Child Leukemia Again Linked to Power Lines
By Daniel DeNoon, WebMD Medical News

June 2, 2005 -- Living near high-voltage power lines raises children's
risk of leukemia by 69%, a British study shows.

That doesn't prove that power lines cause the deadly blood cancer, the
study's authors are quick to point out. Despite 30 years of research,
scientists still can't come up with a plausible reason why the weak
magnetic fields near power lines might cause leukemia.

Gerald Draper, DPhil, director of the childhood cancer research group
at Oxford University, led the study. Draper's team compared more than
29,000 children with cancer, including 9,700 children with leukemia,
to age-, sex-, and birthplace-matched children without cancer. The
children's birth homes were located on the power grids of England and
Wales.

Compared with children who lived more than 600 meters from a
high-voltage power line, those who lived within 200 meters of the
power lines had a 69% greater risk of leukemia. Those living 200 to
600 meters from power lines had a 23% higher risk of leukemia. The
findings appear in the June 4 issue of the British Medical Journal.

There is a slight tendency for the birth addresses of children with
leukemia to be closer to these lines than those of children matched
for comparison, Draper and colleagues write. "We have no satisfactory
explanation for our results in terms of causation by magnetic fields,
and the findings are not supported by convincing laboratory data or
any accepted biological mechanism."

An Unusual Disclaimer

That's an unusual disclaimer for a researcher who has found a
statistically significant link. But the data leave Draper and other
experts scratching their heads for an explanation.

There are many theories about how power lines might cause leukemia.
The most obvious one is that the magnetic fields created by power
lines somehow make cancer cells grow in susceptible people. But
there's a problem with this theory, notes Heather Dickinson, PhD,
principal research associate at the Center for Health Services
Research at the University of Newcastle in England.

"What is puzzling is that the magnetic field from power lines is only
1% of the earth's magnetic field, which surrounds us all," Dickinson
tells WebMD. "Your fridge or vacuum generates a magnetic field of
about the same strength. In England and Wales, only 5% of the exposure
to magnetic fields comes from high voltage pylons. So if this is a
hazard, people with appliances should be just as concerned."

John E. Moulder, PhD, director of radiation biology at the Medical
College of Wisconsin, is an expert on how exposure to various kinds of
electromagnetic fields and radiations might cause cancer.

"Power lines cannot be proven absolutely safe," Moulder tells WebMD.
"But people have looked very hard for a causal relationship between
power lines and cancer and nobody has found one. People aren't going
to like this. They really want to be told we are absolutely sure one
way or the other, and we are not."

Moulder, like Dickinson, points out that animals exposed to strong
magnetic fields -- much stronger than those found near power lines --
don't get cancer.

In June 2002, the U.S. National Institute of Environmental Health
Sciences updated its 1999 report on possible risks from
electromagnetic fields (EMF).

"Over the past 25 years, research has addressed the question of
whether exposure to power-frequency EMF might adversely affect human
health. For most health outcomes, there is no evidence that EMF
exposures have adverse effects," the NIEHS report concludes.

Power Lines and Infections

Dickinson suggests that the Draper team's findings are real. But she
thinks that living near power lines is linked to something else --
something that really does increase a child's leukemia risk.

"We know the rate of leukemia varies by a factor of two or three
between isolated rural areas," Dickinson says. "And this is related to
an influx of population that can change pattern of the infections to
which a child is exposed."

Sudden exposure of once-isolated children to a lot of new childhood
diseases, Dickinson suggests, may be linked to leukemia risk. She
suggests that this may be a "confounding factor" in the Draper team's
findings.

But even if living near power lines does raise a child's risk of
leukemia, Dickinson notes that the risk is small.

"A 70% increase in leukemia means that the 1 in 2,000 risk of leukemia
becomes a 1 in 1,200 risk," she says. "In the U.K., this means that
five extra children might get leukemia. We need to keep this in
perspective -- look at the thousands of children hurt in road
accidents each year."

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SOURCES: Draper, G. British Medical Journal, June 4, 2005; vol 330: pp
1290-1295. Dickinson, H.O. British Medical Journal, June 4, 2005; vol
330: pp 1279-1280. Heather Dickinson, PhD, principal research
associate, Center for Health Services Research, University of
Newcastle, England. John E. Moulder, PhD, professor and director of
radiation biology, department of radiation oncology, Medical College
of Wisconsin, Milwaukee.