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.
|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.|
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.