In vitro testing for genotoxicity of the herbicide terbutryn: cytogenetic and primary DNA damage.

Terbutryn is a widely used preemergence and postemergence s-triazine herbicide. This pesticide is used in agriculture as a control agent for most grasses and many annual broadleaf weeds in cereal and legume fields, and under fruit trees. Unexpectedly, this compound was found to persist in the environment (240 and 180 days in pond and river sediment, respectively) and to have the tendency to move from treated soils to water compartments through water runoff and leaching. However, only scant information is available about the genotoxic properties of terbutryn. In the present in vitro study, we investigated the relationship between cytogenetic damage, as evaluated in the sister-chromatid exchange (SCE) assay and the micronucleus (MN) test, and primary DNA damage (as evaluated by the "comet" assay). Cytogenetic and primary DNA damage were recorded in vitro in freshly isolated human peripheral blood leukocytes. Our results showed that the tested compound failed to produce any significant increases in SCE or MN, neither in the absence nor in the presence of S9-mix. However, terbutryn was found to induce primary DNA damage, more pronounced without S9 mix, even though in the absence of a clear trend for dose-dependence and in the presence of a concomitant mild cytotoxic effect.