Response to Professor Foster’s Comments on Systematic Derivation of Safety Limits for Time-Varying 5G Radiofrequency Exposure Based on Analytical Models and Thermal Dose

Esra Neufeld and Niels Kuster, Health Physics 2018, Volume 117, Issue 1, July 2019, pp. 70–71, online 01 July 2019; doi:10.1097/HP.0000000000001091

Kenneth R. Foster, Professor of Bioengineering at the University of Pennsylvania, published a commentary on the paper "Systematic Derivation of Safety Limits for Time-Varying 5g Radiofrequency Exposure Based on Analytical Models and Thermal Dose (Neufeld and Kuster, 2018) in the journal Health Physics. Prof. Foster criticized the employed simplification of assuming surface energy deposition, which led him to incorrectly discard the concerns raised in our original paper regarding the inherent safety of emerging exposure safety standards for short mmWave pulses. Esra Neufeld and Niels Kuster replied to all comments and added additional analysis to substantiate their arguments:

  • The conservativeness of the assumption regarding surface power deposition was, in fact, already discussed in the assumptions section of the original paper
  • In view of Prof. Fosters comments, new simulations performed to quantify that conservativeness on the basis of published penetration depths (Walters et al. 2000) demonstrate that the overestimation remains below 25% and thus does not affect the conclusions of the original paper
  • In view of the longevity of standards and the rapidity of technological changes, standards should be intrinsically safe and consistent, rather than dependent on implicit assumptions about current and future technological limitations; furthermore, it should be noted that pulses shorter than 1 µs are already foreseen in current 5G technology (source: Qualcomm)
  • In summary, while the surface energy deposition approximation produces quantifiable overestimations, the conclusions of our original publication, that full exploitation of the proposed guidelines can result in substantial temperature rises that are inconsistent with the framework of safety standards, remain valid.