Forschungsgemeinschaft Funk e.V.

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Edition No. 14 June 1998
The Effect of High-Frequency Electromagnetic Fields on Cell Cycle and Sister-Chromatid Exchanges:
Analyses with Human Lymphocytes in Culture

High-frequency electromagnetic fields found in connection with mobile telephone D and E systems and with the BOS system for authorities with public safety tasks, and their effects on biological systems were studied. The mobile telephone D and E systems frequencies of 0.9 GHz and 1.8 GHz, respectively. They are modulated at the GSM standard. In order to simplify this GSM standard, pulse modulation of a pulse duration of 0.577 ms and pulse period of 4.615 ms were used. The frequency for the BOS system is 380 MHz. In this experiments it was modulated at a pulse duration of 13.11 ms and a pulse period of 56.67 ms. Cells exposed to electromagnetic fields are compared with non-exposed control cells.

To generate the electromagnetic field for the D and E systems, a rectangular hollow waveguide for each system was chosen and constructed at the Technical University of Braunschweig. In both cases, the H10 mode was stimulated. The middle section of the waveguide can be opened to fit the sample holder with polystyrol tubes, filled with 5 ml culture medium and surrounded by a whiteoil circuit keeping the temperatue of the culture medium at a constant temperature of 370 C.

The input power was calculated in such a way that a desired SAR value of 208 mW/kg and 1700 mW/kg, respectively, was reached.

A short monopole antenna was put into the waveguide at its rear end. Thus a signal was received, rectified by a high-frequency detector diode and recorded by a personal computer throughout the duration of the experiment.

In the BOS experiment the nutritive medium had to be exposed to a SAR value of 82,9 mW/kg in a TEM cell.

We investigated the velocity of the cell cycle and the frequency of SCE (sister-chromatid exchange) in cultured human lymphocytes exposed to high-frequency electromagnetic fields. Both phenomena were not affected (Lit. 24). This result is of particular interest because in the same test system the cell cycles were accelerated in the presence of 50-Hz/5mT fields, but as with high frequency fields SCE were not induced (Lit. 18, 19). Accelerated cell cycles could be important in connection with a possible cancer induction by electromagnetic fields. Cells already revealing DNA damages would grow faster in the presence of a 50-Hz field and would hence not have sufficient time to repair damages, which in turn would have a higher probability to be transformed to mutations. Accelerated cell cycles can therefore be regarded as promoting or co-promoting processes with respect to the development of cancer. Similar promoting effects are discussed by Prof. Löscher and coworkers (Lit. 25, 26, 27).

Human lymphocytes are particularly well suited for cell cycle analyses. In the peripheral blood, most of these cells are in the G0- phase of the cell cycle. When these cells are cultured and exposed to a mitogenic stimulus (here phytohemaglutinin), they enter the cell cycle synchronously and become mitotically active. The frequencies of first, second and third mitoses in culture (M1, M2, M3+) thus provide an indication of the velocity of the cell cycle progression. Chromosomal damage, such as SCE, can also be analysed in these cells (Lit. 28, 29, 30, 31).

Cell cycles can also be accelerated by elevated temperatures (Lit. 18). It is thus essential for field exposure tests to preclude any increase in temperature, a condition met by our test installations. Cell cycle acceleration due to the effects of EMF are also described by other authors (Lit. 20). Our findings demonstrate that this effect is induced by low, but not by the high-frequency fields.

The essential features of exposure equipments for investigating the effect of modulated radio frequency radiation around 900 MHz and 1800 MHz on human blood cells are described.

The peripherical lymphocytes were cultivated in a nutrient solvent, 5 cm3 of which was filled into each of several test tubes. The technical task was to develop rf exposure systems achieving well-defined and reproducible electromagnetic field distributions at high SAR to power conversion ratios and yielding an exposure of the culture medium as uniform as possible among the different tubes at maximum overall test volume.

As basic components two rectangular waveguides were chosen and designed for fundamental mode operation in the two frequency bands. With help of extensive numerical field calculations the suitable number and location of the test tubes inside the waveguides could be determined. The electrical properties of the biological material were acquired by measurements. A number of 6 tubes arranged along the waveguide axes was found to be a good compromise between test volume and field homogeneity.

Detailed data of waveguide dimensions, field strengths and specific absorption rates are given.

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