THE radiation given off by pylons, power cables and electrical appliances may
be giving two children in Britain cancer every year. A new study commissioned by
the National Radiological Protection Board (NRPB) says that the 1 in 200
children exposed to high levels of electromagnetic radiation in their homes
could be doubling their chances of contracting leukaemia.
For years controversy has raged over the possible links between
electromagnetic fields and cancers, fuelled by a series of contradictory and
inconclusive investigations worldwide
(快猫短视频, 9 August 1997, p 16).
This week, however, the argument has shifted significantly in favour of a
causal link, with the publication of a long-awaited report by a team of
scientists headed by epidemiologist Richard Doll of the Cancer Studies Unit at
Oxford.
The report, which is the first major review of the issue since 1992 by the
NRPB鈥檚 Advisory Group on Non-Ionising Radiation, finds no evidence that
extremely low-frequency fields cause cancer 鈥渋n general鈥�. But there are some
statistical associations. 鈥淭aken by themselves these results could be due to
chance,鈥� says Doll. But the report concludes that 鈥渢he possibility remains that
intense and prolonged exposures to magnetic fields can increase the risk of
leukaemia in children鈥�.
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The danger arises, says the NRPB, when children are exposed to
electromagnetic fields of 0.4 microteslas or more, as are 1 in 200 children in
Britain and many more abroad. Less than half of the radiation comes from nearby
high-voltage power lines and electricity substations. The report reveals for the
first time that the remainder probably comes from a combination of wiring,
computers, TVs and other electrical equipment, but this needs further
research.
Children exposed to such levels could increase their risk of contracting
leukaemia before they are 15 from 1 in 1400 to 1 in 700, the NRPB suggests. This
means that electromagnetic radiation might trigger two of the 500 childhood
leukaemias, a potentially fatal cancer of the bone marrow, diagnosed every year
in Britain. We previously knew that there was a possibility of a risk. 鈥淲e are
now able to quantify it,鈥� says Doll.
The effect was spotted in a pooled analysis of 3247 childhood
leukaemias in Europe, North America and New Zealand published last year. Doll鈥檚
report says that there is 鈥渘o clear evidence鈥� that electromagnetic fields cause
cancers in adults. But it recommends further studies into the health of people
exposed to a few tens of microteslas at work.
The reason the report stops short of drawing any firm conclusions is because
there are no proven biological mechanisms for electromagnetic radiation to
trigger cancer. 鈥淲e have no possible explanation how radiation of this sort
could cause cancer,鈥� says Doll.
But one researcher, Denis Henshaw from Bristol University, says his studies
suggest that power lines make particles of airborne pollution electrically
charged, and thus more likely to lodge in the lung when inhaled
(快猫短视频, 11 December 1999, p 14).
He welcomes the Doll report. 鈥淭he
possible impact on public health is very significant,鈥� he says.