Electromagnetic fields (incl. ionising and non-ionising)

The omnipresence of electrical devices in everyday life is a source of concern. To date, no scientific study has been able to demonstrate harmful effects due to non-ionizing electromagnetic fields. Some studies have revealed statistical correlations, however they have not been able to explain the link between cause and effect. In case of doubt, the precautionary principle should be applied.

What is an electromagnetic field?

An electromagnetic field is the zone of influence created by the waves from an electric field and a magnetic field.

Together, the two types of waves form waves (oscillations) which are invisible to the naked eye that move steadily and alternately in the environment.

The electromagnetic field waves are measured based on:

  • the Hertz frequency (number of oscillations carried out by the wave in 1 second)
  • the wavelength (distance between the top of a wave and the top of the next wave).

The wavelength is inversely proportional to the frequency: the higher the frequency the shorter the wavelength.

The lower the frequency, the more distinct the electric and magnetic fields.

The higher the frequency, the more the electric and magnetic fields are linked.

Electric field

A lamp which is plugged in but turned off produces an electric field.

The electric field is due to the presence of electric charges when a device is plugged in.

There is an electric field around each plug socket.

An electric field:

  • is linked to the voltage
  • is measured in volts per meter (V/m)
  • remains constant
  • decreases with increasing distance from the source
  • can be weakened by a screen (tree, vegetation, housing, etc.)
  • does not penetrate the body (or only very little)

Magnetic field

A lamp turned on generates an electric field and a magnetic field.

The magnetic field is produced by the movement of electric charges when the current flows.

A magnetic field:

  • is linked to the intensity (quantity of electricity)
  • is measured in amperes per meter (A/m) or microtesla (µT)
  • varies according to the intensity of the electric field
  • the intensity of the magnetic field decreases with distance from the source
  • may not be weakened by a screen (tree, vegetation, housing, etc.)
  • passes through the body

DID YOU KNOW? Alternating current is defined by the alternation between the waves of the electric field and waves of the magnetic field. A direct current has a near zero frequency: there is no distinction between the electric and magnetic field; it is called static electricity/ field.

What is the electromagnetic spectrum?

The electromagnetic spectrum is divided into non-ionizing radiation and ionizing radiation depending on the frequency of electromagnetic waves.

Electromagnetic waves carry energy called “photons” which are the source of the radiation. The radiation energy varies according to the frequency.

Generally “fields” refer to low frequencies and “rays” to high frequencies that diffuse more energy into the space.


Non-ionizing radiation Electromagnetics spectrum fields/rays Frequency Examples
Static fields OHz Battery devices, batteries, magnets, earth’s magnetic field, catenary electrified transport, Magnetic Resonance Imaging (MRI).
Extremely low frequencies 3Hz < 300 H High-voltage power lines, railways (16.7 Hz), all electrical appliances connected to the mains (50 Hz), electric vehicles.
Low or intermediate frequencies 300 Hz < 100 KHz Computer and television screens, anti-theft devices, metal detectors, induction hot plates, energy-saving bulbs
Radiofrequency or radio waves 100 KHz < 300 GHz Radio, mobile phone (900 MHz), antennas, radar, Wi-Fi, baby monitor, Bluetooth, microwave.
Infrared rays 300 GHz < 400 THz Sun, infrared lamps
Visible light 400 THZ < 770 THZ Sun, light bulbs
Ultraviolet rays 750 THz < 900 THz

Sun, tanning beds (UVA, UVB).

Ionizing radiation > 1000 THz UVC (harmful rays filtered by the atmosphere) black light, stars)
X-rays and gamma rays 300 PHz < 30 EHz Radon, uranium, radiation therapy, radiography, radioactive materials, cosmic rays

DID YOU KNOW? Most of the waves we are exposed to in everyday life are low frequency and extremely low frequency waves. The main electricity as well as all electrical devices it supplies are limited to 50 Hz in most European countries (60 Hz in the US and Japan).

Non-ionizing radiation

Non-ionizing radiation is radiation of which the electromagnetic energy is insufficient to cause ionization of atoms or molecules.

The lower the frequency, the less the waves carry energy.

Most of our daily radiation (radio, mobile phones, microwaves, etc.) is non-ionizing.

Ultraviolet rays mark the boundary between ionizing and non-ionizing radiation.

Some ionizing ultraviolet rays (UVC) from the sun are filtered out by the atmosphere and those that reach us are essentially non-ionizing (UVA and UVB).

Ionizing radiation

Ionizing radiation is radiation of which the electromagnetic energy is sufficient to cause the ionization of atoms or molecules and to damage human cells for example. The higher the frequency, the more the waves carry an energy capable of transforming the electric structure of an atom or molecule.

Ionization is the act of adding or removing electrons from an atom or a molecule, which then becomes unstable (ion).

To stabilize itself the ion emits different types of radiation (alpha rays, beta rays, X-rays and gamma rays).

Unstable elements that disintegrate when emitting ionizing radiation are called radionuclides.

There are specific ionizing radiation measurement units:

  • the Becquerel (measures the amount of radiation emitted)
  • the Gray (Gy) measures the dose of radiation received
  • the Sievert (Sv) measures the impact of radioactivity (harmful radiation dose)

Sciensano is a member of the Superior Health Council and advises on the risks associated with mobile communication and other types of non-ionizing radiation, in particular radio frequencies.

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