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 an nual broadleaf weeds in cereal and legume fields, and under fruit trees. Te rbutryn was reported to degrade slowly, with half-lives of 240 and 180 days in pond and river sediment, respectively. The tendency of this herbicide t o move from treated soils to water compartments through water runoff and le aching was demonstrated and residual amounts of terbutryn and its metabolit es have been found in drinking water, and industrial food products, long af ter application. Although this herbicide may be regarded as a contaminant o f our environment, only limited and inconsistent data exist concerning its genotoxic properties. In this study, the DNA-damaging ability of the herbic ide was evaluated in the alkaline single-cell microgel-electrophoresis ("co met") assay by testing terbutryn in the presence of S9mix (rat liver homoge nate containing microsomal enzymes plus cofactors) prepared with liver homo genate from both uninduced (basal) and aroclor 1254-induced rats. DNA damag e was recorded in freshly isolated human peripheral blood leukocytes. A sta tistically significant increase in the extent of primary DNA damage, more p ronounced in the absence of S9mix, took place only when terbutryn concentra tions were high (100 and 150 mug/ml), in the presence of a concomitant mild cytotoxic effect.