報告書番号

V08011

タイトル（和文）

中間周波磁界の生物影響評価 －20 kHz磁界のラット受胎能及び初期胚の発生に関する生殖発生毒性評価－

タイトル（英文）

Reproductive and developmental toxicity of intermediate frequency magnetic field exposure; Effects of 20kHz magnetic field exposure on the rat fertility and early embryonic development to implantation

概要 （図表や脚注は「報告書全文」に掲載しております）

中間周波磁界の着床前期における生殖発生毒性を評価する目的で、雌雄各1群24匹の9週齢Crl:CD(SD)ラットに交配前2週間以上、交尾が成立した雌親はさらに妊娠7日（着床）まで、20 kHz、0.20 mT(rms)の正弦波、垂直磁界を1日22時間曝露した。雌親は曝露終了後、妊娠13日まで無曝露で飼育したのち解剖し生殖発生への影響を検査した。雄動物も交尾成立後、同様に検査した。試験は結果の信頼性を確保するため盲検法で行い、2回繰り返して再現性を確認した。体重、性周期、交尾率、受胎率、黄体数、着床数、生存・死亡胚数、精子数、精子運動性、異常精子率、生殖関連臓器の重量は、対照群と曝露群間で再現性のある統計学的有意差はなかった。剖検および病理組織学的検査での異常所見の発生は極めて少なかった。本実験条件下では、20 kHz磁界はラットの受胎能及び初期胚の発生に影響を与えないことが明らかとなった。

概要 （英文）

Scientific evidence concerning health risk assessment of intermediate frequency magnetic field is insufficient. This study aims to determine whether or not a 20 kHz, magnetic field exposure has effects on fertility and/or early embryonic development to implantation. Male and female Crl:CD(SD) rats, 9 weeks old, were randomly assigned to magnetic field exposed or sham-exposed group, 24 for each group in each sex. They were exposed to 20 kHz, 0.20 mT(rms), vertically polarized sinusoidal MF, or sham-exposed for 22 h/d from 14 days prior to mating and during mating period of 14 days at the maximum. Copulated females were further exposed until gestation day 7. Background plus stray magnetic fields in a sham-exposed facility were less than 0.001 microT(rms) at 20 kHz. Dams were sacrificed at gestation day 13 and examined for developmental toxicity. Mated males were also sacrificed on the day of mating for male fertility evaluation. Obtained results were statistically evaluated. Identical experiments in a blind fashion were conducted twice to confirm the reproducibility of outcome. In the two experiments, no reproducible changes related to magnetic field exposure were found in the female body weight, estrous cycle, copulation index, fertility index, numbers of corpora lutea and implantation sites, numbers of dead and living conceptuses, and uterus weight. Although a difference between the exposed and the sham-exposed groups in ovary weight was found only in the second experiment, it was considered to be due to chance because of the lack of reproducibility. Abnormal findings in gross pathology and histopathology of uteri and ovaries were very low in both groups, and the incidence did not show statistically significant group differences in both experiments. There were also no reproducible significant differences between magnetic field exposed group and sham-exposed group in the male body weight, sperm counts and motility, and weights of testes and epididymides. Although a difference between the exposed and the sham-exposed groups in sperm morphology was observed only in the second experiment, it was considered to be due to chance because of the lack of reproducibility. Abnormal findings in gross pathology and histopathology of testes and epididymides were very low in both groups, and the incidence did not show statistically significant group differences in both experiments. Under the present experimental conditions, a 20 kHz sinusoidal, 0.20 mT(rms) MF exposure during pre-implantation period was neither toxic to fertility nor early embryonic development to implantation in the rat.

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