There has been some talk about 5G and health risks that range from hardly anything to frying your brain and controlling the population. At first, I thought looking into such risks would be a straightforward column. Not so.

In full disclosure, I have no preset opinion on this topic. As an engineer, I prefer to study the facts and draw my own conclusions. Looking at the reports has the side effect that in areas where studies diverge, or are ambiguous, I remain undecided. What I will cover here and in follow-on articles are the key issues and any conclusions that can be gleaned from the studies. I will also try to address what mitigation can be done by manufacturers, carriers, and users to minimize any health risks.

I recently received a news account from a friend about a contentious public meeting in rural northwest Washington that focused on 5G and the health risks. There are quotes such as "I would like to state clearly and unequivocally that you do not have my consent to experiment on my children with 5G technology." While it's easy to stereotype such speakers as luddites, as engineers and scientists we owe it to ourselves to at least look at what the science says.

First, let's set the boundary conditions of the discussion. I will be exploring the health risks posed by mmWave radiation onto humans. Millimeter wave (mmWave) frequencies extend from 30 GHz to 300 GHz, but most 5G systems are between 28 GHz and 80 GHz, the so-called FR2 frequency range, as opposed to the sub-6 GHz FR1 band. From the literature, there can be three high-level concerns: thermal effects, ionizing effects (Figure 1), and electromagnetic (EM) effects. I will address the first two in this column, and the EM effects in the next column. If other risks are brought up by readers, we can add those in future columns as well. Let's begin.

Figure 1. The ionization process occurs when energy, in this case a photon, is sufficient to remove an electron. Photons from mmWaves are well below the threshold for ionization.

The first study I reviewed was from the research center at NYU Wireless. This study addresses both thermal and ionizing effects. The ionizing effects are easier to summarize. The issue is whether a mmWave photon can cause an electron to move from its orbit. This ionization can be a cause of cancer, as we all know from UV radiation from sunlight. From our Physics 1 classes, we know that the energy of a photon can be calculated as E = hf, where h is the Planck constant of 4.136 x 10-15 eV (electron volts). Taking 300 GHz as the highest mmWave frequency, we calculate the energy of a mmWave photon as 1.2 meV, and the energy becomes lower as we descend in frequency.

The ionization energy of carbon is, however, 11.3 eV (reminder: we are carbon-based lifeforms). That's a factor of nearly 10,000 higher than the highest energy mmWave photon. Indeed, the NYU study concluded, "Unlike much higher frequency ultraviolet, X-ray, and gamma radiation, mmWave radiation is non-ionizing." A paper from Infineon also concluded, "The highest photon energy of a mm-wave photon is 1.2 meV while the photon energy needed to remove an electron from its atom is around 12 eV, meaning that mm-wave photon energy is 10,000 times less than what is needed to be ionizing." My first conclusion is that we can eliminate any deleterious effects caused by ionization.

Figure 2. The radiated power from a cell phone can cause localized heating of the skin. The FCC considers 1 mW/cm² a safe level. But what about the electromagnetic effects?

That still leaves thermal concerns. "Thus, the main safety concern is heating of the eyes and skins caused by the absorption of mmWave energy in the human body," stated the NYU study. A meta-study (a study of studies) from EMR Safety, itself part of School of Health at the University of California, Berkeley, provides context for many of the thermal effects. It has a particular focus on 5G mmWave health effects. It points out that mmWaves are mostly absorbed within 2 mm of the skin, and in the surface area of the cornea. Eyes are called out specifically, since there is little blood flow in the eyes to produce a cooling effect. The paper points out that heating effects occur when the power density is above 5 mW/cm². Besides a heating sensation which becomes painful with a longer exposure, the paper also states that temperature elevation “can impact the growth, morphology and metabolism of cells, induce production of free radicals, and damage DNA.”

Will we see the above power densities? The maximum exposure permitted by the FCC is 1.0 mW/cm² for frequencies between 1.5 GHz and 100 GHz, assuming a 30-minute exposure time. According to Infineon, a 24 GHz system operating at maximum radiated power 5 cm from the skin has a power density of 0.3 mW/cm², one-third of the FCC limit and 15 times below significant thermal heating.

So, here my conclusion is a bit more nuanced. It’s not clear to me that the power densities stay below these thresholds if a phone is held directly to the ear. Here, the distance from skin to transmitter may be 2 mm instead of 5 cm, resulting in high power density on the skin. My suggestion here is to use wired headphones or a hands-free device to keep the phone at a safe distance. This may also be good advice even with 3G and 4G phones, though I haven't studied the equivalent effects for these lower frequency devices.


Figure 3. We live in an environment of constant low-level electromagnetic radiation. With 5G, that radiation will also include mmWave frequencies. 


So, with some precautions, are we safe? For ionizing and thermal effects, I believe so. But, after coming to the same conclusion, the EMR Safety paper observed, "Hence, the health consequences of 5G exposure will be limited to non-thermal effects produced by prolonged exposure to MMWs in conjunction with exposure to low- and mid-band radio frequency radiation."

And that opens an entirely new bag of worms, where the science indicates there could very well be some negative effects. We will cover that topic in the next article in the series. In the meantime, I’ll be using my phone in speakerphone mode.

Larry Desjardin is a regular contributor to EDN's Test Cafe. He served in several R&D and executive management positions with Hewlett-Packard and Agilent Technologies, and currently manages a consulting company, Modular Methods.