Power lines

I live near a power line, or am planning to buy a house near one.  Are there any health risks I should be aware of?

After more than 30 years of research, there are no clear indications of health risks for adults living near transmission lines, and only weak evidence of possible risks for children. 

If there are any health effects, people think they may be caused by long term exposures to magnetic fields produced by the electric currents flowing through the lines.  Key points about these are:
  • Even directly beneath a power line, field levels are much lower than the exposure limit recommended by the Ministry of Health.
  • Within 50 – 100 metres of most high voltage lines (those often carried on big pylons), and a few metres of low voltage lines which distribute power to houses,  the field levels have decreased to the “background” levels produced in all houses by electric wiring and appliances.
What about transformers and substations?

Magnetic field levels inside houses are not usually affected by nearby transformers or substations, even if they are next door, or on the street in front of a house. 
  • Magnetic fields around small transformers by the side of the road are much lower than the exposure limit recommended by the Ministry of Health.  They normally decrease to the “background” levels found in most houses within 2 – 3 metres.
  • Magnetic fields around substation boundaries are generally the same as they would be if there were no substation, except where lines going in and out of the substation cross the boundary. 
How can I know the magnetic field levels near a power line?

Field levels near a power line vary depending on the amount of power being carried by the line.  Often the levels are highest in the morning and evening.  The table below shows field levels measured near New Zealand high voltage lines, and in other places for comparison.

Beneath high voltage lines

0.2 – 5 microtesla

40 m from high voltage lines

0.04 – 0.4 microtesla

Near operating electric range

1 – 2 microtesla

Typical “background” levels in houses

0.04 – 0.1 microtesla

30 cm from appliances

0.05 – 5

Recommended limit in New Zealand

200 microtesla


Other areas of this site with relevant information are: