Wifi, Cell Phones, and You
March 6, 2011 6:12 PM   Subscribe

How does the radiation coming from a cell phone handset compare to wifi in terms of wavelength, frequency, intensity, power, and any other important parameters? How similar are they?

I was interested to read about the new study showing increased rates of glucose metabolism in the brain area closest to an active cell phone. Interestingly, it was the part of the brain closest to the antenna that exhibited change, which suggests it's a function of actual electromagnetic radiation, not heating (as has been previously thought).

My question is: how is wifi similar to the radiation emitted by a cell phone?

Bonus question: the studies said the cell phone's radiation is related to the "number of people using cell phones in the area." Any details on this would be appreciated.
posted by enzymatic to Health & Fitness (10 answers total) 2 users marked this as a favorite
FM radio ≈90 Mhz so 3 meters - 0.0000004 electron volts per photon
WiFi ≈2.4Ghz so 125 mm - 0.00001 electron volts per photon
Cell Phone ≈5.6 Ghz so 54 mm - 0.0000232 electron volts per photon
Red Light 450 Thz so 700 nm - 1.77 electron volts per photon

They might be talking about total broadcast energy, they might be talking about repeat requests due to greater noise.
posted by Kid Charlemagne at 8:22 PM on March 6, 2011

Interestingly, it was the part of the brain closest to the antenna that exhibited change, which suggests it's a function of actual electromagnetic radiation, not heating (as has been previously thought).

Is this your interpretation? My understanding is that the expected effect of the electromagnetic radiation is a minute heating, therefore a metabolic increase being proximate to the antenna might not suggest something other than a change in temperature is happening.

My understanding may be wrong, but the article you linked to is consistent with my understanding and said nothing to support your conclusion. Were you reading a more detailed account elsewhere?
posted by -harlequin- at 8:24 PM on March 6, 2011

If this sort of thing interests you, I recommend the book "Mind Hacks". For example - that a magnetic field effects your brain is not news, so at some level you can tell if a cell phone is on, even if it isn't making any sound.

I would not be surprised if thinking about talking on a cell phone was sufficient to cause the phenomenon they observed. (Hack #10).
posted by Kid Charlemagne at 8:43 PM on March 6, 2011

I was going to type up a page or two about cell phone "radiation" but Junk Science summed it up so much cleaner than I could've.
posted by Sphinx at 9:39 PM on March 6, 2011

Bob Park summed this up nicely on Feb 25th.


Cell phones went from zero to ubiquity in a single decade. The Journal of the American Medical Association this week reported an NIH study of 47 healthy recruits injected with a glucose solution and then exposed for 50 min to radiation from a hand-held mobile phone. The side of the head the phone was held against was switched randomly. Positron Emission Tomography (PET) scans exhibited changes associated with glucose metabolism on the side of the brain closest to the cell phone. This was said to demonstrate that exposure to cell phone radiation activates the brain, but "the clinical significance of this finding is unknown." Hmm, that's sort of limp. I am hopeful that someone will explain to me how the effects of metabolism are distinguished from changes in blood flow associated with thermoregulation. The only effect of microwave photons is to excite molecular vibrations (heat). Blood serves as a coolant to keep the temperature of the brain nearly constant in spite of cell phone radiation.

posted by defcom1 at 9:46 PM on March 6, 2011

Sphinx - for future reference, refering to Junkscience is a bit like linking to Rush Limbaugh as if her were authoritative on a topic. They both function to further the propaganda interests of their funders, while both claiming to be neutral third parties. They're both super-sleazy, and neither of them gives a damn about what is true.
posted by -harlequin- at 10:19 PM on March 6, 2011

Sphinx - for future reference:

Thanks for the heads up, I had referenced them back in the 'glory days' of the internet, and apparently mistakenly thought they had kept up with the times.

That being said, I still come to the conclusion that cell phones deliver a tiny/small amount compared to the daily "radiation" that we receive. One can't deny that RF waves dont really penetrate our skin that much, especially if you wear safety equipment. Like a shirt.
posted by Sphinx at 10:50 PM on March 6, 2011

WiFi ≈2.4Ghz or 5Ghz
Cell Phone ≈5.6 Ghz ??

The current approved bands for mobiles are 806-960 MHz, 1710-2025 MHz, 2110-2200 MHz and 2500-2690 MHz in the US.

They share part of the UHF band (300Mhz to 3000 Mhz) with cordless phones, two-way radios and (mostly) digital TV. analog TV is mostly in a lower band, 30 MHz to 300 MHz.

What would be more useful I suspect is watts-delivered per frequency, i.e. how much energy is pumped out by a given transmitter that is received in a given physical space. Last time I looked, TV signals dwarf the rest of the UHF band (i.e. wifi and mobile phones) in watt-per-m^2 delivered, but I'll have to look up the numbers later I'm afraid.
posted by ArkhanJG at 12:35 AM on March 7, 2011

Ah, here we are; EU public health site.

Maximum allowed SAR for the head (i.e. power absorbed by kilo) is 2000mW.

During a 6 minute time-averaged call (digital phones transmit in bursts) the max allowed time averaged power is 250mW. In absolute worst case scenario, i.e. held directly to head, phone broadcasting at full allowed power, the 10 grams that would absorb the most energy receive between 200 and 1500 mW per kilogram, depending upon on phone.

In most circumstances, real mobile phones are broadcasting at hundreds or thousands times lower than that power level.

DECT cordless phone handsets broadcast about 10mW under the same worst case, time-averaged scenario.


At 900 MHz, an important frequency for mobile communication, the EU recommends people not be exposed to a field stronger than 4.5 Watts per square meter (power density).

With UTMS, the current standard, the rate measured is maximum 1mW/m^2 from mobile phone masts, and usually far less. (Note, that's mW, a thousandth of a watt)

Analog radio is around 3 mW/m^2 max (1 mW/m^2 typical), and digital TV in australia is 4 mW/m^2 maximum. Analog TV is around the same power density.

Wireless base stations broadcast at 200mW peak power, but under most circumstances at work and home are at less than 0.5 mW/m^2.

So ranked by field density, it's wifi, UMTS (mobile phone), radio, tv. All of them are less than a thousandth of the maximum recommended field strength under worst case, and usually far less than that.

For example, a razr 3G has 36 mW/kg for the 10g that's most absorbant at worst, and the iphone is at 1300 mW/kg maximum under worst case (regulation is 2000mW/kg) - most circumstances, you're a hundredth of that, so your iphone is 13mW/kg or less.

And you might use your phone for a period, but you're exposed to TV and radio non-ionizing radiation 24/7. So far, TV broadcasts don't appear to have caused any health effects in the last 70 years. Well, the radiation of them, anyway.

On the other hand, radon (especially prevalent in granite areas) causes ionizing radiation, which is proven to be hazardous - it's the 2nd largest cause of lung cancer.
posted by ArkhanJG at 2:14 AM on March 7, 2011

Ohh, forgot the cite for radon - causes up to 2000 deaths by cancer a year in the UK.
posted by ArkhanJG at 2:16 AM on March 7, 2011

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