Scientific Progress - Wireless Phones and Brain Cancer: Current State of the Science

George L. Carlo, PhD, MS, JD, and Rebecca Steffens Jenrow, MPH, Wireless Technology Research, LLCWashington, DC

Medscape General Medicine. 2000;2(2) 

In This Article

WTR Program Findings

Findings from the WTR program began to emerge during the latter part of 1998 and the beginning of 1999. With the newly developed in vitro and in vivo exposure systems specifically designed for extrapolation to human wireless phone usage, and the first epidemiology studies looking at health risks among cellular phone users, the WTR research added much needed perspective to the questions raised by previously published work. Tables 3 and 4 present results from those studies performed under the WTR program.

WTR-sponsored studies addressing genetic damage from wireless phone exposures were conducted simultaneously at 2 GLP facilities, Integrated Laboratory Systems in Research Triangle Park, North Carolina and Stanford Research Institute in Palo Alto, California. Repetitions of the experiments were included in the peer-reviewed protocols along with independent quality assurance audits consistent with GLP procedures.

In vitro assays of bacteria, mouse lymphoma cells, and human lymphocytes, and in vivo studies of rats exposed head only to all types of wireless phone signals -- cellular analog, cellular digital, and 1900 MHz digital -- appear to confirm that RFR energy of the magnitude associated with wireless phones was insufficient to cause breakage of DNA[18,44] (Donner EM. In vitro chromosome aberration assay in human blood lymphocytes exposed to 1909.8 MHz radiofrequency (RF) signals generated by personal communication systems (PCS) technology; Donner EM. In vitro chromosome aberration assay in human blood lymphocytes exposed to voice modulated 837 MHz radiofrequency (RF) signals generated by time division multiple access (TDMA) technology; Donner EM. Salmonella typhimurium/Escherichia coli reverse mutation assay with 1909.8 MHz radiofrequency (RF) signals generated by personal communication systems (PCS) technology; Donner EM. Salmonella typhimurium/Escherichia coli reverse mutation assay with 837 MHz radiofrequency (RF) signals generated by code division multiple access (CDMA) technology; Donner EM. Salmonella typhimurium/Escherichia coli reverse mutation assay with voice modulated 837 MHz fields generated by analog technology; Donner EM. Salmonella typhimurium/Escherichia coli reverse mutation assay with voice modulated 837 MHz radiofrequency (RF) signals generated by time division multiple access (TDMA) technology; Bakke J, Winegar RA. Evaluation of radiofrequency radiation (RFR) in the human peripheral lymphocyte chromosome aberration assay; Riccio E. Evaluation of radiofrequency radiation (RFR) in the Salmonella Escherichia Coli assay. SRI International; Tice R. Mouse lymphoma mammalian mutagenesis assay with voice modulated 837 MHz radiofrequency signals generated by time division access (TDMA) technology; Submitted for publication.).

However, a series of studies addressing genetic damage to human blood cells through the assessment of micronucleus formation were unequivocally positive for all cellular and PCS phone technologies[45,46,47,48] (Donner EM. Chromosome aberration assay in human blood lymphocytes exposed to voice modulated 837 MHz RF fields generated by analog technology; Donner EM. In vitro chromosome aberration assay in human blood lymphocytes exposed to 837 MHz radiofrequency (RF) signals generated by code division multiple access (CDMA) technology; Tice R. DNA damage in brain cells of male rats exposed to voice modulated 837 MHz radiofrequency fields generated by analog technology; Tice R. Evaluation of analog radio frequency signals using the mouse lymphoma mammalian mutagenesis assay; Tice R. Evaluation of analog radiofrequency signals using the leukocyte single cell gel and lymphocyte binucleate micronucleus assays; Tice R. Evaluation of analog radiofrequency signals using the leukocyte single cell gel and lymphocyte binucleate micronucleus assays-24 hour exposure; Tice R. Leukocyte single cell gel and lymphocyte binucleate micronucleus assays using human blood exposed to 837 MHz radiofrequency signals generated from code digital multiple access (CDMA) technology; Tice R. Leukocyte single cell gel and lymphocyte binucleate micronucleus assays using human blood exposed to voice modulated 837 MHz radiofrequecy signals generated from time division multiple access (TDMA) technology; Tice R. Mouse lymphoma mammalian mutagenesis assay with 1909.8 MHz radiofrequency signals generated by personal communication systems (PCS) technology; Tice R. Mouse lymphoma mammalian mutagenesis assay with 837 MHz radiofrequency signals generated by code division multiple access (CMDA) technology; Lai H, Singh NP. DNA single-strand breaks in brain cells of rats acutely exposed to a voice-modulated analog 837-MHZ radiofrequency (RF) signal. Submitted for publication.).

The increase in the number of cells with micronuclei associated with RFR exposure suggests an impairment of the ability of the human blood cells to repair broken DNA. Multinucleated cells can reproduce and lead to proliferation of damaged blood cells. Repeated studies confirmed that the observed effects could not be explained by heating in the experimental system or any other artifact. It is important to note that impairment of DNA repair as the genotoxicity mechanism is consistent with the earlier findings of Lai and Singh, and other investigators have reported this type of genetic damage for RFR in general. The conclusion of the investigators was that under these experimental conditions, the RFR from the wireless phone is genotoxic.[49]

WTR-sponsored epidemiology studies do raise some questions about health risks associated with cellular phone usage. PCS and digital signaling in the cellular frequency bands were not covered in these studies because those technologies were not in widespread use when the studies were conducted. While none of the WTR epidemiologic studies taken alone are persuasive with respect to a definitive public health threat from cellular phone use, these data, supported by the biological plausibility suggested by the positive genetic damage assays, suggest that there could be a pattern of public health risk emerging.[50]

Dreyer and colleagues[51,52,53] (Dreyer NA, Loughlin JE, Rothman KJ. Cause-specific mortality in cellular telephone users. 1999. manuscript in preparation.) completed the largest cohort study to date of analog cellular phone users and found an increase in the rate of brain cancer mortality in hand-held phone users (near field exposures) as compared with car phone users with the antenna on the rear window (far field exposures). The rate of brain cancer death was more than 3 times greater in the hand-held phone group compared with the far field control group; however, since the total number of persons in this group was small and the follow-up period was short (1 year), the difference was not statistically significant.

A study by Muscat and colleagues addressing primary brain cancer is suggestive of a potential risk.[54] This case-control study accrued newly diagnosed cases from 5 hospitals across the United States and was designed to look at both duration and frequency of cellular phone usage. When all primary brain cancer cases and controls were included in the analysis, there was no evidence of increased risk of primary brain cancer associated with cellular phone use history. However, the majority of the brain cancers included in the study were outside of the 2- to 3-inch exposure pattern generally accepted as the depth of RFR penetration from a wireless phone. A histopathologic subtype analysis segregating neuro-epithelial tumors likely in range of the RFR exposure revealed a statistically significant increase in risk associated with cellular phone use. Further, those patients who reported using their phone on the right side of their head had a significant increase in tumors on that side of the head. This finding of laterality was consistent with the observations of Hardell[55] who, in a case control study conducted in Sweden, observed that tumors were more frequently found on the side of the head where the phone was used.

The study by Muscat and coworkers was able to control for factors that may affect cell phone use, such as age and socioeconomic status (SES). Differences in age were accounted for by using age-matched controls, and SES was controlled for in the statistical models by controlling for education.

Currently, the necessary consumer protection and scientific follow-up derivative of the work completed to date is not in place. This lack of clarity in the science is greatly emphasized as a result of the explosion in wireless technology usage across the globe. Recent advertising trends by the wireless industry targeting children, including wireless phones adorned with pictures of Disney characters such as Mickey and Minnie Mouse, are of special concern.[56,57,58] Recent work by Gandhi[59] at the University of Utah shows that penetration of RFR into the heads of children is greater than in adults. Growing mitotic cells in children could be at higher risk for functional genetic damage such as that found in the WTR studies of exposure to RFR.

The first step in empowering physicians to help their patients who are concerned is communicating the current state of knowledge regarding these potential health impacts, as uncertain as they are. Because there are interventions available to minimize exposure to RFR from the wireless phone antenna, patients can then have choices with respect to minimizing their exposure.[60,61]

Many of the models of wireless phones currently available are equipped with headsets and hands-free devices that allow for the phones to be used without the antenna being placed close to the head.

Pagers are available that allow for 2-way messaging similar to wireless phones, but without the concentrated RFR exposure from an antenna placed near the head. Pagers are preferable for young children and teenagers whose tissues are still developing.

Shields are being developed that theoretically limit radiation exposure to the body. A panel of experts in the United Kingdom, chaired by Sir William Stewart, issued a report in May 2000 that recommended children younger than 16 years of age should be discouraged from using mobile phones.[62] The report claims that children are likely to be more vulnerable to any unrecognized health risks from mobile phone use than are adults. "The rationale is as follows: the developing nervous system is likely to be more vulnerable than the mature nervous system to potentially hazardous agents because of their smaller heads, thinner skulls and higher tissue conductivity, children may absorb more energy from a given phone than do adults

if there are detrimental health effects caused by mobile phone signals, those using phones for a longer period of their lives will tend to accumulate a greater risk."

The justification for suggesting that persons under age 16 are at greater risk is as follows: development of the head and nervous system is generally complete by age 16 years. For example, the density of synapses reaches adult level around puberty, and skull thickness and brain size reach adult levels around age 14 or 15. According to the report, "Sixteen is usually recognized as the age at which individuals are sufficiently mature to make informed choices about other 'adult' activities."

The science is not clear enough to enable us to make informed judgments about how wireless phone usage patterns affect health. Studies completed to date do not allow us to distinguish, in terms of health risk, the differences among various patterns of usage. We do not know, for example, whether one 10-minute phone call is better or worse than ten 1-minute phone calls with respect to health impact. We know that the intensity of the RFR exposure is greatest during dialing and ringing, and that the amount of RFR necessary to sustain a call lessens during the call.[13] However, it is premature to speculate that lessening the length of calls, for example, lessens potential health impact. Similarly, it is premature to recommend that lessening the number of calls accrues any health benefit.

Options to reduce exposure to potential harmful RFR and thus reduce the risk of health problems are available, through the efforts of wireless phone manufacturers and other providers of radiation protection devices. However, the scientific bases underlying these potentially protective devices are presently unclear. Because testing of these devices is under way, neither the government nor the industry has pushed the devices in the marketplace, and appropriately so.

The state of our knowledge with respect to meaningful public health intervention with regard to wireless phone usage is qualitative. Moving the antenna beyond the distance threshold of 2-3 inches away from the body is the only science-based recommendation that can be supported by existing data.

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