Lymphocyte cultures for micronuclei assay were set up according to method described by Fenech and Morley . Briefly, cultures were initiated as described in chromosomal aberration assay and at the end of 44th hour of culture Cytochalasin-B at a final concentration of 3 μg/mL culture was added to each vial. The cells were further incubated for 28 hrs at 37°C. The cells were harvested with brief hypotonic treatment and slides were prepared by fixing the cells with Carnoy's fixative. The cell suspensions were dropped onto a clean cooled slide and stained with Giemsa.