Killer Apartment Vs. Persistent Microwave Exposure? 791
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."
depends what you mean by "facing" (Score:1, Informative)
If it's a simple dipole antenna and its long axis is aimed at you, there should be minimal exposure. The power emission profile looks kind of like a doughnut with the long part of the antenna at the middle.
Conductive films, cloths, or plastics... (Score:4, Informative)
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.
It's not microwave (Score:1, Informative)
I am not sure if you were meaning microwave in the strict sense, as a microwave ant pointed at your building would be dumb. Microwave transmissions are very directional. GSM or CDMA are going to be much lower, and mostly benign. You probably have attended a church or worked in a building that has them. You're around them all the time. Also, cellular systems are cellular. Meaning, their transmit power is relatively small so that the frequency can be reused across the same town for obvious freq management reasons.
The facts about urban wireless towers (Score:5, Informative)
Re:On the upside, no worries about poor reception (Score:3, Informative)
The signal power will reduce by the cube of distance from the masts
Square of the distance, actually.
There are a lot of variables (Score:5, Informative)
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.
Re:Yes, you are being a jackass (Score:5, Informative)
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)
Re:Yes, you are being a jackass (Score:5, Informative)
Is that why it has been observed that children living under power lines had a 70% increased risk of leukemia? [newscientist.com]? Is that why DDT has been sprayed directly onto people as a standard anti-mosquito practice? [wikipedia.org]. Is that why asbestos has been used extensively as an insulator and structural material? [wikipedia.org] Is that why lead paint has been the standard paint for home renovation and art? [wikipedia.org] Is that why gasoline is carcinogenic? [wikipedia.org] Is that why wet Portland cement causes serious health problems which include severe burns that damage nerves? [osha.gov]
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.
Field strenght meter (Score:1, Informative)
Why not do this scientifically? Get/procure/rent/borrow a field-strength meter, or hire someone to measure it for you. It's cheap relative to the price you're looking at for a top-floor place in Manhattan.
Then, measure it. Walk all around, sometimes internal reflections can make a further-away side 'hotter' than a closer one.
Then measure your cell phone, right up close a cm or two from the front, as if you were holding it.
The readings will probably be in decibels (dB). Calculate (db of tower) - (db of cellphone). The difference is how much stronger the tower is compared to the cellphone. It goes in powers of 10. 0 dB is equal power. 10 dB is 10x the power. 20 dB is 100x the power. 30 dB is 1000x the power. And so on. If it is negative, it is weaker, by similar power-of-10 ratios.
Then make a decision depending on what you find. Same or less power than a cellphone, you're OK. 10x the power is probably still OK but you'll have to decide depending how you feel about it all. 100x the power, maybe reconsider.
Re:depends what you mean by "facing" (Score:3, Informative)
Re:I heard... (Score:3, Informative)
Again, though, this is just another anecdote too, until you look up some real research.
Re:Yes, you are being a jackass (Score:4, Informative)
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
Re:The facts about urban wireless towers (Score:5, Informative)
But this assumes that the sector antennas are aimed directly at his prospective apartment unit. If they're not aimed at him, the power levels are far lower than just the bare
Now the original post mentioned "panel antennas" which are highly directional and typically used for backhaul. Those I'm almost certain aren't facing his apartment because that would kind of make those antennas useless since they need a clear line of sight.
Re:Yes, you are being a jackass (Score:5, Informative)
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 [quackwatch.org]
Is that why DDT has been sprayed directly onto people as a standard anti-mosquito practice?
http://en.wikipedia.org/wiki/Malaria [wikipedia.org]
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?
who would pay for such a study? (Score:3, Informative)
And if the results were unfavorable, what then?
Here's a recent article on the hazards of transient electromagnetic fields, such as those created by compact fluorescent light bulbs:
While I'm posting, here's a neat little website that plots FCC-registered antennas on a google map:
http://www.antennasearch.com/default.asp [antennasearch.com]
*Buzz* (Score:2, Informative)
A friend of mine lives in close proximity of one of those beasts, and the high pitched humming makes me uncomfortable. Wouldn't want to live there myself.
Re:If you are worried about it... (Score:4, Informative)
Comment removed (Score:5, Informative)
Re:Yes, you are being a jackass (Score:3, Informative)
...and once transmitting at more than 50W, HAMs must conduct a station evaluation to make sure no excessive fields pose a hazard to humans or animals, according to FCC rules. Also, see http://www.fcc.gov/oet/rfsafety/rf-faqs.html [fcc.gov]. When considering these antennae, also consider that they are likely to be very high duty cycle and directional (rather than omnidirectional) which increases the radiation density. When using directional antennae with 2.4 GHz Wifi, you're limited to tens of milliwatts or even less, depending on the gain. Sum: I'd worry.
Re:If you are worried about it... (Score:5, Informative)
see also Force Field Wireless [oninnovations.com] 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.
Inverse square law (Score:3, Informative)
Re:Do you use a cell phone? (Score:3, Informative)
this compared with your constant exposure to radiation while being inside a microwave oven of your 'killer apartment' is another exposure altogether. Besides all this - just thinking of possible even if unlikely danger is going to make him sick anyway. If that does not his girlfriend will. Oh wait we are on /. - forget it. Go on buy it!
Re:strength falls off with cube of distance (Score:2, Informative)
Re:Get a gun. (Score:2, Informative)
Wait... if you're serving time for voluntary manslaughter, that means your strategy is NOT effective, since obviously the landlord did not do what you wanted him to do (otherwise, why shoot him?).
He never said that he dealt this way with only *one* landlord, so your "*the* landlord did not do..." and consequently your complete conjecture about effectiveness is not guaranteed correct.
Re:Yes, you are being a jackass (Score:4, Informative)
When using directional antennae with 2.4 GHz Wifi, you're limited to tens of milliwatts or even less, depending on the gain.
Last time I checked Ham's are authorized 1500 watts @2.4Ghz. They just need to conduct the safety evaluation. Now meeting the safety requirements with a 24dbi dish might prove difficult... But if you can, you're good to go. (yes, I'm serious, think morse code via moon bounce...)
Re:Yes, you are being a jackass (Score:2, Informative)
"The World Health Organization estimates that during the period of its use approximately 25 million lives were saved. ...Many species of insects developed resistance to DDT" ( http://www.3dchem.com/molecules.asp?ID=90 )
"What harmful effects can DDT have on us?
Probable human carcinogen
Damages the liver
Temporarily damages the nervous system
Reduces reproductive success
Can cause liver cancer
Damages reproductive system"
( http://www.epa.gov/pbt/pubs/ddt.htm )
I think we can all agree that DDT has done some good. However, it is hard to argue that widespread use is beneficial. What's the old saying? Something like, "when all you have is a hammer, everything starts to look like a nail."
Re:If you are worried about it... (Score:3, Informative)
One protective paint is yshield.
http://www.yshield.com/ [yshield.com]
Easy and cheap solution: (Score:3, Informative)
If there isn’t a window on that side where the panels are, just get some wallpaper that filters them. You know: Tinfoil hat style. (Well, usually some kind of wireframe suffices, if it’s e.g. 1/3 smaller than the waves.)
But if you want to know EXACTLY, you can always find out the energy (=frequency) of the radiation, and compare it against the bonding energy of e.g. proteins in your body (keyword Van-der-Waals bond) and others. But be aware that the quantum physics of this is often counterintuitive.
Then you don’t have to rely on biased tests or people telling you their bias, but know it yourself.
From what I remember, microwaves can only create 0.1-0.2 degrees Celsius of heating in the body. So less than (the infrared in) sunlight, but deeper penetrating.
Or in simple terms: If you fear microwaves, you should have more fear of sunlight, as it’s much stronger. :)
Buyer's Market (Score:5, Informative)
Re:For what it's worth (Score:4, Informative)
If anyone is interested, here is a summary of the study in a presentation form (PDF):
COFAM study result http://www.who.int/peh-emf/meetings/archive/en/vanrongen_tno.pdf [who.int]
Re:Insert small coil (Score:1, Informative)
At least the country that I live in have this practice outlawed.
It's called energy theft or something like that.
Re:Yes, you are being a jackass (Score:5, Informative)
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
Re:No, he's not being a jackass (Score:5, Informative)
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.
Re:There are a lot of variables (Score:2, Informative)
Probably fine (Score:5, Informative)
Re:Faradays Cage, Measure it! (Score:3, Informative)
Chicken wire is too coarse for microwave.
People who build these things use much finer mesh; take a look [ramayes.com].
Re:There are a lot of variables (Score:2, Informative)
Darnnit! Didn't proofread closely enough. ANSI C95.1 is the correct standard. Thanks phobos512.
Re:Yes, you are being a jackass (Score:4, Informative)
Re:I know what hams are (Score:4, Informative)
You are confused, total ham bandwidth is miniscule. The entity with the properties you describe is the U.S. military.
Re:Biology vs electronics (Score:4, Informative)
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.
Re:No, he's not being a jackass (Score:2, Informative)
I trust you're never going to use wi-fi? :)
Re:Yes, you are being a jackass (Score:3, Informative)
I've heard that, and I've also heard that it was never proven.
Do you have reputable sources for this claim?
Re:Yes, you are being a jackass (Score:4, Informative)
Yeah, it's not worth it to save those kids from malaria, at the expense of the Bald Eagle... in Africa... where bald eagles are...
You're obviously talking about two different instances of banning DDT... but it's worth noting that the GP is full of shit and DDT is still used actively to combat malaria. http://en.wikipedia.org/wiki/DDT#DDT_use_against_malaria [wikipedia.org]
Re:Biology vs electronics (Score:2, Informative)
the radiated power is constant (conservation of energy) the power density decreases as the square of the distance (in the far field ~ 10 wavelengths). A typical E1 interlink would be operating in the 5GHz band with a power of 50 watts or so into the antenna. The antenna has some "gain" (meaning that instead of radiating power uniformly in all directions i.e. isotropically it concentrates into a smaller set of lobes). At a given distance the power density is P = PtG/(4Pir^2) that is to say the power density at a given distance is proportional to the power in times the antenna gain divided by 4 pi r squared. A typical panel antenna in that band has a gain of about 24 dBi (about 250 x an equivalent isotropic radiator) - but we can assume the center of that main lobe is NOT pointed at your apartment (pointless unless the receiving antenna is inside) so its probably safe to say that you will be at the edge of the main lobe - at least 6 dB (a factor of 4) down. At a distance of 10 m that would give a power density of 0.25 mW / cm^2 - the official safety limit for the public (a quite conservative limit) is 5 mW/cm^2 see http://www.arrl.org/news/rfsafety/exposure_regs.html so its nothing to worry about.
Re:If you are worried about it... (Score:4, Informative)
Speaking of low level radiation, and specifically non-ionizing radiation like cell phones, popsci has an article [popsci.com] about a guy that is hypersensitive to it. The online article is four pages (I think the print article was 10-12) and it does cover a lot of ground, including arguments from both sides. I kinda skimmed over it, myself, but if you care about this sort of thing it may be worth a read.
Re:Yes, you are being a jackass (Score:2, Informative)
If DDT were still in use, the Bald Eagle would be extinct, along with several other birds.
As I understand it, before DDT was banned in the U.S., it's main effect on bird reproduction was a result of its being sprayed outside in massive quantities to kill teh bugz. Today, the rest of the world (where it's not banned) has different protocols; turns out small amounts in a room, for example, keeps the room mosquito free. And no one thinks massive outdoor spraying makes sense anymore. Maybe a reaction of "let's use this tool more wisely" would've done just as well at preserving wild birds as the "it's evil, let's ban it" reaction did. And we'd have, y'know, a useful tool available too.
Re:cell tower next to village (Score:3, Informative)
Some crazies in Clearview, Washington (illegally) bulldozed a new AM radio tower, thinking it was giving them brain cancer or something. An AM radio tower. AM.
If AM radio caused brain cancer, you'd think we would have figured that out sometime in the last 80 years we've been using it. Crazy people. Maybe they thought NPR was going to broadcast hypnotic messages into their brains so they'd vote Democrat.
http://www.kirotv.com/news/20723839/detail.html [kirotv.com]
Oh wait it was sports radio. Maybe they have an intense hatred of... high school football? Hell, I dunno.
Re:If you are worried about it... (Score:3, Informative)
Be careful!
There was one guy in a suit over stuff like this. So, they sent out a doctor to go with the patient to confirm the symptoms. The guy demonstrated when and where the problems occurred, and sure enough, they did! But what he didn't know was that the cellular company had TURNED OFF the nearby tower on that day, thus was emitting no "low level" radiation at all.
Killed the lawsuit, the guy turned out to be a crazy, and there will be plenty more. Not saying that there aren't some symptoms of low-level radiation, but when somebody turns out to be "ultra sensitive" to these kinds of things, it's a near certainty is all cooked up in their brains.
Re:If you are worried about it... (Score:3, Informative)
Re:Biology vs electronics (Score:1, Informative)
Did you just express that his number and unit is less valid than yours because your number is higher in a standard unit? Maybe what you should have said is, "The standard measure for power density is watts per square meter, and they may be disingenuously using watts per square micron."
Aluminium, or, A Very Successful Troll (Score:5, Informative)
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.
Re:cell tower next to village (Score:1, Informative)
This is scored "funny" but has happened several times just in the last year or two alone... "Oh the radiation, I've had headaches ever since that antenna went up last month!" moan moan, bitch bitch. The antenna installer then points out they have not even installed any equipment yet, the antenna wasn't going to be transmitting for several months. Pwnage at it's finest.
As for the OP, I agree with the numerous people that have commented that inside a city, the transmit power of cell sites is quite low, since the cover a matter of city blocks instead of miles. I would like to add, I think the exposure from phones is a little exaggerated -- I saw people state a figure of +10dBm... that might be right for GSM, but I've seen CDMA phones in town do -10dBm to -20dBm, and right next to a site like you would be, the phone can drop below -40dBm. I'll add here, what is a dBm? 0dBm is 1 milliwatt, +10 is 10mw, +20 is 100mw, etc. -10 is 1/10th of a mw, -20 1/100th of a mw, etc. The maximum is around +24 dBm for modern phones (250 mw), you'll only see this when you're almost out of service.
Re:Placebo Effect (Score:3, Informative)
Re:If you are worried about it... (Score:3, Informative)
If you need to be made aware of what's around you before you get sick then you're full of it, imo.