and one therefore has a strong cell-phone signal), the handset puts out very little RF power. When there is a weak cell-phone signal, the handset transmits much more RF power. Since the cell phone is the device that is close to one's body/head, the amount of power transmitted by the handset is significant. Why is the radiation from the handset so significant when one is comparing it to the radiation from a full base station? To answer this question, one has to consider the propagation of RF energy. Let us assume that a handset held against the ear is transmitting 1Watt of RF power (this is typical of a handset in a region of poor cell-phone signal). How far from a base station does one have to be to be exposed to the same RF power? Assuming the base station to be transmitting 30 Watts through a 17 dbi antenna, the equivalent distance from the base station is computed to be about 1.6 m from the antenna (8-15m above the ground). If you are 20 m from the base of the base station, the power radiated from the base station is about 1000 times less than that from the handset. Even if the handset is in a region of good cell-phone signal (and therefore transmitting much less power), you are still exposed to about 100 times more RF power from the handset than from a base station 20m away. Most users are exposed to far higher fields from their handsets than from base stations. One could argue that one is only exposed to these high fields from the handset when making a call. This is partly true, because it is when making a call that the handset is held very close to the ear. However, the handset is continuously communicating with the base station even when you are not making a call. If, you are carrying the handset in a pocket, it will be other parts of your anatomy that are exposed to these high fields as opposed to your brain. Page 1

3 We have not yet touched on the subject of whether or not the radiation from handsets or base stations is dangerous. All that has been established is that there is generally a greater exposure to RF power from a handset than from a base station. But is it dangerous? There are many people that are au fait with the physics of radio waves. It is well known that the radiation used in cell-phone networks is non-ionising. This puts these radio waves in a completely different category than, for example, X-rays. The energy contained in an X- ray is about 100 million times that of the energy in cell-phone radiation. X-rays contain enough energy to change the chemistry of important biological molecules in cells like proteins and DNA through a process called ionisation. Cell-phone radiation does not have enough nearly energy to break chemical bonds. So what effect does cell-phone radiation have on living tissue? One answer is that it heats up the tissue into which it propagates. But does it do anything else? This is the issue of great debate when considering the effect of cell-phone radiation on humans. There are reams of un-reviewed articles (articles not peer-reviewed by other scientists working in the same field) on the web which can be extremely convincing, but that fail to follow due scientific process. As a result, many of the conclusions drawn from these un-reviewed articles could be as a result of a phenomenon other than cell-phone radiation; and since the experiment has not been carried out properly it is difficult to work out the cause of the observed effect. It is extremely difficult for an untrained person to sift out the articles that have followed the proper scientific process from those that have not. It is for this reason that I turn to organisations like the World Health Organisation (WHO) for clarity on the matter. The WHO has no bias on the subject of the dangers of cell-phone radiation; its standpoint is simply to find the truth and report on it. The WHO is also in a position to make use of the services of scientists who are knowledgeable about the subject and are able to identify papers that follow the correct process from those that do not. On the subject of radiation from a base station, the WHO stated in May 2006 (fact sheet #304) that From all evidence accumulated so far, no adverse short- or long-term health effects have been shown to occur from the RF signals produced by base stations. This statement refers to continuous exposures at or below the maximum public safety limits. Specifically in relation to any cancer risk associated with emissions from these types of wireless facilities, the WHO says: Over the past 15 years, studies examining a potential relationship between RF transmitters and cancer have been published. These studies have not produced evidence that RF exposure from the transmitters increases the risk of cancer. Likewise, long-term minimal studies have not established an increased risk of cancer from exposure to RF fields, even at levels that are much higher than produced by base stations and wireless networks. More recently, in June 2011, the WHO published a document stating that cell-phones (actually the radiation there from) have been classified as an agent that is possibly carcinogenic to humans. This puts cell-phones in the same category as coffee, gasoline engine exhaust and pickled vegetables. The table below gives three of the classification levels used to grade the carcinogenic properties of various agents. Cell-phones are now in the bottom group in this table. Agents classified by IARC (834) IARC Classification Carginogenic to humans (75) (usually based on strong evidence of carcinogenicity in humans) Probably carcinogenic to humans (59) (usually based on strong evidence of carcinogenicity in animals) Probably carcinogenic to humans (225) (usually based on evidence which is considered credible, but for which other explanations could not be ruled out) Examples of Agents Asbestos Alcoholic beverages Benzene Mustard gas Radon gas Solar radiation Tobacco (smoked and smokeless) X-rays and Gamma Creosotes Diesel engine exhaust Formaldehyde Polychlorinated biphenyls (PCBs) Coffee ELF magnetic fields Gasoline engine exhaust Glass wool Pickled Vegetables Styrene Page 2

4 The studies that resulted in categorising cell-phones as possibly carcinogenic to humans involved studying the occurrence of brain tumours in cell-phone handset users. The finding as reported by the WHO is as follows: There are some indications of an increased risk of glioma (brain tumour) for those who reported the highest 10% of cumulative hours of cell phone use, although there was no consistent trend of increasing risk with greater duration of use. The researchers concluded that biases and errors limit the strength of these conclusions and prevent a causal interpretation. Based largely on these data, IARC has classified radiofrequency electromagnetic fields as possibly carcinogenic to humans (Group 2B), a category used when a causal association is considered credible, but when chance, bias or confounding cannot be ruled out with reasonable confidence. [WHO: Fact sheet N 193] In summary, the current position of the WHO on the subject of the dangers of base station radiation is that no adverse short- or long-term health effects have been shown to occur from the RF signals produced by base stations. Whilst on the matter of handsets, an increased risk of glioma for those who reported the highest 10% of cumulative hours of cell phone use has resulted in cell-phones been classified in Group 2B (possibly carcinogenic to humans) Conclusion So, is there an advantage to having a base station installed on your property? I would say yes, there is an advantage. According to the WHO, the base station itself appears not to be a health hazard. Having a base station relatively close to where you are making a call will reduce the RF power of your handset, thereby limiting your exposure to RF radiation. Not installing a base station will do the opposite. The June, 2011 report from the WHO that discusses the re-classification of handsets into Group 2B is given in the following section. It also discusses various health issues associated with using the cell-phone network read it! It's very interesting. 3. WHO report - Electromagnetic fields and public health: mobile phones Fact sheet N 193 June 2011 Taken from: Key facts Mobile phone use is ubiquitous with an estimated 4.6 billion subscriptions globally. The electromagnetic fields produced by mobile phones are classified by the International Agency for Research on Cancer as possibly carcinogenic to humans. Studies are ongoing to more fully assess potential long-term effects of mobile phone use. WHO will conduct a formal risk assessment of all studied health outcomes from radiofrequency field's exposure by Mobile or cellular phones are now an integral part of modern telecommunications. In many countries, over half the population use mobile phones and the market is growing rapidly. At the end of 2009, there were an estimated 4.6 billion subscriptions globally. In some parts of the world, mobile phones are the most reliable or the only phones available. Given the large number of mobile phone users, it is important to investigate, understand and monitor any potential public health impact. Mobile phones communicate by transmitting radio waves through a network of fixed antennas called base stations. Radiofrequency waves are electromagnetic fields, and unlike ionizing radiation such as X-rays or gamma rays, can neither break chemical bonds nor cause ionization in the human body. Page 3

5 3.1.2 Exposure levels Mobile phones are low-powered radiofrequency transmitters, operating at frequencies between 450 and 2700 MHz with peak powers in the range of 0.1 to 2 watts. The handset only transmits power when it is turned on. The power (and hence the radiofrequency exposure to a user) falls off rapidly with increasing distance from the handset. A person using a mobile phone cm away from their body for example when text messaging, accessing the Internet, or using a hands free device will therefore have a much lower exposure to radiofrequency fields than someone holding the handset against their head. In addition to using "hands-free" devices, which keep mobile phones away from the head and body during phone calls, exposure is also reduced by limiting the number and length of calls. Using the phone in areas of good reception also decreases exposure as it allows the phone to transmit at reduced power. The use of commercial devices for reducing radiofrequency field exposure has not been shown to be effective. Mobile phones are often prohibited in hospitals and on airplanes, as the radiofrequency signals may interfere with certain electromedical devices and navigation systems Are there any health effects? A large number of studies have been performed over the last two decades to assess whether mobile phones pose a potential health risk. To date, no adverse health effects have been established as being caused by mobile phone use. Short-term effects Tissue heating is the principal mechanism of interaction between radiofrequency energy and the human body. At the frequencies used by mobile phones, most of the energy is absorbed by the skin and other superficial tissues, resulting in negligible temperature rise in the brain or any other organs of the body. A number of studies have investigated the effects of radiofrequency fields on brain electrical activity, cognitive function, sleep, heart rate and blood pressure in volunteers. To date, research does not suggest any consistent evidence of adverse health effects from exposure to radiofrequency fields at levels below those that cause tissue heating. Further, research has not been able to provide support for a causal relationship between exposure to electromagnetic fields and self-reported symptoms, or electromagnetic hypersensitivity. Long-term effects Epidemiological research examining potential long-term risks from radiofrequency exposure has mostly looked for an association between brain tumours and mobile phone use. However, because many cancers are not detectable until many years after the interactions that led to the tumour, and since mobile phones were not widely used until the early 1990s, epidemiological studies at present can only assess those cancers that become evident within shorter time periods. However, results of animal studies consistently show no increased cancer risk for long-term exposure to radiofrequency fields. Several large multinational epidemiological studies have been completed or are ongoing, including case-control studies and prospective cohort studies examining a number of health endpoints in adults. The largest retrospective case-control study to date on adults, Interphone, coordinated by the International Agency for Research on Cancer (IARC), was designed to determine whether there are links between use of mobile phones and head and neck cancers in adults. The international pooled analysis of data gathered from 13 participating countries found no increased risk of glioma (type of tumour that starts in the brain or spine) or meningioma (brain tumour that is usually benign) with mobile phone use of more than 10 years. There are some indications of an increased risk of glioma for those who reported the highest 10% of cumulative hours of cell phone use, although there was no consistent trend of increasing risk with greater duration of use. The researchers concluded that biases and errors limit the strength of these conclusions and prevent a causal interpretation. Based largely on these data, IARC has classified radiofrequency electromagnetic fields as possibly carcinogenic Page 4

6 to humans (Group 2B), a category used when a causal association is considered credible, but when chance, bias or confounding cannot be ruled out with reasonable confidence. While an increased risk of brain tumors is not established, the increasing use of mobile phones and the lack of data for mobile phone use over time periods longer than 15 years warrant further research of mobile phone use and brain cancer risk. In particular, with the recent popularity of mobile phone use among younger people, and therefore a potentially longer lifetime of exposure, WHO has promoted further research on this group. Several studies investigating potential health effects in children and adolescents are underway Exposure limit guidelines Radiofrequency exposure limits for mobile phone users are given in terms of Specific Absorption Rate (SAR) the rate of radiofrequency 1, 2 energy absorption per unit mass of the body. Currently, two international bodies have developed exposure guidelines for workers and for the general public, except patients undergoing medical diagnosis or treatment. These guidelines are based on a detailed assessment of the available scientific evidence WHO'S response In response to public and governmental concern, WHO established the International Electromagnetic Fields (EMF) Project in 1996 to assess the scientific evidence of possible adverse health effects from electromagnetic fields. WHO will conduct a formal risk assessment of all studied health outcomes from radiofrequency fields exposure by In addition, and as noted above, the International Agency for Research on Cancer (IARC), a WHO specialized agency, has reviewed the carcinogenic potential of radiofrequency fields, as from mobile phones in May WHO also identifies and promotes research priorities for radiofrequency fields and health to fill gaps in knowledge through its research agendas. WHO develops public information materials and promotes dialogue among scientists, governments, industry and the public to raise the level of understanding about potential adverse health risks of mobile phones. 1 International Commission on Non-Ionizing Radiation Protection (ICNIRP). Statement on the "Guidelines for limiting exposure to time-varying electric, magnetic and electromagetic fields (up to 300 GHz)", Institute of Electrical and Electronics Engineers (IEEE). IEEE standard for safety levels with respect to human exposure to radio frequency electromagnetic fields, 3 khz to 300 GHz, IEEE Std C95.1, Page 5