Behavioral and thermal effects of microwave radiation at resonant and nonresonant wavelengths

Behavioral and thermal effects of radiating an animal with differing wavelengths of microwave energy at the same power density were investigated in the first of two studies. Five Long‐Evans rats were trained to perform a lever‐pressing task and were rewarded with food on a variable interval schedule of reinforcement. Rats were individually exposed in random order to 400‐, 500‐, 600‐, and 700‐MHz CW radiation at a power density of 20 mW/cm 2 with the long axis of the rat's body parallel to the vector of the electric field. Radiation at all wavelengths produced rises of body temperature and stoppage of lever pressing. The averaged rise in body temperature was greatest and work stoppage was most rapid during exposures at 600 MHz. In the second study, six rats were exposed in random order to 600‐MHz CW radiation at power densities of 5, 7.5, 10, and 20 mW/cm 2 while performing the same behavioral task. Exposures at 10 and 20 mW/cm 2 resulted in work stoppage, while exposures at 5 and 7.5 mW/cm 2 did not. In addition, three of the rats were subsequently exposed while responding to 600‐MHz pulsed radiation (1000 pps, 3‐ or 30‐μs pulse durations at a peak power density of 170 mW/cm 2 (averaged 0.51 and 5.1 mWcm 2 ). No work stoppage occurred to pulsed radiation. Taken in sum, the data show that the mature Long‐Evans rat is resonant at a frequency near 600 MHz while work stoppage during short‐term exposures to 600‐MHz radiation occurs at a power density between 7.5 and 10 mW/cm 2 .