Haemopoietic cell proliferation in murine bone marrow cells exposed to extreme low frequency (ELF) electromagnetic fields.

As leukemia is one of the health hazards that is sometimes associated with exposure to extreme low frequency fields, we studied the in vitro effects of ELF fields on haemopoietic cell proliferation. First, the cytotoxic effect of 80 microT, 50 Hz magnetic fields on 3T3 cell proliferation was investigated using the neutral red test. Many chemicals are believed to cause damage because they interfere with basal or "housekeeping" cell functions. The basal cell functions are present in every cell. Non-specialized, actively dividing cells are suitable for measuring cytotoxic effects. Cytotoxic doses can be identified by exposing actively dividing cells in vitro and measuring growth inhibition caused by interference with these basal cell functions. 80 microT, 50 Hz magnetic fields caused no cytotoxicity: we were not able to demonstrate any interference with essential cell functions in the non-differentiated 3T3 cell line. Furthermore, the in vitro effects of ELF fields on murine haemopoietic and stromal stem cell proliferation were studied. Haemopoiesis is a continuous process, where mature blood cells are replaced by the proliferation and differentiation of more primitive progenitor and stem cells. Blood formation is tightly regulated by the stromal micro-environment. Exposure of murine bone marrow cells, from male and female mice, to 80 microT (50 Hz) magnetic fields showed a reduction in the proliferation and differentiation of the granulocyte-macrophage progenitor (CFU-GM) compared to non-exposed bone marrow cells. The results on the effect of the ELF-field on stromal stem cell proliferation (CFU-f) are somewhat equivocal at the moment. CFU-f from female mice showed a reduction while CFU-f from male mice were not decreased.