Proceedings of the Korea Electromagnetic Engineering Society Conference (한국전자파학회:학술대회논문집)

The Korean Institute of Electromagnetic Engineering and Science (한국전자파학회)
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EFFECTS OF 50Hz CIRCULARLY POLARIZED MAGNETIC FIELDS ON SPONTANEOUS MAMMARY TUMORS IN RATS

  • Negishi, T. (Bio-Science Department, Central Research Institute of Electric Power Industry, Japan.) ;
  • Imai, S. (Bio-Science Department, Central Research Institute of Electric Power Industry, Japan.) ;
  • Shibuya, K. (Contract Testing Department, Nippon Institute for Biolgical Science, Japan) ;
  • Ltabashi, M. (Contract Testing Department, Nippon Institute for Biolgical Science, Japan) ;
  • Nishimura, I. (Bio-Science Department, Central Research Institute of Electric Power Industry, Japan.) ;
  • Sasano, T. (Bio-Science Department, Central Research Institute of Electric Power Industry, Japan.)
  • Published : 1999.07.01
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Abstract

Several epidemiological studies have suggested that residential or occupational exposure to power frequency magnetic fields (MF) might increase the risk of cancer. The objective of this study is to elucidate the possible carcinogenic effects of MF exposure using female Sprague-Dawley (Crj:CD)rats. A total of 360rats was randomly divided into 6 groups of 60 rats each. Two groups were served as a negative control (vehicle: sesame oil only) or a positive control (single oral administration of 7, 12dimethylbenz(a)anthracene; DMBA, 90mg/kg body weight at 50-52days of age). Other four groups were simultaneously exposed to 0 (sham-exposed) 7, 70 or 350 $\mu$T(rms), continuous circularly polarized 50HzMF, 22 hrs/day, 7 days/weeks for 30weeks from 8weeks of age. Experiment was conducted under SPF condition and in a blinded manner, Ten animals in each grout were served as satellite animals and their several hormonal concentrations in sera, such as melatonin and prolactin, collected at the midnight were measured. In addition, complete histopathological examination were performed in other 50 animals per each group. In the positive control group, the first mammary nodule was palpated at the 7th weeks of experiment in 5 out of 59 animals. Afterward, the incidence of palpable mammary nodules increased steadily and reached at 76% and 98% of live animals at 14weeks and the end of experiment in sham and 350$\mu$ T-exposed groups were not significantly different from those in the sham-exposed and negative control groups. Histopathologocally, most of palpable nodules were mammary tumors. The incidences of animals with mammary tumors per animals survived ant the end of experiment were 4.1 and 100% in the negative and positive control groups, and 0.0, 6.0, 8.0 and 6.0% in the sham-, 7, 70and 350 $\mu$T-exposed groups, respectively. These incidences in three MF-exposed groups were not significantly different from those in both the sham- exposed and negative control groups. Based on these results, it was not supported that continuous circularly polarized 50 Hz magnetic fields at up to 350$\mu$T affect the incidence of spontaneous mammary tumors in female SD rats under the present experimental conditions.

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