報告書番号

V13010

タイトル（和文）

中間周波磁界の生物影響評価 －ラットを用いた20 kHz磁界の亜慢性毒性評価－

タイトル（英文）

Evaluation of biological effects of intermediate frequency magnetic field - Subchronic toxicity study of 20 kHz magnetic field in the rats -

概要 （図表や脚注は「報告書全文」に掲載しております）

誘導加熱装置などで利用されている中間周波磁界の健康リスク評価に資するため、雌雄各12匹のラットに、20 kHz、0.20 mT（ICNIRP磁界曝露ガイドライン値の7.4倍）の正弦波磁界を1日22時間、13週間曝露し毒性を評価した。実験は結果の信頼性を確保するため盲検法で行い、再現性を確認するため2回繰り返した。雌雄動物とも曝露期間中の死亡はなく、体重は順調に増加した。曝露後に解剖して臓器の異常を検査し、11臓器の重量と血液学的検査10項目、血液生化学的検査17項目を測定した。また、36器官・組織について病理組織学的検査を行った。その結果、全ての検査項目において対照群と曝露群間で統計学的な有意差が再現性をもって現れることはなく、曝露群の器官・組織臓器において毒性を示す病理組織学的変化の有意な増加もなかった。本実験条件下では、20 kHz磁界の亜慢性毒性を示す生物学的証拠は得られなかった。

概要 （英文）

Because of the lack of biological research data on intermediate frequency (IF) magnetic field (MF) exposure, scientific evidence concerning possible health effects is necessary for health risk assessment. This study aims to determine whether or not IF MF exposure has subchronic toxicity in the rat. Twenty four male and 24 female Crl:CD(SD) rats, 6 weeks old, were randomly assigned to MF-exposed or sham-exposed group, 12 for each group per sex. The rats in MF-exposed group were exposed to 20 kHz, 0.20 mT(rms), vertically polarized sinusoidal MF for 13 weeks. The sham-exposed rats were served as control. The emitted MFs at animal exposure space varied less than 2%. At the facility maximum MF intensity of 0.20 mT(rms) at 20 kHz, stray and background MFs in the sham-exposed facility were less than 0.001 microT(rms) at 20 kHz and 0.03 microT(rms) at 50 Hz, respectively. Experiments were conducted in a blind fashion and duplicated. During the exposure, animals were weighed and their health status was observed. No indications of morbidity were found during the exposure. Temporary decreased body weight was observed in exposed males in one experiment, although at the cessation of exposure, the difference between MF-exposed and sham-exposed groups was not statistically significant. After the exposure, animals were sacrificed and organs were weighed and evaluated for gloss pathology. Blood was collected and examined for blood hematology and clinical chemistry. There were significant differences in some organ weights and parameters in hematology and clinical chemistry between exposed and sham-exposed groups. However, because these differences were minor in the magnitude, not repeated in duplicated experiments, and biologically isolated, they were considered to occur by chance. Histopathological examinations were also conducted. Although sporadic pathological changes were observed in some rats, there were no significant group differences. Obtained results, the pathological evidence in particular, indicated absence of subchronic toxicity in the rats exposed to the 20 kHz MF for 13 weeks. Together with our previous acute toxicity study, the evidence does not support the hypothesis that 20 kHz MF exposure bears significant toxicity.

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