報告書番号

V08002

タイトル（和文）

中間周波磁界の生物影響評価 －発生初期から器官成長期の鶏胚による60 kHz磁界の発生毒性評価－

タイトル（英文）

Developmental toxicity evaluation of intermediate frequency magnetic field exposure in chick embryos; Effects of 60 kHz, sinusoidal field exposure in the early 2, 7 & 11 days of embryonic development

概要 （図表や脚注は「報告書全文」に掲載しております）

中間周波磁界の生物研究が少ないため、動物個体レベルで強い磁界を曝露できる鶏胚を用いて磁界の発生毒性を評価した。1群60個の有精卵に60 kHz、0.11 mT(rms)（ICNIRP公衆ガイドラインの17.6倍）の正弦波、垂直磁界をふ卵開始から2日、7日および11日間曝露する実験を、盲検法により各3回繰り返して実施した。2日間曝露（初期胚）では、胚の発生段階、体節数、体長、総異常（形態異常と死亡）出現率、7日間曝露（器官形成期）では、胚の発生段階、翼長、脚長、総異常出現率、11日間曝露（器官成長期）では胚の発生段階、嘴長、翼指長、脚指長と骨格異常を含む総異常の出現率を評価した。全ての評価項目に関し、繰り返し実験で対照群と曝露群間に統計学的な有意差は認められず、磁界影響は無かった。

概要 （英文）

Biological studies to evaluate the effects of the intermediate frequency electromagnetic field exposure are insufficient. Because some existing developmental studies with chick embryos have shown inconsistent results, they have to be further substantiated. This study aims to determine whether or not a 60 kHz, magnetic field (MF) exposure has effects on the chick embryonic development. A magnetically permeable incubator was placed in the middle of a pair of Helmholtz-type coils that produced sinusoidal vertical MF. The MF inside the incubator varied less than +/- 3 %. The incubator had a water-jacketed structure to maintain the temperature at 38 +/- 0.4 oC. Relative humidity was controlled at 70 +/- 10 %. At the maximum intensity of 0.11 mT(rms) MF at 60 kHz, background plus stray fields in the control incubator were less than 0.001 microT(rms) at 60 kHz and 0.03 microT(rms) at 50 Hz. White Leghorn, fertile eggs were purchased from an experimental animal breeder. A group of 60 eggs was exposed to sinusoidal 60 kHz, vertical MF for 2, 7 or 11 days. The employed intensity of 0.11 mT is 17.6 times higher than the guidelines of International Commission on Non-Ionizing Radiation Protection exposure limit for general public, 6.25 microT. The same number of intact eggs was served as sham-exposed. Experiments were conducted in a blind fashion. After MF exposure, live embryos were fixed in 10 % neutral buffered formalin, and they were examined under stereoscopic microscope for morphological abnormalities such as exencephaly and anophthalmia, delayed development, and skeletal abnormalities such as crossbite and tailbone defect. Developmental stages under H&H definition, wing finger and leg finger lengths were recorded. Statistical evaluation revealed that there have been no adverse effects of the MF exposures on all endpoints measured or observed when the MF exposed group was compared to the sham-exposed group. The same results were obtained consistently in the 3 times repeated experiments in either 2, 7 or 11 days of exposure. Under the present experimental conditions, a 60 kHz sinusoidal, 0.11 mT(rms) MF exposure for 2, 7 or 11 days from the first day of embryogenesis did not produce any significant adverse effects on the chick embryo development.

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