Rats were kept under normal light conditions (i.e. 12 h light/ 12 h dark) and were exposed either to static or to variable magnetic fields (MF). Exposure conditions were chosen 0.5 and 3 h per day, respectively for a time periode of 2 years. One part of the animals recived a single intravenously injection of 50 mg/kg of the chemical carcinogen NMU. None-NMU-treated and none-exposed animals served as control.
Without prior administration of NMU, magnetic filed exposure lead only to a week development of mammary carcinomas. Incidence and latent period of mammary tumors depend on duration and kind of the magnetic field exposure. A 3 h exposure and exposure with variable magnetic field were more effective than a 0.5 h exposure and exposure with static magnetic fields, respectively. Beside prevailed mammary adenocarcinomas neoplasms were found occassionaly in kidneys, ovary, large intestine, uterus and thyroid gland.