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No sufficient data on effects of long exposure to electromagnetic field - expert
Philippines Created: 30 Nov 2007
Dr Kintanar Quintin, chairman, health sciences division of the National Academy of Science and Technology (NAST) said that the International Commission on Non-Ionizing Protection (ICNIRP) do not have sufficient data on the potential long term effects of exposure to Electro Magnetic Field (EMF) which increased the risk of cancer,.

Kintanar was in Davao City on Thursday as one of the resource persons during the Forum on Extemely Low Frequency Electric Magnetic Field held at Grand Regal Hotel and attended by various stakeholders from Mindanao initiated by the National Transmission Corporation.

Kintanar quoting ICNIRP said the available data are insufficient to provide basis for setting exposure restrictions.

However, the epidemiological research has provided suggestive but unconvincing evidence of association between possible magnetic flux densities substantially lower than those recommended in the guidelines, he said.

He said that when controversies arise concerning possible health risks from exposure to electromagnetic fields from power lines, the experts recommends that such issues be resolved by taking appropriate measurements of such fields by a team composed of all the sectors concerned under the close supervision of a multidisciplinary team of experts and scientists.

Kintanar said numerous studies arrived at the same conclusions that current evidence does not confirm the existence of any health consequences from exposure to low level electromagnetic field. But gaps in knowledge about biological effects exist and need further research.

However, he said that with regards to high voltage power lines, is a matter of balancing the overall benefits against the risks.

Dr. Filemon A. Uriater, Jr., member of engineering sciences and technology division of NAST said that distance is the best way of reducing EMF exposure.

He said the farther the person the EMF exposure is reduced.

Comparing electric fields (EF) against magnetic fields (MF) he said EF is produced by voltage while MF by current.

He cited as an example that a lamp plugged in but turned off, the voltage produces an electric field but lamp plugged in and turned on, the current produces a magnetic field.

He said the effective magnetic shielding material available is the mu-metal, an alloy of 77 percent nickel, 16 percent iron, five percent copper and two percent chromium, which is annealed in a hydrogen atmosphere to increase its permeability.

"But mu-metal is extremely expensive," he said.

Other materials that could be used is the Giron that cost $37.95 per linear foot, full roll of 81 feet would cost $2,459.00, the metals of an inch wide cost $2.50/lin ft and one pound spools cost $599.00, the finemet per line foot cost $17.99 and a full roll at $4,200.

He said active magnetic shielding systems consist of three basic elements, a sensor to monitor the power line field, control and power unit, and network of driven coils.

Burying transmission lines he said can reduce their magnetic fields but the reduction occurs because the underground lines use rubber, plastic or oil for insulation rather than air, thus allowing the conductors to be placed much closer together resulting in the greater phase cancellation.

But he said a buried line would be closer to the ground level than an overhead line, magnetic field exposure from a buried line could be about the same as from an overhead line.

The cost of underground transmission lines (TL) are generally five to 10 times more than overhead lines, maintenance of underground TL is difficult and time-consuming and repair of underground transmission lines is difficult and expensive.

The country has 20,238 kilometers of transmission lines. Of this figure Mindanao accounted to about 5,000 kilometers.
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Source: Philippine Information Agency, Prix D Banzon, 30 Nov 2007

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