originally appearing in The Lancet 2000; 356: 1833-36
(page 2 of 5)
There have been many investigations to estimate, using phantom heads,5 the rate at which thermal energy is deposited in the head during use of a mobile phone--the so-called absorption rate. These studies indicate that, for most handsets, safety guidelines are not violated. In publicly accessible areas near a base-station, thermal influences of the emitted MWR can be totally discounted; the microwave intensity is far too low. Nevertheless, in both cases there are reports of adverse health effects of subthermal intensities, the possible origin of which will now be considered.
Biological effects: non-thermal
The possibility that the pulsed, low-intensity MWR currently used in GSM mobile telephony can exert subtle, non-thermal influences on a living organism arises because microwaves are waves; they have properties other than the intensity that is regulated by safety guidelines. This microwave radiation has certain well-defined frequencies, which facilitate its discernment by a living organism (despite its ultralow intensity), and via which the organism can, in turn, be affected. The human body is an electrochemical instrument of exquisite sensitivity whose orderly functioning and control are underpinned6 by oscillatory electrical processes of various kinds, each characterised by a specific frequency, some of which happen to be close to those used in GSM. Thus some endogenous biological electrical activities can be interfered with via oscillatory aspects of the incoming radiation, in much the same way as can the reception on a radio.
The biological electrical activities that are vulnerable to interference from GSM radiation include highly organised electrical activities at a cellular level whose frequency happens to lie in the microwave region, and which are a consequence of metabolism.7 Although not universally accepted, there is experimental evidence7-9 consistent with these endogenous activities, in terms of which effects of ultralow-intensity microwave radiation of a specific frequency on processes as fundamental as cell division, for example, can be understood in a rather natural way.10 Furthermore, the DTX pulse frequency at 2 Hz and the TDMA frequency of 8·34 Hz correspond to frequencies of electrical oscillations found in the human brain, specifically the delta and alpha brain-waves, respectively. It is thus quite possible that living organisms have a two-fold sensitivity to the pulsed GSM signal--ie, to both the microwave carrier and the lower frequency pulsings of the TDMA and DTX signals. To deny this possibility yet admit the importance of ensuring electromagnetic compatibility with electronic instruments by banning the use of mobile phones on aircraft11 and hospitals (a prohibition driven by concerns about non-thermal interference) seems inconsistent.
Thus, in contrast to heating, which relies on an organism's ability to absorb energy from the irradiating field, the possibility of non-thermal effects arises from an "oscillatory similitude" between the radiation and the living organism, which makes it possible for the living organism to respond to low-intensity, pulsed MWR via its ability to recognise certain frequency characteristics of that radiation. The intensity of radiation needed for this recognition is many orders of magnitude below even that currently associated with non-thermal effects. This influence is possible only when the organism is alive, with excited endogenous frequencies; the dead have flat electroencephalograms. Non-thermal effects thus depend on the state of the person when exposed to the radiation--ie, non-thermal effects are non-linear. A low-intensity field can entail a seemingly disproportionately large response (or none at all), and vice versa, quite unlike the predictable thermal responses. Thus not everyone can be expected to be affected in the same way by identical exposure to the same radiation.
A good example of human vulnerability to a non-thermal, electromagnetic influence is the ability of a light flashing at about 15 Hz to induce seizures in people with photosensitive epilepsy.12 It is not so much the amount of energy absorbed from the light that provokes the seizure, but rather the information transmitted to the brain by the (coherent) regularity of its flashing, at a frequency that the brain "recognises" because it matches or is close to a frequency utilised by the brain itself.
What do we know experimentally about non-thermal biological influences of MWR (both pulsed and continuous) of an intensity close to that near a mobile phone handset, but often at higher microwave carrier frequencies? A selection of in vitro studies is given in panel 1.
Panel 1: Selected in vitro studies of non-thermal effects of microwave radiation of various frequencies and intensities Effect Ref Epileptic activity in rat brain slices in conjunction with certain drugs 13 Resonant effects on cell division of Saccharomyces cerevisiae, and on the genome conformation of Escherichia coli 9, 14 Synchronisation of cell division in S carlsbergenis 15 "Switch-on" of epigenetic processes, such as -phage and colicin synthesis 16, 17 Altered ornithine decarboxylase activity 18 Reduced lymphocyte cytotoxicity 19 Increased permeability of erythrocyte membrane 20 Effects on brain electrochemistry (calcium efflux) 21 Increase in chromosome aberrations and micronuclei in human blood lymphocytes 22 Synergism with cancer-promoting drugs such as phorbol ester 23
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.
Panel 2: Selected in vivo studies of non-thermal microwave exposure, including GSM radiation Effect Ref Epileptiform activity in rats, in conjunction with certain drugs 24 Depression of chicken immune systems (melatonin, corticosterone and IgG levels) 25 Increase in chick embryo mortality 25 Increased permeability of blood-brain barrier in rats 26 Effects on brain electrochemistry (dopamine, opiates) 27 Increases in DNA single and double strand breaks in rat brain 28 Promotion of lymphomas in transgenic mice 29 Synergistic effects with certain psychoactive drugs 30
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