In Europe, the power system normally uses alternating current at a frequency of 50 Hz (hertz = cycles per second). Electric and magnetic fields have the same frequency and are therefore often termed 'extremely low-frequency fields'. As such, they are not directly comparable to waves coming from radios, televisions and mobile phones, which operate at frequencies of up to millions or billions of hertz. Consequently, their properties are completely different from those of ionising radiation (eg gamma radiation), whose frequencies are far higher than those of radar and radio waves.
Researchers and international organisations often refer to 50 Hz magnetic fields as 'extremely low-frequency fields' (ELF).
Differences between fields and radiation
One factor determining whether a certain type of electromagnetic radiation or electromagnetic field is harmful to the cells in the human body is the frequency. The higher the frequency, the higher the energy content and the more harmful the effect could be.
We know for example:
- that ionising radiation (eg from radioactive sources) may directly damage cells and DNA
- that the sun's rays may contribute to the development of skin cancer
that the sun's rays may cause burns. They can be serious and painful but are normally transient
- that microwaves can be used to heat our food, but they can be harmful to ourselves at short distances were microwave ovens not designed to shield humans from the fields
- that fields emanating from mobile phones may have an acute heat effect, but researchers have been unable to prove any harmful long-term effects
- that extremely low frequency fields are not in themselves capable of destroying the cells in the human body or produce a heat effect in the same way that fields emanating from mobile phones can. If fields affect public health in any way, an hitherto unknown mechanism is responsible.
The electric currents which 50 Hz fields emanating from electricity supply installations are capable of creating in the human body are many times smaller than the currents occurring naturally in the organism. This is one of the reasons why it is very difficult for science to come up with an explanation of how relatively weak low-frequency fields can be harmful to humans.