Risk assessment of pesticide residues in water samples from river Gongola, Adamawa state, Nigeria

Abstract

Pesticides used in agricultural fields pose harmful effect to non-target organisms such as humans and many other aquatic and terrestrial organisms either directly or indirectly especially when they find their way into water bodies. This study is aimed at conducting a risk assessment of pesticide residues in water samples from River Gongola, Adamawa State, Nigeria. Samples were collected randomly from different points along the river. Water samples were collected by lowering pre-cleaned plastic bottles into the bottom of the water body, 30cm deep, and allowed to over flow before withdrawing. Sampling points were approximately 50m away from each other. Pesticide residues in the collected samples were determined using GC/MS analysis with helium gas as a carrier. The levels of pesticides detected were compared with the maximum residue levels (MRL), the estimated daily intake (EDI) and health risk index (HRI) of each pesticide residue. Results of the analysis revealed nineteen (19) different pesticide residues belonging to organochlorines, organophosphates and pyrethroid class of pesticides. The concentrations of the pesticide residues detected in the water samples occurred below the maximum residue levels but above the acceptable daily intake set by European Union. The health risk index of each pesticide residue detected was below 1. Hence, life time consumption of water containing these pesticides poses no significant health threat. However, the presence of banned organochlorine pesticide residues is a cause for alarm.