Thermal Aspects of Electromagnetic Field Interactions with Bound Calcium Ions at the Nerve Cell Surface
T. S. Tenforde · 1980
A 1980 theoretical analysis concluded that weak-field alteration of calcium binding at nerve cell surfaces very likely proceeds by a mechanism other than thermal energy transfer.
Plain English Summary
This 1980 letter by T.S. Tenforde evaluated on theoretical grounds the minimum electric field strength that would be required to produce the observed alteration in calcium ion binding at nerve cell surfaces if the field interaction occurred by thermal energy transfer. The calculation used the experimental conditions of Bawin et al. (1975), who exposed brain tissue to an amplitude-modulated 147 MHz radio-frequency field. The required field is at least 100 times greater than the field actually present in the exposed brain tissue, so the observed effect very likely proceeds by a mechanism other than thermal energy transfer.
Why This Matters
This 1980 letter addresses a question central to early work on weak electromagnetic fields: whether a thermal mechanism could explain the observed change in calcium ion binding at the surface of nerve cells. Experiments had shown a change of approximately 15 to 20% in the binding of 45Ca to brain cells following a 20-minute exposure to low frequency sinusoidal electric fields (1-75 Hz) or to radio-frequency fields amplitude-modulated at frequencies of 35 Hz or below. The calculation for the 147 MHz conditions gave a field amplitude of 99 V/m, a temperature change of 3.3 K, and a required field at least 100 times greater than the field actually present in the exposed brain tissue.
The author concludes that the observed alteration very likely proceeds by a mechanism other than thermal energy transfer. The percentage release of calcium ions depends strongly on the frequency of amplitude modulation, with the maximum effect in the range 6-20 Hz, which suggests that the field interaction may involve a resonant or co-operative energy transfer mechanism.
Exposure Details
- Power Density
- 1-2 mWcm² mW/cm²
- Electric Field
- 99 Vm⁻¹ V/m
- Exposure Duration
- 20 minutes
Exposure Context
This study used 1-2 mWcm² mW/cm² for radio frequency:
- 100Mx above the Building Biology guideline of 0.1 μW/m²
- 1.7Mx above the BioInitiative Report recommendation of 0.0006 μW/cm²
This study used 99 Vm⁻¹ V/m for electric fields:
- 330x above the Building Biology guideline of 0.3 V/m
Building Biology guidelines are practitioner-based limits from real-world assessments. BioInitiative Report recommendations are based on peer-reviewed science. Check Your Exposure to compare your own measurements.
Where This Falls on the Concern Scale
Study Details
To evaluate on theoretical grounds the minimum electric field strength that would be required to produce the observed alteration in calcium ion binding if the field interaction occurred by a thermal energy transfer mechanism
Theoretical analysis based on the theory of ion adsorption developed originally by Stern (1924), rel...
A calculation of Eo was made for the experimental conditions employed by Bawin et al. (1975) in stud...
The value of Eo predicted theoretically to achieve an 18-5% release of bound calcium ions from nerve cell surfaces is therefore of the same order of magnitude as the applied field strength in air in the experiments of Bawin et al. (1975), but is at least 100 times greater than the field actually present in the exposed brain tissue. From these theoretical considerations, it can be concluded that the observed alteration of calcium ion binding by weak fields very likely proceeds by a mechanism other than thermal energy transfer. The percentage release of calcium ions by the applied field has been found to depend strongly upon the frequency of amplitude modulation, with the maximum effect occurring in the frequency range 6-20 Hz. This observation suggests that the field interaction may involve a resonant or co-operative energy transfer mechanism.
Show BibTeX
@article{thermal_aspects_of_electromagnetic_field_interactions_with_bound_calcium_ions_at_g7368,
author = {T. S. Tenforde},
title = {Thermal Aspects of Electromagnetic Field Interactions with Bound Calcium Ions at the Nerve Cell Surface},
year = {1980},
}