The Effects of Extremely Low-Frequency Magnetic Fields on Mutation Induction in Mice

Extremely low-frequency magnetic fields (ELF-MF) are classified as possibly carcinogenic, despite inconsistent data and no plausible biological mechanism linking their universal exposure with childhood leukaemia and genotoxic effects. Given discrepancies in mutagenic data and widespread public concern over genotoxic effects, this study was designed to provide an in-depth analysis of potential molecular changes induced by ELF-MF exposure in vivo. Seven-week old, BALB/c x CBA/Ca hybrid F1 male mice were exposed to 50 Hz magnetic fields of 10, 100 and 300 μT for 2- or 15 hours. Blood and sperm DNA samples were collected 12 weeks post-exposure and mutation induction frequencies established at the Expanded Simple Tandem Repeat (ESTR) Ms6-hm loci using single-molecule PCR (SM-PCR). Likewise, Ms6-hm mutation induction frequencies were established in age-matched sham-treated hybrid males (control group) and those exposed to 1 Gy acute X-rays (positive controls). No significant increases in ESTR mutation frequencies were detected in either tissue at any ELF-MF exposure parameter compared to their sham-treated controls. Whilst a marginally significant increase was observed in the mutation induction frequency of pooled sperm data, these data should be regarded cautiously due to the lack of correlating dose-dependent responses. Conversely, germline and somatic ESTR mutation frequencies were significantly elevated in males exposed to acute 1 Gy X-rays. These data were validated in a high-throughput microarray pilot study, whereby no significant alterations in gene expression in kidney cells of hybrid males were detected following ELF-MF exposure. In contrast, five transcripts were significantly up-regulated in the irradiated males. Ultimately, these findings indicate that, within the analysed range of doses, the in vivo effects of ELF-MF exposure on mutation induction and gene expression are likely to be negligible. This study represents the first methodical attempt to determine mutation frequencies in vivo after continuous exposure to 50 Hz ELF-MFs up to 300 μT.