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Multiple power-density windows and their possible origin.

C F Blackman1, L S Kinney, D E House

  • 1Health Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711.

Bioelectromagnetics
|January 1, 1989
PubMed
Summary

Exposure to specific radiofrequency electromagnetic radiation (RF-EMR) at 50 MHz, amplitude modulated (AM) at 16 Hz, enhances calcium ion efflux in chick brain tissue. This effect is observed only within certain power density ranges, suggesting a non-thermal, frequency-dependent mechanism.

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Area of Science:

  • Neuroscience
  • Electromagnetic Biology
  • Biophysics

Background:

  • Previous research indicated that 50-MHz radiofrequency electromagnetic radiation (RF-EMR), amplitude modulated (AM) at 16 Hz, selectively enhances calcium ion efflux in chick forebrain tissue.
  • The initial findings identified specific, narrow power-density windows for this effect, with no observed impact at other tested levels.

Purpose of the Study:

  • To confirm and extend previous findings on the effects of 50-MHz AM RF-EMR on calcium ion efflux in chick forebrain tissue.
  • To investigate the dose-dependent relationship between RF-EMR power density and calcium ion efflux.
  • To explore potential mechanisms underlying the observed frequency and power-density dependencies.

Main Methods:

  • In vitro incubation of chick forebrain tissue (1-7 days old) with radioactive calcium ions.

Related Experiment Videos

  • Exposure of labeled tissue to 50-MHz RF-EMR, AM at 16 Hz, within a transverse electric and magnetic field (TEM) cell at 37°C.
  • Assay of radioactive calcium activity in the surrounding physiological salt solution to quantify efflux, testing a range of power densities.

    • Main Results:

    • Enhanced calcium ion efflux was observed at specific power densities: 1.75, 3.85, 5.57, 6.82, 7.65, 7.77, and 8.82 mW/cm².
    • No significant change in calcium efflux was detected at other tested power densities, including 0.75, 2.30, 4.50, 5.85, 7.08, 8.19, 8.66, 10.6, and 14.7 mW/cm².
    • The highest specific absorption rate (SAR) tested was 0.005 W/kg, deemed too low to cause generalized heating.

    Conclusions:

    • The study confirms that 50-MHz AM RF-EMR can enhance calcium ion efflux in chick forebrain tissue, but this effect is highly dependent on specific power density ranges.
    • The results support a non-thermal mechanism for RF-EMR bioeffects, as the observed SAR values are insufficient to induce heating.
    • A hypothetical model involving dynamic systems is proposed to explain the observed power-density and frequency dependencies of RF-EMR and extremely-low-frequency (ELF) field interactions.