The interaction between electromagnetic fields at megahertz, gigahertz and terahertz frequencies with cells, tissues and organisms: risks and potential

Abstract

Since regular radio broadcasts started in the 1920s, the exposure to human-made electromagnetic fields has steadily increased. These days we are not only exposed to radio waves but also other frequencies from a variety of sources, mainly from communication and security devices. Considering that nearly all biological systems interact with electromagnetic fields, understanding the affects is essential for safety and technological progress. This paper systematically reviews the role and effects of static and pulsed radio frequencies (10⁰-10⁹ Hz), millimetre waves (MMWs) or gigahertz (10⁹-10¹¹ Hz), and terahertz (10¹¹-10¹³ Hz) on various biomolecules, cells and tissues. Electromagnetic fields have been shown to affect the activity in cell membranes (sodium versus potassium ion conductivities) and non-selective channels, transmembrane potentials and even the cell cycle. Particular attention is given to millimetre and terahertz radiation due to their increasing utilization and, hence, increasing human exposure. MMWs are known to alter active transport across cell membranes, and it has been reported that terahertz radiation may interfere with DNA and cause genomic instabilities. These and other phenomena are discussed along with the discrepancies and controversies from published studies.

Keywords: DNA; cell; electric field; millimetre wave; terahertz radiation; tissue.

Figure 1.

The progress in research measured as number of publications studying the effect of an electric field (a), radio waves (b), MMWs (c) and terahertz radiation (d) on various biology samples (DNA, RNA, proteins, cell membranes, tissues and other biology). The data are taken from the PubMed portal (www.ncbi.nih.gov). (Online version in colour.)

Figure 2.

Comparison of the heating effects induced by MMW irradiation (filled circles) at three instant power density levels (represented via a sample's temperature) and by gradual bath heating (grey triangles) on changes in the subsequent AP parameters in the Retzius cells of medicinal leech: (a) Δfiring rate at 10 s after initiation of MMW exposure, and average Δfiring rate at 10–60 s after initiation of MMW exposure (b). Data are means ± standard error. **p < 0.01; ***p < 0.001 for one-tailed t-test comparing the MMW and bath heating effects at the heating level of 0.6°C. Linear regression lines are shown for MMW irradiation (solid) and gradual bath heating (dashed). Reproduced from [74].

Figure 3.

Amplitude spectra of nsPEF pulses of various shapes (speed of rising and decay front). The shapes of four different of nsPEF (60 ns, 1 kV cm⁻¹) are shown in the inset. Note, the Gaussian-shaped pulse has the most monotonic spectrum.

Figure 4.

The graphic representation of diverse effects on a membrane, organelle and molecular level caused by application of nsPEF pulses to the cells. Data summarized from different studies and obtained from experiments conducted on different cell types. Thus, the involvement of a particular mechanism may vary. Also, depending on nsPEF pulse parameters, the final cell fate could be different as well, which is represented in quatrefoil. (Online version in colour.)

Figure 5.

The absorption spectra in terahertz range for distilled water (blue), physiological saline —0.9% NaCl (green) and water solution of 100 mM Glycine (red). In lower terahertz range, all three spectra well overlap due to dominant absorption by water. The divergence between absorption spectra for all three samples demonstrated in the inset. Note, the presence of ‘bound’ water causes an increase in absorption.

Figure 6.

Terahertz imaging of a guinea pig skin scar (made by surgical scissors 7 days prior to imaging and sutured using surgical silk, the skin was shaved prior to imaging). (a) The photograph of the scar (depicted by yellow arrows), the needle was placed on the side of the photograph for orientation and terahertz contrast purposes; (b) terahertz imaging of scar at the superficial layer of the skin, the big dark spots along the scar are left after removal of sutures; (c) terahertz imaging of the scar in depth (approx. 100 µm). Red arrows indicate additional inhomogeneous formations near the scar caused by deeper tissue damage. The scan resolution is 100 µm; the images were acquired with a TeraPulse 4000 (TeraView Ltd, Cambridge, UK).