Involvement of eddy currents in the mutagenicity of ELF magnetic fields.

Possible carcinogenic and/or mutagenic activity of extremely low frequency magnetic fields was examined using somatic mutation and recombination test system of Drosophila melanogaster. An X-linked semi-dominant DNA repair defective mutation mei-41(D5) was introduced into the conventional mwh/flr test system to enhance mutant spot frequency. Virgin females of w mei-41(D5)/FM6; flr/TM6 were crossed with w mei-41(D5)/Y; mwh jv; spa(pol) males. The F(1) third instar larvae were exposed to a 50Hz, 20mT sinusoidal AC magnetic field for 24h. After moulting from pupal cases, their wings were examined under a bright field microscope to detect hair spots with mwh or flr mutant morphology. The exposure caused a statistically significant enhancement in somatic recombination spot frequency. Mutant spots arising due to chromosomal non-disjunction or terminal deletion also increased but the frequency of spots resulting from point mutation was not altered. The enhancement in the recombination spot frequency was suppressed to the control level when a culture medium without electrolytes was used during exposure. When larvae were exposed to a magnetic field in an annular dish, flies from the outer ring showed more mutant spots compared to those from the inner ring. These results suggest that the detected mutagenic activity was that of the induced eddy current, rather than that of the magnetic field itself.

Increase in the mitotic recombination frequency in Drosophila melanogaster by magnetic field exposure and its suppression by vitamin E supplement.

In order to estimate possible mutagenic and/or carcinogenic activity of electromagnetic fields, wing spot tests were performed in Drosophila melanogaster. A DNA repair defective mutation mei-41D5 was introduced into the conventional mwh/flr test system to enhance mutant spot frequency. Third instar larvae were exposed to a 5-Tesla static magnetic field for 24 h, and after molting, wings were examined under a microscope to detect hair spots with mutant morphology. The exposure caused a statistically significant enhancement of somatic recombination compared with the unexposed control. This enhancement was suppressed to the control level by supplement of vitamin E, a non-specific antioxidant. It is inferred that the magnetic field enhanced the genotoxic effect of spontaneously produced free radicals, possibly by affecting the lifetime of the radicals. Enhancement of non-disjunction, terminal deletions and gene mutations were not detected.