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.

By: Sinha RK

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.

Endpoint

endocrine changes: thyroid hormone changes
cognitive/behavioral endpoints: behavioral changes

Exposure

- 2.45 GHz
- microwaves
- microw. oven/heating device

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
Type	electromagnetic field
Exposure duration	repeated daily exposure, 2 h/day, for up to 21 days

Modulation

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.

Parameters

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

Measurement and calculation details

The maximum power output was measured using a power sensor and power meter. The power transmitted by the antenna was estimated. The average SARs parallel to the E plane and to the H plane were calculated by simple empirical equations [Gandhi et al., 1977 and Gandhi, 1974, respectively]. The phenomenon of polarization was studied theoretically and experimentally by previously described methods [Bachmann et al., 2005 and Hinrikus et al., 2005].

Reference articles

Hinrikus H et al. (2005): Non-Thermal Effect of Microwave Radiation on Human Brain
Bachmann M et al. (2005): Effect of 450 MHz Microwave Modulated with 217 Hz on Human EEG in Rest
Gandhi OP et al. (1977): Deposition of electromagnetic energy in animals and in models of man with and without grounging and reflector effects
Ghandi OP (1974): Polarization and frequency effects on whole animal absorption of RF energy

Exposed system:

animal
rat/Charles Foster
whole body

Methods Endpoint/measurement parameters/methodology

morphol./histopathol. changes: brain water content (brain weight: determination of edema and edematous swelling)
endocrine changes: thyroid hormone changes (triiodothyronine, thyroxine and thyroid stimulating hormone: radioimmunoassay)
cognitive/behavioral endpoints: behavioral changes (open field to measure fearfulness and reactiveness; elevated plus maze to test emotionality or anxiety)
core temperature

Investigated system:

isolated organ
brain
investigation on living organism

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:

medical/biological study
experimental study
full/main study
blind study

Study funded by

not stated/no funding

Salunke BP et al. (2015): Behavioral in-effectiveness of high frequency electromagnetic field in mice
Khirazova EE et al. (2012): Effects of GSM-Frequency Electromagnetic Radiation on Some Physiological and Biochemical Parameters in Rats
Dimida A et al. (2011): Electric and magnetic fields do not modify the biochemical properties of FRTL-5 cells
Esmekaya MA et al. (2010): Pulse modulated 900 MHz radiation induces hypothyroidism and apoptosis in thyroid cells: A light, electron microscopy and immunohistochemical study
Szemerszky R et al. (2010): Stress-related endocrinological and psychopathological effects of short- and long-term 50Hz electromagnetic field exposure in rats
Kumar RS et al. (2009): Hypoactivity of Wistar rats exposed to mobile phone on elevated plus maze
Cosquer B et al. (2005): Whole-body exposure to 2.45 GHz electromagnetic fields does not alter anxiety responses in rats: a plus-maze study including test validation
Cosquer B et al. (2005): Whole-body exposure to 2.45 GHz electromagnetic fields does not alter 12-arm radial-maze with reduced access to spatial cues in rats
Cassel JC et al. (2004): Whole-body exposure to 2.45 GHz electromagnetic fields does not alter radial-maze performance in rats
Cobb BL et al. (2004): Radial arm maze performance of rats following repeated low level microwave radiation exposure
Wang B et al. (2000): Acute exposure to pulsed 2450 MHz microwaves affects water-maze performance of rats
Mitchell CL et al. (1988): Some behavioral effects of short-term exposure of rats to 2.45 GHz microwave radiation
DeWitt JR et al. (1987): Behavioral effects of chronic exposure to 0.5 mW/cm2 of 2,450-MHz microwaves
Lu ST et al. (1985): The relationship of decreased serum thyrotropin and increased colonic temperature in rats exposed to microwaves
Lu ST et al. (1981): Microwave-induced temperature, corticosterone, and thyrotropin interrelationships
Abhold RH et al. (1981): Studies on acute in vivo exposure of rats to 2450-MHz microwave radiation. II. Effects on thyroid and adrenal axes hormones
Galloway WD (1975): Microwave dose-response relationships on two behavioral tasks
King NW et al. (1971): Behavioral sensitivity to microwave irradiation