Effects of 50 Hz magnetic field exposure on the rate of DNA synthesis by normal human fibroblasts

Interest in the potential adverse biological effects of exposure to power-frequency magnetic fields has centred on the possibility that these fields may influence tumour promotion, possibly by increasing the rate of cell proliferation. In order to investigate whether exposure to magnetic fields can indeed affect the rate of cell proliferation, normal human fibroblasts were serum starved overnight and then exposed to 50 Hz magnetic fields in a purpose-built facility. The rate of DNA synthesis was taken as a measure of cell proliferation, and was determined by following the incorporation of [H-3]-thymidine into macromolecular material. The rate of DNA synthesis in exposed cells was compared with that in control cultures maintained in a standard CO2 incubator where they were exposed to background magnetic fields of < 200 nT. Positive controls were maintained in the same CO2 incubator, but were treated with human recombinant fibroblast growth factor to check that the cells were responsive to growth stimuli. Magnetic fields at 50 Hz and at a range of flux densities between 20 mu T and 20 mT had no detectable effect on the rate of DNA synthesis by cells exposed for up to 30 h.