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Harvard Commentaries
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Reviewed by the Faculty of Harvard Medical School

Medical Myths Medical Myths

Power Lines and Your Health

October 23, 2012

By Robert H. Shmerling M.D.

Beth Israel Deaconess Medical Center

The idea that living near high-voltage power lines is bad for your health has been around for many years. Illnesses attributed to power lines include childhood leukemias, other cancers, abnormal heart rhythms, miscarriages, low birth weight, birth defects and other illnesses that might lead to premature death. Despite the conclusions of many studies that find no detectable risk, many people remain unconvinced about the safety of power lines. So, is the notion that power lines are hazardous a myth, fact or, as with many controversies, is there merit to both sides of the argument?

Why Is There Concern About Power Lines?

High-voltage power lines create electromagnetic fields around them and expose anything nearby to electromagnetic radiation. This is not unique to power lines — microwave ovens, radio and televisions transmitters, and cellular phone transmitters do the same thing, though the amounts of radiation emitted vary. From any source, the amount of radiation falls dramatically as the distance from that source increases (there's a complicated formula involving the square of the distance that describes this). As a result, even power lines that are easily visible from one's home (or from one's appliances or cell phone) lead to radiation exposure that experts consider harmless. That's why there are not more rules and regulations about living near power lines.

When laboratory animals have been exposed to radiation of this sort, some researchers (but not others) have been able to demonstrate health problems, including new cancers or accelerated growth of existing cancer. The question is whether any of the potential effects on animals apply to humans, recognizing that we generally are exposed to much lower amounts of radiation in our everyday lives when compared with the animals' experimental conditions. On the other hand, certain occupations, including power-line maintenance workers, may have higher exposures.

Scattered, anecdotal reports of a higher-than-expected number (called clusters) of leukemia or other cancers in a neighborhood near high-voltage power lines have been proof enough for some people that there must be a connection. As a result, despite the low amounts of radiation involved and the lack of convincing evidence that power lines are hazardous to humans, the issue continues to raise concern.

During the last 20 years, multiple studies have been published reviewing the effect of high-power voltage lines on human health. Among the most recent was a study from England of more than 83,000 workers in the electricity industry. Researchers found no increase in brain cancer or overall death rate when compared with those who did not work around electromagnetic fields. A study in 2012 from Italy compared exposure to high voltage lines among children with birth defects and normal children. They found no increased exposure among the kids with birth defects. Reports from major research centers in at least nine countries have come to similar conclusions:

  • There is no compelling evidence of any health hazard from power lines.
  • If power lines have any effect on human health, it is small.
  • Research should continue to look for even a small effect on health.

These results are reassuring, although they cannot completely declare power lines risk-free. In fact, in another study (published in June 2005), children living within 600 meters of a power line had higher rates of leukemia than those living farther away. However, based on limitations of this type of research (including the fact that electromagnetic fields were not actually measured in the homes of these children), the authors of this study were not convinced that power lines truly caused a higher than expected rate of childhood leukemia.

Why Is a Definitive Answer So Hard To Find?

Researchers trying to prove or disprove a small risk have a difficult job — among the biggest problems are difficulties in measuring the outcome of interest (such as cancer or miscarriage) and the possibility that other factors may affect the results. The challenge is particularly great when considering power lines: The number of outcomes of interest includes many different diseases or conditions, other sources of radiation could affect these outcomes, and the small amounts of radiation are hard to detect. One study found that radiation produced by power lines varies over the course of hours or days, so that simply measuring distance from the lines may not be an accurate way to estimate exposure.

Other medical concerns face the same uncertainty: A higher rate of illness or death related to breast implants or cellular telephones has been difficult or impossible to detect. Still, even with reassuring studies, a rare medical problem related to these exposures remains possible.

Measuring Small Effects: An Example

Consider this example: Imagine that your neighborhood gas station sells you an additive that is supposed to improve your car's fuel efficiency. You are assured that you will save money because you'll need less gasoline, and a neighbor reports improved mileage in his car.

You may be skeptical enough to measure how many miles per gallon your car gets before and after the additive is purchased. If you notice no change, perhaps it's because the driving conditions were different — if you drove on the highway before and in the city after using the additive, your mileage could be affected. Or, perhaps the weather changed between measurements — heat, humidity, or use of the car's air-conditioner could affect the results. Finally, how you measure the number of miles driven per gallon of gas may not be accurate or precise enough to detect a small improvement. You might ask, "If the improvement is so small I cannot detect it, why should I buy the additive?" It's a good question.

Many who have studied power lines' effect on human health would ask a similar question: If the effect on health is so small that we cannot even be sure it's present, shouldn't we be reassured?

The Bottom Line

Every day we encounter countless exposures. Some are harmful, some are beneficial and most are probably of no consequence at all. Deciding which to worry about enough to avoid is not easy, especially given the multiple sources of information and advice we all have. It may never be possible to say with absolute confidence that high-power voltage lines, or other common exposures, are harmless. But it should provide some comfort to know that there are researchers continuing to look into it and that some (though not all) of the best evidence shows no significant impact on health.

Robert H. Shmerling, M.D. is associate physician at Beth Israel Deaconess Medical Center and associate professor at Harvard Medical School. He has been a practicing rheumatologist for over 20 years at Beth Israel Deaconess Medical Center. He is an active teacher in the Internal Medicine Residency Program, serving as the Robinson Firm Chief. He is also a teacher in the Rheumatology Fellowship Program.

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