What
do recent reports from scientific meetings and journals say?
What
about the report that exposure of mice to cell phone radiation causes
damage to the DNA in their brain cells?Revisionsv2.6.3, Oct-2000:
v2.6.2, Sep-2000:
v2.6.0, Jul-2000:
v2.5.1, Apr-2000:
- Cross references to other questions are indicated by the letter Q followed
by the question number; for example, (Q9) indicates that
further information is found in Question 9.
- Technical references are shown in brackets; for example, [2]
is a reference to technical note 2.
- Technical notes follow the main FAQ.
- "International notes" are appended to regular
technical notes, so [International note 2] is a section within technical note 2.
1) Are there health hazards associated with living, working, playing, or going to school near a cellular phone or PCS base station antenna?
No. The consensus of the scientific community, both in the US and internationally, is that the power from these 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 radio-frequency radiation; and towers or masts, the structures that the antennas are placed on. It is the antennas that people need to keep there distance from, not the towers that hold the antennas.
Not really. There are some reasons to be concerned about human health effects from the hand-held cellular and PCS phones themselves (although it is not certain that any risks to human health actually exist). These concerns exist because the antennas of these phones can deliver large amounts of radiofrequency energy to very small areas of the user's body [83]. Base station antennas do not create such "hot spots", 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 ICNIRP report [1], the reviews by Moulder and colleagues [95, 131], the review by the Royal Society of Canada [99], and the report of the UK Independent Expert Group on Mobile Phones (the "Stewart Commission") [128]
No. There are many technical differences between cell phones, PCS phones, and the types of "cell" 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 radiowaves from some base stations (e.g., those for the cell phones used in the U.S.) may be absorbed by humans somewhat more than the radiowaves from other types of base stations (e.g., those for the PCS phones used in the U.S.) [23]. However, once the energy is absorbed the effects are the same.
Yes and no. The radiowaves from some antennas (particularly FM and VHF-TV broadcast antennas) are absorbed more by humans than the radiowaves from other sources (such as cellular phone or PCS base station antennas); but once the energy is absorbed the effects are basically the same.
In addition, FM and TV antennas are 100 to 5000 times more powerful than base station antennas, but are mounted on much higher towers (typically 800 to 1200 ft).
Yes. Cellular and PCS phones and their base station antennas are 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, radiowaves 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 (change in direction) per second, and 1 megahertz (MHz) is one million cycles 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 MHz. Cellular phones operate at 860-900 MHz, and PCS phones operate at 1800-2200 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 radiowaves, the energy of the particles is much too low to break chemical bonds. Thus radiowaves are "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 (radiowaves) [4].
The Electromagnetic Spectrum |
 |
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 radiowaves produce biological effects [4, 53]. There appears to be no similarity between the biological effects of power line "EMF" and the biological effects of radiowaves.
Yes. There are national and international safety guidelines for exposure of the public to the radiowaves produced by cellular phone and PCS 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 (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 cellular phone and PCS base station antennas [11]. The FCC standards for cellular phone and PCS 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 PCS and cellular phone frequencies). Where there are multiple antennas, these standards apply to the total power produced by all antennas [13].
Yes. When scientists examined all the published literature on the
biological effects of radiowaves they found that the literature agreed on a
number of key points [see 1, 5, 6,
7, 14, 53, 83,
90, 95, 96 and 99
for details]:
ANSI/IEEE and FCC applied a 10-fold safety margin to establish occupational exposure guidelines. 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 energy absorption, 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]. 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 for details.
Yes. Until 1996 the U. S. Federal Communication Commission (FCC) used an out-dated (1982) ANSI standard that was really designed for occupational, rather than public exposure. In 1996 the FCC adopted a new standard that is based on the newer (1992) ANSI standard, but which is not identical to it [11].
The new FCC standard for mobile phone base stations is 0.57 mW/cm-sq for cellular phone frequencies and 1.0 mW/cm-sq for PCS phone frequencies. 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, cellular phone and PCS base station antennas can meet all safety standards by a wide margin.
A low-gain base station antenna, mounted 10 meters (30 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 (600 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, and with both cellular phone and PCS antennas on the same tower, power densities will be less than 2% of the guidelines at all heights and at all distances of more than 60 meters (180 ft) from an antenna site.
Further than about 200 meters (600 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].
Peterson et al [77] measured power densities around cell phone base stations. The measurements were for 1600 W (ERP) low-gain antennas (see Q14H for a discussion of antenna power and gain) on towers that ranged from 40 to 83 meters (120 to 250 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 (60-240 feet) from the base of the towers. Within 100 meters (300) 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 |
 |
| 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 |
 |
| 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 cellular phone and PCS base station antenna could violate safety standards.
Safety standards for uncontrolled (public) exposure could be violated if antennas were mounted in such a way that the public could gain access to areas within 20 feet (horizontal) of the antennas themselves [18]. This could arise for antennas mounted on, or near, the roofs of buildings. For antennas mounted on towers, it is very difficult to imagine a situation that would not meet the safety standards.
Safety standards for controlled (occupational) exposure could be violated if antennas were mounted on a structure where worker access to areas within 10 feet the antennas is required [18]. Peterson et al [77], for example, found that 2-3 feet from a 1600 W (ERP) low-gain 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).
While specific recommendations require a detailed knowledge of the site, the antenna, and the mounting structure, some general criteria can be set.
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:
Because siting criteria for high- and low-gain antennas are different it is important to be able to tell them apart (see Q14H for a discussion of antenna gain). Fortunately, the antennas look rather different:
Distinguish the Two Antenna Types |
 |
Even from a distance the site (towers) for high- and low-gain antennas look different. When high-gain antennas are mounted on buildings, they may not be obvious, particularly if they are mounted to the sides of building, or more commonly to the sides of penthouses.
Different Ways to Mount Antennas |
 |
The RF patterns for the two different types of antennas are very different. For a low-gain (whip) antenna with a typical 1000 W ERP (see Q14H for a discussion of antenna power and gain) of the type used by most cell phone bases stations, the pattern looks like this:
RF Emissions from a 1000 W ERP Low-Gain
Antenna
|
 |
Very close to 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
|
 |
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 PCS base stations, the pattern looks like this:
RF Emissions from a Single 1000 W ERP
High-Gain Antenna
|
 |
Keep in mind that a typical PCS base station will use 3 (or occasionally 4) of these transmission antennas, all pointing in different directions.
Very close to a single high-gain antenna (in what is technically known as the "near field"), the power density around an antenna looks like this:
RF Emissions from a Single 1000 W ERP
High-Gain Antenna
|
 |
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 cellular or PCS 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.
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])
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) and antenna gain of the base station antenna is known (see Q14H for a discussion of ERP and gain) and the height of the antenna is known, then "worst case" calculations of ground level power density can be made. However, the calculation method is not simple and the ERP is often unknown (height and antenna gain can be estimated by visual inspection of a site).
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, NRPB is ICNIRP standards 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].
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 was omni-directional and 100% efficient, then transmitter power and ERP would be the same. But mobile phone base station antennas (like most 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; it is measured in decibels (dB). For example, a 30 W transmitter with a 15 dB antenna (reasonably typical for a sectored mobile phone base station) would have an ERP of 950 W.
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 panel 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].
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 standards.
In a 25-Jul-96 letter to Reed Hunt (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 Hunt (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 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 RF exposure 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 et al 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 Q16
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); 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. Roger Coghill (U.K.) and Neil Cherry (New Zealand) have been quoted in the mass media as claiming that there is evidence that RF exposure is hazardous at intensities well below the ANSI, FCC, ICNIRP and NRPB guidelines.
Roger Coghill appears to be an "environmental manager", who runs a laboratory that makes [permanent?] magnets "to help people suffering from muscular or arthritic pain" [59]. He has self-published a document [58] that explains "Coghill's hypothesis of cerebral morphogenic radiation". Apparently, Coghill believes that "the brain is actually a organic fully operational radio transmission station... that is in radio contact with every cell in its body" [59]. He appears to base his theory heavily on "Eastern European" research that has not been published in the West [59].
Neil Cherry is an elected official from New Zealand. and a "Senior Lecturer in Agricultural Meteorology" [60]. Like Coghill, he has self-published a document on the hazards of exposure to low-intensity RF [60]. Cherry has been quoted in the mass media as saying that "EMF exposure" is "highly statistically associated with health effects although there is no scientific proof that EMF caused the health effects" [61]. According to Cherry, these health effects include "cancer at many sites in the body, sleep disruption, chronic fatigue syndrome, miscarriage, birth defects, altered human EEG and circadian rhythms and several other adverse effects." [61]. Cherry's ideas appear to depend heavily on the views of Goldsmith (Q15C) and Hocking (Q15B).
Neither Coghill nor Cherry have published anything in the peer-reviewed scientific literature to support their claims. Both Coghill and Cherry mix discussions of power-frequency fields and RF as though they were biologically equivalent (which is almost certainly not correct), and to rely heavily on unpublished and non-reviewed sources (which are impossible to check). Their comments to the mass media have been very vague as to the scientific basis for their opinions. Until Coghill and Cherry present their theories in a peer-reviewed scientific forum, and back their theories with actual data, it is impossible for any scientist to take their theories seriously.
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 letter sent to public officials in 1999, 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 basis for these claims.
In the summer and fall of 1999 (and repeated in the Spring of 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 biology study was presented at a meeting in March, 1999 and published abstracts are available [102, 103]. The epidemiology study was presented at a meeting in June 1999, but there is not even a published abstract.
The U.S. Food and Drug Administrations (FDA) appears to have seen the studies, and published the following comments of 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 a hospital-based, case-control study, researchers looked for an association between mobile phone use and either glioma (a type of brain cancer) or acoustic neuroma (a benign tumor of the nerve sheath). No statistically significant association was found between mobile phone use and acoustic neuroma. There was also no association between mobile phone use and gliomas when all types of types of gliomas were considered together. It should be noted that the average length of mobile phone exposure in this study was less than three years. When 20 types of glioma were considered separately, however, an association was found between mobile phone use and one rare type of glioma, neuroepithelliomatous tumors. It is possible with multiple comparisons of the same sample that this association occurred by chance. Moreover, the risk did not increase with how often the mobile phone was used, or the length of the calls. In fact, the risk actually decreased with cumulative hours of mobile phone use. Most cancer causing agents increase risk with increased exposure. An ongoing study of brain cancers by the National Cancer Institute is expected to bear on the accuracy and repeatability of these results. [Muscat et al. Epidemiological Study of Cellular Telephone Use and Malignant Brain Tumors. In: State of the Science Symposium;20 June 1999; Long Beach, California. ]"
Oddly, the FDA's description of the work of Tice and colleagues does not completely match their published abstracts [102, 103]. The abstracts state that five different genotoxicity tests were done at SARs of 1, 2.5, 5 and 10 W/kg with both a 837 MHz analog signal and a 1900 MHz digital signal; and that none of the tests showed increased DNA damage, increased micronucleus frequency, increased mutations or increased chromosome damage.
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] 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:
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 radiowaves. For a recent review see Elwood [94].
In general, epidemiology studies of radiowaves and cancer have not found
significant correlations between exposure and cancer. The studies include:
- studies of cancer in people occupationally exposed to radiowaves,
- geographic correlation studies that compare cancer rates among areas with
different potential exposures to radiowaves,
- "cancer cluster" studies.
Geographic correlation studies (see Q15B, Q15D and Elwood [94]) estimate the strength of radiowaves 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.
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
radiowaves, and reports of "cancer clusters" are of essentially no
value in determining whether exposure to radiowaves is a cause of cancer (see
Elwood [94] for details of these studies).
The majority of the occupational studies of radiowaves exposure have deficiencies in exposure assessments because occupation or job title was used as an estimate of exposure; that is, actual radiowave exposure levels are not known.
There are four epidemiological studies 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], Thomas et al [105], and Dreyer et al [122]) have more limitations in exposure assessment, case ascertainment, or follow-up time; but they also do not suggest that radiowave 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 radiowave 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 radiowave 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".
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 mobile phone use was deaths from motor vehicle collisions.
To date, only one case-control study has evaluated cancer in mobile phone users. Hardell et al. [100A, 100B] conducted a study of brain tumors in Swedish mobile phone users, 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, occipital and temporoparietal 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 increase was seen for use of analog phones, but not for the use of digital phones [100A].
Brain Cancer in Cell Phone Users |
 |
| 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 [79]. 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 last 4 rows look at which side of the head (L=Left, R=Right) the phone was used on. The line highlighted in red is probably the one most relevant to cancer risk assessment as it looks at long-term heavy use. |
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 RFR exposure no elevation in rates of brain cancer, leukemia and lymphoma were found. Actual peak and/or average RFR exposure levels are not known.
The lack of associations between exposure to radiowaves and total cancer, and the lack of consistent associations between exposure to radiowaves and any specific type of cancer, suggests that radiowaves are unlikely to have a strong causal influence on cancer.
In his recent 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.
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. This could be important, since cell and PCS phones and 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 radiowaves 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 Q15H
Although the public's principle health concern about cell phone and PCS base station antennas appears to be the possibility of a cancer connection (see Q21 and Q23B-Q23D), 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 cellular phone or PCS base station antennas will interfere with cardiac pacemakers or other implanted medical devices as long as exposure levels are kept within the ANSI standard for uncontrolled exposure (see Q8 and Q12).
It is possible that PCS 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 PCS phones and some types of pacemakers [46, 137].
There is no reason to think so. There are anecdotal reports that cell phones cause headaches (see Frey [48], and the discussion of Mild et al and Sandstrom et al [25] in Q23). There have been no serious epidemiological studies of the issue, and there are no real biophysical or physiological bases for expecting a connection.
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"
- Mann and Röschke [113] reported that exposure to a mobile phone signal could cause slight changes in sleep patterns, but a subsequent study by the same group [115] found no evidence for the effect. In a more recent study, Borbély [110] reported that exposure to a mobile phone signal at 1 W/kg could cause slight changes in sleep patterns.
- 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 (see Figure
below). The press coverage was extensive, but the actual study has no obvious
implications for human health:
Cell Phone Use and Reaction Time |
 |
| Reaction time data from Preece et al [97]. Reaction times are shown for seven separate reaction time tests. The "analog" signal was a 915 MHz sine wave. The "digital" signal was a 915 MHz sine wave modulated with a 217 Hz square wave at a 12.5% duty cycle. According to the authors, the analog test group for the "choice reaction time" test (marked in red) was considered to be significantly lower than the sham exposure value, but no other differences were considered to be statistically significant. |
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. The Koivisto et al [132] conclude that:
"With respect to behavioral consequences of the RF fields in humans, all available evidence point to the same direction: RF fields facilitate rather than disrupt performance. The physiological mechanisms underlying such influences are poorly understood, and it is too early to conclude what the significance of the observed effects is on human health."
In 2000 Tsurita et al [133] reported that RF radiation had no effect on the blood-bain 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.
For a recent review of the behavioral effects of RF radiation see D'Andrea [96].
Yes. If exposure is sufficiently intense, radiowaves 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 cellular phone and PCS 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]. 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 [124].
No. Even at high levels of exposure, there is no substantial evidence that radiowaves 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 radiowaves at the power levels associated with public exposure to radiowaves from cellular phone and PCS 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 recent laboratory reports that RF exposure might produce cancer, or cancer-related injuries in animals. These studies are discussed in Q23B and Q23D. 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 radiowaves sufficient to cause whole body heating can cause miscarriages or birth defects. The power produced by cellular phone and PCS base station antennas is far too low to cause such heating. There is no laboratory or epidemiological evidence at all that radiowaves at the power levels associated with public exposure to radiowaves from cellular phone and PCS base station antennas are associated with miscarriages or birth defects [see refs in 1, 5, 6, 7 and 14 for details].
See also the discussion of Bastide et al [26] in Q23A.
There is a constant flow of new information. This section will attempt to summarize this new information. Studies which attract major attention will often get their own sections, such as the epidemiological studies discussed in Q15B, Q15C, Q15D and Q15E, the mouse studies discussed in Q23B and Q23C, and the DNA strand break studies discussed in Q23D.
A 1997 study [37] reports that lymphoma-prone mice exposed for 18 months to strong, but intermittent, radio-frequency fields 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 standard (Q8), and are far above those that exist in publicly-accessible areas near cellular phone and PCS base station antennas [16].
While this study is very interesting, its impact on regulation of RF exposure
of the general public is quite unclear:
See the Technical notes for the reference [37], quotes from the authors' abstract [38], quotes from the authors' discussion [39], and for further technical details [40].
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,
- the exposure-response relationship for the effect must be known,
- the induction of other types of tumors must be studied.
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 10 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 Q23C for details.
A difference in tumor incidence 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. If animals are unrestrained in cages, the RF dose (the SAR [8]) varies with the position of the animal, with its orientation to the antenna, with the presence of other animals, and with the animal size. To get well-defined RF doses, the animals must be confined in small holders, and the daily handling and confinement this requires can produce biological effects all by itself. 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 10 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 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". 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.
- At a meeting in 1999, Zook et al [104] reported the absence of an effect on brain tumor incidence in rats exposed to 860-MHz radio-frequency radiation at 1.0 W/kg. Zook et al also reported that the same RF protocol did not promote chemically induced brain cancer.
- 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 RFR or 848 MHz pulsed RFR 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.
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):
On contrast, other recently published studies found some evidence for RF
exposure might be genotoxic: