Within the immediate vicinity of radio-frequency or wireless transmitters, thermal effects dominate*, which means that the body and/or specific parts of the body are heated through the absorption of radiation energy.
The degree of heating depends on the intensity and frequency of the radiation (the lower the frequency, the greater the penetration depth), but also on the type of tissue, its location in the body, and its blood supply.
Since water molecules are highly involved in the conversion of radiation into heat energy (absorption) and poor blood circulation conflicts with the rapid dissipation of this heat, those organs containing a lot of water and possessing poor blood circulation are especially vulnerable. The eyes are one of the first organs to be affected.
The evaluation of RF thermal effects is based on the energy absorbed by a given tissue during a specific time. It is referred to as the specific absorption rate (SAR). Its measurement unit is W/kg. The whole-body SAR value is derived by averaging the absorbed and converted energy across the whole body. If only parts of the body are exposed, for example the head region during a cell phone call, so-called hot spots* may occur, which necessitate the use of local or partial-body SAR values.
Normally the body can compensate for an increase in body temperature: More sweat is produced which cools the body as it evaporates. The pores of the skin open so that more heat can dissipate through the surface of the skin. This thermoregulation of the body temperature, however, also has its limits. Moreover, the body's ability to self-regulate its body temperature may not only be impaired in people having a high temperature, in diabetics, and the elderly, but also in certain organs or tissue.
A longer-lasting, above-normal hyperthermia can wreak havoc on the entire metabolism* and the nervous system. A multitude of chemical reactions, for example, run faster at higher temperatures; the rather fragile and complex cascade of metabolic processes is thrown out of balance. In the region of the eyes, this may promote the formation of cataracts and other eye problems.
Just how much heat is too much? Numerous studies have concluded that an increase of more than one degree Celsius* represents a health risk and should be avoided. This is the basis for many international and national exposure guidelines, including Germany. Critics, however, complain that so-called nonthermal effects, which clearly exist below the thermal-effects threshold, are not taken into consideration.
The rather heated discussion about nonthermal or athermal effects, whereby the absorbed energy is not high enough to heat human tissue, does not question its existence, but rather its effect on the human body.
Since we know rather little about the effect mechanisms, the focus of the experiments as well as their actual subject matter are quite diverse. And because the exposure levels and the associated biological effects are low, it does not surprise that the results are often inconsistent and difficult to compare.
Research regarding cancer-causing effects of radio-frequency radiation on the human body is mainly based on epidemiological studies. This means that the frequency of cancer in exposed population groups is compared to those not exposed. The fast-paced expansion of cell phone networks, however, presents us with two dilemmas. On the one hand, for an illness like cancer, which can be latent for many years, it is still too early to produce conclusive results, on the other hand, due to the country-wide coverage of the cell phone networks, it is now nearly impossible to find the required unexposed population group.
Despite all of these problems, we already have significant studies that challenge the safety of the observed effects. Even below the current exposure limits, effects on the central nervous system and cognitive functions, the weakening of the immune system as well as effects on different types of cancers have been discovered.
The parties involved in this discussion such as researchers, institutes and government agencies have one thing in common: Most of them are unable to make any clear statement concerning the effects of radio-frequency radiation. Thus, expressions like the following prevail: "evidence suggests," "evidence is slowly emerging," or "safety can no longer be assumed." For this reason, all experts call for further research in this area.
And as the debate about the biological effects and more stringent exposure limits continues, you can already protect yourself against electromagnetic radiation-to a certain degree-in your own home.