Repeated exposure of C3H/HeJ mice to ultra-wideband electromagnetic pulses: lack of effects on mammary tumors

It has been suggested that chronic, low-level exposure to radiofrequency (R F) radiation may promote the formation of tumors. Previous studies, however , showed that low-level, longterm exposure of mammary tumor-prone mice to 4 35 MHz or 2450 MHz RF radiation did not affect the incidence of mammary tum ors. In this study, we investigated the effects of exposure to a unique typ e of electromagnetic energy: pulses composed of an ultra-wideband (UWB) of frequencies, including those in the RF range. One hundred C3H/HeJ mice were exposed to UWB pulses (rise time 176 ps, fall time 3.5 ns, pulse width 1.9 ns, peak E-field 40 kV/m, repetition rate 1 kHz). Each animal was exposed for 2 min once a week for 12 weeks. One hundred mice were used as sham cont rols. There were no significant differences between groups with respect to incidence of palpated mammary tumors, latency to tumor onset, rate of tumor growth, or animal survival. Histopathological evaluations revealed no sign ificant differences between the two groups in numbers of neoplasms in all t issues studied (lymphoreticular tissue, thymus, respiratory, digestive and urinary tracts, reproductive, mammary and endocrine systems, and skin). Our major finding was the lack of effects of UWB-pulse exposure on promotion o f mammary tumors in a well-established animal model of mammary cancer. (C) 2001 by Radiation Research Society.