On the Non-ionizing Radiation Red Herring
Reports relating radiofrequency (RF) energy exposures to humans seem inevitably to note distinctions between ionizing and non-ionizing radiation. For those not formally trained as scientific researchers, and even for non-physicist bioeffects professionals, there persists a notion that this demarcation, ionizing versus non-ionizing, establishes some barrier separating hazardous from non-hazardous exposures. The common argument holds that since x-rays and ultraviolet rays are ionizing radiations known to cause various kinds of cancers that it must only be ionizing radiation that causes cancer. The truth of the matter is that researchers don't know that the ionizing capability of the radiation is the causative mechanism.
Ionization as it is referred to in this context means the liberating of an electron from an atom. Only electromagnetic radiation of sufficient energy can liberate an electron from an atom. For metals, such as gold or copper, the concept of ionization energies is straightforward and describes the effect of absorption of photons within the material. However, in biologic systems comprised of complex organs, cell structures, and extensive molecules such as DNA the restriction of disruptive effects via ionization is entirely removed. In short, maintaining and professing a belief that only ionizing radiation holds a capability to damage tissue is of itself without scientific foundation.
In fact, the scattering of ionizing radiation throughout biological tissue efficiently breaks the covalent bonds that are the basis for construction of organic molecules. It may well be this effect and not the inherent ionizing capability of a particular frequency or wavelength that gives rise to initiation or promotion of cancers. It's somewhat like a bullet shot into a concrete room and ricocheting from the walls, ceiling and floor. Each time the bullet hits a surface it loses a little energy while continuing to bounce about until the energy is fully spent. For a high-energy photon scattering through living tissue, each of the multiple contacts leaves behind some energy that can destroy the bonds that form the molecules.
The distinction between ionizing and non-ionizing loses all meaning for biological applications. The ionization potential refers to the photoelectric effect whereby an electron is liberated from an atom or dissociated from an atom in an ionic molecule and is accomplished via a single photon absorption event.
By contrast, of interest for biological applications is the energy necessary to disrupt one or more covalent bonds of which the biological system is comprised. For example, covalent bonds in human tissue may be disrupted at energy levels hundreds of times lower than necessary for ionization.
In the presence of an exogenous energy source of sufficient magnitude sequential photon absorption may lead to continually increasing excited energy states until bond disruption occurs. No such comparable mechanism or effect is available for ionization since the allowed energy states do not provide for sequential photon absorption to achieve ionization. It's like the old saying, "you can't get there from here". Well, for the ionization argument it's true. RF energy doesn't let you get to ionization. But, most important is that ionization never has been the threshold. Clearly, by now we must all agree that it is not necessary to ionize a DNA molecule to disrupt one or more of the molecule's covalent bonds. For the instance of covalent bond disruption in complex molecules the energy may be provided by means other than single photon absorption. And since that is accepted the ionizing/non-ionizing argument becomes inconsequential.
Single atoms have well defined and distinct energy bands that allow only specific energy states for the electrons. In order to ionize, eject an electron, it is necessary to provide a photon having sufficient energy to move the electron from an allowed energy state to a completely free state in one step. Multiple photon absorption is not permitted. This is the basis for the photoelectric effect - i.e. ionization.
Atoms in close proximity to one another establish a more complex system of allowed energy states. As atoms move close together the probability density functions indicate that there is some overlap and energy band shifting occurs. That is, additional allowed energy states are created due to the proximity of multiple atoms. For complex macromolecules, such as human DNA comprised of many thousands of interrelated atoms, the allowed energy states form a virtual continuum. The complex energy state structure of macromolecules provides for a significantly different energy absorption and dissipation profile. This energy state structure is so dissimilar from the single atom picture that it makes it impossible to apply the ionization argument.
RF energy absorption in biologic tissue takes place via an energy conversion process. Photon energy is converted to phonon energy better known as heat energy. Phonon energy is more familiarly observed as vibrational, translational, or rotational motion of atoms constrained by their covalent bonds. The absorbed energy may either reside at the absorption site, in which case the site is said to be in an excited state, or the energy may be dispersed through the system. If RF energy is incident at a rate that is greater than the energy dispersion rate then subsequent photon absorptions at any particular site, which has experienced a prior absorption event, will lead to a change in energy state to a second higher allowed energy level. Succeeding photon energy absorptions may continue up to the point where the covalent bond ceases to exist by virtue of the increasingly excited energy state.
Although the energy conversion process yields heat energy - phonon energy - there need not be any measurable temperature variation. In fact, the very use of the distinctions between thermal and non-thermal, or athermal is another "red herring". Since all energy absorption is thermal by nature there is, strictly speaking, no such thing as non-thermal or athermal energy absorption.
Instead, when speaking of energy absorption it may be more appropriate to speak of measurable or not measurable temperature rise. In either case there is an increase in thermal energy whether it be on the order of pico-joules (immeasurable by typical thermometric means) or milli-joules.
RF energy photons are particularly suited for deep penetration into human tissue. Infrared, visible light, and ultraviolet radiation does not penetrate human tissue to any appreciable extent. However, the penetration capabilities of RF radiation puts it in the same category as x-ray radiation, which is also a deep penetrating energy. This penetrating characteristic of x-ray radiation and RF radiation provides that a single photon of x-ray energy may scatter through the tissue or molecule and disrupt many, many covalent bonds even without liberating an electron from an atom (in other words an ionizing event is not required) while RF radiation may be less extensive in bond disruptions until exposures are encountered that overcome inherent energy dispersion mechanisms. In essence the effects can be identical - the disruption of covalent bonds is essentially what destroys DNA molecules and genetic information and leads to neo-plastic transformation of cells.
Although a single x-ray photon may destroy molecular bonds RF energy can effect damage by multiple photon absorption. For example, a cell phone emits about 8.9 x 1021 photons per second per square centimeter at the surface of the human head. For those unfamiliar with the scientific notation of that number, its magnitude appears more dramatic when written in standard notation as 8,900,000,000,000,000,000,000 photons per square centimeter per second.
Consider, then, that the energy from each and every photon absorbed will disturb the equilibrium of the system while the energy is being diffused and dispersed. Biological systems, and in particular the human brain do not have the capability to handle the massive dose of photon energy coming from such radiation absorption. Under normal circumstances, when not exposed to high doses of RF energy, the body compensates for naturally occurring damages. During high dose RF energy exposures the biological protection and repair mechanisms may be overwhelmed and irreparable disruptions, caused by the radiation, lead to widespread submicroscopic damage including permanent DNA damage.
It will serve as little comfort to know that exposure to cell phone towers provides an RF energy dose only slightly lower at about 7 x 1018 photons per square centimeter per second (7,000,000,000,000,000,000) and that's at a distance of a few hundred feet from the tower.