Smartphone manufacturers often specify a SAR value in the product description of their devices. This is the information about the wireless performance of a smartphone. Users can thus find out whether the radiation exposure of their mobile phone is within the norm or is perhaps even too high.
Radiation is inevitably generated when data is sent – for example when making a phone call or sending a WhatsApp or Facebook Messenger message. The electromagnetic field created during operation emits radio waves that are absorbed by the body and converted into heat. The term SAR value, “Specific Absorption Rate”, indicates exactly this amount of energy that is finally absorbed by the body. This also results in the quantity in watts per kilogram (W/Kg).
This is what the SAR value of your smartphone tells you
In addition to the amount of energy consumed, the SAR value also indicates the maximum transmission power of the device. With daily use, the radiation value is usually below the specified maximum value. However, in areas with a less good network and poor reception, the value is often higher because the device has to emit stronger waves for the data to reach a transmission mast.
Therefore, the SAR value that a cell phone emits is never constant. Not only the network reception causes fluctuations, but also the number of transmission masts in the area and the isolation from walls affect how strong a mobile phone has to transmit. In principle, the more sources of interference there are, the stronger the emitted radiation. Unfortunately, the information provided by the manufacturer does not reveal whether a device transmits more or less in the GSM, UMTS or LTE network.
The SAR value is now a prominent indication for smartphones. But of course it is also measured on other devices that emit radiation, such as a WLAN router or a microwave. An additional piece of information that is also of interest to concerned mobile phone users is the radiation factor: This indicates how high the radiation is on average – the value is therefore usually significantly lower than the absorption rate.
In principle, the value indicates the power that is transmitted to a ten gram area of the human body in the worst case, when the corresponding device is very close to the head.
Health risks from cell phone radiation
For years, research has been concerned with the question of how harmful cell phone radiation is to health. However, there is no agreement on specific risks. Studies partially contradict each other. For example, an increased risk of cancer is suspected, but cannot be definitively confirmed. In addition, the rays are said to have a negative effect on sleep.
In particular, people who use the phone a lot should be careful, despite the consequences that have not been definitively proven, since they are exposed to the most radiation on their heads. In addition, the mobile phone should not be placed directly next to or under your head at night.
Also interesting: Attention! These popular smartphones emit the most radiation
What is the maximum SAR value?
The World Health Organization (WHO) has set an upper limit for mobile phone radiation: a maximum of 2 W/kg is permitted on the head and thus in the decisive measuring zone. A European standard was introduced back in 2001 for uniform measurement and meaningful data. Since then, the measuring method has been the same for all devices.
In addition, in 2002 the “Blue Angel” eco-label for mobile phones was introduced, which distinguishes mobile phones with particularly low levels of radiation. For the award of the mark (as of 2017) according to the Federal Office for Radiation Protection the following criteria are met:
- SAR value of a maximum of 0.5 W/kg on the head during a call and a maximum of 1.0 W/kg when carrying the mobile phone on the body
- Basic due diligence when handling conflict minerals
- socially responsible device manufacturing
- sustainable, environmentally and recycling-friendly production
This is how the SAR value is determined
When determining the SAR, the device is tested at maximum transmission power on a replica of the human head. Inside the model is a liquid that has electrical properties similar to those of brain tissue. The field strength within the model is recorded using highly sensitive probes and first the area of the maximum SAR value is determined in order to then determine the electric field distribution in the volume area.
Similarly, the value on the body is determined by positioning the device in a typical wearing position on the model filled with electrolyte mass. As already mentioned, a measurement per ten grams of tissue applies in Europe; in the USA, for example, it is only one gram. As a rule, this results in a slightly higher value in the US measurement.
If you want to find out how high the SAR of your smartphone is, you can find the corresponding information either directly in the manufacturer’s product descriptions or at the Federal Office for Radiation Protection. The authority regularly publishes its investigation values in a extensive list.