Study type: Medical/biological study (experimental study)

Chronic non-thermal exposure of modulated 2450 MHz microwave radiation alters thyroid hormones and behavior of male rats. med./bio.

Published in: Int J Radiat Biol 2008; 84 (6): 505-513

Aim of study (acc. to author)

To determine the effects of chronic exposure to low energy 2450 MHz nonthermal microwave irradiation on thyroid hormones and to analyze how these changes in thyroid hormones, if any, affect the reactiveness and emotional behavior of rats.

Background/further details

Twenty male rats of 4-5 weeks of age were analyzed. Blood was taken from the tails of each rat on the 1st, 6th, 11th, 16th and 21st day immediately after two hours irradiation or sham exposure.



Exposure Parameters
Exposure 1: 2,450 MHz
Modulation type: pulsed
Exposure duration: repeated daily exposure, 2 h/day, for up to 21 days
  • power: 12.5 mW
  • power density: 16.5 µW/cm² (at the bottom of the holder)
  • SAR: 3.6 µW/g average over mass (whole body) (parallel to the E plane)
  • SAR: 0.98 µW/g average over mass (whole body) (parallel to the H plane)

Exposure 1

Main characteristics
Frequency 2,450 MHz
Exposure duration repeated daily exposure, 2 h/day, for up to 21 days
Modulation type pulsed
Repetition frequency 1 kHz
Pulse type rectangular
Exposure setup
Exposure source
  • horn antenna
  • pyramidal, "throat dimension" 7.2 x 3.4 cm, length 10 cm, flair angle 9.6°
Distance between exposed object and exposure source 23 cm
Chamber The flair angle of the antenna was 9.6° in both the electric (E) and the magnetic (H) plane. The distance of the antenna from the top of the animal holder was 23 cm. The 3 dB points for both H and E planes were calculated and used in the design of the animal holder for five rats that consisted of a Perspex box with five compartments on a 10-cm Styrofoam base of 29.87 x 25.3 cm. The internal partitioning was made of pine wood due to its low dielectric constant and loss tangent. All external and internal walls, excluding the base were perforated at uniform distances to make the holder anechoic. An absorber made of carbon coated Styrofoam with cones on its surface was placed below the holder to reduce reflected radiation.
Setup The long axis was positioned parallel to the E-field for two of the compartments and parallel to the H-field for the other three. Rats were not restrained and were free to change their posture within the cage. They were rotated daily from one chamber to the next chamber in succession.
Sham exposure A sham exposure was conducted.
Additional info Tests and analyses were performed on the 1st, 6th, 11th, 16th and 21st day of the experiment immediately after RF or sham exposure.
Measurand Value Type Method Mass Remarks
power 12.5 mW - estimated - -
power density 16.5 µW/cm² - calculated - at the bottom of the holder
SAR 3.6 µW/g average over mass calculated whole body parallel to the E plane
SAR 0.98 µW/g average over mass calculated whole body parallel to the H plane

Reference articles

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

Concerning behavioral changes in open field, significant increase in mobility, rearing, and central/peripherial ambulation were found in exposed rats on the 16th and 21st days of exposure. In elevated plus maze, rats showed increased activity with decreased time spent in the open arm and more time spent in the center on the 11th, 16th and 21st day after irradiation. The changes in behavioral parameters were accompanied by decreased levels of triiodothyronine on the 16th day and 21st day and increased levels of thyroxine on the 21st day of exposure.
The authors conclude that low energy microwave irradiation may be harmful as it is sufficient to alter the levels of thyroid hormones as well as the emotional reactivity of rats.

Study character:

Study funded by

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