MH Repacholi: Health risks from the use of mobile phones. Toxicol Let 120:323-331, 2001.
H Frumkin, A Jacobson et al: Cellular phones and risk of brain tumors. CA Cancer J Clin 51:137-141, 2001.
What are mobile phone base stations and are there health hazards associated with living, working, playing, or going to school near one?
Is anyone seriously concerned about possible health risks from mobile phone base station antennas?
What are the difference between a high-gain antenna and a low-gain antenna?
What do the phrases "antenna gain", "transmitter power" and "effective radiated power (ERP)" mean?
What is the difference between the RF patterns for high-gain and low-gain antennas?
How do you assess compliance with radio-frequency radiation guidelines for mobile phone base stations?
Did microwave irradiation of the US Embassy in Moscow cause cancer or other injuries to people working there?
What do the most recent scientific laboratory studies of RF radiation and cancer show?
Where can I get more information?
What's New?v3.0, Jun-2001:
v2.8, Jan-2001:
Jan-2000 thru Dec-2000:
1) What are mobile phone base stations and are there health hazards associated with living, working, playing, or going to school near one?
Mobile phone base stations are low-power multi-channel two-way radios. A mobile phone (cell phone) is a low-power, single-channel, two-way radio. When you talk on such a mobile phone, you (and perhaps dozens of other people around you) are talking to a nearby base station. From that base station your phone call goes into the regular land-line phone system.
Because mobile phones and their base stations are two-way radios, they produce radio-frequency radiation (that's how they communicate), and they expose people near them to radio-frequency (RF) radiation. However, because both the phones and the base stations are low power (short range), the RF radiation exposure levels from them are generally very low.
The consensus of the scientific community, both in the US and internationally, is that the power from these mobile phone base station antennas is far too low to produce health hazards as long as people are kept away from direct access to the antennas (see Q13 and Q14 ).
It is critical to be aware of the difference between antennas, the objects that produce RF radiation; and towers or masts, the structures that the antennas are placed on. It is the antennas that people need to keep their distance from, not the towers that hold the antennas.
It is also important to be aware that there are many different designs of mobile phone base stations that vary widely in their power, their characteristics, and their potential for exposing people to RF radiation.
Not really. There are some reasons to be concerned about human health effects from the hand-held mobile (cellular) phones themselves (although it is not certain that any risks to human health actually exist). These concerns exist because the antennas of these phones deliver much of their radiofrequency energy to very small volumes of the user's body [83]. Base station antennas do not create such "hot spots" (unless you are standing directly in front of one), so the potential safety issues concerning the phones have no real applicability to the base station antennas.
For further discussion of health issues related to hand-held phones see the 1996 ICNIRP report [1], the 1999 and 2000 reviews by Moulder and colleagues [95, 131], the 2000-2001 review by the Royal Society of Canada [99], the 2000 report of the UK Independent Expert Group on Mobile Phones (the "Stewart Commission") [128], the 2001 IEEE position paper [26], the 2001 review from the World Health Organization [165], and 2001 the review from American Cancer Society [163].
No. There are many technical differences between cell phones, PCS phones, and the types of "mobile" phones used in other counties [2, also see international note 2]; but for evaluation of possible health hazards, the only distinction that matters is that they operate at slightly different frequencies. The RF radiation from some base stations (e.g., those for the older 800 MHz cell phones used in the U.S.) may be absorbed by humans somewhat more than the RF radiation from other types of base stations (e.g., those for the 1800-2000 MHz "PCS" phones used in the U.S.) [23]. However, once the energy is absorbed the effects are the same.
Yes and no. The RF radiation from some antennas (particularly FM and VHF-TV broadcast antennas) are absorbed more by humans than the RF radiation from other sources (such as mobile phone base station antennas); but once the energy is absorbed the effects are basically the same.
FM and TV antennas send out 100 to 5000 times more power than base station antennas, but are usually mounted on much higher towers (typically 800 to 1200 ft).
Yes. mobile (cellular) phones and their base station antennas are two-way radios, and produce radiofrequency (RF) radiation [3]; that's how they work. This radiofrequency radiation is "non-ionizing", and its biological effects are fundamentally different from the "ionizing" radiation produced by x-ray machines [see Q6].
No. The interaction of biological material with an electromagnetic source depends on the frequency of the source [4]. X-rays, RF radiation and "EMF" from power lines are all part of the electromagnetic spectrum, and the parts of the spectrum are characterized by their frequency. The frequency is the rate at which the electromagnetic field changes direction and is given in Hertz (Hz), where one Hz is one cycle (wave) per second, and 1 megahertz (MHz) is one million cycles (waves) per second.
Electric power in the US is at 60 Hz. AM radio has a frequency of around 1 MHz, FM radio has a frequency of around 100 MHz, microwave ovens have a frequency of 2450 MHz, and X-rays have frequencies above one million million MHz. Cellular (mobile) phones operate at a variety of frequencies between about 800 and 2200 MHz [also see international note 2].
At the extremely high frequencies characteristic of X-rays, electromagnetic particles have sufficient energy to break chemical bonds (ionization). This is how X-rays damage the genetic material of cells, potentially leading to cancer or birth defects. At lower frequencies, such as RF radiation, the energy of the particles is much too low to break chemical bonds. Thus RF radiation is "non-ionizing". Because non-ionizing radiation cannot break chemical bonds, there is no similarity between the biological effects of ionizing radiation (x-rays) and nonionizing radiation (RF radiation) [4].
The Electromagnetic Spectrum |
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No. Power lines produce no significant non-ionizing radiation, they produce electric and magnetic fields. In contrast to non-ionizing radiation, these fields do not radiate energy into space, and they cease to exist when power is turned off. It is not clear how, or even whether, power line fields produce biological effects; but if they do, it is not in the same way that high power RF radiation produces biological effects [4, 53]. There appears to be no similarity between the biological effects of power line "EMF" and the biological effects of RF radiation.
Yes. There are national and international safety guidelines for exposure of the public to the RF radiation produced by mobile phone base station antennas. The most widely accepted standards are those developed by the Institute of Electrical and Electronics Engineers and American National Standards Institute (ANSI/IEEE) [5], the International Commission on Non-Ionizing Radiation Protection (ICNIRP) [6], and the National Council on Radiation Protection and Measurements (NCRP) [7].
These radiofrequency standards are expressed in "plane wave power density", which is measured in mW/cm-sq (milliwatts per square centimeter) [8]. For PCS (about 1800-2000 MHz) antennas, the 1992 ANSI/IEEE exposure standard for the general public is 1.2 mW/cm-sq. For analog cellular phones (about 900 MHz), the ANSI/IEEE exposure standard for the general public is 0.57 mW/cm-sq [9]. The ICNIRP standards are slightly lower and the NCRP standards are essentially identical [10].
In 1996 the U.S. Federal Communications Commission (FCC) released radiofrequency guidelines for the frequencies and devices they regulate, including mobile phone base station antennas [11]. The FCC standards for mobile phone base station antennas are essentially identical to the ANSI/IEEE standard [5].
The public exposure standards apply to power densities averaged over relatively short periods to time, 30 minutes in the case of the ANSI/IEEE, NCRP, and FCC standards (at mobile phone frequencies). Where there are multiple antennas, these standards apply to the total power produced by all antennas [13].
See international note 12 and Erdreich and Klauenberg [164].
Yes. When scientists examined all the published literature on the biological effects of RF radiation they found that the literature agreed on a number of key points [see 1, 5, 6, 7, 14, 53, 83, 90, 95, 96, 99, and 164 for details]:
To establish occupational exposure guidelines, ANSI/IEEE and FCC applied a 10-fold safety margin to the lowest energy absorption rate shown to have biological effects . They then applied an additional 5-fold safety margin for continuous exposure of the general public. Finally, detailed studies were done to establish the relationship of power density, which can be routinely measured, to the energy absorption rate (SAR), which really matters [8].
The result was a highly conservative public exposure guideline that was set at a level that is only 2% of the level where replicated biological effects have actually been observed.
No. There are differences between the standards. ANSI/IEEE, ICNIRP, NCRP and FCC all use the same biomedical data, and the same general approach to setting safety guidelines. However, there are differences in the models used by the different groups, and hence there are slight differences in the final numbers [17, 164]. No biological significance should be associated with these slight differences.
A number of countries have their own regulations for public exposure to RF radiation from mobile phone base station antennas. While most of these regulation follow the same patterns and rationales used by ANSI/IEEE [5] and ICNIRP [6], they do differ. See note 12 and Erdreich and Klauenberg [164] for details.
Yes. Until 1996 the U. S. Federal Communications Commission (FCC) used an out-dated (1982) ANSI standard. In 1996 the FCC adopted a new standard [11] that was based on a combination of the 1992 ANSI standard [5] and the 1986 NCRP guidelines [7].
The new FCC standard for mobile phone base stations is 0.57 mW/cm-sq at 900 MHz and 1.0 mW/cm-sq at 1800-2000 MHz. This 1996 FCC standard applied to all new transmitters licensed after 15-Oct-97, but pre-existing facilities had until 1-Sep-2000 to demonstrate compliance.
The FCC power-density standards described above apply to whole-body public exposure to radio-frequency radiation from mobile phone base stations; they do not apply to exposure from the phones themselves or to occupational exposure. For a discussion of exposure from the phones or a discussion of occupational RF radiation exposure see FCC OET Bulletin 56 [135], the FCC guideline itself [11], and Foster and Moulder [131].
Yes. With proper design, mobile phone base station antennas can meet all safety standards by a wide margin.
A mobile phone base station antenna, mounted 10 meters (33 ft) off the ground and operated at the maximum possible intensity, might produce a power density as high as 0.01 mW/cm-sq on the ground near the antenna site; but ground level power densities will more often be in the 0.00001 to 0.0005 mW/cm-sq range [57, 77, 123, 130]. These power densities are far below all the safety standards, and the standards themselves are set far below the level where potentially hazardous effects have been seen.
Within about 200 meters (650 ft) of the base of the antenna site, the power density may be greater at elevations above the base of the antenna site (for example, at the second floor of a building or on a hill). Even with multiple antennas on the same tower, power densities will be less than 5% of the FCC guidelines at all heights and at all distances of more than 55 meters (180 ft) from an antenna site.
Further than about 200 meters (650 ft) from the antenna site power density does not rise with increased elevation.
Power density inside a building will be lower by a factor of 3 to 20 than outside [54,130].
Petersen et al [77] measured power densities around cell phone base stations. The measurements were for 1600 W (ERP) antennas (see Q14C for a discussion of antenna power) on towers that ranged from 40 to 83 meters (130 to 275 ft) in height. The maximum power density on the ground was 0.002 mW/cm-sq, and the maximum was at 20 to 80 meters (65-265 feet) from the base of the towers. Within 100 meters (330) feet of the base of the towers, the average power density was less than 0.001 mW/cm-sq. These maximum RF power densities are all less than 1% of the FCC, ANSI/IEEE, NRPB and ICNIRP standards for public exposure.
In 1999 in Vancouver Canada, Thansandote et al [123] measured RF levels in five schools, three of which had base stations on them or near them. All schools met Canadian, US and international RF standards by a wide margin. The maximum readings are shown in the following table.
| School
| Base Station Location | Maximum RF Level |
| 1 | PCS base station across street | 0.00016 mW/cm-sq |
| 2 | analog base station on roof | 0.0026 mW/cm-sq |
| 3 | analog base station across street | 0.00022 mW/cm-sq |
| 4 and 5 | no antennas nearby | less than 0.00001 mW/cm-sq |
| Canadian Standard | less than 0.57 mW/cm-sq |
In 2000, the U.K. National Radiation Protection Board [130] measured radiofrequency radiation levels at 118 publicly-accessible sites around 17 cell phone base stations. The maximum exposure at any location was 0.00083 mW/cm-sq (on a playing field 60 meters from a school building with an antenna on its roof). Typical power densities were less than 0.0001 mW/cm-sq (less than 0.01% of the ICNIRP public exposure guidelines). Power densities indoors were substantially less than power densities outdoors. When radiofrequency radiation from all sources (cell phone, FM radio, TV, etc.) was taken into account the maximum power density at any site was less than 0.2% of the ICNIRP public exposure guidelines. Details are shown in the following figure.
Radiofrequency Radiation Levels Near Mobile Phone Base Stations in the UK |
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| The relationship between the RF power density and distance from the base of the tower or building on which the mobile phone base antenna was located. Adapted from Mann et al. [130]. |
The relationship between the RF levels required to produce known biological effects, the RF levels specified in the FCC safety guidelines, and the RF levels found around mobile phone base stations is shown in the following figure.
Standards for Mobile Phone Base Stations |
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| The relationship between the RF power density level required to produce known biological effects, the RF power density levels specified in the FCC safety guidelines, and the RF power density levels found around mobile phone base stations. Because the RF power density required to produce biological effects is dependent on frequency, this figure only applies to frequencies between 800 and 2200 MHz (that is, those currently used by analog and digital cellular phones). |
Yes. There are some circumstances under which an improperly designed (or inadequately secured) mobile phone base station antennas could fail to meet safety standards.
Safety guidelines for uncontrolled (public) exposure could be exceeded if antennas were mounted in such a way that the public could gain access to areas within 6 meters/20 feet (horizontal) of the antennas themselves [18]. This could arise for antennas mounted on or near the roofs of buildings. Petersen et al [77], for example, found that 2-3 feet (1 meter) from a 1600 W (ERP) roof-top antenna, the power density was as high as 2 mW/cm-sq (compared to the ANSI [9] public exposure standard of 1.2 to 0.57 mW/cm-sq). For antennas mounted on towers, it is very difficult to imagine a situation that would not meet the safety guidelines.
While specific recommendations require a detailed knowledge of the site, the antenna, and the mounting structure, some general criteria can be described.
The FCC guidelines [11] require detailed calculations and/or measurement of radiofrequency radiation for some high-power rooftop transmitters, and some high-power transmitters whose antennas are mounted on low towers [19].
In general, the above guidelines will always be met when antennas are placed on their own towers. Problems, when they exist, are generally confined to:
There are many different types of base station antennas, and the RF radiation patterns from them can be quite different. The most basic difference is between high-gain antennas and a low-gain antennas. Because siting and safety issues for high- and low-gain antennas are different, it is important to be able to tell them apart (see Q14C for a discussion of antenna gain). In the early days of mobile phones, you could usually tell by looking. Unfortunately, the development of newer antenna designs and the variety of different ways to stealth (hide) antennas now often makes it impossible to determine what kind of antenna has been installed just by looking,
The power of a mobile phone base station is usually described by its effective radiated power (ERP) which is given in watts (W). Alternatively, the power can be given as transmitter power (in watts) and the antenna gain.
Transmitter power is a measure of total power, while ERP is a measure of the power in the main beam. If an antenna were omni-directional and 100% efficient, then transmitter power and ERP would be the same. But mobile phone base station antennas (like all antennas) are not omni-directional; they are moderately (low-gain antennas) to highly (high-gain antennas) directional. The fact that they are directional means that they concentrate their power in some directions, and give out much less power in other directions. Antenna gain is a measure of how directional an antenna is, and it is measured in decibels. As a result, a 20-50 W base station transmitter with a high-gain antenna could produce an ERP of anywhere from several hundred watts to over 1000 watts.
Perhaps the concept of "gain" and "ERP" are best explained by analogy to light bulbs. Compare a regular 100 W light bulb and a 100 W spot light. Both have the same total power, but the spot light is much brighter when you are in its beam and very weaker when you are outside its main beam. A mobile phone base antenna (particularly a high-gain sector antenna) is like the spot light, and ERP is equivalent to the power in the spot light's main beam.
For a more complete technical discussion of these issues see Section 2.2.11 of NCRP Report No. 119 [134].
The RF patterns for different types of antennas are very different. For a low-gain antenna with a 1000 W ERP (see Q14C for a discussion of antenna power and gain) of the type formerly used by many cell phone base stations, the pattern can look like this:
RF Emissions from a 1000 W ERP Low-Gain Antenna |
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Very close to such a low-gain antenna (in what is technically known as the "near field"), the power density around an antenna looks like this:
RF Emissions from a 1000 W ERP Low-Gain Antenna |
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The data for the above figure were adapted (with permission) from drawings provided by UniSite Inc. of Tampa, Florida (http://www.unisite.com).
For a high-gain (sector) antenna of the type used in many of the newer base stations, the pattern can look like this:
RF Emissions from a Single 1000 W ERP High-Gain Antenna |
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Keep in mind that mobile phone base station that use high-high-gain sectored antennas will usually use 3 (or occasionally 4) of these transmission antennas, all pointing in different directions.
Very close to a single high-gain sector antenna like this (in what is technically known as the "near field"), the power density can look like this:
RF Emissions from a Single 1000 W ERP High-Gain Antenna |
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The data for the above figure were adapted (with permission) from drawings provided by UniSite Inc. of Tampa, Florida (http://www.unisite.com).
In general this will not be a problem.
No. Radiofrequency safety guidelines do not require either setbacks or use restrictions around mobile phone base station antenna sites, since power levels on the ground are never high enough to exceed the guidelines for continuous public exposure (see Q8 and Q12).
As discussed in Q13 and Q14, there may be circumstances where use restrictions will have to be placed around the antennas themselves.
Some people have argued that base stations should be kept some distance away from "sensitive" areas.
There is little logic to this argument:
A detailed discussion of radio-frequency radiation occupational safety guidelines is beyond the scope of this FAQ.
In a detailed discussion of guidelines for telecommunications antenna installation, Tell [116] makes the following recommendations:
Specific Antenna Installation Guidelines (from Tell [116])
Work Practices for Reducing Radio-frequency Radiation Exposure (from Tell [116])
Also see Bernardi et al [147] for an analysis of actual exposure levels to a person on a roof near a base station antenna.
Compliance can be assessed through measurements or calculations. Both methods require a solid understanding of the physics of RF radiation, and measurements require access to sophisticated and expensive equipment.
Calculation: If the effective radiated power (ERP), the antenna pattern and the height of the base station antenna is known (see Q14C for a discussion of ERP and gain), then "worst case" calculations of ground level power density can be made. However, the calculation method is not simple and the ERP and antenna pattern are often unknown.
Measurement: Actual measurement of power density from mobile phone base stations requires sophisticated and expensive equipment and considerable technical knowledge. The instruments designed to measure power line fields and the instruments designed to test microwave ovens are not suitable for measuring base stations. Determining that base stations meet ANSI/IEEE, FCC, or ICNIRP guidelines is "relatively easy", but the instruments required cost well over US$ 2000. Actual measurement of the power-density from a base station antenna is much more difficult, as there are many other sources of RF radiation at a typical site (see Mann et al [130]).
For a technical discussion of measurement techniques and instrumentation see Mann et al [130] and NCRP Report No. 119 [134].
Not everyone. Even among scientists there are a few people who claim that there is evidence that low level exposure to RF is hazardous (see, for example, Q15B and Q15C). However, even these scientists generally do not argue that power densities as low as those found around properly-designed base station antenna sites are hazardous.
Yes. The EPA asked the FCC to adopt parts of the 1986 NCRP guidelines [7] rather than the entire 1992 ANSI guidelines [5]. This the FCC did [11], and EPA has formally endorsed the FCC safety guidelines.
In a 25-Jul-96 letter to Reed Hundt (Chairman of the FCC), Carol Browner (Director of EPA) wrote:
"We have reviewed... 'FCC Draft of July 2, 1996, in the Matter of Guidelines for Evaluating The Environmental Effects of Radiofrequency Radiation'. This new approach... addresses our concerns about adequate protection of public health. I commend you for taking this approach..."
In a 17-Jan-97 follow-up letter to Reed Hundt (Chairman of the FCC), Mary Nichols (EPA Assistant Administrator for Air and Radiation) wrote:
"I would like to reiterate EPA's support of FCC's final RF exposure guidelines issued in August [of 1996] as providing adequate protection of public health."
In a 30-April-1999 letter to the FCC, Robert Brenner (EPA Acting Deputy Assistant Administrator for Air and Radiation) stated:
"The FCC guidelines expressly take into account thermal effects of RF energy, but do not directly address postulated non-thermal effects, such as those due to chronic exposure. That is the case largely because of the paucity of scientific research on chronic, non-thermal health effects. The information base on non-thermal health effects has not changed significantly since the EPA's original comments in 1993 and 1996. A few studies report that at non-thermal levels, long term exposure to RF energy may have biological consequences. The majority of currently available studies suggests, however, that there are no significant non-thermal human health hazards. It therefore continues to be EPA's view that the FCC exposure guidelines adequately protect the public from all scientifically established harms that may result from RF energy fields generated by FCC licensees."
Yes and no. That claim was made in 1996, but follow-up studies in Australia (see below) and in the UK (see Q15D) contradict this claim.
Hocking and colleagues [28] published an "ecological" epidemiology study that compares municipalities "near TV towers" to those further away. No RF radiation exposures were actually measured, but the authors calculate that exposures in the municipalities "near TV towers" were 0.0002 to 0.008 mW/cm-sq. No other sources of exposure to RF are taken into account, and the study is based on only a single metropolitan area. The authors report an elevated incidence of total leukemia and childhood leukemia, but no increase in total brain tumor incidence or childhood brain tumor incidence.
More detailed epidemiology studies of FM/TV antennas in the U.K. have not found evidence for a cancer connection (see Q15D).
In 1998, McKenzie and colleagues [62] repeated the Hocking study [28]. McKenzie and colleagues looked at the same area, and at the same time period; but they made more precise estimates of the exposure to RF radiation that people got in various areas. They found increased childhood leukemia in one area near the TV antennas, but not in other similar areas near the same TV antennas; and they found no significant correlation between RF exposure and the rate of childhood leukemia. They also found that much of the "excess childhood leukemia" reported by Hocking occurred before high-power 24-hour TV broadcasting had started. This replication study, plus the failure to find any effect in the larger UK studies (see Q15D), suggests that correlation reported by Hocking et al [28] was an artifact.
Yes. In a 1995 article labeled an "opinion piece", Goldsmith [29A] argues that there is evidence that RF exposure is associated with mutations, birth defect, and cancer. This review is based largely on what the author admits to be "non-peer-reviewed sources", most of which are stated to be "incomplete" and to lack "reliable dose estimates". The author further states that "no systematic effort to include negative reports is made; thus this review has a positive reporting bias".
In an article based on a 1996 meeting presentation [29B] Goldsmith argues that epidemiological studies "suggest that RF exposures are potentially carcinogenic and have other health effects". His conclusions are based largely on:
- studies of RF exposure at the US embassy in Moscow (see Q15H and Hill [68]);
- the "geographical correlation" studies of Hocking et al [28] and Dolk et al [34, 35] that are discussed in Q15B and Q15D;
- the study of Korean war radar operators by Robinette et al [67] that is discussed in Q16.
Few scientists agree with the opinions expressed by Goldsmith (see, for examples the reviews of the RF epidemiology in 1, 5, 6, 7, 14, 53, 94, 139); and even fewer would be willing to base a conclusion on the types of data sources that Goldsmith relies on.
Yes and no. Dolk and colleagues [34] investigated a reported leukemia and lymphoma cluster near a high-power FM/TV broadcast antenna at Sutton Coldfield in the UK. They found that the incidence of adult leukemia and skin cancer was elevated within 2 km of the antenna, and that the incidence of these cancers decreased with distance. No associations at all were seen for brain cancer, male or female breast cancer, lymphoma or any other type of cancer.
Because of this finding, Dolk and colleagues [35] extended their study to 20 other high-power FM/TV broadcast antennas in the UK. Cancers examined were adult leukemia, skin melanoma and bladder cancer, and childhood leukemia and brain cancer. No elevations of cancer incidence were found near the antennas, and no declines in cancer incidence with distance were seen. This large study does not support the results found in the much smaller studies by the same authors at Sutton Coldfield [34] or by Hocking et al [28] in Australia.
Yes and no. Dr. Henry Lai (Department of Bioengineering, University of Washington, Seattle) has claimed at meetings that "low intensity" RF radiation has effects on the nervous system of rats. Dr. Lai has further claimed at meetings that there are published studies showing that RF radiation can produce "health effects" at "very low field" intensities.
Dr. Lai's own research has no obvious relevance to the safety of cell phone base stations since most of his studies were conducted with RF radiation intensities far above those that would be encountered near base stations. In general, Dr. Lai's studies were done with at a power density of 1 mW/cm-sq and an SAR of 0.6 W/kg [31, 92, 93]. This RF radiation intensity is over 100 times greater than that would be encountered in publicly-accessible areas near FCC-compliant base stations [16], and substantially exceeds the SAR limit that forms the basis of the FCC [11] and ANSI [5] safety guidelines for public exposure [17]. For further discussion of the research on possible effects of RF radiation on the nervous system see reviews by Lai [93] and Juutilainen and de Seze [90].
At a meeting in Vienna in 1998, and in a letters sent to public officials, Dr. Lai referenced six studies in support of his claim that there is data showing that RF radiation can produce "health effects" at "very low field" intensities. These studies were:
There appears to be no real scientific basis for these claims.
In the summer and fall of 1999 (and repeated in 2000), programs on British, American and French TV claimed that there was new data suggesting that RF radiation from cell phones could cause injury to humans. Four sources of "new" information were generally cited:
The last two of these "new" studies were only vaguely described in the TV reports, but they appear to be references to studies sponsored by the mobile phone industry in the US (under the program called WTR).
The WTR epidemiology study was presented at a meeting in June of 1999, and has now been published in the peer-reviewed literature [138]. The published version reports no significant association between malignant brain cancer and the use of hand-held cell phones. See further discussion of the study in Q16.
The WTR genotoxicity study was presented at a meeting in March of 1999 and published abstracts are available [102, 103]. However, it has never been published and details are not publicly available. Despite the fact that the study has not been published, Vijayalaxmi et al [150] have already reported that they cannot confirm the findings.
The U.S. Food and Drug Administrations (FDA) appears to have seen the WTR genotoxicity studies, and published the following comments on 20-Oct-99 [for full text see http://www.fda.gov/cdrh/ocd/mobilphone.html].
"Researchers conducted a large battery of laboratory tests to assess the effects of exposure to mobile phone RF on genetic material. These included tests for several kinds of abnormalities, including mutations, chromosomal aberrations, DNA strand breaks, and structural changes in the genetic material of blood cells called lymphocytes. None of the tests showed any effect of the RF except for the micronucleus assay, which detects structural effects on the genetic material. The cells in this assay showed changes after exposure to simulated cell phone radiation, but only after 24 hours of exposure. It is possible that exposing the test cells to radiation for this long resulted in heating. Since this assay is known to be sensitive to heating, heat alone could have caused the abnormalities to occur. The data already in the literature on the response of the micronucleus assay to RF are conflicting. Thus, follow-up research is necessary. [Tice et al. Tests of mobile phone signals for activity in genotoxicity and other laboratory assays. In: Annual Meeting of the Environmental Mutagen Society; 29 March 1999, Washington, D.C.; and personal communication, unpublished results.]."
In May 2000, a special committee in the U.K., the "Independent Expert Group on Mobile Phones" (also known as the "Stewart Commission") issued a report on mobile phone safety issues [128]. The full text is available at: http://www.iegmp.org.uk/IEGMPtxt.htm.
On the general issue of radio-frequency radiation safety, the U.K. Independent Expert Group concluded that:
"The balance of evidence to date suggests that exposures to RF radiation below NRPB [14] and ICNIRP [6] guidelines do not cause adverse health effects to the general population." [Section 1.17]
"There is now scientific evidence, however, which suggests that there may be biological effects occurring at exposures below these guidelines. This does not necessarily mean that these effects lead to disease or injury, but it is potentially important information..." [Section 1.18]This "new scientific information" the Stewart Commission refers to is largely the reaction time studies of Preece et al [97] and Koivisto et al [117] that are discussed in Q19C, and studies by dePomerai et al [127, 148] which suggest that nonthermal exposures of nematode worms can lead to expression of heat shock proteins.
With respect to mobile phone base stations, the U.K. Independent Expert Group concluded that:
"The balance of evidence indicates that there is no general risk to the health of people living near to base stations on the basis that exposures are expected to be small fractions of guidelines." [Section 1.33]However, the U.K. Independent Expert Group was quite critical of the planning process used for siting base stations in the U.K., and recommended that:
"...the siting of all new base stations should be subject to the normal planning process." [Section 1.36]
"...protocols be developed, in concert with industry and consumers, which can be used to inform the planning process and which must be assiduously and openly followed before permission is given for the siting of a new base station." [Section 1.37]
"[the protocols should include] a requirement for public involvement, an input by health authorities/health boards and a clear and open system of documentation which can be readily inspected by the general public." [Section 1.38]
"...an independent random, ongoing, audit of all base stations be carried out to ensure that exposure guidelines are not exceeded outside the marked exclusion zone... and that particular attention should be paid initially to the auditing of base stations near to schools..." [Sections 1.40 and 1.41].Specifically with respect to schools, the U.K. Independent Expert Group also recommended that:
"...[for] base stations sited within school grounds, that the beam of greatest intensity should not fall on any part of the school grounds or buildings without agreement from the school and parents. Similar considerations should apply to base stations sited near to school grounds." [Section 1.42].
Probably the most controversial recommendations made by the U.K. Independent Expert Group referred to the phones themselves rather than base stations, when they recommended that:
"...drivers be dissuaded from using either hand-held or hands-free phones while on the move." [Section 1.22]and that:
"...the widespread use of mobile phones by children for non-essential calls should be discouraged and... that the mobile phone industry should refrain from promoting the use of mobile phones by children." [Section 1.53].
The recommendation that children be discouraged from using phones is based largely on the cognitive effect studies of Preece et al [97] and Koivisto et al [117] and on the European Union "Precautionary Principle" [129].
This recommendation has been criticized on multiple grounds:
The exposure to RF radiation occurred, but there is no real evidence that it caused any health effects.
From 1953 to 1976, low-intensity microwaves were aimed at the American Embassy building in Moscow. Lilienfeld et al [709] performed a comprehensive survey of the health experience of 1827 foreign service employees who had been assigned to work at the embassy (and their dependents). Their health experience was compared to 2561 foreign service workers assigned to other East European embassies (and their dependents). Measurements of several different exposed areas of the Moscow embassy in three time periods indicated the maximum exposure was at 0.015 mW/cm-sq (at 0.5 to 9 GHz) for 18 hours/day. For most of the exposure period, the maximum level was lower. The embassies of the comparison population were said to be at background levels.
Lilienfeld et al [70] found no evidence that individuals in the Moscow group experienced higher mortality for any cause, or higher mortality from cancer in general or from any cancer subtype. Although this study was well-designed, the relatively small cohort size and short follow-up time limited its power. The power of this study is also limited by the extremely low RF radiation levels, although it should be noted that the RF levels are larger than those found near most mobile phone base station antennas.
The study concluded that:
"Personnel working in the American Embassy in Moscow suffered no ill effects from the microwaves beamed at the Chancery"
Yes and no. While there have been no epidemiology studies of cancer and cell phone base stations, there have been epidemiology studies of cancer and other types of exposure to radiofrequency radiation. For reviews see Elwood [94] and Rothman [139].
In general, epidemiology studies of radiofrequency radiation and cancer have not found significant correlations between exposure and cancer. The studies include:
Geographic correlation studies
Geographic correlation studies estimate the strength of RF radiation in geographic areas and correlate these estimates with disease rates in these areas. Even when the design of geographic correlation studies is optimal, they are considered exploratory and are not used for determining causality.
The geographical correlation studies done to date show no consistent relationship between exposure to RF radiation and either adult of childhood cancer. See Q15B, Q15D and Elwood [94] for further discussion of these studies.
Cancer cluster studies
Reports of clusters of cancer provide little practical information. The major steps in evaluating reports of "cancer clusters" are:
- define a logical (as opposed to arbitrary) boundary in space and time,
- determine whether an excess of a specific type of cancer has actually occurred,
- identify common exposures and characteristics.
The above steps, however, have not generally been followed in studies of RF radiation, and reports of "cancer clusters" are of essentially no value in determining whether exposure to RF radiation is a cause of cancer (see Elwood [94] for details of these studies).
Occupational exposure studies
The majority of the occupational studies of RF radiation exposure have deficiencies in exposure assessments because occupation or job title was used as an estimate of exposure; that is, actual RF radiation exposure levels are not known.
There are four epidemiological studies of occupational exposure to RF radiation that are generally considered to have acceptable design and analysis, adequate sample size, and sufficient follow-up time: Robinette et al [67], Hill [68], Milham [69], and Morgan et al [118]. These four studies do not show statistically-significant associations between exposure to radio-frequency radiation and either cancer in general or any specific kind of cancer.
The other studies of acceptable design (Lilienfeld et al [70], Lagorio et al [71], Muhm [72], Tynes et al [73], Grayson et al [33], and Thomas et al [105]) have more limitations in exposure assessment, case ascertainment, or follow-up time; but they also do not suggest that RF radiation exposure increases the risk of either cancer in general or any specific kind of cancer.
Szmigielski [79] studied Polish military personnel who may have had RF radiation exposure. The incidence of cancer of all types, brain cancer, leukemia and lymphoma are reported to be elevated in exposed personnel. Because the methods of data collection and analysis are inadequately described or unsuitable, and because assessment of RF radiation exposure is very deficient, the report does not meet basic epidemiological criteria for acceptability. Elwood [94] also concludes that the methods used in the Szmigielski study may have created a systematic bias "that would be expected to produce an increased relative risk for all types of cancer".
Studies of exposure to mobile phone RF radiation
In 1996, Rothman et al. [121] published a study that reviewed health records of more than 250,000 mobile phone users. They found no difference in mortality between the users of hand-held portable phones (where the antenna is placed close to the head) and mobile cellular phones (where the antenna is mounted on the vehicle). In a 1999 follow-up study [122], the same group examined specific causes of death among nearly 300,000 mobile phone users in several U.S. cities. The investigators found no difference in overall cancer rates, leukemia rates, or brain cancer rates between the users of hand-held portable phones and the users of mobile cellular phones. The only specific cause of death that correlated with use of hand-held mobile phones was death from motor vehicle collisions.
In 1999-2001, three case-control studies evaluated brain cancer in users of hand-held cell phones: the first by Hardell et al [100], the second by Muscat et al [138] and the third by Inskip et al [143]. None of studies found associations between cell phone use and brain cancer, and none found exposure-response trends. In general, the temporal lobe of the brain gets the highest RF radiation exposure in users of hand-held cell phones; Hardell et al [100] reported a non-significant excess of temporal lobe tumors, but Muscat et al [138] and Inskip et al [143] reported a non-significant decrease of these tumors. Hardell et al [100] reported a non-significant excess of temporal lobe tumors on the side of the head where the patients reported using their phones, but Muscat et al [138] and Inskip et al [143] reported non-significant trends in the opposite direction.
In the first of the cell phone studies, Hardell et al. [100] analyzed mobile phone use in 233 Swedish brain tumor patients, some of whom has used hand-held mobile phones for as long as 10 years. This was done as part of a larger study of possible causes of brain cancer (other possible causes evaluated included occupation, radiation therapy for cancer, exposure to diagnostic radiation, and exposure to a wide variety of chemicals). Exposure was assessed by questionnaires, and analyses were based on use of hand-held cellular telephones (use of "hands-free" devices and use in a car with a fixed antenna were not considered to be "exposure"). No elevation of brain tumor incidence was found in users of either digital or analog phones, and no exposure-response trend was observed (see figure below). When analysis was restricted to temporal lobe (or temporal, occipital plus temporoparietal lobe) tumors on the same side of the brain where the cell phone was reported to have been used, a non-significant excess incidence was found. This "handedness" was seen for use of analog phones, but not for the use of digital phones [100A].
Brain Cancer in Cell Phone Users |
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Relative risk of brain cancer (odds ratio with 95% confidence interval) in users of hand-held cell phones from the epidemiological study of Hardell et al [100]. The number of cases in the overall analysis, and the sub-analyses are shown in parentheses. The analog phones are either at 450 (NMT 450) or 900 MHz; the digital phones are GSM. The lines highlighted in red are probably the ones most relevant to cancer risk assessment as they look at long-term heavy use. The line highlighted in blue refers to tumors in the lobe of the brain that should get the highest RF radiation exposure in users of hand-held phones. The last 4 rows look at which side of the head (L=Left, R=Right) the phone was used on. |
In December 2000, Muscat et al [138] published a similarly-designed study of 469 brain tumor patients in the US, some of whom has used hand-held mobile phones for as long as 4 years. Exposure was assessed on the basis of in-hospital interviews. No elevation of brain tumor incidence was found in users of hand-held phones, and no exposure-response trend was observed (see figure below). The incidence of temporal lobe tumors (where RF radiation exposure should be the greatest in users of hand-held phones) was not elevated. There was a non-significant trend for tumors to be on the side of the head where the patients reported using their phones; but when analysis was confined to the temporal lobe tumors, there were fewer tumors than expected on the side of the head where the phones were used.
When Muscat et al [138] analyzed tumors by histopathological type, there was no excess of gliomas (the most common and deadly form of brain tumors); but there was an excess of neuroepitheliomas (see figure below). This increase was not statistically significant. Hardell et al. [100] did not explicitly analyze this histopathological subtype of tumor, but Inskip et al [143] found a decreased incidence of neuroepitheliomas.
Brain Cancer in Cell Phone Users |
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Relative risk of brain cancer (odds ratio with 95% confidence interval) in users of hand-held cell phones from the epidemiological study of Muscat et al [138]. The number of cases in the overall analysis, and the sub-analyses are shown in parentheses. The analysis is for a mix of analog (88%) and digital phones.
The lines highlighted in red are probably the ones most relevant to cancer risk assessment as they look at long-term heavy use. The line highlighted in blue refers to tumors in the lobe of the brain that should get the highest RF radiation exposure in users of hand-held phones. The last 3 rows look at different histological types of brain tumors. |
As soon as Muscat et al [138] was published, NEJM rushed a similar study onto their website that had been scheduled for publication in January of 2001. Inskip et al [143] studied 782 brain tumor patients in a different part of the US, some of whom had used hand-held mobile phones for as long as 5 years. They found no elevation of brain tumor incidence in users of hand-held phones, and observed no exposure-response trend (see figure below). The incidence of temporal lobe tumors (where RF radiation exposure should be the greatest in users of hand-held phones) was not elevated. There was a non-significant trend for tumors to be on the side of the head opposite to where the patients had reported using their phones. When Inskip et al [143] analyzed tumors by histopathological type, there was no significant excess of any types of malignant or benign brain tumors (see figure below).
Brain Cancer in Cell Phone Users |
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Relative risk of brain cancer (odds ratio with 95% confidence interval) in users of hand-held cell phones from the epidemiological study of Inskip et al [143]. The number of cases in the overall analysis, and the sub-analyses are shown in parentheses. The phones used were "primarily analog".
The lines highlighted in red are probably the ones most relevant to cancer risk assessment as they look at long-term heavy use. The line highlighted in blue refers to tumors in the lobe of the brain that should get the highest RF radiation exposure in users of hand-held phones. The last 3 rows look at different histological types of brain tumors. |
In early 2001, Johansen et al [155] published a retrospective cohort study of all types of cancer in Danish cell phone users, some of whom has used cell phones as long as 5 years. This included 154 brain cancer patients. Cell phone use was associated with a significantly decreased overall risk of cancer that was attributable largely to less smoking-related cancer. No increased risk of brain cancer, leukemia, lymphoma, ocular cancer or melanoma was found in cell phone users. No significant increase in any types of cancer were found in cell phone users. No exposure response trends in leukemia or brain cancer incidence were seen in cell phone users. There was no increase in temporal or occipital lobe tumors in cell phone users. See figure below.
In the accompanying editorial [155B] Park wrote:
"Regardless of how convincing the evidence exonerating cell phones may be, there will continue to be those who will argue that the issue has not been completely settled. In science, few things ever are. The scientific community has a responsibility to put all the evidence in to perspective for the public."
Cancer in Cell Phone Users |
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Relative risk of cancer (odds ratio with 95% confidence interval) in users of hand-held cell phones from the epidemiological study of Johansen et al [155]. The number of cases in the overall analysis, and the sub-analyses are shown in parentheses.
The line highlighted in red is probably the one most relevant to brain cancer risk assessment as it looks at long-term heavy use. The line highlighted in blue refers to tumors in the lobe of the brain that should get the highest RF radiation exposure in users of hand-held phones. The last 4 rows look at other types of cancer. |
In a study published in early 2000, Morgan and colleagues [118] studied all major causes of mortality (with emphasis on brain cancer, lymphoma and leukemia) in employees of Motorola, a manufacturer of wireless communication products. Based on job titles, workers were classified into high, moderate, low, and background RF exposure groups. For workers with moderate or high RF radiation exposure no elevation in rates of brain cancer, leukemia and lymphoma were found. Actual peak and/or average RF radiation exposure levels are not known.
In January 2001, Stang et al [152] reported that the use of "radio sets, mobile phones, or similar devices at [the] workplace for at least several hours per day" was associated with uveal (intraocular) melanoma. Of 118 individuals with intraocular melanoma, 6 (5.1%) reported that they were "probable or certain" to have "ever been exposed" to mobile phones at work. According to the authors, this occupational mobile phone use is 4 times higher than expected. Mobile phone use outside of work was not assessed, and other risk factors (for example, UV exposure and light skin color) were not assessed. In the only other comparable study, Johansen et al [155] found less melanoma and ocular cancer than expected in cell phone users. According to the accompanying editorial [153]:
Stang and colleagues raise that possibility that we should add a new type of cancer to those already under leading consideration as possible hazards of RF radiation, and it may well be that future studies will support their hypothesis. At this point , however, given the small size of the study, the relatively crude exposure assessment, the absence of attention to UVR exposure or other possible confounding variables, and limited support from the literature, a cautious interpretation of their results is indicated.
Summary of the epidemiology
The lack of associations between exposure to RF radiation and total cancer, and the lack of consistent associations between exposure to RF radiation and any specific type of cancer, suggests that RF radiation is unlikely to have a strong causal influence on cancer.
In a 1999 review of the RF epidemiology literature, Elwood [94] concluded that:
Several positive associations suggesting an increased risk of some types of cancer in those who may have had greater exposure to RF emissions have been reported. However, the results are inconsistent: there is no type of cancer that has been consistently associated with RF exposures. The epidemiologic evidence falls short of the strength and consistency of evidence that is required to come to a reasonable conclusion that RF emissions are a likely cause of one or more types of human cancer. The evidence is weak in regard to its inconsistency, the design of the studies, the lack of detail on actual exposures, and the limitations of the studies in their ability to deal with other likely relevant factors. In some studies there may be biases in the data uses.
In a 2000 review of the RF epidemiology literature, Rothman [139] concluded that:
Based on the epidemiological evidence available now, the main public health concern is clearly motor vehicle collisions, a behavioral effect rather than an effect of RF exposure as such. Neither the several studies of occupational exposure to RF nor the few of cellular telephone users offer any clear evidence of an association with brain tumors of other malignancies. Even if the studies in progress were to find large relative effects for brain cancer, the absolute increase in risk would probably be smaller than the risk stemming from motor vehicle collisions.
Possibly, but there is no replicated evidence for such effects. It has been suggested that amplitude-modulated (AM) RF radiation might have different effects than continuous-wave (CW, unmodulated) RF radiation (see for example Hyland [140]. This could be important, since mobile phones and their base stations produce a modulated signal, and much of the research has been done with unmodulated RF sources.
This issue had been reviewed in detail by Juutilainen and de Seze [90] who concluded that:
The literature relevant to the possible biological effects of AM radiofrequency radiation consists of scattered observations using a wide variety of experimental models and exposure parameters... Several studies have reported findings consistent with effects on the nervous system and cancer-related biological processes. However, the methods and exposure parameters vary widely, and no independent replications of the positive finds have been reported. The results available today fail to support the existence of well-defined modulation-specific bioeffects from exposure to radiofrequency radiation.
Possibly. Some groups in the general population might be more sensitive to the effects of RF radiation than others, but no such groups have actually been found. The possible existence of such sensitive individuals is one of the main reasons that an additional 5-fold safety margin is added to the public exposure guidelines (see Q9).
See the discussion of whether children should use hand-held mobile phones in Q15G
Although the public's principal health concern about mobile phone base station antennas appears to be the possibility of a cancer connection (see Q21 and Q23A-Q23C), other health-related issues come up periodically. Particularly common are questions about interference with heart pacemakers (covered in Q19A). This section will also cover less common issues. The possibility of a connection with miscarriages and birth defects is covered in Q22.
No. There is no evidence that mobile phone base station antennas will interfere with cardiac pacemakers or other implanted medical devices as long as exposure levels are kept within the ANSI guideline for uncontrolled exposure (see Q8 and Q12).
It is possible that digital mobile phones themselves might interfere with pacemakers if the antenna is placed directly over the pacemaker. This problem is reported to occur with only some types of digital phones and some types of pacemakers [46, 137].
It is possible that use of cell phones causes headaches.
In 1998, Frey [48] reported anecdotal evidence that cell phones cause headaches.
In 2000, Oftedal et al [154] found that users of cell phones commonly report having headaches, but since the study contains no data on non-users it is not known whether the rate of headaches reported by these cell phone users is unusual. An extension of the study by Sandström et al [162] reported that headaches and other symptoms were higher in users of analog (NMT 900) phones than users of digital (GSM) phones.
In 2000, Chia et al [142] reported that headaches were significantly more common among users of hand-held cell phones than among non-users (65% vs 54%). Headache prevalence increase significantly with duration of use, and the use of hand-free equipment eliminated the increase.
No one has claimed that there is scientific evidence that base stations cause headaches, and there are no biophysical or physiological bases for expecting such an effect.
There are unreplicated reports of such effects. There are some studies that suggest that RF radiation from hand-held mobile phones might cause subtle physiological or behavioral changes. However, none of the studies provides substantial evidence that mobile phone base stations might pose a health hazard:
- Braune et al [82] reported that human volunteers using a GSM cell phone for 35 minutes showed a 5-10 mm Hg rise in blood pressure. The study is small and was not blinded, and a rise in blood pressure of this magnitude has no known health consequences.
- Eulitz et al [84] reported that cell phones can alter the electrical activity of the brain. However, the effect may be an artifact caused by RF interference with the EEG leads.
- Freude et al [111] exposed human volunteers to RF from a 916 Mhz 350 mW GSM digital phone. Small changes in EEG were seen that "did not indicate any influence on human performance, well-being and health"
- In 1996 Mann and Röschke [113] reported that exposure to a mobile phone signal at 0.05 mW/cm-sq could cause slight changes in sleep patterns; but subsequent studies by the same group found no significant effect when the power density was lowered to 0.02 mW/cm-sq [115], and no effect at all when the power density was increased to 5 mW/cm-sq [159].
- In 1999, Borbély, Huber and colleagues [110, 141] reported that exposure to a mobile phone signal at 1 W/kg could cause slight changes in sleep patterns and sleeping EEG.
- De Seze et al [113] reported that exposure of human volunteers to cell phone RF had no effect on night-time secretion of melatonin. Effects on melatonin have been suggested as a mechanism by which power line fields might affect human health (see note 4).
- Wang and Lai [109] reported that rats exposed to 2450 MHz pulsed radio-frequency radiation showed "defects in long-term memory". The RF-exposed animals were slower than normal animals to learn a maze. Animals received whole-body RF exposure for 1 hr/day. The average SAR was 1.2 W/kg with peaks of 3-4 W/kg. The signal is quite different from that associated with a mobile phone base station and the peak SAR may have been high enough to cause thermal stress. The exposure intensity (SAR) was 15 times higher than the FCC standard for whole-body exposure of the general public. In 2000 Sienkiewicz et al [120] performed a similar experiment in mice (but using a signal and a power-density simulating a European digital cell phone base station signal) and found no effects on maze performance.
- In 1999, Preece et al [97] reported that exposure of human volunteers to cell phone RF radiation might decrease reaction times. The press coverage was extensive; but the actual study has no obvious implications for human health, since the effect was seen for just one of many tests of cognitive function and it appears to be far too small to have any real functional significance.
- In 2000, Koivisto et al [117, 132] reported studies of human volunteers who were exposed to 902 MHz RF from a 250 mW digital (GSM) phone and given a battery of reaction time tests. For some tests, exposure reduced (improved) the time required, other tests showed less significant time improvements. Some tests showed no significant effects. For the test in which Preece et al [97] found an effect for the analog signal, Koivisto et al [117] found no effect for a digital signal. The tests showing effects are stated to be tests of cognitive function. In further studies in 2001, Koivisto et al [160] found that a 30-60 minute exposure to RF radiation from GSM phones had no detectable subjective effects on human volunteers.
- In 2000, Krause et al [146] reported a study of human volunteers who were exposed to 902 MHz RF from a 250 mW digital (GSM) phone and given memory and reaction time tests. Effects on error rate and reaction time were not significant. Some effects on EEG were observed under some test conditions. According to the authors: "The present results do not allow any conclusions concerning the possible effects of cellular phone use on cognition".
- In 2000 Tsurita et al [133] reported that RF radiation had no effect on the blood-brain barrier in rats. These rats were exposed to a 1339 MHz digital (TDMA) signal for one hour per day for 2-4 weeks. The average whole body SAR was 0.25 W/kg and the brain SAR was 2 W/kg, and no changes in body temperature were observed. No effects were observed on body weight, brain morphology or blood-brain barrier permeability. The Tsurita et al [133] paper includes a detailed discussion of previous studies of RF effects on the blood-brain barrier.
- In 2000, Bornhausen and Scheingraber [145] reported that exposure of pregnant rats to RF radiation has no effect on the behavior of their off-spring. Free-roaming pregnant rats were continuously exposed to 900 MHz GSM RF at 0.1 mW/cm-sq (SARs ranged from 17.7-75 mW/kg). No cognitive deficits were found in their offspring.
For a review of the behavioral effects of RF radiation see D'Andrea [96].
Yes. If exposure is sufficiently intense, RF radiation can cause biological effects. Possible injuries include cataracts, skin burns, deep burns, heat exhaustion and heat stroke. Most, if not all, of the known biological effects from exposure to high-power radiofrequency sources are due to heating [20]. The effects of this heating range from behavioral changes to eye damage (cataracts) [see refs in 1, 5, 6, 7 14, 53, 83, 90, 99 and 99]. Except possibly within a few feet of the antennas themselves [128], the power produced by mobile phone base station antennas is too low to cause heating.
There have been scattered reports of effects [21] that do not appear to be due to heating, the so called non-thermal effects [20, 25, 158]. None of these effects have been independently replicated, and none have any obvious connections to human health risks.
The lack of biological effects from exposures to radio-frequency radiation that do not produce biologically significant temperature changes is not surprising, as there are no known biophysical mechanisms that would suggest that such effects were likely [25, 124, 158, 165 ].
In a 2001 review, Pickard and Moros [158] conclude that:
"The prospects of UHF (300-3000 MHz) irradiation producing a nonthermal bioeffect are considered theoretically and found to be small... This supports previous arguments for the improbability of biological effects at UHF frequencies unless a mechanism can be found for accumulating energy over time and space and focusing it. Three possible mechanisms are then considered and shown to be unlikely... Finally, it is concluded that the rate of energy deposition from a typical fields and within a typical tissue is so small as to make unlikely any significant nonthermal biological effect."
No. Even at high levels of exposure, there is no substantial evidence that RF radiation can either cause or contribute to cancer (for an opinion to the contrary see the reports discussed in Q15B and Q15C). Although research in this area has been extensive, there is no replicated laboratory or epidemiological evidence that RF radiation at the power levels associated with public exposure to RF radiation from mobile phone base station antennas are associated with cancer [see refs in 1, 5, 6, 7, 14, 74, 83, 95, 99 and 128 for details].
There are two laboratory reports that exposure to RF radiation might produce cancer, or cancer-related injuries in animals. These studies are discussed in Q23A and Q23C. Both studies use RF levels far above those found in publicly-accessible area near base station antennas, and neither study has been replicated.
The epidemiological studies of RF show no consistent association with total cancer, or with any specific type of cancer (see Q16).
Indirectly, yes. Exposure to levels of RF radiation sufficient to cause whole body heating can cause miscarriages or birth defects. The power produced by mobile phone base station antennas is far too low to cause such heating. There is no laboratory or epidemiological evidence at all that RF radiation at the power levels associated with public exposure to RF radiation from mobile phone base station antennas are associated with miscarriages or birth defects [see refs in 1, 5, 6, 7 and 14 for details].
There is a constant flow of new information. Studies which attract major attention will often get their own sections, such as the mouse and rat cancer studies discussed in Q23A and Q23B, and the DNA strand break studies discussed in Q23C.
A 1997 Australian study by Repacholi et al [37] reported that lymphoma-prone mice exposed for 18 months to strong, but intermittent, RF radiation of the type used by digital cellular phones have an increased incidence of lymphomas. No increases in the incidence of other types of tumors were found. The field intensities used are above the guidelines for public exposure recommended in the ANSI/IEEE guideline (Q8), and are far above those that exist in publicly-accessible areas near mobile phone base station antennas [16].
While this study is interesting, its impact on regulation of RF exposure of the general public is quite unclear, as it cannot be determined from the study whether lymphomas can be induced in normal (as opposed to cancer-prone) animals by exposure to RF radiation, or what level of RF radiation exposure level is required for induction of lymphoma in cancer-prone mice.
Clearly the study will need to be repeated with both normal and lymphoma-prone mice. If the effect can be replicated, it will be critical to determine the dose-response relationship for lymphoma induction, and to determine whether the effect occurs for other tumors and/or in other species.
Several questions have been repeatedly asked about this study:
No. Before this study can be related to human risk assessment it must be replicated, a similar study must be done with normal mice, and the exposure-response relationship for the effect must be known.
When you want to know whether something might cause cancer, you usually start with a sensitive strain of animals and a high dose of the agent. This maximizes your chance of finding something. If you find nothing under these circumstances, then you can be fairly confident that the agent does not cause this cancer. If you do find excess cancer, you then need to determine whether this will also happen in normal animals and/or at more reasonable doses. If you first do normal animals at low doses, and you find no excess cancer, you still would need to test cancer-prone animals at high doses.
An additional problem with using normal mice and low doses of RF to study induction of lymphoma, is that lymphoma is rare in normal mice (1-3% lifetime incidence). To detect a 50% increase in this normal rate would require over 2000 mice.
There are at least 15 other studies of long-term exposure of rodents to radiofrequency radiation. None of these studies used lymphoma-prone mice and none have reported excess lymphoma. See Q23B for details.
A difference in tumor induction between normal animals and animals that have been genetically-altered to make them cancer prone is not unexpected, as other studies (for example, Johnson [112]) have shown that the genetically-altered animals often show different responses than normal animals in carcinogen screening tests.
It is not easy to expose animals to uniform levels of RF radiation. If animals are unrestrained in cages, the RF dose (the SAR [8]) varies with the position of the animal, with the animals's orientation to the antenna, with the presence of other animals, and with the animal's size. To get well-defined RF radiation exposure, the animals must be confined in small holders, and the daily handling and confinement this requires can produce biological effects all by itself (see Stagg et al [161]). Even under these conditions, the SAR may change as the animals increase in size. Basically, the experimenter has a choice: treat free-running animals with minimal disturbance, and accept uncertain dosimetry; or get good dosimetry, and risk artifacts due to handling and confinement. Either choice is open to criticism.
There are at least 15 other studies of long-term exposure to rodents to radio-frequency radiation.
- In 1971, Spalding el al [64] published a study of mice that had been exposed to 800-MHz RF for 2 hr/day, 5 days/week, for 35 weeks at a SAR of 13 W/kg. The average life span of the RF-exposed group (664 days) was slightly, but not significantly, longer than that of the sham-exposed group (645 days).
- In 1982 Szmigielski et al [65] published a study of mice that were exposed to 2450-MHz RF for 2 hr/day, 6 days/wk, for up to 6 months. Exposures were at 2-3 and 6-8 W/kg. Controls included both sham-irradiated animals and animals subject to "confinement stress" (see Stagg et al [161]). Both RF exposure and confinement stress significantly accelerated the appearance of both chemically-induced skin tumors and chemically-induced breast tumors. The dosimetry in this study is questionable, and seems likely that the mice exposed at the higher dose were subjected to physiologically-significant heating.
- In 1988 Saunders et al [98] published a study of male mice that were exposed to 2450-MHz RF radiation (power density of 10 mW /cm-sq and SAR of 4 W/kg) for 6 h per day for a total of 120 h over an 8-week period. At the end of the treatment the mice were mated with unexposed females. There was no significant reduction in pregnancy rate, so that there had been no increase in dominant lethal mutations. Examination of spermatogonia showed no increase in chromosome aberrations. The authors conclude that "there is no evidence in this experiment to show that chronic exposure of male mice to 2450-MHz microwave radiation induces a mutagenic response".
- In 1994 Liddle et al [66] published a study that examined the effects of life-time 2450-MHz RF exposure in mice. Mice were exposed for 1 hr/day, 5 days/week throughout their life at either 2 or 6.8 W/kg. Life span was significantly shortened in mice exposed at 6.8 W/kg (median of 572 days vs 706 days in the sham-exposed group). However, at 2 W/kg, the RF-exposed animals lived slightly, but not significantly longer (median of 738 days) than the sham-exposed group. The authors suggested that the heating from exposure at 6.8 W/kg was stressful enough to decrease life span.
- In 1992, Chou et al [43] published a study of 100 normal rats that were exposed to pulsed 2450 MHz RF at 0.15-0.40 W/kg [8] for 21.5 hrs/day and 25 months. No effects were observed on life-span or cause of death. An increase in total cancer was seen in exposed group, with no effect on survival. The malignancy rates in the controls was unusually low for this strain, and no increase in benign tumors were observed. Two primary lymphomas were seen in the exposed animals, and two in the controls. No benign or malignant brain tumors were seen in either exposed or control rats.
The authors concluded:
Microwave exposure... showed no biologically significant effects on general health... The findings of an excess of primary malignancies in exposed animals is provocative. However, when this single finding is considered in light of other parameters, it is conjectural whether the statistical difference reflects a true biological influence. The overall results indicate that there are no definitive, biologically significant effects...
- In 1994, Wu et al [56] published a report on 26 mice that were exposed to a chemical carcinogen plus 2450 MHz RF at 10 mW/cm-sq (10-12 W/kg). Exposure continued for 3 hrs/day, 6 days/week for 5 months. The chemical carcinogen is one that causes colon cancer. No difference in colon cancer rates were seen between animals treated with the carcinogen alone and the animals treated with the carcinogen plus RF.
- In 1997, Toler el [45] published a report on 200 mammary-tumor-prone mice exposed to pulsed 435 MHz RF at 1.0 mW/cm-sq (0.32 W/kg). Exposure continued for 22 hrs/day, 7 days/week for 21 months. The authors reported no differences in survival or mammary tumor incidence. The authors reported that there was no difference in the rates of any types of tumors between the exposed and the control group. Of particular note, there was no difference in the lymphoma, leukemia or brain tumor rate between the exposed and the control group.
- In 1998, Frie et al [44] published a report on 100 mammary-tumor prone mice that were exposed to 2450 MHz RF at a SAR of 0.3 W/kg. Exposure was for 20 hrs/day, 7 days/week for 18 months. The study found no difference in tumor incidence or survival between the exposed and the control group.
- Later in 1998, Frie et al [47] published a second study using the same mouse model and the same exposure regimen, but a higher SAR of 1.0 W/kg. Again, the study found no difference in tumor incidence or survival between the exposed and the control group. There were no differences in lymphoma, leukemia or brain tumor incidence between the exposed and the control group in either study.
- In 1998 Imaida et al [63a] published a report on 48 rats that were given a chemical carcinogen that cause liver cancer, and were then exposed to 929 MHz RF an a SAR of 0.6-0.9 W/kg. Exposure was for 90 min/day, 5 days/week for 6 weeks. No difference in liver cancer rates were seen between RF-exposed rats and rats given only the chemical carcinogen.
- In a second 1998 paper, Imaida et al [63b] reported a similar lack of liver cancer promotion in rats exposed to 1500 MHz RF at a SAR of 2.0 W/kg. Again, exposure was for 90 min/day, 5 days/week for 6 weeks.
- In 1998 Adey et al [24] reported that exposure to pulse-modulated 837 MHz RF did not induce or promote brain tumors in rats. RF exposure started with continuous whole-body far-field exposure of pregnant rats and continued through weaning. At 7 weeks of age, localized near-field exposure of the head was begun, and this exposure continued for 22 months (2 hrs/day, 7.5 min on - 7.5 min off, 4 days/week). Some rats were also treated with a chemical brain tumor carcinogen (ethylnitrosourea, ENU). Brain SARs ranged from 0.7 to 1.6 W/kg, and whole-body SAR ranged from 0.2 to 0.7 W/kg; the range of SARs was due to changes in weight and variability in animal positioning. The number of brain tumors was less in the RF-exposed groups than in the sham-exposed groups, but the difference was not statistically significant. This non-significant decrease was seen in both rats treated with RF alone, and in rats treated with RF plus the chemical brain tumor carcinogen.
- In 2000, Adey et al [50] reported that exposure to continuous wave 837 MHz RF did not induce or promote brain tumors in rats. Other than the difference in modulation, the 2000 study used the same design and exposure protocol as the 1999 study.
- In 1999, Chagnaud et al [106] reported that exposure of rats to a GSM signal did not promote chemically-induced breast cancer. At various times after exposure to a chemical carcinogen, rats were exposed for 2 weeks at 2 hours per days to a 900-MHz GSM signal at 0.075 or 0.27 W/kg. No effects on tumor incidence, tumor growth or animal survival were observed.
- Also in 1999, Higashikubo et al [107] reported that exposure of rats that had brain tumors to radio-frequency radiation had no effect on the growth of these brain tumors. Rats were exposed to either 835 MHz continuous wave RF radiation or 848 MHz pulsed RF radiation at SARs of 0.75 W/kg. Exposure was for 4 hrs/day, 5 days per week, starting 28 days prior to tumor implantation and continuing for 150 days after tumor implantation.
- In 2001, Zook and Simmens [104] reported the absence of an effect on brain tumor incidence in rats exposed to continuous-wave or pulsed 860-MHz radio-frequency radiation at 1.0 W/kg. Exposure was for 6 hrs/day, 5 days/week for 22 months, starting when the rats were 2 months old. Zook and Simmens also reported that the same RF protocols did not promote chemically induced brain cancer. No statistically-significant RF-related increases in overall cancer or any specific types of cancer (including lymphoma) were found.
- Also in 2001, Jauchem et al [156] reported that there were no significant effects on mammary tumor development or animal survival in mammary tumor-prone mice exposed to pulses composed of an ultra-wideband (UWB) of frequencies, including those in the RF range. Histopathological evaluations revealed no significant effect on the numbers of neoplasms in any tissue studied (including lymphomas).
Thus it would appear that induction of lymphoma, and tumors in general, by life-time exposure of rodents to RF is not a general phenomena.
Agents that can damage the DNA of cells are presumed to have carcinogenic potential [4]. Agents that can damage DNA are called genotoxins, or are referred to as having genotoxic activity. In general, studies of cells exposed to RF have not found evidence for genotoxicity unless the SAR was high enough to cause thermal (heat) injury [5, 6, 7, 14].
In 1995 and 1996, Lai and Singh [31] reported that RF caused DNA damage (genotoxic injury) in rats. In these experiments, rats were exposed to 2450 MHz RF at 0.6 and 1.2 W/kg. After exposure, the animals were killed, and their brain cells were analyzed for DNA injury. The authors reported an increase in DNA stand breaks 4 hours after exposure.
The work of Lai and Singh [31] has failed independent attempts at replication. In 1997, Malyapa et al [49a, 49b] reported that they could not detect the effect seen by Lai and Singh, but there were some differences between the studies. In 1998, Malyapa et al [49c] reported that they could not detect the effect in an exact replicate of the Lai and Singh [31] study.
Other recently published studies on the genotoxic potential of RF have reported no evidence for genotoxicity (damage to DNA):
In contrast, other 1996-1998 studies found some evidence for RF exposure might be genotoxic:
Two reviews of the genotoxic potential of RF were published in 1998.
Verschaeve and Maes [80] concluded that:
"According to a great majority of papers, RF fields, and mobile telephone frequencies in particular, are not genotoxic: they do not induce genetic effects in vitro [in cell culture] and in vivo [in animals], at least under non-thermal conditions [conditions that do not cause heating], and do not seem to be teratogenic [cause birth defects] or to induce cancer."Brusick et al [81] concluded that:
"The data from over 100 studies suggest that RF radiation is not directly mutagenic and that adverse effects from exposure of organisms to high power intensities of RF radiation are predominantly the result of hyperthermia [heating]; however, there may be some subtle indirect effects on the replication and/or transcription of genes under relatively restricted exposure conditions."
The documentation of the various radiofrequency standards [5, 6, 7 and 14] contain extensive references. Reasonably up-to-date reviews of this area include:
This FAQ sheet was written by Dr. John Moulder, Professor of Radiation Oncology, Radiology and Pharmacology/Toxicology at the Medical College of Wisconsin. Dr. Moulder has taught, lectured and written on the biological effects of non-ionizing radiation and electromagnetic fields since the late 1970's.
The original version of this FAQ was written in 1995 under a contract with the City of Brookfield, Wisconsin. The FAQ has been maintained and expanded since 1995 as a teaching aid at the Medical College of Wisconsin. The web server and web management is provided by the General Clinical Research Center at the Medical College of Wisconsin. The development and maintenance of this document is not supported by any person, agency, group or corporation outside the Medical College of Wisconsin.
Parts of this FAQ are derived from the following peer-reviewed publications:
1. International Commission on Non-Ionizing Radiation Protection: Health issues related to the use of hand-held radiotelephones and base transmitters. Health Physics 70:587-593, 1996.
2. PCS (Personal Communication Systems) phones are hand-held two-way radios that use a digital, rather than the analog transmission system used by most "cell phones". In the U.S., most of the older cellular phones operate at 860-900 MHz, while PCS phones operate at 1800-2200 MHz. In appearance, cellular and PCS phones and their base station antennas are similar. In the U.S., "cordless" phones operate at frequencies ranging from 45 to 2500? MHz, and "citizens band (CB)" two-way radios operate at about 27 MHz. Some cordless phones operate at power levels that equal or exceed some cellular phones.
International note: Around the world a variety of other frequencies are used for both analog and digital hand-held transceivers and mobile radios, and other names are given to the systems (see Table 1 in Stuchly [83] for details). The most common frequencies for "cellular" systems are 800-900 MHz (analog and digital) and 1800-2200 MHz (digital); but hand-held transceivers exist that use frequencies from as low as 45 MHz to as high as 2500 MHz. Power output from hand-held units seldom exceeds 2 W, but power output from vehicle-mounted units such as those used by law enforcement personnel can be as high as 100 W.
Canada: Analog and digital phones operate around 800-900 MHz, and there is a new 2000 MHz digital system (similar or identical to PCS service in the US).
Australia: The analog AMPS phones operate around 800-900 MH\z and the digital GSM phones operate around 900-1000 MHz.
Europe: Analog systems at about 900 MHz; digital (GSM) systems at around both 900 and 1800 MHz.
3. The specific frequencies used by mobile (cellular) phones can be called either microwaves (MW) or radiofrequencies (RF) or radiofrequency radiation (RFR) or radiowaves. For the discussion of health effects the distinction between radiowaves and microwaves is semantic, and the term radiowaves (or radiofrequency or RF or RFR) is used in this document for all frequencies between 3 kHz and 300 GHz.
4. For a detailed discussion see:
- JE Moulder and KR Foster: Biological effects of power-frequency fields as they relate to carcinogenesis. Proc Soc Exper Biol Med 209:309-324, 1995;
- JE Moulder: Power-frequency fields and cancer. Crit Rev Biomed Engineering 26:1-116, 1998.
5. IEEE Standards Coordinating Committee 28 on Non-Ionizing Radiation Hazards: Standard for safety levels with respect to human exposure to radio frequency electromagnetic fields, 3 kHz to 300 GHz (ANSI/IEEE C95.1-1991), The Institute of Electrical and Electronics Engineers, New York, 1992.
6. International Commission on Non-Ionizing Radiation Protection: Guidelines for limiting exposure to time-varying electric, magnetic and electromagnetic fields. Health Physics 74:494-522, 1998.
7. National Council on Radiation Protection and Measurements: Biological effects and exposure criteria for radiofrequency electromagnetic fields. NCRP Report No. 86, 1986.
8. The biological effects of RF radiation depend on the rate at which power is absorbed. This rate of energy absorption is called the Specific Absorption Rate (SAR) and is measured in watts/kilogram (W/kg). SARs are difficult to measure on a routine basis, so what is usually measured is the plane wave power density. Average whole body SARs can then be calculated from the power density exposure (see Stuchly [83] for details).
Note that some documents express power density as µW/cm-sq (microwatts/cm-sq), where 1000 µW/cm-sq (1000 microwatts/cm-sq) equals 1 mW/cm-sq.
9. The power density guidelines are stricter for some frequencies than for others because humans absorb RF radiation more at 860 MHz than at 1800 MHz, and it is the amount of power absorbed that really matters [8].
10. Specifically, the ICNIRP standard is 0.40 mW/cm-sq at 800 MHz and 0.90 mW/cm-sq at 2000 MHz, while the NCRP guidelines are 0.57 mW/cm-sq and 1.00 mW/cm-sq for these same frequencies.
11. Guidelines for Evaluating the Environmental Effects of Radiofrequency Radiation (FCC 96-326), Federal Communications Commission, Washington, D.C., 1996. Available from the FCC web page.
12. International note -- Standards for public exposure to RF radiation from mobile phone base station antennas in countries other than the U.S. This list is not comprehensive or necessarily up-to-date; the information should be checked with the appropriate regulatory authorities in each country. Also see Erdreich and Klauenberg [164].
Australian standard:
The Australian situation is rather complex. Until 1998, RF exposure in Australia was regulated by "AS2772.1-1990 Radiofrequency radiation, Part 1: Maximum exposure levels-100 kHz to 300 GHz including Amendment No. 1/1994" from the Standards Association of Australia.
In that standard the allowable general public exposure limit for the frequencies used by mobile phone services was 0.2 mW/cm-sq; this was a factor of 2 - 6 lower than the FCC, ANSI/IEEE, ICNIRP and NCRP standards.
This standard was revised in 1998 on an interim basis, and the allowable general public exposure limits in the new "interim" standard [AS/NZS2772.1(Int):1998] appeared to similar to the ICNIRP standard [6] except at higher frequencies where the lower limits of the 1990 Standard were retained. This interim standard was effective until 5-March-99, when it was to have been "confirmed, withdrawn or revised". The committee responsible for the standard was unable to achieve the required level of consensus to confirm or revise the interim standard and it was subsequently withdrawn.
When the AS/NZS2772.1(Int):1998 lapsed, the Australian Communications Authority (ACA) stepped in and adopted its own radiocommunications RF standard. The ACA standard appears to be largely identical to AS/NZS2772.1(Int):1998, except that it applies only to RF radiation used for communications.
New Zealand standard:
In 1998 the Australian and New Zealand standards were merged as an "interim" standard [AS/NZS2772.1(Int):1998]. The same confusion that applied to the Australian standard occurred in New Zealand. However, unlike Australia, New Zealand has adopted a final standard, "NZS 2772.1:1999 Radiofrequency fields - Part 1: Maximum exposure levels - 3 kHz to 300 GHz", that aligns fully with the ICNIRP Guidelines [6] and does not contain the reduced exposure levels at higher frequencies that were part of the earlier standards.
Canadian standard: [Health Canada: Limits of exposure to radiofrequency fields at frequencies from 10 kHz - 300 GHz Safety Code 6, Canada Communication Group, Ottawa, Canada, (1993)] At the frequencies of relevance to base stations the Canadian standard appears to be identical to the FCC standard.
UK standard: In mid-2000 the UK stopped using its own standard for mobile phones and mobile phone base stations [14] and adopted the ICNIRP standard [10].
Greek standard [Measures for protection of the public from operation of land-installed antennas. Athens, Hellenic Republic, 2000]: The standard is essentially identical to ICNIRP [6] standard.
Swiss standard [Regulation about Protection against Nonionizing Radiation. Swiss Federal Council, 1999]:
For wireless communication transmitters above 6 W (ERP) the standard is 4.0 V/m (0.0042 mW/cm-sq) at 900 MHz and 6.0 V/m (0.0095 mW/cm-sq) at 1800 Mz. For broadcast radio (and TV?) the standard is 3.0-8.5 V/m (0.0024-0.019 mW/cm-sq).
Italian standard:
Ministero Dell'Ambientem, Decreto 10 Settembre 1998, n. 381, Regolamento recante norme per la determinazione dei tetti di radiofrequenza compatibili con la salute umana.
At mobile phone frequencies the standard appears to be 0.10 mW/cm-sq. For situations where exposure is expected to exceed 4 hours/day, the limit appears are further reduced to 0.010 mW/cm-sq. Local regional administrations appear to have the authority to further reduce these limits, and several regions appear to have limits 4 times lower (0.0025 mW/cm-sq).
13. Where there are multiple transmitting antennas at different frequencies, the method for assuring adherence to the ANSI [5] or FCC [11] standards is complex. However, there is also an easy way to check adherence under these conditions: add the power densities of all the antennas and apply the strictest power density standard. Anything which passes this easy check will pass the more stringent and complex test. Something that fails this easy check must be analyzed by the more stringent and complex method described in the ANSI standard.
14. National Radiation Protection Board: Restrictions on human exposure to static and time varying electromagnetic fields and radiation. Doc NRPB 4:1-69, 1993.
15. The 1992 ANSI standard [5], for example, is based on the review of 321 papers from the peer-reviewed literature; and the NCRP guidelines [7] are based on a review of nearly 1000 reports.
16. Specifically, no potentially-hazardous effects have been consistently shown below a SAR of 4 W/kg.
- At mobile phone frequencies it would require a power density of 20-100 mW/cm-sq to achieve a SAR as high as 4 W/kg.
- Under worst-case assumptions (multiple low-gain, high-ERP antennas), the SAR of a human in publicly-accessible locations near a FCC-compliant base station would be less than 0.01 W/kg.
- Under realistic conditions the SAR to a human near such a base station would be less than 0.0005 W/kg.
17. ANSI, ICNIRP and NCRP all agree that whole body exposure of the general public should be kept below a whole body SAR of 0.08 W/kg. Where the standards disagree is about the specific relationship of SAR to power-density, a relationship that is determined from a combination of dosimetry and biophysical modeling.
International note: As a result of differences between approaches and frequencies used, world-wide standards for the continuous exposure of the public to RF from base station antennas ranges from 0.20 to 1.20 mW/cm-sq.
18. For the high-gain sector antennas used by most newer base stations, the area of concern is only at the front of the antennas. For the low-gain antennas used in many older base stations, the area of concern would be in all directions. This differences becomes clearer after an examination of the RF patterns from each type of antenna (see Q14D). Unfortunately, the RF radiation pattern from an antenna cannot always be determined from looking at it.
These general statements about minimum safe distances assume that total ERPs per sector for base station antennas will not exceed 2000 W. In the U.S., this is generally the case; and under the U.S. FCC guidelines, sites with total ERPs above 2000 W will require specific site evaluations [see note 19].
International note: More powerful antennas may be used elsewhere, in which case the minimum safe distances would be larger. Minimum safe distances will also be larger when there are multiple antennas broadcasting in the same sector.
19. Specifically, the FCC will require evaluations for:
International note: Strictly speaking, these criteria only apply in the U.S. Nevertheless, they are useful criteria for determining what types of antenna sites are most likely to violate RF standards.
20. One distinction that is often made in discussions of the biological effects of RF radiation is between "nonthermal" and "thermal" effects. This refers to the mechanism for the effect: non-thermal effects are a result of a direct interaction between the RF radiation and the organism, and thermal effects are a result of heating. There are some reported biological effects of RF radiation whose mechanisms are unknown, and it is difficult (and not very useful) to try to draw a distinction between "thermal" and "nonthermal" mechanisms for such effects. Also see Valberg [25], Foster [124] and Pickard and Moros [158].
21. These effects have included changes in the electrical activity of the brain, changes in enzyme activity, and changes in calcium ion transport across membranes [for details see 1, 5, 6, 7 and 14]. Also see Hyland [140].
23. The increased human absorption at 900 MHz (U.S. cell phone frequency) versus 2000 MHz (U.S. PCS phone frequency) applies to whole body exposure at a distance from the antenna (the case for public exposure near a base station antenna site). This difference may not apply to partial body exposures in very close proximity to an antenna.
24. WR Adey, CV Byus et al: Spontaneous and nitrosourea-induced primary tumors of the central nervous system in Fischer 344 rats chronically exposed to 836 MHz modulated microwaves. Radiat Res 152:293-302, 1999.
25. PA Valberg: Radio frequency radiation (RFR): the nature of exposure and carcinogenic potential. Cancer Causes Control 8:323-332, 1997.
26. Human Exposure to Radio Frequency and Microwave Radiation from Portable and Mobile Telephones and Other Wireless Communication Devices, A COMAR Technical Information Statement. IEEE Eng Med Biol, Jan/Feb 2001, pp 128-131. Online at:
http://www.seas.upenn.edu:8080/~kfoster/phone.htm
27.Safety Issues Associated With Base Stations Used for Personal Wireless Communications, A COMAR Technical Information Statement. IEEE Eng Med Biol, Mar/Apr 2001, pp 110-114. Online at:
http://www.seas.upenn.edu:8080/~kfoster/base.htm
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29B. JR Goldsmith: Epidemiologic evidence relevant to radar (microwave) effects. Environ Health Perspec 105:1579-1587, 1997.
30. A discussion of the problems with interpreting ecological epidemiology studies is beyond the scope of document. For discussion of this issue see:
- S Piantadosi et al: The ecological fallacy. Am J Epidem. 127(5):893-904, 1988.
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31a. H Lai and NP Singh: Acute low-intensity microwave exposure increases DNA single-strand breaks in rat brain cells. Bioelectromag 16:207-210, 1995
31b. H Lai and NP Singh: Single- and double-strand DNA breaks in rat brain cells after acute exposure to radiofrequency electromagnetic radiation. Int J Rad Biol 69:513-521, 1996.
32. A Maes et al: 954 MHz microwaves enhance the mutagenic properties of mitomycin C. Environ Molec Mutagen 28:26-30, 1996.
33. JK Grayson: Radiation exposure, socioeconomic status, and brain tumor risk in US Air Force: A nested case-control study. Amer J Epidem 143:480-486, 1996.
34. H Dolk et al: Cancer incidence near radio and television transmitters in Great Britain I. Sutton Coldfield Transmitter. Amer J Epidem 145:1-9, 1997.
35. H Dolk et al: Cancer incidence near radio and television transmitters in Great Britain. II. All high power transmitters. Amer J Epidem 145:10-17, 1997.
36. MR Scarfi et al: Genotoxic effects of mitomycin-C and microwave radiation on bovine lymphocytes. Electro Magnetobio 15:99-107, 1996.
37. MH Repacholi et al: Lymphomas in Eµ-Pim1 Transgenic Mice Exposed to Pulsed 900 MHz Electromagnetic Fields. Rad Res 147:631-640, 1997.
41a. Vijayalaxmi et al: Frequency of micronuclei in the peripheral blood and bone marrow of cancer-prone mice chronically exposed to 2450 MHz radiofrequency radiation. Rad Res 147:495-500, 1997.
41b. Vijayalaxmi et al: Proliferation and cytogenetic studies in human blood lymphocytes exposed in vitro to 2450 MHz radiofrequency radiation. Int J Rad Biol 72:751-757, 1997.
42. CD Cain et al: Focus formation of C3H/10T1/2 cells and exposure to a 836.55 MHz modulated radiofrequency field. Bioelectromag 18:237-243, 1997.
43. CK Chou et al: Long-term, low-level microwave irradiation of rats. Bioelectromag 13:469-496, 1992.
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46. DL Hayes et al: Interference with cardiac pacemakers by cellular telephones. New Eng J Med 336:1473-1479, 1997.
47. MR Frei et al: Chronic low-level (1.0 W/Kg) exposure of mammary cancer-prone mice to 2450 MHz microwaves. Rad Res 150:568-576, 1998.
48. AH Frey: Commentary: Headaches from cellular telephones: Are they real and what are the implications? Environ Health Perspec 106:101-103, 1998.
49a. RS Malyapa et al: Measurement of DNA damage following exposure to 2450 MHz electromagnetic radiation. Rad Res 148:608-617, 1997.
49b. RS Malyapa et al: Measurement of DNA damage following exposure to electromagnetic radiation in the cellular communications frequency band (835.62 and 847.74 MHz). Rad Res 148:618-627, 1997.
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51. T Shirai et al: Lack of promoting effects of the electromagnetic near-field used for cellular phones (929 MHz) on rat liver carcinogenesis in medium-term bioassay. 2nd World Congress, Bologna, 1997.
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54. Measurements show that signal strength in a building is anywhere from 5% to 40% of the level measured in the street outside. In general, signal attenuation is greater at ground level than higher up in the building, and attenuation is less at higher (1800-2000 MHz) frequencies than at lower (800-900 MHz) frequencies (JD Parsons, The Mobile Phone Propagation Channel, Wiley and Sons, NY, 1992).
55. A worst-case calculation (2000 W ERP low-gain antenna mounted directly on a low-attenuation roof) predicts a power density of less than 0.10 mW/cm-sq on the floor below. A calculation for a more typical roof-top mount (1000 W ERP high-gain antenna, mounted 2 meters above a typical roof) predicts a power density of less than 0.001 mW/cm-sq on the floor below.
Actual measurements in the top floor apartments of a building with high-gain sector base stations antennas mounted to the outside of the parapet just above the apartments found a maximum power density of 0.0004 mW/cm-sq [101]. Measurements in a corridor in the floor directly below a roof-top base station (antennas 3 meters above the main roof) found a maximum power density of 0.008 mW/cm-sq. Both maximums assume that the base stations are operating at their maximum capacity [101].
In 2000, NRPB (UK) [130] made measurements in multiple apartment buildings and schools that had a wide variety of mobile phone base station antennas on their roofs. On the top floor of these buildings the maximum RF power density from all sources combined was 0.0001 mW/cm-sq.
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