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.
|Frequency||50 Hz–1 kHz|
|Exposure duration||continuous for 12 h (20.00 to 08.00 o'clock)|
|Additional info||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)|
|Chamber||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|
|Setup||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|
|Sham exposure||A sham exposure was conducted.|
|Additional info||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.