Differences in Energy Absorption Between Heads of Adults and Children in the Near Field of Sources

Abstract

This paper was motivated by a recent article in which the levels of electromagnetic energy absorbed in the heads of mobile phone users were compared for children and adults at the frequencies of 835 MHz and 1,900 MHz. Significant differences were found, in particular substantially greater absorption in children's heads at 835 MHz. These findings contradict other studies in which no significant changes had been postulated. The clarification of this issue is crucial to the mobile communications industry since current SAR evaluations as required by the FCC are only performed with phantoms based on the heads of adults. In order to investigate the differences in absorption between adults and children due to their differing anatomies, simulations have been performed using head phantoms based on MRI scans of an adult (voxel size 2 x 2 x 1 mm3) and two children (voxel size 2 x 2 x 1.1 mm3) of the ages of 3 and 7 y. Ten different tissue types were distinguished. The differences in absorption were investigated for the frequencies of 900 MHz and 1,800 MHz using 0.45 lambda dipoles instead of actual mobile phones. These well-defined sources simplified the investigation and facilitated the comparison to previously published data obtained from several numerical and experimental studies on phantoms based on adults. All simulations were performed using a commercial code based on the finite integration technique. The results revealed no significant differences in the absorption of electromagnetic radiation in the near field of sources between adults and children. The same conclusion holds when children are approximated as scaled adults.

Acute Mobile Phones Exposure Affects Frontal Cortex Hemodynamics as Evidenced by Functional Near-Infrared Spectroscopy

“…This hypothesis has recently been proposed especially for the highest frequencies, in which dielectric and resistive heating could increase the local temperature and increase the entropy of the exposed biologic system (Sheppard et al, 2008). However, a thermal mechanism should be rejected taking into account that: (1) the distance between the antenna and the head drastically reduces the absorbed power (Schö nborn et al, 1999); (2) increase of skin temperature would be easily dissipated through the blood flow (Van Leeuwen et al, 1999); and (3) near-infrared light penetrates through the brain at least 1.5 cm in-depth, in which temperature changes are far below the danger level (Wang and Fujiwara, 1999;Bernardi et al, 2000). Thus, several nonthermal mechanisms could be involved, such as: (1) proteins conformational variations resulting in proteins functional changes; (2) modifications in the binding of ligands, such as Ca + + to cell receptors, also resulting in a changed receptor function; (3) absorption of RF energy by the vibrational states of biologic components, such as microtubules; (4) enhanced attraction amongst cells (the pearl-chain effect); and (5) demodulation of a modulated RF signal, producing extremely lowfrequency electric fields (for a review, see Challis, 2005).…”

The Effect of Mobile Telephone Electromagnetic Field on Human Brain Bioelectric Activity and Information Processing Speed

“…These radio waves take the form of oscillating electric and magnetic fields, known as an electromagnetic field (EMF). With the understanding of the partial absorption of a mobile telephone electromagnetic field (MP-EMF) by the skull and brain, 1 there has been a proliferation in concern for one's health and the potential adverse effects caused by an MP-EMF. Consequently, studies concerning the technology have increased.…”

Children's Mobile Phone Use and Dosimetry

“…Schönborn et al [12] analyzed the electromagnetic energy absorption using anatomical head models based on magnetic resonance imaging (MRI) scans of a 7-and a 3-year-old children. No significant differences were found between adults and children in terms of the absorption of electromagnetic radiation in the near field of sources.…”

“…Several studies have measured electromagnetic absorption in realistic child and adult head models that were developed based on medical images and compared this to absorption in the SAM phantom exposed to radiation from a mobile phone antenna [12,[16][17][18][19][20]. Some studies comparing the peak local SAR in the MRI-based head models from adults and children have found either no significant difference or a statistically higher peak SAR in the larger (adult) head [12,16,17].…”

“…Some studies comparing the peak local SAR in the MRI-based head models from adults and children have found either no significant difference or a statistically higher peak SAR in the larger (adult) head [12,16,17]. The results of [16,17] showed that the SAM gives a conservative estimate of the exposure in the anatomical head models that were considered for two standards, IEEE C95.…”