Power lines and substations
After more than 40 years of research, there are no clear signs that the EMFs from power lines and substations pose health risks for adults, and only weak evidence that there may be risks for children.
What EMFs are found near power lines and substations?
The electric current flowing through a power line, or in a substation, produces a magnetic field. The voltage produces an electric field. Exactly the same kinds of magnetic and electric fields are found around anything that carries mains electricity. This includes house wiring and home appliances.
The electric fields are easily shielded by trees and buildings, and have generally been discounted as causing any health effects. The magnetic fields are not shielded, but the strength of the fields drops off quite quickly as you move away from whatever is producing them.
Measurements around many power lines in New Zealand (the high voltage lines usually supported by large pylons) show that once you are 50 to 100 metres away from any line the magnetic fields are lower than, or similar to, the levels found in houses which are far away from any lines. if the house is more than 100 metres away, the lines will almost certainly make little or no difference to the magnetic fields inside it.
If the house is less than 50 metres away, the magnetic fields will probably be higher than in most houses, but similar to the levels found near many appliances (such as an electric range or a vacuum cleaner). Even directly beneath the lines, the magnetic field will be much lower than the limits recommended by the Ministry of Health.
The magnetic fields at a substation boundary are generally little different to the levels found in many houses. If a power line crosses over the boundary the magnetic fields will be higher there - but the fields are produced by the power line, not the substation.
Magnetic fields in houses near a substation, even right next door to one, will almost certainly be unaffected by the substation.
After more than forty years of research, there is still no clear indication that the magnetic fields, or some other factor to do with being near a power line, have any effects on health. The key unanswered question is whether children living near transmission lines, or exposed over long periods (years) to relatively high average levels of magnetic fields for some other reason, have an increased risk of leukemia. Some studies suggest that they might have a small increased risk, but the people who did this work caution that the apparent risk could be due to other factors. A lot of other work shows no reason to suspect that magnetic fields at these levels could have any effects on health at all.
A research project in New Zealand looked at all cases of childhood leukemia reported over a four year period, and found that none of the children had been exposed to high average levels of magnetic fields. While this doesn't prove that the magnetic fields had no effect, it does give an idea of how rare any effect, if there really is one, must be. We probably all face greater, known, risks every day without thinking too much about them.
I am interested in measurements
Measurements will probably tell you not much more than the information above. You will still have to decide what you do or don't want to live with. But if you would like to ask about measurements, or hiring a meter, get in touch.
Where can I find more information?
EMFs in the home
Ministry of Health information booklet
WHO information sheet
Last reviewed: 12 October 2023