KILLING FIELDS THE EPIDEMIOLOGICAL EVIDENCE The threat posed by low frequency fields emerged initially because a reseacher, looking for environmently factors in childhood leukaemia, observed a link between low voltage, high current power lines and disease occurrence. Cellular evidence now supports the findings but epidemiology still leads the argument. by: Simon Best Today living systems are exposed to a level of man-made electromagnetic fields (EMF's) in all aspects of modern life to a degree never experienced before on this planer, most of it resulting from technological advances over the past 40 years. Whether at home or at work, EM fields generated by domestic wiring, overhead high voltage lines and occupational equipment, as well as other environmental sources such as radar, microwave communication systems, radio and television broadcasting, cellular telephones, and the ubiquitous VDT, all contribute to an indivual's cumulative chronic exposure. Growing awareness of this situation has led to the question being debated and researched, for at least the past 30 years by Western scientists (and even longer by the Russians), as to whether and to what extent this chronic exposure is harmful. The often heated debate continues but over the past few years there are signs that certain scientific and legislative authorities, particularly in the United States, are beginning to accept the need for revised protective regulations and safety legislation, despite continued official denial or ambivalence in some quarters, notably in Britian. The UK's National Radiological Protection Board (NEPB) recently published its final guidelines (1) on restricting public and occupational exposure in both the extremelylow frequency (ELF) 50Hz power frequency and the much higher frequency RF and microwave parts of the electromagnetic spectrum. Although these go further than any previous such guidelines, they can be criticized on a number of counts, as will be described below. Also, they are proposed only as guidelines, with decisions on new legislation left to the relevant minister; significantly, no mention of electromagnetic fields was made in the Government's recent proposed Green Bill. Bioelectromagnetics is the study of the effects of electromagnetic fields on biological systems and an understanding of significant events and issues in its recent history is necessary to appreciate currend debate and developments. Research on the possible harmful effects of EM fields began to appear in earnest after the war, partly due to the advent of radar, emerging as an issue in the 1960's mainly as a result of Russian work (2). Observed health problems affecting switchyard workers and others occupationally exposed to EM fields led the Russians to develop a standard for public exposure to microwave and RF EM fields that was , at 10uW/cm^2, 1000 times lower than that considered safe in America and other Western countries. The Americans, however, developed their guidelines, such as they were, from a model of human absorption of electromagnetic energy tahat took account only of the effects of heating body tissue - the so-called thermal mode. In the 1950's, Professor Herman Schwan, a physicist who arrived in the US after teh War and has been based at the University of Pennsylvania ever since, mainly funded by the Department of Defense, invented the microwave oven for use in submarines. Schwan used metal balls and flasks of salt water to model the human body's ability to dissipate heat to estimate a danger level of exposure. Observing that significant heating only occurred above 100mW, he incorporated a safety factor of 10 and, in 1953, proposed a safey limit of 10mW/cm^2 for human exposure. By 1957/58 industry and the military had, with little real debate or further experimentation - and none for nonthermal effects - accepted the level as an informal guideline. In 1965 the Army and Air Force formally adopted the 10mW/cm2 limit and one year later the American National Standards Institute (ANSI) accepted it as an occupational exposure standard. The ANSI decision is remarkable, since Schwan has consistently maintained that his dosage limit is safe for probably no more than an hour. As will be discussed below, current debate on revising the ANSI standard is suggesting reductions by between 10 and 100 times. And it is the growing and accumulated evidence supporting the reality of non-thermal effects that has fuelled this debate, much of which, in the face of opposition and limited funding, has been finally carried out over the past decade. The first well-controlled Western study lining power line fields and childhood leukaemia was reported by University of Chicago researchers Drs. Nancy Wertheimer and Ed Leeper in 1979, from a case-control study of 344 children aged 18 and under in the Denver area (3). Using a wire coding and configuration assessment of the high-current electric cables near the children's homes to indicate 60Hz magnetic-field exposure, they found a statistically significant increase in childhood cancer in the exposed children, a relationship tht increase with proximity. In the UK in the same year an Albrighton GP, Dr. Stephen Perry, collaborated with three US researchers in New York to study suicide in the Shropshire/Staffordshire area. He measured teh residential magnetic-field strength outside the front door of homes and found significantly higher fields (0.1uT or more) at those of suicides as opposed to controls (less than 0.1ut); the results were published in 1981 (4). A significant trend in risk of suicide was shown with increasing field strength. A year later Tomenius, in Sweden, reported a two-fold increase in the incidence of childhood cancers in homes within 150m of visible 200kV power lines, his work being published in a revised form in 1986 (5). (As in the UK, Europe uses a 50Hz power frequency.) At addresses where the magnetic field exceeded 0.3uT, the relative risk was 2.7 (95% CI 1.2-5.9); when the sample was restricted to those living at the same address since birth, the relative risk rose to 5.6 (95% CI 1.8-17.9). One year before Wertheimer and Leeper's study, the New York Public Service Commission reached a decision in a hearing concerning two proposed 765kV lines to run from the Canadian border to locations in New York State. After an acrimonious hearing the New York Public Service Commission permitted the lines to be erected but only on two conditions: that the power utilities involved fund a five-year, five-million-dollar research project, known as the New York State Power Lines Project (NYSPLP), to study possible hazards from power-frequency EM fields; and that a 350 feet right-of-way (ROW) corridor either side of the lines be established within which no human dwelling ws to be permitted, as already existed for 345kV lines. Almost simultaneously, a public inquiry in the UK was taking place into the proposed re-routing of power lines near the village of Innsworth, Gloucestershire. Is eventual result, however, was very different, with the objection being overruled by the two inspectors (one each from the Departments of Energy and the Environment), but without any independent medical assessment of the evidence. That illustrates the stark contrast between legislative progress in the US compared to the UK. Today, 10 years later, despite seven American states having now adopted similar ROW's to those in New York state, no such recognition is given in the UK of the need for ROW's around power lines. The results of Wertheimer and Leeper, Perry and Tomenius, as well as teh setting up of the NYSPLP, led to a growing number of studies of both residential and occupational exposure to ELF EM fields. Wertheimer and Leeper extended their research to adults and observed at least a two-fold increase in adult leukaemia linked to fields from wires near the home (6), while others found correlations with occupational groups exposed to ELF fields, such as electrical and electronics workers and repairmen, and leukaemia in general; Milham (7) and Stern (8) in the States, Coleman and colleagues in the UK (9) and Pearche in New Zealand (10). Similar occupational studies have linked pharyngeal cancer (11), eye melanoma (12), and primary brain tumour (13,14). One of the most consistent connections was observed with myeloid leukaemia, with studies from teh UK (15,16), Sweden (17) and the US (18,19) all finding an elevated risk. Some of the results of the occupational studies have been criticized on the basis that workers might have also been exposed to fumes and substances (such as PCB's) then used in electrical components or asseblies. However, in one of the US studies of myeloid leukaemia, Milham (19) studied radio amateurs and found a greatly increased risk of myeloid and unspecified leukaemias in both those with and without occupational exposure, thus supporting the hypotheses that it is the electromagnetic fields themselves that are the hazard. Meanwhile, on the question of residential exposure and cancer, the CEGB hac, by 1985, caried out only one piece of research, a pilot study of childhood leukaemia reported at a conference (20), an inconclusive result which the authors nonetheless admitted had certain shortcomings and of which a revised version has apparently now finally been submitted for publication. During this time, other laboratory work was confirming the ability of low-intensity EM fields to cause biological effects below the thermal level and revealing some frequency-specific actions of modulated fields. Dr. Ross Adey and his coworkers have demonstrated the effect of specific modulated frequencies on the efflux of calcuim ions from cats' brains (21,22), which has been confirmed by Blackman and others (22,23). The combination of the highly suggestive epidemiological results and the growing evidence from animal and cellular studies led, in 1986, to a landmark pronouncement by the American Advisory Committee on the Non-Thermal Effects of Non-Ionizing Radiation. Reporting to the United States National Academy of Sciences' National Research Council, it finally accepted the reality of non-thermal effects and stated that "Abundant fragmentary evidence has been presented in support of possible biological effects from non-ionizing radiation, at both transmission and microwave frequencies. These effects often appear to be unaccompanied by macroscopic thermal changes" (24). The report drew the distinction between a biological effect and the point at which it becomes a hazard and stopped short of discussing when this might occure, but the announcement was a significant turning-point in the continuing debate. A further significant event occurred on July 1, 1987 when the New York State Power Line Project finally reported amid wide media coverage (25) (a copy resides in the House of Commons library). Of the 17 funded studies, 12 reported significant disease and depression . . ." was reported in those living near the cable. A further provocative finding was that, if only those blocks with underfloor or storage electric heating were considered, the proportion of cases of "depression" living in flats near the rising cable rose by 82%. (Wertheimer and Leeper have recently linked increased miscarriage rates with EM fields from ceiling-cable heating; see below (33).) It is interesting that even Perry's lowest measurements of fields in apartments distant from the cable are 50% above the average residential fields measured by Bowman, while his average `near' readings were over three times Bowman's figure. It is also worth noting that when Savitz revised and refined his original data on childhood leukaemia (26), he found that, whereas when he had used a 0.2uT cutoff for classifying the 60Hz exposed group he had observed a relatively weak, if two-fold, association between measured magnetic field and leukaemia, when he increased the cut-off to 0.3uT, the risk became "... notably larger". Thys, Tomenius', Savitz' and Perry's (two) studies together indicate that there may be a residential level between 0.2 and 0.3uT at which chronic power-frequency EM field exposure begins to manifest as a recognised clinical condition; in which case, occupational levels of between 1uT and 5uT and above, as measured by Bowman, may represent a considerable hazard, despite exposure being confined only to working hours. Currently the NRPB is recommending a level of 2mT for both public and occupational magnetic-field exposure, approximately 10,000 times above the levels indicated by Savitz, Perry and others as hazardous. But what is equally disquieting is that in 1986, in a set of proposed standards on which the NRPB invited comments (34), it was suggesting both one set of standards for workers and two different sets for the public: for workers (two hours exposure per day), 30kV/m and 1.88mT: for the public, 12kV/m and 0.76mT (up to five hours per day) and 2.6kV/m and 0.174mT for continuous exposure. With the published research after 1986 increasingly pointing to am EM field hazard both occupationally and residentially, particularly from magnetic fields as low as 0.2-0.3uT, as outlined above, one must ask on what basis did the NRPB, three years later, decide to recomment that public and occupational continuous exposure levels be revised upwards, in the case of continuous residential exposure to electric and magnetic fields by, respectively, some five and ten times? Following Perry's investigation of depression, a further study of depression and chronic headache was carried out by another British GP, Dr. David Dowson, in the Southampton area (35). Giving a questionnaire to patients living within various distances of overhead lines and a control group living three miles away, Dowson found that 15 in the former group versus one in the latter reported recurrent headaches, the highest number (10) living at 80-100m from a 132kVline. Nine patients in the study group reported depression (seven lived within 40m of the lines), as against onl one in the control group. No measurements of electric or magnetic field were taken. In the US, Wertheimer and Leeper, in a study first presented to the New York Academy of Sciences in 1984, reported theat pregnancies among couples using electric blankets were more likely to end in miscarriage than those among couples who did not heat their beds electrically (36). They found a trend toward slower foetal development among babies born to parents using electric blankets or water beds, which generate magnetic fields of 1.0-1.5 and 0.3-0.4uT respectively. The researchers observed a clustering of spontaneous abortions from September to June among electric blanket users; for those using either electric blankets or water beds the miscarriage rate was significantly higher during the September-June period. No such seasonal pattern was observed among non-users. Wertheimer and Leeper implicated electric blankets in a further study (37) in which they re-analysed the apparently negative results of Stevens on the incidence of acute non-lymphocytic leukaemia in adults exposed to ELF fields redidentially, originally funded as part of NYSPLP. Using Stevens' data, they were able to assess the chronic use of electric blankets, waterbed heaters and electric mattress pads. By taking these and other refinements into account, Wertheimer and Leeper calculated that the risk of leukaemia in those exposed to EM fields from either power lines or electrically heated beds rose 50-90% and, if exposed to both, by 110-260%. Most recently, Wertheimer and Leeper, in an attempt to distinguish heating from EM field effects, have also linked miscarriage and domestic EM fields from ceiling cable heating (38). It has been hypothesized that electric blankets may interfere with the menstrual cycle by affecting the pineal gland's secretion of melatonin, which in turn may also led to depressive states in men and women. A study is presently under way at the Yale School of Medicine on the prevalence of electric-blanket use in a group of 4000 pregnant women to determine the feasibility of studying the growth of children exposed to EM fields in utero. Regarding adult leukaemia, Wertheimer and Leeper have extensively analysed teh cancer incidence among adults living near high-current power line in and around Denver, Colorado (39). They found that certain cancer subtypes, especially nervous-system cancers, were associated with two measures of exposure to 60Hz magnetic fields. Both those exposed occupationally and residentially showed similarities in the subtypes they contracted. In a further memorandum, the researchers discuss a possible explanation for why some studies have reported no linear increase in cancer in children with increased intensity of EM field exposure prenatally (40). They confirm that, in their own and other studies, moderate exposure prenatally was associated with increased cancer after birth, whereas extreme exposure prenatally was not. They hypothesise that this occurs because magnetic fields "... can have an adverse effect on tissue development which, if it is severe and occurs in the first trimester of pregnancy, may often lead to prenatal abortion rather than postnatal cancer". Clearly, if valid, their suggestion may also help explain some of the contradictory findings on leukaemia clusters and ionizing radiation sources in the UK, notably nuclear reprocessing and military installations. Synergistic interactions between ionizing and non-ionizing radiation generated around such sites (the latter from the power lines that often originate from such locations) should also not be overlooked. All of which does not apparently, impress the NEPB, whose safety guidelines are firmly based only on thermal considerations, although their May 1989 document states that they intend to publish a "... review of the existing biological and epidemiological evidence in the near future". Not suprisingly, the CEGB tends to hold a similar view regarding the lack of hazard from power line or domestic wiring EM fields. However,in March 1988, possibly galvanised by Savitz' results and the NYSPLP Report in the previous year, they announced a L500,000 research project on ELF eM field bioeffects, involving studies of theri own staff, childhood leukaemian and domestic measurements. But no results are yet available and may ot be for some time. When evaluating US and UK residential research, on needs to consider the differences in the distribution of power to homes between the two countries. In the US, transmission lines carry up to 765kV, while poles carry local distribution wires down the streets and at intervals also carry transformers which step down the 7.6kV area feed to 115vV for domestic use. Indeed, it was the clustering of childhood cancer cases in homes at certain cistances from these pole-mounted transformers and associated 3-phase wiring which first caught Wertheimer's atention in the mid-1970's. From these, a single-phase supply then enters the house half way up the building, very often at or near the bedrooms. By contrast, in Britain transmission lines carry 132, 345 or 400kV, with most domestic supply ariving underground, having been stepped down from the area substation by smaller local transformers (from 33 to 11kV, and from 11kV to the domestic 240V). The cables, carrying the wires in a close, helical arrangement, thus generating a minimal unbalanced current, then enter the house through the basement or ground floor to connect to a meter (except in high-rise blocks, where they run up the side of the building). However, this is not always the case, as in parts of Norfolk, Suffolk and other rural areas, where supply arrives on poles down the streets, as in the United States. Nonetheless, with both methods, significant magnetic fields in the home can be generated by unbalanced ground return currents. Because some have argued that these differences in mode of domestic supply and associated EM fields may explain the generally more positive American residential study results against the relatively few but more megative or ambibalent UK results (20,41), it could be very illuminating if the CEGN or other researchers were to compare the incidence of major and minor illness (from cancer, heart disease and immune system problems to miscarriage, depression and sleeping problems) in samples of both adults and children living in homes supplied by the two different methods. In Myers' preliminary results (20) of childhood cancer in the north of England, of which a revised update is apparently to be published shortly, some 7% of the controls lived within 100m of an overhead power line; the relative risk for those living within 50m was a non-significant 1.25 for leukaemia and lymphoma (95% CI 05.-3.1) and 1.61 for solid tumours (95% CI 0.6-4.6). Criticism of the small number of exposed subjects and other shortcomings must await the final published version. McDowell's cohort study (41) of 7631 people living in East Anglia within 30m of an overhead power line or within 50m of a transformer substation found a significant excess in lung cancer in women though not in men, although no smoking data was available. For those living within 15m of a source, the standardized mortality ratios were higher for lung cancer, leukaemia and other lymphomas, though numbers of deaths were small. The results applied mainly to substations, since only 0.2% of the sample lived within 30m of an overhead power line. The inconclusive results of Coleman and colleagues in the recent publication of a study, first reported in 1985, of leukaemia in those living near overhead power lines or substations in four London boroughs (42) emphasizes the problems of estimating exposure and obtaining a sufficient sample to provide a meaningful result. In the study only 0.6% of subjects lived within 100m of a power line, whereas over 40% lived within 100m of a substation. Nonetheless, for those under 18 the relative risk of leukaemia from residence within 50m of a substation was in fact higher than in adults (RR=1.5, 95% CI 0.7-3.4). Besides the problem of sampling, any future residential studies must now also consider the occupational exposure of the working adults involved, given the many studies linking electric occupations with greatly increased risk of various cancers (and vice versa for o occupational studies). Exposure to other known environmental hazards must also be controlled for, including the increasingly recognised hazard of (ionizing) radon. The location of a child's school near overhead power lines or substation would also be significant. but the question one still has to ask is whether ther is already enough suggestive evidence on which to recommend some preventative action. Epidemiological studies are rarely conclusive, but when teh majority of occupational and residential studies, despite differences in design and possible confounding variables, seem to point in the same direction, perhaps it is time to err on the side of caution and, for example, to call for a moratorium on the erection of power lines over homes and schools, and vice versa. The CEGB is unlikely to accept such a proposition, particularly with the implications for its looming privatisation, without some form of exemption fromlegal liability. But if a system of no-fault compensation could be introduced, as exists in countries such as New Zealand and Sweden, whereby the state accepteed basic responsibility for treating and possibly compensating people exposed to such a hazard, a way forward acceptable to the CEGB and local area boards and favourable to the public might be found. With some US and UK researchers publicly stating that they would not live under a power line, perhaps the CEGN might at least be required to offer to purchase homes under or very near power lines at market value to resell to those prepared to take the risk, as a utility in British Columbia in Canada recently did. Certainly, long and expensive litigation, as has occurred in the US, may only serve to entrench both sides and delay help for those at risk, though it has definitely brought the issues to the attention of the public and the media there. The case need not be that the evidence is conclusive, merely that it is now sufficient to warrant certain precautionary measures, both for domestic and occupational exposure. Regarding the latter, the Industrial Injuries Advisory Council (IIAC) will take some persuading, it would seem, judging by their opinion on the hazards of non-ionizing radiation from various occupational sources (43). Their statement that "The available evidence indicates that chronic low level exposure to non-ionizing radiations appears to be generally harmless: would be greeted with something approaching derision by most researchers, even taking account of its date of consideration in March 1987. Whether or not the CEGN disappears, the problem will remain for the private tranmission and distribution companies, who can no longer claim ignorance of research findings and will presumably be required to carry on the CEGB's research in this area. Is it worth risking the negative publicity and threat of class-action litigation in the future tht would cloud privatisation plans, or will the electricity industry, in conjunction with the Government, consider it wise to `green' their respetive images and work out some sort of solution to the problem of electromagnetic fields in the environment which many now feel pose a growing and chronic threat to their health? Evidence of electromagnetic bioeffects mounts despite official ambivalence.