この研究は、居住環境中で遭遇する低周波および中間周波の磁界（MF）を人工的に作成し、その実験的ばく露により、ホルモン（特にメラトニン）の夜間分泌が影響を受けるか否かを、ヒトボランティア実験で調べた。被験者は10人の健康な男性である。被験者は、実験のために、間をおいて2夜、実験室（3軸メリットコイルを備えた、１辺2.7 mの立方体）内に滞在した。１夜は、直線偏波の50 Hz、20 μTの正弦波磁界（3次（30％）および5次（10％）高調波および反復性の過渡波（1 kHzのバースト波（1バースト/秒、ピーク振幅100 μT、持続時間50 msで指数関数的減衰）を含む）のばく露に用い、別の１夜は、ブラインドコントロールに用いた。血液サンプルの採取は、夜間（睡眠時間2300-0700を含む2000-0800）は1時間間隔で行い、特に2200-0200の間は10分間で行なった。前者の試料は、血漿ホルモン（メラトニン、成長ホルモン（GH）、コルチゾール、プロラクチン）のレベル測定、後者は、睡眠で誘発されるGHサージの観察に用いた。その結果、4つのホルモンのプロファイルには、2夜の間に有意差はなかった、と報告している。
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The effects of exposure of subjects to a 50 Hz and intermediate frequency magnetic field on the nighttime blood plasma levels of melatonin and other hormones should be investigated.
10 male subjects participated in the study and each attended 3 night sessions (but only samples from 9 subjects were analyzed). The first session was for habituation to the experimental conditions, the other 2 sessions were for exposure or sham exposure, respectively, with the order being unknown to the subjects.
Blood samples were automatically collected every hour during exposure and sham exposure in general and every 10 minutes between 22.00 and 02.00 o'clock.
|50 Hz–1 kHz
|continuous for 12 h (20.00 to 08.00 o'clock)
|the following components were superimposed on the primary 50 Hz field: third harmonics with 30% intensity of primary field (effective value) fifth harmonics with 10% intensity of the primary field (effective value) 1 kHz with initial 100 µT (peak) field, which attenuated exponentially over a duration of 50 ms and repeated at 1 s intervalls (1 burst/s)
|the exposure room had a dual structure with an inner room (cube with 2.7 m side length) being completely enclosed within a larger outer room (cube with 4 m side length); frame for room was made of wood; interior resembled a small room of a house with textured walls, equipped with a small table and a bed
|4 coil-square loop configuration with 3-axis Merritt coils; the outer two coils had 16 turns each and the inner coils had 8 turns; coils were located in the space between the inner and outer rooms; the coils were set in the same manner in each of the three dimensions of the room except that the horizontal inner coils were wound around the door; all of the windings were formed with a twisted pair of copper wires; temperature was maintained at ± 1°C and relative humidity at ± 5%; room was not shielded from intruding fields; direction of the field coincided with the longer axis of the bed
|A sham exposure was conducted.
|sham exposure conditions were set by changing the current direction in one of the pair of wires of the coil
All hormones showed time-dependent variabilities in their concentrations over the investigation period, which corresponded to typical physiological rhythms. However, no significant differences were found between exposure and sham exposure conditions.
The authors conclude that exposure of subjects to a 50 Hz and intermediate frequency magnetic field shows no effects on the nighttime blood plasma levels of melatonin and other hormones.