New evidence from Sweden has convinced many authorities of links between household exposure to electromagnetic fields and leukemia.
The question of health hazards from power-line electromagnetic fields (EMFs), has recently become the focus of much media attention in the UK.
In the first such case in Europe, a Lancashire couple are suing the local power company for the death of their 13-year-old son of leukemia. Furthermore, a group of residents in north London recently won a Judicial Review, due to take place in late July, over the laying of a 275,000 volt cable under their streets.
Considerable evidence now shows that living near relatively low levels of magnetic fields from mains electricity or power lines can raise the chances of your child getting leukemia by three or four times. In 1979, two American researchers, Nancy Wertheimer and Ed Leeper, published the first major Western study linking EMFs from power lines and domestic wiring configurations to an increase in childhood cancer (Am J Epidemiol 1979; 109: 273-84).
Since then the evidence has got stronger; today, with recent Swedish results in particular, the National Grid can no longer dismiss it and is being forced to defend itself against a barrage of enquiries from the public and the press, and even threats of legal action.
There are now some 12 studies of residential exposure to EMFs, of which nine show an elevated risk of childhood cancer; the three studies which do not have been criticized for the way they were put together. Teslas are a measure of the density of magnetic fields. An average household level is 70 nanoteslas (nT = one thousandth of a millionth Tesla); the level beneath power lines can rise to over 1000 nT.
On average the positive studies have found a significant increased risk at 200-300 nanotesla, whereas the National Radiological Protection Board's (NRPB) will only begin to investigate at a level of 1600 microtesla (uT = millionth of a Tesla) a difference of between 5,400 and 8,000 fold.
In the US the situation is very different. Many researchers advocate a general policy of "prudent avoidance" recommending a number of safety measures to avoid excessive exposure. At least 10 states have requirements on the level of EMFs allowed in houses built near power lines. There is also considerable litigation over health hazard claims from residential and occupational exposure.
Electric and magnetic fields surround all electrical conductors, including power lines, appliances and the wiring in your house. EMFs are comprised of electrical fields and magnetic fields. Electrical fields, determined by voltage, from 240 volts in houses up to 400,000 volts on main power lines, are generally highest around high-voltage transmission lines. The fields are similar to the static electricity you feel when you get a small shock from a new carpet. Unless you live near a power line, this isn't going to be a major problem, since they can be shielded by trees and walls.
Magnetic fields, on the other hand, are generated by electrical current whenever you use electricity. They are more worrisome because they can travel through walls and can't be shielded against, except with lead shields, careful design of wiring and electrical equipment.
The crux of the argument over what levels of EMFs constitute a hazard concerns the difference between thermal and non-thermal effects and the perception of their harm. All electrical fields generate the same type of energy as ordinary sunlight. Thermal effects refer to those that occur when tissue is heated to a specific level at which damage takes place by a given frequency at a given intensity. This is how a microwave cooks food.
Non-thermal effects are those that occur below in many cases well below the level at which tissue heating occurs. Many scientific papers have shown that non-thermal effects do exist a conclusion which the NRPB and other orthodox scientists accept. Where the disagreement lies is over the question of the level at which these effects actually become harmful.
Here, independent researchers and other concerned parties are at loggerheads with the NRPB, which does not yet accept the implications of the majority of residential results pointing to the at risk onset level of 200-300 nT for childhood cancer. The NRPB is the appointed body charged with advising the Government and other bodies, including the National Grid and Health & Safety Executive. It continues to base any exposure guidance on a level of relating to thermal levels or known levels of damage.
In September 1992 Drs Maria Feychting and Anders Ahlbom, at the Institute of Environmental Medicine at the Karolinska Institute in Stockholm, announced the results of a large-scale epidemiological study, which found that children exposed to average domestic EMFs of 300 nT or more had almost four times the rate of leukemia than expected. The study has now been published in the American Journal of Epidemiology (1993; 138(7): 467-81).
The subjects were the 500,000 odd people who had lived within 300 metres of the country's network of 220 and 400 kV powerlines between 1960 and 1985, of whom 142 children developed cancer.
Probablyone of the soundest studies to date in terms of methodology, the Swedish study established for the first time a clear dose response correlation between level of magnetic field exposure and increased incidence of leukemia. Children exposed to above 100 nT EMFs had twice, those exposed to above 200 nT nearly three times, and those exposed to over 300 nT nearly four times the incidence of leukemia than those exposed to less than 100 nT. Similar results were obtained when exposure was defined by proximity to power lines.
Such was the impact of this and another study released at the same time, which also found a strong link with brain tumours in men occupationally exposed to EMFs (Cancer Causes Control, 1993; 4: 465-76), that Sweden's National Board for Industrial and Technical (NUTEK) formally announced that from henceforth it "would act on the assumption that there is a connection between exposure to power frequency magnetic fields and cancer, in particular childhood cancer."
In addition, NUTEK has advocated a moratorium on erecting power lines creating fields of 200 nT near houses and school buildings until further guidance, currently being drafted.
Indeed, even Professor Richard Doll, who now chairs the UK's NRPB's Advisory Group on Non-Ionizing Radiation, has admitted that the Swedish study is significantly better controlled and designed than previous ones and thus increased the pressure on his organization to carry out equally well-controlled studies of its own.
This is now about to be attempted in the form of a five-year, £5m study by the UK Coordinating Committee for Cancer Research (UKCCCR), chaired by Professor Doll and funded by several medical charities and the electrical and nuclear industries. However, although EMFs are one of the factors researchers will be considering, there is concern by some independent researchers that certain specific factors may not be measured.
Roger Coghill, who runs one of the UK's few independent consultancies on EMFs in Pontypool, Wales, has also argued that, whereas the magnetic field has been the main parameter considered in exposure studies to date, electric fields may in fact be the more significant factor. At present the measure is not incorporated into the UKCCCR study's protocol.
The Feychting and Ahlbom study corroborates previous research by Dr John Peters in the US who found a significant link between wiring configurations in the home and childhood leukemia (Am J Epidemiol 1991; 134: 923-7) and Dr David Savitz who also observed a two to threefold increased risk in homes where the estimated magnetics exceeded 250-300nT (Am J Epidemiol 1988, 128: 21-38).
This cut-off level of increased risk has generally been supported by the other positive studies to date.
Pooling the results of three Nordic studies including the recent Swedish one, Ahlbom and Feychting show a consistent doubling of childhood leukemia risk (The Lancet, 20 November 1993). Nevertheless, the earlier studies, including that of Savitz, have confused researchers because they showed a positive association between the power load of the overhead lines and distance from the home, but not with the measurements inside the homes of children who developed leukemia (JAMA, 5 Aug 1992). This was the main reason that researchers rejected the earlier data.
Gerald Draper, director of the Childhood Cancer Research Group, spoke for the orthodox view when he argued that the "lack of consistency" among published studies and the absence of an "accepted biological explanation for such a relation" means that no causal relation has been established, although with the Swedish study it could no longer be dismissed (BMJ, 9 October 1993).
A further dimension to the whole power lines/EMF concern is that childhood leukemia is but one of the possible health hazards identified, albeit the most researched. Other studies have found links with depression, heart attack and suicide, as well as minor problems, such as headaches, insomnia and irritability.
As in the past, the UK continues to take a conservative view. Until recently, Michael Heseltine, UK's Secretary for Trade and Industry, was sitting on the Report of the inspectors on the Yorkshire Powerline Enquiry, the largest public enquiry ever held in the UK since November last year. The enquiry concerns the proposed route of a 50 mile 400,000 power line from Enron power station in North Yorkshire and took place between May and September 1992. The report, which has just been released, has given the power line the go ahead, but not only if landowners agree which could lead to another Judicial Review.
Dr Leonard Sagan from the Electric Power Research Institute in Palo Alto believes that the most important research on EMFs must attempt to isolate which kind of exposure causes damage. "We must understand . . . whether there is a threshold level of exposure (dose) that must be surpassed to produce effects, or whether there are 'windows of exposure' of intensity or frequency, within which EMF may cause an effect," he says.
Simon Best is editor of Electromagnetics & VDU News, which publishes quarterly news report of EMF hazards. For details or a list of EMF consultants send a SAE to PO Box 25 Liphook, Hants GU30 7SE.