WiFi waves, cell phones, connected devices... Our daily lives are filled with devices that emit electromagnetic waves. With them comes a question that often surfaces: what are the risks to our health? At the heart of this debate lies a key indicator: SAR. This article explains everything you need to know about Specific Absorption Rate to help you understand it better.
What is SAR?
SAR, or Specific Absorption Rate, is a measurement that indicates the amount of electromagnetic energy absorbed by the human body when exposed to a device that emits radio waves (such as a mobile phone, tablet or WiFi router). This measurement is expressed in watts per kilogram (W/kg). A SAR of 1 W/kg means that one kilogram of body tissue absorbs one watt of power from radio waves. The lower this value, the less intense the exposure.
It therefore allows the potential effects of electromagnetic waves on biological tissue to be assessed. SAR is mainly used to:
- Assess the compliance of devices with safety standards.
- Inform consumers.
- Protect public health.
What are the regulatory limits for SAR in Europe?
To ensure user safety, health authorities have set limits that must not be exceeded. In Europe, these limits are defined by Directive RED 2014/53/EU and the recommendations of the International Commission on Non-Ionising Radiation Protection (ICNIRP). The SAR limit values are as follows:
- SAR head and trunk: 2 W/kg (for a device used near the ear or body).
- SAR limb: 4 W/kg (for a device held in the hand or in a trouser pocket).
These regulations apply to a wide range of equipment, including mobile phones, tablets, smartwatches, Bluetooth headsets and WiFi routers. In the UK, the the Office of Communications (Ofcom) is responsible for monitoring the compliance of these devices.
Which devices emit the most?
Comparative electromagnetic field intensity according to distance from APequipment , landline phones, smartphones, laptops and Bluetooth mice
Please note that the measurements expressed in this table are not in W/kg. It is the equipment manufacturers who communicate the SAR in order to access the European market. Manufacturers must compile a file proving that they meet the obligations defined by European Union directives.
This table describes the intensity level of the electromagnetic field received by equipment (with standard power) according to distance.
When comparing the most commonly used everyday devices, the transmission power of a WiFi router or computer is much lower than that of a mobile phone.
Thus, a person working on their computer, connected to a terminal located 2 metres away and having a telephone conversation (in 4G mode) with a customer will be exposed to 19.822 mW of electromagnetic field intensity.
The distance between the device and the body plays a crucial role. A router is usually located some distance away, whereas a phone is often held close to the head or carried in a pocket.
Illustration of average SAR by type of equipment*
Sources: Belgium Public Health and EMF-Portal
All equipment from manufacturing partners must comply with marketing requirements, particularly for SAR, thereby ensuring the health and safety of customers and end users.
WiFi waves and health: untangling preconceived ideas
Organisations such as the WHO, ANSES and the European Commission agree that, at regulated exposure levels, WiFi does not pose a proven health risk. However, as a precautionary measure, certain recommendations exist, such as turning off WiFi at night.
In summary, SAR is an essential indicator for assessing exposure to electromagnetic waves. While mobile phones are the main source of personal exposure, WiFi remains relatively low in intensity, especially given the distance of use: the network infrastructure deployed by Wifirst therefore poses no danger to customers and end users.
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