- Cell phones are tested for their radiation exposure to your head and other body parts.
- Cell networks use frequencies near radio waves, which are non-ionizing radiation.
- All radioactivity is radiation, but not all radiation is radioactivity.
Rumors have swirled for years, but we finally have some firm numbers on the amount of radiation emitted by different smartphones from Germany’s Federal Office for Radiation Protection (BFS). Which phones are glowing the most, and how are these measurements taken? Hold your phone at a respectful distance and read on.
You may hear the word “radiation” and jump to something like radioactivity. That’s a slight category error. Radiation is any directional energy that travels at the speed of light, like the sun’s rays, as well as radioactive energy. The spectrum of electromagnetic radiation includes microwaves, radio waves, the visible colors of light, infrared, ultraviolet, and X-rays and gamma rays.
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Some waves pass through people or walls, or else you couldn’t use your radio inside the house or car, right? X-rays pass through soft tissue, but not bone. Other waves—like infrared, ultraviolet, and the visible light spectrum—don’t pass through most materials. The sun’s rays, for instance, cast a shadow when they hit solid objects.
Radioactivity is a specific kind of radiation; it’s when an atom wants to emit radiation in the form of particles sprayed out from its contents, as in the case of nuclear radiation. So all radioactivity is radiation, but not all radiation is radioactivity. The process of atoms shedding their particles during radioactivity is called decay. Radioactive isotopes usually decay until they settle into a stable, nonradioactive isotope.
Another key difference is ionizing versus non-ionizing radiation. Ionizing radiation, like gamma and X-rays, sweeps through materials and steals their electrons. This ability to basically chemically alter materials like living tissue means ionizing radiation is harmful—it’s why you cover the rest of your body with a lead apron at the dentist’s office.
Non-ionizing radiation, like radio and microwaves, can travel through certain materials, but does not chemically alter the materials it touches. You may have seen some hocus pocus about “microwaved water” that we can assure you is just clickbait, because microwaved water is just water with more heat energy.
When you use a cell phone, it’s constantly sending and receiving information over the air in the region of the electromagnetic spectrum near radio waves. This is why cell towers are huge antennae similar to those used by radio and TV broadcasters, with waves that definitely travel through our walls. At the same time, it’s why early cell phones struggled more with coverage in brick buildings or in basements.
Now you’re totally up to speed on the topic du jour. Back to cell phones. Radiation energy absorbed by the body is measured as the specific absorption rate (SAR). This is a value stated as watts per kilogram, where the kilograms are body tissue or other materials that can absorb radiation. Even though radio waves are ambient and quite harmless, targeted, localized radiation is potentially harmful.
A dose of two watts per kilogram is considered the beginning of the harmful range of radiation. This radiation can affect us when we talk on the phone, holding the device close to our heads. It can also affect us from inside our pockets or when holding phones in our hands.
So which phones are the worst offenders? According to data from Germany’s Federal Office for Radiation Protection—citing figures for the European Union market—the 2020 Motorola Edge is by far the worst offender with radiation coming in at 1.79 watts per kilogram, flirting with the harmful range. The Google Pixel 6, iPhone 13 Pro, and iPhone 12 all have just about 1.00 watts per kilogram of radiation. Samsung’s Galaxy S21 Ultra has just 0.71 watts per kilogram of radiation, and the Google Pixel 5A has a very low .47 watts per kilogram. The complete list with data for hundreds of phones is available here.
If you’re really worried about radiation exposure, consider choosing a lower-radiation phone model or even just storing your phone on your desk or in your purse instead of carrying it in a pocket. And when possible, put the phone on speaker or use headphones and set it on the desk or table while you talk. But overall, remember that this small amount of radiation is still in the safe range below two watts per kilogram.
Update, April 27, 2022: This story has been updated to reflect that the smartphone radiation figures are for devices in the European Union.
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