Wisdom on Overhead Lines

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A recent INMR Editorial posed the question: “what happened to our love affair with overhead lines?” That is what my ancestors in ancient Greece would call a rhetorical question since it is still very much there. In fact stronger than ever – at least for those who have grown up alongside them and can better appreciate their contribution to mankind. Still, as in any old romance, it is important to offer reassurances from time to time that the love is intact.

I recall how my own love affair with overhead lines began. As a young engineer back in the mid 70s, I was recruited by a German line contractor. The work took me across the globe and changed my life. Back then, transmission lines were welcomed in developing countries as purveyors of modern amenities. For example, I’ll never forget one new 132 kV line in Arabia. We had just finished tower erection and, even before stringing, hospitable locals came to us with a traditional cooked lamb … and a TV, expecting to hook it already to the line. You can imagine their disappointment.

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But these are tempi passati. Access to electricity is now considered a right. Moreover, almost everyone, politicians and media included, seems to think that electricity comes from a socket. Yet to reach that socket, it has to pass through one of the most complex technical structures ever conceived – namely an electrical grid. And looking after this immense structure are a relatively small number of engineers, together responsible for reliable, high quality and fairly cheap power.

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In recent decades, another and subtle issue began to arise, apart from how they look visually. In line with the megatrend growing environmental awareness, it began to be purported that they carry possible health risks. It all started in 1979 with a study carried out in Denver, Colorado where the authors examined environmental factors around the homes of children stricken with cancer. The magnetic field produced by current flowing through residential wiring was estimated at about 0.2 μT and it was suggested that this might be a cause for the association. The design of the original Denver study was exploratory in nature and subject to numerous possible sources of error. Still, despite the skepticism, the study was given serious consideration by governments, academia and industry and spawned vast international research. Practically all studies found that an association between proximity of power lines and incidence of childhood leukemia could almost certainly not be attributed to the magnetic fields being generated. Indeed, some research focused on lines workers exposed to average fields up to 20 times – and even as high as 1000 times for short time spans – typical residential levels. Those studies failed to demonstrate any increased cancer risk. In fact, results showed cancer mortality rates 20 to 30 percent lower among these workers versus the general public – an observation that came to be known as the ‘healthy worker effect’.

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Other studies examined carcinogenicity in animals given that humans share similar physiology to all mammals. For example, among the hundred or so confirmed human carcinogens, all have also been shown to be equally carcinogenic to animals. As such, it would be perfectly reasonable to test for magnetic field carcinogenicity on animals. Results here were consistent: no reported evidence of increase in incidence of benign or malignant tumors, including leukemia.

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In addition, several experimental studies were carried out on volunteers at field levels of from 100 to 3000 μT. Subjects were unable to perceive the presence of these high fields and there were no adverse health effects or signs of toxicity. The absence of toxicity at levels up to 50,000 times the average field found in homes (i.e. 0.1 μT) confirms that a carcinogenic effect is extremely unlikely. Incidentally, notwithstanding such findings, the International Commission on Non-Ionizing Radiation Protection recommended, as a precaution, that maximum exposure limit for the public be set at 200 μT and 1000 μT in the case of power industry workers.

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We can therefore safely assume that the hypothesis raised by the Denver study was a false alarm. The exceptional volume of data over the past 35 years confirms that fields below the above-recommended power-frequency magnetic fields are just too weak to influence our biology. It is time to be reasonable and reassure the public. And to reconfirm our love affair with overhead lines. Because, paraphrasing a great but recently retired U.S. President, we can only be certain of three things: Death, taxes and overhead lines.

Dr. Konstantin O. Papailiou