Seminar

Physics and biology of mobile telephony

G J Hyland

Lancet 2000; 356: 1833-36

See Commentary (Philip P Dendy )

Department of Physics, University of Warwick, Coventry, UK; and International Institute of Biophysics, Neuss-Holzheim, Germany (G J Hyland PhD)

Correspondence to: Dr G J Hyland, Department of Physics, University of Warwick, Coventry CV4 4AL, UK (e-mail:G.J.Hyland@...)

Physics of mobile telephony
Biological impacts: thermal
Biological effects: non-thermal
Possible associated adverse health reactions
References

Although safety guidelines--to which mobile telephones and their base-stations conform--do protect against excessive microwave heating, there is evidence that the low intensity, pulsed radiation currently used can exert subtle non-thermal influences. If these influences entail adverse health consequences, current guidelines would be inadequate. This review will focus on this possibility. The radiation used is indeed of very low intensity, but an oscillatory similitude between this pulsed microwave radiation and certain electrochemical activities of the living human being should prompt concern. However, being so inherently dependent on aliveness, non-thermal effects cannot be expected to be as robust as thermal ones, as is indeed found; nor can everyone be expected to be affected in the same way by exposure to the same radiation. Notwithstanding uncertainty about whether the non-thermal influences reported do adversely affect health, there are consistencies between some of thes! e effects and the neurological problems reported by some mobile-telephone users and people exposed longterm to base-station radiation. These should be pointers for future research.

Public concern over possible adverse health impacts from exposure to the radiation used in GSM (Global System for Mobile communication) mobile telephony shows little sign of abating, despite assurances from the industry and official bodies such as the UK National Radiological Protection Board (NRPB) that all is well. In March, 1999, the UK Government set up the Independent Expert Group on Mobile Phones, under the chairmanship of Sir William Stewart. The Stewart Report,1 published in May, 2000, makes some sensible recommendations, but unfortunately some of its greyer areas are now being exploited by the industry to obfuscate the issue. As yet unresolved is the question of adverse health impacts provoked by the contentious non-thermal effects of the low intensity, pulsed microwave radiation (MWR) used. For these effects are not taken into account in current safety guidelines,2 which simply restrict the intensity of the radiation to prevent tissue heating in excess of what the bo! dy's thermoregulatory mechanism can cope with. Whilst these guidelines, which are the result of careful investigation over many years, are clearly necessary, the question remains as to whether they are comprehensive enough. For in the case of living systems (and only living ones) there are many reports over the past 30 years that MWR can exert non-thermal influences, at intensities well below those necessary to cause any detectable heating.3

The purpose of this review is to introduce clinicians to the physics of mobile telephony and to explain how low-intensity, pulsed microwaves can affect living organisms, both thermally and non-thermally; and then to identify some of the reported biological impacts of exposure to this radiation, particularly those provoked by the contentious non-thermal effects. It is thereby hoped to alert clinicians to the possibility that certain presenting symptoms might well be a consequence of non-thermal exposure to this kind of radiation. A companion Lancet review4 covers the epidemiological evidence for effects of mobile telephony on human health. Physics of mobile telephony

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In vivo evidence of non-thermal influences, including exposure to actual GSM radiation, comes predominantly from animal studies (panel 2). Finally, human in vivo studies, under GSM or similar conditions, include effects on the EEG and on blood pressure. A delayed increase in spectral power density (particularly in the alpha band) has been corroborated31 in the "awake" EEG of adults exposed to GSM radiation. Influences on the "alseep" EEG include a shortening of rapid-eye-movement (REM) sleep during which the power density in the alpha band increases,32 and effects on non-REM sleep.33 Exposure to mobile phone radiation also decreases the preparatory slow potentials in certain regions of the brain34 and affects memory tasks.35 In 1998, Braune et al36 recorded increases in resting blood pressure during exposure to radiofrequencies.

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Possible associated adverse health reactions

It is important to stress that the existence even of established non-thermal effects does not make adverse health consequences inevitable. Nonetheless GSM radiation does seem to affect non-thermally a variety of brain functions (including the neuroendocrine system), and health problems reported anecdotally do tend to be neurological, although formal confirmation of such reports, based on epidemiological studies, is still lacking. For example, reports of headache are consistent with the effect of the radiation on the dopamine-opiate system of the brain27 and the permeability of the blood-brain barrier,26 both of which have been connected to headache.40,41 Reports of sleep disruption are consistent with effects of the radiation on melatonin levels25 and on rapid-eye-movement sleep.32 Furthermore, since there is no reason to suppose that the seizure-inducing ability12 of a flashing visible light does not extend to microwave radiation (which can access the brain through the skull)! flashing at a similarly low frequency, together with the fact that exposure to pulsed MWR can induce epileptic activity in rats,24 reports of epileptic activity in some children exposed to base-station radiation are perhaps not surprising. I have heard of one child whose seizures diminish when, unbeknown to her or her family, the mast is not functioning (or when she is away), only to increase again when the base-station is working again or when she returns home.

Finally, the significant increase (by a factor of between 2 and 3) in the incidence of neuroepithelial tumours (the laterality of which correlates with cell-phone use) found in a nationwide US study42 is consistent not only with the genotoxicity of GSM radiation, as indicated by increased DNA strand breaks28 and formation of chromosome aberrations and micronuclei but also with its promotional effect on tumour development.43 However, as Rothman's accompanying review shows,4 the overall epidemiological evidence for an association with cell-phone use is rather weak. Nevertheless, it cannot be denied that non-thermal effects of the MWR used in mobile telephony do have the potential to induce adverse health reactions of the kind reported, and this possibility should not be ignored even if only a small minority of people are at risk. Whether a person is affected or not could depend, for example, on the level of stress before exposure; if it is high enough, the additional contributio! n from MWR exposure might be sufficient to trigger an abnormality that would otherwise have remained latent. It is often argued that anecdotal reports of health problems should be dismissed. However, given the paucity of systematic epidemiological studies of this new technology, such reports are an indispensable source of information, a point acknowledged in the 1999 report of the UK parliamentary committee.44

Preadolescent children can be expected to be more vulnerable to any adverse health effects than adults because absorption of GSM microwaves is greatest5 in an object about the size of a child's head, because of the "head resonance" effect and the greater ease with which the radiation can penetrate the thinner skull of an infant1. Also the multiframe repetition frequency of 8·34 Hz and the 2 Hz pulsing in the DTX mode of cellphones lie in the range of the alpha and delta brain-waves, respectively. In a child, alpha waves do not replace delta waves as a stable activity until the age of about 12 years. Furthermore, the immune system, whose efficacy is degraded19,25 by this kind of radiation, is less robust in children. This makes them less able to cope with any adverse health effect that might be provoked by chronic exposure, not only to the pulsed microwave radiation but also to the the more penetrating low-frequency magnetic fields associated with the current surges f! rom the handset battery which can reach 40 µT (peak) near the back of the case.45 Indications of the biological noxiousness of these magnetic fields (in animals) can be found in ref 25.

In the context of base-station radiation, reports relating to animals are of particular value since it cannot here be claimed that the effects are psychosomatic. Of particular interest is a publication on cattle,43 recording severely reduced milk yields, emaciation, spontaneous abortions, and stillbirths. When cattle are removed to pastures well away from the mast, their condition improves, but it deteriorates once they are brought back. The adverse effects appeared only after GSM microwave antennae were installed on a tower formerly used to transmit only non-pulsed television and radio signals.

Finally, in support of the reality of an adverse health impact of non-thermal influences of the kind of radiation used today in mobile telephony, we should recall that during the "cold war" the Soviet irradiation of western embassies with microwave radiation (of an intensity intermediate between that in the vicinity of a handset and a base-station), done with the express intention of inducing adverse health effects, was quite successful