Brain Cancer Worries? Look Up Your Phone's SAR 165
CWmike writes "With recent news of a possible link between cell phone radiation and risk of brain cancer, you may have a new-found interest in knowing how much radiation your mobile handset is giving off — or, more importantly, how much your body might be absorbing. The FCC's legal limit for mobile phones is 1.6 Watts of radiofrequency energy per kilogram, using a measure called Specific Absorption Rate (SAR). The Environmental Working Group, which tracks SAR data for more than 1,300 cell phone and smartphone models, notes that several factors besides your handset affect your actual level of exposure. Look up your phone's SAR; or see a full chart of phones." And relax — have a coffee.
Cell phones cannot cause cancer. Here's WHY. (Score:5, Informative)
The reason is that the frequencies cell phones use are below the spectrum of ultraviolet light. It is near the spectrum of ultraviolet light where the first ionizing radiation occurs, which is required to be able to cause cancer. Ionizing means that the energy level of the individual photons of the transmission have enough energy to disturb the molecular structure of live cells. Microwave "radiation" (which has absolutely nothing to do with nuclear radiation) is far within the level of the non-ionizing radiation spectrum, so there is no possibility of it having the energy required to cause cancer.
Cell phones use frequencies around 800 MHz to around 2 GHz or so. 3 GHz has an energy level of about 12.4 ueV; ultraviolet light where the first ionizing radiation is possible is around 124ev -- that's a 10,000,000:1 difference in energy level. Have a look at the energy level chart on the right hand side of:
http://en.wikipedia.org/wiki/Electromagnetic_spectrum [wikipedia.org]
or even better, see page 3 of FCC OET Bulletin 56, which is a Q&A on Biological Effects and Potential Hazards of Radiofrequency Electromagnetic Fields:
http://www.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet56/oet56e4.pdf [fcc.gov]
People are also afraid of the cell base stations, because they don't know how safe they actually are. The transmitters for these typically send 20 - 40 watts -- that's all. This is then sent through directional "sectored" antennas that typically have 120 degrees of horizontal beam width and only 6 to 15 degrees of vertical beam width; so the three-dimensional antenna pattern is like a 120 degree slice of a pancake, yielding gain of about 13 dBi. This focusing is where the "gain" of antennas comes from -- by focusing where the energy is transmitted.
In the U.S., the standard for specifically what frequencies and power levels are considered safe is the IEEE C95.1 standard, which is unfortunately not freely available, however there's a an overview here: http://www.interferencetechnology.com/uploads/media/AG_07.pdf [interferen...nology.com]
This standard is incredibly long to read, but boils down to this: the only proven effect of microwave radiation in 60 years of research is the effect of microwave heating. No cancer. Further than that, the standard narrows down to the power levels that are safe for various frequency regions concerning microwave heating.
But if you really want something to "bite your teeth on", have a look at the international ICNIRP guidelines: http://www.icnirp.de/documents/emfgdl.pdf [icnirp.de]
Now, if you go through the MATH of how close you have to be to the antennas of a cell tower for it to be "unsafe", the result is pretty interesting:
Spec limit for human-absorbed power per IEEE C95-1 at 900 MHz: 50 Watts/m^2
13 dBi gain = gain of 20
EIRP = 20 W transmitted power * gain of 20 = 400 W
400 W / 4*pi*R^2 = 50 W/m^2
R = 0.636 meters
0.636 meters = 2.09 feet
So at 900 MHz and with a typical transmit power of 20 Watts and a sectored antenna with 13 dBi gain, you need to be 2 feet in front of the antenna while it's transmitting for it to be considered unsafe. This means the only way it's unsafe for a human being is if they're not only on the tower, but right in front of the antenna while it's operating at full power.
The cell phones themselves have a limit on how much power they are allowed to transmit. There are different power limits in various countries; in the U.S. the limit is 1.6 W/kg SAR, in Canada I believe the limit is 10 W/kg SAR. SAR stands for "Specific Absorption Rate". What you really want to know is "what SAR power level is unsafe?", and the answer is that in lab t
Re:only brain cancer? (Score:2, Informative)
no (Score:5, Informative)
FCC says SAR not appropriate to compare. [fcc.gov]
So uh... (Score:3, Informative)
Where is even the correlation, let alone causative link, to brain cancer?
This was on NPR the other day and it was all "LOL we don't know but it /might/ cause brain cancer even though every study we have shows there isn't any correlation."
And the brain cancer it supposedly causes is a rare type that has not shown an increase in incidence from the time of no cell phones to the time of cellphones everywhere.
This is fucking pseudoscience scare mongering. There is a moneyed interest here somewhere for the scare mongering. Grants? Maybe. But that doesn't explain the actions of Sweden. Who wants to scare people into not using cellphones, and why?
That would explain this bullshit.
--
BMO
No worry. Consider the physics. (Score:5, Informative)
Any transmitted energy from a cell phone in a pants pocket would need to travel through a leg to get to testicles.
Danger -- The Sun is a big electromagnetic radiation transmitter in the sky. Walking from the shade into the sun will heat your body much more than the energy of a cell phone transmitting during a call.
Standing in the sun absorbing high-energy ultraviolet radiation is truly damaging; severe exposure can cause sores and even eventually skin cancer. The photons of ultraviolet light are more than a million times more energetic than cell phone radiation, and the sun emits far, far more energy than a cell phone.
The entire earth receives [wikipedia.org] 1,218,000,000,000,000 Watts from the Sun. The earth receives more total solar energy from the Sun in one hour than is generated and used by humans in an entire year. The average energy received over the entire earth is about 250 Watts per square meter over a 24 hour day [wikipedia.org], ignoring clouds.
The sun emits energy in the same wavelengths as cell phones. The only difference between the sun's energy and cell phone emissions is that the cell phone energy is at one specific frequency, and the sun emits energy at all frequencies. GSM cell phones use frequency bands at 850, 900, 1800, and 1900 MegaHertz. GSM [wikipedia.org] is the most popular kind of cell phone transmitter design.
But no one has shown any frequency-specific interaction, and the physics is quite clear that there cannot be any. High energy electromagnetic waves definitely can have a strong effect on chemical bonds, but not low energy waves. The energy emitted by cell phones is perhaps 1/10,000 or 1/100,000 of the energy needed.
I haven't yet calculated how much energy is received from the Sun at those frequencies. However, there is no way for the energy from cell phones to be resonant in the body; the wavelength of cell phone radiation is too long. So the cell phone energy just heats the body, as does the Sun's energy. Without resonance, there is insignificant coupling to specific chemical processes.
Instant fame There are many, many very well-educated people in the world who would love to discover a new way that electromagnetic energy interacts with matter. Such a discovery would make any physicist or chemist instantly famous, and would earn him or her a Nobel Prize. The motivation to make such a discovery is enormous for people working in those fields.
The fact that no such discovery of a new kind of interaction has been made indicates at least that it is not easy. Another indication is that apparently no one has even proposed a mechanism for low-energy long-wavelength electromagnetic radiation to have an effect on chemistry.
It's not as though it hasn't occurred to anyone to do research.
People may say that there may be some subtle effect that we have not yet discovered. And there may be. However, those comments often give the impression that they think that the discovery of a new subtle interaction would have a subtle effect on our understanding of the world. That isn't true. In fact, the discovery of a new kind of interaction between electromagnetic radiation and matter would create a revolution in Physics, in areas we think we know well, in areas where our understanding has been stable for many decades. For example, Planck's constant is known with an uncertainty of only 89 parts per billion.
That makes a new discovery seem less likely.
Einstein's discovery of relativity revolutionized our understanding o