Study type: Medical/biological study (experimental study)

Lack of teratological effects in rats exposed to 20 or 60 kHz magnetic fields med./bio.

By: Nishimura I, Oshima A, Shibuya K, Negishi T
Published in: Birth Defects Res B Dev Reprod Toxicol 2011; 92 (5): 469-477
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Aim of study (acc. to author)

To study whether 20 and 60 kHz intermediate magnetic field exposures have embryotoxic, fetotoxic, and/or teratogenic potential in rats.

Background/further details

Pregnant rats (25 per group) were exposed to a 20 kHz or 60 kHz sinusoidal magnetic field or sham exposed for 22 hr/day during organogenesis, and their fetuses were examined for malformations on gestation day 20. Experiments were duplicated for each frequency to confirm consistency of data.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 20 kHz
Exposure duration: continuous for 22 h/day from day 7 to day 17 of gestation
Exposure 2: 60 kHz
Exposure duration: continuous for 22 h/day from day 7 to day 17 of gestation

Exposure 1

Main characteristics
Frequency 20 kHz
Type
Waveform
Exposure duration continuous for 22 h/day from day 7 to day 17 of gestation
Exposure setup
Exposure source
Setup two Merritt-type four square coil systems positioned 37.4 m apart; coils layered horizontally in a wooden structure with a side length of 150 cm and a height of 161 cm; coils spaced at 60, 41 and 60 cm; coils with 26:11:11:26 turns of wire; 3 racks placed inside the coil system to house 36 rat cages, 12 on each rack in a 3-row by 4-column layout; one rat per cage; 100 cm x 100 cm x 100 cm exposure area in the center of the coil system with MF variability less than 3%; structural outer walls, high roof and deep basement, contained steel-bar reinforcement grids to reduce MF leakage to the outside
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 0.2 mT effective value measured - -
Additional parameter details

50 Hz background MF during exposure: < 0.02 µT MF for sham exposure: < 0.001 µT at 20 kHz and 60 kHz, 0.03 µT at 50 Hz geomagnetic field: 48.3 µT

Exposure 2

Main characteristics
Frequency 60 kHz
Type
Waveform
Exposure duration continuous for 22 h/day from day 7 to day 17 of gestation
Exposure setup
Exposure source
Setup same setup as in Exposure 1, but coils with 7:3:3:7 windings
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 0.1 mT effective value measured - -
Additional parameter details

50 Hz background MF during exposure: < 0.02 µT MF for sham exposure: < 0.001 µT at 20 kHz and 60 kHz, 0.03 µT at 50 Hz geomagentic field: 48.3 µT

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

No exposure-related alterations were revealed in clinical signs, gross pathology, or number of implantation losses. The number of live fetuses and low-body-weight fetuses as well as the incidence of external, visceral, and skeletal malformations in the fetuses did not indicate significant differences between exposed and sham exposed groups. Although some fetuses showed isolated changes in sex ratio and skeletal variation and ossification, such changes were neither reproduced in duplicate experiments nor were they common to specific field frequencies. No magnetic field frequency-specific response was manifested in any of the endpoints
The authors conclude that exposure of rats to magnetic fields during organogenesis did not show a significant reproducible teratogenicity under these experimental conditions. The data do not support the hypothesis that an intermediate frequency magnetic field exposure after implantation carries a significant risk for mammalian fetuses development.

Study character:

Study funded by

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