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Powerwatch Frequently Asked Questions[Home Page] [Guide to EMFs] [Guidance Levels] [Unit Conversion] [Studies List] [Bias] [EMFs pre-2000] [FAQs] [Publications] [Links] General Site FAQsMobile and Cordless Phones
Mobile Phone Masts / Base Stations
Wifi and Computing
Housing and Wiring
Other FAQs
General Site FAQsFAQs on using the Powerwatch WebsiteDue to popular request, the following will give step by step instructions on the different sections of our site. Each of the pages will open in its own, separate window: Mobile and Cordless PhonesAre Digital Cordless Phones (DECT) dangerous?There has been quite a lot of publicity about the research showing that using digital cordless (DECT) phones results in similar adverse health effects as using a mobile phone, including the risk of developing brain tumours [1,2,3,4]. We have had concerned parents on the phone to us, explaining that their children do not use their mobile phones at home, due to the possible health effects, so they talk for long periods of time on the cordless phones instead. They appreciate the privacy of a cordless phone, and can shut themselves in their bedroom, the bathroom, anywhere to keep their calls private. Unfortunately, it may have unforeseen consequences that neither they nor their parents could have anticipated. We have written a much more detailed article on DECT phones in our article library, available from here. References1. P
Hardell L et al, (October 2006) Tumour risk associated with use of cellular telephones or cordless desktop telephones, World J Surg Oncol 2006 Oct 11;4:74 [View Author's abstract conclusions] [View
on Pubmed]
2. P
Hardell L et al, (February 2006) Case-control study of the association between the use of cellular and cordless telephones and malignant brain tumors diagnosed during 2000-2003, Environ Res. 2006 Feb;100(2):232-41 [View Author's abstract conclusions] [View
on Pubmed]
3. P
Hardell L et al, (September 2005) Use of cellular or cordless telephones and the risk for non-Hodgkin's lymphoma, Int Arch Occup Environ Health. 2005 Sep;78(8):625-32 [View Author's abstract conclusions] [View
on Pubmed]
4. P
Hardell L et al, (2005) Case-control study on cellular and cordless telephones and the risk for acoustic neuroma or meningioma in patients diagnosed 2000-2003, Neuroepidemiology. 2005;25(3):120-8 [View Author's abstract conclusions] [View
on Pubmed]
Are phones with low SARs safer?It was recommended by the Stewart Report, in 2000, that information about Specific Absorption Rates (SARs) should be provided with every mobile phone bought, making it easier to compare them. SARs are one way of measuring the amount of radiation emitted by the phone. The higher the SAR, the greater the amount of microwaves that are likely to be absorbed by the head. ICNIRP sets an SAR standard of 2 W/kg maximum in any 10 grammes of tissue, which applies to many European countries including the UK. SARs cannot be measured directly, only by using sophisticated models and computer mathematical modelling techniques to simulate the radiation from the phones. The results vary depending on the test equipment used, the design of the mobile phone's antenna, and the position in which the phone is held by the user. Measurements in test situations do not necessarily accurately reflect the differences in head tissue type and age of the exposed person. The SAR is greatly affected by how you hold your fingers on the back of the phone in order to press the phone to your ear - especially in phones with internal antennas. One of the main shortcomings of the SAR as a useful guide is that they are measured with the handset operating at full power, taking no account of the efficiency of any given handset, which can be considerable. In response to low signal strength, an efficient handset powers up less than an inefficient handset, thus exposing the head to lower radiation. Some phones with a high peak SAR actually produce lower SARs under normal use conditions than phones with a low peak SAR. The maximum power output from a GSM mobile phone is around 2 W peak, but this can reduce in a sequence of 15 steps down to around 0.002 W during calls, a power reduction factor of 1000. This is primarily dependent on the signal level in the area the phone is being used. The other issue is that SAR values are based on the assumption of "total RF dose" (i.e. with the dose delivered at a constant level over a fixed period of time). In reality, exposure to mobile phones and cordless phones is an exposure to a series of high powered "pulses". Imagine an ordinary egg: If you put a constant firm pressure on the egg, it will survive intact for some considerable time. If, however, you hit it sharply several times a second (but with exactly the same 'average' force), it is most unlikely to remain unbroken for the same amount of time. It is possible that peak values of the pulses is more important to measure than a time-weighted average. New phones in the UK are forced by law to display maximum SAR levels in the manual that comes with the phone. However, Powerwatch's opinion is that SARs are only minimally useful as they are based only on thermal effects. Most recent scientific literature indicating concern from mobile phone usage indicate non-thermal effects, for which SAR values are irrelevant. If you are concerned about exposure but wish to continue using your phone, then you would be much better using a airtube hands-free kit (conventionally wired hands-free kits can increase your exposure as the fields can travel up the wires from the handset to the headphones) which can reduce the effective SAR to your head by 500-fold. Is GSM more dangerous than CDMA technology?GSM and DECT technology use a series of low-frequency periodic (regular) bursts of microwave radiation. CDMA should have been less problematic as the modulation is less "aggressive" and the power is spread over a wider bandwidth of microwave frequencies and therefore has a lower signal strength for the same amount of transmitted power. However we are finding far more problems being reported by people in the UK with the two CDMA based systems used here - 3G (UMTS) and TETRA. These do not fully comply with true CDMA in that they both also impose regular low frequency timing pulses into the signal. Also the phase modulation used produces a lot of electrical/electronic noise in the 1000 to 20000 Hz (audio) frequency band (that sounds like a field of amplified crickets or circadas if demodluated and listened to - e.g. with an Electrosmog Dectector). It may be this noise that is the most bioactive. Do answerphones for ordinary and cordless phones give off EMFs?All answerphones with plug-in transformers (the "box-like" adapter plugs) are surrounded by significant levels of mains-frequency magnetic fields within 50 centimetres, but do not give off RF electromagnetic fields. With a cordless phone however, the answerphone is built into the base unit. The base unit for a digital cordless phone is likely to be giving off RF electromagnetic fields at all times, even when the handsets are not in use. The only way to be sure whether or not the answerphone attached to your phone is giving off EMF radiation is to measure the fields. Mobile Phone "Chips"How do I know whether I can trust the research done to support mobile phone EMF safety microchips?Evaluating the usefulness of support documentation for devices that protect against EMFs:1. Valid CitationAll citations for studies and papers should be correctly referenced, mainly so that it is easy to validate that the person stated as the author exists, and the organisation they work for has a recognised authoritative voice, with any potential biases expressed or likely to be known by the wider scientific community. The journal and page numbers on which the paper was published in should also be present. 2. Experimentation MethodExperiments should give details of the participants, and as much information as possible on the environment they were in at the time of experiment. If doses / levels of substances or other such values are used, the reasons for using these values should be explained with citations where appropriate. Measurements and values should always have units, which should be recognised units of measurement for the objective values being taken. Experimental conditions should be fully explained, with acknowledgements for any possible confounders (such as selection bias) that may affect the efficacy of the experiment. 3. Results and ConclusionsResults and conclusions should be based firmly on what was tested, with appropriate reservations and tentative hypotheses, as necessary, clearly expressed as such. No extravagant claims should be made which appear to be out of context, or are unsupported by the research findings. With regard to devices that are supposed to protect against microwave radiation, there are some companies which claim that using their device makes the person healthier than normal. This is a clearly extraordinary claim, and should be regarded as suspicious. Claims should be not only supported by the research, but by common sense as well. The conclusions should be more than a statistical summary of the results. There should be an explanation as to how the results are actually achieved experimentally, and some comments to explain the results produced. There should be references to other work that show similar results or that look at closely related science, and how the current study fits into the ongoing scientific debate. SummaryResearch that does not at least partially address all of these issues is likely to have been poorly conducted. Studies without good independent research backing up the findings with a plausible explanation, need to be further investigated before being accepted as a valid evaluation of a product. What are EMX Biochips? Do they really work?EMX biochips are a technology based on genuine scientific research. These are not the same as "protection devices" that are widely marketed yet have no real effect (other than placebo). The EMX devices work on the basis of superimposing random, low frequency magnetic fields over other electromagnetic fields (EMFs) being emitted by other devices. The theory behind this is that the extra fields hide the unwated EMFs, in a similar way to music being played in a restaurant hides conversations between other people on nearby tables. A number of peer-reviewed scientific studies have been carried out and replicated, showing that this has genuine scientific basis. [1,2,3]. While this appears to be effective, we do not think that increasing EMFs is an ideal solution, and we believe that other options should be explored first. References1. -
Di Carlo AL et al, (January 2001) Mechanical and electromagnetic induction of protection against oxidative stress, Bioelectrochemistry. 2001 Jan;53(1):87-95 [View Author's abstract conclusions] [View
on Pubmed]
2. -
Farrell JM et al, (1998) The superposition of a temporally incoherent magnetic field inhibits 60 Hz-induced changes in the ODC activity of developing chick embryos, Bioelectromagnetics. 1998;19(1):53-6 [View Author's abstract conclusions] [View
on Pubmed]
3. -
Litovitz TA et al, (1994) Superimposing spatially coherent electromagnetic noise inhibits field-induced abnormalities in developing chick embryos, Bioelectromagnetics. 1994;15(2):105-13 [View Author's abstract conclusions] [View
on Pubmed]
Who are Exradia? Do their products really work?Exradia is a company that has bought up the rights to the EMX technology that was developed by the late Ted Litovitz of Washington State University. The only application so far available are special Nokia mobile phone batters with the noise pulsing circuits built into them. We have not tested them, but they are based on EMX technology which has scientifically supported claims of positive effects. (See refs in section above) Mobile Phone Masts / Base StationsWhat Planning regulations may apply to mobile phone base stations?Many of the planning guidelines for mobile phone infrastructure, such as PPG8, are only guidelines, they are not legally binding. Some of the guidelines have been challenged in law, and have created case-law precedence which will have more force of law than the guidelines themselves. Scotland have their own guidelines NPPG19 and PAN62 advice note and Wales have their TAN19 panning guidelines. We give some brief comments below, but probably the most informative websites with respect to UK mobile phone mast planning issues are www.planningsanity.co.uk, www.mastsanity.org and www.mastaction.co.uk. Planning permissionGeneral Permitted Development OrdersTelecommunications 'transmission devices' require planning permission unless they are "permitted development" as defined in the General Permitted Development Order (as amended). Masts up to 15 metres high, and most antennas on buildings, come within "permitted developments" and local councils can have little say over the siting of these. They can suggest alternative sites, but few councils actually do this. Masts over 15 metres high do need full planning permission. GPDO Order 2001 paragraphs A.1(g) and A.1(h) set a limit on the number of antenna systems that may be placed on a particular building without the need to seek planning permission. Operators have managed to effectively get around most of the restrictions by claiming that they offer "a mobile phone network" that uses both GSM and 3G and allows them to have GSM900, GSM1800 and 3G counted as "one system". Small antennas and 'de minimis' developmentsThese do not need full planning permission. Small antennas can be fixed to most existing structures and no permission is required, just notification. 'De minimis' additions are outside of planning and are considered as those which are not being development within the meaning of Section 55 of the Town and Country Act 1990 (subsection 2), and not materially affecting the external appearance of the building or other structure. See: link for further information about such base-station antennas. Breaches of output conditionsPlanning permission is solely granted on the condition that the exposure guidelines are not exceeded. In practice it is most unlikely that masts will ever exceed the high ICNIRP Guidance levels that are currently in force. Planning Policy Guideline 8 (PPG8)In August 2001, the UK Government announced the revised PPG8 on telecommunications. This should be read bearing in mind the following points:
(Notice No. 12 HC 330 had suggested "Operators should make a declaration that emissions likely to be produced by a new base station are 'as low as reasonably practicable', as suggested in the Stewart Report".
In summary, there is usually little you can do to oppose a new mast. If you act quickly then you can insist that other sites are considered. However, most masts are now sited in residential areas to cope with the large number of mobile phone calls residents are making from their houses and so there is limited scope for using alternative sites. The "radius" for fill-in coverage is often only several hundred metres and in towns and cities small base stations are sometimes necessary every 50 to 100 metres in every direction! People need to greatly reduce their mobile phone use to avoid more base-stations being installed close to their homes (often on lamp-posts now). How can I find out when a mobile phone mast was erected?The best place to find out is the local council. If planning permission was necessary to erect the mast, they should have the records. If planning permission wasn't needed, and it was the subject of a General permitted Development Order (GPDO), the council may have the information as operators often inform the council, though they are not obliged to do so in all circumstances. If the council do not have the details, you may want to contact the operator direct, either from the information on the mast, or through the sitefinder website query section. What is the difference between a macrocell, a microcell and a picocell?MacrocellsThe antennas for macrocells are mounted on ground-based masts, rooftops or other existing structures, at a height that provides a clear view over the surrounding buildings and terrain. They have a clear view over the rooftops of any surrounding buildings. The area a macrocell is intended to cover is very variable, from at least 500 metres up to a maximum of about 35 km dependent upon capacity and clutter. The powers above need multiplying by the maximum number of active carriers and by the forward gain of the antennas, resulting in EIRPs between about 50 watts (17 dBW) and 1000 watts (30 dBW) per carrier frequency. Base stations typically have 4 carriers, but may have up to 16. MicrocellsMicrocells are designed to provide radio infill coverage and additional call capacity for high traffic densities in urban and suburban areas to users both outdoors and within buildings. They are smaller than macrocell antennas and when mounted on existing structures can often be disguised as building features. Microcell base station antennas are lower than nearby building rooftops, typically on the external walls of existing structures, lampposts and other street furniture, so the coverage area is primarily defined by the street layout. Cell coverage is usually up to 200 metres, possibly up to 500. Typical radiated powers should be only a few watts, resulting in Equivalent Isotropic Radiated Power (EIRP) in the range 2 to 15 dBW (1.6 to 30 watts) per channel. They should not exceed 17 dBW per carrier. Micro base stations typically have between 2 and 6 carriers. PicocellsPicocells provide more localised coverage than microcells, such as inside buildings where coverage is poor or there are high numbers of users, such as shopping precincts, airports and train stations. The antennas for picocells are mounted inside buildings, typically on walls, ceilings or in ceiling cavities. Picocells provide coverage within a building and more than one may be required to cover an entire building. Users may be both mobile and fixed; fixed users are exemplified by wireless local area networks (wLANs) between computers. Coverage is defined by the shape and characteristics of rooms, and service quality is dictated by the presence of furniture and people. Picocell base stations have lower output powers than microcells, typically less than one watt - i.e. comparable with a single mobile phone. The official (ETSI) figures for the transmitter power per channel are:
The Stewart 2 report "Mobile Phones and Health 2004" released in January 2005, said in the Executive Summary paragraph 30 "The Board notes that whilst the planning process applies to macrocells, it does not obviously apply to microcells and picocells. It is important that, as the networks develop, there is a need for clarity in terms of the legal responsibilities and regulations in relation to the installation of microcells and picocells and the availability of information about their deployment." This issue needs to be addressed urgently as in a recent sitefinder survey by Powerwatch, we found 63% of masts in Soho were under 10 metres in height (microcells) which do not need planning permission. Always remember that the more people who own a mobile phone, and the more any mobile phone is used, the more masts will be needed in the community to provide the network to support the calls. How do you know that the operators are keeping the power from masts as low as possible?Local Planning Authorities use policy guidelines in order to make decisions about planning matters: Planning Policy Guidelines 8 (PPG8), revised in August 2001 stated: "Mobile phone operators already keep their RF power outputs to the lowest possible levels commensurate with effective service provision" We know that this is not so in a lot of circumstances. In order to find out whether the base stations near you conform to this guideline, we have devised an index (the REI) which gives you a quick rule-of-thumb means of assessing base stations to check if the operator is actually radiating the local population at a level that is "as low as possible". To calculate the REI for each base station, find the base station on the Ofcom database, note the EIRP, given in dBW, and the height of the antennas. This is only the power per channel (carrier), and most antennas have 4-6, sometimes more, channels. However, this information is not easily available, so for comparison purposes, we compare the single measurement as given on the database. Convert EIRP in dBW to watts. Divide the EIRP number by 10 and then use the antilog function on a calculator (usually shift + log), or use old fashioned antilog tables, or in EXCEL spreadsheet use the cell formula: =10^(dBW/10) which returns the value in watts. A summary table of some key values is given below for checking purposes. Divide this number of watts by the square of the height of the mast in metres (Excel:"=watts/(height x height)") e.g. a 20 dBW (100 watt) 7 metre mast has an REI of (100/49) = 2.0 Ideally base stations should have REIs of 1 or less, but 2 is acceptable away from housing and schools. In our opinion anything above 2 is unacceptable and either: (i) the mast should be higher, or (ii) the power should be lower. This will identify the masts that are irradiating the local population the most. You can then measure the microwave levels, using a COM, or Acousti-meter (both available from EMFields). On high rise buildings, where the base station antennas are within about 200 metres of other residential high rise buildings, then instead of using the absolute height from the ground, the difference in height from the top floor of the nearest residential building to the antenna height should be used - e.g. an antenna listed as a 43 metre high site may only have a 5 metre vertical difference from a room window in a neighbouring residential block, then the 5 metre figure should be used which will produce a MUCH higher REI value for the base station. Power unit conversion chart
Wifi and ComputingAre the concerns about the health effects of using Wireless Local Area Network (wLAN) systems in school classrooms unfounded?A number of schools have dismantled their wireless networks after lobbying by worried parents and teachers, and others are under pressure to follow suit. We ask whether this level of concern is warranted. We have covered this subject in detail on our WiFi overview. Why is my laptop is giving off microwave (RF) radiation?Most laptops now are sold with WiFi built-in, as it is assumed by the manufacturers that they will be used at home with a wireless internet system, or whilst the purchaser is 'on the move'. If you do not wish to use it in this way, you may want to disable the WiFi system as your laptop will continue to radiate RF until it is disabled. Laptops vary as to how to achieve this, so we recommend that you look at the manufacturer's instructions to find out how this can be done. You may need to contact them directly if it is not clear. Some software updates may re-enable your WiFi system, so it is worth while checking every now and again to ensure that the wireless capacity remains disabled. Increasingly, laptops are being sold with a Bluetooth capability as well. This may be situated in a different part of the laptop to the WiFi circuitry, and will have to be separately disabled. Again, we refer you to the manufacturer's instructions or we suggest you contact them directly. If you are unsure whether your laptop is emitting RF radiation or not, you can easily find out by hiring or buying one of EMFields RF monitors. I don't want a WiFi connection to broadband internet - what options do I have?To connect to the internet, you need one of two things: either a cable connection (via a company such as NTL) or a standard phone line. Modern internet connections normally use a technology called ADSL (Asymmetrical Digital Subscriber Line), which allows the phone to be used at the same time as surfing on the internet. This technology needs to be enabled at your local telephone exchange, but two thirds of the UK (as of Summer 2007) is now supported. Contact your phone provider (for example BT) and ask them if they can provide broadband to your house - if so they are also likely to send a package containing all you need to connect your computer to the internet (modem, ADSL filter and cables). The modem enables the computer to connect, and the filter ensures that you can use the telephone at the same time as the internet (with only one line) without having either service compromised. Both cable and ADSL internet connections are entirely free of microwave EMF emissions, and we have no reason to believe they could be a risk to health. It is very important however, if you are concerned about health effects from wireless communication devices, not to use one of the "BT Home hubs" to connect your computer to the internet, as they act as both a wireless access point (WiFi) and a DECT base unit (cordless phones) whenever they are powered. For an alternative, ask in your local computer store for a non-wireless "router" - there are a number of brands that manufacture these, and they are secure, reliable and require very little setting up. Home Networking: What are dLAN devices and are they an EMF-safe alternative to WiFi?dLAN devices, are an alternative solution to WiFi. They connect to one another through the mains wiring in a building, allowing access to the network/internet from any mains socket in the building. What kind of EMFs do they emit?Homeplug devices do add some RF noise to the mains wiring. However, the levels we have measured (a few tens of microvolts) are negligible in comparison with WiFi devices, and what increase in fields that we did see was only in very close proximity to mains wiring (within a few tens of centimetres). Since we already advise against spending large amounts of time in such close proximity to mains wiring, we believe that the fields generated are unlikely to cause problems other than in the the most highly electrically sensitive people. We still think that wired Ethernet is the best option, however dLAN units seem to be a reasonable compromise provided that you are aware that there are potential problems, and we consider it to be vastly preferential to WiFi. Security ConsiderationsThere are additional security considerations when it comes to dLANs. Because they use the mains wiring to transfer data, this means that anybody on your wiring circuit can add their own dLAN unit and listen to the network traffic. Since most houses have their own wiring circuit, this is only relevant in shared housing and some flats. Some dLAN units offer features to encrypt the network, which would eliminate this issue. We still consider dLAN units to be significantly more secure than WiFi, which can be listened to simply by being nearby, without requiring physical access to a plug socket. WiFi encryption systems provide some level of security, but they are still not completely secure from network intrusion. I have more than one computer and want them all to be able to use the internet - do I have to use WiFi?No, not at all. If you have purchased a router for your internet connection (see FAQ above), then you will have a number of network "ports". These are the sockets at the back of the router that you plug the network cable from your computer into. You can have as many computers as you have ports provided you have a cable for each. The router will make sure that the machines can all share the internet at the same time. If your computers are in different rooms, WiFi is still completely unnecessary. The best options for this is using two dLAN units (see FAQ above), which can connect computers and laptops using the power circuitry in the building. The units are plugged into a standard power socket on the wall, and have a computer network port for attaching the laptop or computer to. Plug one into a socket near your router (see our broadband FAQ if you are unsure whether you have a router or what one is) and connect it to the router with normal computer networking cable. The whole house should now be connected to the network, and you can use the other dLAN unit in any room you would like to use your laptop in - just plug it in, turn it on, and connect the laptop via computer networking cable. Are games consoles safe?Many games consoles, especially older ones, are no different to most other standard household electronic goods and should not expose you to significant levels of EMFs. The latest-generation consoles (XBOX 360, Nintendo Wii, Sony Playstation 3) are all wirelessly enabled. These all have the capability to have wireless controllers, and have either integrated or add-on WiFi. Some modern handheld consoles (Nintendo DS, Sony PSP) also have WiFi built in. There is currently no research either way on WiFi at the moment, however WiFi enabled devices give off similar strength EMFs as an average Mobile Phone Mast would give at under 100m. There is strong scientific evidence for mobile phone masts causing a variety of serious health issues, so we consider it prudent to take a precautionary approach and avoid prolonged use of WiFi enabled devices. Is it true that trains are all going to become WiFi enabled?Many people who suffer from electrical sensitivity are finding it harder to travel by train. Far from 'letting the train take the strain' they are increasingly being excluded from access to public transport. One person told us "I couldn't contemplate taking a train journey in a carriage offering wireless internet facilities. I get headaches after 10 minutes of exposure to radiofrequency radiation." She continues "electrosensitives will become increasingly isolated from work places and public spaces." Ten stations, Reading, Bristol Temple Meads, Bath Spa, Didcot Parkway, Swindon, Exeter St Davids, Bristol Parkway, Plymouth, Newbury and Slough this summer began to offer online internet access for use by business passengers waiting for trains on platforms or in the waiting areas. There is a charge for the service that may put off people wanting to use the system to watch video or play games or music, but many may decide to use the system to pass the time. First Great Western and First Great Western Link have signed a contract with The Cloud to bring wireless Internet access to every one of its 85 stations. Icomera, a Swedish company, is providing the commercial 3G Wi-Fi service used on GNER's fleet of trains. They have been testing the system on GNERs East Coast route and by May 2007, every GNER train will be fitted with the new wireless 3G data communication system. All 13 diesel trains and 30 electric trains will have the facilities of 'a mobile office'. Virgin Voyager trains have already got a 'Connected Carriage' system offering the same service and T-Mobile and Southern are providing a faster broadband service. Housing and WiringWhat is the best way to wire a house to reduce electromagnetic fields in the home?The current UK practice of wiring a house using 'ring' circuits can often lead to high electric and magnetic fields. In Europe 'radial' or 'tree and branch' wiring is more common than in the UK and these result in much lower levels of EMFs in buildings. In addition, running wires in metal conduit will reduce the fields to virtually zero. For new build homes this is the best option. There are different types of screened cable available when running wires in metal conduits is not possible: Mineral insulated cables can be expensive to install, some are fire retardant and are likely to need extra residual current devices or RCDs. There are difficulties with some braided cables which need earthing at every junction point, and some need extra space to allow for the necessary larger bending requirement. Most cables, including reasonably priced, flexible cable can be bought from an electrical goods supplier, such as used by professional electricians. Very competent DIYers can also re-wire houses, but it is important to remember that it is now illegal for unqualified people to undertake major electrical work without formal independent third-party inspection and test. Our library article House electrical Installations and EMFs, has detailed information about the different types of circuit, cable specifications and what type to use in which situation, for the use of the competent DIYer, or professional electrician. Are there wall insulation materials that can stop incoming microwaves?Some insulation materials that look like metallised plastic do screen against microwaves, some do not! There are too many brands and types (models are changed from time to time, which may well have different properties to the ones tested) to be able to provide a definitive list of ones that do and ones that don't. You often cannot tell by looking at them. The only way to find out for certain is to measure the fields with a suitable instrument before screening large areas. Other FAQsPowerlines, substations and mobile phone base stations. How far away is safe?This is a question we are often asked and, unfortunately, there is no easy answer. The research into the health effects of electric and magnetic fields (EMFs) from these structures has primarily focused on field levels rather then distance. The only way to know for sure whether you are in levels of EMF below those at which health effects have been found, is to measure them. EMFields stock a range of instruments for sale and hire that can measure both ELF and RF electromagnetic fields. PowerlinesPowerlines, which are part of the electricity distribution system, come in various sizes (voltages) from 400 kilovolts (kV) (largest) to 230 volts (smallest). On the whole, the higher the voltage of the line, the higher the EMFs and the further you have to be away for the fields to drop away to a background level. A significant exception to this is the 132kV lines, which can carry very unbalanced power loads, which mean they have much higher EMFs than you would expect from the size. Electric fields have been less researched as they are stopped by most building materials. However, we have found that about half of UK homes can have high electric fields due to the way the house wiring is done. Substations or transformersSubstations generate low frequency EMFs such as those which are found near powerlines. Magnetic fields can extend out for some distance, depending on the size of the substation and the type of demand for electricity that it supplies. Underground cables run from the substation to the house, businesses, etc. that it supplies. The cables give off very high levels of magnetic field close by. This can be a particular problem for houses with small or no front gardens, or where the cables pass near the garden. The way that substations are connected can sometimes give rise to 'net' currents which can produce very high fields indeed in the houses between them. The electricity supply is unaffected and the electricity company does not usually see the high fields as a problem. Mobile phone masts or base stationsHigh frequency EMFs, or microwaves, are radiated from mobile phone masts. The levels you may be exposed to depend on a number of factors: The number of operators, the height of the base station, the power of the antennas, the direction of the antennas and the type of buildings and building structures in the immediate area. It is impossible to determine the amount of exposure in any one place based only on the distance to the nearest mast (or mast complex). The only way to find out for certain is to measure the strength of the field in volts per metre. Why do I have high ambient levels of magnetic fields in my home?If you have high levels of magnetic fields in your home that you cannot easily pin down to electrical equipment, it may be due to faulty wiring or net / stray currents. What are net currents?Substations supplying an area with electricity are interconnected in a way that is intended to ensure a constant voltage supply, to avoid equipment malfunction. Some properties have high levels of magnetic fields as a result of a fault or faults having developed in the supply cables between two substations. This produces an unbalanced or net current. The net current forms a loop between the substations and because it isn't balanced out by a current in the opposite direction (as it would be in a single cable carrying both 'go' and 'return' currents) then it can create quite high EMFs over a wide area. Magnetic fields coming into a property from outside are usually from underground cables carrying the power supply from house to house, often running under the pavement outside. If there is no front garden or the property is a basement flat, the magnetic fields could be quite high even without net currents, but should fall off rapidly as you move away from the cables by a couple of metres. If the magnetic field in a property is higher that usual (say above 0.1 microtesla) and is similarly high throughout the ground floor, the house is likely to be within the net current loop, which can affect a few houses, or even a few streets. If the field drops away slowly, as you move away from the source, the property may be affected by the net current but not within the loop. Net Currents and Stray CurrentsStray currents are net currents that have transferred to metal water or gas pipes, or even to the Earth itself. In most UK areas the final electricity circuits are connected as Protective Multiple Earth (PME) circuits. This connects the Neutral conductor to Earth every hundred metres or so. Undetected faults in the Neutral conductor lead to currents transferring to the Earth (damp earth is a surprisingly good conductor), which then also 'takes rides on' any underground metal pipework. The effects of raising EMF levels are similar to simple Net currents but it is usually harder to locate the problem and cure the fault. Usual drop off distance from a supply sourceWith powerlines, magnetic fields reduce with the square of the distance. That is, if you double the distance from the source, the magnetic field levels are a quarter the strength. From transformers (substations), the field levels will reduce to an eighth at twice the distance. The fields from cables fall away somewhere between linear (twice the distance, half the field level) and square (twice the distance, one-quarter the level). How do you know whether a property is affected by a net current?Because net currents arise from an uncorrected distribution fault, they are unpredictable. The only way to find out if a property is affected is by measuring the magnetic field levels and determining whether they reduce as predicted above, or whether they fall away very slowly, or hardly at all. The last two instances mean that the property is likely to be affected by net currents. Your decision as to whether to buy or rent such a property may be affected by this discovery. Responsibility of electricity supply companiesElectricity supply companies see their responsibility in terms of ensuring power distribution at accepted voltage supply guidelines i.e. 230 volts +16% - 8%, rather than minimising electromagnetic field levels to customers. Therefore, if a fault develops which results in net currents affecting some properties, they usually do not feel the need to do anything. Proving a Net Current problemThe electricity company needs to measure the net current around a supply cable. The best way to do this is with a current meter that uses a Rogowski coil sensor - a special open ended flexible pipe (like a hose pipe) that can be wrapped loosely around a cable bundle to check if the net current is zero. See ROCOIL Rogowski Coils Ltd for more information. If the underground cable is a 3 or 4 core composite cable a few (say 6) centimetres in diameter, then a large jaw Clamp Ammeter can be used. These are more commonly carried in the repair vehicles than Rogowski coil meters. If they refuse to do this, then you need to plot the fall off of magnetic field with distance to the cable using a suitable meter, such as the EMFields Pro (EMFields hire and sell these). If the EMF level falls off more slowly than with the square of the distance, then you probably have some degree of net or stray current involvement. The graph, below, assumes you measure 5 microtesla measured at 1 metre from the source - you will have to scale it for other values of starting magnetic field level. If it falls off at or below the thick middle line (square) then net or stray currents are not a problem. The higher the readings are above this line, the more net and stray currents are a part of the problem. If the readings are above the top dotted line then it is likely that there are a number of stray current problems in the area. There is a caution with regard to these fall-off curves. If the starting level at one metre away from the main source (e.g. the cables under the pavement) is less than about 0.5 microtesla, then the fall-off will slow down rapidly as in most residential areas there is a background level everywhere of about 0.02 or 0.03 microtesla and the fall-off below about 0.05 microtesla will be very slow.
Do the benefits of cooking food by microwaves outweigh the potential disadvantages?Good quality fruit, vegetables and whole grains contain all of the vitamins and minerals essential for health. It is not only important to obtain good quality food, but to cook it in a way that preserves its nutritional qualities without causing harm. The evidence is quite sparse with regard to the changes in food that result from cooking using microwaves, but none of it is good news. Vitamins and amino acids are changed, baby milk may be made toxic, and bacteria and microbes seem to survive this way of heating food [1,2,3,4]. Some types of packaging and ways of 'crisping' the food, results in poisons contaminating the food that may then be eaten [5]. There have been changes in the blood of people after they have eaten microwaved food [6]. Microwave ovens give off EMFs at powerfreqency and microwave frequency. There is more microwave radiation in a kitchen when an oven is working, than you will be exposed to from your local mobile phone mast base station. There is a more in-depth referenced analysis of the changes that have been found in the article library. References[1] Food Additive Contamination June 2002 [6] Tom Valentine in Search for Health, Spring 1992 Do EMFs present a problem for hearing aids?The power used by hearing aids is very small, there are few mains-frequency EMF problems associated with their use as far as we are aware. If switched to inductive loop mode, hearing aids can buzz close to high power electricity cables or transformers. Hearing aids are often sensitive to microwaves, especially digital pulsing ones such as are emitted by GSM mobile phones and base stations. These can cause buzzing noises and a high pitched whine. Wireless Local Area computer networks can cause clicking / scratching sounds, as can some 3G mobile phone systems. The hearing aids should be protected by good design, but often aren't. It is a defect in the hearing aid. Older aids were particularly prone to these problems but some new models still seem to have the problem. Induction loops amplify sound for the hard of hearing in their own home for watching TV, or in public places, like theatres, meeting rooms, etc. Sound is amplified and transmitted using a large loop of wire wound around the room or building. This sound cannot be heard directly but is picked up by a special loop and receiver worn by the person who is hard of hearing, and fed to a hearing aid. This induction loop system causes quite high levels of EMFs that change continually with the broadcast sound. There is no scientific evidence of any harm from EMFs generated by audio induction loops, and we are unaware of any anecdotal evidence that suggests otherwise. Infra-red systems work by transmitting the sound signal using an infra-red beam, from the television or hi-fi to a head set worn by the person who is hard of hearing. This use of infra-red light uses very low power and is free of any electromagnetic hazard. Microwave systems have a microwave transmitter attached to the television set or hi-fi. The receiver is in the headset worn by the person listening. The headsets are safe, but the transmitter gives off high fields. You should sit a reasonable distance away from the transmitter unit. Are interactive whiteboards in classrooms an EMF problem?Interactive whiteboards in classrooms can be a very valuable teaching and learning tool. From an EMF point of view, systems which are powered using wires are not a problem at all. There are other ways of powering the systems that we are not as happy with.
The teacher will be subject to constant low levels of microwaves whilst the system is working. Children going up to use the console will be exposed during the time of use, but not otherwise.
Although this works at a lower power, we cannot recommend it, as some people, and it is impossible at the moment to predict who, can be affected by levels of microwave exposure as low as 0.05 volts per metre. The effects reported have included memory, learning and concentration difficulties and behavioural disturbances, not problems you want to introduce into a classroom, see references below.
This type of system means that all members of the class are exposed to a continual background microwave exposure whilst the system is operational, whether they are using the console or not. In view of the concerns about microwave exposure, even at low levels, we feel we would not like to see this type of system in use in places of learning, especially when a wired system is easy to install. The following problems were identified by researchers looking at the effects of exposure to low levels of microwaves. In most cases the exposure source was a mobile phone mast, and the subjects were nearby residents; it is not clear how long each day the subjects were exposed to the mast signals, compared with potential classroom exposure. As interactive whiteboards are newer than mobile phone masts, the studies have not yet been done, though the amount of exposure may be similar in many cases. Learning and memory problems (Freiburger 2002, Santini 2002, Navarro
2003, Oberfeld 2004, Abdel-Rassoul 2006) The school study reported by Powerwatch showed that both parents and teachers were concerned about "uncharacteristic behaviour" shown by pupils in a school which had had a mast for nearly three years when compared with one without. If you want to find out more about the health risks from microwaves, there is a very informative article 'Radiofrequency EMFs and Health Risks' in our article library. How do the different units of magnetic field measurement compare?The most usual measure of magnetic flux in the UK is the microtesla. In the
US the Gauss is found more frequently.
Are there any dangers from EMF based pest control devices?Combined EMF and ultrasonic devices seem to be effective at keeping mice away. There are questions about how effective the EMF ones are on their own, without the ultrasonic component. They operate at VLF frequencies and we do not know of any readily available instruments which measure this frequency. They do give off an audible 'click' every few seconds in operation but, by and large, it is unobtrusive. EMFs are very low, but we would not recommend placing one of the units next to the bedhead in a bedroom or a chair which is sat in for lengthy periods of time. |
