報告書番号

V07003

タイトル（和文）

中間周波磁界の生物影響評価 －20 kHz磁界のラット胚・胎児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 20 kHz, 0.2 mT, sinusoidal magnetic field exposure on the rat organogenesis -

概要 （図表や脚注は「報告書全文」に掲載しております）

生殖発生過程で重要な器官形成期にあるラットを用いて、中間周波磁界の生殖発生毒性を評価した。1群25匹の妊娠Crl:CD(SD)ラットに、20 kHz、0.2 mT(rms) （ICNIRP公衆ガイドラインの32倍）の一様な正弦波、垂直磁界を1日22時間、妊娠7～17日目に曝露した。妊娠20日目に雌親を解剖して胎児を摘出し、生殖発生への影響を検査した。曝露実験は盲検法にて実施し、2回繰り返して再現性を確認した。対照群と曝露群間で、雌親の妊娠中の体重増加、血液学的検査、血液生化学的検査、および、着床後の胚や胎児死亡率、生存胎児数や胎児体重、胎児の性比、雌親あたりの胎児外表異常、内臓異常、骨格異常出現率のいずれにおいても、再現性のある統計学的な有意差はなかった。本実験の中間周波磁界は、ラットの胚および胎児の発生過程に影響を与えないことが示唆された。

概要 （英文）

Biological studies to evaluate the effects of the intermediate frequency electromagnetic field exposures are needed because of lack of such studies for the assessment on potential health risks. This study aims to determine whether or not a 20 kHz, magnetic field (MF) exposure has embryotoxic, fetotoxic and/or teratogenic potential. Two identical animal exposure facilities were constructed, and a Merritt-type exposure coil was set in the center of each animal room. Animal cages were made of polycarbonate to avoid induced currents by MF exposure. The generated vertical, sinusoidal MF inside the coils varied less than 2 %. At the maximum MF intensity of 0.2 mT(rms) at 20 kHz, background plus stray MFs in the sham-exposed facility were less than 0.001 micro-T(rms) at 20 kHz and 0.03 micro-T(rms) at 50 Hz. Fifty pregnant Crl:CD(SD) rats were randomly assigned to sham-exposed or MF-exposed group, 25 for each. From gestation day 7 to day 17, the pregnant rats were sham-exposed or exposed to the MF for 22hr/d. Dams were sacrificed at gestation day 20, and their fetuses were examined. Experiments were conducted in a blind fashion. Identical experiments were repeated twice to confirm the reproducibility of outcome.
In the two identical experiments, no reproducible changes related to MF exposure were found in the body weight gain, clinical signs, hematology, blood biochemistry and gross pathology of dams. Although total leukocyte counts in the MF-exposed group was significantly low in the second experiment, it was considered to be a chance because it was not observed in the first experiment and no other changes in the hematological endpoints as well as differential leukocyte counts were obtained in both experiments. Number of implants, number of post implantations, number and body weight of live fetuses, sex ratio and incidence of low body weight fetuses also did not significantly differ between sham- and MF-exposed groups. No significant changes due to the MF exposures were found in the incidence of external, skeletal and visceral malformations. One type of skeletal variation, dumbbell-shape of thoracic vertebral body was significantly high in fetuses of the MF-exposed group in the first experiment. However, the incidence was very low and considered to fall within a range of spontaneous occurrence. Number of fetuses with other type and total skeletal variations in the MF exposed group was comparable to that of sham-exposed group. Fetal ossification did not exhibit statistically significant change due to MF exposure.
Under the present experimental conditions, a 20 kHz sinusoidal, 0.2 mT(rms) MF exposure during organogenesis was neither embryo/fetotoxic nor teratogenic and did not interfere the fetal development in the rat.

報告者

キーワード