Mutation Research, 292 (1993) 231-239 231 © 1993ElsevierSciencePublishersB.V. All rightsreserved 0165-1161/93/$06.00 MUTENV 08895 Studies on the genotoxicity of monocrotophos, an organophosphate insecticide, in the chick in vivo test system S.P. Bhunya * and G.B. Jena Laboratory of Genetic Toxicology, P.G. Department of Zoology, Utkal University, Bhubaneswar-751 004 Orissa, India (Received 14 April 1993) (Revisionreceived30 June 1993) (Accepted 8 July1993) Keywords: Monocrotophos; Chromosomeaberration; Micronucleus;Bone marrow;Peripheralblood erythrocytes; Chicken Summary The mutagenic potential of an organophosphate pesticide, monocrotophos, was evaluated in the chick in vivo system using the chromosome aberration (CA) assay in bone marrow cells and the micronucleus test (MNT) in both bone marrow and peripheral blood erythrocytes. A significant induction of chromo- some aberrations was observed only after 24 h of exposure with the highest dose (5 mg/kg). In general, monocrotophos induced a significantly higher incidence of micronuclei in bone marrow and peripheral blood erythrocytes over controls. From the present results it is concluded that monocrotophos is genotoxic in this in vivo test system. It is further concluded that the neonatal chick in vivo system provides new methodology for screening xenobiotics for mutagenicity. The indiscriminate use of synthetic chemical pesticides in todays' agriculture and the direct and indirect entry of pesticides into food chains might pose a serious threat to the genetic mate- rial of the surrounding flora and fauna especially after a long latent period. The detection of these chemicals in our environment is both feasible and necessary (WHO Scientific Group, 1971; Com- mittee 17, 1975). Several assay systems with rapid and reliable methods for this purpose are avail- able now (Kihlman, 1971; Schmid, 1973; Tono- mura and Sasaki, 1973; Kada et al., 1974; Sasaki * Corresponding author. and Abe, 1974; Ames et al., 1975; Yahagi et al., 1976). So far, the avian test system has been used infrequently for mutagenicity studies (Bloom, 1978; Bhunya and Jena, 1992; Jena and Bhunya, 1992). However, in recent years some encourag- ing results have also been obtained using embry- onic and neonatal chicks for screening chemically induced cellular and genetic damages (Todd and Bloom, 1980; Sawyer et al., 1986; Nikolaides et al., 1988), immunotoxicity (Wilmer and Bloom, 1991; Wilmer et al., 1992) and teratogenicity stud- ies (Gebhardt, 1972; Farage-Elawar, 1990; Hatano and Hatano, 1992). The handling and rearing of chicks are easier than mammals. The low cost of chicks and the