Dichlorvos is an organophosphate insecticide used indiscriminately in Nigeria in various insecticide formulations due to its cheap production, accessibility, efficacy and affordability. Reactive oxygen species formation has been implicated in the mechanism of dichlorvos toxicity. Reports on antioxidant-prooxidant status in human users of dichlorvos are scarce and the few available reports are conflicting. 35 wistar rats were divided into 7 groups of 5 rats per group as follows; unexposed group, six groups exposed to dichlorvos for 1week, 2weeks, 3weeks, 4weeks, 5weeks and 6weeks in a poorly ventilated compartment. Dichlorvos was prepared in a dilution of 1:1 as recommended by the manufacturer for domestic use. Exposure to dichlorvos was done for 4hours daily. At completion of exposure, animals were anaesthetized and blood was drawn from the heart, plasma was separated and used for measurement of hydrogen peroxide (H2O2), malondialdehyde (MDA), superoxide dismutase (SOD) activity and catalase (CAT) activity. Results showed a significant decrease in plasma MDA concentration in rats exposed to dichlorvos for 4weeks, 5weeks and 6weeks when compared with unexposed control group. There was a significant increase of plasma CAT activity in rats exposed for 3weeks when compared to unexposed control. It could be concluded from this study that long term dichlorvos inhalation may alter plasma prooxidant-antioxidant balance, hence the need for cautious use.
