EMF action
World Health Organization (WHO) resources on electromagnetic fields (EMFs)
Selected publication:
"Establishing a dialogue on risks from electromagnetic fields" (2002)
https://www.who.int/publications/i/item/9241545712
How do electric and magnetic fields act on the human body?
It is noted that electric fields build up a charge on the surface, while magnetic fields encounter no obstacle. More details below.
Featuring Figure 2 (page 4) - figure text: Electric fields do not penetrate the body significantly but they do build up a charge on its surface, while exposure to magnetic fields causes circulating currents to flow in the body.
Electric properties of materials
If a conductor conducts electric currents how does it protect/shield from electric fields?
Materials are distinguished into two categories depending on their response to an electric field: conducting materials and dielectric materials (insulators).
An electric field will exert a force on both positive and negative charges or charged groups of a material. As a result they well tend to move away from each other, creating two poles, a negative and a positive one. Due to this internal polarization process, an internal electric field will be created. If this internal field is strong enough, it will oppose completely the external electric field.
Conductors have free electrons i.e. electrons that are free to move. The negatively charged electrons are free to move away from the positive charges. The internal polarization will be maximal and therefore the opposition to the external field will be maximal. As a result, a conductor will be able to block an electric field. Also, the electrons will be free to move and constitute a charged particle current that is propagated. A current will be conducted.
Dielectrics do not have free electrons. Under the effect of the electric field, positive groups will tend to move away from negative groups. Due to this displacement, an internal polarization of a certain degree will be established, that will oppose the external electric field.
Reference: https://youtu.be/4hpLxJYEBHA.
Conductivity (σ) is a measure of the ability of a material to conduct an electric current.
It represents a constant for the material's conductance, which is the reciprocal of resistance. It is linked to the opposition of a material to an electric current.
Permittivity ε (epsilon) is a measure of the degree of electric polarizability of a material.
It represents a constant for the material's capacitance, which is its capability to store an electric charge in the form of polarized (by displacement) negative and positive groups.
When an electric field is in proximity to a dielectric material or a conductor, we distinguish the following cases:
A dielectric material permits the creation of an internal electric field due to internal polarization but does not have free electrons to conduct current.
A conductor has free electrons and therefore conducts current; also it will demonstrate maximal internal polarization and therefore develop a maximal internal electric field which will will cancel out the external electric field, and therefore provide shielding.
It is noted that a person is electrically characterized by his/her resistance and capacitance. More details:
Jonassen N. Human body capacitance: static or dynamic concept? [ESD]. Technical University of Denmark, DTU Orbit (Technical University of Denmark, DTU). Published online November 27, 2002. doi:https://doi.org/10.1109/eosesd.1998.737028 (Full text here)
The FCC site provides a tool for these calculations at this link: https://www.fcc.gov/general/body-tissue-dielectric-parameters.
It is based on the modelling study "Compilation of the Dielectric Properties of Body Tissues at RF And Microwave Frequencies" by Camelia Gabriel in the corresponding U.S. Air Force Report AFOSR-TR-96 (https://apps.dtic.mil/sti/pdfs/ADA303903.pdf).
An authorized mirror exists on the site of the Italian National Research Council.
https://niremf.ifac.cnr.it/docs/DIELECTRIC
(cf. http://niremf.ifac.cnr.it/ & http://niremf.ifac.cnr.it/emfref/)
Note: The interested reader may also refer to the page "FCC Policy on Human Exposure to Radiofrequency Electromagnetic Fields"
EMF mechanism of action via Voltage-Gated Channels
"The Harmful Effects of Electromagnetic Fields Explained" (2023-08-09) (Linked to an earlier reference available here). Includes interview (video & transcription) with Pall M.L.
Pall, M. L. (2022). Low Intensity Electromagnetic Fields Act via Voltage-Gated Calcium Channel (VGCC) Activation to Cause Very Early Onset Alzheimer’s Disease. Current Alzheimer Research, 19(2), 119–132. https://doi.org/10.2174/1567205019666220202114510
Pall, M. L. (2016). Microwave frequency electromagnetic fields (EMFs) produce widespread neuropsychiatric effects including depression. Journal of Chemical Neuroanatomy, 75(Pt B), 43–51. https://doi.org/10.1016/j.jchemneu.2015.08.001
Pall, M. L. (2013). Electromagnetic fields act via activation of voltage-gated calcium channels to produce beneficial or adverse effects. Journal of Cellular and Molecular Medicine, 17(8), 958–965. https://doi.org/10.1111/jcmm.12088 (Citing this study [5] referring to catecholamine release).