Comparison of the microbicidal effectiveness of 150 kV x-rays and cobalt-60 gamma rays

The radiation response, quantified by the dose-log survival curve, of spores of Bacillus pumilus subjected to irradiation in a 150 kV x-ray beam was examined and compared with the response obtained by irradiation in a reference cobalt-60 beam. The spores were irradiated at doses ranging from 2 kGy to 11 kGy. The response was the same for both beam qualities within measurement uncertainties. Combining these findings with our previously published data, the radiation resistance of B. pumilus spores is determined to be independent of beam quality for low and high energy x-rays, low and high energy electron beams, and cobalt-60 gamma beams.