reopens power-line debate
February 10, 2004
It is the first experiment to conclusively link an electromagnetic field with a health-adverse chemical effect in the presence of an animal, said Steven Goheen, a scientist at the Department of Energy lab and lead author of a paper published in the current issue of the journal Bioelectromagnetics.
"All this time, we were looking in the wrong place," Goheen said. "We had been looking inside animals for an effect from the electromagnetic fields. Now it appears that the danger is in the air surrounding animals that are near a large electromagnetic field."
Electromagnetic fields are present in devices that use or carry electricity. Goheen and colleagues report that the ozone was produced when rats were present during a "corona discharge," an uncommon phenomenon in which electrons escape from a sharp surface of an electrical conductor at high voltage.
The researchers placed rats in a Plexiglas cage hooked up to a device that produced 10 kilovolts, or roughly the power of air ionizers marketed as health aids. In an empty cage, the ozone level peaked at 22 parts per billion with or without a corona discharge. When the animals were present and a centimeter from the corona source - an electrode inserted through the top of the cage ozone levels were high, more than 200 parts per billion, or double the amount considered toxic at chronic exposure in human beings. The ozone was flushed from the cage quickly for measurements, and the rats were unharmed.
The electric field used in the rat experiments is greater than that of a casual passer-by near any high voltage power line, Goheen said, the distance being the key consideration. "Distance was one variable we measured in the rats. When they were more than about 5 centimeters away from the source, we didn't see much effect."
This effect should be of concern only to those working much closer to power lines such as linemen or anyone else who spends many hours a day close to high voltage devices. Goheen is quick to note that such workers have more immediate concerns than whiffing a little ozone such as electrocution and falling.
But he notes that if ozone is produced, it is possible that other so-called reactive species may be produced near human beings in the presence of high voltage and that "these results raise new questions about the relationships between electric fields and adverse biological effects."
Among the questions Goheen and colleagues are now wrestling with is what, precisely, happens to convert ambient air surrounding an animal's electrified surfaces into its chemical cousin ozone.
In an earlier experiment, Goheen measured similar amounts of ozone in grounded water under a corona source, invoking by way of explanation something called "the Taylor cones phenomenon." A liquid surface at high field strength is unstable, with spots of slightly-higher surface charge that protrude from the surface. The tips can elongate and grow so sharp that droplets and even electrons can be ejected.
Since most mammals are mostly
water and produce surface moisture in sweat glands, saliva and
eyes, perhaps here is a connection. Goheen and his co-authors
suggest that along with the exposed moist places, "pointed
rat whiskers and hairs, as well as ears, nose, and tails, at
sufficiently high field strength" contribute somehow to
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