In vitro genotoxicity of terbutryn evaluated by the alkaline single-cell microgel-electrophoresis "comet" assay

Terbutryn, a s-triazine herbicide, is extensively used in agriculture as a selective pre- and postemergence control agent for most grasses and many annual broadleaf weeds in cereal and legume fields, and under fruit trees. Terbutryn was reported to degrade slowly, with half-lives of 240 and 180 days in pond and river sediment, respectively. The tendency of this herbicide to move from treated soils to water compartments through water runoff and leaching was demonstrated and residual amounts of terbutryn and its metabolites have been found in drinking water, and industrial food products, long after application. Although this herbicide may be regarded as a contaminant of our environment, only limited and inconsistent data exist concerning its genotoxic properties. In this study, the DNA-damaging ability of the herbicide was evaluated in the alkaline single-cell microgel-electrophoresis ("comet") assay by testing terbutryn in the presence of S9mix (rat liver homogenate containing microsomal enzymes plus cofactors) prepared with liver homogenate from both uninduced (basal) and aroclor 1254-induced rats. DNA damage was recorded in freshly isolated human peripheral blood leukocytes. A statistically significant increase in the extent of primary DNA damage, more pronounced in the absence of S9mix, took place only when terbutryn concentrations were high (100 and 150 microg/ml), in the presence of a concomitant mild cytotoxic effect.