1. INTRODUCTION. 1.1 Mobile telephony

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1 Mobile Telephony: Evidence of Harm? Bernard Veyret PIOM laboratory, ENSCPB/EPHE, University of Bordeaux, France Abstract. Mobile telephony has developed rapidly over the past ten years and it has led to concerns about health effects caused by exposure to the microwaves emitted by mobile telephones and base stations. Research on biological effects of mobile telephone signals has been very active. Epidemiological research so far has been inconclusive. In the laboratory, no evidence has been obtained of well-established effects in human, animal, and cellular models. Major research projects are ongoing worldwide and the findings will help evaluate health risks by INTRODUCTION Mobile (or cellular) telephony has developed very rapidly over the past ten years. It is now part of the basic equipment of modern life and over 1.3 billion phones are in use worldwide. Concerns about health effects caused by exposure to the microwaves emitted by mobile telephones and base stations have increased over the last few years becoming a major societal issue in some countries, or at least among part of the population. This short chapter reviews the scientific knowledge acquired on the biological effects associated with mobile telephony signals, together with conclusions about related health hazards. Stories about health risks from radiofrequency radiation (RFR) from mobile phones and base stations have become common in the media over the past five years. In the United Kingdom for example, one early infamous headline warned that cell phones might "fry" the brain! 1 In contrast, the media do not often communicate on official scientific reports firmly concluding that there is no evidence of a health hazard from mobile phones. 1.1 Mobile telephony Several systems are used in mobile telephony worldwide, all based on the same principle, i.e. cellular mapping of the territory. In each cell, a base station (BTS) emits towards and receives signals from the mobile telephones active in that cell (up to around 50). There are, for example, 30,000 BTS in France used by three networks. The carrier frequency varies from 400 to 2100 MHz and the voice or data information is coded digitally either by frequency or phase modulation mobile telephones Mobile telephones are two-way radio transmitters operating in the MHz frequency range. In the GSM system, for example, the peak power emitted is 2 W, but the time-averaged power is always below 1/8 of this value, as power control reduces emission to the lowest level required. About half of the emitted power is absorbed by the user s head, i.e. a maximum of 125 mw. Power absorption is expressed as the specific absorption rate (SAR) in W/kg. Major improvements have been achieved in measuring the SAR in liquid phantoms and calculating power distribution in the head using numerical phantoms over the last ten years. Today, the worst-case SAR associated with the average GSM phone on the market is ca. 0.5 W/kg, i.e. 1/4 of the recommended local-exposure limit value [1]. It is now known with certainty that temperature increases in the brain periphery caused by the waves emitted by mobile telephones does not exceed 0.1 C. 1 Sunday Times, 4 April 1996

2 As a result of current changes in usage increasing use of text and image messages and hands-free kits mobile telephones are less frequently placed against the ear. This dramatically reduces exposure of the tissues in the head Base stations GSM base-station antennas have an emitting power of ca. 20 W. They are usually placed on rooftops and the emission beam is disc-shaped. Maximum exposure occurs on the ground, approximately 200 m from the BTS and it is almost zero at the bottom of the building or mast on which the antenna is mounted. Exposure of the public to the RFR emitted by base stations is typically 1/10000 of the recommended limit in terms of incident power. There is a consensus in the scientific community that base stations do not represent a health hazard. Therefore, in spite of the concerns of part of the public about antennas, they will not be mentioned further in this review. 1.2 Scientific approach to heath risk assessment The scientific approaches to health risk assessment related to non-ionizing electromagnetic fields are the same as in the ionizing range, i.e. epidemiology, experimental studies on humans, animals, and cells in culture. The experimental protocols are also similar but the choice of exposure systems and biological models are different. There is much scientific evidence, based on existing research, that warrants limiting exposure to highlevel RFR due to the thermal effects caused by heating of the tissues at SAR levels that correspond to a temperature elevation of a few degrees. However, this does not occur with mobile telephones. The search is thus for non-thermal effects and most of the research activity has been aimed at defining the thresholds for these effects, with respect to existing exposure guidelines [1] based on acute effects known to be due to heating [2]. Health risk assessment associated with RFR benefits from a database spanning over 50 years and including more than 350 studies specifically related to mobile telephony. Half of these studies relate to cancer and have been overwhelming in finding no evidence that RFR exposure initiates or promotes cancer. 2. MAIN RESULTS The WHO and IEEE databases list about 1,300 peer-reviewed publications, from biophysical theoretical analyses to human epidemiological studies [3]. Recently, 11 review papers have been published on cancer, reproduction, calcium efflux, behaviour, thermoregulation, the nervous system, ocular and auditory effects, homeostasis and metabolism, longevity, epidemiology, and in vitro studies [3]. About half of the published studies are directly relevant to the issue of whether low-level exposure to RFR initiates or promotes cancer. The table below gives an update on completed and ongoing studies [4]. Type of study Completed Ongoing Total Cancer relevant or related Epidemiological studies Standard bioassays Sensitized in vivo studies Acute in vivo studies In vitro studies Total cancer studies Non-cancer studies Epidemiological studies Human studies

3 Acute in vivo studies In vitro studies Total non-cancer studies Grand totals Epidemiology Several epidemiological studies of mobile phone users have been performed worldwide, with mainly negative findings. However, they are not very informative, either due to poor exposure assessment or an insufficient statistical basis [5]. Overall, while occasional significant associations between various brain tumours and analogue mobile phone use have emerged, no single association has been consistently reported across population-based studies. The most recent study dealt with acoustic neurinomas and was again negative [6]. In view of the fact that the health of a huge population of mobile telephone users is potentially at stake, and the inconclusive findings of the published studies, a major multinational epidemiological study has been initiated, including 13 countries. It is led by IARC 2 and deals with three types of cancer of the head and neck. The results of this Interphone project will be known at the end of 2004 in some of the countries and a final conclusion will be drawn in In the mean time, parallel studies have shed some light on the association between mobile telephone development and increased cancer incidence. One of these studies showed no such association between the trend in incidence of adult primary intracerebral tumours and mobile telephone use in four Nordic countries [7]. WHO recommendations for short-term epidemiological projects are: Exposure surveys (in contrast to simple source evaluations) to assess an individual s total exposure. This includes, for instance, the relative contribution of occupational and residential exposures, and the impact of age, gender and mobility. Regional variations also need to be assessed. Future epidemiology study design and interpretation depend on data from studies started now. Additional exposure assessment research to permit the proper design of residential and occupational epidemiological studies. 2.2 Laboratory studies Humans In spite of the obvious limitations of human experiments in terms of endpoints and exposure characterization, several investigations have been performed using various models. Findings have either been negative or difficult to replicate (sleep, EEG, cognitive functions, etc.). Today, there is no conclusive evidence from human studies of the detrimental health effects of mobile telephones. However, a report from a Dutch laboratory has drawn a lot of attention from the media and the scientific community as it reported minor effects on the well-being and cognitive functions of volunteers exposed to weak base-station signals [8]. This work, which is not yet published, has been heavily criticized but its protocol may serve as the basis of some more-refined work. However, it is not directly relevant to mobile telephone exposure. Clearly, the main issue today is the potential greater sensitivity of children to mobile telephone RFR. Their lifetime exposure, the fact that their CNS is still developing, and, possibly, increased RFR absorption in the head, have led to concerns that cannot be easily resolved through laboratory investigations and numerical modelling. A WHO scientific meeting, to be held in Istanbul in June 2004, will be devoted to this issue. WHO recommendations for short-term projects on humans are: Replication and extension of the studies which demonstrated effects on sleep. Studies of RF exposure and headaches in a controlled laboratory setting. Studies of memory performance should be expanded to include children. 2 International Agency for Research on Cancer

4 2.2.2 Animals A large number of animal experiments have been performed over the past forty years, using various RFR frequencies and modulations. It is clear from these data that the vast majority of the reported biological effects are due to heating. These effects result either from a rise in tissue or body temperature exceeding 1 C or in physiological and behavioural responses aimed at minimising the total heat load. Major improvements in exposure system design have made it possible to better characterize the SAR within the organism, and allow for either local exposure that mimics mobile telephone use (e.g. loop antenna, carousel) or whole-body exposure related to base-stations (e.g. Ferry s wheel, reverberation chamber, circular waveguide). Results on most of the non-cancer endpoints have been negative (memory, EEG, hearing, etc.) except for data on the permeability of the blood-brain-barrier, which was found to be increased by two research groups but not by several others [9]. Therefore, most of the major ongoing studies deal with cancer models. All of the long-term bioassays or sensitized studies have given negative results except for one using transgenic mice, [10] genetically modified to increase the background incidence of lymphomas, an increased tumour incidence was found following GSM exposure. No such finding emerged from a recent confirmation study, using a different design [11]. While awaiting the results of a further replication study, there is no convincing evidence from animal investigations that the incidence of lymphomas and other types of tumours is influenced by lifetime, daily exposure to mobile telephony RFR. WHO recommendations for short-term projects on animals are: Follow-up studies to immune system studies that suggest an effect of RF exposure (i.e., Russian publications from several years ago). Studies to assess the accuracy and reproducibility of published RF effects on the permeability of the blood-brain barrier and other neuropathologies (e.g., dura mater inflammation, dark neurones). Additional studies of the effect of RF exposure on sleep are recommended. More quantitative studies on the effects of heat on the development of the central nervous system, particularly the cortex, in the embryo and foetus using morphological and functional endpoints Cells In spite of their inherent limitations related to the lack of cell-to-cell interactions and altered genetic characteristics, in vitro investigations on cells have provided some useful information at a fast rate and moderate cost. A number of replication studies that addressed some positive findings on enzyme activity, gene expression, and DNA alteration have all proven negative so far. Research is currently very actively investigating possible alterations of heat shock proteins, seen as potential markers for RFR exposure and/or leading to physiological alterations in cells. A wide range of short-term, low-level in vitro experiments have shown that exposure did not cause cell death, implying that RFR is not a toxic agent. Furthermore, the weight of evidence available today (induction of DNA strand breaks, chromosome aberrations, micronuclei formation, DNA repair synthesis, sister chromatid exchange, and phenotypic mutation) supports the conclusion that RFR is not genotoxic. However, a major international study is being planned to finally resolve this issue in terms of low-level biological effects. Moreover, the synergy of RFR with chemical agents or other physical agents still needs further investigation. WHO recommendations for short-term projects on cellular systems are: The expression of stress (heat shock) proteins in mammalian cells exposed to RF should be studied experimentally to followup recently published data. Biologically relevant hypotheses, if supported by experimental data (in particular if related to the function of the central nervous system), should be tested to explore the utility of such data in risk assessment.

5 3 HEALTH RISK ASSESSMENT The process of health risk assessment by bodies such as ICNIRP, IEEE, IARC, and WHO relies heavily on judging the quality of investigations. As stated above, the quality of exposure systems has greatly improved and can now be considered adequate. The use of well-grounded experimental protocols (shamexposure, blinding of exposure and biological tests, positive controls) has become generalized. Moreover, it is now common practice in the field of bioelectromagnetics to ascertain that any positive results are replicated in at least one independent laboratory [11]. In spite of these improvements, it should be noted that only a few top-level biology laboratories have engaged in this type of research, partly due to interferences created by societal and media pressure. Within its EMF International Programme, WHO has reviewed the science and issued the research recommendations quoted above [12]. The main conclusion from these reviews is that EMF exposures below the limits recommended in the ICNIRP guidelines do not appear to have any known impact on health. However, there are still some key gaps in knowledge requiring further research to provide definitive health risk assessments: IARC will issue a cancer classification of RFR in 2005 and WHO and ICNIRP s evaluations on RFR and health are due in Remaining uncertainties in the science database have led to pressure to introduce precautionary measures until gaps in knowledge are filled. If precautionary measures are introduced to reduce RFR levels, it is recommended that they should be voluntary and that health-based exposure limits be mandated to protect public health. 4 CONCLUSIONS Following the very rapid development of mobile telephony, a major research effort has been carried out worldwide (tens of millions of euros per year). Europe is most active (UK, Germany, Italy, and Finland, in particular), but many research groups are contributing in Japan, US, and Australasia. Most governments have addressed the issue of mobile telephony and health and several international and national expert committees have written accurate summaries of current knowledge (see the list of the most recent reports in the reference section). Their conclusions converge towards an absence of health effects related to mobile telephones, but all encourage continuing research in some areas. The CSTEE 3 was asked to prepare a revision of the 1999 European Commission recommendation and its conclusion in 2002 was that: The additional information which has become available on carcinogenic and other nonthermal effects of radiofrequency and microwave radiation frequencies in the last years does not justify a revision of exposure limits set by the Commission on the basis of the conclusions of the 1998 opinion of the Steering Scientific Committee. In answer to the question: mobile telephony: evidence of harm? one must conclude that the weight of scientific evidence does not support health concerns or indicate any health risks from mobile phones in normal use, nor that there is any accepted mechanism for potential health effects at the low levels associated with these devices. Findings to date, including epidemiological studies and laboratory studies of animals exposed both short-term and for their entire lifetimes, have not provided evidence that exposure causes cancer, or affects biological tissues in a manner that might lead to, or augment, any disease. However, there are still some issues pending, in particular those related to the potentially greater sensitivity of children. The many ongoing research projects should help clarify these issues by the end of References [1] ICNIRP. Guidelines for limiting exposure to electric, magnetic and electromagnetic fields (up to 300 GHz). Health Physics 74 (1998) Scientific Committee on Toxicity, Ecotoxicity and the Environment

6 [2] ICNIRP Statement: General approach to protection against non-ionizing radiation. Health Physics 82 (2002) [3] Reviews of Effects of RF Fields on Various Aspects of Human Health, in Bioelectromagnetics as Supplement 6 (2003), (www3.interscience.wiley.com/). [4] [5] Boice J.D and McLaughlin J.K., Epidemiologic Studies of Cellular Telephones and Cancer Risk, A Review. SSI report : 2002:16 september 2002, ISSN [6] Christensen H.C., Schüz J., Kosteljanetz M., Poulsen H.S., Thomsen J., and Johansen C., Am J Epidemiol 159 (2004) [7] Lönn S, Klaeboe L, Hall P, Mathiesen T, Auvinen A, Christensen HC, Johansen C, Salminen T, Tynes T, Feychting M. Int J Cancer 108 (2004) [8] Zwamborn A.P.M., Dr. ir. Vossen S.H.J.A., Ir. van Leersum B.J.A.M, Ing. Ouwens M.A., Makel W.N., Effects of global communication system radio-frequency fields on well being and cognitive functions of human subjects with and without subjective complaints. Sept 30, 2003, TNO-report FEL-03-C148 [9] Hossmann K.A. and Hermann D.M., Bioelectromagnetics 24 (2003) [10] Repacholi M., Basten A., Gebski V., Noonan D., Finni J., Harris A.W., Rad. Res 147 (1997) [11]Utteridge T.D., Gebski V., Finnie J.W., Vernon-Roberts B. and Kuchel T.R.,. Radiat Res 158 (2002) [12] Repacholi M.H., Toxicol Lett 120 (2001) [13] WHO research recommendations: Useful Websites: COST Action 281: UK research programme: National Radiological Protection Board: Swedish Radiological Protection Board: European Bioelectromagnetics Association: Bioelectromagnec Society: International Commission on Non Ionizing Radiation Protection: IEEE subcommittee: grouper.ieee.org/groups/scc28/sc4/ WHO EMF International Programme: Recent national reports: - Proposal for limiting exposure to electromagnetic fields (0-300 GHz). (in press, consultation diocument at - Health Council of the Netherlands. Electromagnetic Fields: Annual Update The Hague: Health Council of the Netherlands, 2004; publication no. 2004/01. ( - AGNIR. Documents of the NRPB: Health effects from radiofrequency electromagnetic fields volume 14, no2, ( - Recent Research on Mobile Telephony and Cancer and Other Selected Biological Effects: First annual report from SSI s Independent Expert Group on Electromagnetic Fields. SSI s Independent Expert Group on Electromagnetic Fields, 2003 (

7 - Rapport à l'agence Française de Sécurité Sanitaire Environnementale : Téléphonie mobile et santé. March 2003 ( - IEGMP. Independent Expert Group On Mobile Phones (Chairman: Sir William Stewart). Mobile phones and health. Chilton, Didcot: Independent Expert Group On Mobile Phones, 2000 (