報告書番号

V09007

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（その2）－

タイトル（英文）

Chick embryotoxicity evaluation of intermediate frequency magnetic field exposure -Modification of chemically induced embryotoxicity by exposure to 60 kHz magnetic field up to 11 days of embryogenesis

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、最近利用が広がっている60 kHz磁界の発生毒性を評価した。1群60個の有精卵に化学物質を投与してある程度の奇形を誘発させ、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日間重畳曝露する実験を、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、磁界は予め誘発した異常の発生を増強しなかった。

概要 （英文）

Biological studies to evaluate the effects of the intermediate frequency electromagnetic field exposure are inconclusive. Because some studies with chick embryos have suggested that magnetic field (MF) exposure might modify the embryotoxic effects of known teratogens, they need to be substantiated. This study aimed to determine whether a 60 kHz MF exposure could modify chick embryonic development. A magnetically permeable incubator was placed in the middle of a pair of Helmholtz-type coils producing a 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 C. 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 0.00 microT(rms) at 60 kHz and 0.03 microT(rms) at 50 Hz. White Leghorn, fertile eggs were treated with all-trans retinoic acid (RA) to produce teratogenic responses in about 40–60% of intact embryos. A group of 60 RA-treated 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 exposure limit guidelines of the International Commission on Non-Ionizing Radiation Protection for the general public of 6.25 microT. The same number of RA-treated eggs served as sham-exposed controls. Experiments were triplicated and conducted in a blind fashion. After MF exposure, live embryos were fixed in 10% neutral buffered formalin and examined under stereoscopic microscope for morphological abnormalities such as exencephaly and anophthalmia, delayed development and skeletal abnormalities such as crossbite and tailbone defects. Developmental stages based on H&H definition (for all embryos), numbers of somite pairs and body length (2-day embryos), wing and leg lengths (7-day embryos), and upper beak and wing and leg digit lengths were recorded. Statistical evaluation showed that there were no adverse effects of MF exposure on any of the endpoints measured or observed when the MF-exposed group was compared with the sham-exposed group. The same results were obtained consistently in the triplicate experiments at 2, 7 or 11 days of exposure. Under these 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 modifications of RA-induced teratogenic effects on chick embryo development.

報告者

キーワード