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SAR / Device Absorption

The effect of increase in dielectric values on specific absorption rate (SAR) in eye and head tissues following 900, 1800 and 2450 MHz radio frequency (RF) exposure.

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Keshvari J, Keshvari R, Lang S. · 2006

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Children's higher tissue water content increases RF absorption by only 5% on average, but other developmental factors may create greater vulnerability.

Plain English Summary

Summary written for general audiences

Researchers used computer modeling to examine how radiofrequency energy from cell phones is absorbed by children's heads compared to adults, accounting for the fact that children's tissues have higher water content. They tested common cell phone frequencies (900, 1800, and 2450 MHz) and found that even when tissue water content was increased by 5-20% to simulate children's physiology, energy absorption (SAR) varied by only about 5% on average. The study suggests that tissue composition differences between children and adults may have less impact on RF absorption than previously thought.

Why This Matters

This Nokia-funded study addresses a critical question in EMF safety: whether children absorb more radiofrequency energy than adults due to their different tissue composition. The research is technically sound but comes with important caveats. While the authors found relatively modest changes in SAR when accounting for children's higher water content, this doesn't address other factors that make children more vulnerable to RF exposure, including their thinner skulls, developing nervous systems, and longer lifetime exposure. The science demonstrates that children face unique risks from wireless radiation that extend far beyond simple absorption rates. What this means for you is that SAR measurements, while useful, don't tell the complete story about children's EMF vulnerability. The reality is that multiple independent studies continue to show children may be at greater risk, making precautionary measures for young wireless device users particularly important.

Exposure Information

A logarithmic frequency spectrum from 10 Hz to 100 GHz showing where this study's 2.45 GHz exposure sits relative to common EMF sources.Where This Frequency Sits on the EMF SpectrumELFVLFLF / MFHF / VHFUHFSHFmm10 Hz100 GHzThis study: 2.45 GHzPower lines50/60 Hz5G mm28 GHzLogarithmic scale

Specific exposure levels were not quantified in this study. The study examined exposure from: 900, 1800 and 2450 MHz

Study Details

The objective of this study was to investigate possible variation in specific absorption rate (SAR) in the head region of children and adults by applying the finite-difference time-domain (FDTD) method and using anatomically correct child and adult head models.

In the calculations, the conductivity and permittivity of all tissues were increased from 5 to 20% b...

The analyses suggest that increasing the value of dielectric parameters does not necessarily mean th...

Cite This Study
Keshvari J, Keshvari R, Lang S. (2006). The effect of increase in dielectric values on specific absorption rate (SAR) in eye and head tissues following 900, 1800 and 2450 MHz radio frequency (RF) exposure. Phys Med Biol. 51(6):1463-1477, 2006.
Show BibTeX
@article{j_2006_the_effect_of_increase_2276,
  author = {Keshvari J and Keshvari R and Lang S.},
  title = {The effect of increase in dielectric values on specific absorption rate (SAR) in eye and head tissues following 900, 1800 and 2450 MHz radio frequency (RF) exposure.},
  year = {2006},
  
  url = {https://pubmed.ncbi.nlm.nih.gov/16510956/},
}
PubMed: 16510956

Cited By (76 papers)

View all 76 citing papers on Semantic Scholar

Quick Questions About This Study

A 2006 computer modeling study found that even when tissue water content increased by 5-20% to simulate children's physiology, radiation absorption (SAR) from 900-2450 MHz cell phone frequencies varied by only about 5% on average, suggesting less impact than previously thought.
Research shows that at higher frequencies like 2450 MHz, particularly in eye exposure, volume-averaged SAR actually decreases when tissue dielectric values increase. The thickness and composition of different tissue layers play a more significant role than tissue parameter variations.
Computer modeling research found that increasing tissue dielectric conductivity or permittivity by up to 20% caused SAR variations of less than 20%, usually around 5%. Tissue layer thickness and composition have more impact on radiation absorption than dielectric parameter changes.
Studies testing 900, 1800, and 2450 MHz frequencies found that higher frequencies, specifically 2450 MHz during eye exposure, showed decreased volume-averaged SAR when tissue dielectric values increased, contrary to what might be expected from increased tissue water content.
Research using computer models found that even significant increases in tissue water content (5-20% higher dielectric values) only changed SAR measurements by about 5% on average across 1, 5, or 10 gram tissue masses, suggesting current measurements remain relatively accurate.