Study type: Medical/biological study (experimental study)

Effects of magnetic fields on mammary tumor development induced by 7,12-dimethylbenz(a)anthracene in rats. med./bio.

Published in: Bioelectromagnetics 1993; 14 (2): 131-143

Aim of study (acc. to author)

To determine the possible copromoting effects of magnetic field exposure (MF) on the development and growth of chemically induced brest cancer in rat. Cancerogenesis was induced by DMBA and rats were exposed under differend conditions.

Background/further details

Four different experiment were conducted:
1) 18 animals were exposed to a homogeneous DC-MF of 15 mT. 18 animals were sham exposed and 8 animals served as reference control (i.e. animals in a seperate room).
2) 18 animals were exposed to a homogeneous AC (50 HZ)-MF of 30 mT. And two groups of 18 animals were used as sham or reference control, respectively.
3) Experiment 3 correspond to experiment 2 with the exeption that only 9 animals served as reference control.
4) 36 animals were exposed to to a gradient AC (50 Hz)-MF of 0.3-1.0 µT. Also 36 animals were sham exposed. No reference controll was used in this experiment.
DMBA was administered at doses which induced mammary tumors in about 50% of rats under control conditions. All groups of rats recived the first DMBA administration (5 mg) on the onset of exposure or sham exposure, respectively. Oral treatment with DMBA was repeated three times at weekly intervals. Reference controls were treated in the same way.

Endpoint

Exposure

Exposure Parameters
Exposure 1:
Exposure duration: repeated daily exposure, 24 h/day for 91 days
Exposure 2: 50 Hz
Exposure duration: repeated daily exposure, 24 h/day for 91 days.
Exposure 3: 50 Hz
Exposure duration: repeated daily exposure, 24 h/day for 91 days.

Exposure 1

Main characteristics
Frequency
Type
Exposure duration repeated daily exposure, 24 h/day for 91 days
Exposure setup
Exposure source
Setup Animals were placed in groups of three in plastic cages which were introduced to the coils.
Additional info Additional groups of animals were used as reference control.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 15 mT - measured - -

Exposure 2

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration repeated daily exposure, 24 h/day for 91 days.
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 30 mT effective value measured - -

Exposure 3

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration repeated daily exposure, 24 h/day for 91 days.
Additional info Gradient magnetic field
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 300 nT minimum measured - 1 µT max value.

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

In sham exposed and reference control animals the tumor incidence varied between 50-70% in all conducted experiments. Not any kind of MF exposure did alter this tumor incidence. However, tumor weight was significantly enhanced due to DC-MF exposure at 15 mT. The number of tumors per tumor-bearing animal was significantly increased due to AC-MF exposure. No effect could be observed at gradient AF-MF exposure at 0.3-1.0 µT. These experiments seem to indicate that MF may act as a copromotor of breast cancer.

Study character:

Study funded by

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