NEWS: Wi-fi health fears are 'unproven'

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]
Reply to
John Navas
Loading thread data ...

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...

Reply to
Mark McIntyre

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.

Reply to
Kurt Ullman

On Mon, 21 May 2007 21:59:44 +0100, Mark McIntyre wrote in :

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

Reply to
John Navas

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.

More than you ever wanted to know about microwave absorption by water molecules:

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.

Reply to
Jeff Liebermann

On Mon, 21 May 2007 21:22:00 -0700, Jeff Liebermann wrote in :

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

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]

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]

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.

Reply to
John Navas

John Navas hath wroth:

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.

Reply to
Jeff Liebermann

| | > "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. | | | More than you ever wanted to know about microwave absorption by water | molecules: | | | 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.

Reply to
NotMe

"NotMe" hath wroth:

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

So near field, yet so far away.

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.

Reply to
Jeff Liebermann

Thanks, been years (more than I care to admit to) since I played with the math. | | The World of the Near Field |

| 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). | | | 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.

Reply to
NotMe

"NotMe" hath wroth:

Well, get back to doing the math and physics. If you're going to argue with someone, there's no better way to automatically win than to bury your victim in these. To most people, math is tasteless, odorless, unpalatable, and very distasteful. Physics is alien technology. Just remember that a confused person is more easily convinced.

Math is also very versatile. If you want to clear the room, put everyone to sleep, or end the meeting early, just dig out the math.

Well, it's not a full dummy. For cellular, it's just the head and the hand. Such testing has become so fashionable, that there are companies devoted solely to supporting the researchers: (UK)

They're not that realistic looking. However, I do recall hearing stories of universities and test labs initially disemboweling department store dummies and skeletal cadavers for use as patterns to mold heads and hands out of whatever gel or goo simulates human flesh.

There were equally strange stories about purchasing anatomically correct inflatable models, which I won't go into. One lab, where I was working on something else, had decided that since the human body was 70% water, the cheapest simulation would be one of these life size inflatable dolls, filled with a 70% water and foam. I wasn't around when it blew, but did see photos of the mess it left.

The wireless industry was eventually saved from destruction or terminal embarrassment by the standardization of the test models and procedures.

Reply to
Jeff Liebermann

"Jeff Liebermann" | | >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. | | They're not that realistic looking. However, I do recall hearing | stories of universities and test labs initially disemboweling | department store dummies and skeletal cadavers for use as patterns to | mold heads and hands out of whatever gel or goo simulates human flesh.

My wife is a semi retired medical illustrator and I've done some biomedical engineering/research in the dark ages of the late 50' and mid 60's. Coincidently much of the work was on RF for the DoD.

What you see on CSI is nothing like the real thing.

We had a commercial fridge and freezer that is used for unusual purposes. We had a wedding at our house a few years back and the caterer INSISTED she

*would* use the spare cooler for her over cook extras. We lost about half the catering staff because the woman would not follow our express instructions.

Thankfully my wife had worked for the local DA on several cases so we had a pass on spending time in the gray bar Hilton.

| There were equally strange stories about purchasing anatomically | correct inflatable models, which I won't go into. One lab, where I | was working on something else, had decided that since the human body | was 70% water, the cheapest simulation would be one of these life size | inflatable dolls, filled with a 70% water and foam. I wasn't around | when it blew, but did see photos of the mess it left. | | The wireless industry was eventually saved from destruction or | terminal embarrassment by the standardization of the test models and | procedures.

As I recall the process the CTIA was very active in funding the standardization process.

Reply to
NotMe

"NotMe" hath wroth:

I got a summer job working at the UCLA Radiation Biology lab in the early 1960's. Most of the research was on biological effects of nuclear devices, which included blast, flash, ionizing, RF pulse, and fallout. There was also a ludicrous side project on the effects of marijuana. Mostly on rabbits and mice. The prime incentive was federal funding. I became fairly immune to dealing with dissections, body parts, animal bites, and mountains of paperwork. Lots of great exercise picking up lead bricks (about 30 lbs each). Yeah, those were the fun days. Somewhat later, I got my first real job working at a mortuary, which supplied the necessary graveside manners and jokes.

I don't watch CSI. I did watch one episode where they were discussing something in computer buzzwords. Unfortunately, it made no sense, so I gave up and watched something closer to reality.

Trivia... How long can you look at yourself in a mirror? Most people don't last very long and go on to something else. Try it. Yet, the same people can look out a window at a view for literally hours. We just don't like to see ourselves as we really appear. That's the reason we don't have realistic TV shows and why genuine reality doesn't sell.

For a wedding? That must have been bizarre. One of my long lost customers ran a taxidermy business out of his house. He used the older "skin them and freeze them" method, which meant that there were several freezers around the house stocked with exotic animal parts. Unfortunately, I was attempting to become a vegetarian at the time, so I missed the opportunity for an exotic steak dinner.

I currently have two refrigerators. One is full of chemicals, batteries, and some ancient film packs. The other is for food. Visitors often try the wrong refrigerator and wonder if I eat epoxy for dinner.

Yeah, that would be difficult to explain. I was told a story by a very marginal mechanical engineer, who once worked in Detroit in the destructive testing lab. At the time, crash test dummies were being invented, but nobody had a clue how close to reality the dummies represented. So, someone contrived the bright idea of running a test with some real cadavers and comparing results. Nobody wanted to do it in the USA, so the whole crew, cards, dummies, test equipment, and photo crew where shipped off to some place in Mexico. There was just one problem. It was so hot that the dummies melted and the cadavers started to rot even inside the refrigeration truck. Everyone wanted to leave as fast as possible so packing was done in haste. When they arrived at the US border, someone discovered that there were human bodies in the refrigeration truck. Explanations, bribes, threats, and finally politicians were involved before the border authorities would allow the crew to re-enter the USA. I vaguely recall that they were stuck at the border for at least a week.

Well, yes, sorta. The way it works is that the FCC quietly announces that they are considering imposing rules, guidelines, dockets, hearings, standards, regulations, restrictions, fees, fines, and bureaucracy in some industry segment. SAR limits are NOT a good example because the FCC was directly involved in the original research and guideline creation. The FCC then approaches the leading industry groups and suggest that it would be better for everyone involved if the industry regulates itself without FCC involvement. The industry is more than happy to avoid yet another regulatory debacle and voluntarily does everything the FCC had planned to do, but without the draconian enforcement, fees, fines, inspections, and such. It's much like the film industry rating system, that is voluntarily imposed instead of having a government run censorship system. Any semblance to government expediency and mild extortion is strictly coincidental.

Reply to
Jeff Liebermann

Cabling-Design.com Forums website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.