What is SAR?

When you see mobile phone radiation being discussed, you might see the acronym SAR crop up rather often. SAR means ‘specific absorption rate’, which is probably no less confusing! Here, we’ll explain what SAR is and how it’s measured. 

Your Body And Radiation 

Many electronics emit at least some radiation but phones emit considerably more, especially when you’re on a call and the device is placed right next to your head. Our bodily tissues are like sponges, they effectively absorb the radiation emitted by our phones. 

SAR, measured in watts/kg of tissue, measures the rate that radiofrequency (RF) radiation is absorbed into the body from the device being measured, usually phones. 

This helps measure the penetration of radiation and discover how much travels through our bone and skin into more vulnerable tissues, like the brain. 

The regulatory limits are 2W/kg in Europe and 1.6W/kg in the USA. Independent labs are used to carry out the tests and report them to regulatory bodies

The Measurement Process 

SAR is typically measured using phantom or fake body parts of the head and body. These are usually filled with liquids that are designed to emulate human tissues.Phones are usually tested in 3 ways:

  • At maximum power across all the radio frequencies at which it operates
  • In various operating frequencies 
  • In different positions next to the head and torso, for varying periods of time

Results are compiled and usually, only the highest measurements will be used. Manufacturers must publish the SAR data of their phones in most regions worldwide. 

The Unreliability of SAR

SAR is tricky to message and there is much controversy surrounding its usefulness. Whilst it is necessary to determine that a phone isn’t simply far too dangerous to market, it is a poor measurement that neglects many technical aspects of modern mobile phones and social aspects of the ways we use them. 

The Issues

  • Labs generally position phones 5mm from the test object whereas we regularly press them against out heads or bodies which can result in much higher readings
  • Tests are short term, just a few minutes, whereas calls and other phone usages can last hours in real life
  • Mobile phone signal can fluctuate greatly in real life, especially if a phone is struggling to find reception, thus causing temporary spikes in radiation
  • Lab models are standardised to that of a bulky individual, smaller people and children will have much thinner skulls  

Summary

SAR is an indicator of how much phone radiation is absorbed by our body’s tissues. It gives us some idea but overall, it’s a pretty measurement that doesn’t shed many clues on whether or not a phone is safe or not. Overall, evidence suggests that phones are generally not safe, even if their SAR falls well below regulatory limits. The best thing to do is to use a shielding case and limit usage.