A few days ago the iPhone 12 was news in France (and, therefore, in half the world). The French authorities detected that hundreds of analyzed terminals of this model slightly exceeded the permitted power limit that ends up being absorbed by our body. Specifically, it narrowly exceeded the ceiling set specifically for limbs. This led to the withdrawal of the product from the French market, a measure that was later revoked after Apple, the manufacturer of the model, made a software update that reduced the levels of the radio frequency waves of the terminal. The case generated some alarm and put on the table the debate about whether the waves emitted by mobile phones can become harmful to health. Well, the experts have no doubts.

To start, and before getting into the subject, it is necessary to talk about the specific absorption rate (SAR, for its acronym in English), which is nothing more than “the measure that indicates how much power is absorbed per kilogram of the human body when the latter is exposed to non-ionizing electromagnetic radiation [type of low-energy radiation]”, explains Fernando Las-Heras, professor of the Department of Electrical Engineering at the University of Oviedo, to La Vanguardia. Specifically, the terminal of the bitten apple company recorded 5.74 watts per kilogram (W/kg) for the limbs, when the limit is 4 W/kg.

The question is: can this difference of 1.74 W/kg translate into harm to people’s health? Judge for yourself.

Las-Heras explains that, “based on scientific studies”, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) considered a SAR value of 4 W/kg for the whole body (not for the limbs) from which the biological effect of being subjected to an electromagnetic field could become a biological risk (potentially harmful to health). Because? Because the body temperature could rise above one degree centigrade, which would generate thermoregulation problems and, therefore, biological damage.

Based on this figure, the body established recommendations for any radioelectric terminal setting a limit for the whole body of 0.08 W/kg for the general public. “In other words, he lowered the bar up to 50 times”, Las-Heras points out. He also set the ceiling at 2 W/kg (measured on a mass of 10 grams) for the head and trunk, and 4 W/kg for the limbs.

“Much more SAR is allowed when you receive the radiation in areas that are not so sensitive, such as the extremities,” argues Las-Heras. “It is not the same to receive it in the eye, which is a very exposed area due to the poor blood supply of the lens – so it dissipates less heat than other tissues -, than in an arm”.

He understands that, even if the iPhone 12 emitted 5.74 W/kg (something that has already been corrected), “it did not automatically generate biological damage”. Despite this – he continues -, “it does enter the safety margin of biological risk”, which is why he defends that if a safety limit has been legally established, as is the case, “it must be complied with”.

And who certifies that a mobile emits within the permitted SAR parameters? Two actors come into play here: on the one hand, there are the testing laboratories and, on the other, the certification bodies. The Applus company performs both roles: it has several laboratories and certification teams. In addition, it monitors the SAR tests performed by other laboratories.

José María Laborda, the technical director of the electronic area, explains that there are four families of tests within what is radio frequency. The first has to do with electromagnetic compatibility. “In other words, there are different devices (mobile, computer, headphones…) that emit electromagnetic waves and they all have to coexist with each other. These tests make it possible to corroborate that there is no interference or anomalous behaviour.

The second concerns the protection of the electromagnetic spectrum. “In other words, that the emission flows through the band that corresponds to it and with the relevant characteristics. Communication on one side cannot interfere in any way on the adjacent side”.

Interoperability is the third. “Each technology requires a form of communication, with a specific coding of signals. Verifying that this coding is the relevant one is what is called interoperability”.

And the last is the part of human exposure to electromagnetic waves. “And this is where the SAR measures come in,” Laborda points out. In Europe, he explains, “if the device in question operates with transmission powers greater than 20 milliwatts and will be used less than 20 cm from the person, SAR measurement tests must be carried out”.

How do testing laboratories measure the SAR emitted by a mobile phone? There is a protocol. The first step is to fill a kind of dummy with a liquid that simulates the electromagnetic properties of human tissues. The composition of the fluid varies depending on the tissue to be simulated. “The head is not the same as an arm”, argues Laborda.

One should not imagine a mannequin in use (see the graphic accompanying these lines). In reality, it is a mold that is placed horizontally and filled. It is thanks to this horizontal position (otherwise the fluid would spread) that it is possible to pass under the terminal in all the possible positions in which the user will end up using it while a probe is inserted into the liquid (through the upper of the mold) to take measurements of the radiation emitted by the mobile.

“At the ends of the mold there are two heads. They are used to measure the left and right sides. Because? Because there are terminals that are not completely symmetrical”, explains Laborda, who emphasizes that different ways of holding the phone are simulated: “We look for the most unfavorable case. If there is a possibility, however remote, of taking the terminal, it is measured”.

The SAR limit in the body and towards Europe is 2 W/kg, averaged over 10 grams of tissue. In the US, the Federal Communications Commission requires phones to have a SAR value of 1.6 W/kg or less, measured in 1 gram of human tissue. In the North American country (also in France since 2020), the limb test is required. It was precisely in this test that the French authorities detected an excess of emissions from the iPhone 12.

“The marked limits are extremely low”, asserts Laborda. And give an example. “If you put your hand in the sun for five minutes, you feel the heat after a short while. With the mobile, the generation of heat by radiation is considerably lower meeting the regulatory limits. I’m not saying that you can’t notice a little in your ear if you’ve been talking on the phone for an hour, without contact between the terminal and the ear, but there’s no point of comparison.”

He defends that the level of security is enormous and that manufacturers are the first to not want to waste energy. “They, within the limits of electromagnetic emissions, are the first interested in using the essential energy to be able to have the coverage that allows good communication, which translates into good functionality, with convenient energy efficiency and, for both, autonomy”.

“What is clear – he adds – is that with worse coverage there is more radiation power, more battery consumption and possible higher SAR measurements”.

In fact – he asserts – there are certain voices in the industry that ask for these limits to be relaxed a little. “The emissions according to the current regulation are far from harming health, so slightly higher limits would allow a much less complex technological development, or a better operation in scenarios with low coverage, for example”.

However, he assures that “since the current limits have proven to be safe and at the same time do not represent an indestructible barrier for the industry, there is no intention or plan right now to relax them”.