Organochlorine Pesticide Residues in Fish Samples from Alau Dam, Borno State, North Eastern Nigeria

Abstract

In this study, the levels of organochlorine (gamma-BCH, Alpha-BCH, aldrin, o,p’-DDE, endosulfan, dieldrin, p,p’-DDT, lindane, p,p’-DDD, o,p’-DDD and methoxychlor) pesticide residues in Alau Dam from Konduga Local Government, Borno State, Nigeria, was investigated using fish samples as a case study. Four fish species (Clarias gariepinus, Heterotis niloticus, Oreochromis niloticus and Tilapia zilli) were collected for this analysis. Fish samples of uniform size were collected in order to avoid possible error due to size differences. The fish samples were labeled with a unique identification number. Samples of fishes were transported to the laboratory on the same day and later dissected to remove the flesh, liver, stomach and Gills of each species of fish and store using 4% formalin pending extraction and analysis. The extraction, clean up and de-fattening of the fishes organs were carried out using standard procedures. The levels of all the pesticide residues were determined using GC/MS SHIMADZU (GC – 17A) equipped with electron capture detector (ECD). Eleven organochlorine pesticides were detected in all the fish samples studied. Endosulfan was the most abundant pesticide residue in the studied tissues of all the fish species with a value of 8.98 ± 0.02 μg/g in the liver of Oreochromis niloticus. This study also revealed that, all the pesticide residues in the fish samples studied were above the maximum residues limits (MRLs) and dietary intake (ADI) and could be an important process of transferring pesticides to humans. It also indicated the extensive presence and usage of these pesticides in the study environment, which include recent use of this pesticide for agricultural purposes. Thus, the use of these pesticides to control pest by farmers within the study area with little or no knowledge must be checked through adequate control of the trade and use of pesticides and the enforcement of appropriate sanctions.