Click here to go to our page on microwave heating
Click here to go to our page on cell phones
Doc Bruce Banner,
Belted by gamma rays,
Turned into the Hulk.
Ain't he unglamo-rays!
We don't take a lot of time to monitor statistics on this web site. But here's an interesting one. Some time around 2008, for a week this was the most-viewed page on Microwaves101, by far. Noticing this we zoomed in on where the clicks were coming from. Turns out the Islamic Republic of Iran was very interested in biological effects of microwaves. Wonder what they had in mind?
For September 2010, we are posting a counter to our original thoughts on the subject. There's new evidence that non-ionizing radiation may be harmful (or at least affect people), that we should all pay attention to. Here's an email from CS, and we appreciate his point of view!
One comment/question on your section regarding the "biological effects of electromagnetic radiation":
You are correct in expressing some exasperation and humor at the general public's concern about non-ionizing radiation (for example, from cell-phones) with regard to the carcinogenic potential of such exposure. All of the available science says we're 'good to go' with such radiation being all around us. As you say, there's plenty of workers with daily exposure who do not have significantly higher cancer profiles than the public at large.
I would caution, however, that the cancer-causing properties of EM radiation are only ONE potential pathological pathway. In other words, cancer is not the only way that EM radiation can effect us.
There are numerous recent peer-reviewed studies (the abstracts of which a google search can locate) which look at the effects of EM radiation on biological systems and how EM radiation effects the production and use of histamines, a ubiquitous protein type that has important functions in the body's immune system, brain function, and gastro-intestinal tract. Even if these effects, once sorted out, turn out to be non-permanent, EM energy may still affect our bodies adversely during such exposure.
I offer this as straight-forward advice to the moderators of a great site: there's nothing worse the pronouncing something "safe" only to find out later that the proper statement should have carried a caveat. So, safe compared to what? -Perhaps: "...EM radiation is non-carcinogenic" is a more adequately supported conclusion.
-Just my two cents for free, because a lot of things have been pronounced safe until science later realized how they had potential to harm.
Before we get on with the original
content on this page, here's an interesting fact about this page.
One month back in 2008 this page got numerous hits, so it stood
out in the top ten Microwaves101 pages. We don't often
track the stats (who's got time?), but that month we looked
at page views by country, just to see where the interest was coming
from. Almost all of the hits came from the Islamic Republic of Iran.
We wonder they were up to...
Now back to our original thoughts on the subject... words we may have to one day eat!
Believe it or not, this is a frequently asked question at this web site. Or maybe it is a "frequency asked question". Time to put the rumors to bed, you scared-i-catsâ€¦ your cell phone, your microwave oven, and the neighborhood cell towers are not going to hurt you. Or cause another Godzilla attack. Sorry.
Disclaimer: this information we provide is for your reference, and is not meant to stand up in court against attacks from some tricky lawyer.
Here's two relevant government bulletins on the subject:
Assessment of Public Health Concerns Associated with Pave Paws Radar Installations
(by Massachusetts Department of Health)
Some of this info on this page was found in Introduction to Microwaves, by Fred E. Gardiol. Merci! Not bad for a French speaking Swiss!
There are people on jobs that get thousands of times higher exposure levels that the rest of us get. If microwave radiation was as deadly as some fools would have you believe, there would be a steady line of cell tower workers, radar operators, and RF lab technicians all taking an early dirt nap. There is no evidence that this is the case. Speaking of cases, how come television lawyer James R. Sokolove doesn't advertise he'll take on electromagnetic radiation liability cases? Maybe he's smarter than he looks. It would be a losing proposition.
Ionizing versus non-ionizing radiation
Microwave energy is non-ionizing electromagnetic radiation. Ionizing radiation messes up molecules, non-ionizing radiation merely heats them. You heat your body every day when you take a shower with more energy than your cell phone could ever muster. Ionizing radiation starts at ultraviolet frequencies (UV), and includes X-rays and gamma rays, as you go up the scale of deadliness. The effects of gamma rays are what changed Dr. Bruce Banner into The Amazing Hulk; if you are worried about gamma rays buy yourself a Geiger counter.
Here's a figure that we shamelessly stole from one of the government publications. Notice that ionizing radiation is higher in frequency than visible light. Microwave radiation is far below visible light; indeed, there is a huge band of infrared between the two. No one worries much about the infrared food warmer and its effect on cafeteria workers, do they?
Electromagnetic energy is carried by photons. The higher the frequency, the higher the energy in each photon. When a certain energy level is reached, the photon has enough energy to knock off electrons from molecules that it encounters. At this point it is called ionizing radiation. The critical energy level is 10 electron volts (eV). One Joule is 6.2x10E18 electron volts, so a single electron volt is immeasurably small. Here's how to calculate the energy of a photon, depending on its frequency:
h=Planck's constant = 6.626E-34 Joule-seconds
For the ISM band (2.45 GHz) where your microwave oven operates, energy of each photon is therefore 0.00001 electron volts. The power needed to ionize a molecule is one million times higher than this, so it simply won't happen.
Sunlight is far higher in frequency than microwaves, it doesn't penetrate the body, so it is more dangerous at the same power level. Sunlight provides a power level of 100 mW/cm2 during the summer months, mostly infrared, but with some visible and ultraviolet energy. The cause and effect of skin cancer is well known, it's the higher frequency UV light that is going to kill you. This is why sunblock that advertises "blocks UV rays" is a good thing!
Tanning beds do far more damage than microwaves. What is wrong with people, why do you need so badly to change your skin color? Please consider interracial marriage so your kids don't have to participate in this ridiculous and injurious pastime.
You refer to X-rays and gamma-rays as "ionizing radiation" (as opposed to "non-ionizing radiation") and you are absolutely correct in doing so. You are absolutely correct because you are an Emag / microwave / RF guy (just like me). Those radiation / nuke / physicist guys, however, might tell you that X-rays and gamma rays are "indirectly ionizing radiation" (as opposed to "directly ionizing radiation"). "Directly" ionizing radiation is a charged particle that hits you and BLAM the charged particle is an ion that is now inside you. "Indirectly" ionizing is a neutral particle or a high energy photon (neither have charge) and BLAM it knocks some electrons loose that were already inside you to begin with but made some ions and has the same effect.
Microwave exposure levels
A safety factor of 10 applied to the solar radiation level has been widely adopted for RF radiation, the standard is 10 mW/cm2 maximum. This standard applies to continuous exposure; you can get whacked with higher power for short time with no permanent effects.
Microwave radiation exposure is often expressed in terms of incident power density, in mW/cm2. The following table shows the effects of exposure to certain power levels, without time limit:
|Power level||Long-term effect on human body||Notes|
|5 mW/cm2||Nothing||Accepted standard for microwave oven leakage|
|10 mW/cm2||Nothing||Accepted standard for maximum continuous exposure to radiated emissions (cell phones, etc.)|
|30 mW/cm2||You can feel heat|
|100 mW/cm2||Cataracts can be produced||Summer sunlight is at this level.|
|1000 mW/cm2||Pain is induced|
|5000 mW/cm2||Cooking commences||Set the timer, lasagna in five minutes!|
Exposure to higher power levels has been shown to cause cataracts. How do we know this? During WWII, there were no guidelines for how much radiation a radar operator could take. Solders and sailors were exposed by radars. At a power level of 1W/cm2, pain is induced, so their medical problems were caused by radiation below that level. Thanks to these guinea pigs, we know where the limit is. If anyone has a good "radar burn" story they want to share, send it in and we'll send you a free gift!!!
Cell phones can muster 2 watts. If the antenna was right next to your head, and half the power went into your skull, maybe a power level of 100 mW/cm2 could be produced, but we doubt it. Certainly this power level will never heat up your eyeballs, unless you hold the antenna over your eye when you talk. If you suffer from cataracts, you didn't get them from Lucky Goldstar. Many modern phones pump up the power in areas of low signal quality, so if you really want to minimize your exposure, then consider 1. going outside when you are calling, 2. talking less, listening more, and 3. moving closer to the cell tower! But wait, this correction came from Rick. Even if you are just listening, your cell phone is transmitting.
Cell phones are full-duplex devices. The base station and your cell antenna are transmitting at all times during a call... on a long-distance call, there is a delay from when you speak and the other party acknowledges you that makes you believe there is only half-duplex transmission.
Thanks for setting us straight!
Now, here's some thoughts on the topic from Mike:
Read your article on Biological Effects of Microwave Radiation. Very informative, however you are incorrect when you say all cell phone are full duplex. The GSM type cell phone systems (ATT , ALTEL etc.) are not full duplex. WCDMA, CDMA 2000 Cell phone systems are full duplex (Verizon Sprint etc).
One of these day's we'll create a separate page on this topic...
This saves network noise level low and keeps the batteries running longer.
The above information is correct but lacking a certain detail that makes the difference. There are typically two types of transmission between cell phone and the cell antenna: a. signalling b. data/voice transmission. When it is voice transmission, there are 20 ms sampling windows and if there is silence or a certain sound form (say vowel "e" as in "seed") the phone sends only one short message that the former 20 sec window is repeated. If it is silence, it may not even send anything but that it is silence signal and the transcoder in the switching part generates a hush sound for ambient comfort. And this messages are generally sent at signalling channels not in traffic channels. So in short, the mobile phone may be transmitting at all times but not all the time.
No study has proven that RF radiation at less than 10 mW/cm2 could cause cancer. It is possible that a cell phone were near enough to male genitals, temporary sterility could be caused. When your phone is not placing a call but just left on, it still needs to communicate to a nearby tower every two or so minutes just so the phone company knows where to find you. If you have your phone in your pocket all day, you will be radiated (of course not as much as when connected to a call). In any case, there is no shortage of people on the planet, so a little temporary sterility isn't a bad thing, just don't blame this biological problem on your phone.
Microwave ovens are allowed to leak 5 mW/cm2 at a distance of 2 inches away. Power level will drop off as the square of the distance, so 20 inches away it can be no more than 0.05 mW/cm2.
Cell towers will never put out anywhere near 10 mW/cm2 to pedestrians near by. Maximum effective radiated power (ERP) is on the order of 100 watts, but remember, ERP includes antenna gain; the actual power that is radiated is on the order of a few watts. By the time it reaches pedestrians, out at 100 meters for example, the power density is no more than 0.001 mW/cm2.
Pacemakers are designed to handle 10 mW/cm2, no problemo.
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