Medical/biological study (experimental study)

Nonthermal effects of mobile-phone frequency microwaves on uteroplacental functions in pregnant rats med./bio.

By: Nakamura H, Matsuzaki I, Hatta K, Nobukuni Y, Kambayashi Y, Ogino K

Published in: Reprod Toxicol 2003; 17 (3): 321-326

Aim of study (acc. to author)

To investigate the effects in pregnant rats exposed to non-thermal 915 MHz microwaves.

Background/further details

In six different treatment groups a total of 36 rats were examined: 1.) rats exposed to microwaves at 0.6 mW/cm², 2.) rats exposed to microwaves at 3 mW/cm², 3.) rats immersed in water at 38°C (induced the same colonic temperature increase as the group exposed to 0.6 mW/cm² microwaves), 4.) rats immersed in water at 40°C (induced the same colonic temperature increase as the group exposed to 3 mW/cm² microwaves), 5.) rats immersed in 34°C water (considered to be thermo-neutral), 6.) control rats.

Endpoint

utero-placental blood flow, endocrine changes, effects on immunological system

Exposure

- microwaves
- mobile communications
- mobile phone

Exposure	Parameters
Exposure 1: 915 MHz Modulation type: CW Exposure duration: continuous for 90 min	power density: 0.6 mW/cm² (±10%) SAR: 0.4 W/kg power density: 3 mW/cm² (±10%) SAR: 2 W/kg

Exposure 1

Main characteristics

Frequency	915 MHz
Type	electromagnetic field
Exposure duration	continuous for 90 min
Additional info	Padilla JM, Bixby RR. Using Dewar flask calorimetry and rectal temperatures to determine the SARs of small rodents. USAFSAM-TP-86-3. TX, USA: Brooks AFB 1986.

Modulation

Modulation type	CW

Exposure setup

Exposure source	magnetron, applicator (350 mm x 470 mm x 455 mm)
Chamber	The environment of the exposure facility was maintained at 21-23 °C and 50-60% humidity.
Setup	Rats were placed individually into semi-cylindrical acrylic plastic holders (inner diameter 60 mm, length 170 mm, walls 5 mm) and exposed in the device described previously [Inaba et al., 1992]. Two holders were put into the applicator with their long axis oriented parallel to the electric field.
Additional info	Rats were assigned to six groups: exposed to EMF at 0.6 or 3 mW/cm²; immersed in water at 38, 40 °C (inducing about the same increase in colonic temperature as the EMF) or at 34 °C (thermoneutral) or in a control group.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
power density	0.6 mW/cm²	-	measured	-	±10%
SAR	0.4 W/kg	-	measured	whole body	-
power density	3 mW/cm²	-	measured	-	±10%
SAR	2 W/kg	-	measured	whole body	-

Measurement and calculation details

The incident power was measured using a probe inserted into the applicator and varied by about ±10% at each location. Whole-body SAR was determined for each animal using a Dewar flask calorimetric technique described by Padilla and Bixby [1986].

Reference articles

Inaba R et al. (1992): Effects of whole body microwave exposure on the rat brain contents of biogenic amines

Exposed system:

animal
rat/Wistar
whole body

Methods Endpoint/measurement parameters/methodology

effects on the immune system: splenic natural killer cell activity (chromium release assay)
endocrine changes: estradiol, progesterone level (radioimmunoassay)
thermoregulation: colonic temperature (probe)
utero-placental blood flow (hydrogen gas electrolytic method)

Investigated system:

isolated bio./chem. substance
intact cell/cell culture

Investigated organ system:

Time of investigation:

before exposure
during exposure
after exposure

Main outcome of study (acc. to author)

Significant differences in the utero-placental circulation and in the placental endocrine functions between pregnant rats immersed in water at 34 and 38°C were identified, but not between rats immersed at 38°C and those exposed to microwaves at 0.6 mW/cm². By contrast, significant decreases in the utero-placental blood flow and estradiol level in rats exposed to microwaves at 3 mW/cm² as compared with those immersed in water at 40°C were observed. Therefore, microwaves at exposure levels that increase core temperature by about 3.5°C seem likely to produce utero-placental dysfunctions through thermal and nonthermal actions.
The microwave exposure to 0.6 mW/cm² and water immersion at 38°C reduced splenic natural killer cell activity, but microwaves at 3 mW/cm² did not change splenic natural killer cell activity as compared to the group exposed to 34°C water immersion.
In conclusion, the exposure to microwaves at 0.6 mW/cm² (maximum permissible exposure level recommended by ANSI) do not exert nonthermal effects on the utero-placental blood flow, blood estriol and progesterone level, and splenic natural killer cell activity.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

Ministry of Education, Culture, Sports, Science and Technology, Japan

Kismali G et al. (2012): The influence of 1800 MHz GSM-like signals on blood chemistry and oxidative stress in non-pregnant and pregnant rabbits
Seyednour R et al. (2011): Effects of Exposure to Cellular Phones 950 MHZ Electromagnetic Fields on Progesterone, Cortisol and Glucose Level in Female Hamsters (Mesocricetus auratus)
Yamashita H et al. (2010): Short-term exposure to a 1439-MHz TDMA signal exerts no estrogenic effect in rats
Sommer AM et al. (2009): Effects of radiofrequency electromagnetic fields (UMTS) on reproduction and development of mice: a multi-generation study
Valbonesi P et al. (2008): Evaluation of HSP70 expression and DNA damage in cells of a human trophoblast cell line exposed to 1.8 GHz amplitude-modulated radiofrequency fields
Nakamura H et al. (2000): Uteroplacental circulatory disturbance mediated by prostaglandin f2alpha in rats exposed to microwaves
O'Connor ME (1999): Intrauterine effects in animals exposed to radiofrequency and microwave fields
Nakamura H et al. (1997): Effects of exposure to microwaves on cellular immunity and placental steroids in pregnant rats