TITLE:
The Impact of Thermal Modeling on Limiting RF-EMF
AUTHORS:
Norbert Leitgeb
KEYWORDS:
Electromagnetic Fields; Radio Frequency; Health Risks; Tissue Heating; Specific Absorption Rate
JOURNAL NAME:
Journal of Electromagnetic Analysis and Applications,
Vol.5 No.4,
April
10,
2013
ABSTRACT:
The paper quantitatively assesses the
relationship between specific
energy absorption rates (SAR) of
radio frequency (RF) electromagnetic fields (EMF) and resulting intracorporal
tissue temperature changes (ΔT) at
whole body exposure of a small person to resonant RF EMF. Applied thermal modeling allowed accounting also for dynamic thermoregulatory responses. As expected from physical laws the
correlation of all local SAR values and ΔT data was fairly good. However, at local level SAR proved to be only weakly associated
with ΔT. Even if averaged, over any 10 g tissue the ratio ΔT10g/SAR10g still varied by almost two orders of
magnitudes. Blood perfusion was found to play a major role in affecting local temperature changes
and caused even net cooling. The results demonstrate that local SAR is a poor surrogate for local
temperature change, and that conventional static thermal modeling
underestimates body core temperature. Results demonstrated that recommended
reference levels of RF EMF fail to reliably prevent from exceeding yet legally
binding basic restrictions not only with regard to whole-body SAR but also with regard to
whole-body temperature rise (ΔT).
Consequently, from
a legal point of view general presumption of conformity is no longer justified. While thermal basic restrictions were
exceeded if related to the whole-body averaged value, compliance could not be
excluded with regard to body-core related values. Further results might allow improving
EMF limiting in terms of relating it more closely to the basic health-relevant parameter which is
tissue temperature change.