Low-powered, intermittent, or inaccessible RF antennas and facilities including many cell sites are normally "categorically excluded" from the requirement of routine evaluation for RF exposure.
These exclusions are based on calculations and measurement data indicating that such transmitting stations or devices are unlikely to cause exposures in excess of the guidelines under normal conditions of use.
It should be emphasized, however, that these exclusions are not exclusions from compliance, but, rather, only exclusions from routine evaluation. Transmitters or facilities that are otherwise categorically excluded from evaluation may be required, on a case-by-case basis, to demonstrate compliance when evidence of potential non-compliance of the transmitter or facility is brought to the Commission's attention [see 47 CFR 1.
In recent years, publicity, speculation, and concern over claims of possible health effects due to RF emissions from hand-held wireless telephones prompted various research programs to investigate whether there is any risk to users of these devices There is no scientific evidence to date that proves that wireless phone usage can lead to cancer or a variety of other health effects, including headaches, dizziness or memory loss.
However, studies are ongoing and key government agencies, such as the Food and Drug Administration FDA continue to monitor the results of the latest scientific research on these topics. Also, as noted above, the World Health Organization has established an ongoing program to monitor research in this area and make recommendations related to the safety of mobile phones.
The FDA, which has primary jurisdiction for investigating mobile phone safety, has stated that it cannot rule out the possibility of risk, but if such a risk exists, "it is probably small. The Government Accountability Office GAO prepared a report of its investigation into safety concerns related to mobile phones.
The report concluded that further research is needed to confirm whether mobile phones are completely safe for the user, and the report recommended that the FDA take the lead in monitoring the latest research results. The safe limit for a mobile phone user is an SAR of 1. Somewhat less restrictive limits, e. Measurements and analysis of SAR in models of the human head have shown that the 1. The same can be said for cordless telephones used in the home.
Testing of hand-held phones is normally done under conditions of maximum power usage, thus providing an additional margin of safety, since most phone usage is not at maximum power. The SAR is a value that corresponds to the rate at which RF energy absorbed in the head of a user of a wireless handset. Information on SAR for a specific cell phone model can be obtained for almost all cellular telephones by using the FCC identification ID number for that model. In many cases, you will have to remove the battery pack to find the number.
Once you have the number proceed as follows. Go to the following website: Equipment Authorization. Then click on "Start Search. Click on a check under "Display Grant" and the grant should appear. This section should contain the value s for typical or maximum SAR for your phone. For portable phones and devices authorized since June 2, , maximum SAR levels should be noted on the grant of equipment authorization. For phones and devices authorized between about mid and June , detailed information on SAR levels is typically found in one of the "exhibits" associated with the grant.
Therefore, once the grant is accessed in the FCC database, the exhibits can be viewed by clicking on the appropriate entry labeled "View Exhibit. Although the FCC database does not list phones by model number, there are certain non-government Web sites such as www.
However, the FCC has not reviewed these sites for accuracy and makes no guarantees with respect to them. In addition to these sites, some mobile phone manufacturers make this information available at their own Web sites. Also, phones certified by the Cellular Telecommunications and Internet Association CTIA are now required to provide this information to consumers in the instructional materials that come with the phones. If you want additional consumer information on safety of cell phones and other transmitting devices please consult the information available below.
If you have any problems or additional questions you may contact us at: rfsafety fcc. You may also wish to consult a consumer update on mobile phone safety published by the U. In addition, because the phone, which is the source of the RF emissions, will not be placed against the head, absorption of RF energy in the head will be reduced. Therefore, it is true that use of an ear piece connected to a mobile phone will significantly reduce the rate of energy absorption or "SAR" in the user's head.
On the other hand, if the phone is mounted against the waist or other part of the body during use, then that part of the body will absorb RF energy. Even so, mobile phones marketed in the U. So either configuration should result in compliance with the safety limit.
Note that hands-free devices using Bluetooth technology also include a wireless transmitter; however, the Bluetooth transmitter operates at a much lower power than the cell phone. A number of devices have been marketed that claim to "shield" or otherwise reduce RF absorption in the body of the user. Some of these devices incorporate shielded phone cases, while others involve nothing more than a metallic accessory attached to the phone. Studies have shown that these devices generally do not work as advertised.
In fact, they may actually increase RF absorption in the head due to their potential to interfere with proper operation of the phone, thus forcing it to increase power to compensate. The FCC does not normally investigate problems of electromagnetic interference from RF transmitters to medical devices.
Some hospitals have policies, which limit the use of cell phones, due to concerns that sensitive medical equipment could be affected. Cellular wireless radio services transmit using frequencies between and megahertz MHz. More recently, advanced wireless services have been or are being introduced that transmit at frequencies in the , , , , , , MHz spectrum ranges. Antennas used for cellular and PCS transmissions are typically located on towers, water tanks or other elevated structures including rooftops and the sides of buildings.
The combination of antennas and associated electronic equipment is referred to as a cellular or PCS "base station" or "cell site. A cellular base station may utilize several "omni-directional" antennas that look like poles, 10 to 15 feet in length, although these types of antennas are less common in urbanized areas. In urban and suburban areas, cellular and PCS service providers commonly use "sector" antennas for their base stations. These antennas are rectangular panels, e.
Panel antennas are usually arranged in three groups of three each. It is common that not all antennas are used for the transmission of RF energy; some antennas may be receive-only. At a given cell site, the total RF power that could be radiated by the antennas depends on the number of radio channels transmitters installed, the power of each transmitter, and the type of antenna.
While it is theoretically possible for cell sites to radiate at very high power levels, the maximum power radiated in any direction usually does not exceed watts. The RF emissions from cellular or PCS base station antennas are generally directed toward the horizon in a relatively narrow pattern in the vertical plane. In the case of sector panel antennas, the pattern is fan-shaped, like a wedge cut from a pie. As with all forms of electromagnetic energy, the power density from the antenna decreases rapidly as one moves away from the antenna.
Consequently, ground-level exposures are much less than exposures if one were at the same height and directly in front of the antenna. Measurements made near typical cellular and PCS installations, especially those with tower-mounted antennas, have shown that ground-level power densities are hundreds to thousands of times less than the FCC's limits for safe exposure.
This makes it extremely unlikely that a member of the general public could be exposed to RF levels in excess of FCC guidelines due solely to cellular or PCS base station antennas located on towers or monopoles.
When cellular and PCS antennas are mounted at rooftop locations it is possible that a person could encounter RF levels greater than those typically encountered on the ground. However, once again, exposures approaching or exceeding the safety guidelines are only likely to be encountered very close to and directly in front of the antennas.
For sector-type antennas, RF levels to rear are usually very low. As discussed above, radiofrequency emissions from antennas used for cellular and PCS transmissions result in exposure levels on the ground that are typically thousands of times below safety limits.
These safety limits were adopted by the FCC based on the recommendations of expert organizations and endorsed by agencies of the Federal Government responsible for health and safety. Therefore, there is no reason to believe that such towers could constitute a potential health hazard to nearby residents or students. Other antennas, such as those used for radio and television broadcast transmissions, use power levels that are generally much higher than those used for cellular and PCS antennas.
Therefore, in some cases there could be a potential for higher levels of exposure to persons on the ground. However, all broadcast stations are required to demonstrate compliance with FCC safety guidelines, and ambient exposures to nearby persons from such stations are typically well below FCC safety limits. Radio and television broadcast stations transmit their signals via RF electromagnetic waves. There are thousands of radio and TV stations on the air in the United States.
Broadcast transmitter power levels range from less then a watt to more than , watts. Some of these transmission systems can be a significant source of RF energy in the local environment, so the FCC requires that broadcast stations submit evidence of compliance with FCC RF guidelines. The amount of RF energy to which the public or workers might be exposed as a result of broadcast antennas depends on several factors, including the type of station, design characteristics of the antenna being used, power transmitted to the antenna, height of the antenna and distance from the antenna.
Note that the power normally quoted for FM and TV broadcast transmitters is the "effective radiated power" or ERP not the actual transmitter power mentioned above. ERP is the transmitter power delivered to the antenna multiplied by the directivity or gain of the antenna. Major RF transmitting facilities under the jurisdiction of the FCC-such as radio and television broadcast stations, satellite-earth stations, experimental radio stations, and certain cellular, PCS, and paging facilities-are required to undergo routine evaluation for RF compliance whenever an application is submitted to the FCC for construction or modification of a transmitting facility or renewal of a license.
Failure to comply with the FCC's RF exposure guidelines could lead to the preparation of a formal Environmental Assessment, possible Environmental Impact Statement, and eventual rejection of an application. Broadcast Antennas Radio and television broadcast stations transmit their signals via RF electromagnetic waves. Operating powers can be as little as a few hundred watts for some radio stations or up to millions of watts for certain television stations.
Some of these signals can be a significant source of RF energy in the local environment, and the FCC requires that broadcast stations submit evidence of compliance with FCC RF guidelines. The amount of RF energy to which the public or workers might be exposed as a result of broadcast antennas depends on several factors, including the type of station, design characteristics of the antenna being used, power transmitted to the antenna, height of the antenna and distance from the antenna.
Since energy at some frequencies is absorbed by the human body more readily than energy at other frequencies, the frequency of the transmitted signal as well as its intensity is important. Public access to broadcasting antennas is normally restricted so individuals cannot be exposed to high-level fields that might exist near antennas.
Measurements made by the FCC, EPA, and others have shown that ambient RF radiation levels in inhabited areas near broadcasting facilities are typically well below the exposure levels recommended by current standards and guidelines. Antenna maintenance workers are occasionally required to climb antenna structures for such purposes as painting, repairs, or beacon replacement.
Both the EPA and OSHA have reported that in these cases it is possible for a worker to be exposed to high levels of RF energy if work is performed on an active tower or in areas immediately surrounding a radiating antenna. Therefore, precautions must be taken to ensure that maintenance personnel are not exposed to unsafe RF fields. Portable Radio Systems "Land-mobile" communications include a variety of communications systems that require the use of portable and mobile RF transmitting sources.
These systems operate in narrow frequency bands between about 30 and 1, MHz. Radio systems used by the police and fire departments, radio paging services, and business radio are a few examples of these communications systems. There are essentially three types of RF transmitters associated with land-mobile systems: base-station transmitters, vehicle-mounted transmitters, and handheld transmitters.
The antennas used for these various transmitters are adapted for their specific purpose. For example, a base-station antenna must radiate its signal to a relatively large area, and, therefore, its transmitter generally has to use higher power levels than a vehicle-mounted or handheld radio transmitter.
Although these base-station antennas usually operate with higher power levels than other types of land-mobile antennas, they are normally inaccessible to the public since they must be mounted at significant heights above ground to provide for adequate signal coverage. Also, many of these antennas transmit only intermittently.
For these reasons, such base-station antennas have generally not been of concern with regard to possible hazardous exposure of the public to RF radiation. Studies at rooftop locations have indicated that high-powered paging antennas may increase the potential for exposure to workers or others with access to such sites, for example, maintenance personnel. Transmitting power levels for vehicle-mounted land-mobile antennas are generally less than those used by base-station antennas but higher than those used for handheld units.
Handheld portable radios such as walkie-talkies are low-powered devices used to transmit and receive messages over relatively short distances. Because of the low power levels used, the intermittence of these transmissions, and the fact that these radios are held away from the head, they should not expose users to RF energy in excess of safe limits.
Therefore, the FCC does not require routine documentation of compliance with safety limits for push-to-talk two-way radios. Microwave Antennas Point-to-point microwave antennas transmit and receive microwave signals across relatively short distances from a few tenths of a mile to 30 miles or more.
Electron Physician. Published online May Mosa Moradi 1 M. Hamidreza Hemmati 3 Ph. Majid Asadi-Samani 4 Ph. Mahmoud Bahmani 5 Ph. Author information Article notes Copyright and License information Disclaimer. Corresponding author: Dr. Received Jan 12; Accepted Apr This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License , which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
This article has been corrected. See Electron Physician. This article has been cited by other articles in PMC. Abstract Introduction Public and occupational exposure to electromagnetic fields due to the growing trend of electronic devices may cause adverse effects on human health.
Methods In this study, we measured the emitted dose from a radiofrequency device, such as switching high voltage at different frequencies using a scintillation detector. Results We investigated the risks that result from the waves, according to a report by International Commission on Non Ionizing Radiation Protection ICNIRP , to every organ of the body is defined by the beam and electromagnetic radiation from this electronic device on people.
Conclusion The results of this study and International Commission of Non Ionization Radiation Protection ICNIRP reports showed the people who spend more than 50 minutes a day using a cell phone could have early dementia or other thermal damage due to the burning of glucose in the brain.
Introduction Many people are not aware of the harmful effects of radiofrequency waves RF and their role in cancer and other serious risks. Open in a separate window. Figure 1. Material and Methods 2. Figure 2. The prototype of constructed high voltage power supply module.
RF Dosimetry The body exposure that is caused by RF waves of electric and magnetic fields, which varies with the intensity of the output signal was determined. RF penetration depth measurements The penetration depth of the RF wave enters into biological tissues and the frequency of the emitted wave are inversely related. Figure 3. Figure 4. The dose rate at a distance of 1. Discussion Numerous epidemiological studies, the association between public and occupational exposure, particularly exposure to ELF fields and the risk of Cancer, including leukemia, brain tumors and breast cancer has shown 8.
Conclusions NCRP reporting threshold of biological effects caused by occupational exposure to RF radiation absorption to 0. Acknowledgments This work is a part of a large project aimed at developing an accurate, low ripple and safe high voltage power supply for using in the medical equipment. Footnotes iThenticate screening: April 11, , English editing: April 20, , Quality control: April 26, Conflict of Interest: There is no conflict of interest to be declared.
This can lead to burns and body tissue damage. Although RF radiation is not thought to cause cancer by damaging the DNA in cells the way ionizing radiation does, there has been concern that in some circumstances, some forms of non-ionizing radiation might still have other effects on cells that might somehow result in cancer. Some people can have significant RF exposure as part of their jobs.
This includes people who maintain antenna towers that broadcast communication signals and people who use or maintain radar equipment. Most people are exposed to much lower levels of man-made RF radiation every day due to the presence of RF signals all around us.
They come from radio and television broadcasts, WiFi and Bluetooth devices, cell phones and cell phone towers , and other sources. Microwave ovens work by using very high levels of a certain frequency of RF radiation in the microwave spectrum to heat foods. When food absorbs microwaves, it causes the water molecules in the food to vibrate, which produces heat. Microwaves do not use x-rays or gamma rays, and they do not make food radioactive. Microwave ovens are designed so that the microwaves are contained within the oven itself.
The oven only makes microwaves when the door is shut and the oven is turned on. When microwave ovens are used according to instructions, there is no evidence that they pose a health risk to people.
0コメント