WiFi Overview - Wi-Fi and Health
[Radio and TV]
There has been plenty of media coverage of WiFi and the potential dangers in
2007. There is a lot of misunderstanding and misrepresentation of evidence
being thrown into the mix, and it is becoming very hard to follow the strands of
a) what the exposure levels are, b) what the evidence is actually saying, and
c) what other aspects need to be considered on WiFi.
Many of the concerns were summarised in a Memorandum on WiFi signed by eight
members of the Health Protection Agency's EMF
Discussion Group and sent to the HPA at the end of 2007 following the
announcement of research, costing about £300,000 of public money, which
does not address any of the health concerns. The HPA have chosen not to respond
to this Memorandum, so on 25 April 2008 a copy has been posted here for members
of the public to read. [Download in full] 9 pages, 73 KB
Schools without Wifi
On request, we have started collecting a list of submitted schools that are
confirmed to have (or not have) WiFi installed. Due to obvious restrictions
there is only a very small proportion of schools represented, but in case it may
be helpful you may want to look through our current list.
If you would like, you can sign the government petition with regards to removing WiFi from schools.
Last in 2008 a new website appeared providing a rational and well supported scientific argument for the validity in precaution of the use of WiFi in primary and secondary schools. This is also well worth spending some time looking around if you are concerned about the use of wireless technologies in a local school.
General Exposure Levels
Michael Clark, senior HPA spokesperson, has publicly stated that "Being on a
phone for 20 minutes is equivalent to 1 year in a WiFi classroom". This is both
factually incorrect and highly misleading.
Whilst Mike Clark is right that a mobile phone, working on full power and
with you talking continuously (not listening) can technically expose you up to
about 50% of the SAR limits. In normal use, with a good number of signal
strength bars showing on the display (say 75% signal level), the phone will be
working at somewhere between one-thousandth and one-twentieth of this level.
Let's average this at about one fiftieth as a reasonable level for the phone to
be operating at most of the time. Then, if you are talking 50% of the time, this
would reduce the transmitted pulses (using DTX) by another factor of 2. So, a
typical exposure would not be 50% of the SAR limit but more like 0.5% of the SAR
limit which we should assume to be 0.5% of the the ICNIRP limit (for a typical
11/10/2007 - This has been updated to more accurately
reflect expected real life power outputs from Wireless access points in
Now we come to a slightly different exposure regime in the classroom in that
you are not holding the wLAN card to your head. 2.4 GHz wLANs (most common in
the UK) operate at 0.03 watts output power (5-6 GHz ones can use up to 20 times
this). So we have one wLAN node in the classroom (0.03 W) and, say, 20 laptops
all at 0.03 W. However, they are only transmitting much power when actually
transferring files. So, let's say that we have the equivalent of one laptop
operating absolutely continuously (actually the combined output of 20 may well
be more that this), and that we are on average 2 metres from the antennas. This
seems reasonable based on the fact that there are 20 in the room. So E = (sq.root
(30*0.03*2))/2 = 0.67 V/m equivalent continuous. Now the ICNIRP guidance at 2.4
GHz is 61.5 V/m. So the signal strength is about 1/100th of what is allowed.
Power is proportional to signal strength squared so that would be around
1/10000th of the ICNIRP power level.
So, we have a mobile phone call next to head typically 0.5% (1/200th) of the
ICNIRP guidance. We also have being in a 20 PC wLAN classroom being something in
the order of 0.01% (or 1/10000th) of ICNIRP guidance, about a 50-fold
Therefore 20 minutes on a mobile phone running at typical power levels
would be equivalent to about 16 hours in a classroom with 20 wLAN PCs,
approximately eight standard school days.
These figures have been updated from our "dispelling the wireless myths"
news article as 1m seems an unreasonable average distance from the laptops.
However, we have encountered a number of access points that are sending short
bursts of data a few times per second, and the signal strength of these are all
reasonably high - If this is the case, the average exposure from any access
point will be much higher than in the calculations above.
However, these figures are assuming that it is cumulative absorbed power that
is being implicated in RF research, and that then implies a linear dose-response
relationship model. From the evidence that has found a risk, this seems
unlikely to be the case. Peak signal strength received may also be important,
and people using WiFi enabled laptops would regularly be exposed to electric
fields of 2 to 3 V/m. Whilst this is far below ICNIRP, it is far above the
levels where adverse health effects are being reported (~0.05 V/m).
It is also an interesting contrast to our own HPA, as highlighted by a
recent correspondence between
Michael Clark and Dr. Grahame Blackwell.
Firstly, it is very important to stress that there is currently (as of July
2007) nothing that we are aware of in the scientific literature that looks at
WiFi. So initially the answer would be "none". However, when anecdotal evidence
of problems are being reported, it is prudent to do two things: Firstly,
prioritise research to be done looking specifically at effects from typical WiFi
exposure, and secondly, to have a look at the literature published on exposures
and technologies that may be relevant.
TV and Radio Transmitters use relatively similar frequencies, but are not
digitally pulsed transmissions (AM and FM radio are entirely continuous wave and
TV is almost entirely continuous wave). There is a reasonable chance that, if
humans react to TV and Radio transmissions, it may be very differently to the
reaction to a digitally pulsed signal, so even though there is evidence of a
possible risk these may not be
relevant to WiFi.
Mobile Telecommunication systems (CDMA, GSM and 3G) are both closer in
frequency and are also digitally pulsed information carrying signals - these
are sufficiently close to WiFi that the research into phones and their base
stations may be applicable to exposure from WiFi.
Firstly, typical exposure from a phone in use is likely to be far higher
than from a typical WiFi laptop or access point due to the different in
proximity to the device in question. So whilst, again, there is research showing
that there may be a risk, this may not be relevant.
However, signal strength from a mobile phone base station where it reaches
the ground (approximately 70 to 100 metres from the base station) is typically
between 0.5 and 1.5 V/m, exactly the same as we measured in a WiFi classroom in
a school in Norwich, and the same as found in the above calculations, and seems
therefore to be very relevant. A quick survey of the literature looking very
specifically into mobile phone base station epidemiology finds some
statistically significant health effects. Many of these are
summarised, with helpful graphs, etc, in our library article "Radiofrequency EMFs and health
risks". There is, in fact, very little research looking at base stations
that has failed to find an effect. Also interesting is that many of the effects
in the papers above (non-cancer effects) are those being reported in the
anecdotal evidence from WiFi exposure.
In essence then, there is sufficient evidence to warrant some degree of
precaution regarding WiFi until research has been done very specifically into
its effects. With dLAN systems and ordinary CAT5/6 wired networks offering
better stability, bandwidth and security, there is simply no need for most homes,
organisations and schools to switch to wireless networks, apart from the savings
of the slight inconvenience in cables.
The HPA have recently announced a £300,000 study into measurements of
typical WiFi system exposure levels. We have noticed however that this research
has already been repeatedly been done, and we have provided a short summary of said research for
As briefly mentioned above, there are other serious drawbacks to using WiFi
that are important considerations when implementing computer networks. Firstly,
the bandwidth is really not very good. Modern wired network cables are running
at 1 GBit/sec, and even older networks are running at 100 MBit/sec. WiFi on the
other hand typically performs at around 8-15 MBit/sec, even though the specs
suggest it should be capable of about 54 MBit/sec. On top of the speed
restriction, WiFi is also susceptible to interference. An access point is
typically only designed to accept concurrent connections from a handful of
laptops, else the system can easily start getting confused. Likewise, it is easy
to disable a network by blasting the area with higher powered 2.4 GHz radiation.
Then lastly, and from an IT point of view, is security. Without technical
knowledge, many access points come without having WEP encryption set up, and not
doing so can leave your wireless network very vulnerable to intrusion from other
wireless devices. It is very easy to drive around a city residential area, and
with the right hardware, find an unsecured wireless network adaptor and simply
"hook in" to someone else network and internet connection. Aside from the usage
of their payed for bandwidth, this has a risk of letting them access files on
other computers on the network, and also performing illegal activity whilst
effectively framing the owner of the internet connection. Again, wired networks
are simply secure unless someone comes into your house and plugs a laptop of
theirs into your router / switch.
Having said this, Wireless network does have the rather useful advantage of
not having to cable up various rooms in your house (where you would intend on
using a laptop) with networking sockets. However, again, there is a more secure
and stable alternative, at pretty much the same price: dLAN units allow you to
use the buildings mains circuitry as an extension to your computer network, so
all you have to do is plug one dLAN unit into the wall (and network to your
router / wired network) and the whole building is networked. Plug the other unit
into any other socket on the same power circuitry, and voila, you have a new
network connection. Because the network traffic is still travelling down wires,
and it doesn't get out beyond the house's consumer unit, the network is secure
from those that do not have physical access to the house itself. It can also
carry a higher bandwidth than a wireless network (typically 80 MBit/sec).
So there really is no need to use WiFi anyway, barring the convenience of not
having to plug your laptop into anything at all (but for those that need a mains
socket anyway, dLAN just uses one extra wire from the same socket as the laptop
adaptor). For schools we would recommend wiring up all the classrooms that need
to have network access, preferably by putting the power and network cabling
through the same trunking. If done by IT staff, this is a lot cheaper than
wireless networking equipment anyway. If there is no-one capable, or allowed
(perhaps on health and safety grounds), again dLAN is the next best option as
this reduces the need for expensive sub-contracting work.
Dr. Magda Havas (Environmental and Resources department, Trent University,
Ontario, Canada), has written an excellent precautionary paper, prepared for the
Board of Supervisors, City and County of San Fransisco. This 51 page document is
available from here, and covers a wide range of literature and scientific findings on RF
research, and presents them in a logical and progressive manner.
Concerned parents Jane Smith and Vanessa Spedding have recently fought a
successful campaign to prevent WiFi being installed in Wigmore Primary School,
Herefordshire. Their campaign succeeded using a common sense approach combining
precaution against the possible health effects, cost, and IT practicality. They
are happy with us presenting their letter, an accompanying letter from Prof. Olle Johansson, and a full implementation costing from an
IT company that installs network systems. It is also important to note that,
contrary to the text in the letter, many schools in Canada do still use WiFi
for their classrooms.
BECTA have provided a very thorough albeit technical
article on WiFi and wireless specifications.
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2007). "Radio-Frequency Radiation Exposure from AM Radio Transmitters and
Childhood Leukemia and Brain Cancer". Am J Epidemiol 166(3):270-9. - [View Abstract]
 - Lönn S, Ahlbom A, Hall P, Feychting M (November 2004).
"Mobile phone use and the risk of acoustic neuroma". Epidemiology
15(6):653-9 - [View Abstract]
 - Lennart Hardell, Kjell Hansson Mild, Michael Carlberg, and
Fredrik Söderqvist (2006). "Tumour risk associated with use of cellular
telephones or cordless desktop telephones". World J Surg Oncol. 2006; 4:
74 - [View Abstract]
 - Abdel-Rassoul G, El-Fateh OA, Salem MA, Michael A, Farahat F,
El-Batanouny M, Salem E (March 2007). "Neurobehavioral effects among
inhabitants around mobile phone base stations". Neurotoxicology.
28(2):434-40 - [View Abstract]
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P, Gumustas K, Seker S (2006). "GSM base station electromagnetic radiation
and oxidative stress in rats". Electromagn Biol Med. ;25(3):177-88 - [View Abstract]
 - "Risk Evaluation of Potential Environmental Hazards From Low
Frequency Electromagnetic Field Exposure Using Sensitive in vitro Methods".
EU Programme, "Quality of Life and Management of Living Resources" - [View Foreword and Download Report]
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"Investigation on the health of people living near mobile telephone relay
stations: I/Incidence according to distance and sex". Pathol Biol (Paris).
50(6):369-73 - [View Abstract]
 - Santini R, Santini P, Danze JM, Le Ruz P, Seigne M (September
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antennas and other electromagnetic factors". Pathol Biol (Paris).
51(7):412-5 - [View Abstract]
 - Balmori Alfonso (2005). "Possible Effects of Electromagnetic
Fields from Phone Masts on a Population of White Stork (Ciconia ciconia)".
Electromagnetic Biology and Medicine, 24: 109-119 - [View Summary and Download Report]
 - Wolf R, Wolf D (April 2004). "Increased incidence of cancer
near a cell-phone transmitter station". International Journal of Cancer
Prevention Vol1, No2, - [Download Report]
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Voit (April 2004). "The Influence of Being Physically Near to a Cell Phone
Transmission Mast on the Incidence of Cancer". Umwelt Medizin Gesellschaft
17 - [View Summary and Download Report]
 - Oberfeld Gerd, Navarro A. Enrique, Portoles Manuel, Maestu
Ceferino, Gomez-Perretta Claudio (August 2004). "The Microwave Syndrome -
Further aspects of a Spanish Study". Conference Proceedings - [View Summary and Download Report]