NEWS: Wi-fi health fears are 'unproven'

<http://news.bbc.co.uk/2/hi/technology/6676129.stm>

Scientists have said there is no evidence to suggest a link between
the use of wi-fi and damage to health.

BBC programme Panorama found that radiation levels from wi-fi in one
school was up to three times the level of mobile phone mast
radiation.

The readings were 600 times below the government's safety limits but
there is ongoing debate about wi-fi use.

Sir William Stewart, chairman of the Health Protection Agency, has
said there needs to be a review of wi-fi.

He told Panorama that there was evidence that low-level radiation -
from devices like mobile phones and wi-fi - did cause adverse health
effects.

But some experts in the scientific community have disagreed with
[his] assessment.

"Wi-fi seems unlikely to pose any risk to health," said Professor
Lawrie Challis, of Nottingham University.

Prof Challis, chairman of the Mobile Telecommunications and Health
Research (MTHR) programme management committee, said: "Wi-fi
exposures are usually very small - the transmitters are low power and
some distance from the body.

....

Medical physics expert Professor Malcolm Sperrin told BBC News that
the fact wi-fi radiation in a particular school was three times
higher than a mobile phone mast was irrelevant, unless there was any
evidence of a link to health effects.

"Wi-fi is a technique using very low intensity radio waves. Whilst
similar in wavelength to domestic microwave radiation, the intensity
of wi-fi radiation is 100,000 times less than that of a domestic
microwave oven.

"Furthermore, tissue can only be effectively heated by a wavelength
that is closely matched to the absorption, and there are strict
guidelines for ensuring such absorption peaks are avoided."

....

The Health Protection Agency has said that sitting in a wi-fi hotspot
for a year results in receiving the same dose of radio waves as
making a 20-minute mobile phone call.

"Some people suspect a non-thermal interaction but there is no
evidence to suggest that this exists and indeed it is unlikely," said
Prof Sperrin.

[MORE]

--
Best regards, FAQ for Wireless Internet: <http://Wireless.wikia.com>
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Fixes to Wi-Fi Problems: <http://wireless.wikia.com/wiki/Wi-Fi_Fixes>

On Mon, 21 May 2007 19:19:53 GMT, in alt.internet.wireless , John
Navas <(E-Mail Removed)> wrote:

><http://news.bbc.co.uk/2/hi/technology/6676129.stm>
>
> Scientists have said there is no evidence to suggest a link between
> the use of wi-fi and damage to health.

I watched the programme. Oddly, it was /significantly/ more alarmist
than even the BBC's own news article on it.

They had a whole sheaf of tinfoil-hat types (seriously, some of the
participants actually had tinfoil wallpaper) and quite a lot of other
bad science. Here's an example:

They took a group of volunteers, who as far as I could work out all
claimed to be able to detect wifi (ie a self-selecting group). There
was apparently no control group though I may be mistaken. They did
some tests and announced that ONE subject could detect when a router
was on 2/3 of the time. The other results "were still being analysed"
but this was apparently evidence of a real effect.

So:
- they published data based on one single result, and ignored the
rest of their data.
- What was so tricky to analyse about the other results?
- and how many tests did they do per subject?

Pot luck could get 2 out of 3 right. Heck, half the time I can pick
two out of three.

So not precisely rigorous science. And yet this was seemingly put
forward a 'evidence' that there was a measurable effect.

Now maybe there was more real science done behind the scenes; in that
case someone must have ignored the inconvenient bits - given the
whole tone of the programme which was "yack, our children are being
sterilised / lobotomised by mad scientists laptops " I would bet that
the rest of the results were a wee bit different...


--
Mark McIntyre

In article <(E-Mail Removed)>,
Mark McIntyre <(E-Mail Removed)> wrote:

> They took a group of volunteers, who as far as I could work out all
> claimed to be able to detect wifi (ie a self-selecting group). There
> was apparently no control group though I may be mistaken. They did
> some tests and announced that ONE subject could detect when a router
> was on 2/3 of the time. The other results "were still being analysed"
> but this was apparently evidence of a real effect.
>

Reminds me of some of the early work on Extra sensory perception. The
researcher would set up with a bunch of cards with symbols (IIRC,
square, wavy lines, triangle and a couple of others) and "send" to the
other person.
They got similar results.

On Mon, 21 May 2007 21:59:44 +0100, Mark McIntyre
<(E-Mail Removed)> wrote in
<(E-Mail Removed)>:

>On Mon, 21 May 2007 19:19:53 GMT, in alt.internet.wireless , John
>Navas <(E-Mail Removed)> wrote:
>
>><http://news.bbc.co.uk/2/hi/technology/6676129.stm>
>>
>> Scientists have said there is no evidence to suggest a link between
>> the use of wi-fi and damage to health.
>
>I watched the programme. Oddly, it was /significantly/ more alarmist
>than even the BBC's own news article on it.
>[SNIP]

IMO the program was pandering to mass hysteria that was unworthy of the
BBC. Maybe Geraldo was a producer.

--
Best regards, FAQ for Wireless Internet: <http://Wireless.wikia.com>
John Navas FAQ for Wi-Fi: <http://wireless.wikia.com/wiki/Wi-Fi>
Wi-Fi How To: <http://wireless.wikia.com/wiki/Wi-Fi_HowTo>
Fixes to Wi-Fi Problems: <http://wireless.wikia.com/wiki/Wi-Fi_Fixes>

On Mon, 21 May 2007 19:19:53 GMT, John Navas
<(E-Mail Removed)> wrote:

><http://news.bbc.co.uk/2/hi/technology/6676129.stm>

> "Furthermore, tissue can only be effectively heated by a wavelength
> that is closely matched to the absorption, and there are strict
> guidelines for ensuring such absorption peaks are avoided."

Wrong. RF heating of human "tissue" (70% water) can occur at almost
any microwave frequency and is not dependent on some resonant effect.
If there were such a mythical water absorptive resonance effect in a
microwave oven, all the energy would be absorbed by the outer layers
of meat, leaving the insides stone cold.
<http://howthingswork.virginia.edu/page1.php?QNum=1456>

More than you ever wanted to know about microwave absorption by water
molecules:
<http://www.martin.chaplin.btinternet.co.uk/microwave.html>
<http://www.martin.chaplin.btinternet.co.uk/vibrat.html>
Note that none of the various resonances in water are even close to
2.4GHz (12.5cm wavelength).

Also, note that water vapor absorbes the most energy at optical
wavelengths, which should offer a clue as to the effect of atmospheric
water vapor on global warming.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558 (E-Mail Removed)
# http://802.11junk.com (E-Mail Removed)
# http://www.LearnByDestroying.com AE6KS

On Mon, 21 May 2007 21:22:00 -0700, Jeff Liebermann
<(E-Mail Removed)> wrote in
<(E-Mail Removed)>:

>On Mon, 21 May 2007 19:19:53 GMT, John Navas
><(E-Mail Removed)> wrote:
>
>><http://news.bbc.co.uk/2/hi/technology/6676129.stm>
>
>> "Furthermore, tissue can only be effectively heated by a wavelength
>> that is closely matched to the absorption, and there are strict
>> guidelines for ensuring such absorption peaks are avoided."
>
>Wrong. RF heating of human "tissue" (70% water) can occur at almost
>any microwave frequency and is not dependent on some resonant effect.
>[SNIP]

The key word there is "effectively". And you need to watch out for
confusion and even misinformation on the Internet. See...

<http://www.osha.gov/SLTC/radiofrequencyradiation/exposure.html>

RF exposures are directly linked to absorption and distribution of RF
energy in the body, and the absorption and distribution are strongly
dependent on body size and orientation and on FREQUENCY and
polarization of the incident radiation. A common measure of exposure
is the Specific Absorption Rate (SAR), the rate of energy absorption
in tissue, measured in watts per kilogram of tissue. [emphasis added]

<http://ieeexplore.ieee.org/iel5/6668/19775/00918259.pdf>

The induced electric field is a complex function of several physical
and biological variables, which include microwave FREQUENCY, source
size and polarization, and tissue type, composition, and geometry, as
well as orientation. [emphasis added]

<http://www.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet65/oet65.pdf>

The new FCC exposure limits are also based on data showing that the
human body absorbs RF energy at some frequencies more efficiently
than at others. As indicated by Table 1 in Appendix A, the most
restrictive limits occur in the frequency range of 30-300 MHz where
whole-body absorption of RF energy by human beings is most efficient.
At other frequencies whole-body absorption is less efficient, and,
consequently, the MPE limits are less restrictive.

Microwave Radiation Effects on Humans, Stephen F. Cleary
BioScience, Vol. 33, No. 4 (Apr., 1983), pp. 269-273

The absorption of RF and microwave radiation also depends upon the
tissue electrical parameters e and cr, which are frequency dependent.

--
Best regards, FAQ for Wireless Internet: <http://Wireless.wikia.com>
John Navas FAQ for Wi-Fi: <http://wireless.wikia.com/wiki/Wi-Fi>
Wi-Fi How To: <http://wireless.wikia.com/wiki/Wi-Fi_HowTo>
Fixes to Wi-Fi Problems: <http://wireless.wikia.com/wiki/Wi-Fi_Fixes>

John Navas <(E-Mail Removed)> hath wroth:

>On Mon, 21 May 2007 21:22:00 -0700, Jeff Liebermann
><(E-Mail Removed)> wrote in
><(E-Mail Removed)>:
>
>>On Mon, 21 May 2007 19:19:53 GMT, John Navas
>><(E-Mail Removed)> wrote:
>>
>>><http://news.bbc.co.uk/2/hi/technology/6676129.stm>
>>
>>> "Furthermore, tissue can only be effectively heated by a wavelength
>>> that is closely matched to the absorption, and there are strict
>>> guidelines for ensuring such absorption peaks are avoided."
>>
>>Wrong. RF heating of human "tissue" (70% water) can occur at almost
>>any microwave frequency and is not dependent on some resonant effect.
>>[SNIP]
>
>The key word there is "effectively". And you need to watch out for
>confusion and even misinformation on the Internet. See...

RF exposure effects are frequency dependent, but not resonant
(absorption peaks).

Modifying the allegation using the word "effectively" to wiggle out of
the possibility that 2.4GHz exposure is not a resonant effect, is not
my idea of a proper claim. My problem is not with the word
"effectively". It's with the claim that 2.4GHz Wi-Fi heating is
somehow related to a vague resonant phenomenon, which the author
called "absorption peaks". There are such peaks at resonance, but
they're at 23, 180, and 320GHz. There's no water resonance at 2.4GHz
or anywhere nearby.

As for the word "effectively", that's pure baloney. It either heats
or it doesn't. The amount of heating is measured in hundredths of a
degree. It's also VERY difficult to calculate and model. For the
ultimate in heating, just use a common infra-red heat lamp or light
bulb, but that would be too easy.

You cite several sources which indicate that frequency is involved in
the degree of absorption. I have no problem with that. The higher
the frequency, the greater the biological and heating effects. At
very low frequencies, RF simply goes through the body leaving it
unaffected. As the frequency increases, skin effect and bulk
absorption cause more and more RF losses, which are usually converted
to heat. The body is quite good at removing such surplus heat. At
very high microwave frequencies, the degree of penetration is only a
few mm resulting in localized heating causing RF burns and such.

The effects are not linear with frequency. There are water and body
part resonant frequencies which have a greater effect than other
frequencies nearby. Fortunately, these are also frequencies at which
atmospheric absorption is highest. Therefore, the chances of getting
zapped by a nearby microwave link at 23, 180, and 320GHz is
"effectively" minimized.

Other frequencies have little to do with heating effects. There are
frequencies that allegedly interfere with brain waves, cellular
reproduction, immunological responses, antibodies, and the way my
re-heated coffee tastes. Few of these effects have been properly
demonstrated in repeatable experiments. None are specific to 2.4GHz
Wi-Fi.

As for confusion and misinformation, I know these when I write them.



><http://www.osha.gov/SLTC/radiofrequencyradiation/exposure.html>
>
> RF exposures are directly linked to absorption and distribution of RF
> energy in the body, and the absorption and distribution are strongly
> dependent on body size and orientation and on FREQUENCY and
> polarization of the incident radiation. A common measure of exposure
> is the Specific Absorption Rate (SAR), the rate of energy absorption
> in tissue, measured in watts per kilogram of tissue. [emphasis added]
>
><http://ieeexplore.ieee.org/iel5/6668/19775/00918259.pdf>
>
> The induced electric field is a complex function of several physical
> and biological variables, which include microwave FREQUENCY, source
> size and polarization, and tissue type, composition, and geometry, as
> well as orientation. [emphasis added]
>
><http://www.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet65/oet65.pdf>
>
> The new FCC exposure limits are also based on data showing that the
> human body absorbs RF energy at some frequencies more efficiently
> than at others. As indicated by Table 1 in Appendix A, the most
> restrictive limits occur in the frequency range of 30-300 MHz where
> whole-body absorption of RF energy by human beings is most efficient.
> At other frequencies whole-body absorption is less efficient, and,
> consequently, the MPE limits are less restrictive.
>
>Microwave Radiation Effects on Humans, Stephen F. Cleary
>BioScience, Vol. 33, No. 4 (Apr., 1983), pp. 269-273
>
> The absorption of RF and microwave radiation also depends upon the
> tissue electrical parameters e and cr, which are frequency dependent.
--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

"Jeff Liebermann" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
| On Mon, 21 May 2007 19:19:53 GMT, John Navas
| <(E-Mail Removed)> wrote:
|
| ><http://news.bbc.co.uk/2/hi/technology/6676129.stm>
|
| > "Furthermore, tissue can only be effectively heated by a wavelength
| > that is closely matched to the absorption, and there are strict
| > guidelines for ensuring such absorption peaks are avoided."
|
| Wrong. RF heating of human "tissue" (70% water) can occur at almost
| any microwave frequency and is not dependent on some resonant effect.
| If there were such a mythical water absorptive resonance effect in a
| microwave oven, all the energy would be absorbed by the outer layers
| of meat, leaving the insides stone cold.
| <http://howthingswork.virginia.edu/page1.php?QNum=1456>
|
| More than you ever wanted to know about microwave absorption by water
| molecules:
| <http://www.martin.chaplin.btinternet.co.uk/microwave.html>
| <http://www.martin.chaplin.btinternet.co.uk/vibrat.html>
| Note that none of the various resonance in water are even close to
| 2.4GHz (12.5cm wavelength).
|
| Also, note that water vapor absorbes the most energy at optical
| wavelengths, which should offer a clue as to the effect of atmospheric
| water vapor on global warming.


One critical fact that is clearly ignored is that the effects of RF
absorption are focused in the near field. At 800 MHz this is on the order
of 2 cm at 2.4G less than 1 cm. (I'll leave the math to others).

This has been substantiated in both mathematical analysis and in real world
test of cadavers (do a search of Dr. Oue Balzasno (spl) of Motorola).

For comparison the near field @ 60 Hz is on the order of 3000 miles.

There are a few suspected effects based on calcium ion migrations in single
cells but these drop out of the data at RP power levels above 0.6 W for 800
MHz.

"NotMe" <(E-Mail Removed)> hath wroth:

>One critical fact that is clearly ignored is that the effects of RF
>absorption are focused in the near field. At 800 MHz this is on the order
>of 2 cm at 2.4G less than 1 cm. (I'll leave the math to others).

The math is simple:
Near Field Radius = Wavelength / 2Pi
For 2.4GHz, the wavelength is 12.5cm.
r = 12.5cm / 6.28 = 2.0 cm
The problem is that the transition between linear field effects (near
field) and square law effects (far field) is not abrupt. It also
varies with the size of the radiator. For that it's:
r = 0.62 sqrt(D^3/wavelength)
where D is the diameter of the radiator in the same units of measure
as the wavelength. So, for a common wi-fi panel antenna, the near
field starts at:
r = 0.62 sqrt(15^3/12.5) = 1.0 cm

The World of the Near Field
<http://www.evaluationengineering.com/archive/articles/1005/1005the_world.asp>
So near field, yet so far away.

>This has been substantiated in both mathematical analysis and in real world
>test of cadavers (do a search of Dr. Oue Balzasno (spl) of Motorola).

<http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=120141>
I couldn't find the freely available article on the web with Google.
However, I can download a copy from IEEE Comm Society.

If the test subjects were already dead, they need not worry about RF
exposure, unless one were trying to communicate with the dead.

>For comparison the near field @ 60 Hz is on the order of 3000 miles.
>
>There are a few suspected effects based on calcium ion migrations in single
>cells but these drop out of the data at RP power levels above 0.6 W for 800
>MHz.


--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

"Jeff Liebermann" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
| "NotMe" <(E-Mail Removed)> hath wroth:
|
| >One critical fact that is clearly ignored is that the effects of RF
| >absorption are focused in the near field. At 800 MHz this is on the
order of 2 cm at 2.4G less than 1 cm. (I'll leave the math to others).
|
| The math is simple:
| Near Field Radius = Wavelength / 2Pi
| For 2.4GHz, the wavelength is 12.5cm.
| r = 12.5cm / 6.28 = 2.0 cm
| The problem is that the transition between linear field effects (near
| field) and square law effects (far field) is not abrupt. It also
| varies with the size of the radiator. For that it's:
| r = 0.62 sqrt(D^3/wavelength)
| where D is the diameter of the radiator in the same units of measure
| as the wavelength. So, for a common wi-fi panel antenna, the near
| field starts at:
| r = 0.62 sqrt(15^3/12.5) = 1.0 cm

Thanks, been years (more than I care to admit to) since I played with the
math.
|
| The World of the Near Field
|
<http://www.evaluationengineering.com/archive/articles/1005/1005the_world.asp>
| So near field, yet so far away.
|
| >This has been substantiated in both mathematical analysis and in real
world test of cadavers (do a search of Dr. Oue Balzasno (spl) of Motorola).
|
| <http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=120141>
| I couldn't find the freely available article on the web with Google.
| However, I can download a copy from IEEE Comm Society.
|
| If the test subjects were already dead, they need not worry about RF
| exposure, unless one were trying to communicate with the dead.
|

Original work was done with cadavers but over time a 'crash test dummy'
model has been developed.

FWIW Dr. Balzano (spl?) was found of telling a story about a security guard
that was instructed NOT to open the shipping package containing the cadaver
head. According to reports the lady will not open ANY contains for
inspection.