Differences between ELF and RF EMFs
This website deals with power-frequency EMFs – EMFs produced by the power system. The scientific term for these EMFs is “Extremely Low Frequency” (ELF).
At much higher frequencies, EMFs produced by broadcast, wireless technologies etc are described as “radiofrequency” or RF. This website doesn’t cover RF fields. But we provide a page of links to organisations that do cover RF EMFs. And here we summarise some of the key differences.
|Power-frequency EMFs||Radiofrequency EMFs|
|The frequency is 50 hertz (60 hertz in the USA) and harmonics
(a hertz is one complete cycle per second. Harmonics are higher frequency but linked to the mains frequency – exactly twice the frequency, exactly three times, etc. See our tutorial.)
|The frequency is hundreds of kilohertz upwards, all the way up to tens of gigahertz – millions or tens of millions times higher than power frequencies|
|They are produced by mains electricity – power lines, substations, electricity in the home, appliances||They are produced by many different technologies – broadcast TV and radio, cell phones and other radio communications, wi-fi, wi-max, Tetra, etc etc|
|There haven’t been many major changes in the technologies producing them for many decades||The technologies are changing all the time|
|The electric and magnetic fields are separate phenomena – you can have one without the other||The electric and magnetic fields are coupled together as radiation|
|They can induce currents in the body but do not cause significant heating||They can cause heating in the body|
|They tend to be relatively straightforward waveforms (a sine wave with only a few harmonics)||The modulations used to transmit signals mean the waveforms are highly complex|
There are some similarities as well though:
- neither causes ionisation in body tissues. This doesn’t mean they can’t have any interaction with the body at all, but whatever they may or may not do, they can’t cause ionisation in the way that say x-rays do. See more on mechanisms of interaction.
- both are the subject of exposure limits.
- both have been classified by IARC as “possibly carcinogenic”, though based on completely different bodies of evidence.
- both are now inextricably linked with modern societies and lifestyles.