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This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (April 2008) |
- For mobile phones, see Mobile phone radiation and health
The World Health Organization has acknowledged that electromagnetic fields (EMFs) are influencing the environment (but not people), and that some people are worried about possible effects.[1] In response to public concern, the World Health Organization established the International EMF Project in 1996 to assess the scientific evidence of possible health effects of EMF in the frequency range from 0 to 300 GHz. They have stated that although extensive research has been conducted into possible health effects of exposure to many parts of the frequency spectrum, all reviews conducted so far have indicated that exposures are below the limits recommended in the ICNIRP (1998) EMF guidelines, covering the full frequency range from 0-300 GHz, and do not produce any known adverse health effect.
International guidelines on exposure levels to microwave frequency EMFs such as ICNIRP limit the power levels of wireless devices and it is uncommon for wireless devices to exceed the guidelines. These guidelines only take into account thermal effects, as nonthermal effects have not been conclusively demonstrated.[2] The official stance of the Health Protection Agency is that “[T]here is no consistent evidence to date that WiFi and WLANs adversely affect the health of the general population.” And also that “...it is a sensible precautionary approach...to keep the situation under ongoing review...”.[3] Sir William has resisted any calls to further explain his comments.[4]
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Exposure difference to mobile phones
While users of wireless devices are typically exposed for much longer periods than for mobile phones, the range of wireless devices (and hence their strength) is significantly less. As well, the devices are located significantly farther away from users' heads, resulting in far less exposure overall: The Health Protection Agency claims that if a person spends one year in a Wi-Fi hotspot, they will receive the same dose of radio waves as if they had made a 20-minute call on a mobile phone.[5]
Wireless LAN
EMF levels for WiFi devices are much lower than mobile phones, and there is less public concern about any suggested health issues for wireless LAN devices. Most wireless LAN equipment is designed to work within predefined standards. Wireless access points are also often in close proximity to humans, but the drop off in the already low power is fast, following the inverse-square law. WiFi has been anecdotally linked to electromagnetic hypersensitivity, but no studies have researched this association to date.
The HPA's position is that “...radio frequency (RF) exposures from WiFi are likely to be lower than those from mobile phones.” It also saw “...no reason why schools and others should not use WiFi equipment.”[3] In October 2007, the HPA launched a new “systematic” study into the effects of WiFi networks on behalf of the UK government, in order to calm fears that had appeared in the media in a recent period up to that time".[6] Dr Michael Clark, of the HPA, says published research on mobile phones and masts does not add up to an indictment of WiFi.[7]
Bluetooth
Bluetooth also uses the microwave frequency spectrum in the range of 2.4 GHz to 2.4835 GHz. The radiated output power of Bluetooth devices varies between 1 and 100 mW, and can operate continuously or sporadically (on demand), so total exposure to EMF radiation is quite variable. Bluetooth devices have not been linked with any health issues.
Other devices
Radio frequency in the microwave and radio spectrum is used in a number of practical devices for professional and home use, such as:
- DECT and other cordless phones operating at a wide range of frequencies
- Remote control devices for opening gates, etc.
- Portable two-way radio communication devices, such as walkie-talkies
- Wireless security (alarm) systems
- Wireless security video cameras
- Radio links between buildings for data communication
- Baby monitors
In addition, electrical and electronic devices of all kinds emit EM fields around their working circuits, generated by oscillating currents. Humans are in daily contact with computers, video display monitors, TV screens, microwave ovens, fluorescent lamps, electric motors of several kinds (such as washing machines, water pumps, etc.) and many others. The typical background power of electromagnetic fields in the home can vary from zero to 5 milliwatts per meter squared.[citation needed] Long-time effects of these electromagnetic fields on human and animal health are still unknown, and most of the studies available have shown no effect. However, the powerful fields produced by radio (and then TV) transmitters have been present for more than 100 years now with no established effects on people's health.
See also
References
- ^ "Electromagnetic fields (EMF)". World Health Organization. Retrieved on 2008-01-22. “Electromagnetic fields of all frequencies represent one of the most common and fastest growing environmental influences, about which anxiety and speculation are spreading. All populations are now exposed to varying degrees of EMF, and the levels will continue to increase as technology advances.”
- ^ Levitt, B. Blake (1995). Electromagnetic Fields. San Diego: Harcourt Brace & Company, 29-38.
- ^ a b "WiFi Summary". Health Protection Agency. Retrieved on 2008-01-22.
- ^ Kewney, Guy (2006-11-25). "Mast debaters strike again, ban Wi-Fi in UK schools". The Register. Retrieved on 2008-01-23.
- ^ "Wi-fi health fears are 'unproven'", BBC News, BBC (2007-05-21). Retrieved on 22 January 2008.
- ^ "Health Protection Agency announces further research into use of WiFi". Health Protection Agency. Retrieved on 2008-08-28.
- ^ "Wi-fi: should we be worried?", The Times. Retrieved on 16 September 2007. "All the expert reviews done here and abroad indicate that there is unlikely to be a health risk from wireless networks. … When we have conducted measurements in schools, typical exposures from WiFi are around 20 millionths of the international guideline levels of exposure to radiation. As a comparison, a child on a mobile phone receives up to 50 per cent of guideline levels. So a year sitting in a classroom near a wireless network is roughly equivalent to 20 minutes on a mobile. If WiFi should be taken out of schools, then the mobile phone network should be shut down, too—and FM radio and TV, as the strength of their signals is similar to that from WiFi in classrooms."
