Dosimetric evaluation and comparison of different RF exposure apparatuses used in human volunteer studies

In a recent publication, Boutry et al. [2008] reported on a dosimetric evaluation and comparison of radiofrequency (RF) exposure setups used to study mobile phone effects on brain activity in human volunteer studies. The authors address two particularly important issues in electromagnetic (EM) bioeffects research, and do so in a detailed and technically proficient manner. While we agree with the authors that a lack of detailed exposure and dosimetric data leads to limitations in the interpretation and replication of studies, and that there are important distinctions between the exposure setups employed in such research, we believe that there are some important inaccuracies in their article that require clarification. The authors claim that brain structures need to be exposed appropriately for risk assessment research to be relevant to the use of mobile phones in realistic scenarios.We agreewith this. However, the authors also claim that their study confirmed that this cannot be achieved using modified or generic mobile phones as the exposure source, and they argue for this by demonstrating the difference between the more heterogeneous handset-type exposures and the substantially more homogeneous exposures produced by their own planar exposure system. Specifically, whereas the planar patch antennas employed in their laboratory produce a relatively homogeneous SAR distribution across the exposed hemisphere, a phone-type exposure produces a muchmore localized SAR distribution, with SARs reduced by factors of up to 10 subcortically, and up to 100 at certain cortical regions which are more distant from the phone. While we agree with their characterization of the different exposure sources, we do not find this demonstration to be relevant to their conclusion. Rather, it would appear to argue the contrary, showing how different their planar exposure system is to the everyday exposure of a real mobile phone handset. There are clearly separate endpoints to which the two systemsmay be variously better suited. If the aim of a study was to ascertain whether bioeffects can occur at the maximum exposure level that is permitted by the relevant exposure standards anywhere in the human head (even if one is never likely to receive such exposures from a real handset in normal use), then the patch antenna would be an appropriate exposure source since it can generate such exposures in a defined and uniform way. However, if the aim of a study was to ascertain whether bioeffects can occur from typical mobile phone-type exposures, then the more representative phone source would seem to be the more appropriate choice. This clarification is particularly important when we consider the issue that many are attempting to address, that is, whether or not mobile phones, such as those that are used in the community, cause bioeffects. As was demonstrated by Boutry et al. [2008], by exposing the entire cortex with the planar exposure system used in the Zurich setup, some areas of the brain are over-exposed by 100 times (relative to what would occur using a real mobile phone), and so might incur bioeffects that are not representative of real mobile