Intermittent exposure of rats to 2450 MHz microwaves at 2.5 mW cm2: behavioral and physiological effects

Long-Evans male adult rats were intermittently exposed for 14 weeks to continuous wave (CW) 2450-MHz microwaves at an average power density of 2.5 mW/cm2. The mean specific absorption rate was 0.70 W/kg (+/- 0.02 SEM). The rats were exposed 7 h/day, 7 days/week in a radiation chamber with a monopole above ground, while housed in Plexiglas cages. Weekly measures of body mass and food intake did not indicate statistically significant effects of microwave irradiation. Assessments of threshold for electric-footshock detection revealed a significant difference between microwave and sham-exposed animals. Assessments of cholinesterase and sulfhydryl groups in blood and 17-ketosteroids in urine did not distinguish the two groups of rats. Behavioral measures made at the end of the 14-week exposure included an open-field test, shuttlebox avoidance performance, and schedule-controlled lever-pressing for food pellets. Statistically significant differences between microwave- and sham-exposed rats were observed for these measures. Examination of adrenal tissue, plasma electrolytes, and organ masses after 14 weeks of exposure revealed no difference between the two groups of rats.     

Reduced weight in mice offspring after in utero exposure to 2450-MHz (CW) microwaves

Time-bred CD-1 mice (100) were sham-irradiated or irradiated with 2450-MHz (CW) microwaves at 28 mW/cm² for 100 minutes daily from the 6th through 17th day of gestation. The offspring were examined either as fetuses after hysterotomy on the 18th day of gestation or as naturally born neonates on the 1st and 7th day of age. Fetuses of half of the dams were examined on the 18th day of gestation. The incidence of pregnancy and the numbers of live, dead, resorbed, and total fetuses were similar in both groups. The mean weight was significantly lower (10%) in live microwave-irradiated fetuses, and ossification of sternal centers was significantly delayed. In the offspring that were born naturally, the mean weight of microwave-irradiated 7-day-old suckling mice was significantly lower (10%) than that of the sham-irradiated group. Survival rates of neonates in these two groups were not different. These data demonstrate that the decreased fetal weight seen in microwave-irradiated mice is retained at least 7 days after birth. Evidence from other published studies is presented to show that the retarded growth is persistent and might be interpreted as permanent stunting.     

Behavioral and physiological effects of chronic 2,450-MHz microwave irradiation of the rat at 0.5 mW/cm2

Adult male Long-Evans rats were intermittently exposed to 2450 MHz CW microwaves at an average power density of 0.5 mW/cm2 for 90 days. The resulting SAR was 0.14 W/kg (range 0.11 to 0.18 W/kg). The animals were exposed 7 h/day, 7 days/wk, for a total of 630 h in a monopole-above-ground radiation chamber while housed in Plexiglas holding cages. Daily measures of body mass and food and water intake indicated no statistically significant effects of microwave exposure. Monthly assessment of reactivity to electric footshock, levels of cholinesterase and sulfhydryl groups in blood, and 17-ketosteroids in urine revealed no reliable differences between 14 sham-exposed and 14 microwave-exposed rats. After the 90 days of exposure, seven rats, randomly chosen from each group, were assessed for open-field behavior, shuttlebox performance, and schedule-controlled (IRT schedule) lever pressing for food pellets. Statistically significant differences between microwave-exposed and sham-exposed rats were observed in shuttlebox performances and lever pressing. Post mortem measures of mass of several organs and microscopic examination of adrenal tissue revealed no differences between the two groups of animals.     

Behavioral effects of chronic exposure to 0.5 mW/cm2 of 2,450-MHz microwaves

Adult male, Long-Evans rats were exposed 7 h a day for 90 days to continuous wave (CW) 2,450-MHz microwaves at an average power density of 0.5 mW/cm2. Exposures were in a monopole-above-ground radiation chamber with rats in Plexiglas cages. The resulting specific absorption rate (SAR) was 0.14 W/kg (+/- 0.01 SEM). Additional rats served as sham-exposed and home-caged controls. All were evaluated daily for body mass and food and water intakes. Once each 30 days, throughout baseline and exposure phases of the experiment, rats in the sham- and microwave-exposed groups were tested for their sensitivity to footshock. After 90-days of exposure, the rats were evaluated an open field, an active avoidance task and an operant task for food reinforcement. Performance of sham- and microwave-irradiated rats was reliably different on only one measure, the lever-pressing task. The general conclusion reached was that exposure to CW 2,450-MHz microwave radiation at 0.5 mW/cm2 was below the threshold for behavioral effects over a wide range of variables, but did have an effect on a time-related operant task, although the direction of the effect was unpredictable.     

Cardiovascular, hematologic, and biochemical effects of acute ventral exposure of conscious rats to 2450-MHz (CW) microwave radiation

In this study the influence of acute (6 hr) exposure to 2450 MHz (CW) microwave radiation on certain cardiovascular, biochemical, and hematologic indices was examined in unanesthetized rats. Under methoxyflurane anesthesia, a catheter was inserted into the right femoral artery, which was used for monitoring blood pressure, heart rate, and blood sampling. Colonic temperature was monitored via a VITEK thermistor probe inserted rectally to a depth of 5 cm. The rat was subsequently placed into a ventilated restraining cage which was located inside an anechoic chamber. The temperature and humidity in the chamber were maintained at 22 +/- 0.5 degrees C and 60 +/- 5% (means +/- S.E.), respectively, during the experimental period. Rats (60) were exposed to either 0 (sham) or 10 mW/cm2 (exposed) for 6 hr. During exposure rats were oriented perpendicular to the E-field, and the measured specific absorption rate (SAR) was 3.7 mW/g. In the sham and exposed rats, the preexposure (time 0) mean +/- S.E. arterial blood pressure (MABP), heart rate, and colonic temperature were approximately 120 +/- 5 mmHg, 450 +/- 10 beats/min, and 37.0 +/- 0.2 degrees C, respectively. In the sham-exposed rats these values remained stable throughout the 6-hr exposure period. In the exposed rats, no effects were noted on MABP or colonic temperature; however after 1 hr of exposure, a significant reduction in heart rate was noted (450 versus 400 beats/min). This decrease in heart rate persisted throughout the remainder of the exposure period. None of the hematologic or biochemical parameters examined were affected by the microwave exposure. Although other mechanisms may be responsible, this decrease in heart rate may have been due to subtle cardiovascular adjustments because of microwave-induced heating with a resultant reduction in resting metabolic rate.