Radiofrequency dosimetry (DAS/SAR)

Over the last few decades, the increasing use of telecommunication devices such as cell phones and other wireless networks, both in the workplace and in public places, has raised the question of exposure to electromagnetic fields and their effects on health.

Radiofrequency electromagnetic dosimetry refers to the set of measurement and modeling techniques used to establish the relationship between the incident electromagnetic field distribution and the fields induced in human body tissues, and to calculate the absorbed electromagnetic radiation power.

The Specific Absorption Rate or SAR, defined as the electromagnetic power dissipated per unit mass of biological tissue, expressed in watts per kilogram, is the basic dosimetric parameter, because of its use in international regulations on protection against electromagnetic fields, and because it makes it possible to assess the biological effects observed under different exposure conditions.

While a cell phone generally emits a few watts, a cell phone base station can emit power in the hundreds of watts. On the other hand, it is clear that the power levels absorbed in the near field by the cell phone user will be greater than the exposure levels in the vicinity of a base station.

In order to rigorously determine SAR levels for the various possible configurations, dosimetry methods and techniques have been developed. These can be experimental, theoretical or numerical.

Experimental dosimetry involves measuring the SAR directly in a sample of biological tissue exposed to electromagnetic fields, or when this is not feasible, in a mannequin or phantom created to represent, as faithfully as possible, the morphological and electromagnetic properties of all or part of the human body. To achieve this, electric field probes or thermal probes can be used, as SAR results from the distribution of the electromagnetic field in the tissues, which in turn leads to heating of these tissues.

Theoretical and numerical dosimetry is the direct resolution of Maxwell's equations describing the interaction between the electromagnetic field and the biological medium or equivalent. Advances in both calculation codes and computing resources have considerably improved the performance of this type of analysis, making it possible to process increasingly complex, accurate and realistic models of the exposed environment quickly and efficiently.

This article deals with DAS and the theoretical and experimental means that can be used to assess it.

In the first part, we present the normative and societal context, which is important for this field. On the basis of scientific work carried out over many decades,...