Low-Level Thermal Signals: An Understudied Aspect of Radio Frequency Field Exposures with Potential Implications on Public Health

By Lucas A. Portelli. Chapter 6: 129-162. Abstract
Protection from the hazards of radio frequency (RF) fields is currently aimed at confining the RF-induced thermal changes in tissue to within limits which are currently considered as safe. In this regard, hazardous effects of such exposures are traditionally investigated, catalogued, and interpreted from a perspective based on presumably adequate approximations and assumptions that simplify several dosimetric and biological aspects. While these simplifications are certainly useful and convenient, they tend to obscure the existence of dosimetric artifacts and subtle biological responses which may be of relevance to human health when observed from the microdosimetric or chronic perspectives. Increasingly realistic human models, for example, can unveil the existence of localized hot-spots and thermal transients which are invisible when using simpler models or space and time averaging as is customary for the safety regulatory practice. This results in exposures which can be in reality many times greater than the supposed and reported exposures. Similarly, from the biological perspective, the classical thermal hazard paradigm assumes that thermal damage only occurs after certain relatively high temperatures are reached for short amounts of time, inducing safety regulations to limit rather acute thermal exposures accordingly. However, while this perspective is practical and apparently sufficient to protect the population under the current paradigm, it is impervious to the possibility of the existence of the effects of chronic exposures to low-levels of thermal challenges. Such exposures may cause small amounts of thermal damage directly or indirectly (e.g., via the stimulation of compensatory physiological reactions) which may add up over time.
In this regard, one must recognize that localized thermal transients (collections of which form Thermal Signals) are an unavoidable result of exposure to modulated RF fields, even if the exposure is within the limits which are currently considered as safe. One can contemplate, for example, how such a thermal signal can appear when tissue is exposed to an intermittent RF field (e.g., ...on-off-on-off...) as the deposited heat is actively or passively redistributed by physical or physiological means throughout the organism and back into the environment.
The fact that such signals are inherent to RF exposures alone makes the studying of their biological effects a necessity to guarantee human safety. Nevertheless, at present, the possibility of biological effects of thermal signals is not mentioned, contemplated or investigated since they are deemed inconsequential under the current paradigm. Yet, sensitivity to minute thermal changes is an inherent aspect of physicochemical laws which govern the dynamics and function of biochemical reactions and structures. Such structures and reactions can potentially act as transducers of thermal signals into the cellular processes, which may translate into biological and ultimately health effects. Consequently, the study of thermal signals may open a myriad of possibilities for noninvasive, nonchemical interaction with biochemical signals at the cellular level which may have broad implications in the scientific, industrial, regulatory, and therapeutic arenas.

Conclusions

It is an undeniable fact that complex biological systems, from the molecular to the full organism level, are built around very rigorous thermal specifications making them very sensitive and responsive to small temperature changes in their internal or external vicinity. Hence, thermal signals which are invariably linked to the imposition of RF fields have the potential to be accompanied by compensatory biochemical responses from tissue at a local or global level in the organism. Such thermal signals might initially have modest effects on biochemical reactions and structures, however, these effects may then be amplified by the biological system into relevant biological and health effects.
From the public health perspective, a necessary question to answer is: what are the biological effects of chronic exposures to low-level thermal signals and what are the relative health risks? (i.e., compared to a smoking certain number of cigarettes a day, for example). However, to date, our currently poor understanding about the true biological relevance of thermal signals is insufficient to draw useful scientific conclusions which can affect decisions, recommendations, and policy to protect the public from potential hazards. In fact, the amount of data available is much less than would be considered the bare minimum. How "small" a thermal signal is can only be judged from a biological system perspective by generating the appropriate set of experiments and interpreting them from a paradigm that includes this possibility. While, in essence, the characteristics of this thermal signal will be a result of the antagonistic thermal processes (heat-in versus heat-out) specific to the details of the exposure, the need for consideration of the effects from the cellular spatio-temporal scale might require significant amounts of effort and complications. However, such apparent complications, in return, may hold substantial scientific, industrial, and therapeutic potential at best or understanding of realistic safety thresholds at worst.

Therefore, in view of the pervasiveness and potential relevance of low-level thermal signals, the paradigm centered around the notion of a "thermal damage threshold" on which the current safety standards and recommendations for mobile communications are currently based might be incomplete. For this reason alone, basic research in this area is imperative. Therefore, scientists and executives who are seriously concerned about the implications of mobile communications on public health must consider directing their scientific resources towards unveiling the true biological relevance of RF-induced small thermal signals to such a degree as these are directed towards the study of RF-induced "thermal" and "nonthermal" effects. In this regard, thermal signals may not only appear as a secondary effect in other instances of intermittent energy deposition (ultrasound or light), but it could also be purposely generated to achieve therapeutic levels, should these exist....