Powerlines Factsheet

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• By far the cheapest way to transport electricity is by means of overhead cables, supported by large transmission towers or pylons.
• The towers themselves do not give off electromagnetic fields. It is the cables that are strung between them which emit magnetic and electric fields.
• The electric field is proportional to the line voltage, while the magnetic field depends on the load current. Typically, high voltage transmission lines carry high current and therefore give off both high electric and high magnetic fields.
• The largest powerlines, 400kV and 275kV are owned and maintained by the National Grid.
• Some of the 132kV lines are owned by National Grid and some by the area Electricity Company. These lines are often 'unbalanced', that is, the current on one side of the line cables is very different to that on the other. This leads to much higher electromagnetic fields than if they were both the same.
• Most 132kV and all lower voltage lines (e.g. 33kV, 11kV, 415 volts and 230 volts) are owned by the power companies. These may be British or international companies.
• There are two types of field produced by the powerlines. The electric field depends on the voltage and is there all the time, the magnetic field is caused by electric current flowing when people use electrical power and can therefore vary considerably.
• Electric fields are stopped by most building materials, but magnetic fields go through everything as if it wasn't there. The only thing that reduces magnetic fields is distance from the source.
• A study (the Draper report), released in June 2005, showed that the risk of serious ill-health effects (childhood leukaemia was especially looked at) was increased for people living within 600 metres of high voltage powerlines.
• We do not believe it is safe for children to play near high-voltage overhead lines above 11kV, especially with the research from Bristol University about electric field aerosol effects. Magnetic fields over 0.2 microtesla (200 nanotesla (nT), or 2 milliGauss (mG)) is associated with a doubling of the incidence of childhood leukaemia.
• Underground powerline cables: The electric fields will be zero as they are screened by earth, concrete, sand etc. The magnetic fields are very high near to the cable, higher than from overhead cables because they are closer to you. They fall off more rapidly than the fields from overhead wires, because the cables are closer together and cancel out each other's effects more quickly.
• Although research has shown there is an increased risk of illness in high fields, most people, including most children will not be seriously affected by them. It is important not to panic, but to take reasonable precautions.
• The health problems associated with electromagnetic fields are cancer, especially childhood leukaemia, also adult leukaemia and adult brain cancer, miscarriage, depression, Alzheimer's Disease, cot death, ME, electrical sensitivity, and other less serious effects. Research has been done on power-frequency electric and magnetic fields, looking at pylons, substations, occupational exposure, and electrical appliances in the home.
• If you have a powerline crossing your property, our book 'Buying an "EMF safe" Property' explains what to do. You may be able to get rid of it. This publication is also available for download from our subscription section.

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