Slashdot Log In
How Bad Can Wi-fi Be?
Posted by
Zonk
on Tue May 22, 2007 09:38 AM
from the good-thing-we-have-real-experts-here dept.
from the good-thing-we-have-real-experts-here dept.
An anonymous reader writes "Sunday night in the UK, the BBC broadcast an alarmist Panorama news programme that suggested wireless networking might be damaging our health. Their evidence? Well, they admitted there wasn't any, but they made liberal use of the word 'radiation', along with scary graphics of pulsating wifi base stations. They rounded-up a handful of worried scientists, but ignored the majority of those who believe wifi is perfectly harmless. Some quotes from the BBC News website companion piece: 'The radiation Wi-Fi emits is similar to that from mobile phone masts ... children's skulls are thinner and still forming and tests have shown they absorb more radiation than adults'. What's the science here? Can skulls really 'absorb' EM radiation? The wifi signal is in the same part of the EM spectrum as cellphones but it's not 'similar' to mobile phone masts, is it? Isn't a phone mast several hundred/thousand times stronger? Wasn't safety considered when they drew up the 802.11 specs?"
Related Stories
[+]
Hardware: BBC Rules That Wi-Fi Radiation Findings Were Wrong 210 comments
Stony Stevenson writes "A Panorama programme claiming that Wi-Fi creates three times as much radiation as mobile phone masts was 'misleading', an official BBC complaints ruling has found. The team involved in the research came under fire from the school where the 'investigations' were held for scaremongering, but now the BBC has come out with an official ruling. 'The programme included only one contributor (Professor Repacholi) who disagreed with Sir William, compared with three scientists and a number of other speakers (one of whom was introduced as a former cancer specialist) who seconded his concerns.'"
This discussion has been archived.
No new comments can be posted.
The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.
Won't somebody please... (Score:5, Insightful)
Seriously, it's sad that supposed "news" programs air things like this just to get ratings. What's even sadder is that lots of people believe them, so tech-savvy people like us now have to spend time explaining to Aunt Jane that the big evil wifi will not give her cat cancer.
What crap. (Score:5, Insightful)
The only thing that's frying our kid's brains are their ideas. I'm not overlooking child safety, but there are WAY more harmful waves out there than WiFi.
In the meantime, their children are outside getting burnt without sunscreen.
Re:What crap. (Score:5, Funny)
*shivers*
OMG SOMEBODY THINK OF THE CHIIILDREN
Parent
Re:What crap. (Score:5, Funny)
Please stop, it's too horrible! The worst of it all is that my PC is as we speak radiating heat.
That's the same kind of radiation that is used in conventional ovens!
It can cook stuff to death!
Parent
Re:What crap. (Score:5, Interesting)
Actually, in the late 1890's and early 1900's people who worked in the field of XRays often died from over exposure of radiation. They simply didn't know what they heck they were working with. Thomas Edison was so horrified of what happened to his worker Clarence Dally [wikipedia.org] due to radiation poisoning that he abandoned any further research with X-rays. Not to mention Marie Curie death due to exposure to radiation and countless others that worked in her field.
Back then of course people thought drinking radium was a good health product and that shoe sales man could operate their x-ray on a casual basis to fit shoes giving them more REM exposure in a day than a modern nuclear power plant worker is allowed a year.
I'm not saying that WiFi is dangerous, but as a precedent people have often generally underestimated some dangers with emerging technologies and we should never discount such a thing could happen. Of course we due scientific study than complete news worthy paranoia.
Parent
Eek! (Score:5, Funny)
Re:Eek! (Score:5, Insightful)
Parent
Re:Eek! (Score:5, Interesting)
They did however mention that Sweden recognises electro-sensitivity as an official disability so there is perhaps some credibility in the whole idea, how much is still questionable of course.
Parent
WiFi is microwaves (Score:5, Informative)
802.11b/g uses 2.4GHz radio waves. That's the same frequency range as microwave ovens. Microwave ovens work because the microwaves are absorbed by the bonds in the water molecules of food (which is why dry food does not cook in microwave ovens).
So yes, human tissue that contains water can absorb WiFi radiation. That is a fact.
What is not known is: how much absorption of that radiation is bad for the kids?
Re:WiFi is microwaves (Score:5, Informative)
1. Your body absorbs EM radiation from the infra-red band! Also known as heat, IR sources are everywhere and can eliminate the need for you to wear thick clothing.
2. Your skin absorbs EM radiation from the optical spectrum! Black people are particularly vulnerable to this type of radiation absorption.
3. Your skin absorbs radiation from the UV spectrum! Millions of people develop tans and synthesize vitamin D every year due to UV radiation absorption.
Notice that in all these cases, we're talking about the conversion of energy to *heat* by the absorbing tissue. Raising an alarm about this is like getting up in arms about the dangers of "dihydrogen monoxide". In fact, radio-band emissions are even lower-energy than the energy spectra listed above, and is thus generally even more benign.
Dangerous radiation is high-energy ionizing radiation, like that found in the X-ray and gamma spectra. Such radiation has the capacity to damage cell DNA and cause radiation sickness, but that's a completely different animal than what this article is dealing with.
Parent
Re:WiFi is microwaves (Score:5, Informative)
2.4GHz was used because it was available for use, i.e., it would not interfere with frequencies already allocated to other services in the microwave area.
In other words, the thought process (if you can call it that) was not, "let's find a frequency for 802.11b that is free of interference from other sources". It was more along the lines of, "let's find a frequency for 802.11b so that 802.11b won't mess up anything of import, i.e., microwave ovens don't really care about interference from your wireless router.
By the way, the same "thought" process was used to pick a frequency for the 2.4GHx wireless phones.
Parent
Re:WiFi is microwaves (Score:5, Informative)
For this reason, 2.4 GHz wasn't too hot for long-haul communications due to water vapor in the air, so no one was in a rush to license spectrum for it, and no one fought designating it as an "Industrial, Scientific, Medical" band. (with the primary use in all three of those categories being to take advantage of that water absorption peak for heating.) Now, because the band is such a cesspool, no one minded allowing low-power unlicensed communications in that band.
Now, as to the health effects of this - Yes, the water in your body is more likely to absorb 2.4 GHz RF. No, that absorption will not do any cumulative damage. Absorbing 2.4 GHz RF will make the water molecules in your body vibrate a little more (i.e. it will heat you up.) At high powers, this does become dangerous as the heat basically cooks you from the inside (just like a microwave oven). At low powers (with 802.11 being a great example), the body is able to safely dissipate the heat rapidly enough so that not only is no damage done, the change in temperature at any point in the body is negligible. You're more likely to get burned by touching the heatsink of the RF amp than you are by touching a circuit trace carrying RF at those power levels.
RF radiation is nothing like nuclear radiation - the critical difference is that nuclear radiation is ionizing, that is to say that it can not only vibrate molecules a bit, but it has enough energy to alter them. This has the effect of "flipping bits" in your DNA and other such nasty stuff. Since "bit flipping" can have cumulative effects, low levels of ionizing radiation can be dangerous in the long term, because the damage accumulates. With RF, it doesn't unless power levels are so high as to induce temperatures that cause thermal damage.
Prior to graduate school, I worked at a company that built RF power amplifiers for cell towers (30-45W average power output), and many of my coworkers had been working with microwave RF amps since the very first cell system Motorola deployed. (Yes, we had some ex-Motorola old hands there, who had interesting stories from the early days when the system designers were also heavily involved with the installation process of new base stations.) No health problems whatsoever.
Since graduate school, one of the tasks of my department is taking equipment through EMI testing. We're frequently right at OSHA RF exposure limits - no health problems with any of us (Well, at least no new ones that weren't preexisting conditions), even our mentor who has been doing this for 20-30 years.
Parent
Re:WiFi is microwaves (Score:5, Informative)
http://en.wikipedia.org/wiki/Microwave_oven [wikipedia.org]
Parent
Re:WiFi is microwaves (Score:5, Funny)
Parent
Researchers. On. Drugs. (Score:5, Informative)
the FCC has specifications of radiation density versus frequency that are limits in their rulebooks, limits used to isolate access to radio facilities from microwaves to commercial broadcasters... to ham radio operators burning electrons in the basement. these have been codified by medical research. if you're going for an advanced ham license, you have to study the milliwatts per meter limits, the question occasionally comes up on the test.
so there are 3/4 million americans who know this, not just ten academics in the tower.
where the hell did this whining of Luddites come from, and why wasn't it left there?
The BBC should know better... (Score:5, Insightful)
This is arguably the worst case of the BBC scrambling for ratings I've ever witnessed. Never before have I seen them stoop so low to try and raise viewing figures. I was sat watching it waiting for the part where they offer the opposing view of the situation to allow people to make their own minds up, unfortunately however, that never came - it was one sided anti-wifi propaganda all the way through, from start to finish.
About the only attempt at offering an opposing view was the brief mention that the WHO states that there is no known risk of wifi at this time, this brief mentioning was followed by a couple of minutes of slagging off the credibility of the WHO.
I'm no expert when it comes to wifi, radiation and so forth and I'm not claiming that wifi is 100% safe - it may well pose risks. The problem with the program however seemed to be that it's entire argument is based on the premise that there is some other danger to human health from radiation other than the heating effect, and from what I've read elsewhere, there is absolutely no evidence that there is any effect other than the heating effect. I'm sure those with better scientific knowledge may be able to correct me on this if I'm wrong, but if it's true as has been reported by other news outlets (and in fact even by the BBC themselves online) then the majority of the program was fundamentally flawed in it's arguments.
What bothers me most is that we've gone from one lazy teacher looking for an excuse to get time off work claiming that wifi gives him headaches to a national wifi scandal. The worst part is that most reports that refer to the teacher in question who sparked this row ignore the fact that in scientific tests the teacher could neither a) tell whether wifi was on or off and b) now claims he gets these headaches wherever he is, even when not around wifi!
If Wifi does indeed pose a threat then I agree we need to do something, but thus far this seems equivalent to the whole terrorism/think of the children/drugs/computer games make people kill FUD.
Leukaemia (Score:5, Interesting)
My neighbours all have wireless, cordless and mobiles so I eventually turned all mine back on. Two years on and no-one else in the house, including my 2 other boys, have cancer.
Who knows what caused it. Live life to the full, make the kids smile and if low power wireless gadgets worry you, please get out more.
Trade one for the other (Score:5, Funny)
It's not the flight I'm afraid of, it's the notebook's landing that's the dealbreaker.
To quote Lionel Hutz (Score:5, Funny)
Well, Your Honor, we've plenty of hearsay and conjecture. Those are kinds of evidence.
Parent
Re:What's the Science in This? (Score:5, Insightful)
Maybe they read the article, which points out various scientists who argue that there IS evidence about it.
I've got to say, the ridiculously emotional backlash I see on
I personally don't believe cell phone signals or wifi signals are strong enough to cause health problems. But I'm certainly not going to be arrogant enough to proclaim that there absolutely are no health problems and we shouldn't even look at the problem.
I thought
Please, half of
Parent
Re:What's the Science in This? (Score:5, Insightful)
One of them was about the dangers of black holes. They'll boil the oceans, suck the life right off the planet, there's a super massive one at the center of our galaxy, they feed and then they stay silent, drifting through space until WHAM. Lots of sound bytes of scientists saying "it's only a matter of time", "you can't see them, but we know they're there", "we have no idea how many there are", etc. In only 5 billion years our galaxy will collide with another one, and we might drift right into that galaxy's super massive black hole, etc, etc.
It's that sort of programming, and if they convince laypeople that more money needs to be spent on researching this than is really necessary it only does damage.
Parent
Re:FUD (Score:5, Insightful)
All you have to do is consider the receive power. It is typical to receive a wifi signal at -65dBm, while a cell signal indoors is seldom stronger then -80dBm. Even if you consider multiple channels and multiple carriers on each cell tower, you would seldom get a composite power level greater then -70dBm indoors. -65dBm is approximately 3 times stronger then -70dBm. Of course these are typical levels, but when you consider how many wifi networks you usually pick up in your own home (esp. apartment), you will almost always receive a far greater exposure to electromagnetic radiation from wifi then from cell phone towers.
Full disclosure: I perform power density theoretical studies and measurement levels for the wireless industry, and also design in-building wireless repeater systems so I have a fair bit of experience here.
Parent
Re:FUD (Score:5, Insightful)
1. Observe.
2. Hypothesise.
3. Test.
4. Repeat.
Presumably this scientist was on phase 3; attempting to test his hypothesis. When they testing indicated that the hypothesis was false, he altered it to conform to the newer observations.
Unfortunately life is not Star Trek. The pragmatic method is:
1. Hypothesise.
2. Beg.
3. "Prove".
4. Publish.
Science costs money. Money comes from benefactors. Benefactors don't like surprises. You publish the results you were paid to discover, or you don't get more money. Welcome to the real world. Wear a helmet.
Parent
Re:Sounds familiar (Score:5, Funny)
Parent
Kill bit (Score:5, Funny)
Parent