Debate Continues on Hazards of Electromagnetic Waves
JULY 7, 2014
Time Travel
This occasional column explores topics covered in Science
Times 25 years ago to see what has changed — and what has not.
Everywhere in the modern world, the throb of alternating
current generates electromagnetic waves — from the television, the blender, the
light bulbs, the wires in the wall.
Because the oscillations are very slow (just 60 hertz, or
cycles per second), this type of radiation is called “extremely low-frequency.”
It was long thought harmless because it is too weak to knock out electrons and
directly damage molecules in the body.
But on July
11, 1989, Science Times reported the uncomfortable possibility that
this ubiquitous background radiation might cause cancer.
Laboratory experiments provided more reasons for concern.
Electromagnetic radiation, particularly the magnetic part of it, changed some
functioning in cells and altered the action of neurotransmitters. Pulses of
60-hertz radiation increased the number of abnormal embryos in chicken eggs.An
epidemiological study comparing children in Denver who died of cancer from 1950
to 1973 with a control group of other children found that those who lived near
electrical distribution lines were twice as likely to develop the disease as
those who did not. A subsequent study, by other scientists who sought to
eliminate what were seen as flaws in the first study, had nearly identical
conclusions.
The article quoted Dr. David O. Carpenter,
then the dean of the School of Public Health at the State University of New
York at Albany: “The whole thing is very worrisome. We see the tips of the
iceberg, but we have no idea how big the iceberg is. It ought to concern us
all.”
25 YEARS LATER Dr. Carpenter is still at the
same university, as the director of the Institute for Health and the
Environment. He still finds 60-hertz radiation worrisome.
“Almost nothing has changed in 25 years in terms of the
controversy, although the evidence for biological effects of electromagnetic
fields continues to grow stronger,” he wrote via email last week.
In reviewing the research, the World Health Organization has
categorized extremely low-frequency waves as “possibly carcinogenic”: There
appears to be an increase in leukemia rates with long-term exposure to magnetic
fields stronger than 0.4 microtesla. The earth’s magnetic field is about 100
times stronger, but it is not oscillating, a crucial distinction. (Concerns
about other childhood cancers have largely abated.)
But only a small fraction of people are exposed to extremely
low-frequency waves that strong. “It’s not a very normal type of exposure,”
said Emilie van Deventer, the leader of a W.H.O. project to assess the
health effects of electromagnetic fields.
One reason for the continuing uncertainty is that scientists
have yet to explain how such waves could lead to cancer. Leukemia is a
relatively rare disease, striking fewer than one in 5,000 children in the
United States; its causes are hard to study, and even if a link were
established, any effort to shield the world from low-frequency radiation would
at best prevent a small number of cancers.
“In terms of a public health perspective and in terms of
what one would think of suggesting in terms of regulations, you can see that
the risk-benefit ratio would be quite unbalanced,” Dr. van Deventer said. “And
this is if we were able to show causality.”
In recent years, concerns have migrated to frequencies that
oscillate not 60 times a second but millions to billions of times — those used
by cellphones, cordless phones and wireless networks. Dr. Carpenter, for
example, would like to keep Wi-Fi out of schools, even though there is no
direct evidence of harm as of yet and it broadcasts at lower energy levels than
cellphones; the W.H.O. calls the radio frequencies used by cellphones, Wi-Fi
and other telecommunication devices also “possibly carcinogenic.”
“Which is a little bit difficult to explain to the public,”
Dr. van Deventer said. “People like to have a black-and-white answer.
“Looking at trends over the last 20, 30 years, we don’t see
an increase” in cancer, she said. “But again, we don’t know. If it takes cancer
10 years to promote, maybe we will see it in the next 10 years.”
The possible hazards have not deterred her from a modern
lifestyle. “Yes, I am calling you, talking to you using my cellphone,” she
said. “I have a microwave. I have everything. It doesn’t change anything for
me.”
She added, ”But from a professional point of view, it’s
important that we stay on top of it.”
The W.H.O. project is working on a new report summarizing the
health risks of radio-frequency fields, to be published next year.
A version of this article appears in print on July 8, 2014,
on page D6 of the New York edition with the headline: Debate
Continues on Hazards of Electromagnetic Waves.
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