Biological studies with continuous-wave radiofrequency (28 MHz) radiation.

Effects of high-frequency (28 MHz) continuous-wave radiation have been studied in the rat and monkey. No histopathological (rat-125 mW cm-2 for 28 days) or hematological (monkey-25 mW cm-2 for 24 days) changes could be attributed to the radiation. In the monkey (125 mW cm-2 for 11 days) there was an increase in urinary calcium concentration which was most likely due to restricted movement. In the rat (220 mW cm-2 for 13 days) there was reduced uptake of iodine by the thyroid, lower levels of plasma thyroid-stimulating hormone, and reduced ratio of protein bound to nonprotein bound iodine. Food consumption was also decreased. The changes are likely to have arisen as a compensatory response to an induced heat load. A nonthermal effect of continuous-wave high-frequency radiation has not been shown in this study. The effects were likely to be associated with either physiological compensation for induced heating or restriction of movement.