Mutagenicity of ultrasound in cultured mammalian cells

Chinese hamster V79 cells were exposed in suspension to 1 MHz continuous wave ultrasound at spatial peak intensities of 7 and 35 W/cm2. Exposure durations were from 10 to 180 sec, so as to encompass the first decade of decreased survival at each intensity. Exposure at 35 W/cm2 resulted in the induction of 6-thioguanine-resistant mutants. The mutation frequency was approximately one-tenth that induced by x rays at similar survival levels. No mutagenesis was observed at 7 W/cm2. Results are consistent with free radical formation as the mechanism responsible for ultrasound-induced mutagenesis.