A test by Penumbra Brands to measure how much radiofrequency energy an iPhone 11 Pro gives off found that the phone emits more than twice the amount allowable by the U.S. Federal Communications Commission.
The FCC measures exposure to RF energy as the amount of wireless power a person absorbs for each kilogram of their body. The agency calls this the specific absorption rate, or SAR. For a cellphone, the FCC’s threshold of safe exposure is 1.6 watts per kilogram. Penumbra’s test found that an iPhone 11 Pro emitted 3.8 W/kg.
Ryan McCaughey, Penumbra’s chief technology officer, said the test was a follow up to an investigation conducted by the Chicago Tribune last year. The Tribune tested several generations of Apple, Samsung, and Motorola phones, and found that many exceeded the FCC’s limit.
Penumbra used RF Exposure Labs, an independent, accredited SAR testing lab for the tests (The Tribune also used the San Diego-based lab for its investigation). Penumbra was conducting the test, which also included testing an iPhone 7, to study its Alara phone cases, which the company says are designed to reduce RF exposure in a person.
There are reasons to take the results with a grain of salt, however. McCaughey clarified that Penumbra supplied RF Exposure Labs with one iPhone 7 and one iPhone 11 Pro for the tests—phones the company had purchased off the shelf. He attributed not testing more phones to the cost of purchasing multiple iPhones.
More notably, when the FCC conducted a follow-up investigation after the Tribune published its story, the agency did not find evidence that any of the phones exceeded SAR limits. That said, while the Tribune and Penumbra both used off-the-shelf phones, the FCC largely tested phones supplied by the manufacturers, including Apple.
Joel Moskowitz, a researcher at UC Berkeley who studies the health effects of wireless radiation, points to one of two possibilities. According to him, one option could be that there’s a systematic problem with RF Exposure Lab’s testing methods. Alternatively, he says, when Apple provided phones to the FCC for the follow-up investigation, “it would be easy to dummy the phone with a software update” and ensure it didn’t put out enough power to exceed the SAR limit.
Apple declined to comment on the record for this story.
There may be uncertainty in which results carry weight, but McCaughey and Moskowitz both agree that the FCC’s RF exposure testing is woefully out of date. McCaughey points out that the limits were set well before the invention of smartphones, and reflect what the FCC deemed safe 25 years ago.
“The FCC limits are over 20 years old,” says McCaughey. “Some might argue that the limit is antiquated at this point.”
The SAR limit is primarily concerned with a phone’s thermal effects—essentially, the power is limited to 1.6 W/kg to ensure that no one is burned by using their phone. A phone’s SAR is determined by placing the phone between 5 and 15 millimeters from a tray of dummy fluid designed to approximate the consistency of the human body. While the phone broadcasts, a probe on the end of a robotic arm moves across the fluid and pokes it at different points, measure the absorption rate at each location.
Just for testing thermal effects, the test may be inadequate. “The dummy fluid is homogenous, unlike the body,” says Moskowitz. The dummy fluid also doesn’t consider accessories like metal jewelry, which can affect how and where people absorb RF energy. And by testing only for thermal effects, the FCC isn’t considering other potential health effects, like decreasing sperm counts.
More fundamentally, the SAR test doesn’t accurately replicate how most people interact with their phones. Testing phones from 5 millimeters away from the body may seem close, but for anyone carrying their phone in a pocket, the distance is closer to 2 millimeters. Because wireless power falls off exponentially with distance, what might be a safe amount of RF exposure at 5 millimeters could be much higher at 2 millimeters.
McCaughey offers some best practices for anyone looking to decrease their RF exposure: Use wired headphones for calls, and don’t carry your phone in a pant pocket. He also suggests to be aware of places with poor reception. “If you have one bar or something, it’s going to turn the power way up,” he says.
Ultimately, however, what’s needed most is for more robust and comprehensive RF exposure testing from the FCC. But don’t hold your breath for that to happen any time soon. “The matter of changing the limit is more complicated,” says McCaughey. “It’s hard to define what’s a safe limit. There’s no consensus on what safe limits are.”
Michael Koziol is an associate editor at IEEE Spectrum where he covers everything telecommunications. He graduated from Seattle University with bachelor's degrees in English and physics, and earned his master's degree in science journalism from New York University.