Journal of the Royal Society of Medicine Volume 83 February 1990
63
Editorials Health effects of electromagnetic fields
Magnetism and the phenomena of electricity have been appreciated and progressively better understood since the 17th century, while electrophysiology is primarily a 20th century science but still long enough established to be widely understood by the scientific community and, at least, apparent to the general public. For many years it has been thought that some animal species, particularly birds and whales, are sensitive to the Earth's magnetic field and use it for navigational purposes. One may well ask therefore why the public, comfortable with using electricity all their lives and for two or three previous generations familiar with its phenomena, and appreciative of its benefits and safety, should suddenly have become so suspicious about its long term effects. The answer I believe lies largely outside anything to do with electromagnetism itself. It is more a result of a better educated and enquiring and less easily satisfied public; the pervasive and profound influence of the media; an emotive and disproportionate concern about cancer and a sensitized distrust of large institutions whether Government or commercial. In spite of their better education, however, the public are still persuaded by much quasi-scientific work on electromagnetic fields (EMF), unsupported by acceptable scientific evidence. In 19791 the public and the media seized upon a poor epidemiological study, which was hypothesis generating and not hypothesis based, whose authors were impressed by the sight of electrical wiring configurations in the vicinity of childhood cancer cases. From an epidemiological point of view this paper is open to criticism - the controls are of poor comparability to the cases, the investigators knew which were cases and which were controls, the epidemiological analysis was poor and there is a remarkable and surprising consistency among the comparisons which stretches its credibility. Nevertheless, this paper caused many other researchers to attempt to confirm or refute these surprising findings in various population studies2. The Savitz3 study is, perhaps, the most definitive epidemiological study so far. However, the numbers were small, Savitz himself admits that the responses by the controls, especially, were poor, and although there was a weak but statistically significant relationship between cases and wiring confilguration in the highest wiring codes, this was not apparent where magnetic fields were measured. He only had a 71% response rate for cases and he was unable to characterize the non-participants. Magnetic field measurements were only performed for 36% of the cases and, while he produced 66 odds ratios, only seven were statistically significant. Savitz himself admits:
'As indicated in the press coverage, our study suggests a link between prolonged magnetic field exposure from electric power lines near residences and risk of childhood cancer. It shouId be kept in mind, however, that we have not proven that magnetic fields cause cancer. Subsequent research will indicate whether we are on the right track or whether our results are in error. Thus, there is a suggestion of a possible hazard which has yet to be resolved. Given these circumstances, it seems that interest or concern may be justified, but our study is not sufficiently convincing to warrant drastic action by homeowners'.
Ahlbom4 has recently reviewed the various studies and notes some consistency between them. However, he states that it is not possible, from the available information, to conclude whether or not exposure to magnetic fields increases the risk of cancer. Rather more epidemiological studies have been done on occupational groups and most of these studies do show an increased risk of leukaemia2. The problem with all these studies is the lack of definition of 'electrical workers' or the inclusion of non-electrical workers. Lin5 for example, included in his cohort all workers in the industry whether they worked in generation or accounts, transmission or transport. It is also known, of course, that many electrical workers also handle chemicals, solvents, fluxes and other materials which are known to be leukaemogenic or are suspected carcinogens. While these studies contain many uncertainties and confounding factors, the fact that so many of them show a proportional incidence ratio or a proportional mortality ratio of 130 to almost 3006 has led many people to assume that a trend must be concluded. An objective assessment of the epidemiological evidence must, I think, lead one to the conclusion that it is weak and unconvincing. Apart from its intrinsic weaknesses it lacks two vitally important components: (i) a plausible biological hypothesis and (ii) any direct measurements of exposure to either electric or magnetic fields. The biological work which has been done in this field includes exposure experiments using alternating and direct current, sinusoidal and pulsed fields, predominantly electrical or predominantly magnetic fields with frequency and amplitude modulation on a variety of models from cell cultures to chick embryos and whole rodents to whole men. The field strengths used are generally orders of magnitude greater than those implicated by the epidemiological findings. It comes as no surprise to find that a wide variety of effects have been reported. Most researchers have concentrated on the cell membrane in the search for a hypothesis to explain these observations and Sagan (personal communication) has defined a number of phenomena related to membrane function including: (i) Changes in calcium binding to cell surfaces. (ii) Reduced binding of cytotoxic lymphocytes to cell surface receptors. (iii) Changes in membrane transport and secretion, eg decreased insulin release from pancreatic cells and calcium flux in lymphocytes. (iv) Diatom motility. In addition there is some evidence of an effect on genetic transcription and some researchers have
0141-0768/90/ 020063-02/$02.00/0 © 1990 The Royal Society of Medicine
64
Journal of the Royal Society of Medicine Volume 83 February 1990
claimed in vitro effects which might compromise the immune system. However these observations are from a very limited number of laboratories and ,th ei aigrklf ce would be increased if they were independently replicated. A plausible explanation for any harmful effect of such weak electric and magnetic fields as we are considering, would be surprising on two grounds. (1) The sort of currents and fields which would would be induced in the body by exposure to an ambient power frequency EMF would be much less than those which are occurring naturally. For example, the natural currents arising from the muscular activity of the heart or the neurotransmitting activity of the brain are in the region of 10 to 100 milli amps per square metre compared with the whole body induced current of about 3 milli amps per square metre from standing in a field of 10 kV per metre, the highest normally encountered by any member of the public. (2) The total energy imparted to a cell by such weak fields is extremely small. It is for this reason that it is necessary to invoke other explanations such as trigger effects or some sort of resonance to explain how such minute quantities of energy could have such apparently significant effects. A magnetic field may change the direction of motion of a charged particle but it can never change its kinetic energy which is why it would be surprising if an oscillating magnetic field was more effective in producing biological effects than an oscillating electric field. While, therefore, it is conceivable that electrophysiological processes in the organism may be affected by exposure to weak electrical or magnetic fields, it is difficult to envisage a mechanism by which such influences may effect cell transformation. The other factor lacking from all the epidemiology is any exposure measurement. Tomenius7 measured fields at the doors of dwellings and Myers et al.8 calculated fields from knowledge of loads and distances. Savitz3 measured fields in some dwellings but no epidemiological study has been based on measured personal exposure and all attempts to estimate this have been based on surrogate estimations such as the distance from lines or the number and proximity of distribution wires - the sow-alled 'wiring configuration'. Good measurements of actual exposures both of the general public of all ages and occupations and of employees in 'electrical industries' are needed
urgently. From the public health point of view Ahlbom9 has estimated that EMFs might cause 1000 childhood
Planning 'new' genetics services
The science of genetics has developed rapidly during the last few years. It is thought that all inherited disorders will be mapped to their chromosomal location by the year 20001. Research suggests that many ofthe major killer diseases have a genetic basis and that it will be possible to screen people for their propensity for serious disorders and ensure that
cancers annually in the USA if the estimated risk ratios from the Wertheimer and Leeperl and Savitz3 studies are confirmed. In the UK the equivalent number might be 150 to 200 cases. If EMFs are shown to have health effects in adults and at the levels postulated by Savitz of about 2 milligauss, then there could be a significant public health problem because of the ubiquity of fields of this magnitude. I think it is clear that the evidence at present is not sufficient to say that there is a problem and far less to quantify it. On the other hand it is not possible to say that there is no problem. Most independent researchers are doubtful that any problem concerning ill health in humans exists or will be found. On current evidence it is my opinion that electric and magnetic fields may have real effects on a broad spectrum of biological systems but that the fields from power frequency systems do not have any significant health effects for the general public. R A F Cox Chief Medical Officer CEGB References 1 Wertheimer N, Leeper E. Electrical wiring configurations and childhood cancer. Am JEpidemiol 1979;109:273-84 2 Repacholi MH. Non-ionising radiations: physical characteristics, biological effects and health hazard assessment. International Radiation Protection Association, 1988 3 Savitz D. Case-control study of childhood cancer and exposure to 60 Hz magnetic fields. Am J Epidemiol 1988;14:337-43 4 Ahlbom A. A review of the epidemiological literature on magnetic fields and cancer. Scand J Work Environ Health 1988;14:337-43 5 Lin R. Mortality patterns among employees of electric power company in Taiwan. Abstract presented to Contractors' Review Meeting, November, Kansas City, Kansas, USA 1987. 6 Milham S Jr. Mortality in workers exposed to electro
magnetic fields. Environ Health Perspect 1985;62:297-300 7 Tomenius L. 50-Hz electromagnetic environment and the incidence of childhood tumours in Stockholm county. Bioelectro-magnetics 1986;7:191-207 8 Myers A, Cartwright RA, Bonnell JA, Male JC, Cartwright SC. Overhead power lines and childhood cancer. In: Proceedings of the International Conference on Electric and Magnetic Fields in Medicine and Biology. London, 1985 9 Ahlbom A, Albert EN, Fraser-Smith A, et al. Biological effects of Power Line Fields. New York Power Lines Project Scientific Advisory Panel Final Report, 1 July 1987
they are aware of, and can avoid, environmental and dietary factors which may precipitate the disease. DNA probes which can read the human genome have provided the major advance in genetics. Much of the work on DNA has been pure research, but there comes a time when research has to be converted into service, with subsequent problems of planning and organization. There needs to be public debate about service development because there are difficult ethical issues to be faced. To achieve this, education of both public and professionals in genetics is essential to clarify the implications for current and future generations.
0141-0768/90/ 020064-02/S02.00/0 © 1990 The Royal Society of Medicine
63
Editorials Health effects of electromagnetic fields
Magnetism and the phenomena of electricity have been appreciated and progressively better understood since the 17th century, while electrophysiology is primarily a 20th century science but still long enough established to be widely understood by the scientific community and, at least, apparent to the general public. For many years it has been thought that some animal species, particularly birds and whales, are sensitive to the Earth's magnetic field and use it for navigational purposes. One may well ask therefore why the public, comfortable with using electricity all their lives and for two or three previous generations familiar with its phenomena, and appreciative of its benefits and safety, should suddenly have become so suspicious about its long term effects. The answer I believe lies largely outside anything to do with electromagnetism itself. It is more a result of a better educated and enquiring and less easily satisfied public; the pervasive and profound influence of the media; an emotive and disproportionate concern about cancer and a sensitized distrust of large institutions whether Government or commercial. In spite of their better education, however, the public are still persuaded by much quasi-scientific work on electromagnetic fields (EMF), unsupported by acceptable scientific evidence. In 19791 the public and the media seized upon a poor epidemiological study, which was hypothesis generating and not hypothesis based, whose authors were impressed by the sight of electrical wiring configurations in the vicinity of childhood cancer cases. From an epidemiological point of view this paper is open to criticism - the controls are of poor comparability to the cases, the investigators knew which were cases and which were controls, the epidemiological analysis was poor and there is a remarkable and surprising consistency among the comparisons which stretches its credibility. Nevertheless, this paper caused many other researchers to attempt to confirm or refute these surprising findings in various population studies2. The Savitz3 study is, perhaps, the most definitive epidemiological study so far. However, the numbers were small, Savitz himself admits that the responses by the controls, especially, were poor, and although there was a weak but statistically significant relationship between cases and wiring confilguration in the highest wiring codes, this was not apparent where magnetic fields were measured. He only had a 71% response rate for cases and he was unable to characterize the non-participants. Magnetic field measurements were only performed for 36% of the cases and, while he produced 66 odds ratios, only seven were statistically significant. Savitz himself admits:
'As indicated in the press coverage, our study suggests a link between prolonged magnetic field exposure from electric power lines near residences and risk of childhood cancer. It shouId be kept in mind, however, that we have not proven that magnetic fields cause cancer. Subsequent research will indicate whether we are on the right track or whether our results are in error. Thus, there is a suggestion of a possible hazard which has yet to be resolved. Given these circumstances, it seems that interest or concern may be justified, but our study is not sufficiently convincing to warrant drastic action by homeowners'.
Ahlbom4 has recently reviewed the various studies and notes some consistency between them. However, he states that it is not possible, from the available information, to conclude whether or not exposure to magnetic fields increases the risk of cancer. Rather more epidemiological studies have been done on occupational groups and most of these studies do show an increased risk of leukaemia2. The problem with all these studies is the lack of definition of 'electrical workers' or the inclusion of non-electrical workers. Lin5 for example, included in his cohort all workers in the industry whether they worked in generation or accounts, transmission or transport. It is also known, of course, that many electrical workers also handle chemicals, solvents, fluxes and other materials which are known to be leukaemogenic or are suspected carcinogens. While these studies contain many uncertainties and confounding factors, the fact that so many of them show a proportional incidence ratio or a proportional mortality ratio of 130 to almost 3006 has led many people to assume that a trend must be concluded. An objective assessment of the epidemiological evidence must, I think, lead one to the conclusion that it is weak and unconvincing. Apart from its intrinsic weaknesses it lacks two vitally important components: (i) a plausible biological hypothesis and (ii) any direct measurements of exposure to either electric or magnetic fields. The biological work which has been done in this field includes exposure experiments using alternating and direct current, sinusoidal and pulsed fields, predominantly electrical or predominantly magnetic fields with frequency and amplitude modulation on a variety of models from cell cultures to chick embryos and whole rodents to whole men. The field strengths used are generally orders of magnitude greater than those implicated by the epidemiological findings. It comes as no surprise to find that a wide variety of effects have been reported. Most researchers have concentrated on the cell membrane in the search for a hypothesis to explain these observations and Sagan (personal communication) has defined a number of phenomena related to membrane function including: (i) Changes in calcium binding to cell surfaces. (ii) Reduced binding of cytotoxic lymphocytes to cell surface receptors. (iii) Changes in membrane transport and secretion, eg decreased insulin release from pancreatic cells and calcium flux in lymphocytes. (iv) Diatom motility. In addition there is some evidence of an effect on genetic transcription and some researchers have
0141-0768/90/ 020063-02/$02.00/0 © 1990 The Royal Society of Medicine
64
Journal of the Royal Society of Medicine Volume 83 February 1990
claimed in vitro effects which might compromise the immune system. However these observations are from a very limited number of laboratories and ,th ei aigrklf ce would be increased if they were independently replicated. A plausible explanation for any harmful effect of such weak electric and magnetic fields as we are considering, would be surprising on two grounds. (1) The sort of currents and fields which would would be induced in the body by exposure to an ambient power frequency EMF would be much less than those which are occurring naturally. For example, the natural currents arising from the muscular activity of the heart or the neurotransmitting activity of the brain are in the region of 10 to 100 milli amps per square metre compared with the whole body induced current of about 3 milli amps per square metre from standing in a field of 10 kV per metre, the highest normally encountered by any member of the public. (2) The total energy imparted to a cell by such weak fields is extremely small. It is for this reason that it is necessary to invoke other explanations such as trigger effects or some sort of resonance to explain how such minute quantities of energy could have such apparently significant effects. A magnetic field may change the direction of motion of a charged particle but it can never change its kinetic energy which is why it would be surprising if an oscillating magnetic field was more effective in producing biological effects than an oscillating electric field. While, therefore, it is conceivable that electrophysiological processes in the organism may be affected by exposure to weak electrical or magnetic fields, it is difficult to envisage a mechanism by which such influences may effect cell transformation. The other factor lacking from all the epidemiology is any exposure measurement. Tomenius7 measured fields at the doors of dwellings and Myers et al.8 calculated fields from knowledge of loads and distances. Savitz3 measured fields in some dwellings but no epidemiological study has been based on measured personal exposure and all attempts to estimate this have been based on surrogate estimations such as the distance from lines or the number and proximity of distribution wires - the sow-alled 'wiring configuration'. Good measurements of actual exposures both of the general public of all ages and occupations and of employees in 'electrical industries' are needed
urgently. From the public health point of view Ahlbom9 has estimated that EMFs might cause 1000 childhood
Planning 'new' genetics services
The science of genetics has developed rapidly during the last few years. It is thought that all inherited disorders will be mapped to their chromosomal location by the year 20001. Research suggests that many ofthe major killer diseases have a genetic basis and that it will be possible to screen people for their propensity for serious disorders and ensure that
cancers annually in the USA if the estimated risk ratios from the Wertheimer and Leeperl and Savitz3 studies are confirmed. In the UK the equivalent number might be 150 to 200 cases. If EMFs are shown to have health effects in adults and at the levels postulated by Savitz of about 2 milligauss, then there could be a significant public health problem because of the ubiquity of fields of this magnitude. I think it is clear that the evidence at present is not sufficient to say that there is a problem and far less to quantify it. On the other hand it is not possible to say that there is no problem. Most independent researchers are doubtful that any problem concerning ill health in humans exists or will be found. On current evidence it is my opinion that electric and magnetic fields may have real effects on a broad spectrum of biological systems but that the fields from power frequency systems do not have any significant health effects for the general public. R A F Cox Chief Medical Officer CEGB References 1 Wertheimer N, Leeper E. Electrical wiring configurations and childhood cancer. Am JEpidemiol 1979;109:273-84 2 Repacholi MH. Non-ionising radiations: physical characteristics, biological effects and health hazard assessment. International Radiation Protection Association, 1988 3 Savitz D. Case-control study of childhood cancer and exposure to 60 Hz magnetic fields. Am J Epidemiol 1988;14:337-43 4 Ahlbom A. A review of the epidemiological literature on magnetic fields and cancer. Scand J Work Environ Health 1988;14:337-43 5 Lin R. Mortality patterns among employees of electric power company in Taiwan. Abstract presented to Contractors' Review Meeting, November, Kansas City, Kansas, USA 1987. 6 Milham S Jr. Mortality in workers exposed to electro
magnetic fields. Environ Health Perspect 1985;62:297-300 7 Tomenius L. 50-Hz electromagnetic environment and the incidence of childhood tumours in Stockholm county. Bioelectro-magnetics 1986;7:191-207 8 Myers A, Cartwright RA, Bonnell JA, Male JC, Cartwright SC. Overhead power lines and childhood cancer. In: Proceedings of the International Conference on Electric and Magnetic Fields in Medicine and Biology. London, 1985 9 Ahlbom A, Albert EN, Fraser-Smith A, et al. Biological effects of Power Line Fields. New York Power Lines Project Scientific Advisory Panel Final Report, 1 July 1987
they are aware of, and can avoid, environmental and dietary factors which may precipitate the disease. DNA probes which can read the human genome have provided the major advance in genetics. Much of the work on DNA has been pure research, but there comes a time when research has to be converted into service, with subsequent problems of planning and organization. There needs to be public debate about service development because there are difficult ethical issues to be faced. To achieve this, education of both public and professionals in genetics is essential to clarify the implications for current and future generations.
0141-0768/90/ 020064-02/S02.00/0 © 1990 The Royal Society of Medicine
