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Killer Apartment Vs. Persistent Microwave Exposure?
An anonymous reader writes "I am considering buying a penthouse apartment in Manhattan that happens to be about twenty feet away from a pair of panel antennas belonging to a major cellular carrier. The antennas are on roughly the same plane as the apartment and point in its direction. I have sifted through a lot of information online about cell towers, most of which suggest that the radiation they emit is low-level and benign. Most of this information, however, seems to concern ground-level exposure at non-regular intervals. My question to Slashdot is: should the prospect of persistent exposure to microwave radiation from this pair of antennas sitting twenty feet from where I rest my head worry me? Am I just being a jackass? Can I, perhaps, line the walls of the place with a tight metal mesh and thereby deflect the radiation? My background is in computer engineering — I am not particularly knowledgeable about the physics of devices such as these. Please help me make an enlightened decision."
There is a product called Scotch-Tint that is a EMF reducer for windows. Combine that with some metallic fabrics on the walls on that side. www.lessemf.com is one of many suppliers for those products. I've used a conductive plastic from those folks to make a shielded rack for some RF sensitive equipment.
The facts about urban wireless towers is that they're very low power because of the high population density. They use very small cells in urban towers to achieve a very small coverage radius so that they can put up more towers in the city and reuse the same spectrum. Furthermore, just being in-doors cuts the power level 10-fold and I'd really doubt that you're getting more than -40 dBm which is equivalent to 100 nanowatts of power even if you're outside the windows. My Wi-Fi Access Point is 5 feet from me and it's got a power level of -13 dBm which is about 1000 times stronger than a -40 dBm signal. Now if you think that's high, your cell phone probably has a signal strength of +10 dBm which means the power density is 100,000 times stronger than a -40 dBm signal. And if you think the phone is dangerous, check out this article from me http://www.digitalsociety.org/2009/09/sar-ratings-are-not-a-measure-of-radiation/ and this article http://www.digitalsociety.org/2010/01/cell-phone-exposure-prevents-or-reverses-alzheimer-in-mice/. So really, worrying about that cellular tower is just silly. If you're really worried about it, buy one of those $100 "Electrosmog" meters and measure the signal strength yourself at various places.
I work with high power RF for a living. There are a lot of variables that contribute to non-ionizing radiation. Proximity, transmitter power, antenna radiation pattern, materials between you and the antenna, etc. There are ways to estimate the field intensity, but unless you know all the necessary factors, your calculations could be off by orders of magnitude. Having said that, the poster who commented that urban cells are lower power is generally correct, however, in a major metropolitan area, the cell can have many channels active at once, and the effect is cumulative. ANSI C95.2 is the safety standard covering this radiation. It's pretty technical, but the gist is the licensee (in this case the carrier) is responsible for making sure they don't cook the public.
The carrier must certify to the FCC that there are no publicly accessible areas that receive unsafe RF fields. The exact number varies by frequency, but generally there are two levels specified, one for publicly accessible areas and another for areas where personnel who have been trained in RF can work in levels above the public ones. These areas are normally calculated by the carrier prior to installation and they won't install if there's any chance they might exceed the safe levels.
As an example, I did an RF survey at one location where there was a multiple-transmitter FM antenna installed on top of a building that was across the street from another taller building. We had three FM broadcast transmitters operating on this antenna with about 250 kilowatts of radiated power, and the measured levels in the building across the street were not over the limits for public access. This was about 150 feet horizontally from the antenna. The solar coating on the building's glass stopped enough RF that it wasn't a problem.
If you want to measure it yourself, there are some inexpensive meters that are pretty accurate that will give you an indication of how much RF you're seeing. The one I have is this one: http://www.trifield.com/TrifieldMeter.htm It's about $150. I've seen these for sale at Fry's.
I have calibrated mine against a $5000 Narda commercial RF radiation meter and it's pretty close, certainly close enough for a "go/no-go" test which is what I use it for.
----- Leghorn "Not responsible for program content"
800+ watts in the 2.4ghz band is a known killer.
Most consumer devices run at under 5 watts.
Amateur radio operators have been using devices that can put out 5 to 1500 watts since the 1930s (possibly earlier)
Is that why it has been observed that children living under power lines had a 70% increased risk of leukemia?? Is that why DDT has been sprayed directly onto people as a standard anti-mosquito practice?. Is that why asbestos has been used extensively as an insulator and structural material? Is that why lead paint has been the standard paint for home renovation and art? Is that why gasoline is carcinogenic? Is that why wet Portland cement causes serious health problems which include severe burns that damage nerves?
Just because something is banal, widely used and is seen as an accepted practice it doesn't mean that it is perfectly safe and free from any nasty side effects. History has a pretty long damning list of cases where the dangers are only known after the stuff that causes them is widely deployed.
Slashdot, fix your code or at least hire someone who is competent at it to do it for you.
The studies that found a higher risk of leukemia in children didn't control for family income or any other social factors. It was correlation which isn't particularly useful
Is that why it has been observed that children living under power lines had a 70% increased risk of leukemia?
http://www.quackwatch.org/01QuackeryRelatedTopics/emf.html
Is that why DDT has been sprayed directly onto people as a standard anti-mosquito practice?
http://en.wikipedia.org/wiki/Malaria
History has a pretty long damning list of cases where the dangers are only known after the stuff that causes them is widely deployed.
So your solution is .... avoid everything? How much does it cost to live in a clean-room, anyway?
Just out of curiosity, I gotta ask ... why do you hate science?
Malaria is rather more dangerous than DDT. DDT was banned by a politician, who was overriding the decision of his own regulators who had actually heard and read all the evidence and concluded that the benefits of DDT outweighed the risks that alarmists trumped up.
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
see also Force Field Wireless for paint additive, although you could also experiment with various metallic powders on your own.
Ditto Storm windows with metal frames and screens. Apparently prefinished flooring also contains metallic powder which can reduce wifi signals. The new double pane windows also have metallic coatings that can reduce wifi.
Normal cell phone reception would have to come from the side of the building opposite where the transmitters are located.
"It is a greater offense to steal men's labor, than their clothes"
It's a buyer's market for luxury property in Manhattan right now. Express your concerns to the sellers and hint that you'll need to have a survey team out to test for EMF exposure before you'd consider buying. Build an image in their minds of 3-4 guys in Tyvek jumpsuits walking around with meters on the roof and in the halls and knocking on your future neighbor's doors. (There's no reason for them to wear Tyvek jumpsuits, but you get the idea.) They'll likely offer to drop the price in exchange for you not doing that. More than enough to cover the cost of shielding and chemotherapy.
Prisencolinensinainciusol. Ol Rait!
No, you are not being a jackass. It is far better to ask questions and be INFORMED than make assumptions that might not be true.
As an Extra class amateur radio operator licensee I can tell you that the FCC considers exposure to RF radiation a significant risk. To obtain an amateur radio license and to be granted greater privileges, tests are given and several questions pertain to safe exposure limits. While I would doubt that the antenna poses a hazard, for your own peace of mind there is some homework you must do, questions you must ask of the company that owns the antenna and possibly the FCC.
Is the antenna used for receiving, transmitting or both? Is the antenna directional? What kind of gain does the antenna exhibit? What does the energy distribution look like? Are you able to see a site evaluation? (the FCC might have that on record) Find out the name of the company that owns the antenna and ask these question.
Many systems use separate antennas for receiving and transmitting. Doing so allows the antenna to be optimized for the job. It is quite possible that the antenna in question is used purely for reception of the cell signals from another tower. In that case the antenna poses no risk what so ever.
If the antenna is used for transmission of microwave signals a whole new can of worms is opened and RF exposure must be considered. RF radiation exposure limits are divided into two categories, a controlled environment and an uncontrolled environment. Basically, these two categories refer to the exposure limits of people working with the equipment and the general public. Several things are considered when looking at RF exposure limits; antenna type, power delivered to the antenna and the effective power radiated. A highly directional antenna can direct the input wattage into a very narrow beam called a lobe, effectively amplifying the signal in that direction. So a signal of 200 watts can effectively become a signal of much higher strength depending upon the gain of the antenna. One of the advantages of this is that the signal to the sides of the main lobe is extremely weak. From a safety stand point, only something directly in the path of the lobe is being exposed to radiation.
Again, ask the questions I gave to you earlier of an electrical engineer working at the company owing the antenna. Make an appointment to meet at the site of the apartment. The FCC requires they keep detailed information available on their systems just for answering this type of issue.
Regards,
W2TKW
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The FCC enforces on a case-by-case basis. Unless someone has turned this situation (this SPECIFIC apartment being this close to a transmitting antenna) to the FCC, then chances are that they have no idea the situation even exists.
Most urabn cell phone towers have a 20W average power (100W in rural areas), since they want a large coverage area the gain will only be 3dB (parabolic dish 25 dB gain) at 6 meters with a 100W power source and 25dB of gain the power density is 6.7718 mW/cm2 using typical numbers 20W 3dB 6 meters the power density is 0.0086 mW/cm2 the "safe exposure level" for 2.4 GHz as defined by national association for amerature radio is 30 mW/cm2 for uncontrolled and 100 mW/cm2 for controlled. A cell phone with 3W 2.2dB of gain (diapole) at 1 inch would have a power density of 61.4108 mW/cm2.
Knowledge = Power
P= W/t
t=Money
Money = Work/Knowledge so the less you know the more you make
I am a PE and have done hundreds of RF emissions studies on wireless facilities, including rooftop installations like the one you describe. My initial thought is that twenty feet would be an unusually small distance between the antennas and your window. It may very well be much larger then that (50' or more is more likely - and would have much lower emission levels) but seems closer due to the perspective of the surrounding panoramic view. If it were truly only 20', and the building hosted antenna arrays from many wireless carriers (and FM transmitters), then there is a very slight possibility that the levels in your apartment could be near the public exposure limit. This situation is quite unlikely however. Most wireless carriers have an independent RF emissions study performed on rooftop installations that include measurements of the pre-existing antennas, so if you reached the right person and were persuasive enough you might be able to get them to share that with you (very unlikely). Another poster recommended a cheap meter. I'm not convinced of their accuracy, but you could give it a try if it worries you. Someone else mentioned low-E glass and correctly stated that it blocks a significant amount of RF energy. If you have low-e glass then even 20' away would mean your apartment is below the public exposure limit.
--- There are two kinds of people, those who accept dogmas and know it, and those who accept dogmas and don't know it
Nice! Except power density is expressed in watts per square METER. Not watts per square micron. So while your calculation suggests that 1 / 3,716,121,600,000th is a tiny number, there's a trillion square microns in a square meter. So while the power measured is a tiny amount of what you'd measure at one micron, it's not such a small number when measuring using meters.
Fascism trolls keeping me up every night. When I starts a preachin', he HITS ME WITH HIS REICH!
The man who discovered aluminum in 1808, a British chemist named Humphrey Davy, first named it "alumium." When he published in 1812 he had renamed it to "aluminum," which is the name still used in America. So where did that extra "i" come from? Wikipedia has the answer.
'An anonymous contributor to the Quarterly Review, a British political-literary journal, in a review of Davy's book, objected to aluminum and proposed the name aluminium, "for so we shall take the liberty of writing the word, in preference to aluminum, which has a less classical sound."'
That's right. All of the haughtiness with which the British defend their extra syllable, all of the bloodshed spilled over the difference, and all of the mutual incomprehension that ensued is due to a change made against the discoverer's wishes based on the rant of an Anonymous Coward. If that isn't a successful troll I don't know what is.
Your brain is not a computer.