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Can your toaster give you cancer of the blood, breast or brain? Has
it the electric toothbrush got it in for you? Will a stroll beneath overhead
power lines interfere with your sleeping patterns? Is the wiring behind
the walls and under the floorboards an insidious deathtrap?

People have demanded answers to these questions since 1979, when Nancy
Wertheimer, an epidemiologist, wrote a paper with Ed Leeper, an independent
physicist in Boulder, Colorado, purporting to show that children living
close to power transmission lines were twice as likely to contract leukaemia
as children in homes farther away.

Leeper and Wertheimer, who works at the Health Sciences Center at the
University of Colorado, drew a storm of protest when they first announced
their findings. Other scientists complained because the two investigators
had calculated, not measured, the size of the electromagnetic fields involved.

Public alarm ensured that further studies followed, but the questions
still loom almost as large as they did in 1979, according to Tony Barker
of the Royal Hallamshire Hospital at the University of Sheffield, who chaired
a working party commissioned by the Institution of Electrical Engineers
to report on progress to date. Barker stresses three fundamental problems.
The first is that epidemiological studies are unlikely to throw much light
on the problem, primarily because it is difficult to attribute an illness
unequivocally to electromagnetic fields rather than to something else. Secondly,
laboratory experiments to measure the effects of electromagnetic fields
on living things have proved almost impossible to replicate. Moreover, the
results from different laboratories are difficult to compare because of
the lack of common experimental procedures.

WEAK FIELDS POSE A PUZZLE

The third big problem is that the inconclusive epidemiological and experimental
material available has made it almost impossible to advance theories to
explain how, if at all, electromagnetic fields disrupt the functioning of
living cells. How do such tiny electric and magnetic fields impart enough
energy to do any damage to cells or tissue?

Speaking last month at a conference in London on the biological effects
of low-frequency electromagnetic fields, Barker said that international
collaboration is required to avoid the sort of duplication of effort that
occurs in states in the US where researchers produce thousands of uncorrelated
papers. The second objective, said Barker, was to agree on experimental
protocols to make it easier for scientists to repeat one another’s work.
‘We should develop models that are robust and work in more than one person’s
laboratory,’ he said.

The unreliability of the scientific data means that regulatory authorities
have no basis on which to recommend limits on exposure, said Zenon Sienkiewicz
of the National Radiological Protection Board. To set limits, you must first
establish that a form of radiation is harmful. Then you have to establish
a relationship between the dose that people receive and the harm it does
to them. Finally, you have to establish the biological mechanism by which
the radiation damages tissue. Sienkiewicz said that none of these preconditions
had yet been met.

A fortnight ago the NRPB published a progress report* on the matter.
While reaffirming its view that the evidence so far is inconclusive, the
board stressed the need to begin new, rigorous studies to tackle the outstanding
questions. It also endorsed most of the comments made by Barker.

It says of the experimental studies so far: ‘The available evidence
weighs against electromagnetic fields acting directly to damage cellular
DNA, implying that these fields may not be capable of initiating cancer.’
The board is equally unconvinced by epidemiological studies to date, saying
that they ‘provide no firm evidence of the existence of a carcinogenic hazard
from exposure of paternal gonads, the fetus, children or adults to the extremely
low-frequency electromagnetic fields that might be associated with residence
near major sources of electricity supply, the use of electrical appliances,
or work in the electrical, electronic and telecommunications industries’.

The NRPB’s Advisory Group on Non-Ionising Radiation, which compiled
the report under the chairmanship of Richard Doll, the epidemiologist credited
with establishing a link between smoking and lung cancer, suggests that
research should focus on consolidating ‘positive’ findings. ‘It was considered
important to explore further the possibility that specific frequency and
amplitude windows exist for the induction of biological effects,’ it goes
on. If these ‘windows’ could be proved to exist, it might lead people to
abandon the idea that there is a relationship between the size of the dose
and the risk of disease.

Likewise, the Electric Power Research Institute (EPRI) in Palo Alto,
California – which is funded by electricity companies in the US – is spending
$15 million a year on studies to investigate possible links. One of its
major projects – due for completion next year – is a $5 million epidemiological
study to calculate the electromagnetic fields to which 130 000 electrical
workers have been exposed. The institute is also conducting a wide range
of laboratory studies on animals and on cultures of cells.

But speakers at the recent meeting in London doubted whether research
will ever produce any meaningful results. John Male of the National Grid
Technology and Science Laboratories at Leatherhead in Surrey summarised
the most salient work so far. He pointed out that Reba Goodman of Columbia
University in New York had shown that leukaemic cells exposed to a 100-hertz
electromagnetic field produced three to four times as much messenger RNA
as they would normally. These strands of RNA are involved in the synthesis
of proteins, and Goodman’s findings imply that such proteins and others
may become overabundant in people exposed to electromagnetic fields, with
unpredictable results.

But some of the most influential experiments showed certain tiny marine
organisms known as diatoms move around faster when exposed simultaneously
to both weak static fields – such as that of the Earth – and weak alternating
fields typical of those generated by overhead power lines or electrical
appliances. At a particular frequency of alternating field the cells in
the diatoms absorbed more free calcium ions, and this caused them to more
around more. What was interesting was that this frequency, 16 hertz, corresponds
to the so-called ‘cyclotron frequency’ for a calcium ion.

SEARCHING FOR AN EXPLANATION

Valeri Lednev, a biophysicist at the former Soviet Institute of Biological
Physics in Puschino came up with some results that appeared to take account
of this effect (New ÐÓ°ÉÔ­´´, Science, 4 August 1990). Lednev claims to
have demonstrated that calmodulin, a calcium-binding protein, worked more
efficiently at phosphorylating (adding elements of phosphoric acid to) myosin,
a muscle protein, when exposed simultaneously to the Earth’s steady magnetic
field and an alternating field of 16 hertz.

But there is a catch. ‘These results look very plausible, but no other
group has been able to repeat them,’ said Male. ‘We are a long way from
finding whether the model is valid and whether it has consequences for living
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Keith McLauchlan, a chemist at the University of Oxford, is confident
that chemistry, rather than physics, can supply an explanation which is
both reproducible and well understood (see Science). His theory, summarised
at the London meeting and published in January in Physics World, is the
latest plausible explanation and is based on the well-understood effects
of magnetic fields on the spins of unpaired electrons in highly reactive
chemical intermediates called radicals.

These entities are generated in their billions during metabolic processes
in all living things, and without them life could not exist. But in some
circumstances, they can be overproduced and – because they are so reactive
– they damage DNA in tissues and cells. Normally, any mutations are repaired,
but if the damage is too widespread, mutations may persist and initiate
the processes leading to tumour growth. McLauchlan’s theory is relevant
because it suggests that radicals could be freer to roam around and cause
damage in people exposed to low-frequency electromagnetic fields.

‘Anything which creates a large number of free radicals increases the
number of errors in DNA and if the number of errors increases by as little
as 0.01 per cent, the effect of that DNA on body replication could be enough
to do real harm,’ warned McLauchlan. ‘The magnetic field changes the probability
that these free radicals will wander round in the local medium, and if they
can get out and around, they can damage DNA.’

McLauchlan also had stern words for regulators and epidemiologists searching
for relationships between dose and effects. ‘I don’t trust that language,’
he said. ‘I don’t see why there should be a dose-response relationship.’
He said that multiplying a field by 1000 did not produce any greater effect
in the reactions he has studied. ‘If a cancer is caused by an isolated event,
it’s not necessarily dose-sensitive,’ he concluded.

*Electric fields and the risk of cancer, NRPB, vol 3, no 1.