Medical/biological study (experimental study)

Long-term exposure of Sprague Dawley rats to 20 kHz triangular magnetic fields med./bio.

By: Lee HJ, Kim SH, Choi SY, Gimm YM, Pack JK, Choi HD, Lee YS

Published in: Int J Radiat Biol 2006; 82 (4): 285-291

Aim of study (acc. to author)

This study was conducted to investigate the effects of long-term (12 or 18 months) exposure to 20 kHz intermediate frequency magnetic fields on physiological parameters in rats.

Background/further details

80 three-week-old rats were used (half male and female in each sham exposed and exposed groups). The applied magnetic flux density of 6.25 µT represents the exposure limit for the public of 20 kHz magnetic fields in Korea.

Endpoint

effects on organ weight, morphology

Exposure

- magnetic field
- intermediate frequency

Exposure	Parameters
Exposure 1: 20 kHz Modulation type: pulsed Exposure duration: repeated daily exposure, 8 h/day for 12 or 18 months	magnetic flux density: 6.25 µT effective value

General information

Male and females were equally divided into 2 groups for sham and active exposures.

Exposure 1

Main characteristics

Frequency	20 kHz
Type	magnetic field
Waveform	sawtooth-shaped
Exposure duration	repeated daily exposure, 8 h/day for 12 or 18 months
Additional info	Vertical magnetic field was used for exposure.

Modulation

Modulation type	pulsed

Exposure setup

Exposure source	coil(s)

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	6.25 µT	effective value	measured	-	-

Measurement and calculation details

Magnetic field strength and uniformity at top and bottom locations in the exposure system was measured using 3 axis magnetic field probe.

Exposed system:

Methods Endpoint/measurement parameters/methodology

morphol./histopathol. changes: organ weights, histopathological examination (hematoxylin-eosin stain, light microscopy)
morbidity, mortality; body weight; blood biochemical analyses (e.g. hemoglobin, leucocyte/thrombocytes count; total protein, creatinine, glucose); urine analysis (e.g. blood content, pH, glucose)

Investigated system:

isolated bio./chem. substance
isolated organ
blood, urine
investigation on living organism

Investigated organ system:

reproductive system
immune system
cardiovascular system
respiratory system
brain/CNS
thymus, stomach, intestine, lung, liver, kidney, testis, ovary, spleen, brain, heart

Time of investigation:

after exposure

Main outcome of study (acc. to author)

The body weight was significantly reduced in both male and female rats of the 18 months exposure group. Blood examinations revealed significantly increased number of neutrophils after 12 months exposure, and significantly decreased number of lymphocytes in the 18 months exposure group, but only in female rats. Other investigated parameters were unaffected.
In conclusion, these results indicate that long-term exposure of rats to 20 kHz magnetic fields do not induce any significantly harmful effects, except changes in neutrophils and lymphocytes in female rats. These hematological changes need to be further investigated.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

Ministry of Information and Communication, Korea

Lee HJ et al. (2010): Chronic exposure of Sprague-Dawley rats to 20 kHz triangular magnetic fields
Contalbrigo L et al. (2009): Effects of different electromagnetic fields on circadian rhythms of some haematochemical parameters in rats
Kim SH et al. (2006): Toxicity bioassay in Sprague-Dawley rats exposed to 20 kHz triangular magnetic field for 90 days
Kim SH et al. (2004): Teratological studies of prenatal exposure of mice to a 20 kHz sawtooth magnetic field
Svedenstal BM et al. (1998): Effects of exposure to 50 Hz or 20 kHz magnetic fields on weights of body and some organs of CBA mice
Svedenstal BM et al. (1998): Leukocytes and micronucleated erythrocytes in peripheral blood from mice exposed to 50 Hz or 20 kHz magnetic fields
Ubeda A et al. (1997): Hematological changes in rats exposed to weak electromagnetic fields