Abstract: Municipal treated wastewater may contain genotoxic pollutants which are hazardous to the environment and humans. With stringent regulations concerning wastewater reuse in agriculture, there is a great need to determine levels of such genotoxic pollutants and the easiest way to do so, to use the comet DNA assay. The assay was carried out on mouse primary spleen cell cultures as a target cells. A great number of cells with comets were observed in those treated cells in vitro with polluted water samples (23.1-69.11%) than those in the controls (19.33-21.56%). These results indicate that the comet assay can have an application in biomonitoring studies for determining the potential genotoxicity of water pollutants.