Wireless communication devices and networks are nearly everywhere and they give us the ability to communicate with each other from nearly anywhere to nearly anywhere. Getting in touch with a friend, colleague, client or employee does not depend on where you are or where they are. This communication ability is a boon to business people, students, internet junkies and really, just about everybody because our communication is no longer limited to any particular location.

Does this ability to communicate come at a cost to us in anyway? There is potentially a social cost, possibly because we no longer have to communicate face-to-face, but I’ll leave the question of a social cost to the psychologists and sociologists (armchair ones and otherwise). There is also potentially a health cost and I want to make a few comments about electromagnetic radiation and health.

### Ways That EM Radiation is Known to be Harmful

Electromagnetic radiation is undeniably dangerous to your health in two ways. First, if electromagnetic signals have a high enough power, they can literally cook you. If you were able to climb inside a microwave oven, and turn it on, you would feel sorry about doing so afterwards. You are extremely unlikely to encounter signals with high enough power to cook you like a microwave in your day to day activities.  Second, if the electromagnetic radiation is at a high enough frequency, it can ionize atoms and molecules and damage them.  If you have ever had a sunburn, you have felt the harmful effects UV radiation which is in a class called ionizing radiation, however communication systems do not use electromagnetic signals in the ionizing part of the spectrum.

UV radiation is in a class of EM radiation that is called ionizing radiation. Ionizing radiation is any kind of radiation that can ionize atoms or molecules. More specifically, the photons of ionizing radiation carry enough energy per photon to damage atoms by knocking electrons out of their orbitals. Energy in a photon is directly proportional to the frequency of the electromagnetic signal (inversely proportional to the wavelength) by Planck’s equation:

$E = h\times f$

• E is energy Joules.
• h is Planck’s constant: $6.63 \times 10^{-34} J\dot s$
• f is the frequency in Hertz.

In order to ionize oxygen or hydrogen, the atom must be struck by a photon and that photon must carry at least 14 electron-volts (an eV is approximately $1.9\times 10^{-19}J$) of energy.

Using Planck’s equation, we can find that 14eV corresponds to a frequency of about 2.4 PHz which is the frequency of near ultraviolet light. So electromagnetic radiation in the ultraviolet range and above is considered ionizing. While 14eV is about the minimum energy to cause ionization, the energy levels probably need to be a bit higher to have significant effects on human health since the molecules in the body have higher ionization energy than oxygen or hydrogen.

Fortunately, there are not a many sources of ionizing radiation that we would encounter daily. The most dangerous ionizing radiation would come from outer space, but the earth’s atmosphere is a good shield against that source. On Earth, there are a few natural sources such as Radon (which can seep into your basement from the ground underneath), Potassium-40 (found in bananas), Uranium and Polonium (found in tobacco). There are also a few man-made sources such as medical x-rays, medical and industrial tracers, radiation therapy for treating cancer, and smoke detectors. For the most part exposure to these sources can be easily minimized.

### Other Effects of EM Radiation on Health

We know that EM radiation with either high enough power, or high enough frequency can damage biological tissue. What about low powered EM radiation that is non-ionizing, can it be harmful? Researchers are still investigating this question and have completed many epidemiological as well as in vitro and in vivo studies to try and answer this question. None of them have been completely conclusive.

A few things that we do know are

• EM radiation can heat up biological tissue, however, at the very low power of the communication networks we are exposed to, the heating effect is unlikely to be harmful
• EM radiation also seems to have non-heating effects on biological tissue, especially on nervous system tissue (i.e., nerves)
• While these effects are measurable, it is still uncertain as to whether the effects are harmful
• Blue light seems to have a suppressive effect on melatonin production and may lead to interference with normal human biological rhythms
• Mobile phone signals are deemed “possibly carcinogenic to humans” by the World Health Organization which means that the risk of cancer cannot be ruled out by the available data.
• Because the results are not conclusive, the WHO recommends following the precautionary principle: “a risk management policy applied in circumstances with a high degree of scientific uncertainty, reflecting the need to take action for a potentially serious risk without awaiting the results of scientific research.”