Reducing your Exposure from Powerlines

Powerlines come in different shapes and sizes. The highest power ones (400 kilovolts or kV) are the long-distance lines from the generating power station to the places where the power is needed. The pylons supporting these power cables are large, metal structures, which have long strings of insulators from which the cables hang. The smallest 230 volt lines start from local substations and supply the power needs for a relatively small area. In between these two extremes are a variety of other types of lines carrying different voltages.

There are two types of electromagnetic fields (EMFs) associated with powerlines; electric fields and magnetic fields. These are at their highest to either side of the central cable of large lines, and underneath the cables (which tend to be one on top of the other, or 'plaited' together) of smaller lines. The EMFs come from the cables, not the pylons as the pylons are insulated from the fields generated. As you move away from the line, the fields begin to drop away. How far they extend depends on the line voltage for the electric field, and the power being supplied for the magnetic field.

Reducing your exposure from Electric fields

Homes will be screened from electric fields by the building materials used in their construction. All materials reduce electric fields, some better than others. The exception to this is window glass (whether single or double glazed) which hardly reduces electric fields at all.

• To reduce electric fields coming through windows from powerlines, you would need to use a wire mesh frame attached to the outside of the window. We recommend 6 mm mesh, though you might find bigger mesh sizes also effective (and would let through more light). You might want to experiment. It is then important to earth the wire mesh frame.

Gardens will not be screened by building materials.

• You might be able to reduce the fields a little by planting trees and bushes. 'Sappy' trees (some pines, cherry, etc) are better than non-sappy trees at reducing field levels. Deciduous trees are less good in winter when they lose their leaves.

Reducing your exposure from Magnetic fields

There is absolutely nothing you can do about magnetic fields. Lead or steel sheets are ineffective. There is a metal called mu-metal which does reduce the fields, but it is very expensive. Mu-metal foil is for use in audio processes and is not suitable for screening magnetic fields from powerlines.

Other possibilities

The cables on local supply lines can be either 4 individual ones, or sometimes, they are twisted together forming what is known as ABC (aerial bundled conductor) cabling. Fields are lower from ABC cabling than from the 4 individual cables.

• Encourage your local electricity company to replace 4 individual cables with ABC cabling. They may be willing to consider this 'for maintenance' reasons.

Power cables can be undergrounded. Electric fields will be absorbed by the earth above a buried cable. Magnetic fields will be higher immediately above an underground cable than they will be below an overhead line, because you are closer, but the fields reduce much more quickly from an underground cable. The Electricity Association reckons the cost of putting cables underground is twenty times higher than allowing them to go overhead, less for lower-voltage lines.

• You could try to negotiate undergrounding the powerline. The Electricity Association will expect you to bear the cost.

High electric fields around power cables attract all sorts of airborne pollutants, if you live in an area where these are generated, such as near a main road, chemical factory, sprayed fields, etc. These are then deposited downwind or in rain.

• Close your windows and don't go out in the garden when the wind blows from the powerlines to your home, if you live in a place where pollutants could be a problem.

If you would like more information on this topic, you could read our articles, "Buying an "EMF safe" property", "Powerfrequency EMFs and health risks", "Powerfrequency protection for you and your family" which contain far more information on this subject. We extensively cover this area in our subscription area.