The optimization of experimental conditions for radiolytic removal of organic pollutants from water and waste with the use of ionizing radiation via controlling the concentration of target compound(s) requires also monitoring the toxicity changes during the process. Commonly used herbicides 2,4-D and dicamba were shown to increase toxicity measured with the Microtox test at low irradiation doses resulting from formation of more toxic transient products, which can be decomposed at larger doses. The changes of toxicity were examined with respect to dose magnitude and the presence of commonly occurring scavengers of radiation.