The proposal of a couple of high voltage electric power lines in northwest Arkansas has some concerned about health effects of those who may be living nearby. The larger of the two is a 750 kilovolt DC transmission line which will move excess electricity generated from wind turbines in Oklahoma and Kansas across Arkansas to connect with the Tennessee Valley Authority network in Memphis.
The health concern is all about exposure to electromagnetic fields (EMF) emanating from the power lines. Are there health effects? What are they? How close do you have to be? There is no question that those giant pylons with the looping wires are unsightly, and in the minds of some unnecessary, but are they a health risk? The short answer is more than likely not, but it will take some discussion.
First and foremost we are bathed in electromagnetic radiation from birth to death. The sun provides many forms; visible radiation (sunlight) by which we see. Infrared radiation from the sun warms us. Ultraviolet radiation tans us.
In addition to these natural forms of radiation we are exposed to man made electromagnetic radiation from radio, television, and cell phone transmissions. Electrical wiring and all electrical devices in the home create electromagnetic fields.
The evidence of harm from Power lines is scant and contradictory. It all started with a study in Denver in 1979. Researchers found a correlation between living near power lines and childhood leukemia, even though it is not biologically plausible. Basically what the researchers proved again that income correlates with cancer, and those who live near power lines are in a lower socioeconomic bracket.
Since that time there have been literally tens of thousands of peer reviewed studies which show no clear indication of harm. An important principle of toxicology, the science of poisons, is the dose response relationship. The greater the dose – the the greater the harm. Any of the studies which did suggest harm did not correlate with exposure.
Magnetic fields are measured in units of Gauss (G). For example the magnetic field in a medical diagnostic device called a MRI is huge, of the order of 70,000 G . There is no evidence of harm from MRI scans.
Other magnetic fields that we are exposed to include those from small electric devices in the home. A hair dryer in use produces a field strength thousands of times smaller, 20 G with a similar values for an electric razor. A refrigerator produces a field of about .02 G.
So what about a power line? The field strength drops off rapidly with distance from the source so the actual field strength under or near a power line is quite small. At a distance of 30 meters the field strength is a fraction of a thousandth of a Gauss (.004 G.) This is hundreds to thousands of times lower than exposures in average homes.
At the expense of repeating myself there is essentially no proof of either toxic or carcinogenic risks associated with living near power lines. Argue if you will that they are ugly, or that you don’t want them on your land, or that they aren’t necessary. Arguments about health effects however will fall on deaf ears.