Micronucleus induction in Syrian hamster embryo cells following exposure to 50 Hz magnetic fields, benzo(a)pyrene, and TPA in vitro

Electromagnetic fields (EMFs) have been associated with increased incidence of cancer suggested by epidemiological studies. To test the carcinogenic p otency of EMF, the in vitro micronucleus assay with SHE cells has been used as a screening method for genotoxicity. A50 Hz magnetic field (MF) of 1 mT field strength was applied either alone or with the tumour initiator benzo (a)pyrene (BP) or the tumour promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). All three treatments were applied in single, double or triple treatm ent regimes. MF or TPA (1 nM) alone did not affect the number of micronucle i (MN) in initiated and non-initiated SHE cells. Changing the schedule of t he typical initiation protocol, namely applying the initiator (BP) during e xposure to NM, results in an 1.8-fold increased MN formation compared to BP treatment alone. Combined experiment with BP, TPA and MF did not cause fur ther MN formation. Since initiation during MY exposure caused a significant increased MN formation, our findings suggest that MFs enhance the initiati on process of BP. We think that this MF-enhanced co-carcinogenic effect is caused by an indirect "cell activation" process. The resulting genomic inst ability is proposed to be due to free radicals and/or to the unscheduled "s witching-on" of signal transduction pathways. (C) 2001 Elsevier Science B.V . All rights reserved.