Effects of long-term exposure to 50 Hz magnetic fields on cell viability, genetic damage, and sensitivity to mutagen-induced damage

Abstract

Until today, it remains controversial whether long-term exposure to extremely low-frequency magnetic fields (ELF-MF) below the legislative exposure limits could result in adverse human health effects. In the present study, the effects of long-term in vitro MF exposure on three different study endpoints (cell viability, genetic damage, and sensitivity to damage induced by known mutagens) were investigated in the human B lymphoblastoid (TK6) cell line. Cells were exposed to 50 Hz MF at three selected magnetic flux densities (i.e., 10, 100, and 500 μT) for different exposure periods ranging from 96h up to 6 weeks. Cell viability following MF exposure was assessed using the ATP-based cell viability assay. Effects of MF exposure on cell genetic damage and cell sensitivity to mutagen-induced damage were evaluated using the in vitro alkaline comet assay and the in vitro cytokinesis block micronucleus assay. The results showed that long-term exposure up to 96h to 50 Hz MF at all tested flux densities could significantly increase TK6 cell viability. In contrast, long-term MF exposure did not affect cell genetic damage, and long-term pre-exposure to MF did not change cell sensitivity to damage induced by known mutagens. At certain time points, statistically significant difference in genotoxicity test results were observed between the MF-exposed cells and the control cells. However, these observations could not be confirmed in the repeat experiments, indicating that they are probably not biologically significant.

Keywords: ATP-based assay; Adaptive response; Co-exposure; Electromagnetic fields; Genotoxicity; Non-ionizing radiation.

Fig. 1

Combined results (of three individual experiments) of the ATP-based viability assay in cultures exposed to 50 Hz MF at 10, 100, or 500 μT for 0h up to 96h. The unexposed culture was used as the negative control. Data presented as mean ± SD, n = 3.

Fig. 2

The results of the ATP-based viability assay for one of the three individual experiments in cultures exposed to 50 Hz MF at 10, 100, or 500 μT for 0h up to 96h. The unexposed culture was used as the negative control. Data presented as mean ± SD, n = 4, *—p ≤ 0.05, **—p ≤ 0.01, ***—p ≤ 0.001.

Fig. 3

Results of the in vitro comet assay (A, B, C) and the in vitro cytokinesis block micronucleus assay (D, E, F) for the MF-exposed and unexposed cultures in one of the two individual long-term experiments with 50 Hz MF at 10 μT, 100 μT, and 500 μT over 6 weeks. MN frequency was calculated as the number of micronucleated cells per 1000 binucleated cells. Data are presented as mean ± SD, n = 3, *—p ≤ 0.05.

Fig. 4

In vitro comet assay results for the MF-exposed and unexposed cultures in the second repeat experiment with 50 Hz MF at 500 μT over 6 weeks. Data are presented as mean ± SD, n = 3, **—p ≤ 0.01.

Fig. 5

Results of the in vitro comet assay and the in vitro cytokinesis block micronucleus assay for the mutagen-exposed and co-exposed cultures in one of the two individual long-term experiments with 50 Hz MF at 10 μT, 100 μT, and 500 μT over 6 weeks. MN frequency was calculated as the number of micronucleated cells per 1000 binucleated cells. Data are presented as mean ± SD, n = 3, *—p ≤ 0.05.