この研究は、OF1マウスに、15 T（rms）、50 Hzの正弦波磁界（東西方向）の慢性ばく露を実施し、この非電離放射線の白血病誘発性を評価した。この慢性ばく露下で、第１世代の交配と妊娠、第2世代の雌マウスの出生、哺乳、成獣期までの発達が進行した。第2世代の雌マウスが14〜15週齢および50〜52週齢の時点で、対照群とばく露群の血液学的検査を実施した。その結果、本来、この系統のマウスでは26週齢未満での悪性腫瘍発症への抵抗性が知られているにも拘らず、14〜15週齢のメスのばく露群で、血中の白血球増殖性異常の発生率が上昇した（相対リスク（RR）= 3.00、p = 0.0033）；特にリンパ性白血病（RR = 6.50、p = 0.0021）および慢性白血病（RR = 4.00、p = 0.0153）で、ばく露に関連した発生率上昇が顕著であった；50〜52週間のばく露後、ばく露群の死亡率30％に対し、対照群では0％であった；死亡したメスラットのうちの67％で、何らかのタイプの悪性腫瘍が見られた；ばく露群での血中白血球増殖性異常における生存のRRは2.57であった（p = 0.0351）；特に重要なのは、長期（50〜52週間）ばく露後の慢性白血病の割合であった（RR = 8.57、p = 0.0118）、と報告している。
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The effects of a chronic exposure of mice to a 50 Hz magnetic field on the development of leukemia should be investigated.
Mice of the parental generation (P1 mice) were randomly divided into an exposure and a control group. P1 mice in the exposure group were exposed to the magnetic field for 14 weeks, then mating was induced. Pregnancy with the first filial generation (F1 mice) as well as birth, lactation, weaning and development until the end of the experiment took place under exposure conditions. The same procedure was conducted with the control group but without exposure to the magnetic field. Only F1 mice were investigated.
F1 mice were divided into 4 groups: 1) exposure to the magnetic field for 14-15 weeks after birth (medium-term exposure, young adults; n=30), 2) control group for group 1 without exposure (n=30), 3) exposure to the magnetic field for 50-52 weeks after birth (chronic exposure, adults; n=20), 4) control group for group 3 without exposure (n=20).
|ばく露時間||continuous during pregnancy and for 14-15 or 50-52 weeks after birth|
|チャンバの詳細||standard macrolon cages with methacrylate plastic cover|
|ばく露装置の詳細||set of Helmholtz coils oriented in east-west direction, each with a radius of 0.375 m and 220 turns of 1.2 mm copper wire; temperature was maintained at a daily mean of 22 ± 2°C|
|Sham exposure||A sham exposure was conducted.|
|磁束密度||15 µT||effective value||測定値||-||-|
The relative risk for mice exposed to the magnetic field for 50-52 weeks (group 3) to develop a chronic leukemia was significantly increased compared to the control group.
Individual hematologic diagnosis revealed a significantly higher risk for proliferative disorders of leukocytes in 14- to 15-week-old exposed mice (group 1) compared to the control group. The incidence for chronic lymphocytic leukemia was significantly higher in exposed animals after 14-15 and 50-52 weeks compared to the respective control groups.
After 50-52 weeks of exposure, the mortality of exposed mice was 30% versus 0% in the control group. 67% of these dead mice showed malignant alterations associated with leukemia. The mean life span of surviving animals was significantly shorter in exposed animals compared to the control group.
The authors conclude that a chronic exposure of mice to a 50 Hz magnetic field could be related to the development of leukemia and that this result agrees with the results of numerous epidemiological studies.