GENOTOXIC EFFECTS OF THE CARBAMATE INSECTICIDE METHOMYL .1. IN-VITRO STUDIES WITH PURE COMPOUND AND THE TECHNICAL FORMULATION LANNATE-25

The carbamate insecticide methomyl and the methomyl-containing technic al formulation ''Lannate 25'' were tested on whole blood human lymphoc yte cultures. Both products induced dose-dependent increases in chromo some aberrations and micronuclei. Lannate 25 induced DNA damage as mea sured by the alkaline elution assay and hydroxylation of guanine at th e C8 position. Sister chromatid exchanges were not increased significa ntly with either product. Overall, the technical formulation was more active than the pure compound, when compared at similar concentrations of active principle. Moreover, a different ratio of CREST-positive/CR EST-negative micronuclei was observed with the two products, pure meth omyl being relatively more active than Lannate 25 in the induction of CREST-positive micronuclei. On the basis of these results, previous ev aluations of methomyl as a nongenotoxic compound should be reconsidere d. (C) 1994 Wiley-Liss, Inc.